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c. This alternate provides vertical bar screens upstream <br />from the headgates to prevent migrating fish from entering the power <br />canal, if necessary. <br />d. The main and auxiliary water supply for the ladder <br />enters from the forebay through trashracks located on the upstream face <br />of the diversion dam. The-water is piped to one diffuser at the <br />entrance for attraction flow, and two diffusers in the junction pool for <br />the ladder flow. The quantity of water at each diffuser is adjusted with <br />a valve. The maximum exit velocity from the diffusers is 0.5 fps. The <br />drop in water surface at the fishway entrance is regulated by a side- <br />opening slide gate. <br />e. Security fencing will be installed across the west side <br />of the sluice gate area. Also, grating will be installed to cover the <br />fish trap and provide access over the ladder. For additional security <br />measures, provisions f or future grating installation will be made to <br />cover the entire ladder, if necessary. <br />2. Description of Standard Operation. <br />• <br />a. For low flow conditions, the experimental ladder will <br />operate similar to the full-size ladder of Alternate No. 1 described pre- <br />viously. For 10-foot-long pools and 0.5 foot of head drop per pool, the <br />total ladder flow is approximately 18 cfs. This quantity of flow will be <br />regulated by the valves at the two junction pool diffusers. <br />b. At high flows and tailwater, flow could be maintained <br />at 18 cfs. Then, the backwater effect would result in head drop of 0.2 <br />foot at the downstream end of the ladder varying to only 0.23 foot at the <br />junction pool weir. If experiments were desired for 0.5 foot of head <br />drop per pool at high tailwater, the ladder flow required would be 30 <br />cfs. However, the top of the ladder walls would need to be constructed <br />higher to accommodate this larger flow and deeper pools (6 feet deep). <br />Also, larger diffusers would be required in the junction pool to distrib- <br />ute the larger flows. <br />c. This ladder will also be subject to higher flows. For <br />riverflows above 6,000 cfs and below 8,000 cfs, the upstream barrier wall <br />will protect the ladder from being overtopped by water. However, the <br />tailwater elevation at 8,000 cfs will flood the bottom pools of the <br />ladder so that it will not function properly. <br />23 <br />