Traverse City – State, local, federal and tribal agencies are monitoring and joining in a "Unified Command" incident in which officials say hundreds of gallons of potentially toxic coolant fluid have leaked from two electric power cables in the waterway that links Lake Huron and Lake Michigan.

American Transmission Co. located in Pewaukee, Wisconsin, says the fluid is a mineral-based synthetic oil used for insulation that can be harmful if released into the environment. The company has six transmission lines that run parallel to each other under the straits. All six of the lines have been de-energized, according to a news release from the Michigan Department of Environmental Quality, and are considered inoperable and decommissioned, it said.

District Supervisor Joe Haas of the Michigan Department of Environmental Quality says the agency is investigating but it’s too early to know the extent of the damage in the Straits of Mackinac.

The company said the cables carried electricity between Michigan’s Upper Peninsula and Lower Peninsula. Beginning Wednesday, the news release said, "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 plan is to pump for 12 hours and then assess recovery."

Agencies will collect a sample during pumping and have it analyzed, the DEQ said.

"At this time, residents should not notice any adverse effects from the de-energized lines," the DEQ said. "ATC has taken action to control the leak and there is no immediate public health threat."

The U.S. Coast Guard is the lead agency in the incident response, the DEQ said. In addition to the DEQ, it is working with the U.S. Environmental Protection Agency, National Oceanographic and Atmospheric Administration, U.S. Fish and Wildlife Service, Department of Natural Resources, Michigan State Police Emergency Management and Homeland Security Division and Michigan Public Service Commission.

Spokeswoman Jackie Olson said it hasn’t been determined what caused the leak of about 550 gallons, which was discovered after two circuits went offline Sunday night.

“It was an extraordinary set of circumstances, but ultimately, the decision to shut down the cables had to be made,” said Mark Davis, ATC chief operating officer, in a statement. “We will continue to investigate the cause of the incident, determine any necessary remediation efforts and continue communicating with the appropriate regulatory agencies.”

The Enbridge Line 5 Pipeline, which carries about 23 million gallons of oil and some liquid natural gas through the straits each day and crosses the U.S.-Canadian border, is not affected, the DEQ said.


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