Ruskin Dam Seismic Upgrade
By BC Hydro standards, Ruskin is a small dam. Situated in a narrow valley of the Stave River just above Mission, Ruskin pales in comparison to its Interior cousins like Bennett, Mica or Keenleyside. But the seismic renovation and re-fit project currently underway at Ruskin is anything but small. It is, in fact, a superb feat of engineering and technical skill, a world class project employing world class companies and people. It is also a huge economic boost for Mission.
“Ruskin has pumped well over $2 million into the Mission area economy so far,” says BC Hydro Capital Projects spokesperson Judy Dobrowolski. “And we’re less than halfway complete.” Project Safety Advisor Adam Kingsbury adds his on-the-job experience. “Almost everything we require is locally sourced,” he says. “The cranes, most of the dump trucks, heavy equipment, concrete, wood materials – all using mostly local companies and people. We have about 140 to 150 workers on site every day, and a substantial number of them live in Mission.”
Viewed from the powerhouse bridge immediately below the dam, the project reveals its complexities. Huge construction cranes tower over the site, and the seismic portion of the work underway is impressive indeed. A huge yet movable steel barrier wall has been constructed immediately upstream of the dam itself, allowing workers access to the original spillway piers and gates. “In the event of a severe earthquake,” says Adam, “BC Hydro requires that spillway gates continue to operate reliably to allow for a post earthquake drawdown or to provide safe passage of water. So we are removing the original eight piers and seven gates, and will replace them with six new piers containing five new gates as well as new operating systems for improved reliability. Plus we are adding thickness and reinforcing the entire structure. And it will be wide enough to accommodate a two-lane road and pedestrian sidewalk across the top of the dam once these upgrades are complete.”
All of this seismic renovation has been carefully engineered to withstand a major earthquake – “a one in 10,000 year event,” says Adam. And none of it is simple or straightforward. To install the new piers, steps need to be cut into the spillway face – an extremely steep curving structure of smooth concrete. Big hanging platforms have been installed, allowing the expert crew and specialized equipment access to the face itself. Although BC Hydro and its contractors hire locally wherever possible, some aspects of the work are so specialized that they have to be sourced internationally, and here is an example. “Those guys are from Alabama,” explains Adam, pointing to the platforms. “And the machines they use to make precision cuts in the concrete are really cool.” He laughs. “Most of them had never been to Canada,” he says. “They were really afraid of Canadian winters. But with our mild weather for most of this year, they love it here. They’ve all rented houses in Mission, and they’d really like to stay.”
As a former senior project manager for Peter Kiewit Construction, with several years experience in Fort McMurray, Adam Kingsbury knows what he’s talking about. He’s from Maple Ridge, and took advantage of low real estate prices to purchase his Silverdale acreage in 2009. He didn’t much like McMurray, and his wife was unhappy that he was never home. “It was sheer luck that I got this job with Hydro,” he says. “I’ve never understood why people want to cram into little condos in Vancouver. We have everything out here – fresh air, beautiful scenery and a great lifestyle. And, best of all, I’m now only five minutes away from work.”
We notice a hub of construction activity near the bottom of the right spillway, and this leads to a discussion of the environmental challenges faced by this project. Working at the base of the dam, a crew is lowering large concrete blocks into place, and backing them up by timber walls.
“They’re building a containment pond to catch concrete debris and dirty water,” Adam says. “Before we can do any removal of old concrete – or any other material in fact – we have to be sure that it doesn’t end up in the river. And the same goes for any water either used or dirtied in the process.” And what will they do with the waste concrete material? “Chip it up and use it for fill,” he says.
The environment is a priority
He goes on to explain that the environment is a key priority. Water levels in the river below the dam must be closely controlled so as not to interfere with fish habitat. Water quality everywhere around the project must be maintained to protect both the aquatic environment and the drinking water supply. Pointing to the spillways at either outside edge of the dam, he then mentions another maybe less obvious environmental impact common to all dams. “When we need to spill water, these are the ones we always open first,” he says.
Project Environmental Monitor Jeff Greenbank enters the conversation. He explains that water tumbling over a dam (or in a natural waterfall) becomes highly aerated. Spillways located near the middle of the dam will drive this aerated water deep into the river, as opposed to the ones at the edges, where the water crashes onto the rock ledges.
“If fish encounter this super saturated water maybe a metre or more down below the surface,” he explains, “they are at risk when they come up. It’s like divers who get the bends when they ascend too quickly. That’s why we spill as much water as possible at the edges.”
Mission’s Ruskin Dam is indeed a complex undertaking, and there is still much work to be done. Nevertheless, a lot of work, particularly seismic upgrading, has been completed. Slope stabilization along the west (right) abutment has been finished along with a seepage cut-off wall tied into the dam structure itself. It has been this work that has required the re-alignment of Wilson Street and the single lane situation at the dam. “The site is extremely narrow,” explains Judy Dobrowolski. “There was no access to the west side of the dam unless we moved the road. And that access will be required for quite a while yet, so we won’t be opening the second lane any time soon.”
The original powerhouse, opened in November 1930, was expanded from two generators to three in 1950, but the exterior facade design was not carried through. The seismic upgrade work created an opportunity to remove the existing asbestos panels from the 1950s expansion by completely re-cladding the powerhouse envelope, including Power Smart windows. Adam Kingsbury points out that the dividing line between old and new is barely discernible. This phase will be completed in the spring of 2014.
The construction crew is particularly proud of its work to tie in the seepage cut-off wall to the dam. “Once we started, it was a round-the-clock operation that required great precision,” says Judy. All external factors- even temperature- had to be just right, and there was no turning back for a second chance. But we did it! It was completed on time (July 2013) and under budget.”
It seems that everyone on site shares her enthusiasm. Adam Kingsbury sums up the general feeling. “This is the most challenging and exciting project I’ve ever worked on,” he says. “Between the environmental challenges, maintaining structural integrity and worker safety under trying conditions – it’s massive. But also a lot of fun.”
The Ruskin Dam project will be ongoing into 2018. Its positive economic impact will continue. Mission BIZ eNews will offer periodic update articles about its progress.