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1 f� 1 1 BMP C231: Brush Barrier Purpose The purpose of brush barriers is to reduce the transport of coarse sediment from a con- struction site by providing a temporary physical barrier to sediment and reducing the run- off velocities of overland flow. Conditions of Use . Brush barriers may be used downslope of all disturbed areas of less than one - quarter acre. • Brush barriers are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be con- veyed through the drainage system to a sediment pond. The only circumstance in which overland flow can be treated solely by a brush barrier, rather than by a sed- iment pond, is when the area draining to the barrier is small. . Brush barriers should only be installed on contours. Design and Installation Specifications . Height 2 feet (minimum) to 5 feet (maximum). . Width 5 feet at base (minimum) to 15 feet (maximum). • Filter fabric (geotextile) may be anchored over the brush berm to enhance the fil- tration ability of the barrier. Ten -ounce burlap is an adequate alternative to filter fab- ric. • Chipped site vegetation, composted mulch, or wood -based mulch (hog fuel) can be used to construct brush barriers. . A 100 percent biodegradable installation can be constructed using 10-ounce bur- lap held in place by wooden stakes. Figure II-4.2.11 Brush Barrier (p.366) depicts a typical brush barrier. Maintenance Standards . There shall be no signs of erosion or concentrated runoff under or around the bar - der. If concentrated flows are bypassing the barrier, it must be expanded or aug- mented 9 � p g mented by toed -in filter fabric. . The dimensions of the barrier must be maintained. 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter 4 - Page 365