State assisting with multi-agency response to utility line leak in Straits of Mackinac
Local, state and federal agencies are actively monitoring and participating in the Unified Command incident response to the dielectric oil release in the Straits of Mackinac caused by a break in two underwater power lines that extend from the Upper Peninsula to lower Michigan.
Dielectric fluid is part of the mineral oil family and functions as an electrical insulation and as a coolant.
The lines are owned by the American Transmission Company (ATC) located in Pewaukee, Wisconsin. The company has six transmission lines that run parallel to each other under the straits. All six of the lines have been de-energized.
The leaking cables are now considered inoperable and decommissioned. The company is currently investigating the cause of the leak. Starting tomorrow morning, ATC will begin pumping air in from the Mackinaw City side at low pressure (10 psi) and simultaneously pumping fluid out at the same pressure on the St. Ignace end using a vacuum truck, all through 1" valves, so this will go slowly. The fluid will be pumped into a frac tank. The plan is to pump for 12 hours and then assess recovery. Response agencies will collect a sample from within the pipe during the pumping and send it for analysis.
At this time residents should not notice any adverse effects from the de-energized lines. ATC has taken action to control the leak and there is no immediate public health threat.
This continues to be a multi-agency response effort of local, state, tribal and federal partners in coordination with ATC. The U.S. Coast Guard is the lead responding agency in coordination with the U.S. Environmental Protection Agency, National Oceanographic and Atmospheric Administration, U.S. Fish and Wildlife Service, Michigan Department of Environmental Quality, Department of Natural Resources, Michigan State Police Emergency Management and Homeland Security Division and Michigan Public Service Commission. State agencies remain actively involved in response efforts.
A local Joint Information Center (JIC) is also being assembled. ATC (the responsible party) has issued a press release. The ATC media hotline is 877-506-6117.
The Enbridge Line 5 Pipeline is not reported to be affected and is unrelated to this response.