How deep will the Great Lakes Tunnel be dug under the Straits of Mackinac?

Our Answer

The depth of cover over the tunnel in the deep-water portions of the lake will range from at least 60 feet to more than 200 feet.

The minimum depth of cover over the tunnel in the deepwater portions of the lake (greater than 80 feet water depth) will be at least 60 feet below the lake bottom. In these deepwater areas, portions of the tunnel may be in thick deposits of glacial till that fill the deep channel.

Where the tunnel approaches the entry and exit points at the shorelines, it will be entirely in rock. In these areas, the minimum depth of cover over the tunnel will be at least 10 feet below top of rock.