2014-09-04_HYDROLOGY - M1977023 - Laserfiche WebLink

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Mr. Peter Foster, P.E. Page 2 August 29, 2014 acres exposed after December 31, 1980. The area exposed prior to 1981 is shown on the attached Figure 4. The credits for the pre -1981 area are tied to the location identified on Figure 4 and may not be re- allocated to other areas of ground water exposure within the gravel pit permit boundary. In accordance with the letter dated April 30, 2010 (copy attached) from the Colorado Division of Reclamation, Mining, and Safety ( "DRMS "), all sand and gravel mining operators must comply with the requirements of the Colorado Reclamation Act and the Mineral Rules and Regulations for the protection of water resources. The April 30, 2010 letter from DRMS requires that you provide information to DRMS to demonstrate you can replace long term injurious stream depletions that result from mining related exposure of ground water. In accordance with approach no. 4, you have provided a letter dated April 30, 2013 that dedicates 3.125 cfs of the Applicant's 4.33 cfs in the Seventy Five Ditch water as replacement water solely for this SWSP for as long as there are depletions at this gravel pit site or until such time as another replacement source is obtained. A copy of the April 30, 2013 letter is attached to this SWSP. For the purposes of this SWSP, this letter will be accepted for the dedication of the shares; however, if the State Engineer determines that a different affidavit or dedication process is necessary to assure proper dedication of the shares, additional information may be required prior to future SWSP approvals. Depletions You have provided a monthly breakdown of the annual depletions totaling 10.5 acre -feet of evaporative loss from 17.8 acres of exposed surface area, 2.9 acre -feet of water lost with mined product associated with 100,000 tons of aggregate, and 1.30 acre -feet of water used for dust control. Consumptive use at the pit totals 14.7 acre -feet per year. Computation of evaporation under this plan was reduced during the ice covered period. You have assumed the ice covered period to occur during the months of November, December, January, February and March based on the average monthly temperatures of 27.9 °F for November, 13.45 °F for December, 9.15 °F for January, 14.6 °F for February and 26.6 °F for March. Temperature data were obtained from the Gunnison SW weather station. The ice covered periods may be used to reduce the amount of evaporative losses that need to be replaced; however, for the purpose of this SWSP, the Applicant shall replace the net evaporation depletions from the exposed ground water surface area that may occur during the assumed ice covered period (November, December, January, February and March) for any time that the pit is not completely covered by ice. Computation of evaporation under this plan was also reduced by credit for the elimination of native vegetation on lands inundated by the exposed ground water in the gravel pit. You have also claimed the historical consumptive use credit for dry-up of lands formerly irrigated by the Seventy -Five Ditch. The combined credit for elimination of native vegetation and for dry-up of historically irrigated lands totals 2.2 acre -feet per acre and is shown in the attached Tables 1A and 3. Total credit for the 17.8 acres of ground water exposed after 1980 is 39.6 acre -feet.