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East 8`h Street SWSP December 3, 2018 <br /> Plan ID 4701 Page 2 of 6 <br /> Pit is located. Greeley will provide replacement water from their waste water treatment plant <br /> pursuant to the mining lease agreement between the Applicant and Greeley. The final reclamation <br /> plan for the pit is to create a lined storage reservoir for the City of Greeley. <br /> Depletions <br /> The total exposed surface area at this site is expected to remain at 11.5 acres during this plan <br /> period, consisting of the west cell, settling ponds, and dewatering trenches in the east cell. Net <br /> evaporative loss was determined to be 2.93 feet per exposed acre, as approved in previous SWSPs. <br /> This value was calculated using a gross annual evaporation of 45 inches from the exposed water <br /> surface, with a credit of 9.9 inches for effective precipitation, based on average annual precipitation <br /> of 14.14 inches for the Greeley UNC weather station. Net evaporative losses at the site are therefore <br /> estimated to total 33.64 acre-feet for the 11.5 acres exposed during this plan period. <br /> The Applicant anticipates mining up to 50,000 tons of aggregate during this plan period. The <br /> material will be mined below the groundwater table in a dewatered state and not washed; therefore <br /> the water retained in the mined product is considered to be 2.0% of the mined material by weight. <br /> This results in a groundwater loss of 0.74 acre-feet. <br /> The Applicant projects using up to 0.50 acre-feet of water per year from the pit for dust <br /> control purposes. All water used for dust control purposes is assumed to be 100% consumed. <br /> The total consumptive use of ground water at the East 81h Street Pit (including evaporative <br /> and operational losses) is estimated to be 34.87 acre-feet for this plan period. <br /> The east cell will be continuously dewatered during this SWSP period, and all such water will <br /> be discharged to the Cache la Poudre River. As long as the pit is continuously dewatered and all <br /> water is discharged to the Cache la Poudre River, the accretions to the stream system should be <br /> sufficient to replace the lagged dewatering depletions. All site dewatering must be accounted for in <br /> a method satisfactory to the division engineer and water commissioner. Adequate measuring devices <br /> may be required in order to adequately account for the dewatering. <br /> After cessation of dewatering the west cell in July 2016, the cell filled to a depth of <br /> approximately 4 feet with a surface area of 7 acres, for a total fill volume of 28 acre-feet. You have <br /> assumed that the refilling occurred evenly over the three-month period of August, and September, <br /> and October 2016. The lagged depletions associated with the temporary refilling of the west cell, <br /> including lagged depletions from evaporation off the increased surface area of the cell, will be <br /> replaced under this SWSP. <br /> The IDS Alluvial Water Accounting System (AWAS) analytical stream depletion model, which <br /> uses the Glover method, was used to calculate the lagged depletions to the Cache la Poudre River. <br /> The following parameters were used in the model: transmissivity (T) = 120,000 gallons per day per <br /> foot, specific yield (SY) = 0.2, the distance from the river to the edge of the alluvium = 11,000 feet, <br /> and the distance from the centroid of the exposed surface water areas to the river = 600 feet. The <br /> total lagged depletions were determined to be 33.93 acre-feet for this plan period. This amount <br /> includes lagged depletions resulting from past consumptive use at the site that are projected to <br /> impact the river during this plan period, including those from the refilling of the west cell in 2016. <br /> The attached Table 1 shows the monthly breakdown of evaporative, operational, and lagged <br /> depletions. <br />