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→Planning
[[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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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"/>.
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For a table summarizing information on planning considerations and site constraints see [[Site considerations]].
==Design==
==Design==
*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.
===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 %.
==Landscaping==
==Landscaping==
Filter strip vegetation can consist of [[Turf|turf grasses]], meadow [[Graminoids: List|grasses]], [[Perennials: List|wildflowers]], shrubs, and [[trees]]. Trees and shrubs with deep rooting capabilities are recommended for planting to maximize soil infiltration capacity <ref>Philadelphia Water Department (PWD). 2007. Philadelphia Stormwater Management Guidance Manual. Philadelphia, PA.</ref>.
The context of filter strips is often natural, informal and somewhat informal. Filter strip vegetation can consist of [[Turf|turf grasses]], meadow [[Graminoids: List|grasses]], [[Perennials: List|wildflowers]], shrubs, and [[trees]]. Trees and shrubs with deep rooting capabilities are recommended for planting to maximize soil infiltration capacity <ref>Philadelphia Water Department (PWD). 2007. Philadelphia Stormwater Management Guidance Manual. Philadelphia, PA.</ref>.
*Filter strips used for snow storage and treatment should be planted with non-woody vegetation. Designers should choose vegetation that stabilizes the soil and is salt tolerant where the filter strip will be used for snow storage or to treat road runoff.
*Filter strips used for snow storage and treatment should be planted with non-woody vegetation. Designers should choose vegetation that stabilizes the soil and is salt tolerant where the filter strip will be used for snow storage or to treat road runoff.
*Vegetation at the toe of the slope (where ponding may occur) should be able to withstand both wet and dry soil conditions.
*Vegetation at the toe of the slope (where ponding may occur) should be able to withstand both wet and dry soil conditions.
*Whatever the type of vegetation used, it must be densely planted to slow runoff, collect sediment, and allow for infiltration.
Although filter strips are often grassed, alternatives include forested filter strips or multi-zone filter strips, which feature several vegetation zones providing a gradual transition from turf to meadow to shrub and forest. The multi-zone filter strip design can be effective as a buffer zone to an existing natural heritage feature.
Although filter strips are often grassed, alternatives include forested filter strips or multi-zone filter strips, which feature several vegetation zones providing a gradual transition from turf to meadow to shrub and forest. The multi-zone filter strip design can be effective as a buffer zone to an existing natural heritage feature.
{{:Filter strips: Performance}}
{{:Filter strips: Performance}}
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[[Category: Pretreatment]]
[[Category: Pretreatment]]