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→Berms
*Filter strips should drain continuously as sheet flow until reaching a [[swales|swale]], [[bioretention]] facility, or other LID practice.
*Filter strips should drain continuously as sheet flow until reaching a [[swales|swale]], [[bioretention]] facility, or other LID practice.
===Berms===
===Berms===
When designed as a stand alone water quality BMP (i.e., not pretreatment to another BMP) the vegetated filter strip should be designed with a pervious berm of [[sand]] and gravel at the toe of the slope for shallow ponding of runoff.
*When designed as a stand alone water quality BMP (i.e., not pretreatment to another BMP) the vegetated filter strip should be designed with a pervious berm at the toe of the slope for shallow ponding of runoff.
The berm should be 150 to 300 mm in height above the bottom of the depression and should contain a perforated pipe [[underdrain]] connected to the storm sewer
*Media for the berm should consist of 40% excavated [[soil]], 40% [[sand]], and 20% [[gravel]].
Runoff ponds behind the berm and gradually flows through it, into the underdrain connected to the storm sewer system. The volume ponded behind the berm should be equal to the water quality storage requirement. During larger storms, runoff will overtop the berm and flow directly into a storm sewer inlet. <ref>Cappiella, K., T. Schueler, and T. Wright. 2006. Urban Watershed Forestry Manual, Part 2. Conserving and Planting Trees at Development Sites. Center for Watershed Protection. Prepared for United States Department of Agriculture, Forest Service.</ref>.
*The berm should be 150 to 300 mm in height above the bottom of the depression and should contain a perforated pipe [[underdrain]] connected to the storm sewer,
*Runoff ponds behind the berm and gradually flows through it, into the underdrain connected to the storm sewer system. The volume ponded behind the berm should be equal to the water quality storage requirement. During larger storms, runoff will overtop the berm and flow directly into a storm sewer inlet. <ref>Cappiella, K., T. Schueler, and T. Wright. 2006. Urban Watershed Forestry Manual, Part 2. Conserving and Planting Trees at Development Sites. Center for Watershed Protection. Prepared for United States Department of Agriculture, Forest Service.</ref>.
===Soil Amendments===
===Soil Amendments===
If soils on the filter strip site are highly compacted, or of such low fertility that vegetation cannot become established, they should be tilled to a depth of 300 mm and amended with compost to achieve an organic content of 8 to 15% by weight or 30 to 40% by volume.
If soils on the filter strip site are highly compacted, or of such low fertility that vegetation cannot become established, they should be tilled to a depth of 300 mm and amended with compost to achieve an organic content of 8 to 15% by weight or 30 to 40% by volume.