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Jovian Design - Permeable Surface Stormwater Management Feasibility Study

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Myself and colleagues studied the feasibility of permeable surfaces for the City of London during a Consulting Project.

Myself and colleagues studied the feasibility of permeable surfaces for the City of London during a Consulting Project.

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Jovian Design - Permeable Surface Stormwater Management Feasibility Study Jovian Design - Permeable Surface Stormwater Management Feasibility Study Presentation Transcript

  • PERMEABLE SURFACE STORMWATER MANAGEMENTFEASIBILITY STUDY WONDERLAND POWER CENTRE, LONDON, ONTARIO, CANADA FINAL REPORT APRIL 2010 City of London Engineering Review Division Environmental & Engineering ServicesDisclaimer: This report is an academic exercise conducted by graduate students from the University of WesternOntario. Jovian Design is a fictional entity and has been created only for the purposes of this exercise.
  • DANIEL BITTMAN | ANIRUDDHA DHAMORIKAR | STEVEN DIXON | JENNA SIMPSON | SYED ZAIDI
  • April 23, 2010Lois Burgess, P.Eng. Ismail Abushehada, Ph.D., P. Eng.Division Manager Development Services EngineerEngineering Review Division Engineering Review DivisionEnvironmental & Engineering Services Environmental & Engineering ServicesCity of London City of LondonRE: Final Report: Permeable Surface Stormwater Management Feasibility Study: Wonderland Power Centre, London,Ontario, CanadaDear Ms. Burgess and Mr. Abushehada,The following document is the Final Report of the Permeable Surfaces Stormwater Management Feasibility Study that has beenrequested 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 thisproject.Sincerely,Jenna Simpson, Project ManagerJovian Design1151 Richmond Street,London, Ontario, CanadaN6A 3K7 View slide
  • Table of ContentsTable of Contents ............................................................................................................................................................................ iTable of Tables ............................................................................................................................................................................. viiTable of Figures ........................................................................................................................................................................... viiiGlossary of Terms ..........................................................................................................................................................................ixList of Abbreviations ...................................................................................................................................................................... xiiExecutive Summary ..................................................................................................................................................................... xiii1. Introduction ................................................................................................................................................................................ 1 1.1 General ................................................................................................................................................................................. 1 1.2 Urbanization in the City of London ........................................................................................................................................ 22. City of London Development Objectives ..................................................................................................................................... 4 2.1 Introduction ........................................................................................................................................................................... 4 2.2 Official Plan for the City of London ........................................................................................................................................ 4 2.3 Needs & Guidelines .............................................................................................................................................................. 43. 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 i View slide
  • 3.9 Net Water Savings................................................................................................................................................................ 5 3.10 Financial Analysis ............................................................................................................................................................... 6 3.11 Conclusions & Recommendations ...................................................................................................................................... 64. Site Context – Wonderland Power Centre .................................................................................................................................. 75. 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 ............................................................................................................................................................. 126. 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 ....................................................................................................................................... 167. Permeable Surfaces Overview ................................................................................................................................................. 17 7.1 Introduction......................................................................................................................................................................... 17 7.2 Permeable Asphalt ............................................................................................................................................................. 19 7.2.1 Introduction .................................................................................................................................................................. 19 7.2.2 Function and Application .............................................................................................................................................. 19ii
  • 7.2.3 Durability ...................................................................................................................................................................... 20 7.2.4 Maintenance ................................................................................................................................................................. 21 7.2.5 Cost.............................................................................................................................................................................. 21 7.2.6 Benefits and Limitations ............................................................................................................................................... 217.3 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 7.3.6 Benefits and Limitations ............................................................................................................................................... 28 7.3.7 Supplementary Cementitious Materials ........................................................................................................................ 297.4 Permeable Pavement De-icing agents ................................................................................................................................ 297.5 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 7.5.8 Benefits and Limitations ............................................................................................................................................... 38 7.5.9 Public Policy ................................................................................................................................................................. 387.6 Additional Benefits of Permeable Surfaces ......................................................................................................................... 38 iii
  • 7.6.1 Urban Heat Island ........................................................................................................................................................ 38 7.6.2 LEED ........................................................................................................................................................................... 408. Product Analysis ...................................................................................................................................................................... 41 8.1 Introduction......................................................................................................................................................................... 41 8.2 PICP ................................................................................................................................................................................... 41 8.3 Concrete & Asphalt............................................................................................................................................................. 41 8.4 Green Roofs ....................................................................................................................................................................... 429. 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 ............................................................................................................................... 5010. Financial Analysis .................................................................................................................................................................. 52 10.1 Introduction....................................................................................................................................................................... 52iv
  • 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 ................................................................................................................. 5711. Conclusions............................................................................................................................................................................ 59 11.1 Durability........................................................................................................................................................................... 59 11.2 Net water Savings ............................................................................................................................................................. 59 11.3 Financial Analysis ............................................................................................................................................................. 60 11.4 Summary .......................................................................................................................................................................... 6112. Recommendations ................................................................................................................................................................. 63 12.1 Durability........................................................................................................................................................................... 63 12.2 Net Water Savings ............................................................................................................................................................ 63 12.3 Financial Analysis ............................................................................................................................................................. 63 12.4 Additional Recommendations ........................................................................................................................................... 63References................................................................................................................................................................................... 64Appendices .................................................................................................................................................................................. 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 v
  • Appendix B. 3: Financial Analysis: Calculations........................................................................................................................ 94 Appendix C: Project Timeline ................................................................................................................................................... 99vi
  • Table of TablesTable 1: Surface Analysis for the WPC Study Site ......................................................................................................................... 9Table 2: Bradley Avenue SWM facility volume summary .............................................................................................................. 14Table 3: SWM facility discharge and storage summary for varying rain events............................................................................. 15Table 4: Factors affecting infiltration rates of permeable concrete products ................................................................................. 23Table 5: Base storage capacity of PICP and CGP ........................................................................................................................ 25Table 6: Applications of pervious concrete ................................................................................................................................... 26Table 7: Comparison between extensive and intensive green roof systems ................................................................................. 33Table 8: Component costs of extensive green roofs assuming an existing building with sufficient loading capacity, roof hatch and ladder access ................................................................................................................................................................ 36Table 9: Component cost of intensive green roofs assuming an existing building with sufficient loading capacity, roof hatch and ladder access ................................................................................................................................................................ 37Table 10: Comparison of feasibility parameters for various permeable products .......................................................................... 43Table 11: Runoff coefficients ........................................................................................................................................................ 45Table 12: Comparison of runoff reductions for conventional and permeable surfaces at the WPC: Pavement and green roofs .... 48Table 13: SWM facility volume reduction resulting from pervious surface coverage at the WPC: Pavement and green roofs ....... 48Table 14: Comparison of runoff reductions for conventional and permeable surfaces at the WPC: PICP and green roofs ........... 51Table 15: SWM facility volume reduction resulting from pervious surface coverage at the WPC: PICP and green roofs .............. 51Table 16: Financial comparisons of different surfaces .................................................................................................................. 55Table 17: Financial comparisons of different surface applications at the WPC ............................................................................. 57Table 18: Financial benefits of green roofs in Toronto, Ontario assuming 50 Million m2 of available roof space ........................... 58Table 19: Overall product comparisons ........................................................................................................................................ 62 vii
  • Table of FiguresFigure 1: The relationship between impervious and pervious area and extent of sewerage ........................................................... 2Figure 2: Study Area ...................................................................................................................................................................... 8Figure 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 .................................................................... 10Figure 4: Asphalt surfaces in the WPC Study Area ...................................................................................................................... 11Figure 5: Commercial concrete sidewalks in the WPC Study Area ............................................................................................... 11Figure 6: Medians are dispersed throughout commercial parking lots to help guide traffic and provide aesthetic relief from dominating impervious pavements ............................................................................................................................... 12Figure 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 ...................................................................................................................... 12Figure 8: Other surfaces within the WPC include a) roofed shopping cart corrals and b) landscaped areas ................................. 13Figure 9: Interaction between rainwater and tradition/conventional pavement .............................................................................. 18Figure 10: Interaction between rainwater and permeable pavement ............................................................................................ 18Figure 11: Typical cross-section of a permeable asphalt surface ................................................................................................. 19Figure 12: Winter performance vs. general indicators, including runoff control, pollution control, and level of integration, for different stormwater components ................................................................................................................................. 21Figure 13: a) PICP, b) CGP, c) PC ............................................................................................................................................... 22Figure 14: Typical installation for exfiltration ................................................................................................................................. 24Figure 15: Typical installation of porous concrete surface ............................................................................................................ 26Figure 16: Typical cross-section of a green roof ........................................................................................................................... 31Figure 17: Rural and urban heat characteristics ........................................................................................................................... 39viii
  • Glossary of TermsAnnual Precipitation – The annual total precipitation is the De-icing Agent – A snow and ice control strategy forsum of the rainfall and the assumed water equivalent of the prevention of a strong bond between frozen precipitation orsnowfall for a given year (Natural Resources Canada, 2003) frost and a pavement surface by application of a chemical freezing point depressant prior to or during a storm (Fischel,Asphalt – Also known as conventional asphalt; an 2001)impermeable surface comprised of asphalt cement andcoarse aggregates, including stone, sand, and gravel Eutrophication – The enrichment of water with nutrients,compacted together (Freemantle, 1999) such as phosphorus resulting in the increase in numbers of aquatic algae in the water (Fischel, 2001)Baseflow – Water that, having infiltrated the soil surface,percolates to the groundwater table and moves laterally to Evapotranspiration – The merging of evaporationreappear as surface runoff (University of Florida, 2010) (movement of free water molecules away from a wet surface into air that is less saturated) and transpiration (movement ofBiodegradation – The breaking down of organic and water vapour out through the pores in vegetation) into oneinorganic substances by biological action, a process usually term (Christopherson, 2005)involving bacteria and fungi (Fischel, 2001) Exfiltration – A loss of water from a drainage system as theBradley Avenue Stormwater Management Facility – The result of percolation or absorption into the surrounding soilStormwater Management Facility at Wonderland Power (HydroCAD, 2009)Centre Freeze-thaw – A weathering process in which intermittentConcrete – Also known as conventional concrete; an periods of freezing and thawing act upon a substance,impermeable construction material comprised usually of leading to its gradual breakdown by forces of water crystalPortland cement, and other materials, including aggregates, expansion and contraction (Christopherson, 2005)water, and chemical admixtures (ICPI, 2008) Green Roof – A roof with a vegetative cover, used passivelyClient – Also known as the City of London; the City; to address environmental issues in mainly urban settingsEnvironmental & Engineering Services Department, (Kosreo & Ries, 2007)Engineering Review Division Green Space – Areas generally planted with trees, shrubs,Consultant – Jovian Design; the Design team herbaceous perennials and decorative grasses, rocks, and water features; used mainly for aesthetics and recreation ix
  • Groundwater – Water beneath the surface that is beyond Permeable Asphalt – Also known as porous or perviousthe soil-root zone; a major source of potable water asphalt; an adaptation of conventional asphalt in which fine(Christopherson, 2005) sediments are removed, resulting in a network of continuously linked voids to allow the passage of fluidsImpermeable Surfaces – Consist of surfaces which restrict through the surface (Beecham, 2007; Boving, 2008)infiltration of precipitation due to decreased drainagecapacity (Shuster et al., 2005) R-value – A commercial unit used to measure the effectiveness of thermal insulation. The R-value of theInfiltration – Also known as percolation; water access to insulator is defined as 1 divided by the thermal conductancesubsurface regions of soil moisture storage through per inch (Rowlett, 2002)penetration of the soil surface (Christopherson, 2005) Rational Method – An equation that postulates aLeadership in Energy and Environmental Design (LEED) proportionality between peak discharge and rainfall intensity– A green building rating system that encourages and (Dingman, 2002)accelerates the global adoption of sustainable green buildingand development practices through the creation and Return Period – The frequency with which one wouldimplementation of universally accepted performance criteria expect, on average, a given precipitation event to recur(CaGBC, 2004) (Cornell University, 2007)Low-Traffic Urban Roadways – Roads and access Roof – A cover used to protect the interior and structuralroadways generally characterized by low to moderate components of a building from weather elements, particularlyspeeds and low to moderate volumes of automobiles per day precipitationMedian – A raised structure used to organize and direct Sidewalk – A raised structure used to provide a suitableautomobile traffic, as well as to provide shade and enhance transit route and safe place for pedestrians to walkaesthetic value to commercial parking lots (Celestian &Martin, 2003) Storm Drain – An opening that leads to an underground pipe or open ditch for transporting surface runoff, separatePermeable Surfaces – Consist of a variety of types of from a sanitary sewer or wastewater system (Environmentalpavement, pavers and other devices that provide stormwater Services Water Quality Division, 2009)infiltration while serving as a structural surface (University ofFlorida, 2008) Stormwater Management (SWM) Facilities – Facilities designed to temporarily collect runoff from localized stormx
