(The Center Square) – The Michigan Public Service Commission unanimously approved a permit for Enbridge Energy to replace the existing Line 5 dual oil pipelines in the Straits of Mackinac with an underground pipeline tunnel.
The replacement project proposed by Enbridge consists of construction of a single 30-inch diameter pipeline to be located within a concrete line tunnel beneath the lake bed in the straits.
Enbridge’s Line 5, a 645-mile oil pipeline, runs 4.5 miles across the lakebed of the Straits of Mackinac, a waterway connecting Lake Michigan and Lake Huron.
The pipeline transports light crude oil, light synthetic crude and natural gas liquids used to heat homes and businesses and fuel vehicles. Line 5 supplies 65% of propane demand in the Upper Peninsula, and 55% of Michigan’s statewide propane needs.
The pipeline will be constructed with steel that is .625 inches thick before the pipeline is placed into operation, it will undergo testing at pressures greater than its maximum allowable operating pressure.
The 21-foot in diameter tunnel will be constructed between 60 and 370 feet below the lake bed, primarily through rock using a tunnel boring machine with precast tunnel lining.
The order found “there is a public need for line 5 products and a public need for the replacement project to protect the resources of the Great Lakes.”
The order also found the route location and design is reasonable and a “significant improvement over the dual pipeline configuration.”
Since 2019, Michigan Gov. Gretchen Whitmer and Attorney General Dana Nessel have sought to shut down Line 5, which has been pumping about 540,000 gallons of hydrocarbons daily across the lakebed of Lake Michigan since 1953.
The move would eliminate the risk of anchor strikes and will serve as secondary containment to prevent product from reaching the streets.
The order finds that none of the alternatives evaluated are feasible to the proposed project, and many would have a greater environmental impact than the tunnel project.
Enbridge must receive all governmental approvals and there be may be no significant changes to the route and location of the replacement segment without further application to an approval by the commission.
The order requires Enbridge to implement additional procedures and testing for girth weld that exceed federal pipeline safety requirements.
Whitmer and Nessel say they fear a spill similar to the 2010 oil spill near the Kalamazoo River – the largest inland oil spill in U.S. history.
Michigan is among the top five states in residential sector petroleum use and ranks first in residential sector consumption of propane, according to the U.S. Energy Information Information Administration.
The Mackinac Center for Public Policy says if Line 5 was shut down, then switching to electric heat would increase each household’s costs between $3,400 and $3,900 per year.
Enbridge’s Great Lakes Tunnel Project was approved during the administration of former Republican Gov. Rick Snyder.
Experts interviewed by The Center Square say shutting down the pipeline would shift oil transportation to more costly and less efficient methods, like by rail or truck, that could lead to higher emission output relative to using the Line 5 pipeline.
The Center Square previously reported it would take 2,150 trucks crossing the Mackinac Bridge daily to replace the pipeline’s volume.
