Permavoid System Technical Manual

Permavoid System Technical Manual
PMVTM1
JANUARY 2016
Permavoid System Technical Manual
Planning, design, specification and installation guide
Welcome to Polypipe
At Polypipe, conceiving, designing, manufacturing and delivering the most advanced products and
systems is more than just an occupation. We see it as our passion. Everything we do has always been
based around a few simple beliefs: Quality always beats quantity. Products are nothing without service
and support. Sustainability isn’t just a ‘green’ word and working with our customers is much better than
simply supplying them.
Polypipe is the UK’s largest plastic piping
systems manufacturer
With over 20,000 product lines, a substantial fleet of over
400 vehicles and employing over 2,000 people, we have an
enviable reputation amongst installers, contractors, stockists
and specifiers.
The broadest product range available in the UK
With over 100 product systems, our unrivalled
portfolio offers dependable, innovative solutions for pressure
and non-pressure applications, enabling the movement of
water, air, power, chemicals and telecoms throughout the
built environment.
Market-sector focused
We operate through sector-focused businesses, ensuring
that our Sales and Technical Teams are equipped to meet
the specific needs of residential, civils and infrastructure,
commercial and industrial projects.
Innovating for today’s construction challenges
Recognising the twin challenges of managing water and
carbon resources, we have invested for many years in
our water management and carbon efficient solutions,
with systems that meet all legislative requirements.
Polypipe intelligent engineering
Through initial involvement our substantial technical
knowledge and capabilities can be utilised, ensuring our
customers can engage with the project team to deliver the
most appropriate and cost-effective solutions and supporting
them in a close working relationship from design right
through to installation.
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Permavoid Technical Manual
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3
Overview - our company, our products, our people
Intelligent engineering
Our product knowledge and service teams provide an unrivalled level of technical support.
Working closely with our customers, we can help guide them through current legislation and
complex building regulations. This helps us to match the right product range with the correct
project requirements, or develop a fully engineered system for specific project needs.
The market leaders in surface water management
We invest heavily in research and new production technology that
allows us to provide high quality products with more precise
performance specifications and even greater reliability. Our
products are covered by third party accreditations including BBA,
BSI Kitemark and WRc, which ensure we meet specification
standards. Supporting our product accreditations, our business
systems are regularly assessed by BSI to ensure we maintain our
BS EN ISO 9001:2008 and BS EN ISO 14001:2004 certifications.
These independent assessments confirm that we adhere to strict
regulatory requirements and ensure we provide greener
credentials for our products.
UKAS accredited laboratories
Our in-house research and development facility is one of the
most advanced of its kind and includes the independent UKAS
accredited Berry & Hayward Laboratory. This operates 24 hours a
day and gives us the body of knowledge and expertise needed to
produce the most advanced range of products and solutions.
Design
Our team of fully qualified drainage specialists, civil engineers and technical support experts offer invaluable
experience and knowledge through each and every stage of a project. We provide the most commercially viable
solution for a project through our ability to be unbiased. As we offer both pipe and geocellular systems, we have
a truly holistic range of products meaning we can tailor our solutions to your needs. You can contact our team on
+44 (0) 1509 615100 or arrange a visit from one of our commercial or technical specialists.
From the outset, our Design Team will bring
their technical expertise and experience
to bear, providing assistance with hydraulic,
structural and flotation calculations supported
by system CAD designs and specifications.
Installation guidance
Providing guidance at the critical installation
stage, coordinating deliveries and ensuring
the most cost and time efficient pathways
to completion.
The calibre of our people
The calibre of the people within our support
team is a reflection of the importance we place
on customer service in helping to deliver a
successful project outcome. They include fully
qualified design engineers who, through their
experience and in-depth product knowledge, can
help to provide detailed specification guidance.
Our accreditations
Polypipe is a member of influential bodies
such as the British Plastics Federation (BPF)
and Construction Products Association (CPA).
We also work with organisations such as
DEFRA, CIRIA and Constructing Excellence,
which enable us to have an active involvement
and understanding of industry drivers.
Combining this industry involvement with
the high calibre of our staff enables us to
provide an unrivalled level of service.
Full technical design and
fabrication service
Polypipe is unique in having its own in-house fabrication
unit. In the 2600m2 facility, our skilled and highly experienced
technicians deliver modular engineered drainage and water
management systems. These are provided ready-to-install,
maximising the benefits of pre-fabrication, for ease of
delivery and reduced installation time on-site.
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5
Water management solutions
Our water management solutions embrace a comprehensive range of
sustainable drainage systems (SuDS) and services that together address the
surface water management requirements of every commercial and
domestic project, regardless of the project size.
With a choice of market leading products, plus the highest level of technical support, you can depend on Polypipe
to help you deliver the most effective and compliant surface water management plan.
Whether your scheme is adoptable or non-adoptable, we have the right solution for you; retention, attenuation
or infiltration systems combined with or without treatment solutions, all supported by our fabrication service that
provides off-site engineered solutions.
Stormwater retention,
attenuation and infiltration
Large diameter pipes and geocellular systems offer
a versatile method of creating shallow or deep
buried water storage systems, capable of holding
back the impacts of rainfall events and helping to
mitigate the risk of surface water flooding.
At Polypipe we understand that every project and
site is unique and many have significant challenges
when it comes to the design and construction of an
efficient and effective drainage system. That is why
we have developed the industry’s largest range of
pipe and geocellular retention, attenuation and
infiltration systems.
What is the Permavoid system?
Polystorm
Ridgistorm-XL
Permavoid
Rainstream RXL
Permavoid is a geocellular sub-base replacement system,
designed to provide shallow stormwater retention,
attenuation or infiltration. Permavoid can be used as
part of an engineered or soft SuDS solution. It enables
designers to offer a source control system incorporating
water treatment to manage water where it lands.
Our Permavoid system has been extensively tested over
the last decade with Salford and Coventry University, the
Transport Research Laboratory and Highways England, to
ensure that the system meets the legislative requirements
set out by CIRIA, the Environment Agency, SEPA and PPG.
Academic site wide trials include:
Surface water treatment
Regulations on the management of surface water through
source control and the use of SuDS are now well established.
Increasingly, legislation is presenting developers and
designers with additional challenges in the control of
surface water pollution. New standards aimed at reducing
pollution levels in groundwater and rivers are often based
on the Polluter Pays Principle (PPP), so our range of water
treatment systems are designed to intercept and extract
pollution as close to source as possible.
At Polypipe you will find the largest range of treatment
solutions for silt removal, collection and separation. From our
silt traps and oil interception, to advanced treatment textiles
such as Permafilter Geotextile for the removal of heavy metals
and RIDGISTORM-X4 for dissolved pollutants. They can all be
integrated within an overall ‘Roof to River’ solution and can be
combined to form progressively more efficient treatment
depending on anticipated contamination levels.
6
Permavoid Technical Manual
• Transport Research Laboratory - A pilot-scale trial of reservoir pavements for drainage attenuation incorporating
Permavoid sub-base replacement system.
Permafilter
Permachannel
•Coventry University - Assessment and monitoring of
the oil retention and performance of the Permaceptor Treatment System.
• SEPA-Perth Prison - A 2 year field monitoring exercise
of macro-pervious pavement and car park installation incorporating Permachannel oil and silt retention devices.
RIDGISTORMSeparate
RIDGISTORM-X4
Permavoid Technical Manual
7
Index - pages
Index - illustrations & tables
How this manual is organised
Description
This manual is presented in clearly marked sections to help you find the information you require
quickly and easily.
Section 2 - Permavoid system overview and applications
Section 1 – Legislation and regulations
Section 6 – Surface water treatment
Section 2 – Permavoid system overview and applications
Section 8 – Standard details
Section 4 – Hydraulic design
Section 9 – Case studies
Section 5 – Structural design
Typical layout-rainwater downpipe
drainage into sub-base reservoir
Permaceptor performance
15
Figure 3.1.1
37
www.polypipe.com/toolbox
Figure 6.1.1
51
Sub-base infiltration detail
Figure 8.1.1
59
Permavoid permeable pavement
sub-base attenuation detail
Figure 8.1.2
59
Permavoid with Permachannel shallow
cellular attenuation detail
Figure 8.2.1
60
Permavoid with Permachannel SuDSAGG
attenuation detail
Figure 8.2.2
60
Permavoid with Permachannel deep cellular
attenuation detail with Medium Duty Biomat
Figure 8.3.1
61
Pollution control - Permachannel
50
Permavoid with Permachannel
shallow cellular infiltration detail
Figure 8.3.2
61
Pollution control - Permaceptor
51
Permavoid with Permachannel SuDSAGG
infiltration detail
Figure 8.4.1
62
Process integration
13
Pollution control - Permavoid Biomat
52
Permavoid with Permachannel
deep cellular infiltration detail
Figure 8.4.2
62
Section 2 - Permavoid system overview and applications
Pollution control - Permafilter Geotextile
53
Permavoid with Gullyceptor detail
Figure 8.5.1
63
Geocellular solutions - for shallower depths
Section 7 - Delivery, installation & maintenance
Permavoid rainwater pipe connection detail
Figure 8.5.2
63
15 - 17
Permavoid applications
18
Permavoid in the urban environment
Passive capillary irrigation
19 - 20
21
Section 3 - Permavoid system components
22 - 23
Permavoid system - components
24 - 37
38
Section 4 - Hydraulic design
Hydraulic design - attenuation
Attenuation
Hydraulic design - infiltration
Infiltration
Geotextiles and Geomembranes
Installation
Maintenance
54
55 - 57
58
Section 8 - Standard details
General design details
Permavoid system
Suitable drainage systems - selector & design
Delivery and storage
within this publication are available
as downloadable CAD drawings from:
12
Permavoid - at a glance
www.polypipe.com/toolbox
*Please note: Illustrations shown
Legislation and regulations
14
For updates and a PDF of this
manual go to:
Section 8 - Standard details
Section 6 - Surface water treatment
10 - 11
Figure 2.1.1
Section 6 - Surface water treatment
Section 10 – Summary
Section 1 - Legislation and regulations
Page
Section 3 - Permavoid system components
Section 7 – Delivery, installation & maintenance
Section 3 – Permavoid system components
The growing importance of SuDS
Typical Permavoid system vs.
traditional aggregate sub-base
Illustrations*
59 - 65
Section 9 - Case studies
Case study - Longstanton Park and Ride
66
Case study - Coronation Street
67
Section 10 - Summary
39
40 - 41
42
43 - 44
Product summary
68
Associated products
69
Enabling sustainable building technology
70
Literature and website
71
45
Section 5 - Structual design
Structural design
8
Permavoid Technical Manual
46 - 49
Permavoid Technical Manual
9
SECTION
SECTION 1
1
Legislation and regulations
LEGISLATION AND
REGULATIONS
The growing importance of SuDS
‘Making Space for Water’ is an integrated, forward-thinking strategy
for managing future flood risk in England, first published in 2004.
Among its many recommendations is the adoption of a ‘joined-up’ approach to drainage management
in high-risk urban areas and the widespread use of sustainable drainage systems (SuDS) to control the rate
at which rainwater runs off paved areas and into sewer networks and rivers.
SECTION
2
Government planning policy has defined the need for sustainable drainage systems (SuDS)
to ensure that flood risk is taken into account during all stages of the planning process.
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
SECTION
3
CIRIA (SuDS Manual)
The SuDS Manual provides guidance on all aspects of the
design, construction, operation and maintenance of SuDS.
In particular, it places a real emphasis on the use of source
control techniques and requires designers to consider
pollution removal.
Urbanisation has led to an increasing number of negative
impacts on the environment, in particular pollution.
Depending on the land use, the following typical surface
pollutants can be found in surface water run-off:
• Hydrocarbons and oils
The SuDS Manual defines that a sustainable drainage
system should consider certain basic requirements,
including:
•Sediments
• Run-off from a developed area should be no
greater than the run-off prior to development
• Fertilisers and pesticides
• Run-off from a developed area should not result
in any down-grading of downstream watercourses
or habitat
• Animal wastes
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
• Heavy metals
•Salts
SECTION
5
STRUCTURAL
DESIGN
•Pathogens
• Consideration should be given at the development
feasibility stage to water resource management and
control in the developed area
• Run-off should replicate, as far as possible, the natural
response of the site to rainfall
Traditionally, pollutants are collected from impermeable
surfaces into the drainage systems and treated downstream
via large, deep, in-line separators that are typically designed
to treat the first 'flush' only. Emulsified oils and hydrocarbons
can still be discharged downstream, the discharge of oil and
hydrocarbons constitutes a major pollution source and is a
serious threat to groundwater sources.
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
The SuDS Management Train
This is a staged design concept used in sustainable drainage systems (SuDS) which controls volume and quality of surface water
run-off. Permavoid gives designers a versatile source control system.
SECTION
8
STANDARD
DETAILS
Run-off &
pollution
Management
& prevention
SECTION
Evapotranspiration
9
CASE STUDIES
Source Control
SECTION
Conveyancing
Site Control
The challenge each developer faces on both greenfield and brownfield developments is knowing what to do with the excess
run-off generated by the development which has to be retained in and around the site. BS8533:2011, 'Assessing and Managing
Flood Risk in Development Code of Practice', has been created to help designers analyse flood risk and to guide the selection
of appropriate flood risk management solutions.
Permavoid Technical Manual
SUMMARY
Regional Control
Soft SuDS alone may not provide sufficient storage on certain sites due to space constraints, particularly driven by the
housing density requirements in PPS3:Housing. The Permavoid system can help address these challenges, by providing an
effective controlled retention, attenuation or infiltration system to suit site specific requirements.
10
10
Conveyancing
Infiltration into ground or discharge to water course
Permavoid Technical Manual
11
SECTION
1
LEGISLATION AND
REGULATIONS
Legislation and regulations
Process integration
We understand how important it is to keep up to date with legislation.
That is why our advice and system selection is informed by the very
latest regulations and standards.
BS EN 752:2008
The Flood and Water Management Act (FWMA) 2010
requires the Lead Local Flood Authority (LLFA) to be
responsible for co-ordinating flood risk management within
its area. They have the responsibility for managing the risk
of flooding from surface water, groundwater and ordinary
watercourses and for developing, maintaining and applying
a strategy for local flood risk management. LLFAs are also
responsible for maintaining a register of significant flood
risk assets.
The Flood and Water Management Act (FWMA) came into
effect in 2010 with the aim to mitigate flood risk and
improve water management. As part of the Act, Schedule 3
requires new developments to implement sustainable
drainage systems (SuDS) on all new developments using
natural and proprietary features in place of conventional
drainage, to reduce surface water run-off, mitigate flood
risk and improve water quality.
Building Regulations
Building Regulations Approved Document H3 requires
rainwater to be either stored in a tank or discharged in
the following order:
1.Soakaway or other infiltration
2.Rivers and watercourses
3.Direct to sewers
Many developments are being built on land that is not suitable
for infiltration. Brownfield sites, sites with contaminated
ground, high water tables, poor percolation and with natural
aquifiers are all examples of this. Rivers and watercourses are
not always in close proximity/reasonable construction distance
from the site, resulting in a very large number of sites still
having to utilise mains sewer connections as their only viable
means of stormwater discharge.
