~By Andrew Hudson
Enbridge is doing extensive geotechnical work to avoid the risk of landslides along the proposed route of the Northern Gateway pipelines, says director of engineering Raymond Doering.
“We understand, totally, the features in the area that have resulted in slides that might have affected other pipelines or highways or railways,” he said.
“What we’ve done is work to identify a route that avoids those hazards.”
Doering said the proposed route runs south of existing pipelines, such as the Pacific Natural Gas pipeline that crosses the Telkwa Pass. Other new pipeline proposals, like the Pacific Trails Pipeline, are following that lead.
Over the last 30 years, landslides cut the more northern PNG pipeline three times.
But geotechnical knowledge has come a long way since then, Doering said.
For example, he said, surveyors now realize why it’s important to know that some 10,000 years ago, the Kitimat Valley was the bottom of the ocean. That land rebounded as Ice Age glaciers melted away, leaving pockets of glacial marine clay that is unstable.
“That’s a very well understood condition now,” Doering said.
“But it wasn’t well understood when the original PNG pipeline was routed down to Kitimat over 40 years ago.”
Enbridge is doing ongoing fieldwork—digging bore holes, doing remote-sensing flyovers and aerial photography—to assess such risks, he said. Enbridge began its geotechnical surveys in 2005. Last year, the company submitted a long report detailing its geotechnical surveys for the Joint Review Panel that is assessing the project.
“We don’t just look on the corridor,” Doering explained. “We look as far to either side of the corridor as necessarily, and sometimes it’s many kilometres.”
Wherever possible, Doering said the proposed route avoids geohazards. Where hazards are unavoidable, his team will engineer ways to mitigate risk.
Enbridge plans to dig two tunnels, one 6.5 km and one 6.6 km long, to route its twin pipelines under the Coast Mountains.
“It’s a huge investment in the safety of the workers and for the long-term operation in the pipeline,” he said.