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<br />001680 <br /> <br />surveys were performed on 9-, 10-, and 16-inch-diameter tie rods. Modal surveys are performed <br />using magnetic-based accelerometers, which' are attached temporarily to the tie rods without <br />surface preparation, unless the painted surfaces are extremely irregular. The tie rod is struck with <br />a 5 pound plastic-tipped hammer, from which frequencies and relative amplitudes of displacement <br />are obtained. <br /> <br />[. <br />I <br />~ ' <br /> <br />The TSC has also performed two tests at facilities where operational data was obtained from tie <br />rods. The first was at Palisades Dam in March 1982, when tests were performed on two tie rods <br />located at wye branches. The pipe installation was similar to that at Navajo Dam. A 1-I/2-inch- <br />diameter hole was drilled through the concrete and steel pipe, at a location two feet upstream of <br />the tie rod to be instrumented. Strain gages were mounted at the top of the tie rod, and the wires <br />were fed through a special watertight fitting installed in the pipe. Data were collected of the <br />strains and frequencies for a range of discharges. A similar test, also requiring drilling through <br />concrete and a steel pipe, was performed at Glendo Dam in May 1983. We are currently <br />scheduling tests at Hoover Dam to obtain operational responses from two tie rods. <br /> <br />B. Auxiliary Outlet Works <br /> <br />1. 4- by 4-foot tandem outlet gates. - The 4- by 4-foot outlet gates are hydraulically operated. <br />There are two gates in tandem (series). The upstream gate is a guard gate and the downstream <br />gate is for flow regulation. The downstream gate has two hydraulic operating systems. One was <br />originally provided by Reclamation, while the other system, which is newer, was provided by the <br />City ofFannington for remote operation should the power plant experience a transient generation <br />event requiring shutdown of the main outlet works. The City ofFannington's hydraulic system <br />will then operate the auxiliary outlet works regulating gate to maintain flow in the San Juan River. <br /> <br />The City ofFannington's hydraulic system was designed as a mirror of the original Reclamation <br />system. There are no common controls between the systems. As a result, it is possible to pump <br />all the oil from one system into the reservoir of the other system and fail to operate the regulating <br />gate [20]. This would not cause a failure, but it could dump oil into the drain or require operation <br />of the guard gate at high flows. It is likely some Cavitation damage would result from such an <br />event. ' <br /> <br />Long term operation of the 4- by 4-foot outlet gates at flows above 1,700 fWs, and at reservoir <br />levels above elevation 6050, would substantially increase the possibilities of cavitation damage. <br />The gates have been operated in these ranges in the past, with some minor cavitation damage <br />occurring. Operation of the auxiliary outlet works extending beyond 7 days at these levels should <br />be expected to cause some damage, requiring inspections before and after sustained operations. <br /> <br />V. Conclusions <br /> <br />Discharge capacities for the existing outlet works at Navajo Dam have been estimated based on <br /> <br />23 <br />