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• • • H~vlogie laata buapetmioe and rmpact Aaemrov for the Permit and Adjocau.Lem 1991, discharge from the plant averaged 5050 gpd. This discharge is approximately 0.0019 percent of the average dairy flow of 395 cfs observed in the North Fork during the year. Discharge monitoring results from the waste water treatment plant, conducted under NPDFS Permit No. CO-0038776, are includedw Appendu J. The results of the analyses suggest the wazte water discharge has no measurable effect on water quality in the Nonh Fork Gunnison River. past the overflow from a 25 year, 24 hour precipi- tation event safely. The West Elk 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 a small precip- itation event Mlne Water Mine inflows during water year 1991 were small. The total mine water inflow was 5.0 aae feet during the year. The total water exiting the mine is estimated to have been 76.1 aae feet The quality of mine water is considered good and offers no problem for treatment and discharge. Mine water was primarily discharged from the No. 2 Ponal. No discharges occurred from Sylves- ter Gulch or Portal No. 5. Mine water inflow for water year 1992 is expected to be less than that experienced during water year 1991. After development of the "B" seam longwall panels and West Mains are complete, only the amount of water necessary for mining will be imported into the mine. Mine water is expected to have water quality characteristics similar to that reported in Table 5. Because of the small quantity of mine water anticipated, any discharge from ponds would normally be dominated by water quality character- istics of disturbed area runoff az desaibed in the following section. Runoff from Disturbed Area 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 determined 10 year, 24 hour precipitation evcnt as well az a calculated sediment storage volume. The ponds are also designed to 15 The sediment ponds are treated with cationic floavlent when necessary to speed clarifiption and settling of suspended solids. The ponds MB-1, MB-2, MB-5, and MBA have manually controlled dewatering devices. Ponds MB-3 and MBA have automatic dewatering capability. Ponds MB-1, MB-2, MB-5 and MBA are dewatered intermit- tently with most discharges coming during early spring runoff Dewatering procedures take usually less than one day for all ponds except MB-5. Pond MB-5 is responsive to a high spring groundwater table and sometimes has to be dewatered more often. Ponds MB-3 and MBA did not discharge during 1991 and records indicate they have not discharged since they were constructed. MB-4 sometimes catches hydraulic oil spills from the Unit Train loadout. When this occurs, the pond is pumped by a licensed contract hauler or the MCC vacuum truck. The pumped oil is deposited in the shop waste oil tank which is in turn pumped by a li- censed waste oil recycling firm. This standard procedure waz unnecessary during 1991. Flowmeters are installed on all discharge points from sediment ponds which discharge intermittent- ly to continuously record flows. Information on flows, sampling points, and quality of water dis- charged from the mine site sediment ponds during 1991 is included in Appendix J. All water dis- charged was in compliance with NPDES permit effluent limitations. During spring runoff condi- tions, azwell azsome precipitation events, quality of water in the Nonh Fork of the Gunnison is much worse than the quality of discharges from MCC sediment ponds. It is also well outside