Laserfiche WebLink
<br />Chapter II Description of Alternatives 20 <br /> <br />wave, and earthquake loads. <br /> <br />The structure would extend from below the trashrack at approximate elevation 3,445 to the <br />maximum water surface of3,7l5. A hoist deck would be provided at the top of the structure <br />at elevation 3,715. A combination of solid cladding panels and gates would be provided to <br />control the flow of the water into the structure. Cladding panels would be provided on the <br />bottom and along the sides from the bottom elevation of 3,435 feet to elevation 3,670. These <br />cladding panels would seal the bottom and the sides of the structure to the dam and prevent <br />inflow of water during turbine operation. <br /> <br />A series of cladding panels and gates would be provided on the upstream face of each <br />structure to allow selective withdrawal of the water from various elevations. The upstream <br />face of the structure would be configured as follows: <br /> <br />Trashracks would be provided on the upstream face of all gates. Each gate would have a <br />dedicated slot to provide unlimited movement of the gate within its operating range and for <br />removal of the gates. A hoist/operating deck would be provided on the top of the rigid frame. <br />This deck would contain hoists and controls to facilitate individual operation of each of the <br />gates. <br /> <br />Additional trashracks would be provided on the two sides of the structure and on the front of <br />the structure between elevation 3,670 and the top of the structure. This would allow <br />overdraw on all three sides during high water levels. <br /> <br />The external frame structure allows maximum flexibility in the withdrawal of various levels <br />of water from the reservoir. The upper and middle gates can be used to follow the water <br />elevation of the reservoir and allows withdrawal of warm water as required at water <br />elevations from 3,710 feet down to 3,580 feet. The lower gate can be used at any time to <br />withdraw the colder water from the penstock elevation. This would serve to conserve the <br />warmwater pool near the top of the reservoir. <br /> <br />Proposal No. SA - Air-controlled curtain to direct flow into penstocks. The initial <br />appraisal level construction cost of this proposal is $14,500,000. The life cycle cost of this <br />proposal is $26,000,000. Life-cycle cost was calculated for this proposal due to its short <br />service life. Failure of the curtain could be catastrophic, since the curtain could float into the <br />dam and plug the penstocks. The benefits of this proposal were moderate costs and low head <br />loss. The disadvantages of short service life, potential failure, and high maintenance made <br />this proposal infeasible. <br /> <br />The air-controlled curtain concept consists of a 60-mil fabric reinforced Hypalon-rubber <br />curtain that would span across the canyon approximately 500 feet upstream of the dam. The <br />canyon is approximately 1,000 feet wide at this location. The top of the curtain is at <br />elevation 3,650 and the bottom is at elevation 3,250. <br /> <br />The curtain would be configured in four horizontal sections, each approximately 100 feet <br />wide. The bottom two sections extend from elevation 3,250 to elevation 3,450 and would be <br />