The San Juan Islands Conservation District actively promotes sustainable land use practices. Our Natural Resources Planner is trained in LID design techniques and is available for individual site visits to help landowners conserve their natural resources.
Contact us if you are interested in a site visit to assess your soil and water resources. A follow-up report will contain information on the soils of your site, an aerial photo, LID fact sheets and site specific information such as vegetation management plan, a raingarden handbook and native plant lists.
|LID Practices||Peak Flow Control||Volume Reduction||Water Quality Improvement||Water Conservation|
|Parking Lot Islands|
|Narrow Road Design|
|Tree Box Filter|
Facilities are landscaped shallow depressions that capture and filter stormwater runoff. As stormwater passes down through the planting soil, pollutants are filtered, adsorbed and biodegraded by the soil and plants. Because they are not contained within an impermeable structure, they may allow for infiltration. For sites not passing the infiltration feasibility an impermeable liner may be needed to prevent incidental infiltration.
Provide bioretention treatment control measures that are completely contained within an impermeable structure with an underdrain (they do not infiltrate). They are similar to bioretention facilities with underdrains except they are situated at or above ground and are bound by impermeable walls. Planter boxes may be placed adjacent to buildings, structures or sidewalks.
Facilities that are designed for partial infiltration of runoff and partial biotreatment. These are similar to bioretention devices with underdrains but they include a raised underdrain above a gravel sump designed to facilitate infiltration and denitrification. These facilities can be used in areas where there are no hazards associated with infiltration, but infiltration measurements show low infiltration rates or high depths of fill.
Open, shallow channels with dense, low‐lying vegetation covering the side slopes and bottom that collect and slowly convey runoff to downstream discharge points. An effective vegetated swale
achieves uniform sheet flow through the densely vegetated area for a period of several minutes. The vegetation in the swale can vary depending on its location and is the choice of the designer. Most swales are grass‐lined.
Vegetated areas designed to treat sheet flow runoff from adjacent impervious surfaces such as parking lots and roadways, or intensive landscaped areas such as golf courses. While some assimilation of dissolved constituents may occur, filter strips are generally more effective in trapping sediment and particulate‐bound metals, nutrients, and pesticides. Filter strips are more effective when the runoff passes through the vegetation and thatch layer in the form of shallow, uniform flow. Filter strips are primarily used to pre-treat runoff before it flows to an infiltration BMP or another biofiltration BMP.
Infiltration facilities shall be sized to capture and infiltrate the design capture volume (V design) based on the runoff produced from a 0.75‐inch (0.0625 ft) storm event.
V design (cu ft) = 0.0625 x Catchment Area (sq ft)
Where: Catchment Area = (Impervious Area x 0.9) + [(Pervious Area + Undeveloped Area) x 0.1]
For catchment areas given in acres, multiply the above equation by 43,560 sq. ft./acre.
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