The Lower Granite Dam Juvenile Fish Facility Outfall Pipe Relocation was a two-season project aimed at improving fish passage and survival at the facility. This project has several integral components, including offshore drilled shaft construction, crane barge work within the tailrace of the dam, upland fish facility systems upgrades requiring detailed coordination with other concurrent contracts and underwater demolition with AAC's dive crews.
The outfall portion of the project included the installation of 11 each, 60-inch diameter drilled shafts placed in the river. AAC constructed a special barge to facilitate the over-water drilling. Special anchoring devices were developed to hold both the barge and drilling casing in place against the fast-moving current. AAC's experience in offshore construction was a critical component of success for the first winter season at Lower Granite. All 11 drilled shafts were installed successfully despite significant weather and environmental challenges.
The upland work included water supply piping, fish transport piping and systems upgrades within the Juvenile Fish Facility, a variety of site civil features, electrical upgrades to the existing facility, removal of the existing outfall by AAC's divers and installation of the 36" primary bypass pipe. AAC remobilized to the project site in August, 2017 and completed the phase two installations prior to the Juvenile FIsh Facility operational deadline. All systems are currently service allowing for improved fish passage around the Lower Grante Dam.