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<br />001G87 <br /> <br />Table 3. - Discharge Capacities for May-June, Navajo Reservoir (in fi3/s) <br /> <br /> RWS Elevation 6030 RWS Elevation 6050 <br />Feature Flow Equation Discharge Curve Flow Equation Discharge Curve <br />Main Outlet 3,787 3,690 3,908 3,800 <br />Aux. Outlet 1,640 1,570 1,702 1,640 <br />Subtotal 5,427 5,260 5,610 5,440 <br />Additional flow 573 740 390 560 <br />for 6,000 ft3/s <br /> <br />Operations at higher than normal reservoir levels in May and June would increase the discharge ; <br />capacity of the main outlet works to a maximum of 4, II 0 it'1s, and the auxililU)' outlet works to a l <br />maximum of 1,800 fi3/s, at reservoir elevation 6085 (based on the flow equations), for a combined <br />discharge capacity of 5,910 fi3/s. Alternative structural modifications to increase the discharge <br />capacity of the main outlet works by up to 450 ft3/s, and the auxiliary outlet works by up to 220 <br />fills, may be sufficient to meet the desired total release without using the canal outlet works, but <br />at a significant cost. Concurrent operation ofthe existing 30-inch hollow-jet valve would increase <br />total discharge capacity by about 100 fi3/s, but could promote cavitation in the upstream X 10- <br />inch-diameter pipe and is discouraged. Concurrent operation of the City of Farmington's power <br />plant at levels necessary to avoid cavitation damage to the units would actually reduce the total <br />discharge capacity of the main outlet works, and would require greater canal releases to meet the <br />6,000 fills downstream requirement. <br /> <br />In order to achieve the maximum possible discharge capacities of both the main and the auxiliary <br />outlet works, the current operating restrictions must first be removed. This will require close <br />inspections of all hydraulic features, mechanical repairs, operational testing, and possible <br />structural modifications, as discussed in the following sections. <br /> <br />ill. Hydraulic Model Studies and Field Testing <br /> <br />A. Main outlet works <br /> <br />The main outlet works was designed to serve as the primary diversion structure during dam <br />construction, without gates and valves. Following diversion, the main outlet works was modified <br />by the installation of the fixed-wheel gate and steel pipe, and the downstream hollow-jet basin was <br />completed with two 72-inch valves. Due to the need for achieving a stilling basin that could both <br />meet the demands of diversion and future outlet works operation, the hollow-jet basin was <br />designed to be somewhat larger than the standard design criteria recommended. The basin, as <br /> <br />10 <br />