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Sievers Pit M-77-098 SWSP, Oldcastle SW Group, Inc. Page 7 of 13 <br /> September 30, 2025 <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/feet'/day for clean sand and sand and gravel, and <br /> saturated thickness of 12 feet taken from the Water Resources Engineering, 41n <br /> Edition by Ray K. Linsley, et at, 1992); <br /> • Specific yield (SY) = 0.2; <br /> • Distance from the stream to the centroid of the dewatering trench (X) = 1,300 feet; <br /> and <br /> • Distance from the stream to the location of the parallel impermeable boundary = <br /> 2,500 feet from the stream. <br /> For the current submittal, a Unit Response Function (URF) was developed with the <br /> characteristic values given above and is provided in Appendix B. The lagged groundwater <br /> mining depletions for the proposed renewal are provided in Table 2. During the requested <br /> plan approval period, the annual lagged stream depletions from groundwater withdrawals <br /> are estimated to be 20.64 acre-feet per year, or 41.28 acre-feet for this SWSP approval <br /> period. <br /> The impact of surface water withdrawals, with an annual total of 10.44 acre-feet (7.13 acre- <br /> feet of evaporative losses from the 1.9-acre pond and 3.31 acre-feet for aggregate washing), <br /> is expected to be instantaneous. Therefore, the calculated total mining depletions <br /> annually during the proposed renewal period is 31.07 acre-feet per year, or 62.16 acre- <br /> feet for this SWSP period). <br /> Replacements <br />