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Mr. Hal Simpson • • <br />May 21, 1995 <br />Page 2 <br />DEPLETIONS <br />Owens plans to mine 300,000 tons per year. The water surface area exposed to the <br />atmosphere will consist of a small area of residual water in the sump and dewatering <br />trench that will line the circumference of the mining area.. We estimated that there will <br />be no more than 2 acres of water exposed during the mining. <br />The depletions from mining of the Del Camino Pit will result from evaporation and water <br />lost in the product. The gross evaporation of 40.5 inches per year was determined from <br />the NOAH Technical Report NWS 33. The monthly distribution is based on the SEO <br />draft criteria dated February, 1995. <br />Table 1 shows the estimated evaporation depletion on a monthly basis. The depletions <br />are shown on a calendar year. Since the water surface area will not increase, the area <br />exposed will remain the same during mining and the monthly product mined will vary. <br />No water will be used for dust suppression. <br />REPLACEMENT PLAN <br />Owens proposes to replace depletions using effluent from the City of Longmont and <br />water from the Last Chance Ditch released at the metro plant. Presently, the property <br />is being irrigated by the Last Chance Ditch. The enclosed Vicinity Map shows the Last <br />Chance Ditch. The historic irrigated acreage is the area within the mining boundary. <br />The cropping pattern for at least the past decade has been to plant 50% corn and 50% <br />alfalfa. We estimate the potential crop consumptive use to be 22.7 inches for corn and <br />26.5 inches for alfalfa. The Blaney-Criddle analysis is attached. Based on the Blaney <br />Criddle analysis and an irrigated area of 100 acres, the crops have a total potential <br />crop CU of 278 acre feet per year. The total annual depletion from the mining <br />operation will be 23.7 acre feet. Table 2 summarizes the depletions and replacement <br />amounts. The historic consumptive use credits will offset depletions during the <br />irrigation season. We estimate that 4.2 acre feet of water will be needed from an <br />effluent lease for replacement during non-irrigation months. <br />Owens plans to divert the water from the Last Chance Ditch directly into a small pond <br />