The I-495 bridge in Wilmington isn’t expected to open anytime soon, according to engineers at the Delaware Department of Transportation.
The 4,800-foot span over the Christina River was shut down Monday night by DelDOT after engineers noticed four support columns were tilted.
DelDOT Chief Engineer Rob McCleary said they’re looking into installing a temporary brace, which could take several weeks.
“It’s not going to be something that we do in days. It’s going to be something that takes weeks,” he said. “It will have to be designed around the types of material that we can find locally and employ quickly. We’re considering a variety of different options available to us.”
Engineers believe that whatever is causing the tilt is underground.
“Everything above ground we have ruled out preliminarily as a cause of the tilt. Everything below the ground is 100 percent a possibility, and we’re taking steps to eliminate what those issues are,” said DelDOT Secretary Shailen Bhatt.
Paul Moffitt, geotechnical engineer for th AECOM engineering firm, said they’re trying to look at the sediment underground.
“We’re in a floodplain here,” Moffitt explained. “There’s a lot of marine sediment, which is why this structure is founded on deep foundations and I’m trying to get through that softer zone. That soft soil is very (what is called technically) consolidation or compressive settlement prone.”
He said the materials can compress if there were “large magnitudes of movement.”
DelDOT has also asked a neighboring company to move its massive dirt stock pile, which sits on the edge of the property line almost directly under the affected area of the bridge.
“We determined that pile of dirt could be a factor and the owner of that dirt pile is moving it right now because we want to make sure,” Bhatt added.
Corrosion could also be a factor. “Until we know what is causing it, everything is a possibility,” Bhatt said.
In the meantime, DelDOT is asking motorists to adjust their commutes and to utlize I-95 and I-295. The department is also working with the city of Wilmington to adjust traffic signals and with Delaware State Police to direct traffic.
DelDOT has not put a price tag on how much the bridge project will cost the state, but Bhatt said they’re working with the Federal Highway Administration to see if they’re eligible for any federal emergency relief funding.
Motorists can follow traffic updates through DelDOT’s social media, mobile app and website.