Harbor_TMDL_eutro_revised_final

Harbor_TMDL_eutro_revised_final
REVISED FINAL
Total Maximum Daily Loads of Nitrogen and Phosphorus for
the Baltimore Harbor in
Anne Arundel, Baltimore, Carroll and Howard Counties and
Baltimore City, Maryland
REVISED FINAL
DEPARTMENT OF THE ENVIRONMENT
1800 Washington Boulevard, Suite 540
Baltimore MD 21230-1718
Submitted to:
Watershed Protection Division
U.S. Environmental Protection Agency, Region III
1650 Arch Street
Philadelphia, PA 19103-2029
December 2006
EPA Submittal Date: December 14, 2006
EPA Approval Date: December 17, 2007
Revised: August 31, 2015
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
REVISED FINAL
Table of Contents
List of Figures ................................................................................................................................. i
List of Table .................................................................................................................................. i
List of Abbreviations ...................................................................................................................... ii
EXECUTIVE SUMMARY............................................................................................................ iii
1.0
INTRODUCTION ............................................................................................................ 1
2.0
SETTING AND WATER QUALITY DESCRIPTION ................................................... 2
2.1 General Setting and Source Assessment ................................................................. 2
2.1.1 Watershed Description ................................................................................... 2
2.1.2 Land Use ........................................................................................................ 4
2.1.3 Geology .......................................................................................................... 6
2.1.4 Nutrients Source Assessment ......................................................................... 6
2.1.4.1 Point Sources: Municipal and Industrial Wastewater Treatment Plant
Loads ....................................................................................................................... 6
2.1.4.2 Nonpoint Source Loads and Urban Stormwater Loads .............................. 8
2.2 Water Quality Characterization .............................................................................. 9
2.3 Water Quality Impairment..................................................................................... 13
2.3.1 Dissolved Oxygen Criteria ........................................................................... 14
2.3.2 Chlorophyll a Criteria .................................................................................. 14
3.0
TARGETED WATER QUALITY GOAL ...................................................................... 15
4.0
TOTAL MAXIMUM DAILY LOADS DEVELOPMENT AND ALLOCATION ........ 15
4.1 Overview................................................................................................................... 15
4.2 Analysis Framework ............................................................................................... 15
4.2.1 Computer Modeling Framework.................................................................. 15
4.2.1.1 Eutrophication Model Calibration ............................................................ 17
4.2.2 TMDL Analysis Framework ........................................................................ 18
4.2.2.1 Dissolved Oxygen Analytical Framework ................................................ 18
4.2.2.2 Chlorophyll a Analytical Framework ....................................................... 20
4.3 Scenario Descriptions and Results ......................................................................... 20
4.3.1 Baseline Conditions Scenario ...................................................................... 20
4.3.2 Baseline Conditions Scenario Results ......................................................... 21
4.3.2.1 Dissolved Oxygen Assessment of the Baseline Conditions Scenario ...... 22
4.3.2.2 Chlorophyll a Assessment for the Baseline Conditions Scenario ............ 24
4.3.3 Maximum Anthropogenic Reduction from Baltimore Harbor Scenario ..... 24
4.3.4 Maximum Anthropogenic Reduction Scenario Results ............................... 24
4.3.5 Future Conditions (TMDL) Scenario........................................................... 25
4.3.6 Future Conditions (TMDL) Scenario Results .............................................. 26
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
REVISED FINAL
4.3.6.1 Dissolved Oxygen Criteria Attainment Assessment of the Future
Conditions (TMDL) Scenario ............................................................................... 28
4.3.6.2 Chlorophyll a Criteria Attainment Assessment of the Future Conditions
(TMDL) Scenario.................................................................................................. 29
4.4 TMDL Loading Caps .............................................................................................. 30
4.5 Load Allocations Between Point Sources and Nonpoint Sources ....................... 30
4.5.1 Growing Season TMDL Allocations ........................................................... 30
4.5.2 Average Annual TMDL Allocations .......................................................... 32
4.6 Margin of Safety (MOS) ........................................................................................ 33
4.7 Summary of Total Maximum Daily Loads .......................................................... 35
5.0
ASSURANCE OF IMPLEMENTATION ..................................................................... 36
REFERENCES ............................................................................................................................ 39
APPENDIX A: Baseline Scenario Dissolved Oxygen Criteria
Attainment Assessment ................................................................................................... A1
APPENDIX B: TMDL Scenario Dissolved Oxygen Criteria Attainment Assessment.............. B1
APPENDIX C: Potential TMDL Allocations by Source Category ............................................ C1
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
REVISED FINAL
List of Figures
Figure 1: Location Map of Baltimore Harbor Drainage Basin ...................................................... 3
Figure 2: Predominant Land Uses in the Watershed Draining into Baltimore Harbor .................. 5
Figure 3: Proportions of Land Use in the Basins Draining into Baltimore Harbor ....................... 6
Figure 4: Percentages of Average Annual Nitrogen and Phosphorus Loads from Municipal and
Industrial Point Sources, Urban Stormwater and NPS in Baltimore Harbor, 1995-1997....... 9
Figure 5: Location of Water Quality Stations in Baltimore Harbor ............................................ 11
Figure 6: Time Series of Chlorophyll a Data at Baltimore Harbor Station WT5.1 / M16 .......... 12
Figure 7: Time Series of DO Data at Baltimore Harbor Station WT 5.1 / M16 .......................... 13
Figure 8: Time Series of Model Calibration Results of DO in Harbor Station WT5.1 ............... 17
Figure 9: Time Series of Model Calibration Results of Chl a in Harbor Station WT5.1 ............ 18
Figure 10: Cumulative Frequency Distribution curve representing an approximately 10 percent
allowable exceedance equally distributed between time and space (EPA, 2003) ................ 19
Figure 11: Time Series of Model Results for the Baseline Conditions Scenario for DO in
Baltimore Harbor Station WT5.1 .......................................................................................... 21
Figure 12: Model Results for the Baseline Conditions Scenario for Chl a in Baltimore Harbor
Station WT5.1 ....................................................................................................................... 22
Figure 13: Maximum Anthropogenic Reduction Scenario model results for DO levels in surface
and bottom waters in Baltimore Harbor at Station WT5.1 ................................................... 25
Figure 14: Time Series of Model Results for the TMDL Scenario for DO at Station WT5.1 .... 27
Figure 15: Time Series of Model Results for the TMDL Scenario for Chl a at Station WT5.1 . 27
List of Tables
Table 1: Baltimore Harbor Subwatershed Areas Within Maryland Jurisdictions .......................... 4
Table 2: Baltimore Harbor Subwatershed Areas ............................................................................ 4
Table 3: Average Municipal WWTP Loads, 1992-1997 ................................................................ 7
Table 4: Average Industrial WWTP Loads, 1992-1997 ................................................................. 7
Table 5: Average Daily Flows for Permitted Point Sources Discharging into Baltimore Harbor
during the 1992-1997 Model Calibration Period .................................................................... 7
Table 6: Dissolved Oxygen Criteria and Time Periods for the Designated Use Subcategories ... 14
Table 7: Baseline Conditions Scenario: Percent Nonattainment of Dissolved Oxygen Criteria in
the Baltimore Harbor ............................................................................................................ 23
Table 8: TMDL Scenario: Percent Nonattainment of Dissolved Oxygen Criteria in the Baltimore
Harbor ................................................................................................................................... 29
Table 9: Growing Season Allocations .......................................................................................... 32
Table 10: Average Annual Allocations......................................................................................... 33
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
i
REVISED FINAL
List of Abbreviations
BHEM
BMPs
BNR
CBP
CE-QUAL-ICM
CEWES
CFD
CH3D-WES
Chl a
COMAR
CTIC
CWA
DMCF
DO
ENR
EPA
HSPF
FSA
ISG
LA
lbs/yr
MD
MDA
MDE
MDP
mg/l / g/l
mgd
MOS
MS4
NOAA
NPDES
NPS
PATMH
PCBs
TMDL
TN
TP
WLA
WQIA
WQLS
WWTP
Baltimore Harbor Eutrophication Model
Best Management Practices
Biological Nutrient Removal
Chesapeake Bay Program
Corps of Engineers Water Quality Integrated Compartment Model
Corps of Engineers Waterways Experiment Stations
Cumulative Frequency Distribution
Curvilinear Hydrodynamics in Three Dimensions – Waterways Experiment
Stations
Active Chlorophyll a
Code of Maryland Regulations
Conservation Technology Information Center
Clean Water Act
Dredged Material Containment Facility
Dissolved Oxygen
Enhanced Nutrient Removal
Environmental Protection Agency
Hydrological Simulation Program Fortran
Farm Service Agency
International Steel Group
Load Allocation
Pounds per Year
Maryland
Maryland Department of Agriculture
Maryland Department of the Environment
Maryland Department of Planning
Milligrams per Liter / Micrograms per Liter
Million Gallons per Day
Margin of Safety
Municipal Separate Stormwater Sewer System
National Oceanic and Atmospheric Administration
National Pollutant Discharge Elimination System
Nonpoint Source
Patapsco River Mesohaline Stream Segment
Polychlorinated Biphenyls
Total Maximum Daily Load
Total Nitrogen
Total Phosphorus
Wasteload Allocation
Water Quality Improvement Act
Water Quality Limited Segment
Waste Water Treatment Plant
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
ii
REVISED FINAL
EXECUTIVE SUMMARY
Upon approval by the U.S. Environmental Protection Agency (EPA) this document will establish
Total Maximum Daily Loads for nitrogen and phosphorus in the Patapsco River Mesohaline
Stream Segment – PATMH (not including Bodkin Creek). Hereafter this stream segment will be
referred to as the Baltimore Harbor or the Harbor (basin number 02130903). The Baltimore
Harbor drains into the Chesapeake Bay and is part of the Patapsco/Back River Tributary Strategy
Basin.
Baltimore Harbor (basin number 02130903) was identified on the State’s 1996 list of water
quality limited segments (WQLSs) submitted to the U.S. EPA by the Maryland Department of
the Environment (MDE) as impaired by nutrients. The Baltimore Harbor has also been
identified on the 303(d) list as impaired by bacteria (fecal coliform) (1998), toxics
(polychlorinated biphenyls, or PCBs) (1998), metals (chromium, zinc and lead) (1998),
suspended sediments (1996), and impacts to biological communities (2004). These other
impairments will be addressed separately. The TMDLs described within this document were
developed to address the water quality impairments associated with excess nutrient loadings.
The TMDLs for the nutrients nitrogen and phosphorus were determined using a time-variable,
three-dimensional water quality eutrophication model package, which includes a watershed
model (Hydrological Simulation Program Fortran (HSPF)), a hydrodynamic model (Curvilinear
Hydrodynamic in Three Dimensions (CH3D)), a water quality model (Corps of Engineers-Water
Quality-Integrated Compartment Model (CE-QUAL-ICM)), and a sediment flux model.
Loading caps for total nitrogen and total phosphorus entering the Baltimore Harbor are
established for growing season conditions and for average annual flow conditions.
To assure that critical conditions are addressed, the growing season TMDL for nitrogen is
2,145,750 lbs/growing season, and the growing season TMDL for phosphorus is 149,152
lbs/growing season. These TMDLs apply from May 1 through October 31. The allowable loads
have been allocated between point and nonpoint sources. The nonpoint sources are allocated
459,912 lbs/growing season of total nitrogen, and 12,776 lbs/growing season of total phosphorus.
