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Sievers Pit SWSP <br />August 7, 2013 <br />Page 3 of 7 <br />pond is estimated to be 3.75 acre -feet during the SWSP approval period. Water lost during the <br />washing process is anticipated to equal 2 percent by weight of the mine material, or 5.9 acre -feet <br />during the SWSP approval period. <br />Groundwater for domestic purposes to supply the office and shop on site is withdrawn from <br />well permit no. 43047 -F. However this well is augmented by the West Divide Water Conservancy <br />District ( "WDWCD ") under its umbrella augmentation plan decreed in Case No. 99CW320 and out - <br />of- priority depletions this well are not covered by this SWSP. <br />You have provided a monthly breakdown of the annual depletions made up of 15.50 acre - <br />feet of net evaporative loss from exposed ground water, 5.89 acre -feet of water lost with the mined <br />product, 15.00 acre -feet of water used for dust control, 5.1 acre -feet for asphalt production, 3.75 <br />acre -feet of evaporation loss from the storage pond and 5.89 acre -feet of water lost during the <br />washing process. The attached Table 2 depicts the projected consumptive use including <br />evaporative losses and operational losses from July 2013 through June 2014. A stream depletion <br />model was developed for the Sievers Pit and the effects of the delayed impacts are found on the <br />attached Appendix A. The aquifer characteristics used in the model are: transmissivity (T) _ <br />120,000 gallons per day per foot (which was estimated using a permeability of 104 gallons /feet2 /day <br />for clean sand and sand and gravel, and saturated thickness of 12 feet taken from the Water <br />Resources Engineering, 4`h Edition by Ray K. Linsley, et al, 1992), specific yield (SY) = 0.2, the <br />distance from the stream to the centroid of the dewatering trench = 1,300 feet, and the location of <br />the parallel impermeable boundary was estimated to be 2,500 feet from the stream. <br />The total lagged depletions from evaporation and operational uses are anticipated to equal <br />38.46 acre -feet for the period of July 1, 2013 through June 30, 2014. The dewatering depletions at <br />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 Ditch <br />as decreed in case no. 83CW65 and a lease with the West Divide Water Conservancy District <br />("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 increase 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 3). <br />These releases include a 10% transit losses. The Applicant currently has perpetual lease of 29.1 <br />acre -feet per year with the WDWCD under Contract No. 090521 LW(a). A copy of the contract was <br />submitted with the 2011 SWSP renewal application and is attached to this letter. The source of <br />