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approximately 6 feet. The amount of gate opening can also be estimated by visually <br /> observing the take-up on the wire cables on the drum hoist. When the gate is open 6 <br /> feet, the top of the gate will be approximately 1 foot lower than the top of the operation <br /> deck. <br /> • If the water surface elevation rises to 875.5 feet, maintain Gate No. 2 at 6 feet and open <br /> Gate No. 1 (south gate, farthest from the main weir) 6 feet. Close the Main Street Bridge <br /> to all traffic except emergency vehicles if this has not already been done. <br /> • If the water surface elevation rises to 876.2 feet, maintain Gates Nos. 1 and 2 at 6 feet <br /> and open Gate No. 3 (north gate, nearest to the main weir) to the full open position. (All <br /> gates are equipped with switches that will automatically shut off when the gate reaches <br /> its full open position.) Close the Main Street Bridge to all traffic if this has not already <br /> been done. <br /> • If the reservoir water surface elevation rises to 877.0 feet, maintain Gate No. 3 full open <br /> and open Gates Nos. 1 and2 to the full open position. <br /> • If the reservoir water surface lowers to elevation 871.3 (crest of the overflow weir) at any <br /> time during opening of the gates, then begin closing the gates. Close only one gate at a <br /> time. Close Gate No. 3 first, followed by Gate No. 1, and finally Gate No. 2. Close the <br /> second and third gates only after the previous gate has been closed completely and the <br /> reservoir water surface is at or below 871.3 feet and continuing to drop. <br /> Never stop the gates when water is flowing over the top and under the bottom at the same time. <br /> When open, the top of the gate should be well above the reservoir water surface elevation. If <br /> water flows both over and under the gate at the same time for a prolonged period, vibration may <br /> damage the gate. <br /> NOTE: The fuse plug dikes are designed to be overtopped and erode during extremely large <br /> floods. The increase in reservoir level caused by inflowing flood water will be delayed by this <br /> erosion, and the impact of the flood flow downstream will consequently be reduced. The fuse <br /> plug dikes are constructed of fine sand and silty sand and have been seeded to provide a lawn <br /> area and prevent surface erosion. Neither sand bags nor any other type of erosion protection <br /> should be placed on the embankments to prevent overtopping. <br /> 67 <br />