Laserfiche WebLink
• Use filter fabric foundation under a rock or sand bag check dam. If a <br /> blanket ditch liner is used, this is not necessary. A piece of organic or <br /> synthetic blanket cut to fit will also work for this purpose. <br /> • Rock check dams shall be constructed of appropriately sized rock. <br /> The rock must be placed by hand or by mechanical means (no <br /> dumping of rock to form dam)to achieve complete coverage of the <br /> ditch or swale and to ensure that the center of the dam is lower than <br /> the edges. The rock used must be large enough to stay in place given <br /> the expected design flow through the channel. <br /> • In the case of grass-lined ditches and swales, all check dams and <br /> accumulated sediment shall be removed when the grass has matured <br /> sufficiently to protect the ditch or swale - unless the slope of the swale <br /> is greater than 4 percent. The area beneath the check dams shall be <br /> seeded and mulched immediately after dam removal. <br /> • Ensure that channel appurtenances, such as culvert entrances below <br /> check dams, are not subject to damage or blockage from displaced <br /> stones. Figure 4.13 depicts a typical rock check dam. <br /> Maintenance Check dams shall be monitored for performance and sediment <br /> Standards accumulation during and after each runoff producing rainfall. Sediment <br /> shall be removed when it reaches one half the sump depth. <br /> • Anticipate submergence and deposition above the check dam and <br /> erosion from high flows around the edges of the dam. <br /> • If significant erosion occurs between dams, install a protective riprap <br /> liner in that portion of the channel. <br /> 4-76 Volume II—Construction Stormwater Pollution Prevention February 2005 <br />