  • sewer systems after a rainfall or snowmelt event (Ministry ofEnvironment [MOE], 2003)Stormwater Runoff – Excessive water, derived fromprecipitation or snowmelt that ultimately reaches a drainagearea (Oke, 2006)Toxicity – The potential of a chemical or compound tocause adverse effects on living organisms (Fischel, 2001)Urban Heat Island – An effect caused by the warming ofurban centres in comparison to rural areas as a result ofincreasing surface characteristics which may augmentsurrounding atmospheric temperatures (U.S. EnvironmentalProtection Agency, 2009)Urbanization – The physical growth of urban areas as aresult of global change, in which individuals move from ruralcommunities to more dense urban areas (Barrow, 2003)Water Table – The upper surface of groundwater; thecontact point between the zone of saturation and aeration inan unconfined aquifer (Christopherson, 2005) xi
  • List of AbbreviationsAAR - alkali–aggregate reaction OEPA – Ontario Environmental Protection ActCaCl2 – calcium chloride PC – porous concreteCAD – Canadian dollars PICP – permeable interlocking concrete paversCaGBC - Canadian Green Building Council SCM – supplementary cementitious materialsCGP – concrete grid pavers SS – Sustainability SiteCMA – calcium magnesium acetate SWM – stormwater managementCOTA – City of Toronto Act TRCA – Toronto and Region Conservation AuthorityEAC – Equivalent Annual Cost UHI – Urban Heat Island effectGTA – Greater Toronto Area USD – US dollarsGGBFS – ground granulated blast furnace slag WPC – Wonderland Power CentreICPI – Interlocking Concrete Pavement InstituteKCl – potassium chlorideLEED – Leadership in Energy and Environmental DesignMgCl2 – magnesium chlorideNaCl – sodium chlorideNPV – Net Present ValueO&M – operation and maintenancexii
  • Executive SummaryThe Engineering and Review Division, Environmental and All permeable products proved to reduce the volume ofEngineering Services Department of the City of London has stormwater runoff when compared to conventional surfaces.retained Jovian Design to undertake a Permeable Surfaces Within the scope of the permeable surfaces analyzed, differentStormwater Management Feasibility Study. The primary purpose product typologies offered varying levels of infiltration.of this study is to evaluate the durability, net water reduction and Depending on the level of integration and combination offinancial feasibility of permeable surfaces compared to permeable products, the volume of water being sent toconventional materials, using the following project scope: stormwater facilities can be reduced by up to 62% in ideal conditions. This, in turn, can represent a direct cost savings forThe Consultants will research permeable surfaces and compare new developments, as the size of planned stormwaterpermeable products to existing conventional materials. The management facilities can be reduced.purpose of this comparison is to determine the effectiveness ofeach product including permeability, cost and durability while Most permeable products proved to be more expensive thanensuring that the development objectives of the City are met. The conventional materials. However, depending on the proposedWonderland Power Centre will be assessed as a sample of this application and surface area, some permeable products are verycomparison. similar in Net Present Value and Equivalent Annual Cost to their conventional counterparts. In the case of using porous concretePeer reviewed journal articles and other literature show that for sidewalks, a general cost savings was discovered compared topermeable surfaces are in many instances feasible for large scale using conventional concrete for the same application.developments such as the Wonderland Power Centre. Primaryresearch supported these findings. Several permeable product Properly installed and maintained permeable pavements alsocontractors and distributors operate within Southern Ontario and have the potential to reduce Urban Heat Island effects, improveoffer products that are locally feasible in terms of cost, net-water driving safety, encourage urban tree and plant growth, gain LEEDsavings, and durability. credits, reduce stormwater quantity and enhance water quality. There may also be financial savings due to the benefits ofComparative product analyses for local permeable pavements, stormwater reduction, including the impact on combined sewerpavers, and green roof companies showed that not only are these overflow, improvement in air quality, reduction in direct energyproducts readily available in Southern Ontario, but that the use and other environmental and social benefits such as thelifespan and maintenance requirements of these products are aesthetic improvement of urban landscapes, and increasedcompetitive with conventional pavements and roofing systems. property values. xiii
  • xiv
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY1. Introduction1.1 GeneralJovian Design (Consultants) was retained by the a) Developed a comprehensive site inventory for theEngineering Review Division, Environmental and Wonderland Power Centre including site context,Engineering Services Department of the City of London surface analysis and a stormwater management(Client) to undertake a permeable surface stormwater inventorymanagement feasibility study. The intent of this project is to b) Conducted a literature review of permeable surfacesevaluate the feasibility of various permeable technologies in to outline the function and application, durability,comparison to conventional impermeable materials, as maintenance, cost, and benefits and limitations ofdescribed in the Project Scope below, using the Wonderland each permeable surface type, as well as otherPower Centre in London, Ontario as a baseline study. This pertinent informationanalysis will help determine the feasibility of implementingpermeable surfaces. c) Contacted several local distributors and contractors in order to gather primary information about Project Scope permeable products available in Southern Ontario The Consultants will research permeable surfaces and d) Analyzed the net water savings capacity of each compare permeable products to existing conventional permeable product materials. The purpose of this comparison is to determine e) Conducted a financial analysis of each permeable the effectiveness of each product including permeability, product cost and durability while ensuring that the development objectives of the City are met. The Wonderland Power f) Developed conclusions and recommendations to Centre will be assessed as a sample of this comparison. reflect the findings of the Feasibility Study This Study was completed as a result of contributions from aInitially, a project proposal was developed by the Consultant number of individuals from various organizations. Theand refined in consultation with the Client to better reflect the Consultants would therefore like to thank the following:expectations of the City. Under the guidance of Dr. OmarOuda, the Consultants:APRIL 2010 Page | 1
  • JOVIAN DESIGN Figure 1: The relationship between impervious and pervious areaIsmail Abushehada, Ph.D., P. Eng. Michal Kuratczyk, M.Acc. and extent of sewerageCity of London DeloitteLois Burgess, P.Eng. Connor MalloyCity of London Duo Building Ltd.Darcy Decaluwe Omar Ouda, Ph.D., P.Eng, PMPStone in Style University of Western OntarioVito Frijia Denis Taves, OALASouthside Group Gardens in the SkyCarol Hayward Jarrett WoodwardCity of London Grand River Natural Stone Ltd.1.2 Urbanization in the City of LondonThe City of London is located in the heart of south-westernOntario, within close proximity to both Lake Huron and LakeErie. The City‟s population of more than 350,000 is expectedto grow steadily over the next two decades (StatisticsCanada, 2006). The City has also undergone significantgrowth over the last 15 years due to a persistentdevelopmental strategy (City of London, 2010). Source: Shuster et al., 2005.Increased impervious surface area is a consequence ofurbanization, in which there may be significant ensuing Increasing stress on existing stormwater infrastructureeffects on the hydrologic cycle (Shuster et al., 2005; Barnes provides incentive for municipalities like the City of Londonet al., 2002). This increasing proportion of impervious to explore the feasibility of innovative strategies such as thesurface creates shorter lag times between the arrival of implementation of permeable surfaces.precipitation and consequent high runoff rates and total flowvolume (Shuster et al., 2005). As a result, a municipality‟s Stormwater management facilities present an opportunity forsewershed or stormwater management system may be put the City to implement strategies that address municipalunder increasing pressure in order to compensate for this economic, social, and environmental interests. Currentlyadditional volume of runoff (Figure 1). there are approximately 85 stormwater facilities in London and over 100 more are planned for future developments.Page | 2
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYThese systems are expensive to build and maintain, withfacilities costing millions of dollars each.Permeable surfaces can potentially improve the costeffectiveness of storm water management systems, therebyalleviating pressure on municipal financial resources. Inaddition, the implementation of permeable surfaces canresult in environmental and social benefits. Increasingurbanization and subsequent Urban Heat Island effect,among other things, make the implementation of permeablesurfaces attractive to forward-thinking municipalities.APRIL 2010 Page | 3
  • JOVIAN DESIGN2. City of London Development Objectives 2.3 Needs & Guidelines The following provisions are necessary for parking,2.1 Introduction roadways, sidewalks and related developments in the City ofOne objective of this Study is to establish a basis for the London:inclusion of permeable surface stormwater managementsystems as part of the City of London Design Standards or Accommodate low-level traffic and heavy vehicularurban design guidelines. loads such as fire engines, delivery trucks, and heavy machineryAlthough there is a wide range of permeable products on the Allow for seasonal maintenance and snow clearingNorth American market, not all products are suitable for the Provide easy access and use by handicappedCity of London or meet the City‟s development goals and personsobjectives. As there are currently no specific designstandards in London pertaining to permeable surfaces, the The following objectives should be considered whenConsultants have developed a list of applicable development evaluating permeable surfaces:guidelines in order to aid in the evaluation of availablepermeable products. Enhance hydrology, geomorphology and water quality by protecting and promoting groundwater2.2 Official Plan for the City of London rechargeThe Official Plan for the City of London contains objectives Enhance the pedestrian environment while providingand policies to guide physical development within the easy access and use by all and promoting publicmunicipality (City of London, 2010). It provides direction for safetythe allocation of land use and provision of municipal services Minimize inconvenience and damage from surfaceand facilities in order to promote orderly urban growth and ponding and floodingcompatibility among land uses. Maximize the cost effectiveness of stormwater management facilitiesAlthough the Official Plan‟s primary function is to establish Minimize water and energy consumption throughpolicies for the physical development of the City of London, it resource conservation, landscaping and innovativealso has regard for relevant social, economic and design features and servicing techniquesenvironmental matters. As such, various sections of the Promote the reuse and recycling of wastesOfficial Plan were examined in order to help determine the Protect, maintain and improve surface andCity of London‟s development needs and establish support groundwater quality and quantityfor the implementation of permeable surfaces within the City.Page | 4
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY 3.6 Surface Analysis3. Project Approach & Methodology Using the City of London Public Zoning Map and the findings3.1 Introduction from the Site Visit and Site Context, a detailed Surface Analysis was conducted for the Wonderland Power Centre.The following is an account of the methodology used tocomplete this Report and develop conclusions and 3.7 Stormwater Management Inventoryrecommendations. A detailed project plan timeline can be Functional drawings of the Wonderland Power Centre werefound in Appendix C. provided by the Clients. Using this resource and information3.2 Site Visit Preparation gathered from online databases, the Consultants assessed the stormwater facility on the Study Site with regard to itsMaps and satellite images were gathered from online service capacity, lifespan, and required maintenance.databases to begin the initial geographic analysis of theStudy Site. 3.8 Permeable Surface Research, Analysis &3.3 Site Visit SummaryThe Consultants travelled to the Study Site to perform a A review of the current literature on permeable surfaces,visual analysis of the Wonderland Power Centre for the green roofs and stormwater management approaches andpurposes of the Surface Analysis and Stormwater techniques was conducted. Research was primarily focusedManagement Inventory (below). on the typology, water retention capacity, durability and cost of permeable surfaces and green roofs.3.4 Site Context The Consultants also contacted several local distributors andFollowing the Site Visit, a brief report discussing the existing contractors in order to gather primary information aboutland use patterns and geographic location of the Study Site permeable products available in Southern Ontario.was developed. Findings from the Permeable Surface Research, Analysis &3.5 City of London Development Objectives Summary are found throughout this Report, most notably inA list of applicable development objectives for the the Permeable Surface Overview and Product Analysis.implementation of permeable surfaces was developed basedon discussions with the Client and reviews of policies and 3.9 Net Water Savingsdesign standards governing development within the City of A comparative analysis of the net water savings of each typeLondon. of permeable surface and green roof was conducted using known runoff coefficients and the calculations found within the Surface Analysis of this Report.APRIL 2010 Page | 5
  • JOVIAN DESIGNThe water retention capacity of the existing Study Site andstormwater retention pond was calculated as a baseline, anddifferent permeable surface coverage scenarios wereformulated.3.10 Financial AnalysisThe current capital costs, operational and maintenancecosts, and potential savings from the reduction of stormwatermanagement facilities as a result of each permeable surfacewere compared using the Net Present Value and EquivalentAnnual Cost financial calculations.3.11 Conclusions & RecommendationsConclusions and recommendations were formulated basedon the findings outlined in this Report. The function andapplication, durability, maintenance, cost, and benefits andlimitations of all permeable pavement and green roof optionswere considered.Page | 6
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY developments (the majority of which have low-sloped roofs),4. Site Context – Wonderland Power Centre and there are small landscaped medians dispersedThe Wonderland Power Centre (WPC) is located in the throughout the site. Perhaps most notably, the south-easternsoutheast corner of Wonderland Road and Southdale Road corner of the Study Site contains the stormwaterin London, Ontario. Designated as a “Commercial Policy management facility that collects runoff for the entire StudyArea” in Schedule A of the City of London Official Plan area.(Appendix A) (City of London, 2006), the WPC is a fullyoccupied regional shopping centre, covering approximately With the exception of the soft, landscaped surfaces sparsely20 hectares of commercial land (Southside Group, 2008). located throughout the Site, the Study Area is composed entirely of hard surfaces that do not allow water to permeateThe WPC is bound by the Westmount Estates and into the underlying soil. This is explored in further detail inWestmount Estates II high density residential buildings the following section.(Tricar, 2010) to the east, Southdale Road to the north andWonderland Road to the west. The site is mirrored by a It is important to note that the WPC is only intended tosimilar commercial development, the Westwood Power provide a baseline analysis for this Feasibility Study.Centre, across Wonderland Road which utilizes the samestormwater management (SWM) facility. To the immediatesouth of the WPC commercial development is the “OldWonderland Mall” property. This area has been included aspart of the Study Site (Figure 2).It is important to note that although the entire SWMwatershed includes the Westwood Power Centre, the StudySite used in this Report only includes the fully developedWonderland Power Centre, the Old Wonderland Mall, andthe SWM facility itself.From an aerial perspective, the WPC can be divided intofour general types of hard surfaces: paved parking lotsand/or roadways; concrete sidewalks; roofs, and;landscaped areas. As seen in the map below, the majority ofthe WPC interior is paved asphalt parking spaces orroadways. The perimeter of the site is lined with commercialAPRIL 2010 Page | 7
  • JOVIAN DESIGN 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, 2010Page | 8
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY Approximately 17% of the Study Area is comprised of low-5. Surface Analysis sloped, commercial roofs, whereas sloped or pitched roofs represent approximately 2% of the Study Site.5.1 IntroductionThe Study Area covers approximately 220,000 m2 of land Table 1: Surface Analysis for the WPC Study Site(Table 1), of which approximately 70% is comprised ofimpermeable surfaces. In other words, more than two-thirds Surface Analysis for the Wonderland Power Centreof all precipitation that falls on the site may begin to flow as Surface Type Area (m2) Area (%)urban runoff, with minimal, if any vegetative buffers to Low-sloped Roofs 37,550 17intercept it. This is a substantial amount of surface flow, and Sloped Roofs 5,193 2therefore requires a catchment area (i.e., SWM facility) of Parking Lots/Roadways 96,161 44sufficient size to store the excess water and mitigate further Sidewalks 14,812 7runoff. The cost to build such structures generally requires asignificant amount of funds for municipalities and, ultimately, Medians 9,987 5taxpayers (AECOM, 2009). SWM Pond 42,983 19 Others (e.g., Green Space;The primary impermeable surfaces examined in this section 14,098 6 Temporary Structures)of the Report include roofs, parking lots and low-traffic TOTAL 220,784 100roadways, and sidewalks. Other surfaces that will beexamined include medians, green spaces, and temporarystructures (e.g., shopping cart corrals). Calculations for this The low-sloped roofs are generally sealed with ananalysis were completed through on-site investigations and impervious asphalt layer, while pitched roofs are generallysatellite interpretation using a modified City of London Public covered with impervious asphalt shingles (e.g., LoblawZoning Map (Appendix A). Superstore) or other highly impervious materials such as clay tiles (e.g., Angelo‟s Italian Bakery and Deli). In both5.2 Study Area Surfaces instances, precipitation is directed from the roof to a5.2.1 Roofs drainage system consisting of gutters, downspouts, and piping, and ultimately to the surface below (eitherThe primary function of roofs is to protect the interior and impermeable asphalt or cement, or permeable grassstructural components of a building from weather elements, surfaces which allow infiltration). Vegetated green roofs mayparticularly precipitation. Roofs within the Wonderland act as an intermediate step to this process, interceptingPower Centre are the second most prevalent surface,making-up approximately 20% of the entire Study Area.APRIL 2010 Page | 9
  • JOVIAN DESIGNprecipitation and helping to reduce runoff from reaching theSWM 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 a b c5.2.2 Parking Lots and Low-Traffic Roadways and grid pavers, may be used to divert urban runoff fromThe principal function of parking lots is to accommodate a SWM facilities, as precipitation is able to pass through thesteady volume of visitors and their automobiles. Parking lots paved surfaces and recharge groundwater sources or thewithin the WPC site are the most significant surface water table (Beecham, 2007; Boving, 2008).typology, composing more than 40% of the entire StudyArea. Part of this percentage includes a series of low-trafficroadways connecting the parking lots together. Generallylocated around the peripheries of parking lots and buildings,these features are primarily coated with impermeableasphalt, but may also include concrete pavement as well.Porous pavements, including permeable asphalt, porousconcrete, Permeable Interlocking Concrete Pavers (PICP)Page | 10
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYFigure 4: Asphalt surfaces in the WPC Study Area Figure 5: Commercial concrete sidewalks in the WPC Study Area5.2.3 SidewalksThe main function of sidewalks is to provide a suitable transitroute and safe place for pedestrians to travel, by separatingthem from vehicular traffic. Raised sidewalks within theWonderland Power Centre represent an overall surfacecomposition of close to 7% of the entire Study Area.Sidewalks are generally composed of impermeable concretepavement which prevents percolation of precipitation and 5.2.4 Medianssnow melt (Bean et al., 2007). Permeable pavers and porous The primary function of medians is to organize and directconcrete may be used to help alleviate the stress of surface automobile traffic, as well as to provide shade and enhancerunoff on SWM facilities by increasing infiltration rates on the aesthetic value of commercial parking lots (Celestian &site. Although they make up a small percentage of the total Martin, 2003). Medians within the Wonderland Powerarea of the WPC, sidewalks may be the most feasible Centre are the least prevalent surface, making-up slightlysurface to change, while acting as a consistent penetrable more than 4% of the entire Study Area. They are sparselybuffer. 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 6APRIL 2010 Page | 11
  • JOVIAN DESIGNinches off the ground), medians generally do not help reduce Figure 7: Stormwater Management Pond adjacent to the WPC showing a) an inflow culvert, b) a near full pond, overflowstormwater runoff or flow over the parking lots. spillway and forebay, c) and emergency spillwayFigure 6: Medians are dispersed throughout commercial parking lots to help guide traffic and provide aesthetic relief from a dominating impervious pavements b c5.2.5 Stormwater Management FacilitiesThe main function of a SWM facility is to store runoff fromprecipitation and snow melt, which may otherwise lead toflooding or erosion, and adversely affect water quality (MOE,2003). The SWM facility used to mitigate runoff at theWonderland Power Centre makes up nearly 20% of theentire Study Area. More detail on this facility can be found inthe Stormwater Inventory section of this Report. 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,Page | 12
