Rare design has crews working inside a tunnel to make bridge repairs in Michigan

Updated Aug 8, 2015

In a drive over U.S. 131 Bridge in Michigan, it’d be easy to miss that bridge is in the middle of an extensive rehab project. There may be some traffic barrels along the side, but for a project that’s expected to solidify the bridge for five or more decades, there aren’t too many workers to be seen.

That’s because they’re just a few feet below the bridge in a tunnel that runs its length, according to Michigan Live. Workers are in the bridge tunnel doing external post-tensioning to strengthen the tendons that help support its weight.

The unique bridge construction design is rare, and isn’t considered a part of the modern American Association of State Highway and Transportation Officials code. However, Michigan Department of Transportation project engineer Mike Roberts said the 30-year-old bridge didn’t have much damage from the years of wear and tear.

It’s only one of three bridges with the tunnel type of construction in the state, but the design, while somewhat outdated, does make for at least a cheaper rehab project.

The total cost of the rehab project is $6 million, whereas a new bridge could cost the state up to about $30 million – in addition to the travel headaches bridge replacement would cause. Though, the workers will be out on the bridge later during the construction to repave the bridge surface.