Installation Guidelines
Charleston County ’ s Stormwater Program Permitting Standards and Procedures Manual ( 2017 ) includes the table on the following page ( Table 6 ) that outlines the design parameters for developing an enhanced bioswale for 80 % annual total suspended solids ( TSS ) trapping . According to Charleston County ’ s Permitting Standards and Procedures , enhanced bioswales should be sized at 100 feet in length for a 300 feet stretch of roadway . The slope of the swale “ walls ” should be at 3.5:1 or flatter with a bottom width of at least 3 feet . Additionally , the media used in the enhanced bioswale is specified as a sandy loam to promote infiltration . There may be the ability to utilize soils native to Kiawah Island if they fit this soil classification at the site of construction . The United States Department of Agriculture ( USDA ) Soil Survey for Kiawah Island can be an initial resource to refer to for a quick site evaluation , however , on-site soil sampling will be required for project construction .
Table 6 . Enhanced Bioswale Parameters for 80 % TSS trapping ( Table 4 , Charleston County , 2017 )
Check dams must also be included in the design of the enhanced bioswale . The check dams should be at least 1 foot tall and constructed with either stones ≤ 2 inches in size or coir logs ( similar filter materials also acceptable ). The spacing of check dams will vary slightly , depending on the lane width of the road and longitudinal slope of the enhanced bioswale .
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NATURE-BASED SOLUTIONS MANUAL FOR KIAWAH ISLAND