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<br />The pesticide sample collected in July at site 5 (the Garnet Canal <br />diversion) had detectable concentrations of 2,4-D, parathion, and carbofuran <br />(table 17). The sample from Sweitzer Lake had parathion detected at the <br />reporting limit of 0.01 ~g/L. Parathion concentrations at Sweitzer Lake were <br />considerably smaller than parathion concentrations in the Gunnison and <br />Uncompahgre Rivers. <br /> <br />Excluding the sample collected near the lake bottom in March, the <br />selenium concentrations in Sweitzer Lake (site 7) reported for this recon- <br />naissance investigation were less than the largest concentrations reported by <br />previous studies of Sweitzer Lake (80 ~g/L by the Colorado Division of <br />Wildlife in 1974 and 45 ~g/L by the U.S. Bureau of Reclamation in 1978). <br />There may be more flushing of the lake since the mid-1980's because of the <br />installation of the new headgate on the Garnet Canal. The water quality of <br />Sweitzer Lake described in this report probably will not change in the near <br />future as long as the current (1989) operation of the lake continues, which <br />features a nearly continuous surface inflow into the lake. <br /> <br />Bottom-Sediment Results <br /> <br />Six bottom-sediment samples were collected for trace-element analysis; <br />trace-element concentrations in the less than 0.0625-mm size fraction and <br />the less than 2-mm size fraction are listed in table 18. Three samples were <br />collected for analysis of a standard suite of chlorinated insecticides plus <br />PCN and PCB; these data are listed in table 19. (Tables 18 and 19 are in the <br />"Supplemental Data" section at the back of the report.) The trace-element <br />data were compared to baseline geochemical data for soils for the Western <br />United States (Shacklette and Boerngen, 1984) and to bottom-sediment data <br />collected for the nine initial DOl irrigation-drainage reconnaissance studies <br />(Severson and others, 1987) (table 12). The data for soils from Shacklette <br />and Boerngen (1984) represents analyses of the less than 2-mm size fraction, <br />and the data from Severson and others (1987) represents analyses of the less <br />than 0.0625-mm size fraction. The baselines for soil listed in table 12 were <br />not in Shacklette and Boerngen (1984), but were computed from the information <br />presented in that report. Only the range of values for the DOl irrigation- <br />drainage studies was reported by Severson and others (1987). The results in <br />this report also can be compared to the data for soils near Delta and in the <br />Grand Valley (Grand Junction area in fig. 1); those data were summarized in <br />table 5 in the "Previous Investigations" section of this report. <br /> <br />There were no major differences between trace-element concentrations <br />(table 18) in bottom-sediment samples collected from the Gunnison River at <br />site 3 (Delta) and at site 11 (upstream from Escalante Creek). The selenium <br />concentrations were slightly greater than the upper baseline for soil <br />(table 12) and the boron concentrations were less than the lower baseline for <br />soil at both sites. Boron concentrations reported in table 12 are not <br />directly comparable to the boron concentrations reported for this study. The <br />soils data represent analyses for total boron, whereas the bottom-sediment <br />samples collected for this study were analyzed only for boron that was <br />hot-water extractable. The selenium concentrations for sites 3 and 11 were <br />greater than selenium concentrations in the Grand Valley soils (table 5). <br />Uranium concentration in bottom-sediment samples collected at sites 3 and 11 <br /> <br />46 <br />