People may notice some different sounds coming from the Strathcona, Ladore and John Hart dams from May 25-31.
It’s all part of the process of conducting geophysical field investigations to better understand the rock characteristics below the surface.
“Our dam safety program is always looking at ways to improve our seismic knowledge and how our facilities may respond when a significant earthquake hits the region,” says BC Hydro’s Stephen Watson. “We’ve been fortunate to be able to collaborate with the United States Geological Survey (USGS) to improve our characterization of the rock beneath our three large dams on the Campbell River system. The USGS field crew has limited time in our province and we’ve been able to develop a joint research initiative to carry out some field work.”
The work is happening at four dam sites, with one in the Lower Mainland, and three on the Campbell River system.
Crews will be using long survey lines to monitor various waves directed below the ground surface. These waves present no public risk. How they refract into or reflect from the surface and interfaces will provide engineers with the knowledge of the rock characteristics.
The sound that the energy sources emit may be heard by nearby residents or recreation users. The sound analogy will be like a garbage truck picking up and dropping off a commercial-sized metal garbage bin.
Watson says this survey will clarify how the rock properties vary across the site. Better knowledge of the rock conditions will provide increased confidence on how the facilities may react to ground shaking from an earthquake.
“To do this work, they will have survey lines up to 300 metres long at each site,” says Watson. “The lines will be moved as needed to get a full picture, with staff recording the various waves transmitted through the rock. Some areas may be temporarily cordoned off to keep people from getting too close and therefore reducing the noise effects.
The field crew may consist of up to 15 people from both the USGS and BC Hydro, with perhaps three trucks transporting the equipment.
The plan is to carry out the geophysical work at Strathcona dam on May 25 to 29, John Hart dam on May 27 and 28, and Ladore dam on May 30 and 31. The time of day the work will be happening is 7 a.m. to 6 p.m. Crews will be working seven days a week given the limited USGS staff and equipment availability.
BC Hydro suggests people who plan on using the Strathcona dam campground should look at alternative locations from May 25 to 28 given the survey sounds that will be taking place. The campground will be closed with no accessibility for one day on May 29.
“People may hear these surveys in action so we are trying to be proactive in the awareness of the work, and hopefully save a few curious phone calls wondering what the sound is,” says Watson.
If you have any questions about the work or sounds it creates, contact Stephen Watson at 1-250-755-4795 or steve.watson@bchydro.com.
BC Hydro has proposed seismic upgrades at the John Hart, Ladore and Strathcona hydroelectric facilities, and they may all start as early as 2020/2021.
