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<br />Mrs. Judy Sappington <br />State Engineer's Office <br />August 25, 1992 <br />Page 2 <br />Enclosed with this report is a copy of Exhibit C of the Mined Land <br />Reclamation Division application. During the first few years of <br />mining the dewatering trench will extend around the perimeter of <br />Mining Phase 1. it is anticipated that a maximum of 0.25 acres of <br />water surface will be exposed in the dewatering trench during this <br />first phase of mining. Water will be discharged to the Cache La <br />Poudre River via a county waste ditch. <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 42 inches at the subject location. The <br />monthly evaporation was then calculated by using the monthly <br />percentages as suggested by the Office of the State Engineer in <br />their criteria for these reports (See Table No. 1). <br />Precipitation at the site was found by using data from the <br />publication, 'Climatography of the United States No. 81'. The <br />precipitation at the mine site is estimated to be the same as that <br />found at the nearest weather station which is located in Greeley. <br />The annual mean precipitation is 12.68 inches/year. The breakdown <br />of monthly averages is found in Table No. 1. <br />Effective precipitation was determined in order to compute the net <br />lake evaporation (See Table No. 1). Effective precipitation was <br />computed as 708 of the total precipitation. Effective <br />precipitation was then subtracted from the gross evaporation to <br />obtain the net evaporation. The net annual evaporation from a lake <br />surface at the subject site is 2.76 ft (33.1 inches). <br />in addition to the groundwater exposed due to excavation below the <br />wager table, water will be exposed in the wash ponds that will be <br />constructed on the site. The washing operation is discussed in <br />more detail below. <br />The. dewatering operation will expose 0.25 acres and the wash pond <br />will expose 0.70 acres. Consequently the net evaporation from 0.95 <br />acres of water surface will be 2.62 acre-feet. The total monthly <br />evaporation is listed on Table No. 1. <br />