2013-06-24_HYDROLOGY - M1984094 - Laserfiche WebLink

Home Browse Search

Ben Langenfeld Page 2 Gloria Z Pit SWSP June 19, 2013 31, 1867. Pursuant to the Decree, the water diverted under the subject water right can be used from the middle of May until the middle of September for placer mining. This SWSP does not in any way change the Platte City Ditch water right. To the extent that this water right is used for the placer mining operations at the site, the water must be diverted in priority and used in accordance with the terms and conditions of the Decree. This SWSP is intended to replace the depletions that result from groundwater consumption at the site and consumption from out -of- priority diversions. Depletions Depletions from the Gloria Z Pit will result from evaporation of exposed groundwater and operational losses resulting from mining activity. Currently there are three ponds on the site described as; the plant settling pond (18,000 square- feet), the plant infiltration pond (32,230 square - feet) and the mining pit (6,000 square -feet) for a total exposed surface area of 1.29 acres. The plant settling pond is where tailings from the sluice flow after processing, the plant infiltration pond receives water overflow from the plant settling pond to allow water infiltration back into the local ground water regime and the mine pit is the groundwater pond where the mining of material occurs. The settling and infiltration ponds are not constructed to expose groundwater. 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 December, January and February based on the average monthly temperatures of 31.2 °F for December, 32.0 °F for January and 30.4 °F for February. Temperature data were obtained from the Fairplay S Park RD weather station (052816) for the time period of 2002 through 2012. 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 (December through February) for any time that the pit is not completely covered by ice. Computation of the net evaporation during any time that the pit is not completely covered by ice shall be determined as the pro -rata amount of the monthly gross evaporation rate distribution amount identified in the State Engineer's General Guidelines for Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro -rata amount of the effective precipitation for that period. The attached Table 2 identifies the estimated monthly depletions from evaporation. The total projected annual evaporative consumptive use is 2.68 acre -feet. Operational losses associated with mining activities will include water removed with the mined product and water used for dust control. During 2013, the Applicant is not proposing to sell any of the mined gravel, however the Applicant may mine and sell up to 70,000 tons in 2014 resulting in a consumptive use of 2.06 acre -feet based on a water content of 4% by weight. Since the site will be wet mined, the material removed during this plan period from below the ground water level will also result in depletions due to the first fill. For purposes of calculating the first fill, the Applicant used the total volume proposed to be excavated below the water table, which is 20 feet deep, with a surface area of 6,000 square -feet, resulting in a depletion of 2.8 acre -feet. This excavated area will be created during 2013 and will be maintained by continuously backfilling the site during mining. Therefore, the first fill will be replaced in 2013. The Applicant has estimated an annual dust control requirement of 0.39 acre -feet. Additional depletions will also result due to mined material being piled on site prior to being used to backfill the mining pit. The Applicant has estimated this consumption to total 0.11