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• • Hydrologic Dora lurrpreranon and lmpacr Arrrssmeu for (he Puma and Mljanu Arras A comparison of baseline water quality data in the North Fork of the Gunnison River with WY 1993 monitoring data shows no significant changes in water quality in the North Fork. No apparent changes in the water quality of the North Fork of the Gun- nison River are attributed to affects of min- ing during WY 1993. Mine Water Management and Impact Assessment The discussion of the mine water system and hydrologic impact assessment is organized by the four sources of water: Sanitary Waste Water Discharge point 007 treats sanitary waste water discharge from the Waste Water Treatment Plant (WWTP). This also flows to MB-2 where additional deten[ion occurs. Sanitary waste water discharge from West Elk mining activities into the North Fork during WY 1993 averaged 12 gpm and represents approximately 0.007 percent of the average daily flow of 347 cfs observed in the North Fork during the year. The results of the analyses suggest the waste water discharge has no measurable effect on water quality in the North Fork Gunnison River. • North Fork water • sanitary wastewater • mine water, and • runoff from disturbed areas. Use and discharge of water from these sources is studied for its potential to affect the North Fork. North fork Water MCC's Mt. Gunnison pipeline water rights were out of priority during a portion of WY 1993 (between July 28, 1993 and October 1, 1993) where flows were below 300 cfs. During this period, water from mine site storage rights and leased water rights were utilized. Average daily low flow in the North Fork during WY 1993 was 347 cfs. The maximum withdrawal at the intake is 450 gpm with both pumps operating. This is about 0.3 percent of the observed average daily low flow in the river during the water year. Mine Water Mine inflows during WY 1993 remain relatively small. The total mine water inflow was 117.4 acre feet during the year. The total water exiting the mine is estimated to have been 118.9 acre feet. The increase from 1992 to 1993 was primarily due to the additional water pumped into the mine to accommodate higher coal production levels from the new long wall. The quality of mine water is considered good. In February. 1993, the discharge from MB-1 (002) failed the acute ceriod- aphnia biomonitoring test. The laboratory was unable to pinpoint the source of the failure and subsequent accelerated weekly testing generated results which showed insignificant mortality. Mine water was primarily discharged from the No. 2 Portal. No discharges occurred from Sylvester Gulch or Portal No. 5. Because of the small quantity of mine water anticipated, any discharge from ponds would normally be dominated by water quality characteristics of disturbed area runoff as described in the following section. 15 Re~'ised Onober 9. 1996