Detroit — Walk out onto the Interstate 75 bridge project and you almost feel steel and concrete shifting.
The longtime bridge, denuded in parts and stripped down to its steel, is undergoing long-awaited renovations in a 24 hour-six-day-a-week operation. Repairs are slow-going but on time, engineers and transportation officials say.
“The schedule was written up to be a two-year project and it probably will take all of one construction season to do one direction of the freeway,” said Bill Erben, the Michigan Department of Transportation construction engineer in charge of the project.
A Detroit News reporter joined MDOT on Tuesday to tour construction areas along the bridge.
The work is slow and deliberate. There’s a river 100 feet below. MDOT started the two-year, $165 million project to repair eight miles of I-75 between Springwells in Detroit and Northline in Southgate in February. Since then, the south side is getting all the attention, while drivers pass on the north side.
Or should we say zoom past? You can feel the bridge bounce as traffic zips past dozens of workers.
Built in the 1967 for about $25 million, the bridge is a major artery for truck traffic and Downriver commuters. Itspans 1.63 miles, making it Michigan’s largest bridge by volume of concrete.
Crews are in the process of removing the bridge’s concrete. They cut it out in slabs and pull it out, piece by piece, to minimize disruptions and protect the bridge’s structural steel and coating system.
In one section, a storm grate reveals the river below.
A catwalk has been erected to allow workers to maneuver around the edges of the bridge without fear of dropping into the water. To that end, a special machine lets them hang over the side of the bridge to complete tasks. There’s no extension ladder that reaches that far, engineers say.
So much concrete has been removed that all that remains in some sections is a huge expanse of exposed steel with bars in a crisscross pattern fitted over flat pieces with beams jutting up over the edges. Soon, new concrete will be poured. But not yet. There’s more work to do and more 1960s-era concrete to remove.
The chunks of concrete can be seen in piles near an exit ramp. Soon, the piles will be carted off and the chunks pulverized to go back into the bridge. First, rebar must be removed and sent to scrappers.
Southbound I-75 traffic has been detoured while northbound traffic has been maintained. Next year, northbound traffic will shift to southbound lanes while crews rebuild the other side of the freeway.
Also part of Tuesday’s tour was an up-close look at the work to replace I-75 bridges over Goddard Road. The 2,000-foot-long bridges are about 50 years old.
“When we rebuild things, they have a service life of 30-50 years,” said Dan Grupido, MDOT construction engineer in charge of the Goddard project.
“We expect the freeway to last upwards of 30 years and the bridges much longer. But we’ll have to do maintenance every year. It’s just like your house — you’ve got to paint your walls and fix the door hinges.”