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COR-030000 Stormwater Management Plan <br />i) Check dam <br />Check dams are generally constructed from rock. They are designed to slow water <br />velocity allowing some sediment to settle. Check dams will be used in areas of <br />concentrated flows (along drainage swales and diversion ditches) as necessary. <br />Installation includes stacked rock so that the center of the check dam is lower than the <br />sides. The check dam will be installed across the entire width of the diversion ditch <br />in order to function properly. Check dams will be inspected for proper installation <br />and sediment accumulation on the up-gradient side. Accumulated sediment and <br />debris shall be removed from a BMP when the sediment level reaches one-half the <br />height of the BMP or at anytime that sediment or debris adversely impacts the <br />functioning of the BMP. Clean and replace materials as needed to maintain function <br />and design. <br />ii) Diversion ditches <br />A diversion ditch or dike is a temporary sediment barrier and storm runoff <br />conveyance consisting of an excavation channel and compacted earth ridge. Swales <br />and ditches will be used on a permanent and temporary basis to convey stormwater in <br />a way that minimizes the potential for contamination by sediment. Because some <br />sediment may be present in stormwater, check dams can be used in swales and <br />ditches to reduce the velocity of the water and allow some settling of larger particles. <br />On-site erosion can be greatly decreased when off-site flows, not disturbed by mining <br />activities, are diverted around the site through diversion ditches or channels. <br />Diversion ditches will be inspected immediately after any rainfall and at least daily <br />during prolonged rainfall. Maintenance activities include repairing and stabilizing the <br />channel as necessary, and removing sediment built up in check dams when <br />accumulation reaches one-half the height of the check dam. <br />iii) Erosion Control Blankets (ECBs) and Turf Reinforcement Mats (TRMs) <br />ECBs and TRMs are rarely used at Sunday Mines, and will only be used if conditions <br />warrant. They consist of sheets of straw, excelsior, coconut, manmade fiber, or <br />combination there of, usually contained between layers of netting to provide <br />structural integrity. ECBs/TRMs function by providing ground cover that reduces <br />erosive action. TRMs are able to handle higher levels of concentrated flows and are <br />used mainly in channel applications. ECBs and TRMs may be used in conjunction <br />with other velocity reducing BMPs. ECB/TRM applications include, but are not <br />limited to, slope and Swale protection. ECBsfIRMs will be inspected for erosion <br />underneath and at the sides of the material, sediment accumulation, rips tears and <br />other structural problems. Maintenance will include removing sediment, re-securing <br />material to ground and re-trenching or replacement, as needed. <br />r? <br />Denison Mines (USA) Corp. Sunday Mines SWMP <br />10