The aging Grand Avenue bridge over Interstate 670 will have to be replaced, the Missouri Department of Transportation announced Friday.
The bridge has been closed since May 6, when small pieces of concrete started falling off of it, District Engineer Dan Niec says.
It cannot be repaired.
“The current design of that bridge was modern for that time, for that era, when it was built back in the ’60s,” Niec says. “Those types of bridges are no longer built.”
The Grand Street bridge is what’s known as “voided slab” construction. The deck and girders are poured simultaneously around hollow tubes to keep the weight down.
“What happens is over time, water gets inside of those voids and freezes and thaws, and that starts the deterioration process,” Niec says.
The new bridge will be of a different design and rated to last 75 to 100 years. MoDOT will have to push back other projects to fund the bridge replacement.
“This bridge was not in our current 5-year program for replacement,” says Niec. “It really wasn’t a concern until we noticed the cracking that started taking place a few weeks ago.”
The bridge is closed until further notice. MoDOT plans to close I-670 sometime in August so the old bridge can be demolished. The plan is to have a new bridge open by Dec. 1.
Elle Moxley is a reporter for KCUR. You can reach her on Twitter @ellemoxley.