Sustainable Building Technical Manual - Etn-presco.net

SAMPLE INFILTRATION BASINSource: U.S. Environmental Protection Agency, Office of Research and Development, Urban Runoff Pollution Prevention and Control Planning,EPA/625/R–93/004 (Washington, D.C.: GPO, 1993).Figure 4a . Shape water bodies with peninsulas and islands to extend flow path and treatmenteffectiveness.b . Install sequences of ponds and wetlands along a site’s drainage ways, beginningwith miniature pools high in the drainage area to provide thorough treatment;redundancy is an asset (Figure 3) .c . Where driveways cross roadside swales, use the driveways as checkdams to formsmall wetlands.– Use extreme caution when constructing water bodies at the lowest elevations of a site.Lowland construction of water bodies may disturb existing wetlands and riparianbuffers just as any other construction would.– Use vegetative buffer areas around parking lots. The presence of oil and sediment onparking surfaces and roadways can cause non-point-source pollution through runoff.Buffer-strip plantings around these areas can mitigate the problem.❑ Construct infiltration basins.Infiltration basins are closed depressions in the earth from which water can escape onlyinto the soil. Infiltration is the ideal management and conservation of runoff because itfilters pollutants through the soil, eliminates downstream floods and erosion, andrestores natural flows to groundwater and downstream water bodies (Figure 4).– Design infiltration basins as open or closed systems. Some infiltration basins are openand vegetated; the vegetation maintains their porous soil structure. Others are constructedunder the land surface with open-graded crushed stone, leaving the surface tobe reclaimed for parking or other human or economic use. Their storage capacity issometimes supplemented with perforated pipes or premanufactured chambers. Mostsubsurface basins should include access to the basin bottom for monitoring and maintenance.The cost of construction materials for subsurface basins is substantial, so theytend to be installed only where intense land development demands that the surface bereclaimed for double use.– Place infiltration basins near source of runoff to be most economical and effective.– Avoid placing basins near building foundations and on steep unstable slopes.