Friday, October 21, 2016

Dam failure a quake risk for Campbell River

Residents urged to flee area around river if ground shakes strongly

Officials in Campbell River are urging residents to prepare for massive flooding when the 'Big One' hits.
While many areas on the coast risk inundation from the sea, the danger in Campbell River will come from inland, where there are two large dams to the west of the city.
"It is predicted by BC Hydro that our old dams will not survive a catastrophic earthquake," Shaun Koopman, the protective services coordinator for Strathcona Regional District, said in an interview with On the Island's Gregor Craigie.
If both the earth-filled Strathcona Dam and John Hart Dam breach in a quake, Koopman said, "we would expect about four to six metres of water to flood large areas along the Campbell River, going into our downtown core within half an hour to 40 minutes."
The fast-moving water would devastate Campbell River's downtown area.
"It has the ability to wipe things away and take debris with it," Koopman said, "compromising both our fire hall and ferry terminal, along with local businesses and tourist areas."
John Hart Dam
BC Hydro spokesman Stephen Watson says the John Hart Dam (pictured) and Strathcona Dam are slated for earthquake upgrades starting in 2020. (BC Hydro)
"We have a beautiful ocean walk and that would be a major area affected," he said.
For residents and tourists in the area in an earthquake, Koopman said, "the shaking is their warning."
"Once the shaking starts, try to get as far away from the river as you possibly can if you're in the inundation zone."

Dam breach a worst-case scenario

BC Hydro spokesman Stephen Watson said while it is important to prepare for the worst-case scenario, a dam failure is a possibility, not a certainty.
He said officials can reduce the pressure on the John Hart Dam after an earthquake by releasing water to quickly lower the reservoir 10 metres without flooding the city.
That's not an option for the larger Strathcona Dam reservoir, Watson said.
However, Hydro has plans to reduce the earthquake risk for both the John Hart Dam and the Strathcona Dam at a cost of hundreds of millions of dollars.

Seismic improvements to start in 2020

The John Hart Dam Seismic Upgrade Project still needs final design and regulatory approval. Watson said that work is expected to begin around 2020.
He said Strathcona Dam Low Level Outlet Project is expected to begin around the same time.
The project would construct an underground tunnel that would allow the release of water downstream to relieve pressure from the Strathcona Dam.
Campbell River is not the only Vancouver Island where BC Hydro identified an older earth-filled dam as a risk for failure and flooding in an earthquake.
Earlier this year Hydro finalized the purchase of all but one of the 11 homes in the tiny Vancouver Island community of Jordan River. Those homes were in the path of flooding from a potential dam break, and are expected to be removed.
For the residents downstream of the John Hart and Strathcona dams, BC Hydro estimates it will be 20 years before both dams are fully upgraded to withstand a one-in-10,000-year earthquake.
"We have a good plan," Watson said. "Until then, there is this interim risk."

You may also like:

No comments :

Post a Comment