Cassidy says studies have shown that reservoirs at a height of 60 metres or less, like the Site C project would be, are also drastically less likely to trigger significant earthquakes than taller ones.
“The probability of earthquakes is extremely low, so that probability of triggering earthquakes drops off very quickly with reservoir height,” he argues, adding, “In British Columbia there’s no history of significant reservoir triggered seismicity, either at the much larger Bennett Dam, which is 183 metres, or the Peace Canyon Dam.”
In it its review, NRCan looked at the seismicity hazards in the area, the possible effects of waves generated by earthquakes, as well as the proposed mitigation measures by Hydro. It found that design of the dam would cover the largest induced earthquakes in the area and any sloshes of water from earthquakes would be less than one metre, leaving another 7.6 metres room.
Research scientist for the Geological Survey of Canada Peter Bobrowsky said the same of the information on the geology and terrain hazards presented in the Environmental Impact Statement, adding that the slope stability line and landslide generated wave impact line given are conservative and exceed minimum required standards.
“NRCan is satisfied the Proponent has followed the adopted current standards and best practices used both in Canada and internationally in dealing with slope stability,” he told the JRP. “We have no other recommendations.”
However, NRCan did present concerns in the area of acid rock drainage and metal leaching, the result of natural weathering on sulphide bearing rock.
“Given the abundance of disturbed rocks with high ARDML potential and short lag time to onset of acid generation and non-acid generating overburdens with elevated selenium content,” says Jessica Coulson, Team Leader of NRCan’s Environmental Assessment Division, “ARDML prevention and mitigation can pose some challenges.”
Coulson added that more detailed tests are ongoing, and the lack of better water quality modelling “presents a higher degree of uncertainty.” Among NRCan’s recommendations in that area is the development of an ARDML management plan, as well as the improved water quality monitoring, which Site C Chief Project Engineer John Nunn says B.C. Hydro agrees with.
The hearings continue today with presentations from Transport Canada and the Ministry of Forests, as well as Saulteau First Nations, West Moberly First Nations, Treaty 8 Tribal Association and the Peace River Environmental Society.