ST. IGNACE, MI — Federal regulators are putting a construction method they once considered infeasible back on the table as an option to replace the Enbridge Line 5 oil pipeline under the Straits of Mackinac.

The U.S. Army Corps of Engineers has released a supplemental draft environmental impact statement identifying horizontal directional drilling, or HDD, as a feasible technique that could replace deep tunneling for a new pipeline near the Mackinac Bridge.

The technique, which has been used underneath shorter water bodies elsewhere in the Great Lakes region, would run a new 30-inch pipeline through a narrow borehole nearly four miles under the lakebed — eliminating the need for a concrete utility tunnel.

The draft was quietly public noticed on Nov. 12 with a short public comment wi

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