The National Pollutant Discharge Elimination System (NPDES) point sources, including
municipal wastewater treatment plant (WWTP) loads, NPDES industrial discharge loads and
NPDES regulated urban stormwater loads, are allocated 1,642,014 lbs/growing season of
nitrogen, and 113,212 lbs/growing season of phosphorus. A future allocation (FA) load to
account for future growth and an explicit margin of safety comprises the remainder of the
nitrogen and phosphorus allocations.
The average annual TMDL for nitrogen is 5,323,963 lbs/year, and the average annual TMDL for
phosphorus is 324,309 lbs/year. The allowable loads have been allocated between point and
nonpoint sources. The nonpoint source loads are allocated 1,246,036 lbs/year of total nitrogen
and 34,654 lbs/year of total phosphorus. The point sources, including NPDES WWTP loads,
NPDES industrial discharge loads and NPDES urban stormwater loads, are allocated 3,976,215
lbs/year of total nitrogen and 243,127 lbs/year of total phosphorus. A future allocation (FA) load
to account for future growth and an explicit margin of safety comprises the remainder of the
nitrogen and phosphorus allocations.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
iii
REVISED FINAL
Several legislative and policy-derived programs will be utilized to implement these TMDLs.
First, NPDES permits will reflect TMDL loadings as they are renewed. Additionally, the
Chesapeake Bay Restoration Fund will be used to finance Enhanced Nutrient Removal (ENR)
upgrades to WWTPs discharging into the Baltimore Harbor. Second, Maryland has several wellestablished programs to draw upon, including Maryland’s Tributary Strategies for Nutrient
Reductions, developed in accordance with the Chesapeake Bay 2000 Agreement. Third,
Maryland’s Water Quality Improvement Act (WQIA) of 1998 requires that nutrient management
plans be implemented for all agricultural lands throughout Maryland. Finally, Maryland has
adopted a watershed cycling strategy, which will ensure that future monitoring and water quality
evaluations are conducted.
The water quality goal of these TMDLs is to reduce excessive algal blooms that result in high
chlorophyll a concentrations, and maintain the dissolved oxygen concentrations at levels above
the water quality criteria for the specific designated uses of the Baltimore Harbor. MDE has
described the legislative and policy-derived programs that will result in significant nutrient
reductions and the achievement of water quality standards for all designated uses in the
Baltimore Harbor except the Deep Channel.
Based on information generated in the TMDL analysis, MDE is unable to ensure that the Deep
Channel Refuge designated use water quality criterion for dissolved oxygen can be met at all
times that it is applicable. The regions to which the Deep Channel Refuge designated use applies
represent approximately 10% of the area of the Harbor. These regions include the main
navigation channel of the Harbor, the channels into Curtis Bay, Middle Branch, and Northwest
Branch and associated anchorages (COMAR 26.08.02.08). The region subject to potential nonattainment is in the main shipping channel, from the mouth of the Harbor to Fort McHenry, and
represents < 5% of the area of the Harbor. The volume of water that does not meet the dissolved
oxygen criteria represents approximately 3% of the total volume of the Harbor.
The reason that the designated use cannot be fully attained is due to the deepening of the natural
river channel into a navigation channel that began in 1836 and continues today. In the past 170
years the dredging effort has incrementally deepened and expanded the size of the channels and
their associated turning basins and anchorages. As a result, the channels and the water that flows
within them, has been hydrologically modified. In a portion of the main navigation channel,
from the mouth of the Harbor to Fort McHenry, it has been observed that water from the upper
portion of the water column does not mix with the lower portion of the water column. This
observed stratification of the water column, and the lack of mixing associated with it, occurs
every spring/summer/fall. As a result, there is a limited region within the navigation channel that
does not meet the dissolved oxygen criteria during the observed spring/summer/fall stratification
period. Additionally, a computer model simulation was conducted that removed all
anthropogenic sources of nutrients to the system and returned the watershed to a forest. Even
under these conditions, the results indicated that the designated use could not be attained.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
iv
REVISED FINAL
1.0
INTRODUCTION
Section 303(d)(1)(C) of the federal Clean Water Act (CWA) and the U.S. Environmental
Protection Agency’s (EPA) implementing regulations direct each state to develop a Total
Maximum Daily Load (TMDL) for each impaired water quality limited segment (WQLS) on the
Section 303(d) list, taking into account seasonal variations and a protective margin of safety
(MOS) to account for uncertainty. A TMDL reflects the total pollutant loading of the impairing
substance a waterbody can receive and still meet water quality standards.
TMDLs are established to achieve and maintain water quality standards. A water quality standard
is the combination of a designated use for a particular body of water and the water quality criteria
designed to protect that use. Designated uses for the Patapsco River Mesohaline Stream Segment
– PATMH (hereafter referred to as the Baltimore Harbor or the Harbor) are: (1) Migratory Fish
Spawning and Nursery, (2) Seasonal Shallow Water Submerged Aquatic Vegetation, (3) Open
Water Fish and Shellfish Habitat, (4) Deep Water Seasonal Fish and Shellfish Habitat, and (5)
Deep Channel. Water quality criteria consist of narrative statements and numeric values designed
to protect the designated uses. Criteria differ among waters with different designated uses.
The Baltimore Harbor (basin number 02130903) was first identified on the 1996 303(d) list
submitted to EPA by the Maryland Department of the Environment (MDE). It was listed as
impaired by nutrients due to signs of eutrophication, expressed as high levels of chlorophyll a
(Chl a) and low concentrations of dissolved oxygen (DO). Eutrophication is the over-enrichment
of aquatic systems by excessive inputs of nutrients (nitrogen and/or phosphorus). The nutrients
act as a fertilizer leading to excessive growth of algae. The algae die and are eventually
consumed by bacteria. During the consumption process the bacteria utilize the available DO,
which results in decreased DO concentrations in the water column particularly when stratification
or layering prevents oxygen in the surface layers from mixing with deeper layers. Therefore,
MDE uses measures of DO and Chl a to understand the impact of the nitrogen and phosphorus on
the ecosystem. For these reasons, this document, upon EPA approval, establishes TMDLs for the
nutrients nitrogen and phosphorus in the Baltimore Harbor.
The Baltimore Harbor has also been identified on the 303(d) list as impaired by bacteria (fecal
coliform) (1998), toxics (polychlorinated biphenyls (PCBs) (1998), metals (chromium (Cr), zinc
(Zn), and lead (Pb)) (1998), suspended sediments (1996), and impacts to biological communities
(2004). To date, Cr and Zn impairments in Bear Creek and the Inner Harbor/Northwest Branch
and Pb in the Inner Harbor/Northwest Branch have been addressed with water quality analyses.
The remaining impairments will be addressed separately.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
1
REVISED FINAL
2.0
SETTING AND WATER QUALITY DESCRIPTION
2.1 General Setting and Source Assessment
2.1.1 Watershed Description
The watershed draining into the Baltimore Harbor estuary is the Patapsco River Watershed. The
Patapsco River Watershed is located in the western shore region of Maryland (Figure 1), and
includes the mainstem Patapsco and the tributaries of Jones Falls, Gwynns Falls, Colgate Creek,
Bear Creek, Curtis Creek, Stony Creek, and Rock Creek. The Patapsco River Mesohaline
(PATMH) segment, or Baltimore Harbor estuary, is located on the west side of the upper
Chesapeake Bay about 160 miles from the Virginia Capes at the entrance to the Bay. The Harbor
estuary is the 15-mile tidal region of the lower Patapsco River. It is the end of the Patapsco River
where it joins the Chesapeake Bay. The PATMH segment includes the Baltimore Harbor estuary
and the tidal segments of the Colgate Creek, Bear Creek, Curtis Creek, Stony Creek, Rock Creek
and Bodkin Creek tributaries. Bodkin Creek is identified in the 303(d) list as a separate
waterbody and will be addressed in the future.
Natural water depths in the Harbor are generally less than 20 feet except for the main navigation
channel maintained by the U.S. Army Corps of Engineers, which is maintained at a depth of 50
feet. The tidal range in the Harbor is approximately one foot. Other than the Patapsco River, the
only sizable tributaries entering the Harbor directly are Jones Falls and Gwynns Falls.
The Jones Falls, Gwynns Falls and Patapsco River discharge into the Baltimore Harbor. The
South Branch and mainstem of the Patapsco River flows about 85 miles (134 km) from Parr's
Spring in Carroll County to the Middle Branch. The North Branch, formed at the confluence of
the East Branch and West Branch, flows into Liberty Reservoir where it is retained for drinking
water purposes. A small segment of the North Branch exists below the dam and joins the South
Branch near the Town of Sykesville. After flowing through Baltimore Harbor, the Patapsco River
discharges into the Chesapeake Bay.
The subwatersheds draining into the Harbor are located within Baltimore City and Baltimore,
Anne Arundel, Carroll, and Howard Counties. The total area of these subwatersheds is 268,671
acres (1,087 square kilometers), excluding the land area above Liberty Reservoir. Water from the
subwatershed draining into Liberty Reservoir typically does not drain to the Baltimore Harbor
because it is used for drinking water.
Table 1 shows the area in acres that the Patapsco River watershed (not including Liberty
Reservoir watershed) occupies in each of the above counties. Table 2 shows the area in acres for
each of the four major subwatersheds draining into the Baltimore Harbor estuary.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
2
REVISED FINAL
Figure 1: Location Map of Baltimore Harbor Drainage Basin
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
3
REVISED FINAL
Table 1: Baltimore Harbor Subwatershed Areas Within Maryland Jurisdictions
Jurisdictions
Area (acres)
Anne Arundel County
46,223
Baltimore City
40,476
Baltimore County
100,600
Carroll County
40,182
Howard County
41,190
Total
268,671
Table 2: Baltimore Harbor Subwatershed Areas
Subwatersheds
Area (acres)
Gwynns Falls
41,701
Jones Falls
37,273
Patapsco River
130,662
Baltimore Harbor
59,035
Total
268,671
2.1.2 Land Use
The land use in the Baltimore Harbor watershed is diverse. The land cover consists of urban,
suburban, rural, industrial, forest, and agricultural land uses. One of the largest forested areas in
the watershed is the Patapsco Valley State Park.
The watershed draining into the Baltimore Harbor (not including the watershed draining into the
Liberty Reservoir) has an area of approximately 268,671 acres (1,087.3 square kilometers). The
land uses in the watershed consist of forest and other herbaceous growth (77,077 acres or 29%),
mixed agriculture (41,848 acres or 15%), water (1,806 acres or 1%), and urban (147,940 acres or
55%). Land use information was derived from the 1997 Maryland Department of Planning
(MDP) land cover database, the Farm Service Agency (FSA), the 1997 Agricultural Census, and
information from the 1996 Conservation Technology Information Center (CTIC). See Figure 2
for the predominant land uses in the Baltimore Harbor watersheds. Figure 3 shows the relative
amounts of different land uses in the watersheds draining into the Baltimore Harbor.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
4
REVISED FINAL
Figure 2: Predominant Land Uses in the Watershed Draining into Baltimore Harbor
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
5
REVISED FINAL
Mixed
Agriculture
15%
Urban
55%
Forest and Other
Herbaceous - 29%
Water
1%
Figure 3: Proportions of Land Use in the Basins Draining into Baltimore Harbor
2.1.3 Geology
The watersheds draining into the Baltimore Harbor lie primarily within the Piedmont and, to a
lesser extent, the Coastal Plain provinces of Central Maryland. The surficial geology is
characterized by crystalline rocks of volcanic and sedimentary origin, consisting primarily of
schist and gneiss. These formations are resistant to short-term erosion, and often determine the
limits of stream bank and streambed. Crystalline formations decrease in elevation from northwest
to southeast, eventually extending beneath the younger sediments of the Coastal Plain. The fall
line represents the transition between the Atlantic Coastal Plain Province and the Piedmont
Province. The Atlantic Coastal Plain surficial geology is characterized by thick, unconsolidated
marine sediments deposited over the crystalline rock formations of the Piedmont Province
(Coastal Environmental Services, 1995).
