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PART IV COLORADO RIVER WATER QUALITY ASSESSMENT e The San Miguel River below Uravan and the Dolores River below the San Miguel confluence have not consistently met the water quality stand- ard for un-ionized ammonia. These river segments downstream from Union Carbide's Uravan uranium milling site are the only instance of un- ionized ammonia attributable to an industrial source in Colorado. Several headwater streams in the basin, located in the Colorado mineral belt, are contaminated with high concentrations of heavy metals, especially lead, copper, zinc, and cadmium. Drainage from inactive mine tunnels, mill wastes, and tailing piles is responsible for much of the contamination. The major streams that do not currently meet water quality standards for metals within the basin include segments of the Eagle, Blue, Crystal, Dolores, Slate, Yampa, Animas, and Uncompahgre Rivers. Improvement to the quality of Coal Creek by treating wastewaters of the abandoned Keystone Mine by the AMAX Corporation has resulted in the restoration of aquatic life in Coal Creek. The quality of water in the Slate River below Coal Creek has also been improved as a result of this treatment. e Two new reservoirs are now under construction--Ridgway in the Gunnison drainage and McPhee on the Dolores River. Reclamation is moni- toring the inflow to these reservoirs and has agreed to install an aera- tion system to prevent Ridgway Reservoir from becoming anaerobic if a condition is found which allows heavy metals and trace elements to re- enter the water in solution. Depending on the biological availability of the pollutants from the sediments into the food chain, the fisheries, or at least the edibility of the fish flesh, may be impaired in Ridgway Reservoir and, to a lesser extent, possibly in McPhee Reservoir. If these reservoirs act as per- manent traps for heavy metals, downstream water quality could benefit. Municipal and industrial water from Dallas Creek Project's Ridgway Reser- voir will be provided by an exchange of the irrigation water for a higher quality source. This will reduce the impacts from metal pollutants. There are several major sources of salt loadings to the Colorado River that are found within Colorado. They include saline springs on the Dolores River in ~he Paradox Valley, Glenwood-Dotsero Springs, and agricultural return flows in the Grand Valley, McElmo Creek, and Lower Gunnison areas. D. Arizona e Water quality along the Colorado River is protected for agriculture, aquatic life, drinking water supply, fishing, full body contact recrea- tion, and wildlife uses by Arizona Water Quality Standards. To insure that these standards are being met, a sampling program has been imple- mented. In 1982 and 1983, 150 locations were sampled in the Colorado River Main Stream Basin in Arizona. The sampling program has not re- vealed any deterioration in the quality of water in the basin insofar as 19