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CITY OF EVERETf STORMWATER MANAGEMENT MANUAL <br /> i <br /> � 12. Level spreaders,when installed every so often in grassy swzles,keep the Flows Gom <br /> wncenhating. Materials that can be used include sand bags,lumber,logs,concrete, and pipe. To <br /> function properly,the material nceds to be installed level and on conrour. <br /> Maintenanee Sfandards <br /> 1. '['he spreader should be inspected after every runoff event to ensure that it is functioning <br /> cocrectly. <br /> 2. The contractor should avoid the placemcnt of any material on the stmchue and should prevent <br /> construction traftic From crossiug over the swcture. <br /> 3. If the spreader is dumaged by consttvction traffic,it shall be immediately repared. <br /> 3.3.8 BMP C207: Check Dams <br /> Purpose <br /> Conshuction of small dems across a;wale or ditch reduces the velocity of concentra�ed flow and <br /> dissipates energy at the check dem. <br /> CondlNans of Use <br /> I. Where temporary channels or pertnanent channels are not yet vegetated,channel lining is <br /> infeasible,and velocity checks are reyuired. <br /> 2. Check dams may not be piaced in streams unless approved by the WDF�V. Check dams may not <br /> be placed in wetlands without approval from a pertnining agency. <br /> � 3. Check dams s6a11 not be placed below the expected backwatet from any salmonid beanng water <br /> beNreen October I and May 31 to ensure that there is uo loss of high ilow refuge 6abitat for <br /> ove;wintering juveni►e salmonids end emergent salmonid fry. <br /> Design and Installation Specificatfons <br /> I. Whatever material is used,t6e dam should fotm a triangle when vicwed&om the side. This <br /> prevents undercuttiag as water flows ovcr the face of the dam rather than falling d'uectly onro the <br /> ditch bottom. <br /> 2. Check dams in associa:ion with sumps work more effectively at slowing ilow and retaining <br /> sediment than just a check dam alone. A deep sump should be provided immediately upstream of , <br /> the check dam. <br /> 3. In some cases,if carefully located and dc;igned,check dams can remain as pertnanent <br /> installations with vcry minor rcgrading. They may bc IeR as either spillways,in which casc <br /> accumulatcd sedimcnt would bc graded and seeded,or as check da�ns to prevent Curiher sedimeN <br /> from leaving the sitc. <br /> 4. Cher,k dams can be constmcted of eithcr rock or pca-gravel filled bags. Straw bales are not an <br /> allowed conswction material. Numerous new ptoducts are also available for ttvs purpose. They <br /> tcnd to bc rwsable,quick and easy lo install,efTcctive,and cost efficient. <br /> 5. Check dams should be placed pecpendiculcr ro the flow of water. <br /> 6. The maximum spacing between the dams shall be such tNat the toc of the upstrcam dam is at thc <br /> same elevation as the top of the downstream dam. <br /> 7. Keep the maximum height at 2 feet at the cenrer of the dam. <br /> Volume 11—Construction Stormwafer Poll�tion Prevention <br /> 3-46 <br />