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25th Avenue Pit SWSP, (Amendment) Page 3 of 9 <br />May 30, 2017 <br /> <br />Lagged operational depletions from both past and projected operations at the site are estimated to <br />total 11.19 acre-feet during the first year of this plan period, and 11.46 acre-feet during the second <br />year of this plan period (Table 13A-Column 9). <br /> <br />Dewatering <br />Dewatering at Flatiron Pits 3 and 4 began in June 2012 and is anticipated to continue throughout <br />this plan period. Water pumped from Flatiron Pits 3 and 4 is continuously discharged directly to <br />the Cache la Poudre River with no beneficial use. The initial dewatering rate, required to empty <br />the filled pits, was approximately 6,800 gallons per minute (“gpm”). After the initial high <br />dewatering rate, a lower pumping rate of 850 gpm was required to maintain a dewatered state. <br />The initial dewatering was assumed to be made up of both lake water and alluvial aquifer (ground) <br />water. For the purposes of this SWSP it was assumed that the initial dewatering depleted the <br />alluvial aquifer at a rate equal to the maintenance pumping rate. Therefore, only 850 gpm of the <br />initial pumping rate of 6,800 gpm was assumed to be a ground water depletion. After the initial <br />dewatering, pumping occurred at the maintenance dewatering rate of 850 gpm (1,700 gpm at 50% <br />daily duty cycle) and was assumed to be made up of only alluvial aquifer water. The maintenance <br />dewatering rate decreased beginning in December 2013 to a pumping rate of approximately 180 <br />gpm. For the purposes of this SWSP, you have estimated that Flatiron Pits 3 and 4 will be <br />dewatered at a constant rate of 260 gpm during this plan period. Dewatering depletions were <br />lagged to the river using the AWAS program with the parameters identified above. Lagged <br />depletions associated with the dewatering of Flatiron Pits 3 and 4 are estimated to total 423.85 <br />acre-feet during the first year of this plan period, and 421.50 acre-feet during the second year of <br />this plan period, which are partially offset with a credit of 419.38 acre-feet during the first year of <br />this plan period and 419.39 acre-feet during the second year of this plan period for dewatering <br />water discharged to the river (Table 13A-Columns 10 and 11). Actual monthly meter readings must <br />be used to determine the actual dewatering rate and the resulting depletions under this SWSP. <br />Flatiron Pit 5 was temporarily dewatered from August through October of 2012 at a rate of 850 <br />gpm. After October 2012, Flatiron Pit 5 began to refill and was estimated to have refilled <br />completely within two months. Lagged depletions associated with the dewatering and refilling of <br />Flatiron Pit 5 are estimated to total 4.03 acre-feet during the first year of this plan period, and <br />1.93 acre-feet during the second year of this plan period (Table 13B-Column 7). <br /> <br />Replacement <br />The proposed source of replacement water under this SWSP is water rights owned or controlled by <br />the City of Greeley in the Cache la Poudre river basin. In particular, Greeley will use 138 shares in <br />the Boyd and Freeman Ditch (WDID 0300935) that were previously owned by Flatiron Paving Co. and <br />used in previous gravel pit SWSPs for the Greeley West Pit. Greeley now owns these shares and will <br />dedicate these shares as a replacement source in this SWSP. <br />Previous SWSPs relied on a historical consumptive use (“HCU”) analysis for the 138 Boyd and <br />Freeman Ditch shares submitted by W.W. Wheeler and Associates, Inc. (“Wheeler”) on July 13, <br />1990 for the Greeley West Pit. Since the Wheeler analysis appeared to rely on the average <br />headgate diversions and crop consumptive use for the period of 1950-1980, as opposed to a yearly <br />analysis and the analysis did not take into consideration the decline in irrigated acreage as a result <br />of conversion to mining operations that began in the mid-1970’s we requested the Applicant to <br />provide an updated HCU analysis calculated on a yearly basis, including any periods of non-use, or <br />periods for an undecreed or unauthorized use. As requested by the current SWSP an updated HCU <br />analysis was provided with the SWSP amendment request.