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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 3 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 11-4.2.12 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 ll-Chapter 4 -Page 367 <br />