MD SWM Volume 2

MD SWM Volume 2
Landscaping Guidance for Stormwater BMPs
Appendix
A
Appendix A. Landscaping Guidance for Stormwater BMPs.......... General Landscaping Guidance
Introduction
Landscaping is a critical element to improve both the function and appearance of stormwater best
management practices (BMPs). This Appendix provides landscaping criteria and plant selection
guidance for effective stormwater BMPs. It is organized as follows:
The first section, A.1, outlines general guidance that should be considered when landscaping any
stormwater practice. Section A.2 then presents more specific guidance on landscaping criteria and
plant selection for individual BMP designs. These include:
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Stormwater ponds and wetlands
Infiltration and sand filter practices
Bioretention
Open Channels
Filter Strips and Buffers
In Section A.3, key factors in selecting plant material for stormwater landscaping are reviewed,
including hardiness zones, physiographic regions, hydrologic zones, and cultural factors. Section
A.4 contains a detailed plant list of native woody and herbaceous species that can be used when
preparing a stormwater planting plan.
Native Species
This manual encourages the use of native plants in stormwater management facilities. Native plants
are defined as those species which evolved naturally to live in this region. Practically speaking, this
refers to those species which lived in Maryland before Europeans explored and settled in America.
Many introduced species were weeds brought in by accident; others were intentionally introduced
and cultivated for use as medicinal herbs, spices, dyes, fiber plants, and ornamentals.
Introduced species can often escape cultivation and begin reproducing in the wild. This is
significant ecologically because many introduced species out-compete indigenous species and begin
to replace them in the wild. Some introduced species like kudzu, phragmites, and dandelions are
invasive, have few predators, and can take over naturally occurring species at an alarming rate. By
planting native species in stormwater management facilities, we can protect Maryland’s natural
heritage and provide a legacy for future generations.
Native species also have distinct genetic advantages over non-native species for planting in
Maryland. Because they have evolved to live here naturally, indigenous plants are best suited for
our local climate. This translates into greater survivorship when planted and less replacement and
maintenance during the life of a stormwater management facility. Both of these attributes provide
cost savings for the facility owner.
Finally, people often plant exotic species for their ornamental value. While it is important to have
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Appendix A. Landscaping Guidance for Stormwater BMPs.......... General Landscaping Guidance
aesthetic stormwater management facilities for public acceptance and the maintenance of property
value, it is not necessary to introduce foreign species for this purpose. Many native species are
aesthetically pleasing and can be used as ornamentals. For example, the following species are part
of Maryland’s natural heritage and provide high aesthetic value throughout the year: rhododendron,
pink azalea, red maple, pin oak, sycamore, flowering dogwood, mountain laurel, willow, hemlock,
white pine, bald cypress, atlantic cedar, american holly, black-eyed susan, sunflower, lobelia,
pickerel weed, marsh hibiscus, and yellow pond lily. When selecting ornamentals for stormwater
management facilities, planting preference should be given to native ornamentals. Please refer to the
plant list in Section A.4 for a comprehensive list of native species available for stormwater
management facility planting.
A.1
General Landscaping Guidance for All Stormwater BMPs
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Trees, shrubs, and/or any type of woody vegetation are not allowed on the
embankment.
Plant trees and shrubs at least 15 feet away from the toe of slope of a dam.
Trees or shrubs known to have long taproots should not be within the vicinity of the
earth dam or subsurface drainage facilities.
Plant trees and shrubs at least 25 feet away from perforated pipes.
Plant trees and shrubs at least 25 feet away from a principal spillway structures.
Provide 15 foot clearance from a non-clogging, low flow orifice.
Herbaceous embankment plantings should be limited to 10 inches in height.
Use erosion control mats and fabrics in channels to reduce the potential for erosion.
Stabilize all emergency spillways with plant material that can withstand strong flows.
Root material should be fibrous and substantial but lacking a taproot.
Sod channels that are not stabilized with erosion control mats.
Divert flows temporarily from seeded areas until stabilized.
Check water tolerances of existing plant materials prior to inundation of area.
Stabilize aquatic and safety benches with emergent wetland plants and wet seed
mixes.
Do not block maintenance access to structures with trees or shrubs.
To reduce thermal warming, shade inflow and outflow channels as well as southern
exposures of ponds.
Avoid plantings that will require routine or intensive chemical applications (i.e. turf
area).
Have soil tested to determine if there is a need for amendments.
Native plant species should be specified over exotic or foreign species because they
are well adapted to local on-site soil conditions and require little or no additional
amendments.
Decrease the areas where turf is used. Use low maintenance ground cover to absorb
run-off.
Plant stream and water buffers with trees, shrubs, ornamental grasses, and
herbaceous materials where possible, to stabilize banks and provide shade.
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Appendix A. Landscaping Guidance for Stormwater BMPs.......... General Landscaping Guidance
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Maintain and frame desirable views. Be careful not to block views at entrances,
exits, or difficult road curves. Screen unattractive views into the site. Aesthetics and
visual characteristics should be a prime consideration.
Use plants to prohibit pedestrian access to pools or steeper slopes.
The designer should carefully consider the long-term vegetation management
strategy for the BMP, keeping in mind the “maintenance” legacy for the future
owners. Provide a planting surface that can withstand the compaction of vehicles
using maintenance access roads. Make sure the facility maintenance agreement
includes requirements to ensure vegetation cover in perpetuity.
If a BMP is likely to receive excessive amounts of deicing salt, salt tolerant plants
should be used.
Provide signage for:
Stormwater Management Areas to help educate the public.
Wildflower areas, when possible, to designate limits of mowing.
Avoid the overuse of any plant materials.
Preserve existing natural vegetation when possible.
It is necessary to test the soil in which you are about to plant in order to determine the following:
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pH; whether acid, neutral, or alkaline
major soil nutrients; Nitrogen, Phosphorus, Potassium
minerals; such as chelated iron, lime
Have soil samples analyzed by experienced and qualified individuals, such as those at the
Agricultural Extension Office, who will explain in writing the results, what they mean, as well as
what soil amendments would be required. Certain soil conditions, such as marine clays, can present
serious constraints to the growth of plant materials and may require the guidance of qualified
professionals. When poor soils can not be amended, seed mixes and plant material must be selected
to establish ground cover as quickly as possible.
Areas that recently have been involved in construction can become compacted so that plant roots
cannot penetrate the soil. Also seeds will lie on the surface of compacted soils and are often washed
away or eaten by birds. For planting success, soils should be loosened to a depth of three to five
inches. Hard soils may require disking to a deeper depth. The soil should be loosened regardless of
the ground cover. This will improve seed contact with the soil, increase germination rates, and allow
the roots to penetrate the soil. For areas to be sodded, disking is necessary so that the roots can
penetrate the soil. Providing good growing conditions can prevent poor vegetative cover. This saves
money because vegetation will not need to be replanted.
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Appendix A. Landscaping Guidance for Stormwater BMPs.......... General Landscaping Guidance
Whenever possible, topsoil should be spread to a depth of four to eight inches and lightly compacted
to minimum thickness of four inches. This provides organic matter and important nutrients for the
plant material. The use of topsoil allows vegetation to become established faster and roots to
penetrate deeper. This ensures quicker and more complete stabilization, making it less likely that
the plants will wash out during a heavy storm.
If topsoil has been stockpiled in deep mounds for a long period of time, it is necessary to test the soil
for pH as well as microbial activity. If the microbial activity has been destroyed, it is necessary to
inoculate the soil after application.
Remember that newly installed plant material requires water in order to recover from the shock of
being transplanted. Be sure that some source of water is provided, especially during dry periods.
This will reduce plant loss and provide the new plant materials with a chance to establish root
growth.
A.2
Specific Landscaping Criteria for BMP Groups
A.2.1 Ponds and Wetlands
For planting within a stormwater management facility, it is necessary to determine what hydrologic
zones will be created. Hydrologic zones describe the degree to which an area is inundated by water.
Plants have differing tolerances to inundation and the six zones described in this section will dictate
which plants will survive where. Every facility does not necessarily exhibit all of these zones.
Table A.1 Hydrologic Zones
Zone #
Zone Description
Hydrologic Conditions
Zone 1
Deep Water Pool
1-6 foot deep permanent pool
Zone 2
Shallow Water Bench (low marsh)
6 inches to 1 foot deep
Zone 3
Shoreline Fringe (high marsh)
Regularly inundated
Zone 4
Riparian Fringe
Periodically inundated
Zone 5
Floodplain Terrace
Infrequently inundated
Zone 6
Upland Slopes
Seldom or never inundated
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
Zone 1: Deep Water Area (1 to 6 feet)
Ponds and wetlands both have deep pool areas that comprise Zone 1. These pools range from one to
six feet in depth, and are best colonized by submergent plants, if at all. This pondscaping zone has
not been routinely planted for several reasons. First, the availability of plant materials that can
survive and grow in this zone is limited, and it is also feared that plants could clog the stormwater
facility outlet structure. In many cases, these plants will gradually become established through
natural recolonization (e.g., transport of plant fragments from other ponds by waterfowl). If
submerged plant material becomes more commercially available and clogging concerns are
addressed, this area can be planted. The function of the planting is to reduce sedimentation and
improve oxidation while creating a greater aquatic habitat.
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Plant material must be able to withstand constant inundation of water of one foot or
greater in depth.
Plants may be submerged partially or entirely.
Plants should be able to enhance pollutant uptake.
Plants may provide food and cover for waterfowl, desirable insects, and other aquatic
life.
Some suggested emergent or submergent species include, but are not limited to lotus, wild celery,
and redhead grass.
Zone 2: Shallow Water Bench/Low Marsh (6 inches to 1 foot)
Zone 2 includes all areas that are inundated below the normal pool to a depth of one foot, and is the
primary area where emergent plants will grow in stormwater wetlands. Zone 2 also coincides with
the aquatic bench found in stormwater ponds. This zone offers ideal conditions for the growth of
many emergent wetland species. These areas may be located at the edge of the pond or on low
mounds of earth located below the surface of the water within the pond. When planted, Zone 2 can
be an important habitat for many aquatic and nonaquatic animals, creating a diverse food chain.
This food chain includes predators, allowing a natural regulation of mosquito populations, thereby
reducing the need for insecticide applications.
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Plant material must be able to withstand constant inundation of water to depths
between six inches and one foot deep.
Plants will be partially submerged.
Plants should be able to enhance pollutant uptake.
Plants may provide food and cover for waterfowl, desirable insects and other aquatic
life.
Plants will stabilize the bottom of the pond, as well as the edge of the pond, absorbing wave impacts
and reducing erosion, when water level fluctuates. In addition to slowing water velocities and
increasing sediment deposition rates, plants can also reduce resuspension of sediments caused
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
by the wind. Plants can also soften the engineered contours of the pond, and can conceal drawdowns
during dry weather.
Some suggested species for Zone 2 include lobelia, bayberry, many asters, turtlehead, pond cypress,
iris, and blue flag. It is important to recognize that a plant typically found in wetlands may be
cultivated in nonwetland conditions. Hence the importance of obtaining plant stock which is
cultivated in similar hydrologic and soil conditions as those present in the stormwater management
facility. A plant typically found in wetlands, but cultivated in nonwetland conditions, may not
survive if installed in wetland conditions. A nonwetland plant cultivated in wetland conditions
should thrive when introduced to wetland conditions.
Table A.2
Common Emergent Wetland Plant Species Used for Stormwater Wetlands
and on Aquatic Benches of Stormwater Ponds
Common Name
Scientific Name
Inundation Tolerance
Arrow Arum
Arrowhead/Duck Potato
Broomsedge
Broad Water Weed
Bushy Beardgrass
Common Three-square
Marsh Hibiscus
Spatterdock
Rice Cutgrass
Sedges
Soft Rush
Switchgrass
Peltandra virginica
Saggitaria latifolia
Andropogon virginicus
Elodea canadensis
Andropogon glomeratus
Scirpus pungens
Hibiscus moscheutos
Nuphar luteum
Leersia oryzoides
Carex spp.
Juncus effusus
Panicum virgatum
up to 12 inches
up to 12 inches
up to 3 inches
at least 12 inches
up to 12 inches
up to 6 inches
up to 3 inches
up to 3 inches
up to 3 inches
up to 3 inches
up to 3 inches
up to 3 inches
Note 1: Inundation tolerance is maximum inches below the normal pool; most plants prefer
shallower depths than the maximum indicated.
Note 2: for additional plant options, consult the stormwater planting list at the end of this
appendix. Other good sources include the 1994 Maryland Standards and Specifications for
Soil Erosion and Sediment Control (MDE, 1994), Design of Stormwater Wetland Systems
(Schueler, 1992) and Planting Guide for the Northeastern United States (Environmental
Concern, 1993).
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
Zone 3: Shoreline Fringe/High Marsh (regularly inundated)
Zone 3 encompasses the shoreline of a pond or wetland, and extends vertically about one foot in
elevation from the normal pool. This zone includes the safety bench of a pond, and may also be
periodically inundated if storm events are subject to extended detention. This zone occurs in a wet
pond or shallow marsh and can be the most difficult to establish since plants must be able to
withstand inundation of water during storms, when wind might blow water into the area, or the
occasional drought during the summer. In order to stabilize the soil in this zone, Zone 3 must have a
vigorous cover.
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Plants should stabilize the shoreline to minimize erosion caused by wave and wind
action or water fluctuation.
Plant material must be able to withstand occasional inundation of water. Plants will
be partially submerged at this time.
Plant material should, whenever possible, shade the shoreline, especially the
southern exposure. This will help to reduce water temperature.
Plants should enhance pollutant uptake.
Plants may provide food and cover for waterfowl, songbirds, and wildlife. Large
plants could also be selected and located to control overpopulation of waterfowl.
Plants should be located to reduce human access where there are potential hazards,
but should not block the maintenance access.
Plants should have very low maintenance requirements, because they may be
difficult or impossible to reach.
Plants should be resistant to disease and other problems which require chemical
applications (since chemical application is not advised in stormwater ponds).
Native plants are preferred because they are low maintenance and disease resistant.
Many of the emergent wetlands plants outline in Table A.2 also thrive in Zone 3. Some other
species that do well include bentgrass, foxtail, panic grass, and hawthorn. If shading is needed along
the shoreline, the following tree species are suggested— river birch, ash, willow, red maple and
willow oak.
Zone 4: Riparian Fringe (periodically inundated)
Zone 4 extends from one to four feet in elevation above the normal pool. Plants in this zone are
subject to periodic inundation after storms, and may experience saturated or partly saturated soil.
Nearly all of the temporary ED area is included within this zone.
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Plants must be able to withstand periodic inundation of water after storms, as well as
occasional drought during the warm summer months.
Plants should stabilize the ground from erosion caused by run-off.
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
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Plants should shade the low flow channel to reduce pool warming whenever possible.
Plants should enhance pollutant uptake.
Plant material should have very low maintenance, since they may be difficult or
impossible to access.
Plants may provide food and cover for waterfowl, songbirds and wildlife. Plants
may also be selected and located to control overpopulation of waterfowl.
Plants should be located to reduce pedestrian access to the deeper pools.
Native plants are preferred because they are low maintenance and disease resistant.
Some frequently used plant species in Zone 4 include coneflower, violets, primrose, milkwort,
nannyberry, lespedeza, lilies, flatsedge, hollies, horsythia, lovegrass, hawthorn, spiraea, birch, and
sugar maple.
Zone 5: Floodplain Terrace (infrequently inundated)
Zone 5 is periodically inundated by floodwaters that quickly recede in a day or less. Operationally,
Zone 5 extends from the maximum two year or Cpv water surface elevation up to the 10 or 100 year
maximum water surface elevation. Key landscaping objectives for Zone 5 are to stabilize the steep
slopes characteristic of this zone and establish low maintenance natural vegetation.
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Plant material should be able to withstand occasional but brief inundation during
storms. In between storms, typical moisture conditions may be moist, slightly wet, or
even swing entirely to drought conditions during the dry weather periods.
Plants should stabilize the basin slopes from erosion.
Ground cover should be very low maintenance, since they may be difficult to access
on steep slopes or if frequency of mowing is limited. A dense tree cover may help
reduce maintenance and discourage resident geese.
Plants may provide food and cover for waterfowl, songbirds, and wildlife.
Placement of plant material in Zone 5 is often critical, as it often creates a visual
focal point and provides structure and shade for a greater variety of plants.
Some commonly planted species in Zone 5 include solomon’s seal, nannyberry, many fescues, many
viburnums, cherries, chestnut oak, post oak, and phlox.
Zone 6: Upland Slopes/Pond Buffer (seldom or never inundated)
The last zone extends above the maximum 100 year water surface elevation, and often includes the
outer buffer of a pond or wetland. Unlike other zones, this upland area may have sidewalks, bike
paths, retaining walls, and maintenance access roads. Care should be taken to locate plants so they
will not overgrow these routes or create hiding places that might make the area unsafe.
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Plant selections should be made based on soil condition, light, and function within
the landscape because little or no water inundation will occur.
Ground covers should require infrequent mowing to reduce the cost of maintaining
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
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this landscape.
Placement of plants in Zone 6 is important since they are often used to create a visual
focal point, frame a desirable view, screen undesirable views, serve as a buffer, or
provide shade to allow a greater variety of plant materials. Particular attention
should be paid to seasonal color and texture of these plantings.
Some frequently used plant species in Zone 6 include eastern cottonwood, american yew, linden,
bald cypress, magnolia, and mountain ash.
Figure A.1 Hydrologic Zones Around Stormwater Facilities – Legend
12”-36” depth below normal pool elevation
Water Lily, Deep Water Duck Potato, Sago Pond Plant, Wild Celery,
Redhead Grass
0”-12” depth below normal pool elevation
Blue Flag Iris, Duck Potato, Flowering Bulrush, Softrush, Sedges, Lobelia,
Pond Cypress, various asters
0” to 12” elevation above normal pool elevation
New England Aster, Marsh Aster, Marsh Marigold (Appalachian Plateau), Tussock Sedge,
Spotted Joe Pye Weed, Forget Me Nots, Inkberry, Purple Osier Dogwood, Pin Oak, River
Birch, Sycamore, Swamp White Oak (Coastal Plain), Weeping Willow, Dawn Redwood
1’ to 4’ elevation above normal pool elevation
Purple Cone Flower, Birds Foot Trefoil, Slender Rush, Deer Tongue Grass,
Lespedeza, Switch Grass, Serviceberry, Gray Birch, Hackberry, Sweet Pepper
Bush (Coastal Plain, Gray stem Dogwood, Red Osier Dogwood, Green Ash,
Qp2 or Cpv to Qp10 or Qf water surface elevation
(Many Wildflowers and native grasses) American Holly, Witch Hazel,
Ninebark, Red Oak, American Elderberry, American Hemlock, Lowbush
Blueberry, Maple Leaf Viburnum, Nannyberry, Blackhaw Viburnum
Qf water surface elevation and above (Floodplain)
Mostly ornamentals as long as soils drains well. Many natives. All
species must be able to tolerate flood plain conditions. Hackberry, Pitch
Pine, Sheep Fescue, Wildflowers, many Native Grasses.
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
Figure A.2 Hydrologic Zones Around Stormwater Facilities
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
Figure A.3 Section of Typical Stormwater Management Detention Pond
Figure A.4 Section of Typical Shallow Extended Detention Wetland System
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
A.2.2 Infiltration and Filter Systems
Infiltration and filter systems either take advantage of existing permeable soils or create a permeable
medium such as sand for WQv and Re v. In some instances where permeability is great, these
facilities may be used for Qp as well. The most common systems include infiltration trenches,
infiltration basins, sand filters, and organic filters.
When properly planted, vegetation will thrive and enhance the functioning of these systems. For
example, pre-treatment buffers will trap sediments that often are bound with phosphorous and
metals. Vegetation planted in the facility will aid in nutrient uptake and water storage.
Additionally, plant roots will provide arteries for stormwater to permeate soil for groundwater
recharge. Finally, successful plantings provide aesthetic value and wildlife habitat making these
facilities more desirable to the public.
Design Constraints:
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Planting buffer strips of at least 20 feet will cause sediments to settle out before
reaching the facility, thereby reducing the possibility of clogging.
Determine areas that will be saturated with water and water table depth so that
appropriate plants may be selected (hydrology will be similar to bioretention
facilities, see figure A.5 and Table A.4 for planting material guidance).
Plants known to send down deep taproots should be avoided in systems where filter
fabric is used as part of facility design.
Test soil conditions to determine if soil amendments are necessary.
Plants shall be located so that access is possible for structure maintenance.
Stabilize heavy flow areas with erosion control mats or sod.
Temporarily divert flows from seeded areas until vegetation is established.
See Table A.5 for additional design considerations.
A.2.3 Bioretention
Soil Bed Characteristics
The characteristics of the soil for the bioretention facility are perhaps as important as the facility
location, size, and treatment volume. The soil must be permeable enough to allow runoff to filter
through the media, while having characteristics suitable to promote and sustain a robust vegetative
cover crop. In addition, much of the nutrient pollutant uptake (nitrogen and phosphorus) is
accomplished through absorption and microbial activity within the soil profile. Therefore, soils must
balance their chemical and physical properties to support biotic communities above and below
ground.
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
The planting soil should be a sandy loam, loamy sand, loam (USDA), or a loam/sand mix (should
contain a minimum 35 to 60% sand, by volume). The clay content for these soils should be less than
25% by volume [Environmental Quality Resources (EQR), 1996; Engineering Technology Inc. and
Biohabitats, Inc. (ETAB), 1993]. Soils should fall within the SM, ML, SC classifications or the
Unified Soil Classification System (USCS). A permeability of at least 1.0 feet per day (0.5"/hr) is
required (a conservative value of 0.5 feet per day is used for design). The soil should be free of
stones, stumps, roots, or other woody material over 1" in diameter. Brush or seeds from noxious
weeds (e.g., Johnson Grass, Mugwort, Nutsedge, and Canada Thistle or other noxious weeds as
specified under COMAR 15.08.01.05.) should not be present in the soils. Placement of the planting
soil should be in 12” to 18” lifts that are loosely compacted (tamped lightly with a backhoe bucket
or traversed by dozer tracks). The specific characteristics are presented in Table A.3.
Table A.3
Planting Soil Characteristics
(Adapted from EQR, 1996; ETAB, 1993)
Parameter
Value
pH range
5.2 to 7.00
Organic matter
1.5 to 4.0% (by weight)
Magnesium
35 lbs. per acre, minimum
Phosphorus (phosphate - P2O5)
75 lbs. per acre, minimum
Potassium (potash - K2O)
85 lbs. per acre, minimum
Soluble salts
500 ppm
Clay
10 to 25%
Silt
30 to 55%
Sand
35 to 60%
Mulch Layer
The mulch layer plays an important role in the performance of the bioretention system. The mulch
layer helps maintain soil moisture and avoids surface sealing which reduces permeability. Mulch
helps prevent erosion, and provides a microenvironment suitable for soil biota at the mulch/soil
interface. It also serves as a pretreatment layer, trapping the finer sediments which remain suspended
after the primary pretreatment.
The mulch layer should be standard landscape style, single or double shredded hardwood mulch or
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
chips. The mulch layer should be well aged (stockpiled or stored for at least 12 months), uniform in
color, and free of other materials, such as weed seeds, soil, roots, etc. The mulch should be applied
to a maximum depth of three inches. Grass clippings should not be used as a mulch material.
Planting Guidance
Plant material selection should be based on the goal of simulating a terrestrial forested community of
native species. Bioretention simulates an upland-species ecosystem. The community should be
dominated by trees, but have a distinct community of understory trees, shrubs and herbaceous
materials. By creating a diverse, dense plant cover, a bioretention facility will be able to treat
stormwater runoff and withstand urban stresses from insects, disease, drought, temperature, wind,
and exposure.
The proper selection and installation of plant materials is key to a successful system. There are
essentially three zones within a bioretention facility (Figure A.5). The lowest elevation supports
plant species adapted to standing and fluctuating water levels. The middle elevation supports plants
that like drier soil conditions, but can still tolerate occasional inundation by water. The outer edge is
the highest elevation and generally supports plants adapted to dryer conditions. A sample of
appropriate plant materials for bioretention facilities are included in Table A.4. The layout of plant
material should be flexible, but should follow the general principals described in Table A.5. The
objective is to have a system which resembles a random and natural plant layout, while maintaining
optimal conditions for plant establishment and growth. For a more extensive bioretention plan,
consult ETA&B, 1993 or Claytor and Schueler, 1997.
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
Figure A.5 Planting Zones for a Bioretention Facilities
Optional Curtain Drain
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
Table A.4 Commonly Used Species for Bioretention Areas
Trees
Shrubs
Herbaceous Species
Acer rubrum
Aesculus pariviflora
Andropogon virginicus
Red Maple
Bottlebrush Buckeye
Broomsedge
Betula nigra
Cephalanthus occidentalis
Eupatorium perpurea
River Birch
Buttonbush
Joe Pye Weed
Juniperus virginiana
Hamemelis virginiana
Scirpus pungens
Eastern Red Cedar
Witch Hazel
Three Square Bulrush
Chionanthus virginicus
Vaccinium corymbosum
Iris versicolor
Fringe-tree
Highbush Blueberry
Blue Flag
Nyssa sylvatica
Ilex glabra
Lobelia cardinalis
Black Gum
Inkberry
Cardinal Flower
Diospyros virginiana
Ilex verticillata
Panicum virgatum
Persimmon
Winterberry
Switchgrass
Platanus occidentalis
Viburnum dentatum
Dichanthelium scoparium
Sycamore
Arrowwood
Broom Panic Grass
Quercus palustris
Lindera benzoin
Rudbeckia laciniata
Pin Oak
Spicebush
Tall Coneflower
Quercus phellos
Myrica pennsylvanica
Scirpus cyperinus
Willow Oak
Bayberry
Woolgrass
Salix nigra
Vernonia noveboracensis
Black willow
New York Ironweed
Note 1: For more options on plant selection for bioretention, consult Bioretention Manual
(ETAB, 1993) or the Design of Stormwater Filtering Systems (Claytor and Schueler, 1997).
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Appendix A. Landscaping Guidance for Stormwater BMPs.............Specific Landscaping Criteria
Table A.5 Planting Plan Design Considerations
¾ Native plant species should be specified over exotic or foreign species.
¾ Appropriate vegetation should be selected based on the zone of hydric tolerance.
¾ Species layout should generally be random and natural.
¾ A canopy should be established with an understory of shrubs and herbaceous materials.
¾ Woody vegetation should not be specified in the vicinity of inflow locations.
¾ Trees should be planted primarily along the perimeter of the bioretention area.
¾ Stressors (e.g., wind, sun, exposure, insect and disease infestation, and drought) should be
considered when laying out the planting plan.
¾ Noxious weeds shall not be specified or used.
¾ Aesthetics and visual characteristics should be a prime consideration.
¾ Traffic and safety issues must be considered.
¾ Existing and proposed utilities must be identified and considered.
Plant Material Guidance
Plant materials should conform to the American Association of Nurserymen’s publication, the
American Standard Nursery Stock. The planting plan shall include a sequence of construction; a
description of the contractor's responsibilities; a planting schedule and installation specifications;
initial maintenance requirements; and a warranty period stipulating requirements for plant survival.
Table
A.6
presents
some
typical
issues
for
planting
specifications.
A.17
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Table A.6 Planting Specification Issues
Specification Element
Elements
Sequence of Construction
Describe site preparation activities, soil amendments, etc.; address
erosion and sediment control procedures; specify step-by-step
procedure for plant installation through site clean-up.
Contractor's Responsibilities
Specify the contractor's responsibilities, such as watering, care of
plant material during transport, timeliness of installation, repairs due
to vandalism, etc.
Planting Schedule
and Specifications
Specify the plants to be installed, the type of materials (e.g., balled
and burlap, bare root, containerized); time of year of installations,
sequence of installation of types of plants; fertilization, stabilization
seeding, if required; watering and general care.
Maintenance
Specify inspection periods; mulching frequency (annual mulching is
most common); removal and replacement of dead and diseased
vegetation; treatment of diseased trees; watering schedule after
initial installation (once per day for 14 days is common); repair and
replacement of staking and wires.
Warranty
Specify the warranty period, the required survival rate, and expected
condition of plant species at the end of the warranty period.
A.2.4 Open Channels
Consult Table A.7 for grass species that perform well in the stressful environment of an open
channel. For more detailed information, please consult the 1994 Maryland Standards and
Specifications for Soil Erosion and Sediment Control. If a BMP is likely to receive excessive
amounts of deicing salt, salt tolerant plants should be used.
A.2.5 Filter Strips and Stream Buffer
For design and plant selection of filter strips and stream buffers, please consult the USDA Natural
Resources Conservation Service Maryland Conservation Practice Standard No. 391 “Riparian
Stream Buffers.”
A.18
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Table A.7 Common Grass Species for Open Channels
Common Name
Scientific Name
Notes
Big Bluestem
Andropogon gerardii
Warm, not for Wet Swale
Creeping Bentgrass
Agrostis palustris
Cool,
Red Fescue
Festuca rubra
Cool, not for Wet Swale
Reed Canary grass
Phalaris arundinacea
Cool, Wet Swale
Redtop
Agrostis alba
Cool,
Smooth Brome
Bromus inermis
Cool, not for Wet Swale
Switch grass
Panicum virgatum
Warm
Note 1: These grasses are sod-forming and can withstand frequent inundation, and are thus
ideal for the swale or grass channel environment. Most are salt-tolerant, as well. Cool refers
to cool season grasses that do well in the western part of the State, Warm refers to warm
season grasses that work well in the eastern part of the State (see Table A.8).
Note 2: Where possible, one or more of these grasses should be in the seed mixes. For a more
thorough listing of seed mixes, consult the 1994 Maryland Standard and Specifications for
Soil Erosion and Sediment Control (MDE, 1994) or the MD NRCS Code 391 Riparian Forest
Buffer Standard, Table 2 (Zone 3).
A.3
Plant Selection for Stormwater Facilities
A.3.1 Hardiness Zones
Hardiness zones are based on historical annual minimum temperatures recorded in an area. A
BMPs location in relation to plant hardiness zones is important to consider first because plants differ
in their ability to withstand very cold winters. This does not imply that plants are not affected by
summer temperatures. Given that Maryland summers can be very hot, heat tolerance is also a
characteristic that should be considered in plant selection.
A.19
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Table A.8 Average Annual Minimum Temperature
Zone
USDA Minimum
Temperature (oF)
Temperate Zone 1
below -50o
Temperate Zone 2
-50o to -40o
Temperate Zone 3
-40o to -30o
Temperate Zone 4
-30o to -20o
Temperate Zone 5
Temperate Zone 6
Temperate Zone 7
-20o to -15o
a
b
a
b
a
b
-15° to -10°
-10o to -5o
-5° to 0°
0o to 5o
5° to 10°
10o to 20o
Temperate Zone 8
It is best to recommend plants known to thrive in specific hardiness zones. The plant list included at
the end of this appendix identifies the hardiness zones for each species listed as a general planting
guide. It should be noted, however, that certain site factors can create microclimates or
environmental conditions which permit the growth of plants not listed as hardy for that zone. By
investigating numerous references and based on personal experience, a designer should be able to
confidently recommend plants that will survive in microclimates.
A.20
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Figure A.6 USDA Plant Hardiness Zones in Maryland
A.3.2 Physiographic Provinces
There are five physiographic provinces in Maryland that describe distinct geographic regions in the
State with similar physical and environmental conditions (Figure A.7). These physiographic
provinces include, from west to east, the Appalachian Plateau, Valley and Ridge, Blue Ridge,
Piedmont, and Coastal Plain. Each physiographic region is defined by unique geological strata, soil
type, drainage patterns, moisture content, temperature and degree of slope which often dictate the
predominant vegetation. Because the predominant vegetation has evolved to live in these specific
conditions, a successful stormwater management facility planting design can be achieved through
mimicking these natural associations. The five physiographic regions are described below with
associated vegetation listed as general planting guidance. For more detailed information and plant
listings please refer to Woody Plants of Maryland (Brown and Brown, 1992).
A.21
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Figure A.7 Physiographic Provinces and Forest Types of Maryland
Appalachian Plateau
Piedmont
Valley & Ridge
Blue Ridge
Coastal Plain
Appalachian Plateau Province
The Appalachian Plateau Province is where Maryland’s highest elevations occur with Backbone
Mountain being the greatest at 3,360 feet above sea level. In the higher elevations of the
Appalachian Plateau, the climate becomes similar to that of the northern states and Canada.
Slopes in the Appalachian Plateau are often steep and deeply carved by winding streams. This
province has mountainous soils composed of clay and clay loams. The predominant forest types
in this province are the Northern Hardwood and Oak-Hickory.
Tree Species
Common Species of the Appalachian Plateau Province
Understory
eastern hemlock, white pine, mountain pine, pitch pine, red
spruce, sugar maple, white basswood, american basswood,
beech, yellow birch, sweet birch, cucumber tree, tulip tree,
white oak, chestnut oak, scarlet oak, red oak, white ash,
black walnut, and white walnut
ateau Province
A.22
hydrangea, flowering dogwood, pink azaleas, greenbriers,
witch hazel, iron wood, hazelnut, blueberries, huckleberries,
dewberries, dockmackie, deerberry, great laurel, hobble
bush, mountain maple, striped maple, red-berried elder,
bush honeysuckle, canadian yew, mountain holly, red
raspberry, allegheny menziesia, and dwarf cornel
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Within the Appalachian Plateau are bog and swamp areas which support unique vegetation. For
stormwater management facilities that will remain wet year-round, many species found in these
bog and swamp areas will likely do well. Around the edges of these bogs, red spruce, white
pine, hemlock, black gum, red maple, large and small toothed aspen, and pussy willow are
common. Interior bog species include tamarack or larch, alders, swamp rose, winter berry, wild
raisin, arrowwood, mountain holly, great laurel, smooth service berry, high bush blueberry,
swamp dewberries, and cranberries.
Valley and Ridge, Blue Ridge, and Piedmont Provinces
The Valley and Ridge Province is where parallel ridges and valleys of the Appalachian
Mountains create an alternating pattern. This province has mountainous soils composed of clay
and clay loams, as well as sandy or stony loams. Often, the soils are shallow, and shale barrens
may be found. The climate is dry. Most of the precipitation from the west is blocked by the
Allegheny Mountain range, and precipitation from the east is blocked by the Blue Ridge
Mountains.
The Blue Ridge Province is on the eastern edge of the Appalachian Mountains. This province has
mountainous soils composed of sandy or stony loams. The climate is similar to that in the Piedmont
Province, but somewhat cooler and moister.
The Piedmont Province is an area of rolling uplands with elevations ranging from 100 to 500 feet
above sea level. Soils of the Piedmont are derived from granite rock and consist of loams and clays
with rock fragments and gravel. The climate is moderate throughout this central Maryland province.
Common Species of the Valley and Ridge, Blue Ridge. and Piedmont Provinces
Tree Species
Understory
hickory, chestnut oak, scarlet oak, scrub oak, white oak, red
oak, black oak, scrub pine, pitch pine, short leaf pine, white
pine, hemlocks, beech, black jack oak, shingle oak, fringe
tree, and chinquapin
Sweet fern, flowering dogwood, black haw, chinquapin,
sassafras, redbud, mountain laurel, blueberry, fringe tree, pink
azalea, hydrangea, spicebush, and maple-leaved arrowwood
In the Hagerstown region of the Ridge and Valley Province, limestone outcrops produce alkaline
soils which are conducive to red cedar communities. Other common species include oaks, black
locust, redbud, fragrant sumac, hop hornbeam, hackberry, and slippery elm. Between Cumberland
and Flintstone a series of shale barrens occur. These areas have a low water holding capacity and
surfaces can get hot on sunny days. Common species associated with the shale barrens include scrub
pine, scrub oak, post oak, yellow oak, fragrant sumac, dwarf sumac, single-flowered hawthorn,
dwarf hackberry, New Jersey tea, Allegheny plum and pasture rose.
Coastal Plain Province
A.23
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
The Coastal Plain Province is recognized by flat or gently rolling topography and elevations rising
from sea level to about 100 feet. Coastal Plain marshes and swampy tidal flats surround the
Chesapeake Bay. Sands, sandy loams, and silt loams make up the soils of the Coastal Plain. The
climate is mild and sometimes rainy, similar to that found further south.
Forest Species
Common Species of the Coastal Plain Province
Understory
loblolly pine, virginia pine, pitch pine, pond pine, sweet gum,
willow oak, water oak, basket oak, pin oak, post oak, spanish
oak, black cottonwood, pale hickory, bitternut hickory, sweet
bay, american holly, beech, tulip tree, and river birch
blueberry, huckleberry, greenbier, sand blackberry, beach
plum, beach heather, bay berry, sweet pepper bush, azalea,
maleberry, stagger bush, fetter bush, inkberry, and alder
Because of low topographic relief and proximity to sea level, extensive swamp areas are common to
the Coastal Plain Province. Most notable are the cypress swamps found on both the Eastern and
Western Shores. As with the bogs of the Appalachian Province, species common to Coastal Plain
swamps will grow well in wet stormwater management facilities because of the similar hydrology.
In addition to bald cypress, other common species to these swamps are southern white cedar, black
gum, red maple, and swamp bay. Common understory include evergreen laurel-leaved greenbrier,
red-berried greenbrier, red choke berry, swamp haw, smooth winterberry, virginia willow, bay berry,
inkberry, and swamp rose.
Floodplain Regions in Maryland
Floodplains occur across Maryland’s physiographic provinces as low-lying areas adjacent to streams
and rivers. Floodplain plant communities are similar across most of the State because of common
soil characteristics governed by occasional flooding and high groundwater. Because stormwater
management facilities are often located in floodplains, plant associations in these areas can provide
valuable information for successful BMP plantings.
A.24
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Common Species of Floodplain Regions
Understory
Forest Species
river birch, willows, silver maple, sweet gum, sycamore, box
elder, green ash, american elm, swamp white oak, bur oak,
honeylocust, and hackberry
shrub willows, ninebark, silkey cornel, buttonbush, spicebush,
black alder, winterberry, black elderberry, and alders
A.3.3 Hydrologic Zones
For planting within a stormwater management facility, it is necessary to determine what hydrologic
zones will be created. Hydrologic zones describe the degree to which an area is inundated by water.
Plants have differing tolerances to inundation and as an aid to landscape designers, these tolerance
levels have been divided into six zones and corresponding plant species have been identified.
Section A.4 includes a native plant list with appropriate hydrologic zones designated for each
species. The hydrologic zones which are bracketed [ ] are where the plants tend to occur. There
may be other zones listed outside of these brackets. The plants may occur in these zones, but are not
typically found in them. Just as plants may, on occasion, be found outside of their hardiness zone,
they may also be found outside of their hydrologic zone. They tend to grow where they can compete
and survive. Additionally, hydrologic conditions in a stormwater management facility may fluctuate
in unpredictable ways; thus the use of plants capable of tolerating wide varieties of hydrologic
conditions greatly increases a successful planting. Conversely, plants suited for specific hydrologic
conditions may perish when hydrologic conditions fluctuate, expose the soil, and increase the chance
for erosion.
Table A.9 Hydrologic Zones
Zone #
Zone Description
Hydrologic Conditions
Zone 1
Deep Water Pool
1-6 foot deep permanent pool
Zone 2
Shallow Water Bench (low marsh)
6 inches to 1 foot deep
Zone 3
Shoreline Fringe (high marsh)
Regularly inundated
Zone 4
Riparian Fringe
Periodically inundated
Zone 5
Floodplain Terrace
Infrequently inundated
Zone 6
Upland Slopes
Seldom or never inundated
A.3.4 Other Considerations in Stormwater BMP Landscaping
A.25
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Use or Function
In selecting plants, consider their desired function in the landscape. Is the plant needed as ground
cover, soil stabilizer, or a source of shade? Will the plant be placed to frame a view, create focus, or
provide an accent? Does the location require that you provide seasonal interest to neighboring
properties? Does the adjacent use provide conflicts or potential problems and require a barrier,
screen, or buffer? Nearly every plant and plant location should be provided to serve some function
in addition to any aesthetic appeal.
Plant Characteristics
Certain plant characteristics are so obvious, they may actually be overlooked in the plant selection.
These are:
¾
¾
Size
Shape
For example, tree limbs, after several years, can grow into power lines. A wide growing shrub may
block an important line of sight to oncoming vehicular traffic. A small tree, when full grown, could
block the view from a second story window. Consider how these characteristics can work for you or
against you, today and in the future.
Other plant characteristics must be considered to determine how the plant provides seasonal interest
and whether the plant will fit with the landscape today and through the seasons and years to come.
Some of these characteristics are:
¾
¾
¾
¾
Color
Texture
Seasonal Interest (e.g., flowers, fruit, leaves, stems/bark)
Growth Rate
If shade is required in large amounts, quickly, a sycamore might be chosen over an oak. In urban or
suburban settings, a plant's seasonal interest may be of greater importance. Residents living next to
a stormwater system may desire that the facility be appealing or interesting to look at throughout the
year. For example, willows are usually the first trees to grow leaves signaling the coming of spring.
Pink and white dogwoods bloom in mid-spring to early summer, while witch hazel has a yellow
bloom every fall which can be contrasted with the red fall foliage of a sugar maple. Careful
attention to the design and planting of a facility can result in greater public acceptance and increased
property value.
Availability and Cost
A.26
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Often overlooked in plant selection is the availability from wholesalers and the cost of the plant
material. There are many plants listed in landscape books that are not readily available from local
nurseries. Without knowledge of what is available, time spent researching and finding the one plant
that meets all the needs will be wasted. It may require shipping, therefore, making it more costly
than the budget may allow. Some planting requirements may require a special effort to find the
specific plant that fulfills the needs of the site and the function of the plant in the landscape.
In some cases, it may be cost effective to investigate nursery suppliers for the availability of wetland
seed mixtures. Specifications of the seed mix shall include wetland seed types and the relative
proportion of each species. Some suppliers provide seed mixtures suitable for specific wetland,
upland, or riparian habitat conditions. This option may best be employed in small stormwater
facilities such as pocket wetlands and open swales, or to complement woody vegetation plantings in
larger facilities.
A.4
Stormwater Plant List
The pages at the end of this appendix present a list of herbaceous, tree and shrub plants native to
Maryland and suitable for planting in stormwater management facilities. The list is intended as a
guide for general planting purposes and planning considerations. Knowledgeable landscape
designers and nursery suppliers may provide additional information for considering specific
conditions for successful plant establishment and accounting for the variable nature of
stormwater hydrology.
The planting list is in alphabetical order according to the common name, with the scientific name
also provided. Life forms indicate whether a plant species is an “annual,” “perennial,” “grass,”
“fern,” “shrub,” or “tree”.
Each plant species has a corresponding hydrologic zone provided to indicate the most suitable
planting location for successful establishment. While the most common zones for planting are
listed in parenthesis, the listing of additional zones indicates that a plant may survive over a
broad range of hydrologic conditions.
The wetland indicator status (from Region 1, Reed, 1988) has been included to show “the
estimated probability of a species occurring in wetlands versus nonwetlands” (Reed, 1988).
Reed defines the indicator categories as follows:
Obligate wetland (OBL): Plants, which nearly always (more than 99% of the time) occur
in wetlands under natural conditions.
Facultative Wetland (FACW): Plants, which usually occur in wetlands (from 67 to 99%
of the time), but occasionally found in non wetlands.
A.27
Appendix A. Landscaping Guidance for Stormwater BMPs.................................... Plant Selection
Facultative (FAC): Plants, which are equally likely to occur in wetlands and non
wetlands and are found in wetlands from 34 to 66% of the time.
Facultative Upland (FACU): Plants, which usually occur in non wetlands (from 67 to
99% of the time), but occasionally found in wetlands (from 1 to 33% of the time).
Upland (UPL): Plants, which almost always (more than 99% of the time) under natural
conditions occur in non wetlands.
A given indicator status shown with a “+” or a “-“ means that the species is more (+) or
less (-) often found in wetlands than other plants with the same indicator status without
the “+” or “-“ designation.
Since the wetland indicator status alone does not provide an indication of the depth or duration
of flooding that a plant will tolerate, the “Inundation Tolerance” section is designed to provide
further guidance. Where a plant species is capable of surviving in standing water, a “yes” is
designated in this column. Additional information is provided for depth of inundation for
aquatic vegetation and tolerance for seasonal inundation or saturated soil conditions. Because
individual plants often have unique life requirements difficult to convey in a general listing, it
will be necessary to research specific information on the plant species proposed in order to
ensure successful plant establishment.
Pollution tolerance and salt tolerance information are indicated to identify plantings that would
be most appropriate in pollution hot spots.
Hardiness zones are provided for the U.S.D.A. hardiness zones. The herbaceous plant list
identifies the range of zones the plant may survive in, while the tree and shrub list shows the
coldest zone where the plant may naturally occur.
