Nov. 28–MACKINAW CITY, Mich. — Enbridge Energy wants to start drilling the Straits of Mackinac lake bottom next spring to determine the rock composition about two hundred feet beneath.
The initial survey work is next step in planning design and construction for the proposed Line 5 tunnel, said Enbridge Energy spokesperson Ryan Duffy.
“I think it’s just us wanting to keep the process moving forward, and we see the tunnel as a good solution moving forward,” Duffy said. “We think it’s building for the future.”
The lake-bottom boring is currently under permitting review by state and federal authorities and open to public comment through at least Dec. 7.
Plans call for 14 to 24 boreholes running parallel to the existing Line 5 oil and gas pipeline on the Straits’ floor, according to the permit application submitted Oct. 26.
The boreholes would be distanced 60 to 150 feet from Line 5. The borehole depths range from 115 to 220 feet below the lake bottom, the permit states.
The lake-bottom boring and additional onshore activity roughly outline where the proposed tunnel would go, Duffy said.
The tunnel would begin at the Enbridge Line 5 Mackinaw Station just west of Mackinaw City, run under the Straits parallel to the existing Line 5 and then emerge at the Enbridge Line 5 North Straits Station on Point La Barbe.
After Gov. Rick Snyder on Oct. 3 announced plans to house Line 5 in a tunnel beneath the Straits, Enbridge Energy subsidiary Tri-State Holdings, LLC began buying up properties in and around the south shore work area, according to Emmet County property records.
The subsidiary has accumulated five properties so far for a sum of $1.15 million, records show.
Duffy confirmed Tri-State Holdings is connected to Enbridge and that land has been purchased on the south shore. U.S. Securities and Exchange Commission filings show Tri-State Holdings is an Enbridge subsidiary.
The land work on the south and north shorelines consists of seven sonic and auger holes, five rock-coring boreholes and six test pits, the permit states.
Land work would require another state permit, as it calls for temporarily matting 1,600 square feet of wetlands to allow equipment transit without long-term impact to vegetation, said Scott Rasmusson, who works in DEQ’s Water Resource Division.
Enbridge wants land drilling to happen in early 2019.
Altogether, the work would give the Canadian energy company an idea of the underground landscape along the “proposed tunnel alignment,” according to the permit.
“This geotechnical investigation is the next step to define the subsurface environment to better inform the feasibility and design of a tunnel crossing the Straits,” the permit states.
The proposed tunnel to replace the current 65-year-old Line 5 oil and gas pipelines and house a new one was announced by Gov. Snyder on Oct. 3. Snyder called the proposal a “common-sense solution” to safeguard the Straits from an oil spill while maintaining the pipeline connection.
Calls to shutdown the controversial oil and gas pipeline were renewed in April when an anchor struck it. The line was damaged with three dents and an abrasion but has since been patched up with composite sleeves.
Snyder wants to seal the deal on final tunnel agreements before the end of his term, which runs through this year.
Those agreements, as somewhat outlined in his second agreement with Enbridge on Oct. 3, would see Enbridge pay for the design and construction of the tunnel — an estimated cost between $350 million and $500 million.
If all goes to plan, the tunnel will be operational sometime between 2025 and 2028, with the existing Line 5 decommissioned afterward.
Enbridge would then hand tunnel ownership over to the Mackinac Bridge Authority, the independent state agency which operates the Mackinac Bridge, which would then lease space to Enbridge’s new Line 5 and other utility companies.
Mackinac Bridge Authority Board Chairman Patrick “Shorty” Gleason cast doubt on whether the bridge authority could negotiate and discuss any agreement before the end of Snyder’s term.
Enbridge and the bridge authority must still agree to numerous details, including those about construction, maintenance and who pays for minor and major malfunctions of the tunnel infrastructure.
State department representatives are working out those details, and they’ll be presented to the bridge authority board for discussions and approval when completed.
The board is also awaiting a finalized agreement between Enbridge and the state, as well as action on state legislation introduced this month that would allow the authority to take ownership of the tunnel.
The Line 5 pipeline, built in 1953, runs 645 miles from Superior, Wisconsin, to Sarnia, Canada, and transports up to 540,000 barrels of light crude oil and natural gas liquids per day.
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