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<br />. <br /> <br />- 4......, l.' <br />:J.)~U <br /> <br />Manganese also exceeded recommended quality criterion during 1974- <br />1975, but not during 1975-1976. Herrmann and Mahan (1976) attributed <br />much of the erratic behavior of manganese in the reservoir to <br />exchange with the sediments. They had observed that the preimpound- <br />ment sediments were not so greatly enriched in manganese. However, <br />there was considerable enrichment of .the sediments near the inlet <br />following impoundment. This manganese would be available to the <br />overlying waters given a favorable physicochemical environment. <br /> <br />Cadmium concentrations were generally below detectable limits and <br />averaged well below recommended levels (Herrmann and Mahan, 1976). <br />However, excessive concentrations were observed during 1974-1975 <br />throughout the water column near the dam, but none greater than <br />the recommended criterion were observed during the 1975-1976 <br />sampling year. The greatest concentrations of cadmium were <br />observed in the reservoir sediments at the farthest upstream <br />station, indicating possible loadings of the sediments and loss <br />of cadmium from the overlying water as it passed through the <br />reservoir. <br /> <br />. <br /> <br />Nitrate concentrations are also of concern in municipal water <br />supplies. A recommended upper limit of 10 milligrams per liter <br />of nitrate as nitrogen bas been established for both raw source <br />water and finished drinking water (EPA, 1976; Colorado Department <br />of Health, 1977). During studies of the reservoir, nitrate concen- <br />trations were not monitored. However, the Geological Survey monitors <br />nitrate levels upstream and downstream from the reservoir. These should <br />reflect the effects of passage of the water through the reservoir. <br />During WaL~L L~ar-1975, toe upstream and downstream stations averaged <br />0.12 and 0.29 milligrams per liter of N03-N, respectively. At <br />no time was the recommended limit approached at either site. It <br />is not expected that the reservoir will exhibit excessive nitrate <br />concentrations. <br /> <br />Pueblo City-County Health Department has monitored fecal coliform <br />levels in the reservoir since 1975. The samples were collected <br />from the swimming areas. During June 1976 the north swim area <br />was closed to swimming due to excessive colony counts. An <br />estimated 4,000 colonies per 100 ml were found in one sample. <br /> <br />. <br /> <br />III-IS <br />