2008-08-13_HYDROLOGY - M2000158 - Laserfiche WebLink

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Melanie Lawrence August 11, 2008 Page 2 The final reclamation of the pit includes backfilling or lining of all exposed groundwater within the permit boundary. The applicant has bonded for lining and backfilling of the pit as part of their permitting process through the Division of Minerals and Geology. Depletions This plan describes the projected uses for 2008. According to the information submitted, no water surface was exposed within the permit boundary prior to January 1, 1981. The anticipated consumptive use for 2008 consists; of 38.55 acre-feet of evaporation loss from an exposed ground water surface area of 13 acres and 5.0 acre-feet of water used for dust control (total 43.55 acre-feet). The 13 acres of ground water wars exposed due to previous mining that occurred outside of the liner. At some point during 2008, the Applicant anticipates backfilling some of the currently exposed pit with overburden material', thereby reducing the exposed ground water surface area to 5 to 7 acres. This SWSP currently assumes that the entire 13 acres will be exposed for the entire plan period. The depletions from evaporation and dust control were) lagged to the stream using a Glover analysis and assuming a distance to the stream of 2,900 feet, distance to the impermeable boundary of 16,100 feet, permeability of 1,043 ft/day, saturated thickness of 20 feet and specific yielq,of:Os2. The..Applicant has provided a monthly schedule of lagged actual depletions to the river-system,??together with a schedule of replacement requirements. This SWSP accounts for actual depletions determined to accrue to the steam system during this plan period. Replacements The proposed sources of replacement for this pit are! fully consumable wastewater treatment plant effluent or reservoir releases from a lease with the City of Longmont (Longmont Sewer (WDID 0502300)), and water stored in priority within Sharkey's Reservoir. The City of Longmont wastewater treatment plant is located approximately 20 miles upstream of this existing mining operation. A 0.5 percent per mile transit loss (10.0 percent overall loss) has been accounted for in the replacements for April through October and a 0.25 percent per mile transit loss (5.0 percent overall loss) has been accounted for in the replacements for November through March. The monthly consumptive use and lagged depletions are shown in the table below: Month Consumptive Use (acre-feet) Lagged Depletions (acre-feet) Jan 1.31 3.29 Feb 1.73 2.91 Mar 2.48 2.83