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Sievers Pit M-77-098 SWSP, Oldcastle SW Group, Inc. Page 6 of 12 <br /> August 7, 2025 <br /> back to the Roaring Fork River, the Applicant will need to account for any lagged dewatering <br /> depletions at the site. In addition, if it is determined by the Water commissioner or Division <br /> Engineer that the pit is not continuously dewatered at a relatively constant rate, the <br /> Applicant must track depletions and dewatering return flows in their accounting and replace <br /> any dewatering depletions that are not offset by dewatering return flows. <br /> Total Depletions and Lagged Depletions <br /> Total depletions are 31 .07 acre-feet per year due to evaporation from the exposed <br /> groundwater in the dewatering trenches and ponds, surface water evaporation, the water <br /> lost with the mined product, and the increased amount of water used for dust control are as <br /> follows and on attached Table 2: <br /> • Total groundwater depletions = 20.64 acre-feet per year <br /> o Groundwater depletions covered under this SWSP = 11.14 acre-feet per year <br /> • Total surface water depletions = 10.44 acre-feet per year (includes evaporation from <br /> the 1 .9-acre storage pond and aggregate washing) <br /> • Depletions to be replaced under this SWSP = 21.58 acre-feet <br /> Any other uses of water at the mining site will not exceed the amounts described in the <br /> decree in Case No. 83CW65. <br /> A stream depletion model was developed for the Sievers Pit and described in previous <br /> SWSPs. The aquifer characteristics used in the model are as follows: <br /> • Transmissivity (T) = 120,000 gallons per day per foot (which was estimated using a <br /> permeability of 104 gallons/feet2/day for clean sand and sand and gravel, and <br /> saturated thickness of 12 feet taken from the Water Resources Engineering, 4rn <br /> Edition by Ray K. Linsley, et at, 1992); <br /> • Specific yield (SY) = 0.2; <br />