2.1.4 Nutrients Source Assessment
2.1.4.1 Point Sources: Municipal and Industrial Wastewater
Treatment Plant Loads
The Patapsco Wastewater Treatment Plant (WWTP) and Cox Creek WWTP are municipal point
sources that discharge directly into Baltimore Harbor. International Steel Group (ISG), Grace
Davison, Erachem-Comilog, US Gypsum, and Millenium Specialty are the five industrial point
sources that discharge directly into the Harbor. The combined estimated average annual loads
from municipal WWTPs for 1992-1997 (the model calibration period) are 3,455,063 lbs/yr for
total nitrogen (TN) and 216,099 lbs/yr for total phosphorus (TP). The combined estimated
average annual loads from industrial WWTPs for 1992-1997 are 3,001,015 lbs/yr for TN and
89,376 lbs/yr for TP. Thus, the total average annual loads from all WWTPS are 6,456,078 lbs/yr
for TN and 305,475 lbs/yr for TP. This information was obtained from discharge monitoring
reports stored in MDE’s point source database. The municipal average annual point source loads
for 1992-1997 are presented in Table 3. The industrial average annual point source loads for
1992-1997 are shown in Table 4. Table 5 lists the average daily flows for all permitted point
sources discharging into Baltimore Harbor during 1992-1997 in millions of gallons per day
(mgd).
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
6
REVISED FINAL
Table 3: Average Municipal WWTP Loads, 1992-1997
Year
TN
TP
lbs/yr
lbs/yr
1992
1993
1994
1995
1996
1997
2,762,146
3,814,825
5,132,577
3,049,908
3,059,893
2,911,024
207,976
235,890
220,309
243,216
221,403
167,800
Average
3,455,063
216,099
Table 4: Average Industrial WWTP Loads, 1992-1997
TN
TP
Year
lbs/yr
lbs/yr
1992
1993
1994
1995
1996
1997
3,506,205
2,846,814
2,636,706
2,697,273
3,127,613
3,191,478
93,862
88,115
84,041
85,333
90,767
94,140
Average
3,001,015
89,376
Table 5: Average Daily Flows for Permitted Point Sources Discharging into Baltimore
Harbor during the 1992-1997 Model Calibration Period
Facility
Type
Patapsco WWTP
Cox Creek WWTP
Erachem-Comilog
Grace Davison
US Gypsum-1
US Gypsum-2
ISG-1
ISG-2
ISG-3
ISG-4
ISG-5
ISG-6
ISG-7
Millennium 001
Millennium 002
Municipal
Municipal
Industrial
Industrial
Industrial
Industrial
Industrial
Industrial
Industrial
Industrial
Industrial
Industrial
Industrial
Industrial
Industrial
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
7
Average Flow
(mgd)
47.96
11.18
0.089
2.38
0.001
0.000
37.34
5.66
55.42
3.60
0.064
3.94
1.51
0.067
0.589
REVISED FINAL
These flow and point source load estimates represent actual discharge into the Baltimore Harbor
from municipal WWTPs and industrial plants from 1992-1997. It is important to note that these
plants were not all discharging at their maximum flow capacities and/or nutrient permit limits
during this period. For example, the Patapsco River and Cox Creek municipal WWTPs
discharged an average of 3.5 million lbs/yr of TN and 0.22 million lbs/yr of TP during the 19921997 study period. If these plants discharged consistently at their maximum capacity flow, their
loads could increase to 3.9 million lbs/yr of TN and 0.46 million lbs/yr of TP, assuming the TN
concentration was the same as the actual 1992-1997 concentrations and the TP concentration
equal to the current permit limit of TP = 2.0 mg/l for both plants. Similarly, industrial facilities
loads could increase significantly if they discharged at maximum capacity for long periods of
time.
2.1.4.2 Nonpoint Source Loads and Urban Stormwater Loads
Nonpoint source loads and urban stormwater loads entering the Baltimore Harbor were estimated
using the Hydrologic Simulation Program-Fortran (HSPF). The HSPF model is used to estimate
flows, suspended solids and nutrient loads from the watershed’s sub-basins. Nonpoint source and
urban stormwater loads are linked to a three-dimensional, time-variable hydrodynamic model and
a water quality model coupled with a sediment process model designed specifically for Baltimore
Harbor. The water quality model is used to determine the maximum load of nutrients that can
enter the Harbor while maintaining the water quality criteria associated with its designated uses.
The water quality modeling framework is shown in Section 4.2.
The Baltimore Harbor HSPF watershed model used the following assumptions: (1) variability in
patterns of precipitation were estimated from existing National Oceanic and Atmospheric
Administration (NOAA) meteorological stations; (2) hydrologic response of land areas were
estimated for a simplified set of land uses in the basin; and (3) agricultural information, like crop
types and tilling practices, were estimated from MDP land use data, the 1997 Agricultural Census
Data, and the Farm Service Agency (FSA) data. The HSPF simulates nonpoint source and urban
stormwater loads and integrates all natural and human-induced sources, including direct
atmospheric deposition and loads from septic tanks, which are associated with river base flow
during growing season conditions. Details of the HSPF watershed model developed to estimate
these urban and non-urban loads are found in the “Patapsco/Back River Watershed HSPF Model
Report” (MDE, 2001).
Figure 4 presents the relative average annual amounts of nitrogen and phosphorus from nonpoint
source, municipal and industrial point source, and urban stormwater delivered loadings to the
Baltimore Harbor during the 1995-1997 period.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
8
REVISED FINAL
Total Nitrogen 1995-1997
Municipal & Industrial
Point Sources
71%
Urban-Stormwater
12%
Total Phosphorus 1995-1997
Mixed
Agriculture
12%
Municipal &
Industrial Point
Sources
58%
Other
5%
Urban-Stormwater
29%
Mixed
Agriculture
8%
Other
6%
Figure 4: Percentages of Average Annual Nitrogen and Phosphorus Loads from Municipal
and Industrial Point Sources, Urban Stormwater and NPS in Baltimore Harbor, 1995-1997
The calibration of the model was conducted for the 1992-1997 period. The TMDL analysis was
conducted using the 1995-1997 period as a baseline, which includes dry, wet and average years.
For these reasons, the delivered loads percentages in the figures represent an average for the
1995-1997 period.
In the Baltimore Harbor watershed, the estimated 1995-1997 average annual TN delivered load
from nonpoint sources (NPS) is 1,364,400 lbs/yr, and the NPS TP delivered load is 37,465 lbs/yr.
The estimated 1995-1997 average annual TN load for point sources, including regulated urban
stormwater TN load, is 7,053,689 lbs/yr and the estimated 1995-1997 average annual point source
TP load is 317,423 lbs/yr.
2.2 Water Quality Characterization
Eutrophication is the over-enrichment of aquatic systems by excessive inputs of nutrients
(nitrogen and/or phosphorus). The nutrients act as a fertilizer leading to excessive growth of
algae. The algae grow rapidly, die and are subsequently consumed by bacteria. The bacterial
consumption of the algae results in the use of available dissolved oxygen in the water column,
which produces hypoxic (low oxygen) or anoxic (no oxygen) conditions. Eutrophication has
probably been more extensively studied in the Chesapeake Bay and its tributaries than in any
other coastal ecosystem. Scientists have uncovered the relationships of how nutrients stimulate
biological productivity in the Bay, and how eutrophication results in oxygen depletion, increased
turbidity, loss of submersed vegetation, and alteration of food webs (Boesch et al., 2001).
Portions of the Chesapeake Bay and its tributaries often show signs of eutrophication. The
Baltimore Harbor has shown clear indications of eutrophication for several decades (Robertson,
1977; Magnien et al., 1993; Boynton et al., 1998). For example, extensive and persistent anoxic
or hypoxic conditions were observed regularly in the bottom waters of the Baltimore Harbor.
The Chesapeake Bay Water Quality Monitoring Program has recorded measurements in the
Baltimore Harbor indicating anoxic and hypoxic events occur as early as April and extend until
October every year. Also, increased algal blooms have been found to occur yearly during the
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
9
REVISED FINAL
warm season (Wang et al., 2004). Anoxic conditions occur at the bottom of the navigation
channel as well as in most tributaries, such as the Inner Harbor and the Middle Branch. Anoxic
water exists in the mainstem of the Chesapeake Bay each summer. However, Wang et al (2004)
and Liu (2002) hypothesize that the origin of low DO in the Harbor is not from the intrusion of
anoxic Bay water, but rather is an internal process of the Harbor.
Wang et al,. (2004) indicate that the water circulation and exchange within the Baltimore Harbor
region are generally regulated by local wind forces, which overwhelm the weak currents driven
by river and tidal forces. Pritchard and Carpenter (1960) inferred the existence of a three-layered
circulation in Baltimore Harbor based on salinity and dye distributions. This was confirmed by
Boicourt and Olson (1982) with direct measurements. This unique hydrodynamic feature has to
be taken into consideration because it can affect the dynamics of water quality parameters.
Data for the 1992-1997 period have been selected for the development of the eutrophication
model and the subsequent nutrient TMDL analyses. There are 24 water quality stations located in
the Baltimore Harbor that MDE and the Chesapeake Bay Program (CBP) surveyed during the
model calibration period. The reader is referred to Figure 5 for the locations of the water quality
sampling stations.
The CBP has sponsored a long-term water quality sampling station (WT5.1) in the Baltimore
Harbor since 1984 to monitor its physical, chemical, and biological parameters. MDE also
monitored the Baltimore Harbor intensively at the other 23 stations during the period March 1994
to May 1995 for parameters similar to those monitored by the CBP. A detailed list of all
parameters measured in these surveys can be found in the report “The Development of a Water
Quality Model for Baltimore Harbor, Back River and the Adjacent Upper Chesapeake Bay”
(Wang et al., 2004).
The time series data for dissolved oxygen (DO) and chlorophyll a (Chl a) at stations WT5.1 and
M16 are presented in this report to provide a trend analysis of the two parameters associated with
Maryland water quality standards. Additional time series and longitudinal data profiles from the
MDE and CBP stations for various nutrient parameters are available upon request and through the
MDE TMDL website as supporting documentation. The time series data files are too large to
incorporate as appendices to this report.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
10
REVISED FINAL
Figure 5: Location of Water Quality Stations in Baltimore Harbor
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
11
REVISED FINAL
Figure 6 presents the time series of Chl a concentrations in the Baltimore Harbor from January
1992 to December 1997 for the CBP long-term monitoring station WT5.1 (MDE Station M16)
located in the middle of the Harbor, approximately 8.8 km from the Harbor’s mouth.
1992
X

1993
1994
1995
1996
1997
CBP Observed Chlorophyll a Data
MDE Observed Chlorophyll a Data
Figure 6: Time Series of Chlorophyll a Data at Baltimore Harbor Station WT5.1 / M16
As Figure 6 shows, surface Chl a concentrations include observations that are above 50 g/l every
year, with a seasonal pattern of higher values during warmer months and lower values during
colder months. Concentrations rarely exceed 100 g/l, except in the summers of 1994 and 1995
when maximum concentrations were close to 200 g/l. Bottom Chl a is normally below 20 g/l,
except during the springs of 1995 and 1996 where concentrations reached 100 g/l and 85 g/l,
respectively (probably weather-related, as several snowstorms may have resulted in unusual
patterns of thermal stratification).
