Large Diameter PE Pipe Gets the Call in Dam Project

The Bigfork Hydroelectric project in Montana gets its water via a mile-long channel, which diverts water from the Swan River into the dam’s turbines. One component of the channel was a buried 9-ft. diameter woodstave pipe that helped direct the water into the turbines. In 2000, portions of the 100-year-old pipe collapsed and the owner of the hydro plant, Pacificorp, began evaluating replacement pipe systems.

Pacificorp decided to replace the woodstave pipe with 120 in. I.D. (10-ft.) HDPE pipe manufactured by KWH Pipe, headquartered in Mississauga, ON. The pipe, an advanced HDPE low pressure system called Weholite, was manufactured at KWH’s facility in Saskatoon, SK. Weholite is a lightweight, tough flexible piping system that works with a wide range of fittings. The piping can be assembled in a variety of ways including bell and spigot connections, Weho-seal couplings, PE fittings and extrusion welding, the method that would be used to join the pipe in this project.

Nearly 1,700 linear ft. of PE pipe was required. KWH fabricated the pipe in 42-ft. sections.

The double-walled pipe is made by extruding a rectangular section and winding it on a drum while the plastic is still hot. The sections are fused together by an extrusion welding process. Ribs approximately six inches in length separate the inner and outer walls; each wall is about 3/4 in. thick.

Each section of pipe weighed approximately six tonnes, which was relatively easy to move using standard hydraulic equipment.

The Weholite pipe will operate under internal pressure of 6.5 psi and will handle more than 350 cu. ft. of water per second. Pacificorp expects that the new HDPE pipeline’s service life will meet or exceed the woodstave line it replaced.