A recent study ranked Missouri seventh worst in the United States for the overall condition of its bridges.
But there’s no need to hold your breath while crossing bridges in the St. Louis region or throughout the state, said Mark Croarkin, a bridge maintenance engineer for the Missouri Department of Transportation.
“They included two categories in that list, bridges that are structurally deficient and bridges that are functionally obsolete,” Croarkin said. “There’s not necessarily any problems with bridges that are functionally obsolete.”
Bridges by the numbers
In the St. Louis region, 121 of the 180 bridges (see list in photo section) on the Transportation for America list were functionally obsolete, not structurally deficient. A list of the St. Louis region’s bridges is included with this article.
Functionally obsolete bridges might have narrow shoulders, the undercarriage might be too low, or the bridge design is no longer in use, explained Stacy McMillan, a MoDOT project engineer.
“Sometimes an insufficient clearance or weight limit might mean it’s structurally deficient,” McMillan said.
“If they were being designed today, they would be designed differently, but they could be in great shape,” Croarkin added.
He said if there are a lot of accidents on a functionally deficient bridge, MoDOT takes a look at the design to see if adjustments or improvements are needed.
“The St. Louis region has some of the best bridge conditions in Missouri,” Croarkin said.
Safe and sound
MoDOT recently celebrated repairing or replacing 600 of the worst bridges in the state through its Safe and Sound program.
“We’re eliminating structurally deficient bridges on major highways and the worst of the structurally deficient bridges on minor highways,” McMillan said.
The average bridge in the program is 24 feet wide and 147 feet long, he said. McMillan said.
“Most of these are unglamorous structures that get overlooked by most people,” he said. “On some, you’re across them before you know they’re there.”
Ken Warbritton, MoDOT’s Safe and Sound project manager, the program will complete 300 to 350 bridge projects in one year.
“That’s a phenomenal number,” Warbritton said.
Most of the bridges on the Safe and Sound list are in rural areas, but they did include a handful of metro St. Louis bridges:
- Highway 109 over Bonhomme Creek in Wildwood
- St. Charles Rock Road over Coldwater Creek in Overland
- Interstate 270 over Coldwater Creek in Hazelwood
- Highway B over Dardenne Creek in St. Charles County
- Highway 141 over Highway 21 near Arnold
Blanchette and Boone
Two heavily used bridges in metro St. Louis area also will undergo major repairs.
- The Daniel Boone Bridge over the Missouri River on Interstate 64 will be replaced;
- and the westbound Blanchette Bridge on Interstate 70 will undergo major repairs in 2012.
“Those two bridges are getting to where they need constant maintenance,” Croarkin said. “I look at the Blanchette Bridge every three months. I look for fatigue cracks in the superstructure. I don’t want to scare people, but steel does crack.”
MoDOT , which will be taken out of service for about one year in January.
The westbound Boone bridge, built back in 1935, will be replaced in a $125 million project. The bridge has developed a pack rust problem, including rust between its members, as difficult issue to address short of a complete overhaul, Croarkin said.
Deficient bridges are not necessarily unsafe despite needed maintenance or repairs, Croarkin said. They simply need significant repair or maintenance.
“Any bridge that is unsafe is taken out of service immediately,” he said.
There’s a law of diminishing returns when it comes to restoring older bridges.
“The first time you rehab a bridge, it may last another 30 years,” Croarkin said. “A second rehab may last just 20 years. As a bridge gets older, there’s less time between rehabs.”