Y--Bonneville Lock and Dam Washington Shore Ladder Entrance Modifications

This work is located at Bonneville Lock and Dam, Washington Shore Fish Ladder. Contractor access to the work site will be primarily from SR-14 on the Washington side of the Columbia River. This work is for improvements to the entrance (downstream end) of the Washington shore fish ladder. The improvements are to address existing lamprey fish passage delays. Work elements include water management, dive work, concrete cutting and boring, steel fabrication, fabrication and installation of gravity water supply system, fabrication and underwater installation of Lamprey Flume System, maintaining the fish ladder in a dewatered state, Government Furnished Property relocation, Government Furnish Property installation, crane support for research operations, and additional work as indicated in the Specifications and Drawings. Construction methods will include dive work, dewatering, concrete demolition, concrete construction, steel erection, mechanical installation, and electrical installation. The construction work will be required to interface with on-going operations, other construction contractors, in-water work seasons, existing avian wire array downstream of the dam, and spillway operations for fish passage. The improvements consist primarily of a gravity water supply system which feeds water to a Lamprey Flume System (LFS). The gravity water supply pulls excess screened water from the Down Stream Migratory (DSM) dewatering system which is capable of providing 52.5 cfs (70 cfs maximum) to the Lamprey Flume System. The gravity supply system begins with a collection trough located after the overflow weirs which control the dewatering of the DMS. The collection trough is roughly 33.5 feet in length and spans across all or part of weirs 12 thru 16. A slide gate in the trough provides closure to the top to the gravity water supply pipe. A 36 inch pipe, roughly 375 feet long, will convey the water out of the DSM structure, down the hill and under the road and through the upper part of the fish ladder to connect to the water supply header. The water supply header is a manifold of smaller pipe branches that feed the diffusers of the Lamprey Flume System. The LFS is submerged in the tailrace and attached to the south wall of the fish ladder. The LFS is roughly 130 feet in length and branches into two picketed entrances. 4 Pit Tag Detectors will be integrally installed as components of the LFS. Located near the entrance to the fish ladder, in the Lamprey Flume System (LFS) Valve Room, a PLC will control a butterfly valve to maintain the flow in the Lamprey Flume System at an adjustable set point.