BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

4.3.1.9 SUBSURFACE DRAINAlternate Names: French Drain, Subsurface Perforated Drain, SubsurfaceConveyance SystemDESCRIPTIONA subsurface drain is a trench or system of trenches containing a perforatedpipe surrounded by gravel. It is designed to collect stormwater runoff orgroundwater and convey it from undesirable locations to a stable dischargepoint or hydrologic source control such as an infiltration basin or rain garden.While a perforated pipe may permit some infiltration, credit is typically notgiven because it is negligible and the primary purpose of a subsurface drain isconveying stormwater to a separate treatment and/or infiltration BMP in amore appropriate location.BMP DESIGN APPROACHPollutant SourceControlHydrologic SourceControlStormwater TreatmentSCALE OF APPLICATIONAll SFR and MFR < 1acreMFR 1-5 Acre andCICU < 5 acresMFR and CICU > 5acres and all WQIPsTYPE OF APPLICATIONTemporaryPermanentSubsurface drain around a residential structure is conveying stormwater to an area on-sitewhere there is more room for infiltration.APPLICABILITYSubsurface drains are suitable where local site conditions, such as slowinfiltrating soils, steep slopes, sensitive areas, or limited space constrain orprevent natural infiltration in the direct vicinity.Advantages• Conveys stormwater runoff or groundwater away from foundations,roads, and other sensitive areas to an area that is more appropriate forinfiltration or discharge.TRPA BMP HandbookChapter 4: BMP Toolkit2012 4.3.1.9-Subsurface DrainPage 1