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Mountain Coal Company 2000 Annual Hydrologr• Report West Elk Mine Pond FW-1 • During WY00, there were no discharges from pond FW-1 to the North Fork. Diversions from the North Fork that exceeded the capacity of pond FW-1 were allowed to spill back to the North Fork. Pond FW-1 was lined with a HDPE liner in May 1998. Seepage from FW-1 was also suspected of contributing water to the mine site landslide. Similar to MB-1, the liner has been extremely effective in eliminating seepage to the landslide. Furthermore, the liner has improved the efficiency of using water diverted from the North Fork by not losing water to seepage. RPE Pond The RPE pond became operational in 1997. The pond collects runoff from the refuse pile expansion (RPE) area. In WY00, the RPE pond discharged approximately five acre feet of water to the North Fork. Pond SG-1 During Wl'00, runoff from disturbed areas and water encountered and used during development of the mine ventilation shafts were collected and discharged from pond SG-1 to Sylvester Gulch. A total volume of less than one acre foot was discharged during WY00. As shown in Table 8, these discharges were incompliance with CDPS permit limits. • Biomonitoring Testing for Toxicity During WY00, MCC conducted numerous biomonitoring tests for toxicity, utilizing whole effluent toxicity or "WET" tests. Samples were collected on a quarterly basis for discharges from Lone Pine pipeline and the MWPF. Toxicity tests are presented for both acute (48-hour) static tests, and for chronic (96-hour) static tests. The acute test organism was Daphnia magna. The chronic test organism was the fathead minnow (Pimephales promelos). To ensure that the dilution water itself is not toxic, toxicity tests on dilution water without any effluent (referred to as "controls") were conducted. There were no WET test failures during WY00. r~ 831-03?.550 Page 18 lVriglrr WorerEngineers