Cushman Hatcheries and Floating Surface Collector

As part of the expansion of their Lake Cushman Hydroelectric project, Tacoma Power retained Schnabel to plan and design two new state-of-the-art hatcheries and a floating surface collector (FSC). Schnabel served as the lead engineering design consultant responsible for the supply, treatment, and storage of the new hatcheries’ water, including yard piping, pump stations, and aeration/degassing systems. Our team was also responsible for the mechanical and hydraulic design of the entire FSC facility, which was created to facilitate the downstream passage of juvenile fish.

Completed in December of 2015, the 1.1-acre Saltwater Park Hatchery raises up to 2 million sockeye annually on the shore of Hood Canal. The hatchery’s Cornell circular tanks accommodate adult holding and final rearing. Water for incubation, rearing, and adult holding is supplied from a spring emanating from the hillside west of the Cushman No. 2 Powerhouse.

The three-acre North Fork Hatchery, which was completed in 2016, rears spring Chinook salmon, coho, and steelhead on Lake Kokanee. The hatchery’s rehabilitated well system provides incubation water while a surface water pumping station supplies rearing water. Our design for the 76 total Cornell circular raceways pioneered new solids-flushing and flow-control systems for circular raceways that have since become the standard for Cornell circulars in the Pacific Northwest.

The Cushman floating surface collector is considered a breakthrough project in downstream fish passage over tall dams. Its design is the third generation of FSCs in the Pacific Northwest. The 210-foot-long vessel incorporates design improvements that make it half the cost of similar structures, yet with better operational performance. The FSC’s 10 primary pumps and two submersible dewatering pumps create a current to attract fish, while guide nets extend out to each side of the lake to direct migrating salmonids into the facility. The 215,000-lb. structure was constructed upside down, launched into the lake, and then flipped upright by filling selected pontoons on one side of the structure to perform a controlled rollover.