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Afountain Coa/Compam~ 2000 Annual Hydrology Report WestE/k Mine Sedimentation Ponds . There are seven ponds, MB-l, MB-2R, MB-3, MBA, MB-5, RPE pond, and SG-1, at the West Elk Mine that are utilized to manage mine operation water, stormwater runoff, and wastewater treatment effluent. In addition, there is a "freshwater" pond, FW-l, that is used to equalize diversions from the North Fork. Pond FW-1 serves as the raw water supply for the mine for both domestic and in-mine purposes. In WY00, pond MB-2R discharged about 112 acre-feet to the North Fork, whereas ponds MB-3, MB-4 and MB-5 did not discharge. Pond MB-1 discharged approximately five acre feet during WY00. Pond SG-1, located in Sylvester Gulch, discharged less than one acre foot during WY00. The pond receives runoff from the ventilation shafts area. The RPE pond discharged approximately five acre feet during WY00. Pond discharges to the North Fork are made in accordance with the MCC CDPS Discharge Permit No. CO-0038776. Table 8 summarizes the water chemistry of all discharges during WY00. Table 9 provides the numeric discharge limits for the sedimentation ponds, as per the CDPS permit. No discharge point had a discharge that exceeded numeric standards during W Y00. Ponds MB-1 and MB-2R Pond MB-I receives mine surface operations water and stormwater runoff, and can be discharged to either the North Fork or transferred to pond FW-]. Pond MB-2R receives surface operations water, stormwater runoff and effluent from the wastewater treatment plant (W WTP), and is released to the Norih Fork or occasionally sent to pond FW-1. Both ponds operate in a • "batch" mode; i.e. water is detained while settling occurs then discharged to the Norih Fork. Pond MB-I was re-lined with a HDPE liner in January 1998 to eliminate a suspected source of water to the mine site landslide. It was believed that the previous liner was damaged, thereby allowing water to seep out of the pond and to contribute inflow to the mine site landslide. The new liner has been extremely effective in eliminating seepage from MB-l, which, in turn, has aided in stabilizing the landslide. Use of the NW Panels sealed sump and the NE Panels sealed sump resulted in improved water management in sedimentation ponds MB-] and MB-2R. This fact is evident by the reduced volume of water treated in the ponds and the lack of discharge exceedences. The water quality of the North Fork is better protected during upset conditions due to the storage capacity of the in- minesumps. Ponds MB-3, MB-4 and MB-5 During W Y-00, none of ponds MB-3, MB-4 and MB-5 discharged water to the North Fork. Pond MB-5 received exclusively stormwater runoff and ponds MB-3 and MB-4 received runoff as well as washdown water from conveyors, the silos and the loadout facilities. However, none of the ponds received sufficient volumes of water to necessitate discharge. 831-03?.550 Page 17 ti'righr W'orer Engineers