ELBA — This isn't your average road repair.
"Normally, when we build roads, we're in and out," said Craig Johnson, project supervisor for Minnesota Department of Transportation District 6. "This is more meticulous work."
Starting back in February, and likely not finishing until close to Halloween, crews from Environmental Associates Inc., a company that specializes in historic stone restoration work, will be painstakingly repairing four bridges built by combined crews from the Works Progress Administration and Civilian Conservation Corps back in 1936.
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The $4.6 million MnDOT project has turned Minnesota Highway 74 south of Whitewater State Park into a construction zone through the summer and fall — the park can be accessed from the north via Highway 74 or from the east or west via Winona County Road 39.
But the long construction time is needed to maintain the historical accuracy of the bridges, which were constructed 85 years ago as part of an effort to put Americans to work during the Great Depression.
Raymond Stenglein, project manager for EAI, the contractor on the project, said he appreciates the craftsmanship that went into the original construction.
"This has been here for 80 years, and it's still in good shape," he said.
Rehabilitating the hand-built stone bridges means using the same techniques and materials that were used in 1936, Stenglein said. The bridges help direct runoff water that crisscrosses back and forth under the highway as the road descends into the valley where the park is located.
And that means matching the color of the stone and the consistency of the sand.
For the mortar sand, Stenglein found a source in Byron where the sand has the right amount of clay and silica, and the stone came from Biesanz Stone in Winona.
For each of the four bridges, Stenglein's crews must catalog the place and size of each stone before removing any of the rock or mortar, then for stones that need to be replaced, they must shape a new stone from the matching material to the same size as the one being replaced.
"We have to tape and number every single stone," he said. "We measure them and put it all in a three-ring binder because we have to make sure each stone gets back in the right location."
The goal is to maintain the historical accuracy of each bridge, making sure it's built with the same craftsmanship as when it was created nearly a century ago.
Currently, the crews are working simultaneously on the two southern bridges. Stenglein said it takes about five or six weeks per bridge, and they're mostly done with the first of the four. That includes creating reinforced soil slopes leading to each culvert-like bridge to help reduce the force of the water hitting the stone walls and concrete floor underneath, in the hopes of helping these bridges last another 85 years — maybe more.
"The runoff in 2007 (from the flood that summer) took out some soil," Stenglein said, adding that the flood that year led to a weakening of support around the walls of the bridges, which is why the project is needed now.
The final bridge, the one closest to the state park, is the biggest and will take the most time — a couple weeks longer than the other three. Right now, he said, the job is ahead of schedule, but a wet summer full of heavy rainstorms could take a bite out of their timeframe.
It's stone-by-stone work — something he and his company have done 58 times for MnDOT around the state — but the detailed effort is worth it.
"I absolutely appreciate the work," Stenglein said. "This is satisfying knowing in 80 years, my great-grandchildren can come here and see this."