The rehabilitation will consist of upgrading the East and West Low-Level Outlet (LLO) Works isolation/maintenance and flow regulating gate equipment. The existing 150-foot tall cylindrical, steel isolation gates in each outlet tower will be demolished and replaced with new isolation butterfly valves, added to the existing buried conduits. The existing downstream, dual high-pressure slide gates have suffered long-term operation problems. The oil hydraulic operating machinery for these gates, all require upgrades. A new control building will also be added to operate the gates as well as other monitoring functions. Dredging of the reservoir immediately in front of the intakes, to remove years of accumulated shotcrete debris from the dam domes, will be required to unblock the flow entrances to the towers.
Design, supply, and installation of two new, electrically operated isolation 96-inch diameter butterfly valves, fittings, and couplings to connect them to the existing steel conduits. One new hydraulic power unit (HPU) system, complete to replace the two-existing problematic HPU’s to operate the 4 existing hydraulically operated bonneted slide gates.
New electrical local and remote-control system for the four (4) existing hydraulically operated bonneted slide gates. Underwater installation and removal of a new, temporary isolation bulkhead to permit dewatering of the low-level conduits in support of the construction. Dredging, removal, and disposal of gunite debris (from old dam dome coating) now submerged in the reservoir and impinging on the outlet tower entrances. Will require underwater work. Demolition of two off-site wood-framed house structures.
Demolition of a section of the two existing low-level conduits for the addition of the new butterfly isolation valves and modifications to the existing valve vaults to suit. Repainting of the full length of the two existing low-level conduits. Selective modification to a section of each of the two existing 96 in. steel conduits to incorporate a new thrust block structure. Repair of existing reinforced concrete paving slab under the central dome at the powerhouse.
Demolition and removal of two existing 150 ft. high by 8.75 ft. diameter cylinder gates, hydraulic operating machinery, and appurtenances which will require underwater work. Underwater removal, rehabilitation, and re-installation of 16 existing intake trash racks sections. Removal of existing stilling well structure on the west outlet tower and supply and installation of a series of new stilling wells and water level sensor equipment.