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYshrubs, herbaceous perennials and decorative grasses,rocks, and maintained grass lawns. Although their functionis mainly for aesthetic and recreational purposes, urbangreen spaces may help alleviate the problem of surfacerunoff by increasing infiltration rates and acting as apenetrable buffer (Benedict & McMahon, 2002).Landscaped green spaces may be intensified to provide amore significant role or function, both as an aesthetic tooland as a buffer, especially in commercial and residentialzones where impermeable surfaces generally dominate.Temporary structures, including roofed shopping cart corralsand seasonal greenhouses are also present within the StudyArea.Figure 8: Other surfaces within the WPC include a) roofed shopping cart corrals and b) landscaped areasAPRIL 2010 Page | 13
  • JOVIAN DESIGN 6.3 Servicing Capacity of Bradley Avenue SWM Facility6. Stormwater Management Inventory The City of London averages 987mm of precipitation per6.1 Introduction year (Environment Canada, 2010).The WPC is wholly serviced by the Bradley Avenue As illustrated in Table 2, the Bradley Avenue SWM facilityStormwater Management Facility within the Pincombe Drain has a total stormwater retention capacity of 45,238m3.catchment area (Appendix A). A Stormwater Management Generally speaking, the facility has a total permanentInventory is required to assess the present condition and volume of 7.500m3, with a drawdown time of 72 hoursrequired maintenance of the SWM facility at the Wonderland (Development Engineering, 2005).Power Centre. As such, functional designs, entitled FinalStormwater Management Report for the Bradley Avenue Table 2: Bradley Avenue SWM facility volume summaryStormwater Management Facility were obtained from the Bradley Avenue SWM Facility Volume SummaryCity of London Engineering and Review Division, and used Water Quality Volume Required Providedto assess the servicing capacity, present condition andrequired maintenance of the SWM facility. Permanent pool volume per hectare based on protection 115 m3/ha 118 m3/ha6.2 Construction of Bradley Avenue SWM Facility level and imperviousness (MOE) The total projected cost for the Bradley Avenue SWM facility was $2,456,660 of which the cost for Total Permanent pool volume 5615 m3 7500 m3 construction of inlet/outlet sewers was $636,660 (AECOM, 2009). Total SWM Facility Volume – 45238 m3 Prior to construction, on-site siltation and erosion Baseflow and Erosion Volume Required Provided control measures were taken in order to prevent the transportation of eroded soils off-site into Total storage volume per hectare 200 m3/ha 160 m3/ha downstream properties or watercourses. These Total baseflow and erosion measures included the installation of 140m of regular 12685 m3 10147 m3 duty silt fences and 300m of heavy duty silt fences. volume Source: Development Engineering, 2005 A sediment trap of approximately 70m x 20m x 1m was constructed adjacent to the SWM Facility, to store sediment deposition.Page | 14
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYTable 3 summarizes the return period of flooding as used in Table 3: SWM facility discharge and storage summary for varying rain eventsthe Bradley Avenue SWM facility modeling. The stormwaterdischarge into the SWM facility, for return periods of 2, 5, 10, Discharge and Storage Summary for 2-250 Year Rainfall Events25, 50, 100 and 250 years has been tabulated and the Return Discharge Discharge Storage Pondvolume corresponding to the respective flooding events has Period into SWM from volume elevation/depthbeen calculated (Development Engineering, 2005). facility SWM utilization (m)In the event of a 250 year storm (6 hour duration), 26,524 m3 (m3/s) facility (m3)of the SWM facility will be utilized. This number represents (m3/s)approximately 59% of the total volume of the facility at 2 year 5.90 0.28 13271 266.0845,238 m3. Thus, the anticipated single-event volumeutilization from the SWM facility is less than the maximum 5 year 7.68 0.85 16380 266.27available storage volume (Development Engineering, 2005). 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 11.72 2.56 21571 266.58 year 250 15.01 3.10 26524 266.86 year 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).APRIL 2010 Page | 15
  • JOVIAN DESIGN6.4 Subsurface Conditions Annual maintenance costs for the SWM facility at the WPCA subsurface analysis was carried out at the WPC site in is estimated at $20,000 per year (Weber, 2010).order to install standpipes and the groundwater table wasdiscovered to be 7.9m to 8.1m below the surface(Development Engineering, 2005). According to Brown(2008), these depths are suitable for the installation ofpermeable surfaces, which require a groundwater table of atleast 1.1m to 1.5m from the surface.6.5 Maintenance of the SWM FacilityThe maintenance responsibilities for the Bradley AvenueSWM facility are separated into general maintenance,sediment maintenance and sediment disposal (DevelopmentEngineering, 2005).General maintenance is carried out three or four times ayear. The activities include weed control, grass cutting andoutlet pipe opening maintenance. Sediment maintenance iscarried out when the sediment removal efficiency is reducedby 5%. Sediment disposal is carried out after a sedimentchemical analysis is completed. The Ministry of Environmentguidelines for Use at Contaminated Sites in Ontario and theOntario Environmental Protection Act (OEPA), Regulation347, Schedule 4 Leachate Test, Ref. 15 provide theapplicable guidelines for determining sediment disposaloptions (Development Engineering, 2005).Inspection is carried out at least once per month during dryweather, and a Sediment & Erosion Control Maintenance &Monitoring Report is completed (Development Engineering,2005).Page | 16
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY7. Permeable Surfaces Overview7.1 IntroductionThe level of urbanization is rising; by 2030 it is expected that83% of people in developed countries will live in urban areas(Mentens, Raes & Hermy, 2005). Urbanization results in thedisplacement of cropland, grassland and forests by theimplementation of impervious surfaces. This greatlyintensifies stormwater runoff, diminishing groundwaterrecharge and enhancing stream channel and river erosion(Mentens, Raes & Hermy, 2005).Permeable surfaces are surfaces which allow water topercolate or travel through their structure into the underlyingground layer, thereby relieving pressures on traditionalstormwater management systems (SWITCH, 2007). Theadvancement of new technologies has brought many newpermeable products onto the market; including porousasphalt, permeable concrete, green roofs and otheremerging technologies. If properly installed and maintained,permeable pavements are typically designed to handle asmuch as 70-80% of annual rainfall (Metropolitan AreaPlanning Council, 2010).APRIL 2010 Page | 17
  • JOVIAN DESIGN 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 2006). As urbanization increases, so too does the need forinfiltration of water into the underlying soil for the purposes of increased stormwater infrastructure. The development of agroundwater recharge (Sansalone, Kuang & Ramieri, 2008). new individual stormwater management facility for a city theRather, rainfall is carried over the surface of pavements as size of London can cost anywhere between just over $1runoff (Figure 9), and must be captured using municipal million (CAD) to just under $7 million (CAD); including landstormwater management infrastructure. In addition to the acquisition, construction of ponds, and necessary pipingnegative environmental impacts associated with systems (AECOM, 2009).impermeable surfaces (i.e., the movement of pollutants intonatural systems and increasing runoff peaks and volumes), Permeable surfaces, on the other hand, serve as moreimpermeable surfaces are also a costly economic environmentally conscious, low-impact developmentexpenditure (Sansalone et al., 2008; Gilbert & Clausen, materials for rainwater runoff control (Figure 10) (Sansalone, Figure 10: Interaction between rainwater and permeable pavement Modified from: Sansalone et al., 2008, p. 667)Page | 18
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYet al., 2008). Although some surfaces have higher porosities 23 cm minimum with aggregates between 4 and 7.5 cm inthan others, they all work to restore the in situ hydrology of a size with 40% voids is recommended), an optional bottomsite by reducing runoff, filtering and treating infiltrating runoff filter course, filter fabric (e.g., geotextile fabric) and subgradeand reducing thermal pollution and temperature (Sansalone material consisting of larger aggregates that acts as aet al., 2008). By reducing the rate and quantity of temporary storage capacity to hold the collected waterstormwater runoff, permeable pavements reduce the (Walker, 2006). Figure 11 shows a typical cross-section of ademand on stormwater treatment facilities (Landers, 2008), permeable asphalt surface.thereby reducing costs for capital infrastructure, Figure 11: Typical cross-section of a permeable asphalt surfacemaintenance and operation (SWITCH, 2007).7.2 Permeable Asphalt7.2.1 IntroductionConventional asphalt is comprised of asphalt cement andcoarse aggregates, including stone, sand, and gravelcompacted together (Freemantle, 1999). Traditionally, thismedia consists of impermeable substances which do notallow precipitation or surface runoff to infiltrate into the soil orrock beds. A novel solution to impervious asphalt was first Source: Fancher & Townsen, 2003developed in the 1970s, in which fine sediments (e.g., sandwith a grain size less than 0.075 mm in diameter) were Many factors must be taken into account before a projectremoved, resulting in a network of continuously linked voids can be proposed or designed using permeable asphalt,to allow the passage of fluids through the pavement surface including local soil characteristics, local topography, climate,and ultimately to groundwater sources or the water table and traffic loading (Brattebo & Booth, 2003). For instance, it(Beecham, 2007; Boving, 2008). is recommended that permeable asphalt pavement be used on sites with gentle slopes (e.g., surface grade less than7.2.2 Function and Application 5%), permeable soils (i.e., well drained or moderately wellWalker (2006) suggests that the permeable asphalt surface drained), and relatively deep water table and bedrock levels(e.g., approximately 5 to 10 cm in depth with 15-25% voids (Gunderson, 2008; Beecham, 2007).or pore space) should be generally underlain by a top filtercourse (e.g., 5 cm of 1.3 cm crushed stone aggregate), a Conventional asphalt is largely used as a material toreservoir course (determined by the average storage construct highways, roadways, airfields, and parking lots.volume, structural capacity, or frost depth; usually an 20 or Alternatively, permeable asphalt pavement is appropriate forAPRIL 2010 Page | 19
  • JOVIAN DESIGNlow-traffic applications such as walkways, low-traffic streets, Despite the results of this Study, many researchers maintainand along highway shoulders (Freemantle, 1999; Brattebo & that porous asphalt pavement performs relatively well in coldBooth, 2003). weather climates compared to conventional design (Gunderson, 2008; Roseen & Ballestero, 2008; Roseen et7.2.3 Durability al., 2009; Backstrom and Viklander, 2000). TheseThe lifespan of a parking lot situated in a northern climate, researchers argue that porous asphalt, and other low impactand made from conventional pavements is approximately 15 development designs, have a high level of functionalityyears (EPA, 2009). A properly designed, installed, and during winter months and that frozen filter media, generally,maintained permeable asphalt pavement, on the other hand, do not reduce performance. Figure 12 shows wintermay have a lifespan of 20 to 30 years (Gunderson, 2008). performance of different stormwater components.The regional climate of Southwestern Ontario, andspecifically London, presents many obstacles to theeffectiveness of permeable asphalt pavement due to coldweather. For instance, Backstrom and Bergstrom (2000)found that at freezing point, the infiltration capacity of porousasphalt was about 40% lower (7.4 mm/min) than that near20oC (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 thiscapacity up to 90%. As a result, typical snowmelt conditionsfor porous asphalt may only yield an estimated 1-5 mm/mininfiltration capacity (Backstrom & Bergstrom, 2000;Stenmark, 1995). However, several confounding variablesfound during experimentation may be at fault for the overallpoor performance. Firstly, the asphalt pieces were takenfrom a field site which had been in operation for two years.Secondly, the asphalt was not cleaned; nor were the porespaces 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, allowingwater to effectively infiltrate the media.Page | 20
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYFigure 12: Winter performance vs. general indicators, including Dust and sand tends to clog the pores of porous asphalt runoff control, pollution control, and level of integration, for different stormwater components 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 isSource: Backstrom and Viklander, 2000 approximately $5.50 to $10.76 (USD) per metre squared (EPA, 2009). However, the underlying stone bed is usually7.2.4 Maintenance more expensive than those found in a conventional sub-Due to the nature of porous asphalt pavement, regular base, due to the greater depths of aggregates requiredinspection for surface clogging must be undertaken, (Beecham, 2007).especially after large storm events, which may also increasesandy discharge (Beecham, 2007). In cases of clogged or Special training or techniques are not generally required forreduced surface porosity, the pavement can be cleaned by a application of porous asphalt, as the laying process is similarvacuum sweeper or pressure washer 2 to 4 times per year to to that of conventional asphalt (Walker, 2006).avoid build-up of debris, and to prevent potential decreases 7.2.6 Benefits and Limitationsin infiltration capacity (Bean et al., 2007; Balades et al., The key advantage of permeable asphalt is that it retains1995). stormwater onsite, which may decrease surface runoff withFor large commercial developments, however, this implies low peak discharge (Bean et al., 2007; Rushton, 2001). Itan additional cost that should be taken into consideration may also act as a potential water quality treatment processwhen comparing product types. by intercepting the contaminants of urban stormwater runoffAPRIL 2010 Page | 21
  • JOVIAN DESIGNprior to infiltration into soil (Beecham, 2007; Brattebo & 7.3 Permeable ConcreteBooth, 2003; Bean et al., 2007). 7.3.1 IntroductionAnother possible benefit of using porous asphalt in cold Concrete in the form of permeable interlocking concreteweather climates is that melted water infiltrates through the pavers (PICP), concrete grid pavers (CGP) and porousmedia before it freezes, which may cause fewer problems concrete (PC) (Figure 13) is commonly used to increasewith slipperiness and black ice related accidents, for surface infiltration rates, thereby mitigating stormwater fromexample, during cold nights (Backstrom & Bergstrom, 2000). conventional stormwater systems (Bean, Hunt, & Bidelspach, 2007a). Infiltration rates depend on a number ofParking lots and roads tend to be sources of water pollution factors, including the type of permeable concrete productbecause of their extensive impervious surfaces, in which that is applied, soil infiltration rate, and installation of themost precipitation that falls becomes urban runoff. Motor permeable concrete product (i.e. the aggregate material thatvehicles are a constant source of pollutants, the most is used as a filler, and the size and type of sub-base that issignificant being gasoline, motor oil, polycyclic aromatic installed) (Table 4) (Bean et al., 2007a).hydrocarbons (found in the combustion by-products ofgasoline, as well as in asphalt sealants used to maintain Figure 13: a) PICP, b) CGP, c) PCparking lots), and heavy metals (Bean et al., 2007; Rushton,2001; Boving et al., 2008). According to a cold climate studyby Backstrom and Viklander (2000), cold vehicle enginesproduce 2 to 8 times more potentially harmful particles thandoes a warm engine, which may accumulate onimpermeable surfaces and be subject to runoff, withimplications for water contamination.Another study by Boving et al. (2008) suggests that porousasphalt is effective at removing organic and metalcontaminants. However, permeable asphalt surfaces, whichallow liquid infiltration, may lead to possible groundcontamination within the surface of the parking lot. Althoughthis process can filter the water, contaminants may seepdirectly into groundwater, especially where there isgroundwater abstraction downstream for drinking water(Howard & Beck, 1993; Legret & Colandini, 1999). Source: Bean et al., 2007bPage | 22
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYResults from runoff studies indicate that permeable concretepavements may not only reduce runoff, but also eradicaterunoff 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 productsFactors Affecting Infiltration Rates of Permeable Concrete Products Site Slope Thickness of Permeable Surface Base SIRProduct Soil Filler Base (m2) (%) (mm) (mm) (mm/h) Kalmia sandy Coarse grade CGP 630 0.5 90 Yes; sand 50 580 soil sand Seagate fine PC 370 0.33 200 NA No NA 230 graded sand Bay Meade Yes; stone & PICP 740 0.4 76 NA 275 20 X 1013 sandy soil gravel Loamy sand Yes; stone & PICP 120 NA 76 NA 275 40 X 1013 soil gravelSIR = Surface Infiltration Rate; Source: Bean et al., 2007a7.3.2 Function and Application blocks with inner voids between the blocks that permit waterPICP is defined as concrete block pavers that, when in to infiltrate in the same way as PICP. PC is defined asplace, create voids located at the corners and midpoints of altered standard concrete, as fine aggregate has beenthe pavers, allowing water to infiltrate through an aggregate removed from the standard mix, permitting interconnectedmaterial (Bean et al., 2007b). CGP is defined as concreteAPRIL 2010 Page | 23
  • JOVIAN DESIGNvoid spaces to form during curing, thus allowing water to Figure 14: Typical installation for exfiltrationinfiltrate through the material (Bean et al., 2007b).7.3.2.1 Function and Application of PICP and CGPThe primary difference between permeable pavers andconventional pavers is base materials and void space (Beanet al., 2007b; Unilock, 2009). Permeable paver systems usecrushed, angular, open-graded aggregate base materialsthat have a void space or porosity of approximately 40%.Base storage capacities depend on a number of factorsincluding rainfall and base depth (Table 5) (Unilock, 2009).The proper installation of the base is very important to theoptimal function of PICP and CPG systems (Smith, 2006).Figure 14 illustrates the appropriate installation of a typical Source: Uni-EcoLocTech, 2008exfiltration system including base compositions andmeasurements. This system fully exfiltrates, by infiltrating The application of PICP and CGP products depend on thewater directly into the base and extruding it to the soil. specific material that is being used as well as the location ofOverflows are managed through perimeter drainage to the project. Unilock, a company that sells permeableswales, bio-retention areas or storm sewer inlets. Partial pavers, manufactures its products to meet the ASTM C936exfiltration systems are less common than full exfiltration standard which allows the product to support semi-trucksystems and include drainage by perforated pipes. In this traffic, heavy-traffic and high-load environments (Unilock,case, excess water is drained from the base by pipes to 2009). The application of Unilock products varies greatly.sewers or a stream (Smith, 2006). 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 occasionallyPage | 24
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYused 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 Rainwater Harvest Base Storage Surplus/(Deficit) Criteria Volume Capacity Storage Rainfall Surface Area Base Depth Void % (m3) (m3) (m3) (mm/hr) (m2) (cm) Space 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, 20097.3.2.2 Function and Application of PC concrete contains between 15% and 25% voids that typicallyPC is a paste composed of water and cementitious materials allow flow rates of approximately 34 mm/s, although it canthat forms a thick coating around aggregate particles be much higher (Figure 15) (Tennis, et al., 2004).(Tennis, Leming, & Akers, 2004). Void space is created byadding little or no sand which results in a system that ishighly permeable and drains quickly. The hardenedAPRIL 2010 Page | 25
  • JOVIAN DESIGNFigure 15: Typical installation of porous concrete surface Table 6: Applications of pervious concrete Applications of Porous Concrete Low-volume pavements Artificial reefs Residential roads, alleys, and Slope stabilization driveways Sidewalks and pathways Well liningsSource: National Ready Mixed Concrete Association, 2010 Parking lots Tree grates in sidewalksPC can be applied in a variety of settings. It can be used in Low water crossings Foundations/floors forparking lots, tennis courts, greenhouses and as pervious greenhouses, fish hatcheries,base layers under heavy duty pavements (Table 6) (Tennis aquatic amusement centres,et al., 2004). Properly installed PC can achieve strengths in and zoosexcess of 20.5 MPa and flexural strengths of more than 53.5MPa. This strength is more than sufficient for most low- Tennis courts Hydraulic structuresvolume pavement applications, including high axle loads forgarbage truck and emergency vehicles such as fire trucks Subbase for conventional Swimming pool decks(Tennis et al., 2004). As PC matures, its compressive concrete pavementsstrength increases (Park & Tia, 2003). Special mix designs,structural designs and placement techniques can be altered Patios Pavement edge drainsto accommodate more demanding applications (Tennis etal., 2004). Walls (including load-bearing) Groins and seawalls Source: Tennis et al., 2004Page | 26