A time series for surface and bottom DO concentrations at station WT5.1 is depicted in Figure 7,
showing that the observed surface DO levels did not fall below 5.0 mg/l. The surface DO ranged
from 5.2 mg/l to 18.0 mg/l with average DO concentrations around 10 mg/l. There is some
degree of seasonal variation with higher DO values during winter months and lower values during
summer months, due to seasonal changes in temperature. The bottom water DO concentrations
range from 0 mg/l to 11 mg/l and display a distinct seasonal pattern. Anoxic conditions can be
observed at the bottom waters starting as early as April in some years and lasting until the end of
summer every year. During early fall, DO levels start to increase rapidly, reaching the 5.0 mg/l
level by November.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
12
REVISED FINAL
1992
X
O
1993
1994
1995
1996
1997
CBP Observed DO Data
MDE Observed DO Data
Figure 7: Time Series of DO Data at Baltimore Harbor Station WT 5.1 / M16
2.3 Water Quality Impairment
The Maryland Water Quality Standards Stream Segment Designation [Code of Maryland
Regulations (COMAR) 26.08.02.08K(2)(b)] for the Patapsco River Mesohaline (PATMH) (not
including Bodkin Creek) is Use II: Tidal Waters: Support of Estuarine and Marine Aquatic Life
and Shellfish Harvesting. Designated Uses present in the Baltimore Harbor Segment are: 1)
Migratory Spawning and Nursery, 2) Shallow Water Submerged Aquatic Vegetation, 3) Open
Water Fish and Shellfish, 4) Seasonal Deep Water Fish and Shellfish, and 5) Deep Channel. No
areas in the Harbor are designated as Shellfish Harvest Use areas.
The designated uses described above and the associated criteria are the result of MDE’s adoption
of water quality standards developed by the Chesapeake Bay Program. MDE adopted the
standards in the fall of 2005 and the Baltimore Harbor TMDL represents the second application of
these standards to Maryland’s estuarine waters.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
13
REVISED FINAL
2.3.1 Dissolved Oxygen Criteria
Table 6 presents descriptions of the numeric DO criteria for designated uses present in the
Harbor. The DO level is based on specific numeric criteria for Use II waters set forth in the
COMAR 26.08.02.03-3C(2)(8). However, due to data limitations MDE will follow EPA
guidance and assess the DO attainment based on 30-day component of the Open Water Use
designated use for the Migratory Fish Nursery and Spawning Use, and Seasonal Shallow Water
Submerged Aquatic Vegetation designated uses. The Deep Water Use will also be assessed using
a 30-day methodology, however the requisite concentration is different from the Open Water Use.
Table 6: Dissolved Oxygen Criteria and Time Periods for the Designated Use Subcategories
Period
Designated Use II
Dissolved Oxygen Criteria
Subcategory
Seasonal Migratory
February 1
Fish Spawning and
through May 31
 Open Water criteria apply
Nursery
inclusive
April 1 through
Seasonal Shallow
October 31
Water Submerged
 Open Water criteria apply
inclusive
Aquatic Vegetation
Open Water Fish and
Shellfish
Seasonal Deep Water
Fish and Shellfish
January 1
through
December 31
inclusive
June 1 through
September 30
inclusive

5.0 mg/l
30-day average

3.0 mg/l
30-day average*
June 1 through
September 30
  1 mg/l instantaneous minimum
inclusive
* Allows a restoration variance of up to 7% applied spatially or temporally in combination
from June 1 through September 30
Seasonal Deep Channel
Refuge
2.3.2 Chlorophyll a Criteria
The Chl a concentration goal used in this analysis are based on guidelines set forth by Thomann
and Mueller (1987) and by the EPA Technical Guidance Manual for Developing Total Maximum
Daily Loads, Book 2, Part 1 (1997). The Chl a narrative criterion (COMAR 26.08.02.03-3C(10)
state: “Chlorophyll a - Concentrations of chlorophyll a in free-floating microscopic aquatic plants
(algae) shall not exceed levels that result in ecologically undesirable consequences that would
render tidal waters unsuitable for designated uses.” The Thomann and Mueller guidelines
acknowledge that “‘Undesirable’ levels of phytoplankton [Chl a] vary considerably depending on
water body.” MDE has determined, per Thomann and Mueller, that it is acceptable to maintain
Chl a concentrations below a maximum of 100 µg/L, and to target, with some flexibility
depending on waterbody characteristics, a 30-day rolling average of approximately 50 µg/L.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
14
REVISED FINAL
Consistent with the guidelines set forth above, MDE’s interpretation of narrative criteria for Chl a
in the Baltimore Harbor is comprised of the following water quality goals:
(1) Ensure that instantaneous concentrations remain below 100 µg/L at all times and
(2) Minimize exceedances of the 50 µg/L, 30-day rolling average, to a frequency that will
not result in ecologically undesirable conditions.
The water quality impairment being addressed by this TMDL analysis consists of DO
concentrations less than the numeric criteria presented in Section 2.3.1 and Chlorophyll a (Chl a)
concentrations above the MDE interpretation of the narrative criteria presented in Section 2.3.2
(See Figures 6&7). The achievement of the DO and Chl a criteria is required for all the uses
throughout the water column of the Baltimore Harbor system. In the Harbor, data are not
sufficient to assess the 7-day average and instantaneous minimum DO criteria for attainment of
the designated uses; thus, the calibrated model results are used to evaluate conditions.
3.0
TARGETED WATER QUALITY GOAL
The objective of the nutrient TMDLs established in this document is to ensure that DO and Chl a
concentrations in the Baltimore Harbor meet the criteria associated with specific designated uses.
Specifically, the TMDLs for nitrogen and phosphorus are intended to control excessive algal
growth and increase DO concentrations in areas not currently meeting water quality criteria.
4.0
TOTAL MAXIMUM DAILY LOADS DEVELOPMENT AND ALLOCATION
4.1 Overview
The following sections describe the modeling frameworks for simulating nutrient loads,
hydrology, and water quality responses. Section 4.2 summarizes the TMDL analysis framework
and model calibration. Section 4.3 describes the scenarios and results that were generated using
the modeling framework. Sections 4.4–4.5 describe how the nutrient TMDLs and load
allocations for point sources and nonpoint sources were developed for the Baltimore Harbor.
Section 4.6 explains the rationale for the margin of safety and the last section summarizes the
TMDLs for the growing season and average annual conditions.
4.2 Analysis Framework
4.2.1 Computer Modeling Framework
To develop a TMDL, a linkage must be defined between the selected water quality targets or
goals and the identified pollutant sources. This linkage establishes the cause-and-effect
relationship between the sources of the pollutant of concern and the water quality response of the
impaired water quality segment to that pollutant. For nonpoint sources, the relationship can vary
seasonally due to factors such as precipitation. Once defined, the linkage yields the estimate of
total loading capacity or TMDL (EPA, 1999).
MDE chose a set of time-variable models as the analysis tool to link the sources of nutrient
loadings to the DO criteria and chlorophyll a goal. The computational framework chosen for the
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
15
REVISED FINAL
Baltimore Harbor nutrients TMDLs is the three-dimensional, time-variable Baltimore Harbor
Eutrophication Model (BHEM). This water quality simulation package provides a generalized
framework for modeling nutrient fate and transport in surface waters (Cerco and Cole, 1995).
The BHEM package includes a watershed model, a hydrodynamic model, a water quality model
and a sediment flux sub-model, and represents twenty-two water quality parameters from the
water column and sediment bed. For detailed information, please refer to the report “The
Development of a Water Quality Model for Baltimore Harbor, Back River and the Adjacent
Upper Chesapeake Bay” (Wang et al., 2004).
Since many studies have shown the significant influence of the Chesapeake Bay on its tributaries,
the spatial domain of the BHEM extends longitudinally from the mouth of the Susquehanna River
about 90 miles seaward (south) to the mouth of the Patuxent River, which is defined as the upper
Chesapeake Bay. Baltimore Harbor is located on the western shoreline of the upper Chesapeake
Bay. This modeling domain is represented by BHEM model segments. A diagram of the model
segmentation is presented in Wang et al (2004).
The water quality model, Corps of Engineers Water Quality Compartment Model (CE-QUALICM), is externally coupled with the three-dimensional, time-variable hydrodynamic model,
Curvilinear Hydrodynamic in Three Dimensions, (CH3D). As its name indicates, CH3D makes
hydrodynamic computations on a curvilinear or boundary-fitted platform grid that allows the
model to accurately represent the deep navigation channel and irregular shoreline. The CH3D
simulates physical processes such as tides, wind, density effects (salinity and temperature),
freshwater inflows, turbulence, and the effect of the earth’s rotation. The model outputs are used
to drive the water quality model (Johnson et al., 1991).
The sediment flux model developed by DiToro and Fitzpatrick (1993), and coupled with CEQUAL-ICM for Chesapeake Bay water quality modeling efforts, is used in the present model
application. The state variables, resulting fluxes, and complete model documentation can be
found in Wang et al (2004), and also in DiToro and Fitzpatrick (1993).
The stormwater load and nonpoint source loading estimation was conducted using a HSPF
watershed model, which simulates the fate and transport of pollutants over the entire hydrologic
cycle. Details of this effort are described in Section 2.1.4.2. For detailed information, see
“Patapsco/Back River Watershed HSPF Model Report” (MDE, 2001).
The BHEM package described above was calibrated to reproduce observed water quality
characteristics for 1992-1997 conditions. The calibration of the model for these six years
establishes an analytical tool that may be used to assess a range of scenarios with differing flow
and nutrient loading conditions. For a detailed explanation of the calibration of the watershed
model, hydrodynamic model, water quality model and sediment flux model please refer to MDE,
2001 and Wang et al., (2004).
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
16
REVISED FINAL
4.2.1.1 Eutrophication Model Calibration
The calibration and verification of the BHEM modeling package was reviewed and accepted by
various modeling technical groups, i.e., Chesapeake Bay Program Modeling Subcommittee and
Baltimore Harbor Stakeholder Advisory Group. The calibration of the eutrophication model is
the process of modifying the model input parameters until the model output matches the set of
observed water column data in an optimal way. Observed water quality, hydrological, and
loading data collected during the period 1992-1997 were used to calibrate the BHEM. Figures 8
and 9 show the results of the model calibration for chlorophyll a and DO at station WT5.1 in both
surface and bottom water. Additional time series and longitudinal data profiles from the MDE
and CBP stations for various nutrient parameters may be found in Wang et al (2004) and are also
available upon request and through the MDE TMDL website as supporting documentation. The
time series data files are too large to incorporate as appendices to this report.
1992
1993
1994
1995
1996
1997
X CBP Observed DO Data
O MDE Observed DO Data
Model Calibration results: Weekly Minimum and Maximum DO
Model Calibration results: Weekly Average DO
Figure 8: Time Series of Model Calibration Results of DO in Harbor Station WT5.1
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
17
REVISED FINAL
1992
X
1993
1994
1995
1996
1997
CBP Observed Chlorophyll a Data
O MDE Observed Chlorophyll a Data
Model Calibration results: Weekly Minimum and Maximum Chlorophyll a
Model Calibration results: Weekly Average Chlorophyll a
Figure 9: Time Series of Model Calibration Results of Chl a in Harbor Station WT5.1
4.2.2 TMDL Analysis Framework
The nutrient TMDL analysis consists of two broad elements: an assessment of growing season
loading conditions and an assessment of average annual loading conditions. Both the growing
season and the average annual flow TMDL analyses investigate the critical conditions under
which symptoms of eutrophication are typically most acute. During excessively dry or wet years
the flux in loadings impact water quality significantly. Additionally, water quality is impacted
during late summer when flows are low, the system is poorly flushed, and sunlight and
temperatures are most conducive to excessive algal production. The TMDL analysis allows a
comparison of current loading conditions to future conditions that project the water quality
response to various simulated load reductions of the impairing substances.