It is a requirement under the FWMA that LLFAs develop
a local flood risk strategy focused on local issues. The
strategy should incorporate effective and robust surface
water drainage systems for new developments in
accordance with SuDS principles.
Permavoid Technical Manual
• Planners and drainage approval bodies: In setting
consistent drainage criteria and principles (for new
The diagram below demonstrates pertinent key links between the development planning process and the drainage
system design process, emphasising the involvement of stakeholders throughout.
Planning Policy
Development
masterplan
• Remove pollutants from urban run-off at source
Local Planning Authorities
When determining planning applications Local Planning
Authorities (LPAs) should ensure that any new or
redevelopment avoids flood risk to people and property,
does not increase flood risk elsewhere and mitigates any
flood risk taking into account the impacts of climate change.
Development
concept
Confirmation of
approval and
adoption process
• Reduce the causes and impacts of flooding
Information on how this should be applied is provided in
the DEFRA non-statutory technical standards for sustainable
drainage systems (SuDS).
We can provide help and
support at every stage of
the planning process.
Local surface water management, flood risk management and green
infrastructure policies.
The National Planning Policy Framework (NPPF) requires that
development is undertaken in a sustainable manner and has
a presumption in favour of sustainable development. The
systems should be designed to control surface water run-off
close to where it falls and mimic natural drainage as closely
as possible to:
• Combine water management with green space with
benefits for amenity, recreation and wildlife
In addition, this standard gives recommendations on
the planning, design, construction and maintenance
of surface water management systems for new
developments and redevelopment sites, focusing
on the sustainable management of flood risks arising
from surface water run-off.
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
SECTION
5
STRUCTURAL
DESIGN
SECTION
National Planning Policy Framework
The LPA will be required to consult with the LLFA as a
statutory consultee on major developments with surface
water drainage requirements along with other statutory
and non-statutory consultees as required.
12
This Code of Practice is for surface water management
for development sites. The standard has been developed
to support:
Drainage
concept
Stakeholder consultation
Flood and Water Management Act
2010 (amended 2012)
BS 8582:2013
• Designers: In planning and implementing safe,
robust surface water management systems that
meet the criteria and principles referred to above.
Outline drainage
design
Flood risk
assessment/
drainage
assessment
Data collation
and investigations
Full planning
consent
Drainage system approvals
and construction consents
Ref:- Page 8 of British Standard BS 8582:2013.
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
SECTION
9
CASE STUDIES
Outline planning
permission
Detailed drainage
design, drainage
impact assessment
NOTE: The need for the steps given
in colour would depend on the nature
and /or scale of the development and type
of planning application and is determined
by agreement with the planning authority
and drainage approval body.
Detailed data
and modelling
Outline planning stage
The Water Framework Directive (WFD) is a piece of EU
legislation to improve water quality in watercourses and
coastal areas. It identifies the treatment of pollution at
source as one of the most effective ways of reducing
pollution and improving water quality. Our geocellular
solutions can meet that challenge by integrating a number
of surface water treatment and water management control
systems into your attenuation and soakaway structures
at source.
developments and redevelopments) that deliver
effective surface water flood risk management as
sustainably as possible while contributing towards
the delivery of relevant environmental, sustainability
and urban design planning objectives for the site
and local area.
Pre-application stage
Lead Local Flood Authorities
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Full planning stage
Water Framework Directive
BS EN 752:2008 takes a more integrated view of designing
sewer systems in the context of the wider urban drainage
system and water environment. It helps engineers
understand and implement integrated urban drainage
systems and management. The National Annex provides
information on how to incorporate BS EN 752:2008
practices within the UK.
SECTION
SECTION
10
SUMMARY
Building Regulations approval
CSH certification (SUR 1)
Drainage system adoption
Permavoid Technical Manual
13
SECTION
SECTION 2
1
Permavoid system overview and applications
LEGISLATION AND
REGULATIONS
Geocellular solutions - for shallower depths
Permavoid - at a glance
Polypipe provides the widest range of geocellular solutions to meet the needs
of SuDS in a wide variety of applications.
The Permavoid system offers a means of providing integrated source control drainage solutions that can
meet the volume control and water treatment demands of current guidance and regulations.
Application
• Can be installed above a high
water table
• Allows water to be spread across
a wide area
• Ideal for brownfield or
contaminated sites
• Provides treatment to remove silt
and hydrocarbon deposits
Design
Shallower applications
The Permavoid system extends the choice and flexibility
of the Polypipe range by providing robust, effective source
control through retention, attenuation or infiltration at
shallower levels.
Shallower retention, attenuation or infiltration structures
are often necessary because the ground at greater depths can
present a construction challenge. This could be the presence
of chemicals or contamination left behind from previous land
use, a high water table or perched water and hard rock areas.
A shallower approach reduces or omits the requirement for
expensive pumping equipment. Shallower systems have a
lower environmental impact, requiring less excavation,
temporary works and fewer trips to transport infill and
rubble to and from the site reducing construction costs.
• Designed and tested for retention,
attenuation and infiltration at
shallower depths
• Removes the requirement for
pumping stations
• Oil interception at source – no need
for petrol interceptors
• Can be used in combination with the
full range of Polystorm geocellular
solutions for deeper applications
Installation
• Interlocking raft for rigidity and a
high compressive and tensile strength
under load
• Suitable for use beneath porous
and non-porous surfaces
Figure 2.1.1: Typical Permavoid system vs. traditional aggregate sub-base
The Permavoid system is designed to be used in
place of a traditional aggregate sub-base within
trafficked pavements. It provides a unique, high
strength, consistent structural raft in accordance
with BS7533-13:2009, 'Guide for the Design of
Permeable Pavements Constructed with Concrete
Paving Blocks and Flags, Natural Stone Slabs, Setts
and Clay Pavers'.
Finish
Sand
Geotextile
Permavoid
Geotextile
Bedding layer
Aggregate
4
HYDRAULIC
DESIGN
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
Key benefits
• Individual modular units tie together using
Permatie interlocking connectors
• The Permaties have integral creep resistance
• The Permatie provides rigidity and minimises
deflections
• On multi-layer systems, Shear Connectors are
inserted to maintain rigidity and minimise
lateral displacement
• Permavoid geocellular units are manufactured
from recycled polypropylene and can be recycled
at the end of their useful life
• Permavoid sub-base replacement systems comply
fully with the latest CIRIA guidance on structural
design of geocellular drainage tanks
SECTION
8
STANDARD
DETAILS
SECTION
9
• Reduction in excavation depth and cost
• No need for trench supports or
plant to deliver and remove trench
support panels
3
SECTION
For car park applications
Permavoid cells have a 95% void ratio, thus considerably
enhancing the attenuation capacity of a pavement and
also enabling the reduction of aggregate requirements
in hydraulic pavements. The system is suitable beneath
asphaltic, block-paved or concrete pavements and for the
full range of traffic conditions from domestic driveways to
highways. The units have a high compressive strength and
are joined together with Permaties, a unique patented
tapered jointing system, to create a horizontal structural raft.
SECTION
PERMAVOID
SYSTEM
COMPONENTS
Typically 330mm
• Provides effective source control
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Typically 605mm
Key benefits
SECTION
CASE STUDIES
Soft SuDS /
Swales / Basins
Roads /
Highways
Driveways /
Car Parks
Leisure Areas /
Play Areas
SECTION
10
SUMMARY
Permavoid modular cell
95% void ratio
14
Permavoid Technical Manual
Traditional aggregate
30% void ratio
Please note: Illustrations are for guidance only. Not to scale.
Permavoid Technical Manual
15
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid - at a glance
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Source control
In traditional stormwater drainage systems, silt/debris and contaminants are managed within the system via
in-line separators typically installed downstream in the system. This requires larger and deeper chamber installations.
Source control is a vital element of the SuDS Management Train, allowing silt/debris and contaminants to be
managed at the head of the system. The versatility of the Permavoid geocellular system allows for numerous
variations of stormwater treatment.
Permavoid is an effective interception system supported by over 10 years of laboratory and field trials to ensure
effectual water treatment close to source at shallower depths.
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
Surface Water Treatment System Selector
SECTION
Roof interception to incorporate:
retention/attenuation/passive irrigation/re-use
Roof
Podium
Goods Vehicle Parking
Access Roads
Car Parking
•
•
•
•
Light contamination
Occasional spillages
Permeable
Surface
Impermeable
Surface
Permafilter
Permavoid
Biomat
Permavoid
Medium Duty
with Biomat
Permachannel
Permafilter
Permavoid Biomat
Permavoid
Medium Duty
with Biomat
Regular contamination
Frequent spillages
•
•
Impermeable Surface
Permachannel
Permafilter
Permavoid Biomat
Permavoid
Medium Duty
with Biomat
Ridgigully
Permafilter
Permaceptor
Permavoid
Medium Duty
with Biomat
4
Highways
HYDRAULIC
DESIGN
Regular contamination
Frequent spillages
Impermeable Surface
Permachannel
Permafilter
Permavoid Biomat
Permavoid
Medium Duty
with Biomat
Ridgigully
Permafilter
Permaceptor
Permavoid
Medium Duty
with Biomat
SECTION
Source Control
SOURCE CONTROL DRAINAGE SYSTEM
SECTION
A Choice of...
Retention
Attenuation
Infiltration
Permavoid/Polystorm
Orifice Flow Control
Permatex 300
Permavoid/Polystorm
Orifice Flow Control
Geomembrane
Permatex 300
Permavoid/Polystorm
Permatex 300
Basement
SECTION
7
Soft SuDS
Attenuation
Infiltration
Swales
Retention Pond
Permavoid
Flow Control
Polystorm
Ridgistorm-XL
Permavoid
Flow Control
Polystorm
Ridgistorm-XL
Permavoid
Increasingly, regulations and design guidance highlight developer's obligations to mitigate the risk of pollutants
emanating from contaminated run-off from hardstanding surfaces. The most common diffuse pollutants are
hydrocarbons and contaminated silts. The Permavoid system offers an integrated technique for the source control
treatment of polluted run-off using advanced geotextiles and flotation techniques.
Site Control
A Choice of Site Control Options
Treatment/attenuation
For pollution management
6
SURFACE WATER
TREATMENT
Regional Control
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
Regional
Control
Flow control/treatment /retention /attenuation /infiltration
5
STRUCTURAL
DESIGN
STANDARD
DETAILS
SECTION
9
CASE STUDIES
SECTION
Source
Site
Regional
Key benefits
• Effluent loading under normal conditions
treated and degraded at source
• Accidental and catastrophic spills
recoverable at source
• Outperforms Class l and ll separators as
defined by PPG3
16
Permavoid Technical Manual
Permavoid Technical Manual
10
SUMMARY
• Low velocity water flow throughout,
minimising emulsification and sediment
mobilisation
• No large deep storage tanks or access required
• Routine maintenance easily achieved at source
17
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid applications
Permavoid in the urban environment
The Permavoid system can be incorporated into the full range of traffic conditions from domestic driveways
The introduction of SuDS in urban areas allows landscape architects
and engineers to design multifunctional urban spaces.
to HGV applications and is suitable below pervious and impervious asphaltic, block paved or concrete paved
areas. The Permavoid system complies with the requirements of BS 7533-13 and incorporates a high vertical
compressive strength of 715 kN/m2 and lateral compressive strength of 156 kN/m2.
High water tables
Soft landscaped areas
High water tables and even perched water at shallow
depths require specific design and construction measures
to avoid issues such as flotation of attenuation structures
and often prevents the use of soakaways. Anti-flotation
and temporary dewatering measures are invariably very
expensive. The Permavoid system can provide the
attenuation or infiltration solution for such projects
avoiding groundwater issues.
The Permavoid system can be used to provide pre-treatment
of stormwater run-off before it enters a swale, dry basin,
pond or wetland (Diagram 1). It is even possible to install
Permavoid below swales and dry basins to improve treatment
and increase storage capacity (Diagram 2).
The Permavoid system can help enhance natural features in built-up areas. As it provides excellent source control
at shallow depths, the system can not only manage, but also treat water from high stormwater volumes. It also creates
a structural platform on which green areas can be cultivated, irrigated and oxygenated.
Key benefits
2 Raised
•Provides effective drainage
1 Planter
•Can be installed above a higher
water table
Redevelopment of brownfield sites is commonplace and
issues of ground contamination often come hand in hand.
The use of the Permavoid system can often negate the
need to excavate into contaminated soils that invariably
incur significant costs in either on-site remediation or
off-site disposal, as well as numerous associated
environmental issues.
The Permavoid systems can very often avoid the need for
pumping that might otherwise be required with
conventional drainage or deep attention tank solutions.
Pumped solutions can be costly to install and maintain
and are considered to be environmentally unsustainable.
Limited access sites
The Permavoid system can be easily manhandled into
place without any heavy lifting or off-loading equipment.
The footprint of the tank does not have to be square.
Segmented tanks can fit into the available space.
Ground stabilisation
Due to its high compressive strength and bending resistance
within the joints, Permavoid cells create a horizontal
consistent structural raft providing a stable structure.
18
Permavoid Technical Manual
•Removes silt and hydrocarbons
to improve biodiverity
Geotextile
1
Shallow swale
3 Rainwater recovery
supply for irrigation
building services
Permeable paving
Permavoid
•Helps establish calming,
tranquil spaces
•Promotes health & wellbeing
1
SHALLOW SWALE & PLANTER
Permeable paving
Planter
Permeable surfaces can be used to
attenuate run-off. Intercepting, storing
and re-using surface water at source,
this enhances stormwater management
and enhances biodiversity.
Shallow swale
Outfall to
drain complete
with flow
control,
if required
2
Infiltration if suitable
Permavoid
SECTION
7
SECTION
8
STANDARD
DETAILS
9
Permafilter
Collected surface water can be used
to irrigate planter areas through
passive irrigation, providing amenity,
infiltration and evapotranspiration,
assisting with cooling in urban areas.
Permavoid
Wicking geotextile
RAINWATER RECOVERY
Permeable paving
Water for
re-use,
irrigation,
building
services
6
SURFACE WATER
TREATMENT
Wicking geotextile
CASE STUDIES
SECTION
10
SUMMARY
Overflow to drain
or infiltration
Driveways
Any domestic driveway or front garden over 5m2 that is being
paved must incorporate SuDS to minimise the risk of flooding.
The Permavoid system, used in conjunction with permeable
paving, can help adhere to these requirements whilst allowing
a wide range of landscaping options.
SECTION
Raised planter
Permeable paving
3
5
STRUCTURAL
DESIGN
SECTION
RAISED PLANTERS (RAINGARDEN)
Public open spaces / Leisure and play areas
SECTION
DELIVERY,
INSTALLATION &
MAINTENANCE
Permafilter
Acting as both a sub-base replacement system and
drainage component, the Permavoid system can give
maximum attenuation and infiltration capabilities for
both natural and artificial surfaces and can be integrated
into site-wide sustainable drainage systems more
effectively. The result is a sustainable development in
line with the DEFRA national standards for delivery
of sustainable drainage systems.
