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Mid-Continent Resources'Stream Impairment Study 3 <br /> In summary, Sites 2 and 3 were most affected by the 016 discharge due to high sulfate and <br /> alkalinity. Site 4 was moderately affected by sulfate and alkalinity. These three sites had flow entirely <br /> due to the 016 effluent. Site 5, which was just below the confluence of the discharge channel and <br /> Dutch Creek, and Site 7 showed low level effects during the low flow period. These effects were <br /> probably due to a combination of sulfate levels and sedimentation. The control Sites (1 and 6) may <br /> have been affected by sedimentation which was reflected in the biological condition index. Effects <br /> were most notable during the spring. <br /> Introduction <br /> Located four miles west of Redstone Colorado, Mid-Continent Resources' Coal Basin Mine <br /> lies within the watershed carrying Dutch Creek and Coal Creek to the Crystal River. Mining at the <br /> site ceased in 1991 and the mine property is currently being reclaimed. <br /> Water quality monitoring has been conducted at the mine since 1976. These data were <br /> collected at 2-3 week intervals until 1980. From 1980 until 1992, samples were collected 2-4 times <br /> per year. Biomonitoring testing in accord with an NPDES permit issued for the 016 discharge has <br /> been conducted quarterly since 1989. Aquatic toxicity tests have shown toxicity to Ceriodapht.is <br /> dubia. The beginning of the toxic events appeared to coincide with decreased activity at the mine. <br /> Although fathead minnows (Pimephales promelas) have also been tested as part of the aquatic <br /> toxicity testing program, this species has not shown any sensitivity to the mine effluent. <br /> Under the NPDES requirements, Mid-Continent Resources initiated a THE/TIE (toxicity <br /> reduction evaluation/toxicity identification evaluation) to determine the possible causes of toxicity. <br /> These investigations concluded that high alkalinities which contributed to a high TDS were a probable <br /> cause of the observed effluent problems. <br /> Under guidance from the Water Quality Control Division (WQCD) of the Colorado <br /> Department of Health, a comprehensive stream impairment study was initiated to determine the <br /> possible effect of the mine discharge on aquatic life downstream of the discharge. The assessment <br /> incorporated studies of aquatic toxicity tests (Ceriodaphnia and Hyalella azteca); characterizations <br /> of habitat, water quality, and physical characteristics; and benthic invertebrate surveys. <br /> Study Area <br /> The North Fork of Dutch Creek begins at an altitude of approximately 9250 feet and flows <br /> through the Mid-Continent Coal Mine Basin to a confluence with Coal Creek (Figure 1). Coal Creek <br /> originates at approximately 9800 feet and joins with the Crystal River at the town of Redstone, <br /> Colorado. Mine drainage enters Dutch Creek from a series of settling ponds which lie below the main <br /> Rock Tunnel Portal and the tunnel excavation disposal pile. Additional mine drainage enters Coal <br /> The SeaCrest Group <br />