A.28
Table A.4.1 Stormwater Plant List - Woody Vegetation
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
TOLERANCE
POLLUTION
HARDINESS
SALT
ALDER,BROOK-SIDE
Alnus serrulata
Tree
[1,2],3
OBL
0-3"
ALDER,SEASIDE
Alnus maritima
Tree
[1,2],3
OBL
YES
ALDER,SPECKLED
Alnus rugosa
Tree
1[2,3]
FACW+
YES
2
ARROW-WOOD
Viburnum dentatum
Shrub
[3,4],5
FAC
SEASONAL
2
ASH,BLACK
Fraxinus nigra
Tree
[2,3],4
FACW
SATURATED
2
ASH,GREEN
Fraxinus pennsylvanica
Tree
[2,3],4
FACW
SEASONAL
2
ASH,WHITE
Fraxinus americana
Tree
[4,5],6
FACU
NO
3
ASPEN,BIG-TOOTH
Populus grandidentata
Tree
[4,5,6]
FACU
NO
3
ASPEN,QUAKING
Populus tremuloides
Tree
[4,5],6
FACU
YES
1
AZALEA,DWARF
Rhododendron atlanticum
Shrub
[2,3,4],5
FAC,FAC+
YES
AZALEA,EARLY
Rhododendron prinophyllum
Shrub
[2,3,4],5
FAC,FAC+
YES
AZALEA,HOARY
Rhododendron canescens
Shrub
[2,3],4
FACW
YES
AZALEA,PINK
Rhododendron periclymenoides
Shrub
2,[3,4],5
FAC
SEASONAL
3
AZALEA,SMOOTH
Rhododendron arborescens
Shrub
[3,4],5
FAC
YES
4
AZALEA,SWAMP
Rhododendron viscosum
Shrub
[1,2,3],4
FACW+,OBL
SEASONAL
3
Tree
3,[4,5],6
FACU
NO
2
2
3
BASSWOOD,AMERICAN
Tilia americana
BAYBERRY,NORTHERN
Myrica pennsylvanica
Shrub
[3,4],5
FAC
SEASONAL
BAYBERRY,SOUTHERN
Myrica cerifera
Shrub
[2,3,4],5
FAC,FAC+
REG.INUNDA
BEECH,AMERICAN
Fagus grandifolia
Tree
[4,5],6
FACU
NO
3
BIRCH,GRAY
Betula populifolia
Tree
[3,4],5
FAC
SEASONAL
5
BIRCH,RIVER
Betula nigra
Tree
[2,3],4
FACW
SEASONAL
4
BIRCH,YELLOW
Betula alleghaniensis
Tree
[3,4],5
FAC
YES
3
BLACK GUM, SWAMP TUPELO
Nyssa sylvatica
Tree
1,[2,3]
FACW+
SEASONAL
4
Stormwater Plant List - Woody Vegetation
A.29
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
BLACK-HAW
Viburnum prunifolium
BLACK-HAW,RUSTY
Viburnum rufidulum
Shrub
[3,4,5],6
FACU,FACU+
YES
TOLERANCE
POLLUTION
HARDINESS
SALT
3
Shrub
3,[4,5,6]
UPL,FACU
NO
5
Shrub-Tree
[3,4],5
FAC
YES
3
Vaccinium uliginosum
Shrub
2,3,4,5,6
FACU+,FACW+
YES
BLUEBERRY,CREEPING
Vaccinium crassifolium
Shrub
[2,3,4],5
FAC,FAC+
YES
BLUEBERRY,HIGHBUSH
Vaccinium atrococcum
Shrub
[2,3]
FACW
SEASONAL
3
BLUEBERRY,LOWBUSH
Vaccinium angustifolium
Shrub
3,[4,5,6]
FACU-,FACU
NO
2
BLUEBERRY,VELVET-LEAF
Vaccinium myrtilloides
Shrub
1,2,[3,4,5],
FACU,FACW-
YES
2
BOX-ELDER
Acer negundo
Tree
2,[3,4]
FAC+
SEASONAL
2
BUCKTHORN,CAROLINA
Rhamnus caroliniana
Shrub
2,[3,4,5,6]
FACU-,FAC
YES
5-6
BUCKTHORN,LANCE-LEAF
Rhamnus lanceolata
Shrub
6
NI
NO
5
BUFFALO-BERRY,CANADA
BLADDERNUT, AMERICAN
Staphylea trifolia
BLUEBERRY,BOG
Shepherdia canadensis
Shrub
6
NI
NO
BURNING-BUSH,EASTERN
Euonymus atropurpureus
Shrub
[2,3,4,5],6
FACU,FAC+
YES
4
BUTTERNUT
Juglans cinerea
Tree
[3,4,5,6]
FACU-,FACU+
YES
3
BUTTONBUSH,COMMON
Cephalanthus occidentalis
Shrub
[1,2],3
OBL
0-3'
CEDAR,ATLANTIC WHITE
Chamaecyparis thyoides
Tree
[1,2],3
OBL
SATURATE
3
CEDAR,EASTERN RED
Juniperus virginiana
Shrub
4,5,6
FACU
NO
2
CEDAR,NORTHERN WHITE
Thuja occidentalis
Tree
[2,3],4
FACW
SEASONAL
2
CHERRY,BLACK
Prunus serotina
Tree
[4,5],6
FACU
NO
3
CHERRY,CHOKE
Prunus virginiana
Tree
4,5,6
FACU
YES
5,6
CHERRY,FIRE
Prunus pensylvanica
Tree
4,5,6
FACU
NO
2
COTTON-WOOD,EASTERN
2
Populus deltoides
Tree
[3,4],5
FAC
SEASONAL
COTTON-WOOD,SWAMP
Populus heterophylla
Tree
[2,3]
FACW+
YES
CRANBERRY,MOUNTAIN
Vaccinium vitis-idaea
Shrub
2,[3,4],5
FAC
YES
2
CRANBERRY,SMALL
Vaccinium oxycoccos
Shrub
[1,2],3
OBL
YES
2
Stormwater Plant List - Woody Vegetation
A.30
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
CRANBERRY,SOUTHERN MOUNTAIN
Vaccinium erythrocarpum
CYPRESS,BALD
Taxodium distichum
Shrub
TOLERANCE
POLLUTION
HARDINESS
SALT
2,[3,4],5
FAC
YES
5
4
Tree
[1,2],3
OBL
SATURATED
Gaylussacia frondosa
Shrub
2,[3,4],5
FAC
YES
Vaccinium stamineum
Shrub
[3,4,5,6]
FACU-,FACU+
YES
5
DOG-HOBBLE,COASTAL
Leucothoe axillaris
Shrub
[1,2,3,4],5
FACW,FACW+
YES
6
DOG-HOBBLE,RED-TWIG
Leucothoe recurva
Shrub
3,[4,5],6
FACU
NO
5
DOGWOOD, GRAY
Cornus racemosa
Shrub
2[3,4]
FAC+
SEASONAL
DOGWOOD,FLOWERING
Cornus florida
Shrub-Tree
4,5,6
FACU-
NO
DOGWOOD,ROUGH-LEAF
Cornus asperifolia
Shrub
1,2,[3,4,5]
FAC-,FACW-
YES
DOGWOOD,ROUGH-LEAF
Cornus drummondii
Shrub
2,[3,4],5
FAC
YES
4
DOGWOOD,SILKY
Cornus amomum
Shrub
[2,3],4
FACW
SEASONAL
5
ELDER,EUROPEAN RED
Sambucus racemosa
Shrub
[3,4,5],6
FACU,FACU+
YES
4
Tree
[3,4],5
FAC
YES
3
DANGLE-BERRY
DEERBERRY
4
ELM,SLIPPERY
Ulmus rubra
FALSE-WILLOW,EASTERN
Baccharis halimifolia
Shrub
1,[2,3,4],5
FAC,FACW
0-6"
FARKLEBERRY
Vaccinium arboreum
Shrub
3,[4,5],6
FACU
NO
7
FETTER-BUSH
Leucothoe racemosa
Shrub
1,[2,3,4],5
FACW
SEASONAL
5
FETTER-BUSH
Lyonia lucida
Shrub
1,[2,3,4],5
FACW
YES
GERMANDER,AMERICAN
Teucrium canadense
Shrub
1,[2,3,4],5
FAC+,FACW
YES
GROUNDSEL TREE
Baccheris halimifolia
Shrub
[2,3]4
FACW
GUM,SWEET
Liquidambar styraciflua
Tree
[3,4],5
FAC
YES
4
HACKBERRY,COMMON
Celtis occidentalis
Shrub-Tree
4,5,6
FACU
SEASONAL
5
HAWTHORN,BEAUTIFUL
Crataegus pulcherrima
Tree
2,[3,4],5
FAC
YES
4
HAWTHORN,COCKSPUR
Crataegus crus-galli
Tree
2,[3,4,5],6
FACU,FAC
YES
4
HAWTHORN,DOWNY
Crataegus mollis
Tree
1,2,[3,4,5],
FACU,FACW-
YES
4
HAWTHORN,GREEN
Crataegus viridis
Tree
1,[2,3,4],5
FAC,FACW
YES
4
Stormwater Plant List - Woody Vegetation
A.31
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
HAWTHORN,LITTLE-HIP
Crataegus spathulata
Tree
1,[2,3,4],5
FAC,FACW
HAWTHORN,PARSLEY
TOLERANCE
POLLUTION
HARDINESS
SALT
YES
4
Crataegus marshallii
Tree
[1,2,3,4],5,
FACU+,FACW
YES
4
HAWTHORN,WASHINGTON
Crataegus phaenopyrum
Tree
2,[3,4,5]
FAC-,FAC
YES
4
HAZEL-NUT,AMERICAN
Corylus americana
Shrub
3,[4,5,6]
UPL,FACU
NO
4
HAZEL-NUT,BEAKED
Corylus cornuta
Shrub
3,[4,5,6]
UPL,FACU
NO
4
HEATHER
Calluna vulgaris
Shrub
2,[3,4],5
FAC
YES
4
HEMLOCK,EASTERN
Tsuga canadensis
Tree
4,5,6
FACU
NO
3
HICKORY,BIG SHELLBARK
Carya laciniosa
Tree
1,[2,3,4],5
FAC,FACW
YES
5
HICKORY,BITTER-NUT
Carya cordiformis
Tree
4,5,6
FACU+
NO
4
HICKORY,PECAN
Carya illinoensis
Tree
1,[2,3,4,5],
FACU,FACW
YES
5
HICKORY,RED
Carya ovalis
Tree
3,[4,5,6]
UPL,FACU
NO
4
HICKORY,SHAG-BARK
Carya ovata
Tree
[3,4,5,6]
FACU-,FACU+
YES
4
HICKORY,SWEET PIGNUT
Carya glabra
Tree
3,[4,5,6]
FACU-,FACU
NO
4
HOLLY, WINTERBERRY
Ilex laevigata
Shrub
[1,2],3
OBL
YES
4
HOLLY,AMERICAN
Ilex opaca
Shrub
4,5,6
FACU
LIMITED
5
HOLLY,BAY-GALL
Ilex coriacea
Shrub
1,[2,3,4],5
FACW
YES
HOLLY,DECIDUOUS
Ilex decidua
Shrub
1,[2,3,4,5]
FACW-,FACW
SEASONAL
HOLLY,GEORGIA
Ilex longipes
Shrub
1,[2,3,4],5
FAC,FACW
YES
HOLLY,SARVIS
Ilex amelanchier
Shrub
[1,2],3
OBL
YES
HOP-HORNBEAM,EASTERN
Ostrya virginiana
Shrub-Tree
[3,4,5,6]
FACU-,FACU+
YES
4
HORNBEAM,AMERICAN
Carpinus caroliniana
Tree
[3,4],5
FAC
SOME
2
HUCKLEBERRY,BLACK
Gaylussacia baccata
Shrub
3,[4,5],6
FACU
NO
2
HUCKLEBERRY,DWARF
Gaylussacia dumosa
Shrub
2,[3,4],5
FAC
YES
2
HYDRANGEA,PANICLE
Hydrangea paniculata
Shrub
2,[3,4],5
FAC
YES
4
HYDRANGEA,WILD
Hydrangea arborescens
Shrub
3,[4,5,6]
UPL,FACU
NO
4
Stormwater Plant List - Woody Vegetation
A.32
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
INK-BERRY
Ilex glabra
Shrub
[2,3],4
FACW-
LAUREL,MOUNTAIN
Kalmia latifolia
Shrub
4,5,6
4,5,6
TOLERANCE
POLLUTION
HARDINESS
SALT
SEASONAL
3
FACU
NO
4
FACU
YES
5
LOCUST,BLACK
Robinia pseudoacacia
Tree
MAGNOLIA,UMBRELLA
Magnolia tripetala
Tree
2,[3,4,5],6
FACU,FAC
YES
4
MALEBERRY
Lyonia ligustrina
Shrub
1,[2,3,4],5
FACW
YES
3
MAPLE,MOUNTAIN
Acer spicatum
Tree
4,5,6
FACU
NO
2
MAPLE,RED
Acer rubrum
Tree
[3,4],5
FAC
SEASONAL
3
MAPLE,SILVER
Acer saccharinum
Tree
[2,3],4
FACW
SEASONAL
3
MAPLE,STRIPED
Acer pensylvanicum
Shrub-Tree
3,[4,5,6]
FACU-,FACU
NO
3
MARSH ELDER
Iva frutescens
Shrub
1[2,3]
FACW+
MEADOW-SWEET,BROAD-LEAF
Spiraea latifolia
Shrub
[2,3,4]
FAC+,FACW
YES
2
MEADOW-SWEET,NARROW-LEAF
Spiraea alba
Shrub
[1,2,3,4],5
FACW,FACW+
YES
4
MEADOW-SWEET,VIRGINIA
Spiraea virginiana
Shrub
1,[2,3,4,5],
FACU,FACW
YES
5
MEADOW-SWEET,WILLOW-LEAF
Spiraea salicifolia
Shrub
1,[2,3]
FACW+
YES
4
NANNYBERRY
Viburnum lentago
Shrub
[3,4],5
FAC
SEASONAL
2
NINEBARK,EASTERN
Physocarpus opulifolius
Shrub
[2,3],4
FACW-
YES
2
OAK, PIN
Quercus palustris
Tree
[2,3],4
FACW
SEASONAL
4
OAK, SCARLET
Quercus coccinea
Tree
6
OAK,BUR
Quercus macrocarpa
Tree
3,[4,5],6
FAC-
YES
2
OAK,CHERRY-BARK
Quercus falcata var. pagodafolia
Tree
1,[2,3,4],5
FAC+,FACW
YES
5-6
OAK,CHESTNUT
Quercus prinus
Tree
4,5,6
FACU
NO
5,6
OAK,CHINKAPIN
5
NO
Quercus muhlenbergii
Tree
[3,4],5
FAC
YES
OAK,LAUREL
Quercus laurifolia
Tree
1,[2,3,4,5]
FACW-,FACW
YES
OAK,LIVE
Quercus virginiana
Tree
4,5,6
FACU
YES
7
OAK,OVERCUP
Quercus lyrata
Tree
[1,2],3
OBL
YES
5
Stormwater Plant List - Woody Vegetation
A.33
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
OAK,POST
Quercus stellata
Tree
OAK,RED
3,[4,5,6]
UPL,FACU
NO
TOLERANCE
POLLUTION
HARDINESS
SALT
5
Quercus rubra
Tree
6
OAK,SHINGLE
Quercus imbricaria
Tree
[3,4],5
FAC
YES
NO
5
OAK,SHUMARD
Quercus shumardii
Tree
2,[3,4]
FAC+
YES
5
OAK,SWAMP CHESTNUT
Quercus michauxii
Tree
1,[2,3,4,5]
FACW-,FACW
YES
OAK,SWAMP WHITE
Quercus bicolor
Tree
1,[2,3]
FACW+
SEASONAL
3
OAK,WATER
Quercus nigra
Tree
[3,4],5
FAC
SEASONAL
6
OAK,WHITE
Quercus alba
Tree
[4,5,6]
FACU
YES
4
OAK,WILLOW
Quercus phellos
Tree
2,[3,4]
FAC+
SEASONAL
5
PEPPER-BUSH,SWEET
Clethra alnifolia
Shrub
2,[3,4]
FAC+
SEASONAL
3
PINE,EASTERN WHITE
Pinus strobus
Tree
4,5,6
FACU
NO
3
PINE,JERSEY
Pinus viginiana
Tree
6
PINE,LOBLOLLY
Pinus taeda
Tree
3,[4,5],6
FAC-
SEASONAL
NO
PINE,PITCH
Pinus rigida
Tree
4,5,6
FACU
SEASONAL
PINE,POND
Pinus serotina
Tree
[1,2],3
OBL
YES
REDBUD,EASTERN
Cercis canadensis
Shrub-Tree
3,[4,5,6]
UPL,FACU
NO
4
RHODODENDRON
Rhododendron canadense
Shrub
1,[2,3,4],5
FACW
YES
2
RHODODENDRON,ROSEBAY
Rhododendron maximum
Shrub
[3,4],5
FAC
YES
3
ROSEMARY,BOG
Andromeda polifolia
Shrub
[1,2],3
OBL
YES
SAND-MYRTLE
Leiophyllum buxifolium
Shrub
3,4,[5,6]
FACU-
NO
SASSAFRAS
Sassafras albidum
Tree
3,[4,5,6]
FACU-,FACU
NO
SERVICE-BERRY,DOWNY
Amelanchier arborea
Shrub-Tree
2,[3,4,5],6
FAC-
YES
3,[4,5],6
FAC
YES
SHEEP-LAUREL
Kalmia angustifolia
Shrub
SILVER-BERRY,AMERICAN
Elaeagnus commutata
Shrub
[6]
UPL
NO
SNOWBELL,BIG-LEAF
Styrax grandifolia
Shrub
3,[4,5,6]
FACU-,FACU
NO
Stormwater Plant List - Woody Vegetation
A.34
4
4
2
5
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
TOLERANCE
POLLUTION
HARDINESS
SALT
SPICEBUSH,NORTHERN
Lindera benzoin
Shrub
[2,3],4
FACW-
SEASONAL
3-5
STAGGER-BUSH,PIEDMONT
Lyonia mariana
Shrub
2,[3,4,5,6]
FACU-,FAC
YES
5
STEEPLE-BUSH
Spiraea tomentosa
Shrub
1,[2,3,4],5
FACW
YES
4
STRAWBERRY-BUSH,AMERICAN
Euonymus americanus
Shrub
1,[2,3,4,5],
FACU,FACW
YES
5
SUGAR-BERRY
Celtis laevigata
Shrub
1,[2,3,4,5,6
UPL,FACW
YES
SWEETSHRUB
Calycanthus fertilis
Shrub
[3,4,5],6
FACU,FACU+
YES
SYCAMORE,AMERICAN
Platanus occidentalis
Tree
[2,3],4
FACW-
SATURATED
TEABERRY
Gaultheria procumbens
Shrub
3,[4,5],6
FACU
NO
3
TREE,TULIP
Liriodendron tulipifera
Tree
2,[3,4,5],6
FACU,FAC
YES
4
VIBURNUM,MAPLE-LEAF
Viburnum acerifolium
Shrub
3,[4,5,6]
UPL,FACU
NO
3
VIBURNUM,POSSUM-HAW
Viburnum nudum
Shrub
[1,2],3
OBL
YES
6
WILLOW,BLACK
Salix nigra
5
Tree
[2,3]
FACW+
SEASONAL
3
Salix cordata
Shrub
1,[2,3,4],5
FAC,FACW
YES
3
WILLOW,SILKY
Salix sericea
Shrub
[1,2],3
OBL
YES
3
WILLOW,TALL PRAIRIE
Salix humilis
Shrub
3,[4,5],6
FACU
NO
3
WILLOW,VIRGINIA
Itea virginica
Shrub
[1,2],3
OBL
0-6"
5
WINTERBERRY,COMMON
Ilex verticillata
Shrub
1,[2,3]
FACW+
SEASONAL
3
WITCH-ALDER,DWARF
Fothergilla gardenii
Shrub
1,[2,3,4],5
FACW
YES
WITCH-HAZEL, AMERICAN
Hamamelis virginiana
Shrub-Tree
3,[4,5],6
FAC-
NO
4
WITCH-HAZEL,AMERICAN
Hamamelis virginiana
Shrub-Tree
2,3,[4,5],6
FACU,FAC-
NO
4
WITHE-ROD
Viburnum cassinoides
Shrub
1,[2,3,4],5
FACW
YES
3
YAUPON
Ilex vomitoria
Shrub
3,[4,5],6
FAC-
YES
Taxus canadensis
Shrub
2,[3,4,5],6
FACU,FAC
YES
WILLOW,HEART-LEAF
YEW,AMERICAN
Stormwater Plant List - Woody Vegetation
A.35
2
Appendix A.4.2 Stormwater Plant List - Herbaceous Vegetation
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
ARROW-GRASS,MARSH
Triglochin palustre
Grass
[1,2],3
OBL
YES
ARROW-HEAD,BROAD-LEAF
Sagittaria latifolia
Perennial
[1,2],3
OBL
0-2'
ARROW-HEAD,COASTAL
Sagittaria falcata
Perennial
[1,2],3
OBL
YES
ARROW-HEAD,GRASS-LEAF
Sagittaria graminea
Perennial
[1,2],3
OBL
0-1'
ARROW-HEAD,NORTHERN
Sagittaria cuneata
Perennial
[1,2],3
OBL
YES
ARROW-HEAD,SHORT-BEAK
Sagittaria brevirostra
Perennial
[1,2],3
OBL
YES
ARROW-HEAD,WAPATO DUCK POTATO
Sagittaria latifolia
Perennial
[1,2],3
OBL
0-2'
ASTER,ANNUAL SALTMARSH
Aster subulatus
Annual
[1,2],4
OBL
YES
ASTER,BOG
Aster nemoralis
Perennial
[2,3],4
FACW+
YES
ASTER,BUSH
Aster dumosus
Perennial
[3,4],5
FAC
NO
ASTER,CALICO
Aster lateriflorus
Perennial
[2,3,4]
FACW-
SEASONAL
ASTER,CROOKED-STEM
Aster prenanthoides
Perennial
[3,4],5
FAC
NO
ASTER,FLAT-TOP WHITE
Aster umbellatus
Perennial
[2,3],4
FACW
YES
ASTER,NEW ENGLAND
Aster novae-angliae
Perennial
[2,3],4
FACW
YES
ASTER,NEW YORK
Aster novi-belgii
Perennial
[2,3],4
FACW+
YES
ASTER,ONTARIO
Aster ontarionis
Perennial
[3,4],5
FAC
NO
ASTER,PANICLED
Aster simplex
Perennial
[2,3],4
FACW
YES
ASTER,PERENNIAL SALTMARSH
Aster tenuifolius
Perennial
1,[2,3]
OBL
YES
ASTER,SMALL WHITE
Aster vimineus
Perennial
[3,4,5]
FAC
NO
ASTER,SWAMP
Aster puniceus
Perennial
1,[2,3]
OBL
YES
Stormwater Plant List - Herbaceous Vegetation
A.36
TOLERANCE
POLLUTION
HARDINESS
SALT
3-8
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
ASTER,TRADESCANT
Aster tradescanti
Perennial
[2,3],4
FACW
YES
ASTER,WHITE HEATH
Aster ericoides
Perennial
3,[4,5,6]
FACU
NO
ASTER,WILLOW-LEAF
Aster praealtus
Perennial
[2,3],4
FACW
YES
BABY-BLUE-EYES,SMALL-FLOWER
Nemophila aphylla
Annual
[2,3],4
FACW
YES
BEACHGRASS,AMERICAN
Ammophila breviligulata
Grass
4,[5,6]
FACU-
NO
BEAKRUSH,FASCICULATE
Rhynchospora fascicularis
Grass
[1,2],3
OBL
YES
BEAKRUSH,GRAY'S
Rhynchospora grayi
Grass
2,3,4,5,6
FAC
NO
BEAKRUSH,PINELAND
Rhynchospora perplexa
Grass
[2,3],4
FACW+
YES
BEAKRUSH,TALL
Rhynchospora macrostachya
Grass
[1,2],3
OBL
YES
BEARDTONGUE
Penstemon digitalis
Perennial
3,4,5
FAC
NO
BEARDTONGUE,LONG-SEPAL
Penstemon calycosus
Perennial
[4,5,6]
UPL,FACU
NO
BEARDTONGUE,LOWLAND
Penstemon alluviorum
Perennial
[2,3,4]
FACW
YES
BEEBALM
Monarda didyma
Perennial
3,4,5
FAC+
SATURATED
BENTGRASS,BROWN
Agrostis canina
Grass
[4,5,6]
FACU
NO
BENTGRASS,PERENNIAL
Agrostis perennans
Grass
[4,5],6
FACU
YES
BENTGRASS,SPREADING
Agrostis stolonifera
Grass
[2,3],4
FACW
YES
BENTGRASS,WINTER
Agrostis hyemalis
Grass
[3,4],5
FAC
NO
BERGAMOT,WILD
Monarda fistulosa
Perennial
[4,5,6]
UPL
NO
BLACK-EYED SUSAN
Rudbeckia hirta (yellow)
Perennial
4,5,6
FACU-
NO
BLADDERWORT,COMMON
Utricularia macrorhiza
Perennial
[1,2],3
OBL
YES
BLOODROOT
Sanguinaria canadensis
Perennial
4,[5,6]
UPL,FACU-
NO
BLUEBELLS,VIRGINIA
Mertensia virginica
Perennial
[2,3],4
FACW
YES
Stormwater Plant List - Herbaceous Vegetation
A.37
TOLERANCE
POLLUTION
HARDINESS
SALT
3-8
4-8
3-7
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
BLUE-EYE-GRASS
Sisyrinchium capillare
BLUEFLAG,SOUTHERN
TOLERANCE
POLLUTION
HARDINESS
SALT
Grass
[2,3]4
FACW+
YES
Iris shrevei
Perennial
1,[2],3
OBL
YES
BLUEFLAG,VIRGINIA
Iris virginica
Perennial
1,[2],3
OBL
YES
BLUEGRASS,BOG
Poa paludigena
Grass
[2,3],4
FACW+
YES
BLUEGRASS,GROVE
Poa alsodes
Grass
2,[3,4],5
FACW-
SEASONAL
BLUEGRASS,LOW
Poa alpigena
Grass
2,[3,4],5
FACW-
SEASONAL
BLUESTEM,BIG
Andropogon gerardii
Grass
[4,5],6
FAC
NO
BLUESTEM,BUSHY
Andropogon glomeratus
Grass
[2,3],4
FACW+
YES
BROOM-SEDGE
Andropogon virginicus
Grass
[4,5],6
FACU
NO
BULRUSH, HARDSTEMMED
Scirpus acutus
Perennial
[1,2],3
OBL
0-3'
8
BULRUSH, SOFTSTEM
Scirpus validus
Perennial
[1,2,],3
OBL
0-1'
8
BULRUSH,ALKALI
Scirpus robustus
Grass
1,[2],3
OBL
SALT, EDGE
BULRUSH,CLINTON'S
Scirpus clintonii
Grass
[4,5,6]
FACU
NO
BULRUSH,OLNEY'S
Scirpus americanus
Grass
[1,2],3
OBL
0-6"
BULRUSH,RIVER
Scirpus fluviatilis
Grass
[1,2],3
OBL
0-1'
BULRUSH,SPREADING
Scirpus divaricatus
Grass
[1,2],3
OBL
YES
BULRUSH,THREE-SQUARE
Scirpus pungens
Grass
[2,3],4
FACW+
0-6"
BURREED,AMERICAN
Sparganium americanum
Grass
[1,2],3
OBL
0-1'
BURREED,GIANT
Sparganium eurycarpum
Grass
[1,2],3
OBL
YES
BUSHCLOVER,NARROW-LEAF
Lespedeza angustifolia
Groundcover
4,5,6
FACU
NO
BUTTER-CUP,ALLEGHENY MOUNTAIN
Ranunculus allegheniensis
Perennial
[3,4],5
FAC
NO
BUTTER-CUP,POND
Ranunculus subrigidus
Perennial
[1,2],3
OBL
YES
Stormwater Plant List - Herbaceous Vegetation
A.38
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
TOLERANCE
POLLUTION
HARDINESS
SALT
BUTTER-CUP,SEASIDE
Ranunculus cymbalaria
Perennial
[1,2],3
OBL
YES
CAMPION, SNOWY
Silene nivea
Perennial
[3,4],5
FAC
NO
4-8
CARDINAL FLOWER
Lobelia cardinalis
Perennial
1,[2,3],4
FACW+
YES
2-8
CHICORY
Cichorium intybus
Perennial
5,6
UPL
NO
3-8
CLUB,GOLDEN
Orontium aquaticum
Perennial
[1,2],3
OBL
YES
COLTSFOOT,SWEET
Petasites palmatus
Perennial
1,[2,3],4
FACW+
YES
COLUMBINE,WILD
Aquilegia canadensis
Perennial
[3,4],5
FAC
NO
CONEFLOWER,CUT-LEAF
Rudbeckia laciniata
Perennial
[2,3],4
FACW
YES
CONEFLOWER,ORANGE
Rudbeckia fulgida
Perennial
[3,4],5
FAC
NO
CONEFLOWER,SWEET
Rudbeckia subtomentosa
Perennial
[3,4],5
FAC
NO
CORDGRASS,BIG
Spartina cynosuroides
Grass
[1,2],3
OBL
SALT, EDGE
CORDGRASS,PRAIRIE
Spartina pectinata
Grass
[1,2],3
OBL
SALT, EDGE
CORDGRASS,SALTMARSH
Spartina alterniflora
Grass
[1,2],3
OBL
SALT, EDGE
CORDGRASS,SALTMEADOW
Spartina patens
Grass
1,[2,3],4
FACW+
SALT, EDGE
CORNFLOWER
Centaurea cyanus
Perennial
5,6
UPL
NO
CUTGRASS,RICE
Leersia oryzoides
Grass
[1,2],3
OBL
0-6"
DAISY, OXEYE
Chrysanthemum levcanthemum
Perennial
5,6
UPL
NO
DRAGON-HEAD,FALSE
Physostegia virginiana
Perennial
2,[3,4],5
FAC+
SATURATED
DRAGON-HEAD,PURPLE
Physostegia purpurea
Perennial
[2,3],4
FACW
YES
DRAGON-HEAD,SLENDER
Physostegia intermedia
Perennial
[2,[3,4]
FACW-
SEASONAL
DRAGON-HEAD,SLENDER-LEAF
Physostegia leptophylla
Perennial
[1,2],3
OBL
YES
DROPSEED,SEASHORE
Sporobolus virginicus
Grass
1,[2,3],4
FACW+
YES
Stormwater Plant List - Herbaceous Vegetation
A.39
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
DUCKWEED
Lemna trinervis
Perennial
[1,2],3
OBL
Fre Float
DUCKWEED,LEAST
Lemna minima
Perennial
[1,2],3
OBL
Free Float
DUCKWEED,LESSER
Lemna minor
Perennial
[1,2],3
OBL
Free Float
DUCKWEED,MINUTE
Lemna perpusilla
Perennial
[1,2],3
OBL
Free Float
DUCKWEED,PALE
Lemna valdiviana
Perennial
[1,2],3
OBL
Free Float
DWARF PLAINS COREOPSIS
Coreopsis tinctoria (dwarf)
Annual
3,[4,5],6
FAC-
NO
EELGRASS
Zostera marina
Perennial
[1,2],3
OBL
2-6'
FALSE-HELLEBORE,AMERICAN
Veratrum viride
Perennial
[2,3,4]
FACW+
YES
FALSE-SOLOMON'S-SEAL,FEATHER
Smilacina racemosa
Perennial
[4,5],6
FACU-
NO
FERN,CINNAMON
Osmunda cinnamomea
Fern
[2,3],4
FACW
SATURATE
FERN,NEW YORK
Thelypteris noveboracensis
Fern
[3,4],5
FAC
SATURATE
FERN,ROYAL
Osmunda regalis
Fern
[1,2],3
OBL
SATURATE
FERN,SENSITIVE
Onoclea sensibilis
Fern
[2,3],4
FACW
SATURATE
FESCUE,MEADOW
Festuca pratensis
Grass
[3,4,5,6]
FACU-
NO
FESCUE,NODDING
Festuca obtusa
Grass
[4,5],6
FACU
NO
FESCUE,RED
Festuca rubra
Groundcover
[4,5]
FACU
NO
FLATSEDGE,MARSH
Cyperus pseudovegetus
Grass
[2,3],4
FACW
YES
FLATSEDGE,POORLAND
Cyperus compressus
Grass
[3,4],5
FAC+
SATURATE
FLATSEDGE,RUSTY
Cyperus odoratus
Grass
[2,3],4
FACW
YES
FLATSEDGE,SHORT-LEAF
Cyperus brevifolius
Grass
[1,2],3
OBL
YES
FLATSEDGE,SLENDER
Cyperus filicinus
Grass
2,[3,4,5,6]
UPL,FAC
YES
FLAX, VIRGINIA
Linum virginianum
Perennial
5,6
FACU
NO
Stormwater Plant List - Herbaceous Vegetation
A.40
TOLERANCE
POLLUTION
HARDINESS
SALT
3-8
1-8
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
FLOATING-HEART,YELLOW
Nymphoides peltata
Perennial
[1,2],3
OBL
YES
FORGET-ME-NOT,FIELD
Myosotis arvensis
Perennial
[3,4,5,6]
UPL
NO
FOUR-O'CLOCK,HEART-LEAF
Mirabilis nyctaginea
Perennial
[4,5,6]
FACU
NO
FOXTAIL,MEADOW
Alopecurus geniculatus
Grass
[1,2],3
OBL
YES
FOXTAIL,MEADOW
Alopecurus pratensis
Grass
[2,3],4
FACW
YES
FOXTAIL,MOUSE
Alopecurus myosuroides
Grass
[2,3],4
FACW
YES
FOXTAIL,SHORT-AWN
Alopecurus aequalis
Grass
[1,2],3
OBL
YES
FOXTAIL,TUFTED
Alopecurus carolinianus
Grass
[2,3],4
FACW
YES
GLASSWORT,VIRGINIA
Salicornia virginica
Perennial
[1,2],3
OBL
SALT,EDGE
GOLDEN-ROD
Solidago austrina
Perennial
[1,2],3
OBL
YES
GOLDEN-ROD,COAST
Solidago spathulata
Perennial
4,[5,6]
FACU-
NO
GOLDEN-ROD,SEASIDE
Solidago sempervirens
Perennial
[2,3],4
FACW
YES
GOLDEN-ROD,STIFF
Solidago rigida
Perennial
1,2,3
OBL
NO
GRASS,BROOM PANIC
Dichanthelium scoparium
Grass
[2,3],4
FACW
YES
GRASS,CANADA MANNA
Glyceria canadensis
Grass
[1,2],3
OBL
0-1'
GRASS,EASTERN MANNA
Glyceria septentrionalis
Grass
[1,2],3
OBL
0-1'
GRASS,FOWL MANNA
Glyceria striata
Grass
[1,2],3
OBL
SEASONAL
GRASS,PANIC
Dichanthelium acuminatum
Grass
[2,3],4
FAC
NO
GRASS,PANIC
Panicum longifolium
Grass
[1,2],3
OBL
YES
GRASS,ROUGH BARNYARD
Echinochloa muricata
Grass
[2,3],4
FACW+
YES
GRASS,SALTMARSH ALKALI
Puccinellia fasciculata
Grass
[1,2],3
OBL
YES
GRASS,SALTMEADOW
Spartina caespitosa
Grass
[1,2],3
OBL
YES
Stormwater Plant List - Herbaceous Vegetation
A.41
TOLERANCE
POLLUTION
HARDINESS
SALT
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
HORNWORT,COMMON
Ceratophyllum demersum
HORSETAIL,ROUGH
Equisetum hyemale
INDIAN-TOBACCO
Perennial
[1,2],3
OBL
1-5'
Grass
[2,3],4
FACW
YES
Lobelia inflata
Perennial
[4,5,6]
FACU
NO
IRIS, BLUE WATER
Iris versicolor
Perennial
[1,2],3
OBL
0-6"
IRIS,BEACH-HEAD
Iris hookeri
Perennial
4,[5,6]
FACU-
NO
IRIS,BEACH-HEAD
Iris setosa
Perennial
[3,4],5
FAC
NO
IRIS,COPPER
Iris fulva
Perennial
[1,2],3
OBL
YES
IRIS,LAMANCE
Iris brevicaulis
Perennial
[1,2],3
OBL
YES
JACK-IN-THE-PULPIT,SWAMP
Arisaema triphyllum
Perennial
[2,3],4
FACW
SEASONAL
JACOB'S LADDER
Polemonium reptans
Perennial
[4,5],6
FACU
NO
JACOB'S-LADDER,BOG
Polemonium van-bruntiae
Perennial
[3,4],5
FAC+
SATURATED
LILY,CANADA
Lilium canadense
Perennial
2,[3,4]
FAC+
YES
LILY,CAROLINA
Lilium michauxii
Perennial
[3,4,5]
FAC
NO
LILY,GRAY'S
Lilium grayi
Perennial
3,[4,5],6
FACU
NO
LILY,SOUTHERN RED
Lilium catesbaei
Perennial
[2,3,4]
FACW
YES
LILY,TURK'S-CAP
Lilium superbum
Perennial
[2,3,4]
FACW+
YES
LIZARDS TAIL
Saururus cemuus
Perennial
2,3,4
OBL
0-1'
LOBELIA,BOYKIN'S
Lobelia boykinii
Perennial
[1,2],3
OBL
YES
LOBELIA,BROOK
Lobelia kalmii
Perennial
[1,2],3
OBL
YES
LOBELIA,DOWNY
Lobelia puberula
Perennial
[2,3,4]
FACW-
SEASONAL
LOBELIA,ELONGATED
Lobelia elongata
Perennial
[1,2],3
OBL
YES
LOBELIA,GEORGIA
Lobelia georgiana
Perennial
[2,3,4]
FACW
YES
Stormwater Plant List - Herbaceous Vegetation
A.42
TOLERANCE
POLLUTION
HARDINESS
SALT
2-7
3-8
2-8
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
TOLERANCE
POLLUTION
HARDINESS
SALT
LOBELIA,GREAT BLUE
Lobelia siphilitica
Perennial
[2,3],4
FACW+
YES
LOBELIA,NUTTALL'S
Lobelia nuttallii
Perennial
[2,3,4]
FACW
YES
LOBELIA,PALE-SPIKE
Lobelia spicata
Perennial
[3,4,5]
FAC-
NO
LOBELIA,SOUTHERN
Lobelia amoena
Perennial
[1,2],3
OBL
YES
LOBELIA,WATER
Lobelia dortmanna
Perennial
[1,2],3
OBL
YES
LOTUS,AMERICAN
Nelumbo lutea
Perennial
[1,2],3
OBL
1-5'
LOTUS,SACRED
Nelumbo nucifera
Perennial
[1,2],3
OBL
1-5'
LOVEGRASS,MEADOW
Eragrostis refracta
Grass
[2,3,]4
FACW
YES
LOVEGRASS,PURPLE
Eragrostis pectinacea
Grass
[4,5],6
FAC
NO
MALLOW,VIRGINIA SEASHORE
Kosteletzkya virginica
Perennial
[1,2],3
OBL
SALT, EDGE
MARSH MARIGOLD
Caltha palustris
Perennial
3,4
OBL
6"SATURATE
3-8
MARSH SMARTWEED
Polygonum hydropiperoides
Perennial
2,3
OBL
0-1'
2-8
MARSH SMARTWEED
Polygonum puntatum
Perennial
2,3
OBL
SATURATE
2-8
MARSH-MALLOW,COMMON
Althaea officinalis
Perennial
[1,2,3]
FACW+
YES
MEADOW-RUE,PIEDMONT
Thalictrum macrostylum
Perennial
[2,3,4]
FACW
YES
MILKWORT,MARYLAND
Polygala mariana
Annual
[2,3,4]
FACW
YES
MONKEY-FLOWER
Mimulus ringens
Perennial
[1,2],3
OBL
YES
MONKEY-FLOWER,COMMON LARGE
Mimulus guttatus
Annual
[1,2],3
OBL
YES
MOUNTAIN-MINT,NARROW-LEAF
Pycnanthemum flexuosum
Perennial
[2,3,4]
FACW
YES
MUHLY,MARSH
Muhlenbergia glomerata
Grass
[2,3],4
FACW
YES
NIMBLE-WILL
Muhlenbergia schreberi
Grass
[3,4,5]
FAC
NO
NUTRUSH
Scleria flaccida
Grass
[2,3],4
FACW
YES
Stormwater Plant List - Herbaceous Vegetation
A.43
3-8
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
PANSY,FIELD
Viola bicolor
PARTRIDGE-BERRY
Mitchella repens
PENNSYLVANIA SMARTWEED
Polygonum pensylvanicum
PENNY-WORT,MANY-FLOWER
Annual
[4,5,6]
FACU
NO
Groundcover
[4,5],6
FACU
NO
Annual
[2,3]
FACW
0-6"
Hydrocotyle umbellata
Perennial
[1,2],3
OBL
0-1'
PHLOX,FALL
Phlox paniculata
Perennial
[4,5],6
FACU
NO
PHLOX,MEADOW
Phlox maculata
Perennial
[2,3,4]
FACW
YES
PHLOX,WOODLAND
Phlox divaricata
Perennial
[4,5,6]
FACU
NO
PICKERELWEED
Pontederia cordata
Perennial
2,3
OBL
0-1'
PLANTAIN,SEASIDE
Plantago maritima
Perennial
1,2,3,4
FACW
YES
PLUMEGRASS,SUGARCANE
Erianthus giganteus
Grass
[2,3]
FACW+
YES
PONDWEED,CLASPING-LEAF
Potamogeton perfoliatus
Perennial
[1,2],3
OBL
1' MIN-6'
PONDWEED,LONG-LEAF
Potamogeton nodosus
Perennial
[1,2]
OBL
1' MIN-6'
PONDWEED,SAGO
Potamogeton pectinatus
Perennial
[1,2]
OBL
1' MIN-24'
PRIMROSE,BIRDSEYE
Primula laurentiana
Perennial
[4],5
FAC
NO
REED, MEADOWGRASS
Glyceria maxima
Grass
[1,2],3
OBL
YES
REEDGRASS,BLUE-JOINT
Calamagrostis canadensis
Grass
[1,2],3
FACW+
6"SATURATE
ROCKCRESS,ALPINE
Arabis alpina
Perennial
[3,4,5]
FAC+
SATURATE
ROSE-GENTIAN,NARROW-LEAF
Sabatia brachiata
Annual
[4,5,6]
FACU
NO
RUSH,ARCTIC
Juncus arcticus
Grass
[1,2],3
OBL
YES
RUSH,GRASS-LEAF
Juncus marginatus
Grass
[2,3],4
FACW
YES
RUSH,NARROW-PANICLE
Juncus brevicaudatus
Grass
[1,2],3
OBL
YES
RUSH,NEEDLEGRASS
Juncus roemeranus
Grass
[1,2],3
OBL
SALT, EDGE
Stormwater Plant List - Herbaceous Vegetation
A.44
TOLERANCE
POLLUTION
HARDINESS
SALT
2-8
2-8
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
TOLERANCE
POLLUTION
HARDINESS
SALT
RUSH,SALTMEADOW
Juncus gerardii
Grass
[2,3],4
FACW+
YES
RUSH,SLIM-POD
Juncus diffusissimus
Grass
[2,3],4
FACW
YES
RUSH,SOFT
Juncus effusus
Grass
[2,3],4
FACW+
0-1'
RUSH,TURNFLOWER
Juncus biflorus
Grass
[2,3],4
FACW
YES
RYEGRASS,PERENNIAL
Lolium perenne
Groundcover
[4,5,6]
FACU-
NO
SALTGRASS,SEASHORE
Distichlis spicata
Grass
[2,3,]4
FACW+
SALT, EDGE
SAWGRASS,SMOOTH
Cladium mariscoides
Grass
[1,2],3
OBL
YES
SAXIFRAGE,SWAMP
Saxifraga pensylvanica
Perennial
[1,2],3
OBL
YES
SAXIFRAGE,VIRGINIA
Saxifraga virginiensis
Perennial
[4,5]
FAC-
NO
SEA-LAVENDER,CAROLINA
Limonium carolinianum
Perennial
[1,2],3
OBL
YES
SEA-LAVENDER,NORTHERN
Limonium nashii
Perennial
[1,2],3
OBL
YES
SEA-OATS
Uniola paniculata
Grass
[4,5,6]
FACU-
NO
SEDGE,BEARDED
Carex comosa
Grass
[1,2],3
OBL
6"SATURATE
SEDGE,BENT
Carex styloflexa
Grass
2,[3,4]
FACW-
YES
7-8
SEDGE,CAT-TAIL
Carex typhina
Grass
[2,3],4
FACW+
YES
5-8
SEDGE,CRESTED
Carex cristatella
Grass
[1,2],3,4
FACW
YES
SEDGE,FESCUE
Carex festucacea
Grass
[3,4,5]
FAC
NO
SEDGE,FOX
Carex vulpinoidea
Grass
[1,2],3
OBL
SAT. 0-6"
SEDGE,FRINGED
Carex crinita
Grass
[1,2],3
OBL
YES
SEDGE,GRACEFUL
Carex gracillima
Grass
[4,5],6
FACU
NO
SEDGE,HOARY
Carex canescens
Grass
[1,2],3
OBL
YES
SEDGE,INLAND
Carex interior
Grass
1,[2,3]
OBL
YES
Stormwater Plant List - Herbaceous Vegetation
A.45
4-8
4-6
7
5-8
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
TOLERANCE
POLLUTION
HARDINESS
SALT
SEDGE,LAKEBANK
Carex lacustris
Grass
[1,2],3
OBL
SAT. 0-2'
SEDGE,LOOSE-FLOWERED
Carex laxiflora
Grass
[4,5,6]
FACU
NO
SEDGE,RETRORSE
Carex retrorsa
Grass
[2,3],4
FACW+
SAT. 0-6"
SEDGE,SHALLOW
Carex lurida
Grass
[1,2],3
OBL
YES
5-8
SEDGE,SWAN'S
Carex swanii
Grass
[4,5,6]
FACU
NO
5-8
SEDGE,UPTIGHT
Carex stricta
Grass
[1,2],3
OBL
SAT.0-6"
SEDGE,WOOLY
Carex lanuginosa
Grass
[1,2],3
OBL
SAT.0-6"
SEDGE,YELLOW-FRUIT
Carex annectens
Grass
[2,3,]4
FACW+
YES
SEEDBOX
Ludwigia x lacustris
Annual
[1,2],3
OBL
YES
SENNA,MARYLAND
Cassia marilandica
Groundcover
3,[4,5]
FAC+
SATURATED
SKULLCAP
Scutellaria churchilliana
Perennial
[2,3],4
FACW
YES
SOLOMON'S-SEAL,GREAT
Polygonatum commutatum
Perennial
[4,5,6]
FACU
NO
SOLOMON'S-SEAL,SMALL
Polygonatum biflorum
Perennial
[4,5,6]
FACU
NO
SPIKERUSH,BLUNT
Eleocharis obtusa
Grass
[1,2],3
OBL
0-6"
SPIKERUSH,CREEPING
Eleocharis palustris
Grass
[1,2],3
OBL
SEASONAL
SPIKERUSH,ENGELMANN'S
Eleocharis engelmannii
Grass
[2,3],4
FACW+
YES
SPIKERUSH,SQUARE-STEM
Eleocharis quadrangulata
Grass
[1,2],3
OBL
0-1'
SPRING BLUE EYE, MARY
Collinsia verna
Perennial
4,5,6
FAC-
NO
ST. JOHN'S-WORT,MARSH
Triadenum fraseri
Perennial
[1,2],3
OBL
YES
STARWORT,MARSH
Stellaria palustris
Perennial
[5],6
FACU
NO
STONECROP,ROCK
Sedum pulchellum
Perennial
[4,5,6]
FACU
NO
STONECROP,ROSEROOT
Sedum rosea
Perennial
3,4,5,6
FACU
NO
Stormwater Plant List - Herbaceous Vegetation
A.46
5-8
1-8
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
TOLERANCE
POLLUTION
HARDINESS
SALT
SWAMP MILKWEED
Asclepias incarnata
Perennial
2,3
OBL
SATURATED
3-8
SWAMP ROSE MALLOW
Hibiscus moscheutos
Perennial
2,3
OBL
0-3"
4-8
SWAMP SMARTWEED
Polygonum coccineum
Perennial
2,3,4
OBL
0-3'
2-8
SWAMP-LOOSESTRIFE,HAIRY
Decodon verticillatus
Perennial
[1,2],3
OBL
YES
SWITCHGRASS
Panicum virgatum
Grass
2,[3,4],5
FAC
SEASONAL
TREFOIL, BIRD'S-FOOT
Lotus corniculatus
Perennial
4,5,6
FACU-
NO
TURTLEHEAD,RED
Chelone obliqua
Perennial
[1,2],3
OBL
YES
TURTLEHEAD,WHITE
Chelone glabra
Perennial
[1,2],3
OBL
YES
VALERIAN,EDIBLE
Valeriana edulis
Perennial
[1,2],3
OBL
YES
VERVAIN,BLUE
Verbena hastata
Perennial
2,3,4
FACW+
YES
VIOLET,APPALACHIAN BLUE
Viola appalachiensis
Perennial
[4,5],6
FACU
NO
VIOLET,COASTAL
Viola brittoniana
Perennial
[3,4],5
FAC
NO
VIOLET,COMMON BLUE
Viola papilionacea
Perennial
[3,4,5]
FAC
NO
VIRGINIA WILD RYE
Elymus virginicus
Grass
2,[3,4]
FACW-
YES
WATER SMARTWEED
Polygonum amphibium
Perennial
2,3
OBL
6"-Sat
WATER-CRESS,TRUE
Nasturtium officinale
Annual
[1,2],3
OBL
2"-1'
WATER-LILY,PYGMY
Nymphaea tetragona
Perennial
[1,2],3
OBL
1-3'
WATER-LILY,WHITE
Nymphaea odorata
Perennial
[1,2],3
OBL
1-3'
WATER-LILY,WHITE
Nymphaea tuberosa
Perennial
[1,2],3
OBL
1-3'
WATER-LILY,YELLOW/ SPATTERDOCK
Nuphar advena/luteum
Perennial
[1,2],3
OBL
1-3'
WHORLED COREOPSIS
Coreopsis verticillata
Perennial
[2,3],4
FACW
YES
WIDGEON-GRASS
Ruppia maritima
Grass
[1,2],3
OBL
1' MIN
Stormwater Plant List - Herbaceous Vegetation
A.47
2-8
2-8
3-8
COMMON
SCIENTIFIC
FORM
ZONE
INDICATOR
INUNDATION
WILD-LILY-OF-THE-VALLEY
Maianthemum canadense
WITCHGRASS,HELLER'S
Perennial
[4,5],6
FAC-
NO
Dichanthelium oligosanthes
Grass
[4,5,6]
FACU
NO
WITCHGRASS,NEEDLE-LEAF
Dichanthelium aciculare
Grass
[4,5,6]
FACU
NO
WOOD-REEDGRASS,SLENDER
Cinna latifolia
Grass
[2,3,4]
FACW
YES
WOODRUSH,COMMON
Luzula multiflora
Grass
[4,5,6]
FACU
NO
WOOL-GRASS
Scirpus cyperinus
Grass
[2,3],4
FACW+
SEASONAL
Stormwater Plant List - Herbaceous Vegetation
A.48
TOLERANCE
POLLUTION
HARDINESS
SALT
Appendix A. Landscaping Guidance for Stormwater BMPs...........................................References
Section A.5
References
The following is a list of resources used in compiling these guidelines and the list of plant materials:
Art, Henry W. 1986. A Garden of Wildflowers, 101 Native Species and How to Grow Them.
Storey Communications, Inc. Pownal, VT.
Brown, Melvin L. and Brown, Russell G. 1984. Herbaceous Plants of Maryland. Port City Press.
Baltimore, MD.
Brown, Melvin L. and Brown, Russell G. 1992. Woody Plants of Maryland. Port City Press.
Baltimore, MD.
Clausen, Ruth Rogers and Ekstrom, Nicolas, H. 1989. Perennials for American Gardens. Random
House. New York, NY.
Dirr, Michael A. 1990. Manual of Woody Landscape Plants, Their Identification, Ornamental
Characteristics, Culture, Propagation, and Uses. 4th Edition. Stipes Publishing Company.
Champaign, IL.
Engineering Technology Associates Inc. and Biohabitats, Inc. (ETA&B). 1993. Design Manual for
Use of Bioretention in Stormwater Management. Prince Georges County Dept. of Environmental
Resources. Upper Marlboro, MD.
Greenlee, John. 1992. The Encyclopedia of Ornamental Grasses, How to Grow and Use Over 250
Beautiful and Versatile Plants. Rodale Press. Emmas, PA.
Hill, Steven R. and Duke, Peggy K. 1985-86. 100 Poisonous Plants of Maryland. Bulletin No. 314.
University of Maryland Cooperative Extension Services. Ellicott City, MD.
Longenecker, G. 1983. Woody Plant List for West Virginia. Landscape Architecture Department,
Division of Resource Management, West Virginia University. Morgantown, WV.
Maryland Department of the Environment. 1994. Water Management Administration and Maryland
Soil Conservation Service. 1994 Maryland Standards and Specifications for Soil Erosion and
Sediment Control. Baltimore, MD.
Maryland Natural Heritage Program, Department of Natural Resources. 1994. Invasive and Exotic
Plants of Wetlands and Floodplains in Maryland. Maryland Natural Heritage Program, Department
of Natural Resources, Tawes State Office Building. Annapolis, MD.
A.49
Appendix A. Landscaping Guidance for Stormwater BMPs...........................................References
Maryland Natural Heritage Program, Department of Natural Resources. 1994. Rare Species of
Submerged Aquatic Vegetation in Maryland. Maryland Natural Heritage Program, Department of
Natural Resources, Tawes State Office Building. Annapolis, MD.
Miles, B. 1996. Wildflower Perennials for Your Garden, A Detailed Guide to Years of Bloom from
America's Native Heritage. Stackpole Books. Mechanicsburg, PA.
Newcomb, L. 1977. Newcomb's Wildflower Guide. Little Brown and Company. Boston, MA.
Reed, Porter B. Jr. 1998. National List of Plant Species that Occur in Wetlands: Northeast (Region
1), For National Wetlands Inventory. U.S. Fish and Wildlife Service, U.S. Department of the
Interior, Washington, D.C.
Schueler, Thomas R. 1987. Controlling Urban Runoff: A Practical Manual for Planning and
Designing Urban BMP's. Department of Environmental Programs Metropolitan Washington
Council of Governments, Metropolitan Information Center. Washington, D.C.
Schueler, Thomas R. 1996. Design of Stormwater Wetland Systems: Guidelines for Creating
Diverse and Effective Stormwater Wetland Systems in the Mid-Atlantic Region. Department of
Environmental Programs Metropolitan Washington Council of Governments, Metropolitan
Information Center. Washington, D.C.
Schueler, Thomas R. and Claytor, Richard A. 1997. Design of Stormwater Filtering Systems:
Appendix B and C. Chesapeake Bay Consortium. Silver Spring, MD.
The Pennsylvania State University, College of Agriculture, Cooperative Extension Service. Weed
Identification. File No. IVC9 10M386, U. Ed. 85-439 and File No. IVC9 10M587 U.Ed. 86-356.
The Pennsylvania State University, College of Agriculture, Cooperative Extension Service.
University Park, PA.
Thunhorst, Gwendolyn A. 1993. Wetland Planting Guide for the Northeastern United States: Plants
for Wetland Creation, Restoration, and Enhancement, Environmental Concern, Inc. St. Michael,
MD.
Tiner, Ralph W. Jr. 1988. Field Guide to Non-Tidal Wetland Identification. U.S. Fish and Wildlife
Service and Maryland Department of Natural Resources and Maryland Geological Survey.
Annapolis, MD.
A.50
NRCS-MD Code No. 378 Pond Standards/Specifications
Appendix
B.1
Pond MD-378-1
USDA
NATURAL RESOURCES
CONSERVATION SERVICE
MARYLAND
CONSERVATION PRACTICE
STANDARD
POND
CODE 378
(Reported in No.)
DEFINITION
A water impoundment made by constructing a
dam or an embankment or by excavating a pit or
dugout.
In this standard, ponds constructed by the first
method are referred to as embankment ponds,
and those constructed by the second method are
referred to as excavated ponds. Ponds constructed by both excavation and the embankment
methods are classified as embankment ponds if
the depth of water impounded against the embankment at the principal spillway storm design
high water elevation is 3 feet or more (See Table
1).
This 3 feet shall be measured from the low point
on the upstream toe of the embankment to the
design high water.
PURPOSE
To provide water for livestock, fish and wildlife,
recreation, fire control, crop and orchard spraying, and other related uses, and to maintain or
improve water quality. This standard also applies to stormwater management ponds.
CONDITIONS WHERE PRACTICE
APPLIES
General - This practice applies where it is determined that stormwater management, water
supply, or temporary storage is justified and it is
feasible and practicable to build a pond which
will meet local and state law requirements.
This standard establishes the minimum acceptable quality for the design and construction of
ponds if:
1. Failure of the dam will not result in loss of
life; in damage to homes, commercial or industrial buildings, main highways, or railroads; or interruption of the use or service of
public utilities.
2. The product of the storage times the effective
height of the dam is less than 3,000. Storage
is the volume, in acre-feet, in the reservoir
below the elevation of the crest of the emergency spillway.
The effective height of the dam is the difference in elevation, in feet, between the emergency spillway crest and the lowest point on
a profile taken along the centerline of the
dam, excluding the cutoff trench. If there is
no emergency spillway, the top of the dam
becomes the upper limit for determining the
storage and the effective height.
3. For dams in rural areas, the effective height
of the dam (as defined above) is 35 feet or
less and the dam is hazard class ”a”. For
dams in urban areas, the effective height of
the dam is 20 feet or less and the dam is hazard class ”a”.
Ponds exceeding any of the above conditions
shall be designed and constructed according to
the requirements of Technical Release 60.
Exemptions - Soil Conservation District small
pond approval is not required for small class “a”
structures where the following exists:
1. Ponds or other structures have less than four
(4) feet of embankment, or
2. The storage at emergency spillway design
high water elevation according to Table 1
does not exceed 40,000 cubic feet, and the
Conservation practice standards are reviewed periodically, and updated if needed. To obtain the current version of this standard,
contact the Natural Resources Conservation Service
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-2
height of the embankment is 6 feet or less.
The height of the embankment shall be measured
from the top of the dam to the lowest point of
excavation, excluding the cutoff trench, along
the centerline of the dam.
In addition, an embankment pond that meets the
criteria below shall be considered an excavated
pond and is also exempt from small pond approval.
Soils Investigation - A soils investigation is required on all ponds. As a minimum it shall include information along the centerline of the proposed dam, in the emergency spillway location,
and the planned borrow area. The type of
equipment used and the extent of the investigation will vary from site to site. All investigations
shall be logged using the Unified Soil Classification System.
1. The calculation of 10H+20=L, where
H=height from the pond bottom to the top of
the dam, is provided, and
Road Embankments - Where road embankments
are being designed to impound a specific volume
of water, either as a permanent pool or temporary stormwater storage, special design and
evaluation criteria may be required as determined by Appendix B.
2. The projection of L horizontally downstream
from the pond bottom is below the existing
or proposed ground, and
CONSIDERATIONS
3. The existing or proposed downstream ground
slope within the projection of L is less than
10% at any point.
The review and design of such class “a” structures shall be based on sound engineering judgment assuring a stable outfall for the ten (10)
year, 24-hour storm event.
Site Conditions - Site Conditions shall be such
that runoff from the design storm can be safely
passed through (1) a natural or constructed emergency spillway, (2) a combination of a principal
spillway and an emergency spillway, or (3) a
principal spillway.
Drainage Area - The drainage area above the
pond must be protected against erosion to the
extent that expected sedimentation will not
shorten the planned effective life of the structure.
For ponds whose primary purpose is to trap
sediment for water quality, adequate storage
should be provided to trap the projected sediment delivery from the drainage area for the life
of the pond.
If the intent is to maintain a permanent pool, the
drainage area should be at least 4 acres for each
acre-foot of permanent storage. These recommendations may be reduced if a dependable
source of ground water or diverted surface water
contributes to the pond. The water quality shall
be suitable for its intended use.
NRCS - MARYLAND
Water Quantity - The following items should be
considered for water quantity:
1. Effects upon components of the water
budget, especially effects on volumes and
rates of runoff, infiltration, evaporation, transpiration, deep percolation, and ground water
recharge.
2. Variability of effects caused by seasonal or
climatic changes.
3. Effects on the downstream flows or aquifers
that could affect other water uses or users.
4. Potential for multiple use.
5. Effects on the volume of downstream flow to
prohibit undesirable environmental, social or
economic effects.
Water Quality - The following items should be
considered for water quality:
1. Effects on erosion and the movement of
sediment, pathogens, and soluble and sediment attached substances that are carried by
runoff.
2. Effects on the visual quality of on-site and
downstream water resources.
3. Short-term and construction-related effects of
this practice on the quality of downstream
water courses.
JANUARY 2000
Pond MD-378-3
4. Effects of water level control on the temperatures of downstream waters to prevent undesired effects on aquatic and wildlife communities.
5. Effects on wetlands and water-related wildlife habitats.
6. Effects of water levels on soil nutrient processes such as plant nitrogen use or denitrification.
7. Effects of soil water level control on the soil
chemistry, soil water, or downstream water.
8. Potential for earth moving to uncover or redistribute sulfidic bearing soils.
CRITERIA
Embankment Ponds
Structure Hazard Classification - Documentation of the classification of dams is required.
Documentation is to include but is not limited to
location and description of dam, configuration of
the valley, description of existing development
(houses, utilities, highways, railroads, farm or
commercial buildings, and other pertinent improvements), potential for future development,
and recommended classification. It is also to
include results obtained from breach routings, if
breach routings are used as part of the classification process. The class (“a”, “b”, and “c”) as
contained in this document is related to the potential hazard to life and property that might result from a sudden major breach of the earth embankment. Structure classification and land use
for runoff determination must take into consideration the anticipated changes in land use
throughout the expected life of the structure.
The classification of a dam is the responsibility
of the designer, and subject to review and concurrence of the approving authority.
The classification of a dam is determined only by
the potential hazard from failure, not by the criteria. Classification factors in the National Engineering Manual, as supplemented, are given
below:
age non-inhabited buildings, agricultural
land, floodplains or county roads.
Class “b” - Structures located in rural, agricultural, or urban areas where failure may
damage isolated homes, main highways or
minor railroads or cause interruption of use
or service of relatively important public utilities.
Class “c” - Structures located where failure
may cause loss of life or serious damage to
homes, industrial and commercial buildings,
important public utilities, main highways, or
railroads.
“Rural areas” is defined as those areas in which
residents live on farms, in unincorporated settlements, or in incorporated villages or small
towns. It is where agriculture, including woodland activities, and extractive industries, including seafood harvesting, provides the primary
employment base for residents and where such
enterprises are dependent on local residents for
labor.
Non-rural areas shall be classified as urban.
Peak Breach Discharge Criteria - Breach routings are used to help delineate the area potentially impacted by inundation should a dam fail
and can be used to aid dam classification. The
breach hydrograph is the outflow hydrograph
attributed to the sudden release of water in reservoir storage. This is due to a dam breach during
non-storm conditions.
Stream routings made of the breach hydrograph
are to be based upon topographic data and hydraulic methodologies mutually consistent in
their accuracy and commensurate with the risk
being evaluated.
The minimum peak discharge of the breach hydrograph, regardless of the techniques used to
analyze the downstream inundation area, is as
follows:
Qmax = 3.2 Hw2.5 where,
Qmax = the peak breach discharge, cfs.
