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<br />-5- <br /> <br />The report further states that a plan involving construction of <br />a dam at the Mustang Site is most eoonomioally justified. Suoh a dam would <br />provide flood proteotion to the lower valley and yield 5.200 aore-feet an- <br />nually of dependable oonservation benefits. aooording to U. S. Bureau of <br />Reolamation estimates. <br /> <br />The proposed dam would be a oonorete gravity type structure. 197 <br />feet in height. having aJ11l...ungated overflow spillway with a oapaoity of <br />209,000 o.f.s. The reservoir would have 20,000 aore-feetof dead storage <br />oapaoity. and the remaining additional oapaoity of 42.500 aore-feet. up to <br />the spillway ore st. would be for oonservation storage. Hydraulio studies of <br />the Army Engineers indioates that a 40,000 o.f.s. flood ooming into the re- <br />servoir, when it was full to ,thll spillway, would be reduoed to 10,000 o.f.s. <br />by tllmporary detention in the first 5-foo~ inorement above the spillway ore~t. <br />Any inorease of depth over the spillway would resultininoreased disoharge <br />ranging frolll 10 ,000 o.f.s. 1;0 209,000 o.f.s., when depth of water on the <br />spillway would range from 5 feet to 34 feet. <br /> <br />(12) Annual benefits are oaloulated as the sum of preventable <br />direot and indireot flood, losses and irrigation benefits. Benefits attri- <br />butable to flood loss prevention wereoomputed for experienoed flows and <br />greater than experienoed flows. The latter item being the estimated addi- <br />tional losses whioh might result from a 40.000 c.f.s. flood. Irrigation <br />benefits were estilTlited by '\;he U. S. Bureau of Reolalffl,tion to be $10.00 per <br />aore-foot. The following table is from the report: <br /> <br />ESTIMATED AVERAGE ANNUAL BENEFITS FOR <br />THE DUAL-PURPOSE MUSTlWG RESERVOIR <br /> <br /> I Benefits Based : Benefits Based : Total <br />Item I on Experienced : On Greater I Estimated <br /> : Flows I than Expe- I .Annual <br /> . : rienoed Flows I Benefits <br /> . <br /> I $ I $ I $ <br />Preventable direot flood losses J 2,050 I 435 J 2,485 <br />Preventable indireot flood losses: 2,b50 : 435 J 2,485 <br />Irrigation Benefits J 52.000 I . 52.000 <br />Total Estimated Annual Benefits I 56.100 : 870 . 56,970 <br />. <br /> : : . <br /> . <br /> <br />(13) Allooation of oost to irrigation is on the basis of the ratio <br />of irrigation benefits to total benefits. or 91.28% of the total oost. <br />