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c. This alternate provides vertical bar screens upstream from the headgates to prevent migrating fish from entering the power canal. Also, louvers extend from the ladder exit to the dam crest. These features will only be necessary if fish migrate through the ladder- into the forebay. d. The ladder has provisions for auxiliary water supply at the fish entrance. Water enters from the forebay through a trashrack near the ladder exit and is piped to the diffuser. A valve is provided at the diffuser to adjust the quantity of attraction water. The maximum velocity into the trashrack and from the diffuser is 0.5 fps. Additional attraction water is provided by a new sluice gate through the spillway. The drop in water surf ace at the fish ladder entrance is regulated by side-opening slide gates across the entrance openings. e. If vandalism occurred at the fish ladder, grating could be installed over the ladder pools. Grating over the trap will be included for initial security measures. 2. Description of Standard Operation. a. The vertical placement of the fish ladder entrances and exit accommodates low flow conditions as well as higher flows. A minimum 3-foot water depth i s desired i n the entrance pool and al 1 1 adder pool s during normal operation. From preliminary tailwater computations, low tailwater was calculated as elevation 4,563.0 feet. This elevation was based on a reasonable design low flow of 300 cfs, which is 50-percentile expected flow for August. The fish ladder entrance was then set at 4,560.0 feet elevation to maintain a 3-foot minimum pool depth. Using the low tailwater elevation and an upstream water surface elevation of 4,575.0 feet, the change in water surf ace elevation from below to above Redlands Diversion Dam is approximately 12 feet. The upstream water level of 4,575.0 feet elevation is the desired minimum water depth main- tained by RWPC. The basic design of the ladder uses the biological and technical criteria of 8-foot-wide, 10-foot-long, 3-foot-deep pools; 0.5 foot of head drop per pool; 1-foot-wide vertical slot; and 1-foot-wide by 1.5-foot-high orifice (slot and orifice inverts placed flush with the ladder floor). With 0.5 foot of head drop per pool and water surface difference of 12 feet (at low tailwater), the ladder has 23 vertical slot/orifice weirs and one drop in water surface elevation at the slide gate fish entrances. For this operational condition, total ladder flow is approximately 18 cfs. b. The reasonable design high flow was chosen as 6,000 cfs • passing over the spillway, which is approximately the 80-percentile expected flow for May. At the higher flows, the location of this fish 27