Class “a” - Structures located in rural, agricultural or urban areas dedicated to remain in
flood tolerant usage where failure may damNRCS - MARYLAND
Hw = depth of water at the dam at the time of
failure, feet. This is measured to
JANUARY 2000
Pond MD-378-4
the crest of the emergency spillway or to design high water, if no
emergency spillway exists. Use
“nonstorm” conditions downstream of the dam.
for infrequent vehicle crossings, the minimum
top width shall be 10 feet. Guardrails or other
safety measures are to be used where necessary
and are to meet the requirements of the responsible road authority.
Where breach analysis has indicated that only
overtopping of downstream roads will occur, the
following guidelines will be used:
Side Slopes - The combined upstream and downstream side slopes of the settled embankment
shall not be less than five horizontal to one vertical (5:1) with neither slope steeper than 2:1. If
the dam is used as a road crossing with a top
width greater than 26 feet, then the combined
side slopes of the settled embankment shall not
be less than 4 horizontal to one vertical (4:1)
with neither slope steeper than 2:1. Slopes must
be designed to be stable in all cases, even if flatter side slopes are required.
Class
“a”
“b” & “c”
Depth of Flow
(d) ft.
d<1.5
d>1.5
Use and importance of the roadway shall be considered when making a classification.
Hydrology - Principal and emergency spillways
will be designed within the limitations shown on
TABLE 1. The storm duration used shall be 24
hours except where TR-60 is specified. The
pond shall be designed to safely pass the base
flow along with volume and peak rates of runoff
from design storms, specified in Table 1. All
storm water management ponds shall be designed using urban criteria. This can be done by
using principal and emergency spillways. The
following shall be used to determine runoff rates
and volumes:
1. NRCS “Engineering Field Handbook, Part
650” or;
2. NRCS, NEH, Section 4, Hydrology” or;
3. NRCS, TR-55, “Urban Hydrology for Small
Watersheds” or;
4. NRCS, TR-20, “Computer Program for Project Formulation” or,
5. Computer programs using NRCS hydrology
methods with identifiable inputs and outputs
as approved by the reviewing agency.
Earth Embankment
Top Width - The minimum top width of the dam
is shown in Table 2. When the embankment top
is to be used as a public road, the minimum
width is to be 16 feet for one-way and 26 feet for
two-way traffic. If the embankment is to be used
NRCS - MARYLAND
Earth Cuts - If cuts in an existing fill or in natural ground are required for the rehabilitation of
an existing pond spillway or the construction of
a new pond, the slope of the bonding surfaces
between the existing material in place and the fill
to be placed shall not be steeper than a ratio of
two horizontal to one vertical (2:1).
Foundation Cutoff - A cutoff trench of relatively impervious material shall be provided under the entire length of the dam and shall be located at or upstream from the centerline of the
dam. The cutoff trench shall have a bottom
width adequate to accommodate the equipment
used for excavation, backfill and compaction operations, with the minimum width being 4 feet,
and shall have side slopes no steeper than one
horizontal to one vertical. Minimum depth shall
be 4 feet.
Impervious Core - Any impervious core within
the embankment shall be located at or upstream
from the centerline of the dam, and shall extend
up the abutments to the 10-year water surface
elevation. The impervious core shall extend vertically from the cutoff trench up to the 10-year
water surface elevation throughout the embankment.
Seepage Control - Seepage control is to be included: (1) if pervious layers are not intercepted
by the cutoff; (2) if seepage from the abutments
may create a wet embankment; (3) if the phreatic
line intersects the downstream slope; or (4) if
special conditions require drainage to insure a
stable dam. The phreatic line shall be drawn on
JANUARY 2000
Pond MD-378-5
a 4:1 slope starting on the inside slope at the
normal pool elevation. For stormwater management ponds, normal pool shall be considered as
the 10-year water surface elevation.
Seepage may be controlled by (1) foundation
abutment or embankment drains; (2) reservoir
blanketing; or (3) a combination of these measures. Foundation drains may control seepage
encountered in the cutoff trench during construction. These drains must be located downstream
of the dam centerline and outside the limits of
the proposed cutoff trench. All drains must be
designed according to the section Principal Spillway, Conduit Piping and Seepage Control.
Wave Erosion Protection - Where needed to
protect the face of the dam, special wave protection measures such as a bench, rock riprap, sandgravel, soil cement or special vegetation shall be
provided. (Reference NRCS Technical Releases
56 & 69)
Freeboard - The top elevation of the settled embankment shall be determined in accordance
with minimum criteria established in Table 1
Allowance for Settlement - The design height of
the dam shall be increased by the amount needed
to insure that the design top of fill elevation will
be maintained after all settlement has taken
place. This increase shall not be less than 5 percent, except where detailed soil testing and lab
analyses indicate a lesser amount is adequate.
Principal Spillway
Capacity - A conduit, with needed appurtenances, shall be placed under or through the
dam, except where a weir type structure is used.
The minimum capacity of the principal spillway
shall be that required in Table 1.
Crest Elevation of Inlet - The crest elevation of
the principal spillway shall be no less than 1.0
foot below the crest of the emergency spillway.
The crest elevation is the invert elevation of the
lowest opening 6 inches or larger in any direction.
The inlet or riser size for the pipe drops shall be
such that the flow through the structure goes
from weir-flow control to pipe-flow control
without going into orifice-flow control in the
NRCS - MARYLAND
riser. The inlets and outlets shall be designed
and analyzed to function satisfactorily for the
full range of flow and hydraulic head anticipated.
The riser shall be analyzed for flotation assuming all orifices and pipes are plugged. The factor
of safety against flotation shall be 1.2 or greater.
Pipe Conduits - Pipe conduits under or through
the dam shall meet the following requirements:
1. All pipes shall be circular in cross section
except for cast-in-place reinforced concrete
box culverts.
2. Pipe shall be capable of withstanding the external loading without yielding, buckling, or
cracking.
3. Pipe strength shall be not less than those
shown on Tables 3, 4 and 5 for corrugated
steel, aluminum, and plastic pipes and applicable ASTM’s for other materials.
4. Where inlet or outlet flared sections are used,
they shall be made from materials compatible
with the pipe.
5. All pipe joints shall be made watertight by
the use of flanges with gaskets, coupling
bands with gaskets, bell and spigot ends with
gaskets, or by welding. See Construction
Specifications for details.
6. The joints between sections of pipe shall be
designed to remain watertight after joint rotation and elongation caused by foundation
consolidation.
The capacity of the pipe conduit shall be adequate to discharge long duration, continuous or
frequent flows without flow through the emergency spillway. The diameter of the pipe shall
be not less than 6 inches.
For dams 20 feet or less in effective height, the
following pipe materials are acceptable: castiron, ductile iron, steel, corrugated steel or aluminum, concrete with rubber gaskets, plastic,
and cast-in-place reinforced concrete box culverts. Plastic pipe that will be exposed to direct
sunlight should be made of ultraviolet resistant
materials and protected by coating or shielding.
Connections of pipe to less flexible pipe or strucJANUARY 2000
Pond MD-378-6
tures must be designed to avoid stress concentrations that could rupture the pipe.
For dams over 20 feet in effective height, conduits are to be reinforced concrete pipe, cast-inplace reinforced concrete box culverts, corrugated steel, ductile iron, welded steel or aluminum pipe. The maximum height of fill over any
principal spillway steel, aluminum, or plastic
pipe must not exceed 25 feet.
Concrete pipe shall have a concrete cradle extending up the sides of the pipe at least 50% of
its outside diameter with minimum thickness of
6 inches. Where a concrete cradle is not needed
for structural reasons, flowable fill may be used
as described in the CONSTRUCTION
SPECIFICATIONS section of this standard.
Gravel bedding is not permitted. Cantilever outlet sections, if used, shall be designed to withstand the cantilever load. Pipe supports shall be
provided when needed. Other suitable devices
such as plunge basin, stilling basin, impact basin,
or rock riprap spreader should be used to provide
a safe outlet. Cathodic protection is to be provided for welded steel and corrugated steel pipe
where the need and importance of the structure
warrant. Cathodic protection should normally be
provided for corrugated steel pipe where the
saturated soil resistivity is less than 4,000 ohmscm or the pH is lower than 5. The National
Handbook of Conservation Practices, Irrigation
Water Conveyance, Steel Pipeline Standard
(430-FF), provides criteria for cathodic protection of welded steel pipes.
Multiple Conduits - Where multiple conduits are
used, there shall be sufficient space between the
conduits and the installed anti-seep collars to allow for backfill material to be placed between
the conduits by the earth moving equipment and
for easy access by hand operated compaction
equipment. This distance between conduits shall
be equal to or greater than half the pipe diameter
but not less than 2 feet.
Conduit Piping and Seepage Control - Seepage
along pipe conduit spillways extending through
the embankment shall be controlled by use of (1)
anti-seep collars, or (2) filter and drainage diaphragm. Seepage control will not be required on
pipes 6 inches in diameter or less.
NRCS - MARYLAND
Anti-seep collars shall be installed around all
conduits through earth fills according to the following criteria:
1. Sufficient collars shall be placed to increase
the seepage length along the conduit by a
minimum of 15 percent of the pipe length located within the saturation zone.
2. The assumed normal saturation zone shall be
determined by projecting a line at a slope (4)
horizontal to (1) vertical from the point
where the normal water elevation meets the
upstream slope to a point where this line intersects the invert of the pipe conduit or bottom of the cradle, whichever is lower. For
Stormwater Management ponds, the phreatic
line starting elevation shall be the 10-year
water elevation.
3. Maximum collar spacing shall be 14 times
the required projection above the pipe. The
minimum collar spacing shall be 5 times the
required minimum projection.
4. Anti-seep collars should be placed within the
saturated zone. In cases where the spacing
limit will not allow this, at least one collar
will be in the saturated zone.
5. All anti-seep collars and their connections to
the conduit shall be watertight and made of
material compatible with the conduit.
6. Collar dimensions shall extend a minimum of
2 feet in all directions around the pipe.
7. Anti-seep collars shall be placed a minimum
of two feet from pipe joints except where
flanged joints are used.
8. For pipes with concrete cradles, the projection shall be measured from the cradle.
Filter and drainage diaphragms are always recommended, but are required when the following
conditions are encountered:
1. The pond requires design according to TR60.
2. Embankment soils with high piping potential
such as Unified Classes GM, SM, and ML.
JANUARY 2000
Pond MD-378-7
Filter and drainage diaphragms shall be designed
in accordance with procedures from NRCS TR60, Earth Dams and Reservoirs, Section 6, Principal Spillways, as described below.
The drainage diaphragm shall usually consist of
sand, meeting the fine concrete aggregate requirements (ASTM C-33). A design analysis
shall be made using Part 633 of the National Engineering Manual, Chapter 26, Gradation Design
of Sand and Gravel Filters.
The drainage diaphragm shall be a minimum of 3
ft thick and extend vertically upward and horizontally at least three times the conduit outside
diameter or the width of the cradle, whichever is
greater except that:
1. The vertical extension need be no higher than
the maximum potential reservoir water level, and
2. The horizontal extension need be no further
than 5 feet beyond the sides and slopes of any
excavation made to install the conduit.
3. The minimum soil cover over any portion of
the filter-drainage diaphragm measured normal
to the nearest embankment surface shall be at
least 2 feet.
It shall extend vertically downward at least 2 ft
beneath the conduit outside diameter or bottom
of the cradle, whichever is greater. The drainage
diaphragm shall be located immediately downstream of the cutoff trench, approximately parallel to the centerline of the dam but no further upstream than the centerline of the dam.
The drainage diaphragm shall outlet at the embankment downstream toe, preferably using a
drain backfill envelope continuously along the
pipe to where it exits the embankment. Protecting drain fill from surface erosion will be necessary.
It is required that the outlet for the filter diaphragm is sized to safely discharge the design
flow. Where a drain backfill envelope is used as
the outlet, it is recommended that it be designed
so the hydraulic head does not exceed the depth
of the drain outlet. The exposed area of the drain
outlet must also be protected from external attack such as surface erosion and slope instability
due to horizontal seepage pressures. A weighted
NRCS - MARYLAND
toe cover such as riprap can be effective if protected with a properly designed filter between
the sand drain material and the riprap cover.
If pipe drain outlets are used, consideration must
be given to the structural design of the conduit in
resisting external loading and the design life of
the pipe must be consistent with the design life
of the dam and physical conditions of the site.
Also, the pipe must be designed for capacity and
size of perforations as outlined in NEH Part 633,
Chapter 26 and Soil Mechanics Note 3. If the
pipe corrodes, is crushed by exterior loading, or
is otherwise damaged, the outlet of the filter diaphragm is lost and a piping failure may occur.
The design quantity (Q) used to size the outlet
can be calculated by Darcy's Law, Q = kiA
where:
k = permeability of the embankment or drain
outlet material (ft/day)
i = hydraulic gradient where i = h/l
h = head differential (ft)
l = seepage path (ft)
A = area of flow (diaphragm or outlet) (ft2)
Anti-vortex Devices - Drop inlet spillways are to
have adequate anti-vortex devices. Splitter type
anti-vortex devices shall be placed in line with
the barrel. An anti-vortex device is not required
if weir control is maintained in the riser through
all flow stages.
Trash Racks - All pipe and inlet structures shall
have a trash rack. Openings for trash racks shall
be no larger than 1/2 of the barrel conduit diameter, but in no case less than 6 inches.
Flush grates for trash racks are not acceptable.
Inlet structures that have flow over the top shall
have a non-clogging trash rack such as a hoodtype inlet extending a minimum of 8 inches below the weir openings, which allows passage of
water from underneath the trash rack into the
riser.
For inlet structures with solid covered tops, the
bottom of the cover slab must be set at an eleva-
JANUARY 2000
Pond MD-378-8
tion to prevent orifice flow control before pipe
flow control governs.
Low stage releases, where the opening is larger
than 6 inches, shall have a non-clogging trash
rack with openings no larger than half the low
flow dimension.
For all low stage releases 6 inches or smaller in
any direction, the emergency spillway design
storm shall be routed assuming the release has
failed, using storage and discharge only above
the elevation of the next opening larger than 6
inches in all directions. This design storm routing shall not overtop the dam.
Drain Pipe - A pipe with a suitable valve shall
be provided to drain the pool area, where needed
for proper pond management. The principal
spillway conduit may serve as a pond drain,
when so located, to accomplish this function.
Water Supply Pipes or Utilities - All pipes
through the dam shall have an inside diameter of
not less than 1 1/4 inches. Pipes / utilities not
parallel to the axis of the dam shall meet all principal spillway requirements (i.e. filter diaphragm, embankment soils, etc.). Pipes / utilities
parallel to the axis of the dam shall be constructed with no granular bedding.
Earth Emergency Spillways
Emergency spillways are provided to convey
large flood flows safely past earth embankments.
An emergency spillway must be provided for
each dam, unless the principal spillway is large
enough to pass the routed design hydrograph
peak discharge and any trash without overtopping the dam. The only design that may be utilized without an emergency spillway is: a principal spillway with a cross-sectional area of 3
square feet or more and an inlet that will not
clog, such as a hood-type inlet which allows passage of water from underneath the trash rack into
the riser.
Capacity - The minimum capacity of emergency
spillways shall be that required to pass the peak
flow expected from a design storm of the frequency and duration shown in Table 1 less any
reduction creditable to conduit discharge and
detention storage.
NRCS - MARYLAND
The emergency spillway shall (1) safely pass the
storm design peak or (2) the storm runoff shall
be routed through the reservoir. The routing
shall start with the water surface at the elevation
of the crest of the principal spillway, or at the
water surface after 10 days drawdown, whichever is higher. The 10-day drawdown shall be
computed from the crest of the emergency spillway or from the elevation that would be attained
had the entire design storm been impounded,
whichever is lower. Emergency spillways are to
provide for passage of the design flow at a nonerosive velocity to a point downstream where the
dam will not be endangered.
Component Parts - Earth spillways are open
channels and usually consist of an inlet channel,
level section, and an exit channel. The minimum
difference in elevation between the crest of the
emergency spillway and the settled top of dam
shall be 2.0 feet.
Cross-Section - Earth spillways shall be trapezoidal and shall be located in undisturbed earth.
The side slopes shall be stable for the material in
which the spillway is to be constructed, but not
steeper than 2:1. The emergency spillway shall
have a bottom width of not less than 8 feet.
The inlet channel may be curved to fit existing
topography; however, it should be flared to allow
unrestricted flow to the level section. The level
section should be located as near the centerline
of dam as possible. The level section shall be 25
feet in length, and shall be rectangular or square.
Exit channel centerline shall be perpendicular to
the level section downstream edge and must be
straight for a distance beyond the downstream
toe, so that discharges will not reach the earth
embankment. The grade of the exit channel shall
fall within the range established by discharge
requirement and permissible velocities.
The crest of any “token” spillway will be located
at or above the 100-year storm elevation in undisturbed earth and have a minimum depth of
one foot and bottom width of 8 feet.
Permissible Velocities - Earth spillways shall be
designed for non-erosive velocities through the
control section and to a point downstream where
the dam will not be endangered. The maximum
permissible velocity for the grass and grass mixJANUARY 2000
Pond MD-378-9
ture to be used shall be selected from Table 6.
Velocities exceeding these values will require
use of linings other than vegetation.
will not be allowed within the buffer zone (15
feet from the toe of the dam), and will not be allowed within a 25-foot radius around the inlet
structure.
Infiltration / Water Quality Basins – Ponds, either excavated or embankment, that are designed
solely for infiltration or as water quality basins
will have an emergency spillway. The capacity
of the spillway will be determined by the following procedure:
Roadway Embankments - Trees and/or shrubs
will not be allowed on any embankment, except
for dry stormwater management structures that
will be utilized as a roadway under all the following conditions:
Pass the routed 100-Year Storm with 1 foot of
freeboard to the top of dam elevation. Routing
will begin at the emergency spillway crest.
1. Plantings may only be on top of the dam
along the roadway and/or sidewalks.
Structural Emergency Spillways
2. The top of the dam shall have a minimum of
50-foot top width.
Chutes or drops, when used for principal spillways or principal-emergency or emergency spillways, shall be designed in accordance with the
principals set forth in the National Engineering
Handbook, Section 5 “Hydraulics”; Section 11
“Drop Spillways”; and Section 14 “Chute Spillways”. The minimum capacity of a structural
spillway shall be that required to pass the peak
flow expected from a design storm of the frequency and duration shown in Table 1 less any
reduction creditable to conduit discharge and
detention storage.
Visual Resource Design
The visual design of ponds shall be carefully
considered in areas of high public visibility and
those associated with recreation. The underlying
criterion for all visual design is appropriateness.
The shape and form of ponds, excavated material, and plantings are to relate visually to their
surroundings and to their functions.
The embankment may be shaped to blend with
the natural topography. The edge of the pond
should be shaped so that it is generally curvilinear rather than rectangular. Excavated material
shall be shaped so that the final form is smooth,
flowing, and fitting to the adjacent landscape
rather than angular geometric mounds. If feasible, islands may be added for visual interest and
to attract wildlife.
Trees and Shrubs
3. Plantings will not be allowed on the side
slopes of the embankment.
4. Plantings will not be allowed within the
buffer zone (15 feet from the toe of the dam).
5. Plantings will only be shallow rooted (roots
less than 3’ deep) trees or shrubs.
6. The pond is a “dry” structure (normal pool
not exceeding 18 inches).
7. A landscape plan showing type and location
of planting must be prepared by a Landscape
Architect certifying shallow rooted plants
(roots less than 3’ deep) under mature conditions.
8. A minimum of 3 feet freeboard above the
100-year water surface elevation must be
maintained.
9. The structure is a low hazard (Class “a”)
pond.
Safety
Special considerations should be made for safety
and access during the design of a pond. Measures to be considered may include fencing, slope
benching, access roads, flattened side slopes, etc.
When fencing a structure, the fence will be located so it will not interfere with the operation of
the emergency spillway.
Non-Roadway Embankments - Trees and/or
shrubs will not be allowed on any embankment,
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-10
Excavated Ponds
General - Excavated ponds that create a failure
potential through a constructed or created embankment will be designed as embankment
ponds. Excavated ponds that include a pipe or
weir outlet control system for urban stormwater
management shall be designed using the principal and emergency spillway hydrologic criteria
for Embankment Ponds, Table 1.
tance equal to the depth of the pond, but not
less than 12 feet from the edge of the pond;
3. Shaped to a designed form that blends visually with the landscape;
4. Used for low embankment and leveling; or
5. Hauled away.
Reservoir Area for Wet Ponds
Side Slopes - Side slopes of excavated ponds
shall be such that they will be stable and shall
not be steeper than 1 horizontal to 1 vertical.
Flatter slopes are to be utilized where safety for
children, livestock watering, etc. is a design factor.
Perimeter Form - Where the structures are used
for recreation or are located in high public view,
the perimeter or edge should be shaped to a curvilinear form.
Inlet Protection - When the excavated pond is a
bypass type and water is being diverted from a
stream, the minimum size inlet line shall be a 4inch diameter pipe. All state laws concerning
water use and downstream rights shall be strictly
adhered to.
For most ponds, the topography of the site shall
permit storage of water at a depth and volume
that ensures a dependable supply, considering
beneficial use, sedimentation, season of use, and
evaporation and seepage losses. Soils in the reservoir shall be impervious enough to minimize
seepage losses or shall be of a type that sealing is
practical.
Excavation and shaping required to permit the
reservoir area to suitably serve the planned purpose shall be included in the construction plans.
Reservoirs designed specifically for fish production or wildlife management shall follow design
criteria in the standards and specifications for
Fish Pond Management (MD-399) and Wildlife
Wetland Habitat Management (MD-644), as appropriate.
Where surface water enters the pond in a natural
or excavated channel, the side slope of the pond
shall be protected against erosion.
Outlet Protection – An excavated pond with a
low embankment (combination excavation / embankment pond) shall be designed to ensure a
stable outfall for the 10-year, 24-hour frequency
storm.
Placement of Excavated Material - The material
excavated from the pond shall be placed in one
of the following ways so that its weight will not
endanger the stability of the pond side slopes and
where it will not be washed back into the pond
by rainfall:
1. Uniformly spread to a height not exceeding 3
feet with the top graded to a continuous slope
away from the pond;
2. Uniformly placed or shaped reasonably well
with side slopes no steeper than 2 to 1. The
excavated material will be placed at a disNRCS - MARYLAND
JANUARY 2000
Pond MD-378-11
TABLE 1
HYDROLOGIC CRITERIA FOR PONDS
Structure
Class
Storage
Height
Product1
Watershed
Area
(Acres)
Height To
Emergency
Spwy Crest
(Feet)
Normal
Surface
Area
(Acres)
Spillway Capacity5
Principal2
Rural
Urban
Emergency3, 4
Rural
Urban
Freeboard6
Rural & Urban
“c” & “b”
Any
Any
Any
Any
TR 60
TR 60
TR 60
TR 60
TR 60
“a”
3,000 or
more
Any
Any
Any
TR 60
TR 60
TR 60
TR 60
TR 60
320
>20 - 35
>12
25 YR
TR 60
100 YR
100 YR
and
<20
>12
10 YR
25 YR
100 YR
100 YR
Larger
<15
<12
5 YR
10 YR
50 YR
100 YR
100
>20 - 35
>12
10 YR
TR 60
100 YR
100 YR
2.0’ above E.S.
Design Storm
to
<20
>12
5 YR
10 YR
50 YR
100 YR
1.0’ above E.S.
Design Storm
320
<15
<12
2 YR
5 YR
25 YR
100 YR
1.0’ above E.S.
Design Storm
Less
>20 - 35
>12
5 YR
TR 60
50 YR
100 YR
Than
<20
>12
2 YR
5 YR
25 YR
100 YR
100
<15
<12
10% of
25 YR
Peak
5 YR
25 YR
100 YR
Less
“a”
than
3,000
2.0’ above E.S.
Design Storm
1.0’ above E.S.
Design Storm
NOTES
1) The storage is defined as the original capacity of the reservoir in acre-feet at the elevation of the crest of the emergency spillway. The effective height is the difference in elevation in feet between the emergency spillway crest and the lowest point on a
profile taken along the centerline of the dam, excluding the cutoff trench. If there is no emergency spillway, this height shall be to
the top of the dam.
2) Principal - minimum storm to be contained below the crest of the emergency spillway including any combination of temporary
storage and principal spillway discharge.
3) Emergency - minimum storm used to proportion the emergency spillway to meet the limitations for shape, size, velocity and
exit channel. This storm can be handled by any combination of principal spillway discharge, emergency spillway discharge and
storage.
4) For ponds without a separate emergency spillway, the principal spillway functions as the emergency spillway. In this situation,
the principal spillway must comply with the emergency spillway hydrologic criteria.
5) All ponds, which are being designed to meet local stormwater requirements, will be required to use the urban criteria. Storm
duration used shall be 24 hours except where TR-60 is specified.
6)
For ponds without a functioning open channel emergency spillway, minimum freeboard will be 2 feet.
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-12
TABLE 2
Total
Height Of Embankment
(Feet)
Minimum
Top Width
(Feet)
10 or less
11 - 14
15 - 19
20 - 24
25 - 34
35 or more
6
8
10
12
14
15
TABLE 31,2
MINIMUM GAGES
TABLE 41,2
MINIMUM GAGES
CORRUGATED STEEL PIPE
2 - 2/3 inches x 1/2 inch Corrugations
CORRUGATED ALUMINUM PIPE
2 - 2/3 inches x 1/2 inch Corrugations
Fill Height
Over Pipe
(Feet)
1 - 15
15 - 20
20 - 25
Pipe Diameter in Inches
24 &
Less
16
16
16
30
16
12
10
36
14
10
*
42
10
*
*
48
10
*
*
CORRUGATED STEEL PIPE
3 inches x 1 inch or 5 inch x 1 inch Corrugations
Fill Height
Over Pipe
(Feet)
1 - 15
15 - 20
20 - 25
36
16
16
14
42
16
16
14
* Not Permitted.
1
2
3
Pipe Diameter (Inches)
Flowable Fill
3
48
54
603 663
16
14
14
14
12
14
14
14
10
14
14
14
Fill Height
Over Pipe
(Feet)
1 - 15
15 - 20
20 - 25
Pipe Diameter in Inches
21 &
Less
16
12
10
24
14
10
*
30
10
*
*
CORRUGATED ALUMINUM PIPE
3 inches x 1 inch Corrugations
723
14
14
14
Fill Height
Over Pipe
(Feet)
1 - 15
15 - 20
20 - 25
Pipe Diameter in Inches
30
16
16
12
36
16
12
*
42
14
*
*
48
10
*
*
543
14
*
*
* Not Permitted.
Coatings for corrugated metal shall be as specified by the MD-378 Construction Specifications.
Tables 3 and 4 were developed using the modified Spangler equation. Sizes other than those shown
above are not permitted.
Must use flowable backfill as specified by the MD-378 Construction Specifications and the pipe must be
bituminous coated.
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-13
TABLE 5
TABLE 6
ACCEPTABLE PLASTIC PIPE FOR USE IN
EARTH DAM1, 2
Permissible Velocities (Ft/Sec)
For Emergency Spillways Lined with Vegetation
Slope Of Exit Channel
Nominal Pipe
Size (inches)
6 - 24
6 - 24
6 – 24
6 - 24
Schedule or Standard
Dimension Ratio
(SDR)
PVC Schedule 40
PVC Schedule 80
PVC SDR 26
Corrugated HDPE
Maximum
Depth
of Fill Over 3
10
15
10
10
Type of Cover
0 - 5%
5 - 10%
Bermudagrass
6
5
Reed Canarygrass
5
4
Tall Fescue
5
4
Kentucky Bluegrass
5
4
Grass-legume mixture
4
3
1
See Specifications, Plastic Pipe
2
All designs based on Technical Release 77, Reference 20. Other diameters and / or fill heights may be
used that meet all the requirements of TR-77.
3
larger fill heights may be permitted when using flowable fill.
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-14
CONSTRUCTION SPECIFICATIONS
These specifications are appropriate to all
ponds within the scope of the Standard for
practice MD-378. All references to ASTM
and AASHTO specifications apply to the
most recent version.
Site Preparation
Areas designated for borrow areas, embankment, and structural works shall be cleared,
grubbed and stripped of topsoil. All trees,
vegetation, roots and other objectionable material shall be removed. Channel banks and
sharp breaks shall be sloped to no steeper
than 1:1. All trees shall be cleared and
grubbed within 15 feet of the toe of the embankment.
Areas to be covered by the reservoir will be
cleared of all trees, brush, logs, fences, rubbish and other objectionable material unless
otherwise designated on the plans. Trees,
brush, and stumps shall be cut approximately
level with the ground surface. For dry
stormwater management ponds, a minimum
of a 25-foot radius around the inlet structure
shall be cleared.
All cleared and grubbed material shall be disposed of outside and below the limits of the
dam and reservoir as directed by the owner or
his representative. When specified, a sufficient quantity of topsoil will be stockpiled in
a suitable location for use on the embankment
and other designated areas.
Earth Fill
Material - The fill material shall be taken
from approved designated borrow areas. It
shall be free of roots, stumps, wood, rubbish,
stones greater than 6”, frozen or other objectionable materials. Fill material for the center
of the embankment, and cut off trench shall
conform to Unified Soil Classification GC,
SC, CH, or CL and must have at least 30%
passing the #200 sieve. Consideration may
be given to the use of other materials in the
embankment if designed by a geotechnical
engineer. Such special designs must have
construction supervised by a geotechnical
engineer.
NRCS - MARYLAND
Materials used in the outer shell of the embankment must have the capability to support
vegetation of the quality required to prevent
erosion of the embankment.
Placement - Areas on which fill is to be
placed shall be scarified prior to placement of
fill. Fill materials shall be placed in maximum 8 inch thick (before compaction) layers
which are to be continuous over the entire
length of the fill. The most permeable borrow material shall be placed in the downstream portions of the embankment. The
principal spillway must be installed concurrently with fill placement and not excavated
into the embankment.
Compaction - The movement of the hauling
and spreading equipment over the fill shall be
controlled so that the entire surface of each
lift shall be traversed by not less than one
tread track of heavy equipment or compaction
shall be achieved by a minimum of four complete passes of a sheepsfoot, rubber tired or
vibratory roller. Fill material shall contain
sufficient moisture such that the required degree of compaction will be obtained with the
equipment used. The fill material shall contain sufficient moisture so that if formed into
a ball it will not crumble, yet not be so wet
that water can be squeezed out.
When required by the reviewing agency the
minimum required density shall not be less
than 95% of maximum dry density with a
moisture content within ±2% of the optimum.
Each layer of fill shall be compacted as necessary to obtain that density, and is to be certified by the Engineer at the time of construction. All compaction is to be determined by
AASHTO Method T-99 (Standard Proctor).
Cut Off Trench - The cutoff trench shall be
excavated into impervious material along or
parallel to the centerline of the embankment
as shown on the plans. The bottom width of
the trench shall be governed by the equipment used for excavation, with the minimum
width being four feet. The depth shall be at
least four feet below existing grade or as
shown on the plans. The side slopes of the
trench shall be 1 to 1 or flatter. The backfill
shall be compacted with construction equipment, rollers, or hand tampers to assure
JANUARY 2000
Pond MD-378-15
maximum density and minimum permeability.
Embankment Core - The core shall be parallel to the centerline of the embankment as
shown on the plans. The top width of the
core shall be a minimum of four feet. The
height shall extend up to at least the 10 year
water elevation or as shown on the plans.
The side slopes shall be 1 to 1 or flatter. The
core shall be compacted with construction
equipment, rollers, or hand tampers to assure
maximum density and minimum permeability. In addition, the core shall be placed concurrently with the outer shell of the embankment.
Structure Backfill
Backfill adjacent to pipes or structures shall
be of the type and quality conforming to that
specified for the adjoining fill material. The
fill shall be placed in horizontal layers not to
exceed four inches in thickness and compacted by hand tampers or other manually
directed compaction equipment. The material
needs to fill completely all spaces under and
adjacent to the pipe. At no time during the
backfilling operation shall driven equipment
be allowed to operate closer than four feet,
measured horizontally, to any part of a structure. Under no circumstances shall equipment be driven over any part of a concrete
structure or pipe, unless there is a compacted
fill of 24” or greater over the structure or
pipe.
Structure backfill may be flowable fill meeting the requirements of Maryland Department
of Transportation, State Highway Administration Standard Specifications for Construction and Materials, Section 313 as modified.
The mixture shall have a 100-200 psi; 28 day
unconfined compressive strength. The flowable fill shall have a minimum pH of 4.0 and
a minimum resistivity of 2,000 ohm-cm. Material shall be placed such that a minimum of
6” (measured perpendicular to the outside of
the pipe) of flowable fill shall be under (bedding), over and, on the sides of the pipe. It
only needs to extend up to the spring line for
rigid conduits. Average slump of the fill
shall be 7” to assure flowability of the material. Adequate measures shall be taken (sand
NRCS - MARYLAND
bags, etc.) to prevent floating the pipe. When
using flowable fill, all metal pipe shall be bituminous coated. Any adjoining soil fill shall
be placed in horizontal layers not to exceed
four inches in thickness and compacted by
hand tampers or other manually directed
compaction equipment. The material shall
completely fill all voids adjacent to the flowable fill zone. At no time during the backfilling operation shall driven equipment be allowed to operate closer than four feet, measured horizontally, to any part of a structure.
Under no circumstances shall equipment be
driven over any part of a structure or pipe
unless there is a compacted fill of 24” or
greater over the structure or pipe. Backfill
material outside the structural backfill (flowable fill) zone shall be of the type and quality
conforming to that specified for the core of
the embankment or other embankment materials.
Pipe Conduits
All pipes shall be circular in cross section.
Corrugated Metal Pipe - All of the following
criteria shall apply for corrugated metal pipe:
1. Materials - (Polymer Coated steel pipe) Steel pipes with polymeric coatings shall
have a minimum coating thickness of
0.01 inch (10 mil) on both sides of the
pipe. This pipe and its appurtenances
shall conform to the requirements of
AASHTO Specifications M-245 & M-246
with watertight coupling bands or flanges.
Materials - (Aluminum Coated Steel
Pipe) - This pipe and its appurtenances
shall conform to the requirements of
AASHTO Specification M-274 with watertight coupling bands or flanges. Aluminum Coated Steel Pipe, when used
with flowable fill or when soil and/or water conditions warrant the need for increased durability, shall be fully bituminous coated per requirements of
AASHTO Specification M-190 Type A.
Any aluminum coating damaged or otherwise removed shall be replaced with
cold applied bituminous coating compound. Aluminum surfaces that are to be
in contact with concrete shall be painted
JANUARY 2000
Pond MD-378-16
with one coat of zinc chromate primer or
two coats of asphalt.
Materials - (Aluminum Pipe) - This pipe
and its appurtenances shall conform to the
requirements of AASHTO Specification
M-196 or M-211 with watertight coupling
bands or flanges. Aluminum Pipe, when
used with flowable fill or when soil
and/or water conditions warrant for increased durability, shall be fully bituminous coated per requirements of
AASHTO Specification M-190 Type A.
Aluminum surfaces that are to be in contact with concrete shall be painted with
one coat of zinc chromate primer or two
coats of asphalt. Hot dip galvanized bolts
may be used for connections. The pH of
the surrounding soils shall be between 4
and 9.
2. Coupling bands, anti-seep collars, end
sections, etc., must be composed of the
same material and coatings as the pipe.
Metals must be insulated from dissimilar
materials with use of rubber or plastic insulating materials at least 24 mils in
thickness.
3. Connections - All connections with pipes
must be completely watertight. The drain
pipe or barrel connection to the riser shall
be welded all around when the pipe and
riser are metal. Anti-seep collars shall be
connected to the pipe in such a manner as
to be completely watertight. Dimple
bands are not considered to be watertight.
All connections shall use a rubber or neoprene gasket when joining pipe sections.
The end of each pipe shall be re-rolled an
adequate number of corrugations to accommodate the bandwidth. The following type connections are acceptable for
pipes less than 24 inches in diameter:
flanges on both ends of the pipe with a
circular 3/8 inch closed cell neoprene
gasket, pre-punched to the flange bolt circle, sandwiched between adjacent
flanges; a 12-inch wide standard lap type
band with 12-inch wide by 3/8-inch thick
closed cell circular neoprene gasket; and
a 12-inch wide hugger type band with oring gaskets having a minimum diameter
NRCS - MARYLAND
of 1/2 inch greater than the corrugation
depth. Pipes 24 inches in diameter and
larger shall be connected by a 24 inch
long annular corrugated band using a
minimum of 4 (four) rods and lugs, 2 on
each connecting pipe end. A 24-inch
wide by 3/8-inch thick closed cell circular
neoprene gasket will be installed with 12
inches on the end of each pipe. Flanged
joints with 3/8 inch closed cell gaskets the
full width of the flange is also acceptable.
Helically corrugated pipe shall have either continuously welded seams or have
lock seams with internal caulking or a
neoprene bead.
4. Bedding - The pipe shall be firmly and
uniformly bedded throughout its entire
length. Where rock or soft, spongy or
other unstable soil is encountered, all
such material shall be removed and replaced with suitable earth compacted to
provide adequate support.
5. Backfilling shall conform to “Structure
Backfill”.
6. Other details (anti-seep collars, valves,
etc.) shall be as shown on the drawings.
Reinforced Concrete Pipe - All of the following criteria shall apply for reinforced concrete pipe:
1. Materials - Reinforced concrete pipe shall
have bell and spigot joints with rubber
gaskets and shall equal or exceed ASTM
C-361.
2. Bedding - Reinforced concrete pipe conduits shall be laid in a concrete bedding /
cradle for their entire length. This bedding / cradle shall consist of high slump
concrete placed under the pipe and up the
sides of the pipe at least 50% of its outside diameter with a minimum thickness
of 6 inches. Where a concrete cradle is
not needed for structural reasons, flowable fill may be used as described in the
“Structure Backfill” section of this standard. Gravel bedding is not permitted.
JANUARY 2000
Pond MD-378-17
3. Laying pipe - Bell and spigot pipe shall
be placed with the bell end upstream.
Joints shall be made in accordance with
recommendations of the manufacturer of
the material. After the joints are sealed
for the entire line, the bedding shall be
placed so that all spaces under the pipe
are filled. Care shall be exercised to prevent any deviation from the original line
and grade of the pipe. The first joint must
be located within 4 feet from the riser.
4. Backfilling shall conform to “Structure
Backfill”.
5. Other details (anti-seep collars, valves,
etc.) shall be as shown on the drawings.
Plastic Pipe - The following criteria shall apply for plastic pipe:
1. Materials - PVC pipe shall be PVC-1120
or PVC-1220 conforming to ASTM D1785 or ASTM D-2241. Corrugated High
Density Polyethylene (HDPE) pipe, couplings and fittings shall conform to the
following: 4” – 10” inch pipe shall meet
the requirements of AASHTO M252
Type S, and 12” through 24” inch shall
meet the requirements of AASHTO M294
Type S.
2. Joints and connections to anti-seep collars
shall be completely watertight.
3. Bedding -The pipe shall be firmly and
uniformly bedded throughout its entire
length. Where rock or soft, spongy or
other unstable soil is encountered, all
such material shall be removed and replaced with suitable earth compacted to
provide adequate support.
4. Backfilling shall conform to “Structure
Backfill”.
5. Other details (anti-seep collars, valves,
etc.) shall be as shown on the drawings.
Drainage Diaphragms - When a drainage
diaphragm is used, a registered professional
engineer will supervise the design and construction inspection.
NRCS - MARYLAND
Concrete
Concrete shall meet the requirements of
Maryland Department of Transportation,
State Highway Administration Standard
Specifications for Construction and Materials, Section 414, Mix No. 3.
Rock Riprap
Rock riprap shall meet the requirements of
Maryland Department of Transportation,
State Highway Administration Standard
Specifications for Construction and Materials, Section 311.
Geotextile shall be placed under all riprap
and shall meet the requirements of Maryland
Department of Transportation, State Highway
Administration Standard Specifications for
Construction and Materials, Section 921.09,
Class C.
Care of Water during Construction
All work on permanent structures shall be
carried out in areas free from water. The
Contractor shall construct and maintain all
temporary dikes, levees, cofferdams, drainage
channels, and stream diversions necessary to
protect the areas to be occupied by the permanent works. The contractor shall also furnish, install, operate, and maintain all necessary pumping and other equipment required
for removal of water from various parts of the
work and for maintaining the excavations,
foundation, and other parts of the work free
from water as required or directed by the engineer for constructing each part of the work.
After having served their purpose, all temporary protective works shall be removed or
leveled and graded to the extent required to
prevent obstruction in any degree whatsoever
of the flow of water to the spillway or outlet
works and so as not to interfere in any way
with the operation or maintenance of the
structure. Stream diversions shall be maintained until the full flow can be passed
through the permanent works. The removal
of water from the required excavation and the
foundation shall be accomplished in a manner
and to the extent that will maintain stability
of the excavated slopes and bottom required
excavations and will allow satisfactory perJANUARY 2000
Pond MD-378-18
formance of all construction operations. During the placing and compacting of material in
required excavations, the water level at the
locations being refilled shall be maintained
below the bottom of the excavation at such
locations which may require draining the water sumps from which the water shall be
pumped.
Stabilization
All borrow areas shall be graded to provide
proper drainage and left in a sightly condition. All exposed surfaces of the embankment, spillway, spoil and borrow areas, and
berms shall be stabilized by seeding, liming,
fertilizing and mulching in accordance with
the Natural Resources Conservation Service
Standards and Specifications for Critical Area
Planting (MD-342) or as shown on the accompanying drawings.
Erosion and Sediment Control
Construction operations will be carried out in
such a manner that erosion will be controlled
and water and air pollution minimized. State
and local laws concerning pollution abatement will be followed. Construction plans
shall detail erosion and sediment control
measures.
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-19
OPERATION AND MAINTENANCE
An operation and maintenance plan in accordance with Local or State Regulations will be
prepared for all ponds. As a minimum, the
dam inspection checklist located in Appendix
A shall be included as part of the operation
and maintenance plan and performed at least
annually. Written records of maintenance and
major repairs needs to be retained in a file.
The issuance of a Maintenance and Repair
Permit for any repairs or maintenance that
involves the modification of the dam or spillway from its original design and specifications is required. A permit is also required
for any repairs or reconstruction that involve
a substantial portion of the structure. All indicated repairs are to be made as soon as
practical.
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-20
SUPPORTING DATA AND
DOCUMENTATION
7. Compute earth fill (if needed).
The following is a list of the minimum data
needed:
8. Special design feature details; watering,
fire hydrants, fish management, irrigation,
outfall stabilization, etc.; structural details
with design loadings, if applicable, should
be shown on the drawings.
1. Profile along centerline of structure.
9. Complete data required on MD-ENG-14.
2. Profile along centerline of principal spillway.
10. Record seeding plan on drawings or MDCONS-10.
3. Profile along centerline of emergency
spillway.
11. A written Operation and Maintenance
Plan.
4. Survey of storage area to develop topography and storage volumes.
Construction Check Data/As-built
Field Data and Survey Notes
5. Soil investigation logs and notes.
Design Data
Record on appropriate engineering paper.
The following is a list of the minimum required design data:
1. Determine pond class and list appropriate
spillway design criteria, including map.
Record on survey note paper, SCS-ENG-28.
Survey data for ponds will be plotted in red.
All construction inspection visits shall be recorded on the CPA-6 or appropriate documentation paper. The documentation shall
include the date, who performed the inspection, specifics as to what was inspected, all
alternatives discussed, and decisions made
and by whom. The following is a list of the
minimum data needed for As-Builts:
1. A profile of the top of the dam.
2. Determine peak runoff from the contributing area for the design storms selected,
including topo map.
2. A cross-section of the emergency spillway at the control section.
3. Develop a stage-storage/discharge curve
for the site.
3. A profile along the centerline of the emergency spillway.
4. Determine the pipe spillway by storm
routing using the procedure in the SWM
Pond Design Manual; Chapter 11, EFH;
Chapter 6, TR-55; or TR-20.
4. A profile along the centerline of the principal spillway extending at least 100 feet
downstream of the fill.
5. Design emergency spillway using EFH
11-61.
6. Drawings should show the following as a
minimum: profile along centerline of
dam; profile along centerline of emergency spillway; cross section through
dam at principal spillway; cross section
through emergency spillway; plan view;
and construction details & notes and soil
logs.
NRCS - MARYLAND
5. The elevation of the principal spillway
crest.
6. The elevation of the principal spillway
conduit invert (inlet and outlet).
7. The diameter, length, thickness and type
of material for the riser.
8. The diameter, length, and type of material
for the conduit.
JANUARY 2000
Pond MD-378-21
9. The size and type of anti-vortex and trash
rack device and its elevations in relation
to the principal spillway crest.
10. The number, size and location of the antiseep collars.
11. The diameter and size of any low stage
orifices or drain pipes.
12. Show the length, width, and depth of contours of the pool area so that design volume can be verified.
13. Notes and measurements to show that any
special design features were met.
14. Statement on seeding and fencing.
15. Notes on site clean up and disposal.
16. Sign and date check notes to include
statement that practice meets or exceeds
plans and specifications.
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-22
REFERENCES
1.
12.
National Handbook of Conservation
Practices, USDA, Natural Resources
Conservation Service.
13.
Standard Specifications for Materials
and Methods of Sampling and Testing, Nineteenth Edition, American
Association of State Highway and
Transportation Officials, Washington
D.C., 1998.
14.
Standard Specifications for Construction and Materials, Maryland Department of Transportation, State
Highway Administration, Baltimore,
Maryland, October 1993.
15.
Technical Release No. 20, Computer
Programs for Project Formulation
Hydrology, USDA, Natural Resources
Conservation Service, 1992.
16.
Technical Release No. 55, Urban Hydrology for Small Watersheds,
USDA, Natural Resources Conservation Service, 1986.
17.
Maryland Technical Guide, Section
IV, Standards and Specifications,
USDA, Natural Resources Conservation Service.
Technical Release No. 56, A Guide
for Design and Layout of Vegetative
Wave Protection for Earth Dam Embankments, USDA, Natural Resources
Conservation Service, 1974.
18.
National Engineering Handbook, Section 4, Hydrology, USDA, Natural
Resources Conservation Service,
March 1985.
Technical Release No. 60, Earth
Dams and Reservoirs, USDA, Natural
Resources Conservation Service,
1985.
19.
Technical Release 69, Riprap for
Slope Protection Against Wave Action, USDA, Natural Resources Conservation Service, 1983.
AWWA Standards, American Water
Works Association, Denver, Colorado.
2.
ASTM Standards, American Society
for Testing and Materials, Philadelphia, Pennsylvania.
3.
Engineering Field Handbook, Part
650, USDA, Soil Conservation Service.
4.
5.
6.
7.
8.
Handbook of PVC Pipe Design and
Construction, First Edition, Uni-Bell
Plastic Pipe Association, Dallas,
Texas, 1980.
Handbook of Steel Drainage and
Highway Construction Products,
Third Edition, American Iron and
Steel Institute, Washington, D.C.,
1983.
Maryland Dam Safety Manual, Maryland Department of Natural Resources, Water Resources Administration, Annapolis, Maryland, June 1993.
9.
National Engineering Handbook, Section 5, Hydraulics, USDA, Natural
Resources Conservation Service, August 1956.
10.
National Engineering Handbook, Section 11, Drop Spillways, USDA,
Natural Resources Conservation Service, April 1968.
11.
National Engineering Handbook, Section 14, Chute Spillways, USDA,
Natural Resources Conservation Service, October 1977.
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-23
20.
Technical Release No. 77, Design and
Installation of Flexible Conduits,
USDA, Natural Resources Conservation Service, 1990.
NRCS - MARYLAND
21.
National Engineering Handbook, Part
633, Chapter 26, Gradation Design of
Sand and Gravel Filters, USDA,
Natural Resources Conservation Service, October 1994.
JANUARY 2000
Pond MD-378-24
APPENDIX A
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-25
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-26
NRCS - MARYLAND
JANUARY 2000
Pond MD-378-27
APPENDIX B
ROADWAY EMBANKMENT
DESIGN CRITERIA
HW - TW > 10'* AND HW/D > 2, OR
PERMANENT POOL > 3' OR
PROPOSED RISER
No
NO SPECIAL DESIGN
Yes
MEETS SMALL POND CRITERIA, AND
CLASS "A"
No
MDE DAM SAFETY
REVIEW
Yes
8:1 PROJECTION LINE INTERSECTS
DOWNSTREAM SLOPE OF THE
EMBANKMENT
No
SPECIAL
EMBANKMENT
DESIGN
Yes
MD 378
Design
Use any nonorganic soils for the
embankment, elimination of the
cut-off trench and core based on
approval of geotechnical engineer
and acceptable to local jurisdictions.
Filter diaphragm is required.
All other MD 378 criteria apply.
NRCS - MARYLAND
JANUARY 2000
Supplemental Pond and Wetland Specifications (Non-378)
Appendix
B.1.1
Appendix B.1.1 Supplemental Specifications (Non-378)
Supplemental Stormwater Pond and Wetland Specifications (Non-378)
These notes and specifications are in addition to the MD-378 Specifications. If there is any question
as to their applicability, the MD-378 Specifications supercede.
1.
It is preferred to use the same material in the embankment as is being installed for the core
trench. If this is not possible because the appropriate material is not available, a dam core
with a shell may be used. The cross-section of the stormwater facility should show the limits
of the dam core (up to the 10-year water surface elevation) as well as the acceptable
materials for the shell. The shape of the dam core and the material to be used in the shell
should be provided by the geotechnical engineer.
2.
If the compaction tests for site improvements is using a Modified Proctor (AASHTO T-180),
then to maintain on-site consistency, the Modified Proctor may be used in lieu of a Standard
Proctor (AASHTO T-99). The minimum required density using the Modified Proctor test
method shall be at least 92% of maximum dry density with a moisture content of ±2% of the
optimum. The minimum required density using the Standard Proctor test method shall be at
least 95% of the maximum dry density with a moisture content of ±2% of the optimum.
3.
For all stormwater management facilities, a geotechnical engineer or their representative
must be present to verify compaction in accordance with the selected test method. This
information needs to be provided in a report to the design engineer, so that certification of
the construction of the facility, in accordance with MD-378 specifications, can be made.
4.
A 4-inch layer of topsoil shall be placed on all disturbed areas of the dam embankment.
Seeding, liming, fertilizing, mulching, etc. shall be in accordance with Maryland Soil
Conservation Service MD-342 or the 1994 Maryland Standards and Specifications for Soil
Erosion and Sediment Control “Permanent Seeding,” Section in Chapter 20. The purpose of
the topsoil is to establish a good growth of grass which is not always possible with some of
the materials that may be placed for the embankment fill.
5.
Geotextile placed beneath rip-rap shall be Class “C” geotextile or better (see Section 24.0,
Material Specifications, 1994 Standards and Specifications for Soil Erosion and Sediment
Control (MDE, 1994). Some acceptable geotextiles that meet the Class “C” criteria include:
Amoco 4552
GEOLON N70
WEBTEC N07
Carthage FX-70S
Mirafi 180-N
B.1.1.1
Appendix B.1.1 Supplemental Specifications (Non-378)
This is only a partial listing of available geotextiles based on information provided by the
manufacturers to the 1997 Specifier's Guide dated December 1996. It is the responsibility of
the engineer to verify the adequacy of the material, as there are changes in the manufacturing
process and the type of fabric used, which may affect the continued acceptance.
6.
A rule of thumb to determine when an excavated pond may need to be considered an
embankment pond is as follows:
•
Provide calculation of 10H + 20 feet = L, where H equals height from pond bottom
to top of dam. If the projection of L, downstream in a horizontal line from the
upstream toe of slope is below existing ground, the pond can be considered an
excavated pond. In addition, the existing ground slope, downstream of the toe, must
be less than 10%.
7.
The design engineer and geotechnical engineer should make the determination that the
settlement of the pond will not cause excessive joint extension. For further information on
joint extension analysis, see NRCS Publication TR-18.
8.
Fill placement shall not exceed a maximum 8-inch. Each lift shall be continuous for the
entire length of the embankment.
9.
The embankment fill shall not be placed higher than the centerline of the principal spillway
until after the principal spillway has been installed. If the embankment needs to be
excavated to install the principal spillway, the side slope shall be no less than 2:1.
10.
The side slopes of a cut to repair a dam, install a principal spillway for an excavated pond, or
other repair work, shall be no less than 2:1.
B.1.1.2
Appendix
MDE Dam Safety Division Small Pond Review Criteria
B.1.2
MDE Dam Safety Division Small Pond Review and Approval Criteria
Appendix B.1.2. Small Pond Approval Criteria
The following criteria are established for the MDE Dam Safety Division small pond review and
approval:
1) If any of the following apply, a permit is required from the MDE Dam Safety Division:
a) Drainage area of the pond is greater than 640 acres.
b) Dam embankment height is greater than 20 feet (top of dam to lowest point on the
upstream toe).
c) Pond is an intermediate or high hazard structure the failure of which is likely to cause
damage to homes, public transportation, loss of life or property (NRCS Class b & c).
2) If the pond is in a USE III watershed, a permit is required if the pond will be:
a) Capturing a flowing stream (stream with a base flow*),
b) Capturing any spring, or
c) A wet pond, or
d) Located within 100 feet of a flowing stream, or
e) Proposes extended detention for the one year storm longer than 12 hours.
3) If the pond is located within the drainage of the Gwynns Falls, Jones Falls, or Herring Run
streams situated in or adjacent to Baltimore City, approval is required in accordance with the
provisions of the Maryland Environment Article 5-503.
4) If the pond is to be constructed across a stream, excluding USE III waters, SCD may approve
the pond with verification that the 100 year pool based on ultimate development with current
zoning does not increase flooding on adjacent properties or is in a floodplain easement. The
in-stream closure period must be noted on the plans.
5) If the pond is in the floodplain, an MDE Nontidal Wetlands and Waterways Permit may be
required. The pond will be evaluated for potential impacts in the floodplain and to nontidal
wetlands. However, the pond construction plans may be approved by the SCD.
* “Base Flow” or “Dry Weather Flow” - Stream flows originating from groundwater or spring
contributions that are not influenced by storm events. Base flow measurements should not be
made within two days of a storm event.
B.1.2.1
Appendix B.1.2. Small Pond Approval Criteria
Figure B.1.2.1 Small Pond Review Flow Chart
This flow chart is intended to determine whether MDE or the local SCD will review construction plans.
SCD pond approval does not relieve the applicant from obtaining other necessary approvals associated
with pond construction such as impacts to nontidal wetlands.
