1996-02-06_REVISION - M1977493 (14)

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Chapter 4-Site-Specific /ndustrAorm Water BMPs Brush Barrier What Is It A brush barrier is a temporary sediment barrier constructed from materials resulting from onsite clearing and grubbing. It is usually constructed at the bottom perimeter of the disturbed area. Filter fabric is sometimes used as an anchor over the barrier to increase its filtering efficiency. Brush barriers are used to trap and retain small amounts of sediment by intercepting the flow from small areas of soil disturbance. ?•/ter fabric Ora?f?/ ?_ __ prey Bri.sh R/? and . 9eu?red in trench wii>t/i - _ - _- Con.Pacfed --? of Brq?h Ba?ri?/' R%fh _ -- ftei?e Fwstued >? -- = - ?? - pahri wed Vwker [?tfG7iYf ?fpry S/,B/TIlfi t Fvrir. 9air?'tr. FIGURE 4.22 BRUSH BARRIER (Modified from Washington State, 1992) F hen and Where to Use It W A brush barrier should only be used to trap sediment from runoff which is from a small drainage area. The slope which the brush barrier is placed across should be very gentle. Do not place a brush barrier in a swale or any other channel. Brush barriers should be constructed below areas subject to erosion. What to Consider The construction of a brush barrier should be started as soon as clearing and grubbing has produced enough material to make the structure. Wood chips should not be included in the material used for the barrier because of the possibility of leaching. When the site has been stabilized and any excess sediment has been disposed of properly, the filter fabric can be removed. Over time, natural vegetation will establish itself within the barrier, and the barrier itself will decompose. • • You will not have to maintain the brush barrier unless there is a very large amount of sediment being deposited. If used, the filter fabric anchor should be checked for tears and the damaged 4-80