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<br />O;11'7":>C <br />U..) .:.. .': U <br /> <br />HYDROPOWER <br /> <br />Outcome <br /> <br />As evidenced in past minimum flow releases through the <br />powerplant at Navajo Dam, the generating unit experiences <br />cavitation at flows below 350 cf~. Damage noted after the <br />Test was slight "frosting" (erosion) on the leading edge of the <br />turbine blades. No other damage was observed, but it is <br />anticipated further damage would be associated with long- <br />term flows of less than 350 cfs. <br /> <br />During the Test, the minimal variation in power production <br />seemed to have a significant effect on noise from the unit. <br />The noise from the turbine runner sounded like gravel <br />passing through the unit, and there appears to be a direct <br />correlation with the wicket gate adjustment on the unit and <br />the noted noise. As the wicket gates are closed to reduce the <br />passing flows to the generating unit, the noise in the <br />generating unit appears to increase. <br /> <br />The hydropower generating unit is owned and operated by <br />the city of Farmington. The unit has averaged 15.4 mega- <br />watts (MW) daily power generation capacity since it was <br />installed in 1989 and was initially designed to provide <br />optimum power generation at release flows of 1,000-2,000 <br />cfs. <br /> <br />Method <br /> <br />Before the Test, the unit was opened, inspected, and <br />photographed in detail to note existing conditions. The unit <br />was also inspected immediately after the Test to document <br /> <br />-20- <br /> <br />Summer Low Flow Report - November 2001 <br />