Five bridges near Solon were recently found to have major structural issues resulting in the immediate lowering of their weight limits with detours for certain traffic and an uncertain timeline for replacements. County Engineer Paul Wittau advised the Johnson County Board of Supervisors of the findings of the recent inspections (required every two years) of seven bridges (out of 211 total in the county) maintained by the Secondary Roads Department during a Wednesday, Nov. 12 work session.
“The youngest one is 70 years old, the oldest is estimated at 125, so they’ve all exceeded their lifetimes and we’re seeing the result of heavier modern traffic loadings and age, and some of the ones that were already posted, we can’t be there all the time and people don’t always follow those postings (weight limits) and that can cause things to deteriorate quicker than we would like,” said Wittau.
The bridges
Bridge A-22-1 on 160th St. NE, east of Wapsie Ave.
This bridge did not previously have a weight posting but Wittau told the supervisors the bridge inspector is recommending a ten-ton limit on the structure, which was built in 1955.
“It’s a timber substructure, the piling is decaying, the bearing piles are starting to crush, the piles themselves are starting to bow and up at the top they’re starting to deform,” said Wittau.
Bridge I-9-4 on Morse Road, NE, just west of Putnam St. NE (F36)
Wittau said there was a plan to pave Morse Road, including across the bridge deck but it needed a load rating first.
“Unfortunately, the results showed it should be posted at six tons, which is pretty low. It’s going to be a pretty big impact on travelling.”
Those impacts will prohibit school buses and trucks on a road with over 1,200 vehicles per day.
“We’ve already started designing a new structure for that and hopefully this time next year we’ll be in-construction on that. We’re accelerating that one as quickly as we can,” he said.
One issue that has Wittau scratching his head is three feet of fill that was placed on the bridge deck at some point, adding to the dead load and making the side rails more like curbs. His best guess is the work was done sometime in the 1950s. The bridge was built in 1930.
“We’re going to try to get it replaced as soon as we can,” he said adding the shortest detour is nearly seven miles.
Bridge I-21-5 on Rapid Creek Road, NE, approximately 450 feet west of Elmira Rd. NE
This bridge, built in 1950, is being posted at three tons, “about as low as we ever post,” Wittau said, “which just about limits it to passenger vehicle traffic.”
Wittau pointed to “significant section loss and corrosion” on the beams supporting the structure as he showed photos to the supervisors. “That’s the primary reason we’re deciding to go so low, so we can hopefully keep it in-service without having to close it.”
Wittau added he is currently exploring the possibility of a retrofit to return the bridge to 23-ton posting it has had for at least a decade. The retrofit would involve securing new piles to the existing piles in an effort to take the load off of them.
“Three tons, you’re talking no farm equipment, and probably not a lot of construction vehicles, it’s really your personal car. So this is a really significant posting,” said Supervisor Rod Sullivan.
Impacts to school transportation, emergency services, and garbage pick-up were noted with Wittau stating he was in contact with the various entities.
“Its unfortunate and where it is in the county, there really isn’t a good way to get around it,” said Wittau.
Bridge H-31-2 on Rapid Creek Road, NE just east of Hwy. 1
“That one is in the same condition (also built in 1950) and recommended at the same posting of three tons,” said Wittau.
The ”best” detour is about 8-1/2 miles, he added.
“Its definitely going to impact people and we’re trying to expedite where we can,” he said adding he would like to get the retrofit done on both bridges before the end of the year but wasn’t certain it will be possible. However a bridge contractor is working in the county currently and Wittau said he would reach out to them as an option while also soliciting quotes from other companies.
He added the retrofits could “buy some time” allowing his department to design and budget for full replacement in a few years. Wittau also noted the Department of Transportation is now considering 75 years (the age of the Rapid Creek bridges) as the standard life cycle for bridges, which were designed for the traffic of the day.
“It’s time for them to be replaced,” Wittau said.
Bridge I-25-1 on 310th St. NE just west of Cedar-Johnson Road
“We are recommending a ten-ton posting, it’s one of the older three-vehicle postings, 1928-38, the piling is starting to decay and we’re seeing some crushing at the top, basically what you would expect to see with a bridge this old made of timber,” said Wittau.