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West Elk Mine 2003 Annual Hydrology Report settling of sediment occurs prior to discharge (batch mode). In WY2003, pond MB-1 did not have any discharges and MB-2R discharged 252 ac-ft of water to the North Fork. 4.3.2 Ponds MB-3, MB-4, and MB-S Ponds MB-3 and MB-4 receive stormwater runoff and wash down water from the conveyors, silos, and load out facilities. Pond MB-5 collects only stormwater runoff. In WY2003 pond MB-4 collected a small amount of water resulting in discharges of about 0.6 ac-ft. Water was not discharged from ponds MB-3 and MB-5 in WY2003. 4.3.3 Pond FW-I Pond FW-1 is designed to store raw fresh water from the North Fork diversion intake gallery. Pond FW-1 water is pumped to the WWTP and the Project's domestic water system. If the pond overfills, excess water is discharged back to the North Fork. No dischazge to the North Fork occurred in WY2003. 4.3.4 RPE Pond The RPE Pond collects runoff from the refuse pile expansion area. In WY2003 no discharge occurred from the RPE pond. 4.3.5 Pond SG-1 Pond SG-1 was built to collect runoff during and after construction of the mine ventilation shafts. Discharge from SG-1 is routed to Sylvester Gulch. In WY2003 pond SG-1 did not have any discharges. 4.4 Biomonitoring Testing for Toxicity During WY2003, MCC conducted biomonitoring tests as required for the CPDS permit. Testing included whole effluent toxicity or "WET" tests. Biomonitoring samples were collected quarterly from the West Fork of Sylvester Gulch effluent discharge (outfall 017). Static toxicity tests for acute (48-hour) and chronic (96-hours) conditions were run. The test organisms included the daphnid (Daphnia magna) and the fathead minnow (Pimephales promelas). The test results indicated that the effluent was not acutely toxic to either species in WY2003 and that the West Elk Mine was in compliance with its CPDES permit WET limitations. C~ 28 September 2004 HydroGeo, Inc.