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY7.3.3 Durability PC can be susceptible to the effects of aggressive chemicals in soils or water, such as acids and sulphates (Tennis et. al.,7.3.3.1 Durability of PICP 2008). If isolated from high-sulphate soils and groundwater,PICP is particularly durable and has the capacity to PC can be used. Abrasion resistance is also a concern aswithstand high traffic areas and climatic uncertainty (Toronto PC has a rough surface texture and open structure. PC canand Region Conservation Authority [TRCA], 2007). A study be particularly problematic where snowploughs are used toby the TRCA (2007) indicated that permeable pavement clear pavements although studies indicate that PC can allowcontinued to function normally throughout the winter months snow to melt faster thus requiring less ploughing (Tennis et.during winter rain events, with minor amounts of infiltrate al., 2008).measures even during very cold periods. 7.3.4 Maintenance7.3.3.2 Durability of CGPCGP is recommended for light-duty use, thus applications 7.3.4.1 Maintenance of PICP, CGP and PCvary (Pavers by Ideal, 2005). Certain CGP products have Clogging can occur as a result of fine particle accumulationthe capacity to withstand harsh winter climates and are in the void spaces of permeable pavements (Bean, Hunt,“snow-plough safe.” Freeze-thaw conditions have no Bidelspach & Burak, 2004). The rate of clogging increasesdemonstrated effect on certain CGP products (Pavers by as more fine particles (fines) are trapped since smallerIdeal, 2005). particles trap larger particles. In most cases, clogging reduces surface infiltration rates. Clogging can be limited,7.3.3.3 Durability of PC however, through regular maintenance, either by a vacuumPC is often criticized for its vulnerability to freeze-thaw sweeper or pressure washing thereby improving surfaceconditions (Tennis et. al., 2008). However, freeze-thaw infiltration rates from unmaintained infiltration rates (Bean etresistance depends on the saturation level of the voids in the al., 2007b; Smith, 2006). Clogging can also be limitedconcrete at the time of freezing. Because PC drains rapidly, through strategic site placement away from disturbed soilsaturation is often prevented from occurring. In fact, areas.evidence suggests that snow-covered pervious concretemelts quicker as voids in the material allow snow to thaw One study concluded that maintenance was vital tomore quickly than conventional pavements. Different factors sustaining high surface infiltration rates of CGP in particularimprove durability of PC in freeze-thaw conditions. For (Bean et al., 2007b). Without maintenance, the medianexample, entrained air in the PC paste can dramatically average infiltration rate of CGP was 4.9 cm/h; while withimprove freeze-thaw protection. Placement also plays an maintenance, the median infiltration rate was 8.6 cm/h (Beanimportant role as specific installation is recommended in et al., 2007b).freeze-thaw environments (Tennis et. al., 2008).APRIL 2010 Page | 27
  • JOVIAN DESIGNThe study also concluded that the selected site of permeable permeable pavements may not require a collection pond aspavement applications was a significant factor in preserving large as impervious-paved surfaces, space can be usedhigh surface infiltration rates (Bean et al., 2007b). In more efficiently (ICPI, 2008).particular, locating PICP and PC away from disturbed soil 7.3.6 Benefits and Limitationsareas was of great importance in maintaining high surfaceinfiltration rates. The authors of this particular study also PICP and CPG have the capacity to remove pollutants,found that permeable pavements installed in sandy soil improving the quality of exfiltrate (Tennis et al., 2008). Theenvironments maintained relatively high surface infiltration material allows the rainfall to percolate into the ground whererates, regardless of pavement age or type (Bean et al., soil chemistry and biology are able to “treat” the polluted2007b). water naturally. This results in the reduction or elimination of stormwater retention areas. Also, “groundwater and aquiferBean et al. (2007b) suggest that a storage layer improves recharge is increased, peak flow through drainage channelsrunoff reduction potential. Keeping the permeable surface is reduced and flooding is minimized” (Tennis et. al., 2008,free of fine particles, performing regular maintenance and p.4). PICP is also easy to replace as individual pavers canconstruction on sandy, in situ soils may also increase runoff be removed in the event of damage (Park & Tia, 2003). Thisreduction potential. results in lower replacement costs and lessens the negative environmental impact of large scale product replacementIn climates where snow removal equipment is employed, (Hirshorn, 2010).damage can occur to PICP and CGP. This may require thereplacement of damaged blocks thereby increasing PC has the capacity to remove pollutants from infiltrate atmaintenance costs. high rates (Park & Tia, 2003). Pollutant removal rates are variable as water purification can be affected by the size of7.3.5 Cost aggregate and void content in the PC paste. One study7.3.5.1 Cost of PICP, CGP, and PC indicates that PC composed of a smaller size of aggregateThe cost of permeable concrete pavement varies according and a higher void content greatly removes total nitrogen (T-to location, distributor, and scope of project (among other N, mg/l) and total phosphorous (T-P, mg/l) from the testfactors). For example, PICP is generally more expensive water in comparison to PC pastes with a larger sizethan conventional asphalt or concrete pavements that rely aggregate and a lower void content. Smaller sizedon a stormwater collection pond (Interlocking Concrete aggregate and higher void content increase the surface areaPavement Institute [ICPI], 2008). PICP may be cost-effective of the concrete‟s porosity. The composition of the PC pastein a new development where regulations limit impervious can largely affect the ability of the material to removecover and space is limited. Because PICP and other pollutants (Park & Tia, 2003).Page | 28
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYPermeable surfaces should not be used in locations with the production of each cubic meter of concrete (Bouzoubaâhigh pollutant loads. These locations include commercial & Fournier, 2005). SCMs were used mainly due to their lownurseries, recycling facilities, fuelling stations, industrial costs and performance-enhancing aspects. Fly ash is usedstorage, marinas, some outdoor loading facilities, public in various concrete applications because of improvement inworks yards, hazardous materials generators (if containers workability, reduction of heat of hydration, increased waterare exposed to rainfall), vehicle service and maintenance tightness and ultimate strength, and enhanced resistance toareas and vehicle and equipment washing and steam sulphate attack (especially in western Canada) and alkali–cleaning facilities (Hirshorn, 2010). Permeable paving aggregate reaction (AAR) throughout Canada (Bouzoubaâ &should also not be used in high traffic and/or high speed Fournier, 2005).areas as permeable paving has lower load-bearing capacitythat conventional pavement (Hirshorn, 2010). The use of SCMs in the cement and concrete industries can render benefits in engineering, economic, and ecological7.3.7 Supplementary Cementitious Materials terms (Malhotra & Mehta, 1996). Engineering benefits of theThe National Ready Mixed Concrete Association (2008) incorporation of SCMs into a concrete mixture includeclaimed that the construction industry is committed to improvement in the workability and the reduction of thecontinuous environmental improvement through process water. This mixing enhances the ultimate strength,innovation and product standards that lead to reduced permeability, and durability to chemical attack along with anenvironmental impact. One method of improving product improved resistance to thermal cracking.standards is through the mixing of Portland cement withsupplementary cementitious materials (SCMs) for various In terms of residential application, concrete is used inuses. basement walls and floors, driveways, steps, sidewalks and a small amount of concrete products such as paving blocks,Bouzoubaâ and Foo (2005) contend that SCMs, including fly retaining walls, and masonry blocks. Specifically, SCMsash, ground granulated blast furnace slag (GGBFS), silica have proven to be very effective in producing durable,fume and natural pozzolans can be mixed with Portland freeze-thaw tolerant sidewalks (Bouzoubaâ & Fournier,cement. These blended cements are less energy intensive 2005).and made with by-products or wastes. Therefore, theyreduce the solid waste burden on landfills and offer 7.4 Permeable Pavement De-icing agentsperformance benefits for certain applications (Committee E- In many northern countries, such as Canada and the USA,701 Materials for Concrete Construction, 2001). One of the one of the main de-icing agents of choice for safe drivingmain objectives of increasing the use of SCMs in concrete conditions in municipal areas is common salt (sodiumproduction is to reduce the release of CO2 associated with chloride) because of its cost effectiveness (Liu et al., 2006). Urbanization leads to increases in impervious surfaces andAPRIL 2010 Page | 29
  • JOVIAN DESIGNcomplex systems, such as roads, parking lots, and sidewalks USA (Feig & Paya, 1998). In the past few years, high levelsthat receive chemical de-icer to keep them free of ice and of sodium and chloride (>2000 mg/L) have been found insnow during winter (Daley et al., 2009). As a result of these many shallow groundwater wells in and around the GTAlarger surfaces, additional road salts are required which may where urbanization is greater than 80% (Williams et al.,adversely affect soil and vegetation systems, human health, 1999). In general, only wells or reservoirs near salt-treatedas well as the quality of water systems (e.g., groundwater surfaces or salt storage facilities are most likely to becomeand streams) due to increased levels of Cl- (Williams et al., susceptible to salt infiltration, whereby road salts can enter2005; Williams et al., 1999). drinking water supplies by migrating through soil into groundwater or by runoff and drainage directly into surfaceThe Greater Toronto Area alone applies more than 100,000 water (Werner & diPretoro, 2006).tonnes of salt each winter (Williams et al., 1999) andapproximately 5 million tonnes of sodium chloride are Due to concerns of clogged pores by sand and salt, a liquidconsumed each year in Canada for de-icing roles de-icer is therefore recommended for use on permeable(Environment Canada and Health Canada, 2001). If high pavements as it drains out with the snow and ice duringenough concentrations of these road salts reach melting, leaving the porosity of the pavement largely intactgroundwater zones, contamination can occur and negatively (Walker, 2006). However, less research has been devotedaffect drinking water quality, fresh water systems, and towards liquid de-icers, including CaCl2, KCl, and MgCl2aquatic ecosystems (Ramakrishna & Viraraghavan, 2005). (Ramakrishna & Viraraghavan, 2005). Generally the chlorideDe-icing salts, particularly NaCl contribute ions to the soil, ions of these substances have similar environmental impactsaltering pH and the soil‟s chemical composition, which may as rock salt (NaCl), but have been found to present lesslead to vegetative stress and disrupt plant function toxicity to aquatic organisms, as well as having a limited(Bogemans et al., 1989; Guntner & Wilke; Trombulak & impact on human health (Fischel, 2001).Frissell, 2000). NaCl is also an environmental concernbecause of its toxicity to aquatic organisms; its alterations to Another option for snow and ice removal on permeablesoil structure and decreased permeability (Ramakrishna & pavement is the liquid form of calcium magnesium acetateViraraghavan, 2005; Fischel, 2001); and its adverse effects (CMA) which may provide the most environmentally friendly,on human health (Environment Canada and Health Canada, although a more expensive alternative to sodium chloride,2001). while leaving the porosity of the pavement largely intact. CMA is an organic de-icing agent which may largely beThe main human impact of ingesting large amounts of salt is broken down by biodegradation (Fischel, 2001; Ramakrishnahypertension leading to cardiovascular disease, which could & Viraraghavan, 2005). There is, however, some concernaccount for thousands of deaths a year in Canada and the that the acetate-based de-icer has the potential to causePage | 30
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYoxygen depletion in rivers, streams, and lakes; however, it is Figure 16: Typical cross-section of a green roofhoped that the agent breakdown before such an occurrence(Fischel, 2001; Ramakrishna & Viraraghavan, 2005). Thereis also some debate over pH alterations and the corrosivepotential caused by the agent (Ramakrishna &Viraraghavan, 2005). Due to CMA containing phosphorousand nitrogen, eutrophication may occur to nearby waterbodies, and as a result adversely affect aquatic ecosystems(Fischel, 2001).7.5 Green Roofs7.5.1 Introduction Source: Kosareo & Ries, 2007Roof surfaces account for a large portion of impervious 7.5.2 Function and Applicationcover in urban areas. Establishing vegetation on roof-tops, Green roofs are an emerging strategy for mitigatingknown as green roofs, is one method of recovering lost stormwater runoff. They offer numerous benefits such as:green space that can aid in mitigating stormwater runoff (van Stormwater mitigation; insulation for buildings; an increase inWoert, et al., 2005). the life span of a typical roof by protecting the roof components from exposure to ultraviolet rays, extremeA green roof, i.e., a roof with a vegetative cover (Figure 16), temperatures and rapid temperature fluctuations; filtration ofis one passive technique that can be used to address harmful air pollutants; an aesthetically pleasing environmentenvironmental issues in an urban setting (Kosareo & Ries, to live and work in; habitat for a range of organisms, and; the2007). Green roofs have been a standard construction potential to reduce Urban Heat Island effect (van Woert etpractice in many countries for hundreds, if not thousands of al., 2005). However, many consider stormwater runoffyears, mainly due to the excellent insulative qualities of the mitigation to be the primary function of green roofs due tocombined plant and soil layers (sod) (Peck & Kuhn, n.d.). In the prevalence of impervious surfaces in urban areas (vanthe cold climates of Iceland and Scandinavia, sod roofs Woert et al., 2005). Furthermore, green roofs have thehelped to retain heat, while in warm countries such as potential to improve thermal performance of a roofing systemTanzania, green roofs keep buildings cool. Canadian through shading and evapotranspiration, thus reducing aexamples of early green roofs, imported by the Vikings and building‟s energy demand for space conditioning (Kiu &later the French colonists, can be found in the provinces of Baskaran, 2003).Newfoundland and Nova Scotia (Peck & Kuhn, n.d.).APRIL 2010 Page | 31
  • JOVIAN DESIGNGreen roofs help mitigate the impact of high-densitycommercial and residential development by restoringdisplaced vegetation (van Woert et al., 2005). Studies haveshown that green roofs can absorb water and release itslowly over a period of time as opposed to conventionalroofs where stormwater is immediately discharged (vanWoert et al., 2005).There are two basic types of green roof systems – extensiveand intensive (Peck & Kuhn, n.d.; Kosareo & Ries, 2007).They are differentiated mainly by the cost, depth of growingmedium and the choice of plants. (Table 7) below providesan in-depth look at the advantages and disadvantages ofboth systems.Green roofs are thought to have a number of benefitscompared to a conventional roof. An extensive green roofcan reduce stormwater runoff by 60%, whereas an intensivegreen roof by 85% (Kosareo & Ries, 2007). On a yearlybasis, rainfall-retention capability of green roofs ranges from75% for intensive green roofs to 45% for extensive greenroofs (Mentens, Raes & Hermy, 2006).Page | 32
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYTable 7: Comparison between extensive and intensive green roof systemsComparison between Extensive and Intensive Green Roof Systems EXTENSIVE GREEN ROOF INTENSIVE GREEN ROOFThin growing medium; little or no irrigation; stressful conditions Deep soil; irrigation system; more favourable conditions for plants;for plants; low plant diversity. high plant diversity; often accessible.Advantages: Advantages:• Lightweight; roof generally does not require reinforcement. • Greater diversity of plants and habitats.• Suitable for large areas. • Good insulation properties.• Suitable for roofs with 0 - 30° (slope). • Can simulate a wildlife garden on the ground.• Low maintenance and long life. • Can be made very attractive visually.• Often no need for irrigation and specialized drainage systems. • Often accessible, with more diverse utilization of the roof (i.e., for• Less technical expertise needed. recreation, growing food, as open space).• Often suitable for retrofit projects. • More energy efficiency and storm water retention capability.• Can leave vegetation to grow spontaneously. • Longer membrane life.• Relatively inexpensive.• Looks more natural.• Easier for planning authority to demand as a condition of planning approvals.Disadvantages: Disadvantages:• Less energy efficiency and storm water retention benefits. • Greater weight loading on roof.• More limited choice of plants. • Need for irrigation and drainage systems requiring energy, water,• Usually no access for recreation or other uses. materials.• Unattractive to some, especially in winter. • Higher capital & maintenance costs. • More complex systems and expertise.Source: Peck & Kuhn (n.d.), p. 5APRIL 2010 Page | 33
  • JOVIAN DESIGN7.5.3 Durability The green roof is also more effective in reducing heat gain inThe average life span of conventional roofing systems is 10- spring/summer than heat loss in fall/winter (Liu & Baskaran,20 years (Kosareo & Ries, 2007) depending on the quality of 2003). This is because the green roof can reduce heat gainthe roof. Extensive green roof systems have an expected life through shading, insulation and evapotranspiration. This isspan of approximately 40 years; double that of a “high- effective on summer evenings, but not in winter when thegrade” conventional roof. In Europe, the development of growing medium is frozen and the improved insulation andgreen roofs has gone on for decades; research shows that decreased radiation heat loss effects are dominated by snowgreen roofs can be maintained for about 50 years. In the coverage (Liu & Baskaran, 2003).case of intensive green roofs, substantial vegetation can begrown because of additional layers of soil. The intensive 7.5.4 Maintenancegreen roofs also improve the roof life span and provide The extensive green roof was developed for use onadditional insulation; however, the decision to include them contemporary residential buildings in the early 1900s by ain the design of a project needs to be made early so that the German roofer (Köhler et al., 2002). In many German citiesproper structural membranes can be selected to support the these roofs were built as a form of fire protection. This typeadditional weight that accompanies this kind of construction of roof proved to be very durable and almost totally free of(Kosareo & Ries, 2007). maintenance (Köhler et al., 2002). Building owners however, are hesitant to consider the use of a green roof due to itsA generic extensive green roof is able to significantly reduce increased initial costs and uncertainties in the constructionthe daily temperature fluctuation of a roof surface in warmer and maintenance of such roofs. Studies on life cyclemonths (spring and summer) (Liu & Baskaran, 2003). In the assessment of green roofs find that the life cycle cost ofcase of a conventional roofing system, diurnal temperature extensive roofs are less than conventional roofs, althoughfluctuations create thermal stresses, affecting the system‟s intensive systems have a higher life cycle cost (Kosareo &long-term performance and its ability to protect a building Ries, 2007).from water infiltration. However, a green roof enhances thethermal performance of the roof by providing shading, As mentioned earlier, conventional roofs requireinsulation and evaporative cooling. In the winter months, maintenance and replacement over 10-20 years. Foronce the snow coverage is established, the heat flow extensive green roofs, maintenance is only required for plantthrough both conventional roofs and green roofs is the same, growth and waterproofing. For intensive green roofs, theas snow coverage provides good insulation and stabilized system requires the same additional layers as an extensiveheat flow through the roof (Liu & Baskaran, 2003). roof, only the growing medium layer is greater in depth, thus maintenance is same as the extensive roofs (Kosareo & Ries, 2007).Page | 34
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYRegular maintenance inspections should be scheduled as considered, improved air quality results in a mean NPV forfor any conventional roof installation. Plant maintenance the green roof that is approximately 25% to 40% less thanranges from two to three yearly inspections to check for the mean NPV of a conventional roof. This valuationweeds or damage, to weekly visits for irrigation, pruning and scenario reveals that over 40 years, green roofs cost lessreplanting (Peck & Kuhn, n.d.). The maintenance of the than conventional roofs (Clark et al., 2008).waterproofing membrane can be complicated since thegreen roof system completely covers the membrane.Although the green roof protects the membrane frompuncture damage and solar radiation, thus doubling its lifespan, leaks can still occur at joints. The replacement time forgreen roof membranes is 30-50 years, longer thanconventional roofs (Peck & Kuhn, n.d.).7.5.5 CostThe initial cost of a green roof is high as installation costsremain at a premium, thereby preventing widespreadinvestment in green roof technology (Clark, Adriaens, &Talbot, 2008). The benefits of green roofs are mainlyincreased roof longevity, reduced stormwater runoff, anddecreased energy consumption. The Net Present Value(NPV) of an extensive green roof system in comparison to aconventional roof is approximately 20% to 25% less than theNPV for a conventional roof over 40 years (Clark et al.,2008).If stormwater, energy, and air pollution benefits arequantitatively integrated into an economic model, theadditional upfront investment in green roof technology isrecovered at the time when a conventional roof would bereplaced. If the value of improved air quality is quantitativelyAPRIL 2010 Page | 35
  • JOVIAN DESIGN7.5.6 Extensive Green RoofsTable 8: Component costs of extensive green roofs assuming an existing building with sufficient loading capacity, roof hatch and ladder accessComponent Costs of Extensive Green RoofsComponent Cost Notes and Variables 5% - 10% of total The number and type of consultants required depends on the size and complexity ofDesign & Specifications roofing project cost the project.Project Administration & 2.5% - 5% of total The number and type of consultants required depends on the size and complexity ofSite Review roofing project cost. the project.Re-roofing with root- Cost factors include type of existing roofing to be removed, type of new roofing $100.00 - $160.00/m2.repelling membrane system to be installed, ease of roof access, and nature of flashing required.Green Roof System(curbing, drainage layer, Cost factors include type and depth of growing medium, type of curbing, and size offilter cloth, growing $55.00 - $110.00/m2 project.medium, decking andwalkways)Plants $11.00 - $32.00/m2 Cost factors include time of year, type of plant, and size of plant - seed, plug, or pot. Cost factors include equipment rental to move materials to and on the roof (rental of 2Installation/Labour $32.00 - $86.00/m a crane could cost as much as $4,000.00 per day), size of project, complexity of design, and planting techniques used. $13.00 - $21.00/m2 Costs factors include size of project, timing of installation, irrigation system, and sizeMaintenance For the first 2 years and type of plants used. only Optional, since the roof could be watered by hand. Cost factors include type ofIrrigation System $21.00 - $43.00/m2 system used.Source: Peck& Kuhn (n.d.) p. 15Page | 36
