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BMP C232: Gravel Filter Berm • <br />Purpose <br />A gravel filter berm is constructed on rights -of -way or traffic areas within <br />a construction site to retain sediment by using a filter berm of gravel or <br />crushed rock. <br />Conditions of Use <br />Where a temporary measure is needed to retain sediment from rights -of - <br />way or in traffic areas on construction sites. <br />Design and <br />• Berm material shall be 3/4 to 3 inches in size, washed well -grade gravel <br />Installation <br />or crushed rock with less than 5 percent fines. <br />Specifications <br />Spacing of berms: <br />— Every 300 feet on slopes less than 5 percent <br />— Every 200 feet on slopes between 5 percent and 10 percent <br />— Every 100 feet on slopes greater than 10 percent <br />• Berm dimensions: <br />— 1 foot high with 3H:1 V side slopes <br />— 8 linear feet per 1 cfs runoff based on the 10-year, 24-hour design <br />storm <br />Maintenance <br />• Regular inspection is required. Sediment shall be removed and filter <br />Standards <br />material replaced as needed. • <br />BMP C233: Silt Fence <br />Purpose Use of a silt fence reduces the transport of coarse sediment from a <br />construction site by providing a temporary physical barrier to sediment <br />and reducing the runoff velocities of overland flow. See Figure 4.2.12 for <br />details on silt fence construction. <br />Conditions of Use Silt fence may be used downslope of all disturbed areas. <br />• Silt fence shall prevent soil carried by runoff water from going <br />beneath, through, or over the top of the silt fence, but shall allow the <br />water to pass through the fence. <br />• Silt fence is not intended to treat concentrated flows, nor is it intended <br />to treat substantial amounts of overland flow. Convey any <br />concentrated flows through the drainage system to a sediment pond. <br />• Do not construct silt fences in streams or use in V-shaped ditches. Silt <br />fences do not provide an adequate method of silt control for anything. <br />deeper than sheet or overland flow. <br />• <br />Volume H Construction Stormwater Pollution Prevention - August 2012 <br />4-88 <br />