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Tri-County Gravel Pit, M77-205 Page 6 of 13 <br /> February 27, 2025 <br /> Water Lost with Mined Product <br /> During this SWSP period, mining at the site will continue under dewatered conditions <br /> with production of material expected to expand to 160,000 tons annually. The <br /> augmentation plan in case no. 99CW216 will replace 3.09 acre-feet per year of water <br /> lost with 105,120 tons of mined product under dewatered condition. The 54,880 tons <br /> of additional mined material depletions not covered under the augmentation plan will <br /> be replaced under this SWSR Of the 54,880 additional tons per year mined; 49,392 <br /> tons will be mined in a dewatered state, therefore the groundwater lost with the <br /> unwashed mined product during this period is estimated at 2 percent by weight or <br /> 0.73 acre-feet per year; and the 5,488 tons will be mined in a dewatered state and <br /> washed, therefore the groundwater lost with the mined product during this period is <br /> estimated at 4 percent by weight, or 0.16 acre-feet per year. The water lost with the <br /> 54,880 additional tons of mined product is projected to total 0.89 acre-feet per year <br /> for the SWSP period as shown in Table 2 (attached). <br /> Lagged Depletions <br /> A stream depletion model was developed for the Tri-County Gravel Pit and the effects <br /> of the delayed impacts are found on the attached Tables 3 and 4. The aquifer <br /> characteristics used in the model for are as follows: <br /> Transmissivity (T) = 35,000 gallons per day per foot <br /> Specific yield (SY) = 0.15 <br /> Distance from stream to centroid of Dewatered Pit (X) = 1,037 feet <br /> Distance from stream to aquifer boundary of Dewatered Pit (W) = 3,657 feet <br /> Distance from stream to centroid of the Reclaimed Pit (X) = 557 feet <br /> Distance from stream to aquifer boundary for Reclaimed Pit (W) = 4,077 feet <br /> Distance from stream to centroid of Irrigation Return Flow (X) = 1,091 feet <br />