B.1.2.2
Construction Specifications for Infiltration Practices
Appendix
B.2
Appendix B.2. Construction Specifications for Infiltration Practices
B.2.A Infiltration Trench General Notes and Specifications
An infiltration trench may not receive run-off until the entire contributing drainage area to the
infiltration trench has received final stabilization.
1.
Heavy equipment and traffic shall be restricted from traveling over the proposed location of
the infiltration trench to minimize compaction of the soil.
2.
Excavate the infiltration trench to the design dimensions. Excavated materials shall be
placed away from the trench sides to enhance trench wall stability. Large tree roots must be
trimmed flush with the trench sides in order to prevent fabric puncturing or tearing of the
filter fabric during subsequent installation procedures. The side walls of the trench shall be
roughened where sheared and sealed by heavy equipment.
3.
A Class “C” geotextile or better (see Section 24.0, Material Specifications, 1994
Standards and Specifications for Soil Erosion and Sediment Control, MDE, 1994) shall
interface between the trench side walls and between the stone reservoir and gravel filter
layers. A partial list of non-woven filter fabrics that meet the Class “C” criteria follows.
Any alternative filter fabric must be approved by the plan approval authority.
Amoco 4552
GEOLON N70
WEBTEC N07
Carthage FX-80S
Mirafi 180-N
The width of the geotextile must include sufficient material to conform to trench perimeter
irregularities and for a 6-inch minimum top overlap. The filter fabric shall be tucked under
the sand layer on the bottom of the infiltration trench for a distance of 6 to 12 inches. Stones
or other anchoring objects should be placed on the fabric at the edge of the trench to keep the
trench open during windy periods. When overlaps are required between rolls, the uphill roll
should lap a minimum of 2 feet over the downhill roll in order to provide a shingled effect.
4.
If a 6 inch sand filter layer is placed on the bottom of the infiltration trench, the sand for the
infiltration trench shall be washed and meet AASHTO-M-43, Size No. 9 or No. 10. Any
alternative sand gradation must be approved by the plan approval authority.
5.
The stone aggregate should be placed in a maximum loose lift thickness of 12 inches. The
gravel (rounded “bank run” gravel is preferred) for the infiltration trench shall be washed
and meet one of the following AASHTO-M-43, Size No. 2 or No. 3.
6.
Following the stone aggregate placement, the filter fabric shall be folded over the stone
aggregate to form a 6-inch minimum longitudinal lap. The desired fill soil or stone
aggregate shall be placed over the lap at sufficient intervals to maintain the lap during
subsequent backfilling.
B.2.1
Appendix B.2. Construction Specifications for Infiltration Practices
7.
Care shall be exercised to prevent natural or fill soils from intermixing with the stone
aggregate. All contaminated stone aggregate shall be removed and replaced with
uncontaminated stone aggregate.
8.
Voids may occur between the fabric and the excavation sides shall be avoided. Removing
boulders or other obstacles from the trench walls is one source of such voids. Therefore,
natural soils should be placed in these voids at the most convenient time during construction
to ensure fabric conformity to the excavation sides.
9.
Vertically excavated walls may be difficult to maintain in areas where soil moisture is high
or where soft cohesive or cohesionless soils are dominant. These conditions may require
laying back of the side slopes to maintain stability.
10.
PVC distribution pipes shall be Schedule 40 and meet ASTM-D-1785. All fittings shall
meet ASTM-D-2729. Perforations shall be 3/8 inch in diameter. A perforated pipe shall be
provided only within the infiltration trench and shall terminate 1 foot short of the infiltration
trench wall. The end of the PVC pipe shall be capped. Note: PVC pipe with a wall
thickness classification of SDR-35 meeting ASTM-D-3034 is an acceptable substitute for the
Schedule 40 pipe.
11.
The observation well is to consist of 6-inch diameter perforated PVC Schedule 40 pipe (M
278 OR F758, Type PS 28) with a cap set 6 inches above ground level and is to be located
near the longitudinal center of the infiltration trench. The pipe shall have a plastic collar
with ribs to prevent rotation when removing the cap. The screw top lid shall be a cleanout
with a locking mechanism or special bolt to discourage vandalism. The depth to the invert
shall be marked on the lid. The pipe shall be placed vertically within the gravel portion of
the infiltration trench and a cap provided at the bottom of the pipe. The bottom of the cap
shall rest on the infiltration trench bottom.
12.
Corrugated metal distribution pipes shall conform to AASHTO-M-36, and shall be
aluminized in accordance with AASHTO-M-274. Aluminized pipe in contact with concrete
shall be coated with an inert compound capable of preventing the deleterious effect of the
aluminum on the concrete. Perforated distribution pipes shall conform to AASHTO-M-36,
Class 2 and shall be provided only within the infiltration trench and shall terminate 1 foot
short of the infiltration trench wall. An aluminized metal plate shall be welded to the end of
the pipe.
13.
If a distribution structure with a wet well is used, a 4-inch drain pipe shall be provided at
opposite ends of the infiltration trench distribution structure. Two (2) cubic feet of porous
backfill meeting AASHTO-M-43, Size No. 57 shall be provided at each drain.
B.2.2
Appendix B.2. Construction Specifications for Infiltration Practices
14.
If a distribution structure is used, the manhole cover shall be bolted to the frame.
B.2.B Infiltration Basins Notes and Specifications
An infiltration basin may not receive run-off until the entire contributing drainage area to the basin
has received final stabilization.
1.
The sequence of various phases of basin construction shall be coordinated with the overall
project construction schedule. A program should schedule rough excavation of the basin
with the rough grading phase of the project to permit use of the material as fill in earthwork
areas. The partially excavated basin, however, cannot serve as a sedimentation basin.
Specifications for basin construction should state: (1) the earliest point in progress when
storm drainage may be directed to the basin, and (2) the means by which this delay in use is
to be accomplished. Due to the wide variety of conditions encountered among projects, each
should be separately evaluated in order to postpone use as long as is reasonably possible.
2.
Initial basin excavation should be carried to within 2 feet of the final elevation of the basin
floor. Final excavation to the finished grade should be deferred until all disturbed areas on
the watershed have been stabilized or protected. The final phase excavation should remove
all accumulated sediment. Relatively light tracked equipment is recommended for this
operation to avoid compaction of the basin floor. After the final grading is completed, the
basin should provide a well-aerated, highly porous surface texture.
3.
Infiltration basins may be lined with a 6- to 12-inch layer of filter material such as coarse
sand (AASHTO-M-43, Sizes 9 or 10) to help prevent the buildup of impervious deposits on
the soil surface. The filter layer can be replaced or cleaned when it becomes clogged. When
a 6-inch layer of coarse organic material is specified for discing (such as hulls, leaves, stems,
etc.) or spading into the basin floor to increase the permeability of the soils, the basin floor
should be soaked or inundated for a brief period, then allowed to dry subsequent to this
operation. This induces the organic material to decay rapidly, loosening the upper soil layer.
4.
Establishing dense vegetation on the basin side slopes and floor is recommended. A dense
vegetative stand will not only prevent erosion and sloughing, but will also provide a natural
means of maintaining relatively high infiltration rates. Erosion protection of inflow points to
the basin shall also be provided.
5.
Selection of suitable vegetative materials for the side slope and all other areas to be
stabilized with vegetation and application of soil amendments (e.g., lime, fertilizer, etc.)
shall be done in accordance with the NRCS Standards and Specifications for Critical Area
B.2.3
Appendix B.2. Construction Specifications for Infiltration Practices
Planting (MD-342) or the 1994 Maryland Standards and Specifications for Soil Erosion and
Sediment Control.
6.
Grasses of the fescue family are recommended for seeding primarily due to their adaptability
to dry sandy soils, drought resistance, hardiness, and ability to withstand brief inundations.
The use of fescues will also permit long intervals between mowings. This is important due
to the relatively steep slopes which make mowing difficult. Mowing twice a year, once in
June and again in September, is generally satisfactory. Refertilization with 10-6-4 ratio
fertilizer at a rate of 500 lb per acre (11 lb per 1000 sq ft) may be required the second year
after seeding.
B.2.4
Construction Specifications for
Sand Filters, Bioretention and Open Channels
Appendix
B.3
Appendix B.3. Construction Specifications for Sand Filters, Bioretention and Open Channels
B.3.A Sand Filter Specifications
1.
Material Specifications for Sand Filters
The allowable materials for sand filter construction are detailed in Table B.3.1.
2.
Sand Filter Testing Specifications
Underground sand filters, facilities within sensitive groundwater aquifers, and filters designed to
serve urban hot spots are to be tested for water tightness prior to placement of filter media. Entrances
and exits should be plugged and the system completely filled with water to demonstrate water
tightness. Water tightness means no leakage for a period of 8 hours.
All overflow weirs, multiple orifices and flow distribution slots are to be field-tested to verify
adequate distribution of flows.
3.
Sand Filter Construction Specifications
Provide sufficient maintenance access (i.e., 12-foot-wide road with legally recorded easement).
Vegetated access slopes are to be a maximum of 10%; gravel slopes to 15%; paved slopes to 25%.
Absolutely no runoff is to enter the filter until all contributing drainage areas have been stabilized.
Surface of filter bed is to be level.
All underground sand filters should be clearly delineated with signs so that they may be located
when maintenance is due.
Surface sand filters may be planted with appropriate grasses; see Appendix A.
“Pocket” sand filters (and residential bioretention facilities treating areas larger than an acre) shall
be sized with a stone “window” that covers approximately 10% of the filter area. This “window”
shall be filled pea gravel (3/4 inch stone).
B.3.1
Appendix B.3. Construction Specifications for Sand Filters, Bioretention and Open Channels
4.
Specifications Pertaining to Underground Sand Filters (F-2)
Provide manhole and/or grates to all underground and below grade structures. Manholes shall be in
compliance with standard specifications for each county but diameters should be 30” minimum (to
comply with OSHA confined space requirements). Aluminum and steel louvered doors are also
acceptable. Ten inch wide (minimum) manhole steps (12” o.c.) shall be cast in place or drilled and
mortared into the wall below each manhole. A 5’ minimum height clearance (from the top of the
sand layer to the bottom of the upper/surface slab) is required for all permanent underground
structures. Lift rings are to be supplied to remove/replace top slabs on pre-fabricated structures.
Manhole covers should allow for proper ventilation.
Underground sand filters should be constructed with a gate valve located just above the top of the
filter bed for dewatering in the event that clogging occurs.
Underground sand beds shall be protected from trash accumulation by a wide mesh geotextile screen
to be placed on the surface of the sand bed; screen is to be rolled up, removed, cleaned and reinstalled during maintenance operations.
B.3.2
Material
sand
Specification/Test Method
clean AASHTO-M-6 or ASTM-C-33
concrete sand
Size
0.02” to 0.04”
Notes
Sand substitutions such as Diabase and Graystone #10 are not acceptable.
No calcium carbonated or dolomitic sand substitutions are acceptable. No
“rock dust” can be used for sand.
peat
ash content: < 15%
pH range: 5.2 to 4.9
loose bulk density 0.12 to 0.15 g/cc
n/a
The material must be reed-sedge hemic peat, shredded, uncompacted,
uniform, and clean.
leaf compost
underdrain gravel
geotextile fabric (if required)
impermeable liner
(if required)
B.3.3
underdrain piping
AASHTO-M-43
ASTM-D-4833 (puncture strength 125 lb.)
ASTM-D-4632 (Tensile Strength 300 lb.)
ASTM-D-4833 (thickness)
ASTM-D-412 (tensile strength 1,100
lb., elongation 200%)
ASTM-D-624 (Tear resistance - 150
lb./in)
ASTM-D-471 (water adsorption: +8
to -2% mass)
F 758, Type PS 28 or AASHTO-M278
concrete (cast-in-place)
MSHA Standards and Specs. Section
902, Mix No. 3, f’c = 3500 psi,
normal weight, air-entrained; reinforcing to meet ASTM-615-60
concrete (pre-cast)
non-rebar steel
per pre-cast manufacturer
ASTM A-36
n/a
0.375” to 0.75”
0.08” thick
equivalent opening
size of #80 sieve
Must maintain 125 gpm per sq. ft. flow rate. Note: a 4” pea gravel layer
may be substituted for geotextiles meant to “separate” sand filter layers.
30 mil thickness
Liner to be ultraviolet resistant. A geotextile fabric should be used to
protect the liner from puncture.
4” - 6” rigid
schedule 40 PVC
or SDR35
n/a
3/8” perf. @ 6” on center, 4 holes per row; minimum of 3” of gravel over
pipes; not necessary underneath pipes
n/a
n/a
on-site testing of poured-in-place concrete required:
28 day strength and slump test; all concrete design (cast-in-place or precast) not using previously approved State or local standards requires
design drawings sealed and approved by a professional structural
engineer licensed in the State of Maryland
SEE ABOVE NOTE
structural steel to be hot-dipped galvanized ASTM-A-123
Appendix B.3. .. ............Construction Specifications for Sand Filters, Bioretention and Open Channels
Table B.3.1 Material Specifications for Sand Filters
Appendix B.3. Construction Specifications for Sand Filters, Bioretention and Open Channels
B.3.B Specifications for Bioretention
1.
Material Specifications
The allowable materials to be used in bioretention area are detailed in Table B.3.2.
2.
Planting Soil
The soil shall be a uniform mix, free of stones, stumps, roots or other similar objects larger than two
inches. No other materials or substances shall be mixed or dumped within the bioretention area that
may be harmful to plant growth, or prove a hindrance to the planting or maintenance operations. The
planting soil shall be free of Bermuda grass, Quackgrass, Johnson grass, or other noxious weeds as
specified under COMAR 15.08.01.05.
The planting soil shall be tested and shall meet the following criteria:
pH range
organic matter
magnesium
phosphorus (phosphate - P2O5)
potassium (potash - K2O)
soluble salts
5.2 - 7.0
1.5 - 4% (by weight)
35 lb./ac
75 lb./ac
85 lb./ac
not to exceed 500 ppm
All bioretention areas shall have a minimum of one test. Each test shall consist of both the standard
soil test for pH, phosphorus, and potassium and additional tests of organic matter, and soluble salts.
A textural analysis is required from the site stockpiled topsoil. If topsoil is imported, then a texture
analysis shall be performed for each location where the top soil was excavated.
Since different labs calibrate their testing equipment differently, all testing results shall come from
the same testing facility.
Should the pH fall out of the acceptable range, it may be modified (higher) with lime or (lower) with
iron sulfate plus sulfur.
3.
Compaction
It is very important to minimize compaction of both the base of the bioretention area and the
required backfill. When possible, use excavation hoes to remove original soil. If bioretention
areas are excavated using a loader, the contractor should use wide track or marsh track equipment, or
light equipment with turf type tires. Use of equipment with narrow tracks or narrow tires, rubber
tires with large lugs, or high pressure tires will cause excessive compaction resulting in reduced
B.3.4
Appendix B.3. Construction Specifications for Sand Filters, Bioretention and Open Channels
infiltration rates and is not acceptable. Compaction will significantly contribute to design failure.
Compaction can be alleviated at the base of the bioretention facility by using a primary tilling
operation such as a chisel plow, ripper, or subsoiler. These tilling operations are to refracture the soil
profile through the 12 inch compaction zone. Substitute methods must be approved by the engineer.
Rototillers typically do not till deep enough to reduce the effects of compaction from heavy
equipment.
Rototill 2 to 3 inches of sand into the base of the bioretention facility before backfilling the optional
sand layer. Pump any ponded water before preparing (rototilling) base.
When backfilling the topsoil over the sand layer, first place 3 to 4 inches of topsoil over the sand,
then rototill the sand/topsoil to create a gradation zone. Backfill the remainder of the topsoil to final
grade.
When backfilling the bioretention facility, place soil in lifts 12” to 18”. Do not use heavy equipment
within the bioretention basin. Heavy equipment can be used around the perimeter of the basin to
supply soils and sand. Grade bioretention materials with light equipment such as a compact loader
or a dozer/loader with marsh tracks.
4.
Plant Material
Recommended plant material for bioretention areas can be found in Appendix A, Section A.2.3.
5.
Plant Installation
Mulch should be placed to a uniform thickness of 2” to 3”. Shredded hardwood mulch is the only
accepted mulch. Pine mulch and wood chips will float and move to the perimeter of the bioretention
area during a storm event and are not acceptable. Shredded mulch must be well aged (6 to 12
months) for acceptance.
Root stock of the plant material shall be kept moist during transport and on-site storage. The plant
root ball should be planted so 1/8th of the ball is above final grade surface. The diameter of the
planting pit shall be at least six inches larger than the diameter of the planting ball. Set and maintain
the plant straight during the entire planting process. Thoroughly water ground bed cover after
installation.
Trees shall be braced using 2” by 2” stakes only as necessary and for the first growing season only.
Stakes are to be equally spaced on the outside of the tree ball.
Grasses and legume seed should be drilled into the soil to a depth of at least one inch. Grass and
legume plugs shall be planted following the non-grass ground cover planting specifications.
The topsoil specifications provide enough organic material to adequately supply nutrients from
natural cycling. The primary function of the bioretention structure is to improve water quality.
B.3.5
Appendix B.3. Construction Specifications for Sand Filters, Bioretention and Open Channels
Adding fertilizers defeats, or at a minimum, impedes this goal. Only add fertilizer if wood chips or
mulch are used to amend the soil. Rototill urea fertilizer at a rate of 2 pounds per 1000 square feet.
6.
Underdrains
Underdrains are to be placed on a 3’-0” wide section of filter cloth. Pipe is placed next, followed by
the gravel bedding. The ends of underdrain pipes not terminating in an observation well shall be
capped.
The main collector pipe for underdrain systems shall be constructed at a minimum slope of 0.5%.
Observation wells and/or clean-out pipes must be provided (one minimum per every 1000 square
feet of surface area).
7.
Miscellaneous
The bioretention facility may not be constructed until all contributing drainage area has been
stabilized.
B.3.6
Material
Plantings
planting soil
[2.5’ to 4’ deep]
Specification
see Appendix A, Table A.4
sand
35 - 60%
silt
30 - 55%
clay
10 - 25%
mulch
pea gravel diaphragm and
curtain drain
shredded hardwood
pea gravel: ASTM-D-448
geotextile
B.3.7
underdrain gravel
underdrain piping
poured in place concrete (if
required)
sand
[1’ deep]
ornamental stone: washed
cobbles
Class “C” - apparent opening
size (ASTM-D-4751), grab
tensile strength (ASTM-D4632), puncture resistance
(ASTM-D-4833)
AASHTO M-43
F 758, Type PS 28 or AASHTO
M-278
MSHA Mix No. 3; f’c = 3500
psi @ 28 days, normal weight,
air-entrained; reinforcing to
meet ASTM-615-60
AASHTO-M-6 or ASTM-C-33
Size
n/a
n/a
Notes
plantings are site-specific
USDA soil types loamy sand, sandy loam or loam
aged 6 months, minimum
pea gravel: No. 6
stone:
2” to 5”
n/a
0.375” to 0.75”
4” to 6” rigid schedule 40
PVC or SDR35
n/a
0.02” to 0.04”
for use as necessary beneath underdrains only
3/8” perf. @ 6” on center, 4 holes per row; minimum of 3” of
gravel over pipes; not necessary underneath pipes
on-site testing of poured-in-place concrete required:
28 day strength and slump test; all concrete design (cast-in-place
or pre-cast) not using previously approved State or local
standards requires design drawings sealed and approved by a
professional structural engineer licensed in the State of Maryland design to include meeting ACI Code 350.R/89; vertical loading
[H-10 or H-20]; allowable horizontal loading (based on soil
pressures); and analysis of potential cracking
Sand substitutions such as Diabase and Graystone #10 are not
acceptable. No calcium carbonated or dolomitic sand substitutions
are acceptable. No “rock dust” can be used for sand.
Appendix B.3. Construction Specifications for Sand Filters, Bioretention and Open Channels
Table B.3.2 Materials Specifications for Bioretention
Appendix B.3. Construction Specifications for Sand Filters, Bioretention and Open Channels
B.3.C Specifications for Open Channels and Filter Strips
1.
Material Specifications
The recommended construction materials for open channels and filter strips are detailed in Table
B.3.3.
2.
Dry Swales
Permeable soil mixture (20” to 30” deep) should meet the bioretention “planting” soil specifications.
Check dams, if required, shall be placed as specified.
System to have 6” of freeboard, minimum above 2 year water surface elevation.
Side slopes to be 3:1 maximum; (4:1 or flatter is preferred).
No gravel or perforated pipe is to be placed under driveways.
Bottom of facility to be above the seasonally high water table per Table 2 of Appendix D.1.
Seed with flood/drought resistant grasses; see Appendix A, Section 2.4.
Longitudinal slope to be 4%, maximum.
Bottom width to be 8’ maximum to avoid braiding; larger widths may be used if proper berming is
supplied. Width to be 2’ minimum.
3.
Wet Swales
Follow above information for dry swales, with the following exceptions: the seasonally high water
table may inundate the swale; but not above the design bottom of the channel [NOTE: if the water
table is stable within the channel, the WQv storage may start at this point – see Figure 3.19]
Excavate into undisturbed soils; do not use an underdrain system.
4.
Filter Strips
Construct pea gravel diaphragms 12” wide, minimum, and 24” deep minimum.
B.3.8
Appendix B.3. Construction Specifications for Sand Filters, Bioretention and Open Channels
Pervious berms to be a sand/gravel mix [sand (35-60%), silt (30-55%), and gravel (10-25%)].
Berms to have overflow weirs with 6 inch minimum head.
Slope range to be 2% minimum to 6% maximum.
5.
Plant Selection
Recommended grass species for use in establishing permanent ground cover are provided in Section
2.4 of Appendix A.
B.3.9
Material
dry swale soil
dry swale sand
check dam (pressure treated)
check dam (natural wood)
filter strip sand/gravel pervious
berm
B.3.10
pea gravel diaphragm and curtain
drain
underdrain gravel
underdrain
geotextile
rip rap
Specification
USCS; ML, SM, SC
ASTM C-33 fine
aggregate concrete sand
AWPA Standard C6
Black Locust, Red
Mulberry, Cedars,
Catalpa, White Oak,
Chestnut Oak, Black
Walnut
sand: per dry swale sand
gravel; AASHTO M-43
Size
n/a
0.02” to 0.04”
Notes
soil with a higher percent organic content is preferred
6” by 6” or 8” by 8”
6” to 12” diameter;
notch as necessary
do not coat with creosote; embed at least 3’ into side slopes
do not use the following, as these species have a predisposition towards rot:
Ash, Beech, Birch, Elm, Hackberry, hemlock, Hickories, Maples, Red and
Black Oak, Pines, Poplar, Spruce, Sweetgum, Willow
sand: 0.02” to 0.04”
gravel: ½” to 1”
ASTM D 448
varies (No. 6) or (1/8”
to 3/8”)
0.25” to 0.75”
4” to 6” rigid schedule
40 PVC or SDR35
n/a
mix with approximately 25% loam soil to support grass cover crop;
sand (35-60%), silt (30-55%), and gravel (10-25%)
see Bioretention planting soil notes for more detail.
use clean bank-run gravel
AASHTO M-43
F 758 Type PS 28 or
AASHTO M-278
Class “C” - apparent
opening size (ASTM-D4751), grab tensile
strength (ASTM-D4632), puncture
resistance (ASTM-D4833)
per county criteria; if
none given, use MSHA
Standards and Specs
Section 905
size per county DOT
requirements based on
10-year design flows
3/8” perf. @ 6” on center, 4 holes per row; minimum of 3” of gravel over
pipes; not necessary underneath pipes
Appendix B.3. .. ............Construction Specifications for Sand Filters, Bioretention and Open Channels
Table B.3.3 Open Channel Systems and Filter Strip Materials Specifications
Construction Specifications for ESD Practices
Appendix
B.4
Appendix B.4. Construction Specifications for Environmental Site Design Practices
B.4.A Green Roof Specifications
1. Material Specifications
Because there is significant variation in green roof assemblies and methods, providing
comprehensive specifications is not feasible. Material specifications for green roofs will vary
based on each roofing system and specific information should be obtained from the appropriate
manufacturer or retailer. The following information and specifications, which include acceptable
materials for generic applications, is not exclusive or limiting.
2. Planting Media
Planting media should be a soil-like mixture with an organic content of 15% or less. The grain
size distribution is necessary for to attain proper moisture content, permeability, nutrient
management and non-capillary porosity, and soil structure. Grain size guidelines vary for single
and dual media green roof assemblies.
The planting media shall be tested and meet the following criteria:
•
•
•
•
•
•
•
•
•
•
Non-Capillary Pore Space at Field Capacity, 0.333 bar
(TMECC 03.01, A)
Moisture Content at Field Capacity
(TMECC 03.01, A)
Maximum Media Water Retention (FLL)
Alkalinity, CaCO3 equivalents (MSA)
Total Organic Matter by Wet Combustion (MSA)
pH (RCSTP)
Soluble Salts (DTPA saturated media extraction –
RCSTP)
Cation Exchange Capacity (MSA)
Saturated Hydraulic Conductivity (FLL):
o Single Media Assemblies
o Dual Media Assemblies
≥ 15% (volume)
≥ 12% (volume)
≥ 30% (volume)
≤ 2.5%
≤ 3–15% (dry wt.)
6.5 – 8.0
≤ 6 mmhos/cm
≥ 10 meq/100 g
≥ 0.05 in/min
≥ 0.30 in/min
Mineral Fraction Grain Size Distribution (ASTM D422):
o
o
o
o
o
o
Single Media
0
≤ 5%
≤ 10%
5 – 50%
20 – 70%
75 – 100%
Clay Fraction (2 micron)
% Passing #200 Sieve
% Passing # 60 Sieve
% Passing #18 Sieve
% Passing ⅛ inch Sieve
% Passing ⅜ inch Sieve
B.4.1
Dual Media
0
5 – 15%
10 – 25%
20 – 50%
55 – 90%
90 – 100%
Supp. 1
Appendix B.4. Construction Specifications for Environmental Site Design Practices
3. Green Roof Layers
Root Barriers – should be thermoplastic membranes with minimum thickness of 30 mils.
Membranes certified for use as root barriers are recommended. However, only FLL currently
offers a recognized certification test. Many FLL-certified materials are locally available.
Granular Drainage Media – should be a non-carbonate mineral aggregate meeting the following
specifications:
•
•
•
•
•
•
•
Saturated Hydraulic Conductivity
Total Organic Matter (by wet combustion)
Abrasion Resistance (ASTM C131-96)
Soundness (ASTM C88 or T103 or T103-91)
Porosity (ASTM C29)
Alkalinity, CaCO3 equivalents (MSA)
Grain Size Distribution (ASTM C136)
o Percent Passing #18 Sieve
o Percent Passing ¼ inch Sieve
o Percent Passing 3/8 inch Sieve
≥ 25 inches/minute
≤ 1%
≤ 25% loss
≤ 5% loss
≥ 25%
≤ 1%
≤1%
≤ 30%
≤ 80%
Separation Fabric – should be a lightweight, non-woven geotextile that is easily penetrated by
roots while providing a durable separation between drainage and growth media layers.
Separation fabrics should meet the following:
•
•
•
•
Unit Weight (ASTM D3776)
Grab Tensile Strength (ASTM D4632)
Mullen Burst Strength (ASTM D4632)
Permittivity (ASTM D4491)
Supp. 1
B.4.2
≤ 4.25 ounces per square yard
≤ 90 lbs.
≥ 135 lbs/inch
≥ 2 sec-1
Appendix B.4. Construction Specifications for Environmental Site Design Practices
B.4.B Specifications for Permeable Pavements & Reinforced Turf
These specifications include information on acceptable materials for typical applications and are
not exclusive or limiting. The designer is responsible for developing detailed specifications for
individual projects and specific conditions.
1.
Pervious Concrete Specifications
Design Thickness - Pervious concrete applications shall be designed so that the thickness of the
concrete slab shall support the traffic and vehicle types that will be carried. Applications may be
designed using either standard pavement procedures (e.g., AASHTO, ACI 325.9R, ACI 330R) or
using structural values derived from flexible pavement design procedures.
Mix & Installation – Traditional Portland cements (ASTM C 150, C 1157) may be used in
pervious concrete applications. Phosphorus admixtures may also be used. Materials should be
tested (e.g., trial batching) prior to construction so that critical properties (e.g., settling time, rate
of strength development, porosity, permeability) can be determined.
Aggregate – Pervious concrete contains a limited fine aggregate content. Commonly used
gradations include ASTM C 33 No. 67 (¾ in. to No. 4), No. 8 (⅜ in. to No. 16) and No. 89 (⅜ in.
to No. 50) sieves. Single-sized aggregate (up to 1 inch) may also be used.
Water Content – Water-to-cement ratios between 0.27 and 0.30 are used routinely with proper
inclusion of chemical admixtures. Water quality should meet ACI 30a. As a general rule,
potable water should be used although recycled concrete production water meetingASTM C 94
or AASHTO M 157 may also be used.
Admixtures – Chemical admixtures (e.g., retarders or hydration-stabilizers) are used to obtain
special properties in pervious concrete. Use of admixtures should meet ASTM C 494 (chemical
admixtures) and ASTM C 260 (air entraining admixtures) and closely follow manufacturer’s
recommendations.
Base Course – The base course shall be AASHTO No. 3 or 4 course aggregate with an assumed
open pore space of 30% (n = 0.30).
2.
Permeable Interlocking Concrete Pavements (PICP)
Paver Blocks – Blocks should be either 3⅛ in. or 4 in. thick, and meet ASTM C 936 or CSA
A231.2 requirements. Applications should have 20% or more (40% preferred) of the surface
area open. Installation should follow manufacturer’s instructions, except that infill and base
course materials and dimensions specified in this Appendix shall be followed.
Infill Materials and Leveling Course – Openings shall be filled with ASTM C-33 graded sand or
sandy loam. PICP blocks shall be placed on a one-inch thick leveling course of ASTM C-33
sand.
B.4.3
Supp. 1
Appendix B.4. Construction Specifications for Environmental Site Design Practices
Base Course - The base course shall be AASHTO No. 3 or 4 course aggregate with an assumed
open pore space of 30% (n = 0.30).
3.
Reinforced Turf
Reinforced Grass Pavement (RGP) – Whether used with grass or gravel, the RGP thickness shall
be at least 1¾” thick with a load capacity capable of supporting the traffic and vehicle types that
will be carried.
B.4.C Specifications for Micro-Bioretention. Rain Gardens, Landscape Infiltration &
Infiltration Berms
1.
Material Specifications
The allowable materials to be used in these practices are detailed in Table B.4.1.
2.
Filtering Media or Planting Soil
The soil shall be a uniform mix, free of stones, stumps, roots or other similar objects larger than
two inches. No other materials or substances shall be mixed or dumped within the microbioretention practice that may be harmful to plant growth, or prove a hindrance to the planting or
maintenance operations. The planting soil shall be free of Bermuda grass, Quackgrass, Johnson
grass, or other noxious weeds as specified under COMAR 15.08.01.05.
The planting soil shall be tested and shall meet the following criteria:
•
•
•
•
Soil Component - Loamy Sand or Sandy Loam (USDA Soil Textural Classification)
Organic Content - Minimum 10% by dry weight (ASTM D 2974). In general, this can be
met with a mixture of loamy sand (60%-65%) and compost (35% to 40%) or sandy loam
(30%), coarse sand (30%), and compost (40%).
Clay Content - Media shall have a clay content of less than 5%.
pH Range – Should be between 5.5 - 7.0. Amendments (e.g., lime, iron sulfate plus sulfur)
may be mixed into the soil to increase or decrease pH.
There shall be at least one soil test per project. Each test shall consist of both the standard soil
test for pH, and additional tests of organic matter, and soluble salts. A textural analysis is
required from the site stockpiled topsoil. If topsoil is imported, then a texture analysis shall be
performed for each location where the topsoil was excavated.
3.
Compaction
It is very important to minimize compaction of both the base of bioretention practices and the
required backfill. When possible, use excavation hoes to remove original soil. If practices are
Supp. 1
B.4.4
Appendix B.4. Construction Specifications for Environmental Site Design Practices
excavated using a loader, the contractor should use wide track or marsh track equipment, or light
equipment with turf type tires. Use of equipment with narrow tracks or narrow tires, rubber tires
with large lugs, or high-pressure tires will cause excessive compaction resulting in reduced
infiltration rates and is not acceptable. Compaction will significantly contribute to design
failure.
Compaction can be alleviated at the base of the bioretention facility by using a primary tilling
operation such as a chisel plow, ripper, or subsoiler. These tilling operations are to refracture the
soil profile through the 12 inch compaction zone. Substitute methods must be approved by the
engineer. Rototillers typically do not till deep enough to reduce the effects of compaction from
heavy equipment.
Rototill 2 to 3 inches of sand into the base of the bioretention facility before backfilling the
optional sand layer. Pump any ponded water before preparing (rototilling) base.
When backfilling the topsoil over the sand layer, first place 3 to 4 inches of topsoil over the sand,
then rototill the sand/topsoil to create a gradation zone. Backfill the remainder of the topsoil to
final grade.
When backfilling the bioretention facility, place soil in lifts 12” to 18”. Do not use heavy
equipment within the bioretention basin. Heavy equipment can be used around the perimeter of
the basin to supply soils and sand. Grade bioretention materials with light equipment such as a
compact loader or a dozer/loader with marsh tracks.
4.
Plant Material
Recommended plant material for micro-bioretention practices can be found in Appendix A,
Section A.2.3.
5.
Plant Installation
Compost is a better organic material source, is less likely to float, and should be placed in the
invert and other low areas. Mulch should be placed in surrounding to a uniform thickness of 2”
to 3”. Shredded or chipped hardwood mulch is the only accepted mulch. Pine mulch and wood
chips will float and move to the perimeter of the bioretention area during a storm event and are
not acceptable. Shredded mulch must be well aged (6 to 12 months) for acceptance.
Rootstock of the plant material shall be kept moist during transport and on-site storage. The plant
root ball should be planted so 1/8th of the ball is above final grade surface. The diameter of the
planting pit shall be at least six inches larger than the diameter of the planting ball. Set and
maintain the plant straight during the entire planting process. Thoroughly water ground bed
cover after installation.
B.4.5
Supp. 1
Appendix B.4. Construction Specifications for Environmental Site Design Practices
Trees shall be braced using 2” by 2” stakes only as necessary and for the first growing season only.
Stakes are to be equally spaced on the outside of the tree ball.
Grasses and legume seed should be drilled into the soil to a depth of at least one inch. Grass and
legume plugs shall be planted following the non-grass ground cover planting specifications.
The topsoil specifications provide enough organic material to adequately supply nutrients from natural
cycling. The primary function of the bioretention structure is to improve water quality. Adding
fertilizers defeats, or at a minimum, impedes this goal. Only add fertilizer if wood chips or mulch are
used to amend the soil. Rototill urea fertilizer at a rate of 2 pounds per 1000 square feet.
6.
Underdrains
Underdrains should meet the following criteria:
•
•
•
•
•
•
Pipe- Should be 4” to 6” diameter, slotted or perforated rigid plastic pipe (ASTMF 758, Type PS
28, or AASHTO-M-278) in a gravel layer. The preferred material is slotted, 4” rigid pipe (e.g.,
PVC or HDPE).
Perforations - If perforated pipe is used, perforations should be ⅜” diameter located 6” on center
with a minimum of four holes per row. Pipe shall be wrapped with a ¼” (No. 4 or 4x4) galvanized
hardware cloth.
Gravel – The gravel layer (No. 57 stone preferred) shall be at least 3” thick above and below the
underdrain.
The main collector pipe shall be at a minimum 0.5% slope.
A rigid, non-perforated observation well must be provided (one per every 1,0000 square feet) to
provide a clean-out port and monitor performance of the filter.
A 4” layer of pea gravel (⅛” to ⅜” stone) shall be located between the filter media and underdrain
to prevent migration of fines into the underdrain. This layer may be considered part of the filter
bed when bed thickness exceeds 24”.
The main collector pipe for underdrain systems shall be constructed at a minimum slope of 0.5%.
Observation wells and/or clean-out pipes must be provided (one minimum per every 1000 square feet
of surface area).
7.
Miscellaneous
These practices may not be constructed until all contributing drainage area has been stabilized
Supp. 1
B.4.6
Appendix B.4. Construction Specifications for Environmental Site Design Practices
Table B.4.1 Materials Specifications for Micro-Bioretention, Rain Gardens & Landscape InfiltrationMaterial
Plantings
Planting soil
[2’ to 4’ deep]
Organic content
Mulch
Pea gravel diaphragm
Curtain drain
Geotextile
Gravel (underdrains and
infiltration berms)
Specification
see Appendix A, Table A.4
loamy sand (60 - 65%) &
compost (35 – 40%)
or
sandy loam (30%),
coarse sand (30%) &
compost (40%)
Min. 10% by dry weight
(ASTM D 2974)
shredded hardwood
pea gravel: ASTM-D-448
ornamental stone: washed
cobbles
AASHTO M-43
Size
n/a
n/a
Notes
plantings are site-specific
USDA soil types loamy sand or sandy loam; clay content < 5%
aged 6 months, minimum; no pine or wood chips
NO. 8 OR NO. 9
(1/8" TO 3/8”)
stone:
2” to 5”
n/a
NO. 57 OR NO. 6
AGGREGATE
(3/8" to 3/4")
4” to 6” rigid schedule 40
PVC or SDR35
Underdrain piping
F 758, Type PS 28 or AASHTO
M-278
Poured in place concrete (if
required)
MSHA Mix No. 3; f’c = 3500
psi @ 28 days, normal weight,
air-entrained; reinforcing to
meet ASTM-615-60
n/a
Sand
AASHTO-M-6 or ASTM-C-33
0.02” to 0.04”
B.4.7
PE Type 1 nonwoven
Slotted or perforated pipe; 3/8” perf. @ 6” on center, 4 holes per
row; minimum of 3” of gravel over pipes; not necessary
underneath pipes. Perforated pipe shall be wrapped with ¼-inch
galvanized hardware cloth
on-site testing of poured-in-place concrete required:
28 day strength and slump test; all concrete design (cast-in-place
or pre-cast) not using previously approved State or local
standards requires design drawings sealed and approved by a
professional structural engineer licensed in the State of Maryland
- design to include meeting ACI Code 350.R/89; vertical loading
[H-10 or H-20]; allowable horizontal loading (based on soil
pressures); and analysis of potential cracking
Sand substitutions such as Diabase and Graystone (AASHTO)
#10 are not acceptable. No calcium carbonated or dolomitic sand
substitutions are acceptable. No “rock dust” can be used for sand.
Supp. 1
Design Example 1 – Shallow Wetland (W-1)
Appendix
C.1
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Design Example 1 – Shallow Wetland (W-1)
The following example demonstrates the process for the design of a shallow wetland (W-1)
BMP.
Site Specific Data
Clevenger Community Center is a recreational center located in Charles County, Maryland. The
site area and drainage area to the proposed stormwater management facility is 5.3 acres. The
project consists of constructing the community center and parking for a total impervious area of
1.94 acres. Existing ground at the outlet of the facility is 44.5’ above mean sea level (MSL).
Soil borings indicate that the seasonally high water table is at elevation 41’. The underlying soils
are loams. TR-55 calculations for the existing and developed hydrologic conditions are shown in
Figures C.1.2 and C.1.3.
Confirm Design Criteria
The site is within the Eastern Rainfall Zone and located on the Western Shore of the Chesapeake
Bay (see Volume I, Chapter 2, Figures 2.1 and 2.4). Additionally, the site is located within a
USE I watershed. Therefore, the following criteria apply:
1.
2.
3.
4.
WQv treatment is required. In the Eastern Rainfall Zone, P = 1”.
Rev treatment is required.
Cpv treatment is required.
Qp10 may be required by the local jurisdiction. For this example, Qp10 will be
required.
5. Qf may be required by the local jurisdiction. For this example, Qf will not be
required. However, safe conveyance of the 100-year design storm is required through
the proposed stormwater management facility.
Preliminary Design
Step 1. Compute WQv
Step 1a. Compute Volumetric Runoff Coefficient (Rv)
Rv
= 0.05 + (0.009)(I); I = 1.94 acres / 5.3 acres = 0.366 or 36.6%
= 0.05 + (0.009)(36.6) = 0.379
Step 1b. Compute WQv
WQv
= [(P)(Rv)(A)]!12
= [(1”)(0.379)(5.3 ac)]!12
= 0.167 ac-ft (7,292 cf.)
C.1.1
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Figure C.1.1 Clevenger Community Center Site Plan
C.1.2
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Figure C.1.2 Clevenger Community Center – Existing Conditions
(source: TR-55 computer printouts)
RUNOFF CURVE NUMBER COMPUTATION
Version 2.00
Project : CLEVENGER COMMUNITY CENTER
User: SRC
Date: 06-18-99
County : CHARLES
State: MD
Checked: ____
Date: ________
Subtitle: EXISTING
------------------------------------------------------------------------------Hydrologic Soil Group
COVER DESCRIPTION
A
B
C
D
Acres (CN)
------------------------------------------------------------------------------OTHER AGRICULTURAL LANDS
Meadow -cont. grass (non grazed) ---5.0(58)
Woods
good
0.3(55)
Total Area (by Hydrologic Soil Group)
5.3
------------------------------------------------------------------------------TOTAL DRAINAGE AREA: 5.3 Acres
WEIGHTED CURVE NUMBER: 58*
------------------------------------------------------------------------------* - Generated for use by GRAPHIC method
TIME OF CONCENTRATION AND TRAVEL TIME
Version 2.00
------------------------------------------------------------------------------Flow Type
2 year
Length
Slope Surface
n
Area
Wp
Velocity Time
rain
(ft)
(ft/ft)
code
(sq/ft) (ft) (ft/sec) (hr)
------------------------------------------------------------------------------Sheet
3.3
75
0.013
F
0.221
Shallow Concent'd
550
0.016
U
0.075
Open Channel
250
4.0
0.017
Time of Concentration = 0.31*
--- Sheet Flow Surface Codes --A Smooth Surface
F Grass, Dense
--- Shallow Concentrated --B Fallow (No Res.)
G Grass, Burmuda
--Surface Codes
--C Cultivated < 20 % Res.
H Woods, Light
P Paved
D Cultivated > 20 % Res.
I Woods, Dense
U Unpaved
E Grass-Range, Short
J Range, Natural
* - Generated for use by GRAPHIC method
GRAPHICAL PEAK DISCHARGE METHOD
Version 2.00
Data: Drainage Area
: 5.3 * Acres
Runoff Curve Number : 58 *
Time of Concentration: 0.31 * Hours
Rainfall Type
: II
Pond and Swamp Area : NONE
=========================================================================
| Storm Number
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|----------------------|------|------|------|------|------|------|------|
| Frequency (yrs)
|
1 |
2 |
5 | 10 | 25 | 50 | 100 |
| 24-Hr Rainfall (in) | 2.7 | 3.3 | 4.4 | 5.3 |
6 | 6.6 | 7.5 |
| Ia/P Ratio
| 0.54 | 0.44 | 0.33 | 0.27 | 0.24 | 0.22 | 0.19 |
|
Used
| 0.50 | 0.44 | 0.33 | 0.27 | 0.24 | 0.22 | 0.19 |
| Runoff (in)
| 0.18 | 0.38 | 0.85 | 1.34 | 1.76 | 2.14 | 2.76 |
| Unit Peak Discharge |0.460 |0.615 |0.835 |0.904 |0.929 |0.946 |0.967 |
|
(cfs/acre/in)
|
|
|
|
|
|
|
|
| Pond and Swamp Factor| 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
|
0.0% Ponds Used
|
|
|
|
|
|
|
|
|----------------------|------|------|------|------|------|------|------|
| Peak Discharge (cfs) |
0 |
1 |
4 |
6 |
9 |
11 |
14 |
=========================================================================
* - Value(s) provided from TR-55 system routines
C.1.3
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Figure C.1.3 Clevenger Community Center – Developed Conditions
(source: TR-55 computer printouts)
RUNOFF CURVE NUMBER COMPUTATION
Version 2.00
Project : CLEVENGER COMMUNITY CENTER
User: SRC
Date: 06-18-99
County : CHARLES
State: MD
Checked: ____
Date: ________
Subtitle: DEVELOPED
------------------------------------------------------------------------------Hydrologic Soil Group
COVER DESCRIPTION
A
B
C
D
Acres (CN)
------------------------------------------------------------------------------FULLY DEVELOPED URBAN AREAS (Veg Estab.)
Open space (Lawns,parks etc.)
Good condition; grass cover > 75%
- 3.06(61)
Impervious Areas
Paved parking lots, roofs, driveways
- 1.94(98)
OTHER AGRICULTURAL LANDS
Woods
good
0.3(55)
Total Area (by Hydrologic Soil Group)
5.3
------------------------------------------------------------------------------TOTAL DRAINAGE AREA: 5.3 Acres
WEIGHTED CURVE NUMBER: 74*
------------------------------------------------------------------------------* - Generated for use by GRAPHIC method
TIME OF CONCENTRATION AND TRAVEL TIME
Version 2.00
------------------------------------------------------------------------------Flow Type
2 year
Length
Slope Surface
n
Area
Wp
Velocity Time
rain
(ft)
(ft/ft)
code
(sq/ft) (ft) (ft/sec) (hr)
------------------------------------------------------------------------------Sheet
3.3
70
0.013
F
0.209
Shallow Concent'd
310
0.013
P
0.037
Open Channel
5.0
0.007
Time of Concentration = 0.26*
--- Sheet Flow Surface Codes --A Smooth Surface
F Grass, Dense
--- Shallow Concentrated --B Fallow (No Res.)
G Grass, Burmuda
--Surface Codes
--C Cultivated < 20 % Res.
H Woods, Light
P Paved
D Cultivated > 20 % Res.
I Woods, Dense
U Unpaved
E Grass-Range, Short
J Range, Natural
* - Generated for use by GRAPHIC method
GRAPHICAL PEAK DISCHARGE METHOD
Version 2.00
Data: Drainage Area
: 5.3 * Acres
Runoff Curve Number : 74 *
Time of Concentration: 0.26 * Hours
Rainfall Type
: II
Pond and Swamp Area : NONE
=========================================================================
| Storm Number
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|----------------------|------|------|------|------|------|------|------|
| Frequency (yrs)
|
1 |
2 |
5 | 10 | 25 | 50 | 100 |
| 24-Hr Rainfall (in) | 2.7 | 3.3 | 4.4 | 5.3 |
6 | 6.6 | 7.5 |
| Ia/P Ratio
| 0.26 | 0.21 | 0.16 | 0.13 | 0.12 | 0.11 | 0.09 |
|
Used
| 0.26 | 0.21 | 0.16 | 0.13 | 0.12 | 0.11 | 0.10 |
| Runoff (in)
| 0.72 | 1.10 | 1.90 | 2.61 | 3.18 | 3.70 | 4.48 |
| Unit Peak Discharge |0.995 |1.033 |1.076 |1.098 |1.110 |1.119 |1.124 |
|
(cfs/acre/in)
|
|
|
|
|
|
|
|
| Pond and Swamp Factor| 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
|
0.0% Ponds Used
|
|
|
|
|
|
|
|
|----------------------|------|------|------|------|------|------|------|
| Peak Discharge (cfs) |
4 |
6 |
11 |
15 |
19 |
22 |
27 |
=========================================================================
* - Value(s) provided from TR-55 system routines
C.1.4
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Step 2. Compute Rev
Step 2a. Determine Soil Specific Recharge Factor (S) Based on Hydrologic Soil Group
Soils found throughout the site are loams and silt loams therefore S = 0.26
Step 2b. Compute Rev Using Percent Volume Method
Rev
= [(S)(Rv)(A)]!12
= [(0.26)(0.379)(5.3)]!12
= 0.0456 ac-ft. (1,986 cf)
Step 2c. Compute Rev Using Percent Area Method
Rev
= (S)(Ai)
= (0.26)(1.94 ac.)
= 0.50 acres
The Rev requirement may be met by: a) treating 1,986 cf using structural methods, b) treating
0.50 acres using non-structural methods, or c) a combination of both (e.g. 994 cf structurally and
0.25 acres non-structurally).
Step 3. Compute Cpv
The proposed community center is located within a USE I watershed, therefore an extended
detention time (T) of 24 hours for the one-year storm event. The time of concentration (tc) and
one-year runoff (Qa) are 0.26 hours and 0.72” respectively (see Fig. C.1.3).
Use the MDE Method to Compute Storage Volume (Appendix D.11):
Initial abstraction (Ia) for CN of 74 is 0.703: (TR-55) [Ia = (200/CN)-2]
Ia/P = (0.703)!2.7” = 0.26
tc = 0.26 hours
qu = 625 csm/in.
(Figure D.11.1, Appendix D.11)
qi = quAQa
where A is the drainage area in square miles
= (625 csm)(0.0083 square miles)(0.72”)
= 3.7 cfs; qi > 2.0 cfs ∴ Cpv is required.
Knowing qu and T (extended detention time), find qo/qi from Figure D.11.2, “Detention Time
Versus Discharge Ratios.”
Peak outflow discharge / peak inflow discharge (qo/qi) = 0.030
C.1.5
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
With qo/qi, compute Vs!Vr for a Type II rainfall distribution,
Vs!Vr = 0.683 - 1.43(qo/qi) + 1.64(qo/qi)2 – 0.804(qo/qi)3 ; (Appendix D.11)
Vs!Vr = 0.64
Therefore, Vs = [(Vs!Vr)(Qa)(A)] ! 12
= [(0.64)(0.72”)(5.3 ac.)] ! 12
= 0.204 ac-ft (8,886 cf.)
With qo/qi, compute the Cpv release rate,
qo = (qo/qi)(qi); qi = 4.0 cfs
= (0.030)(4.0 cfs)
= 0.12 cfs
With qo, determine the required orifice area (Ao) for extended detention design:
Ao =
qo
qo
=
C 2 gho 4. 81 ho
“ho” is the maximum storage depth associated with Vs. For this example, assume ho to be
no more than 3.0 ft.
∴ Ao = (0.12 cfs) ! (4.81√3.0 ft)
= (0.12 cfs) ! (8.33 ft)
= 0.014 sf.
With Ao, determine the required orifice diameter (do):
do =
4 Ao
π
= 4 × 0. 014 sf
π = 0. 134 ft
(1.6”) USE 1.5”
“do’s” of less than 3” are subject to local jurisdictional approval, and are not recommended
unless an internal control for orifice protection is used. For this example, use a do of 3”.
Step 4. Compute Qp10 Storage Volume
Per TR-55, Figure 6-1 (Page 6-2 of TR-55) for an inflow (Qin) of 15 cfs and an allowable
outflow (Qout) of 6 cfs, the volume of storage (Vs) necessary for control is 0.37 ac-ft, with a
developed CN of 74 (see TR-55 Worksheet 6a, Page 6-5 of TR-55). Note that there is 5.3 inches
of rainfall during this event with 2.6 inches of runoff.
Step 5. Compute Qf
For this example, management of Qf is not required. However, the 100-year storm event must be
C.1.6
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
conveyed safely through the stormwater management practice.
Table C.1.1 Summary of General Storage Requirements for Clevenger Community Center
Step
Requirement
Volume Required
Notes
(acre-feet)
1.
2.
WQv
Rev
3.
4.
5.
Cpv
Qp10
Qf
0.167
0.0456
(or 0.50 acres)
0.204
0.36
N/A
volume is included within the WQv
storage
Cpv release rate is 0.10 cfs
10-year release rate is 6.0 cfs
provide safe passage for the 100-year
event in final design
Final Design
Step 1. BMP Selection Process
While the stormwater management BMP’s listed in Chapter 2.7 (Volume I) are
equivalent in meeting the established pollutant removal goals, site characteristics are an
important consideration in selecting the most appropriate BMP for a specific design. The
process outlined in Chapter 4 (Volume I) provides guidance for screening BMP’s as part of the
selection process.
∂
Watershed Factors: Is the project located in a watershed that has special design
objectives or constraints that must be met? This project is located in a USE I watershed
and there are no other special objectives or constraints that must be considered.
•
Terrain Factors: Is the project located in a portion of the State that has particular
design constraints imposed by local terrain and or underlying geology? The project is
located in a region of the State that has no constraints imposed by local terrain or underlying
geology
÷ Stormwater Treatment Suitability: Can the BMP meet all five stormwater criteria at
the site or are a combination of BMPs needed? For this project, a single BMP will not
satisfy all of the required criteria (see Table 4.3 BMP Selection Matrix No. 3). Therefore,
one BMP will treat WQv, Cpv, and Qp10 while a separate BMP will treat Rev.
C.1.7
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
≠ Physical Feasibility Factors: Are there any physical constraints at the project site that
may restrict or preclude the use of a particular BMP? Although the soils encountered are
infiltratable, the depth to the existing water table is less than 4.0’. Therefore infiltration is
not feasible for treating WQv. Additionally, the soils indicate that wet pond designs may
require a liner. Sand filters will require substantial pretreatment as the proposed
imperviousness is near 37%. The drainage area, 5.3 acres, is marginally low to support either
ponds or wetlands. However, the groundwater table may be sufficient to support a shallow
wetland.
≡ Community and Environmental Factors: Do the remaining BMPs have any important
community or environmental benefits or drawbacks that might influence the selection
process? The projected use of the site as a community center may require that BMPs
possess a greater acceptance by the community. Additionally, habitat quality is important if
environmental education is provided at the center. Finally, ease of maintenance and costs
relative to drainage area are important considerations as the sources of future funding may be
limited.
≈ Location and Permitting Factors: What environmental features must be avoided or
considered when locating the BMP system at a site to fully comply with local, State and
federal regulations? There are no wetlands, stream buffers, floodplains or forest
conservation areas located on the site although the area of existing woods should be
preserved if possible.
After considering all factors and the site layout, use a shallow wetland (W-1) for treating WQv.
Cpv and Qp10 will be treated by providing sufficient storage above the shallow wetland. Finally,
Rev will be treated prior to the wetland by providing storage around the inlet, I-1.
Step 2. Shallow Wetland (W-1) Design
Using the information developed in Preliminary Design Steps 1 and 2, design a shallow wetland
to treat WQv (see Figure C.1.4).
A. Calculate Design Volume
Because Rev will be treated prior to the shallow wetland, Rev may be subtracted from the
WQv for the design of this BMP:
WQv9 = WQv - Rev
= 7,292 cf. – 1,986 cf.
= 5,306 cf.
