Getting the Right Dimensions: Retrofitting Fish Screens at Bigfork Hydroelectric Project                        

PacifiCorp’s Bigfork Hydroelectric Project is located on the Swan River near Bigfork, MT and includes a water intake structure and one-mile long flow line. Accumulated debris along the intake structure had to be removed by hand to clear the way for water flow into the power canal and reduce the differential between the downstream and upstream of the intake.

JR Merit recently completed a major retrofit project to demolish and remove the existing intake fish screens, trash racks, and appurtenances and install new automated traveling fish screens, blanking panels, water backwash system and piping, debris conveyor system, and a debris boom upstream of the intake. We also fabricated and installed an expanded access walkway and guardrail for around the new equipment. Construction began in late December 2021 and was completed in late February 2022.

Thorough Field Investigations Yield Precision Dimensions

Our team conducted extensive, multiple dimensional field checks to determine the precision dimensions required for fabricating the intake access platform and the underwater stainless-steel pier covers. This required verifying both above water dimensions and coordinating with a dive crew to acquire underwater column dimensions for fabrication. We field verified and modified the access platform’s construction design a couple times in collaboration with the engineer of record and completed the platform shop drawings for fabrication in our shop. Our verifications and attention to detail paid off—no field modifications were needed for fit-up and install of the platform.

Investigating the underwater stainless pier covers required close coordination with the drive crew. We provided a sketch and a table of the dimensions needed to design the pier covers. With this information, the dive crew was able to record video and data with measurements of all six piers. We use this video and data to design the new piers covers using Fusion 360’s sheet metal tools. All the pier covers fit correctly per the design and made the intake “fish tight” such that no fish can enter the power canal and pen stocks.

‍Working Around Winter Weather

A delay in the construction start date meant our crews worked through the winter months and harsh winter conditions including snow,ice, and freezing temperatures. Our crews worked nimbly and safely to execute construction in just two months despite the conditions.

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