BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

• Consider incorporating trees or shrubs along bioswales to aestheticallyintegrate the design with the landscape.INSTALLATION CONSIDERATIONS• Prior to swale construction, stabilize the drainage area to the facility withtemporary BMPs to keep runoff and sediment from entering the swale.• Scrape away and stockpile any organic topsoil for later use prior toexcavating.• Where site conditions allow, excavate the swale bottom to be relatively flatwith a longitudinal slope of 1 percent or less.• Side slopes should be 3:1 (run to rise) or flatter to encourage growth ofvegetation and slope stability.• Where topsoil is lacking or has been depleted, amend the soil with at least 4to 6 inches of organic compost incorporated into the soil prior to planting.• Ensure proper energy dissipation is provided at inlets and outlets of theswale.• Establish vegetation as soon as possible to prevent erosion and scour.Consider a construction schedule that allows for planting early in thegrowing season or in late fall when successful vegetation establishment ismost likely.• Temporary or permanent irrigation may be necessary to assure vegetationestablishment.INSPECTION AND MAINTENANCE• Inspect after large runoff events and the spring melt period. Inspect foroverall plant health; inflow and outflow function; and accumulation ofsediment, trash, and debris.• If a large quantity of sediment has discharged to the bioswale, examine thedrainage area and identify potential sources of sediment that may beaddressed through other pollutant source control BMPs identified in thisHandbook. Alternatively, consider retrofitting the inlet to the bioswale toinclude a pretreatment device.• Remove sediment when it creates an unfavorable condition for vegetation orhinders the function of the bioswale. Vegetation may need to be replaced orreplanted after sediment removal. Salvage existing plants to the greatestextent possible.• Reseed or replant bare areas. Consider planting alternative species in theevent of unsuccessful vegetation establishment.• If erosion occurs at the inlet or outlet, stabilize with rock riprap or othertypes of energy dissipation and stabilization BMPs identified in thisHandbook.TRPA BMP HandbookChapter 4: BMP Toolkit2012 4.4.1.2-BioswalePage 3