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Sievers Pit M-77-098 SWSP, Oldcastle SW Group, Inc. Page 6 of 13 <br /> September 30, 2025 <br /> Dewatering <br /> Dewatering at this site will produce delayed depletions to the stream system. As long as the <br /> pit is continuously dewatered, the water returned to the stream system should be adequate <br /> to offset the depletions attributable to the dewatering operation. Dewatering must be <br /> continuous to the extent that is necessary to prevent intermittent fill and be measured with <br /> a device or method acceptable to the Division Engineer. At least 3 years prior to completion <br /> of dewatering, a plan must be submitted that specifies how the post pumping dewatering <br /> depletions (including refilling of the pit) will be replaced, in time, place and amount. Should <br /> it be determined by the Water Commissioner or Division Engineer that dewatering water is <br /> being diverted for any purpose by the operator and accounting is not adequate to show that <br /> one hundred percent (100%) of the dewatering water is returned back to the river, the <br /> Applicant will need to account for any lagged dewatering depletions at the site. In addition, <br /> if it is determined by the Water Commissioner or Division Engineer that the pit is not <br /> continuously dewatered to the extent that is necessary to prevent intermittent fill, 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 />