In May 2015, Columbia Energy finished a unique fabrication project: The Cowlitz Rotary Screw Trap (RST). The screw trap is used to catch, examine and analyze juvenile fish. In October 2014, Columbia Energy was contracted by the Tacoma – Power Generation. The Cowlitz RST is placed in the lower Cowlitz River to evaluate the abundance of all hatchery and natural-origin salmonids and to collect genetic samples from natural-origin Chinook proportional to their weekly outmigration abundance. The Cowlitz RST also determines the migration timing and speed of the Cowlitz Salmon and Cowlitz Trout hatchery smolt releases, and evaluates the hatchery-origin smolt predation on naturally produced salmonid juveniles.

“Basically we want to know what the juvenile Chinook are doing in the lower Cowlitz River, and are the hatchery fish eating the natural-origin (wild) fish,” said Mark LaRiviere, Senior Fisheries Biologist for Tacoma Power.

The Beginning of the Cowlitz Rotary Screw Trap

The Tacoma Power sent Columbia Energy a cellphone picture of the blueprint of a similar pontoon boat built in the 1970s. From there, the Columbia Energy Fabrication Team had to piece together the design to build something that functioned to the expectations of the client.

Columbia Energy was very proud to have been given the opportunity to finish such a unique project. Most commercial pontoon boats are about 12-feet wide, making it insufficient for the scope required by the Tacoma Power Fisheries. The Tacoma Fish Trap designed and built by Columbia Energy is 15,500 pounds, 40 feet long and 15 feet wide. Columbia Energy designed and built the deck, arches, nose cones, tables, and the boat. The project started in October and shipped in May.

“We bid on the fabrication of a pontoon boat, but we agreed instead of fabrication job it had to be a design-build project, so it progressed from the initial scope,” said Frank Dunn, Director of projects at Columbia Energy, “it was also unique in that it was done with aluminum welding, they hadn’t seen fabrication of the quality we were able to produce so we were extremely happy.”

For more information on Columbia Energy Machining and Fabrication services visit