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Moun(ain Coa! Comparry~ 1998 Auoual Hydrology Report Wes! E!k Mine <br />Pond FW-1 <br />. During WY98, there were no dischazges from pond FW-1 to the North Fork. Diversions from <br />the North Fork that exceeded the capacity of pond FW-] were allowed to spill back to the North <br />Fork. Discharge points 002A (MB-I) and OO6A (FW-1) were discontinued in the 3`d quarter and <br />replaced by 016A for both ponds. Discharge point 016A also includes any direct dischazge of <br />mine water. Biomonitoring samples are not collected unless MB-1 contains mine water or has <br />been directly discharged. <br />Pond FW-1 was lined with a HDPE liner in May 1998. Seepage from FW-1 was also suspected <br />of contributing water to the mine site landslide. Similaz to MB-1, the liner has been extremely <br />effective in eliminating seepage to the landsiide. Furthermore, the liner has improved the <br />efficiency of using water diverted from the North Fork by not losing water to seepage. <br />Pond SG-1 <br />During WY98, runoff from disturbed areas and water encountered and used during development <br />of the mine ventilation shafts were collected and discharged from pond SG-1. A total volume of <br />approximately 8 acre-feet was discharged during WY98. As shown in Table 8, these discharges <br />were in compliance with CDPS permit limits. <br />Biomonitoring Testing for Toxicity <br />During WY98, MCC conducted numerous biomonitoring tests for toxicity, utilizing whole <br />• effluent toxicity or "WET" tests. Samples were collected on a quarterly basis for ponds MB-1 <br />and MB-2R. Toxicity tests aze presented for both acute (48-hour) static tests, and for chronic <br />(96-hour} static tests. The acute test organism was Daphnia magna. The chronic test organism <br />was the fathead minnow (Pimephales promelas). To ensure that the dilution water itself is not <br />toxic, toxicity tests on dilution water without any effluent (refen•ed to as "controls") were <br />conducted. There were no WET test failures during WY98. <br />• <br />83 - 3 .500 Pagel Wrrg t ater Engineers <br />