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IMPOUNDMENT DOCUMENTATION FOR <br />EXISTING AREA 1 PIT TEMPORARY WATER STORAGE BASIN <br />Background <br />The Area 1 Pit Temporary Water Storage Basin (Area 1 Basin), utilized~in conjunttion with ongoing mine water <br />handling operations, has existed for years and was not previously identified or considered as an "impoundmem° <br />under the regulatory definition. As a resuk of changes in regulatory imerpretation, however, the CDMG has <br />determined that this existing water body falls under the broad definition of "impormdmerrts" and should be <br />idemified and regulated as such. Because a is an existing water storage facility and was not specifically designed or <br />constructed as an impoundment, the applicable requirements of Rule 4.05.9 are addressed in this context by the <br />following description and the referenced existing configuration drawing: <br />a 1 Tentnorarv Water Storage Basin DesiQ*+- Ooerttion Maintenance. Instxction. and Reclamation <br />The Area 1 Basin is a renurarit surface mine pit adjacem to the Run-of-Mine Coal Stockpile, as shown on Map 24, <br />Surface Facilities, and by Figure Ex8V-1. The pit was mined as part of the former Energy No. 1 more operations. <br />Given that concurrem surface muting and reclamation operations for the EnergyNo. 1 Mine ceased in 1980, this pit <br />area has been in-place for approximazely 25 years. The remnaztt pit area is a totally incised excavation varying in <br />depth from approximately 40 to 50 feet, as shown by Figure Ex8V-1, Area 1 Pit Wazer Storage Basin. The pit area <br />is enclosed by tmdisturbed natural ground on the north and west sides and backfilled surface mine spoils on the <br />south and east sides and has an estimated maximrun water storage capacity of approximately 126 acre-feet. Given <br />that the existing mine excavation is beurg used for temporary water storage, it is not a designed impoundment per <br />se, although an appropriate engineered water discharge system (fixed pumping station) has been designed and <br />installed. <br />The Area 1 Basin is used for temporary storage of excess mine water, as part of the closed-loop mine dewazering <br />and recycle system Water inputs to the pit are limited to minor spoil spring dscharge from the adjacent reclaimed <br />surface mine spoils, minor incident precipuazion, and excess dewazering flows from the mine dewatering systems. <br />The discharge pipe to the Area 1 Basin is located near the northeast comer of the pit area. While an 24-inch <br />culvert outlet at the low point on the crest of the pu allows for minor discharge flow through the overflow channel <br />(Site 7, design capacity of 0.8 cfs) to Pond D if the water reaches this level, the temporary storage basin is managed <br />as a storage impoundment (consistent with applicable provisions of Rule 4.05.9(2)(e)), with controlled pumping to <br />keep wazer levels below the discharge pipe. A fixed pumping station has been established on the northwest edge of <br />the basin area to reclaim water for mine use and control wazer level The pump station consists of several <br />cantilevered steel beams extending over the edge of the basin, with a platform, gantry, walkway, and safety rails <br />for access. A submersible pump, along with associated support and electrical cable, and discharge hoses and <br />piping, is suspended from the pump station gantry within the basin. A winch on the pump station platform <br />allows adjustment of the support cable to set the pump at the desired elevation. The pump has a capacity of 250 <br />gpm. Power for the pump comes from a separate transformer and short (350') distribution line. <br />The Area 1 Basin pumping installation discharges to a de-sander located az an old well site, and then to the Coal <br />Preparation Plant or the mine water recycling system, or directly to Pond D for discharge to Foidel Creek TCC <br />has also obtained approval (6/26/02) from the CDPHE to discharge from the Area 1 Basin directly to Foidel <br />Creek, contingent on construction of a new outfall (Outfall 020). The proposed new outfal] has not been <br />constructed at this time. Management of the Area 1 Basin involves regular monitoring of water levels, inspection <br />and maintenance of pumping systems, and reduction of wazer levels prior to spring discharge to provide additional <br />water storage capacity for any minor increases in subsequent spoil spring discharge. As an impoundment, the Area 1 <br />Basin will be inspected on a monttily basis by a qualified professional using the inspection approach, criteria, and <br />documentation forms used for MSHA impoundments, including specific inspection criteria under Rule 4.05.9(15). <br />A copy of completed inspection forms will be provided to the CDMG, and a copy will be retained on-site and will <br />be available for inspection and review by authorized persons. If observations during an inspection indicate that a <br />TR 05-47 Ex8V-l Revised -March 2005 <br />