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6.2 Process Water <br /> • <br /> A dry crushing process will be used for the mined aggregate and <br /> therefore no water will be used for this process. The only <br /> consumptive use of water for the mining operation, other than <br /> evaporation will be water retained in the material excavated from <br /> the site and water pumped from the pit which will be used for dust <br /> control. <br /> Aggregate which has been stockpiled for a week is generally <br /> considered to contain 4% water by weight. This would be an <br /> appropriate water content for pit run aggregate. Calculations of <br /> water content in the annual production rate of 200,000 tons of <br /> aggregate equals approximately 5. 89 acre-feet (af) of consumptive <br /> use. <br /> Approximately 3/8 inch of water will be applied a day to 2.5 acres <br /> (2900 linear feet of Weld CR 24 1/2 and a maximum of 2000 linear <br /> feet at plant) of roads to control dust. Dust control will be <br /> required approximately 60 days each year. Therefore the annual <br /> consumptive use for dust control is estimated at 6.2 acre-feet. <br /> 6.3 Evaporative Losses <br /> The NOAA Technical Report NWS 33, 'Evaporation Atlas for the <br /> • Contiguous 48 United States' , published by the U.S Department of <br /> Commerce was used to determine the amount of evaporation. The <br /> annual evaporation is 39 inches at the subject location. <br /> Lake freezing is expected to occur in the months of January and <br /> February and consequently the annual net evaporation is reduced by <br /> 6. 1 percent. The net annual evaporation from a lake surface at the <br /> site is 3 .05 ft (36.6 inches) . <br /> Due to high water table conditions at the site groundwater <br /> consumptive use has occurred historically. A consumptive use <br /> credit is therefore applied to the net evaporation reducing the net <br /> evaporation by 12 inches annually. Hence the net consumptive use <br /> due to exposure of groundwater is 2.05 ft or 24 .6 inches <br /> During the final phase of mining, phase IV, the other lakes will be <br /> filled with groundwater. The annual consumptive use during this <br /> final phase of mining will be as follows: <br /> Evaporation from Phase I, II, III Lakes: 98.8 acre-feet <br /> (48.21 surface acres) <br /> Water retained in excavated material: 5.9 acre-feet <br /> Dust Control water: 6.2 acre-feet <br /> ------------- <br /> Total 110.9 acre-feet <br />