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY7.5.7 Intensive Green RoofsTable 9: Component cost of intensive green roofs assuming an existing building with sufficient loading capacity, roof hatch and ladder accessComponent Costs of Intensive Green RoofsComponent Cost Notes and Variables 5% - 10% of total The number and type of consultants required depends on the size andDesign & Specifications roofing project cost complexity of the project. 2.5% - 5% of total The number and type of consultants required depends on the size andProject Administration & Site Review roofing project cost. complexity of the project. Cost factors include type of existing roofing to be removed, type of new $100.00 -Re-roofing with root-repelling membrane roofing system to be installed, ease of roof access, and nature of $160.00/m2 flashing required.Green Roof System (curbing, drainage Cost factors include type and depth of growing medium, type and $160.00 -layer, filter cloth, growing medium, height of curbing, type of decking, and size of project. (Cost does not $320.00/m2decking and walkways) include freestanding planter boxes. Cost is completely dependent on the type and size of plant chosen, $54.00 -Plants since virtually any type of plant suitable to the local climate can be $2,150.00/m2 accommodated (one tree may cost between $200.00 and $500.00).Irrigation System $21.00 - $43.00/m2 Cost factors include type of system used and size of project. Cost factors include type of fencing, attachment to roof, and size ofGuardrail/Fencing $65.00 - $130.00/m project / length required. Cost factors include equipment rental to move materials to and on roof,Installation/Labour $85.00 - $195.00/m2 size of project, complexity of design, and planting techniques used. Costs factors include size of project, irrigation system, and size and typeMaintenance $13.50 - $21.50/m2 of plants used.Source: Peck & Kuhn (n.d.), p. 16APRIL 2010 Page | 37
  • JOVIAN DESIGN7.5.8 Benefits and Limitations 7.5.9 Public PolicyThe two most important benefits of green roofs are improved In order to properly quantify the environmental benefits ofstormwater retention and reduction of Urban Heat Island green roofs, policies that affect green roofs may first need toeffect (Peck & Kuhn, n.d.). Green roofs also provide other be changed in order to overcome perceived hurdles. Clarkservices, such as ecological advantages, discussed below. et al. (2008) identify two strategies that have the potential to resolve the price discrepancy between green andStormwater retention is the basic and most important benefit conventional roofs: (i) proper valuation of infrastructure costsof green roofs (Peck & Kuhn, n.d.). First, the plants capture via stormwater fees, and (ii) market-based tradable permitand hold rainwater. Water is then stored in the growing schemes for contribution to impaired local waterways. Inmedia and is released through evapotranspiration, thus terms of air pollution, direct incentives or programs thatreducing the flow of stormwater onto the ground. A heavily incorporate green roofs as an abatement technology intovegetated green roof can hold 10-15 cm of water (Peck & existing regional air pollution emission allowance marketsKuhn, n.d.). could further reduce the economic deterrence of green roofsA stormwater retention study for the City of Portland, (Clark et al., 2008).Oregon, found that if half of all the buildings in the downtown The City of Toronto Act (COTA) of 2006 provided Torontoarea had green roofs, an estimated 250 million litres of water City Council with the authority to pass a bylaw requiring andwould be retained annually. The study indicated that governing the construction of green roofs (City of Toronto,stormwater discharge would be reduced by 11% to 15% 2010). Toronto is the first city in North America to have a(Peck & Kuhn, n.d.). bylaw to require and govern the construction of green roofsGreen roofs are also known to filter out fine, airborne on new development. It was adopted by Toronto City Councilparticulate matter as the air passes over the plants (Peck & in May 2009, under the authority of Section 108 of the City ofKuhn, n.d.). Based on data from trees, it was estimated that Toronto Act. The bylaw requires green roofs on newabout 4,000 kg of dirt can be removed from the air per year commercial, institutional and residential development with a(2 kg/m2 of green roof) (Peck & Kuhn, n.d.). minimum gross floor area of 2,000 square metres as of January 31, 2010 (City of Toronto, 2010).Green roofs can be specifically designed to mimicendangered ecosystems, such as the Great Lakes Region 7.6 Additional Benefits of Permeable Surfaceshabitat in Canada (Peck & Kuhn, n.d.). Thusly, extensive 7.6.1 Urban Heat Islandgreen roof systems can become home to sensitive plants as Urban Heat Island (UHI) effect refers to the warming ofwell as bird species that prefer to nest on the ground (Peck urban centres in comparison to rural areas as a result of high& Kuhn, n.d.). density impermeable surface cover and other infrastructurePage | 38
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYthat increases surface and atmospheric temperatures According to Golden and Kaloush (2005) the UHI can(Figure 17) (U.S. Environmental Protection Agency, 2009). negatively impact the sustainability of a region by increasingRecently, there has been some concern about the heating the dependence on mechanical cooling, which requireseffects due to an increasing area of dark-coloured electrical consumption (producing greenhouse gasimpermeable surfaces (e.g., conventional asphalt) (Asaeda emissions and using significant amounts of water& Ca, 2000). For instance, the UHI effect occurs due to the resources), and may raise the cost of living for residents.prevalence of low albedo surfaces that absorb incident The UHI can also have an impact on heat-related illnesses,radiation and prevent the radiation from being reflected back especially from elevated night-time temperatures due toto the atmosphere (Oke, 2006). Because there are increased heat storage and release (Golden & Kaloush,insufficient pores in impermeable surfaces, day time 2005).evaporation is not as effective in impermeable surfaces aspermeable surfaces (Golden & Kaloush, 2005). Without In terms of asphalt, however, Asaeda and Ca (2000) suggestevaporation, latent energy may not be liberated, which is that there may be only a slight difference in UHI betweengenerally required to cool the surrounding air (Asaeda & Ca, traditional asphalt and that which is more porous in nature.2000). As a result, overall ambient air temperatures increase The large pore size of the porous material still leaves thein comparison to the adjacent rural areas where pavement rather dry, in which little evaporation is observedevapotranspiration is more prevalent (Oke, 2006). at the surface. Further research may be required to get a better understanding of how thermal environments areFigure 17: Rural and urban heat characteristics affected by porous media. In terms of PICP and CGP, proper selection of materials and colours can help reduce UHI effect (Unilock, 2009). PC can also lower the UHI effect as the light colour of PC absorbs less heat from solar radiation than darker pavements, and the open pore structure of PC pavement stores less heat. In addition, PC allows adjacent trees to receive more air and water (Park & Tia, 2003). Green roofs intercept solar radiation which would be reflected by dark roof surfaces, thereby reducing the greenhouse effect (Peck & Kuhn, n.d.; Ball, 2008). A studySource: Ngan, 2004 conducted in Chicago concluded that if, over a period of ten years, all of the buildings in the City were retrofitted withAPRIL 2010 Page | 39
  • JOVIAN DESIGNgreen roofs, the annual savings would amount toapproximately $100,000,000 (USD) from reduced coolingload requirements in all buildings (Peck & Kuhn, n.d.).7.6.2 LEEDA particularly attractive benefit for using permeable surfacesas opposed to conventional surfaces is the opportunity togain Leadership in Energy and Environmental Design(LEED) credits. For instance, according to the CanadianGreen Building Council (CaGBC, 2004), porous pavementsystems, including pervious cement and asphalt, vegetativeroofs and permeable pavers, have the potential to earn up tofour Sustainability Sites (SS) category credits toward LEEDcertification. Systems can earn one credit for reducing waterquantity and runoff (e.g., SS Credit 6.1 StormwaterManagement, Rate and Quality); one for improving waterquality (e.g., SS Credit 6.2 Stormwater Management,Treatment); and two for mitigating Urban Heat Island effects(e.g., SS Credit 7.1 Heat Island Effect, Non-roof; SS Credit7.2 Heat Island Effect, Roof). On the other hand, permeablepavements and surfaces can also add credits in theMaterials and Resources category (e.g., Credit MR 2.1 –5.2) that already exists for conventional surface materials(NAPA, 2008; CaGBC, 2004). The importance of convertingto these innovative types of surfaces is to encourage andaccelerate global adoption of sustainable green building anddevelopment practices in order to mitigate and preventfurther negative environmental impacts (CaGBC, 2004).Page | 40
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY labour costs, thus reducing overall costs (Decaluwe, 2010).8. Product Analysis Unilock and Permacon offer PICP products that provide high levels of permeability and durability while maintaining8.1 Introduction reasonable costs. The products are quite similar in terms ofIn order to gather accurate data of permeable surface permeability and durability, differing in cost largely as aproducts, local distributors and contractors were contacted result of aesthetics (Woodward, 2010). Because PICPfor information regarding specific characteristics of products require similar maintenance, the use of a vacuumpermeable products including: Permeability, durability and or sweeping agent 1 to 2 times per year, the cost ofcost of locally supplied permeable products. The distributors maintenance and operation is the same for each product.and contractors who participated in the analysis weregenerally eager to provide information about a range of In terms of the cost of installation and subbase materials, theproducts. In terms of cost, when ranges were provided, the durability and retention capacity of all products are similar.average of the range was calculated. In some cases, upon The Eco-Optiloc and Subterra products are quitethe advice of distributors, the lower portion of the range was comparable in all categories despite the fact that they areutilized in order to reflect economies of scale for large supplied by two different companies. The major differencecommercial development projects. The products in this between the two products is the cost of the stone. The costanalysis meet the City of London needs and development of Eco-Priora is more than double the cost of the other twoguidelines and are thereby considered practical options for products.commercial application. The following analysis is dividedamong permeable surface typology, including: PICP, 8.3 Concrete & AsphaltPermeable Asphalt and Porous Concrete, and Green Roofs The characteristics of conventional concrete and asphalt are(Table 10). compared to porous concrete and permeable asphalt to illustrate the differences in permeability, durability and cost.8.2 PICP The costs include the price of the product, the price of theThe PICP products, Eco-Optiloc, Eco-Priora, and Subterra, subbase, and installation of both products. For this survey,provide three practical options for PICP implementation. In Jovian Design consulted with Lafarge Canada and Cocoterms of the installation of PICP, it is assumed that the Asphalt Engineering. The total costs including installationproducts are installed with a modern paving machine, the and subbase of porous concrete are high in comparison toToro H 88, which is locally owned and operated. Due to the permeable asphalt. However, the differences in lifespan arescope of commercial applications, the utilization of a paving noteworthy, affecting total costs. Maintenance costs aremachine is appropriate. The employment of the Toro H 88 approximately the same among the conventional andnot only increases installation efficiency but decreases permeable products as vacuums and sweepers should beAPRIL 2010 Page | 41
  • JOVIAN DESIGNemployed 1 to 2 times per year. The lifespan of the products labour, miscellaneous costs and HST. The LiveRoof productalso vary between 20 and 30 years. cost includes material costs and installation.8.4 Green Roofs In most cases the maintenance costs for the first 1 to 2 yearsA range of green roofs are presented in order to are in included in the initial costs. This practice is andemonstrate the variety of options that exist. The green roof industry standard employed by green roof contractors toproducts that are denoted with an asterisk (*) include the ensure the stability and longevity of the green roof system.price of the supply, delivery and installation of complete Maintenance costs largely depend on the depth of the soilgreen roof assemblies. In all cases the assembly includes a and the plants used in green roof applications. Therefore,root barrier, a drainage layer component, a filter fabric, intensive roof maintenance costs are higher than extensivegrowing medium (soil), vegetation and an automatic roof maintenance costs. The runoff coefficient also dependsirrigation system. The cost includes typical contractor on the depth of the soil and the plants that are used.attendance at required site meetings, the provision of Permeability depends on the depth of the soil and the plantssubmittal documentation, bonding, permits and insurance. that are used. Therefore, extensive roofs have a higherThe price also includes a standard two-year maintenance runoff coefficient than intensive roofs. The durability ofprogram including condition monitoring and reporting, green roofs is on average the same.weeding, plant replacement, debris and drain cleaning,irrigation adjustment and winterizing in the overall price ofthe product. The price does not include general roofinsulation or waterproofing, roof drains, roof drain inspectionchambers, railings/guards, benches or other furniture,decking, fall protection devices, flood testing or a permanentleak detection system. The price does not include paver orballast materials surrounding the areas of vegetation, the soilcontainment features, whether those are restraint edging,curbing, planters of guard-height planter walls (Taves, 2010).The Floradrain products are priced to include the cost of theentire system, therefore consisting of the product costs andinstallation, as well as 1 to 2 years of maintenance service.The cost of the product supplied by Duo Building Ltd.includes the material costs, shipping, equipment rental,Page | 42
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY Table 10: Comparison of feasibility parameters for various permeable products Permeable Product Comparisons Product Cost Operation and Maintenance Durability Runoff Coefficient PICP Eco-Optiloc $82.7/m2 $10.76/m2/year 25 years 0.25 Eco-Priora $126.5/m2 $10.76/m2/year 25 years 0.25 Subterra $80.87/m2 $10.76/m2/year 25 years 0.25 Concrete Porous Concrete $170/m3 $0.07/m2/year 30 years 0.4 Conventional Concrete $215/m3 $0.07/m2/year 30 years 0.9 Asphalt Permeable Asphalt $95/m3 $0.11/m2/year 20 years 0.4 Conventional Asphalt $95/m3 $0.09/m2/year 25 years 0.9 Green Roof Extensive Floradrain FD 25 $107.6/m2 $1.35/m2/year 40 years 0.5 Floradrain FD 25 $215.2/m2 $1.35/m2/year 40 years 0.5 LiveRoof $150.64/m2 $1.35/m2/year 40 years 0.5 Duo Building Ltd. $206.67/m2 $1.35/m2/year 40 years 0.5 Soprema Taiga* $161.45/m2 $1.35/m2/year 40 years 0.5 Sedum Master* $193.75/m2 $1.35/m2/year 40 years 0.5 LiveRoof* $322.90/m2 $1.35/m2/year 40 years 0.5 Intensive Connon Nursery* $269.10/m2 $8.07/m2/year 40 years 0.3 Floradrain FD 60 $322.8/m2 $8.07/m2/year 40 years 0.3*The cost for these products includes the first two years of maintenance. APRIL 2010 Page | 43
  • JOVIAN DESIGN A runoff coefficient of 0.9 was applied to asphalt pavement,9. Net Water Savings concrete pavement, and conventional roofs (Dingman, 2002); 0.5 was applied to green roofs with thicknesses of 6-9.1 Introduction 10 cm and slopes less than 15o (Ngan, 2004); 0.25 wasA simplified version of the Rational Method was employed in applied to permeable interlocking concrete pavement (ICPI,order to analyze the net-water savings of conventional and 2007); and 0.4 was applied to porous asphalt, concrete, andpermeable products. This method is acceptable for use in grid pavers (ICPI, 2008) (Table 11).this analysis as it is commonly applied in the calculation ofurban drainage (Dingman, 2002). It is assumed that each runoff coefficient is averaged due to the varying nature and range of storm intensities andThe imperviousness of various surface materials and their durations in any specific study area (ICPI, 2005). Accordingrelationship to subsequent runoff due to rainfall events was to ICPI (2007), it is important to account for these variablesevaluated in order to estimate a reduction in the quantity of because the prevalence of storms (either by close or greaterrunoff (%) observed under several scenarios. These spacing) and the level of saturation of the soil will affect thescenarios were contrasted with conventional surfaces to overall runoff coefficient.evaluate the effectiveness of installing permeablepavements and extensive green roofs. It is reasonable to assume that the reduction in runoff is directly proportionate to the runoff coefficient. For theThe modified calculations were derived from the Interlocking purposes of this Report, the results of the calculations alsoConcrete Paving Institute (ICPI) (2007) and based on the provide a rough estimate of a proportional reduction in thefollowing equations: total SWM facility volume. Finally, it was assumed that evaporation was not significant, and that rainfall either becomes runoff (i.e., reaches a stormwater management facility) or does not (i.e., infiltrates).Page | 44
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYTable 11: Runoff coefficients The first group of scenarios (1a, 1b, 1c, 1d) includes the use of permeable asphalt or porous concrete andRunoff Coefficients for Different Surface Typologies % extensive green roofs. Runoff % Runoff The second group of scenarios (2a, 2b, 2c, 2d) Surface Infiltration Coefficient per m2 per m2 includes the use of PICP and extensive green roofs.Conventional Asphalt 0.9 90% 10% Conventional The volume of water utilized by the WPC SWM facility was 0.9 90% 10% calculated using a ratio of the Study Site‟s drainage area to Concrete Conventional Roof 0.9 90% 10% the total drainage area. Since the WPC Study Site Permeable Asphalt 0.4 40% 60% encompasses approximately 39% (22 hectares) of the total Porous Concrete 0.4 40% 60% drainage area (56 hectares), it is assumed the volume of the PICP 0.25 20% 75% Bradley Avenue SWM Facility that is utilized by the StudyExtensive Green Roof 0.5 50% 50% Site is 39% of 45,238 m3, or 17,643m3. 9.2.1 Scenario 1a: 100% Pervious Coverage of Hard Surfaces9.2 Wonderland Power Centre using Permeable Asphalt or Porous Concrete and ExtensiveThe current pavement on the WPC Study Site is gently Green Roofssloped and underlain with relatively sandy soils with In this scenario permeable asphalt or porous concrete andsatisfactory infiltration capacity, while the groundwater table extensive green roofs are completely (i.e., 100%) substitutedis at an acceptable level from the surface for adequate for conventional surfaces, with runoff coefficients ranginginfiltration (Development Engineering, 2005). The physical from 0.4 to 0.5.conditions of the WPC Study Site provide an excellent As seen in Table 12, if only extensive green roofs arecontext to perform pavement comparisons. For the purpose installed (with no ground material substitution) a runoffof identifying the most feasible permeable surface, several reduction of approximately 12% of the total Study Site wouldscenarios were considered. be observed. Alternatively, if only sidewalks are replaced byIn the following scenarios, the assumption has been made porous concrete or permeable asphalt, a runoff reduction ofthat either permeable pavements (asphalt or concrete) or more than 5% for the total area would be generated. Finally,permeable interlocking concrete pavers will be used as a if only the parking lots are completely replaced by poroussubstitute ground material. All scenarios include the use of concrete or permeable asphalt, a runoff reduction ofextensive green roofs. As such: approximately 34% for the total area would be observed. By substituting 100% of all surfaces, a 51% reduction in runoff can be achieved.APRIL 2010 Page | 45
  • JOVIAN DESIGNUnder these conditions, the maximum volume of the SWM conventional surfaces, with runoff coefficients ranging fromfacility could therefore be reduced from 45,238m3 to 0.4 to 0.5.36,293m3, a reduction of 8,945m3 (Table 13). As seen in Table 12, if only extensive green roofs are9.2.2 Scenario 1b: 75% Pervious Coverage of Hard Surfaces installed (with no ground material substitution) a runoffusing Permeable Asphalt or Porous Concrete and Extensive reduction of approximately 6% of the total Study Site wouldGreen Roofs be observed. Alternatively, if only sidewalks are replaced byIn this scenario permeable asphalt or porous concrete, and porous concrete or permeable asphalt, a runoff reduction ofgreen roofs are substituted for 75% of conventional surfaces, approximately 3% for the total area would be generated.with runoff coefficients ranging from 0.4 to 0.5. Finally, if only the parking lots are partially replaced by porous concrete or permeable asphalt, a runoff reduction ofAs seen in Table 12, if only extensive green roofs are less than 17% for the total area would be observed. Byinstalled (with no ground material substitution) a runoff substituting 50% of all hard surfaces, a 25% reduction inreduction of approximately 9% for the total Study Site would runoff can be achieved.be observed. Alternatively, if only sidewalks are replaced byporous concrete or permeable asphalt, a runoff reduction of Under these conditions, the volume of the SWM facility could4% for the total area would be generated. Finally, if only the therefore be reduced from 45,238m3 to 40,757m3, aparking lots are partially replaced by porous concrete or reduction of 4,481m3 (Table 13).permeable asphalt, a runoff reduction of approximately 25%for the total area would be observed. By substituting 75% of 9.2.4 Scenario 1d: 25% Pervious Coverage of Hard Surfacesall hard surfaces, a 38% reduction in runoff could be Using Permeable Asphalt or Porous Concrete and Extensive Green Roofsachieved. In this scenario permeable asphalt or porous concrete, andUnder these conditions, the maximum volume of the SWM extensive green roofs are substituted for 25% offacility could therefore be reduced from 45,238m3 to conventional surfaces, with runoff coefficients ranging from38,534m3, a reduction of 6,704m3 (Table 13). 0.4 to 0.5.9.2.3 Scenario 1c: 50% Pervious Coverage of Hard Surfaces As seen in Table 12, if only extensive green roofs areUsing Permeable Asphalt or Porous Concrete and Extensive installed (with no ground material substitution) a runoffGreen Roofs reduction of approximately 3% for the total Study Site wouldIn this scenario permeable asphalt or porous concrete, and be observed. Alternatively, if only sidewalks are replaced byextensive green roofs are substituted for 50% of porous concrete or permeable asphalt, a runoff reduction of more than 1% for the total area would be generated. Finally,Page | 46
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYif only the parking lots are partially replaced by porousconcrete or permeable asphalt, a runoff reduction ofapproximately 8% for the total area would be observed. Bysubstituting 25% of all hard surfaces, a 13% reduction inrunoff could be achieved.Under these conditions, the maximum volume of the SWMfacility could therefore be reduced from 45,238m3 to42,997m3 , a reduction of 2,241m3 (Table 13).APRIL 2010 Page | 47
