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Alternative 3— New Spillway and slide gates, employing existing radial gate <br /> The third alternative would be to demolish and rebuild the entire spillway structure utilizing <br /> the existing radial gate. The proposed structure would be a complete replacement of the <br /> structure (in-kind) and include two new 4-foot x 4-foot slide gates at the head of the canal, <br /> and a new concrete spillway with access bridge. The existing structure and temporary repair <br /> would be demolished and removed. The new structure would be constructed in the same <br /> location with an improved foundation and tie-in to the canal bed and banks. The existing <br /> radial gate would be reused to allow sediment flushing and the canal to spill in the event of <br /> emergency. The proposed structure would include stop log slots around all gates to allow <br /> for operational flexibility and ease of maintenance. The primary drawback of this alternative <br /> is that it will be difficult to maintain a watertight seal using the existing radial gate, and that <br /> the rate of leakage will be unacceptable in a water-short ditch suffering from prolonged <br /> drought. Construction of the spillway structure is estimated to take approximately 2 months, <br /> beginning in January, 2015. The total estimated cost for Alternative 3 is approximately <br /> $330,000 (cost estimate provided in Appendix D). <br /> Alternative 4 - New spillway, slide gates, and new overshot gate in-lieu of radial gate <br /> The fourth alternative (preferred) would be to demolish and rebuild the entire spillway <br /> structure employing an automated overshot gate in-lieu of the existing radial gate. An <br /> overshot gate offers a number of advantages over a radial gate in this application. First, an <br /> automated overshot gate would allow water control over a range of elevations, maintaining <br /> consistent canal deliveries at the Company's in-priority diversion rate. Second, an <br /> automated overshot gate can include high-water alarms to allow the gate to respond to <br /> upstream flooding by spilling the ditch. The alarms can also include automated notification <br /> to the ditch superintendent. Third, an overshot gate can also be lowered to flush sediment <br /> from the canal. Construction of this alternative is estimated to take approximately 2 to 3 <br /> months, and would be completed during the 2015 off-season. The total estimate cost for <br /> Alternative 4 is approximately $400,000 (cost estimate provided in Appendix D). <br /> September 2014 Draft <br /> Page 114 <br />