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1 ' The sediment ponds aze treated with cationic flocculent when necessary to speed clarification and settling of suspended solids. The ponds MB-1, NID- 2, NIB-5, and MB-6 have manually controlled dewatering devices. Ponds MB-3 ' and MB-4 have automatic dewatering capability. Ponds N1B-1, MB-2, MB-5 and MB-6 are dewatered intermittently with most discharges Doming during early spring runoff. Dewatering procedures take usually less than one day with the exception of ~~ID-5 which is responsive to a high spring groundwater table and sometimes has to be dewatered more often. Ponds NID-3 and NIB-4 have not discharged during 1986 and records indicate they have not discharged since they were constructed. MB-4 sometimes catches hydraulic oil spills from the Unit Train Loadout and is pumped by a licensed contract hauler or the WECC vacuum truck which deposits the oil in the shop waste oil tank which is in turn pumped by a licensed waste oil recycling firm. This is a standard procedure. ' Flowmeters have been installed on all discharge points from sediment ponds which discharge intermittently to continuously record flows. The Quarterly Hydrology Reports wntain information on flays, sampling ' points, and quality of water discharge from the mine site sediment ponds in 1986. All water discharged was in compliance with NPDFS permit effluent limitations. During spring runoff conditions as well as some precipitation events quality of water in the North Fork of the Gunnison is much worse than the quality of discharges from WEOC sediment ponds and well outside NPDES effluent limitations. During winter baseflad and summer conditions water quality in the North ' Fork is better and is within NPDFS effluent limitations, however, this is the time of year when WE~C's ponds are rarely discharged. ' Flow amounts from NIDOC sediment ponds are low in comparison to the North Fork of the Gunnison flows. Even during low flow conditions on the North Fork I+~OC discharges represent an imperceptible difference in stream ' quality. It is apparent from the analyses that sediment pond discharges have had no adverse impact on the North Fork of the Gunnison River. The quality of discharges usually exceeds the quality of the North fork; and discharge flows are so small that incremental changes in concentrations in the North Fork are imperceptible. ' Discharges of surface runoff is 1987 are expected to be similar to 1986. 1 L ' (19)