  • JOVIAN DESIGN Table 12: Comparison of runoff reductions for conventional and permeable surfaces at the WPC: Pavement and green roofs Runoff Reductions Resulting from Pervious Surface Coverage at the WPC: Pavement and Green Roofs Percent Runoff Reduction for: SURFACE 100% Pervious Coverage 75% Pervious Coverage 50% Pervious Coverage 25% Pervious Coverage (Scenario 1a) (Scenario 1b) (Scenario 1c) (Scenario 1d) Permeable Asphalt Parking Lots 33.6 25.2 16.8 8.4 Porous Concrete Sidewalks 5.2 3.9 2.6 1.3 Extensive Green Roofs 11.9 9.0 6.0 3.0 Total Runoff Reduction 50.7 38.0 25.4 12.7 Full calculations for Table 12 can be found in Appendix B Table 13: SWM facility volume reduction resulting from pervious surface coverage at the WPC: Pavement and green roofs Stormwater Facility Volume Reduction Resulting from Pervious Surface Coverage at the WPC: Pavement and Green Roofs Reduction in Stormwater Facility Volume for: 100% Pervious 75% Pervious Coverage 50% Pervious Coverage 25% Pervious Coverage 3 SURFACE Coverage (m ) (m3) (m3) (m3) (Scenario 1a) (Scenario 1b) (Scenario 1c) (Scenario 1d) Permeable Asphalt Parking Lots 5,928 4,446 2,964 1,482 Porous Concrete Sidewalks 917 688 459 229 Extensive Green Roofs 2,100 1,588 1,059 529 Total Reduction 8,945 6,704 4,481 2,241Page | 48
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY9.2.5 Scenario 2a: 100% Pervious Coverage of Hard Surfaces PICP, a runoff reduction of 5% for the total area would beusing PICP and Extensive Green Roofs generated. Finally, if only the parking lots are partiallyIn this scenario permeable interlocking concrete pavement replaced by PICP, a runoff reduction of approximately 33%and extensive green roofs are completely (i.e., 100%) for the total area would be observed. By substituting 75% ofsubstituted for conventional surfaces, with runoff coefficients all hard surfaces, a 47% reduction runoff could be achieved.ranging from 0.25 to 0.5. Under these conditions, the maximum volume of the SWMAs a seen in Table 14, if only extensive green roofs are facility could therefore be reduced from 45,238m3 toinstalled (with no ground material substitution) a runoff 36,999m3, a reduction of 8,239m3 (Table 15).reduction of approximately 12% for the total Study Sitewould be observed. Alternatively, if only sidewalks are 9.2.7 Scenario 2c: 50% Pervious Coverage of Hard Surfacesreplaced by PICP, a runoff reduction of less than 7% for the using PICP and Extensive Green Roofstotal area would be generated. Finally, if only the parking lots In this scenario permeable interlocking concrete pavementare completely replaced by PICP, a runoff reduction of and extensive green roofs are substituted for 50% ofapproximately 44% for the total area would be observed. By conventional surfaces, with runoff coefficients ranging fromsubstituting 100% of all hard surfaces, a 62% reduction in 0.25 to 0.5.runoff could be achieved. As seen in Table 14, if only extensive green roofs areUnder these conditions, the maximum volume of the SWM installed (with no ground material substitution) a runofffacility could therefore be reduced from 45,238m3 to reduction of approximately 6% for the total Study Site would34,246m3, a reduction of 10,992m3 (Table 15). be observed. Alternatively, if only sidewalks are replaced by PICP, a runoff reduction of more than 3% for the total area9.2.6 Scenario 2b: 75% Pervious Coverage of Hard Surface would be generated. Finally, if only the parking lots areusing PICP and Extensive Green Roofs simply replaced by PICP, a runoff reduction of approximatelyIn this scenario permeable interlocking concrete pavement 22% for the total area would be observed. By substitutingand extensive green roofs are substituted for 75% of 50% of all hard surfaces, a 31% reduction in runoff could beconventional surfaces, with runoff coefficients ranging from achieved.0.25 to 0.5. Under these conditions, the maximum volume of the SWMAs seen in Table 14, if only extensive green roofs are facility could therefore be reduced from 45,238m3 toinstalled (with no ground material substitution) a runoff 39,733m3, a reduction of 5,505m3 (Table 15).reduction of approximately 9% for the total Study Site wouldbe observed. Alternatively, if only sidewalks are replaced byAPRIL 2010 Page | 49
  • JOVIAN DESIGN9.2.8 Scenario 2d: 25% Pervious Coverage of Hard Surfaces Using an ideally installed permeable pavement andusing PICP and Extensive Green Roofs extensive green roof system may allow the WPCIn this scenario permeable interlocking concrete pavement Study Site to reduce the size of the SWM facility toand extensive green roofs are substituted for 25% of approximately 34,000m3conventional surfaces, with runoff coefficients ranging from0.25 to 0.5. As seen in Table 14, if only extensive green roofs areinstalled (with no ground material substitution) a runoffreduction of approximately 3% for the total Study Site wouldbe observed. Alternatively, if only sidewalks are replaced byPICP, a runoff reduction of nearly 2% for the total area wouldbe generated. Finally, if only the parking lots are partiallyreplaced by PICP, a runoff reduction of approximately 11%for the total area would be observed. By substituting 25% ofall hard surfaces, a 16% reduction in runoff could beachieved.Under these conditions, the maximum volume of the SWMfacility could therefore be reduced from 45,238m3 to42,486m3, a reduction of 2,752m3 (Table 15).9.3 Net-Water Savings Analysis Summary The WPC Study Site is an ideal location for substituting conventional surfaces with permeable surfaces, providing a suitable example for other similar areas within the City of London Each scenario shows a general reduction in surface imperviousness and particularly runoff quantity, ranging from a minimum of 1% to a maximum of 62% depending on the configuration and implementation of each surfacePage | 50
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYTable 14: Comparison of runoff reductions for conventional and permeable surfaces at the WPC: PICP and green roofsRunoff Reductions Resulting from Pervious Surface Coverage at the WPC: PICP and Green Roofs Percent Runoff Reduction for: SURFACE 100% Pervious Coverage 75% Pervious Coverage 50% Pervious Coverage 25% Pervious Coverage (Scenario 2a) (Scenario 2b) (Scenario 2c) (Scenario 2d)PICP Parking Lots 43.7 32.7 21.8 10.9PICP Sidewalks 6.7 5.0 3.4 1.7Green Roof 11.9 9.0 6.0 3.0Total Runoff Reduction 62.3 46.7 31.2 15.6Full calculations for Table 14 can be found in Appendix BTable 15: SWM facility volume reduction resulting from pervious surface coverage at the WPC: PICP and green roofsStormwater Facility Volume Reduction Resulting from Pervious Surface Coverage at the WPC: PICP and Green Roofs Reduction in Stormwater Facility Volume for: 100% Pervious 75% Pervious Coverage 50% Pervious Coverage 25% Pervious Coverage SURFACE Coverage (m3) (m3) (m3) (m3) (Scenario 2a) (Scenario 2b) (Scenario 2c) (Scenario 2d)PICP Parking Lots 7,710 5,769 3,846 1,923PICP Sidewalks 1,182 882 600 300Green Roof 2,100 1,588 1,059 529 Total Reduction 10,992 8,239 5,505 2,752APRIL 2010 Page | 51
  • JOVIAN DESIGN Capital costs, operation and maintenance costs, and the10. Financial Analysis product lifespan were calculated using information provided by contractors and distributors and various sources of10.1 Introduction literature as described in the “Product Analysis” section ofA financial analysis of each product typology was conducted this Report. Where applicable, an average of the costs ofusing both the Net Present Value (NPV) and Equivalent each product within a specific typology was used toAnnual Cost (EAC). The following formulas were used to determine the capital cost. The average capital costs ofcalculate NPV and EAC: each product reflect the entire cumulative cost of installation. The interest rate of 5% was provided by the Clients as a standard measurement used by the City of London. 10.2 Net Present Value & Equivalent Annual Cost 10.2.1 Net Present Value and Prorated Net Present Value For all capital-intensive municipal infrastructure projects, it is assumed that the total cost of a project will be paid over a period of time. Net Present Value calculations wereWhere: conducted in order to compare the current dollar value of ∑ represents the sum of each discounted cash flow each surface type, taking inflation and potential savings from over the lifespan of the individual product the reduction of stormwater management facilities into i = the annual interest rate, calculated at 5% account. In essence, the lower the present dollar value per t = the time of the cash flow metre squared of a product, the more financially feasible it is. R = the net cash flow at time t For the purposes of this Study, a “prorated” Net Present Value was also calculated in order to compare the currentWhere: dollar value of each product over the lifespan of the longest- lasting product of the same general typology (i.e., ground i = the annual interest rate, calculated at 5% cover vs. roof). Although this calculation provides a good t = the lifespan of the individual product visual comparison between products over a common lifespan, it is important to note that none of the products can be extended beyond their lifetime without doubling their lifetime. For example, the lifespan of conventional asphalt (25 years) cannot be extended by only 5 years in order toPage | 52
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYgive it an equal lifespan of conventional or porous concrete Therefore, irrespective of their stormwater retention(30 years). Rather, it must be renewed for an additional 25 capacity, long-term savings could exist even if onlyyears. For this reason, the Equivalent Annual Cost sidewalks were constructed with one of thesecalculation was used in order to establish a more accurate products.comparison of the dollar value per square metre of eachproduct, as discussed below. Conventional asphalt and permeable asphalt had similar costs, with permeable asphalt amounting to10.3 Equivalent Annual Cost only $0.97/m2 more than asphalt. As previouslyEAC reflects the cost per year of owning and operating an mentioned, this number does not take intoasset over its entire lifespan. The calculation uses the Net consideration the potential cost savings fromPresent Value of an asset as well as an Annuity Value that is stormwater reduction, and therefore could be moreunique to each asset, or product, based on its lifespan. financially feasible for new developments thanSince each product in this Report has a different life traditional pavement.expectancy, this calculation is an excellent way to compareand evaluate the cost of each product on an annual basis, Although the capital cost of PICP is comparable togiven that the products will likely be renewed indefinitely both conventional and permeable asphalt, the EAC and NPV are much higher for this product as a resultafter each lifecycle, and the City will continue to pay for themyear after year. of its increased maintenance costs. Therefore, it is likely that PICP would not be financially feasible for10.4 Product Comparisons the City of London.Net Present Value and Equivalent Annual Cost per square Without considering potential savings from reducedmetre of each product are shown in Table 16, below. For stormwater infrastructure, the three most financiallythese initial calculations, no value has been given to the feasible options for ground coverage are: 1.potential SWM pond reduction savings that may occur when Conventional asphalt; 2. Permeable asphalt, and; 3.implementing permeable surfaces. This benefit will be Porous concrete.incorporated into the scenario calculations conducted for theWPC in the following subsection. With respect to roofs, four surface types were analyzed:With respect to ground surface coverage, a few key findings Low-grade conventional roofs, high-grade conventionalfrom the financial analysis are present: roofs, extensive green roofs and intensive green roofs. Based on information gathered from industry professionals, First, porous concrete and permeable asphalt had a low-grade roofs were determined to be roofs built for better EAC and NPV than conventional concrete. approximately $75/m2 that had a lifespan of approximatelyAPRIL 2010 Page | 53
  • JOVIAN DESIGNseven years. High-grade roofs were determined to be those Intensive green roofs are the most expensive roofroofs that were built using the most recent knowledge and surface and as such are likely not a financiallyhighest quality installation methods. These roofs cost feasible option for the City of London.approximately $124/m2 yet last for an average of 20 years.In this analysis, the capital cost of the high-grade roof hasbeen added to the cost of both extensive and intensivegreen roofs to reflect the added structural cost needed tosupport a green roof system.The first two years of operation and maintenance (O&M) forextensive green roofs are more intensive and therefore havean increased cost compared to subsequent years. However,this increased cost is included in the capital cost of extensivegreen roofs. Therefore, the operation and maintenancecosts for extensive green roofs are the same as conventionalroofs after the first two years because they require the sameamount of attention.The following results were calculated for roof surfaces: The high-grade conventional roof is the most financially feasible option of all roof types, not accounting for potential stormwater cost savings. The EAC of extensive green roofs is $1.76/m2 more than the high-grade conventional roof. This is mainly due to their extended lifespan of 40 years. However, it should be noted that the lifespan for green roofs in Southern Ontario is a high-level estimation and may be inexact, given that green roofs are a relatively new product in this region.Page | 54
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYTable 16: Financial comparisons of different surfacesFinancial Comparisons of Different Surfaces Capital Cost O&M Life Span Net Present EACSurface Material ($/m2) ($/m2/year) (years) Value ($/m2) ($/m2)Ground MaterialsConventional Asphalt 95.00 0.09 25 54.77 3.89Conventional Concrete 215.00 0.07 30 111.27 7.24Permeable Asphalt 95.00 0.11 20 60.54 4.86Porous Concrete 170.00 0.07 30 88.21 5.74PICP 96.77 10.76 25 206.21 14.63RoofsConventional Roof (Low Grade) 75.35 1.35 7 70.10 12.11Conventional Roof (High Grade) 123.79 1.35 20 93.96 7.54Extensive Green Roof 317.82 1.35 40 159.50 9.30Intensive Green Roof 295.95 8.07 40 265.43 15.4710.5 Wonderland Power Centre reduction in stormwater runoff and the reduction in the costThe Surface Analysis of the Wonderland Power Centre can of the stormwater facility has been assumed. However, abe used in conjunction with the calculated NPV and EAC for more detailed study would show that real costs are noteach surface type in order to determine the cost of linear.constructing a development similar to the WPC. A key part Reduced capital costs and reduced annual maintenanceof this analysis is the financial benefit gained from reducing costs of the WPC SWM facility have been included in thethe size of the stormwater management facility. For the NPV calculations of each surface type.purposes of this Report, a direct relationship between theAPRIL 2010 Page | 55
  • JOVIAN DESIGNThe adjusted NPV, EAC, and a prorated NPV for each With respect to sidewalk materials, the following results wereproduct are calculated for three general applications (parking found:lots, sidewalks and roofs). The results are presented inTable 17, below. For each application, it is assumed that Both the NPV and EAC for porous concrete are lesseach surface material covers 100% of its applicable area of than those of conventional concrete when used forthe WPC Study Site, as outlined in the 3.6 Surface Analysis sidewalks, representing a significant cost savings.above. PICP has the highest financial savings resulting fromWith respect to parking lot materials, the following results reduced stormwater capital and maintenance costs,were found: yet has the highest NPV and EAC of any sidewalk material. Compared to conventional concrete, the Conventional asphalt and permeable asphalt have EAC of PICP is approximately $42,000 more. the lowest NPV and EAC of all parking lot materials. The NPV of permeable asphalt is lower than conventional asphalt because of the potential SWM With respect to roofing materials, the following results were facility savings it provides. However, due to the found: shorter lifespan of permeable asphalt, the EAC for High-grade conventional roofs have the lowest EAC this product is slightly more than the EAC for of any roof material. conventional asphalt. Extensive green roofs resulted in significant SWM Porous concrete and PICP result in significant cost facility savings, but had nearly twice the EAC of high- increases compared to either conventional or grade conventional roofs. As such, it is unlikely that permeable asphalt. It is therefore not likely that developers will construct green roofs unless there are either option would be financially feasible to use for incentives or regulations established by the City. large parking surfaces. All permeable parking lot surfaces provide significant capital SWM facility savings when compared to conventional asphalt. As such, the City may benefit from further exploring the feasibility of implementing these surfaces in parking lots on a limited basis.Page | 56
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYTable 17: Financial comparisons of different surface applications at the WPCFinancial Comparisons of Different Surface Applications at the WPC Area of WPC Capital SWM Net Present Prorated NetSurface Material Application (m2) Facility Savings Value Present Value EACGround Materials (over 30 years)Conventional Asphalt Parking Lots 96,161 $0 $8,808,960 $11,386,424 $625,017Permeable Asphalt Parking Lots 96,161 $321,822 $8,482,263 $11,468,370 $680,639Porous Concrete Parking Lots 96,161 $321,822 $15,324,022 $15,324,022 $996,850PICP Parking Lots 96,161 $417,632 $22,017,796 $25,662,507 $1,562,217Conventional Concrete Sidewalks 14,812 $0 $3,048,241 $3,048,241 $198,292Porous Concrete Sidewalks 14,812 $49,133 $2,360,879 $2,360,879 $153,579PICP Sidewalks 14,812 $63,873 $3,391,958 $3,953,370 $240,668Roofs (over 40 years)Conventional Roof (Low Grade) Roofs 42,744 $0 $3,346,228 $10,060,504 $578,294Conventional Roof (High Grade) Roofs 42,744 $0 $5,703,279 $7,852,785 $457,646Extensive Green Roof Roofs 42,744 $113,006 $13,750,459 $13,750,459 $801,351Intensive Green Roof Roofs 42,744 $113,006 $17,515,574 $17,515,574 $1,020,77510.6 Additional Economic Benefits advantages or disadvantages of particular products increase or decrease the costs incurred by stakeholders (e.g.,10.6.1 Monetary Value of Environmental Benefits developers, municipalities, provincial or federalIn order to fully express the benefits of permeable surfaces, governments) over the short or long term, those costs shouldenvironmental and social benefits may be considered in be accurately quantified. Efforts to quantify theterms of their potential monetary value. Similarly, it is environmental and social advantages and disadvantages ofimportant that the environmental and social disadvantages of particular products are documented and appear to be anproducts be taken into consideration by decision-makers. If emerging field of study.APRIL 2010 Page | 57
  • JOVIAN DESIGNBanting et al. (2005) conducted an extensive literature roofs as amenity spaces, the use of green roofs for foodreview to determine the environmental benefits of green production, and increased biodiversity. Table 18 provides aroofs. The study mainly focuses on the quantification of synopsis of a portion of their findings.benefits and potential monetary savings. In their study, thebenefits from stormwater flow reduction including the impact According to Clark et al. (2008), if the value of improved airon combined sewer overflow, improvement in air quality, quality resulting from green roofs is quantitativelyreduction in direct energy use, and reduction in UHI effect considered, improved air quality results in a mean NPV forwere evaluated. These factors were considered the most the green roof that is approximately 25% to 40% less thanquantifiable benefits of green roofs in terms of monetary the mean NPV of a conventional roof. This valuationvalue. The authors also indicated benefits such as the scenario reveals that over 40 years, green roofs cost lessaesthetic improvement of urban landscape, an increase in than conventional roofs (Clark et al., 2008).property values, benefits resulting from the use of green 2Table 18: Financial benefits of green roofs in Toronto, Ontario assuming 50 Million m of available roof spaceFinancial Benefits of Green Roofs Initial Cost Initial Cost Savings Annual Cost Annual Cost SavingsCategory of Savings ($) ($/m2) Savings ($) ($/m2)BenefitStormwater 118,000,000 2.36Combined Sewer 46,600,000 0.93 750,000 0.02OverflowAir Quality 2,500,000 0.05Building Energy 68,700,000 1.37 21,560,000 0.43Urban Heat Island 79,800,000 1.60 12,320,000 0.25Total 313,100,000 6.26 37,130,000 0.74Source: Banting, 2005Page | 58
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY for commercial developments such as the WPC, this11. Conclusions maintenance is dependent on building managers as opposed to the City. Agreements may need to be11.1 Durability established between the City and privateResearch conducted for each permeable surface analyzed in stakeholders in order to provide incentives forthis Report showed that the longevity of permeable products adequate property maintenance.is comparable to, if not greater than, conventional surfacematerials. Based on the findings pertaining to the lifespan and maintenance requirements of the products analyzed in this Porous concrete and conventional concrete have report, permeable surfaces may be considered as a viable equivalent lifespans of 30 years each; longer than option for new commercial developments within the City of any other pavement material analyzed in this Report. London. Although there may be some unforeseen costs associated with the maintenance of porous concrete 11.2 Net water Savings over time, this product is still highly comparable to Across the board, permeable surfaces result in a general net conventional concrete and may be ideal for smaller water savings by reducing the amount of runoff that may applications throughout the City, such as sidewalks. otherwise need to be collected by stormwater management facilities. Although permeable asphalt does not have as long of a lifespan as conventional asphalt, it could be applied PICP had the greatest net water savings of any in a limited capacity, such as commercial or product when used for either parking lots or recreational areas that experience very low levels of sidewalks. Even at minimal coverage (25%), PICP vehicular traffic. The City has a history of has the potential to reduce overall runoff by up to maintenance issues with PICP, and therefore they 11% when used in large parking lots (approximately should not be used to cover large surface areas. 100,000m2). As such, the City may want to explore However, if used in conjunction with other permeable the use of PICP in low-traffic areas on a limited or conventional surfaces (such as concrete), on a basis. limited basis, PICP may be an adequate material for stormwater mitigation. Porous concrete provided significant net water savings (approximately 5%) if used for all sidewalk With proper maintenance, extensive green roofs can surfaces in a development such as the WPC. If double the lifespan of conventional roofs while used for municipal applications, porous concrete providing valuable environmental services. However,APRIL 2010 Page | 59
