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• III IIIIIIIIIIIII III • <br />999 <br />Piceance Pit Water Use Calculations <br />1) Case 1 -While Mining Operation is Active (2 years) <br />Water will initially be pumped at the rate of approximately 5000 gallons per minute for <br />a period of 30 days. Pumping will [hen be reduced for the next 11 months to a rate of <br />500 gallons per minute. <br />This rate is 662 acre-feet for the first month and 66 acre feet for each of the remaining <br />11 months of the year. The total amount pumped annually is therefore 1390 acre-feet. <br />Almost all of this amount will be pumped into a wetland which is located immediately <br />north of the permit area. Water from the wetland will overflow directly into the White <br />River, which is immediately north of the wetland, as shown on the enclosed mine map. <br />The following table shows the uses for the amount pumped from the pit lake. it should <br />be noted that these amounts are worst case. <br />All consumptive uses are shown below: <br />1) The permanent lake will be approximately 4.2 acres in size, which may fluctuate <br />between 3.8 acres and 4.6 acres, depending upon the river level. Since the lake bottom <br />and sides are always saturated due to the level of alluvial water, no losses will occur <br />due to infiltration. Losses will occur due to evaporation at the water surface. Based <br />upon evaporation data for this location from the State Engineers office and <br />precipitation data for this area, this pond will evaporate 2.23 acre-feet of water per acre <br />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 <br />air before it is run through the crushing/screening operation and trucked off site. This <br />evaporation use is estimated at 4% of the annual excavated tonnage, which will be <br />based on a higher annual tonnage than that shown for this permit (69,500 tons per <br />year). The tonnage used will be 90,000 tons per year. Therefore, this consumptive use <br />will be 4800 tons of water per year or 2.64 acre-feet annually. It is estimated that the <br />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 <br />weight mined to exit the property with the end product as a consumptive use. Since full <br />tonnage evaporation cannot take place at the same time that the lake is at full size, a <br />highest consumptive use scenario is based on the lake being at full size while the <br />operation is winding down in the second year, therefore, a discount of 50% is applied <br />to the evaporation losses associated with the gravel mined. This results in 50% of 2.64 <br />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 <br />