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Sievers Pit SWSP Page 3 of 7 <br />November 24, 2014 <br />lost during the washing process is 'anticipated to equal 2 percent by weight of the mine material, <br />or 5.9 acre -feet during the SWSP approval period. <br />Groundwater for domestic purposes to supply the office and shop on site is withdrawn <br />from well permit no. 43047 -F. However this well is augmented by the West Divide Water <br />Conservancy District ( "WDWCD ") under its umbrella augmentation plan decreed in Case No. <br />99CW320 and out -of- priority depletions from this well are not covered by this SWSP. <br />You have provided a monthly breakdown of the annual depletions made up of 15.50 <br />acre -feet of net evaporative loss from exposed ground water, 5.89 acre -feet of water lost with <br />the mined product, 15.00 acre -feet of water used for dust control, 5.1 acre -feet for asphalt <br />production, 3.75 acre -feet of evaporation loss from the storage pond and 5.89 acre -feet of water <br />lost during the washing process. The attached Table 2 depicts the projected consumptive -use <br />including evaporative losses and operational losses from July 2014 through June 2015. A <br />stream depletion model was developed for the Sievers Pit and the effects of the delayed <br />impacts are found on the attached Appendix A. The aquifer characteristics used in the model <br />are: transmissivity (T) = 120,000 gallons per day per foot (which was estimated using a <br />permeability of 104 gallons /feet2 /day for clean sand and sand and gravel, and saturated <br />thickness of 12 feet taken from the Water Resources Engineering, 4th Edition by Ray K. Linsley, <br />et al, 1992), specific yield (SY) = 0.2, the distance from the stream to the centroid of the <br />dewatering trench = 1,300 feet, and the location of the parallel impermeable boundary was <br />estimated to be 2,500 feet from the stream. <br />The total lagged ground water depletions from evaporation and operational uses are <br />anticipated to equal 38.46 acre -feet for the period of July 1, 2014 through June 30, 2015, based <br />on the assumption that the system has reached steady -state conditions. The dewatering <br />depletions at the Sievers Pit were calculated to have reached a steady -state condition. <br />Replacements <br />Oldcastle will replace all lagged depletions created by expanded mining activity at the <br />Sievers Pit during the historical call period from April 1 through October 31 of each year using a <br />combination of consumptive use credit from the dry-up of irrigated lands of the Kaiser - Sievers <br />Ditch as decreed in Case No. 83CW65 and a lease with the West Divide Water Conservancy <br />District ( "WDWCD "). <br />Pursuant to Case No. 83CW65, a total of 22.1 acres of historically irrigated lands have <br />been dried up as a result of the gravel mining operation, resulting in a consumptive use credit of <br />32.5 acre -feet during the May through October time period. These credits are not sufficient to <br />replace the increased depletions from the Sievers Pit under this SWSP, therefore the remaining <br />replacements will be provided by releases from WDWCD totaling 29.1 acre -feet per year (Table <br />3). These releases include a 10% transit loss. The Applicant currently has perpetual lease of <br />29.1 acre -feet per year with the WDWCD under Contract No. 090521 LW(a). A copy of the <br />contract was submitted with the 2011 SWSP renewal application and is attached to this letter. <br />The source of replacement water from WDWCD was identified as Ruedi Reservoir, Green <br />Mountain Reservoir, Alsbury Reservoir or from other sources available to the District. <br />1313 Sherman Street, Room 821, Denver, CO 80203 P 303.866.3581 F 303.866.2223 www.water.state.co.us <br />