  • JOVIAN DESIGN may be an excellent alternative to conventional Although it is not traditionally used as a sidewalk concrete sidewalks. material, permeable asphalt also proved to be a more cost effective alternative to conventional concrete Extensive green roofs also provided significant sidewalks. reductions in stormwater runoff, even if implemented on a limited basis. For example, roofs The NPV and EAC of permeable asphalt were very which are equipped with 50% extensive green roof similar to conventional asphalt when used for parking coverage can reduce stormwater runoff by 6% for a lot surfaces. Given the stormwater retention development such as the WPC. capabilities of permeable asphalt, the City may want to further explore the benefits of using this productBased on these findings, the City of London may benefit despite its increase in cost.from exploring the options for implementing permeablesurfaces on both public and private properties. In the case When used for parking lots or sidewalks, PICPof private developments, agreements would likely have to be represented a significant cost increase compared tomade with developers to establish a mutual benefit for the any other surface material. As such, it is not likelyimplementation of permeable surfaces. financially feasible to use this product for large parking lot or sidewalk applications. However, the11.3 Financial Analysis City may want to explore the limited use of PICP inAlthough all permeable surfaces provide for potential cost conjunction with more financially feasible surfaces tosavings due to reduced stormwater management take advantage of its high capacity to retaininfrastructure, most permeable surfaces require higher stormwater.overall capital expenditures and annual costs than theirconventional counterparts. However, this is not without With respect to roofing systems, both intensive andexception. extensive green roofs were not found to be financially feasible given their increased capital and annual When used for sidewalk applications, it was costs. Extensive roofs may be more financially determined that porous concrete was more cost feasible if implemented on a limited basis, such as effective than conventional concrete. As such, the 50% coverage or less. However, because the City may want to further examine the feasibility of developer must incur the cost of constructing a green using porous concrete for future sidewalk roof, and the property manager must incur the cost of construction projects. Porous concrete was not maintaining it, the City would likely have to look into financially feasible for parking lot surfaces. establishing regulation(s) or an incentive program(s)Page | 60
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY to encourage the use of extensive green roofs in London. If properly quantified, the additional financial benefits gained indirectly from permeable surfaces may provide further justification for the development of public policy or design standards which encourage and/or regulate the use of permeable surfaces.The financial analysis of this Report showed that in mostcases, permeable surfaces are more expensive than theirconventional counterparts. Therefore, the City might onlyconsider implementing them on a limited basis in order totake advantage of their environmental benefits. However,porous concrete sidewalks are a financially viable option thatcould be implemented on a larger scale.11.4 SummaryAfter considering all three analyses conducted in this Report,the City may realize tangible benefits from pursuingpermeable surface stormwater management, particularlythrough the use of porous concrete for sidewalk surfaces.Table 19 below, provides a summary of the findings of thisReport. Each product is evaluated against its conventionalcounterpart for each application. The evaluations have beendivided into three parts: Cost, durability and water savings.Where there is a green check (√), the permeable productperformed better than its conventional counterpart. Wherethere is a red x (X), the permeable product did not performas well as its conventional counterpart.APRIL 2010 Page | 61
  • JOVIAN DESIGNTable 19: Overall product comparisons Comparisons between Permeable Products and their Conventional Counterparts Application Evaluation Product Porous Concrete PICP Permeable Asphalt Extensive Green Roof Cost √ X √ - Sidewalks Durability √ X X - Water Savings √ √ √ - Cost X X X - Parking Lots Durability √ X X - Water Savings √ √ √ - Cost - - - X Roofs Durability - - - √ Water Savings - - - √Page | 62
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDY 12.4 Additional Recommendations12. Recommendations Further research should be conducted regarding the most suitable way to encourage and/or regulate the use of12.1 Durability permeable surfaces in private developments. Part of thisSite-specific research should be conducted to determine any research should include evaluating the permeable surfaceadditional maintenance fees associated with the implementation strategies adopted by other municipalities inimplementation of permeable surfaces (particularly porous Southern Ontario.concrete) in future developments within the City of London. A survey of the public‟s perception of permeable products12.2 Net Water Savings may also help support the integration of these products intoGiven that all permeable surfaces provide a significant level public policy and/or development standards.of net water savings, further research should be conductedregarding the most suitable way to encourage and/orregulate the use of permeable surfaces in privatedevelopments.12.3 Financial AnalysisSite-specific studies for future developments with plannedstormwater facilities should be conducted in order toaccurately quantify the savings resulting from reducedinfrastructure costs.Further research should be conducted with respect to thefeasibility of using porous concrete instead of conventionalconcrete for sidewalks.Further research should be conducted pertaining to thefinancial feasibility of using permeable asphalt, porousconcrete and/or PICP on a limited scale in parking lots inorder to take advantage of their environmental benefits.APRIL 2010 Page | 63
  • JOVIAN DESIGNReferencesAECOM. (2009). Storm drainage/SWM servicing development charges update 2008: DC Study Final Executive Summary. Prepared for the City of London.Asaeda, T. & Ca, V.T. (2000). Characteristics of permeable pavement during hot summer weather and impact on the thermal environment. Building and Environment, 35, 363-375.Backstrom, M. & Bergstrom, A. (2000). Draining function of porous asphalt during snowmelt and temporary freezing. Canadian Journal of Civil Engineering, 27, 594-598.Backstrom, M. & Viklander, M. (2000). Integrated stormwater management in cold climates. Journal of Environmental Science and Health, Part A, 35(8), 1237-1249.Balades, J. D., Legret, M., & Madiec, H. (1995). Permeable pavements: Pollution management tools. Water Science and Technology, 32(1), 49-56.Ball, T. (2008). Urban heat island effect. Friends of Science, 1-8. Retrieved from http://www.friendsofscience.org/assets/ documents/ FoS_Urban%20Heat%20Island.Banting, D., Doshi, H., Li, J., Missios, P., Au, A., Currie, B.A., & Verrati, M. (2005). Report on the Environmental Benefits and Costs of Green Roof Technology for the City of Toronto. Prepared for City of Toronto and Ontario Centres of Excellence – Earth and Environmental Technologies (OCE-ETech) and report. Retrieved from http://www.toronto.ca/greenroofs/pdf/fullreport103105.pdfBarnes, K.B., Morgan, J.M., & Roberge, M.C. (2002). Impervious surfaces and the quality of natural and built environments. Retrieved from http://pages.towson.edu/morgan/ files/Impervious.pdfBarrow, C.J. (2003). Environmental change and human development. Oxford University Press, New York, NY: +252 pp.Bean, Z.B., Hunt, W.B., & Bidelspach, D.A. (2007a). Evaluation of four permeable pavement sites in eastern North Carolina for runoff reduction and water quality impacts. Journal of Irrigation and Drainage Engineering, November/December, 583- 592.Page | 64
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYBean, Z.B., Hunt, W.B., & Bidelspach, D.A. (2007b). Field survey of permeable pavement surface infiltration rates. Journal of Irrigation and Drainage Engineering, 133 (3), 249-255.Bean, Z.B., Hunt, W.B., Bidelspach, D.A., & Burak, R.J. (2004). Study on the surface infiltration rate of permeable pavements. Proceedings of the 2004 World Water and Environmental Resources Congress: Critical Transitions in Water and Environmental Resources Management, Salt Lake City, Utah, 749-758.Beecham, S. & Myers, B. (2007). Structural and design aspects of porous and permeable block pavement. Journal of Australian Ceramic Society, 43(1), 74-81.Bogemans, J., Nierinck, L., & Stassart, J.M. (1989). Effect of de-icing chloride salts on ion accumulation in Spruce. Plant and Soil, 113, 3-11.Bouzoubaa, N. & Foo, S. (2005). Use of fly ash and slag in concrete: A best practice guide. Government of Canada Action Plan 2000 on Climate Change. Retrieved from http://www.scm.gc.ca/docs/bestpractices.pdf#page=27Bouzoubaa, N. & Fournier, B. (2005). Current situation with the production and use of supplementary cementitious materials (SCMs) in concrete construction in Canada. Canadian Journal of Civil Engineering, 32(1), 129-143.Boving, T.B, Stolt, M.H., Augenstern, J., & Brosnan, B. (2008). Potential for localized groundwater contamination in a porous pavement parking lot setting in Rhode Island. Environmental Geology, 55, 571-582.Brattebo, B.O. & Booth, D.B. (2003). Long-term stormwater quantity and quality performance of permeable pavement systems. Water Research, 37, 4369-4376.Brown, K. (2008). Permeable paving. Toronto Regional Conservation Authority with Credit Valley Conservation. Retrieved from http://www.creditvalleyca.ca/ sustainability/lid/designtool/ fact_sheets/TRCA_LID_10-PermeablePaving121708.pdfCaGBC. (2004). LEED Green Building Rating System for New Construction and Major Renovations (LEED – Canada NC Version 1.0). Canadian Green Building Council, Ottawa, Ontario, December 2004.City of London. (2010). Understanding growth in London. Retrieved from http://www.london.ca/d.aspx?s=/About_London/londongrowth.htmCity of London. (2006). Schedule A to the City of London Official Plan – Land Use Map No. 7. City of London Official Plan.APRIL 2010 Page | 65
  • JOVIAN DESIGNCity of Toronto. (2010). Green roofs. Living in Toronto. Retrieved from http://www.toronto.ca/greenroofs/overview.htmClark, C., Adriaens, P., & Talbot, F. B. (2008). Green roof valuation: A probabilistic economic analysis of environmental benefits. Environmental Science & Technology, 42(6), 2155-2161.Committee E-701 Materials for Concrete Construction. (2001).Cementitious materials for concrete. ACI Education Bulletin, E3-1- E3-25. Retrieved from http://www.concrete.org/general/fE3-01.pdfCornell University. (2007). Precipitation. Department of Crop and Soil Sciences. Retrieved from http://www.css.cornell.edu/faculty/hmv1/watrshed/Return.htmDaley, M.L., Potter, J.D., & McDowell, W.H. (2009). Salinization of urbanizing New Hampshire streams and groundwater: Effects of road salt and hydrologic variability. Journal of the North American Benthological Society, 28(4), 929-940.Decaluwe, D. (2010). Personal interview. Stone in Style. 26 February 2010.DeMarco, F. (2010). Personal interview. TCG Asphalt and Construction. 8 March 2010.Development Engineering (London) Limited. (2005). Final stormwater management report for the Bradley Avenue stormwater management facility. City of London, County of Middlesex. Prepared for Southside Construction, + 37pp.Dingman, S.L. (2002). Physical hydrology (Second Edition). Pearson Education Canada, Ltd., Toronto, Ontario. + 646 pp.Elite Surfacing. (2010). Driveways. Retrieved from http://elitesurfacing.com/Driveways/tabid/835/language/en-US/Default.aspxEnvironment Canada. (2010). Canadian climate normals 1971-2000. National Climate Data and Information Archive. Retrieved from http://climate.weatheroffice.gc.ca/climate_normals/ results_e.html?Province =ALL&StationName=London&SearchType=BeginsWith&LocateBy=Province&Proximity=25&ProximityFrom=City&Station Number=&IDType=MSC&CityName=&ParkName=&LatitudeDegrees=&LatitudeMinutes=&LongiEnvironment Canada and Health Canada. (2001). Priority substances list assessment report for road salts. Minister of Public Works and Government Services, Ottawa, Ontario.Environmental Services Water Quality Division. (2009). Stormwater Glossary. Wake County, North Carolina. Retrieved from http://www.wakegov.com/water/stormwater/taskforce/links/ glossary.htmPage | 66
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYFancher, S. & Townsen, S. (2003). Sustainable infrastructure: Alternative paving materials subcommittee report. City of Portland, Bureau of Environmental Services, October 2003, 1-20.Feig, D.I. & Paya, R. (1998). Road salt impacts on drinking water. American Heart Association Journal: 99-112.Fischel, M. (2001). Evaluation of selected de-icers based on a review of the literature. Prepared by the SeaCrest Group, Colorado Department of Transportation. Denver, Colorado: +117 pp.Fisher Tracks. (2010). Polyurethane track surfaces. Retrieved from http://www.fishertracks.com/polyurethane_tracks.htmlFreemantle, M. (1999). Asphalt. Chemical & Engineering News, 77(47), 81.Gilbert, J.K. & Clausen, J.C. (2006). Stormwater runoff quality and quantity from asphalt, paver, and crushed stone driveways in Connecticut. Water Research, 40, 826-832.Golden, J. & Kaloush, K. (2005). A hot night in the Big City: How to mitigate the urban heat island. Public Works Online, December. Retrieved from http://www.pwmag.com/industry-news.asp?sectionID=770&articleID=268116Google Maps. (2010). London Ontario. Retrieved from http://maps.google.com/mapsGovers, K. Personal interview. (2010). LiveRoof Ontario. 15 March 2010.Gunderson, J. (2008). Pervious pavements: new findings about their functionality and performance in cold climates. Stormwater, September, 1-3. Retrieved from http://www.stormh2o.com/september-2008/pervious-asphalt-concrete.aspxGuntner, M. & Wilke, B.M. (1983). Effects of de-icing salt on soil enzyme activity. Water, Air, and Soil Pollution, 20, 211-220.Hirshorn, S. (2010). Paving with drainage. Landscape Trades, 32(1), 8-10.Howard, K.W.F. & Beck, P.J. (1993). Hydrogeochemical implications of groundwater contamination by road de-icing chemicals. Journal of Contaminant Hydrology, 12, 245–268.HydroCAD. (2009). Understanding Exfiltration. HydroCAD Stormwater modelling. Retrieved from http://www.hydrocad.net/exfilt.htmAPRIL 2010 Page | 67
  • JOVIAN DESIGNInterlocking Concrete Pavement Institute (ICPI). (2008). Permeable interlocking concrete pavement. Washington, DC: ICPI. Retrieved from http://www.romanstone.com/pdfs/PICPcomparisonGuide.pdfInterlocking Concrete Pavement Institute (ICPI). (2007). Achieving LEED credits with segmental concrete pavement. Tech Spec, 16, 1-24. Burlington, ON.Kohler, M., Schmidt, M., Grimme, F.W., Laar, M., de Assuncao Paiva, V.C., & Tavares, S. (2002). Green roofs in temperate climates and in the hot-humid tropics – far beyond the aesthetics. Environmental Management and Health, 13(4), 382- 391.Kosareo, L. & Ries, R. (2007). Comparative environmental life cycle assessment of green roofs. Building and Environment, 42(7), 2606-2613.Landers, J. (2008). Chicago uses permeable materials to make alleys „green‟. Civil Engineering, January, 26-28.Legret, M. & Colandini, V. (1999). Efffects of a porous pavement with reservoir structure on runoff water: Water quality and fate of heavy metals. Water Science and Technology, 39, 111-117.Li, Z., Li, F., & Li, J.S.L. (1998). Properties of concrete incorporating rubber tire particles. Magazine of Concrete Research, 50(4), 297-304.Liu, K. & Baskaran, B. (2003). Thermal performance of green roofs through field evaluation. Institute for Research in Construction, 1-10.LiveRoof. (2010). Prevegatated invisible modular green roof system. www.liveroof.comLui, G., Widger, R.A., & Jin, Y.C. (2006). Trend analysis of road salt impacts on groundwater salinity at a long-term monitoring site. Annual Conference of the Transportation Association of Canada, Charlottetown, Prince Edward Island: pp. 1-13.Malhotra, V.M., & Mehta, P.K. (1996). Pozzolanic and cementitious materials. Advances in concrete technology. Vol. 1. Gordon and Breach Science Publishers, Amsterdam, The Netherlands.Mallay, C. (2010). Personal interview. Duo Building Ltd. 1 March 2010.Mentens, J., Raes, D., & Hermy, M. (2005). Green roofs as a tool for solving the rainwater runoff problems in the urbanized 21st century? Landscape and Urban Planning, 77, 217-226.Page | 68
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYMetropolitan Area Planning Council. (2010). Fact sheet: Permeable paving. Massachusetts Low Impact Development Toolkit. Retrieved from http://www.mapc.org/sites/default/files/LID_Fact_Sheet_-_Permeable_Paving.pdfMutual Materials. (2010). Permeable pavers. Retrieved from http://www.mutualmaterials.ca/Homeowner_product_permeable_pavers_SF_rima.phpNational Asphalt Pavement Association (NAPA). (2008). Asphalt pavements and the LEED green building system. Lanham, MD.National Ready Mixed Concrete Association. (2008). Concrete CO2 fact sheet. National Ready Mixed Concrete Association. Retrieved from http://www.nrmca.org/GreenConcrete/CONCRETE%20CO2%20FACT%20SHEET%20JUNE%202008.pdfNational Ready Mixed Concrete Association. (2010). Pervious concrete: Engineering properties. National Ready Mixed Concrete Association. Silver Spring, MD. Retrieved from http://www.perviouspavement.org/engineering%20properties.htmNatural Resources Canada. (2003). The Atlas of Canada - Annual Precipitation. Retrieved from http://atlas.nrcan.gc.ca/auth/english/maps/archives/3rdedition/ environment/climate/025Ngan, G. (2004). Green roof policies: Tools for encouraging sustainable design. +49 pp. Retrieved from www.gnla.ca.Oke, T.R. (2006). Boundary layer climates (2nd edition). Methuen & Co. Ltd. +338 pp.Park, S., & Tia, M. (2003). An experimental study on the water-purification properties of porous concrete. Cement and Concrete Research, 34(2), 177-184.Pavers By Ideal. (2005). Turfstone Grid Pavers. Pavers By Ideal, Westford, Massachusetts. Retrieved from http://www.paversbyideal.com/pdf/Turfstone.pdfPeck, S. & Kuhn, M. (n/d), Design guidelines for green roofs. Canadian Mortgage and Housing Corporation. Retrieved from http://www.cmhc.ca/en/inpr/bude/himu/coedar/loader.cfm?url=/commonspot/security/getfile.cfm&PageID=70146Permacon. (2010). Subterra pavers. Retrieved from http://www.permacon.ca/products.html?product_id=491&z=SubterraPratt, C.J. (1999). Use of permeable, reservoir pavement constructions for stormwater treatment and storage for re-use. Water Science and Technology, 39(5), 145-151.Presto. (2010). GeoSystems. Retrieved from http://www.prestogeo.com/geoblockAPRIL 2010 Page | 69
  • JOVIAN DESIGNProdanovic, P. & Simonovic, S.P. (2007). Development of rainfall intensity duration frequency curves for the City of London under the changing climate. Water Resources Research Report, no. 054. Department of Civil and Environmental Engineering, University of Western Ontario, London, Ontario. +50 pp.Rajani, B., & Zhan, C. (1997). Performance of concrete sidewalks: Field studies. Canadian Journal of Civil Engineering, 24, 303- 312.Ramakrishna, D.M., & Viraraghavan, T. (2005). Environmental impact of chemical de-icers – A review. Water, Air, and Pollution, 166, 49-63.Robinson, D., Terella, M., & Rosenfeld, B. (2009). Stormwater Inventory Masterplan. Prepared for Pasco County, Florida. Retrieved from http://proceedings.esri.com/library/userconf/serug09/papers/ pasco_county_stormwater_inventory_master_plan.pdfRoseen, R.M. & Ballestero, T.P. (2008). Porous asphalt pavements for stormwater management in cold climates. Hot Mix Asphalt Technology, May/June 2008.Roseen, R.M., Ballestero, T.P., Houle, J.J., Avellaneda, P., Briggs, J, Fowler, G., et al. (2009). Seasonal performance variations for stormwater management systems in cold climate conditions. Journal of Environmental Engineering, 135(3), 128-137.Rowlett, R. (2002). How many? A dictionary of units of measurement. The university of North Carolina of Chapel Hill. Retrieved from http://www.unc.edu/~rowlett/units/dictR.htmlRushton, B. (2001). Low-impact parking lot design reduces runoff and pollutant loads. Journal of Water Resources Planning and Management, 127(3), 172-179.Sansalone, J., Kuang, X., & Ranieri, V. (2008). Permeable pavement as a hydraulic and filtration interface for urban drainage. Journal of Irrigation and Drainage Engineering,134(5), 666-674.Shuster, W.D., Bonta, J., Thurston, H., Warnemuende, E., & Smith, D.R. (2005). Impacts of impervious surface on watershed hydrology: A review. Urban Water Journal, 2(4), 263-275.Smith, D. R. (2006). Permeable interlocking concrete pavements: Selection, design, construction, maintenance. Burlington, Ontario: Interlocking Concrete Pavement Institute.Page | 70
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYSmith, T. (2006). Helping build a sustainable future by constructing roadways with Portland cement concrete pavement. Cement Association of Canada. Retrieved from http://www.tacatc.ca/english/resourcecentre/readingroom/conference/conf2006/docs/s012/tsmith.pdfSouthside Group. (2010). Wonderland Power Centre – London, Ontario. Retrieved from http://www.southsidegroup.ca/commercial/d/cc_wonderland_pc.htmlStatistics Canada. (2006). Projected population and dwelling count (municipalities) according to a medium growth scenario. Statistics Canada, 2006 Census.Stenmark, C. (1995). An alternative road construction for stormwater management in cold climates. Water Science and Technology, 32(1), 79-84.SWITCH Urban Water. (2007). Briefing notes: Sustainable stormwater management. SWITCH Resources. Retrieved from http://switchurbanwater.lboro.ac.uk/outputs/results.php?pubtype_select=1Taves, D. (2010). Personal interview. Gardens in the Sky, Flynn Canada. 22 March 2010.Tennis, P.D., Leming, M.L., & Akers, D.J. (2004). Pervious concrete pavements. Portland Cement Association, Skokie, IL., and National Ready Mix Concrete Association, Silver Spring, MD. +25 ppToronto and Region Conservation Authority (TRCA). (2007). Performance evaluation of permeable pavement and a bioretention swale Seneca College, King City, Ontario. Toronto, Ontario: TRCATricar Group. (2010). Luxury Apartments – London. Retrieved from http://www.tricar.com/ap_london.html#west.Troumbulak, S.C. & Frissell, C. (2000). Review of ecological effects of roads on terrestrial and aquatic communities. Conservation Biology, 14(1), 18-30.Uni-EcoLocTech. (2008). Uni-Ecoloc. Mutual Materials, Vancouver, Washington.Unilock. (2009). Directions in Sustainable Design. Hangestone Holdings, Inc., Toronto, ON.Unilock. (2010). Permeable Products. Retrieved from http://www.unilock.com/products/product.php?prodid=14APRIL 2010 Page | 71
  • JOVIAN DESIGNUnited States Environmental Protection Agency (EPA). (2009). Porous Asphalt Pavement. National Pollutant Discharge Elimination System, September 2009.United States Environmental Protection Agency (EPA). (1999). Stormwater Technology Fact Sheet: Wet Detention Ponds. Municipal Technology Branch, September 1999. Retrieved from http://www.epa.gov/owm/mtb/wetdtnpn.pdfUnited States Environmental Protection Agency. (2009). Heat Island Effect: Basic Information. Washington DC: EPA. http://www.epa.gov/heatisland/about/index.htmUniversity of Florida. (2008). Florida field guide to low impact development. Program for Research Efficient Communities. Retrieved from http://buildgreen.ufl.edu/Fact_sheet_ Permeable_Surfaces.pdfUniversity of Florida. (2007). Glossary of water related terms. CSREES Florida Water Quality Program. Retrieved from http://waterquality.ifas.ufl.edu/Glossary/Glossary .htm#BaseflowVan Woert, N.D., Rowe, D.B., Andersen, J.A., Rugh, C.L., Fernandez, R.T., & Xiao, L. (2005). Green roof stormwater retention: Effects of roof surface, slope and media depth. Journal of Environmental Quality, 34, 1036-1044.Vasiliu, G. (2010). Personal interview. Coco Asphalt Engineering. 5 March 2010.Veldjesgraaf, B. & Yantzi, R. (2008). Permeable interlocking concrete pavements PICP. Received from Darcy DecaluweVonk, J. (2010). Personal interview. Zinco Canada. 24 February 2010.Walker, D. (2006). Porous Asphalt Reduces Storm Water Runoff. Asphalt: Online Magazine. Retrieved from http://www.asphaltmagazine.com/singlenews.asp?item_ ID=1178&comm=0&list _code_int=mag01-intWerner E. & diPretoro, R.S. (2006). Rise and fall of road salt contamination of water-supply springs. Environmental Geology, 51, 537-543.Williams, D.D., Williams, N.E., & Cao, Y. (1999). Road salt contamination of groundwater in a major metropolitan area and development of a biological index to monitor its impact. Water Resources, 34(1), 127-138.Williams, M., Hopkinson, C., Rastetter, E., Vallino, J., & Claessens, L. (2005). Relationships of land use and stream solute concentration in the Ipswich River Basin, Northeastern Massachusetts. Water, Air, and Soil Pollution, 161, 55-74.Page | 72
