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10 0 <br />Chapter 4-Site-Specific Industrial Stortn Water B'*Sps <br />• <br />Check Dams <br />What Are They <br />A check dam is a small, temporary or permanent dam constructed across a drainage ditch, swale, <br />or channel to lower the speed of concentrated flows. Reduced runoff speed reduces erosion and <br />gullying in the channel and allows sediments and other pollutants to settle out. <br />LOG CHECK DAM <br />Logs <br />Flow <br />??I;?--- ----r, _=I•?i,-+ .I'll I -- 'i-,-?- <br />J <br />r ? <br />ROCK CHECK DAM <br />Flow <br />FIGURE 4.28 TYPICAL CHECK DAMS <br />(Modified from Commonwealth of Virginia, 1980) <br />When and Where to Use Them <br />A check dam should be installed in steeply sloped svvales, or in swales where adequate vegetation <br />cannot be established. A check dam may be built from logs, stone, or pea gravel-filled sandbags. <br />4-93