C.1.8
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
B. Calculate Pretreatment (Forebay) Volume
Forebays shall be sized to capture 10% of the design runoff volume (in this case WQv9) at
each inflow point; assume that inflow is divided equally between the two inflow points for
this design.
forebay volume
= (10%)(5,306 cf.! 2)
= 265.3 cf. at each inflow point
forebay volume provided =
800 cf. and 700 cf. respectively
B. Determine Shallow Wetland Size Criteria
Using the design criteria set forth in Chapter 3 for the design of shallow wetland systems, the
configuration shown in Figure C.1.4, and the information in Table C.1.2, design a shallow
wetland to treat WQv9. Specific criteria that govern the configuration of the shallow wetland
design are as follows.
1. Surface area 〈 1.5% 3 drainage area
〈 1.5% 3 5.3 acres
〈 0.0795 acres (3,463 sf.)
Surface area of shallow wetland at elevation 44.0 = 0.1366 acres (5,950 sf.) -OKAY
2. Deepwater (depth 〈 4’) zones 〈 25% 3 WQv9
〈 25% 3 5,306 cf.
〈 1,326.5 cf.
Deepwater zones provided = 1,950 cf. (forebays and micropool)
3. High marsh (depth [ 6”) zones 〈 35% 3 total surface area
〈 35% 3 3,463 sf.
〈 1,212.1 sf.
High marsh area provided = 2,160 sf.
4. Total marsh area (depth [ 18”) zones 〈 65% 3 total surface area
〈 65% 3 3,463 sf.
〈 2,251 sf.
Total marsh area provided = 4,200 sf.
5. Check for water balance (see Appendix D.3) for maintenance of wet pool:
a. Calculate maximum drawdown:
C.1.9
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Inflow Runoff Volume = P x E where P = Precipitation & E = Runoff Efficiency
- for a CN of 74, Volume of runoff (2 year storm) = 1.10”
- for Charles County, P (2 year rainfall) = 3.3” (0.275’)
- E = 1.1”!3.3” = 0.33
∴ Inflow = P x E = 0.275’ x 0.33 x 5.3 acres = 0.48 ac-ft
Outflow = surface area x evaporation losses
= 0.137 acres x 0.54 ft (see Table D.3.2)
= 0.074 ac-ft
Inflow (0.48 ac-ft) is greater than Outflow (0.074 ac-ft) –OKAY
b. Check for drawdown over an extended period without rainfall:
Using 45 day “worst case” drought conditions
- highest evaporation occurs in July – 0.54 ft per month
- average evaporation per day = 0.54/31 days = 0.017 ft/day
- over 45 day interval, evaporation loss = 45 x 0.017 ft/day = 0.78 ft.
- assume surface of wetland may drop up to 0.78 ft. over this interval -OKAY
C.1.10
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Table C.1.2 Stage – Storage Data for Stormwater Management Design
Elevation
Δ Storage
Stage - Storage Data
Storage
Storage
(cubic feet)
40.0
41.0
42.0
43.0
44.0
45.0
45.5
46.0
47.0
48.0
0.0
372.0
665.0
1,428.0
3,990.0
11,200.0
8,478.0
8,987.0
19,530.0
21,646.0
Storage Above WQv
(acre-feet)
0.0
372.0
1,037.0
2,465.0
6,455.0
17,665.0
26,133.0
35,120.0
54,650.0
76,296.0
Figure C.1.4 Plan View of Shallow Wetland Design
C.1.11
(acre-feet)
0.0
0.0085
0.0238
0.0566
0.1482
0.4055
0.5999
0.8062
1.2546
1.7515
0.0
0.2573
0.4517
0.6581
1.1064
1.6033
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Step 3. Cpv Design
Using the information from Preliminary Design Step 3, the stage–storage data from
Table C.1.2, and the stage-discharge data for the 3” orifice in Table C.1.3, design an extendeddetention basin to treat Cpv.
Table C.1.3 Stage – Discharge Data for Clevenger Community Center
Elevation
44.00
44.25
44.50
44.75
45.00
45.50
46.00
47.00
48.00
3” Orifice
Stage - Discharge Data
5.2’ Weir2
10.0’ Weir3
centerline – 44.125’
crest @ 45.00’
crest @ 45.50’
1
Head (h)
Discharge
0.0
0.1
0.4
0.6
0.9
1.4
1.9
2.9
3.9
0.00
0.085
0.150
0.194
0.229
0.287
0.335
0.415
0.482
Head (h)
0.0
0.5
1.0
2.0
3.0
Discharge
0.0
5.70
16.12
45.59
83.76
Head (h)
0.0
0.5
1.5
2.5
Total
Discharge
Discharge
0.0
10.96
56.95
122.53
0.00
0.085
0.150
0.194
0.229
5.70
27.08
102.54
206.29
1. Using orifice equation Q = ca 2 gh where c=0.61, a=0.05 sf., and g= 32.2 ft/sec2
2. Using weir equation Q = clh 3 2 where c= 3.1 & l =5.2’
3. Using weir equation Q = clh 3 2 where c= 3.1 & l =10.0’
From Preliminary Step 3, the storage volume (Vs) for Cpv is 0.204 ac-ft and the required orifice
diameter (do) is 3”. Using Table C.1.2 and starting at elevation 44.0, the storage volume of the
proposed stormwater management structure is 0.2573 ac-ft at elevation 45.0’. Therefore, Cpv
treatment will be provided between elevations 44.0’ and 45.0’.
Step 4. Qp10 Treatment
From Preliminary Step 5, the estimated storage volume (Vs) for treating Qp10 is 0.36 ac-ft and the
allowable discharge rate is 6.0 cfs. Using Table C.1.2 and starting at elevation 44.0’, the storage
volume of the proposed stormwater management structure is 0.4517 ac-ft at elevation 45.5’.
Therefore, design a control structure that will produce a discharge rate of 6.0 cfs at storage
elevation 45.5’. This will be a conservative design since the volume provided (0.4517 ac-ft) is
greater than the 0.36 ac-ft required. Using a weir with crest at elevation 45.0’ and including flow
from the 3” orifice, the ten-year discharge (q10) may be computed as follows:
q10 = cw lhw3 2 + co a 2 gho
where:
q10 = 10 yr. discharge = 6.0 cfs
C.1.12
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
cw = weir coefficient = 3.1
l = length of weir
hw = head on weir; at elevation 45.5, hw = 0.5’
co = orifice coefficient = 0.61
a = area of 3” orifice = 0.05
g = gravitational acceleration = 32 ft/sec2
ho = head on orifice; at elevation 45.5, ho = 1.375
therefore:
q10 = (3.1)(l)(0.5)3/2 + (0.61)(0.05)[(2)(32.2)(1.375)]1/2
6.0 cfs = 1.1l cfs + 0.29 cfs
by rearranging this equation and solving for l; l = 5.2’
use a 5.2’ weir with crest at elevation 45.0 –OKAY
Step 5. Qf Treatment
From Preliminary Step 5, the 100-year storm event must be conveyed safely through the
stormwater management facility. From Figure C.1.3, 100-year discharge rate (q100) is 27 cfs and
from Figure C.1.4, the top of the proposed stormwater management facility is at elevation 48.0’.
Allowing for 2.0’ of freeboard, design a control structure that will discharge 27 cfs at elevation
46.0’. Using a weir with crest at elevation 45.5’, including flow from the 5.5’ weir and assuming
that the 3” orifice is clogged, q100 may be computed as follows:
32
q100 = cl100 h100
+ cl10 h103 2
where:
q100 = 100 yr. discharge = 27 cfs.
c = weir coefficient = 3.1
l100 = length of 100 yr. weir
h100 = head on 100 yr. weir; at elev. 46.0’, h100 = 0.5’
l10 = length of 10 yr. weir = 5.2’
h10= head on 10 yr. weir; at elev. 46.0’, h10 = 1.0’
therefore:
q100 = (3.1)(l100)(0.5)3/2 + (3.1)(5.2’)(1.0)3/2
27 cfs = 1.1l100 cfs + 16.1 cfs
by rearranging this equation and solving for l100; l100 = 9.89’
use a 10.0’ weir with crest at elevation 45.5’ –OKAY
See Figure C.1.5 for a schematic of the control structure and Figure C.1.6 for a profile through
the centerline of the dam and control structure. See Figures C.1.7 and C.1.8 for the TR-20 input
and summary tables.
C.1.13
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Figure C.1.5 Schematic of Control Structure
Step 6. Investigate Potential Pond Hazard Classification
Using NRCS-MD Code No. 378 Pond Standards/Specifications (Appendix B.1), review
downstream conditions and compute a preliminary Breach Peak Discharge (Qmax) to determine
pond hazard classification.
Qmax = (3. 2 )( H w5 2 )
where:
Qmax = Breach Peak Discharge
Hw = depth of water at the dam at time of failure, in feet, and is measured
from the design high water to the lowest point in the original cross section
at the centerline of the dam; Hw = 46.0’ – 44.0’ = 2.0’
Qmax = (3.2)(2.0)5/2 = 18.1 cfs
Qmax will not overtop downstream roads or infrastructure, therefore the stormwater management
facility may be considered as a Class “a” low hazard structure per the NRCS-MD 378 standards.
C.1.14
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Figure C.1.6 Profile of Principle Spillway
C.1.15
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Figure C.1.7 TR-20 Computer Program Input File
JOB TR-20
TITLE
3 STRUCT
8
8
8
8
8
8
8
8
8
9 ENDTBL
6 RUNOFF
6 RESVOR
6 RUNOFF
ENDATA
7 INCREM
7 COMPUT
ENDCMP
7 INCREM
7 COMPUT
ENDCMP
7 INCREM
7 COMPUT
ENDCMP
7 INCREM
7 COMPUT
ENDCMP
ENDJOB
EXAMPLE1 ECON
FULLPRINT PASS=001 SUMMARY
DESIGN EXAMPLE 1 CLEVENGER COMMUNITY CENTER
01
44.0
0.0
0.0
44.25
0.12
0.060
44.5
0.17
0.128
44.75
0.21
0.180
45.0
0.24
0.2573
45.5
5.70
0.4517
46.0
27.08
0.6581
47.0
102.54
1.1064
48.0
206.29
1.6033
GRAPHICS
1 001
2
01 1
1 003
6
7
1
6
7
1
6
7
1
6
7
1
2
1 .00828
2 44.0
3 .00828
74.
0.26
58.
0.31
1 1
1 1 1
1 1 1 1 1 1
1 1
1 1 1
001
003
0.10
0.0
2.7
1.0
2 2
01
01
001
003
0.10
0.0
3.3
1.0
2 2
01
02
001
003
0.10
0.0
5.3
1.0
2 2
01
10
001
003
0.10
0.0
7.5
1.0
2 2
01
99
C.1.16
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Figure C.1.8 TR-20 Computer Program Output Summary Table
SUMMARY TABLE 1
--------------SELECTED RESULTS OF STANDARD AND EXECUTIVE CONTROL IN ORDER PERFORMED.
A CHARACTER FOLLOWING THE PEAK DISCHARGE TIME AND RATE (CFS) INDICATES:
F-FLAT TOP HYDROGRAPH
T-TRUNCATED HYDROGRAPH
R-RISING TRUNCATED HYDROGRAPH
XSECTION/
STRUCTURE
ID
STANDARD
CONTROL
OPERATION
DRAINAGE
AREA
(SQ MI)
RUNOFF
AMOUNT
(IN)
PEAK DISCHARGE
-----------------------------------ELEVATION
TIME
RATE
RATE
(FT)
(HR)
(CFS)
(CSM)
RAINFALL OF
2.70 inches AND 24.00 hr DURATION, BEGINS AT
RAINTABLE NUMBER 2,
ARC 2
MAIN TIME INCREMENT
.100 HOURS
ALTERNATE
1
STORM
1
--------------------------XSECTION
1 RUNOFF
.01
STRUCTURE 1 RESVOR
.01
XSECTION
3 RUNOFF
.01
XSECTION
3 RUNOFF
.01
RAINFALL OF
3.30 inches AND
ALTERNATE
1
STORM
2
--------------------------XSECTION
1 RUNOFF
.01
STRUCTURE 1 RESVOR
.01
XSECTION
3 RUNOFF
.01
.72
.71
.71
.71
---------
12.07T
.00
.00
.00
24.00 hr DURATION, BEGINS AT
1.10
1.09
.38
-------
12.06
.00
12.14T
RAINFALL OF
5.30 inches AND 24.00 hr DURATION, BEGINS AT
MAIN TIME INCREMENT
.100 HOURS
ALTERNATE
1
STORM
10
--------------------------XSECTION
1 RUNOFF
.01
STRUCTURE 1 RESVOR
.01
XSECTION
3 RUNOFF
.01
RAINFALL OF
7.50 inches AND
ALTERNATE
1
STORM
99
--------------------------XSECTION
1 RUNOFF
.01
STRUCTURE 1 RESVOR
.01
XSECTION
3 RUNOFF
.01
2.60
2.59
1.34
--45.50
---
12.05
12.32
12.10
24.00 hr DURATION, BEGINS AT
4.48
4.43
2.75
C.1.17
--45.84
---
12.04
12.18
12.09
.0 hrs.
4T
0
0
0
400.0
.0
.0
.0
.0 hrs.
7
0
1T
700.0
.0
100.0
.0 hrs.
16
6
7
1600.0
600.0
700.0
.0 hrs.
28
20
16
2800.0
2000.0
1600.0
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Step 7. Rev Treatment
Using the information developed n Preliminary Step 2, design a structural practice to treat Rev.
Non-structural practices will not be utilized therefore the entire Rev (1,986 cf) must be treated.
For this example, design an infiltration area around inlet I-1 (see Figure C.1.9) that will treat the
entire Rev. Because of its high visibility and the communal nature of the project, this infiltration
area will be designed and planted similar to a bioretention area.
The surface area around I-1 that is available for this practice has an area (A) of 2,250 sf. Using a
porosity (n) of 0.30* for the sand and planting soil mixture, the required depth (d) to treat the
entire Rev is equal to: [(Rev)!(A)] ! n
= [(1,986 cf.)!(2,250 sf.)] ! 0.30
= 0.883 ! 0.30
= 2.94 ft. Use d = 3.0 ft.
*Note: The porosity of mixed-grained sand varies from 0.30 (dense) to 0.40 (loose). Using the
minimum value, 0.30, results in a more conservative design.
Using a depth of 3.0’, a surface area of 2,250 sf. and a n of 0.3, storage for Rev treatment is equal
to:
(A3 d)3 n
= (2,250 sf. 3 3.0 ft.) 3 0.3
= 2,025 cf. -OKAY
Using the dimensions above, a cross section of the infiltration area is shown in Figure C.1.10.
Step 8. Landscaping
The BMP’s for both WQv and Rev treatment have specific landscaping requirements for proper
implementation. Therefore, landscaping plans developed in accordance with Chapter 3 and
using the guidelines provided in Appendix A will be required with submittal of the final design.
C.1.18
Appendix C.1. Design Example 1 – Shallow Wetland (W-1)
Figure C.1.9 Location of Rev Treatment
Figure C.1.10 Cross Section “A-A”
C.1.19
Design Example 2 – Water Quality BMPs
Appendix
C.2
Appendix C.2. Design Example 2 – Water Quality BMPs
Design Example 2 – Water Quality BMPs
The following example demonstrates the design of several different BMPs for WQv and Rev
treatment including filtering, infiltration, and open channel practices.
Figure C.2.1 Comstock Commercial Center Site Plan
Site Specifc Data
Comstock Commercial Center is a 0.77 acre retail store located in Howard County, Maryland.
The developed area of the site may be divided into two drainage areas of 0.20 and 0.22 acres
respectively with a remaining drainage area of 0.35 acres. Total impervious area for the
development is 0.36 acres; 0.16 acres in DA-1 and 0.20 acres in DA-2. Existing and proposed
topography are not given for this exercise; it may be assumed that these conditions are amenable
for each specific design. Likewise, the seasonally high water table will not be a factor in
infiltration designs. The underlying soils are loams (HSG B). TR-55 calculations for the
developed hydrologic conditions are shown in Figures C.2.2, C.2.3 and C.2.4.
C.2.1
Appendix C.2. Design Example 2 – Water Quality BMPs
C.2.1 Design Criteria
The site is within the Eastern Rainfall Zone and located on the Western Shore of the Chesapeake
Bay (see Volume I, Chapter 2, Figures 2.1 and 2.4). Additionally, the site is located within a
USE I watershed. Therefore, the following criteria apply:
WQv treatment is required. In the Eastern Rainfall Zone, P = 1”.
Rev treatment is required.
Cpv treatment is required.
Qp10 may be required by the local jurisdiction. For this example, Qp10 will not be
required.
5. Qf may be required by the local jurisdiction. For this example, Qf will not be
required. However, safe conveyance of the 100-year design storm is required through
the proposed stormwater management facility.
1.
2.
3.
4.
C.2.2 Preliminary Design
Step 1. Compute WQv
Step 1a. Compute Volumetric Runoff Coefficient (Rv)
Rv
= 0.05 + (0.009)(I); I = (0.36 acres / 0.77 acres) = 0.468or 46.8%
= 0.05 + (0.009)(46.8) = 0.471
Step 1b. Compute WQv
WQv
= [(P)(Rv)(A)]!12
= [(1”)(0.471)(0.77 ac)]!12
= 0.0302 ac-ft (1,316.5 cf.)
C.2.2
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.2 Comstock Commercial Center – Developed Conditions
(source: TR-55 computer printouts)
RUNOFF CURVE NUMBER COMPUTATION
Version 2.10
Project : COMSTOCK COMMERCIAL
User: SRC
Date: 09-17-1999
County : HOWARD
State: MD
Checked: ____
Date: ________
Subtitle: DEVELOPED CONDITIONS
-----------------------------------------------------------------------------Hydrologic Soil Group
COVER DESCRIPTION
A
B
C
D
Acres (CN)
------------------------------------------------------------------------------FULLY DEVELOPED URBAN AREAS (Veg Estab.)
Open space (Lawns,parks etc.)
Good condition; grass cover > 75%
- 0.41(61)
Impervious Areas
Paved parking lots, roofs, driveways
- 0.36(98)
Total Area (by Hydrologic Soil Group)
.77
------------------------------------------------------------------------------TOTAL DRAINAGE AREA: .77 Acres
WEIGHTED CURVE NUMBER: 78*
GRAPHICAL PEAK DISCHARGE METHOD
Project : COMSTOCK COMMERCIAL CENTER
County : HOWARD
State: MD
Subtitle: DEVELOPED CONDITIONS
Data: Drainage Area
:
Runoff Curve Number :
Time of Concentration:
Rainfall Type
:
Pond and Swamp Area :
.77
78
0.10
II
NONE
User: SRC
Checked: ____
Version 2.10
Date: 12-07-1999
Date: ________
Acres
Hours (MINIMUM VALUE)
=========================================================================
| Storm Number
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|----------------------|------|------|------|------|------|------|------|
| Frequency (yrs)
|
1 |
2 |
5 | 10 | 25 | 50 | 100 |
| 24-Hr Rainfall (in) | 2.6 | 3.2 | 4.2 | 5.1 | 5.6 | 6.3 | 7.2 |
| Ia/P Ratio
| 0.22 | 0.18 | 0.13 | 0.11 | 0.10 | 0.09 | 0.08 |
|
Used
| 0.22 | 0.18 | 0.13 | 0.11 | 0.10 | 0.10 | 0.10 |
| Runoff (in)
| 0.85 | 1.27 | 2.05 | 2.80 | 3.23 | 3.85 | 4.66 |
| Unit Peak Discharge |1.511 |1.534 |1.558 |1.572 |1.578 |1.578 |1.578 |
|
(cfs/acre/in)
|
|
|
|
|
|
|
|
| Pond and Swamp Factor| 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
|
0.0% Ponds Used
|
|
|
|
|
|
|
|
|----------------------|------|------|------|------|------|------|------|
| Peak Discharge (cfs) |
1 |
2 |
2 |
3 |
4 |
5 |
6 |
=========================================================================
* - Value(s) provided from TR-55 system routines
C.2.3
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.3 Comstock Commercial Center – Drainage Area (DA) 1
(source: TR-55 computer printouts)
RUNOFF CURVE NUMBER COMPUTATION
Version 2.10
Project : COMSTOCK COMMERCIAL
User: SRC
Date: 09-27-1999
County : HOWARD
State: MD
Checked: ____
Date: ________
Subtitle: DRAINAGE AREA DA-1
------------------------------------------------------------------------------Hydrologic Soil Group
COVER DESCRIPTION
A
B
C
D
Acres (CN)
------------------------------------------------------------------------------FULLY DEVELOPED URBAN AREAS (Veg Estab.)
Open space (Lawns,parks etc.)
Good condition; grass cover > 75%
- .04 (61)
Impervious Areas
Paved parking lots, roofs, driveways
-
0.16(98)
-
-
Total Area (by Hydrologic Soil Group)
.20
====
------------------------------------------------------------------------------TOTAL DRAINAGE AREA: .20 Acres
WEIGHTED CURVE NUMBER: 91*
------------------------------------------------------------------------------* - Generated for use by GRAPHIC method
GRAPHICAL PEAK DISCHARGE METHOD
Project : COMSTOCK COMMERCIAL CENTER
County : HOWARD
State: MD
Subtitle: DEVELOPED CONDITIONS DA-1
Data: Drainage Area
:
Runoff Curve Number :
Time of Concentration:
Rainfall Type
:
Pond and Swamp Area :
User: SRC
Checked: ____
Version 2.10
Date: 12-07-1999
Date: ________
.2
Acres
91
0.10
Hours
II
NONE
=========================================================================
| Storm Number
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|----------------------|------|------|------|------|------|------|------|
| Frequency (yrs)
|
1 |
2 |
5 | 10 | 25 | 50 | 100 |
| 24-Hr Rainfall (in) | 2.6 | 3.2 | 4.2 | 5.1 | 5.6 | 6.3 | 7.2 |
| Ia/P Ratio
| 0.08 | 0.06 | 0.05 | 0.04 | 0.04 | 0.03 | 0.03 |
|
Used
| 0.10 | 0.10 | 0.10 | 0.10 | 0.10 | 0.10 | 0.10 |
| Runoff (in)
| 1.70 | 2.26 | 3.21 | 4.08 | 4.57 | 5.25 | 6.14 |
| Unit Peak Discharge |1.578 |1.578 |1.578 |1.578 |1.578 |1.578 |1.578 |
|
(cfs/acre/in)
|
|
|
|
|
|
|
|
| Pond and Swamp Factor| 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
|
0.0% Ponds Used
|
|
|
|
|
|
|
|
|----------------------|------|------|------|------|------|------|------|
| Peak Discharge (cfs) |
1 |
1 |
1 |
1 |
1 |
2 |
2 |
=========================================================================
C.2.4
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.4 Comstock Commercial Center – Drainage Area (DA) 2
(source: TR-55 computer printouts)
RUNOFF CURVE NUMBER COMPUTATION
Version 2.10
Project : COMSTOCK COMMERCIAL CENTER
User: SRC
Date: 09-21-1999
County : HOWARD
State: MD
Checked: ____
Date: ________
Subtitle: DRAINAGE AREA DA-2 DEVELOPED
------------------------------------------------------------------------------Hydrologic Soil Group
COVER DESCRIPTION
A
B
C
D
Acres (CN)
------------------------------------------------------------------------------FULLY DEVELOPED URBAN AREAS (Veg Estab.)
Open space (Lawns,parks etc.)
Good condition; grass cover > 75%
- 0.02(61)
Impervious Areas
Paved parking lots, roofs, driveways
-
0.20(98)
-
-
Total Area (by Hydrologic Soil Group)
.22
====
------------------------------------------------------------------------------TOTAL DRAINAGE AREA: .22 Acres
WEIGHTED CURVE NUMBER: 95*
------------------------------------------------------------------------------* - Generated for use by GRAPHIC method
GRAPHICAL PEAK DISCHARGE METHOD
Data: Drainage Area
: .22 * Acres
Runoff Curve Number : 95 *
Time of Concentration: 0.10
Hours (MINIMUM VALUE)
Rainfall Type
: II
Pond and Swamp Area : NONE
Version 2.10
=========================================================================
| Storm Number
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|----------------------|------|------|------|------|------|------|------|
| Frequency (yrs)
|
1 |
2 |
5 | 10 | 25 | 50 | 100 |
| 24-Hr Rainfall (in) | 2.6 | 3.2 | 4.2 | 5.1 | 5.6 | 6.3 | 7.2 |
| Ia/P Ratio
| 0.04 | 0.03 | 0.03 | 0.02 | 0.02 | 0.02 | 0.01 |
|
Used
| 0.10 | 0.10 | 0.10 | 0.10 | 0.10 | 0.10 | 0.10 |
| Runoff (in)
| 2.06 | 2.64 | 3.63 | 4.52 | 5.01 | 5.71 | 6.60 |
| Unit Peak Discharge |1.578 |1.578 |1.578 |1.578 |1.578 |1.578 |1.578 |
|
(cfs/acre/in)
|
|
|
|
|
|
|
|
| Pond and Swamp Factor| 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
|
0.0% Ponds Used
|
|
|
|
|
|
|
|
|----------------------|------|------|------|------|------|------|------|
| Peak Discharge (cfs) |
1 |
1 |
1 |
2 |
2 |
2 |
2 |
=========================================================================
* - Value(s) provided from TR-55 system routines
C.2.5
Appendix C.2. Design Example 2 – Water Quality BMPs
Step 2. Compute Rev
Step 2a. Determine Soil Specific Recharge Factor (S) Based on Hydrologic Soil Group
Soils found throughout the site are loams (HSG B) therefore S = 0.26
Step 2b. Compute ReV Using Percent Volume Method
Rev
= [(S)(Rv)(A)]!12
= [(0.26)(0.471)(0.77)]!12
= 0.0078 ac-ft. (342.3 cf)
Step 2c. Compute Rev Using Percent Area Method
Rev
= (S)(Ai)
= (0.26)(0.36 ac.)
= 0.094 acres (4,095 sf.)
The Rev requirement may be met by: a) treating 342.3 cubic feet using structural methods, b)
treating 4,095 square feet using non-structural methods, or c) a combination of both.
Step 3. Compute Cpv
The proposed community center is located within a USE I watershed, therefore use an extended
detention time (T) of 24 hours for the one-year storm event. The time of concentration (tc) and
one-year runoff (Qa) are 0.10 hours and 0.85” respectively.
Use the MDE Method to Compute Storage Volume (Appendix D.11):
Initial abstraction (Ia) for CN of 78 is 0.564: (TR-55) [Ia = (200/CN)-2]
Ia/P = (0.564)!2.6” = 0.22
tc = 0.10 hours
qu = 975 csm/in.
(Figure D.11.1, Appendix D.11)
where A is the drainage area in square miles
qi = quAQa
= (975 csm)(0.0012 square miles)(0.85”)
= 1.0 cfs; qi < 2.0 cfs ∴ Cpv is not required.
C.2.6
Appendix C.2. Design Example 2 – Water Quality BMPs
Step 4. Compute Requirements for Sub-Drainage Areas DA-1, DA-2 and DA-3
DA-1:
Rv = 0.05 + (0.009)(I); I = 0.16 acres / 0.20 acres = 0.80 or 80%
= 0.05 + (0.009)(80.0) = 0.77
WQv = [(P)(Rv)(A)]/12
= [(1”)(0.77)(0.20 ac)]/12
= 0.0128 ac-ft (557.5 cf.)
Rev = [(S)(Rv)(A)]/12
= [(0.26)(0.77)(0.20 ac)]/12
= 0.0033 ac-ft (145 cf.)
DA-2:
Rv = 0.05 + (0.009)(I); I = 0.20 acres / 0.22 acres = 0.91 or 91%
= 0.05 + (0.009)(91) = 0.87
WQv = [(P)(Rv)(A)]/12
= [(1”)(0.87)(0.22 ac.)]/12
= 0.0160 ac-ft (694.8 cf.)
Rev = [(S)(Rv)(A)]/12
= [(0.26)(0.87)(0.22 ac.)]/12
= 0.0041 ac-ft (180.6 cf.)
DA-3:
Rv = 0.05 + (0.009)(I); I = 0.0 acres / 0.35 acres = 0.0 or 0%
= 0.05 + (0.009)(0.0) = 0.05
Because I < 15%, WQv = 0.2”/acre
WQv = [(0.2”)(0.35 ac.)]/12
= 0.0058 ac-ft (254.1 cf.)
Rev = [(S)(Rv)(A)]/12
= [(0.26)(0.05)(0.35 ac.)]/12
= 0.0004 ac-ft (16.5 cf.)
NOTE: Although DA-3 has no proposed impervious surfaces, portions of DA-3 will be
disturbed to construct structural BMPs for DA-1 and DA-2. As a result, WQv and Rev
must be addressed for DA-3. For this example, the portion of DA-3 not disturbed for
BMP construction shall be treated by promoting sheet flow into the adjacent forested
buffer (see Chapter 5.4, “Sheetflow to Buffer Credit”).
C.2.7
Appendix C.2. Design Example 2 – Water Quality BMPs
Table C.2.1 Summary of General Storage Requirements for Comstock Commercial Center
Requirement
WQv*
Rev*
Cpv
Qp10
Qf
Drainage
Area
Total
DA-1
DA-2
DA-3
Volume Required
Notes
1,316.5
557.5
694.8
254.1
The sum of treatment volumes
for DA-1, DA-2 and DA-3 is
greater than that calculated for
the entire site.
Total
DA-1
DA-2
DA-3
342.3 (or 4,095 sf.)
145.6 (or 1,812 sf.)
180.6 (or 2,265 sf.)
16.1
N/A
N/A
N/A
volume is included within the
WQv storage
(cubic feet)
C.2.8
Cpv inflow rate is < 2.0 cfs
not required
provide safe passage for the
100-year event in final design
Appendix C.2. Design Example 2 – Water Quality BMPs
C.2.3 BMP Design Option 1
The first option consists of the design of a perimeter sand filter (F-3) for DA-1 and a pocket sand
filter (F-5) for DA-2. In both designs, Rev storage will be provided below the filter’s underdrain
system. As a result, the entire WQv must be considered in the design of each filter system. A
plan view for Option 1 is shown in Figure C.2.5
C.2.3.1 Perimeter Sand Filter (F-3) for DA-1
Pretreatment
The pretreatment requirements for a perimeter sand filter are as follows:
The pretreatment volume (Vp) for the perimeter sand filter shall be at least 25% of the
computed WQv:
Vp = (0.25)(WQv)
= (0.25)(557.5 cf.)
= 139.4 cf.
The minimum required surface area as computed by the Camp-Hazen equation:
As =
Qo
× E′
W
(see Section 3.4.3 for terms)
For imperviousness (I)> 75%, this equation reduces to:
Asp = (0.0081)(WQv)
= (0.0081)(557.5 cf.)
= 4.52 sf.
Using a width (w) =1.5 ft. and length (l) = 45 ft., the required depth for the sedimentation
chamber = 139.4 cf. ! (1.5 ft.)(45 ft.) = 2.06 ft.; Use a sedimentation chamber 1.5 ft. by
45 ft. by 2.1 ft.
C.2.9
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.5 Design Option 1 - Plan View
Treatment
The treatment requirements for the perimeter sand filter are as follows:
The entire treatment system (including pretreatment) shall temporarily hold at least 75%
of the WQv prior to filtration:
Vtemp = (0.75)(WQv)
= (0.75)(557.5 cf.)
= 418.1 cf.
The required filter bed area (Af) is computed using the following equation:
Af =
(WQv )( d f )
[ k × ( h f + d f ) × t f )]
C.2.10
(see Section 3.4.4)
Appendix C.2. Design Example 2 – Water Quality BMPs
Minimum filter bed depth (df) = 12”; for this design use df = 12” (1.0 ft)
The coefficient of permeability (k) for sand filters = 3.5 ft./day
The average height of water above the filter bed (hf) = (0.5)(design ponding depth). For
this design, the ponding depth =1.0 ft. ∴ hf = 0.5 ft.
The design filter bed drain time (tf) = 1.67 days
Therefore: A f =
(557. 5 cf .)(1. 0 ft.)
= 63.6 sf.
[(3. 5 day )( 0. 5 ft. + 1. 0 ft.)(1. 67 days )]
ft .
Setting the filter chamber width (w) to 1.5 ft., the length (l) of the filter chamber
= 63.6 sf.!1.5 ft. = 42.4 ft; Use a filter chamber 1.5 ft. by 45 ft.
Check Vtemp:
Vtemp = V p + Vtreatment
= 139.4 + [(1.0)(1.5)(45) + (1.0)(1.5)(45)(0.4)] = 236.5 cf.
note: 0.4 is the porosity of the filter media
Approximately 182 cf. of additional storage is needed to meet this requirement. Either
increase the storage in one or both chambers or design parking area to provide additional
storage. For this design, the pretreatment chamber width will be increased to 3.5 ft.
Vtemp = V p + Vtreatment
= (3.5)(45.0)(2.1) + [(1.0)(1.5)(45) + (1.0)(1.5)(45)(0.4)] = 425.25 cf.
Groundwater Recharge (Rev)
Rev storage will be provided within a stone-filled trench adjacent to the perimeter sand
filter. Setting the trench length (l) = 45 ft., and the width (w) = 2.0 ft, the trench depth (d)
needed to store the Rev volume (V =145.6 cf.) is:
V
d
=
where
l×w×n
n is the porosity of stone; use n = 0.4
Therefore, d = 145.6 cf.!(45.0 ft.32.0 ft.30.4) = 4.04 ft.; use a stone-filled trench 45.0 ft.
by 2.0 ft. by 4.1 ft.
Overflow
Flow splitters and overflow devices may be designed using volume or flow rate. For this
example, a weir discharging from the sedimentation chamber into the clear well will
provide volume overflow for the ten-year storm. For DA-1, the ten-year flow (Q10) = 1.0
cfs. Using a weir length of 1.5 ft., the head required to safely convey Q10 may be
calculated using the weir equation: Q=Clh3/2 where C = 3.1, l = weir length (1.5 ft.), and
C.2.11
Appendix C.2. Design Example 2 – Water Quality BMPs
h = head. By rearranging the weir equation and solving for h; h=[Q!(C3l)]2/3 = 0.40 ft.
Design perimeter sand filter with at least 0.4 ft. freeboard to safely convey Q10.
Design details for the perimeter sand filter are shown in Figures C.2.6.
C.2.3.2 Pocket Sand Filter (F-5) for DA-2
Pretreatment
The pretreatment requirements for a pocket sand filter are as follows:
Vp for the pocket sand filter shall be at least 25% of the computed WQv:
Vp = (0.25)(WQv)
= (0.25)(694.8 cf.)
= 173.7 cf.
The minimum required surface area as computed by the Camp-Hazen equation:
Qo
× E′
W
For I > 75%, this equation reduces to:
Asp = (0.0081)(WQv)
= (0.0081)(694.8 cf.)
= 5.62 sf.
As =
Maintaining at least a 2:1 ratio (l:w); set w = 6.5 ft. and l = 13.0 ft. The required d for the
sedimentation area = 173.7 cf. !(6.5 ft.)(13.0 ft.)= 2.0 ft.; Use a sedimentation chamber
6.5 ft. by 13.0 ft. by 2.0 ft.
C.2.12
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.6 Perimeter Sand Filter Design Details
C.2.13
Appendix C.2. Design Example 2 – Water Quality BMPs
Treatment
The treatment requirements for the pocket sand filter are as follows:
The entire treatment system (including pretreatment) shall temporarily hold at least 75%
of the WQv prior to filtration:
Vtemp = (0.75(WQv)
= (0.75)(694.8 cf.)
= 521.1 cf.
The required filter bed area is computed using the following equation:
The minimum df for a pocket sand filter = 18”; for this design use df = 18” (1.5’).
Af =
(WQv )( d f )
[ k × ( h f + d f ) × t f )]
The coefficient of permeability (k) for sand filters = 3.5 ft/day
The average height of water (hf) above the filter bed for this design = 0.5 ft.
The design filter bed drain time (tf) = 1.67 days.
Therefore: A f =
(694. 8 cf .)(1. 5 ft.)
= 89. 2 sf .
[(3. 5 day )( 0. 5 ft. + 1. 5 ft.)(1. 67 days )]
ft .
Setting the filter chamber width (w) to 6.5 ft. l = 89.2 ft.!6.5 ft. =13.7 ft.; Use a filter
chamber 6.5 ft. by 13.7 ft.
Check Vtemp:
Vtemp = V p + Vtreatment
= 173.7 + [(1.0)(6.5)(13.7) + (1.5)(6.5)(13.7)(0.4)] = 316.1 cf.
note: 0.4 is the porosity of the filter media
Approximately 205 cf. of additional storage is needed to meet this requirement. Either
increase the storage in one or both chambers or design parking area to provide additional
storage. For this design, the pretreatment chamber width will be increased to 9.0 ft. and
the depth increased to 3.0 ft.
Vtemp = V p + Vtreatment
= (9.0)(13.0)(3.0) + [(1.5)(6.5)(13.7) + (1.5)(6.5)(13.7)(0.4)] = 538.0 cf
C.2.14
Appendix C.2. Design Example 2 – Water Quality BMPs
Groundwater Recharge (Rev)
Rev storage will be provided within a stone-filled reservoir directly below the filter
chamber’s underdrain system. Using w = 6.5 ft. and l = 13.7 ft., the depth needed to store
the Rev volume (V = 180.6 cf.) is:
V
d=
where n is the porosity of stone; use n = 0.4
l×w×n
Therefore, d = 180.6!(13.7 ft.36.5 ft.30.4)=5.1 ft.; Use a stone-filled reservoir 6.5 ft. by
13.7 ft. by 5.1 ft.
Overflow/Bypass
As the pocket sand filter will be located “off-line” from the main conveyance system, a
flow splitter will be required to divert the WQv into the filter. Flow splitters may be
designed using volume or flow rate. For this example, use a concrete flume with a
bottom width of 4.0 ft designed to divert the flow associated with the WQv. The head
required to divert the WQv flow may be calculated using the weir equation: Q=Clh3/2
where Q is flow associated with WQv (using Appendix D.10, Q= 0.3 cfs), C = 3.1, l = 4.0
ft., and h=head. By rearranging the equation and solving for h; h=[Q!(C3l)]2/3=0.084 ft.
Design flow splitter with a 1 inch high diversion. NOTE: With this type of flow
splitter, runoff in excess of the WQv may continue to flow into the sand filter.
Design details for the pocket sand filter are shown in Figures C.2.7 and C.2.8.
C.2.15
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.7 Pocket Sand Filter – Plan View
C.2.16
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.8 Pocket Sand Filter Design Details
C.2.17
Appendix C.2. Design Example 2 – Water Quality BMPs
C.2.4 BMP Design Option 2.
The second option consists of the design of a bioretention area (F-6) for DA-1 and an infiltration
trench (I-1) for DA-2. For the bioretention system, Rev storage will be provided below the
underdrain system, and as a result, the entire WQv will be used as the design. The infiltration
trench automatically meets the Rev requirement. A plan view of Option 2 is shown in Figure
C.2.9.
Figure C.2.9 Design Option 2 – Plan View
C.2.18
Appendix C.2. Design Example 2 – Water Quality BMPs
C.2.4.1 Bioretention System (F-6) for DA-1
Pretreatment
Adequate
provided:
1.
2.
3.
pretreatment for a bioretention system is provided when all of the following are
20 ft. grass filter strip below a level spreader or an optional sand filter layer;
gravel diaphragm; and
2” to 3” mulch layer.
Treatment
The treatment requirements for the bioretention system are as follows (Section 3.4.3 & 4):
The entire treatment system (including pretreatment) shall temporarily hold at least 75%
of the WQv prior to filtration:
Vtemp = (0.75)(WQv)
= (0.75)(557.5 cf.)
= 418.1 cf.
The required filter bed area (Af) is computed using the following equation:
Af =
(WQv )( d f )
[ k × ( h f + d f ) × t f )]
Recommended filter bed depth (df) for a bioretention system is 2.5 to 4.0 ft. For this
design, use df = 3.0 ft.
The coefficient of permeability (k) for bioretention systems = 0.5 ft./day
The average height of water above the filter bed (hf) = 0.5 ft. (Note: The maximum
ponding depth for a bioretention system is 1.0 ft.)
The design filter bed drain time (tf) = 2.0 days
Therefore: A f =
(557. 5 cf .)( 3. 0 ft.)
= 477. 9 sf .
[( 0. 5 day )( 0. 5 ft. + 3. 0 ft.)( 2. 00 days )]
ft .
Use a bioretention system with minimum surface area =478 sf.
Check Vtemp:
Vtemp = Vtreatment = (1.0)(478 sf ) + (3.0)(478 sf )(0.4) = 1051.6 cf.
note: 0.4 is the porosity of the filter media
C.2.19
Appendix C.2. Design Example 2 – Water Quality BMPs
Groundwater Recharge (Rev)
Rev storage will be provided in a stone-filled reservoir directly below the underdrain
system. Setting the reservoir area (Ar) = 478 sf., the depth (d) needed to store the Rev
volume (V=145.6 cf.) is:
V
where n is the porosity of stone; use n = 0.4
Ar × n
Therefore; d =145.6 cf.!(478.0ft.30.4)=0.76 ft.; Use a stone-filled reservoir 478 sf. by
0.76 ft.
d=
Overflow
Overflow for the ten-year storm shall be provided to a non-erosive outlet. For this
design, a standard inlet will be used to bypass the volume in excess of the WQv by setting
the inlet invert at the elevation corresponding to the WQv treatment volume (1.0 ft. above
the bioretention system filter bed).
Design details and a planting plan for the bioretention system are shown in Figures C.2.10 and
C.2.11.
C.2.20
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.10 Bioretention System Details
Figure C.2.11 Bioretention Planting Plan
C.2.21
Appendix C.2. Design Example 2 – Water Quality BMPs
C.2.4.2 Infiltration Trench (I-1) for DA-2
Pretreatment
The pretreatment requirements for an infiltration trench are as follows:
The pretreatment volume (Vp) for the infiltration trench shall be at least 25% of the
computed WQv:
Vp = (0.25)(WQv)
= (0.25)(694.8 cf.)
= 173.7 cf.
Using a width (w) of 8.0 ft. and a length (l) of 11.0 ft., the required depth for the
sedimentation chamber = 173.7 cf. !(8.0 ft.)(11.0 ft.) = 1.97 ft.; Use a sedimentation
chamber 8.0 ft by 11.0 ft. by 2.0 ft.
Additionally, each infiltration trench shall have at least three of the following measures to
prevent clogging and maintain the long-term integrity of the trench:
1. grass channel;
2. grass filter strip (minimum 20 ft.);
3. bottom sand layer
4. upper sand layer (minimum 6”) with filter fabric at sand/gravel interface; and
C.2.22
Appendix C.2. Design Example 2 – Water Quality BMPs
5. use washed bank run gravel as aggregate.
This design will use a bottom sand layer, upper sand layer, and washed bank run gravel.
Treatment
The treatment requirements for an infiltration trench are as follows:
The practice shall be designed to exfiltrate the entire WQv less the pretreatment volume
through the floor of the practice. The design volume (Vw) = WQv-Vp = 521.1 cf.
Infiltration practices are designed using the methodology in Appendix D.13.
The maximum allowable depth (dmax) of an infiltration trench is
d max = f ×
Ts
n
where:
f is the infiltration rate, for this design f =0.52 inches/hour
Ts is the maximum allowable storage of 48 hours
n is the porosity of the stone reservoir, use 0.4
Therefore, dmax = 0.52inches/hour 3(48 hours!0.4)=62.4 inches (5.2 ft). Use a trench depth
(dt) = 5.0 ft.
Using equation D.13.3, the area of the infiltration trench (At) is:
At =
Vw
nd t + fT
where the time to fill the trench (T) is 2.0 hours.
Use an infiltration trench 7.5 ft. by 35.0 ft. by 5.0 ft.
521.1 cf .
At =
inches
(0.4 × 5.0) + (0.52 hour × 2.0 hours × 1 ft
C.2.23
= 249.7 sf .
12 in
)
Appendix C.2. Design Example 2 – Water Quality BMPs
Groundwater Recharge (Rev)
Infiltration trenches automatically meet the Rev storage requirement; no additional storage is
required.
Overflow
As the infiltration trench will be located “off-line” from the main conveyance system, a flow
splitter will be required to divert the WQv into the filter. Use the flow splitter design from the
pocket sand filter above.
Design details for the infiltration trench are shown in Figures C.2.12.
C.2.5 BMP Design Option 3
The third option consists of the bioretention area (F-6) previously designed for DA-1 and a dry
swale (O-1) for DA-2. In the dry swale design, Rev storage will be provided below the swale’s
underdrain system. As a result, the entire WQv must be considered in the design of the dry
swale. A plan view of Option 3 is shown in Figure C.2.13.
C.2.5.1 Dry Swale (O-1) for DA-2
Pretreatment
The pretreatment requirements for a dry swale are as follows:
Pretreatment storage of 0.1 inch of runoff from impervious area shall be provided. This
is equivalent to 10% of WQv. Therefore, Vp =(10%)(WQv)= 69.5 cf. Use a forebay or
sedimentation chamber sized to store 62.5 cf.
C.2.24
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.12 Infiltration Trench Details
C.2.25
Appendix C.2. Design Example 2 – Water Quality BMPs
Figure C.2.13 Design Option 3 – Plan View
Treatment
The treatment requirements for the dry swale are as follows:
Dry swales shall be designed to temporarily store the WQv for a maximum 48-hour
period. An underdrain system shall provided to ensure the maximum ponding time is not
exceeded.
Dry swales shall have a maximum longitudinal slope (s) of 4.0%. For this design, s=
3.0%.
Channel side slopes (z:1) should be no steeper than 2:1. For this design, side slopes
shall be 4:1 (z=4).
Dry swales shall have a bottom width (wb) no narrower than 2.0 ft. and no wider than 8.0
C.2.26
Appendix C.2. Design Example 2 – Water Quality BMPs
ft. (if wider than 8.0 ft., a meandering drainage pattern shall be established).
Maximum ponding depths (dmid,dend ) of 1.0 ft. at the channel mid-point and 1.5 ft. at the
downstream end shall be maintained. Use dmid = 0.75 ft. and dmax = 1.5 ft.
Due to the length (100 ft.) and grade (3.0%) of the channel, the channel will be divided
into two contiguous channels separated by a check dam to achieve dmid and dend
requirements. Use three check dams located at the entrance, mid-point and end of the
swale.
With three check dams, there will be two ponding areas of equal storage. Using
dmid=0.75’, and setting the total length of the swale to 100 ft., the treatment volume of the
swale is:
WQv − V p = w × l × d mid
By rearranging this equation and solving for the width of storage surface (w):
w=
WQv − V p
l × d mid
=
694. 8 cf . − 69. 5 cf .
= 8. 3 ft.
100 ft. × 0. 75 ft.
Using w =8.3 ft. and 4:1 side slopes, wb = w-(23z3dmid)= 8.3-(23430.75)=2.3 ft. Use a
dry swale with bottom dimensions of 2.3 ft. by 100 ft. with 4:1 side slopes.
Groundwater Recharge (Rev)
Rev storage will be provided within a stone-filled reservoir below the dry swale
underdrain system. Using the swale dimensions (2.3 ft by 100 ft.), the reservoir depth (d)
needed to store the Rev volume (V=180.6 cf.) is:
V
where n is the porosity of stone; use n=0.4
l×w×n
Therefore, d=180.6 cf.!(100 ft.32.3 ft.30.4)=1.96 ft. Use a stone-filled reservoir 2.3 ft.
by 100.0 ft. by 2.0 ft.
d=
Overflow (Q10 Conveyance)
A dry swale is required to safely convey the 10-year design storm with minimum
freeboard of 3 inches. Check the design to ensure that the 10-year storm is conveyed
non-erosively and that the minimum freeboard is provided. For DA-2, the 10-year peak
flow (Q10) =2.0 cfs. At dmax, the width (wmax)=w+(23z3dmid)=14.3 ft. Using a trapezoidal
channel with a bottom width =14.3 ft., 4:1 side slopes, and a longitudinal slope (s)
=3.0%, the depth (d) and velocity (v) of flow can be calculated using the Manning
equation:
v=
1. 49 2 3 1 2
r s
n
C.2.27
Appendix C.2. Design Example 2 – Water Quality BMPs
where: n is the roughness coefficient of the channel lining, use 0.025
r is the hydraulic radius of the channel; at d = 0.10 ft.,
r is very nearly 0.10
Therefore, at d=0.1 ft.:
2
1
1. 49
( 0. 10) 3 ( 0. 03) 2 = 2. 2 fps
0. 025
The cross-sectional area of the channel (A) needed to safely pass Q10 can be calculated
using A=Q10!v =2.0 cfs ! 2.2 fps =0.91 sf. At d = 0.1 ft., A =1.4 sf. The proposed design
will safely convey the 10-year storm.
v=
The minimum depth of the channel (dc) may be determined by adding the required
depths:
dc = dmax + d10 yr. storm + dfreeboard
= 1.5 ft. + 0.1 ft. + 0.25 ft.
= 1.85 ft. Use channel depth (dc) = 2.0 ft.
Design details for the dry swale are shown in Figures C.2.14.
C.2.28
Appendix C.2. Design Example 2 – Water Quality BMPs
C.2.14 Dry Swale Design Details
C.2.29
Testing Requirements for Infiltration,
Bioretention and Sand Filter Subsoils
Appendix
D.1
Appendix D.1 Testing Requirements for Infiltration Bioretention and Sand Filter Subsoils
General Notes Pertinent to All Testing
1. For infiltration trench (I-1) and basin (I-2) practices, a minimum field infiltration rate (fc) of
0.52 inches per hour is required; lower rates preclude the use of these practices. For surface
sand filter (F-1) and bioretention (F-6) practices, no minimum infiltration rate is required if
these facilities are designed with a “day-lighting” underdrain system; otherwise these
facilities require a 0.52 inch per hour rate.
2. Number of required borings is based on the size of the proposed facility. Testing is done in
two phases, (1) Initial Feasibility, and (2) Concept Design.
3. Testing is to be conducted by a qualified professional. This professional shall either be a
registered professional engineer, soils scientist or geologist and must be licensed in the State
of Maryland.
Initial Feasibility Testing
Feasibility testing is conducted to determine whether full-scale testing is necessary, screen
unsuitable sites, and reduce testing costs. A soil boring is not required at this stage. However, a
designer or landowner may opt to engage Concept Design Borings per Table D.1.1 at his or her
discretion, without feasibility testing.
Initial testing involves either one field test per facility, regardless of type or size, or previous
testing data, such as the following:
*
*
*
on-site septic percolation testing, within 200 feet of the proposed BMP location, and on the
same contour which can establish initial rate, water table and/or depth to bedrock,
geotechnical report on the site prepared by a qualified geotechnical consultant, or
Natural Resources Conservation Service (NRCS) County Soil Mapping showing an
unsuitable soil group such as a hydrologic group “D” soil in a low-lying area or a Marlboro
Clay.
If the results of initial feasibility testing as determined by a qualified professional show that an
infiltration rate of greater than 0.52 inches per hour is probable, then the number of concept
design test pits shall be per the following table. An encased soil boring may be substituted for a
test pit, if desired.
D.1.1
Appendix D.1 Testing Requirements for Infiltration Bioretention and Sand Filter Subsoils
Table D.1.1 Infiltration Testing Summary Table
Type of Facility
Initial Feasibility
Testing
I-1 (trench)
1 field percolation
test, test pit not
required
1 field percolation
test, test pit not
required
1 field percolation
test, test pit not
required
I-2 (basin)
Concept Design Testing
(initial testing yields a
rate greater than
0.52”/hr)
1infiltration test and 1
test pit per 50’ of trench
1 infiltration test and 1
test pit per 200 square
feet of basin area
F-1 (surface sand
1 infiltration test and 1
filter)
test pit per 200 square
feet of filter area (no
underdrains required*)
F-6 (bioretention) 1 field percolation 1 infiltration test and 1
test, test pit not
test pit per 200 square
required
feet of filter area (no
underdrains required*)
* underdrain installation is still strongly recommended
Concept Design
Testing (initial testing
yields a rate lower
than 0.52”/hr)
not acceptable practice
not acceptable practice
underdrains required
underdrains required
Documentation
Infiltration testing data shall be documented, and include a description of the infiltration testing
method. This is to ensure that the tester understands the procedure.
Test Pit/Boring Requirements
a.
Excavate a test pit or dig a standard soil boring to a depth of 4 feet below the
proposed facility bottom;
b.
Determine depth to groundwater table (if within 4 feet of proposed bottom) upon
initial digging or drilling, and again 24 hours later;
c.
Conduct Standard Penetration Testing (SPT) every 2’ to a depth of 4 feet below
the facility bottom;
D.1.2
Appendix D.1 Testing Requirements for Infiltration Bioretention and Sand Filter Subsoils
d.
Determine United States Department of Agriculture (USDA) or Unified Soil
Classification (USC) System textures at the proposed bottom and 4 feet below the
bottom of the best management practice (BMP);
e.
Determine depth to bedrock (if within 4 feet of proposed bottom);
f.
The soil description should include all soil horizons; and
g.
The location of the test pit or boring shall correspond to the BMP location; test
pit/soil boring stakes are to be left in the field for inspection purposes and shall be
clearly labeled as such.
Infiltration Testing Requirements (field testing required)
a.
Install casing (solid 5 inch diameter, 30” length) to 24” below proposed BMP
bottom (see Figure D.1.1).
b.
Remove any smeared soiled surfaces and provide a natural soil interface into
which water may percolate. Remove all loose material from the casing. Upon the
tester’s discretion, a two (2) inch layer of coarse sand or fine gravel may be
placed to protect the bottom from scouring and sediment. Fill casing with clean
water to a depth of 24” and allow to pre-soak for twenty-four hours.
c.
Twenty-four hours later, refill casing with another 24” of clean water and monitor
water level (measured drop from the top of the casing) for 1 hour. Repeat this
procedure (filling the casing each time) three additional times, for a total of four
observations. Upon the tester’s discretion, the final field rate may either be the
average of the four observations, or the value of the last observation. The final
rate shall be reported in inches per hour.
d.
May be done through a boring or open excavation.
e.
The location of the test shall correspond to the BMP location.
f.
Upon completion of the testing, the casings shall be immediately pulled, and the
test pit shall be back-filled.
