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• i t <br /> URS Operating Services,Inc. ARR for ESI/61imar <br /> START,EPA Region Vlll 0 Recision: t <br /> Contract No.68-WS-0031 Date: lion: 8 <br /> Page 10 of 37 <br /> discharge downstream to Dillon Reservoir. Concentrations of these elements gradually decreased <br /> as the distance from the site increased. <br /> Chromium, silver, and zinc were detected at elevated concentrations in dissolved metals samples <br /> farther downgradient of the site on Tenmile Creek. Chromium and silver were detected at elevated <br /> concentrations approximately one mile downstream of the CM NPDES outfall. Zinc was detected <br /> at an elevated concentration at approximately two miles downstream of the CM NPDES outfall. <br /> TOTAL METALS-SEDIMENTS: <br /> Total metals values from analysis of sediments collected from Tenmile Creek were compared to two <br /> different upgradient data sets. Upgradient data sets for the Tenmile mining district and the Climax <br /> Mine had minimal differences. Comparative results showed only differences between elevated <br /> concentrations of copper and molybdenum. Because of these differences, these data sets will be <br /> discussed in separate paragraphs. <br /> Sediment metals analysis from the Tenmile mining district indicted elevated concentrations of <br /> molybdenum at the CM NPDES discharge downstream to Dillon Reservoir. Arsenic,copper,silver; <br /> and zinc were detected at elevated concentrations in sediment samples farther downgradient of the <br /> site on Tenmile Creek. Arsenic was detected at elevated concentrations at approximately one,three, <br /> and four miles downstream of the CM NPDES outfall. Copper was detected at elevated <br /> concentrations at approximately four and five miles downstream of the CM NPDES outfall. Silver <br /> was detected at an elevated concentration at approximately eight miles downstream of the CM <br /> NPDES outfall. Zinc was detected at an elevated concentration at approximately four miles <br /> downstream of the CM NPDES outfall. <br /> Total metals analysis in comparison to the Climax Mine indicted elevated concentrations of arsenic, <br /> copper, molybdenum, silver, and zinc in sediments collected from Tenmile Creek. Arsenic was <br /> detected at elevated concentrations at approximately one,three, and four miles downstream of the <br /> CM NPDES outfall. Copper was detected at elevated concentrations at approximately four and five <br /> miles downstream of the CM NPDES outfall. Molybdenum was detected at an elevated <br /> concentration at approximately five miles downstream of the CM NPDES outfall. Silver was <br /> detected at an elevated concentration at approximately eight miles downstream of the CM NPDES <br /> 75-51119.00 <br /> F:\START\CLIMAX\Final.ARR\CLIMAX.TXT.%pd:bas <br />