The big one could hit anytime, crumbling shorelines, snapping pipelines and sending entire parts of B.C.’s coast beneath the grinding techtonic plates.
The Ruskin Dam will have a better chance of withstanding such a quake by 2017 when upgrades to it will be complete.
A recent B.C. Hydro study of seismic conditions in B.C. shows for most of the corporation’s big dams, the risk of a cataclysmic earthquake remains the same or lower because of the constant efforts at strengthening the facilities.
That applies to the Ruskin Dam – a massive structure on the Stave River that produces power for more than 30,000 Metro Vancouver homes. It is getting its own seismic strengthening as part of a complete rebuild.
“It’s not that the [Ruskin] area is more safe. It’s just that our dams are designed to withstand the major earthquake,” explained Judy Dobrowlski, with B.C. Hydro.
“Big earthquakes happen here, of course, given our proximity to the major subduction zone, which is off Vancouver Island. So there’s no change in our understanding of the hazards. It’s just how our facilities are improved to continue operating.”
The study does say, though, that the effects of a quake on parts of Vancouver Island and along Bridge River in the Lilloett area could be worse than anticipated.
The study is the culmination of six years of work by a cross-section of experts, including seismologists, physicists and geologists.
The team studied the history of seismic events across B.C. and adjoining regions and identified where major seismic activity could occur. It developed prediction models and determined resulting seismic ground motions at the various dams.
“This methodology is now a best-in-class model for calculating earthquake hazards for utilities,” says a release.
Dobrowlski said B.C. Hydro has always done seismic studies, but this is the largest, most wide-ranging one ever done. Its data will be shared with municipalities as they plan infrastructure and development.
“Because it’s such a large, comprehensive thorough body of work, it provides more clarity about the seismic hazards across the province.”
Once the $750-million renovation of the Ruskin Dam is done, it will be able to withstand a one-in-10,000 year earthquake. Seven old piers and gates are being replaced by five larger, stronger gates, and six new piers, creating a completely new appearance of the structure. The new gates will weigh twice that of the old ones and have double the amount of steel.
A wider, two-lane road and pedestrian walkway will replace the narrow one-lane passage on top of the dam.
An innovative feature is a new asphalt-like material developed for a buried wall. The material can absorb shocks and can self-heal, preventing leaks from developing in the anchoring wall in the softer soil on the north side of the dam. That wall will attach to a longer buried wall of plastic concrete.
Still to be installed are the guts of the operation – three new turbines to replace those from another age. The first turbine, or generator, is 84 years old. The second is 76 years old and the newest turbine was installed in the 1950s.
The rebuild has reached the halfway point and the contractor that will install the new turbines has just moved on to site. The turbines, eight per cent more efficient, will be installed one at time to allow the dam to keep operating during the refit and to keep producing power for Metro Vancouver.
The whole rebuild is comparable to changing a car’s tire while still driving down the road, said Dobrowlski.
Steady progress is being made towards the 2017-18 completion date, she added.
“There are always surprises when you’re retro-fitting an old facility that was built in the 1930s.”