2010-11-10_HYDROLOGY - M1977151 - Laserfiche WebLink

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Mr. Jared Dains, E.I. Page 2 of 7 November 2, 2010 other permanent water source will be dedicated to the SWSP to assure that all permanent depletions from either an unforeseen abandonment of the site by the Applicant or as a result of long term ground water exposure after completion of mining and reclamation will be replaced so as to prevent injury to other water rights. This information must be provided to this office by April 30, 2011. If the requested information is not provided to the Division of Water Resources, any future SWSP may limit the mining operation so that additional ground water cannot be exposed, beyond that specified in this SWSP. Depletions The depletions that result from the mining operation at the Greeley Pit consist of evaporation from exposed surface area and water used for dust control. The total exposed pond surface area at this site is 67.6 acres. According to the attached Figure 1, a total of 31.4 acres of pond surface was exposed within the Greeley Pit reclamation permit boundary prior to January 1, 1981. An affidavit signed by Joe Kuntz, operator of the Greeley Pit during the 1980-1981 period, indicates that an additional 8.8 acres of excavated area was being dewatered at the time of the aerial photograph (June 1980), but was filled with exposed ground water as of December 31, 1980. Based on the Division 1 Water Court decision in case no. 2009CW49, the replacement of evaporative depletions is not required for ground water exposed to the atmosphere prior to January 1, 1981 through open mining of sand and gravel, regardless of whether open mining operations continued or were reactivated on or after that date. The Water Court effectively held that Senate Bill 120 of 1989, as amended in Senate Bill 93-260, exempted all pre-1981 exposed ground water regardless of whether open mining operations continued or were reactivated on or after January 1, 1981. Accordingly, for the 67.6 acres of ground water currently exposed at the Greeley Pit, replacement of evaporative depletions is only required from the 27.4 acres (67.6 - 31.4 - 8.8 = 27.4) exposed after December 31, 1980. No additional ground water will be exposed during this plan period. Net evaporative depletions were calculated using a gross annual evaporation of 45 inches from the exposed water surface, prorated to 40.95 inches for the plan period of May 2010 through March 2011, with a credit of 8.56 inches for effective precipitation. Based on monthly average temperatures reported for the Greeley UNC weather station, ice cover was assumed for the months of December and January, therefore no evaporative consumptive use was charged for those months. However, for the purposes of this SWSP, the Applicant shall replace the net evaporative depletions from the exposed ground water surface area that may occur during the assumed ice cover period (December and January) for any time that the pit is not completely covered by ice. The net depletion of ground water due to evaporation from the 27.4 acres of the Greeley Pit exposed after December 31, 1980 was calculated to be 70.11 acre-feet for this plan year, as shown on the attached Table 1. The Applicant has estimated that a total of 1.00 acre-foot of water will be used for dust control purposes from March to October, prorated to 0.9 acre-feet for the plan period of May 2010 through March 2011 as shown on the attached Table 2. The material mined at the Greeley Pit will be above the ground water table and will have a moisture content of 2% by weight, but no depletions will be charged because the moisture is not a ground water diversion and the Applicant will not wash the mined material. The majority of the Greeley Pit is located greater than 100 feet from the Cache La Poudre River, thus depletions were not assumed to be instantaneous. A stream depletion model using the Glover infinite aquifer condition was used to calculate the lagged depletions to the Cache La Poudre ? v