The Minnesota Pollution Control Agency is investigating a spill of drilling fluid into the Willow River in Aitkin County last week during construction on the Line 3 oil pipeline.
About 80 to 100 gallons of drilling fluid, or mud, were inadvertently released on July 6 at a construction site near the town of Palisade, Minn., the MPCA said.
Enbridge Energy is drilling beneath the Willow River to install a new crude oil pipeline to replace the existing Line 3. It's one of several river crossings along the 340-mile pipeline corridor across northern Minnesota.
The MPCA said the drilling mud was a combination of bentonite clay, water and xanthan gum, which it says is not toxic and commonly used as a food additive.
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Enbridge spokesperson Juli Kellner stated in an email that the company immediately shut down the drilling operation, and crews began containment and cleanup.
“There were no impacts to any aquifers nor were there downstream impacts because environmental control measures were installed at this location,” Kellner stated.
Environmental groups opposed to the Line 3 project criticized the release, which they call a “frac-out.” They voiced concern that the fine particles in drilling mud could impact aquatic life.
The MPCA said it’s been in regular communication with independent environmental monitors on site and has inspected the cleanup. Enbridge must consult with the agency before it can resume drilling at the site.
Enbridge says construction on Line 3 is more than halfway complete. It expects the pipeline to be operating by the fourth quarter of this year.