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4.6.1.3.3 Stream Channel Diversions <br />Mining operations will not involve the diversion of any stream <br />channels. <br />4.6.1.3.4 Effluent Control and Discharge Structures <br />Mine effluent water quality is currently controlled to acceptable <br />standards under an approved Discharge Plan filed with the Colorado <br />Department of Health {CDOH), Permit No. CO-0029599. <br />The permit allows discharge to North Thompson Creek from the No. 1 <br />and 3 Mines and the sediment ponds. The sediment ponds are <br />designed to contain the entire capacity of storms up to and <br />including the 10-year, 24-hour design event. Storm events in <br />excess of this would discharge to the North Thompson Creek. The <br />impacts of these infrequent events would be minimal since detention <br />time is approximately 24 hours, causing most of the particulate <br />material to settle. Also, the flow in North Thompson Creek would <br />be substantially greater than normal due to runoff from surrounding <br />areas which are not affected by mining operations. This high creek <br />flow would carry substantial suspended material as evidenced by <br />past runoff events from surrounding drainage basins (CWCB,1979). <br />The No. 3 Mine, (Outfall 007), has two separate sources of <br />discharge. One is from a point source (spring) within the Mine <br />that is piped directly to the surface. This good quality point <br />source of water has been the source of the discharge from the No. <br />3 Mine, (Outfall 007), since the mine was sealed in 1986. The <br />other source is water that is contained in the mine workings. The <br />water level in the mine has fluctuated since 1986 but no water has <br />discharged directly from the mine in ten (10) years. During the <br />second quarter, the very wet spring weather evidently caused the <br />mine to fill and begin discharging iron laden water. <br />The discharge was first discovered on Monday, June 26, 1995 at <br />about 9:45 a.m. Approximately 67.5 gpm was flowing from the mine. <br />The discharge was inspected on Wednesday and Friday of the same <br />week and the flow was decreasing quite rapidly. <br /> <br />4-111 <br />Rev. 04-13-96 <br />