A new coat of protective paint will be applied to BC Hydro’s large steel penstock beside the Puntledge River. The work, to protect the steel from corrosion, will take place between spring 2019 and summer 2020. Some occasional public closures to certain sections of the penstock corridor will take place when the work is happening.
“The project is an internal and external recoating program with other related equipment improvements,” said BC Hydro spokesperson, Stephen Watson. “The recoating work will extend the life of the penstock by decades. This includes stripping and recoating the external, above-ground coating including trenching to repair the transition to the protective coating for the buried section. There will also be minor repairs to the penstock steel shell. To do the work, there will be site modifications for access and staging – some of that work has already happened.”
Where there are activities, sections of the penstock corridor may be temporarily closed off to public access. Site safety signage will be updated as needed.
“When we removed the old concrete penstocks a few years ago, people respected our safety closure zones and we look forward to the same adherence for this work,” said Watson.
The steel penstock is partly buried with about a third of it in the ground. The buried underside of the penstock was coated with coal tar enamel during installation in 1954, and the above-ground exterior was coated with an epoxy system.
The exterior recoating for this project is a type of urethane system. Before it is applied, the surface will be prepared using high-pressure water jetting, and then abrasive blasting with garnet to get to a clean steel surface. The existing penstock graffiti tags, which is vandalism, will be removed by the project and the new exterior coating on the penstock will be forest green.
“We were due to recoat the penstock interior earlier but pushed the work out a few years because of the Comox Valley Regional District’s water treatment project and their plan to be off of our penstock system by early 2021, and pulling water directly from the Comox Lake reservoir,” said Watson. “For the internal work and recoating, in 2021, we need to dewater the penstock from about July to October.”
The interior penstock coating system uses an epoxy paint. Hydro says it is a highly skilled recoating process, and includes the use of robotics inside the penstock.
As part of the Puntledge River hydroelectric facility, from the Puntledge diversion dam, water enters a 3.66 metre in diameter penstock or pipe that travels about five kilometres to the generating station. The 1.3 km long woodstave penstock starts near the dam and then transitions to a 3.6 km steel penstock which extends to the powerhouse.
There will also be some work on the woodstave penstocks, such as moss removal.