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 penstocks.
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.