4
HYDRAULIC
DESIGN
• Provides a cooling effect
•Connects people with nature
Shallow outfalls
3
PERMAVOID
SYSTEM
COMPONENTS
•Re-uses water as a resource
Contaminated land
Diagram 2
SECTION
•Controls and manages surface water
run-off at source
Diagram 1
Excavation of hard rock is usually expensive and slow.
However, the Permavoid system is ideal for use on sites
that are underlain by hard rock at shallow depths,
as the systems can be incorporated into the pavement
construction, invariably avoiding any net additional
excavation for the drainage system.
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
SECTION
planter
Excavation of hard rock
SECTION
Rainwater from
roof/podium
Rainwater from adjacent buildings and
porous surfaces can be intercepted and
stored for non-potable water use within
the building, or re-used for irrigation.
Pumping
chamber
Permavoid Technical Manual
Permavoid
Catchpit
19
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid in the urban environment
The management of surface water
run-off from roads and highways can
provide substantial benefits to the
built environment.
Passive capillary irrigation
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Passive capillary irrigation provides enhanced amenity and biodiversity
in urban greenfield developments.
4
Passive capillary irrigation is a method of growing plants and grasses using an inert porous medium to transport water
and oxygen to the root zone by capillary action. The hollow structural columns within the Permavoid geocellular units
are filled with an absorbent rockwool, which draws up the water being stored within the unit.
Water management features can be prime design elements
in road and highway drainage. Incorporated into a new
development or retrofitted into an overall SuDS scheme,
Permavoid can enhance the natural environment by
providing improved attenuation and treatment at source.
2
1
3
1
The Permavoid raft is covered with a proprietary wicking geotextile that supplies water on demand across the structural
raft to irrigate the growing medium. As the vegetation is planted in a growing medium, access to minerals and
nutrients is still available, minimising the requirement for fertilisers and helping to develop a healthy root system.
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
Key benefits
1
Bioretention zones
BIORETENTION ZONE
Permafilter
Growing medium
Road kerb
Pavement
Road
Permavoid
Biomat
Permavoid
Outfall to highway
drain complete with
flow control if required
Infiltration if suitable
2
Key benefits
BIORETENTION ZONE
Road kerb
Pavement
Growing medium
• Traffic calming
Gully cover
Road
Permaceptor
Permafilter
• Reduced pollution loading
Permavoid
• Aesthetically pleasing spaces
Outfall to highway
drain complete with
flow control if required
Infiltration if suitable
•
Creates small source control
sub-catchments
•Air reservoir provides oxygen to root system
Water reservoir
•Provides a consistent high strength raft to support
growing medium, vegetation and amenity
Geomembrane
•Evaporative cooling mitigates the heat island
effect by reducing urban air temperatures
Typical section through Permavoid capillary irrigation
system showing rockwool infilled Permavoid column
•Provides an undersoil drainage system and can be
incorporated into a sustainable stormwater
management system
Growing
medium
Permavoid Wicking
Geotextile
Grass swales
Grass swale
Permafilter
Permavoid
Outfall to highway
drain complete
with flow control
if required
Infiltration if suitable
PARKING ZONE
Road
kerb
Pervious surface
Permafilter
Outfall to
highway drain
complete with
flow control if
required
Infiltration if suitable
Permavoid Technical Manual
•Minimises the requirement for expensive pumping
systems, providing 24 hour irrigation
•Reduces energy requirements
Permafoam irrigation units
Highways England have used grass
swales alongside roads and highways for
many years, due to their cost-effective
nature. Swales are designed to be
shallow for safety reasons, and can be
underdrained to provide effective
retention and treatment.
For smaller areas or individual landscaped areas it is possible
to provide on-demand irrigation using Permafoam units.
Permafoam is an open celled, highly absorbent and
water retentive phenolic foam that is incorporated into
a Permavoid geocellular unit.
Please see datasheet on page 32 for more information.
Parking zones
Road
•Supports the creation of landscapes in urban
settings that mimic nature
•Can remove excess soil moisture through
wicking geotextile
Sub-base
5
STRUCTURAL
DESIGN
•Regulates subterranean irrigation
Air reservoir
Capillary
infill
column
SECTION
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
Pavement
Road
20
•Enhances storage capacity for green
and brown roofs
Wicking geotextile
•
Shallow, easy to
maintain systems
GRASS SWALE
Road kerb
4
•Provides rainwater interception at source
• Easy to retrofit
Road gully
3
Growing medium
The stormwater run-off from highways
and pavement areas can be collected
and treated using bioretention.
Incorporated into traffic calming
zones, bioretention systems can
enhance biodiversity and amenity,
along with providing effective
stormwater management at source.
Pavement
Pervious off-road parking zones can be
incorporated into highway designs,
particularly in residential areas.
Installed beneath pervious surfaces, the
Permavoid range of components
perform as a sub-base replacement and
drainage system to manage the
majority of rainfall events, providing
treatment and retention at source,
at shallow depths.
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
Applications
• Green roofs
• Amenity areas
• Brown roofs
•Landscaped areas
•Bioretention
systems
• Sports pitches
•Raingardens
Permafoam irrigation units
Permavoid Technical Manual
Rockwool filled columns
21
SECTION
SECTION 3
1
Permavoid system components
LEGISLATION AND
REGULATIONS
Permavoid system
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
The Permavoid system comprises of high strength modular cells, channel and
gully components that incorporate silt /oil gravity separation features, floating oil
treatment devices, special oil treatment geotextiles and shallow flow control devices.
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
Below shows the individual components that may be required within a Permavoid system design.
SECTION
For full technical datasheets, see pages 24-37.
Shear Connector
The Permavoid system comprises of:
Securely links multiple layers
of Permavoid together in a
single structure.
See page 29
Permavoid Medium
Duty with Biomat
Comprising of a low density, oil
treating geosynthetic floating mat
for use with the Polystorm range of
modular geocellular units.
See page 30
Permaceptor
A combined run-off collection,
silt/oil interceptor and treatment
system used with road/yard gullies.
4
HYDRAULIC
DESIGN
SECTION
5
See page 31
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
Permavoid (85 and 150mm)
Permachannel
Permavoid Biomat
Geocellular sub-base replacement
system that locks together to form an
interlocking raft of exceptional high
compressive and tensile strength.
A linear treatment system that
combines run-off collection, silt and
effluent interception and water
treatment functions.
High strength geocellular unit
containing a low density, oil
treating, geosynthetic floating mat.
See page 24
See page 25
See page 26
SECTION
7
Permafoam
Permatex 300
An open celled absorbent phenolic
foam incorporated into Permavoid
geocellular units for 'on demand'
irrigation or check dams.
A heavy duty, non-woven,
polypropylene, geotextile designed
to protect and separate Permavoid
geocellular layers.
See page 32
See page 33
Orifice Plate Flow
Control Chamber
A pre-fabricated orifice plate flow
control unit incorporating a removable
filter to protect the orifice.
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
See page 34
SECTION
9
CASE STUDIES
Permafilter Geotextile
Geomembrane
Permaties
A non-woven dimpled,
needle-punched geotextile designed
for hydrocarbon pollution treatment.
An impermeable membrane for
wrapping around Permavoid
structures to form watertight tanks.
Fully interlocking tapered tie
connections to securely link Permavoid
cells together horizontally in a single
structure and to transfer tensile loads.
See page 27
22
Permavoid Technical Manual
See page 28
See page 29
SECTION
10
SUMMARY
Permavoid Saddle
Connectors
Permavoid Wicking
Geotextile
Permavoid Rainwater
Diffuser Unit
A range of spigot and
saddle connectors allowing
piped connection to the
Permavoid structure.
A heavy duty, non-woven
geotextile formulated to provide
passive irrigation to soft and
landscaped areas.
Permavoid units encapsulated
with a 2mm mesh fabric diffuse
the collected run-off into the
surrounding granular sub-base.
See page 34
See page 35
See page 36
Permavoid Technical Manual
23
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid system - components
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Permavoid 85 and 150
Permachannel
Product code: PVPP85 and PVPP150
Permavoid is a geocellular interlocking system designed for
shallow groundwater storage or infiltration, to be used in place of
traditional aggregate sub-base. The system has an exceptionally
high compressive and tensile strength and bending resistance with
a proprietary jointing system to create a horizontal structural
‘raft’ within the pavement that is ideal for the shallow
attenuation of surface water. The system can also be combined in
layers using interlocking shear connectors to increase depth in
85mm and 150mm increments. This is particularly useful in
designing infiltration systems, allowing flexibility in balancing the
soil permeability/infiltration area of the Permavoid storage units
and residual temporary attenuation.
Element
85mm
150mm
2.25kg
3kg
Physical Properties
Weight per unit
Weight per square metre
9kg
12kg
Length
708mm
708mm
Width
354mm
354mm
Depth
85mm
150mm
Applications
The Permavoid units are suitable for use as a
stormwater attenuation and/or infiltration system.
The system comprises of single, interconnected
cells which can be installed in the ground as part
of sub-base formation. Permavoid is suitable
for use in a range of applications including
residential, industrial estates, car parks, sports
pitches, roofs, basements, pedestrian areas and
rainwater harvesting.
Performance
Short Term Compressive Strength
Vertical
715kN/m²
715kN/m²
Lateral
156kN/m²
156kN/m²
Short Term Deflection
Vertical
1mm per 126kN/m² 1mm per 126kN/m²
Lateral
1mm per 15kN/m²
1mm per 15kN/m²
Tensile Strength
The structural load bearing capacity of the
Permavoid units have been tested in accordance
with the following European Standard:
BS 7533-13:2009. The system’s structural design life
expectancy, based upon creep test data (tested in
accordance with CIRIA guidelines) is as follows; for
lightly loaded areas such as car parks, a design life of
50 years is achievable. For areas with prolonged HGV
loading a typical design life may only be 25 years,
depending on the design of the pavement surfacing
and structural layers over the tank.
3
Permachannel is a versatile, linear treatment system that
can provide source control and pollution treatment in a
wide variety of locations and applications.
PERMAVOID
SYSTEM
COMPONENTS
The Permachannel functions as a combined run-off
collection, silt and oil interceptor and treatment system.
It is designed to be ideally laid with zero gradient to
prevent the development of lateral velocities, ‘stilling’
sheet run-off from each sub-catchment and encouraging
silt deposition within each channel. The outlets discharge
from the side of the channel via a weir and baffle
component which separates oils and prevents the
effluent and silt from progressing into the rest of the
drainage system.
SECTION
Element
Value
Physical Properties
Weight per unit
29kg
Length
1000mm
Width
150mm
Depth
Material
Grating
Catchment area
Loading
Average effective perforated surface area
210mm
Polymer concrete
Ductile iron standard
steel safe
30m²
Rated to D400
Polymer concrete
4
HYDRAULIC
DESIGN
SECTION
5
Applications
Permachannel is used for stormwater collection,
interception and the treatment of associated
pollutants. The system comprises of single or multiple
interconnected channels appropriately located to
collect surface water run-off from sub-catchments of
predominantly impervious or pervious pavements.
Permachannel is suitable for use in a range of
applications including residential, industrial estates,
car parks, sports pitches, roofs, basements, pedestrian
areas and rainwater harvesting.
Of a single joint
42.4kN/m²
42.4kN/m²
Of a single joint at (1% secant modulus)
18.8kN/m²
18.8kN/m²
Bending resistance of unit
0.71kN/m
0.71kN/m
Bending resistance of single joint
0.16kN/m
0.16kN/m
Volumetric void ratio
92%
95%
Average effective perforated surface area
52%
52%
Installation standard
All calculations for Permavoid units are based upon
site-specific load cases, pavement construction types
and thicknesses, soil cover and ground conditions
and the suitability must therefore be approved for
each project.
has a capillary-free,
non-porous sealed
Chemical resistance
structure, which makes
it naturally resistant
to most chemicals
1.0 x 10-5
Effluent concentrations are below PPG3 Class I requirements
Key benefits
1.0 x 10-5
Permavoid Permatie Permavoid Permatie
Ancillary
Permavoid Shear
Connector
Material
Permavoid Shear
Connector
Polypropylene (PP) Polypropylene (PP)
Hydraulic Performance 85mm
3 units wide, 1 unit deep
3 units wide, 1 unit deep
(1.06m x 0.15m)
(1.06m x 0.15m)
Free Discharge
Free Discharge
0
1
2
Gradient (%)
0
1
Flow Rate (l/m/s)
4
6
7
Flow Rate (l/m/s)
8
13 15 17 19 21
Permavoid Technical Manual
• High strength, high capacity, shallow,
sub-base replacement system
• Stormwater attenuation and/or
infiltration system
2
3
4
5
SECTION
7
Performance
Permachannel is related to D400 loading in accordance
with BS EN124:1994 when installed with concrete bed
and haunch in accordance with site specific
construction details.
Installation standard
Permachannel must be installed on a load bearing
concrete bed and haunch in accordance with site
specific construction details.
SECTION
8
STANDARD
DETAILS
SECTION
9
Key benefits
CASE STUDIES
• Trapped effluent naturally treated by
aerobic digestion
SECTION
• Can enhance the water quality and eliminate the
need for end of line petrol/oil interceptors
SUMMARY
10
• The system complies with the regulations of the
treatment train criteria in a SuDS scheme as
defined in the PPG3
• 100% recyclable
• Units are manufactured from 90% recycled
polypropylene (PP)
Gradient (%)
6
SURFACE WATER
TREATMENT
• Gravity separation of oil and silts at source
• Used as part of a SuDS scheme to
offer stormwater storage at shallow
construction depths
Hydraulic Performance 150mm
SECTION
(i.e. petrol, oils and acids)
Note: Ancillary Universal Channel Connector 40mm diameter.
Intrinsic permeability (k)
STRUCTURAL
DESIGN
DELIVERY,
INSTALLATION &
MAINTENANCE
The polymer concrete
Other Properties
24
SECTION
Product code: PV03001
• 100% recyclable
Available to download on the website toolbox.
Permavoid Technical Manual
Available to download on the website toolbox.
25
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid system - components
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Permavoid Biomat
Permafilter Geotextile
Product code: PV150BM
Product code: PV23002
Permavoid Biomat is a high strength geocellular unit, containing a low
density, oil treating, geosynthetic floating mat (biomat). The biomat
floats on water and is designed to intercept and treat any potential
residue emulsified oils that may be present within the surface water.
The use of Permavoid Biomat provides additional oil retention and
water treatment capability to an underground water storage system.
Permafilter Geotextile is a non-woven, dimpled, needle-punched
Geotextile that has been specifically designed for hydrocarbon
pollution treatment in sustainable drainage systems (SuDS) and
other civil engineering applications.
SECTION
Element
Element
Value
Physical Properties
Weight per unit
3kg
Length
708mm
Width
354mm
Depth
150mm
Short Term Compressive Strength
Vertical
715kN/m²
Lateral
156kN/m²
Vertical
Lateral
1mm per 126kN/m²
1mm per 15kN/m²
Tensile Strength
Of a single joint
42.4kN/m²
Of a single joint at (1% secant modulus)
18.8kN/m²
Bending resistance of unit
0.71kN/m
Bending resistance of single joint
0.16kN/m
Volumetric void ratio
Average effective perforated surface area
92%
52%
Other Properties
Intrinsic permeability (k)
Oil retention
Effluent discharge at max. oil loading
1.0 x 10-5
56g/m²
10ppm
Permavoid Permatie
Ancillary
Permavoid Shear
Connector
Applications
Permavoid Biomat units are suitable for use as a stormwater
attenuation and/or infiltration system. The system comprises
of single, interconnected cells which can be installed in the
ground as part of a sub-base formation. Permavoid Biomat
is suitable for use in a range of applications including
residential, industrial estates, car parks, sports pitches, roofs,
basements, pedestrian areas and rainwater harvesting.
