LANSING, Mich. (AP) — Michigan’s attorney general sued Thursday to shut down dual oil pipelines in the Great Lakes, saying they pose an “unacceptable risk.”

Democrat Dana Nessel’s move came the same day she also sought to dismiss pipeline operator Enbridge’s request for a ruling on the legality of a deal it struck last year with former Republican Gov. Rick Snyder to put replacement pipes in a tunnel beneath the Straits of Mackinac.

“I have consistently stated that Enbridge’s pipelines in the Straits need to be shut down as soon as possible because they present an unacceptable risk to the Great Lakes,” she said in a written statement.

Nessel said she acted after it became clear talks between Enbridge and Democratic Gov. Gretchen Whitmer stalled.

The pipelines are part of Enbridge’s Line 5, which carries 23 million gallons (87 million liters) of crude oil and natural gas liquids daily between Superior, Wisconsin, and Sarnia, Ontario.

Whitmer ordered her administration not to implement the tunnel plan after Nessel said authorizing legislation enacted in December violated the state constitution.

Enbridge insists the twin pipes, which have been in place since 1953, are in sound condition and could operate indefinitely. But the company, based in Calgary, Alberta, said it is willing to install a tunnel in bedrock 100 feet beneath the lakebed and foot the estimated $500 million bill to eliminate virtually any possibility of a leak.

Opponents contend Enbridge’s refusal to shut down the pipeline until the tunnel is completed means the straits area would be endangered for at least another five years. They point to a vessel anchor strike in April 2018 that dented both pipes while damaging three nearby electric cables, which leaked 800 gallons of insulating mineral oil.