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− | [[File:Vegetated_filter_strip_1.jpg|thumb|Hey Dean, What's the caption for this photo?]] | + | [[File:Vegetated_filter_strip_1.jpg|thumb|Grass filter strip draining to vegetated swale. Source: Trinkhaus Engineering]] |
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| {{TOClimit|2}} | | {{TOClimit|2}} |
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| Once runoff from an impervious surface becomes concentrated, a [[swales|swale]] design should be used instead of a vegetated filter strip <ref name="Barrett2004"/>. | | Once runoff from an impervious surface becomes concentrated, a [[swales|swale]] design should be used instead of a vegetated filter strip <ref name="Barrett2004"/>. |
| </poem> | | </poem> |
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| + | For a table summarizing information on planning considerations and site constraints see [[Site considerations]]. |
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| ==Design== | | ==Design== |
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| *The flow path length across the vegetated filter strip should exceed the maximum flow path length across the impervious surface draining to it. | | *The flow path length across the vegetated filter strip should exceed the maximum flow path length across the impervious surface draining to it. |
| *The filter strip should have a flow path length of ≥ 5 m; however, some pollutant removal benefits are realized ≥ 3 m. | | *The filter strip should have a flow path length of ≥ 5 m; however, some pollutant removal benefits are realized ≥ 3 m. |
| + | *Should be graded to provide a 75 to 150 mm elevation drop between pavement edge or flush curb and filter strip surface to dissipate energy, promote settling and allow for accumulation of sediment and debris between cleanings. |
| ===Pretreatment=== | | ===Pretreatment=== |
− | *A [[gravel diaphragm]] at the top of the slope is always recommended. | + | *A [[level spreader]] or [[gravel diaphragm]] at the top of the slope is always recommended. |
− | *When filter strip slopes are greater than 5 %, a series of [[level spreaders]], [[check dams]] or gravel diaphragms should be used to help maintain sheet flow. | + | *When filter strip slopes are greater than 5%, a series of [[level spreaders]], [[check dams]] or gravel diaphragms should be used to help maintain sheet flow. |
| *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. |
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| ===Soil Amendments=== | | ===Soil Amendments=== |
− | If native 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 matter]] content of 8 - 15 %. | + | If native 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 matter]] content of 5 - 15 %. |
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| ==Landscaping== | | ==Landscaping== |