Rock Sampling Work Complete in Michigan’s Straits of Mackinac

Construction of Enbridge’s Great Lakes Tunnel advanced with the recent completion of sediment and rock sampling at the Straits of Mackinac, a key engineering component needed for the final design of the tunnel, which is needed to replace a section of Line 5 under the strait. The sampling program was a major part of Enbridge’s $40 million investment in the project in 2019.

The specialized deep-water drilling vessel, Highland Eagle, and a team of experts successfully completed the last of the bedrock borings in the deep-water areas at the Straits in mid November. Rock and sediment samples were collected from a total of 27 locations including on-shore, near-shore and deep-water locations.

Geologists will study the rock samples collected. Results of the study will be used to guide the design of the tunnel, as well as the tunnel boring machine, which will be custom-built to suit the characteristics of geology in the Straits.

Completion of this phase of the project on schedule reflects Enbridge’s deep commitment to building the Great Lakes Tunnel and to being part of Michigan’s future. Enbridge believes the tunnel is the best way to protect the community and the Great Lakes while meeting Michigan’s energy needs.