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- Advantages and disadvantages of the alternatives: <br />- The least expensive alternative is Alternative 2A. This alternative provides the lowest flow <br />capacity. Alternative 2A relies on the integrity of the existing concrete bulkhead wall near <br />the mid - section of the outlet conduit. <br />- The most expensive alternative is Alternative 3, which would essentially preserve the <br />existing outlet work layout and operation. <br />- Alternative 1 proved the greatest flow capacity. The mid - section pipes would remain in <br />place and it would be possible to restore mid - section flow control in the future if desired. <br />- Alternatives 2 and 3 were eliminated from consideration because similar results can be obtained <br />from Alternatives 2A and 3A, respectively, at a lower cost. <br />Selected Alternative <br />The Pisgah Reservoir and Ditch Company chose Alternative 1 as their preferred alternative. <br />Project Description <br />The selected alternative consists of removing the existing downstream control valves and installing <br />a new upstream control valve on the existing outlet works intake structure located near the <br />upstream toe of the dam. <br />Assumptions <br />- The reservoir will not be drained, and all construction work will be performed under partial or full <br />reservoir head. <br />- The dam will retain is classification as a large size, significant hazard dam. <br />- Outlet drawdown capacity will meet current operational criteria and State Engineers Office <br />minimum drawdown criteria for a high hazard dam. <br />- A single upstream hydraulically operated gate will be used for both flow control and SEO <br />drawdown requirements. <br />- Electrical power, 220 volt - single phase, is currently available to the existing valve house and will <br />remain available for operation of the hydraulic system for the new control gate. <br />- The existing valve house will be removed and replaced with a new structure that will be located in <br />the same place. The existing concrete foundation and walkway will be used for the new valve house <br />structure. <br />- No additional surveying will be required. <br />- All materials required to be removed for construction purposes will be stockpiled at the site and <br />will remain the property of the Company. <br />- The existing concrete intake structure will not be removed and replaced but will only be modified <br />to the extent necessary to accommodate the proposed improvements. <br />- No modifications to the outlet discharge into the creek channel are included in the design. <br />- The Company will flush deposited sediment in the bottom of the outlet tunnel prior to the <br />commencement of construction activities. This impact will be minimal. <br />- Costs included are for design, plans, specs and required SEO submittals. Detailed costs for Phase II <br />Bidding and Procurement and Phase III Construction will be developed upon completion of the <br />design documents. <br />Maps <br />See Appendix E for Study Area maps and aerial photo. <br />