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Mine Water Control Plan <br />Introduction <br />This exhibit was prepared to reevaluate the mine water control plan at the West Elk Mine <br />as of January 1993. The Mine Water Control Plan serves to describe the controls used to <br />route storm water across the site to a secondary location. In the sediment ponds, water will <br />either be stored, allowing the sediment to settle out of or in cases such as Small Area <br />Exemptions (SAES), the water is filtered to a point below applicable IVPDES standards. <br />This plan describes general ditch systems used to transfer water into the pond system. These <br />ditches may be earthen channels or lined with a material to reduce erosion. Culverts along <br />the ditch system have been designed using inlet control For Corrugated Metal Pipe (CMP). <br />These CMPs have been designed to pass the flow either full or submerged to a maximum <br />height of one-and-a-half times the diameter of the pipe. <br />Program Overview <br />The computer program used to model conditions at the West Elk Mine was SEDCAD+ <br />Version 3.0, produced by Civil Software Designs. Each watershed and subwatershed <br />characteristic was measured or assumed, given the generalization of the watershed's location. <br />Input parameters used in the SEDCAD+ Model are rainfall and rainfall distn'bution for the <br />10.year 24hour storm event, the 25-year 24hour storm event, and in some ponds for the <br />100-year 24-hour stone event of 1.9", 2.3", and 2.8", respectively. In addition, soil particle <br />size distributions, curve numbers, ground cover, and slope assumptions were input on a sub- <br />watershed-specific basis. These parameters were used to predict runoff and sediment <br />production. Additionally, pond configurations were used to estimate discharge and sediment <br />yields. <br />The mine site was broken up into subwatersheds that would flow into containment ponds <br />for the 10-year 24-hour design storm event. These are identified on Map 54. The size, <br />runoff volume and peak discharge from each discrete subwatershed is tabulated in Table 43. <br />Five ponds are present at the West Elk Mine numbered MB-1 through MB-5. Each of these <br />ponds collect water from the mine at different locations. Contributing watershed acreage <br />and condition of the watershed determined the amount of runoff and sediment produced <br />from the storm event. Volumes of these ponds and the correlative storm events aze <br />summarized in Table 42. <br /> <br />1 <br />