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I I 'I ,I I I I I il I ,I I I I I I I I I questionable test result due to the low mean value of a relatively large number of samples (84). However, selenium is easily coagulated and removed by the proposed treatment process, The data on turbidity and total suspended solids for these same waters show large variability throughout the year. Turbidity ranges from 1,000 turbidity units (TU) during high flow periods to 1.6 TU during low flows, while suspended solids range from 8,000 milligrams per liter (mg/l) during high flows to 5 mg/l during low flows, The gross beta radiation value of 98.00 pCi/l shown in Table IV-8 was the result of a single sample; therefore, it is questionable whether it is representative. In any event, it is assumed that the radiation source would be associated with suspended sediment which will be removed by the treatment process to reduce the turbidity to the acceptable levels, The raw water supplies would be monitored for this and the other con- taminants in accordance with EPA requirements. Other parameters of concern in selecting a water treatment process are hardness, taste, odor, color and bacterial quality, Based on the available data, hardness (as CaC03) is in the range of 230 mg/l which is not objectionable, Taste, odor and color are water quality parameters which can raise aesthetic objections from consumers. Data on the levels of these parameters in the Colorado River flows at Rifle are not known. However, the chemical feeding facilities to be provided in the treatment plant will be capable of reducing such water quality parameters below ob- jectionable levels. Bacteria concentrations in the Colorado River fluctuate considerably. Total most probable number (MPN) coliform bacteria per 100 ml have IV-15