4.2.2.1 Dissolved Oxygen Analytical Framework
In April 2003, the CBP published its approach to assessing the attainment of water quality criteria
designed to protect the living resources of the Chesapeake Bay and its tidal tributaries, as defined
by their respective designated uses. In 2005, MDE adopted the CBP DO criteria and its
associated attainment methodology, utilizing DO biological reference curves to represent the
spatial and temporal distribution of DO concentrations. MDE is applying this methodology using
Cumulative Frequency Distributions (CFDs) for the Baltimore Harbor generated from model
output, and compared against the CBP reference curves, to assess spatial and temporal DO criteria
exceedances. This method quantifies the degree of criteria attainment or exceedence by
incorporating the percent of area or volume of a region that meets or exceeds the DO criterion for
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
18
REVISED FINAL
the specific designated uses periods. Using CFDs generated from the model data, the calibrated
and verified assessment results express exceedances above the reference curve (violations of the
allowable criteria limit) as percentages of the total time-volume for the area. These percentages
are then used to determine whether a load reduction (TMDL) is required to meet the designated
use.
The CFDs are derived from empirical, biology-based field data wherever possible. The DO
criteria are intended have several duration curves that reflect in situ conditions: 30-day mean, 7day mean, 1-day mean and the instantaneous minimum. However, given the limitations in
directly monitoring at the temporal scales required for assessing attainment of the instantaneous
minimum, 1-day mean and 7-day mean criteria, EPA indicates that the states can waive
attainment assessments for these criteria until monitoring at the required temporal scales is
implemented or apply statistical methods to estimate probable attainment (EPA, April 2003). For
these reasons, MDE will assess the DO attainment for only the 30-day component of the Open
Water Use and Deep Water Use DO criteria in the Baltimore Harbor. For the Migratory Fish
Nursery and Spawning Use, EPA indicates that until more data are collected to better assess the
attainment of the 7-day mean and instantaneous minimum criteria of this designated use, the Open
Water DO reference curve should be applied. For the Migratory Fish Nursery and Spawning Use
attainment analysis, MDE utilized the Open Water DO reference curve and model output
associated with the Migratory Fish Nursery and Spawning Use period. Figure 10 below is an
example of the CBP DO reference curve adopted by MDE. (For more information on monitoring,
assessment of DO criteria attainment, and CBP DO reference curves, please refer to the CBP
document entitled “Ambient Water Quality Criteria for the Dissolved Oxygen, Water Clarity and
Chlorophyll a for the Chesapeake Bay and its Tidal Tributaries” (EPA, 2003).
Figure 10: Cumulative Frequency Distribution curve representing an approximately 10
percent allowable exceedance equally distributed between time and space (EPA, 2003)
Additionally, the Deep Channel Designated Use area does not have a reference curve. The Deep
Channel is defined as the region below the lower boundary of the pycnocline, extending down to
the water/sediment interface. The Deep Channel Designated Use is applied from June 1st to
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
19
REVISED FINAL
September 30th and requires an instantaneous minimum concentration of 1.0 mg/l. Two factors
have prevented the development and application of a “reference curve” approach as used in the
other segments of the water column. First, the Deep Channel portion of the Chesapeake Bay has
not been monitored as part of the long-term benthic monitoring program and therefore lacks
appropriate data for development of a reference curve. Second, the Deep Channel segment of the
Chesapeake Bay is considered severely degraded and appropriate reference sites with similar
characteristics and non-degraded conditions are not available.
Due to the unavailability of a reference curve to assess attainment, MDE has conducted an
analysis to determine the percentage of time when the modeled DO concentration in the Deep
Channel was below the 1.0 mg/l instantaneous minimum concentration required by the criteria.
The assessment consisted of an evaluation of the modeled scenario DO concentrations versus the
instantaneous minimum concentration.
4.2.2.2 Chlorophyll a Analytical Framework
Model results were compared to the quantitative implementation of the narrative Chl a criteria
stated in Section 3.0 as: (1) ensuring that instantaneous concentrations remain below 100 µg/l at
all times and (2) minimizing exceedances of the 50 µg/l, 30-day rolling average, to a frequency
that will not result in ecologically undesirable conditions.
4.3 Scenario Descriptions and Results
The scenarios are grouped according to baseline conditions, future conditions, and a maximum
anthropogenic reduction from Baltimore Harbor scenario. The baseline condition is intended to
provide a point of reference by which to compare future scenarios that simulate conditions of a
TMDL. The future conditions scenario is associated with TMDLs, while the maximum
anthropogenic reduction from Baltimore Harbor scenario is used as a bounding exercise to
determine if it is possible to achieve water quality standards in the Deep Channel portion of the
Harbor. The baseline and future conditions scenarios were used to estimate growing season and
average annual TMDLs. The period 1995-1997 corresponds to the “baseline” period in analyses
described below. The following analyses allow a comparison between current water quality
conditions and future conditions that project various simulated load reductions of impairing
substances.
4.3.1 Baseline Conditions Scenario
The baseline conditions scenario represents the observed conditions of the Harbor and its
tributaries from 1995-1997. Simulating the system for three years accounts for various loading
and hydrologic conditions, which represent possible critical conditions and seasonal variations of
the system. For example, the 1995-1997 period includes an average year (1995), a wet year
(1996) and a dry year (1997). The modeling approach also specifically examines conditions
during summer months when the river system is poorly flushed, and sunlight and warm water
temperatures are more conducive to creating the water quality problems associated with excessive
nutrient enrichment.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
20
REVISED FINAL
The nonpoint nutrient loads, including urban stormwater loads, were estimated from the HSPF
model of the Patapsco and Back River watersheds. The HSPF model utilized land use
information and hydrology associated with the 1995-1997 period to generate loading estimates for
this scenario. The HSPF model simulates stormwater and nonpoint loadings by integrating all
natural and human-induced sources, including direct atmospheric deposition and loads from
septic tanks. For point source loads, this scenario uses the municipal WWTP and industrial
discharge monitoring data from 1995-1997. Additionally, time series and longitudinal data
profiles from the MDE and CBP stations for various nutrient parameters are available upon
request and through the MDE TMDL website as supporting documentation. The time series data
files are too large to incorporate as appendices to this report.
4.3.2 Baseline Conditions Scenario Results
Results of DO and Chl a concentrations represented in the baseline scenario are summarized in
Figures 11 and 12. Figure 11 displays the observed and modeled DO data while Figure 12
displays the observed and modeled Chl a concentrations at station WT5.1 in both surface and
bottom water.
1995
1996
1997
X CBP Observed DO Data
O MDE Observed DO Data
Model Calibration results: Weekly Minimum and Maximum DO
Model Calibration results: Weekly Average DO
Figure 11: Time Series of Model Results for the Baseline Conditions Scenario for DO in
Baltimore Harbor Station WT5.1
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
21
REVISED FINAL
1995
1996
1997
X CBP Chlorophyll a Observed data
O MDE Chlorophyll a Observed data
Model Calibration results: Minimum and Maximum Chlorophyll a
Model Calibration results: 30-day Rolling Average Chlorophyll a
Figure 12: Model Results for the Baseline Conditions Scenario for Chl a in Baltimore
Harbor Station WT5.1
4.3.2.1 Dissolved Oxygen Assessment of the Baseline Conditions
Scenario
For the DO assessment of the baseline conditions scenario in the Baltimore Harbor, the CBP
reference curve approach for the Migratory Fish and Spawning, Open Water and Deep Water
Designated Uses was used. Due to limited data in the Baltimore Harbor, the calibrated model
output generated during the baseline conditions scenario was used for the attainment analysis.
The attainment assessment procedure is as follows: First, using the calibrated model DO output
for the baseline conditions scenario period (1995-1997), DO attainment curves are developed for
the Migratory Fish and Spawning, Open Water and Deep Water Designated Uses. Second, the
reference curves from the CBP are obtained. Third, MDE generated attainment curves for each of
the designated use areas are compared to the corresponding CBP reference curves. The results of
the comparison allow MDE to quantify the degree of criteria attainment or exceedance based on
the amount of area or volume of a specific designated use region.
A summary of the attainment assessment is presented in Table 7. The baseline scenario
assessment of the DO criteria attainment for the Migratory Fish Spawning and Nursery
Designated Use, which applies from February 1st to May 31st, indicates that there is a period of
nonattainment in time and volume that represents a 3% exceedance of the criteria (See Appendix
A, Figure A4). The assessment of DO criteria attainment for the Open Water Designated Use,
which applies from June 1st to September 30th indicates that there is a period of nonattainment in
time and volume that represents a 3% exceedance of the criteria (See Appendix A, Figure A5).
The assessment of DO criteria attainment for the Open Water Designated Use, which also applies
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
22
REVISED FINAL
from October 1st to January 31st, indicates that there is a period of nonattainment in time and
volume that represents a 2% exceedance of the criteria (See Appendix A, Figure A6). The
assessment of the DO criteria attainment for the Deep Water Designated Use, which applies from
June 1st to September 30th, indicates that there is a period of nonattainment in time and volume
that represents a 23% exceedance of the criteria (See Appendix A, Figure A7).
MDE conducted an analysis of the baseline scenario to determine the percentage of time when the
modeled DO concentration in the Deep Channel was below the 1.0 mg/l instantaneous minimum
concentration required by the criteria. The assessment consisted of an evaluation of the modeled
baseline scenario DO concentrations versus the instantaneous minimum concentration. The result
of this assessment indicates that the Deep Channel exceeded the criteria 87% of the time and
volume.
The Deep Channel segment of the Baltimore Harbor is considered degraded due to two related
factors. The first is the dredging that occurs in the channel, allowing for the passage of ships in
and out of the commercial port areas within the Harbor. The dredging has resulted in
modifications of the Harbor hydrodynamic circulation patterns that effectively separate the Deep
Channel portion of the water column from the remaining water column during the late spring
through fall seasons. This occurs due to temperature and salinity barriers that do not allow
mixing of surface waters with deep channel waters. Second, maintenance dredging and propeller
wash from ship movements result in the periodic disturbance and/or removal of any biological
communities that may be established during the interval between dredging events.
Table 7: Baseline Conditions Scenario: Percent Nonattainment of Dissolved Oxygen
Criteria in the Baltimore Harbor
Designated
Use
%
Nonattainment
Migratory
Fish
Spawning
and Nursery
3%
Open Water
3%
Deep Water
23%
Deep
Channel
87%
October 1st to
January 31st
Open Water
2%
February 1st to
January 31st
Open Water
0%
Period
st
February 1
to May 31st
June 1st to
September 30th
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
23
REVISED FINAL
4.3.2.2 Chlorophyll a Assessment for the Baseline Conditions Scenario
The Chl a levels in the baseline conditions scenario output were analyzed using a 30-day rolling
average as referenced in Section 2.3. The analysis shows that in both surface and bottom water,
Chl a concentrations exceeded 50 g/l during early spring and the summer months of 1995 (see
Figure 12) and occasionally were observed to exceed 100 g/l. Chl a rarely exceeded 50 g/l
during 1996 and 1997.
