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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 a construction <br />site to retain sediment by using a filter berm of gravel or crushed rock. <br />Conditions of Use <br />Where a temporary measure is needed to retain sediment from rights -of -way or in traffic <br />areas on construction sites. <br />Design and Installation Specifications <br />. Berm material shall be %to 3 inches in size, washed well -grade gravel or crushed <br />rock with less than 5 percent fines. <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:1V side slopes <br />8 linear feet per 1 cfs runoff based on the 10-year, 24-hour design storm <br />Maintenance Standards <br />Regular inspection is required. Sediment shall be removed and filter material <br />replaced as needed. <br />BMP C233: Silt Fence <br />Purpose <br />Use of a silt fence reduces the transport of coarse sediment from a construction site by <br />providing a temporary physical barrier to sediment and reducing the runoff velocities of <br />overland flow. See Figure II-4.2.12 Silt Fence (p.369) for details on silt fence con- <br />struction. <br />Conditions of Use <br />Silt fence may be used downslope of all disturbed areas. <br />2014 Stormwater Management Manual for Western Washington <br />Volume 11 - Chapter 4 - Page 367 <br />