How will the Great Lakes Tunnel be built?

Our Answer

The Great Lakes Tunnel will be drilled with the help of a massive, high-tech tunnel boring machine, or TBM. The machine will enter the earth from on shore and begin to cut out the earth as it goes, kind of like a giant electric drill reaching depths of over 100 feet below the lakebed. As the TBM moves, it will stabilize the rock and soil in front of it, then grind through, making sure the lakebed is secure above, and leaving a stable, thick concrete tunnel in its wake. Ultimately, a newly constructed Line 5 will be re-routed to pass through this tunnel and the existing line will be decommissioned.

It’s a complex, but common, process used around the world to build tunnels that are used for various purposes. The work involved to carefully map the rock beneath the lakebed has been vitally important. Geologic experts have taken rock and soil samples and working to ensure they know as much as they can, before bringing in the TBM, to avoid any delays. The TBM must be ready to move through any and all geological conditions it may encounter.