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Colona Pit SWSP Page 5 of 13 <br /> September 30, 2025 <br /> is charged as water lost with mined product. Based on an estimated 7,639 tons/month or <br /> approximately 92,000 tons/year of aggregate removed, the <br /> The water lost with the mined product is estimated at 0.22 acre-feet/month or 2.70 <br /> acre-feet/year, as shown on attached Table 2. <br /> Total Depletions <br /> Total estimated depletions are 55.0 acre-feet/year. <br /> Lagged Depletions <br /> A Glover stream depletion model was used to calculate lagged depletions to the <br /> Uncompahgre River, assuming steady state conditions. The following parameters were used <br /> in the model: transmissivity (T) = 50,000 gallons per day per foot; specific yield (SY) = 0.15; <br /> distance from the centroid of the pit to the river (X) = 2,000 feet; and distance from the <br /> aquifer boundary through the pit to the river (W) = 5,000 feet. The Unit Response Function <br /> (URF) developed using the Glover analysis and the above parameters are shown on attached <br /> Appendix C1. Total lagged depletions are estimated to be 55.0 acre-feet/year, as shown <br /> on attached Table 2 and Appendix C2. <br /> Out-of-priority depletions were determined based on the percentage of days the Gunnison <br /> River fell below 750 cfs during the year 2002 (worst case scenario), as shown on attached <br /> Table 3. Out-of-priority lagged depletions are approximately 32.26 acre-feet/year. <br /> Replacement Water <br /> Ouray Ditch HCU Credits <br /> The primary source of replacement water for this pit during the irrigation season of April <br /> through October is consumptive use credits from the dry-up of 29.2 acres historically <br /> irrigated by 2.5 shares in the Ouray Ditch (WDID 4100549). Based on Ouray Ditch diversion <br /> records, assuming a ditch loss of ten percent (10%) and an irrigation efficiency of fifty <br /> percent (50%), the average annual historical consumptive use (HCU) associated with the <br />