4.3.3 Maximum Anthropogenic Reduction from Baltimore Harbor Scenario
Based on the exceedances of the water quality criteria associated with the baseline scenario,
particularly in the Deep Channel Designated Use, MDE conducted a scenario run to determine
whether the act of removing anthropogenic nutrient sources, both point and nonpoint, would
result in the attainment of water quality standards within the Deep Channel Designated Use
region of the Baltimore Harbor. This scenario provides an estimate of the water quality response
if the maximum amount of anthropogenic nutrient loading reductions were made in the Baltimore
Harbor watershed. To conduct this analysis, the water quality model was run with nutrient loads
from point and nonpoint sources reduced to zero. The sediment model was allowed to continue
running from the initial condition set by the calibration, and the upper Bay loading conditions
were based on the calibration period. With all sources of nutrients removed the model was
allowed to run for six years to determine the impact on water quality.
4.3.4 Maximum Anthropogenic Reduction Scenario Results
Modeled results for the maximum anthropogenic reduction scenario of DO levels in the surface
and bottom waters at station WT5.1 are summarized in Figure 13. Under this scenario, the
attainment assessment results indicate that DO concentration will be < 1.0 mg/l in the Deep
Channel for approximately 57.8% of the time and volume that Deep Channel criteria are in effect.
Therefore, the Deep Channel criteria are not achieved in this scenario.
The results of this model scenario predict that with the removal of anthropogenic point and
nonpoint sources of nutrients, the Baltimore Harbor will not fully meet the Deep Channel
Designated Use water quality standard although all other standards will be met. The constant
manipulation and sequential deepening of the channel over time has created a system in which the
water in the Harbor channel is effectively sealed off from mixing action during the summer
months due to the hydrodynamic circulation pattern. As a result, oxygen is not transferred from
the upper portions of the water column into the Baltimore Harbor channel. Consequently, the
oxygen that is present in the channel during the winter and spring seasons is being consumed but
not replaced during the summer months. The maximum anthropogenic reduction from Baltimore
Harbor scenario indicates that the hydrodynamics of the Harbor system create conditions whereby
the Harbor channel becomes anoxic for periods during the summer.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
24
REVISED FINAL
Figure 13: Maximum Anthropogenic Reduction Scenario model results for DO levels in
surface and bottom waters in Baltimore Harbor at Station WT5.1
4.3.5 Future Conditions (TMDL) Scenario
This scenario provides an estimate of future conditions in the Baltimore Harbor system based on a
simulation with 1) WWTP discharges set at design flow and nitrogen and phosphorus
concentrations based on Maryland’s Enhanced Nutrient Reduction (ENR) strategy, 2) industrial
discharges based on permitted flow and concentrations of nitrogen and phosphorus reduced based
on estimates of loading reductions due to technological improvements, and 3) urban stormwater
and agricultural loads for all subwatersheds draining into the Baltimore Harbor reduced by 15%.
Based on the results of the Maximum Anthropogenic Reduction Scenario, which indicated the
Deep Channel Designated Use would not achieve water quality standards at all times with the
removal of all anthropogenic nutrient sources, MDE developed this scenario to represent the
current limit of technology for municipal WWTPs, and an aggressive nutrient reduction goal for
industrial point sources and nonpoint sources. This scenario was used to estimate both growing
season and average annual flow TMDLs.
The point source loads from the Patapsco and Cox Creek WWTPs were based on National
Pollutant Discharge Elimination System (NPDES) permit flows and ENR-based concentrations of
TN equal to 4 mg/l annual average (3 mg/l in May–October and 5 mg/l in November–April) and
TP of 0.3 mg/l. These levels are consistent with Maryland’s Tributary Strategy and ENR Policy.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
25
REVISED FINAL
Industrial point source flows and concentrations vary for the different facilities, and their effluent
loadings were based on recent performance levels, after having already achieved significant
loading reductions since the initial baselines established in 1985. Their recent performance levels
were then adjusted based on additional potential loading reductions.
Urban stormwater and agricultural TN and TP loads for this scenario were reduced by 15% from
their baseline loads in order to reach the water quality goals for Chesapeake Bay waters. The
baseline urban stormwater and agricultural loads are estimated by the HSPF watershed model as
described in “Patapsco/Back River Watershed HSPF Model Report” (MDE, 2001). The loading
reductions are based on the implementation of urban and agricultural Best Management Practices
(BMPs) that are used to reduce pollution from these land uses. The load reduction was quantified
based on nutrient removal efficiency ratings that have been developed for various BMPs. This
approach is based on the assumptions made by the CBP in its Chesapeake Bay watershed
modeling effort and is consistent with the method used to develop Maryland’s Tributary
Strategies.
The Harbor watershed land uses are comprised of approximately 55% urban, 15% agricultural,
and 29% forest. An assessment of the urban and agricultural land use components indicate that
the baseline load for urban land use is approximately 43% of the average annual TN load, 75% of
the average annual TP load, 49% of the growing season TN load, and 78% of the growing season
TP load from watershed land uses. Similarly, the baseline load for agricultural landuse is
approximately 33% of the average annual TN load, 12% of the average annual TP load, 24% of
the growing season TN load, and 11% of the growing season TP load from watershed land uses.
Other non-urban stormwater and non-agricultural nutrient loads, including forest loads, represent
the remaining contribution to the total load.
4.3.6 Future Conditions (TMDL) Scenario Results
DO and Chl a time series results for water quality station WT5.1 for surface and bottom waters
for the TMDL scenario are summarized in Figures 14 and 15. As displayed in Figure 14, under
the TMDL scenario, the minimum DO concentrations at water quality station WT5.1 are above
6.5 mg/l in the surface water. However, the bottom water DO decreases to below 1 mg/l and
approaches 0 mg/l during the summer months. It can be observed that the anoxic condition starts
later and ends earlier than in the baseline scenario. As displayed in Figure 15, under the TMDL
scenario, Chl a concentrations at Water Quality Station WT5.1 remain below 50 g/l in both the
surface and bottom waters. Additional time series and longitudinal data profiles from the MDE
and CBP stations for various nutrient parameters are available upon request and through the MDE
TMDL website as supporting documentation. The time series data files are too large to
incorporate as appendices to this report.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
26
REVISED FINAL
1995
1996
1997
TMDL Scenario results: Minimum and Maximum DO
TMDL Scenario results: Weekly Average DO
Figure 14: Time Series of Model Results for the TMDL Scenario for DO at Station WT5.1
1995
1996
1997
TMDL Scenario results: Moving 30-day Average Chlorophyll a
Figure 15: Time Series of Model Results for the TMDL Scenario for Chl a at Station WT5.1
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
27
REVISED FINAL
4.3.6.1 Dissolved Oxygen Criteria Attainment Assessment of the Future
Conditions (TMDL) Scenario
The DO attainment assessment of the TMDL scenario in the Baltimore Harbor was performed as
explained in the baseline conditions scenario assessment (Section 4.3.2.1). The attainment and
reference curve assessments generated for the Migratory Fish Spawning and Nursery, Open
Water, and Deep Water Designated Uses are provided in Appendix B. The following is a
summary of the attainment assessment analysis.
The TMDL scenario assessment of the DO criteria attainment for the Migratory Fish Spawning
and Nursery Designated Use, which applies from February 1st to May 31st indicates that the
attainment curve is always below the reference curve and that the designated use is met 100% of
the time (See Appendix B, Figure B1). The assessment of the DO criteria attainment for the Open
Water Designated Use, which applies from June 1st to September 30th and from October 1st to
January 31st, indicates that there is a period of nonattainment; however, this period is not
significant enough in time or volume affected to cause an exceedance of the criteria, therefore the
designated use is being met (See Appendix B, Figures B2 and B3). The assessment of the DO
criteria attainment for the Deep Water Designated Use, which applies from June 1st to September
30th, indicates that there is a period of nonattainment in time and volume that represents a 7%
exceedance of the criteria (See Appendix B, Figure B4). The Deep Water DO criteria allows a
restoration variance of up to 7% applied spatially and/or temporally from June 1 to September 30
(COMAR 26.08.02.03-3 C(8)(e)(vi)); therefore, the assessment of the DO criteria indicates that
the designated use is attained. During the remaining months of the year, these areas are
designated as Open Water and the criteria are met.
MDE conducted an analysis of the TMDL scenario to determine the percentage of time when the
modeled DO concentration in the Deep Channel was below the 1.0 mg/l instantaneous minimum
concentration required by the criteria. The assessment consisted of an evaluation of the modeled
TMDL scenario DO concentrations versus the instantaneous minimum concentration. The result
of this assessment indicates that the Deep Channel exceeded the criteria 78.5% of the time and
volume.
During the October 1st to May 31st period the Deep Water and Deep Channel Designated Use
areas are considered Open Water Designated Use. Results of the attainment assessment utilizing
the reference curve approach indicate that the criteria are achieved. Table 8 presents a summary
of the Baltimore Harbor DO attainment assessment for the TMDL Scenario.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
28
REVISED FINAL
Table 8: TMDL Scenario: Percent Nonattainment of Dissolved Oxygen Criteria in the
Baltimore Harbor
Period
st
February 1
to May 31st
June 1st to
September 30th
October 1st to
January 31st
Designated
Use
%
Nonattainment
Migratory
Fish
Spawning
and Nursery
0%
Open Water
0%
Deep Water*
7%
Deep
Channel
78.5%
Open Water
0%
*The Deep Water designated use DO criterion allows a restoration variance of up to 7% applied spatially and/or
temporally from June 1 to September 30.
4.3.6.2 Chlorophyll a Criteria Attainment Assessment of the Future
Conditions (TMDL) Scenario
Under the TMDL scenario, Chl a concentrations at Water Quality Station WT5.1 remain below
50 g/l in both the surface and bottom waters, indicating attainment of the narrative criteria for
Chl a (see Figure 15 above).
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
29
REVISED FINAL
4.4 TMDL Loading Caps
The TMDLs for nitrogen and phosphorus are presented below. The detailed calculation of TMDL
loading allocations can be found in Appendix C.
For the period of May 1 through October 31, the following TMDLs apply:
Growing Season TMDLs:
NITROGEN TMDL
2,145,750 lbs/growing season
PHOSPHORUS TMDL
149,152 lbs/growing season
The average annual TMDLs for nitrogen and phosphorus are:
Average Annual TMDLs:
NITROGEN TMDL
5,323,963 lbs/year
PHOSPHORUS TMDL
324,309 lbs/year
4.5 Load Allocations Between Point Sources and Nonpoint Sources
This section describes one viable allocation of loads between point sources, nonpoint sources, and
the margin of safety for the nitrogen and phosphorus TMDLs. A more detailed overview of
potential allocations to various sources is provided in the accompanying point and nonpoint
Technical Memorandums. The allocations presented are quantified for growing season (May 1st
through October 31st) and average annual conditions. The State reserves the rights to revise these
allocations provided the allocations are consistent with the achievement of water quality
standards.
4.5.1 Growing Season TMDL Allocations
Load Allocations (LA)

Nonpoint Source Loads
The nonpoint source loads represent the loads from agricultural land, forest and other
herbaceous land, and septic systems. The nitrogen and phosphorus loading reductions
simulated in the TMDL scenario represent a 15% reduction from the baseline agricultural
loads and an explicit margin of safety (MOS) that is approximately 5% of the reduced
agricultural loads for the growing season period. The other nonpoint source loads such as
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
30
REVISED FINAL
septic systems and forest loads were not reduced from baseline condition levels. See
Appendix C for LA calculations.
Waste Load Allocations (WLA)

Stormwater Loads
In November 2002, EPA advised States that Municipal Separate Storm Sewer System
(MS4) stormwater discharges must be addressed by the wasteload allocation (WLA) (See
40 C.F.R. § 130.2(h)). Therefore, MS4 communities regulated by NPDES permits will
have their loads reflected in the WLA. The urban stormwater loads of nitrogen and
phosphorus simulated in the Baltimore Harbor TMDL scenario are reduced 15% from the
baseline urban stormwater loads.
