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Annual Hydrology Report April 28, 1988 Page 21 During Water Year 1987, discharge from the waste water treatment plant averaged 2860 gpd. This discharge is less than 0.018 of the average daily flow of 75 cfs observed in the North Fork during the year. Analysis presented in the quarterly reports show monitoring results from discharges from the waste water treatment plant as required under NPDFS Permit No. CO-0038776. The results of analysis suggest the waste water discharge has no measurable effect on water quality in the North Fork Gunnison River. Mine Water Mine inflows during Water Year 1987 were small. The total mine water inflow was 35.8 acre ft. during the year. The total water exiting the mine is estimated to be 33.0 acre feet. The quality of mine water is considered good and offers no problem for treatment and discharge. Mine water was discharged from Sylvester Gulch and the No. 2 Portal. Table 1.4-1 shows the results of discharge sampling for Sylvester Gulch. Table 1.4-2 shows quality of water discharged at Portal No. 2. Mine water inflow for Water Year 1988 is expected to be similar to that experienced during Water Year 1987. Mine water would be expected to have water quality characteristics similar to that reported in Table 1.4-1, 1.4- 1 2, and 1.4-4. 1 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. Runoff from Disturbed Area J Overland runoff from snowmelt and precipitation within the disturbed areas is routed to one of six sediment ponds on the mine site. The six sediment ponds are designed to contain the predicted runoff from a statistically 1 determined 10 year, 24 hour precipitation event as well as a calculated sediment storage volume. The ponds are also designed to safely pass the overflow from a 25 year, 24 hour precipitation event. The Mt. Gunnison 1 Mine site receives much of its annual precipitation from snowfall during the winter months. When warmer weather begins in late February, March or April, most runoff to the sediment ponds is from snowmelt. It is entirely possible for a volume of runoff greater than the 10 year, 24 hour precipitation event to result from snowmelt or snowmelt coupled with asmall precipitation event. J The sediment ponds are treated with cationic flocculent when necessary to speed clarification and settling of suspended solids. The ponds MB-1, MB- 2, MB-5, and f~-6 have manually controlled dewatering devices. Ponds MB-3 1 and Ms-4 have automatic dewatering capability. Ponds MB-1, MB-2, MB-5 and MB-6 are dewatered intermittently with most discharges Doming during early