26
Permavoid Technical Manual
Weight per unit
300g/m2
The structural load bearing capacity of the Permavoid
Biomat units have been tested in accordance with
the following European Standard: BS 7533-13:2009.
The system’s structural design life expectancy, based
upon creep test data (tested in accordance with CIRIA
guidelines) is as follows; for lightly loaded areas such
as car parks a design life of 50 years is achievable. For
areas with prolonged HGV loading a typical design life
may only be 25 years, depending on the design of the
pavement surfacing and structural layers over the tank.
Roll length
100m
Roll width
2.4m
Roll weight
72kg
Installation standard
Air permeability
All calculations for Permavoid Biomat units are based
upon site-specific load cases, pavement construction
types and thickness, soil cover and ground conditions
and the suitability must therefore be approved for
each project.
Max. oil retention
6L/10m²
Effluent discharge at max. oil loading
10ppm
Short Term Deflection
Mechanical Properties
Tensile strength EN10319 (md/cmd)
9/12kN/m
Static puncture (CBR test) EN12236
1575N
Hydraulic Properties
Water permeability EN ISO 11058
57 l/m²/s
Other Properties
Material
1000 l/m²/s
Modified polyester
Key benefits
Key benefits
SECTION
4
Value
Physical Properties
Performance
3
PERMAVOID
SYSTEM
COMPONENTS
HYDRAULIC
DESIGN
Applications
Permafilter Geotextile is suitable for use in
a range of applications including residential,
industrial estates, swales, sports pitches, car
parks, roofs, basements, pedestrian areas and
rainwater harvesting.
Performance
The dimpled Geotextile comprises a proprietary
blend of polyester fibres that incorporates
hydrophilic (water attracting and oil repellent)
and hydrophobic (oil attracting and water
repellent) properties to achieve superior oil
retention. Permafilter Geotextile is capable of
retaining oil contamination ranging from daily
car drip losses up to catastrophic spillages,
i.e. originating from car oil-sump failures.
The entrapped hydrocarbons are biodegraded
by naturally occurring microorganisms
providing a self-cleansing mechanism.
• Captures residual hydrocarbons
Laying generally
• Secondary treatment phase for potential
residual hydrocarbons
• Removes pollutants by biodegradation
• Pollutant-intercepting floating mat
• Enhances water quality when used as part of a source
Permafilter will be laid to suit site
specific requirements. Overlaps shall be
a minimum of 300mm or heat sealed.
Ensure Geotextile is clean and debris
free before installing Permavoid.
• Same size as Permavoid so can be incorporated
into Permavoid attenuation designs
• Floating medium maintained at air-water
interface allowing optimum conditions for
aerobic degradation
• 100% recyclable
control SuDS and eliminates the need for end of line
petrol/oil interceptors
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
SECTION
9
CASE STUDIES
• Designed to be self-maintaining for the life
of the installation
SECTION
• Self maintaining, degrades residual oils by
absorption and aerobic digestion
10
SUMMARY
• Units are manufactured from 90% recycled
polypropylene (pp)
• 100% recyclable
Available to download on the website toolbox.
Permavoid Technical Manual
Available to download on the website toolbox.
27
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid system - components
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Permavoid Geomembrane
Permaties
SECTION
Product code: PVCLIP
Geomembranes are impermeable liners used in sustainable
drainage systems (SuDS) to form water tight tanks.
The membrane used depends on a risk assessment of the site
and the ground and groundwater conditions.
Element
Value
Thickness mm ±10%
1.0
ASTN D-751
Density g/cm³ minimum
0.9
ASTM D-792
18
ASTM D-638
Tensile stress at break
minimum N/mm²
Elongation at break %
Puncture resistance
minimum N
Tear resistance minimum N
Dimensional stability %
change max
Stress crack resistance
Volatile loss 5% loss max
Ozone resistance
>700
150
60
±2.0
100%
0.2
ASTM D-638
FTMS 101C
method 2065
ASTM D-104
ASTM D-1204
1hr at 100ºC
ASTM 5397
ASTM D-1203
method A
No cracks
ASTM D-1149
Carbon black content
2-3%
ASTM 1603
Moisture vapour g/m²/day
<0.1
ASTM E96
21º
Shear box
0.11 g/m²/
European
day/atm
standard
1.8 x 10-9 m3/m²/s/atm
BRE
Friction angle
(non-woven Geotextile)
Methane permeability
Methane transmission rate
Permeability coefficient
Core material
Element
Test Method
Physical Properties
1.8 x 10-12
SECTION
4
Value
HYDRAULIC
DESIGN
Applications
Weight per unit
The Geomembrane is suitable for use in a range of
applications including residential, industrial estates,
swales, sports pitches, car parks, roofs, basements,
pedestrian areas and rainwater harvesting.
Length
74mm
Width
45mm
Depth
34mm
Performance
Material
30g
SECTION
5
STRUCTURAL
DESIGN
Other Properties
Polypropylene
A robust, heavy duty Geomembrane resistant
to puncture. Geomembrane combines excellent
chemical resistance with low flexural modulus to
provide a malleable, flexible membrane suitable for
nonsmooth surfaces and factory pre-fabrication to
optimise on-site installation. Jointing shall be formed
using fusion or extrusion bead welding in
accordance with manufacturing recommendations.
Key benefits
• Heavy duty polypropylene membrane
• Used to create a water-tight construction
and minimise risk of subgrade softening
• 100% recyclable
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
Shear Connector
Product code: PVSC
SECTION
When two or more layers of Permavoid are used to form
a structure, Shear Connectors are inserted between the
layers to create stability and prevent lateral movement
and shear resistance.
8
STANDARD
DETAILS
Polypropylene
Value
SECTION
Physical Properties
Laying generally
Weight per unit
For retention and attenuation applications the units need
a sealed geomembrane to prevent the release of water and
prevent the ingress of groundwater. All joints should be
sealed, using proprietary techniques recommended by the
manufacturer. Advice on seam testing procedures as given
in CIRIA SP 124:1996. Barriers, lines and cover systems for
containment and control of land contamination.
Permavoid Technical Manual
PERMAVOID
SYSTEM
COMPONENTS
Physical Properties
Element
28
3
Permatie is a patented tapered tie that interlocks the
Permavoid geocellular units into a secure and consistent raft.
Once connected the ties provide tensile resistance within the
Permavoid structure.
9
10g
Length
40mm
Diameter
35mm
CASE STUDIES
Other Properties
Material
SECTION
10
Polypropylene
SUMMARY
Available to download on the website toolbox.
Permavoid Technical Manual
Available to download on the website toolbox.
29
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid system - components
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Permavoid - Medium Duty with Biomat
Permaceptor
Product code: PSM1BM
Product code: PV04002
Permavoid Medium Duty with Biomat is designed for use with
Polystorm attenuation and infiltration systems and comprises
of a tri-laminate of low density plastic composite (biomat).
The biomat floats on water and is designed to intercept and treat
any potential residual emulsified oils that may be present within
the surface water. The use of Permavoid Medium Duty with Biomat
provides additional oil retention and water treatment capability
to an underground water storage system.
The Permaceptor functions as a combined run-off collection,
silt/oil interceptor and treatment system. The system is
designed to be used with conventional road/yard gullies and
ideally laid with zero gradient to prevent the development
of lateral velocities. Thus, its initial function is to ‘still’
sheet run-off from each sub-catchment and to encourage
silt deposition. The outlet discharges via a weir and baffle
component that separates oils and prevents the effluent and
silt from progressing into the rest of the drainage system.
Exact colour may vary
due to recycled materials.
Applications
Technical Specification Overview
Length
1m
Width
0.5m
Depth
0.4m
Total volume
0.2m3
Unit weight
9kg (approx)
Unit storage volume
The Permavoid Medium Duty with Biomat units
are suitable for use as a stormwater retention,
attenuation or infiltration system. Used to provide
hydrocarbon treatment, they are suitable for a
range of applications including, retail, residential,
commercial and off-road car parking.
0.19m3 (190 litres)
Void ratio
95%
Vertical compressive strength
Maximum 610 kN/m2 **
Lateral compressive strength
Maximum 63 kN/m2 **
Short-term vertical deflection
70.1 kN/m2 per mm
Short-term lateral deflection
4.4 kN/m2 per mm
Estimated long term vertical
[Based on an applied test load
0.2798 Ln (design life in hrs)
= 162 kN/m2]
deflection (creep)
Creep data limit 60 years
1.0192 Ln (design life in hrs)
Estimated long term lateral
[Based on an applied test load
deflection (creep)
= 30.8 kN/m2]
Creep data limit 60 years
Other Properties
Intrinsic permeability (k)
Oil retention
-5
Minimum 1.0 x 10
56g/m²
Effluent discharge at max.
oil loading
Performance
The structural load bearing capacity of the
Permavoid units have been tested in accordance
with CIRIA C680. The structural design life is
a minimum 60 years.
The units provide 3D flow and have a void
ratio of 95%.
Weight per unit
29kg
Length
1062mm
Width
708mm
Height
300mm
Short Term Compressive Strength
Vertical
715kN/m²
Lateral
156kN/m²
Short Term Deflection
Vertical
1mm per 126kN/m²
Lateral
1mm per 15kN/m²
Tensile Strength
Of a single joint at (1% secant modulus)
18.8kN/m²
Bending resistance of unit
0.71kN/m
• Pollutant-intercepting floating mat degrades
residual oils by absorption and aerobic digestion
Bending resistance of single joint
0.16kN/m
Volumetric void ratio
92%
• Can be incorporated into Polystorm retention,
attenuation and infiltration systems
Average effective perforated surface area
52%
Key benefits
• 95% void ratio
• Light weight yet robust – excellent health
and safety and installation benefits
• 60 years creep limited life expectancy
Other Properties
Intrinsic permeability (k)
Oil retention
56g/m²
Effluent discharge at max. oil loading
10ppm
Ancillary
Permavoid Permatie
Material
Polymer concrete
Applications
Permaceptor is used for stormwater collection,
interception and the treatment of associated
pollutants. The system comprises of Permavoid
and Permavoid Biomat units located to collect surface
water run-off from sub-catchments of predominantly
impervious or pervious pavements via Polypipe Ridgigully
and Midigully. Permaceptor is suitable for use in a range
of applications including residential, industrial estates,
car parks and basements.
check and suitable installation conditions.
* Each unit includes 4 clips and 2 shear connectors.
** Compressive strength at yield, maximum recommended value
for design purposes.
Available to download on the website toolbox.
Permavoid Technical Manual
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
SECTION
Performance
The structural load bearing capacity of the
Permavoid units have been tested in accordance with
the following European Standard: BS 7533-13:2009.
The system’s structural design life expectancy, based
upon creep test data (tested in accordance with CIRIA
guidelines) is as follows; for lightly loaded areas such
as car parks a design life of 50 years is achievable.
For areas with prolonged HGV loading a typical
design life may only be 25 years, depending on the
design of the pavement surfacing and structural
layers over the tank.
Installation standard
All calculations for Permaceptor units are based
upon site-specific load cases, construction types
and thickness, soil cover and ground conditions
and the suitability must therefore be approved
for each project.
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
Key benefits
• Gravity separation of oils and silts at source
Minimum 1.0 x 10-5
• Units are manufactured from recycled materials
trafficked and pedestrian applications subject to a structural design
Permavoid Technical Manual
Physical Properties
42.4kN/m²
Note: Permavoid Medium Duty With Biomat is ideal for use in
30
Value
Of a single joint
• 100% recyclable
10ppm
Element
SECTION
• Accidental/catastrophic spills recoverable
at source
SECTION
9
CASE STUDIES
• Trapped effluent naturally treated by aerobic
digestion
• Can enhance the water quality and eliminate
the need for end of line petrol/oil interceptors
• The system complies with the regulations of the
treatment train criteria in a SuDS scheme as
defined in the PPG3
SECTION
10
SUMMARY
• 100% recyclable
• Units are manufactured from 90% recycled
polypropylene (PP)
Available to download on the website toolbox.
31
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid system - components
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Permafoam
Permavoid Permatex 300
Product code: PVPP85PF or PVPP150PF
Product code: PV23006
Permafoam is an open-celled, phenolic foam that is highly
absorbent and water retentive. Incorporated into Permavoid
high-strength units, Permafoam has the capacity to store 31 litres
of water for 'on-demand' irrigation or check dams. The Permavoid
structure prevents the foam from damage due to imposed backfill
or traffic loads.
A heavy duty, non-woven, needle punched, polypropylene
geotextile designed to protect and separate Permavoid
geocellular layers. It comprises of a three-layer composite
scrim reinforced with low elongation. 300mm lap-jointing
is required.
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
Element
Value
Physical Properties
Weight per unit
2.5kg or 3.65kg
Length
708mm
Width
354mm
Depth
85mm or 150mm
Short Term Compressive Strength
Vertical
715kN/m²
Lateral
156kN/m²
Applications
Element
Permafoam units are used for stormwater collection
and provide velocity control to drainage flows
within sub-bases laid over sloping surfaces. Due to
the very large surface area compared to traditional
check-gate flow control, Permafoam assures against
the risk of the control clogging associated with
traditional check-gate flow controls. It is used in
conjunction with the Permavoid Wicking Geotextile.
They can be incorporated into irrigation systems to
provide water 'on-demand' around landscaped areas.
Physical Properties
Short Term Deflection
1mm per 126kN/m²
Lateral
1mm per 15kN/m²
Tensile Strength
Of a single joint
42.4kN/m²
Of a single joint at (1% secant modulus)
18.8kN/m²
Bending resistance of unit
0.71kN/m
Bending resistance of single joint
0.16kN/m
Volumetric void ratio
Water storage capacity (foam)
Water permeability (in plane flow)
83%
31 Litres
0.0452 Litres/second/lin.m
Other Properties
Permavoid Permatie
Ancillary
Material
65m
Roll width
5.25m
Mass per unit area
Permavoid Shear
Connector
Polypropylene (CoPo),
polyurethane
Performance
The structural load bearing capacity of the
Permavoid units have been tested in accordance
with the following European Standard:
BS 7533-13:2009. The system’s structural design life
expectancy, based upon creep test data (tested in
accordance with CIRIA guidelines) is as follows; For
lightly loaded areas such as car parks a design life of
50 years is achievable. For areas with prolonged HGV
loading a typical design life may only be 25 years,
depending on the design of the pavement surfacing
and structural layers over the tank.
Test Method
Laying generally
EN ISO 9864
2mm
EN ISO 9863-1
CBR puncture resistance
4000N
EN ISO 12236
Dynamic cone drop
11mm
EN ISO 13433
25kN/m
EN ISO 10319
50%
EN ISO 10319
Tensile strength (min)
at max. load
at max. load
SECTION
• Protection
300g/sq.m
Thickness under load 2kPa
Applications
• Separation
Roll length
Tensile extension (max)
Vertical
Value
Protection efficiency
300N
EN ISO 14575
Breakthrough head
nil
BS EN ISO 10319
Coefficient of permeability
55 x 10-3m/s
EN ISO 11058
Characteristic opening size
70 microns
EN ISO 12956
Permatex protection geotextile shall be laid
continuously around the drainage to suit site
specific requirements. Overlaps shall be a minimum
of 300mm or heat sealed. Ensure geotextile is clean
and debris free before installing Permavoid.
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
SECTION
Installation standard
9
All calculations for Permafoam within designs are based
upon site-specific load cases, construction types and
thicknesses, soil cover and ground conditions and the
suitability must therefore be approved for each project.
CASE STUDIES
SECTION
10
Key benefits
SUMMARY
• Can be used to provide 'on-demand'
irrigation for landscaped areas when used
with Permavoid Wicking Geotextile
• Permafoam units can be used to form check
dams and gates within pervious pavements
32
Permavoid Technical Manual
Available to download on the website toolbox.
Permavoid Technical Manual
Available to download on the website toolbox.
33
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid system - components
Preformed Spigot
Connector with
weldable
membrane
Element
Permavoid Wicking Geotextile
Value
Element
Value
Polypropylene
When forming a Permavoid attenuation or storage
structure, it is necessary to use the Preformed Spigot
Connector with weldable membrane in association with
the Permavoid Geomembrane. A welded joint can be
made to ensure the tank is leak free.
Weight per unit
Length
260mm
Width
180mm
Depth
39mm
Spigot diameter
40mm
Spigot Length
135mm
Other Properties
If required, outlet connections can be extended
using 40mm HDPE pipework.
Element
Value
Physical Properties
Weight per unit
Variable
Minimum diameter
500mm
Height
Variable
Sump depth
Nominal thickness
3.6mm
Surface weight
500gm²
Saturated weight
4.5K/gm²
Roll width
2m
Roll length
25m
Roll weight
26kg
Maximum tensile strength - Longitudinal
10kN/m
Maximum tensile strength - Lateral
28kN/m
Puncture resistance
2600N
Hydraulic Properties
Water retention capacity
Water permeability
SECTION
4
Value
Mechanical Properties
Polypropylene
The Permachannel Connector is installed where
adjacent Permachannel units butt against each other
to form a 40mm diameter outlet. The connector fits
into the outlet from the Permachannel and allows
water to be conveyed from the Permachannel into
the Permavoid system. One connection unit is required
per linear metre of Permachannel.
Orifice Plate
Flow Control
Chamber
Element
Physical Properties
210 g
Material
3
PERMAVOID
SYSTEM
COMPONENTS
A heavy-duty, non-woven, needle-punched geotextile
made from a blend of modified polyester fibres. It is specially
formulated to absorb water to irrigate mineral substrates
when used in conjunction with Permafoam units.
Physical Properties
50g
SECTION
Product code: PV23008
Product code: PV06305
Other Properties
Material
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Universal
Permachannel
Connector
Physical Properties
Weight per unit
SECTION
4 l/m²
37 l/m²/s
HYDRAULIC
DESIGN
Applications
The Wicking Geotextile is suitable for use
in most landscaped applications including
roof gardens, soft SuDS applications and
sports pitches.
SECTION
5
STRUCTURAL
DESIGN
Performance
A robust heavy duty geotextile, when
constantly charged with water, it allows
moisture to be fed naturally by capillary
action to landscaped areas for irrigation.
300mm lap jointing is required. Used in
conjunction with Permafoam units. Water
is drawn by capillary attraction to ensure
the Wicking Geotextile is kept charged.
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
Laying generally
Permavoid Wicking Geotextile shall be laid continuously
to suit the site specific requirements. Overlaps shall be
a minimum of 300mm or heat sealed.
Key benefits
• Passive capillary irrigation
SECTION
8
• Can remove excess soil moisture
STANDARD
DETAILS
Saddle Connector
for infiltration
applications
SECTION
9
300mm as standard,
others available
on request
CASE STUDIES
Other Properties
Element
Material
Polypropylene
Value
Weight per unit
Discharge limitations are normally achieved by the
incorporation of pre-fabricated orifice plate flow control
devices, fitted with removable filters to protect the
orifices. These are sized to suit the permitted discharge
rate and the size of the subcatchment using standard
hydraulic theory.
34
Permavoid Technical Manual
SECTION
Physical Properties
10
80g
SUMMARY
Other Properties
Material
Polypropylene
Proprietary saddle connections for use within Permavoid
storage structures installed to soakaway captured water.
Available to download on the website toolbox.
Permavoid Technical Manual
Available to download on the website toolbox.
35
SECTION
1
LEGISLATION AND
REGULATIONS
Permavoid system - components
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Permavoid Rainwater Diffuser Unit
Element
Permavoid Rainwater Diffuser unit - Configuration options
SECTION
3
Width
Value
PERMAVOID
SYSTEM
COMPONENTS
Physical Properties
3kg
Length
708mm
Width
354mm
Depth
150mm
708mm
Short Term Compressive Strength
Vertical
715kN/m2
Lateral
156kN/m2
Short Term Deflection
Vertical
1mm per 126kN/m2
Lateral
1mm per 15kN/m2
Tensile Strength
Of a single joint
42.4kN/m
Of a single joint at (1% secant modulus)
18.8kN/m2
2
Bending resistance of unit
0.71kN/m
Bending resistance of single joint
0.16kN/m
Volumetric void ratio
95%
Average effective perforated surface area
52%
Run-off from building roofs is collected into
downpipes and flows into a back inlet gully
incorporating an internal filter or catchpit
inspection chambers. The back inlet gully or
chamber discharges the filtered stormwater into
the permeable sub-base via Permavoid Rainwater
Diffuser Unit encapsulated in a 2mm mesh fabric.
The run-off will then diffuse out of the Permavoid
Rainwater Diffuser Unit and into the modified
granular sub-base layer. The Permavoid unit is a
150mm deep modular interlocking plastic unit
storage system designed for use as a combined
drainage component and sub-base replacement
system, ideal for shallow infiltration/attenuation.
Length
Weight per unit
1062mm
1416mm
2124mm
354mm
708mm
1062mm
1416mm
2124mm
ü
ü
ü
ü
ü
ü
ü
ü
ü
û
ü
ü
ü
ü
ü
ü
ü
ü
ü
ü
Depths available are either 150mm or 300mm. Connections available are either Ø110mm or Ø160mm.
Ancillary
Permavoid Shear
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
Connector
Material
SECTION
SECTION
Figure 3.1.1: Typical layout - Rainwater downpipe drainage into sub-base reservoir
Minimum 1.0 x 10-5
Permavoid Permatie
4
HYDRAULIC
DESIGN
Catchpit: 460mm diameter catchpit with 160mm inlet - PSMT 160
460mm diameter catchpit with 110mm inlet - PSMT 110
Other Properties
Intrinsic permeability (k)
SECTION
8
Polypropylene (PP)
STANDARD
DETAILS
Hydraulic Performance
3 units wide, 1 unit deep (1.06m x 0.15m)
SECTION
Free Discharge
Gradient (%)
0
1
2
3
4
5
Flow rate (l/m/s)
8
13
15
17
19
21
9
CASE STUDIES
SECTION
10
SUMMARY
36
Permavoid Technical Manual
Available to download on the website toolbox.
Permavoid Technical Manual
Available to download on the website toolbox.
37
SECTION
SECTION 4
1
Hydraulic design
LEGISLATION AND
REGULATIONS
Sustainable drainage systems - selection & design
Hydraulic design - attenuation
It is important to consider as many factors as possible when selecting the
most appropriate sustainable drainage system. The process below is a guide
to the most efficient design.
Hydraulic design calculations provide the storage volume required on any
particular site that is needed to reduce the speed, frequency and volume
of rainfall run-off into rivers or sewers. The required volume depends on
the site location, the size of the area being drained, the soil infiltration rate
(for soakaways) or allowable discharge rate (for attenuations systems).
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
The design of SuDS should follow the requirements in
the CIRIA Report C 753 The SuDS Manual. This identifies
three types of storage that are required:
Interception storage
The aim is to reduce the frequency of run-off and prevent
run-off from sites for rainfall events up to 5mm in order
to simulate the behaviour of greenfield catchments more
closely. This is achieved using infiltration or source control
methods where evapotranspiration can reduce the
volume of run-off. Typically this is achieved using soft
SuDS solutions. Increased capacity of soft SuDS solutions
can be achieved utilising Permavoid beneath them.
Attenuation storage
Reduces the peak discharge rate from a site
(i.e. how fast water flows off the site) and is used
to store excess water where the rate of discharge is
limited to greenfield run-off rates or stormwater sewer
rates. It is designed to operate for a range of annual
probabilities in accordance with the Environment
Agency and/or local water company requirements.
Long term storage
Used to reduce the additional volume of run-off caused
by developments. Stores excess water that is the difference
in total volume of run-off between the developed and
greenfield site for a 1 in 100 year, 6 hour rainfall event.
Outflow from the long term storage should be to either
infiltration or to a water course or sewer.
Design of attenuation storage
The volume of Permavoid required for attenuation
storage is typically calculated using drainage software
based on the Wallingford Procedure. The volume of
temporary run-off storage required is shown below
and is simply the difference between the volume of
run-off that enters the tank during a design storm and
the volume of water that is allowed to flow out in the
same period (which is governed by the discharge rate
allowed by the regulators). In this way, Permavoid can
be used to limit the peak rate of run-off from a site
(usually to the greenfield run-off rate). The calculations
are completed for a range of return periods and durations.
Attenuation storage volume
4
HYDRAULIC
DESIGN
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
38
Permavoid Technical Manual
Permavoid Technical Manual
39
SECTION
1
LEGISLATION AND
REGULATIONS
Attenuation
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Hydrological rainfall
zones for the UK
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
The table below can be used to size a
Permavoid tank. The tables are based
on the hydrological rainfall regions
shown on the map.
SECTION
4
M5-60
The tables are based on the following
assumptions:
HYDRAULIC
DESIGN
• Storage is provided for development
design events of 1 in 30 years, 1 in
100 years and 1 in 100 years plus 20%
increase for climate change but the
greenfield run-off rate is always
considered to be 5 l/s/ha
r
SECTION
5
STRUCTURAL
DESIGN
• Time of entry and time of concentration
within the drainage system is not
considered
Example of Permavoid sizing
for attenuation storage
• 100% run-off is assumed
A site in London has impermeable area as follows:
Note: HR Wallingford, use of SuDS in high density
developments, defining hydraulic performance
criteria, Report SR 640, December 2003.
SECTION
6
SURFACE WATER
TREATMENT
1200m2 roof area
1475m2 car park and other areas
SECTION
7
Therefore the total impermeable area = 2675m2
Assume the required return period for the drainage design
is 1 in 100 years as agreed with the Environment Agency
From the table on page 40, London is in the region where
M5-60=20mm and r=0.4
Therefore from the table the volume of the Permavoid tank
required is 510m3/ha
Note:
Required attenuation storage (m3 of storage per Ha of impermeable area)
Volumes include allowance for 95% void ratio
of Permavoid.
Permavoid has a void ratio of 95% (i.e. for every 1m
there is 0.95m3 of space available for water storage).
r
1 in 30 year
design event
1 in 100
year event
1 in 100 year event plus
20% climate change
0.4
357
510
643
0.3
413
582
749
0.2
556
770
968
0.4
293
419
545
0.3
335
483
631
0.2
444
637
822
0.3
258
383
511
0.2
335
500
665
3
M5-60 = 20mm
The volume of Permavoid required is therefore
calculated by dividing the required storage volume
by 0.95.
This factor is allowed for in the design table.
M5-60 = 17mm
M5-60 Rainfall depth (mm)
The rainfall depth for the 60 minutes,
5 years return period event
'r' Ratio M5-60 / M5-2 day:
Variable 'r' represents the ratio of the rainfall depth
of the 60 minute to the 2 day, 5 year rainfall event.
40
Permavoid Technical Manual
M5-60 = 14mm
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
Required attenuation storage on this site =
510 x 2675/10000 = 136.4m3
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
Permavoid Technical Manual
41
SECTION
1
LEGISLATION AND
REGULATIONS
Hydraulic design - infiltration
Infiltration
Design of infiltration storage
Step 2 - Fill trial hole with water
Where ground infiltration is suitable for design flows, there are three approaches for hydraulic sizing:
• Fill the pit as quickly as possible with water to at least
75% of the pit depth or the top level of the proposed
soakaway to mimic a real storm event
1.
BS EN 752:2008 'Drain and Sewer Systems Outside Buildings'
2.
Soakaway Design BRE Digest 365
3.
CIRIA Report 156 'Infiltration Drainage - Manual of Good Practice'
A simplified approximate approach can be used on a very small site (i.e. a single house development) where detailed site
infiltration rate information may not be required nor available. Approved document H3 allows a storage volume equal
to the area to be drained multiplied by 10mm for areas up to 25m2. Beyond this size, designs should be carried out in
accordance with BS EN 752-4:2008 or BRE Digest 365.
Percolation test for designing a shallow infiltration system
The depth of the trial pit should reflect the (expected) proposed depth of installation and water depth likely to occur
in the completed structure.
Step 1 - Trial hole excavation
• Where the infiltration test is to be conducted in a 'kept
turfed' area; first carefully cut and remove the turf in
location of the excavation and put to one side
• Place length of level timber or similar across pit with
a mark near the centre (but within easy reach) as
a measure datum
• Excavate a shallow rectangular pit either
by hand or by machine (suggested minimum
2000mm x 1000mm x 500mm depth, subject
to ground conditions), attempting to get the
base as flat and the sides as vertical as possible
(subject to ground conditions). Aiming to get
close to the proposed depth of installation of
the infiltrated device(s)
• If there are any inflows of groundwater into the pit;
record the apparent inflow rate (slow flow etc.) and
delay the start of the test to see if the groundwater
flows away or rises to a constant level. If standing
groundwater is present measure from the datum the
level of any standing water in the base of the pit
• Measuring from the marked point on the datum rod,
record depth to water at start of test
• Then record depth to water at typically:
- 20 second intervals up to 2 minutes, then at
- 30 second intervals up to 5 minutes, then at
- 1 min. intervals up to 10 minutes, then at
- 5 min. intervals up to 30 minutes, then at
- 15 min. intervals up to 2 hours then,
-Hourly thereafter to the end of day if water
has not soaked away
Until the water level drops below 25% of the initial
recorded water depth within the trial pit.
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
SECTION
• Refill and retest the test pit twice more (where time
permits) allowing the trial hole to drain between tests
• Record the weather conditions before and during
the tests, particularly any rainfall (duration and
relative intensity)
• Unless instructed otherwise, place the excavated
material back in the exaction and compact as best
as possible
• If turf was kept, place back over the filled exaction
as best as possible
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
Step 1 and 2 - Illustrated example
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
• Measure and record the dimensions of the pit
STANDARD
DETAILS
• Record the soil type(s) excavated and general
ground conditions, the apparent moisture content
of the soil(s) and any visual or olfactory (odour) evidence
of possible contamination
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
42
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43
SECTION
1
LEGISLATION AND
REGULATIONS
Infiltration
Geotextiles and Geomembranes
Step 3 - The results - soil infiltration rate
The use of geosynthetics is an integral component of a geocellular structure. They are wrapped
around the geocellular units to create attenuation or infiltration tanks. The function of the
geotextiles and geomembranes are to prevent:
Calculation principles
Adopting the approach given in Construction Industry Research and Information Association
(CIRIA) Report 156 Infiltration Drainage - Manual of Good Practice.
• Silt that may be contained in the surface water run-off
from contaminating the surrounding soil (infiltration)
Where:
Vp75-25
Soil infiltration co-efficient,f =
a p50 x t p75-25
Vp75-25 = Volume of the hole from 75% and 25% depth (m3)
• Surrounding soil from entering the units (infiltration)
a p50 = Internal surface area of test hole at 50% depth (including base) (m2)
• The release of surface water into the surrounding
ground (attenuation)
t p75-25 = Time taken for the hole to drain from 75% to
25% depth (sec)
• Inflow of groundwater that may overload downstream systems
and contain pollutants on contaminated sites (attenuation)
The design of the surrounding medium and choice of geosynthetic is an important consideration.
The designer/ installer should confirm with the geosynthetic manufacturer that the specification
of the proposed material is suitable for the application and site conditions. The designer should
determine and define the following:
• The application requirements - retention, attenuation
and infiltration
• Boundary conditions – site investigation to establish in-situ soil
parameters, enabling lateral earth pressures and water flow
conditions to be calculated
• Soil retention requirements – using the in-situ soil parameters,
determine if additional bed and surround measures should
be specified
• Geosynthetic permeability requirements – the breakthrough
head should be considered in addition to water flow rates
• Anti-clogging requirements (infiltration only) – ensure that
the porosity of the geotextile in conjunction with the specified
bed and surround is sufficient to prevent the geotextile from
prematurely clogging
• Resistance to mechanical damage requirements –
the geosynthetic should be sufficiently robust to survive
installation activities
Test hole depth
at 75% and 25%
a(p50) = 0.250 x [2 x (1.000 + 2.000)] + (1.000 x 2.000) = 0.250 x (6.000) + 2.000 = 3.500m2
• Durability requirements – consideration should be given
as to whether the geosynthetic will be subjected to a
significant chemical exposure, either present in the
ground or rainwater run-off
From the completed tests, the longest duration test took 11 and 80 minutes to drain
to 75 & 25% trail hole depths respectively.
t(p75-25) =
80 - 11
= 69 minutes
Therefore:
Soil Infiltration rate, f =
44
0.500
= 3.45 x 10-5 m/sec
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
SECTION
Therefore any damage of the geosynthetic wrap, may lead to a
decreased performance of the tank.
Continuing with the example given:
V(p75-25) = 1.000 x 2.000 x (0.375 - 0.125) = 0.5m3
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
The soil infiltration rate can
be used in volume calculations.
If you require assistance, please
call our Technical Team on
+44 (0) 1509 615100.
3.500 x (69 x 60)
Permavoid Technical Manual
Permavoid Technical Manual
45
SECTION
SECTION 5
1
Structual design
LEGISLATION AND
REGULATIONS
Structural design
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
When designing Permavoid geocellular structures for attenuation or infiltration,
care has to be taken to ensure the finished system is safe to carry the loads they
will be subjected to. A brief summary of the points which should be considered
for a typical installation are given below:
Applied loads and load factors
Loads that may be imposed on a cellular storage
structure such as Permavoid can be broken down into
the following types.
Partial material factors of safety: Permavoid
Applied loads
Partial factors of safety
• Uniformly distributed
• On material properties
• Concentrated
• On loads
Limit state
ƒm
Ultimate limit state
2.75
Serviceability limit state
1.50
• Backfill
Chemical resistance
Unit characteristics
Industry guidance
• Traffic
- Construction
- In service
• Compressive strength
at yield
Permanent (dead) loads
• Earth pressure
• Creep
A generic design method has been developed that can be
applied to most types of cells, using basic structural design
theory and relevant British Standards. Imposed loading on
geocellular plastic tanks may be considered to be similar to
other buried structures. Loads and partial factors of safety
applied to loads and materials detailed in this section have
been based on latest CIRIA Guidance.
CIRIA Guidance
L oads due to pedestrian, vehicle and construction traffic
that are temporary. Traffic wheel loads are normally
given as static loads, with a factor applied to allow for
dynamic effects (a moving wheel will impose more force
on the ground than a static one).
• Deflection
• Uplift
The main design considerations to ensure system
integrity are:
In the case of the Permavoid system, the two limit states
typically considered are:
• Structure failure or collapse – where the structure
cannot support the applied loads
Ultimate Limit State (ULS)
• Excessive deflection or movement of the structure
when vehicles pass over the tank; that compromises the
structural integrity of a surface pavement (i.e. crack)
Limit state design
Current structural design philosophy is based on limit state
criteria, where a number of limit states are considered. The
methodology applies partial factors of safety to the various
design parameters, the magnitude of which is dependent
on the potential variability of that parameter and the
consequences of the limit state being exceeded.
Considers if the strength of the geocellular unit is exceeded
by the applied loads and cause the structure or structural
element to fail.
This is obviously serious, therefore the partial factors of
safety used in this assessment are chosen to ensure the
installation remains serviceable. In the case of Permavoid
this would typically mean that deflections are not excessive
and do not cause damage to overlying surfaces (such as
asphalt pavements) or cause a significant reduction in
the storage volume of the structure.
Serviceability Limit State (SLS)
Considers the operational behaviour of a geocellular
structure to ensure that the installation remains serviceable.
In the case of Permavoid this would typically mean that
deflections are not excessive and do not cause damage to
overlying surfaces (such as asphalt pavements) or cause a
significant reduction in the storage volume of the structure.
Currently the only guidance to the structural design of
geocellular structures is published by CIRIA.
Factors of safety
To minimise the risk of exceeding the limit states,
factors of safety are applied to the geocellular units
characteristic compressive strengths and to any
applied loads.
Material factors
The strength characteristics of the Permavoid cells have
been obtained from laboratory testing. A design strength
is derived by dividing the cell's characteristics strength by
a material partial factor of safety (ƒm), appropriate to
the material and limit state. This takes into consideration
variations due to manufacturing processes, variability
and uncertainties in material strength, damage during
installation and environmental effects.
Structural design life
The design life is based on the scale and frequency of
loadings and extrapolation of creep test data. The lighter
and less frequent the load, the longer the design life.
Large permanent loads (e.g. from a significant depth of fill
on top of a tank) will give shorter design life compared to
light permanent loads. Areas where heavy vehicles are
standing for prolonged periods will give a shorter design
life than where vehicles are mainly transient.
For lightly loaded areas such as car parks a design life of
50 years is achievable. For areas with prolonged HGV
loading a typical design life may only be 25 years,
Permavoid Technical Manual
Permavoid Technical Manual
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
Permavoid is resistant to automotive products such as
motor oil, petrol, diesel, brake fluid, antifreeze, grease
and washer fluid at the concentrations and temperatures
likely to be encountered within a typical surface water
drainage application.
• Stockpiles
• Hydrostatic pressure
(groundwater)
46
depending on the design of the pavement surfacing
and structural layers over the tank. Maintenance of
the pavement will be required after the design life has exceeded. It is recommended structural calculations
are always carried out in accordance with the latest
CIRIA Guidance.
4
HYDRAULIC
DESIGN
SECTION
ermanent loads applied to the Permavoid cells,
P
including the weight of backfill material placed over
the top and lateral (horizontal) earth and water pressure
loads acting on the side of the system.
5
STRUCTURAL
DESIGN
SECTION
Transient (live) loads
Design loads
A design load is obtained by applying a partial factor of
safety to the estimated characteristic load. This allows for
unforeseen variations of loading and also the severity of
the consequences of the limit state occurring. The loads
detailed within CIRIA Guidance have been based on loads
applied in the design of structures using rigid materials
such as concrete and therefore the partial safety factors
for loads that are appropriate to the design of plastic
storage systems are taken from British Standard BS 8110.
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
SECTION
9
Partial material factors of safety
PRODUCT
SUMMARY
Limit state
Imposed vertical
dead load ƒm
Imposed earth
pressure dead
load ƒm
Imposed live
load ƒm
Ultimate
limit state
1.4
1.4
1.6
Serviceability
limit state
1.0
1.0
1.0
SECTION
10
SUMMARY
Additional dynamic amplification factors may be applied
where structures are expected to be heavily trafficked
by HGV's.
If you require assistance, please call our Technical
Team on +44 (0) 1509 615100.
47
SECTION
1
LEGISLATION AND
REGULATIONS
Structural design
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Pavement applications
The Permavoid system has undergone numerous laboratory
tests and instrumented site trials to validate use in pavement
constructions. Permavoid exceeds the minimum unit
performance recommended in industry guidance for
geocellular units installed within a pavement structure.
Many factors should be considered when
designing Permavoid below pavements, including:
• Vehicle types
• Frequency of loading
• Pavement construction
Pavement construction examples
Typical minimum recommended pavement construction details, for a number of loading situations, are reproduced below;
amended to illustrate how Permavoid would typically be installed within these pavement structures.
3 tonnes
The Permavoid system complies with the
requirements of BS 7533-13:2009 and incorporates a
high vertical compressive strength of 715kN/m² and
lateral compressive strength of 156kN/m².
The following guidance documents provide minimum
pavement construction details for a range of typical
installations; the construction detail varying according to
the expected level of vehicle traffic and ground conditions.
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
• Load duration
• Speed
3 tonnes
Industry guidance
12 tonnes
SECTION
British Standard
Interpave
BS 7533-13:2009, Pavements Constructed with Clay,
Natural Stone or Concrete Pavers – Part 13: Guide for
the Design of Permeable Pavements Constructed with
Concrete Paving Blocks and Flags, Natural Stone Slabs
and Setts and Clay Pavers.
Interpave (2010); Permeable Pavements. Guide
to the Design, Construction and Maintenance of
Concrete Block Permeable Pavements; 6th Edition;
British Precast Concrete Federation Ltd.
30 tonnes
4
HYDRAULIC
DESIGN
SECTION
5
60 tonnes
60 tonnes
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
30mm asphalt surface + 60mm asphalt base
+ 40mm Type 1 sub-base
= 130mm
30mm asphalt surface + 90mm asphalt base
+ 140mm Type 1 sub-base
= 260mm
200mm concrete slab
+ 100mm Type 1 sub-base
= 300mm
Applications:
Applications:
Applications:
Applications:
Applications:
Applications:
• Private drives
• Private drives
• Car parks andaccess roads
• Car parks with
height restrictions
•HGV park access and small
estate roads (<15mph)
• Main roads
•Car parks with height restrictions
•Car parks without
height restrictions
80mm block + 50mm sand bed
= 130mm
• Includes for occasional/
accidental HGV overrun
48
Permavoid Technical Manual
• Includes for occasional/
accidental HGV overrun
• Suitable for access roads
200mm concrete slab
+ 200mm Type 1 sub-base
= 400mm
200mm reinforced concrete slab
+ 200mm Type 1 sub-base
= 400mm
STANDARD
DETAILS
SECTION
• Includes for occasional/
accidental HGV overrun
9
PRODUCT
SUMMARY
• Frequent HGV’s
SECTION
Note: Site ground investigations are recommended in accordance with BS 7533-19:2009.
If CBR is below 5% an additional capping layer or geo-grid ground reinforcement is required.
Permavoid Technical Manual
10
SUMMARY
49
SECTION
SECTION 6
1
Surface water treatment
LEGISLATION AND
REGULATIONS
Pollution control - Permachannel
The SuDS Management Train refers to source control
and emphasises 'run-off should be managed as close
to the source as possible'. Using Permavoid it is possible
to collect and treat rainwater adjacent to where it falls.
Silt, debris and hydrocarbons can be managed at the
head of the system using system components preventing
pollution migration into the rest of the stormwater
drainage system and reducing lifetime maintenance.
Calculate required silt and oil storage volumes in
accordance with the Environment Agency's Pollution
Prevention Guideline 3.
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Permaceptor
SECTION
3
Permaceptor is a versatile, efficient and effective source control
volume and treatment system for use with conventional road
and yard gullies.
PERMAVOID
SYSTEM
COMPONENTS
Silt trap capacity
Volume of silt trap in Permachannel = 0.0045m³/m
SECTION
4
Figure 6.1.1: Performance
HYDRAULIC
DESIGN
Sediment load in catchment = 865kg/ha/y
Permachannel
Permachannel is a versatile
linear treatment system that
can provide source control
and pollution treatment in
a wide variety of locations
and applications.
Example silt and oil loading
calculation
Pollution control - Permaceptor
Catchment area = 6800m2
Total sediment load from catchment = 588kg/ha/yr
Can reduce hydrocarbon
pollution loading below 5mg/l
Performance
Permachannel is not used to convey water like conventional
channel drainage, instead it is used to trap silts and oils.
The outlet incorporated in the channel is a weir and baffle
system that captures any silt or free floating hydrocarbons
and retains them in the channel. The performance of the
Permachannel system has been assessed by laboratory
testing of full-scale prototypes. The results show that the
Permachannel alone will outperform conventional Class 2
oil separators and so will meet the design requirements
of the Environment Agency's Pollution Prevention Guideline
PPG3. The performance can be improved by providing
a geotextile filter as a further stage of treatment after
the Permachannel, which will ensure the whole treatment
train meets the requirements of a Class 1 oil separator.
Permachannel performs several key functions in relation
to controlling pollution in run-off, including stilling the
sheet flow to encourage controlled deposition of silt
and effluent, interception and separation at source.
Water treatment design
The design of the Permachannel system should ensure
sufficient pollution removal and storage capacity. A maximum
catchment area of 30m2 should drain to each 1m length of
Permachannel. The volume of the silt trap within the channel
or kerb is required to provide sufficient silt and floating oil
storage capacity. The spacing of the Permachannel outlets
also ensures that flow velocities are not excessive.
SECTION
Assume density of unconsolidated sediment in base
of silt trap is 1200kg/m³ (typical value for dock silt)
then volume of sediment per year from whole car
park = 0.5m³
5
1
STRUCTURAL
DESIGN
Channel length is 700m
SECTION
6
Volume of silt trap in channel in total for the site = 3.15m³
4
So, time to fill this with silt is approximately 6.3 years
(assuming no maintenance is undertaken) (3.15÷0.5)
6
3
SURFACE WATER
TREATMENT
5
Oil trap capacity
2
The amount of oil that can be retained is the difference
in height between the weir and baffle in the separator
SECTION
7
Height difference = 40mm
DELIVERY,
INSTALLATION &
MAINTENANCE
So, volume that can be accommodated = 0.003m3/m
Total volume for site = 2.1m3
Required capacity from PPG 3
SECTION
8
Nominal size of separator = NSB = site area x 0.0018
NSB = 0.0018 x 6800 = 12.2 litres
Required silt storage = NSB x 100 = 1220 litres = 1.2m3
Actual storage = 3.15m3 which is acceptable
Oil storage required
= NSB x 15 = 183 litres = 0.18mm3
Actual is 2.2m3 which is acceptable
STANDARD
DETAILS
One Permaceptor can treat
a catchment area of 150m2
SECTION
Stormwater from impervious surfaces (1) enters
the road/yard gully (2). The gully will slow down the
inflow and silts/debris are separated out. The gullies
incorporate a basic baffle arrangement and some
hydrocarbons are retained or slowed down within
the flow process. Stormwater passes from the gully into
the Permaceptor unit via a raised inlet (3) and flows
through to be 'stilled' by a baffle (4) allowing the water
to pass through the biomat(s) where hydrocarbons are
separated. As the water passes through the chamber
a primary baffle (5) also retains hydrocarbons
allowing clean water to discharge into the drainage
system via a raised outlet (6). The raised outlets create
a permanent pool of water. The chamber incorporates
an inspection and oil recovery heavy duty cover. The
biomats encourage natural biodegrading of free oil
products, acting as an additional stilling element and
prevention of entrainment of oil into drainage system
due to poor maintenance.
9
PRODUCT
SUMMARY
SECTION
10
SUMMARY
Catchment area 30m2
All dimensions in millimeters, unless otherwise stated. All dimensions are nominal and may vary within manufacturing tolerances. All site temporary and enabling works
by others. Ridgistorm-XL units to be installed in accordance with Polypipe Civils recommendations (refer to Polypipe technical guidance for further information); giving
due consideration to the requirements of the organisation who will be taking ultimate ownership of the installation. These drawings are intended for guidance only.
Confirmation of the information contained within this document should be sought from the consulting Engineers before final design or construction activities commence.
50
Permavoid Technical Manual
Permavoid Technical Manual
CAD drawings are also available on the website toolbox
51
SECTION
1
LEGISLATION AND
REGULATIONS
Pollution control - Permavoid Biomat
Pollution control - Permafilter Geotextile
Permavoid Biomat
Permafilter Geotextile
Permavoid Biomat has been specifically designed
to remove hydrocarbon pollutants from surface
water run-off. It comprises of a buoyant
geocomposite located inside the Permavoid unit.
Permafilter Geotextile has been specially designed
to retain hydrocarbon pollutants. Permafilter Geotextile
comprises of a non-woven, needle punched geotextile
made from a proprietary blend of modified polyester
fibres. The entrapped pollutants are either removed
or reduced to levels suitable for discharge into
controlled waters.
The composite interacts with oil deposits, allowing
formation of a 'biofilm' on its solid surface and providing
the opportunity for nutrient recycling which would
allow active biofilm development. The system provides
an environment which encourages the growth of
oil-degrading microorganisms as moisture, oil
and oxygen from the atmosphere are all present
supplied with a large surface area for oil absorption
and biofilm attachment.
Permavoid Biomat has been extensively researched
in partnership with Coventry University. The experiments
included studies of the oil retention, the biofilm
formation and the mineralisation of the entrapped
hydrocarbons. Model systems were used for the study,
comprising of a full pavement cross-section.
Performance
Research has demonstrated that the system is capable of
retaining and biodegrading the hydrocarbon pollutants
from the surface water. The system is capable of retaining
56g of oil per m2. The entrapped hydrocarbons become
part of a complex biofilm, which utilises the oil pollutants
as a nutrient source (mineralisation). The system also
demonstrates other beneficial results, such as that both
unused and used lubricating oil can be degraded.
Permavoid Medium
Duty with Biomat
One Permavoid Biomat cell is
capable of retaining 56g of oil
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
Working principle
The proprietary blend of fibres in Permafilter Geotextile
exhibit specific hydrophilic and hydrophobic properties and
these, combined with the dimpled structure, work together
to form multiple layers with inherent oil retention properties.
The hydrophobic (repelling) material receives and retains the
hydrocarbon pollutants, whilst the hydrophilic (water-attracting)
elements simultaneously facilitate water retention resulting in
a long-term stable biofilm, which subsequently degrades the
entrapped pollutants.
SECTION
5
STRUCTURAL
DESIGN
SECTION
Water mixed
with hydrocarbons
6
SURFACE WATER
TREATMENT
Applications
The range of applications for the Permafilter Geotextile is
virtually unlimited in traditional geotextile applications, where
enhanced hydrocarbon treatment can be achieved. Furthermore,
it is applicable in many retrofit applications where the superior
hydrocarbon retention is an indispensable requirement.
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
Performance
SECTION
Permafilter Geotextile demonstrates retention of up to 6 litres
of oil per 10m2. The maximum discharge of effluent is typically
4.5ppm* during the first flush and during consecutive rain
events only an average concentration of 1.5ppm.
STANDARD
DETAILS
*ppm = parts per million
8
Oil is trapped in fabric
Water passes through
SECTION
9
6 litres of oil retained per 10m2
Permavoid Medium Duty with Biomat is designed
for use with Polystorm attenuation and infiltration
systems. The use of Permavoid Medium Duty with Biomat
provides additional oil retention and water treatment
capability to deeper underground water storage systems.
The size of this unit is 1m x 0.5m x 0.4m.
PRODUCT
SUMMARY
Over time hydrocarbons
biodegrade
SECTION
10
SUMMARY
Microscopic view of
self-maintaining eco-system
52
Permavoid Technical Manual
Permavoid Technical Manual
53
SECTION
SECTION 7
1
Delivery, installation & maintenance
LEGISLATION AND
REGULATIONS
Delivery and storage
Installation
Permavoid
Excavation and preparation
• Permavoid is delivered to site on pallets. Palletised load
measurements are approx. 1.2m x 1.1m x 2.3m high and each
pallet will contain 72 Permavoid units
Excavation
• The excavation is dug to the required plan, dimensions
and level, ensuring that the excavation will allow
installation of connecting pipework. Slopes must be
cut to a safe angle or adequately supported and safe
access must be provided to allow personnel to enter
the excavation. Excavation should be carried out in
accordance with BS 6031:2009, with particular attention
paid to safety procedures.
• Deliveries shall be unloaded using mechanical handling equipment
Permachannel
• Permachannel is delivered to site on pallets. Palletised
load measurements are approx. 1.0m x 0.8m x 1.0m high
and each pallet will contain 20 Permachannel units
• Pallet weight is circa 850kg
• It is recommended that the excavation provides a minimum
• Permachannel is delivered with gratings in position
of 500mm clear zone on all sides of the plan dimensions of
the tank to allow working space for the installation. If
required, suitable protection and earthwork support must
be provided beyond the clear zone to all excavated faces.
• Deflection plates are supplied within the channel and need
to be positioned during installation
• Deliveries shall be unloaded using mechanical handling equipment
Base
Storage
To be trimmed smooth and free from sharp objects and
projections to provide an even formation that shall be free
from undulations. Any present must be excavated and
replaced with compacted granular fill material.
• Position pallets on stable, level ground
• Stacking of pallets is not recommended
• Store away from direct sources of heat or ignition
• Transit banding should not be removed until installation
Tolerance
The formation shall be graded to achieve a maximum
deviation of 5mm in 3m in any direction to prevent formation
of voids below installation which will cause Permavoid units
to ‘rock’. A blinding layer may be used
to achieve required tolerances.
Geotextile and Geomembrane
• Deliveries shall be unloaded using mechanical handling equipment
Blinding
Geosynthetic
Permafilter
Permatex 300
Wicking Geotextile
Geomembrane
Material
Polyester blend
Modified polyester
Polyester blend
Polypropylene
Roll size
2.4m x 100m
5.25m x 65m
2m x 25m
Variable
Weight
300g/m2
300g/m2
500g/m2
900g/m2
Delivery
Single rolls
Single rolls
Single rolls
Single rolls
Permavoid Technical Manual
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
SECTION
3
• Ensure that the ground-bearing capacity at formation level
is adequate for the design loads.
• Pallet weight is circa 220kg
54
SECTION
A 50mm thick blinding layer of 20/6 clean crushed stone or
sand to BS EN13242:2002 shall be used to achieve a suitable
bedding surface.
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
Permatie
Adjacent Permavoid units are connected using Permatie
interlocking pins, which have integral creep resistance.
Permaties must be inserted into all available slots
where units butt together up to a maximum of 5
Permaties per Permavoid unit. The Permatie provides
rigidity and minimises deflections.
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
Shear Connectors
Multi-layered Permavoid tank configurations shall
be fixed with proprietary Shear Connectors
between each layer interface to maintain rigidity
and minimise lateral displacement. A minimum of
four Shear Connectors per square meter at layer
interface is recommended.
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
Drainage connections
Proprietary drainage connections are available where
a drainage connection is required to the Permavoid
installation. There are several different options
available subject to type of tank encapsulation and
whether the connection is at invert or centrally located.
SECTION
8
STANDARD
DETAILS
SECTION
9
CASE STUDIES
Laying
Ensure membrane is clean and free from debris before laying
Permavoid. Check installation plan/details to confirm Permavoid
orientation. Commence laying in corner of installation area and
work forwards in a diagonal line to the opposite corner until
layer is complete. Repeat for further layers.
Permavoid Technical Manual
SECTION
10
SUMMARY
55
SECTION
1
LEGISLATION AND
REGULATIONS
Installation
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Permachannel excavation and
bedding preparation
Attenuation applications
Where required, all penetrations through an
impermeable encapsulation shall be sealed. Create an
impermeable seal using a preformed spigot connector
with a weldable membrane.
To be trimmed smooth and free from sharp objects
and projections. For optimum capacity the Permachannel
should be installed with zero gradient but it can be installed
to shallow gradients should the drainage design require.
The Permachannel should be laid on a 200mm deep concrete
bed with a minimum 150mm thick haunch to both sides.
A 30N/mm2 concrete mix is recommended.
Tolerance
All joints should be sealed, using proprietary techniques
recommended by the manufacturer. Advice on seam
testing procedures is given in CIRIA Report SP124.
Protection
Geotextile for infiltration
Permatex protection geotextile should be installed to the
outside face of the base, top and sides of the installation
as protection layer to geomembrane.
Permafilter Geotextile should be used for infiltrations
applications. The geotextile should be laid with
minimum of 300mm overlap or to lap marker and to
be applied to all external surfaces of Permavoid units.
Adjacent sheets to be lap jointed with a minimum lap
of 300mm or heat sealed. Corners to be formed in folded
welts and heat sealed if required. Ensure geotextile is clean
and free from debris. Trafficking over placed material
to be avoided.
Installation
Corners to be formed into folded welts and heat sealed
if required. Ensure geotextile is clean and free from
debris before installing Permavoid. Trafficking over laid
material to be kept to a minimum.
It is recommended that site vehicle traffic is prevented
from trafficking the Permavoid tanks until the
installation is complete.
Backfilling
The Permavoid tanks shall be backfilled with an initial
layer minimum 50mm thick of 20/6 clean crushed stone
or sand to BS EN 13242:2002. The preferred method of
aggregate placement is for the plant to be situated
on top of a minimum of 300mm thick aggregate layer.
Recommended plant to be used for placement of the
aggregate to be a tracked machine with a maximum
operating bearing pressure of 200kN/m2. Wheeled
machines to have low bearing pressure tyres (maximum
permitted pressure 30psi), maximum tread/cleat
projection 15mm. Under no circumstances should plant
operate in direct contact with Permavoid units.
56
Permavoid Technical Manual
3
PERMAVOID
SYSTEM
COMPONENTS
Base
The adaptors comprise a rigid body and spigot with
a flexible outer membrane manufactured from compatible
material to the geomembrane encapsulating the tank.
Adaptors are available as invert or standard type and come
in a range of diameters. The adaptors are fully welded
to the main tank encapsulation.
Installation
SECTION
Local subgrade below concrete bed tolerance of ±5mm
within any 3m direction. The commensurate level for the
Permachannel installation should allow for the height of the
Permachannel and the depth of the concrete bedding, plus
a further 3-5mm below the finished level to protect the
Permachannel and prevent ponding. Ensure the membrane
encapsulation from the Permavoid tanks (if required) spans
below the Permachannel installation with sufficient length
to return up the rear of the Permachannel run.
Manual handling
It is recommended to remove the gratings and stainless
steel diverter plate prior to installation to reduce the
handling weight from 42kg to 29kg. Consult your
employer for specific manual handling advice.
Installation of Permachannel
Check installation plan/details to confirm Permachannel
orientation in relation to Permavoid tank(s). Align using
a builder's line or suitable laser alignment equipment.
When positioning the Permachannel, insertion of the
stainless diverter plate will assist alignment. The diverter
plate should be positioned so that it spans from the ends
of adjacent Permachannel units to divert rainwater
run-off into the central Permachannel unit. Install the
Permachannel connection units along the length of the
Permachannel run, 1 connection unit required per
linear metre of Permachannel, installed where adjacent
Permachannel units butt against each other to form a
40mm diameter outlet. Install the connection unit by firstly
removing the fresh concrete bed (before hardening) in
immediate area and inserting 'o' ring (supplied with
connection unit) into the rebate of the 40mm diameter
outlet from the Permachannel and then insert 40mm
diameter spigot into the Permachannel aperture.
Permavoid Technical Manual
SECTION
4
HYDRAULIC
DESIGN
Ensure connection unit is seated in a vertical position if
installing Permachannel ahead of the Permavoid tank,
or is butted against the Permavoid tank if installing the
Permachannel after the Permavoid tanks. Redundant
Permachannel outlet, if not used must be blanked prior
to placing concrete haunch. 40mm blanking plugs are
available. Place the concrete haunch to the front and
rear of the Permachannel. The channel elements must
be kept clean during installation. Trafficking over laid
material is to be kept to a minimum.
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
Surface finish options
It is recommended the grating is installed within the
Permachannel prior to construction of the pavement.
Concrete
Between the minimum 150mm concrete surround and
the concrete slab, an expansion joint must be inserted,
as structural engineer's specification.
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
Bituminous bound
To avoid damaging the channels during compaction of
the surfacing, the concrete surround must be haunched
as high as possible (45° back to the Permachannel).
The bituminous bound surfacing can be installed against
the side of the channel. The finished level following
compacting has to be 3-5mm above the height
of the grating.
STANDARD
DETAILS
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
57
SECTION
SECTION 8
1
Standard details
LEGISLATION AND
REGULATIONS
Maintenance
General design details
Like any conventional drainage system, sustainable drainage systems
(SuDS) should be inspected regularly and correctly maintained
to ensure optimum performance.
The Permavoid range of products can be used individually or linked
together to provide unique and flexible water management solutions.
Maintenance plan
This should be initiated by the drafting of routine
maintenance plans to suit the site installation.
A pre-handover inspection should be carried out
and the Permavoid system cleaned prior to
final handover.
Routine inspection and maintenance
should include:
• Inspection of systems
• Removal of silts
• Decanting of oils and hydrocarbons
• Channel jetting
• Water sampling and testing at point
of discharge (if required)
Excess silt/debris held within Permachannel and gullies
should be cleared manually or with a vacuum tank.
We do not recommend pressure led cleaning.
Permaceptor
For Permaceptors the following routine maintenance
procedures are required:
• 3 monthly inspections of road/yard gullies for signs
of blockage and oil spillage
Permachannel
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
The following typical design details highlight a range of solutions available. These drawings are available on the
Polypipe website at www.polypipe.com/toolbox. Individual projects may require tailored solutions that are not
detailed. For more information please contact our Technical Team on +44 (0) 1509 615100.
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
Typical permeable pavements
• Remove litter and blockages as required
Figure 8.1.1: Sub-base infiltration detail
(drawing no. PV_SD_IN_PP_001)
• Every 6 months inspect all Permaceptors
for silt and oil build up
(For illustration purposes, we have shown a permeable block paving system.
For Permeable asphalt a 40mm surface course and 80mm binder course are recommended)
SECTION
5
STRUCTURAL
DESIGN
• Every 12 months sweep external surfaces
• Records of inspections and maintenance undertaken
should be kept by the client
SECTION
6
Accidental spillages
SURFACE WATER
TREATMENT
If accidental spillages occur of oil or other substances
that can cause water pollution, they must be dealt with
immediately. An example of this is if a car sump fails
and there is large spillage of oil on the car park or road
surfaces. A spillage kit appropriate to the size of the car
park should be kept by the site caretaker. This should
include absorbent pads, socks and rain seals.
As soon as a spillage is identified, the drain inlets in that
area should be covered to prevent pollution entering the
system. The pollution should then be cleared from the road
or car park surface. The local channel system and/or
Permaceptor receiving the spillage should be emptied
of all pollution that has entered.
Routine maintenance
SECTION
The Permachannels and Permaceptors should prevent any
significant pollution entering the rest of the drainage
system. The Environment Agency should be informed
of the spillage and the appropriate actions should be taken.
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
Figure 8.1.2: Permavoid permeable pavement sub-base attenuation detail
(drawing no. PV_SD_AT_PP_001)
(For illustration purposes, we have shown a permeable block paving system.
For Permeable asphalt a 40mm surface course and 80mm binder course are recommended)
SECTION
9
CASE STUDIES
For Permachannel the following routine maintenance
procedures are required:
SECTION
10
• 3 monthly inspections of channels for signs of
blockage and oil spillage
SUMMARY
• Remove litter and blockages as required
• Every 12 months inspect all chambers for silt
and oil build up
• Every 12 months sweep external surfaces
• Remove silt as required but at least every year
• Records of inspections and maintenance undertaken
should be kept by the client
58
Permavoid Technical Manual
Permavoid Technical Manual
CAD drawings are also available on the website toolbox
59
SECTION
1
LEGISLATION AND
REGULATIONS
General design details
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Typical permeable pavements - attenuation
Figure 8.2.1: Permavoid with Permachannel shallow cellular attenuation detail
(drawing no. PV_SD_AT_PC_001)
Figure 8.3.1: Permavoid with Permachannel deep cellular attenuation detail with Medium Duty Biomat
(drawing no. PV_SD_AT_PC_003)
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
Figure 8.2.2: Permavoid with Permachannel SuDSAGG attenuation detail
(drawing no. PV_SD_AT_PC_002)
Figure 8.3.2: Permavoid with Permachannel shallow cellular infiltration detail
(drawing no. PV_SD_IN_PC_001)
SECTION
8
STANDARD
DETAILS
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
60
Permavoid Technical Manual
CAD drawings are also available on the website toolbox.
Permavoid Technical Manual
CAD drawings are also available on the website toolbox.
61
SECTION
1
LEGISLATION AND
REGULATIONS
General design details
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Figure 8.4.1: Permavoid with Permachannel SuDSAGG infiltration detail
(drawing no. PV_SD_IN_PC_002)
Figure 8.5.1: Permavoid with Gullyceptor detail
(drawing no. PV_SD_ID_GC_001)
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
Figure 8.4.2: Permavoid with Permachannel deep cellular infiltration detail
(drawing no. PV_SD_IN_PC_003)
DELIVERY,
INSTALLATION &
MAINTENANCE
Figure 8.5.2: Permavoid rainwater pipe connection detail
(drawing no. PV_SD_AT_MC_001)
SECTION
8
STANDARD
DETAILS
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
62
Permavoid Technical Manual
CAD drawings are also available on the website toolbox.
Permavoid Technical Manual
CAD drawings are also available on the website toolbox.
63
SECTION
1
LEGISLATION AND
REGULATIONS
General design details
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Managing permeable pavements on sloping sites:
SECTION
3
THE PROBLEM
SOLUTION 2
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SOLUTION 1
SOLUTION 3
SECTION
8
STANDARD
DETAILS
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
64
Permavoid Technical Manual
Permavoid Technical Manual
65
SECTION
SECTION 9
1
Case studies
LEGISLATION AND
REGULATIONS
Case study - Walthamstow
Case study - Coronation Street
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
SECTION
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
Polypipe was called upon to provide a stormwater
management system for the redevelopment of
Walthamstow Stadium.
Working closely with main contractor Quadrant Construction
and consultant engineers MLM, our Permavoid geocellular
stormwater attenuation system was specified due to its ability
to work perfectly as a sub-base replacement system, avoiding
deep excavation at the site which contained contaminated
ground and a high water table.
Located on the site of the former greyhound stadium and
adjacent to the River Ching, the Walthamstow Stadium
development boasts 294 new homes that incorporate
sustainable drainage features, including brown roofs
and permeable paving.
Utilising the high strength Permavoid system, we designed
and supplied the system beneath 4,500m² of permeable paving
to provide 1,500m³ of stormwater attenuation to meet the
requirements of the Environment Agency.
The design featured 150mm deep Permavoid cells, with
Permafilter geotextile laid on top between the cells and the
permeable paving. The Permafilter acts as a barrier to capture
and treat surface water run-off at source from the permeable
paving above, before entering the tank. The sides and the
bottom of the tank were wrapped in a geomembrane to allow
for stormwater to be attenuated, before discharging at a rate
set by the Environment Agency into the river with the use of
66
Permavoid Technical Manual
flow control devices. In areas of hard standing, without
permeable paving, Permachannel and Permavoid Biomat were
installed to capture, treat and attenuate surface water run-off.
The Permavoid system is capable of handling rainfall
in the event of a ‘1 in 100’ year storm, and reduces
urban stormwater run-off from the site by 80%.
Despite being so lightweight, the strength of the Permavoid cells
allows them to support structural loads across heavily trafficked
areas, making them suitable to withstand the compressive and
dynamic loads produced by vehicles at the site.
A shallow stormwater management system
using Permavoid was specified for use as part
of the construction of the new Coronation
Street set.
Working closely with the construction company, The Carey
Group Plc and international consultancy and construction
company Mace, our supply and install partner, SEL, undertook
an evaluation of the site and its ground conditions. They
recommended a Permavoid system to provide a shallow
solution, due to the site being on brownfield land, having
a high water table and a shallow outfall.
The shallow depth of the solution not only negated the need
for pumping stations, it also reduced the need for temporary
works, which in turn reduced installation and labour costs
as well as Health and Safety risks.
The project saw 28 separate Permavoid
attenuation tanks installed throughout the site,
providing a combined storage capability of
420,000 litres.
Permachannel acts as both a surface water collection
point and a treatment system that intercepts silt and
oil with a zero gradient at pavement level. Water is
then discharged from the side of each Permachannel
into the Permavoid cells, complete with Permavoid
Biomat and Permafilter for further treatment and
storage, allowing only treated water to be discharged
into the local watercourse.
The system incorporates a unique jointing mechanism
that forms an interlocking ‘raft’ that will support
structural loads across the most heavily trafficked areas,
such as those found at the Coronation Street set.
SECTION
7
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
SECTION
9
CASE STUDIES
SECTION
10
SUMMARY
High strength Permavoid cells were combined with
strategically located Permachannel and Permavoid Biomat
cells for the capture, treatment, storage and controlled
discharge of rainwater at source.
Permavoid Technical Manual
67
SECTION
SECTION 10
1
Summary
LEGISLATION AND
REGULATIONS
Product summary
4
PERMACEPTOR
4
PERMAVOID BIOMAT
RETENTION
(RE-USE)
PERMACHANNEL
ATTENUATION
3
INFILTRATION
PERMAVOID
85mm & 150mm
TREATMENT
WATER
CAPTURE
Product
Summary
Associated products
4
4
4
Geocellular storage unit used to capture water for retention, attenuation
or infiltration.
4
3
3
3
A combined run-off collection, silt/oil interceptor and treatment system.
4
3
3
3
A combined run-off collection, silt/oil interceptor and treatment system.
4
3
3
3
Used with Permavoid, Permachannel and Permaceptor to provide additional
water treatment and storage.
PERMAVOID MEDIUM DUTY
WITH BIOMAT
4
3
3
3
Geocellular storage unit for use with Permavoid, Permachannel, Permaceptor
and Polystorm to provide additional water treatment and storage.
PERMAFILTER
4
4
3
3
Specifically designed for hydrocarbon treatment.
4
4
Impermeable membrane used for retention and attenuation.
GEOMEMBRANE
4
PERMATEX 300
PERMAVOID WICKING
3
PERMAFOAM
3
3
3
3
A geotextile designed to protect and separate Permavoid geocellular layers.
4
Formulated to provide passive irrigation to soft and landscaped areas.
4
Phenolic foam filled Permavoid geocellular unit used for irrigation
and flow regulation.
Key Primary Application
3
Additional Application
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
Permavoid
RIDGISTORMCheck
A sub-base replacement
Flow control chambers available with
geocellular water
pre-fabricated vortex flow controllers
management system for
and orifice plates.
use at shallower depths.
Polystorm
RIDGISTORMSeparate
A geocellular system used A range of upstream catchpits and silt
for retention, attenuation
traps to separate slit and other
and infiltration at particles before entering a drainage deeper depths.
system or the environment.
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
SECTION
Ridgistorm-XL
RIDGISTORMControl
An engineered, large diameter
A range of pre-fabricated chambers
pipe solution for surface water, with flow control components such
foul water and combined as Gate Valves, Flap Valves and
sewer applications.
Penstocks.
5
STRUCTURAL
DESIGN
SECTION
6
SURFACE WATER
TREATMENT
Rainstream
Rainwater re-use systems 4
SECTION
for both commercial and
residential applications.
RIDGISTORMAccess
Manholes
SECTION
7
Pre-fabricated manholes to provide
easy access into a pipeline.
Ridgidrain
RIDGISTORM-X4
A high strength HDPE surface
Advanced 4 stage water water drainage piping system,
treatment system.
used for surface and sub-surface
DELIVERY,
INSTALLATION &
MAINTENANCE
SECTION
8
STANDARD
DETAILS
drainage applications.
Polysewer
Landcoil
A PVCu sewer pipe A land drainage system for
system available in the management of excess
sizes 150mm-300 mm.
land water.
SECTION
9
CASE STUDIES
SECTION
68
Permavoid Technical Manual
Ridgisewer
Cable protection
A highly durable and versatile
Protects cables and conduits
polypropylene sewer pipe carrying power, motorway system, available in sizes communications, lighting and
400mm-600mm.
utilities in almost every application.
Permavoid Technical Manual
10
SUMMARY
69
SECTION
1
LEGISLATION AND
REGULATIONS
Enabling sustainable building technology
Literature and website
At Polypipe, we provide plastic piping systems that enable the effective installation and performance
of sustainable building technology, helping meet the twin global challenges of carbon reduction and
water management.
Literature
SECTION
2
PERMAVOID
SYSTEM
OVERVIEW AND
APPLICATIONS
All of our literature is available
at www.polypipe.com/toolbox
Product literature
SECTION
3
PERMAVOID
SYSTEM
COMPONENTS
SECTION
4
HYDRAULIC
DESIGN
Civils & Infrastructure Civils & Infrastructure
Product Guide
Pocket Guide
Ridgistorm-XL
Technical Manual
SECTION
Polystorm
Technical Guide
5
STRUCTURAL
DESIGN
Solutions literature
SECTION
6
SURFACE WATER
TREATMENT
SECTION
7
WMS Sector
Brochure
DELIVERY,
INSTALLATION &
MAINTENANCE
Rail Solutions
Brochure
SECTION
Water management solutions
Sector focus
Market sector literature
Roof to River
Our product systems respond directly to sector-specific
Additional market sector literature is available, please
Offering a comprehensive range of standalone and
requirements thanks to focused Technical and Development
visit www.polypipe.com or contact the telephone
modular SuDS products, rainwater harvesting and surface
Teams with hands on expertise in the following areas:
numbers appearing under each brochure.
water treatment solutions plus legislative and technical
Civils and infrastructure
support services, our Water Management Solutions Team
address the requirements of every construction and civil
engineering project.
Carbon efficient solutions
project planners a complete suite of solutions.
SECTION
Residential
Ever stricter building regulations and ever more
and service solutions for both new build and RMI applications,
environmentally conscious customers are driving the
as well as innovative solutions in response to legislative and
demand for greener building products and technologies.
industry targets for more sustainable housing.
We fulfil that demand with a full range of systems that
Commercial
Major commercial projects from car parks and high rise office
blocks to hospitals, educational premises and shopping centres
and comprehensive service support.
Permavoid Technical Manual
9
CASE STUDIES
in-house Fabrications Team, offer civils and infrastructure
have all benefited from our range of value engineered products
70
SECTION
drainage and cable management systems, supported by our
We offer the broadest range of residential product
heating, ventilation and cooling systems.
All of our literature is available
at www.polypipe.com/toolbox
Delivering performance and sustainability, our surface water
Sustainable indoor environments
enable collection, transmission, emission and control in
8
STANDARD
DETAILS
10
SUMMARY
UK
Residential
Civils and infrastructure
Commercial
+44 (0) 1709 770000
+44 (0) 1709 770000
+44 (0) 1509 615100
+44 (0) 1622 795200
All descriptions and illustrations in this publication are intended for guidance only and shall not constitute a ‘sale by description’. All dimensions given are nominal and Polypipe may modify and
change the information, products and specifications from time to time for a variety of reasons, without prior notice. The information in this publication is provided ‘as is’ in January 2016. Updates
will not be issued automatically. This information is not intended to have any legal effect, whether by way of advice, representation or warranty (express or implied). We accept no liability
whatsoever (to the extent permitted by law) if you place any reliance on this publication you must do so at your own risk. All rights reserved. Copyright in this publication belongs to Polypipe and
all such copyright may not be used, sold, copied or reproduced in whole or part in any manner in any media to any person without prior consent.
is a registered trademark of Polypipe.
All Polypipe products are protected by Design Right under CDPA 1988. Copyright © 2016 Polypipe. All rights reserved.
Permavoid Technical Manual
71
Permavoid System
Technical Manual
Civils & Infrastructure
Polypipe Civils
Charnwood Business Park
North Road, Loughborough
Leicestershire
LE11 1LE
Tel +44 (0) 1509 615100
Fax +44 (0) 1509 610215
Email [email protected]
www.polypipe.com/wms
Printed on 100% recyclable chlorine-free paper. All inks used on this brochure are vegetable based.
www.polypipe.com
Permavoid Technical Manual
72
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