D.1.3
Appendix D.1 Testing Requirements for Infiltration Bioretention and Sand Filter Subsoils
Figure D.1.1 Infiltration Testing Requirements
Laboratory Testing
Use grain-size sieve analysis and hydrometer tests (where appropriate) to determine
USDA soils classification and textural analysis. Visual field inspection by a qualified
professional may also be used, provided it is documented. The use of lab testing to
establish infiltration rates is prohibited.
Bioretention Testing
All areas tested for application of F-6 facilities shall be back-filled with a suitable sandy
loam planting media. The borrow source of this media, which may be the same or
different from the bioretention area location itself, must be tested as follows:
If the borrow area is undisturbed soil one test is required per 200 square feet of borrow
area. The test consists of “grab” samples at one foot depth intervals to the bottom of the
borrow area. All samples at the testing location are then mixed, and the resulting sample
is then lab-tested to meet the following criteria:
D.1.4
Appendix D.1 Testing Requirements for Infiltration Bioretention and Sand Filter Subsoils
a)
USDA minimum textural analysis requirements: A textural analysis is
required from the site stockpiled topsoil. If topsoil is imported, then a
texture analysis shall be performed for each location where the topsoil was
excavated.
Minimum requirements:
sand 35 - 60%
silt
30 - 55%
clay 10 - 25%
b)
The soil shall be a uniform mix, free of stones, stumps, roots or other
similar objects larger than one inch.
c)
Consult the bioretention construction specifications (Appendix B.3.8) for
further guidance on preparing the soil for a bioretention area.
Table D.1.2 Minimum Depth to Seasonably High Water Table
Region
Lower Eastern Shore
Remainder of State
Depth to water table
for infiltration
2
4
D.1.5
Depth to water table for encased or lined
facilities such as an underground concrete
sand filter
0*
0*
*may need professional structural design
Appendix
The following information on BMP design and SWM geotechnical testing
in Karst areas has been adapted from the Carroll County Water Resource
Geotechnical Methods for Karst Feasibility
Testing
D.2
Appendix D.2. Geotechnical Methods for Karst Feasibility Testing
Management Manual and Ordinance (CCWRM) dated July 2, 1996. For a complete discussion
of these items, please refer to the Carroll County document.
Section 1: Stormwater Management in Karst Areas
In general, stormwater runoff should not be concentrated and should be conveyed through
vegetated areas; in addition, the facilities should be designed in accordance with the following
standards:
(1) Detention/retention ponds should be designed and constructed with a synthetic or clay liner
approved by the local plan approval authority.
(2) Discharges from SWM facilities or directly from impervious surfaces should not be routed
within 1000 feet of the edge of any existing unremediated sinkhole. The flow should then be
directed to an area not underlain by carbonate rock. Alternatively, these discharges may be
routed to a stable watercourse via a pipe or lined channel.
(3) Sinkholes occurring within stormwater management structures should be repaired within 72
hours of first observation of occurrence.
(4) Liners: Where natural soil permeabilities are greater than 10-6 cm/sec or 1.4 x 10-3 inches per
hour for the two-foot interval below the depth of the proposed facility, a stable, low
permeability liner shall be installed as follows:
-7
(a) One foot of clay with a permeability less than 10 cm/sec, or;
(b) Two feet of clay with a permeability less than 10-6 cm/sec, or;
(c) Two feet of compacted soil with a permeability less than 10-5 cm/sec with a 30 mil
thick artificial liner with a permeability less than 10-7 cm/sec, or;
(d) A very low permeability base constructed of concrete.
Section 2: Soils Investigation for Karst Areas
The purpose of a karst investigation is to identify subsurface voids, cavities, fractures, or other
discontinuities which could pose an environmental concern or a construction hazard to an
existing or proposed SWM facility. By definition, karst investigations are required only in areas
suspected of containing carbonate rocks. The requirements outlined below should not be
interpreted as all-inclusive. The design of any subsurface investigation should reflect the size
and complexity of the proposed project.
D.2.1
Appendix D.2. Geotechnical Methods for Karst Feasibility Testing
The investigation should determine the nature and thickness of subsurface materials, including
depth to bedrock and to the water table. Subsurface data may be acquired by backhoe
excavation and/or soil boring. These field data should be supplemented by geophysical
investigation techniques, deemed appropriate by a qualified professional. The data listed herein
should be acquired under the direct supervision of a qualified geologist, geotechnical engineer,
or soil scientist who is experienced in conducting such studies. Pertinent site information shall
be collected which should include the following:
1. Bedrock characteristics (type, geologic contacts, faults, geologic structure, rock surface
configuration).
2. Soil characteristics (type, thickness, mapped unit).
3. Photogeologic fracture traces.
4. Bedrock outcrop areas.
5. Sinkholes and/or other closed depressions.
6. Perennial and/or intermittent streams.
Section 3: Location of Borings
Borings should be located to provide representative area coverage of the proposed facilities. The
exact location of borings will be based on the following conditions or features:
1. In each geologic unit present, as mapped by the Maryland and U.S. Geological Surveys
(USGS) and local county records.
2. Placed near on-site geologic or geomorphic indications of the presence of carbonate rock.
3. On photogeologic fracture traces.
4. Next to bedrock outcrop areas (i.e., ten feet from).
5. As near to identified sinkholes and/or closed depressions as possible.
6. Near the edges and center of the proposed facility, and spaced at equal distances from one
another.
D.2.2
Appendix D.2. Geotechnical Methods for Karst Feasibility Testing
7. Near any areas identified as anomalies from any geophysical studies.
Section 4: Number of Borings
The density shall be dependent upon the type and size of the proposed facility such that a
representative sampling is obtained, as follows:
1. Ponds/wetlands - a minimum of three per facility, or three per acre, whichever is greater
with at least one along the centerline of the proposed embankment and the remainder
within the proposed impoundment area.
2. Infiltration trenches - a minimum of 2 per facility.
3. Additional borings - to define lateral extent of limiting horizons, or site specific
conditions, where applicable.
Section 5: Depth of Borings
Borings shall be extended to depths dependent upon bedrock type as follows:
1. Non-carbonate rocks - a minimum depth of 5 feet below the lowest proposed grade,
within the facility unless auger/backhoe refusal is encountered.
2. Carbonate rocks - a minimum of 20 feet below ground surface or proposed grade; where
refusal is encountered the boring may either be extended by rock coring or moving to an
adjacent location within 10 linear feet of the original site, in order that the 20-foot
minimum depth be reached.
Section 6: Identification of Material
All material penetrated by the boring shall be identified, as follows:
1. Description, logging, and sampling for the entire depth of the boring.
2. Any stains, odors, or other indications of environmental degradation.
3. A minimum laboratory analysis of two soil samples, representative of the material
penetrated including potential limiting horizons, with the results compared to the field
descriptions.
4. Identified characteristics shall include, as a minimum: color; mineral composition; grain
D.2.3
Appendix D.2. Geotechnical Methods for Karst Feasibility Testing
size, shape, and sorting; and saturation.
5. Any indications of water saturation shall be carefully logged, to include both perched and
groundwater table levels, and descriptions of soils that are mottled or gleyed should be
provided. Water levels in all borings shall be taken at the time of completion and again
24 hours after completion. The boring must remain fully open to total depth of these
measurements.
6. When conducting a standard penetration test (SPT), estimation of soil engineering
characteristics, including “N” or estimated unconfined compressive strength.
Section 7: Geophysical Investigation
An electromagnetic terrain conductivity survey may be conducted over the entire area of the
facility and extending outward to 200 feet beyond the boundaries of the proposed facility. This
survey may be performed to provide a qualitative evaluation of the area to be utilized. The
survey results may be used to identify “suspect areas” which will be further evaluated using
borings. The use of this technique may reduce the total number of borings for a site by better
defining “suspect areas.” This survey shall include appropriate techniques such that
representative data are collected from a minimum depth of 20 feet below ground surface or the
final proposed grade, whichever is deeper. These data shall then be correlated with boring data
in the site area.
Section 8: Evaluation
At least one subsurface cross section shall be provided. It should extend through a central
portion of the proposed facility, using the actual or projected boring data and the
geophysical data. In addition, an iso-conductivity map should be constructed. Finally, a bedrock
contour map should be developed to include all of the geophysical and boring data. A sketch
map or formal construction plan indicating the location and dimension of the proposed facility
and line of cross section should be included for reference, or as a base map for presentation of
subsurface data.
Section 9: Sinkhole Remediation
Proper sinkhole remediation involves investigation, stabilization and final grading. For more
information, please see the CCWRM, Section 4.2.
Section 10: Sinkhole Stabilization
Sinkholes should be repaired by (1) reverse-graded backfilling, (2) concrete plugging, or (3) an
D.2.4
Appendix D.2. Geotechnical Methods for Karst Feasibility Testing
engineered subsurface structure. For more information on these methodologies, see the
CCWRM, Section 4.2.2.
Section 11: Monitoring of BMPs in Karst Regions
A water quality monitoring system installed, operated and maintained by the owner/operator may
be required in a karst region. For areas requiring monitoring, at least one monitoring well shall
be placed at a point hydraulically up gradient from the BMP and two (2) down gradient
monitoring wells shall be provided within 200' of the facility. The wells shall be fitted with
locking caps. Bi-annual sampling should take place, and an annual report should be filed with
the plan approval authority.
D.2.5
Short Cut Method for Wetland
Drawdown Assessment
Appendix
D.3
Appendix D.3. Short Cut for Wetland Drawdown Assessment
This section presents a simple method for calculating whether a stormwater pond or wetland has an
appropriate water balance to maintain a wet pool over a 30-day period without rainfall. When
conducting this analysis, the following should be considered:
1.
2.
3.
4.
5.
6.
Calculate maximum drawdown during periods of high evaporation and during an extended
period of no appreciable rainfall.
The change in storage within a pond (ΔV) = Inflows - Outflows
Potential inflows: runoff, baseflow and rainfall
Potential outflows: infiltration, surface overflow and evaporation (and evapotranspiration)
Assume no inflow from baseflow, no losses for infiltration and because only the permanent
pool volume is being evaluated, no losses for surface overflows.
Therefore, ΔV = runoff - evaporation
Using Design Example No. 1 - Reker Meadows (see Chapter 2.6) as an example and given the
conditions in Table D.3.1 and table D.3.2, a wetland drawdown assessment may be determined as
follows:
Table D.3.1 Site Data from Design Example 1 for Sample Water Balance Analysis
Drainage Area
Post Developed Conditions CN
2-yr. Design Rainfall Event
2-yr. Design Storm Runoff
Water Quality Volume (WQv)
Groundwater Recharge Volume (Rev)
Surface Area of Wetland
38.0 ac
78
3.1"
1.2"
1.08 ac-ft
0.25 ac-ft
0.58 acres
(minimum 1.5% of drainage area to BMP)
A shallow wetland (W-1) will be designed to treat the water quality volume (WQv) minus the
groundwater recharge volume (Rev). Therefore, the permanent pool volume = 0.83 ac-ft.
Table D.3.2
Evaporation Rates for Maryland Ponds
(from Ferguson and Debo, “On-Site Stormwater Management”, 1990)
Precipitation (ft.)
Evaporation (ft.)
April
0.30
0.36
May
0.35
0.44
June
0.32
0.52
D.3.1
July
0.36
0.54
August
0.38
0.46
September
0.31
0.35
Appendix D.3. Short Cut for Wetland Drawdown Assessment
Calculate maximum drawdown during periods of high evaporation:
•
•
•
•
•
•
•
•
Period of greatest evaporation occurs during the month of July (see Table D.3.2)
Runoff Volume = P x E
where P = Precipitation
E = Runoff Efficiency (ratio of NRCS 2 year storm runoff to rainfall depths)
For CN = 78, Volume of Runoff (2 year storm) = 1.2"
For Frederick County, 2 year storm rainfall = 3.1”
E = 1.2”/3.1” = 0.39
Inflow = P × E
= .36 ft ×.39 = 0.14 ft
over entire site area: (0.14 ft) (38 acres) = 5.32 ac-ft
Outflow = surface area × evaporation losses
= 0.58 ac × 0.54 ft (see Table D.3.2)
= 0.31 ac-ft
Inflow (5.32 ac-ft) is greater than Outflow (0.31 ac-ft) therefore, drainage area is adequate to
support wet pond during normal conditions.
Check for drawdown over an extended period without rainfall:
• Use a 45 day interval using worst case conditions
• Highest evaporation occurs during July – 0.54 ft per month (see Table D.3.2)
• Calculate average evaporation per day = 0.54 ft / 31 days = 0.017 ft/day
• Over 45 day interval, evaporation loss = 45 × .017 ft/day = 0.78 ft
• Assume surface of the permanent pool may drop up to 0.78 ft (9.4”) over this interval.
Therefore, to be safe, specify vegetation for the aquatic shelves (to 10") that can tolerate
periods of drawdowns.
Reference
Ferguson, B. and T.N. Debo. 1990. On-Site Stormwater Management - Applications for Landscape
and Engineering. Van Nodstrandt, Reinhold, New York.
D.3.2
Stormwater Criteria for Maryland
Critical Area IDA Zone
Appendix
D.4
Appendix D.4. Stormwater Criteria of the MD Critical Area IDA Zone ...................... Background
This Appendix has been adapted from the document
Urban Stormwater Quality Guidance for the
Maryland Chesapeake Bay Critical Area
in Intensely Developed Areas
Prepared by:
Peter Kumble
Lorraine Herson-Jones
Thomas Schueler
Additional Information on the 10% Rate, including an applicants guide, can be obtained from
the:
Chesapeake Bay Critical Area Commission
45 Calvert Street
Annapolis, MD 21401
(410) 974-2426
D.4.1
Appendix D.4. Stormwater Criteria of the MD Critical Area IDA Zone ...................... Background
Background
What is the Critical Area?
The Chesapeake Bay Critical Area Act, passed by the Maryland General Assembly in 1984, is
designed to help protect the Chesapeake Bay and its tributaries from resource degradation primarily
resulting from development activity. In 1986, the more specific and comprehensive Critical Area
Criteria were adopted to implement the law. The “Critical Area” is defined as all water and
submerged lands of the Chesapeake Bay to the head of tide, and all land and water within 1000
feet of Mean High Water or from the edge of tidal wetlands. The Criteria mandate certain
restrictions on the use of land within this area. However, the responsibility for implementing the
Criteria is delegated to local governments, where zoning and other land use controls have
traditionally been carried out.
What is an IDA?
In writing the Criteria, the Chesapeake Bay Critical Area Commission was cognizant of the fact
that development already existed within the Critical Area. The Criteria also written with an implicit
acceptance of a limited and controlled level of additional development or redevelopment. One
particular class of land use, termed “Intensely Developed Areas,” or IDAs, was identified as areas
where continued growth could be accommodated through redevelopment and/or new development.
Local governments desiring to permit or promote such projects within the Critical Area have been
encouraged to direct such efforts within the IDA.
What does the 10% Rule mean?
IDAs are designated to each local jurisdiction and are characterized as intensely developed areas
that are predominately commercial, residential or industrial in nature. The Critical Area Criteria
require that any development within the IDA be accompanied by urban “best management
practices (BMPs)” to help mitigate potential water quality impacts associated with stormwater
runoff. The Criteria further specify that these practices should be capable of removing pollutant
loads generated from the development site to a level at least 10% below the load generated at the site
prior to development. This requirement is commonly referred to as the “10% Rule.”
D.4.2
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
Introduction
The requirements set forth in this document relate only to the requirements of the Chesapeake
Bay Critical Area Act passed by the Maryland General Assembly in 1984 as well as the associated
criteria passed in 1986. Under this act, development and redevelopment activities shall be required
to use stormwater management practices appropriate to site development which achieves a ten (10%)
percent reduction of pre-development pollutant loadings.
10% Rule Application Process
A
Is the proposed development in the
IDA of the Critical Area?
If yes, then go to Step B.
If not, the 10% process does not
apply.
B
Is the impervious surface proposed
for the entire project greater than
250 square feet? If not, the 10%
process does not apply.
If yes, then go to Step C.
C
Is the proposed development for a
single lot – single family home?
If yes, go to Step D.
If not, use the Standard Application
Process and go to Part II of the
Applicant’s Guide.
D
Use the Residential Water Quality
Management Process.
E
Go to Part III of the Applicant’s
Guide.
This section details a step-by-step approach for
compliance with the 10% Rule. It is important to note that
these requirements are designed to provide water quality
treatment of urban runoff and that other site environmental
features cannot be substituted towards compliance. For
example, environment requirements for waste water
treatment plants cannot be substituted for urban runoff
BMPs— the Six Step Standard Application process or
Standard Procedure.
Two application processes have been developed for
10% Rule compliance in recognition of the broad scale of
development that occurs within the Critical Area.
z In the Standard Procedure, computations of preand post-development pollutant loadings and pollutant
removal efficiencies of BMPs are used to determine
compliance with the 10% Rule.
z The second procedure provides a streamlined
process for individual, residential lot development. If
the proposed development is eligible, the applicant
must submit a Residential Water Quality Management
Plan for approval.
The 10% Rule provides three different approaches for
compliance:
1) A reduction in impervious surface may lower post-development levels; therefore, Ipost is
lower, and hence, Ipost (post-development load) is lower;
D.4.3
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
2) A stormwater management BMP may remove pollutants from the Critical Area portion of
the site equal to the 10% reduction;
3) A stormwater management BMP may remove pollutants from the Critical Area portion of
the site and portions outside of the Critical Area equal to the 10% reduction.
Who must comply?
An individual planning development or re-development of land in the Critical Area District
zoned as an Intensely Developed Area (IDA) must comply with the 10% Rule. As mentioned above,
IDA refers to the land-use management classification as determined by the Chesapeake Bay Critical
Area Commission and incorporated into a local government’s Critical Area program. IDAs are
areas where residential, commercial, institutional, and/or industrial developed land uses
predominate, and where relatively little natural habitat occurs. IDAs also have at least one of the
following characteristics:
z A density of development equal to or greater than four dwellings per acre;
z Presence of public water and sewer systems with a density of greater than three units per
acre; or,
z Concentration of industrial, commercial, or institutional uses. In addition, these features are
concentrated in an area of at least 30 adjacent acres.
What must be submitted?
For persons proposing development or re-development in areas designated as an IDA on a local
Critical Area map, the specific submittal requirements vary from jurisdiction to jurisdiction.
Applicants should refer to their local Critical Area Program guidelines for preliminary and final site
plan or subdivision plan submittal requirements. As mentioned earlier, this Applicant’s Guide
contains the minimum recommended submittal requirements for two separate 10% Rule application
processes. Schedules for submittal of either document may vary among Critical Area jurisdictions.
What if my project is small?
Check to see if the project meets the criteria for the Residential Water Quality Management Plan.
This program is designed to ease the application process for individual lot residential development
or improvements that involve disturbances of 250 square feet or greater. Projects smaller than 250
square feet of disturbance are exempted from the requirements of 10% Rule.
What if my project will be completed in phases?
Applicants anticipating that their development will occur in phases are required to submit a
conceptual plan indicating the entire scope of work for preliminary review and approval. This will
ensure that the impacts of the project are evaluated in their entirety.
D.4.4
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
Who do I submit it to?
Before commencement of construction, all plans indicating proposed development, (e.g. site
plans, building permits, subdivision plans), shall be submitted to the county or municipality
department which is generally responsible for the administration and enforcement of Chesapeake
Bay Critical Area Program regulations. In most jurisdictions, there is a zoning department that
handles Critical Area projects.
How does this program relate to other stormwater management programs?
Other local or state stormwater regulations may require additional stormwater requirements or
submittal information. For example, the state stormwater requirements require that stormwater
designs be assessed according to the state priorities, (for example: infiltration of runoff as top
priority, followed by wet ponds, etc.). State or local stormwater requirements may also specify
control of larger storms for quantity or flood safety control purposes. It is possible to meet various
design requirements within one facility, but local and state programs must be addressed in addition
to the requirements outlined within this document.
When must the application be submitted?
Any application process for the 10% Rule should parallel the plan review process, for example: a
conceptual 10% Rule Application should be submitted as part of the preliminary review followed by
a final 10% application at the final plan review stage. Upon receipt of the site plan, the local
reviewing agency may conduct a review soliciting technical comments from other departments,
agencies, and officials. Although the process varies between jurisdictions, the site plan shall be
preliminarily approved, subject to final approval, assuming it meets all requirements.
The Standard Application Process provides a six-step method for comparing pollutant loads
before and after development, and assessing the appropriate BMP for a given site. The pollutant
loading methodology is based on relationships between surface imperviousness and concentrations
of pollutants found in urban runoff (Schueler 1987).
D.4.5
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
Table D.4.1 Six Step Method of the Standard Application Process
Worksheet A
STEP #1
STEP #2
STEP #3
STEP #4
STEP #5
Calculate Site Imperviousness
Calculate Pre-Development Pollutant Load
Calculate Post-Development Pollutant Load
Calculate Pollutant Removal Requirement
Identify Feasible Urban BMP
Worksheet B
STEP #6
Define Off-Site Compliance
then..
Submit Application to Critical Area Plan Reviewer
STEP 1: Calculate Site Imperviousness
In this step, the applicant will describe imperviousness of pre- and post- development site
conditions. In general, impervious surfaces are human-made surfaces that are devoid of vegetation.
Refer to Table D.4.2 for detailed definitions of imperviousness.
Impervious Measurement
z Imperviousness must be measured directly from the most recent site plan.
z A table of measured values (planimeter, preferred) listed specifically for each impervious
surface type (roads, rooftops, etc.) must be submitted.
z Estimates of imperviousness based on land use types by computer generated surface runoff
programs (e.g. TR-55), are not appropriate for submission.
z If land is subdivided prior to construction, it is recommended that a 10% Application is
submitted at the time of initial subdivision, with imperviousness calculated using maximum
building envelopes and proposed road layouts. This submittal process is recommended so
that the entire project may be assessed as a whole.
Define Development Category
Using existing site imperviousness data, the proposed development must be categorized as 1) new
development, 2) redevelopment, or 3) single lot residential.
1) New Development:
pre-development imperviousness < 15%
2) Re-development:
pre-development imperviousness > 15%
D.4.6
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
3) Single Lot Residential:
projects involving an individual lot of residential development
which exceed 250 square feet in site disturbance.
Table D.4.2 Definition of Imperviousness
Impervious Surfaces are those that:
1) impede the natural infiltration of rainfall into underlying soils; and,
2) result in an increased volume of surface runoff to adjacent soils. As a simple rule, humanmade surfaces that are not vegetated will be considered impervious (BMPs will be
exempted from this definition).
Surface
Impervious
Design Suggestions
Roads
paved/concrete
gravel
dirt
yes
yes
yes
•
•
minimize road width
avoid curb and gutters; use grassed
swales
Driveways
paved/concrete
gravel
dirt
grid pavers
porous pavement
yes
yes
yes
no
yes
•
•
minimize surface area
use gridded pavers or porous
pavement in areas of low usage
Sidewalks/paths
paved
gravel
grid pavers
porous pavement
wood chip
yes
yes
no
no
no
•
•
minimize surface area
disconnect imperviousness; combine
with vegetation
Rooftops
yes
•
use sheet-flow spouting, dry wells or
french drains
Decks
yes
•
treat runoff under deck area
Swimming pools/ponds
yes
D.4.7
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
STEP 2: Calculate Pre-Development Pollutant Load
In this step the applicant calculates the storm loadings of phosphorous from the site prior to
development (see Technical Guide “Simple Method for Calculating Phosphorous Export”). The
equation shown in Table D.4.3 is a simplification of the equations presented in the 1987 10%
Document. Two loading formulas are used based on the development category (redevelopment or
new development) and site imperviousness. The information needed for these calculations include:
•
•
the area of the site within the IDA of the Critical Area
pre-development site imperviousness.
Table D.4.3 Method for Calculating Pre-Development Phosphorous Loading
Pre-development Phosphorous Loading: Lpre = (Rv)(C)(A) 8.16
Rv = 0.05 + 0.009(I)
where:
Lpre
Rv
C
A
8.16
I
=
average annual load of total phosphorous exported from the site in pounds per year
=
runoff coefficient, which expresses the fraction of rainfall which is converted into runoff
=
flow-weighted mean concentration of phosphorous in urban runoff (mg/l)
C = 0.26 if pre-development I < 20%
C = 1.08 if pre-development I ≥ 20%
=
area of the site within the IDA Critical Area (acres)
=
includes regional constants and unit conversion factors
=
site imperviousness (I = 75 if site is 75% impervious)
New Development Phosphorous Loading: Lpre = 0.5 (A)
where:
Lpre
A
=
=
average annual load of total phosphorous exported from the site in pounds per year
area of the site within the IDA Critical Area (acres)
D.4.8
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
STEP 3: Calculate Post-Development Pollutant Load
The next step involves computing the post-development pollutant load from the site. Again, an
abbreviated version of the Simple Method (Schueler, 1987), described in Step 2 is used for the
calculations. The equations to be used to determined post-development pollutant loads follows
below.
Table D.4.4 Method for Computing Post-Development Pollutant Loadings
Post-Development Pollutant Loading:
Lpost = (Rv)(C)(A)(8.16)
Rv = 0.05 + 0.009(I)
where:
Lpost
=
Rv
=
I
C
=
=
A
8.16
=
=
average annual load of total phosphorous exported from the site through
storm runoff in pounds per year
runoff coefficient, which expresses the fraction of rainfall which is
converted into runoff
site imperviousness (I = 75 if site is 75% impervious)
flow-weighted mean concentration of the pollutant in urban runoff (mg/l)
C = 0.26 if new development activity
C = 1.08 if redevelopment activity
area of the development site (acres)
includes regional constants and unit conversion factors
STEP 4: Calculate the Pollutant Removal Requirement
Phosphorous pollutant loads generated from the site must be reduced so that they are 90% or less
of the load that is generated prior to development. The amount of phosphorous that must be
removed though the use of stormwater BMPs is called the Pollutant Removal Requirement. The
equation in Table D.4.5 expresses this term numerically.
Table D.4.5 Computing Pollutant Removal Requirements
Removal Requirement
=
Post-development phosphorous load - (0.9) Predevelopment phosphorous load
RR = Lpost - 0.9 (Lpre)
D.4.9
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
STEP 5: Identify Feasible Urban Best Management Practices (BMP)
Urban BMP options must be shown to be feasible for the site both in terms of physical suitability
and pollutant removal capabilities (see Volume 1, Chapter 4). It should be noted that the BMPs
which survive the screening procedure still need to undergo more detailed design checks and field
tests to confirm that they are actually feasible. Evidence of site feasibility will be required as part of
the final submittal package.
Table D.4.6 Estimate of Pollutant Load Removed by Each BMP
Load Removed
=
(Post-development Load)(Removal Rate)
LR = Lpost (RR)(% Drainage Area Served)
If the Load Removed is equal to or greater than the Pollutant Removal Requirement computed in
STEP 4, then the on-site BMP complies with the 10% Rule. If not, the designer must evaluate
alternative BMP designs to achieve higher removal efficiencies.
Tables D.4.7 and D.4.8 provide updated phosphorous removal rates for stormwater BMPs used
in this manual, based on a comprehensive national survey of pollutant removal performance
monitoring data (Brown and Schueler, 1997).
D.4.10
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
Table D.4.7 Updated Critical Area Keystone Phosphorous Removal Rates
CODE
BMP LIST
TP%
P-1
Micropool ED
40
P-2
Wet Pond
50
P-3
Wet ED Pond
60
P-4
Multiple Pond
65
P-5
Pocket Pond
50
W-1
Shallow Wetland
40
W-2
ED Wetland
40
W-3
Pond/Wetland
55
W-4
Pocket Wetland
40
I-1
Infiltration Trench
65
I-2
Infiltration Basin
65
F-1
Surface Sand Filter
50
F-2
Underground Sand Filter
50
F-3
Perimeter Sand Filter
50
F-4
Organic Filter
50
F-5
Pocket Sand Filter
40
F-6
Bioretention
50
O-1
Dry Swale
65
O-2
Wet Swale
40
D.4.11
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
Table D.4.8 TP Removal Rates for BMPs Not on the List
BMP LIST
TP%
Detention Facility - 2
10
Dry ED Pond - 7
20
Open Channels - 7
-15
Biofilter - 2
25
Dry Well
Nd
Catchbasin - 1
5
Filterstrip - 1
7
Water Quality Inlets - 1
0
Source: Brown and Schueler, 1997, National Pollutant Removal Database for Stormwater BMPs
STEP 6: Define Off-Site Compliance
In the event that on-site BMPs cannot fully meet the pollutant removal requirement and onsite design cannot be changed, an option exists for off-site mediation, otherwise known as an
Offset Project. Of primary concern is that the project be associated with pollutant removal or
water quality protection for water bodies within the same sub-watershed as the development
project. Similarly, off-site projects should be designed to minimize maintenance requirements.
In such cases where this is not feasilbe, a maintenance agreement should be established so as to
insure long-term water quality protection. Table D.4.9 provides a prioritized list of potential
offset projects.
D.4.12
Appendix D-4. Stormwater Criteria of the MD Critical Area IDA Zone....... Standard Application
Table D.4.9 Prioritized List of Potential Offsite Projects
Having shown that on-site compliance is not feasible, the applicant may choose from the
following Offset options in order of preference.
1.
Construction and operation of an off-site BMP, sized to meet the removal
requirements.
2.
Retrofit an existing BMP or pond structure.
3.
Retrofit an existing storm drain system to encourage infiltration.
4.
Reduce the imperviousness of an existing property through reforestation.
5.
Implement a riparian reforestation project (0.5 acres of tree planting per lb of
removal requirement). Planting plan must meet local Critical Area reforestation
standards, or Maryland Forest Conservation Manual, if no local standards exist.
6.
In rural jurisdictions where retrofit options are limited, finance the installation of
structural agricultural BMP for a farm with a NRCS approved conservation
7.
Other innovative options: restore a degraded tidal or non-tidal wetland that has
been disturbed by previous urban or agricultural drainage activity. This may be
accomplished through removal of fill, restoration of original water circulation
patterns, and wetland plantings.
a
plan.
D.4.13
Documentation of BMP Ability to Meet
the 80% TSS Removal Requirement
Appendix
D.5
Appendix D.5. Documentation of BMP Ability to Meet the 80% TSS Removal Requirement
BMPs employed at new development in the State of Maryland are now required to meet a
performance standard under the recently issued CZARA Coastal Zone 6217(g) management
measures guidance (US EPA, 1993). The specific management measures read “After construction is
completed and the site is permanently stabilized, reduce the average annual total suspended solid
(TSS) loadings by 80% percent...on an average annual basis.”
Based on the 90% capture sizing criteria and published pollutant removal performance data, it may
be presumed that the BMPs contained on the Acceptable BMP List outlined in Chapter 2 can meet
the 80% TSS removal performance standard, if they are designed in accordance with the BMP
performance criteria outlined in Chapter 3. The Acceptable BMP List will be periodically updated as
new monitoring research is conducted and new stormwater treatment technologies are tested.
Table 1 shows the median sediment removal rate measured or projected for the nineteen stormwater
BMPs currently on the approved list. The Table was developed as part of a national assessment of
stormwater BMP monitoring research by the Center for Watershed Protection (Brown and Schueler,
1997).
It should be clearly noted that the median values were obtained from a range of research studies that
varied widely in respect to geography, climate, design, treatment volume, sampling intensity, and
removal efficiency calculation method. In particular, the averages for some pond and wetland
designs reflect facilities that were under-sized or poorly designed, which tends to skew averages
lower than they would otherwise be. Consequently, the numbers in Table 1 should be considered
only as an indicator of expected pollutant removal performance in the State of Maryland.
As can be seen from Table 1, many BMPs on the list are capable of meeting the 80% TSS removal
requirement. Nine of the BMPs, however, had median removal rates that ranged from 60% and
79%. As noted earlier, these slightly lower removal rates may have been caused by the fact that
datasets include some under-sized or poorly designed practices that reduce the overall median.
In addition, performance monitoring data was not available to assess five practices, and their
sediment removal rate had to be projected based on the performance of similar systems. They are:
P-5 Pocket Pond
(presumed to be similar to P-2)
I -2 Infiltration Basin
(published rate based on land application studies [Schueler, 1987])
F-2 Underground Sand Filter (presumed to be similar to F-1)
F-5 Pocket Sand Filter
(presumed to be similar to F-1)
F-6 Bioretention
(presumed to be similar to O-1)
Table D.5.1 TSS Removal Performance List
D.5.1
Appendix D.5. Documentation of BMP Ability to Meet the 80% TSS Removal Requirement
ACCEPTABLE BMPs
N
TSS
80% ?
6 (a)
61
yes (b)
P-2 Wet Pond
30
77
yes
P-3 Wet ED Pond
6
60
yes (b)
P-4 Multiple Pond
pr- W-3
72
yes
P-5 Pocket Pond
pr- W-4
nd
yes
W-1 Shallow Wetland
14
84
yes
W-2 ED Wetland
5
62
yes (b)
W-3 Pond/Wetland
11
72
yes (b)
W-4 Pocket Wetland
1
76
yes (b)
I-1 Infiltration Trench
2
89
yes
I-2 Infiltration Basin
0
nd
yes
F-1 Surface Sand Filter
6
83
yes
see F-1
nd
yes
F-3 Perimeter Sand Filter
3
79
yes
F-4 Organic Filter
2
81
yes
F-5 Pocket Sand Filter
0
nd
yes
F-6 Bioretention
0
nd
yes (pr)
O-1 Dry Swale
4
93
yes
O-2 Wet Swale
5
74
yes
P-1 Micropool ED
F-2 Underground Sand Filter
Notes:
N = number of BMPs sampled
nd = No data
pr = projected removal , based on similar facilities
(a) data from dry ED ponds without micropools
(b) 80% removal can be achieved under proposed design criteria, current
database is biased by under-sized or poorly designed facilities
D.5.2
Appendix D.5. Documentation of BMP Ability to Meet the 80% TSS Removal Requirement
References
Brown, W. and T. Schueler. 1997. National Pollutant Removal Performance Database for
Stormwater BMPs. Center for Watershed Protection. Chesapeake Research Consortium. 220 pp.
U.S. EPA. 1993. Guidance Specifying Management Measures for Sources of Nonpoint Pollution in
Coastal Waters. Issued under authority of Section 6217(g) of the Coastal Zone Act Reauthorization
Amendments of 1990. No. 840-B-92-002. EPA Office of Water. Washington, D.C.
D.5.3
Appendix
Industrial Stormwater NPDES Permit
Requirements
D.6
Section D.6.1 Standard Industrial Classification (SIC) Code
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
Identified by EPA in 40 CFR 122.26(b)(14)(i through xi):
(i)
Facilities subject to stormwater effluent limitations...
No specific SIC codes cited. [Contact MDE/WMA for SIC number if not identified
previously on another NPDES permit; 410-631-3543 or 410-631-3323.]
(ii)
24
26
28
29
31
32
33
344
373
(iii)
10
12
13
14
(except 2434) Lumber and Wood Products, Except Furniture
2434 - Wood Kitchen Cabinets
(except 265 and 267) Paper and Allied Products
265 - Paperboard Containers and Boxes
267 - Converted Paper and Paperboard Products, Except Containers and Boxes
(except 283) Chemicals and Allied Products
283 - Drugs
Petroleum Refining and Related Industries
Leather and Leather Products
(except 323) Stone, Clay, Glass, and Concrete Products
323 - Glass Products made of Purchased Glass
Primary Metal Industries
Fabricated Structural Metal Products
Ship and Boat Building and Repairing
Metal Mining
Coal Mining
Oil and Gas Extraction (including facilities where stormwater comes into contact
with overburden or raw materials)
Mining and Quarrying of Nonmetallic Minerals, Except Fuels
(iv)
Hazardous waste treatment, storage or disposal facilities.
No specific SIC codes cited. [Contact MDE/WMA for SIC number if not identified
previously on another NPDES permit; 410-631-3543 or 410-631-3323.]
(v)
Landfills, land application sites, and open dumps...
No specific SIC codes cited. [Contact MDE/WMA for SIC number if not identified
previously on another NPDES permit; 410-631-3543 or 410-631-3323.]
(vi)
Facilities involved in the recycling of materials...
including, but not limited to;
5015 Motor Vehicle Parts, Used
5093 Scrap and Waste Materials
D.6.1
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
(vii)
Steam electric power general facilities...
No specific SIC codes cited. [Contact MDE/WMA for SIC number if not identified
previously on another NPDES permit; 410-631-3543 or 410-631-3323.]
(viii) Transportation facilities classified as:
40
Railroad Transportation
41
Local and Suburban Transit and Interurban Highway Passenger Transportation
42
(except 4221-4225) Motor Freight Transportation and Warehousing
4221 - Farm Product Warehousing and Storage
4222 - Refrigerated Warehousing and Storage
4225 - General Warehousing and Storage
43
United States Postal Service
44
Water Transportation
45
Transportation by Air
5171 Petroleum Bulk Stations and Terminals
(ix)
Treatment works treating domestic sewage...
No specific SIC codes cited. [Contact MDE/WMA for SIC number if not identified
previously on another NPDES permit; 410-631-3543 or 410-631-3323.]
(x)
Construction Activity
See attached SIC code list for construction activity [Major Group Number 15].
(xi)
20
Food and Kindred Products
21
Tobacco Products
22
Textile Mill Products
23
Apparel and other Finished Products made from Fabrics and Similar Materials
2434 Wood Kitchen Cabinets
25
Furniture and Fixtures
265
Paperboard Containers and Boxes
267
Converted Paper and Paperboard Products, Except Containers and Boxes
27
Printing, Publishing, and Allied Industries
283
Drugs
285
Paints, Varnishes, Lacquers, Enamels, and Allied Products
30
Rubber and Miscellaneous Plastics Products
31
(except 311) Leather and Leather Products
311 - Leather Tanning and Finishing
323
Glass Products, made of Purchased Glass
34
(except 3441) Fabricated Metal Products, Except Machinery and Transportation
Equipment
3441 - Fabricated Structural Metal
35
Industrial and Commercial Machinery and Computer Equipment
36
Electronic and other Electrical Equipment and Components, Except Computer
Equipment
D.6.2
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
37
(except 373) Transportation Equipment
373 - Ship and Boat Building and Repairing
38
Measuring, Analyzing, and Controlling Instruments; Photographic, Medical and
Optical Goods; Watches and Clocks
39
Miscellaneous Manufacturing Industries
4221 Farm Product Warehousing and Storage
4222 Refrigerated Warehousing and Storage
4225 General Warehousing and Storage
D.6.3
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
Section D.6.2 General Discharge Permit - Sample
GENERAL DISCHARGE PERMIT FOR STORM WATER ASSOCIATED WITH
INDUSTRIAL ACTIVITIES
GENERAL DISCHARGE PERMIT NO. 97-SWGENERAL NPDES PERMIT NO. MDR______
Effective Date:________________________________
Expiration
Date:________________________________
Part I. APPLICABILITY.
A. Geographic Coverage. This permit covers all areas of the State of Maryland.
B. Eligible Discharges. This permit may cover all storm water discharges associated with
industrial activity, as defined in 40 CFR 122.26, that discharge to surface waters of the State.
Such discharges may be commingled with wastewater or water discharges not regulated by this
permit. This permit also covers storm water discharges not included in 40 CFR 122.26 that the
Department determines would, if not regulated by a permit, be likely to contribute to a violation
of a water quality standard or be a significant contributor of pollutants to waters of the State,
either surface or ground.
C. Ineligible Discharges. The following discharges are not covered under this general permit.
1. Storm water discharges from any construction activity, as defined in 40 CFR
122.26, except for construction activity associated with an industrial facility that is or
will be covered by this permit;
2. Storm water discharges that are regulated by effluent limitation guidelines.
All or part of the storm water from the following industries are covered by effluent
limitation guidelines: cement manufacturing (40 CFR 411), feedlots (40 CFR 412),
fertilizer manufacturing (40 CFR 418), petroleum refining (40 CFR 419), phosphate
manufacturing (40 CFR 422), steam electric generating (40 CFR 423), coal mining
(40 CFR 434), mineral mining and processing (40 CFR 436), ore mining and dressing
(40 CFR 440), and asphalt emulsion (40 CFR 443);
3. Storm water discharges associated with industrial activity from inactive
mining or inactive oil and gas operations occurring on federal lands; and
4. Storm water discharges whose NPDES permit has been terminated (other than
at the request of the permittee) or denied, or those for which the Department requires
an individual permit or an alternative general permit.
D.6.4
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
D. Individual Permit or Another General Permit Required.
1. Any person who conducts activities which are covered by this General Permit
and does not have a valid individual discharge permit is required to apply for
coverage under this General Permit within 60 days of the issuance of the permit.
2. The Department may require any person authorized by this permit to apply for
and obtain an individual State or State/NPDES discharge permit or to obtain coverage
under another general permit. If an owner or operator fails to submit, in a timely
manner, an application for an individual State or State/NPDES discharge permit or a
Notice of Intent (NOI) for another general permit as required by the Department
under this condition, the applicability of this permit to the owner or operator is
automatically terminated at the end of the day specified by the Department for the
application or NOI submittal.
3. Any person authorized by this permit may request to be excluded from
coverage under this permit by applying for an individual State or State/NPDES
discharge permit or requesting coverage under another general permit. The
Department may grant this request by issuing an individual State or a State/NPDES
discharge permit or by granting coverage under another general permit, if the reasons
cited by the owner or operator are adequate to support the request.
4. When an individual State or State/NPDES discharge permit is issued to a
person otherwise subject to this permit, the applicability of this permit to the
permittee is automatically terminated on the effective date of the individual State or
State/NPDES discharge permit.
5. If there is evidence indicating potential or realized impacts on water quality
due to any activity covered by this permit, the owner or operator of such discharge
may be required to obtain an individual State or a State/NPDES discharge permit or
coverage under another general permit.
6. If a person otherwise covered under this permit is denied coverage under an
individual State or a State/NPDES discharge permit, or another general permit, the
denial automatically terminates, on the date of the denial, the person's coverage under
this general permit, unless otherwise specified by the Department.
7. The Department may terminate coverage under this general permit for an
existing permittee if the Department finds that:
a. The NOI contained false or inaccurate information;
b. Conditions or requirements of the discharge permit have been or are
D.6.5
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
about to be violated;
c. Substantial deviation from plans, specifications, or requirements has
occurred;
d. The Department has been refused entry to the premises for the purpose
of inspecting to insure compliance with the conditions of the discharge
permit;
e. A change in conditions exists that requires temporary or permanent
reduction or elimination of the permitted discharge;
f. Any State or federal water quality stream standard or effluent standard
has been or is likely to be violated; or
g. Any other good cause exists for denying coverage under this permit.
E. Authorization. To be authorized to discharge under this general permit, a person is required
to submit an NOI in accordance with the requirements of Part III of this permit, to pay the
required fee, and to comply with the terms and conditions of this permit. Coverage under this
permit is effective on the date that the NOI is acknowledged by the Department and the NOI fee
is paid to the Department in accordance with the terms stipulated in Part III below. A person
who submits such an NOI is notified of its acceptance by the Department, complies with the
terms and conditions of this permit, and pays the required fee is authorized to discharge under
the terms and conditions of this permit.
If the NOI fee is paid by a check which does not clear for any reason, the person will be given
30 calendar days to make proper payment including any interest and other charges that are due.
If payment is not made within this time, coverage under this permit shall be considered void
from the outset. The permittee should save the cancelled check, a copy of the completed NOI,
and related documents. These documents shall be provided to the Department upon request.
F. Transfer of Authorization.
1. The authorization under this permit is not transferable to any person except in
accordance with this section.
D.6.6
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
2. Authorization to discharge under this permit may be transferred to another person if:
a. The current permittee notifies the Department (Industrial Discharge Permits
Division with copy sent to Inspection and Compliance Program) in writing of the proposed
transfer;
b. A written agreement, indicating the specific date of the proposed transfer of
permit coverage and acknowledging the responsibilities of the current and new permittee for
compliance with the terms and conditions of this permit, is submitted to the Department;
c. The new permittee either confirms in writing that the type of discharge,
number of outfalls, and other information given on the original NOI remain correct or updates
this information;
d. The new permittee confirms in writing that either they will follow the existing
storm water pollution prevention plan or that they have developed a new plan; and
e. Neither the current permittee nor the new permittee receives notification from
the Department, within 30 days of receipt of items I.F.2.a through d above, of intent to terminate
coverage under this permit.
3. The Department may continue coverage for the new permittee under this permit or
may require the new permittee to apply for and obtain an individual State or State/NPDES
discharge permit or obtain coverage under another general permit.
4. A new owner of a facility is responsible for any fees unpaid by the former owner.
G. Continuation of an Expired General Permit. An expired general permit continues in force
and effect until a new general permit is issued; for the next 60 days provided the permittee
submits a new NOI and fee within that period; or until the general permit is revoked or
withdrawn. Only those permittees authorized to discharge prior to the expiration of the general
permit are covered by the continued permit.
Part II. Definitions.
A. "Best management practices (BMP)" means schedules of activities, prohibitions of
practices, maintenance procedures, and other management practices to prevent or reduce the
pollution of waters of this State. BMP also include treatment requirements, operating
procedures, and practices to control plant site runoff, spillage or leaks, sludge or waste disposal,
or drainage from raw materials storage.
B. "CFR" means Code of Federal Regulations.
C. "COMAR" means Code of Maryland Regulations.
D.6.7
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
D. "Construction activity" means clearing, grading, and excavation activities except:
operations that result in the disturbance of less than five acres (or whatever threshold is
currently specified in 40 CFR 122.26) of total land area which are not a part of a larger common
plan of development or sale.
E. "Department" means the Maryland Department of the Environment. Unless stated
otherwise, all submissions to the Department shall be directed to the attention of the Industrial
Discharge Permits Division.
F. "Federal Clean Water Act" means the federal Water Pollution Control Act Amendments of
1972, its amendments and all rules and regulations adopted thereunder.
G. "General permit" means a discharge permit issued for a class of dischargers.
H. "Ground water" means underground water in a zone of saturation.
I. "Includes" or "including" means includes or including by way of illustration and not by
way of limitation.
J. "NPDES permit" means a National Pollutant Discharge Elimination System permit issued
under the federal Clean Water Act.
K. "NOI" means Notice of Intent to be covered by this permit (see Part III of this permit).
L. "Operator" means that person or those persons with responsibility for the management and
performance of each facility.
M. "Permittee" means the person holding a permit issued by the Department.
N. "Person" means an individual, receiver, trustee, guardian, personal representative, fiduciary,
or representative of any kind, and any partnership, firm, association, corporation, or other entity.
Person includes the federal government, this State, any county, municipal corporation or other
political subdivision of this State or any of their units.
O. "Project" means the total area upon which construction activity will occur through stages or
phases over time.
P. "Section 313 water priority chemical" means a chemical or chemical categories which: 1)
are listed at 40 CFR 372.65 pursuant to Section 313 of Title III of the Superfund Amendments
and Reauthorization Act (SARA) of 1986, also titled the Emergency Planning and Community
Right-to-Know Act of 1986; 2) are present at or above threshold levels at a facility subject to
SARA Title III, Section 313 reporting requirements; and 3) that meet at least one of the
following criteria: (i) are listed in Appendix D of 40 CFR 122 on either Table II (organic
priority pollutants), Table III (certain metals, cyanides, and phenols) or Table V (certain toxic
D.6.8
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
pollutants and hazardous substances); (ii) are listed as a hazardous substance pursuant to
Section 311(b)(2)(A) of the Clean Water Act at 40 CFR 116.4; or (iii) are pollutants for which
EPA has published acute or chronic water quality criteria.
Q. "Significant materials" includes, but is not limited to: raw materials; fuels; materials such
as solvents, detergents, and plastic pellets; finished materials, such as metallic products; raw
materials used in food processing or production; hazardous substances designated under Section
101(14) of CERCLA; any chemical the facility is required to report pursuant to Section 313 of
Title III of SARA; fertilizers; pesticides; and waste products, such as ashes, slag and sludge that
have the potential to be released with storm water discharges.
R. "Significant spills" includes, but is not limited to: releases of oil or hazardous substances in
excess of reportable quantities under Section 311 of the Clean Water Act (40 CFR 110.10 and
40 CFR 117.21) or Section 102 of CERCLA (40 CFR 302.4).
S. "State discharge permit" means a discharge permit issued pursuant to the Environment
Article, Title 9, Subtitle 3, Annotated Code of Maryland.
T. "Storm water associated with construction activity" means the discharge from any
conveyance which is used for collecting and conveying storm water and which is directly
related to clearing, grading, and excavation activities. For this permit, groundwater that seeps
into construction excavations shall be considered and regulated as storm water.
U. "Storm water associated with industrial activity" means storm water as defined in 40 CFR
122.26(b)(14).
V. "Surface waters" means all waters of this State which are not ground waters.
W. "Wastewater" means any:
1. Liquid waste substance derived from industrial, commercial, municipal, residential,
agricultural, recreational, or other operations or establishments; and
2. Other liquid waste substance containing liquid, gaseous or solid matter and having
characteristics which will pollute any waters of this State.
X. "Waters of this State" includes:
1. Both surface and underground waters within the boundaries of this State subject to its
jurisdiction, including that part of the Atlantic Ocean within the boundaries of this State, the
Chesapeake Bay and its tributaries, and all ponds, lakes, rivers, streams, tidal and nontidal
wetlands, public ditches, tax ditches, and public drainage systems within this State, other than
those designed and used to collect, convey, or dispose of sanitary sewage; and
D.6.9
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
2. The flood plain of free-flowing waters determined by the Department of the
Environment on the basis of the 100-year flood frequency.
PART III. Notice of Intent Requirements.
A. Deadlines for Notification. Any person who has an existing individual State or State/NPDES
discharge permit for activities covered under this general permit is not obligated to obtain
coverage under this general permit until the individual State or State/NPDES discharge permit
expires. At least 180 days prior to the expiration date of the individual State or State/NPDES
discharge permit for activities covered under this general permit, a person shall submit an NOI
requesting coverage under this general permit. However, a person currently covered under an
individual State or State/NPDES discharge permit may choose to request coverage under this
general permit by submitting an NOI and a fee in accordance with the requirements of this Part
following issuance of this general permit. At least 30 days prior to the commencement of any
new storm water discharge covered under this general permit, a person shall request coverage
by submitting an NOI in accordance with the requirements of this Part. Any person who is
covered under 92-GP-0001 shall submit a new NOI and fee within 60 days of issuance to
continue coverage. A person planning construction activity (disturbing five or more acres) at an
industrial facility must submit an NOI or updated NOI at least 48 hours prior to any land
disturbing activities. The Department may bring an enforcement action for failure to submit an
NOI in a timely manner, or for any unauthorized discharges that occurred prior to obtaining
coverage under this permit.
B. Notice of Intent. A person shall obtain the appropriate NOI form from the Department, and
shall provide the following information:
1. County, name and address (location) of the facility;
2. Name and telephone number of the facility contact;
3. Written description of industrial activity taking place;
4. One four-digit SIC code that best represent the principal products or activities provided by the
facility;
5. Watershed basin code;
6. The latitude and longitude of the approximate center of the facility to the nearest 15 seconds;
7. The name of the receiving water(s), or if the discharge is to a municipal separate storm sewer,
the name of the municipal operator of the storm sewer and the ultimate receiving water(s);
8. Permit number of any other NPDES permit issued for the facility;
9. Area of industrial activity at facility in acres;
10. Status of owner/operator (private, Federal, etc);
11. Federal tax ID number;
12. Name and mailing address of applicant (company that operates the permitted facility;
13.Name and telephone number of operator contact;
14. A summary of all existing quantitative data, if any, describing the concentration of pollutants
in storm water discharges;
15. Where construction is involved, a brief project description, including existing and proposed
D.6.10
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
land uses;
16. Where construction is involved, the total site area, the total proposed disturbed area, the
type(s) of storm water management best management practice(s) (BMP) proposed, and the total
drainage area to be controlled by each type of BMP; and
17. Signiture of applicant.
If a person operates multiple facilities, an NOI is required for each noncontiguous site.
C. Discharge Permit Fee
Persons who intend to obtain coverage under this general permit shall submit to the Department a
fee of $550 with the NOI application. Local and state governments are not required to pay a fee.
As an alternative to a single fee, a person may submit five annual $120 payments beginning with
the submission of the NOI application and every July 1 thereafter.
For facilities which did not begin operating until after September 29, 1995 and which were
previously registered under permit 92-GP-0001, the total fee shall be discounted by 100 dollars for
each full calendar year between January 1, 1993 and the month which operations began.
The discharge fee for new facilities that have commenced operating after July 1 of any year shall
be prorated on a monthly basis.
D. Required Signatures.
1. Certification. Any person signing an NOI shall make the following certification as part
of the NOI.
"I certify under penalty of law that this document and all attachments were prepared under
my direction or supervision in accordance with a system designed to assure that qualified personnel
properly gather and evaluate the information submitted. Based on my inquiry of the person or
persons who manage the system, or those persons directly responsible for gathering the
information, the information submitted is, to the best of my knowledge and belief, true, accurate,
and complete. I am aware that there are significant penalties for submitting false information,
including the possibility of fine and imprisonment for knowing violations."
2. Signatories. The NOI shall be signed as follows:
a. For a corporation: by a responsible corporate officer. For the purpose of this
section, a responsible corporate officer means:
(i) A president, secretary, treasurer, or vice-president of the corporation in
charge of a principal business function, or any other person who performs similar policy or
decision-making functions for the corporation; or
D.6.11
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
(ii) The manager of one or more manufacturing, production, or operating
facilities employing more than 250 persons or having gross annual sales or expenditures exceeding
$25 million (in second-quarter 1980 dollars), if authority to sign documents has been assigned or
delegated to the manager in accordance with corporate procedures.
b. For a partnership or sole proprietorship: by a general partner or the proprietor,
respectively; or
c. For a municipal, State, federal, or other public agency: by either a principal
executive officer or ranking elected official. For purposes of this section, a principal executive
officer of a federal agency includes:
(i) The chief executive officer of the agency; or
(ii) A senior executive officer having responsibility for the overall
operations of a principal geographic unit of the agency (e.g., Regional Administrators of EPA).
3. Report Submission.
a. All reports required by permits, and other information requested by the
Department shall be signed by a person described in Part III E.2 or by a duly authorized
representative of that person. A person is a duly authorized representative only if:
(i) The authorization is made in writing by a person described in Part III
E.2;
(ii) The authorization specifies either an individual or a position having
responsibility for the overall operation of the regulated facility or activity such as the position of
plant manager, operator of a well or a well field, superintendent, position of equivalent
responsibility or an individual or position having overall responsibility for environmental matters
for the company; and
D.6.12
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
(iii) The written authorization is submitted to the Department.
b. If an authorization under this subsection is no longer accurate because a
different individual or position has responsibility for the overall operation of the facility, a new
authorization satisfying the requirements of Part III E.3(a) must be submitted to the Department
prior to or together with any reports, information or applications to be signed by the new authorized
representative.
