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<br />- 23 - <br /> <br />Second cycle sediment samples on the San Miguel River below Uravan <br />show about one-fifth to one-sixth the general level of radioactivity of the <br />first cycle samples. This is probably due to the second cycle rain with its <br />increased stream flows and turbulence scouring the channel bottom to some <br />extent. This set of samples was taken near the end of the cycle, when stream <br />flows had returned to the levels found during the dry first cycle. First <br />cycle samples show radium-226 and gross alpha concentrations to be 29 ~~g/gm <br />and 260 ~~c/gm respectively, 1.6 miles below Uravan. These data and those at <br />the mouth of the San Miguel are indicative of the precipitation process occur- <br />ring along this reach of the river, as was seen in the reduction in weights <br />of dissolved radium-226 and uranium mentioned above. <br /> <br />Data for Station M-2, just above the mouth of the D~lores River, may <br />indicate the accumulation of radioactivity from all sources within the Dolores~ <br />San Miguel River system as well as the entry of contaminants from sources <br />between Gateway and the mouth of the Dolores River. Concentrations of gross <br />alpha radioactivity and radium-226 in sediment were 5 to 6 times as high at <br />the mouth of the Dolores River as at Gateway. <br /> <br />Biological <br /> <br />Bottom Fauna Studies <br /> <br />Stations B-1, B-2, and B-3, all on the Dolores River above the mouth <br />of the San Miguel, yielded few organisms per square yard. Midges (Tendipedidae), <br />beetles, water bugs, and an aquatic worm were the kinds of organisms obtained. <br />All of these are tolerant to poor quality water. <br /> <br />Station B-6, on the San Miguel River below the Naturita mill (closed), <br />some 13 miles above Uravan, yielded a large number of organisms, including <br />many which are not tolerant to poor quality water. There were 880 organisms <br />in a square yard with nine species represented. <br /> <br />Both at the station l.6 miles below Uravan and just above its mouth, <br />the San Miguel yielded about the same variety of organisms as at the station <br />above Uravan. However, there were considerably fewer organisms per unit area <br />and fewer kinds that are tolerant to pollution. Though there was a distinct <br />reduction in the number of organisms below Uravan, a significant number was <br />found, indicating that the stream provided an environment supporting aquatic life <br />in a limited way. Just below the confluence of the Dolores and San Miguel <br />pollution-intolerant organisms were found in approximately twice the number <br />and weight as on the San Miguel below Uravan. This showed an improvement in <br />the environment for bottom fauna. <br /> <br />At the time of sampling at Station B-8 at Gateway, the Dolores River <br />flowed rapidly over rocks but was warmer and more turbid than upstream. <br />Bottom fauna were scarce, with only 15 found per square yard. The poor <br />habitat at Gateway may be attributed to turbidity and temperature. <br /> <br />Table XIII lists the number of each kind of organism collected and <br />showed their total number and weight. <br />