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• Use filter fabric foundation undcr a rock or sand bag check dam. I f a <br />blankct ditch liner is uscd, this is not ncccssary. A piccc of organic or <br />synthetic blankct cut to fit will also �vork far ihis purposc. <br />• Rock chcck dams shall bc constructc ' of appropriatcly sized rock. <br />The rock must be placed by hand or by mechanical means (no <br />dumping of rock to Corni dam) to achieve complete coverage of thc <br />ditch or swalc and to ensure that the cemcr of thc dam is Imti�cr ihan <br />ihe edees. The roc!c used must bc large enough w slay in place given <br />thc cspectcd design Ilo�v through Ihe channcl. <br />• In the casc of grass-lined ditches and s�eales, all check dams and <br />accumulated sediment sh�ll he remoeed µ�hen the grass has matured <br />suflicienNy to protect thc ditch or svale - unless the slope oCthe s�vale <br />is greater ihan 4 percent. The are� beneath the check dams shall be <br />sccdcd anu mulched immcdiatcly:dtcrdam rcmo�al. <br />• Cnsure ihat channel appurtenan¢es, such as culvert entrances belo�� <br />check dams, are not subject �o damaee ot blockage from displaced <br />stones. Figure 4.13 depicts a typical rock chech dam. <br />,lfuinlenance Check dams shall be monitorcd for perCorn�ance and sediment <br />Smndards accumulation during and after each runoff producing rainfail. Sediment <br />shall bc rcmo��cd whcn it rca� hcs one half thc sump dcpth. <br />. ANicipate submcrgcncc and dcposition abovc thc chcck dam and <br />erosion ;rom high flo��s around the edges of the dnm. <br />• If significam erosion occurs bchvccn dams, install a protccti�•c riprap <br />lincr in that portion of thc channcl. <br />4-76 Volume 11— Cansfrvdlon Stomiwater Pollution Prevention February 2005 <br />