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• <br />1) The permanent ]ake will be approximately 4.2 acres in size, which may fluctuate between 3.8 <br />acres and 4.6 acres, depending upon the river level. Since the lake bottom and sides are always satu- <br />rated due to the level of alluvial water, no losses will occur due to infiltration. Losses will occur due <br />to evaporation at the water surface. Based upon evaporation data for this location from the State <br />Engineers office and precipitation data for this area, this pond will evaporate 2.23 acre-feet of water <br />per acre of water surface. This results in a consumptive use of 9.365 acre-feet annually using an <br />area of 4.2 acres. <br />2) Additional evaporation will occur as a result of mining the gravel and exposing it to air before it <br />is run through the crushing/screening operation and trucked off site. This evaporation use is esti- <br />mated at 4% of the annual excavated tonnage, which will be based on a higher annual tonnage than <br />that shown for this permit (69,500 tons per yeaz). The tonnage used will be 90,000 tons per year. <br />Therefore, this consumptive use will be 4800 tons of water per year or 2.64 acre-feet annually. I[ is <br />estimated that the gravel will contain 20% moisture when it is excavated below water level but 16% <br />moisture will seep back into the ground at the location, leaving 4% of the aggregate weight mined <br />to exit the property with the end product as a consumptive use. Since full tonnage evaporation can- <br />not take place at the same time that the lake is at full size, a highest wnsumptive use scenario is <br />based on the lake being at full size while [he operation is winding down in the second year, there- <br />fore, adiscount of 50% is applied to the evaporation losses associated with the gravel mined. This <br />results in 50% of 2.64 acre-feet or 1.32 acre-feet per year. <br />3) Evaporation will occur as a result of pumping water into the wetland and exposing this water to <br />the surface. Since the wetland is normally wet, the increase in area of exposed water is used [o de- <br />termine this consumptive use. This is approximately 3.1 acres. Using the rate calculated above of <br />2.23 acre-feet per acre, this results in a use of 6.91 acre-feet~er year. <br />4) Consumptive use for dust control will be minor since the access road will be primarily main- <br />tained with magnesium chloride. Under very dry conditions and high truck traffic, water may be <br />used. This use is estimated at 0.3 acre-feetper year. <br />5) The portable enclosed crusher and screen plant do use sprays for dust control, although the gravel <br />will be somewhat wet after excavation from below water level, and the need for additional water in <br />Piceance Pit 7/01 16 <br />