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OOlG85 releases can be a major contributor to the entrainment of rock material in the flow. Based on the previous model study findings, it is likely material residing iri the outlet works stilling basin prior to high flows will be flushed out of the basin into the rock trap. However, for the same conditions, additional material may be pulled onto the apron from peripheral areas around the basin. During subsequent operation at intermediate flows (- 3,000 ft3/s), much of the material could move back into the basin. Following the operational testing, a second ROV inspection of the stilling basin, rock trap, and apron should be made to document changes in the quantity and location of material. Some structural modifications may be necessary for higher flows. Prior to operation of the auxiliary outlet works, the downstream discharge tunnel ,and 4- by 4-foot regulating gate should be inspected for any evidence of cavitation damage, and the conditions should be documented. Ifrepairs are found to be necessary, they should be completed prior to operation. I' Improved methods of downstream flow measurement should be considered. Discharge curves for various gate and valve openings can be prepared for both the main outlet works and the auxiliary I~ outlet works, based on hydraulic loss computations and available field data. An existing ultrasonic flow measurement device for the 110-inch-diameter pipe should be used to verify the releases through the 72-inch valves. The accuracy of the downstream gauging station for total flow measurements should also be verified. Following successful completion of the necessary inspections, mechanical repairs, operational testing, and structural modifications (if any are found to be required), it is expected that the current operating restrictions for the outlet works at Navajo Dam would be removed, or relaxed, and the discharge curve drawing (No. 711-D-447) would be revised. 28