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MI, Enbridge to Discuss Straits Utility Tunnel

Friday, June 8, 2018

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Michigan officials are reportedly working with Enbridge Energy on a possible plan to create a new “utility corridor” under the Straits of Mackinac that would contain the company’s Line 5 liquids pipeline as well as other infrastructure running under the waterway.

Straits of Mackinac
U.S. Coast Guard

The new proposal is for a utility corridor to be bored beneath the Straits of Mackinac.

Enbridge is currently finalizing a report to the state, ordered as part of an agreement reached last fall with Gov. Rick Snyder, in which it will discuss the feasibility and merits of several possible replacements for the controversial oil pipeline. According to The Detroit News, the company is expected to recommend a tunnel as a replacement for the submerged pipeline.

The Michigan Tech Proposal

A group of engineering students from Michigan Technological University approached the state last month with a proposal for a shared utility tunnel under the Straits that would consolidate a Line 5 replacement pipeline with utilities like the American Transmission Company’s electric cable, which was damaged in April by what is now believed to have been an anchor strike from a passing tug. Line 5 was dented in that incident.

The Michigan Tech group, working under professor Michael Drewyor and industry advisor James A. Morrison, of ILF Consultants Inc., presented its idea to the Michigan Pipeline Safety Advisory Board in mid-May. The board, which consists of stakeholders including citizens, environmentalists and pipeline operators, serves to advise the state on pipeline matters but does not have decision-making authority.

Tunnel proposal
Michigan Tech, via Michigan Pipeline Safety Advisory Board

The tunnel would have a 21-foot diameter as proposed, to allow for maintenance access via vehicle and to accommodate possible future utility expansion.

The tunnel as proposed by the students would align roughly with the current Line 5 and would accommodate replacements for Line 5, the ATC cables, high-voltage lines Cloverland Electric Cooperative has under the Straits currently, and a natural gas pipeline operated by TransCanada that has been in operation since 1968.

The Detroit News reports that AT&T also has a fiber-optic cable running under the Straits.

The tunnel would have a 21-foot diameter as proposed, to allow for maintenance access via vehicle and to accommodate possible future utility expansion. Rail and rubber-tire vehicles would have access to the tunnel for maintenance purposes.

The tunnel would, according to the Michigan Tech group, cost just under $570 million to build, including $380 million for the tunnel-boring itself. The group estimates the project would take seven years to complete.

Enbridge’s assessment of possible alternatives for the replacement of Line 5 will reportedly be released Friday.

About Line 5

Line 5, which originates in Superior, Wisconsin, where several other Enbridge lines terminate, moves crude oil and natural gas liquids to Sarnia, Ontario, via Michigan. According to Enbridge, while much of the crude coming from Alberta goes to refineries in Sarnia, some is also refined in Michigan and Ohio. At points, sweet crude produced in Michigan is pumped into Line 5 to make its way to refineries as well.

The controversial 65-year-old liquids pipeline has experienced coating loss in recent years. Some citizens, environmentalists and lawmakers insist the line should be shut down due to the risk for an environmental disaster should a breach occur.

Enbridge has held that the pipeline’s integrity has never been compromised. The line has never had a leak in over six decades of service, and this past summer, it passed a pressure test ordered as part of the company’s consent agreement, established after the 2010 spill on its Line 6B.


Tagged categories: Government; Infrastructure; NA; North America; Oil and Gas; Pipelines; Program/Project Management; Tunnel

Comment from Robert Shaw, (6/8/2018, 10:06 AM)

Let's hope the experience of the power tunnel fire that shut down ATL in Atlanta is remembered and considered in design. Power cables and flammable/combustible liquids piping in the same tunnel can be a dangerous situation.

Comment from Michael Halliwell, (6/11/2018, 12:52 PM)

Same thing with the lighting and the rails / vehicle space. Need to make sure that the gas and oil lines are properly isolated so that one short, a blown bulb or someone going to do maintenance doesn't cause an inferno under the Straits of Mackinac.

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