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Wafer Requirements <br />The annual consumptive use for this site is estimated at 29.5 acre-feet. Consumptive uses result <br />from evaporative losses and operational losses. Evaporative losses are dependent on exposed <br />water surface area, which includes settling ponds, dewatering trenches, and collection basins. <br />Operational losses include water used for dust control and water retained in product transported <br />off site. Water will also be used for imgation of newly established vegetation at the reclaimed <br />mining areas. <br />The annual evaporative loss is estimated at 10 acre-feet for 5 acres of exposed water during <br />mining. Total annual evaporative loss is the product of net annual evaporation and total exposed <br />groundwater surface. Net annual evaporation is the difference between gross annual evaporation <br />and effective annual precipitation. The total exposed surface area at the River Valley Resource <br />site will be approximately 7.0 acres during mining. <br />The NOAA Technical Report NWS 33, Evaporation Atlas for the Contiguous 48 United States <br />(U.S. Department of Commerce), was used to determine gross annual evaporation. For this <br />location, gross annual evaporation was estimated at 38 inches. The Colorado Climate Center <br />climatic data for Steamboat Springs was used to estimate annual precipitation. For this station, <br />average annual precipitation was reported as 23.95 inches. Effective annual precipitation was <br />assumed to be 70% of average annual precipitation and was calculated to be 1.4 feet. The net <br />annual evaporation for this site is 1.9 acre-feet/acre. <br />The moisture content of the material transported off the site was assumed to be 4% by weight. <br />The annual amount of mined product for the pit is estimated at 400,000 tons. This results in 11.8 <br />acre-feet of water retained in the amount of product mined annually. Dust control is required for <br />internal haul roads and stockpiles. To manage dust, a 4,000-gallon water truck will spray its <br />entire load each day, Monday through Saturday, for six (6) months out of a year. This <br />assumption results in a consumptive use for dust control of 1.5 acre-feet per year. Water will also <br />be consumed in concrete production. Approximately 5.0 acre-feet will be used throughout the <br />year. In addition, an estimated 1.0 acre-foot of water will be used in asphalt production at the <br />site. The estimated total annual consumptive use associated with the mining operation is <br />summarized as follows: <br />Consum tive Use Annual Water Loss (acre-ft) <br />Evaporation 10.0 <br />Moisture Retained in Product 12.0 <br />Dust Control 1.5 <br />Asphalt Production 1.0 <br />Concrete Production 5.0 <br />Total 29.5 <br />Reclamation of this site will occur concurrently with mining. This will result in a groundwater <br />lake and constructed wetlands. <br />River Volley Resource <br />DMG /12 Permit Amendment <br />Page 73 <br />