E. Where to Submit. A person shall submit a signed copy of the NOI and the required fee, made
payable to the Maryland Department of the Environment, to the following address:
Maryland Department of the Environment
P.O. Box 2057
Baltimore MD 21203-2057
F. Failure to Notify. Persons who discharge storm water associated with industrial activity, who
fail to notify the Department of their intent to be covered under this permit, and who discharge to
waters of this State without an individual State or State/NPDES discharge permit, are in violation
of the federal Clean Water Act and the Environment Article, Annotated Code of Maryland, and
may be subject to penalties.
G. Additional Notification.
Facilities which discharge storm water associated with industrial activity to the municipal
separate storm sewer system of Anne Arundel County, Baltimore (City), Baltimore County, Carroll
County, Charles County, Frederick County, Harford County, Howard County, Montgomery
County, Prince George's County, or the State Highways Administration shall, in addition to filing
copies of the NOI in accordance with condition III.B., submit, concurrently, signed copies of the
NOI to the operator of the municipal separate storm sewer to which they discharge (see NOI form
for addresses).
H. Permit Expiration and Renewal. Within 60 days after the reissuance of this general permit
with new effective and expiration dates, the permittee is required to submit to the Department
either:
1. A notice that the discharge or industrial activity (including the exposure of residual
pollutants from concluded industrial activity) will cease by the expiration date of this permit; or
2. A new NOI and any fee in accordance with the requirements of the reissued general
permit in order to be covered under the reissued general permit.
Part IV. Special Conditions.
D.6.13
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
A. Releases In Excess Of Reportable Quantities
1. The discharge of hazardous substances or oil in the storm water discharge(s) from a facility
shall be prevented or minimized in accordance with the applicable storm water pollution prevention
plan for the facility. This permit does not relieve the permittee of the reporting requirements of 40
CFR part 117 and 40 CFR part 302. Except as provided in condition IV.A.2 (multiple anticipated
discharges) of this permit, where a release containing a hazardous substance in an amount equal to
or in excess of a reporting quantity established under either 40 CFR 117 or 40 CFR 302, occurs
during a 24-hour period:
a. The discharger is required to notify the Department of any oil spill or discharge of oil
by calling its Emergency Response Division at (410) 974-3551 and notify the National Response
Center (NRC) at (800) 424-8802 or, in the Washington, DC metropolitan area, at (202) 426-2675
in accordance with the requirements of COMAR 26.10.01.03, 40 CFR 117 and 40 CFR 302
respectively as soon as he or she has knowledge of the discharge;
b. The permittee shall submit to the Department within 10 working days of knowledge of
the release a written description of: the release (including the type and estimate of the amount of
material released), the date that such release occurred, the circumstances leading to the release, and
steps to be taken in accordance with condition IV.A.1.c (below) of this permit, and any other
information as required by COMAR 26.10.01.03; and
c. The storm water pollution prevention plan required under condition IV.B (storm water
pollution prevention plans) of this permit must be modified within 14 calendar days of knowledge
of the release to: provide a description of the release, the circumstances leading to the release, and
the date of the release. In addition, the plan must be reviewed to identify measures to prevent the
reoccurrence of such releases and to respond to such releases, and the plan must be modified where
appropriate.
2. Multiple Anticipated Discharges - Facilities which have more than one anticipated discharge
per year containing the same hazardous substance in an amount equal to or in excess of a reportable
quantity established under either 40 CFR 117 or 40 CFR 302, which occurs during a 24-hour
period, where the discharge is caused by events occurring within the scope of the relevant
operating system shall comply with conditions IV.A.1.a,b, and c above, but must submit
notifications only for the first such release that occurs during a calendar year (or for the first year of
this permit, after submittal of an NOI).
3. Spills. This permit does not authorize the discharge of hazardous substances or oil resulting
from an on-site spill.
D.6.14
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
B. Storm Water Pollution Prevention Plans - General
The permittee shall develop a storm water pollution prevention plan for each facility covered by
this permit. The storm water pollution prevention plan shall be prepared in accordance with sound
engineering practices. The plan shall identify potential sources of pollution which may reasonably
be expected to affect the quality of storm water discharges associated with industrial activity from
the facility. In addition, the plan shall describe and ensure the implementation of practices which
are to be used to reduce the pollutants in storm water discharges associated with industrial activity
at the facility and to assure compliance with the terms and conditions of this permit.
1.
In developing this plan, the permittee shall use as a reference "Storm Water Management
for Industrial Activities: Developing Pollution Prevention Plans and Best Management Practices"
(EPA Document #EPA832-R-92-006) or, when it is available, an EPA-published summary
document on the same subject. These documents can be obtained from the National Technical
Information Service, 5285 Port Royal Road, Springfield, Virginia 22161 (phone: 703-487-4600).
2.
The plan shall be signed in accordance with Part III, Section E.2 of this permit, and be
retained on site in accordance with Part VI, Section A.2 of this permit. Plans for facilities in
existence at the time of the issuance of this permit shall be completed within one year of obtaining
coverage under this general permit or within one year of notification by the Department of the need
for obtaining a storm water discharge permit, whichever occurs first. Plans shall provide for
compliance with the terms of the plan within 18 months of obtaining coverage under this general
permit or within 18 months of notification by the Department of the need for obtaining a storm
water discharge permit, whichever occurs first. In the case of new facilities, the plan shall be
completed and implemented prior to submitting an NOI to be covered under this permit. The
permittee shall make plans available upon request to the Department, and in the case of a storm
water discharge associated with industrial activity which discharges to a municipal separate storm
sewer system with an NPDES permit, to the municipal operator of the system (those systems are
listed in Condition III. G, addresses are on NOI).
3.
If the plan is reviewed by the Department, the Department may notify the permittee, at
any time, that the plan does not meet one or more of the minimum requirements of this Part. After
such notification from the Department, the permittee shall make changes to the plan to meet the
objections of the Department and shall submit to the Department a written certification that the
requested changes have been made and implemented. Unless otherwise provided by the
Department, the permittee shall have 90 days after such notification to make the necessary changes.
4.
The permittee shall amend the plan whenever there is a change in design, construction,
operation, or maintenance which has a significant effect on the potential for the discharge of
pollutants to the waters of the State or if the storm water pollution prevention plan proves to be
ineffective in achieving the general objectives of controlling pollutants in storm water discharges
associated with industrial activity. Amendments to the plan may be reviewed by the Department as
described above.
D.6.15
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
C. Storm Water Pollution Prevention Plan - Contents
The plan shall include, at a minimum, the following items:
1.
Description of Potential Pollutant Sources
Each plan shall provide a description of potential sources which may be reasonably
expected to add significant amounts of pollutants to storm water discharges. Each plan shall
identify all activities and significant materials which may potentially be significant pollutant
sources. Each plan shall include:
a.
A site map indicating an outline of the drainage area of each storm water outfall;
each existing structural control measure to reduce pollutants in storm water runoff; and surface
water bodies, including drainage ditches and wetlands.
b.
A topographic map (or other map, if a topographic map is unavailable), extending
one-quarter of a mile beyond the property boundaries of the facility. The requirements of this
condition may be included in the site map required under Part IV, Section C.1.a. above, if
appropriate.
c.
A narrative description of significant materials that have been treated, stored, or
disposed in a manner which allowed exposure to storm water at anytime from three years prior to
obtaining coverage under this permit until the time the present method of on-site storage or
disposal was initiated; materials management practices employed to minimize contact of these
materials with storm water runoff; materials loading and access areas; the location and a
description of existing structural and non-structural control measures to reduce pollutants in storm
water runoff; and a description of any treatment the storm water receives.
d.
For each area of the facility that generates storm water discharges associated with
industrial activity with a reasonable potential for containing significant amounts of pollutants, a
prediction of the direction of flow, and an estimate of the types of pollutants which are likely to be
present in storm water discharges associated with industrial activity; and
e.
discharges.
A summary of all existing sampling data describing pollutants in storm water
D.6.16
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
2.
Storm Water Management Controls
Each facility covered by this permit shall develop a description of storm water
management controls appropriate for the facility, and implement such controls. The
appropriateness and priorities of controls in a plan shall reflect identified potential sources of
pollutants at the facility. The description of storm water management controls shall address the
following minimum components, including a schedule for implementing such controls:
a.
Preventive Maintenance. A preventive maintenance program that involves
timely inspection and maintenance of storm water management devices (cleaning oil/water
separators, catch basins) as well as inspecting and testing plant equipment and systems to uncover
conditions that could cause breakdowns or failures resulting in discharges of pollutants to surface
waters.
b.
Good Housekeeping. Good housekeeping that requires the maintenance of a
clean, orderly facility.
c.
Spill Prevention and Response Procedures. If spills have a potential to occur,
procedures for cleaning up spills shall be identified in the plan and made known to the appropriate
personnel. The necessary equipment to implement a cleanup shall be available to the appropriate
personnel.
d.
Sediment and Erosion Prevention. The plan shall identify areas which, due to
topography, activities, or other factors, have a high potential for significant soil erosion, and
identify measures to limit erosion.
e.
Management of Runoff. The plan shall contain a narrative consideration of the
appropriateness of traditional storm water management practices (practices other than those which
control the generation or source(s) of pollutants) used to divert, infiltrate, reuse, or otherwise
manage storm water runoff in a manner that reduces pollutants in storm water discharges from the
site. The plan shall provide that measures determined to be reasonable and appropriate shall be
implemented and maintained. The potential of various sources at the facility to contribute
pollutants to storm water discharges associated with industrial activity (see Part IV, Section C.1. description of potential pollutant sources) shall be considered when determining reasonable and
appropriate measures. Appropriate measures may include: vegetative swales and practices, reuse
of collected storm water (such as for a process or as an irrigation source), inlet controls (such as
oil/water separators), snow management activities, infiltration devices, and wet detention/retention
devices.
f.
Visual Inspections. Qualified plant personnel shall be identified to inspect
designated equipment and plant areas. A site inspection shall be conducted annually by such
personnel to verify that the description of potential pollutant sources required under Part IV,
Section C.1. is accurate, the drainage map has been updated to reflect current conditions, and the
controls to reduce pollutants identified in the storm water pollution prevention plan are being
implemented and are adequate. In particular, material handling areas shall be inspected for
D.6.17
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
evidence of, or the potential for, pollutants entering the drainage system. A tracking or follow-up
procedure shall be used to ensure that each inspection results in an appropriate response.
g.
Recordkeeping and Internal Reporting Procedures. Spills or other discharge
incidents, and information describing the quality and quantity of storm water discharges shall be in
the facility records. Maintenance activities shall be documented and recorded with inspection and
discharge records. All records shall be maintained at the facility, for a minimum of three years.
This period shall be automatically extended during the course of litigation, or when requested by
the Department.
3.
Consistency with Other Plans
Storm water management programs may include requirements for Spill Prevention
Control and Countermeasure (SPCC) plans under Section 311 of the Clean Water Act or Best
Management Practices (BMPs) programs otherwise required by an NPDES permit and may
incorporate any part of such plans into the storm water pollution prevention plan by reference.
4.
Special Requirements for Storm Water Discharges Associated with Industrial
Activity to Municipal Separate Storm Sewer Systems Serving a Population of 100,000 or
More
Facilities covered by this permit shall comply with applicable requirements in municipal
storm water management programs developed under State/NPDES permits issued for the discharge
of the municipal separate storm sewer system that receives the facility's discharge, provided the
municipal operator has notified the discharger of such conditions. These facilities shall make storm
water pollution prevention plans available to the municipal operator of the system upon request.
5.
Salt Storage
Storage piles of salt used for deicing or other commercial or industrial purposes shall be
enclosed or covered to prevent exposure to precipitation.
6.
Pollution Prevention Committee
The description of the storm water Pollution Prevention Committee shall identify specific
individuals within the plant organization who are responsible for developing the storm water
pollution prevention plan and assisting the plant manager in its implementation, maintenance, and
revision. The activities and responsibilities of the committee should address all aspects of the
facility's storm water pollution prevention plan.
D.6.18
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
7.
Employee Training
Employee training programs shall inform personnel at all levels of responsibility of the
components and goals of the storm water pollution prevention plan. Training should address
topics, such as spill response, good housekeeping and material management practices. A pollution
prevention plan shall identify periodic dates for such training.
D.6.19
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
D. STORM WATER POLLUTION PREVENTION PLAN - ADDITIONAL REQUIREMENTS
FOR FACILITIES SUBJECT TO SARA TITLE III, Section 313 REQUIREMENTS
Storm water pollution prevention plans for facilities subject to reporting requirements under
SARA Title III, Section 313 (42 U.S.C.§11023) are required to include, in addition to the
information listed in Part IV, Section C., a discussion of the facility's conformance with the
following (appropriate) guidelines:
1.
In areas where Section 313 water priority chemicals are stored, processed or otherwise
handled, appropriate containment, drainage control and/or diversionary structures shall be
provided. At a minimum, one of the following preventive systems or its equivalent shall be used:
a.
Curbing, culverting, gutters, sewers or other forms of drainage control to prevent
or minimize the potential for storm water runoff to come into contact with significant sources of
pollutants; or
b.
Roofs, covers, liners, or other forms of appropriate protection to prevent storage
piles from leaching or exposure to storm water and wind.
2.
The storm water pollution prevention plan shall include a complete discussion of
measures taken to conform with the following applicable guidelines, other effective storm water
pollution prevention procedures, and applicable State rules, regulations and guidelines.
a.
Liquid storage areas where storm water comes into contact with any
equipment, tank, container, or other vessel used for Section 313 water priority chemicals. No
tank or container shall be used for the storage of a Section 313 water priority chemical unless its
material and construction are compatible with the material stored and conditions of storage, such as
pressure and temperature, etc. Liquid storage areas for Section 313 water priority chemicals shall
be operated to minimize discharges of Section 313 chemicals by means such as secondary
containment for at least the entire contents of the largest single tank plus sufficient freeboard to
allow for precipitation, a strong spill contingency and integrity testing plan, and/or other equivalent
measures.
b.
Truck and rail car loading and unloading areas for liquid Section 313 water
priority chemicals. These areas shall be operated to minimize discharges of Section 313 water
priority chemicals by means such as the placement and maintenance of drip pans (including the
proper disposal of materials collected in the drip pans) where spillage may occur (such as hose
connections, hose reels and filler nozzles) for use when making and breaking hose connections; a
strong spill contingency and integrity testing plan; and/or other equivalent measures.
c.
In plant areas where Section 313 water priority chemicals are transferred,
processed or otherwise handled. Piping, processing equipment and materials handling equipment
shall be designed and operated so as to prevent discharges of Section 313 chemicals, and be
composed of materials that are compatible with the substances handled. Additional protection,
D.6.20
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
such as covers or guards to prevent wind blowing, spraying or releases from pressure relief vents
from causing a discharge of Section 313 water priority chemicals to the drainage system shall be
provided, as appropriate, to control the releases.
d.
Discharges from secondary containment areas.
(1) Drainage from secondary containment shall be restrained by valves or other positive
means to prevent a spill or other excessive leakage of Section 313 water priority chemicals into the
drainage system. After a visual inspection of the storm water and determination that no product is
present, containment areas may be emptied by pumps or ejectors; however, these shall be manually
activated.
(2) Flapper-type drain valves shall not be used to drain containment areas. Valves
used for the drainage of containment areas shall be of manual, open-and-close design.
(3) Records of the frequency and estimated volume (in gallons) of discharges from
containment areas shall be kept at the facility for a minimum of three years.
(4) In lieu of facility drainage engineered as described above, the final discharge of
all in-facility storm sewers shall be equipped with a diversion system that could, in the event of an
uncontrolled spill of Section 313 water priority chemicals, return the spilled material to the facility.
(5) Facility site runoff other than from areas covered by (a), (b), (c) or (d).
Other areas of the facility [those not addressed in paragraphs (a), (b), (c) or (d)], from which runoff
which may contain Section 313 water priority chemicals or spills of Section 313 water priority
chemicals and which could cause a discharge shall incorporate the necessary drainage or other
control features to prevent discharge of spilled or improperly disposed material and ensure the
mitigation of pollutants in runoff or leachate.
3.
Facility Security
Facilities shall have the necessary security systems to prevent accidental or intentional entry
which could cause a discharge. Security systems shall be described in the plan and address
fencing, lighting, vehicular traffic control, and securing of equipment and buildings.
4.
Risk Identification and Assessment/Material Inventory
The storm water pollution prevention plan shall assess the potential of various sources at the
plant to contribute pollutants to storm water discharges associated with industrial activity. The
plan shall include an inventory of the types of materials handled. Facilities shall include in the plan
a description of releases to land or water of SARA Title III water priority chemicals that have
occurred at any time after July 1, 1989. Each of the following shall be evaluated for the reasonable
potential for contributing pollutants to runoff: loading and unloading operations; outdoor storage
activities; outdoor manufacturing or processing activities; significant dust or particulate generating
D.6.21
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
processes; and on-site waste disposal practices. Factors to consider include the toxicity of
chemicals; quantity of chemicals used, produced, or discharged: the likelihood of contact with
storm water; and history of significant leaks or spills of toxic or hazardous pollutants.
E. STORM WATER POLLUTION PREVENTION PLAN - ADDITIONAL REQUIREMENTS
FOR CONSTRUCTION ACTIVITY
1.
Plans and Approvals
Prior to commencing construction, the permittee shall obtain approved erosion and
sediment control plans in accordance with the requirements established in Title 4, Subtitle 1 of the
Environment Article, Annotated Code of Maryland (Sediment Control); and in Code of Maryland
Regulations (COMAR) 26.09.01 (Erosion and Sediment Control); and shall obtain approved storm
water management plans in accordance with the requirements established in Title 4, Subtitle 2 of
the Environment Article, Annotated Code of Maryland (Storm Water Management); and in
COMAR 26.09.02 (Storm Water Management).
2.
Monitoring and Records
For the purposes of monitoring, permittees must do all of the following:
a. During construction, maintain at the site the approved erosion and sediment control plan.
b. Conduct the following inspections:
(1) weekly inspections of implemented erosion and sediment controls; and
(2) inspections of erosion and sediment controls the next business day after a
rainfall event resulting in runoff.
c. During construction, maintain at the site written reports of all inspections conducted by
the permittee that include:
(1) the date and time of the inspection;
(2) the name(s) of the individual(s) who performed the inspection;
(3) an assessment of the condition of erosion and sediment controls;
(4) a description of any erosion and sediment control implementation and maintenance
performed; and
(5) a description of the site's present phase of construction.
d. Maintain all inspection reports and enforcement actions issued to the permittee by the
appropriate enforcement authority.
e. Permittees must retain the records described in Part IV. E. 2. a., c., and d. and records of
all data used to complete the NOI to be covered by this permit for a period of three (3) years from
the date that the site is finally stabilized.
D.6.22
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
3.
Duty to Comply With Plans
It is a condition of this permit that the permittee comply with erosion and sediment control
and storm water management plans approved in accordance with the laws and regulations cited in
Part IV. E. 1 above, and with all conditions of this general permit
4.
Continuation of Coverage Under This Permit
Once construction has commenced, it is a condition of this permit that erosion and sediment
control and storm water management plan approvals be kept in effect. Construction activity may
not continue if these plans have expired, but may resume once plans are renewed without payment
of an additional fee.
V. Violation of Permit Conditions.
A. Compliance With This General Permit and Water Pollution Abatement Statutes. The
permittee shall comply at all times with the terms and conditions of this permit, the provisions of
the Title 7, Subtitle 2, Title 9, Subtitles 2 and 3 of the Environment Article, Annotated Code of
Maryland, and the Federal Act.
B. Civil and Criminal Liability. In issuing or reissuing this permit, the Department does not
waive or surrender any right to proceed in an administrative, civil, or criminal action for any
violations of State law or regulations occurring before the issuance or reissuance of this permit.
Nothing in this permit shall be construed to preclude the institution of any legal action or relieve
the permittee from any civil or criminal responsibilities, liabilities, or penalties for noncompliance
with Title 9 of the Environment Article, Annotated Code of Maryland or any federal, local or other
state law or regulation.
C. Civil Penalties for Violations of Permit Conditions. In addition to civil penalties for
violations of State water pollution control laws set forth in Section 9-342 of the Environment
Article, Annotated Code of Maryland, the Federal Act provides that any person who violates
Section 301, 302, 306, 307, 308, 318, or 405 of the Act, or any permit condition or limitation
implementing any of such sections in a permit issued under Section 402 of the Act or in a permit
issued under Section 404 of the Act, is subject to a civil penalty not to exceed $25,000 per day for
each violation.
D. Criminal Penalties for Violations of Permit Conditions. In addition to criminal penalties for
violations of State water pollution control laws set forth in Section 9-343 of the Environment
Article, Annotated Code of Maryland, the Federal Act provides that:
1. Any person who negligently violates Section 301, 302, 306, 307, 308, 318, or 405 of the
Act, or any permit condition or limitation implementing any of such sections in a permit issued
under Section 402 of the Act, or in a permit issued under Section 404 of the Act, is subject to a fine
D.6.23
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
of not less than $2,500 nor more than $25,000 per day of violation, or by imprisonment for not
more than one (1) year, or by both.
2. Any person who knowingly violates Section 301, 302, 306, 307, 308, 318, or 405 of the
Act, or any permit condition or limitation implementing any of such sections in a permit issued
under Section 402 of the Act, or in a permit issued under Section 404 of the Act, is subject to a fine
of not less than $5,000 nor more than $50,000 per day of violation, or by imprisonment for not
more than three (3) years, or by both.
3. Any person who knowingly violates Section 301, 302, 306, 307, 308, 318, or 405 of the
Act, or any permit condition or limitation implementing any of such sections in a permit issued
under Section 402 of the Act, or in a permit issued under Section 404 of the Act, and who knows at
that time that he thereby places another person in imminent danger of death or serious bodily
injury, is subject to a fine of not more than $250,000 or imprisonment of not more than fifteen (15)
years, or both. A person which is a corporation, shall, upon conviction, be subject to a penalty of
not more than $1,000,000.
E. Penalties for Falsification and Tampering. The Environment Article, §9-343, Annotated
Code of Maryland provides that any person who knowingly makes any false material statement,
representation, or certification in any application, record, report, plan, or other document filed or
required to be maintained under this permit, including monitoring reports or reports of compliance
or noncompliance, or who knowingly falsifies, tampers with or renders inaccurate any monitoring
device or method required to be maintained under this permit shall, upon conviction, be punished
by a fine of not more than $10,000 per violation, or by imprisonment for not more than 6 months
per violation, or by both. The federal Clean Water Act provides that any person who knowingly
falsifies, tampers with, or renders inaccurate any monitoring device or method required to be
maintained under the Act, or who knowingly makes any false statement, representation, or
certification in any records or other documents submitted or required to be maintained under this
permit, including monitoring reports or reports of compliance or noncompliance shall, upon
conviction, be punished by a fine of not more than $10,000, or by imprisonment for not more than
two years, or by both.
D.6.24
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
Part VI. General Conditions.
A. Right of Entry. The permittee shall permit the Secretary of the Department, the Regional
Administrator for the EPA, or their authorized representatives, upon the presentation of credentials:
1. To enter upon the permittee's premises where an effluent source is located or where any
records are required to be kept under the terms and conditions of this permit;
2. To access and copy, at reasonable times, any records required to be kept under the terms
and conditions of this permit;
3. To inspect, at reasonable times, any monitoring equipment or monitoring method
required in this permit;
4. To inspect, at reasonable times, any collection, treatment, pollution management, or
discharge facilities required under this permit;
5. To sample, at reasonable times, any discharge of pollutants;
6. To install ground water monitoring wells; and
7. To take photographs.
B. Property Rights/Compliance with Other Requirements. The issuance of this permit does not
convey any property rights in either real or personal property, or any exclusive privileges, nor does
it authorize any injury to private property or any invasion of personal rights, nor does it authorize
any infringement of federal, State or local laws or regulations.
C. Duty to Provide Information. The permittee shall furnish to the Department, within the time
frame stipulated by the Department, any information which the Department may request to
determine compliance with this permit. The permittee shall also furnish to the Department, upon
request, copies of records required to be kept by this permit.
D. Other Information. If the permittee becomes aware that incorrect information has been
included in the NOI or any other report submitted to the Department, or relevant facts have been
omitted from the NOI or any other report to the Department, the permittee shall submit the correct
information or facts to the Department with 30 calendar days of becoming aware.
E. Availability of Reports. Except for data determined to be confidential under the Maryland
Public Information Act, and Section 308 of the federal Clean Water Act, all submitted data shall be
available for public inspection at the Department.
F. Toxic Pollutants. The permittee shall comply with effluent standards or prohibitions for toxic
pollutants established under the federal Clean Water Act, or under Section 9-314 and Sections 9-
D.6.25
Appendix D.6. Industrial Stormwater NPDES Permit Requirements
322 through 9-328 of the Environment Article, Annotated Code of Maryland. Compliance shall be
achieved within the time provided in the regulations that establish these standards or prohibitions,
even if this permit has not yet been modified to incorporate the requirement.
G. Oil and Hazardous Substances Prohibited. Nothing in this permit shall be construed to
preclude the institution of any legal action or relieve the permittee from any responsibility, liability,
or penalties to which the permittee may be subject under the federal Clean Water Act or under the
Annotated Code of Maryland.
H. Water Construction and Obstruction. This permit does not authorize the construction or
placing of physical structures, facilities, or debris or the undertaking of related activities in any
waters of the State.
I. Severability. The provisions of this permit are severable. If any provisions of this permit shall
be held invalid for any reason, the remaining provisions shall remain in full force and effect. If the
application of any provision of this permit to any circumstances is held invalid, its application to
other circumstances shall not be affected.
Part VII. Authority to Issue General NPDES Permits.
On September 5, 1974, the Administrator of the EPA approved the proposal submitted by
the State of Maryland for the operation of a permit program for discharges into navigable waters
under Section 402 of the federal Clean Water Act, 33 U.S.C. Section 1342.
On September 30, 1990, the Administrator of the EPA approved the proposal submitted by
the State of Maryland for the operation of a general permit program.
Under the approvals described above, this general discharge permit is both a State of
Maryland general discharge permit and an NPDES general discharge permit.
J. L. Hearn, Director
Water Management Administration
D.6.26
MDE/WMA Overview of the NPDES
Stormwater Program
Appendix
D.7
Appendix D.7. MDE/WMA Overview of the NPDES Stormwater Program
Background
The United States Environmental Protection Agency (EPA) issued final regulations in November
1990 that require National Pollutant Discharge Elimination System (NPDES) Permits for stormwater
discharges associated with industrial activity. These regulations require permits for stormwater
discharges associated with eleven categories of industrial activities and municipal separate storm
sewer systems. Within the Maryland Department of the Environment (MDE), these permits are
being administered by the Water Management Administration (WMA). Ten of these industrial
activities are being permitted by one general permit, the General Industrial Discharge Permit,
implemented by WMA’s Wastewater Discharge Permit Program. However, industry-specific
general permits are currently being drafted.
Examples of these activities are hazardous waste treatment facilities; landfills; open dumps
receiving industrial waste; steam electric power generating facilities; mass transit, school bus, and
trucking facilities; hazardous waste storage facilities; land application sites; recycling facilities (junk
yards, etc.); vehicle maintenance facilities; and treatment works for domestic sewage. The eleventh
industrial activity subject to the stormwater discharge permit requirements is construction activity
with a planned total disturbance of five acres* or more. Construction activity, along with municipal
separate storm sewer systems, are permitted by MDE/WMA’s Compliance Program. Construction
activity is being permitted by a general permit that covers only construction, the General Permit for
Construction Activity. * Area of disturbance subject to NPDES regulatory changes.
Regulatory Requirements for Construction Activity in Maryland
EPA’s regulations [40 CFR (Code of Federal Regulations) 122.26] provide for three types of
applications for industrial stormwater discharge permits: an individual application, a group
application, and a Notice of Intent (NOI) to comply with a general permit. 40 CFR 122.26(b)(14)
identifies construction activity, including clearing, grading, and excavating, as one of the categories
of “industrial activity.” 40 CFR 122.26(c)(1)(ii) requires that the following information be provided
on the NPDES permit application for construction activity:
(A) The location and the nature of the construction;
(B) The total area of the site;
(C) Proposed measures, including best management practices, to control pollutants in
stormwater discharges during construction;
(D) Proposed measures to control pollutants in stormwater discharges that will occur after
construction has been completed;
(E) An estimate of the runoff coefficient of the site and the increase in impervious area after
construction; and
(F) The name of the receiving water.
Because Maryland presently has programs in place to control erosion, sediment and stormwater
for new development activities, MDE/WMA has composed its NPDES General Permit in such a way
D.7.1
Appendix D.7. MDE/WMA Overview of the NPDES Stormwater Program
so as not to change current erosion and sediment control and stormwater management requirements.
Through the review and approval and subsequent inspection and enforcement processes for erosion
and sediment control and stormwater management, the majority of information required to be
submitted under 40 CFR 122.26(c)(1)(ii) will have already been supplied to agencies responsible for
construction site evaluation according to Maryland’s current laws and regulations (Environment
Article Title 4. Subtitle 1; Subtitle 2; COMAR 26.17.01; and COMAR 26.17.02). For this reason,
MDE/WMA Simply, operators of construction activity will be complying with 40 CFR 122.26 if
they comply with current Maryland law.
The General Permit
Construction activity in Maryland with a planned total disturbance of five acres* or more will be
required to be covered by the General Permit for Construction Activity. Coverage under this Permit
mandates that the permittee be held accountable for complying with the terms of the General Permit.
Compliance with the terms of the General Permit shall be in compliance with EPA’s stormwater
regulations.
While Maryland law requires erosion and sediment control and stormwater management plan
approval prior to the commencement of construction for any earth disturbance of 5,000 square feet
or more, General Permit coverage will be required only for construction activity with a planned total
disturbance of five acres* or more. Plans must still be approved and remain active during the
construction phase, as per existing Maryland law.
Permittees are encouraged to submit only one NOI for the entire project, even if plans are not
approved for subsequent phases/stages of development. The completed NOI form is considered an
application for coverage under the General Permit. The NOI is to be completed by the permittee and
will require that general information describing the construction activity be provided. The
completed NOI form must be submitted at least 48 hours prior to any earth disturbing activity and
the appropriate application fee must accompany the submitted NOI.
Who Is Covered by the General Permit?
It is intended that the General Permit cover construction activity in Maryland with a planned
total disturbance of five acres* or more. This includes phased/staged construction projects, even if
individual phases will disturb less than five acres. Current Maryland law requiring approved erosion
and sediment control and stormwater management plans for earth disturbances exceeding 5,000
square feet remains unchanged.
The permittee who applies for coverage under the terms of the General Permit shall be held
accountable for complying with all of the terms of the General Permit. A person who has submitted
a Notice of Intent (NOI) and does not intend to be responsible for controlling the permitted
activities on site must transfer authorization under the General Permit to a duly authorized person.
D.7.2
Appendix D.7. MDE/WMA Overview of the NPDES Stormwater Program
Upon transfer, this duly authorized person shall be held accountable for compliance under the terms
stated in the General Permit.
How is Coverage Obtained?
Coverage under the General Permit is obtained by filing a completed Notice of Intent (NOI)
form with the Maryland Department of the Environment, Water Management Administration
(MDE/WMA). The completed NOI form is considered a formal application for coverage and intent
to comply with the terms of the General Permit.
What is the Procedure for Application?
For construction activity with a planned total disturbance of five acres* or more, General Permit
coverage is required. NOI forms are available at local plan review offices and at MDE. NOI forms
must be complete and include the signature of the permittee in order to be processed. Completed
NOI forms must be submitted with the appropriate application fee (see below) to the Maryland
Department of the Environment, Water Management Administration, P.O. Box 1417, Baltimore,
Maryland 21203-1417. Receipt by MDE/WMA of the completed NOI form will authorize coverage
under the terms of the General Permit. Upon receipt of the completed NOI form. MDE will mail a
verification letter and a copy of the General Permit to the permittee. Once the construction activity
is completed, including final stabilization and the elimination of all stormwater discharges
authorized by the General Permit, the permittee must submit a Notice of Termination form to
MDE/WMA. Forms are available at local plan review offices and at MDE.
The application fee schedule for stormwater discharges associated with construction activity is as
follows:
Total Disturbed Area (acres)
less than 5
5 to less than 10
10 to less than 15
15 to less than 20
20 and up
NOI Fee (dollars)
Exempt
$100
$500
$1,500
$2,500
D.7.3
Appendix D.7. MDE/WMA Overview of the NPDES Stormwater Program
What Information is Required on the NOI Form?
Information required on the NOI Form is general information describing the construction
activity. Much of this information can be provided directly by the permittee from prepared site plans
and any other necessary information should be available at the local plan review offices. The
omponent parts of the NOI form are outlined below:
I.
Site Name and Location including name and general location of the site; MD Grid
Coordinates; latitude and longitude; watershed basin code;
II.
Project Description including stormwater management BMPs to be implemented and
drainage area for each type of BMP; brief project description; total site area/disturbed area;
runoff curve numbers; estimate of total impervious surface area; the project types, as a
county/municipal or private entity and its eventual use as residential, commercial or
industrial; Standard Industrial Classification (SIC) code; any other NPDES permit number;
name of eventual receiving waters/ storm sewer system receiving the site’s runoff;
III. Permittee Identification including name/company and address of permittee and name and phone
number of the principal contact person for the site;
IV. Certification including a certification statement to be signed by the permittee;
V.
Fees including the fee amount to be paid with the NOI submission.
MDE issued a new Notices of Intent form for use beginning in 1994. This form is a scanner
compatible “bubble” form, replacing the original single page handwritten form. This form is the one
currently being accepted by MDE and it is available at local plan review offices and at MDE.
Additionally, MDE has developed a new State and Federal NOI form, to be used for all state and
federal construction projects. This is a separate NOI form, labeled “For State and Federal
Government Project Only,” but it is not significantly different from the standard NOI form.
When Must the NOI Form be Submitted?
The completed NOI must be submitted to the Water Management Administration at least 48
hours prior to the commencement of construction activities. This is applicable to all construction
activity with a planned total disturbance of five acres* or more that is active as of October 1, 1992
and any such construction activity beginning on or after October 1, 1992. Such construction will
need to be permitted under the General Permit. The application fee is due at the time of NOI
submission. Checks and money orders only will be accepted and should be made payable to MDE.
D.7.4
Appendix D.7. MDE/WMA Overview of the NPDES Stormwater Program
MDE has supplied local plan review offices with NOI forms. Forms and information may also
be obtained at MDE. It is the responsibility of the permittee to accurately complete the form and
submit it to MDE/WMA.
Miscellaneous
Coverage under the General Permit is effective until MDE is notified by the permittee that
construction is complete. Submission of a Notice of Termination form to MDE will indicate that
construction activity is complete, areas are stabilized, and authorized stormwater discharges have
been eliminated (the address is given at the end of the Appendix).
No effluent limitations have been established for stormwater discharges from construction sites.
However, the General Permit requires Permittees to visually inspect erosion and sediment controls
on a weekly basis and the next work day after a storm event. Permittees are required to maintain, on
site during construction, written documentation of the findings and any subsequent maintenance that
is performed. These records must be kept for a period of three years following final stabilization of
the site and must be made available upon request.
The permittee shall be held accountable for compliance under the term of the General Permit. A
person who has submitted an NOI and does not intend to control the permitted activities on the site
must transfer authorization under the General Permit to a duly authorized person. Upon transfer, the
duly authorized person shall be held accountable for compliance under the terms stated in the
General Permit.
Although coverage under the General Permit does not involve additional regulations, it should be
noted that because construction activity now falls under the Clean Water Act (CWA), federal
penalties will apply to violations. Both state and federal civil and criminal penalties will apply to
violations occurring under General Permit coverage.
Further information regarding the General Permit and the NOI form can be obtained by
contacting:
The Maryland Department of the Environment
Water Management Administration
Compliance Program
2500 Broening Highway
Baltimore, Maryland 21224
(410) 631-3510
D.7.5
Miscellaneous Details for Compliance with
Performance Criteria
Appendix
D.8
Appendix D.8 ............Miscellaneous Details for Compliance with Performance Criteria
Detail 1: Trash Rack for Low Flow Orifice
Detail 2: Expanded Trash Rack Protection for Low Flow Orifice
Detail 3: Internal Control for Orifice Protection
Detail 4: Observation Well for Infiltration Practices
Detail 5: Off-line Versus On-line Schematic
Detail 6: Isolation/Diversion Structure
Detail 7: Half Round CMP Hood
Detail 8: Half Round CMP Weir
Detail 9: Concrete Level Spreader
D.8.2
Appendix D.8. Miscellaneous Details for Compliance with Performance Criteria
Detail 1 Trash Rack Protection for Low Flow Orifice
D.8.3
Appendix D.8. Miscellaneous Details for Compliance with Performance Criteria
Detail 2 Expanded Trash Rack Protection for Low Flow Orifice
D.8.4
Appendix D.8. Miscellaneous Details for Compliance with Performance Criteria
Detail 3 Internal Control for Orifice Protection
D.8.5
Appendix D.8. Miscellaneous Details for Compliance with Performance Criteria
Detail 4 Observation Well for Infiltration Practices
D.8.6
Appendix D.8. Miscellaneous Details for Compliance with Performance Criteria
Detail 5 Off-Line Versus On-Line Schematic
D.8.7
Appendix D.8. Miscellaneous Details for Compliance with Performance Criteria
Detail 6 Isolation Diversion Structure
D.8.8
Appendix D.8. Miscellaneous Details for Compliance with Performance Criteria
Detail 7 Half Round CMP Hood
D.8.9
Appendix D.8. Miscellaneous Details for Compliance with Performance Criteria
Detail 8 Half Round CMP Weir
D.8.10
Appendix D.8. Miscellaneous Details for Compliance with Performance Criteria
Detail 9 Concrete Level Spreader
D.8.11
MD Stream Use Designations
Appendix
D.9
Introduction
This Appendix, adapted from the Code of Maryland Regulations (COMAR) 26.08.02.08 “Stream
Segment Designations”, is reprinted here for informational purposes only. Please use the Code of
Maryland Regulations for the Official Version and for any updates to these designations.
The stream segments are listed in tabular form according to Use designations as follows:
• Water Contact Recreation, and Protection of Aquatic Life (Use I and Use I-P waters)
• Shell Fish Harvesting Waters (Use II waters);
• Natural Trout Waters (Use III and Use III-P waters);
• Recreational Trout Waters (Use IV and Use IV-P waters); and
• Public Water Supply (Use I-P, III-P, and IV-P waters).
For each sub-basin, information is arranged under the following headings:
1) Use – Refers to water classification;
2) Waters – Exact name of stream segment or segments;
3) MCGS – Most downstream point or line for each stream segment using the Maryland
Coordinate Grid System (East/North);
4) Limits – Written description of boundary of stream segment established by MCGS; and
5) Any stream segment not listed may be considered Use I waters.
D.9.1
Figure D.9.1 Maryland 6 Digit Sub-Basins
02-05-03
02-12-02
02-13-01
02-13-02
02-13-03
02-13-04
02-13-05
02-13-06
02-13-07
02-13-08
02-13-09
02-13-10
02-13-11
02-13-99
02-14-01
02-14-02
02-14-03
02-14-05
02-14-10
05-02-02
CONEWAGO CREEK AREA
LOWER SUSQUEHANNA RIVER AREA
COASTAL AREA
POCOMOKE RIVER AREA
NANTICOKE RIVER AREA
CHOPTANK RIVER AREA
CHESTER RIVER AREA
ELK RIVER AREA
BUSH RIVER AREA
GUNPOWDER RIVER AREA
PATAPSCO RIVER AREA
WEST CHESAPEAKE BAY AREA
PATUXENT RIVER AREA
CHESAPEAKE BAY
LOWER POTOMAC RIVER AREA
WASHINGTON METROPOLITAN AREA
MIDDLE POTOMAC RIVER AREA
UPPER POTOMAC RIVER AREA
NORTH BRANCH POTOMAC RIVER AREA
YOUGHIOGHENY RIVER AREA
D.9.2
Stream Segment Designations
Use
Waters
MCGS ∗
Limits
A. SUB-BASIN 02-12-02: LOWER SUSQUEHANNA RIVER AREA
D.9.3
(1) Use I-P: Susquehanna River and all tributaries except those
designated below as Use III-P or Use-IV-P
(2) Use II: None
(3) Use III: None
(4) Use-III-P:
(a) Deer Creek and all tributaries
(b) Basin Run and all tributaries
(c) Kellogg Branch and all tributaries
(d) North Stirrup Run and all tributaries
(e) South Stirrup Run and all tributaries
(f) Deep Run and all tributaries
(g) Gladden Branch and all tributaries
(h) Rock Hollow branch and all tributaries
(i) Love Run and all tributaries
(j) Stone Run and all tributaries
(5) Use IV: None
(6) Use IV-P:
(a) Deer Creek and all tributaries
(b) Octoraro Creek
From 1068.8/625.5
to1056.8/621.3
Mainstem from mouth to MD/PA line
956/671
1040/667
966/655.5
969/650.2
968.3/649
1008.2/677.8
967/658
958/663
1046/678
1050.5/682.5
Above Eden Mill Dam
1040/649.3
1036.7/665
From mouth to Eden Mill Dam
Mainstem only
1321.7/216.4
1323/214
1336.4/189.9
1345/185.5
Above confluence with St. Martins River
Above confluence with St. Martins River at Piney Island
Above Rt. 50
Above entrance to West Ocean City Harbor
B. SUB-BASIN 02-13-01: COASTAL AREA
(1) Use I-P: None
(2) Use II: All portions of the territorial seas and estuarine
portions of bays and tributaries except:
(a) Bishopville Prong and tributaries
(b) Shingle Landing Prong and its tributaries
(c) Herring Creek and its tributaries
(d) Ocean City Harbor
(3) Use III: None
(4) Use IIII-P: None
(5) Use IV: None
(6) Use IV-P: None
C. SUB-BASIN 02-13-02: POCOMOKE RIVER AREA
∗ Most downstream point or line for the segment using the Maryland Coordinate Grid System (MCGS) (East/North)
(1) Use I-P: None
(2) Use II: All estuarine portions of tributaries except:
(a) Manokin River and tributaries
(b) Big Annemessex River and tributaries
(c) Jenkins Creek
(d) Fair Island Canal
(e) Pocomoke River
(3) Use III: None
(4) Use III-P: None
(5) Use IV: None
(6) Use IV-P: None
1165/125.3
1160.8/95.2
From 1127/48 to 1127.3/45.7
From1177.6/51 to 1187.7/50.1
1196/62
Above confluence of Manokin River & Kings Creek
Above River Road
Above mouth
Above MD/VA line
D. SUB-BASIN 02-13-03: NANTICOKE RIVER AREA
(1) Use I-P: None
(2) Use II; All estuarine portions of tributaries except:
(a) Blackwater River and tributaries
(b) Transquaking River and tributaries
D.9.4
(c) Nanticoke River and tributaries
(3)
(4)
(5)
(6)
(d) Wicomico River and tributaries
(e) Monie Creek
Use III: None
Use III-P: None
Use IV: None
Use IV-P: None
From 1083.1/92 to 1084.2/191.6 Above mouth
From 1085.2/196.3 to 1088/197
From 1126/194 to 1128.2/191.2 Above mouth
1147.9/160.5
1138.7/146.7
Above line from Runaway Pt. to Long Pt.
Above ferry crossing at White Haven
Above mouth
E. SUB-BASIN 02-13-04: CHOPTANK RIVER AREA
(1) Use I-P: None
(2) Use II: All estuarine portions of tributaries except:
(a) Choptank River and tributaries
(3)
(4)
(5)
(6)
(b) Tred Avon River and tributaries
Use III: None
Use III-P: None
Use IV: None
Use IV-P: None
F. SUB-BASIN 02-13-05: CHESTER RIVER AREA
(1) Use I-P: None
From 1099.3/308 to 1101/306.5 Above line from Bow Knee Pt. to Wright Wharf
1057.6/341.6
Above Easton Pt.
(2) Use II: All estuarine portions of tributaries except:
(a) Chester River and tributaries
(b) Corsica River
(c) Piney Creek
(3)
(4)
(5)
(6)
(d) Winchester Creek
(e) St. Michaels Harbor
Use III: None
Use III-P: None
Use IV: None
Use IV-P: None
1066.5/502
1060.4/448.4
From 1010.7/419.9 to
1012/418.8
1026.5/416.1
1023/348.7
Above Rt. 213
Above Earl Cove
Above Rt. 50
1129.3/647.5
1096.6/643.1
1065.9/636
Above Md Rt. 213
Above confluence with Stoney Run
Above US Rt. 40
From 1112.8/617 to
1114.8/613.9
From 1108/603.7 to 1109/600
1088.6/561.5
1044/547
From 1031.4/532 to
1032.5/534.7
From 1023.6/524 to 1026/527.5
From 1081.3/623.3 to
1087.6/619.1
1073/634.5
Above line from Bull Minnow Pt. to Courthouse Pt.
995.5/585.5
From Otter Point Creek to upstream boundary of Atkisson
Reservoir
Above mouth
G. SUB-BASIN 02-13-06: ELK RIVER
(1) Use I-P:
(a) Big Elk Creek and all tributaries
(b) Northeast Creek and all tributaries
(c) Mill Creek and all tributaries
(2) Use II: All estuarine portions of tributaries except
(a) Elk River and tributaries
D.9.5
(b)
(c)
(d)
(e)
Bohemia River and tributaries
Sassafras River and tributaries
Stillpond Creek and tributaries (Still Pond)
Worton Creek
(f) Fairlee Creek
(3)
(4)
(5)
(6)
(g) Northeast River
Use III: Principio Creek and all tributaries
Use III-P: None
Use IV: None
Use IV-P: None
Above line from Rich Pt. to Baltery Pt.
Above Ordinary Pt.
Above Kinnaird Pt.
Above mouth
Above mouth
H. SUB-BASIN 02-13-07: BUSH RIVER AREA
(1) Use I-P: Winters Run and all tributaries, including Atkisson
Reservoir
(2) Use II: All estuarine portions of tributaries except:
(a) Bush River and tributaries
(b) Romney Creek
(c) Swan Creek and tributaries
(3)
(4)
(5)
(6)
Use III: Bynum Run and all tributaries
Use III-P: None
Use IV: None
Use IV-P: Winters Run and all tributaries
From 1010.5/576 to
1014.1/574.1
1022.3/567.5
From 1050/603.5 to
1047.5/604.2
1008.9/597.4
Above line from Fairview Pt. to Chillbury Pt.
982.2/604.8
Above Atkisson Reservoir
From 987/561.5 to 991.2/555.5
From 972/536.1 to 970/532.5
Above line from Oliver Pt. to Maxwell Pt.
Above Briar Pt.
Above mouth
I. SUB-BASIN 02-13-08: GUNPOWDER RIVER AREA
(1) Use I-P: None
(2) Use II: All estuarine portions of tributaries except:
(a) Gunpowder River and all tributaries
(b) Middle River
(3) Use III:
(a) Little Gunpowder Falls and all tributaries
D.9.6
(b) Long Green Run and all tributaries
(c) Sweathouse Branch and all tributaries
(4) Use III-P: Gunpowder Falls and all tributaries
(5) Use IV: Whitemarsh Run and all tributaries
(6) Use IV-P: None
Above line from Log Pt. to Turkey Pt.
976.8/5788.8
950/584
950/584
930.8/578.9
964/564
Above B&O railroad bridge ¾ mile south of Rt. 7
(Old Philadelphia Road)
Above Loch Raven
J. SUB-BASIN 02-13-09: PATAPSCO RIVER AREA
(1) Use I-P:
(a) Liberty Reservoir
(b) All tributaries to West Branch Patapsco River
(c) All tributaries to North Branch Patapsco River except
those designated below as Use III-P or Use IV-P
(2) Use II: None
(3) Use III:
(a) Brice Run and all tributaries
(b) Piney Run and all tributaries
(c)
(d)
(e)
(f)
(g)
Jones Falls and all tributaries
Red Run and all tributaries
Gwynns Falls and all tributaries
Gillis Falls and all tributaries
South Branch Patapsco River and all tributaries
830.9/562.1
828.8/621.4
835.8/604.8
850/540
From 828/554 to 815.8/563.6
897.7/567.6
863/572.4
861.5/578.5
782/557
782/557
Above Liberty Dam
Above Liberty Reservoir
From mouth to Slacks Road
(on Springfield State Hospital Grounds)
Above Lake Roland
Above Reistertown Road
Above confluence with Gillis Falls tributaries
D.9.7
(h) Unnamed tributary to the South Branch Patapsco River
at Henryton and all tributaries to this unnamed tributary
(4) Use III-P:
(a) Piney Run and all tributaries
(b) Morgan Run and all tributaries
(c) Norris Run and all tributaries
(d) Cooks Branch and all tributaries
(e) Keysers Run and all tributaries
(f) Beaver Run and all tributaries
(g) Snowdens Run and all tributaries
(h) Stillwater Creek and all tributaries
(i) Carroll Highlands Run and all tributaries
(j) Autumn Run and all tributaries
(k) Locst Run and all tributaries
(l) Glen Falls Run and all tributaries
(m) East Branch Patapsco River and all tributaries
(5) Use IV:
(a) South Branch Patapsco River
(b) Jones Falls
(c) Herring Run and all tributaries
(d) Stony Run and all tributaries
(e) Dead Run and all tributaries
(f) Stemmers Run and all tributaries
(6) Use IV-P:
(a) North Branch Patapsco River
(b) West Branch Patapsco River
(c) Cranberry Branch and all tributaries
823.9/552.9
Above Slacks Road (on Springfield State Hospital Grounds)
815.8/563.6
813.8/589.6
835.1/592.6
836.2/584.4
833.8/596.8
828.3/602.1
825/572
824.8/570.9
825.5/567.4
825.7/567
839.1/572.9
837.4/605.1
830.1/620.4
833.4/552.5
From 908/538.5 to 901/563
929.5/537
905/541
888/536.5
941.4/553.8
Mainstem only
From North Ave. to Lake Roland Dam
Above I-95
833.4/552.2
830.1/620.3
888.1/637.3
Mainstem only above Liberty Reservoir
Mainstem only
Above Md Rt. 852 (Old Manchester Rd)
936.9/455
920.6/451
918.8/410.1
925.7/315.8
924.5/344.2
905/455
Above Henderson Pt
Above mouth of Forked Creek
Above Porter Pt.
Above Mason Beach Road
907.3/454.1
Above Rt.3
Above I-95
K. SUB-BASIN 02-13-10: WEST CHESAPEAKE BAY AREA
(1) Use I-P: None
(2) Use II: All estuarine portions of tributaries except:
(a) Magothy River and tributaries
(b) Severn River and tributaries
(c) South River and tributaries
(d) Rockhold Creek and tributaries
(e) Tracys Creek
(3) Use III: Jabez Branch and all tributaries
(4) Use III-P: None
(5) Use IV: Severn Run and all tributaries
(6) Use IV-P: None
L. SUB-BASIN 02-13-11: PATUXENT RIVER AREA
(1) Use I-P:
(a) Little Patuxent River and all tributaries
(b) Patuxent River and all tributaries except those
designated below aas Use III-P or IV-P
(2) Use II: All estuarine portions of tributaries except Patuxent
River and tributaries
(3) Use III: None
(4) Use III-P: Patuxent River and tributaries
(5) Use IV: None
(6) Use IV-P: Patuxent River and tributaries
866.5/453.8
845.8/467.4
Above Old Forge Bridge (1 mile south of MD Route 198)
Above Rocky Gorge Dam
886.8/316.3
Above Ferry Landing
787.2/510.7
Above Triadelphia Reservoir
813.2/476.8
Between Rocky Gorge Reservoir and Triadelphia Reservoir,
and including Triadelphia Reservoir
M. SUB-BASIN 02-14-01: LOWER POTOMAC RIVER AREA
D.9.8
(1) Use I-P: Tilghman Lake Reservoir
(2) Use II: All estuarine portions of tributaries except Potomac
River and tributaries
(3) Use III: None
(4) Use III-P: None
(5) Use IV: None
(6) Use IV-P: None
817/260
From 723.8/211.8 to
710.9/205.3
Above line from Smith Pt. to Simms Pt.
