Stormwater Source Control Design Guidelines 2005 - Waterbucket

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Stormwater Source Control Design Guidelines 2005Design, Construction and Maintenance ProcessVegetation Management ChecklistLeave existing vegetation in place during the planning andapprovals stages. Pre-clearing vegetation results inincreased costs for temporary revegetation and erosioncontrol, at the same time as increasing runoff andsedimentation unnecessarily.Clear the site in stages as development proceeds. Forinstance, for larger developments, clear only road andutility corridors during each phase of subdivision, leavingthe development parcels vegetated until they are sold,designed, approved and ready for construction.Identify areas where vegetation can permanently remain inthe development. These may be areas of steep slope,stream riparian or wetland areas, wildlife or greenwaycorridors, specimen trees or other site areas with siteconstraints.Protect the soils under vegetation to be retained duringconstruction. It is critical to their stormwater performancethat these areas not be disturbed or compacted byequipment or storage during construction. Temporaryfencing is likely required.In stormwater calculations, consider the contribution thatleave areas of existing vegetation and soils make tostormwater capture targets. These areas will count aspervious area.Consider the possibility for some stormwater managementtechniques to make use of tree leave areas for stormwatercapture. For example, parking areas may be gradedtoward leave areas of existing vegetation, encouragingboth filtration and infiltration of surface water. Roofdrainage could also be directed towards forested leaveareas, provided the drainage is dispersed before enteringthe leave area. Only sheet flow is permitted, notconcentrated flow that can be erosive and have higherconcentrations of pollutants. Sheet discharge should berestricted to limited impervious areas only where the leavearea is owned by the subject site owner and not theproperty of others. Calculations should be undertaken toensure the leave area can “capture” the target runoffvolume. Infiltration trenches or swales can encourageinfiltration just uphill from leave areas, so that shallowgroundwater interflow occurs through the leave area.Although root zones should not be disturbed, developmentschemes have included the addition of drain rock /compost / soil check dams to create vernal infiltrationpools in leave areas.Greater Vancouver Sewerage & Drainage District87
Design, Construction and Maintenance Process Stormwater Source Control Design Guidelines 2005Constraints to Infiltration TechniquesAll sites in the GVRD can incorporate some form of stormwatersource control, even though in some poor drainage soil or siteconditions the choices will be limited to constructed solutionslike green roof, flow through planters or infiltration techniqueswith flow restrictors.The most cost and space effective techniques will be those thatrely on significant infiltration into site soils. To determine ifinfiltration based source controls are advisable on thedevelopment site, professional geotechnical engineers anddesigners should identify site or neighbourhood features thatmay act as constraints.The Infiltration Constraint Checklist below provides a partiallist of constraints to the use of infiltration that should bemapped to determine if they would affect a site design.Infiltration Constraint Checklist Drinking Water Wells: Infiltration should be separatedfrom drinking water wells, against both surface waterintrusion and ground water pollution. Standards forseparation may vary by municipality, soil conditions, andwell operation, but should, at a minimum, equate theseparation required between septic fields and drinkingwater wells by BC Ministry of Health. At time of writing, thisseparation was a minimum of 30.5 m horizontally. Land Uses that are Pollutant Hot Spots: Infiltration shouldnot be undertaken from land uses that present a high riskof groundwater pollution e.g. automobile service yards,wrecking yards, sites storing industrial chemicals or wastes,unless appropriate pretreatment is included. Contaminated Soils: Sites that have previouslycontaminated soils will need geotechnical analysis todetermine if they can be remediated, and if they aresuitable for infiltration once remediated. Seasonally High Water Table: For infiltration to beeffective, the bottom of the infiltration facility should be atleast 600 mm above seasonally high water table. Site testholes and mapping should be completed if areas of highwater table are indicated.88Greater Vancouver Sewerage & Drainage District
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Stormwater Source ControlDesign Gui
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Contents Stormwater Source Control
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Acknowledgements Stormwater Source
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Introduction Stormwater Source Cont
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Summary Posters Stormwater Source C
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DESIGN PRINCIPLES■ Maximize the a
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DESIGN PRINCIPLES■ Literature sug
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DESIGN PRINCIPLES■ Suitable for f
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Rainwater Source Control Around the
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Absorbent Landscape Stormwater Sour
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Infiltration Swale Stormwater Sourc
Page 41 and 42: Infiltration Swale Stormwater Sourc
Page 43 and 44: FLOWGROWING MEDIUMADJACENT GRADE200
Page 45 and 46: FLOWADJACENT GRADE200GROWING MEDIUM
Page 47 and 48: Infiltration Swale Stormwater Sourc
Page 49 and 50: Infiltration Rain Garden Stormwater
Page 51 and 52: Infiltration Rain Garden Stormwater
Page 53 and 54: 12345678910TREE, SHRUB ANDGROUNDCOV
Page 55 and 56: 1123456789101112TREE, SHRUB ANDGROU
Page 57 and 58: 1RAIN WATER LEADER OROTHER INLET4DA
Page 59 and 60: Pervious Paving Stormwater Source C
Page 65 and 66: 1PERMEABLE PAVERS (MIN. 80mm THICKN
Page 69 and 70: Green Roof Stormwater Source Contro
Page 77 and 78: 1WALL CAP FLASHING9WATERPROOF MEMBR
Page 81 and 82: Infiltration Trench and Soakaway Ma
Page 83 and 84: Infiltration Trench and Soakaway Ma
Page 85 and 86: 1 GRASS OR OTHER PLANTING2FINISH GR
Page 87 and 88: Design, Construction and Maintenanc
Page 91: Design, Construction and Maintenanc
Page 125 and 126: Candidate Plant List Stormwater Sou
Page 133 and 134: Glossary Stormwater Source Control
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Page 137 and 138: Stormwater Source Control Design Gu
Page 139 and 140: Key ContactsLast revised 11 April 2
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Stormwater Source Control Design Gu
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Key ReferencesKey AuthorBarry, K.,
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Key ReferencesKey AuthorDeutsche Ve
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Key ReferencesKey AuthorHorner, R.R
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Key ReferencesKey AuthorLower Hunte
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Key ReferencesLast revised 11 April
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Key ReferencesLast revised 11 April
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Key ReferencesKey AuthorUnited Stat
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Stormwater Source Control Design Gu
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