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Mr. Rob Laird Page 2 of 5 <br />November 16, 2011 <br />Depletions <br />The depletions at the site consist of evaporation from exposed surface area, water used <br />for dust suppression, lagged depletions resulting from the cessation of dewatering, and lagged <br />depletions resulting from the `first fill' of the pit. <br />According to,Table Al.1,: the total exposed surface area at this site as of January, 2011 <br />was 26 acres. For the purposes of this SWSP, it was assumed that the pit will be backfilled at a <br />steady rate of 2.5 acres per year, or 0.208 acres per month. Net evaporative depletions were <br />calculated using a gross annual evaporation of 44.5 inches from the exposed water surface, <br />with a credit of 9.93 inches for effective precipitation. The net depletion of ground water due to <br />evaporation from the ground water exposed at the site was calculated to be 71.17 acre -feet for <br />the first year of this plan and 58.93 acre -feet for the second year of this plan, as shown on the <br />attached Tables AI.1 and AI.2. <br />The Applicant has estimated that 0.33 acre -feet of water will be used for dust <br />suppression at the site per year, as shown on the attached Tables AI.3 and AI.4. There will be <br />no material mined at the site during this plan period. <br />The Alluvial Water Accounting System ( "AWAS ") model was used with the alluvial <br />aquifer boundary condition option to lag depletions to the South Platte River. The following <br />parameters were used in the model: transmissivity (T) = 96,043.2 gallons per day per foot, <br />distance (X) from the centroid of the surface of the exposed ground water to the river = 578 feet, <br />distance (W) from the aquifer boundary through the exposed ground water to the river channel = <br />6,800 feet, and specific yield (SY) = 0.2. The location of the stream depletion is assumed to be <br />perpendicular to the river. The lagged depletions due to evaporation and dust control during the <br />SWSP period are shown in Column 4 of Tables AI.3 and AI.4 and are estimated to total 67.16 <br />acre -feet for 2011 and 57.83 acre -feet for 2012. <br />Additional lagged depletions due to previous pumping for dewatering purposes at the <br />site were calculated using the AWAS program. Following shutdown of the dewatering pumps <br />on August 1, 2010, the pit subsequently filled with approximately 156 acre -feet of water over a <br />period of 60 days. The depletions resulting from this "first fill" were included in the determination <br />of lagged depletions. Table AI.7 shows pump rates and lagged depletions due to past pumping <br />for dewatering purposes, pump shutdown, and the subsequent filling of the pit, equaling 85.37 <br />acre -feet in 2011 and 24.19 acre -feet in 2012. <br />Total depletions at the site are estimated to be 152.53 acre -feet for 2011 and 82.02 <br />acre -feet for 2012. <br />Replacements <br />The proposed source of replacement water for this plan is fully consumable effluent <br />leased from the City of Aurora. The applicant has entered into a five -year lease agreement <br />with the City of Aurora ( "Aurora ") whereby Aurora will deliver fully consumable water to the <br />South Platte River at the outfall of the Metro Wastewater Treatment Plant (WDID 0200700). For <br />the period of July 2011 through December 2011, Aurora will deliver 69.75 acre -feet of water. <br />For the period of January 2012 through December 2012, Aurora will deliver 91.23 acre -feet of <br />water. The point of replacement is located approximately 10.62 miles upstream of the Speer <br />