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<br />001681 <br /> <br />hydraulic loss computations assuming maximum losses, and are summarized in table 4 for <br />reservoir elevations 60'30',60'50', and 60'85. Discharge curves for the main outlet works and the <br />auxiliary outlet works indicate values which are 3 to 4 percent lower than the tabulated values. <br />Current operating restrictions for the outlet works are not considered for these discharges, and no <br />releases are assumed from the power plant or the 3O'-inch hollow-jet valve. <br /> <br />I. <br /> <br />Table 4. - Summary of Discharge Capacities - Navajo Dam <br /> . , <br />Feature RWS El. 60'30' R WS El. 60'50' RWS El. 60'85 \ <br />Main Outlet Works 3,787 3,90'8 4,110' I <br />Auxiliary Outlet Works 1,640' 1,70'2 1,80'0' I <br />Main plus Auxiliary O.W. 5,427 5,610' 5,910' , <br />Canal Outlet Works 1,80'0' 1,80'0' 1,80'0' <br /> <br />Actual outlet discharges are expected to be within 5 percent of the values shown above, for the <br />operating conditions assumed. Reservoir elevations 60'30' and 60'50' represent the nonnal range of <br />operating levels for the May-June period, based on historical data. It is shown that the desired <br />6,.90'0' fi3/s peak release from Navajo Dam in May and June of each year cannot be met using the <br />existing outlet works alone. Supplemental releases to the San Juan River necessary to meet a <br />6,0'0'0' Wls downstream requirement would seem to be most easily met by using the available <br />wasteway capacity of the canal outlet works. The Cutter Dam spillway and river outlet works can <br />release more than enough for the desired total release. Some channel improvements may be <br />required along Largo Canyon, however, to accommodate the required release. <br /> <br />Operation of Navajo Reservoir at higher levels in May and June each year would increase the total <br />discharge capacity by no more than 5 percent. Alternative structural modifications to increase the <br />discharge capacity of the main outlet works by up to 450' fi3/s (11 percent), and the auxiliary <br />outlet works by up to 220' fi3/s (12 percent), may be sufficient to meet the desired total release <br />without using the canal outlet works, but the construction costs would probably be prohibitive. <br />Concurrent operation of the existing 3O'-inch hollow-jet valve would increase the total discharge <br />capacity of the main outlet works by about 10'0' fi3/s (less than 3 percent), but could promote <br />cavitation in the upstream 11 O'-inch-diameter pipe and is discouraged. Concurrent operation of <br />the City ofFannington's power plant at levels necessary to avoid cavitation damage to the units <br />would actually reduce the total discharge capacity of the main outlet works by 11 percent at <br />reservoir elevation 60'85, and by greater percentages at lower reservoir elevations. <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 /> <br />24 <br />