BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

4.1.1.6 RAIN GARDENAlternative Names: Small Vegetated Basin, Infiltration Garden, Bio-RetentionGardenDESCRIPTIONRain gardens are small, vegetated depressions used to promote infiltration ofstormwater runoff. Runoff may enter the gardens via sheet flow or pointdischarge. Rainwater gardens can be planned and integrated into both new andexisting developments and usually combine amended soils, shrubs, grasses, andflowering perennials. Plant roots, foliage, and soil help to retain and infiltratewater. Rain gardens can achieve an appealing, aesthetic look and are well suitedfor small sites, such as individual homes, and larger sites, such as common areasand schools.BMP DESIGN APPROACHPollutant Source ControlHydrologic SourceControlStormwater TreatmentSCALE OF APPLICATIONAll SFR and MFR < 1acreMFR 1-5 Acre andCICU < 5 acresMFR and CICU > 5acres and all WQIPsTYPE OF APPLICATIONTemporaryPermanentAPPLICABILITY• Primarily used to treat and infiltrate runoff from small impervious surfacestypically less than 1 acre in size.• Rain gardens may not be suitable to treat the entire design storm for a largedrainage area but they may be able to treat a small sub-drainage area if flowscan be broken up.• Site rain gardens on relatively flat terrain (less than a 5 percent slope).• Not appropriate for soils with infiltration rates less than 1”/hr or areas withseasonally high groundwater (e.g., SEZ) where groundwater contaminationand low infiltration rates are concerns.• Because of the potential to pollute surrounding water sources, rain gardensshall not infiltrate stormwater runoff from pollutant “hot spots” such asTRPA BMP HandbookCHAPTER 4: BMP Toolkit2012 4.1.1.6-Rain GardenPage 1