Enbridge mulls drilling under Mackenzie River to replace pipeline section

The company is considering replacing the affected section of the pipeline - which is under the Mackenzie River, near Fort Simpson -using horizontal directional drilling.

Company looks at possibility of drilling several metres under riverbed to replace pipe

Enbridge shut down the Line 21 pipeline because of a slope stability concern in and around a section of the pipeline under the Mackenzie River, near Fort Simpson, N.W.T. (MVLWB public registry)

More than two months after Enbridge shut it down due to slope stability concerns, the Line 21 pipeline designed to carry oil from Norman Wells, N.W.T., to Zama, AB, remains inoperational.

Now the company is considering replacing the affected section of the pipeline — which is under the Mackenzie River, near Fort Simpson — using horizontal directional drilling (HDD), the same technology being used to drill underground to install parts of the Mackenzie Valley fibre optic link.

"HDD involves drilling a tunnel several meters under the river bed, then pulling the pre-assembled pipe through the tunnel from one side of the slope to the other," according to a recent update Ann Marie Tout, Enbridge's Northern region manager, gave to the Mackenzie Valley Land and Water Board.

The Line 21 pipeline carries oil south from Imperial Oil's Norman Wells oil field. (MVLWB public registry)

"HDD is an engineered solution that would be designed and constructed to ensure the long-term protection of the Mackenzie River and optimize safety and protection of the pipeline from instability along the river bank and the waterway."

No timelines yet

Tout says there's no timeline for either when the HDD program could begin or when the pipeline — which carries oil south from Imperial Oil's Norman Wells field — could be turned back on.

As an initial planning step, geotechnical surveys on both sides of the river, and on the river ice itself, are scheduled for this month and February, she said.

Enbridge shut the pipeline down on Nov. 18. By mid-December, the company had safely removed oil from the pipeline section, according to previous updates from Tout.

In response to the pipeline shutdown, Imperial Oil has reduced oil production at the Norman Wells field to a minimal level.

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