The TMDL, including loads from urban stormwater discharges, is now expressed as:
TMDL = WLA [NPDES point sources* + regulated stormwater point source] + LA + MOS + FA (if applicable)
*NPDES point sources include municipal and industrial wastewater treatment plants.
Phase I and Phase II MS4’s stormwater permits will be considered point sources subject to
WLA assignment in the TMDL. EPA recognizes that limitations in the available data and
information usually preclude stormwater allocations to specific outfalls. Therefore, EPA
guidance allows the urban stormwater WLA to be expressed as a gross allotment, rather
than individual allocations for separate pipes, ditches, construction sites, etc.
Estimating a load contribution to a particular waterbody from the stormwater is imprecise,
given the variability in sources, runoff volumes, and pollutant loads over time. Therefore,
the urban stormwater WLA is based on the best loadings estimate currently available. For
the Baltimore Harbor the current data allows the urban stormwater allocation to be defined
separately for Baltimore City, Baltimore County, Anne Arundel County, Carroll County,
and Howard County. However, it should be noted that these WLAs aggregate municipal
and industrial stormwater, including the loads from highways and construction activity.

Municipal and Industrial Wastewater Treatment Plants Loads1
During the 1995-1997 baseline conditions period, there were seven permitted point
sources discharging nutrients into the Baltimore Harbor. For the TMDLs scenario, all
seven point sources were given an allocation. In addition to the seven permitted point
sources considered in the baseline scenario, the Cox Creek Dredged Material Containment
Facility (DMCF) is included in the TMDL scenario and given an allocation. The Cox
Creek DMCF was not discharging during the 1992-1997 period, therefore was not
considered in the calibration of the model and the baseline scenario.
1 Subsequent to the approval of this TMDL by EPA in December 2007, changes were made to the
list of allocated facilities. No change was made to the overall WLA assigned to WWTPs. These
changes are described in detail in the revised point source technical memorandum.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
31
REVISED FINAL
The Patapsco and Cox Creek WWTPs maximum allowable current permit flows are used
for this scenario. Concentrations were adjusted to reflect Maryland’s ENR Strategy of
maximum total nitrogen concentrations of 3 mg/l from May 1st to October 31st. Total
phosphorus limits are 0.3 mg/l year round. Industrial point source flows and
concentrations vary from plant to plant, and are set at levels based on the implementation
of best available technologies to achieve water quality criteria in both local and
Chesapeake Bay waters. These allocations are also consistent with Maryland’s current
Tributary Strategy. All significant point sources are addressed by this allocation and are
described further in the technical memorandum entitled “Significant Nutrient Point
Sources in the Baltimore Harbor Watershed”. The nitrogen and phosphorus allocations
for growing season conditions are presented in Table 9. See Appendix C for WLA
calculations.
Nonpoint Source1
Point Source2
FA
MOS3
Total
1.
2.
3.
Table 9: Growing Season Allocations
Total Nitrogen
Total Phosphorus
(lbs/growing season)
(lbs/growing season)
459,912
12,776
1,642,014
113,212
33,204
22,848
10,620
316
2,145,750
149,152
Does not include regulated urban stormwater loads.
Includes regulated urban stormwater loads.
Approximately 5% of the reduced agricultural loads.
4.5.2 Average Annual TMDL Allocations
Load Allocations (LA)

Nonpoint Source Loads
The average annual nonpoint source loads represent the average loads from agricultural
land, forest and other herbaceous land, and septic systems. The nitrogen and phosphorus
loadings simulated in the TMDL scenario represent a 15% reduction from the baseline
agricultural loads and an explicit MOS that is approximately 5% of the reduced
agricultural loads. Other nonpoint source loads such as septic systems and forest and
other herbaceous loads were not reduced from baseline condition levels. See Appendix C
for LA calculations.
Waste Load Allocations (WLA)

Urban Stormwater Loads
For the average annual TMDL, the urban stormwater loads of nitrogen and phosphorus
simulated in the TMDLs scenario represent a 15% reduction in TN and TP from average
annual baseline urban stormwater loads.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
32
REVISED FINAL

Municipal and Industrial Wastewater Treatment Plants Loads2
The Patapsco and Cox Creek WWTPs maximum allowable current permit flows are used.
The TN concentration was set to a maximum of 3 mg/l from May 1st to October 31st and 5
mg/l from November 1st to April 30th. The TP concentrations for the two plants were set
at 0.3 mg/l year-round. Industrial point source flows and concentrations vary from plant
to plant, and they are set at levels based on the implementation of best available
technologies to achieve water quality criteria in both local and Chesapeake Bay waters.
These allocations are also consistent with Maryland’s current Tributary Strategy. All
significant point sources are addressed by this allocation and are described further in the
technical memorandum entitled “Significant Nutrient Point Sources in the Baltimore
Harbor Watershed”. The nonpoint and point source nitrogen and phosphorus allocations
for average annual load conditions are shown in Table 10. See Appendix C for WLA
calculations.
Table 10: Average Annual Allocations
Total Nitrogen (lbs/yr) Total Phosphorus (lbs/yr)
Nonpoint Source1
1,246,036
34,654
2
Point Source
3,976,215
243,127
FA
66,410
45,690
3
MOS
35,302
838
Total
5,323,963
324,309
1. Does not include regulated urban stormwater loads.
2. Includes regulated urban stormwater loads.
3. Approximately 5% of the reduced agricultural loads.
4.6 Margin of Safety (MOS) and Future Allocation (FA)
A MOS is required as part of a TMDL in recognition of many uncertainties in the understanding
and simulation of water quality in natural systems. For example, knowledge is incomplete
regarding the magnitude of pollutant loads from various sources due to normal variations in
precipitation and process changes, and the specific impacts of those pollutants on the chemical
and biological quality of complex, natural waterbodies. The MOS is intended to account for such
uncertainties in a manner that is conservative from the standpoint of environmental protection.
Based on EPA guidance, the MOS can be achieved through two approaches (EPA, April 1991).
One approach is to explicitly reserve a portion of the loading capacity as a separate term in the
TMDL (i.e., TMDL = LA + WLA + MOS). The second approach is to incorporate the MOS as
conservative assumptions used in the TMDL analysis (implicit MOS). Maryland has adopted a
MOS for these TMDLs using the first approach. For both the growing season and the average
annual flow TMDLs, the load allocated to the MOS is approximately 5% of the reduced
2 Subsequent to the approval of this TMDL by EPA in December 2007, changes were made to the
list of allocated facilities. No change was made to the overall WLA assigned to WWTPs. These
changes are described in detail in the revised point source technical memorandum.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
33
REVISED FINAL
agricultural loads for nitrogen and phosphorus. The MOS is not considered a part of the reduced
agricultural loads; it is a separate term in the TMDL equation. That is, the sum of the MOS and
the reduced agricultural loads is equal to the load reduction that was used in the model run to
determine the TMDL. These explicit nitrogen and phosphorus margins of safety are presented in
Tables 9 and 10. See Appendix C for MOS calculations.
Future Allocation represents an allowance for future growth, which accounts for reasonably
foreseeable increases in pollutant loads (40 CFR 130.33(b)(9)). Future growth can be included in
the TMDL by reserving a separate allocation for this purpose or by allocating acceptable
wasteloads and loads in a way that incorporates potential growth. In the Baltimore Harbor
nutrients TMDL analysis, the first approach is used for the nitrogen and phosphorus TMDLs to
address the contingency that a seasonal nitrogen limit based on 3 mg/l of nitrogen and a limit of
0.3 mg/l of phosphorus may not be practical for ENR technology at some facilities.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
34
REVISED FINAL
4.7 Summary of Total Maximum Daily Loads
The Growing Season TMDLs, applicable from May 1- October 31, for the Baltimore Harbor:
For Nitrogen:
TMDL
(lbs/growing
season)
2,145,750
=
LA
+
WLA
+
FA
+
MOS
=
459,912
+
1,642,014
+
33,204
+
10,620
=
LA
+
WLA
+
FA
+
MOS
=
12,776
+
113,212
+
22,848
+
316
For Phosphorus:
TMDL
(lbs/growing
season)
149,152
The average annual flow TMDLs for the Baltimore Harbor:
For Nitrogen:
TMDL
(lbs/year)
5,323,963
=
LA
+
WLA
+
FA
+
MOS
=
1,246,036
+
3,976,215
+
66,410
+
35,302
For Phosphorus:
TMDL
(lbs/year)
324,309
=
LA
+
WLA
+
FA
+
MOS
=
34,654
+
243,127
+
45,690
+
838
Where:
TMDL = Total Maximum Daily Load
LA
= Load Allocation (Nonpoint Source)
WLA = Waste Load Allocation (Point Source)
MOS = Margin of Safety
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
35
REVISED FINAL
Average Daily Loads:
The growing season TMDLs will result in average daily loads of approximately 11,662 lbs/day of
nitrogen and 817 lbs/day of phosphorus. Similarly, the average annual flow TMDLs will result in
average daily loads of approximately 14,586 lbs/day of nitrogen and 889 lbs/day of phosphorus.
Since nutrients do not result in acute impacts and the impacts of a given amount of nutrients vary
seasonally, these average daily loads are provided for informational purposes, since daily loads
will not be a factor controlling the ability to meet the water quality standards.
5.0
ASSURANCE OF IMPLEMENTATION
Section 303(d) of the Clean Water Act and current EPA regulations require reasonable assurance
that the TMDL load and wasteload allocations can and will be implemented in order to achieve
water quality standards. In the Baltimore Harbor, both the TMDL and maximum anthropogenic
reduction analyses indicate that reductions of the nutrients nitrogen and phosphorus from all
sources, including the elimination of all point and nonpoint sources, do not result in the water
quality standards being met in all waters of the Harbor at all times. Under the TMDL scenario the
Deep Channel Designated Use region violates the water quality standard 78.5% of time and
volume. Under the maximum anthropogenic reduction scenario, the Deep Channel Designated
Use region violates the water quality standard 57.8% of time and volume. Under both of these
scenarios, however, the water quality standards are achieved for all other designated uses that are
applicable in the Harbor.
The implementation of point source nutrient controls that will be an integral component to meet
water quality standards in the Harbor will be executed through the State’s Enhanced Nutrient
Reduction (ENR) strategy and NPDES permits. The ENR program provides grant funds to local
governments to retrofit or upgrade WWTPs from BNR to ENR at their currently approved design
capacity. Enhanced nutrient removal technologies allow sewage treatment plants to provide a
highly advanced level of nutrient removal. The ENR strategy builds on the success of the
biological nutrient removal (BNR) program already in place. Currently, the Patapsco WWTP is
designing its new ENR facility, Cox Creek WWTP is planning its new ENR facility, and the Back
River WWTP (supplier of processing water to ISG) is planning its new ENR facility. The
completion of the planning, design, and construction of these facilities will lead to significant
reductions in nutrients discharged into Baltimore Harbor. Upon completion of the ENR upgrades,
subsequent NPDES permits for the municipal WWTPs will include nutrient loading limits that
will be based upon achieving ENR levels of treatment. The significant industrial NPDES (>0.5
mgd) point sources will also have nutrient limits incorporated into subsequent permits that are
reissued following the completion of the TMDL. The reissued NPDES permits will attempt to
maintain consistency with the assumptions made in the TMDLs (e.g., flow, nutrients effluent
concentrations, DO, etc.). Deadlines for completion of ENR upgrades will be incorporated into
NPDES permits based on the State’s ENR upgrades schedule and, if the permitting timeframe is
shorter than the ENR schedule, permits will reflect what can reasonably be accomplished with
consideration to the complexity of the engineering and the availability of resources.
