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1) The permanent lake will be approximately 50 acres in size, which may fluctuate between 46 <br />acres and 53 acres, depending upon the groundwater level. Since the lake bottom and sides are <br />always saturated due to the level of alluvial water, no losses will occur due to infiltration. Losses <br />will occur due to evaporation at the water surface. Based upon evaporation data for this location <br />from the State Engineers office and precipitation data for this area, this pond will evaporate 55 <br />inches per year or 4.58 acre-feet of water per acre of water surface. This results in a consumptive <br />use of 238.2 acre-feet annually using a maximum area of 52.0 acres. <br />2) During mine operation, consumptive use will occur as a result of mining the gravel and exposing <br />it to air before it is run through the crushing/screening operation and trucked off site. It is far below <br />what the evaporation is from the lake surface, therefore it does not count in the worst case <br />calculations. It is estimated that the gravel will contain 20% moisture when it is excavated below <br />water level but 16%o moisture will seep back into the ground at the location, leaving 4% of the <br />aggregate weight mined to exit the property with [he end product as a consumptive use. The use <br />will be based on a higher than average annual tonnage for the project or 420,000 tons per year. <br />Therefore, this consumptive use will be 4800 tons of water per year or 10,78 acre-feet per vear. <br />This use will only occur for the years of mining. <br />3) Evaporation will occur as a result of pumping water into the sediment pond and exposing this <br />water to the surface.. Most of the water will seep back into the ground, however, the surface area of <br />the pond will increase by approximately 1.0 acres. Using the rate calculated above of 4.58 acre-feet <br />per acre, this results in a use of 4.58 acre-feet per yeaz. <br />4) Consumptive use for road dust control will be minor since the access road will be primarily <br />maintained with magnesium chloride. Under very dry conditions and high track traffic, water may <br />be used. This use is estimated at 16.0 acre-fee[ per year.. <br />5) Consumptive use for the asphalt plant and the screening/crushing plant dust control sprays are <br />expected to be 17.5 acre-feet per year. <br />Gilsonite Pi[ 10/02 25 <br />