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• Chapter 4-Site-Speck Industrial Storm Water BMPs <br /> <br />• <br />What Are They <br />Vegetated Filter Strips <br />Vegetated filter strips are gently sloping areas of natural vegetation or are graded and artificially <br />planted areas used to provide infiltration, remove sediments and other pollutants, and reduce the <br />flow and velocity of the storm water moving across the terrain. Vegetated filter strips function <br />similarly to vegetated or grassed swales. The filter strips, however, are fairly level and treat <br />sheetflow, whereas grassed swales are indentations (see section on Grassed Swales) and treat <br />concentrated flows. Vegetated filter strips provide permanent storm water control measures on a <br />site. <br />Top Elevation of Strips Berms Placed Perpendicular <br />On Same Contour. and to Top of Strip Prevent <br />i ?s';o,.• Directly Abuts Trench Concentrated Flows <br />Wooded ??. <br />Filter Strip?k <br />Grass <br />Filter StnP fAF <br />Stone Trench 1 <br />Acts as <br />Level Spreader <br />S% Strip Slope or Less <br />FIGURE 4.31 USE OF FILTER STRIPS <br />(Modified from MWCOG, 1987) <br />When and Where to Use Them <br />Vegetated filter strips are suited for areas where the soils are well drained or moderately well <br />drained and where the bedrock and the water table are well below the surface. Vegetated filter <br />strips will not function well on steep slopes, in hilly areas, or in highly paved areas because of the <br />high velocity of runoff. Sites with slopes of 15 percent or more may not be suitable for filtering <br />storm water flows. However, they should still be vegetated (MWCOG, 1987). This practice can <br />be put into place at any time, provided that climatic conditions allow for planting. <br />4-101