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<br />,. .~ ' <br /> <br />no 16 3 9 Affected Environment & Consequences <br /> <br />3-27 <br /> <br />. F!Qro evaluation of data obtained by the USGS, primary sources of selenium to the <br />, Gunnison River are drain RD1, the North Fork of the Gunnison River, and the Bonafide <br />Ditch. Overall selenium concentrations in the Gunnison River above Delta range from <br />about 1 microgram per li ter (J..l.gll) at the North Fork confluence to about 4 J..l.gll at Delta. <br />These values were derived using summer irrigation flows. <br /> <br />During the summer, the proposed AB Lateral Project would decrease flows below the <br />Hartland diversion by about 7 percent. This means dilution would decrease in the same <br />proportion. Concentrations would increase by about 7 percent, reaching 1.1 j.lgll at the <br />North Fork and 4.3 j.lgll at Delta. <br /> <br />Less is known about winter concentrations, as no intensive water quality monitoring has <br />been done. However, the USGS did monitor conditions at station GUN4, which is just <br />upstream of the confluence with the Uncompahgre River. In 3 winter samples, selenium <br />concentrations ranged from 3 to 5 j.lgll and averaged 4 j.lgll. During the winter months, <br />the proposed Project would reduce Gunnison River flows by 20 to 40 percent, thus <br />reducing dilution by the same amounts. Assuming that the water at the Gunnison Tunnel <br />is pure, selenium concentrations could increase by 25 to 65 percent. Thus, selenium <br />levels during the winter could reach 5 to 7 j.lgll in the Hartland reach during the winter. <br />The Project would not introduce any new selenium; it would only increase concentrations <br />in the 3-mile Hartland reach. <br /> <br />Although any increase could be considered adverse, it is important to consider that the <br />increase during the summer months, when pikeminnow use has been documented, is <br />inconsequential (Jess than O.3j.lgll). The cumulative concentration during the summer is <br />still below the criterion of 5 j.lgll for protection of aquatic life. During the winter, when <br />pikeminnow use has not been documented, ambient concentrations may increase by 1 to <br />3 j.lgll, which would increase ambient concentrations to the 5 to 7 j.lgll range. The <br />Sponsors believe this would not adversely impact the pikeminnow, for the following <br />reasons: <br /> <br />. According to the 1991 Recovery Implementation Plan, pikeminnow exhibit very little <br />movement in the winter, and have demonstrated a preference to spend winters further <br />downstream in warmer waters. Thus, it is probable that they would not venture into <br />the Hartland reach during the times of principal project impact. <br /> <br />. The 5 j.lgll selenium target is already exceeded 50 percent of the time in the lower <br />Gunnison (Redlands area) and 37 percent of the time at the Utah state line. A <br />USFWS chart shows average selenium at the Utah/Colorado state line to be 7j.lgll. <br />Eleven USGS measurements for the Gunnison River at Whitewater (downstream <br />from Delta) averaged 6j.lgll. Thus, even if pikeminnow were to enter the Hartland <br />reach during the winter, selenium concentrations would still be equal to or less than <br />the concentrations in other occupied habitat. While lower concentrations would be <br />attractive, the species can clearly tolerate concentrations in the range expected to <br />occur as a result of the proposed Project. Concentrations of selenium downstream <br /> <br />AS Lateral Hydropower Project <br /> <br />July 2000 <br />