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Architecture & Engineering

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January 27, 2014

Best in State: Gold award
Future value to engineering profession

Photo courtesy of MWH Americas [enlarge]
The Lower Baker Dam floating surface collector transported more than 200,000 salmon smolts in its first season of operation — more than four times the previous record.

MWH Americas

Project: Lower Baker floating surface collector

Client: Puget Sound Energy

MWH Americas was retained by Puget Sound Energy to design a new floating surface collector (FSC) to attract, collect and transport migrating fish downstream of Lower Baker Dam near Concrete, Wash.

The FSC is a second-generation collector, patterned after the first surface collector, which was installed at the Upper Baker Reservoir by PSE in 2008. MWH worked with PSE engineers and biologists to propose enhancements to the existing FSC design and to design a new, improved FSC and associated facilities at Lower Baker.

The Lower Baker FSC, completed in early 2013, is a floating fish-capture facility for downstream migrants and is held in position in the reservoir by a series of tensioned mooring lines back to the shore. With a dry weight of nearly 1,000 tons, the hull of the FSC is 140 feet long, 60 feet wide and 24.5 tall from the bottom of its belly tanks to the top of deck.

Downstream migrating fish are guided to the FSC by a guide net that extends across the full depth and width of the reservoir, and a net transition structure. The FSC contains attraction flow pumps, fish screens, holding ponds, and fish handling and transport facilities.

A transport vessel shuttles the fish to a shore-based pier where a jib crane is used to lift the transport tank and load it onto a truck. Downstream migrants are released below the dam near the mouth of the Baker River to continue their migration to saltwater.

The Lower Baker FSC was placed into operation in 2013 and was successful in collecting and transporting over 200,000 salmon smolts in the first season (over four times the previous record). In addition, recapture of tagged and released coho was 92 percent, which also greatly exceeded the previous record recapture rate.

Assisting MWH with the design were Elliott Bay Design Group and Moffatt & Nichol. Skanska USA was the general contractor.

The Lower Baker floating surface collector improved technology to enhance downstream fish migration, and in its first season of operation the project successfully captured and transported record numbers of fish. The successful project was a perfect example of a collaborative engineered solution by PSE and MWH Americas.

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