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Water Requirements <br /> The annual consumptive use for this site is estimated at 50.0 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 irrigation 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 Alias 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 applicant will also use approximately 20.0 acre-feet of water per year to irrigate the <br /> reseeded vegetation on the reclaimed mining areas. The estimated total annual consumptive use <br /> associated with the mining operation is summarized as follows: <br /> Consumptive 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 /> Reclamation irrigation 20.0 <br /> Total 49.5 <br /> Reclamation of this site will occur concurrently with mining. This will result in a groundwater <br /> lake and constructed wetlands. <br /> River Valley Resource <br /> DA1G 112 Perow <br /> Page 14 <br />