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Upper Basin Reservoirs Fontenelle Reservoir (Green River) Water Year 1985 Fontenelle Reservoir's 1985 water year plan of operation was fo maintain the water surface elevation no higher than 6482 feet with a lower bound of approxi. mately the minimum power pool elevation of 6474 feet. This upper elevation restric- tion was imposed due to increased seepage along the left abutment in 1982. and geologic investigations conducted in 1983. The January 9, 1985, forecast of April. July runoff was 106 percent of normal and by April 5, the forecasted Inflow had dropped 10 89 percent of normal. Fonlenelle Reservoir elevation dropped gradually from 6481 feet on January 1, to 6478 the end of March. During April unusual piezometer readings 01 water movement through the dam were noticed, and by the end of April a decision was made to gradually lower the elevation by a hall.foot per day. However, during the last week ot Apnl a piezometer focated near the powerplant had very high readings, and a decision was made to rapidly lower the reservoir elevation to 6443 feet. On May 2, releases were increased to 12.100 cfs and maintained for 4 days and then gradually decreased to match Inflow by May 14, which main- tained the new target elevation 01 approx- imately 6443 feet. The maximum inflow occurred on May 6, of nearly 5,600 cfs. The actual April-July inflow was 656 thousand acre.leet which is 77 percent of normal. DUflng August 01 1985, installation 01 a concrele core wall lest section was started to determine the feasibility of Installing a concrete core wall the entrre length of the dam. This work will be finished In August of 1986, and is pro. gressing very welt. An Environmental Assessment Report was initiated for completion in early 1986, in preparation lor letting a contract lor final modification Jf Fontenelle Dam. Total waler year inllow 10 Fonlenelle was 1.07 maf which IS 87 percent of normal. "eleases totaled 1.21 mat which includes 137,000 acre.feet 10 lower the reservoir o 6443 feet from 6482 feet. i Water Year 1986 The projected plan of operation for water year 1986 is to maintain elevation 6443 feet as near as possible with fluctuations in elevation limited to plus or minus 5 feet, if possible. This elevation range is based on maximum possible downstream releases of 10,000 cIs due to reservoir elevation and minimum releases of 400 cfs. Based on the reasonable maximum and minimum inflow operation studies, releases are expected to stay within the 400 to 10,000 cfs range throughout water year 1986. Present plans for construction modifica. tion are to have Congressional approval late in 1986, and award a contract so construction can start in the spring of 1987. The U.S. Bureau of Reclamation (Reclamation) is continuing to cooperate with the State of Wyoming to complete construction modilication. Fontenelle Active Storage' Chart 1 Reservoir Acre-Feet EI. (Ft.) Maximum Storage 344,834 6506 Rated Head 233,789 6491 Minimum Power 194,962 6485 Surface Area (Full) 8,058 Acres Reservoir Length (Full) 18 Miles Powerplant Number of Units 1 Total Capacily 10,000 Kilowatts . Does (l0! Include 563 aCle.leet 01 deaa storage belo.Y 6406 reel. ,.,-< ~\i..i~ ," ,,~....~ (~~ ~::,~:~:: ::;:~ ;'-,~",: -,.j'\... .. { , .' '"" b>, ~,-\f.''',;:',",-- "'".' (:,<: :.;;';{2:~~;~7:l,t'_. ,.;:. :';'''; ~~.~ Fomenelle Dam