(1) Use I-P: Potomac River and all tributaries except those
designated below as Use III, Use III-P, Use IV or Use IV-P
(2) Use II: None
(3) Use III:
(a) Paint Branch and all tributaries
(b) Rock Creek and all tributaries
(c) North Branch Rock Creek and all tributaries
(4) Use III-P:
(a) Little Seneca Creek and all tributaries
766/401
From MD/DC line to Frederick/Montgomery County line
815.2/433.2
764/475
771.5/468
Above Capital Beltway (I-495)
Above Muncaster Mill Road
Above Muncaster Mill Road
From 704/477.4 to 716/491.3
From the stream’s confluence with Bucklodge Branch to the
Baltimore and Ohio railroad bridge (see Regulation
26.08.02.03-3E(1) of this chapter)
(b) Wildcat Branch and all tributaries
(5) Use IV:
(a) Rock Creek and all tributaries
740.5/504
N. SUB-BASIN 02-14-02: WASHINGTON METROPOLITAN AREA
(b) Northwest Branch and all tributaries
(6) Use IV-P: Little Seneca Creek and all tributaries
O. SUB-BASIN 02-14-03: MIDDLE POTOMAC RIVER AREA
From 766.7/459.3 to 763.5/475
809/413
From Rt. 28 to Muncaster Mill Road
Above east-West Highway (Rt. 410)
719.2/497.4
D.9.9
(1) Use I-P: Potomac River and all tributaries except those
designated below as Use III-P or Use IV-P
(2) Use II: None
(3) Use III: None
(4) Use III-P:
(a) Tuscarora Creek and all tributaries
(b) Carroll Creek and all tributaries
(c) Rocky Fountain Run and all tributaries
(d) Fishing Creek and all tributaries
(e) Hunting Creek and all tributaries
(f) Owens Creek and all tributaries
(g) Friends Creek and all tributaries
(h) Catoctin Creek and all tributaries
(i) Little Bennett Creek and all tributaries
(j) Furnace Branch and all tributaries
(k) Ballenger Creek and all tributaries
(l) Bear Branch and all tributaries
(5) Use IV: None
(6) Use IV-P:
(a) Monacacy River and all tributaries except those
designated above as Use III-P
(b) Catoctin Creek
(c) Israel Creek and all tributaries
671/505.9
694/592
678.5/579.5
681/546
689.2/609.2
698.5/625.5
705.9/635.9
697.2/689.1
640.6/589.8
711/527
675/514
557/683
685.2/531.9
From Frederick/Montgomery County Line to confluence
with Shenandoah River
Above U.S. Rt. 15
Above Alternate U.S. Rt. 40
Above Md. Rt. 355
From confluence with Bennett Creek
696/570
Above U.S. Rt. 40
640.6/538
607/545
Mainstem only, below Alternate U.S. Route 40
543.3/594.4
From confluence of Shenandoah River to the confluence of
the North and South Branches of the Potomac River
P. SUB-BASIN 02-14-05: UPPER POTOMAC RIVER AREA
(1) Use I-P: Potomac River and all Maryland tributaries except
those designated below as Use III-P or Use IV-P
(2) Use II: None
(3) Use III: None
(4) Use III-P:
(a) Town Creek tributaries
(b) Beaver Creek and all tributaries
(c) Marsh Run and all tributaries
(d) Little Antietam Creek and all tributaries
(e) Camp Spring Run and all tributaries
(5) Use IV: None
(6) Use IV-P:
(a) Town Creek
(b) Fifteen Mile Creek and all tributaries
(c) Sideling Hill Creek and all tributaries
(d) Tonoloway Creek and all tributaries
365/618.8
599.9/620.3
605.7/662.1
620/674
536/653
365/618.8
410.1/655
424.5/660
474.8/679.8
In Antietam Creek Watershed
In Antietam Creek Watershed
(e) Licking Creek and all tributaries
(f) Conococheague Creek and all tributaries
(g) Antietam Creek and all tributaries except those
designated above as Use III-P
504/663.5
566.3/645.4
58901/577.8
Q. SUB-BASIN 02-14-10: NORTH BRANCH POTOMAC RIVER AREA
(1) Use I-P:
(a) North Branch Potomac River mainstem
352.3/621.1
(b) Georges Creek mainstem
(c) Mill Run and its tributaries in Allegany County
222.8/607.4
272.2/625.8
(d) an unnamed tributary near Pinto
281.7/636.5
D.9.10
(2) Use II: None
(3) Use III: None
(4) Use III-P: All Maryland tributaries to the North Branch
Potomac River except for:
(a) Those designated below as Use IV-P waters
(b) Those designated above as Use I-P waters
(5) Use IV: None
(6) Use IV-P:
(a) Wills Creek
(b) Evitts Creek
From the confluence of the North and South Branches of the
Potomac River to the MD/WVA State line
From the confluence with N. Branch
From the confluence with N. Branch (near Rawlings and
Rawlings Heights)
Confluence of the unnamed tributary with the North Branch
of the Potomac River
From 352.3/621.1 to MD/WVA From confluence of North and South Branches of the
State line
Potomac River to MD/WVA State line
303.3/655.5
310.2/656.8
Mainstem only
Mainstem only
130/579
232/687
Above Dam
Upstream from confluence with Church Creek
187.7/674.0
223.9/693.9
Confluence of North and South Branches
From MD/PA State line to confluence of Church Creek
126.8/696.2
Upstream of MD/PA State line joining mainstem of the
Youghiogheny River in Maryland
Mainstem only, confluence of South Branch & North Branch
to PA line
R. SUB-BASIN 05-02-02: YOUGHIOGHENY RIVER AREA
(1) Use I-P:
(a) Broad Ford Run and all tributaries
(b) Piney Creek and all tributaries in Maryland
(2) Use II: None
(3) Use III:
(a) South Branch, Casselman River
(b) Piney Creek and all tributaries in Maryland, including
Church Creek
(4) Use III-P: Youghiogheny River and all tributaries
(5) Use-IV: Casselman River
(6) Use IV-P: None
S. SUB-BASIN 02-05-03: CONEWAGO CREEK
(1) Use I-P: None
205.5/694.8
(2)
(3)
(4)
(5)
(6)
Use II: None
Use III: None
Use III-P: None
Use IV: None
Use IV-P: None
T. SUB-BASIN 02-13-99: CHESAPEAKE BAY (PROPER)
(1) Use I-P: None
(2) Use II: All waters of the Chesapeake Bay Proper
D.9.11
(3)
(4)
(5)
(6)
Use III: None
Use III-P: None
Use IV: None
Use IV-P: None
From the Susquehanna River mouth to the Virginia State
line, including the tidal waters of the Chesapeake Bay
bounded generally by the shoreline of the Bay and by “zero
river mile” lines of estuaries and tributaries to the Bay, as
designated by the Department of the Environment, and any
peripheral waters designated as part of the Chesapeake Bay
Proper by the Department of the Environment after
consultation with the Tidewater Administration and the
Forest, Park and Wildlife Service
Designator
D.9.12
02-12-02
02-13-01
02-13-02
02-13-03
02-13-04
02-13-05
02-13-06
02-13-07
02-13-08
02-13-09
02-13-10
02-13-11
02-14-01
02-14-02
02-14-03
02-14-05
02-14-10
05-02-02
02-05-03
02-13-99
Sub-Basin
Lower Susquehanna River Area
Coastal Area
Pocomoke River Area
Nanticoke River Area
Choptank River Area
Chester River Area
Elk River Area
Bush River Area
Gunpowder River Area
Patapsco River Area
West Chesapeake Bay Area
Patuxent River Area
Lower Potomac River Area
Washington Metropolitan Area
Middle Potomac River Area
Upper Potomac River Area
North Branch Potomac River Area
Youghiogheny River Area
Conewago Creek Area
Chesapeake Bay
Method for Computing Peak Discharge
for Water Quality Storm
Appendix
D.10
Appendix D.10. Method for Computing Peak Discharge for Water Quality Storm
METHOD FOR COMPUTING PEAK DISCHARGE FOR WATER QUALITY STORM
(Adapted from Claytor and Schueler, 1996)
The peak rate of discharge is needed for the sizing of off-line diversion structures and to design grass
channels. Conventional SCS methods underestimate the volume and rate of runoff for rainfall
events less than 2". This discrepancy in estimating runoff and discharge rates can lead to situations
where a significant amount of runoff by-passes the filtering treatment practice due to an
inadequately sized diversion structure or leads to the design of undersized grass channels.
The following procedure can be used to estimate peak discharges for small storm events. It relies on
the volume of runoff computed using the Small Storm Hydrology Method (Pitt, 1994) and utilizes
the NRCS, TR-55 Graphical Peak Discharge Method (USDA, 1986).
¾
Using the WQV methodology, a corresponding Curve Number (CN) is computed utilizing the
following equation:
CN =
1000
[10 + 5P + 10Qa − 10 Qa2 + 1. 25Qa P ]
where: P = rainfall, in inches (use 1.0" or 0.9" for the Water Quality Storm)
Qa = runoff volume, in inches (equal to P3Rv)
Note: The above equation is derived from the SCS Runoff Curve Number method described in
detail in NEH-4, Hydrology (SCS 1985) and SCS TR-55 Chapter 2: Estimating Runoff. The
CN can also be obtained graphically using Figure D.10.1 or from TR-55.
¾
Once a CN is computed, the time of concentration (tc) is computed (based on the methods
identified in TR-55, Chapter 3: "Time Of Concentration And Travel Time").
¾
Using the computed CN, tc and drainage area (A), in acres; the peak discharge (Qp ) for the
Water Quality Storm is computed (based on the procedures identified in TR-55, Chapter 4:
"Graphical Peak Discharge Method"). Use Rainfall distribution type II.
- Read initial abstraction (Ia), compute Ia/P
- Read the unit peak discharge (qu) from Exhibit 4-II for appropriate tc
- Using the runoff volume (Qa), compute the peak discharge (Qp); Qp = qu3A3Qa
where:
Qp = the peak discharge, in cfs
qu = the unit peak discharge, in cfs/mi²/inch
A = drainage area, in square miles
Qa = runoff volume, in watershed inches
Example Calculation of Peak Discharge for Water Quality Storm
D.10.1
Appendix D.10. Method for Computing Peak Discharge for Water Quality Storm
Using a 3.0 acre small shopping center having a 1.0 acre flat roof, 1.6 acres of parking, and 0.4 acres
of open space, and using P = 1.0"; the weighted volumetric runoff coefficient (Rv) is:
Rv = 0.05+0.009(I); I = 2.6 acres!3.0 acres = 0.867 (86.7%)
= 0.05+0.009(86.7%)
= 0.83
The runoff volume, Qa is:
Qa = P3Rv
= 1.0"30.83
= 0.83 watershed inches
and WQv is:
WQv =
[(1. 0" )( 0. 83)(3. 0 acres )] 43, 560 ft 2
×
= 9, 039 ft 3
12
acre
Using Qa = 0.83 watershed inches and P = 1.0"; CN for the water quality storm is:
CN =
Using:
1000
[10 + (5)(1. 0" ) + (10)( 0. 83) − 10 ( 0. 83) 2 + 1. 25( 0. 83)(1. 0" ) ]
= 98
tc = 10 minutes (0.17 hour);
Ia=(200!CN)-2=0.041;
Ia !P= (0.041!1.0") = 0.041;
qu = 950 csm/in. (from TR-55 Exhibit 4-II); and
A = 3.0 acres 31!640 mi2 per acre = 0.0047 mi2
Qp = (950 csm/in.)(0.0047 mi2)(0.83") = 3.7 cfs
For computing runoff volume and peak rate for storms larger than the Water Quality Storm (i.e., 2,
10 and 100 year storms), use the published CN’s from TR-55 and follow the prescribed procedure in
TR-55.
In some cases the Rational Formula may be used to compute peak discharges associated with the
Water Quality Storm. The designer must have available reliable intensity, duration, frequency (IDF)
tables or curves for the storm and region of interest. This information may not be available for many
locations and therefore the TR-55 method described above is recommended.
D.10.2
Appendix D.10. Method for Computing Peak Discharge for Water Quality Storm
Figure D-10.1 Curve Number (CN) for Water Quality Storm
- Rainfall (P) =1.0" & 0.9"
100
98
96
94
P=0.9"
D.10.3
Curve Number (CN)
92
P=1.0"
90
88
86
84
82
80
78
76
0
5
10
15
20
25
30
35
40
45
50
55
60
Percent Imperviousness (I )
65
70
75
80
85
90
95
100
Appendix D-10. Method for Computing Peak Discharge for Water Quality Storm
References
Pitt, R., 1994, Small Storm Hydrology. University of Alabama - Birmingham. Unpublished
manuscript. Presented at design of stormwater quality management practices. Madison, WI, May
17-19 1994.
Schueler, T.R. and R.A. Claytor, 1996, Design of Stormwater Filter Systems. Center for Watershed
Protection, Silver Spring, MD.
United States Department of Agriculture (USDA), 1986. Urban Hydrology for Small Watersheds.
Soil Conservation Service, Engineering Division. Technical Release 55 (TR-55).
D.10.4
Method for Computing the Channel Protection
Storage Volume (Cpv)
Appendix
D.11
Appendix D.11................... Method for Computing the Channel Protection Storage Volume (Cpv)
The following procedure shall be used to design the channel protection storage volume (Cpv). The
method is based on the Design Procedures for Stormwater Management Extended Detention Structures
(MDE, 1987) and utilizes the NRCS, TR-55 Graphical Peak Discharge Method (USDA, 1986).
" Compute the time of concentration (tc) and the one-year post-development runoff depth (Qa) in
inches.
" Compute the initial abstraction (Ia) [ I a = 200
CN
− 2 ] and the ratio
Ia
P
where P is the one-year
rainfall depth (see Table 2-2).
" With tc and Ia/P, find the unit peak factor (qu) from Figure D.11.1 and compute the one year postdevelopment peak discharge qi = quAQa where A is the drainage in square miles.
" If qi [ 2.0 cfs, Cpv is not required. Provide for water quality (WQv) and groundwater recharge (Rev)
as necessary.
" With qu, find the ratio of outflow to inflow (qo/qi) for T = 24 hours from Figure D.11.2 (use T=12
hours in USE III/IV waters).
" Compute the peak outflow discharge qo =
qo
qi
× qi
" With qo/qi, compute the ratio of storage to runoff volume (Vs/Vr).
Vs
Vr
= 0.683 − 1.43( qo ) + 1.64( qo ) 2 − 0.804( qo ) 3
qi
qi
qi
" Compute the extended detention storage volume Vs = (Vs ) × Vr (note: Vr = Qa);
Vr
Vs
Convert Vs to acre-feet by
× A , where Vs is in inches and A is in acres.
12
" Compute the required orifice area (Ao) for extended detention design:
qo
qo
=
C 2 gho 4.81 ho
where ho is the maximum storage depth associated with Vs.
Ao =
" Determine the required maximum orifice diameter (do) do = 4 Ao
π .
A do of less than 3.0” is subject to local jurisdictional approval, and is not recommended
unless an internal control for orifice protection is used (App. D.8).
D.11.1
Appendix D-11….Method for Computing the Channel Protection Storage Volume (Cpv)
SCS Graphical Method of Determining Peak Discharge (qu) in csm/in
for 24-Hour Type II Storm Distribution
Figure D.11.1
1000
900
D.11.2
Unit Peak Discharge (qu), csm/in
800
700
Ia/P = 0.10
600
0.30
500
0.40
0.45
0.35
400
0.50
300
200
100
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Time of Concentration (tc) in Hours
0.8
0.9
1
qo
qi
Appendix D-11….Method for Computing the Channel Protection Storage Volume (Cpv)
Detention Time Versus Discharge Ratios (
Figure D.11.2
)
0.500
0.450
D.11.3
Ratio of Outflow to Inflow (qo/qI)
0.400
0.350
0.300
0.250
0.200
0.150
T =12 hr
0.100
0.050
T =24 hr
0.000
50
100
150
200
250
300
350
400
450
500
550
600
650
Unit Peak Discharge (qu), csm/in
700
750
800
850
900
950
1000
Critical Erosive Velocity for Grass and Soil
Appendix
D.12
Appendix D.12. Critical Erosive Velocity for Grass and Soil
Velocity
Maximum permissible velocities of flow shall not exceed the values shown on the following table:
Table D.12.1 Permissible Velocities for Channels Lined with Vegetation
Channel Slope
0-5%
Lining
Reed canarygrass
Tall fescue
Kentucky bluegrass
5
Grass-legume mixture
4
Red fescue
Redtop
Sericea lespedeza
Annual lespedeza
Small grains
5-10%
Greater than
10%
Permissible
Velocity1 (ft/sec)
2.5
Reed canarygrass
Tall fescue
Kentucky bluegrass
4
Grass-legume mixture
3
Reed canarygrass
Tall fescue
Kentucky bluegrass
3
1
For highly erodible soils, permissible velocities should be decreased 25%. An erodibility factor
(K) greater than 0.35 would indicate a highly erodible soil. Erodibility factors (K-factors) for
Maryland soils are listed either in the Soil Survey or on the Soils-5 forms available in each Soil
Conservation District or local NRCS office.
Source: Soil and Water Conservation Engineering, Schwab, et al.
D.12.1
Method for Designing Infiltration Structures
Appendix
D.13
Appendix D.13...............................................Method for Designing Infiltration Structures
Introduction
The following procedures shall be used for designing infiltration trenches (I-1) and basins (I-2)
to meet the water quality (WQv), the channel protection (Cpv), and the overbank flood protection
(Qp) volume requirements. These methods are based on the 1984 Maryland Standards and
Specifications for Infiltration Practices (MDE, 1984) and Modelling Infiltration Practices Using
TR-20 (MDE, 1983).
The use of infiltration practices depends on careful site investigation. The feasibility conditions
listed in Chapter 3.3 and in Appendix D.1 are to be investigated and are equally important in
ensuring the proper function of an infiltration practice. Should a site investigation reveal that
any one of the feasibility tests is not adequate, the implementation of infiltration practices should
not be pursued. Alternate feasibility criteria may be permitted only in those conditions where the
local jurisdictions can justify and ensure proper application.
D.13.1 Soil Textures
The hydrologic design methods presented in this appendix are based on the utilization of two
hydrologic soil properties, the effective water capacity (Cw) and the minimum infiltration rate (f)
of the specific soil textural groups, as shown in Table D.13.1. The effective water capacity of a
soil is the fraction of the void spaces available for water storage, measured in inches per inch.
The minimum infiltration rate is the final rate that water passes through the soil profile during
saturated conditions, measured in terms of inches per hour. The hydrologic soil properties are
obtained by identifying the soil textures by a gradation test for each change in soil profile. The
soil textures presented in Table D.13.1 correspond to the soil textures of the U.S. Department of
Agriculture (USDA) Textural Triangle presented in Figure D.13.1.
The data presented in Table D.13.1 are based on the analysis of over 5,000 soil samples by the
USDA under carefully controlled procedures. The use of the soil properties established in Table
D.13.1 for design and review procedures will offer two advantages. First, it provides for
consistency of results in the design procedures. Second, it eliminates the need for the laborious
and costly process of conducting field and laboratory infiltration and permeability tests.
D.13.1
Appendix D.13...............................................Method for Designing Infiltration Structures
Table D.13.1 Hydrologic Soil Properties Classified by Soil Texture*
Texture Class
Effective Water
Capacity (Cw)
Minimum
Infiltration Rate (f)
(inch per inch)
(inches per hour)
Sand
0.35
Loamy Sand
0.31
Sandy Loam
0.25
Loam
0.19
Silt Loam
0.17
Sandy Clay Loam
0.14
Clay Loam
0.14
Silty Clay Loam
0.11
Sandy Clay
0.09
Silty Clay
0.09
Clay
0.08
*
Source: Rawls, Brakensiek and Saxton, 1982
8.27
2.41
1.02
0.52
0.27
0.17
0.09
0.06
0.05
0.04
0.02
Hydrologic Soil
Grouping
A
A
A
B
B
C
D
D
D
D
D
Based on the soil textural classes and the corresponding minimum infiltration rates, a restriction
is established to eliminate unsuitable soil conditions. Soil textures with minimum infiltration
rates less than 0.52 inches per hour are not suitable for usage of infiltration practices. These
include soils that have a 30 percent clay content, making these soils susceptible to frost heaving
and structurally unstable, in addition to having a poor capacity to percolate runoff. Soil textures
that are recommended for infiltration systems include those soils with infiltration rates of 0.52
inches per hour or greater, which include loam, sandy loam, loamy sand, and sand.
D.13.2
Appendix D.13...............................................Method for Designing Infiltration Structures
Figure D.13.1 USDA Soils Textural Triangle
D.13.3
Appendix D.13...............................................Method for Designing Infiltration Structures
D.13.2 Hydrologic Design Methods
D.13.2.1 General Design Situations
There are two general types of situations where infiltration practices may be used. First , one
may be interested in the dimensions of an infiltration device that is required to provide storage of
the WQv, and/or the Cpv or Qp. Second, site conditions may dictate the layout and capacity of
infiltration measures and one might be interested in determining the level of control provided by
such a layout. In the latter case, control may not be sufficient and additional control, possibly
using other acceptable Best Management Practices (BMPs), may be required. It is important to
emphasize that the same principles of design apply to both cases.
Design methodologies are presented for two infiltration practices: infiltration trenches (I-1) and
infiltration basins (I-2). The design procedures are based on either intercepting the WQv from
the area contributing runoff or using the truncated hydrograph method for control of the runoff
from an area for either Cpv or Qp. The design equations may be defined for either case of
stormwater quality or quantity control because the volume of water (Vw) stored in the individual
infiltration practice may be determined from the methods described in Chapter 2 (for WQv) and
in Appendix D.13.3 for Cpv and/or Qp.
D.13.2.2 Design of Infiltration Trenches (I-1)
The design of an infiltration trench is based on the textural class of the soils underlying the
trench such that a feasible design is possible. The design of an infiltration trench is also based
on the maximum allowable depth of the trench (dmax). The maximum allowable depth should
meet the following criteria:
fT
d max = s
n
Where f is the final infiltration rate of the trench area in inches per hour, Ts is the maximum
allowable storage time in hours, and n is the porosity (Vv/Vt) of the stone reservoir.
An infiltration trench is sized to accept the design volume that enters the trench (Vw) plus the
volume of rain that falls on the surface of the trench (PAt) minus the exfiltration volume (fTAt)
out of the bottom of the trench. Based on the SCS hydrograph analysis, the effective filling time
for most infiltration trenches (T) will generally be less than two hours. The volume of water that
must be stored in the trench (V) is defined as:
where P is the design rainfall event (ft), and At is the trench surface area (ft2). For most design
V = Vw + PAt − fTAt (Equation D - 13.1)
D.13.4
Appendix D.13...............................................Method for Designing Infiltration Structures
storm events, the volume of water due to rainfall on the surface area of the trench (PAt) is small
when compared to the design volume (Vw) of the trench and may be ignored with little loss in
accuracy to the final design.
The volume of rainfall and runoff entering the trench can be defined in terms of trench geometry.
The gross volume of the trench (Vt) is equal to the ratio of the volume of water that must be
stored (V) to the porosity (n) of the stone reservoir in the trench; Vt is also equal to the product of
the depth (dt) and the surface area (At):
Vt = V
n
= d t At n
( Equation D - 13.2)
Combining equations D.13.1 and D.13.2 yields the following relationship:
d t At n = Vw − fTAt
( Equation D - 13.3)
Because both dimensions of the trench are unknown, this equation may be rearranged to
determine the area of the trench (At) if the value of dt were set based on either the location of the
water table or the maximum allowable depth of the trench (dmax):
At =
Vw
nd t + fT
Procedures for Infiltration Trench Design
1. Determine the volume of water for storage using the methods for WQv, Cpv, or Qp found in
Chapter 2 and/or Appendix D.13.3.
2. Compute the maximum allowable trench depth (dmax) from the feasibility equation, d max = fTs n
Select the trench design depth (dt) based on the depth that is the required depth above the
seasonal groundwater table, or a depth less than or equal to dmax, whichever results in the
smaller depth.
3. Compute the trench surface area (At) for the particular soil type using Equation D.13.3.
D.13.5
Appendix D.13...............................................Method for Designing Infiltration Structures
In the event that the sidewalls of the trench must be sloped for stability during construction, the
surface dimensions of the trench should be based on the following equation:
At = ( L − Zd t )(W − Zd t )
where L and W are the top length an( A
d width,
and Z:1 is the trench side slope ratio. The design
t + Ab )d b
V
=
(Equation
- 13.5)
procedure would begin by selecting a top width (W
reater
than 23Zdt for a specified
) that is gD
2
slope (Z). The side slope ratio value will depend on the soil type and the depth of the trench.
At
W − Zd t
The top length (L) may then be determined as:
L = Zd t +
D.13.2.3 Design of Infiltration Basins (I-2)
The design of an infiltration basin is based on the same soil textural properties and maximum
allowable depth as the infiltration trench such that a feasible design is possible. However,
because the infiltration basin uses an open area or shallow depression for storage, the maximum
allowable depth (dmax) should meet the following criteria:
d max = f × T p
where f is the final infiltration rate of the trench area in inches per hour and Tp is the maximum
allowable ponding time in hours.
An infiltration basin is sized to accept the design volume that enters the basin (Vw) plus the
volume of rain that falls on the surface of the basin (PAb) minus the exfiltration volume (fTAb)
out of the bottom of the basin. Based on the SCS hydrograph analysis, the effective filling time
for most infiltration basins will generally be less than two hours therefore use T = 2 hours. The
volume of water that must be stored in the trench (V) is defined as
V = Vw + PAb − fTAb
( Equation D - 13.4)
where P is the design rainfall event (ft), and Ab is the basin surface area (ft2). For most design
storm events, the volume of water due to rainfall on the surface area of the basin (PAb) is small
when compared to the design volume (Vw) of the basin and may be ignored with little loss in
accuracy to the final design.
The volume of rainfall and runoff entering the basin can be defined in terms of basin geometry.
The geometry of a basin will generally be in the shape of an excavated trapezoid with specified
side slopes. The volume of a trapezoidal shaped basin may be approximated by:
where At is the top surface area of the basin (ft2), Ab is the bottom surface area of the basin (ft2),
D.13.6
Ab =
2Vw − At d b
( d b − 2 P + 2 fT )
(Equation D - 13.6)
Appendix D.13...............................................Method for Designing Infiltration Structures
and db is the basin depth (ft). By setting Equations D.13.4 and D.13.5 equal the following
equation may be used to define the bottom area (Ab):
If a rectilinear shape is used, the bottom length and width of the basin may be defined in terms of
the top length and width as:
Lb = Lt − 2 Zd b
Wb = Wt − 2 Zd b
where Z is a specified side slope ratio (Z:1). By substituting the above relationships for Lb and
Wb, into Equation D.13.6, the following equation is derived for the basin top length:
Lt =
Vw + Zd b (Wt − 2 Zd b )
Wt (d b − P ) − Zd b2
(Equation D - 13.7)
Procedures for Infiltration Basin Design
1. Determine the volume of water for storage using the methods for WQv, Cpv, or Qp found in
Chapter 2 and/or Appendix D.13.3.
2. Compute the maximum allowable basin depth (dmax) from the feasibility equation, dmax = fTp.
Select the basin design depth (db) based on the depth that is the required depth above the
seasonal groundwater table, or a depth less than or equal to dmax, whichever results in the
smaller depth.
3. Compute the basin surface area dimensions for the particular soil type using Equation
D.13.6.
Note: If a rectilinear shape is used, the basin top length (Lt) and width (Wt) must be greater
than 2Zdb for a feasible solution. If Lt and Wt are not greater than 2Zdb the bottom
dimensions would be less than or equal to zero. In this case, the basin depth (db) shall be
reduced for a feasible solution.
D.13.3 The Truncated Hydrograph Method for Stormwater Quantity Management
Most stormwater polices require that the peak discharge from the post-developed hydrograph for a
selected return period(s) not exceed the peak discharge from the pre-developed hydrograph after
development for stream channel erosion control and/or flood control purposes. In previous
stormwater quantity management infiltration design methods, the difference between the predevelopment and post-development runoff volumes was stored in the proposed infiltration structure.
In most cases, this volume of runoff occurs prior to the actual hydrograph peak (see Figure D.13.2)
and therefore actual peak discharge control is not provided. Therefore, when considering infiltration
D.13.7
Appendix D.13...............................................Method for Designing Infiltration Structures
practices for peak discharge or stormwater quantity control, the truncated hydrograph method should
be used to determine the necessary infiltration storage volumes.
The pre-development and post-development peak discharges can be computed using standard SCS
methodology (TR-55 Tabular or TR-20). The time (T2) at which the allowable discharge occurs on
the receding limb of the post-development hydrography, as shown in Figure D.13.1 is determined
from the SCS methods. The volume of runoff under the post-development hydrograph and to the left
of the allowable discharge at T2 is the design storage volume (V).
The computed infiltration storage volume, V, may be adjusted to account for the volume of water
which exfiltrates from the infiltration structure during the period of time required to fill the structure.
The exfiltration volume (Ve) is the product of the minimum soil infiltration rate (ft/hr), the filling
time (hrs), and the surface area of the infiltration practice. The filling time (Tf) of the infiltration
practice may be determined directly from the post-development hydrograph as shown in Figure
D.13.1. Tf is the difference between T2, where the allowable discharge occurs on the recession limb
and the time T1 where the discharge value on the rising of the hydrograph is equal to the minimum
infiltration discharge. The minimum discharge is equal to the minimum soil infiltration rate (ft/sec)
times the surface area (ft2) of the infiltration practice.
D.13.8
D.13.9
Appendix D.13...............................................Method for Designing Infiltration Structures
Figure D.13.2 Truncated Hydrograph Method
Eastern Shore (Delmarva) Dimensionless
Hydrograph
Appendix
D.14
Figure D.14.1
SCS Graphical Method of Determining Peak Discharge (qu) in csm/in
For Delmarva Peninsula
Appendix D.14 ...................... Eastern Shore (Delmarva) Dimensionless Hydrograph
800
700
D-14.1
Unit Peak Discharge (qu), csm/in
600
500
400
300
200
100
0
0.10
0.20
0.30
0.40
0.50
0.60
0.70
Time of Concentration (tc) in Hours
0.80
0.90
1.00
Figure D.14.2
Dimensionless Unit Hydrographs
SCS (484) and Delmarva (284)
Delmarva D.U.H. (284)
D-14.2
Dimensionless Time Increment
1
0.8
SCS Standard D.U.H. (484)
0.6
0.4
0.2
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Dimensionless Rate of Flow
0.7
0.8
0.9
1
Appendix D.14 ...................... Eastern Shore (Delmarva) Dimensionless Hydrograph
1.2
Appendix D.14................................Eastern Shore (Delmarva) Dimensionless Hydrograph
Δt
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Table D.14.1 Standard 24-Hour Dimensionless Unit Hydrograph
Dimensionless Time Increment = 0.02
x.x0
x.x2
x.x4
x.x6
x.x8
0.0
0.0300
0.100
0.1900
0.31
0.47
0.66
0.82
0.93
0.99
1.00
0.99
0.93
0.86
0.78
0.68
0.56
0.46
0.39
0.33
0.28
0.241
0.207
0.174
0.147
0.126
0.107
0.091
0.077
0.066
0.055
0.047
0.04
0.034
0.029
0.025
0.021
0.018
0.015
0.013
0.011
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0.0
0.0
0.0
0.0
0.0
Computed Peak Rate Factor = 484.00
Table D.14.2 24-Hour Dimensionless Unit Hydrograph for Use in the Delmarva Peninsula
Dimensionless Time Increment = 0.02
x.x0
x.x2
x.x4
x.x6
x.x8
Δt
0.0
0.0
0.111
0.356
0.655
0.896
0.1
1.000
0.929
0.828
0.737
0.656
0.2
0.584
0.521
0.465
0.415
0.371
0.3
0.331
0.296
0.265
0.237
0.212
0.4
0.190
0.170
0.153
0.138
0.123
0.5
0.109
0.097
0.086
0.076
0.066
0.6
0.057
0.049
0.041
0.033
0.027
0.7
0.024
0.021
0.018
0.015
0.013
0.8
0.012
0.011
0.009
0.008
0.008
0.9
0.006
0.006
0.005
0.005
0.0
1.0
0.0
0.0
0.0
0.0
0.0
Computed Peak Rate Factor = 284.00
D.14.3
Miscellaneous MD SHA Design Charts
for Determining Pipe Inlet Control
Appendix
D.15
Appendix D.15....................................................... Miscellaneous MD SHA Design Charts
D.15.1
Appendix D.15....................................................... Miscellaneous MD SHA Design Charts
D.15.2
Appendix D.15....................................................... Miscellaneous MD SHA Design Charts
D.15.3
Appendix D.15....................................................... Miscellaneous MD SHA Design Charts
D.15.4
Stormwater Credits for Innovative Site Planning
Appendix
E.1
Appendix E.1. Stormwater Credits .......................................................... Introduction
E.1.0 Stormwater Credits
In Maryland, there are many programs at both the State and local level that seek to minimize
the impact of land development. Critical Areas, forest conservation, and local stream buffer
requirements are designed to reduce nonpoint source pollution. Non-structural practices can
play a significant role in reducing water quality impacts and are increasingly recognized as a
critical feature of every stormwater BMP plan, particularly with respect to site design. In most
cases, non-structural practices must be combined with structural practices to meet stormwater
requirements. The key benefit of non-structural practices is that they can reduce the generation
of stormwater from the site; thereby reducing the size and cost of stormwater storage. In
addition, they can provide partial removal of many pollutants. Non-structural practices have
been classified into six broad groups and are designed to mesh with existing state and local
programs (e.g., forest conservation, stream buffers etc.). To promote greater use, a series of
six stormwater credits are provided for designers that use these site planning techniques.
Credit 1.
Credit 2.
Credit 3.
Credit 4.
Credit 5.
Credit 6.
Natural Area Conservation
Disconnection of Rooftop Runoff
Disconnection of Non Rooftop Runoff
Sheet Flow to Buffers
Open Channel Use
Environmentally Sensitive Development
This chapter describes each of the credits for the six groups of non-structural practices,
specifies minimum criteria to be eligible for the credit, and provides an example of how the
credit is calculated. Designers should check with the appropriate approval authority to ensure
that the credit is applicable to their jurisdiction. Clearly both of the site designs used to
illustrate the credits could be more creative to provide more non-structural opportunities.
In general, the stormwater sizing criteria provide a strong incentive to reduce impervious cover
at development sites (e.g., Rev, WQv, Cpv or Qp and Qf). Storage requirements for all five
stormwater sizing criteria are directly related to impervious cover. Thus, significant
reductions in impervious cover result in smaller required storage volumes and, consequently,
lower BMP construction costs.
These and other site design techniques can help to reduce impervious cover, and consequently,
the stormwater treatment volume needed at a site. The techniques presented in this chapter are
considered options to be used by the designer to help reduce the need for stormwater BMP
storage capacity. Due to local safety codes, soil conditions, and topography, some of these site
design features will be restricted. Designers are encouraged to consult with the appropriate
approval authority to determine restrictions on non-structural strategies.
NOTE:
This chapter contains archived material and is presented here for historical
purposes only.
E.1.1
Supp. 1
Appendix E.1. Stormwater Credits ...............................................................................Introduction
These credits are an integral part of a project’s overall stormwater management plan and BMP
storage volume calculation. Therefore, use of these credits shall be documented at the initial
(concept) design stage, documented with submission of final grading plans, and verified with
“as-built” certifications. If a planned credit is not implemented, then BMP volumes shall be
increased appropriately to meet Rev, WQv, Cpv, and Qp where applicable.
Table E.1.1 Summary of Stormwater Credits
Stormwater Credit
WQv
Rev
No credit. Use as
receiving area
w/Percent Area
Method.
Cpv or Qp
Natural Area
Conservation
Reduce Site Area
Reduced Rv
No credit. Use with
Percent Area
Method.
Longer tc
(increased flow path).
CN credit.
Reduced Rv
No credit. Use with
Percent Area
Method.
Longer tc (increased
flow path)
CN credit
Sheet Flow to
Buffers
Subtract
contributing site
area to BMP
Reduced Rev
CN credit
Open Channel Use
May meet WQv
Meets Rev
Longer tc
(increased flow path)
No CN credit
Environmentally
Sensitive
Development
Meets WQv
Meets Rev
No CN credit
tc may increase
Disconnection of
Rooftop Runoff
Disconnection of
Non-Rooftop
Runoff
Supp. 1
E.1.2
Forest/meadow CN for
natural areas
Chapter E.1. Stormwater Credits for Innovative Site Planning .......Natural Area Conservation
Section E.1.1 Natural Area Conservation Credit
Natural Area Conservation Credit
A stormwater credit is given when natural areas are conserved at development sites,
thereby retaining pre development hydrologic and water quality characteristics. A simple
WQv credit is granted for all conservation areas permanently protected under conservation
easements or other locally acceptable means. Examples of natural area conservation
include:
¾
¾
¾
¾
forest retention areas
non-tidal wetlands and associated buffers
other lands in protective easement (floodplains, open space, steep slopes)
stream systems
Under the credit, a designer can subtract conservation areas from total site area when
computing the water quality volume. The volumetric runoff coefficient, Rv, is still
calculated based on the percent impervious cover for the entire site.
As an additional incentive, the post development curve number (CN) used to compute the
Cpv or Qp2, and Qp10 for all natural areas protected by conservation easements can be
assumed to be woods in good condition when calculating the total site CN.
As an example, the required WQv for a ten acre site with three acres of impervious area and
three acres of protected conservation area before the credit would be:
WQv = [(P)(Rv)(A)]/12; where P= 1”, Rv= 0.05+0.009(30%)
WQv = [(1”) (0.32)(10 acres)]/12 = 0.266 acre-feet.
Under the credit, three acres of conservation are subtracted from total site area, which yields a
smaller storage volume:
WQv =[(P)(Rv)(A)]/12; where P=1”, Rv=0.05+0.009(30%)
WQv =[(1”)(0.32)(10-3 acres)]/12 = 0.187 acre-feet.
The recharge requirement (Rev) is not reduced using this credit.
E.1.3
Supp. 1
Appendix E.1. Stormwater Credits ....................................................... Natural Area Conservation
Criteria for Natural Area Credit
To receive the credit, the proposed conservation area:
•
Shall not be disturbed during project construction (e.g., cleared or graded) except for
temporary impacts associated with incidental utility construction or mitigation and
afforestation projects,
•
Shall be protected by having the limits of disturbance clearly shown on all construction
drawings and delimited in the field except as provided for above,
•
Shall be located within an acceptable conservation easement or other enforceable
instrument that ensures perpetual protection of the proposed area. The easement must
clearly specify how the natural area vegetation shall be managed and boundaries will be
marked [Note: managed turf (e.g., playgrounds, regularly maintained open areas) is not an
acceptable form of vegetation management], and
•
Shall be located on the development project.
Supp. 1
E.1.4
Chapter E.1. Stormwater Credits for Innovative Site Planning .......Natural Area Conservation
Example of Calculating Natural Area Credit
Site Data - 51 Single Family
Lots
Area = 38 ac.
Conservation Area = 7.0 ac
Impervious Area = 13.8 ac
Rv = .38, P= 0.9”
Post dev. CN = 78
Original WQv = 1.08 ac-ft.
Original Rev = .25 ac-ft.
Original Cpv = 1.65 ac-ft.
Original Qp10 = 2.83 ac-ft.
Computation of Stormwater Credits
WQv = [(P)(Rv)(A)]/12
= [(0.9)(.38)(38.0 - 7.0 ac.)]/12
= 0.89 ac-ft
Rev = Same as original
(However, area draining to Natural Area may used with the Percent Area Method)
Cpv and Qp10 (total site): CN reduced from 78 to 75
E.1.5
Supp. 1
Appendix E.1. Stormwater Credits ................................................. Rooftop Runoff Disconnection
Section E.1.2 Disconnection of Rooftop Runoff Credit
Disconnection of Rooftop Runoff Credit
A credit is given when rooftop runoff is disconnected and then directed to a pervious area
where it can either infiltrate into the soil or filter over it. The credit is typically obtained
by grading the site to promote overland filtering or by providing bioretention areas on
single family residential lots.
If a rooftop is adequately disconnected, the disconnected impervious area may be deducted
from total impervious cover (therefore reducing WQv). In addition, disconnected rooftops
can be used to meet the Rev requirement as a non-structural practice using the percent area
method (see Chapter 2).
Post development CN’s for disconnected rooftop areas used to compute Cpv and Qp can be
assumed to be woods in good condition.
Criteria for Disconnection of Rooftop Runoff Credit
The credit is subject to the following restrictions:
•
•
•
•
•
•
•
•
•
•
Rooftop cannot be within a designated hotspot,
Disconnection shall cause no basement seepage,
The contributing area of rooftop to each disconnected discharge shall be 500 square feet or
less,
The length of the "disconnection" shall be 75’ or greater, or compensated using Table
E.1.2,
Dry wells, french drains, rain gardens, or other similar storage devices may be utilized to
compensate for areas with disconnection lengths less than 75 feet. (See Table E.1.2 and
Figure E.1.1, dry wells are prohibited in “D” soils),
In residential development applications, disconnections will only be credited for lot sizes
greater than 6000 sq. ft.,
The entire vegetative "disconnection" shall be on an average slope of 5% or less,
The disconnection must drain continuously through a vegetated channel, swale, or through
a filter strip to the property line or BMP,
Downspouts must be at least 10 feet away from the nearest impervious surface to
discourage "re-connections”, and
For those rooftops draining directly to a buffer, only the rooftop disconnection credit or the
buffer credit may be used, not both.
Supp. 1
E.1.6
Chapter E.1. Stormwater Credits ..................................... Rooftop Runoff Disconnection
Figure E.1.1 Schematic of Dry Well
Table E.1.2 Rooftop Disconnection Compensation Storage Volume Requirements
(Per Disconnection Using Drywells, Raingardens, etc.)
Disconnection
0 - 14 ft.
15 - 29 ft. 30 - 44 ft. 45 - 59 ft. 60 - 74 ft.
Length Provided
% WQv Treated
by Disconnect
% WQv Treated
by Storage
Max. Storage
Volume*
≥ 75 ft.
0%
20%
40%
60%
80%
100%
100%
80%
60%
40%
20%
0%
40 cu-ft.
32 cu-ft.
24 cu-ft.
16 cu-ft.
8 cu-ft.
0 cu-ft.
36 cu-ft.
28.8 cu-ft.
21.6 cu-ft.
14.4 cu-ft.
7.2 cu-ft.
0 cu-ft.
(Eastern Rainfall
Zone)
Max. Storage
Volume*
(Western Rainfall
Zone)
*Assuming 500 square feet roof area to each downspout.
E.1.7
Supp. 1
Appendix E.1. Stormwater Credits ................................................. Rooftop Runoff Disconnection
Example of Using the Rooftop Disconnection Credit
Site Data - 51 Single Family Lots
Area = 38 ac., ½ acre lots
Original Impervious Area = 13.80
ac.
Original Rv = .38
Post dev. CN = 78
# of Disconnected Rooftops = 22
Original WQv = 1.08 ac-ft
Original Rev = 0.25 ac-ft
Original Cpv = 1.65 ac-ft
Original Qpv = 2.83 ac-ft
60% B Soils
40% C Soils
Composite S=0.208 (20.8%)
22 Lots Disconnected w/5
Downspouts each.
∴ 2500 sq. ft. each lot
Net impervious area reduction =
(22)(2500)/43560 = 1.3 ac
Net Impervious Area =
13.8 - 1.3 = 12.5 acres
Computation of Stormwater Credit:
New Rv= 0.05+.009 (12.5 ac/38 ac) = .35
∴ WQv= [(0.9)(.35)(38 ac)]!12 = 1.00 ac-ft.
Required Rev (Percent Area Method)
Rev = 20.8%× 13.8 ac. =2.87 acres
Rev treated by disconnection =1.3 acres
Rev remaining for treatment = 1.57 acres non structurally or 0.14 acre-feet structurally
Cpv and Qp (total site): CN reduced from 78 to 76
Supp. 1
E.1.8
Chapter E.1. Stormwater Credits ............................... Non Rooftop Runoff Disconnection
Section E.1.3 Disconnection of Non Rooftop Runoff Credit
Disconnection of Non Rooftop Runoff Credit
Credit is given for practices that disconnect surface impervious cover runoff by directing it
to pervious areas where it is either infiltrated into the soil or filtered (by overland flow).
This credit can be obtained by grading the site to promote overland vegetative filtering or
providing bioretention areas on single family residential lots.
These "disconnected" areas can be subtracted from the impervious area when computing
WQv. In addition, disconnected surface impervious cover can be used to meet the Rev
requirement as a non-structural practice using the percent area method (See Chapter 2).
Criteria for Disconnection of Non Rooftop Runoff Credit
The credit is subject to the following restrictions:
•
•
•
•
•
•
•
•
•
Runoff cannot come from a designated hotspot,
The maximum contributing impervious flow path length shall be 75 feet,
The disconnection shall drain continuously through a vegetated channel, swale, or filter
strip to the property line or BMP,
The length of the "disconnection" must be equal to or greater than the contributing length,
The entire vegetative "disconnection" shall be on an average slope of 5% or less,
The surface impervious area to any one discharge location cannot exceed 1,000 ft2.
Disconnections are encouraged on relatively permeable soils (HSG’s A and B),
If the site cannot meet the required disconnect length, a spreading device, such as a french
drain, rain garden, gravel trench or other storage device may be needed for compensation,
and
For those areas draining directly to a buffer, only the non rooftop disconnection credit or
the stream buffer credit can be used, not both.
E.1.9
Supp. 1
Appendix E.1. Stormwater Credits ......................................... Non Rooftop Runoff Disconnection
Example of Calculating the Non Rooftop Disconnection Credit
Site Data -Community Center
Area = 3.0 ac
Original Impervious Area =
1.9 ac. = 63.3%
Original Rv = .62
Post dev. CN = 83
B Soils, S = 0.26
Original WQv = 6752 ft3
Original Rev = 1688 ft3
Original Cpv = N/A
Original Qp2 = 10,630 ft3
0.33 ac of surface
imperviousness disconnected
Net impervious area
reduction
1.9 - 0.33 = 1.57 ac.
Computation of Stormwater Credit:
New Rv = 0.05+.009 (1.57 ac/3.0 ac)= .52
∴WQv = [(1.0)(0.52)(3.0 ac)]/12 = 0.13 ac-ft (5662.8 cf)
Required Rev (Percent area method)
Rev = (S)(Ai) = (0.26)(1.9 ac.) = 0.49 acres
Rev treated by disconnection = 0.33 acres
Rev remaining for treatment = 0.16 acres non structurally or 551.2 cf structurally
Cpv and Qp Post developed CN may be reduced
Supp. 1
E.1.10
Chapter E.1. Stormwater Credits ..................................................Sheetflow to Buffers
Section E.1.4 Sheetflow to Buffer Credit
Sheetflow to Buffer Credit
This credit is given when stormwater runoff is effectively treated by a natural buffer to a
stream or forested area. Effective treatment is achieved when pervious and impervious area
runoff is discharged to a grass or forested buffer through overland flow. The use of a filter
strip is also recommended to treat overland flow in the green space of a development site.
The credits include:
1.
2.
3.
The area draining by sheet flow to a buffer is subtracted from the total site area in
the WQv calculation.
The area draining to the buffer contributes to the recharge requirement, Rev.
A wooded CN can be used for the contributing area if it drains to a forested buffer.
Criteria for Sheetflow to Buffer Credit
The credit is subject to the following conditions:
•
•
•
•
•
•
The minimum buffer width shall be 50 feet as measured from bankfull elevation or
centerline of the buffer,
The maximum contributing length shall be 150 feet for pervious surfaces and 75 feet for
impervious surfaces,
Runoff shall enter the buffer as sheet flow. Either the average contributing overland slope
shall be 5.0% or less, or a level spreading device shall be used where sheet flow can no
longer be maintained (see Detail No. 9 in Appendix D.8),
Not applicable if rooftop or non rooftop disconnection is already provided (see Credits 2 &
3),
Buffers shall remain unmanaged other than routine debris removal, and
Shall be protected by an acceptable conservation easement or other enforceable instrument
that ensures perpetual protection of the proposed area. The easement must clearly specify
how the natural area vegetation shall be managed and boundaries will be marked [Note:
managed turf (e.g., playgrounds, regularly maintained open areas) is not an acceptable
form of vegetation management].
Figure E.1.2 illustrates how a buffer or filter strip can be used to treat stormwater from
adjacent pervious and impervious areas.
E.1.11
Supp. 1
Appendix E.1. Stormwater Credits ................................................................. Sheetflow to Buffers
Figure E.1.2 Example of Sheetflow to Buffer Credit
Supp. 1
E.1.12
Chapter E.1. Stormwater Credits ..................................................Sheetflow to Buffers
Example of Using the Sheetflow to Buffer Credit
Site Data - 51 Single Family
Area = 38.0 ac
Original Impervious Area =
13.8 ac = 36.3%
Original Rv = .38
Post-dev. CN = 78
Original WQv = 1.08 ac-ft
Original Rev = 0.24 ac-ft
Original Cpv = 1.65 ac-ft
Original Qpv = 2.83 ac-ft
Credit
5.0 ac draining to
buffer/filter strip
Rooftops represent 3% of
site imperviousness = 0.41
acres
Computation of Stormwater Credits
New drainage area = 38 ac.– 5 ac.= 33.0 acres
Rv remains unchanged to BMP; Rv=0.05+0.009(36.3)=0.38
WQv =[(P)(Rv)(A)/!12
=[(0.9)(0.38)(33.0 ac.)]/12
= 0.94 ac-ft
Required Rev (Percent Area Method)
Rev = 20.8%×13.8 ac. = 2.87 acres
Rev treated by disconnection = 0.41 acres
Rev remaining for treatment = 2.46 acres non structurally or 0.214 ac-ft structurally
Cpv and Qp (total site): CN is reduced slightly.
E.1.13
Supp. 1
Appendix E.1. Stormwater Credits .......................................................................... Grass Channel
Section E.1.5 Grass Channel Credit
Grass Channel Credit (in lieu of Curb and Gutter):
Credit may be given when open grass channels are used to reduce the volume of runoff and
pollutants during smaller storms (e.g., < 1 inch). The schematic of the grass channel is
provided in Figure 5.3.
Use of a grass channel will automatically meet the Rev for impervious areas draining into
the channel. However, Rev for impervious areas not draining to grass channels must still be
addressed. If designed according to the following criteria, the grass channel will meet the
WQv as well.
CNs for channel protection or peak flow control (Cpv or Qp) will not change.
Criteria for the Grass Channel Credit
The WQv credit is obtained if a grass channel meets the following criteria:
•
•
•
•
•
•
The maximum flow velocity for runoff from the one-inch rainfall shall be less than or equal
to 1.0 fps (see Appendix D.10 for methodology to compute flowrate),
The maximum flow velocity for runoff from the ten-year design event shall be non erosive,
The bottom width shall be 2 feet minimum and 8 feet maximum,
The side slopes shall be 3:1 or flatter,
The channel slope shall be less than or equal to 4.0%, and
Not applicable if rooftop disconnection is already provided (see Credit 2).
An example of a grass channel is provided in Figure E.1.3.
Supp. 1
E.1.14
Chapter E.1. Stormwater Credits ......................................................... Grass Channel
Figure E.1.3 Example of Grass Channel
E.1.15
Supp. 1
Appendix E.1. Stormwater Credits .......................................................................... Grass Channel
Example of Grass Channel Credit
Site Data - 51 Single Family
Residences
Area = 38.0 ac
Original Impervious Area =
13.8 = 36.3%
Rv = .38
CN = 78
Original WQv = 1.08 ac-ft
Original Rev = 0.25 ac-ft
Original Cpv = 1.65 ac-ft
Original Qpv = 2.83 ac-ft
Credit
12.5 acres meet grass
channel criteria
Computation of Stormwater Credits
New WQv Area = 38 ac - 12.5 ac = 25.5 ac
WQv = [(0.9)(0.38)(25.5 ac.)]/12
= 0.74 ac-ft
Required Rev (Percent Area Method)
Rev =20.8%×13.8 ac. =2.87 acres
4.5 acres of imperviousness lie within area drained by grass channels, and
4.5 acres > 2.87 acres
∴ Rev requirement is met.
Cpv and Qp: No change
Supp. 1
E.1.16
Chapter E.1. Stormwater Credits ...............................................Sensitive Development
Section E.1.6 Environmentally Sensitive Development Credit
Environmentally Sensitive Development
Credit is given when a group of environmental site design techniques are applied to low
density or residential development. The credit eliminates the need for structural practices to
treat both the Rev and WQv and is intended for use on large lots.
Criteria for Environmentally Sensitive Development Credit
These criteria can be met without the use of structural practices in certain low density
residential developments when the following conditions are met:
For Single Lot Development:
• total site impervious cover is less than 15%,
• lot size shall be at least two acres,
• rooftop runoff is disconnected in accordance with the criteria outlined in Section E.1.2, and
• grass channels are used to convey runoff versus curb and gutter.
For Multiple Lot Development:
• total site impervious cover is less than 15%,
• lot size shall be at least two acres if clustering techniques are not used,
• if clustering techniques are used, the average lot size shall not be greater than 50% of the
minimum lot size as identified in the appropriate local zoning ordinance and shall be at
least one half acre,
• rooftop runoff is disconnected in accordance with the criteria outlined in Section E.1.2,
• grass channels are used to convey runoff versus curb and gutter,
• a minimum of 25% of the site is protected in natural conservation areas (by permanent
easement or other similar measure), and
• the design shall address stormwater (Rev, WQv, Cpv, and/or Qp10) for all roadway and
connected impervious surfaces.
E.1.17
Supp. 1
Appendix E.1. Stormwater Credits ............................................................ Sensitive Development
Example of Environmentally Sensitive Development
Site Data - 1 Single Family Lot
Area = 2.5 ac
Conservation Area = 0.6 ac
Impervious Area = .35 ac (includes
adjacent road surface) = 14%
B soils
Eastern Rainfall Zone for WQv
Rv = 0.05+0.009(14) = .18
CN = 65
WQv : Use P=0.2 as I<15%
WQv = [(0.2)(A)]/12
= [(0.2)(2.5)]/12×(43560 ft/ac.)
= 1,815 ft3
Rev = [(S)(Rv)(A)]/12
= [(0.26)(0.18)(2.5)]/12×(43,560ft/ac.)
= 424.7 ft3
Computation of Stormwater Credits:
WQv is met by site design
Rev is met by site design
Cpv and Qp: No change in CN, tc may be longer which would reduce Qp requirements
Supp. 1
E.1.18
Chapter E.1. Stormwater Credits ....................................................... Other Strategies
Section E.1.7 Dealing with Multiple Credits
Site designers are encouraged to utilize as many credits as they can on a site. Greater
reductions in stormwater storage volumes can be achieved when many credits are combined
(e.g., disconnecting rooftops and protecting natural conservation areas). However, credits
cannot be claimed twice for an identical area of the site (e.g. claiming credit for stream buffers
and disconnecting rooftops over the same site area).
Section E.1. 8
Other Strategies to Reduce Impervious Cover
Definition: Site planning practices that reduce the creation of impervious area in new
residential and commercial development and therefore reduce the WQv for the site.
Examples of progressive site design practices that minimize the creation of impervious cover
include:
• Narrower residential road sections
• Angled one way parking
• Subdivisions with open space
• Shorter road lengths
• Smaller front yard setbacks
• Smaller turnarounds and cul-de-sac radii
• Permeable spill-over parking areas
• Shared parking and driveways
• Smaller parking demand ratios
• Narrower sidewalks
• Smaller parking stalls
It should be noted that most site designers may have little ability to control these requirements,
which are typically enshrined in local subdivision, parking and/or street codes.
Where these techniques are employed, it may be possible to reduce stormwater storage
volumes. For example, because the WQv is directly based on impervious cover, a reduction in
impervious cover reduces WQv. For Cpv and Qp, the designer can compute curve numbers
(CN) based on the actual measured impervious area at a site using:
CN =
(98)I + ∑ (CN )(P )
A
where:
CN = curve number for the appropriate pervious cover
I = impervious area at the site
P = pervious area at the site
A = total site area
E.1.19
Supp. 1
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