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1 <br />' Annual Hydrology Report <br /> April 28, 1988 <br /> Page 21 <br />1 <br /> During Water Year 1987, discharge from the waste water treatment plant <br /> averaged 2860 gpd. This discharge is less than 0.018 of the average daily <br />' flow of 75 cfs observed in the North Fork during the year. <br /> Analysis presented in the quarterly reports show monitoring results from <br />' discharges from the waste water treatment plant as required under <br />Permit No. X0038776. The results of analysis suggest the waste NPDFS <br />water <br /> discharge has no measurable effect on water quality in the North Fork <br /> Gunnison River. <br />' i <br /> ne Water <br />M <br /> Mine inflows during Water Year 1987 were small. The total mine water <br />' inflow was 35.8 acre ft. during the year. The total water exiting the mine <br /> is estimated to be 33.0 acre feet. The quality of mine water is considered <br />' good and offers no problem for treatment and discharge. <br /> Mine water was discharged from Sylvester Gulch and the No. 2 Portal. Table <br /> 1.4-1 shows the results of discharge sampling for Sylvester Gulch. Table <br />' 1.4-2 shows quality of water discharged at Portal No. 2. <br /> Mine water inflow for Water Year 1988 is expected to be similar to that <br /> experienced during Water Year 1987. Mine water would be expected to have <br />' water quality characteristics similar to that reported in Table 1.4-1, 1.4- <br /> 2, and 1.4-4. <br />1 <br /> Because of the small quantity of mine water anticipated, any discharge from <br /> ponds would normally be dominated by water quality characteristics of <br />' disturbed area runoff as described in the following section. <br /> Runoff from Disturbed Area <br />' Overland runoff from snowmelt and precipitation within the disturbed areas <br /> is routed to one of six sediment ponds on the mine site. The six sediment <br /> ponds are designed to contain the predicted runoff from a statistically <br />' determined 10 year, 24 hour precipitation event as well as a calculated <br /> sediment storage volume. The ponds are also designed to safely pass the <br /> overflow from a 25 year, 24 hour precipitation event. The Mt. Gunnison <br /> Mine site receives much of its annual precipitation from snowfall during <br />' the winter months. When wanner weather begins in late February, March or <br /> April, most runoff to the sediment ponds is from snowmelt. It is entirely <br /> possible for a volume of runoff greater than the 10 year, 24 hour <br />' precipitation event to result from snowmelt or snowmelt coupled with asmall <br /> precipitation event. <br />' The sediment ponds are treated with cationic flocculent when necessary to <br /> speed clarification and settling of suspended solids. The ponds MB-1, t~ID- <br /> 2, ~-5, and rID-6 have manually controlled dewatering devices. Ibnds hID-3 <br />' and hID-4 have automatic dewatering capability. Ponds <br />MB-6 are dewatered intermittentl <br />t disch <br />ith MB-1, MB-2, .+~-5 and <br />i <br />d <br />l <br />i <br /> y w <br />mos <br />arges com <br />ng <br />ur <br />ng ear <br />y <br /> <br />