Stormwater Quality Design Manual (May 2007) - City of Sacramento ...

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Technical RequirementsGreen RoofGrowth media need to remain viable for decades for both plant growth and water control. Thegrowth medium used in green roofs should:• Not degrade or compress over time;• Be accompanied by third-party laboratory data confirming its essential properties; and• Be covered under warranty if it is defective or degrades within a certain timeframe.Gravel Ballast (if needed) — Gravel ballast is sometimes placed along the roof perimeter and atair vents or other vertical elements. The need for ballast depends on operational and structuraldesign issues. Ballast is sometimes used to provide maintenance access, especially to verticalelements requiring periodic maintenance. In some situations a header or separation board may beplaced between the gravel ballast and adjacent elements (e.g., growth media, drains). If a rootbarrier is used, it must extend under the gravel ballast and growth medium and up the side of thevertical elements.Step 6 – Select VegetationHire experienced horticulturists and/or landscape/green roof contractors who understand the local climateas well as the restrictions of a rooftop environment to select, install and maintain vegetation for the greenroof.Typical green roof vegetation ranges from low-growing succulent plants (e.g., sedums) or groundcovers(characteristic of extensive green roofs) to an assortment of native grasses, shrubs, and trees (more typicalof intensive green roofs). Select plants that:• are adapted to the local climate, considering seasonal temperature ranges and average rainfall, theharsh rooftop environment (exposure to direct sun, frost, wind) and desired irrigation• will tolerate short periods of inundation from storm events during the wet season (October 1 –April 30)• Possess shallow root systems suited for the depth of the growth media• Require little or no irrigation after establishment• are primarily non-deciduous to provide adequate foliage cover year-round and reduce erosionpotential• Have good regenerative qualities (i.e., perennial or self-sowing)• Are low maintenance (i.e., no need for fertilizers, pesticides, or herbicides, little or no mowing ortrimming)• Have growth patterns allowing vegetation to thoroughly cover the soil (at least 90% surface areacoverage should be achieved within 2 years).• Are compatible with the aesthetic preferences of the owner and future building occupants whomay utilize the roof as a green spacePlants of the genus Sedum (family Crassulaceae), which are low-growing succulents, are often used forbecause of their resistance to wind, frost, drought, and fire. A mix of Sedum and other succulent plants isrecommended, because they possess many of the recommended attributes. Herbs, forbs, grasses, and otherlow groundcovers may also be used but typically require more irrigation and maintenance. Although theuse of native vegetation is preferred when possible, some natives may not thrive in the rooftopenvironment. Thus, a mix of approximately 80% Sedum/succulent plants and 20% native plants generallyrecognized for their hardiness is recommended, particularly for extensive green roofs. (Velazquez, 2005)Stormwater Quality Design Manual for the Sacramento and South Placer RegionsGR-6 May 2007
Runoff Reduction Control Measure Fact SheetGreen RoofStep 7 – Determine Irrigation NeedsDetermine irrigation needs based on the vegetation selected; at a minimum, temporary irrigation isrecommended during the first two years of plant establishment. Potable water may be used in a permanentirrigation system, but consider using recycled, non-potable water, such as air conditioning condensate.Analyze any alternative water source to make sure it doesn’t contain compounds harmful to the plants.Step 8 – Incorporate Fire BreaksA Berlin study found that green roofs are more fire resistant than gravel roofs. The City of Portland’s FireBureau recently converted a fire station conventional roof to a green roof. Green roofs may help slow thespread of fire to and from the building through the roof, particularly when the growth medium issaturated. Succulents such as Sedum offer good fire resistance due to their high water content. However,if the plants themselves are dry, they may present a fire hazard. The integration of vegetation-free "firebreaks" at regular intervals across the roof, at the roof perimeter, and around all roof protrusions isrecommended. These breaks should be made of a non-combustible material such as crushed gravel,pebbles, or concrete pavers; be 12 to 36 inches wide; and be situated every 130 feet in all directions.Another option for fire prevention is a sprinkler irrigation system connected to the fire alarm. (Köhler2004; Peck and Kuhn; Velazquez 2005)Construction ConsiderationsConsider hiring an environmental/green roof specialist to oversee the construction process.• Throughout the construction process, protect green roof components, particularly the vegetation,until established.• Prevent erosion by covering the growth media with mulch, jute/cellulose netting, or otherapproved protection methods prior to seeding or planting.• Require consultants and installers to follow appropriate safety measures for working onindustrial/commercial rooftops.Long-Term MaintenanceThe local permitting agencies in the Sacramento and South Placer areas require execution of amaintenance agreement or permit with the property owner prior to final acceptance of a privatedevelopment project that includes a green roof. Such agreements or permits will typically includerequirements such as those outlined in Table GR-2. The property owner or his/her designee is responsiblefor compliance.Stormwater Quality Design Manual for the Sacramento and South Placer RegionsMay 2007GR-7
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Stormwater Quality Design Manualfor
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Stormwater Quality Design Manual wa
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Table of contentsOutdoor Work Areas
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Table of contentsSF-1.SF-2.SF-3.SF-
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Other Development Community Reviewe
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1 IntroductionPurposeThis Stormwate
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IntroductionIn July 2003, the permi
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IntroductionFor redevelopment proje
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Introduction• The Appendices prov
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2 An Integrated Approach toEffectiv
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Integrated ApproachIt is also helpf
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Integrated ApproachPut landscaping
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Integrated Approachfactors will be
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Chapter 3Figure 3-1. Process for Ad
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Chapter 3runoff reduction first (ev
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Chapter 3As the name implies (and a
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Chapter 3Step 9: Establish Long Ter
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Chapter 4Source Control Fact Sheets
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Source Control Measure Fact SheetSt
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Source Control Measure Fact SheetFu
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Technical RequirementsVegetated Swa
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Glossaryexposure of construction ma
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GlossaryLow Impact Development (LID
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GlossaryRegional Stormwater Quality
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Appendix ASubmittal RequirementsThe
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Sacramento County Supplemental Appl
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Example Post Construction Stormwate
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Typically maintenance agreements an
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Example Maintenance Covenant(Sacram
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Device in accordance with the maint
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[attach]DECLARANT’S ACKNOWLEGEMEN
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Recorded at the request of:CITY OF
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9. The obligations herein undertake
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EXHIBIT B[Map/Illustration]
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City of FolsomThe City of Folsom ow
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Appendix D-1: Residential Sites: Ru
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Form D-1d: Alternative Driveway Des
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Form D-2a: Disconnected Pavement Wo
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Appendix D-3Runoff Reduction Credit
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These tables refer to runoff reduct
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Mature TreeShape Canopy (dia.) Heig
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Appendix D4LID Credits Background R
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unoff from the driveway by 60% whil
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The designer must determine how man
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Or the ASCE-WEF method (Sacramento)
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Table 3 - Multipliers Based on Rati
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Using the Effective Area Managed in
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SMRC, The Stormwater Manager’s Re
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Flow-based control measure design s
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4. Apply the Rational Formula to ca
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5. Enter the capture curve selected
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1.201.000.80STORAGE (in)0.600.4024-
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1.201.000.80STORAGE (in)0.600.4048
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Subject: VEGETATED SWALE EXAMPLEPLA
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PART II:Routing Excess Runoff throu
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4. Design the OutletThe outlet shou
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Exhibit 1Water Quality Orifice Outl
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3. Calculate Planter Surface Area A
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• Bottom slopes of 0.01 to 0.05%
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Appendix HDrainage Design and Storm
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