2011-11-29_HYDROLOGY - M1982131 - Laserfiche WebLink

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Mr. Jared Dains Page 3 November 29, 2011 to be mined in WY 2012. A 2% water Toss is assessed as the material will be mined in a dewatered state and will not be washed. The water removed with the mined product is therefore estimated to be 0.74 acre -feet. The Applicant has estimated 6,000 gallons of water per day will be used for dust control purposes during the months of March through October. This water lost to dust control is therefore estimated to be 4.51 acre -feet. The estimated monthly depletions due to operational losses are shown on the attached Table 2. The total projected operational consumptive use for WY 2012 is 5.25 acre -feet. According to the Applicant, dewatering commenced in Amendment Area A in the summer of 1998 and is not projected to cease until 2021. Dewatering occurs through the use of two pumps, with one pump usually running continuously, and two pumps running in high water events. The water is pumped into two settling ponds north of Amendment Area A and immediately adjacent to the Cache la Poudre River, where it is allowed to seep and discharge into the river. Historically, the volume of water pumped has not been accounted for or otherwise tracked. This SWSP approval requires monthly volumes of dewatering discharge into the settling ponds to be recorded. However, these volumes do not need to be analyzed for depletions to the river as long as pumping remains relatively constant month to month. Dewatering operations that are constant and continuous will eventually reach a steady state condition where the accretions to the river generated by dewatering are equal to the depletions to the river generated by dewatering. Given the long duration of historical dewatering operations, it is assumed the pit's dewatering operations are in a steady state condition. At least 3 years from the expected cessation of dewatering, a plan that addresses the replacement of long term lagged depletions, including depletions that occur with the "first fill" of the pit must be submitted to our office. Should dewatering at the pit cease during this SWSP approval period, this SWSP will automatically be void until an amendment is sought and approved. The monthly evaporative and operational depletions to the Cache la Poudre River were lagged from the pit using the Alluvial Water Accounting System (AWAS) program developed by the Integrated Decision Support (IDS) Group at Colorado State University with the following parameters: • Distance from the gravel pit centroid to the river (X) = 1,390 feet • Alluvial aquifer width (W) = 10,650 feet • Specific yield (S) = 0.2 • Transmissivity (T) = 120,000 gallons per day per foot The stream depletion model shows that the Bucklen Pit's stream depletions will total approximately 42.06 acre -feet during WY 2012, as shown on the attached Table 3. Depletions will also occur as a result of using Greeley Irrigation Company (GIC) shares. GIC shares include subsurface return flow obligations which this plan is responsible to cover. This is described in detail under the replacement section for the GIC shares and is shown in Table 4. Replacements The sources of replacement water to be used for this SWSP are: 1) consumptive use credits associated with the historical irrigation use of five shares of the Greeley Irrigation Company ( "GIC "), 2) a lease of 18.9 acre -feet of augmentation water provided by the Platte River Power Authority ( "PRPA "), and 3) a lease of 2.60 acre -feet of augmentation water provided by the Graham Ditch Company ( "GDC "). See Table 5 for a monthly breakdown of replacement water for WY 2012. Greeley Irrigation Company Shares