Saturday, April 28, 2012

Penstocks of the Past, and Future

Having spent most of mid-April dealing with the high style design issues of the Holly Theatre, this past week has seen a return to the more typical aspects of report writing, including covered bridges and compliance documentation.  Staring back at me from my computer screen at the moment is PGE’s Faraday Powerhouse, on the Clackamas River.  

“Penstocks” are the feeder tubes that connect a reservoir to the turbines that spin a generator to create electricity.  They are usually large concrete or steel pipes that drop significantly in elevation to create “head,” increasing the force of the water and spinning the turbines efficiently.  In more recent projects (post-WWII) penstocks are typically underwater, at the bottom of a dam, and so unseen.  But in an early hydro project, like that at Faraday (which was built in 1907-1909), the penstocks are exposed and become highly visible features, dropping from the crest of the dam, down an embankment, to the powerhouse.  Faraday's penstocks are typical, in that these early powerhouses tend to have multiple, smaller, generation units rather than one or two large ones, and so the penstock lines can be pretty dramatic through repetition. At Faraday there are six penstocks, five built by 1909 and one, Unit No. 6 (the larger one, at the extreme right above), that was added in 1956. 

Faraday’s original penstocks are of riveted steel, between eight and nine feet in diameter, and are supported by multiple concrete piers with small semi-circular “saddles” where they meet the steel penstock itself.  This has worked well for over a century, but where the concrete and the steel meet, water is trapped.  Steel and water are a bad mix, and one thing you surely do not want is a weak, rusted, spot in steel tube carrying 1/6 of the Clackamas River at high pressure.

PGE has creatively developed a solution to repair the damaged spots and then modify the top of the concrete piers to re-seat the penstocks with a steel-to-steel connection.  This will reduce the potential for damage and allow the Faraday penstocks to continue to operate into their second century. 

People tend to glaze over when I talk about my interest in hydroelectric generation, penstocks, flow lines and the like and many of these early projects are criticized as unnecessary and un-green.  That's another rant.  Last night I was amused, while watching NBC's filmed-in-Portland fantasy-drama show Grimm, to see that PGE's now-decommissioned Bull Run Powerhouse (built prior to WWI) played a major role.  It’s a shame, and an interesting comment on how our society has changed, that only few people still see the postcard potential in engineering marvels like these early, small scale, powerhouse projects.  Think about that during the next power outage, or when you drive through a sea of wind turbines.


  1. We should have invited you to our Bull Run Powerhouse Grimm-watching party (George - you do know that we finally acquired the site from PGE December 30th, well in advance of the December 31st deadline that would have killed it after four-and-a-half years of negotiation?).

    Not only were be pleasantly surprised that the it was specifically identified as the Bull Run Powerhouse in the dialogue, but we expect the transformer building, otherwise now known as the Beaver Creature's "lodge", to be a recurrent location. Not as ideal as the site still being used for power generation, but it was well-appreciated by the crew as a stunning and powerful facility, and will hopefully continue to help us build interest in its ongoing preservation and creative re-programming.

    Jeff Joslin
    Powerhouse Re Gen llc

  2. Hi Jeff.. my ears perked up at the mention of "Bull Run" too, and I smiled when I thought "they are going to show that LOOONNNGGG stairwell between the powerhouse and tool room, and then they did! Glad that you guys completed purchase with so much time to spare.

    Grimm makes me laugh, as so many of the locations are places I've worked on over the years. Watching is sort of like a little treasure hunt... I will keep my eyes open for the Beaver Creature's lodge in future episodes!

  3. "It’s a shame, and an interesting comment on how our society has changed, that only few people still see the postcard potential in engineering marvels like these early, small scale, powerhouse projects...."

    More than you might think:
    (and of course you are quoted on the latter page).