Stormwater Source Control Design Guidelines 2005 - Waterbucket

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Stormwater Source Control Design Guidelines 2005Infiltration Rain GardenInfiltration Rain GardenPhoto Credit: Lanarc Consultants Ltd.DescriptionThe Infiltration Rain Garden is a form of bioretentionfacility, designed to have the aesthetic appeal of agarden, as opposed to a purely functional appearance.Rain Gardens are commonly a concave landscape areawhere treated runoff from roofs or paving is allowed topond temporarily while infiltrating into deep constructedsoils below (See Drawing 3A).The surface planting of Rain Gardens is dominated bytrees, shrubs, and groundcovers, with planting designsrespecting the various soil moisture conditions in thegarden. Plantings may also include rushes, sedges andother grass-like plants, as well as sodded lawn areas forerosion control and multiple uses.On subsoils with low infiltration rates, Rain Gardensoften have a drain rock reservoir and perforated drainsystem to collect excess water. (See Drawing 3B &3C).The perforated drain system may connect to a controlstructure in a catch basin that provides overflow whilemaintaining a slow decanting of the water in the raingarden between storms (See Drawing 3D).While usually designed as a ‘standalone’ facility withoutconveyance, new designs are evolving that put a seriesof Rain Gardens along linear areas like roads – withweirs and surface conveyance similar to InfiltrationSwales.Other common terms used are Bioretention and DrySwale with Underdrain (Stephens et al., 2002) or Swale /Trench Element (MUNLV-NRW, 2001).Formal rain garden, Buckman Terrace, PortlandOregon.Photo Credit: Lanarc Consultants Ltd.Informal rain garden, Water Pollution ControlLaboratory, Portland OregonPhoto Credit: Lanarc Consultants Ltd.Application and LimitationsApplication and Limitations are similar to InfiltrationSwales.Rain garden overflow, Buckman Terrace, PortlandOregon.Greater Vancouver Sewerage & Drainage District43
Infiltration Rain Garden Stormwater Source Control Design Guidelines 2005Design Guidelines1. The Rain Garden area should be 10-20% of the upstreamimpervious area that it serves, preferably sized bycontinuous flow modelling. Common rain garden size isabout 50 m 2 draining 250m 2 of impervious area, althoughthis sizing and proportion will vary by rainfall and soilcharacteristics. Smaller, distributed Rain Gardens arebetter than single large scale facilities.2. Site Rain Gardens similar to other infiltration facilities –minimum 30m from wells, minimum 3 m downslope ofbuilding foundations, and only in areas where foundationshave footing drains.3. Provide pretreatment erosion control to avoidsedimentation in the garden. Provide non-erodablematerial, sediment cleanout basins, and weir flowspreaders at point-source inlets. Flow to the swale shouldbe distributed sheet flow, travelling through a grassy filterarea or grass swale prior to entering the Rain Garden(500 mm minimum, greater than 3000 mm desirablegrassy pretreatment swale length; Claytor and Schueler,1996).4. Rain Garden bottom (Drawing 3A): flat cross section, witha longitudinal slope of 2% (or 1% by US001, or dished byGE004). Provide a 50mm – 75mm layer of organic mulch– well aged compost, bark mulch or similar weed freematerial. The mulch is important for both erosion controland maintaining infiltration capacity.5. Rain Garden bottom width: 600mm minimum, 3000mmdesirable, length:width ratio of 2:1 (Gibb et al., 1999).6. Rain Garden side slopes 2 horizontal : 1 verticalmaximum, 4:1 preferred for maintenance. Provide organicmulch on side slopes similar to bottom.7. Maximum ponded level: 150mm (Gibb et al., 1999),300mm (NRW).8. Drawdown time for the maximum surface ponded volume:48 hours (72 hours max. - Maryland Dept. EnvironmentalResource Programs, 2001).9. Treatment soil depth: 450mm minimum (City of Portland,2002), 1200mm desirable (Gibb et al., 1999). Treatmentsoil should have a minimum infiltration rate of 13mm/hr,with 6mm/hr used for design.10. Slope of the drain rock reservoir bottom shall be level.11. A non-erodible outlet or spillway must be established todischarge overflow (Maryland Dept. EnvironmentalResource Programs, 2001).44Greater Vancouver Sewerage & Drainage District
Page 1 and 2: Stormwater Source ControlDesign Gui
Page 3 and 4: Contents Stormwater Source Control
Page 5 and 6: Acknowledgements Stormwater Source
Page 7 and 8: Introduction Stormwater Source Cont
Page 13 and 14: Summary Posters Stormwater Source C
Page 15 and 16: DESIGN PRINCIPLES■ Maximize the a
Page 17 and 18: DESIGN PRINCIPLES■ Literature sug
Page 19 and 20: DESIGN PRINCIPLES■ Suitable for f
Page 23 and 24: Rainwater Source Control Around the
Page 29 and 30: Absorbent Landscape Stormwater Sour
Page 39 and 40: 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: Infiltration Swale Stormwater Sourc
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
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Design, Construction and Maintenanc
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Candidate Plant List Stormwater Sou
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Glossary Stormwater Source Control
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Glossary Stormwater Source Control
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Stormwater Source Control Design Gu
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Key ContactsLast revised 11 April 2
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Key ContactsLast revised 11 April 2
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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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