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<br />Mr. Stephen Buechner, P.E. December 7, 2017 <br /> Page 2 of 6 <br />Regulations for the protection of water resources. The April 30, 2010 letter from DRMS <br />requires that you provide information to DRMS to demonstrate you can replace long term <br />injurious stream depletions that result from mining related exposure of ground water. <br /> <br />In accordance with approach nos. 1 and 3, you have indicated that a bond has been <br />obtained for $1,174,724 through DRMS to assure that depletions from groundwater <br />evaporation do not occur in the unforeseen event, or events, which would lead to the <br />abandonment of the Pit. In addition, Front Range Aggregates owns and has dedicated five <br />shares of Twin Lakes Reservoir and Canal Company to cover these potential long term <br />depletions. Front Range Aggregates must continue to commit those shares to this plan <br />until such time as the State Engineer authorizes the release of this commitment. <br /> <br />DEPLETIONS <br /> <br />The depletions that result from the mining operation over the period of this SWSP include <br />evaporation from exposed ground water, dust suppression, dewatering, and water lost with <br />the mined product. Evaporation losses will result from the exposure of ground water in the <br />settling ponds, a gravel washing pond, dewatering trenches and two small sumps. The <br />maximum exposed water surface area during this SWSP period will be 5.0 acres. The areas of <br />currently exposed ground water are shown on the attached Figure 2. <br /> <br />Gross annual evaporation at the gravel pit location is estimated to be 46.0 inches per year <br />and the monthly distribution is as depicted on the attached Table 1. Net evaporation is <br />defined as gross evaporation less the consumptive use of water by vegetation that naturally <br />occurred at the site prior to construction of the pit. The historical consumptive use was <br />assumed to be equal to the effective precipitation, which was estimated as 70% of the 12.51 <br />inches of average annual precipitation based on data from the Cañon City weather station <br />over the period 1893 through 2016. The net evaporation for the exposed water surface is <br />37.32 inches per year with a monthly distribution as shown on the attached Table 1. The <br />total annual stream depletion resulting from the exposure of groundwater is estimated to be <br />15.53 acre-feet, which includes months of potential ice cover (December, January, and <br />February). <br /> <br />Ice covered periods may include the months of December, January, and February based on <br />the Cañon City weather station average temperatures of 22.5°F for December, 26.23°F for <br />January, and 24.13°F for February. However, for the purpose of this SWSP, the Applicant <br />shall replace the net evaporation depletions from the exposed ground water surface area that <br />may occur during the potential ice covered period (the months of December, January, and <br />February) for any time that the exposed ground water in the pit is not completely covered by <br />ice. Computation of the net evaporation during any time that the pond is not completely <br />covered by ice shall be determined as the pro-rata amount of the monthly gross evaporation <br />rate distribution amount identified in the State Engineer’s General Guidelines for Substitute <br />Supply Plans for Sand and Gravel Pits, subtracting the pro-rata amount of the effective <br />precipitation for that period. <br /> <br />You have provided a monthly breakdown of the depletions under this SWSP on the attached <br />Table 2, which includes 15.53 acre-feet of net evaporative loss, 16.92 acre-feet of water lost <br />in product (based on an estimated 500,000 tons of washed aggregate and 150,000 tons of <br />unwashed aggregate), and 12.0 acre-feet for on-site dust control, for a total consumptive use <br />of 44.45 acre-feet.