The implementation of nonpoint source nutrient controls that will be an integral component to
achieve water quality standards in the Harbor will be executed through two approaches,
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
36
REVISED FINAL
stormwater NPDES permits and cooperative agricultural reductions. In November 1990, EPA
required jurisdictions with a population greater than 100,000 to apply for NPDES Permits for
stormwater discharges. The five jurisdictions where the Baltimore Harbor watershed is located,
Baltimore City, Baltimore County, Anne Arundel County, Carroll County and Howard County,
are required to participate in the stormwater NPDES program, and must comply with the NPDES
Permit regulations for stormwater discharges. Subsequently, stormwater management programs
have been implemented by the Counties and the City to control MS4 discharges to the maximum
extent practicable. For example, Baltimore County stormwater management program
encompasses numerous elements including: erosion and sediment control, post-construction
runoff management, controlling pollutants associated with road maintenance activities, public
education and outreach, and illicit discharge detection and elimination. Additionally, in targeted
watersheds, Baltimore County is required to implement watershed restoration for 10% of the
County’s total impervious surface cover. Baltimore City is required to implement those watershed
restoration activities described above for addressing 20% of the City’s impervious surfaces. In
order to meet this goal, annually, the City will have at least two restoration projects in study, two
in design, and two under construction. A brief description of each project, phase, and cost can be
found in the City’s NPDES stormwater annual report. Details of the County and City programs
elements are available through MDE's Water Management Administration – NPDES Stormwater
Program.
Additional significant planned implementation measures in the Baltimore Harbor watershed
involve the upgrade or separation of combined sewer systems in the City and the upgrade of
sanitary sewer systems in Baltimore County. In 2002, Baltimore City, MDE, and U.S.
Environmental Protection Agency (EPA) entered into a civil consent decree to address SSOs and
combined sewer overflows (CSOs)3 within its jurisdictional boundaries. See U.S., et al., v. Mayor
and City Council of Baltimore, JFM-02-12524, Consent Decree (entered Sept. 30, 2002).
Similarly, in 2005, Baltimore County, MDE and EPA entered into a civil consent decree to
address SSOs in the County. See U.S., et al. v. Baltimore County, AMD-05-2028, Consent
Decree (entered Sept. 20, 2006). The consent decrees require the City and the County to adopt
and implement a long term control plan (“LTCP”) to evaluate their sanitary sewer systems and to
repair, replace, or rehabilitate the system as indicated by the results of those evaluations, with all
work to be completed by January 2016 for Baltimore City and by March 2020 for Baltimore
County.
Maryland’s Water Quality Improvement Act requires that comprehensive and enforceable nutrient
management plans be developed, approved and implemented for all agricultural lands throughout
Maryland. This act specifically requires that nutrient management plans for nitrogen be
developed and implemented by 2002, and plans for phosphorus be completed by 2005. It is
reasonable to expect that nonpoint loads can be reduced during growing season conditions. The
nutrient load sources during growing season include dissolved forms of the impairing substances
from groundwater, the effects of agricultural ditching and animals in the stream, and deposition of
3
A “combined sewer system” is a sewer system in which stormwater and sanitary sewerage are conveyed through a
common set of pipes for treatment at a wastewater treatment plant. A CSO is an overflow from such a combined
system. Baltimore City agreed in the Consent Decree to separate the sanitary and stormwater lines in the small area
served by a combined system and has completed that separation.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
37
REVISED FINAL
nutrients and organic matter to the streambed from higher flow events. When these sources are
controlled in combination, it is reasonable to achieve agricultural nonpoint reductions of the
magnitude identified by this TMDL allocation.
Additionally, Howard County is developing a Watershed Restoration Action Strategy for its
portion of the Lower North Branch of the Patapsco River (approximately 38 of 118 square miles).
The county will utilize this strategy to identify and prioritize watershed restoration efforts, which
will include the reduction of nutrient loads from the watershed.
The legislative and policy-derived programs described above will result in significant nutrient
reductions and the achievement of water quality standards for all designated uses in the Baltimore
Harbor except the Deep Channel. Based on information generated in the TMDL analysis, MDE is
unable to ensure that the Deep Channel Designated Use water quality criterion can be met at all
times that it is applicable. The regions to which the Deep Channel designated use applies
represent approximately 10% of the area of the Harbor. The region subject to potential nonattainment of criteria represents < 5% of the area of the Harbor. The volume of water that does
not meet the dissolved oxygen criteria represents approximately 3% of the total volume of the
Harbor.
MDE is unable to assure attainment of the Deep Channel Designated Use due to the effects of 170
years of dredging that has incrementally deepened and expanded the size of the Harbors’
navigation channels and their associated turning basins and anchorages. As a result, the Harbor
has been hydrologically modified. In a portion of the main navigation channel, from the mouth of
the Harbor to Fort McHenry, it has been observed that water from the upper portion of the water
column does not mix with the lower portion of the water column. This observed stratification of
the water column, and the lack of mixing associated with it, occurs every spring/summer/fall. As
a result, there are limited regions within the navigation channel (Deep Channel Designated Use)
that do not meet the dissolved oxygen criteria during the observed spring/summer/fall
stratification period.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
38
REVISED FINAL
REFERENCES
Boicourt, W.C. and P. Olson. A hydrodynamic study of the Baltimore Harbor system. Tech. Rep.
82-10. Chesapeake Bay Institute, The Johns Hopkins University, MD. 1982.
Boesch, Donald F., Brinsfield, Russell B., Magnien, Robert E.. Chesapeake Bay Eutrophication.
Article Symposium Paper. Journal of Environmental Quality 30:303-320. 2001.
Boynton, W. R., Burger, N. H., Stankelis, R. M., Rohland, F.M., Hagy III, J. .D., Frank, J. M.,
Matteson, L. L. and Weir, M. .M. An environmental evaluation of Baltimore Harbor with selected
data from Patapsco River. Prepared for Baltimore City Department of Public Works for Project
613, Comprehensive Wastewater Facilities Master Plan, University of Maryland Center for
Environmental Science, Chesapeake Biological Lab., MD. 1998.
Cerco, C.F. and T.M. Cole. Three-dimensional eutrophication model of Chesapeake Bay: Volume
1, main report. Technical Report EL-94-4, US Army Engineer Waterways Experiment Station,
Vicksburg, MS. 1994.
Cerco, C.F. and T.M. Cole. User's guide to the CE-QUAL-ICM three-dimensional eutrophication
model. Technical Report EL-95-15, US Army Engineer Waterways Experiment Station,
Vicksburg, MS. 1995.
Coastal Environmental Services. Patapsco/Baltimore Harbor Watershed Study: Ambient
Conditions, Pollutant Loads and Recommendation for Further Action. Prepared for Maryland
Department of the Environment, Coastal Environmental Services, Inc., Linthicum, MD. 1995.
Code of Federal Regulations. 40 CFR § 130.2 (h).
Code of Maryland Regulations, 26.08.02.03B(2), 26.08.02.03-3C(2)(8), 26.08.02.03-3C(8),
26.08.02.03-3C(8)(e)(vi), 26.08.02.03-3C(10), 26.08.02.08K(2)(b).
Conservation Technology Information Center (CTIC), 1996 National Crop Residue Management
Survey Data. W. Lafayette (IN): Conservation Tillage Information Center, 1996.
DiToro, D. M. and J.J. Fitzpatrick. Chesapeake Bay Sediment Flux Model. Contract Report EL93-2, US Army Engineer Waterways Experiment Station, Vicksburg, MS, 1993.
Johnson, B. H., Heath, R.E. and Bernard B. Hsieh. User’s Guide for a Three-Dimensional
Numerical Hydrodynamic, Salinity, and Temperature Model of Chesapeake Bay. Technical
Report HL-91-20, US Army Engineer Waterways Experiment Station, Vicksburg, MS. 1991.
Liu, Hui. The Development of a Water Quality Model in Baltimore Harbor, Back River, and the
Adjacent Upper Chesapeake Bay. Thesis Presented to the Faculty of the School of Marine
Science. The College of William and Mary. Virginia, 2002.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
39
REVISED FINAL
Magnien, R.E., Austina, D.K. and B.D. Michael. Chemical/Physical Properties Component. Level
1 Data Report (1984-1991). Maryland Department of Environment, Baltimore, MD. 1993.
Maryland Department of Environment, Patapsco/Back River Watershed Hydrological Simulation
Program Fortran (HSPF) Model Report. 2001.
Maryland Department of Planning. 1997 Reference for Land Use/Land Cover.
Pritchard, D.W., and J.H. Carpenter. Measurements of Turbulent Diffusion in Estuarine and
Inshore Waters. Bull. Inter. Assoc. Sc. Hydrol. 20, 37 pp. 1960.
Robertson, P.G. Back River - An Assessment of Water Quality and Related Fish Mortalities.
Maryland Department of Natural Resources, Water Resources Administration, Water Quality
Service, Annapolis, MD. 133 pp. 1977.
Thomann, Robert V., John A. Mueller. “Principles of Surface Water Quality Modeling and
Control.” HarperCollins Publisher Inc., New York, 1987.
USDA. Maryland Counties Common Land Units Database. Columbia (MD): Maryland State
Farm Service Agency Office, 1996.
USDA. 1997 Census of Agriculture: Maryland State and County Data. Vol. 1, Geographic Area
Series Part 20. Washington DC: National Agricultural Statistical Service, Issued March 1999.
U.S. EPA. “Ambient Water Quality Criteria for the Dissolved Oxygen, Water Clarity and
Chlorophyll a for the Chesapeake Bay and its Tidal Tributaries”. EPA Region III, Chesapeake
Bay Program Office. April 2003.
U.S. EPA Chesapeake Bay Program. “Chesapeake Bay Program: Watershed Model Application
to Calculate Bay Nutrient Loadings: Final Findings and Recommendations,” 1996.
U.S. EPA. “Protocol for Developing Nutrient TMDLs”. EPA 841-B-99-007. Office of Water
(4503F), United States Environmental Protection Agency, Washington D.C. 135 pp. 1999.
U.S. EPA, "Guidance for water quality based decisions: The TMDL process," Office of Water,
Washington D.C., 1991.
U.S. EPA and Maryland Department of the Environment v. Mayor and City Council of Baltimore,
Consolidated Case Number: JFM-02-12524, Consent Decree (entered Sept. 30, 2002).
U.S. EPA and Maryland Department of the Environment v. Baltimore County, Consolidated Case
Number: AMD-05-2028, Consent Decree (entered Sept. 20, 2006).
U. S. EPA. Memorandum. Subject: “Establishing Total Maximum Daily Load (TMDL)
Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements
Based on Those WLAs. Office of Water. Washington, D.C. November, 2002.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
40
REVISED FINAL
U.S. EPA, “Technical Guidance Manual for Developing Total Maximum Daily Loads, Book 2:
Streams and Rivers, Part 1: Biochemical Oxygen Demand/ Dissolved Oxygen and Nutrients/
Eutrophication,” Office of Water, Washington D.C. March 1997.
Wang, Harry V., Liu, Hui, Park, Kyeong Park. “The Development of a Water Quality Model for
Baltimore Harbor, Back River and the Adjacent Upper Chesapeake Bay.” Special Report No. 386
in Applied Science and Ocean Engineering. Virginia Institute of Marine Science. School of
Marine Science. College of William and Mary. Gloucester Point, VA. May, 2004.
Baltimore Harbor Nutrient TMDL
Document version: August 31, 2015
41
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising