Jovian Design - Permeable Surface Stormwater Management Feasibility Study

PERMEABLE SURFACE STORMWATER MANAGEMENT
FEASIBILITY STUDY
FINAL REPORT APRIL 2010
City of London
Engineering Review Division
Environmental & Engineering Services
Disclaimer: This report is an academic exercise conducted by graduate students from the University of Western
Ontario. Jovian Design is a fictional entity and has been created only for the purposes of this exercise.
WONDERLAND POWER CENTRE, LONDON, ONTARIO, CANADA

DANIEL BITTMAN | ANIRUDDHA DHAMORIKAR | STEVEN DIXON | JENNA SIMPSON | SYED ZAIDI

April 23, 2010
Lois Burgess, P.Eng.
Division Manager
City of London
Ismail Abushehada, Ph.D., P. Eng.
Development Services Engineer
City of London
RE: Final Report: Permeable Surface Stormwater Management Feasibility Study: Wonderland Power Centre, London,
Ontario, Canada
Dear Ms. Burgess and Mr. Abushehada,
The following document is the Final Report of the Permeable Surfaces Stormwater Management Feasibility Study that has been
requested by the Engineering Review Division of the Environmental and Engineering Services Department of the City of London.
It has been a pleasure to work with both of you and we would like to extend our thanks for your continued support throughout this
project.
Sincerely,
Jenna Simpson, Project Manager
Jovian Design
1151 Richmond Street,
London, Ontario, Canada
N6A 3K7

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Table of Contents
Table of Contents............................................................................................................................................................................ i
Table of Tables .............................................................................................................................................................................vii
Table of Figures ...........................................................................................................................................................................viii
Glossary of Terms..........................................................................................................................................................................ix
List of Abbreviations......................................................................................................................................................................xii
Executive Summary .....................................................................................................................................................................xiii
1. Introduction ................................................................................................................................................................................ 1
1.1 General................................................................................................................................................................................. 1
1.2 Urbanization in the City of London ........................................................................................................................................ 2
2. City of London Development Objectives..................................................................................................................................... 4
2.1 Introduction........................................................................................................................................................................... 4
2.2 Official Plan for the City of London........................................................................................................................................ 4
2.3 Needs & Guidelines .............................................................................................................................................................. 4
3. Project Approach & Methodology ............................................................................................................................................... 5
3.1 Introduction........................................................................................................................................................................... 5
3.2 Site Visit Preparation ............................................................................................................................................................ 5
3.3 Site Visit................................................................................................................................................................................ 5
3.4 Site Context .......................................................................................................................................................................... 5
3.5 City of London Development Objectives ............................................................................................................................... 5
3.6 Surface Analysis................................................................................................................................................................... 5
3.7 Stormwater Management Inventory ...................................................................................................................................... 5
3.8 Permeable Surface Research, Analysis & Summary............................................................................................................. 5

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3.9 Net Water Savings................................................................................................................................................................ 5
3.10 Financial Analysis............................................................................................................................................................... 6
3.11 Conclusions & Recommendations ...................................................................................................................................... 6
4. Site Context – Wonderland Power Centre.................................................................................................................................. 7
5. Surface Analysis ........................................................................................................................................................................ 9
5.1 Introduction........................................................................................................................................................................... 9
5.2 Study Area Surfaces............................................................................................................................................................. 9
5.2.1 Roofs ............................................................................................................................................................................. 9
5.2.2 Parking Lots and Low-Traffic Roadways ...................................................................................................................... 10
5.2.3 Sidewalks..................................................................................................................................................................... 11
5.2.4 Medians ....................................................................................................................................................................... 11
5.2.5 Stormwater Management Facilities .............................................................................................................................. 12
5.2.6 Other Surfaces............................................................................................................................................................. 12
6. Stormwater Management Inventory ......................................................................................................................................... 14
6.1 Introduction......................................................................................................................................................................... 14
6.2 Construction of Bradley Avenue SWM Facility.................................................................................................................... 14
6.3 Servicing Capacity of Bradley Avenue SWM Facility .......................................................................................................... 14
6.4 Subsurface Conditions........................................................................................................................................................ 16
6.5 Maintenance of the SWM Facility ....................................................................................................................................... 16
7. Permeable Surfaces Overview................................................................................................................................................. 17
7.1 Introduction......................................................................................................................................................................... 17
7.2 Permeable Asphalt ............................................................................................................................................................. 19
7.2.1 Introduction .................................................................................................................................................................. 19
7.2.2 Function and Application.............................................................................................................................................. 19

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7.2.3 Durability ...................................................................................................................................................................... 20
7.2.4 Maintenance................................................................................................................................................................. 21
7.2.5 Cost.............................................................................................................................................................................. 21
7.2.6 Benefits and Limitations ............................................................................................................................................... 21
7.3 Permeable Concrete........................................................................................................................................................... 22
7.3.1 Introduction .................................................................................................................................................................. 22
7.3.2 Function and Application .............................................................................................................................................. 23
7.3.3 Durability ...................................................................................................................................................................... 27
7.3.4 Maintenance................................................................................................................................................................. 27
7.3.5 Cost.............................................................................................................................................................................. 28
7.3.7 Supplementary Cementitious Materials ........................................................................................................................ 29
7.4 Permeable Pavement De-icing agents................................................................................................................................ 29
7.5 Green Roofs ....................................................................................................................................................................... 31
7.5.1 Introduction .................................................................................................................................................................. 31
7.5.2 Function and Application .............................................................................................................................................. 31
7.5.3 Durability ...................................................................................................................................................................... 34
7.5.4 Maintenance................................................................................................................................................................. 34
7.5.5 Cost.............................................................................................................................................................................. 35
7.5.6 Extensive Green Roofs................................................................................................................................................. 36
7.5.7 Intensive Green Roofs.................................................................................................................................................. 37
7.5.9 Public Policy................................................................................................................................................................. 38
7.6 Additional Benefits of Permeable Surfaces ......................................................................................................................... 38

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7.6.1 Urban Heat Island ........................................................................................................................................................ 38
7.6.2 LEED ........................................................................................................................................................................... 40
8. Product Analysis ...................................................................................................................................................................... 41
8.1 Introduction......................................................................................................................................................................... 41
8.2 PICP................................................................................................................................................................................... 41
8.3 Concrete & Asphalt............................................................................................................................................................. 41
8.4 Green Roofs....................................................................................................................................................................... 42
9. Net Water Savings ................................................................................................................................................................... 44
9.1 Introduction......................................................................................................................................................................... 44
9.2 Wonderland Power Centre ................................................................................................................................................. 45
9.2.1 Scenario 1a: 100% Pervious Coverage of Hard Surfaces using Permeable Asphalt or Porous Concrete and Extensive
Green Roofs ......................................................................................................................................................................... 45
9.2.2 Scenario 1b: 75% Pervious Coverage of Hard Surfaces using Permeable Asphalt or Porous Concrete and Extensive
Green Roofs ......................................................................................................................................................................... 46
9.2.3 Scenario 1c: 50% Pervious Coverage of Hard Surfaces Using Permeable Asphalt or Porous Concrete and Extensive
Green Roofs ......................................................................................................................................................................... 46
9.2.4 Scenario 1d: 25% Pervious Coverage of Hard Surfaces Using Permeable Asphalt or Porous Concrete and Extensive
Green Roofs ......................................................................................................................................................................... 46
9.2.5 Scenario 2a: 100% Pervious Coverage of Hard Surfaces using PICP and Extensive Green Roofs.............................. 49
9.2.6 Scenario 2b: 75% Pervious Coverage of Hard Surface using PICP and Extensive Green Roofs ................................. 49
9.2.7 Scenario 2c: 50% Pervious Coverage of Hard Surfaces using PICP and Extensive Green Roofs................................ 49
9.2.8 Scenario 2d: 25% Pervious Coverage of Hard Surfaces using PICP and Extensive Green Roofs................................ 50
9.3 Net-Water Savings Analysis Summary ............................................................................................................................... 50
10. Financial Analysis .................................................................................................................................................................. 52
10.1 Introduction....................................................................................................................................................................... 52

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10.2 Net Present Value & Equivalent Annual Cost.................................................................................................................... 52
10.2.1 Net Present Value and Prorated Net Present Value ................................................................................................... 52
10.3 Equivalent Annual Cost..................................................................................................................................................... 53
10.4 Product Comparisons ....................................................................................................................................................... 53
10.5 Wonderland Power Centre................................................................................................................................................ 55
10.6 Additional Economic Benefits............................................................................................................................................ 57
10.6.1 Monetary Value of Environmental Benefits................................................................................................................. 57
11. Conclusions............................................................................................................................................................................ 59
11.1 Durability........................................................................................................................................................................... 59
11.2 Net water Savings............................................................................................................................................................. 59
11.3 Financial Analysis ............................................................................................................................................................. 60
11.4 Summary .......................................................................................................................................................................... 61
12. Recommendations ................................................................................................................................................................. 63
12.1 Durability........................................................................................................................................................................... 63
12.2 Net Water Savings............................................................................................................................................................ 63
12.3 Financial Analysis ............................................................................................................................................................. 63
12.4 Additional Recommendations ........................................................................................................................................... 63
References................................................................................................................................................................................... 64
Appendices .................................................................................................................................................................................. 75
Appendix A. 1: Site Context ...................................................................................................................................................... 76
Appendix A. 2: Surface Analysis............................................................................................................................................... 77
Appendix A. 3: Stormwater Management Inventory .................................................................................................................. 78
Appendix B. 1: Product Analysis............................................................................................................................................... 79
Appendix B. 2: Net Water Savings: Calculations....................................................................................................................... 80

vi
Appendix B. 3: Financial Analysis: Calculations........................................................................................................................ 94
Appendix C: Project Timeline ................................................................................................................................................... 99

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Table of Tables
Table 1: Surface Analysis for the WPC Study Site ......................................................................................................................... 9
Table 2: Bradley Avenue SWM facility volume summary.............................................................................................................. 14
Table 3: SWM facility discharge and storage summary for varying rain events............................................................................. 15
Table 4: Factors affecting infiltration rates of permeable concrete products ................................................................................. 23
Table 5: Base storage capacity of PICP and CGP........................................................................................................................ 25
Table 6: Applications of pervious concrete ................................................................................................................................... 26
Table 7: Comparison between extensive and intensive green roof systems................................................................................. 33
Table 8: Component costs of extensive green roofs assuming an existing building with sufficient loading capacity, roof hatch and
ladder access ................................................................................................................................................................ 36
Table 9: Component cost of intensive green roofs assuming an existing building with sufficient loading capacity, roof hatch and
ladder access ................................................................................................................................................................ 37
Table 10: Comparison of feasibility parameters for various permeable products .......................................................................... 43
Table 11: Runoff coefficients........................................................................................................................................................ 45
Table 12: Comparison of runoff reductions for conventional and permeable surfaces at the WPC: Pavement and green roofs.... 48
Table 13: SWM facility volume reduction resulting from pervious surface coverage at the WPC: Pavement and green roofs....... 48
Table 14: Comparison of runoff reductions for conventional and permeable surfaces at the WPC: PICP and green roofs ........... 51
Table 15: SWM facility volume reduction resulting from pervious surface coverage at the WPC: PICP and green roofs .............. 51
Table 16: Financial comparisons of different surfaces.................................................................................................................. 55
Table 17: Financial comparisons of different surface applications at the WPC ............................................................................. 57
Table 18: Financial benefits of green roofs in Toronto, Ontario assuming 50 Million m2
of available roof space........................... 58
Table 19: Overall product comparisons ........................................................................................................................................ 62

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Table of Figures
Figure 1: The relationship between impervious and pervious area and extent of sewerage ........................................................... 2
Figure 2: Study Area ...................................................................................................................................................................... 8
Figure 3: Roof surfaces in the WPC Study Area showing a) asphalt shingles on a commercial building, b) low-sloped impervious
roof on a commercial building, and c) clay tiles on a commercial building .................................................................... 10
Figure 4: Asphalt surfaces in the WPC Study Area ...................................................................................................................... 11
Figure 5: Commercial concrete sidewalks in the WPC Study Area............................................................................................... 11
Figure 6: Medians are dispersed throughout commercial parking lots to help guide traffic and provide aesthetic relief from
dominating impervious pavements ............................................................................................................................... 12
Figure 7: Stormwater Management Pond adjacent to the WPC showing a) an inflow culvert, b) a near full pond, overflow spillway
and forebay, c) and emergency spillway ...................................................................................................................... 12
Figure 8: Other surfaces within the WPC include a) roofed shopping cart corrals and b) landscaped areas................................. 13
Figure 9: Interaction between rainwater and tradition/conventional pavement.............................................................................. 18
Figure 10: Interaction between rainwater and permeable pavement ............................................................................................ 18
Figure 11: Typical cross-section of a permeable asphalt surface ................................................................................................. 19
Figure 12: Winter performance vs. general indicators, including runoff control, pollution control, and level of integration, for
different stormwater components ................................................................................................................................. 21
Figure 13: a) PICP, b) CGP, c) PC............................................................................................................................................... 22
Figure 14: Typical installation for exfiltration................................................................................................................................. 24
Figure 15: Typical installation of porous concrete surface............................................................................................................ 26
Figure 16: Typical cross-section of a green roof........................................................................................................................... 31
Figure 17: Rural and urban heat characteristics........................................................................................................................... 39

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Glossary of Terms
Annual Precipitation – The annual total precipitation is the
sum of the rainfall and the assumed water equivalent of the
snowfall for a given year (Natural Resources Canada, 2003)
Asphalt – Also known as conventional asphalt; an
impermeable surface comprised of asphalt cement and
coarse aggregates, including stone, sand, and gravel
compacted together (Freemantle, 1999)
Baseflow – Water that, having infiltrated the soil surface,
percolates to the groundwater table and moves laterally to
reappear as surface runoff (University of Florida, 2010)
Biodegradation – The breaking down of organic and
inorganic substances by biological action, a process usually
involving bacteria and fungi (Fischel, 2001)
Bradley Avenue Stormwater Management Facility – The
Stormwater Management Facility at Wonderland Power
Centre
Concrete – Also known as conventional concrete; an
impermeable construction material comprised usually of
Portland cement, and other materials, including aggregates,
water, and chemical admixtures (ICPI, 2008)
Client – Also known as the City of London; the City;
Environmental & Engineering Services Department,
Consultant – Jovian Design; the Design team
De-icing Agent – A snow and ice control strategy for
prevention of a strong bond between frozen precipitation or
frost and a pavement surface by application of a chemical
freezing point depressant prior to or during a storm (Fischel,
2001)
Eutrophication – The enrichment of water with nutrients,
such as phosphorus resulting in the increase in numbers of
aquatic algae in the water (Fischel, 2001)
Evapotranspiration – The merging of evaporation
(movement of free water molecules away from a wet surface
into air that is less saturated) and transpiration (movement of
water vapour out through the pores in vegetation) into one
term (Christopherson, 2005)
Exfiltration – A loss of water from a drainage system as the
result of percolation or absorption into the surrounding soil
(HydroCAD, 2009)
Freeze-thaw – A weathering process in which intermittent
periods of freezing and thawing act upon a substance,
leading to its gradual breakdown by forces of water crystal
expansion and contraction (Christopherson, 2005)
Green Roof – A roof with a vegetative cover, used passively
to address environmental issues in mainly urban settings
(Kosreo & Ries, 2007)
Green Space – Areas generally planted with trees, shrubs,
herbaceous perennials and decorative grasses, rocks, and
water features; used mainly for aesthetics and recreation

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Groundwater – Water beneath the surface that is beyond
the soil-root zone; a major source of potable water
(Christopherson, 2005)
Impermeable Surfaces – Consist of surfaces which restrict
infiltration of precipitation due to decreased drainage
capacity (Shuster et al., 2005)
Infiltration – Also known as percolation; water access to
subsurface regions of soil moisture storage through
penetration of the soil surface (Christopherson, 2005)
Leadership in Energy and Environmental Design (LEED)
– A green building rating system that encourages and
accelerates the global adoption of sustainable green building
and development practices through the creation and
implementation of universally accepted performance criteria
(CaGBC, 2004)
Low-Traffic Urban Roadways – Roads and access
roadways generally characterized by low to moderate
speeds and low to moderate volumes of automobiles per day
Median – A raised structure used to organize and direct
automobile traffic, as well as to provide shade and enhance
aesthetic value to commercial parking lots (Celestian &
Martin, 2003)
Permeable Surfaces – Consist of a variety of types of
pavement, pavers and other devices that provide stormwater
infiltration while serving as a structural surface (University of
Florida, 2008)
Permeable Asphalt – Also known as porous or pervious
asphalt; an adaptation of conventional asphalt in which fine
sediments are removed, resulting in a network of
continuously linked voids to allow the passage of fluids
through the surface (Beecham, 2007; Boving, 2008)
R-value – A commercial unit used to measure the
effectiveness of thermal insulation. The R-value of the
insulator is defined as 1 divided by the thermal conductance
per inch (Rowlett, 2002)
Rational Method – An equation that postulates a
proportionality between peak discharge and rainfall intensity
(Dingman, 2002)
Return Period – The frequency with which one would
expect, on average, a given precipitation event to recur
(Cornell University, 2007)
Roof – A cover used to protect the interior and structural
components of a building from weather elements, particularly
precipitation
Sidewalk – A raised structure used to provide a suitable
transit route and safe place for pedestrians to walk
Storm Drain – An opening that leads to an underground
pipe or open ditch for transporting surface runoff, separate
from a sanitary sewer or wastewater system (Environmental
Services Water Quality Division, 2009)
Stormwater Management (SWM) Facilities – Facilities
designed to temporarily collect runoff from localized storm

xi
sewer systems after a rainfall or snowmelt event (Ministry of
Environment [MOE], 2003)
Stormwater Runoff – Excessive water, derived from
precipitation or snowmelt that ultimately reaches a drainage
area (Oke, 2006)
Toxicity – The potential of a chemical or compound to
cause adverse effects on living organisms (Fischel, 2001)
Urban Heat Island – An effect caused by the warming of
urban centres in comparison to rural areas as a result of
increasing surface characteristics which may augment
surrounding atmospheric temperatures (U.S. Environmental
Protection Agency, 2009)
Urbanization – The physical growth of urban areas as a
result of global change, in which individuals move from rural
communities to more dense urban areas (Barrow, 2003)
Water Table – The upper surface of groundwater; the
contact point between the zone of saturation and aeration in
an unconfined aquifer (Christopherson, 2005)

xii
List of Abbreviations
AAR - alkali–aggregate reaction
CaCl2 – calcium chloride
CAD – Canadian dollars
CaGBC - Canadian Green Building Council
CGP – concrete grid pavers
CMA – calcium magnesium acetate
COTA – City of Toronto Act
EAC – Equivalent Annual Cost
GTA – Greater Toronto Area
GGBFS – ground granulated blast furnace slag
ICPI – Interlocking Concrete Pavement Institute
KCl – potassium chloride
LEED – Leadership in Energy and Environmental Design
MgCl2 – magnesium chloride
NaCl – sodium chloride
NPV – Net Present Value
O&M – operation and maintenance
OEPA – Ontario Environmental Protection Act
PC – porous concrete
PICP – permeable interlocking concrete pavers
SCM – supplementary cementitious materials
SS – Sustainability Site
SWM – stormwater management
TRCA – Toronto and Region Conservation Authority
UHI – Urban Heat Island effect
USD – US dollars
WPC – Wonderland Power Centre

xiii
Executive Summary
The Engineering and Review Division, Environmental and
Engineering Services Department of the City of London has
retained Jovian Design to undertake a Permeable Surfaces
Stormwater Management Feasibility Study. The primary purpose
of this study is to evaluate the durability, net water reduction and
financial feasibility of permeable surfaces compared to
conventional materials, using the following project scope:
The Consultants will research permeable surfaces and compare
permeable products to existing conventional materials. The
purpose of this comparison is to determine the effectiveness of
each product including permeability, cost and durability while
ensuring that the development objectives of the City are met. The
Wonderland Power Centre will be assessed as a sample of this
comparison.
Peer reviewed journal articles and other literature show that
permeable surfaces are in many instances feasible for large scale
developments such as the Wonderland Power Centre. Primary
research supported these findings. Several permeable product
contractors and distributors operate within Southern Ontario and
offer products that are locally feasible in terms of cost, net-water
savings, and durability.
Comparative product analyses for local permeable pavements,
pavers, and green roof companies showed that not only are these
products readily available in Southern Ontario, but that the
lifespan and maintenance requirements of these products are
competitive with conventional pavements and roofing systems.
All permeable products proved to reduce the volume of
stormwater runoff when compared to conventional surfaces.
Within the scope of the permeable surfaces analyzed, different
product typologies offered varying levels of infiltration.
Depending on the level of integration and combination of
permeable products, the volume of water being sent to
stormwater facilities can be reduced by up to 62% in ideal
conditions. This, in turn, can represent a direct cost savings for
new developments, as the size of planned stormwater
management facilities can be reduced.
Most permeable products proved to be more expensive than
conventional materials. However, depending on the proposed
application and surface area, some permeable products are very
similar in Net Present Value and Equivalent Annual Cost to their
conventional counterparts. In the case of using porous concrete
for sidewalks, a general cost savings was discovered compared to
using conventional concrete for the same application.
Properly installed and maintained permeable pavements also
have the potential to reduce Urban Heat Island effects, improve
driving safety, encourage urban tree and plant growth, gain LEED
credits, reduce stormwater quantity and enhance water quality.
There may also be financial savings due to the benefits of
stormwater reduction, including the impact on combined sewer
overflow, improvement in air quality, reduction in direct energy
use and other environmental and social benefits such as the
aesthetic improvement of urban landscapes, and increased
property values.

PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY
APRIL 2010 Page | 1
1. Introduction
1.1 General
Jovian Design (Consultants) was retained by the
Engineering Review Division, Environmental and
Engineering Services Department of the City of London
(Client) to undertake a permeable surface stormwater
management feasibility study. The intent of this project is to
evaluate the feasibility of various permeable technologies in
comparison to conventional impermeable materials, as
described in the Project Scope below, using the Wonderland
Power Centre in London, Ontario as a baseline study. This
analysis will help determine the feasibility of implementing
permeable surfaces.
Initially, a project proposal was developed by the Consultant
and refined in consultation with the Client to better reflect the
expectations of the City. Under the guidance of Dr. Omar
Ouda, the Consultants:
a) Developed a comprehensive site inventory for the
Wonderland Power Centre including site context,
surface analysis and a stormwater management
inventory
b) Conducted a literature review of permeable surfaces
to outline the function and application, durability,
maintenance, cost, and benefits and limitations of
each permeable surface type, as well as other
pertinent information
c) Contacted several local distributors and contractors
in order to gather primary information about
permeable products available in Southern Ontario
d) Analyzed the net water savings capacity of each
permeable product
e) Conducted a financial analysis of each permeable
product
f) Developed conclusions and recommendations to
reflect the findings of the Feasibility Study
This Study was completed as a result of contributions from a
number of individuals from various organizations. The
Consultants would therefore like to thank the following:
Project Scope
The Consultants will research permeable surfaces and
compare permeable products to existing conventional
materials. The purpose of this comparison is to determine
the effectiveness of each product including permeability,
cost and durability while ensuring that the development
objectives of the City are met. The Wonderland Power
Centre will be assessed as a sample of this comparison.

JOVIAN DESIGN
Page | 2
Ismail Abushehada, Ph.D., P. Eng.
City of London
Michal Kuratczyk, M.Acc.
Deloitte
Lois Burgess, P.Eng.
City of London
Connor Malloy
Duo Building Ltd.
Darcy Decaluwe
Stone in Style
Omar Ouda, Ph.D., P.Eng, PMP
University of Western Ontario
Vito Frijia
Southside Group
Denis Taves, OALA
Gardens in the Sky
Carol Hayward
City of London
Jarrett Woodward
Grand River Natural Stone Ltd.
1.2 Urbanization in the City of London
The City of London is located in the heart of south-western
Ontario, within close proximity to both Lake Huron and Lake
Erie. The City‟s population of more than 350,000 is expected
to grow steadily over the next two decades (Statistics
Canada, 2006). The City has also undergone significant
growth over the last 15 years due to a persistent
developmental strategy (City of London, 2010).
Increased impervious surface area is a consequence of
urbanization, in which there may be significant ensuing
effects on the hydrologic cycle (Shuster et al., 2005; Barnes
et al., 2002). This increasing proportion of impervious
surface creates shorter lag times between the arrival of
precipitation and consequent high runoff rates and total flow
volume (Shuster et al., 2005). As a result, a municipality‟s
sewershed or stormwater management system may be put
under increasing pressure in order to compensate for this
additional volume of runoff (Figure 1).
Figure 1: The relationship between impervious and pervious area
and extent of sewerage
Source: Shuster et al., 2005.
Increasing stress on existing stormwater infrastructure
provides incentive for municipalities like the City of London
to explore the feasibility of innovative strategies such as the
implementation of permeable surfaces.
Stormwater management facilities present an opportunity for
the City to implement strategies that address municipal
economic, social, and environmental interests. Currently
there are approximately 85 stormwater facilities in London
and over 100 more are planned for future developments.

APRIL 2010 Page | 3
These systems are expensive to build and maintain, with
facilities costing millions of dollars each.
Permeable surfaces can potentially improve the cost
effectiveness of storm water management systems, thereby
alleviating pressure on municipal financial resources. In
addition, the implementation of permeable surfaces can
result in environmental and social benefits. Increasing
urbanization and subsequent Urban Heat Island effect,
among other things, make the implementation of permeable
surfaces attractive to forward-thinking municipalities.

JOVIAN DESIGN
Page | 4
2. City of London Development Objectives
2.1 Introduction
One objective of this Study is to establish a basis for the
inclusion of permeable surface stormwater management
systems as part of the City of London Design Standards or
urban design guidelines.
Although there is a wide range of permeable products on the
North American market, not all products are suitable for the
City of London or meet the City‟s development goals and
objectives. As there are currently no specific design
standards in London pertaining to permeable surfaces, the
Consultants have developed a list of applicable development
guidelines in order to aid in the evaluation of available
permeable products.
2.2 Official Plan for the City of London
The Official Plan for the City of London contains objectives
and policies to guide physical development within the
municipality (City of London, 2010). It provides direction for
the allocation of land use and provision of municipal services
and facilities in order to promote orderly urban growth and
compatibility among land uses.
Although the Official Plan‟s primary function is to establish
policies for the physical development of the City of London, it
also has regard for relevant social, economic and
environmental matters. As such, various sections of the
Official Plan were examined in order to help determine the
City of London‟s development needs and establish support
for the implementation of permeable surfaces within the City.
2.3 Needs & Guidelines
The following provisions are necessary for parking,
roadways, sidewalks and related developments in the City of
London:
Accommodate low-level traffic and heavy vehicular
loads such as fire engines, delivery trucks, and heavy
machinery
Allow for seasonal maintenance and snow clearing
Provide easy access and use by handicapped
persons
The following objectives should be considered when
evaluating permeable surfaces:
Enhance hydrology, geomorphology and water
quality by protecting and promoting groundwater
recharge
Enhance the pedestrian environment while providing
easy access and use by all and promoting public
safety
Minimize inconvenience and damage from surface
ponding and flooding
Maximize the cost effectiveness of stormwater
management facilities
Minimize water and energy consumption through
resource conservation, landscaping and innovative
design features and servicing techniques
Promote the reuse and recycling of wastes
Protect, maintain and improve surface and
groundwater quality and quantity

APRIL 2010 Page | 5
3. Project Approach & Methodology
3.1 Introduction
The following is an account of the methodology used to
complete this Report and develop conclusions and
recommendations. A detailed project plan timeline can be
found in Appendix C.
3.2 Site Visit Preparation
Maps and satellite images were gathered from online
databases to begin the initial geographic analysis of the
Study Site.
3.3 Site Visit
The Consultants travelled to the Study Site to perform a
visual analysis of the Wonderland Power Centre for the
purposes of the Surface Analysis and Stormwater
Management Inventory (below).
3.4 Site Context
Following the Site Visit, a brief report discussing the existing
land use patterns and geographic location of the Study Site
was developed.
3.5 City of London Development Objectives
A list of applicable development objectives for the
implementation of permeable surfaces was developed based
on discussions with the Client and reviews of policies and
design standards governing development within the City of
London.
3.6 Surface Analysis
Using the City of London Public Zoning Map and the findings
from the Site Visit and Site Context, a detailed Surface
Analysis was conducted for the Wonderland Power Centre.
3.7 Stormwater Management Inventory
Functional drawings of the Wonderland Power Centre were
provided by the Clients. Using this resource and information
gathered from online databases, the Consultants assessed
the stormwater facility on the Study Site with regard to its
service capacity, lifespan, and required maintenance.
3.8 Permeable Surface Research, Analysis &
Summary
A review of the current literature on permeable surfaces,
green roofs and stormwater management approaches and
techniques was conducted. Research was primarily focused
on the typology, water retention capacity, durability and cost
of permeable surfaces and green roofs.
The Consultants also contacted several local distributors and
contractors in order to gather primary information about
permeable products available in Southern Ontario.
Findings from the Permeable Surface Research, Analysis &
Summary are found throughout this Report, most notably in
the Permeable Surface Overview and Product Analysis.
3.9 Net Water Savings
A comparative analysis of the net water savings of each type
of permeable surface and green roof was conducted using
known runoff coefficients and the calculations found within
the Surface Analysis of this Report.

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The water retention capacity of the existing Study Site and
stormwater retention pond was calculated as a baseline, and
different permeable surface coverage scenarios were
formulated.
3.10 Financial Analysis
The current capital costs, operational and maintenance
costs, and potential savings from the reduction of stormwater
management facilities as a result of each permeable surface
were compared using the Net Present Value and Equivalent
Annual Cost financial calculations.
3.11 Conclusions & Recommendations
Conclusions and recommendations were formulated based
on the findings outlined in this Report. The function and
application, durability, maintenance, cost, and benefits and
limitations of all permeable pavement and green roof options
were considered.

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4. Site Context – Wonderland Power Centre
The Wonderland Power Centre (WPC) is located in the
southeast corner of Wonderland Road and Southdale Road
in London, Ontario. Designated as a “Commercial Policy
Area” in Schedule A of the City of London Official Plan
(Appendix A) (City of London, 2006), the WPC is a fully
occupied regional shopping centre, covering approximately
20 hectares of commercial land (Southside Group, 2008).
The WPC is bound by the Westmount Estates and
Westmount Estates II high density residential buildings
(Tricar, 2010) to the east, Southdale Road to the north and
Wonderland Road to the west. The site is mirrored by a
similar commercial development, the Westwood Power
Centre, across Wonderland Road which utilizes the same
stormwater management (SWM) facility. To the immediate
south of the WPC commercial development is the “Old
Wonderland Mall” property. This area has been included as
part of the Study Site (Figure 2).
It is important to note that although the entire SWM
watershed includes the Westwood Power Centre, the Study
Site used in this Report only includes the fully developed
Wonderland Power Centre, the Old Wonderland Mall, and
the SWM facility itself.
From an aerial perspective, the WPC can be divided into
four general types of hard surfaces: paved parking lots
and/or roadways; concrete sidewalks; roofs, and;
landscaped areas. As seen in the map below, the majority of
the WPC interior is paved asphalt parking spaces or
roadways. The perimeter of the site is lined with commercial
developments (the majority of which have low-sloped roofs),
and there are small landscaped medians dispersed
throughout the site. Perhaps most notably, the south-eastern
corner of the Study Site contains the stormwater
management facility that collects runoff for the entire Study
area.
With the exception of the soft, landscaped surfaces sparsely
located throughout the Site, the Study Area is composed
entirely of hard surfaces that do not allow water to permeate
into the underlying soil. This is explored in further detail in
the following section.
It is important to note that the WPC is only intended to
provide a baseline analysis for this Feasibility Study.

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Figure 2: Study Area
LEGEND
Entire Study Area
WPC & Old
Wonderland Mall
Commercial
Areas
Stormwater
Management
Facility
Stormwater
Management
Watershed
Modified from: City of London, 2010

APRIL 2010 Page | 9
5. Surface Analysis
5.1 Introduction
The Study Area covers approximately 220,000 m2
of land
(Table 1), of which approximately 70% is comprised of
impermeable surfaces. In other words, more than two-thirds
of all precipitation that falls on the site may begin to flow as
urban runoff, with minimal, if any vegetative buffers to
intercept it. This is a substantial amount of surface flow, and
therefore requires a catchment area (i.e., SWM facility) of
sufficient size to store the excess water and mitigate further
runoff. The cost to build such structures generally requires a
significant amount of funds for municipalities and, ultimately,
taxpayers (AECOM, 2009).
The primary impermeable surfaces examined in this section
of the Report include roofs, parking lots and low-traffic
roadways, and sidewalks. Other surfaces that will be
examined include medians, green spaces, and temporary
structures (e.g., shopping cart corrals). Calculations for this
analysis were completed through on-site investigations and
satellite interpretation using a modified City of London Public
Zoning Map (Appendix A).
5.2 Study Area Surfaces
5.2.1 Roofs
The primary function of roofs is to protect the interior and
structural components of a building from weather elements,
particularly precipitation. Roofs within the Wonderland
Power Centre are the second most prevalent surface,
making-up approximately 20% of the entire Study Area.
Approximately 17% of the Study Area is comprised of low-
sloped, commercial roofs, whereas sloped or pitched roofs
represent approximately 2% of the Study Site.
Table 1: Surface Analysis for the WPC Study Site
The low-sloped roofs are generally sealed with an
impervious asphalt layer, while pitched roofs are generally
covered with impervious asphalt shingles (e.g., Loblaw
Superstore) or other highly impervious materials such as
clay tiles (e.g., Angelo‟s Italian Bakery and Deli). In both
instances, precipitation is directed from the roof to a
drainage system consisting of gutters, downspouts, and
piping, and ultimately to the surface below (either
impermeable asphalt or cement, or permeable grass
surfaces which allow infiltration). Vegetated green roofs may
act as an intermediate step to this process, intercepting
Surface Analysis for the Wonderland Power Centre
Surface Type Area (m2
) Area (%)
Low-sloped Roofs 37,550 17
Sloped Roofs 5,193 2
Parking Lots/Roadways 96,161 44
Sidewalks 14,812 7
Medians 9,987 5
SWM Pond 42,983 19
Others (e.g., Green Space;
Temporary Structures)
14,098 6
TOTAL 220,784 100

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precipitation and helping to reduce runoff from reaching the
SWM facility (VanWoert et al., 2005).
Figure 3: Roof surfaces in the WPC Study Area showing a) asphalt shingles on a commercial building, b) low-sloped impervious roof on a
commercial building, and c) clay tiles on a commercial building
5.2.2 Parking Lots and Low-Traffic Roadways
The principal function of parking lots is to accommodate a
steady volume of visitors and their automobiles. Parking lots
within the WPC site are the most significant surface
typology, composing more than 40% of the entire Study
Area. Part of this percentage includes a series of low-traffic
roadways connecting the parking lots together. Generally
located around the peripheries of parking lots and buildings,
these features are primarily coated with impermeable
asphalt, but may also include concrete pavement as well.
Porous pavements, including permeable asphalt, porous
concrete, Permeable Interlocking Concrete Pavers (PICP)
and grid pavers, may be used to divert urban runoff from
SWM facilities, as precipitation is able to pass through the
paved surfaces and recharge groundwater sources or the
water table (Beecham, 2007; Boving, 2008).
a b c

APRIL 2010 Page | 11
Figure 4: Asphalt surfaces in the WPC Study Area
5.2.3 Sidewalks
The main function of sidewalks is to provide a suitable transit
route and safe place for pedestrians to travel, by separating
them from vehicular traffic. Raised sidewalks within the
Wonderland Power Centre represent an overall surface
composition of close to 7% of the entire Study Area.
Sidewalks are generally composed of impermeable concrete
pavement which prevents percolation of precipitation and
snow melt (Bean et al., 2007). Permeable pavers and porous
concrete may be used to help alleviate the stress of surface
runoff on SWM facilities by increasing infiltration rates on
site. Although they make up a small percentage of the total
area of the WPC, sidewalks may be the most feasible
surface to change, while acting as a consistent penetrable
buffer.
Figure 5: Commercial concrete sidewalks in the WPC Study Area
5.2.4 Medians
The primary function of medians is to organize and direct
automobile traffic, as well as to provide shade and enhance
the aesthetic value of commercial parking lots (Celestian &
Martin, 2003). Medians within the Wonderland Power
Centre are the least prevalent surface, making-up slightly
more than 4% of the entire Study Area. They are sparsely
located within each parking section, and generally contain
trees, shrubs, herbaceous perennials, ornamental grasses,
and in some cases decorative stone or mulches. These
decorated medians are not considered to be “hard” surfaces,
and therefore may effectively catch and store incident
precipitation due to their vegetative nature and soil-based
structure. However, due to their elevation (i.e., about 4 to 6

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inches off the ground), medians generally do not help reduce
stormwater runoff or flow over the parking lots.
Figure 6: Medians are dispersed throughout commercial parking lots
to help guide traffic and provide aesthetic relief from
dominating impervious pavements
5.2.5 Stormwater Management Facilities
The main function of a SWM facility is to store runoff from
precipitation and snow melt, which may otherwise lead to
flooding or erosion, and adversely affect water quality (MOE,
2003). The SWM facility used to mitigate runoff at the
Wonderland Power Centre makes up nearly 20% of the
entire Study Area. More detail on this facility can be found in
the Stormwater Inventory section of this Report.
Figure 7: Stormwater Management Pond adjacent to the WPC
showing a) an inflow culvert, b) a near full pond, overflow
spillway and forebay, c) and emergency spillway
5.2.6 Other Surfaces
Landscaped green spaces within the Wonderland Power
Centre site represent slightly more than 6% of the Study
Area. These spaces are generally composed of trees,
a
b c

shrubs, herbaceous perennials and decorative grasses,
rocks, and maintained grass lawns. Although their function
is mainly for aesthetic and recreational purposes, urban
green spaces may help alleviate the problem of surface
runoff by increasing infiltration rates and acting as a
penetrable buffer (Benedict & McMahon, 2002).
Landscaped green spaces may be intensified to provide a
more significant role or function, both as an aesthetic tool
and as a buffer, especially in commercial and residential
zones where impermeable surfaces generally dominate.
Temporary structures, including roofed shopping cart corrals
and seasonal greenhouses are also present within the Study
Area.
Figure 8: Other surfaces within the WPC include a) roofed shopping
cart corrals and b) landscaped areas

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6. Stormwater Management Inventory
6.1 Introduction
The WPC is wholly serviced by the Bradley Avenue
Stormwater Management Facility within the Pincombe Drain
catchment area (Appendix A). A Stormwater Management
Inventory is required to assess the present condition and
required maintenance of the SWM facility at the Wonderland
Power Centre. As such, functional designs, entitled Final
Stormwater Management Report for the Bradley Avenue
Stormwater Management Facility were obtained from the
City of London Engineering and Review Division, and used
to assess the servicing capacity, present condition and
required maintenance of the SWM facility.
6.2 Construction of Bradley Avenue SWM Facility
The total projected cost for the Bradley Avenue SWM
facility was $2,456,660 of which the cost for
construction of inlet/outlet sewers was $636,660
(AECOM, 2009).
Prior to construction, on-site siltation and erosion
control measures were taken in order to prevent the
transportation of eroded soils off-site into
downstream properties or watercourses. These
measures included the installation of 140m of regular
duty silt fences and 300m of heavy duty silt fences.
A sediment trap of approximately 70m x 20m x 1m
was constructed adjacent to the SWM Facility, to
store sediment deposition.
6.3 Servicing Capacity of Bradley Avenue SWM Facility
The City of London averages 987mm of precipitation per
year (Environment Canada, 2010).
As illustrated in Table 2, the Bradley Avenue SWM facility
has a total stormwater retention capacity of 45,238m3
.
Generally speaking, the facility has a total permanent
volume of 7.500m3
, with a drawdown time of 72 hours
(Development Engineering, 2005).
Table 2: Bradley Avenue SWM facility volume summary
Bradley Avenue SWM Facility Volume Summary
Water Quality Volume Required Provided
Permanent pool volume per
hectare based on protection
level and imperviousness (MOE)
115 m3
/ha 118 m3
/ha
Total Permanent pool volume 5615 m3
7500 m3
Total SWM Facility Volume – 45238 m3
Baseflow and Erosion Volume Required Provided
Total storage volume per hectare 200 m3
/ha 160 m3
/ha
Total baseflow and erosion
volume
12685 m3
10147 m3
Source: Development Engineering, 2005

Table 3 summarizes the return period of flooding as used in
the Bradley Avenue SWM facility modeling. The stormwater
discharge into the SWM facility, for return periods of 2, 5, 10,
25, 50, 100 and 250 years has been tabulated and the
volume corresponding to the respective flooding events has
been calculated (Development Engineering, 2005).
In the event of a 250 year storm (6 hour duration), 26,524 m3
of the SWM facility will be utilized. This number represents
approximately 59% of the total volume of the facility at
45,238 m3
. Thus, the anticipated single-event volume
utilization from the SWM facility is less than the maximum
available storage volume (Development Engineering, 2005).
Table 3: SWM facility discharge and storage summary for varying
rain events
Discharge and Storage Summary for 2-250 Year Rainfall Events
Return
Period
Discharge
into SWM
facility
(m3
/s)
Discharge
from
SWM
facility
(m3
/s)
Storage
volume
utilization
(m3
)
Pond
elevation/depth
(m)
2 year 5.90 0.28 13271 266.08
5 year 7.68 0.85 16380 266.27
10 year 8.86 1.51 17713 266.35
25 year 10.08 2.24 19288 266.44
50 year 11.05 2.42 20429 266.51
100
year
11.72 2.56 21571 266.58
250
year
15.01 3.10 26524 266.86
Source: Development Engineering, 2005
However, given that the SWM facility carries a constant
volume, frequent storm events can surpass the maximum
capacity, leading to the submergence of the existing
discharge outlets and a subsequently slow release of water
from the SWM facility (Development Engineering, 2005).

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6.4 Subsurface Conditions
A subsurface analysis was carried out at the WPC site in
order to install standpipes and the groundwater table was
discovered to be 7.9m to 8.1m below the surface
(Development Engineering, 2005). According to Brown
(2008), these depths are suitable for the installation of
permeable surfaces, which require a groundwater table of at
least 1.1m to 1.5m from the surface.
6.5 Maintenance of the SWM Facility
The maintenance responsibilities for the Bradley Avenue
SWM facility are separated into general maintenance,
sediment maintenance and sediment disposal (Development
Engineering, 2005).
General maintenance is carried out three or four times a
year. The activities include weed control, grass cutting and
outlet pipe opening maintenance. Sediment maintenance is
carried out when the sediment removal efficiency is reduced
by 5%. Sediment disposal is carried out after a sediment
chemical analysis is completed. The Ministry of Environment
guidelines for Use at Contaminated Sites in Ontario and the
Ontario Environmental Protection Act (OEPA), Regulation
347, Schedule 4 Leachate Test, Ref. 15 provide the
applicable guidelines for determining sediment disposal
options (Development Engineering, 2005).
Inspection is carried out at least once per month during dry
weather, and a Sediment & Erosion Control Maintenance &
Monitoring Report is completed (Development Engineering,
2005).
Annual maintenance costs for the SWM facility at the WPC
is estimated at $20,000 per year (Weber, 2010).

7. Permeable Surfaces Overview
7.1 Introduction
The level of urbanization is rising; by 2030 it is expected that
83% of people in developed countries will live in urban areas
(Mentens, Raes & Hermy, 2005). Urbanization results in the
displacement of cropland, grassland and forests by the
implementation of impervious surfaces. This greatly
intensifies stormwater runoff, diminishing groundwater
recharge and enhancing stream channel and river erosion
(Mentens, Raes & Hermy, 2005).
Permeable surfaces are surfaces which allow water to
percolate or travel through their structure into the underlying
ground layer, thereby relieving pressures on traditional
stormwater management systems (SWITCH, 2007). The
advancement of new technologies has brought many new
permeable products onto the market; including porous
asphalt, permeable concrete, green roofs and other
emerging technologies. If properly installed and maintained,
permeable pavements are typically designed to handle as
much as 70-80% of annual rainfall (Metropolitan Area
Planning Council, 2010).

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Figure 9: Interaction between rainwater and tradition/conventional pavement
Modified from: Sansalone et al., 2008, p. 667)
Traditionally-paved surfaces do not allow for the natural
infiltration of water into the underlying soil for the purposes of
groundwater recharge (Sansalone, Kuang & Ramieri, 2008).
Rather, rainfall is carried over the surface of pavements as
runoff (Figure 9), and must be captured using municipal
stormwater management infrastructure. In addition to the
negative environmental impacts associated with
impermeable surfaces (i.e., the movement of pollutants into
natural systems and increasing runoff peaks and volumes),
impermeable surfaces are also a costly economic
expenditure (Sansalone et al., 2008; Gilbert & Clausen,
2006). As urbanization increases, so too does the need for
increased stormwater infrastructure. The development of a
new individual stormwater management facility for a city the
size of London can cost anywhere between just over $1
million (CAD) to just under $7 million (CAD); including land
acquisition, construction of ponds, and necessary piping
systems (AECOM, 2009).
Permeable surfaces, on the other hand, serve as more
environmentally conscious, low-impact development
materials for rainwater runoff control (Figure 10) (Sansalone,
Figure 10: Interaction between rainwater and permeable pavement
Modified from: Sansalone et al., 2008, p. 667)

et al., 2008). Although some surfaces have higher porosities
than others, they all work to restore the in situ hydrology of a
site by reducing runoff, filtering and treating infiltrating runoff
and reducing thermal pollution and temperature (Sansalone
et al., 2008). By reducing the rate and quantity of
stormwater runoff, permeable pavements reduce the
demand on stormwater treatment facilities (Landers, 2008),
thereby reducing costs for capital infrastructure,
maintenance and operation (SWITCH, 2007).
7.2 Permeable Asphalt
7.2.1 Introduction
Conventional asphalt is comprised of asphalt cement and
coarse aggregates, including stone, sand, and gravel
compacted together (Freemantle, 1999). Traditionally, this
media consists of impermeable substances which do not
allow precipitation or surface runoff to infiltrate into the soil or
rock beds. A novel solution to impervious asphalt was first
developed in the 1970s, in which fine sediments (e.g., sand
with a grain size less than 0.075 mm in diameter) were
removed, resulting in a network of continuously linked voids
to allow the passage of fluids through the pavement surface
and ultimately to groundwater sources or the water table
(Beecham, 2007; Boving, 2008).
7.2.2 Function and Application
Walker (2006) suggests that the permeable asphalt surface
(e.g., approximately 5 to 10 cm in depth with 15-25% voids
or pore space) should be generally underlain by a top filter
course (e.g., 5 cm of 1.3 cm crushed stone aggregate), a
reservoir course (determined by the average storage
volume, structural capacity, or frost depth; usually an 20 or
23 cm minimum with aggregates between 4 and 7.5 cm in
size with 40% voids is recommended), an optional bottom
filter course, filter fabric (e.g., geotextile fabric) and subgrade
material consisting of larger aggregates that acts as a
temporary storage capacity to hold the collected water
(Walker, 2006). Figure 11 shows a typical cross-section of a
permeable asphalt surface.
Figure 11: Typical cross-section of a permeable asphalt surface
Source: Fancher & Townsen, 2003
Many factors must be taken into account before a project
can be proposed or designed using permeable asphalt,
including local soil characteristics, local topography, climate,
and traffic loading (Brattebo & Booth, 2003). For instance, it
is recommended that permeable asphalt pavement be used
on sites with gentle slopes (e.g., surface grade less than
5%), permeable soils (i.e., well drained or moderately well
drained), and relatively deep water table and bedrock levels
(Gunderson, 2008; Beecham, 2007).
Conventional asphalt is largely used as a material to
construct highways, roadways, airfields, and parking lots.
Alternatively, permeable asphalt pavement is appropriate for

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low-traffic applications such as walkways, low-traffic streets,
and along highway shoulders (Freemantle, 1999; Brattebo &
Booth, 2003).
7.2.3 Durability
The lifespan of a parking lot situated in a northern climate,
and made from conventional pavements is approximately 15
years (EPA, 2009). A properly designed, installed, and
maintained permeable asphalt pavement, on the other hand,
may have a lifespan of 20 to 30 years (Gunderson, 2008).
The regional climate of Southwestern Ontario, and
specifically London, presents many obstacles to the
effectiveness of permeable asphalt pavement due to cold
weather. For instance, Backstrom and Bergstrom (2000)
found that at freezing point, the infiltration capacity of porous
asphalt was about 40% lower (7.4 mm/min) than that near
20o
C (19 mm/min) due to ice formation within the pores.
The authors also found that exposure to snowmelt conditions
(i.e., freeze-thaw) over a two day period further reduced this
capacity up to 90%. As a result, typical snowmelt conditions
for porous asphalt may only yield an estimated 1-5 mm/min
infiltration capacity (Backstrom & Bergstrom, 2000;
Stenmark, 1995). However, several confounding variables
found during experimentation may be at fault for the overall
poor performance. Firstly, the asphalt pieces were taken
from a field site which had been in operation for two years.
Secondly, the asphalt was not cleaned; nor were the pore
spaces unclogged before testing. Thirdly, no apparent de-
icing agents of any sort were used during experimentation,
which may have melted snow and ice more quickly, allowing
water to effectively infiltrate the media.
Despite the results of this Study, many researchers maintain
that porous asphalt pavement performs relatively well in cold
weather climates compared to conventional design
(Gunderson, 2008; Roseen & Ballestero, 2008; Roseen et
al., 2009; Backstrom and Viklander, 2000). These
researchers argue that porous asphalt, and other low impact
development designs, have a high level of functionality
during winter months and that frozen filter media, generally,
do not reduce performance. Figure 12 shows winter
performance of different stormwater components.

Figure 12: Winter performance vs. general indicators, including
runoff control, pollution control, and level of integration,
for different stormwater components
Source: Backstrom and Viklander, 2000
7.2.4 Maintenance
Due to the nature of porous asphalt pavement, regular
inspection for surface clogging must be undertaken,
especially after large storm events, which may also increase
sandy discharge (Beecham, 2007). In cases of clogged or
reduced surface porosity, the pavement can be cleaned by a
vacuum sweeper or pressure washer 2 to 4 times per year to
avoid build-up of debris, and to prevent potential decreases
in infiltration capacity (Bean et al., 2007; Balades et al.,
1995).
For large commercial developments, however, this implies
an additional cost that should be taken into consideration
when comparing product types.
Dust and sand tends to clog the pores of porous asphalt
surfaces and severely restrict percolation through the top
layer of the system (Bean et al., 2007; Balades et al., 1995).
It stands to reason that these surfaces may not be suitable
candidates for areas adjacent to partially landscaped
locations where significant erosion may take place, or
jurisdictions which use sand, and even salt, as a de-icing
agent in winter. A liquid de-icer is therefore recommended as
it drains out with the snow and ice during melting, leaving the
porosity of the pavement largely intact (Walker, 2006).
7.2.5 Cost
The cost of porous asphalt pavement installation is similar in
cost to conventional asphalt, and one of the least expensive
compared to the other permeable surfaces (Boving, 2008). It
is estimated that the cost for porous asphalt pavement is
approximately $5.50 to $10.76 (USD) per metre squared
(EPA, 2009). However, the underlying stone bed is usually
more expensive than those found in a conventional sub-
base, due to the greater depths of aggregates required
(Beecham, 2007).
Special training or techniques are not generally required for
application of porous asphalt, as the laying process is similar
to that of conventional asphalt (Walker, 2006).
7.2.6 Benefits and Limitations
The key advantage of permeable asphalt is that it retains
stormwater onsite, which may decrease surface runoff with
low peak discharge (Bean et al., 2007; Rushton, 2001). It
may also act as a potential water quality treatment process
by intercepting the contaminants of urban stormwater runoff

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prior to infiltration into soil (Beecham, 2007; Brattebo &
Booth, 2003; Bean et al., 2007).
Another possible benefit of using porous asphalt in cold
weather climates is that melted water infiltrates through the
media before it freezes, which may cause fewer problems
with slipperiness and black ice related accidents, for
example, during cold nights (Backstrom & Bergstrom, 2000).
Parking lots and roads tend to be sources of water pollution
because of their extensive impervious surfaces, in which
most precipitation that falls becomes urban runoff. Motor
vehicles are a constant source of pollutants, the most
significant being gasoline, motor oil, polycyclic aromatic
hydrocarbons (found in the combustion by-products of
gasoline, as well as in asphalt sealants used to maintain
parking lots), and heavy metals (Bean et al., 2007; Rushton,
2001; Boving et al., 2008). According to a cold climate study
by Backstrom and Viklander (2000), cold vehicle engines
produce 2 to 8 times more potentially harmful particles than
does a warm engine, which may accumulate on
impermeable surfaces and be subject to runoff, with
implications for water contamination.
Another study by Boving et al. (2008) suggests that porous
asphalt is effective at removing organic and metal
contaminants. However, permeable asphalt surfaces, which
allow liquid infiltration, may lead to possible ground
contamination within the surface of the parking lot. Although
this process can filter the water, contaminants may seep
directly into groundwater, especially where there is
groundwater abstraction downstream for drinking water
(Howard & Beck, 1993; Legret & Colandini, 1999).
7.3 Permeable Concrete
7.3.1 Introduction
Concrete in the form of permeable interlocking concrete
pavers (PICP), concrete grid pavers (CGP) and porous
concrete (PC) (Figure 13) is commonly used to increase
surface infiltration rates, thereby mitigating stormwater from
conventional stormwater systems (Bean, Hunt, &
Bidelspach, 2007a). Infiltration rates depend on a number of
factors, including the type of permeable concrete product
that is applied, soil infiltration rate, and installation of the
permeable concrete product (i.e. the aggregate material that
is used as a filler, and the size and type of sub-base that is
installed) (Table 4) (Bean et al., 2007a).
Figure 13: a) PICP, b) CGP, c) PC
Source: Bean et al., 2007b

Results from runoff studies indicate that permeable concrete
pavements may not only reduce runoff, but also eradicate
runoff entirely under certain rainfall depths, intensities,
maintenance conditions, antecedent conditions and designs
(Bean et al., 2007b).
Table 4: Factors affecting infiltration rates of permeable concrete products
Factors Affecting Infiltration Rates of Permeable Concrete Products
Product
Site
(m2
)
Slope
(%)
Soil
Thickness of Permeable Surface
(mm)
Filler Base
Base
(mm)
SIR
(mm/h)
CGP 630 0.5
Kalmia sandy
soil
90
Coarse grade
sand
Yes; sand 50 580
PC 370 0.33
Seagate fine
graded sand
200 NA No NA 230
PICP 740 0.4
Bay Meade
sandy soil
76 NA
Yes; stone &
gravel
275 20 X 1013
PICP 120 NA
Loamy sand
soil
76 NA
Yes; stone &
gravel
275 40 X 1013
SIR = Surface Infiltration Rate; Source: Bean et al., 2007a
PICP is defined as concrete block pavers that, when in
place, create voids located at the corners and midpoints of
the pavers, allowing water to infiltrate through an aggregate
material (Bean et al., 2007b). CGP is defined as concrete
blocks with inner voids between the blocks that permit water
to infiltrate in the same way as PICP. PC is defined as
altered standard concrete, as fine aggregate has been
removed from the standard mix, permitting interconnected

JOVIAN DESIGN
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void spaces to form during curing, thus allowing water to
infiltrate through the material (Bean et al., 2007b).
7.3.2.1 Function and Application of PICP and CGP
The primary difference between permeable pavers and
conventional pavers is base materials and void space (Bean
et al., 2007b; Unilock, 2009). Permeable paver systems use
crushed, angular, open-graded aggregate base materials
that have a void space or porosity of approximately 40%.
Base storage capacities depend on a number of factors
including rainfall and base depth (Table 5) (Unilock, 2009).
The proper installation of the base is very important to the
optimal function of PICP and CPG systems (Smith, 2006).
Figure 14 illustrates the appropriate installation of a typical
exfiltration system including base compositions and
measurements. This system fully exfiltrates, by infiltrating
water directly into the base and extruding it to the soil.
Overflows are managed through perimeter drainage to
swales, bio-retention areas or storm sewer inlets. Partial
exfiltration systems are less common than full exfiltration
systems and include drainage by perforated pipes. In this
case, excess water is drained from the base by pipes to
sewers or a stream (Smith, 2006).
Figure 14: Typical installation for exfiltration
Source: Uni-EcoLocTech, 2008
The application of PICP and CGP products depend on the
specific material that is being used as well as the location of
the project. Unilock, a company that sells permeable
pavers, manufactures its products to meet the ASTM C936
standard which allows the product to support semi-truck
traffic, heavy-traffic and high-load environments (Unilock,
2009). The application of Unilock products varies greatly.
Over 107.6 million metres squared of Unilock permeable
pavers have been installed throughout Canada and the U.S.
Applications include parks and municipal commons,
commercial parking and vehicular areas, government and
municipal facilities, streets and streetscapes, stadiums,
condominiums and others (Unilock, 2009). Because of the
structural integrity of CGP, this material is intended for light-
duty use such as over-flow parking areas, being occasionally

used in parking lots, and in access to emergency lanes
(Smith, 2006).
Table 5: Base storage capacity of PICP and CGP
Base Storage Capacity of Permeable Interlocking Concrete Pavers and Concrete Grid Pavers
Criteria
Rainwater Harvest
Volume
Base Storage
Capacity
Surplus/(Deficit)
Storage
Rainfall
(mm/hr)
Surface Area
(m2
)
Base Depth
(cm)
Void
Space
(m3
) (m3
) (m3
)
%
Used
25 4,047 30 40% 103 493 391 20.8%
25 4,047 46 40% 103 740 637 13.9%
89 4,047 30 40% 360 493 134 72.9%
89 4,047 46 40% 360 740 380 48.6%
12 4,047 61 40% 520 986.5 473 52.1%
188 4,047 46 40% 761 740 (21) 102.8%
Source: Unilock, 2009
7.3.2.2 Function and Application of PC
PC is a paste composed of water and cementitious materials
that forms a thick coating around aggregate particles
(Tennis, Leming, & Akers, 2004). Void space is created by
adding little or no sand which results in a system that is
highly permeable and drains quickly. The hardened
concrete contains between 15% and 25% voids that typically
allow flow rates of approximately 34 mm/s, although it can
be much higher (Figure 15) (Tennis, et al., 2004).

JOVIAN DESIGN
Page | 26
Figure 15: Typical installation of porous concrete surface
Source: National Ready Mixed Concrete Association, 2010
PC can be applied in a variety of settings. It can be used in
parking lots, tennis courts, greenhouses and as pervious
base layers under heavy duty pavements (Table 6) (Tennis
et al., 2004). Properly installed PC can achieve strengths in
excess of 20.5 MPa and flexural strengths of more than 53.5
MPa. This strength is more than sufficient for most low-
volume pavement applications, including high axle loads for
garbage truck and emergency vehicles such as fire trucks
(Tennis et al., 2004). As PC matures, its compressive
strength increases (Park & Tia, 2003). Special mix designs,
structural designs and placement techniques can be altered
to accommodate more demanding applications (Tennis et
al., 2004).
Table 6: Applications of pervious concrete
Applications of Porous Concrete
Low-volume pavements Artificial reefs
Residential roads, alleys, and
driveways
Slope stabilization
Sidewalks and pathways Well linings
Parking lots Tree grates in sidewalks
Low water crossings Foundations/floors for
greenhouses, fish hatcheries,
aquatic amusement centres,
and zoos
Tennis courts Hydraulic structures
Subbase for conventional
concrete pavements
Swimming pool decks
Patios Pavement edge drains
Walls (including load-bearing) Groins and seawalls
Source: Tennis et al., 2004

7.3.3 Durability
7.3.3.1 Durability of PICP
PICP is particularly durable and has the capacity to
withstand high traffic areas and climatic uncertainty (Toronto
and Region Conservation Authority [TRCA], 2007). A study
by the TRCA (2007) indicated that permeable pavement
continued to function normally throughout the winter months
during winter rain events, with minor amounts of infiltrate
measures even during very cold periods.
7.3.3.2 Durability of CGP
CGP is recommended for light-duty use, thus applications
vary (Pavers by Ideal, 2005). Certain CGP products have
the capacity to withstand harsh winter climates and are
“snow-plough safe.” Freeze-thaw conditions have no
demonstrated effect on certain CGP products (Pavers by
Ideal, 2005).
7.3.3.3 Durability of PC
PC is often criticized for its vulnerability to freeze-thaw
conditions (Tennis et. al., 2008). However, freeze-thaw
resistance depends on the saturation level of the voids in the
concrete at the time of freezing. Because PC drains rapidly,
saturation is often prevented from occurring. In fact,
evidence suggests that snow-covered pervious concrete
melts quicker as voids in the material allow snow to thaw
more quickly than conventional pavements. Different factors
improve durability of PC in freeze-thaw conditions. For
example, entrained air in the PC paste can dramatically
improve freeze-thaw protection. Placement also plays an
important role as specific installation is recommended in
freeze-thaw environments (Tennis et. al., 2008).
PC can be susceptible to the effects of aggressive chemicals
in soils or water, such as acids and sulphates (Tennis et. al.,
2008). If isolated from high-sulphate soils and groundwater,
PC can be used. Abrasion resistance is also a concern as
PC has a rough surface texture and open structure. PC can
be particularly problematic where snowploughs are used to
clear pavements although studies indicate that PC can allow
snow to melt faster thus requiring less ploughing (Tennis et.
al., 2008).
7.3.4 Maintenance
7.3.4.1 Maintenance of PICP, CGP and PC
Clogging can occur as a result of fine particle accumulation
in the void spaces of permeable pavements (Bean, Hunt,
Bidelspach & Burak, 2004). The rate of clogging increases
as more fine particles (fines) are trapped since smaller
particles trap larger particles. In most cases, clogging
reduces surface infiltration rates. Clogging can be limited,
however, through regular maintenance, either by a vacuum
sweeper or pressure washing thereby improving surface
infiltration rates from unmaintained infiltration rates (Bean et
al., 2007b; Smith, 2006). Clogging can also be limited
through strategic site placement away from disturbed soil
areas.
One study concluded that maintenance was vital to
sustaining high surface infiltration rates of CGP in particular
(Bean et al., 2007b). Without maintenance, the median
average infiltration rate of CGP was 4.9 cm/h; while with
maintenance, the median infiltration rate was 8.6 cm/h (Bean
et al., 2007b).

JOVIAN DESIGN
Page | 28
The study also concluded that the selected site of permeable
pavement applications was a significant factor in preserving
high surface infiltration rates (Bean et al., 2007b). In
particular, locating PICP and PC away from disturbed soil
areas was of great importance in maintaining high surface
infiltration rates. The authors of this particular study also
found that permeable pavements installed in sandy soil
environments maintained relatively high surface infiltration
rates, regardless of pavement age or type (Bean et al.,
2007b).
Bean et al. (2007b) suggest that a storage layer improves
runoff reduction potential. Keeping the permeable surface
free of fine particles, performing regular maintenance and
construction on sandy, in situ soils may also increase runoff
reduction potential.
In climates where snow removal equipment is employed,
damage can occur to PICP and CGP. This may require the
replacement of damaged blocks thereby increasing
maintenance costs.
7.3.5 Cost
7.3.5.1 Cost of PICP, CGP, and PC
The cost of permeable concrete pavement varies according
to location, distributor, and scope of project (among other
factors). For example, PICP is generally more expensive
than conventional asphalt or concrete pavements that rely
on a stormwater collection pond (Interlocking Concrete
Pavement Institute [ICPI], 2008). PICP may be cost-effective
in a new development where regulations limit impervious
cover and space is limited. Because PICP and other
permeable pavements may not require a collection pond as
large as impervious-paved surfaces, space can be used
more efficiently (ICPI, 2008).
7.3.6 Benefits and Limitations
PICP and CPG have the capacity to remove pollutants,
improving the quality of exfiltrate (Tennis et al., 2008). The
material allows the rainfall to percolate into the ground where
soil chemistry and biology are able to “treat” the polluted
water naturally. This results in the reduction or elimination of
stormwater retention areas. Also, “groundwater and aquifer
recharge is increased, peak flow through drainage channels
is reduced and flooding is minimized” (Tennis et. al., 2008,
p.4). PICP is also easy to replace as individual pavers can
be removed in the event of damage (Park & Tia, 2003). This
results in lower replacement costs and lessens the negative
environmental impact of large scale product replacement
(Hirshorn, 2010).
PC has the capacity to remove pollutants from infiltrate at
high rates (Park & Tia, 2003). Pollutant removal rates are
variable as water purification can be affected by the size of
aggregate and void content in the PC paste. One study
indicates that PC composed of a smaller size of aggregate
and a higher void content greatly removes total nitrogen (T-
N, mg/l) and total phosphorous (T-P, mg/l) from the test
water in comparison to PC pastes with a larger size
aggregate and a lower void content. Smaller sized
aggregate and higher void content increase the surface area
of the concrete‟s porosity. The composition of the PC paste
can largely affect the ability of the material to remove
pollutants (Park & Tia, 2003).

Permeable surfaces should not be used in locations with
high pollutant loads. These locations include commercial
nurseries, recycling facilities, fuelling stations, industrial
storage, marinas, some outdoor loading facilities, public
works yards, hazardous materials generators (if containers
are exposed to rainfall), vehicle service and maintenance
areas and vehicle and equipment washing and steam
cleaning facilities (Hirshorn, 2010). Permeable paving
should also not be used in high traffic and/or high speed
areas as permeable paving has lower load-bearing capacity
that conventional pavement (Hirshorn, 2010).
7.3.7 Supplementary Cementitious Materials
The National Ready Mixed Concrete Association (2008)
claimed that the construction industry is committed to
continuous environmental improvement through process
innovation and product standards that lead to reduced
environmental impact. One method of improving product
standards is through the mixing of Portland cement with
supplementary cementitious materials (SCMs) for various
uses.
Bouzoubaâ and Foo (2005) contend that SCMs, including fly
ash, ground granulated blast furnace slag (GGBFS), silica
fume and natural pozzolans can be mixed with Portland
cement. These blended cements are less energy intensive
and made with by-products or wastes. Therefore, they
reduce the solid waste burden on landfills and offer
performance benefits for certain applications (Committee E-
701 Materials for Concrete Construction, 2001). One of the
main objectives of increasing the use of SCMs in concrete
production is to reduce the release of CO2 associated with
the production of each cubic meter of concrete (Bouzoubaâ
& Fournier, 2005). SCMs were used mainly due to their low
costs and performance-enhancing aspects. Fly ash is used
in various concrete applications because of improvement in
workability, reduction of heat of hydration, increased water
tightness and ultimate strength, and enhanced resistance to
sulphate attack (especially in western Canada) and alkali–
aggregate reaction (AAR) throughout Canada (Bouzoubaâ &
Fournier, 2005).
The use of SCMs in the cement and concrete industries can
render benefits in engineering, economic, and ecological
terms (Malhotra & Mehta, 1996). Engineering benefits of the
incorporation of SCMs into a concrete mixture include
improvement in the workability and the reduction of the
water. This mixing enhances the ultimate strength,
permeability, and durability to chemical attack along with an
improved resistance to thermal cracking.
In terms of residential application, concrete is used in
basement walls and floors, driveways, steps, sidewalks and
a small amount of concrete products such as paving blocks,
retaining walls, and masonry blocks. Specifically, SCMs
have proven to be very effective in producing durable,
freeze-thaw tolerant sidewalks (Bouzoubaâ & Fournier,
2005).
7.4 Permeable Pavement De-icing agents
In many northern countries, such as Canada and the USA,
one of the main de-icing agents of choice for safe driving
conditions in municipal areas is common salt (sodium
chloride) because of its cost effectiveness (Liu et al., 2006).
Urbanization leads to increases in impervious surfaces and

JOVIAN DESIGN
Page | 30
complex systems, such as roads, parking lots, and sidewalks
that receive chemical de-icer to keep them free of ice and
snow during winter (Daley et al., 2009). As a result of these
larger surfaces, additional road salts are required which may
adversely affect soil and vegetation systems, human health,
as well as the quality of water systems (e.g., groundwater
and streams) due to increased levels of Cl-
(Williams et al.,
2005; Williams et al., 1999).
The Greater Toronto Area alone applies more than 100,000
tonnes of salt each winter (Williams et al., 1999) and
approximately 5 million tonnes of sodium chloride are
consumed each year in Canada for de-icing roles
(Environment Canada and Health Canada, 2001). If high
enough concentrations of these road salts reach
groundwater zones, contamination can occur and negatively
affect drinking water quality, fresh water systems, and
aquatic ecosystems (Ramakrishna & Viraraghavan, 2005).
De-icing salts, particularly NaCl contribute ions to the soil,
altering pH and the soil‟s chemical composition, which may
lead to vegetative stress and disrupt plant function
(Bogemans et al., 1989; Guntner & Wilke; Trombulak &
Frissell, 2000). NaCl is also an environmental concern
because of its toxicity to aquatic organisms; its alterations to
soil structure and decreased permeability (Ramakrishna &
Viraraghavan, 2005; Fischel, 2001); and its adverse effects
on human health (Environment Canada and Health Canada,
2001).
The main human impact of ingesting large amounts of salt is
hypertension leading to cardiovascular disease, which could
account for thousands of deaths a year in Canada and the
USA (Feig & Paya, 1998). In the past few years, high levels
of sodium and chloride (>2000 mg/L) have been found in
many shallow groundwater wells in and around the GTA
where urbanization is greater than 80% (Williams et al.,
1999). In general, only wells or reservoirs near salt-treated
surfaces or salt storage facilities are most likely to become
susceptible to salt infiltration, whereby road salts can enter
drinking water supplies by migrating through soil into
groundwater or by runoff and drainage directly into surface
water (Werner & diPretoro, 2006).
Due to concerns of clogged pores by sand and salt, a liquid
de-icer is therefore recommended for use on permeable
pavements as it drains out with the snow and ice during
melting, leaving the porosity of the pavement largely intact
(Walker, 2006). However, less research has been devoted
towards liquid de-icers, including CaCl2, KCl, and MgCl2
(Ramakrishna & Viraraghavan, 2005). Generally the chloride
ions of these substances have similar environmental impacts
as rock salt (NaCl), but have been found to present less
toxicity to aquatic organisms, as well as having a limited
impact on human health (Fischel, 2001).
Another option for snow and ice removal on permeable
pavement is the liquid form of calcium magnesium acetate
(CMA) which may provide the most environmentally friendly,
although a more expensive alternative to sodium chloride,
while leaving the porosity of the pavement largely intact.
CMA is an organic de-icing agent which may largely be
broken down by biodegradation (Fischel, 2001; Ramakrishna
& Viraraghavan, 2005). There is, however, some concern
that the acetate-based de-icer has the potential to cause

oxygen depletion in rivers, streams, and lakes; however, it is
hoped that the agent breakdown before such an occurrence
(Fischel, 2001; Ramakrishna & Viraraghavan, 2005). There
is also some debate over pH alterations and the corrosive
potential caused by the agent (Ramakrishna &
Viraraghavan, 2005). Due to CMA containing phosphorous
and nitrogen, eutrophication may occur to nearby water
bodies, and as a result adversely affect aquatic ecosystems
(Fischel, 2001).
7.5 Green Roofs
7.5.1 Introduction
Roof surfaces account for a large portion of impervious
cover in urban areas. Establishing vegetation on roof-tops,
known as green roofs, is one method of recovering lost
green space that can aid in mitigating stormwater runoff (van
Woert, et al., 2005).
A green roof, i.e., a roof with a vegetative cover (Figure 16),
is one passive technique that can be used to address
environmental issues in an urban setting (Kosareo & Ries,
2007). Green roofs have been a standard construction
practice in many countries for hundreds, if not thousands of
years, mainly due to the excellent insulative qualities of the
combined plant and soil layers (sod) (Peck & Kuhn, n.d.). In
the cold climates of Iceland and Scandinavia, sod roofs
helped to retain heat, while in warm countries such as
Tanzania, green roofs keep buildings cool. Canadian
examples of early green roofs, imported by the Vikings and
later the French colonists, can be found in the provinces of
Newfoundland and Nova Scotia (Peck & Kuhn, n.d.).
Figure 16: Typical cross-section of a green roof
Source: Kosareo & Ries, 2007
Green roofs are an emerging strategy for mitigating
stormwater runoff. They offer numerous benefits such as:
Stormwater mitigation; insulation for buildings; an increase in
the life span of a typical roof by protecting the roof
components from exposure to ultraviolet rays, extreme
temperatures and rapid temperature fluctuations; filtration of
harmful air pollutants; an aesthetically pleasing environment
to live and work in; habitat for a range of organisms, and; the
potential to reduce Urban Heat Island effect (van Woert et
al., 2005). However, many consider stormwater runoff
mitigation to be the primary function of green roofs due to
the prevalence of impervious surfaces in urban areas (van
Woert et al., 2005). Furthermore, green roofs have the
potential to improve thermal performance of a roofing system
through shading and evapotranspiration, thus reducing a
building‟s energy demand for space conditioning (Kiu &
Baskaran, 2003).

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Jovian Design - Permeable Surface Stormwater Management Feasibility Study