Democratic presidential candidate Pete Buttigieg has joined front-runner Bernie Sanders in calling for the shutdown of Enbridge’s dual pipeline that is at the center of litigation between the company and the state of Michigan.

In a Monday evening tweet, the former South Bend mayor called for a focus on clean energy and the end of Line 5’s 66-year operation in the Great Lakes, becoming the third Democratic candidate to call for the line's closure. The dual lines carry crude oil and natural gas liquids between the Upper and Lower peninsulas.

“With such a high risk of an oil spill under the Great Lakes, Michigan can’t afford to keep the Line 5 pipeline in operation,” Buttigieg wrote. “In every community, we need new clean energy solutions to meet our climate crisis."

Buttigieg made the statement in response to a Michigan Radio article concerning the replacement of a segment of Line 5 running beneath the St. Clair River near Marysville.

Enbridge is replacing the segment beneath the St. Clair River as part of an agreement with the state that was made after extensive study of the pipeline, specifically the section of greatest concern that crosses the Straits of Mackinac.

Line 5 has been a flash point of concern, prompting former Michigan Gov. Rick Snyder to sign a deal for Enbridge to foot the $500 million price tag to build a tunnel housing the pipeline to prevent damage in the event of a rupture. Environmentalists oppose the tunnel and want the immediate closure of the pipeline.

A Michigan Enbridge pipeline ruptured near Marshall in 2010, creating the largest inland oil spill in American history.

The agreement was challenged by Gov. Gretchen Whitmer and Attorney General Dana Nessel, both Democrats who ran on promises to shutter the pipeline. Residents in the Upper Peninsula have opposed the closure, voicing concerns about propane availability should the natural gas supply be cut off.

Like Whitmer, Buttigieg's campaign argued that the timeline for the tunnel's construction left the pipeline in the water for longer than it should be.

"Pete believes that the time it takes to construct a tunnel prolongs the unacceptable environmental risk posed by the existing underwater pipelines," said Tess Whittlesey, a spokesperson for Buttigieg's campaign. "Addressing environmental threats at the Straits fail to address the broader environmental and climate risks of Line 5, and that economic impacts are manageable given proactive policy support."

Enbridge maintained Monday its pipeline is safe and the "best long-term opportunity to secure the energy needs of the state."

"Enbridge remains committed to moving forward with the Great Lakes Tunnel Project, which would invest $500 million into the State to ensure the security of energy supply and reduce risk to the Straits to virtually zero, and could be under construction by 2021 and in service in 2024," Enbridge spokesman Ryan Duffy said.

A Michigan Buttigieg supporter is state Sen. Adam Hollier, D-Detroit, who has backed the construction of a tunnel in the Straits of Mackinac.

When negotiations between Whitmer and Enbridge broke down in June, Enbridge asked the state Court of Claims to rule the agreement was valid and enforceable. A court decision in that case allowed Enbridge to continue work on the tunnel and seek federal and state permits for design and construction.

In a separate suit, Nessel has asked Ingham County Circuit Court to shut down Line 5 as a public nuisance and environmental risk. That case is still pending.

Buttigieg is the third Democratic presidential candidate to call for the pipeline’s shutdown. In July, Sanders and Washington Gov. Jay Inslee called for the shutdown of Line 5. Inslee has since dropped out of the race.

Sanders argued for a Green New Deal that would include a prohibition on “all new fossil fuel infrastructure.” Inslee called for the pipeline’s shutdown and criticized the $500 million tunnel construction to house the Line 5 pipeline.

eleblanc@detroitnews.com

Detroit News Staff Writer Craig Mauger contributed to this report.