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYWendell, O. (2005). Pervious concrete: Frequently asked questions. County Landscape & Design. Retrieved from http://www.owendell.com/perviouscon.htmlWoodward, J. (2010). Personal interview. Grand River Brick & Stone. 2 March 2010.Worton, M. (2010). Personal interview. Lafarge. 17 March 2010.ZinCo Canada. (2009). Life on Roofs: Carlisle, ON. www.zinco.ca.APRIL 2010 Page | 73
  • PERMEABLE SURFACE STORMWATER MANAGEMENT FEASIBILITY STUDYAppendices
  • Appendix A. 1: Site ContextSchedule A to the City of London Official Plan - Landuse
  • Appendix A. 2: Surface AnalysisWPC Surface Analysis Map Low-sloped Roofs Sloped Roofs SWM Pond Parking Lots & Low-traffic Roadways Sidewalks Medians Surface Characteristics of the Wonderland Power Centre study area. Modified from the City of London‟s Public Zoning Map and used for academic purposes: Retrieved February, 2010. Aerial photo taken in April, 2009. Scale = 1 : 3, 030.30
  • Appendix A. 3: Stormwater Management InventoryPinecombe Drainage Catchment Area
  • Appendix B. 1: Product Analysis Summary of PICP Products Characteristics: Cost of RunoffProduct Company Cost of Stone Installation Total of Cost Subbase Durability Operation & Maintenance CoefficientEco-Optiloc Unilock $30.34/m2 $37.66/m2 $68.00/m2 $14.7/m2 25 years Vacuum 1-2 times yearly $10.76/m2/year 0.25Eco-Priora Unilock $74.14/m2 $37.66/m2 $111.8/m2 $14.7/m2 25 years Vacuum 1-2 times yearly $10.76/m2/year 0.25Subterra Permacon $28.51/m2 $37.66/m2 $66.17/m2 $14.7/m2 25 years Vacuum 1-2 times yearly $10.76/m2/year 0.25 Summary of Concrete and Asphalt Product Characteristics: Total cost includingProduct Company installation and sub-base Lifespan Operation and Maintenance Runoff CoefficientPervious Concrete Lafarge Canada Inc. $170/m3 30 years Vacuum 1-2 times yearly $0.07/m2/year 0.4Permeable Asphalt Coco Asphalt Eng. $95/m3 20 years Vacuum 1-2 times yearly $0.11/m2/year 0.4Conventional Concrete Lafarge Canada Inc. $215/m3 30 years Sweep 1-2 times yearly $0.07/m2/year 0.9Conventional Asphalt TCG Asphalt & Construction $95/m3 25 years Sweep 1-2 times yearly $0.09/m2/year 0.9 Summary of Green Roof Characteristics: Price including Green Roof Product Company installation Maintenance Durability Runoff Coefficient Extensive Floradrain FD 25 ZinCo Canada $107.6/m2 $1.35/m2/year 40 years 0.5 Extensive Floradrain FD 25 ZinCo Canada $215.2/m2 $1.35/m2/year 40 years 0.5 Extensive LiveRoof LiveRoof Ontario $150.64/m2 $1.35/m2/year 40 years 0.5 Extensive Duo Building Ltd. Duo Building Ltd. $206.67/m2 $1.35/m2/year 40 years 0.5 Extensive* Soprema Taiga Flynn Canada $161.45/m2 $1.35/m2/year 40 years 0.5 Extensive* Sedum Master Flynn Canada $193.75/m2 $1.35/m2/year 40 years 0.5 Extensive* LiveRoof Flynn Canada $322.90/m2 $1.35/m2/year 40 years 0.5 Intensive* Connon Nursery Flynn Canada $269.10/m2 $8.07/m2/year 40 years 0.3 Intensive Floradrain FD 60 ZinCo Canada $322.8/m2 $8.07/m2/year 40 years 0.3
  • Appendix B. 2: Net Water Savings: Calculations Appendix B: 100% Pervious Coverage of Hard Surface Using Permeable Asphalt or PC and Green Roofs: RUNOFF CONVENTIONALSURFACE AREA (m2) COEFFICIENT, C DESIGN PERVIOUS COVERAGE IMPERVIOUS AREA, (IMPERVIOUSNESS) IMPERVIOUS AREA (m2) (100% of Area) PERVIOUS SEGMENTSAsphalt Pavement 96161 0.9 86545Concrete Pavement 14812 0.9 13331Conventional Roof 42744 0.9 38470Green Roof 0.5 42744 21372Porous Concrete 0.4 14812 5925Permeable Asphalt 0.4 96161 38464Medians and Others 24085 0.2 4817 24085 4817Total Paved Surface Area 177802 143162 177802 70578Total Site Area 220785 220785 220785Site Imperviousness (%) 64.8 32.0 RUNOFF REDUCTION (%) 50.7 SURFACE SURFACE SURFACESURFACE AREA (m2) IMPERVIOUS AREA, IMPERVIOUSNESS IMPERVIOUSNESS IMPERVIOUSNESS PERVIOUS SEGMENTS (GREEN ROOFS) (SIDEWALKS) (PARKING LOTS)Asphalt Pavement 96161 86545 86545Concrete Pavement 14812 13331 13331Conventional Roof 42744 38470 38470Green Roof 21372 21372Porous Concrete 5925 5925Permeable Asphalt 38464 38464Medians and Others 24085 4817 4817 4817 4817Total Paved Surface Area 177802 70578 126065 135756 95082Total Site Area 220785 220785 220785 220785 220785Site Imperviousness (%) 32.0 57.1 61.5 43.1 RUNOFF REDUCTION (%) 50.7 11.9 5.2 33.6
  • Appendix B: 75% Pervious Coverage of Hard Surface Using Permeable Asphalt or PC and Green Roofs RUNOFF CONVENTIONALSURFACE AREA (m2) COEFFICIENT, C DESIGN IMPERMEABLE (IMPERVIOUSNESS) IMPERVIOUS AREA (m2) (25% of Area)Asphalt Pavement 96161 0.9 86545 21636Concrete Pavement 14812 0.9 13331 3333Conventional Roof 42744 0.9 38470 9617Green Roof 0.5Porous Concrete 0.4Permeable Asphalt 0.4Medians and Others 24085 0.2 4817Total Paved Surface Area 153717 143162 34586Total Site Area 220785 220785 220785Site Imperviousness (%) 64.8 SURFACE SURFACESURFACE AREA (m2) IMPERVIOUS AREA, IMPERVIOUSNESS IMPERVIOUSNESS PERVIOUS SEGMENTS (GREEN ROOFS) (SIDEWALKS)Asphalt Pavement 96161 86545 86545Concrete Pavement 14812 13331 3333Conventional Roof 42744 9617 38470Green Roof 25646 16029Porous Concrete 7776 4444Permeable Asphalt 50485Medians and Others 24085 4817 4817 4817Total Paved Surface Area 177802 88724 130339 137608Total Site Area 220785 220785 220785 220785Site Imperviousness (%) 40.2 59.0 62.3 RUNOFF REDUCTION (%) 38.0 9.0 3.9
  • Appendix B: 75% Pervious Coverage of Hard Surface Using Permeable Asphalt or PC and Green Roofs continuedPERVIOUS COVERAGE PERVIOUS COVERAGE IMPERVIOUS AREA, (100% of Area) (75% of Area) PERVIOUS SEGMENTS 42744 16029 25646 14812 4444 7776 96161 28848 50485 4817 153717 49321 88724 220785 40.2 RUNOFF REDUCTION (%) 38.0 SURFACE IMPERVIOUSNESS (PARKING LOTS) 21636 13331 38470 28848 4817 107102 220785 48.5 25.2
  • Appendix B: 50% Pervious Coverage of Hard Surface Using Permeable Asphalt or PC and Green Roofs RUNOFF CONVENTIONALSURFACE AREA (m2) COEFFICIENT, C DESIGN IMPERMEABLE (IMPERVIOUSNESS) IMPERVIOUS AREA (m2) (50% of Area)Asphalt Pavement 96161 0.9 86545 43272Concrete Pavement 14812 0.9 13331 6665Conventional Roof 42744 0.9 38470 19235Green Roof 0.5Porous Concrete 0.4Permeable Asphalt 0.4Medians and Others 24085 0.2 4817Total Paved Surface Area 177802 143162 69173Total Site Area 220785 220785 220785Site Imperviousness (%) 64.8 SURFACE SURFACESURFACE AREA (m2) IMPERVIOUS AREA, IMPERVIOUSNESS IMPERVIOUSNESS PERVIOUS SEGMENTS (GREEN ROOFS) (SIDEWALKS)Asphalt Pavement 96161 86545 86545Concrete Pavement 14812 13331 6665Conventional Roof 42744 19235 38470Green Roof 29921 10686Porous Concrete 9628 2962Permeable Asphalt 62505Medians and Others 24085 4817 4817 4817Total Paved Surface Area 177802 106870 134614 139459Total Site Area 220785 220785 220785 220785Site Imperviousness (%) 48.4 61.0 63.2 RUNOFF REDUCTION (%) 25.4 6.0 2.6
  • Appendix B: 50% Pervious Coverage of Hard Surface Using Permeable Asphalt or PC and Green Roofs continuedPERVIOUS COVERAGE PERVIOUS COVERAGE IMPERVIOUS AREA, (100% of Area) (50% of Area) PERVIOUS SEGMENTS 42744 10686 29921 14812 2962 9628 96161 19232 62505 4817 153717 32881 106870 220785 48.4 RUNOFF REDUCTION (%) 25.4 SURFACE IMPERVIOUSNESS (PARKING LOTS) 43272 13331 38470 19232 4817 119122 220785 54.0 16.8
  • Appendix B: 25% Pervious Coverage of Hard Surface Using Permeable Asphalt or PC and Green Roofs RUNOFF CONVENTIONALSURFACE AREA (m2) COEFFICIENT, C DESIGN IMPERMEABLE (IMPERVIOUSNESS) IMPERVIOUS AREA (m2) (75% of Area)Asphalt Pavement 96161 0.9 86545 64909Concrete Pavement 14812 0.9 13331 9998Conventional Roof 42744 0.9 38470 28852Green Roof 0.5Porous Concrete 0.4Permeable Asphalt 0.4Medians and Others 24085 0.2 4817Total Paved Surface Area 177802 143162 103759Total Site Area 220785 220785 220785Site Imperviousness (%) 64.8 SURFACE SURFACESURFACE AREA (m2) IMPERVIOUS AREA, IMPERVIOUSNESS IMPERVIOUSNESS PERVIOUS SEGMENTS (GREEN ROOFS) (SIDEWALKS)Asphalt Pavement 96161 86545 86545Concrete Pavement 14812 13331 9998Conventional Roof 42744 28852 38470Green Roof 34195 5343Porous Concrete 11479 1481Permeable Asphalt 74525Medians and Others 24085 4817 4817 4817Total Paved Surface Area 177802 125016 138888 141311Total Site Area 220785 220785 220785 220785Site Imperviousness (%) 56.6 62.9 64.0 RUNOFF REDUCTION (%) 12.7 3.0 1.3
  • Appendix B: 25% Pervious Coverage of Hard Surface Using Permeable Asphalt or PC and Green Roofs continuedPERVIOUS COVERAGE PERVIOUS COVERAGE IMPERVIOUS AREA, (100% of Area) (25% of Area) PERVIOUS SEGMENTS 42744 5343 34195 14812 1481 11479 96161 9616 74525 4817 153717 16440 125016 220785 56.6 RUNOFF REDUCTION (%) 12.7 SURFACE IMPERVIOUSNESS (PARKING LOTS) 64909 13331 38470 9616 4817 131142 220785 59.4 8.4
  • Appendix B: 100% Pervious Coverage of Hard Surface Using PICP and Green Roofs RUNOFF CONVENTIONALSURFACE AREA (m2) COEFFICIENT, C DESIGN PERVIOUS COVERAGE IMPERVIOUS AREA, (IMPERVIOUSNESS) IMPERVIOUS AREA (m2) (100% of Area) PERVIOUS SEGMENTSAsphalt Pavement 96161 0.9 86545Concrete Pavement 14812 0.9 13331Conventional Roof 42744 0.9 38470Green Roof 0.5 42744 21372PICP (sidewalk) 0.25 14812 3703PICP (parking lot) 0.25 96161 24040Medians and Others 24085 0.2 4817 24085 4817Total Paved Surface Area 177802 143162 177802 53932Total Site Area 220785 220785 220785Site Imperviousness (%) 64.8 24.4 RUNOFF REDUCTION (%) 62.3 SURFACE SURFACE SURFACESURFACE AREA (m2) IMPERVIOUS AREA, IMPERVIOUSNESS IMPERVIOUSNESS IMPERVIOUSNESS PERVIOUS SEGMENTS (GREEN ROOFS) (SIDEWALKS) (PARKING LOTS)Asphalt Pavement 96161 86545 86545Concrete Pavement 14812 13331 13331Conventional Roof 42744 38470 38470Green Roof 21372 21372PICP (sidewalk) 3703 3703PICP (parking lot) 24040 24040Medians and Others 24085 4817 4817 4817 4817Total Paved Surface Area 177802 53932 126065 133535 80658Total Site Area 220785 220785 220785 220785 220785Site Imperviousness (%) 24.4 57.1 60.5 36.5 RUNOFF REDUCTION (%) 62.3 11.9 6.7 43.7
  • Appendix B: 75% Pervious Coverage of Hard Surface Using PICP and Green Roofs RUNOFF CONVENTIONALSURFACE AREA (m2) COEFFICIENT, C DESIGN IMPERMEABLE (IMPERVIOUSNESS) IMPERVIOUS AREA (m2) (25% of Area)Asphalt Pavement 96161 0.9 86545 21636Concrete Pavement 14812 0.9 13331 3333Conventional Roof 42744 0.9 38470 9617Green Roof 0.5PICP (sidewalk) 0.25PICP (parking lot) 0.25Medians and Others 24085 0.2 4817Total Paved Surface Area 177802 143162 34586Total Site Area 220785 220785 220785Site Imperviousness (%) 64.8 SURFACE SURFACESURFACE AREA (m2) IMPERVIOUS AREA, IMPERVIOUSNESS IMPERVIOUSNESS PERVIOUS SEGMENTS (GREEN ROOFS) (SIDEWALKS)Asphalt Pavement 96161 86545 86545Concrete Pavement 14812 13331 3333Conventional Roof 42744 9617 38470Green Roof 25646 16029PICP (sidewalk) 6110 2777PICP (parking lot) 39666Medians and Others 24085 4817 4817 4817Total Paved Surface Area 177802 76240 130339 135941Total Site Area 220785 220785 220785 220785Site Imperviousness (%) 34.5 59.0 61.6 RUNOFF REDUCTION (%) 46.7 9.0 5.0
  • Appendix B: 75% Pervious Coverage of Hard Surface Using PICP and Green Roofs continuedPERVIOUS COVERAGE PERVIOUS COVERAGE IMPERVIOUS AREA, (100% of Area) (75% of Area) PERVIOUS SEGMENTS 42744 16029 25646 14812 2777 6110 96161 18030 39666 4817 153717 36836 76240 220785 34.5 RUNOFF REDUCTION (%) 46.7 SURFACE IMPERVIOUSNESS (PARKING LOTS) 21636 13331 38470 18030 4817 96284 220785 43.6 32.7
  • Appendix B: 50% Pervious Coverage of Hard Surface Using PICP and Green Roofs RUNOFF CONVENTIONALSURFACE AREA (m2) COEFFICIENT, C DESIGN IMPERMEABLE (IMPERVIOUSNESS) IMPERVIOUS AREA (m2) (50% of Area)Asphalt Pavement 96161 0.9 86545 43272Concrete Pavement 14812 0.9 13331 6665Conventional Roof 42744 0.9 38470 19235Green Roof 0.5PICP (sidewalk) 0.25PICP (parking lot) 0.25Medians and Others 24085 0.2 4817Total Paved Surface Area 177802 143162 69173Total Site Area 220785 220785 220785Site Imperviousness (%) 64.8 SURFACE SURFACESURFACE AREA (m2) IMPERVIOUS AREA, IMPERVIOUSNESS IMPERVIOUSNESS PERVIOUS SEGMENTS (GREEN ROOFS) (SIDEWALKS)Asphalt Pavement 96161 86545 86545Concrete Pavement 14812 13331 6665Conventional Roof 42744 19235 38470Green Roof 29921 10686PICP (sidewalk) 8517 1852PICP (parking lot) 55293Medians and Others 24085 4817 4817 4817Total Paved Surface Area 177802 98547 134614 138348Total Site Area 220785 220785 220785 220785Site Imperviousness (%) 44.6 61.0 62.7 RUNOFF REDUCTION (%) 31.2 6.0 3.4
  • Appendix B: 50% Pervious Coverage of Hard Surface Using PICP and Green Roofs continuedPERVIOUS COVERAGE PERVIOUS COVERAGE IMPERVIOUS AREA, (100% of Area) (50% of Area) PERVIOUS SEGMENTS 42744 10686 29921 14812 1852 8517 96161 12020 55293 4817 153717 24558 98547 220785 44.6 RUNOFF REDUCTION (%) 31.2 SURFACE IMPERVIOUSNESS (PARKING LOTS) 43272 13331 38470 12020 4817 111910 220785 50.7 21.8
  • Appendix B: 25% Pervious Coverage of Hard Surface Using PICP and Green Roofs RUNOFF CONVENTIONALSURFACE AREA (m2) COEFFICIENT, C DESIGN IMPERMEABLE (IMPERVIOUSNESS) IMPERVIOUS AREA (m2) (75% of Area)Asphalt Pavement 96161 0.9 86545 64909Concrete Pavement 14812 0.9 13331 9998Conventional Roof 42744 0.9 38470 28852Green Roof 0.5PICP (sidewalk) 0.25PICP (parking lot) 0.25Medians and Others 24085 0.2 4817Total Paved Surface Area 177802 143162 103759Total Site Area 220785 220785 220785Site Imperviousness (%) 64.8 SURFACE SURFACESURFACE AREA (m2) IMPERVIOUS AREA, IMPERVIOUSNESS IMPERVIOUSNESS PERVIOUS SEGMENTS (GREEN ROOFS) (SIDEWALKS)Asphalt Pavement 96161 86545 86545Concrete Pavement 14812 13331 9998Conventional Roof 42744 28852 38470Green Roof 34195 5343PICP (sidewalk) 10924 926PICP (parking lot) 70919Medians and Others 24085 4817 4817 4817Total Paved Surface Area 177802 120855 138888 140755Total Site Area 220785 220785 220785 220785Site Imperviousness (%) 54.7 62.9 63.8 RUNOFF REDUCTION (%) 15.6 3.0 1.7
  • Appendix B: 25% Pervious Coverage of Hard Surface Using PICP and Green Roofs continuedPERVIOUS COVERAGE PERVIOUS COVERAGE IMPERVIOUS AREA, (100% of Area) (25% of Area) PERVIOUS SEGMENTS 42744 5343 34195 14812 926 10924 96161 6010 70919 4817 153717 12279 120855 220785 54.7 RUNOFF REDUCTION (%) 15.6 SURFACE IMPERVIOUSNESS (PARKING LOTS) 64909 13331 38470 6010 4817 127536 220785 57.8 10.9
  • Appendix B. 3: Financial Analysis: Calculations Cost to cover 100% of Approximate Area of WPCSurface Type Average Cost Proposed Application applicable WPC SWM Capital (m2) surface Savings***ROOFSConventional Roof 1 $ 75.35 all roof surfaces 42,744 $ 3,220,649 $ -Conventional Roof 2 $ 123.79 all roof surfaces 42,744 $ 5,291,067 $ -Extensive Green Roof $ 317.82 all roof surfaces 42,744 $ 13,584,685 $ 113,006Intensive Green Roof $ 295.95 all roof surfaces 42,744 $ 12,650,087 $ 113,006PARKING LOTSConventional Asphalt $ 95.00 parking lot/roadways 96,161 $ 9,135,295 $ -PICP $ 96.77 parking lot/roadways 96,161 $ 9,305,885 $ 417,632Porous Concrete $ 170.00 parking lot/roadways 96,161 $ 16,347,370 $ 321,822Permeable Asphalt $ 95.00 parking lot/roadways 96,161 $ 9,135,295 $ 321,822SIDEWALKSConventional Concrete $ 215.00 sidewalks 14,812 $ 3,184,580 $ -PICP $ 96.77 sidewalks 14,812 $ 1,433,416 $ 63,873Porous Concrete $ 170.00 sidewalks 14,812 $ 2,518,040 $ 49,133Permeable Asphalt $ 95.00 14,812 $ 1,407,140 $ 49,133SWM Facility $ 2,456,660***Assuming a linear relationship between cost of SWM facilities and Net Water Savings
  • Financial Analysis Calculations Continued Maintenance & Lifespan Interest Rate Prorated NPV Annual SWM Operational Cost NPV A value EAC (years) (Annual) over: Savings per Year** 40 years 7 5% $ 57,704 $3,346,228 $10,060,504 5.786 $578,294 20 5% $ 57,704 $5,703,279 $7,852,785 12.462 $457,646 $ 920 40 5% $ 57,704 $13,750,459 $13,750,459 17.159 $801,351 $ 920 40 5% $ 344,944 $17,515,574 $17,515,574 17.159 $1,020,775 30 years $ - 25 5% $ 8,270 $8,808,960 $11,386,424 14.094 $625,017 $ 3,400 25 5% $ 1,034,692 $22,017,796 $25,662,507 14.094 $1,562,217 $ 2,620 30 5% $ 6,892 $15,324,022 $15,324,022 15.372 $996,850 $ 2,650 20 5% $ 10,337 $8,482,263 $11,468,370 12.462 $680,639 30 years 30 5% $ 1,062 $3,048,241 $3,048,241 15.372 $198,292 $ 520 25 5% $ 159,377 $3,391,958 $3,953,370 14.094 $240,668 $ 400 30 5% $ 1,062 $2,360,879 $2,360,879 15.372 $153,579 $ 400 20 5% $ 1,592 $1,307,063 $1,815,043 12.462 $104,882 80 5% $ 20,000
  • Financial Analysis Calculations ContinuedSidewalksPorous Concrete Sidewalks Conventional Concrete Sidewalks PICP Sidewalks Permeable Asphalt SidewalksYear Net Cost Year Net Cost Year Net Cost Year 1 $ 2,468,907 1 $ 3,184,580 1 $ 1,369,543 1 $ 1,358,007 2 $ 662 2 $ 1,062 2 $ 158,857 2 $ 1,192 3 $ 662 3 $ 1,062 3 $ 158,857 3 $ 1,192 4 $ 662 4 $ 1,062 4 $ 158,857 4 $ 1,192 5 $ 662 5 $ 1,062 5 $ 158,857 5 $ 1,192 6 $ 662 6 $ 1,062 6 $ 158,857 6 $ 1,192 7 $ 662 7 $ 1,062 7 $ 158,857 7 $ 1,192 8 $ 662 8 $ 1,062 8 $ 158,857 8 $ 1,192 9 $ 662 9 $ 1,062 9 $ 158,857 9 $ 1,192 10 $ 662 10 $ 1,062 10 $ 158,857 10 $ 1,192 11 $ 662 11 $ 1,062 11 $ 158,857 11 $ 1,192 12 $ 662 12 $ 1,062 12 $ 158,857 12 $ 1,192 13 $ 662 13 $ 1,062 13 $ 158,857 13 $ 1,192 14 $ 662 14 $ 1,062 14 $ 158,857 14 $ 1,192 15 $ 662 15 $ 1,062 15 $ 158,857 15 $ 1,192 16 $ 662 16 $ 1,062 16 $ 158,857 16 $ 1,192 17 $ 662 17 $ 1,062 17 $ 158,857 17 $ 1,192 18 $ 662 18 $ 1,062 18 $ 158,857 18 $ 1,192 19 $ 662 19 $ 1,062 19 $ 158,857 19 $ 1,192 20 $ 662 20 $ 1,062 20 $ 158,857 20 $ 1,192 21 $ 662 21 $ 1,062 21 $ 158,857 21 $ 1,406,740 22 $ 662 22 $ 1,062 22 $ 158,857 22 $ 1,192 23 $ 662 23 $ 1,062 23 $ 158,857 23 $ 1,192 24 $ 662 24 $ 1,062 24 $ 158,857 24 $ 1,192 25 $ 662 25 $ 1,062 25 $ 158,857 25 $ 1,192 26 $ 662 26 $ 1,062 26 $ 1,432,896 26 $ 1,192 27 $ 662 27 $ 1,062 27 $ 158,857 27 $ 1,192 28 $ 662 28 $ 1,062 28 $ 158,857 28 $ 1,192 29 $ 662 29 $ 1,062 29 $ 158,857 29 $ 1,192 30 $ 662 30 $ 1,062 30 $ 158,857 30 $ 1,192
  • Financial Analysis Calculations Continued Parking Lots Conventional Asphalt PICP Parking Lots Porous Concrete Parking Lots Permeable Asphalt Parking Lots Year Net Cost Year Net Cost Year Net Cost Year Net Cost 1 $ 9,135,295 1 $ 8,888,252 1 $ 16,025,548 1 $ 8,813,473 2 $ 8,270 2 $ 1,031,292 2 $ 4,272 2 $ 7,687 3 $ 8,270 3 $ 1,031,292 3 $ 4,272 3 $ 7,687 4 $ 8,270 4 $ 1,031,292 4 $ 4,272 4 $ 7,687 5 $ 8,270 5 $ 1,031,292 5 $ 4,272 5 $ 7,687 6 $ 8,270 6 $ 1,031,292 6 $ 4,272 6 $ 7,687 7 $ 8,270 7 $ 1,031,292 7 $ 4,272 7 $ 7,687 8 $ 8,270 8 $ 1,031,292 8 $ 4,272 8 $ 7,687 9 $ 8,270 9 $ 1,031,292 9 $ 4,272 9 $ 7,687 10 $ 8,270 10 $ 1,031,292 10 $ 4,272 10 $ 7,687 11 $ 8,270 11 $ 1,031,292 11 $ 4,272 11 $ 7,687 12 $ 8,270 12 $ 1,031,292 12 $ 4,272 12 $ 7,687 13 $ 8,270 13 $ 1,031,292 13 $ 4,272 13 $ 7,687 14 $ 8,270 14 $ 1,031,292 14 $ 4,272 14 $ 7,687 15 $ 8,270 15 $ 1,031,292 15 $ 4,272 15 $ 7,687 16 $ 8,270 16 $ 1,031,292 16 $ 4,272 16 $ 7,687 17 $ 8,270 17 $ 1,031,292 17 $ 4,272 17 $ 7,687 18 $ 8,270 18 $ 1,031,292 18 $ 4,272 18 $ 7,687 19 $ 8,270 19 $ 1,031,292 19 $ 4,272 19 $ 7,687 20 $ 8,270 20 $ 1,031,292 20 $ 4,272 20 $ 7,687 21 $ 8,270 21 $ 1,031,292 21 $ 4,272 21 $ 158,857 22 $ 8,270 22 $ 1,031,292 22 $ 4,272 22 $ 158,857 23 $ 8,270 23 $ 1,031,292 23 $ 4,272 23 $ 158,857 24 $ 8,270 24 $ 1,031,292 24 $ 4,272 24 $ 158,857 25 $ 8,270 25 $ 1,031,292 25 $ 4,272 25 $ 158,857 26 $ 9,135,295 26 $ 9,302,485 26 $ 4,272 26 $ 9,132,645 27 $ 8,270 27 $ 1,031,292 27 $ 4,272 27 $ 158,857 28 $ 8,270 28 $ 1,031,292 28 $ 4,272 28 $ 158,857 29 $ 8,270 29 $ 1,031,292 29 $ 4,272 29 $ 158,857 30 $ 8,270 30 $ 1,031,292 30 $ 4,272 30 $ 158,857
  • Financial Analysis Calculations ContinuedRoofsConventional Roof (Low Grade) Conventional Roof (High Grade) Extensive Green Roof Intensive Greef RoofYear Net Cost Year Net Cost Year Net Cost Year Net Cost 1 $ 3,220,649 1 $ 5,291,067 1 $ 13,471,679 1 $ 12,537,080 2 $ 57,704 2 $ 57,704 2 $ 56,784 2 $ 344,024 3 $ 57,704 3 $ 57,704 3 $ 56,784 3 $ 344,024 4 $ 57,704 4 $ 57,704 4 $ 56,784 4 $ 344,024 5 $ 57,704 5 $ 57,704 5 $ 56,784 5 $ 344,024 6 $ 57,704 6 $ 57,704 6 $ 56,784 6 $ 344,024 7 $ 57,704 7 $ 57,704 7 $ 56,784 7 $ 344,024 8 $ 3,220,649 8 $ 57,704 8 $ 56,784 8 $ 344,024 9 $ 57,704 9 $ 57,704 9 $ 56,784 9 $ 344,024 10 $ 57,704 10 $ 57,704 10 $ 56,784 10 $ 344,024 11 $ 57,704 11 $ 57,704 11 $ 56,784 11 $ 344,024 12 $ 57,704 12 $ 57,704 12 $ 56,784 12 $ 344,024 13 $ 57,704 13 $ 57,704 13 $ 56,784 13 $ 344,024 14 $ 57,704 14 $ 57,704 14 $ 56,784 14 $ 344,024 15 $ 3,220,649 15 $ 57,704 15 $ 56,784 15 $ 344,024 16 $ 57,704 16 $ 57,704 16 $ 56,784 16 $ 344,024 17 $ 57,704 17 $ 57,704 17 $ 56,784 17 $ 344,024 18 $ 57,704 18 $ 57,704 18 $ 56,784 18 $ 344,024 19 $ 57,704 19 $ 57,704 19 $ 56,784 19 $ 344,024 20 $ 57,704 20 $ 57,704 20 $ 56,784 20 $ 344,024 21 $ 57,704 21 $ 5,291,067 21 $ 56,784 21 $ 344,024 22 $ 3,220,649 22 $ 57,704 22 $ 56,784 22 $ 344,024 23 $ 57,704 23 $ 57,704 23 $ 56,784 23 $ 344,024 24 $ 57,704 24 $ 57,704 24 $ 56,784 24 $ 344,024 25 $ 57,704 25 $ 57,704 25 $ 56,784 25 $ 344,024 26 $ 57,704 26 $ 57,704 26 $ 56,784 26 $ 344,024 27 $ 57,704 27 $ 57,704 27 $ 56,784 27 $ 344,024 28 $ 57,704 28 $ 57,704 28 $ 56,784 28 $ 344,024 29 $ 3,220,649 29 $ 57,704 29 $ 56,784 29 $ 344,024 30 $ 57,704 30 $ 57,704 30 $ 56,784 30 $ 344,024 31 $ 57,704 31 $ 57,704 31 $ 56,784 31 $ 344,024 32 $ 57,704 32 $ 57,704 32 $ 56,784 32 $ 344,024 33 $ 57,704 33 $ 57,704 33 $ 56,784 33 $ 344,024 34 $ 57,704 34 $ 57,704 34 $ 56,784 34 $ 344,024 35 $ 57,704 35 $ 57,704 35 $ 56,784 35 $ 344,024 36 $ 3,220,649 36 $ 57,704 36 $ 56,784 36 $ 344,024 37 $ 57,704 37 $ 57,704 37 $ 56,784 37 $ 344,024 38 $ 57,704 38 $ 57,704 38 $ 56,784 38 $ 344,024 39 $ 57,704 39 $ 57,704 39 $ 56,784 39 $ 344,024 40 $ 57,704 40 $ 57,704 40 $ 56,784 40 $ 344,024
  • Appendix C: Project Timeline January February Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Task 11 12 13 14 15 18 19 20 21 22 25 26 27 28 29 1 2 3 4 5 8 9 10 11 12 15 16 17 18 19 22 23 24 25 26Kick off MeetingExpression of InterestEstablish Future Meeting Times with ClientObtain Functional Designs from ClientBegin Review of Functional DesignsProject ProposalProposal Meeting with ClientSite Visit PreparationSite VisitSite ContextCity of London NeedsSurface AnalysisStormwater Management InventoryBegin Preliminary Permeable Surface ResearchAlternative Surface Research, Analysis and SummaryNet Water SavingsFinancial AnalysisConclusions and RecommendationsDraft Report Delivered to Client for ReviewDraft Report Meeting with ClientPresentation to ClientConducting Final Edits to ReportFinal Report Delivered to Client Task Timeframe Milestones
  • Project Timeline continued… March April Week 8 Week 9 Week 10 Week 11 Week 12 Week 13 Week 14 Week 15 Task 1 2 3 4 5 8 9 10 11 12 15 16 17 18 19 22 23 24 25 26 29 30 31 1 2 5 6 7 8 9 12 13 14 15 16 19 20 21 22 23Kick off MeetingExpression of InterestEstablish Future Meeting Times with ClientObtain Functional Designs from ClientBegin Review of Functional DesignsProject ProposalProposal Meeting with ClientSite Visit PreparationSite VisitSite ContextCity of London NeedsSurface AnalysisStormwater Management InventoryBegin Preliminary Permeable Surface ResearchAlternative Surface Research, Analysis and SummaryNet Water SavingsFinancial AnalysisConclusions and RecommendationsDraft Report Delivered to Client for ReviewDraft Report Meeting with ClientPresentation to ClientConducting Final Edits to ReportFinal Report Delivered to Client