A major highway through Wilmington, Del. — shut because supports for a bridge it traverses are tilting — could have some lanes reopened around Labor Day, state transportation officials said.

The stretch of Interstate 495, which connects Philadelphia suburbs to Baltimore, has been closed since June 2 because four pairs of columns supporting a span of bridge over the Christina River were leaning as much as 4% out of alignment. Soil underlying the columns is unstable, the Delaware Transportation Department said.

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FOR THE RECORD

An earlier version of this post said a stretch of Interstate 495 has been closed since Monday. It has been closed since June 2.

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“The solution is to sink new foundations deep to bedrock,” Harry Roecker of Aecom, the firm managing design for the repair project, said at a news conference Tuesday.

The department considered three ways to fix the problem, state Transportation Secretary Shailen P. Bhatt said at the news conference.  

One was to jack up the existing bridge, put a support underneath it and very quickly reopen the lanes to traffic. That plan was rejected “because of the very poor soil conditions in that area,” Bhatt said. “We don’t want to put that kind of load on that soil.”

Another option is to tear down the affected 400-foot section of the bridge and build a replacement, a time-consuming move the department is trying to avoid. If that must happen, the bridge would reopen later this year or early next, Bhatt said.

The department is trying instead for a “hybrid solution,” he said: “putting the bridge on a firm foundation and then jacking up the existing structure.” There is less damage on the southbound side of the bridge, so those lanes would reopen first, he said.

“We’re looking at around a Labor Day target of opening the southbound lanes, with the northbound lanes to open two weeks to a month later,” Bhatt said.

He said the department would know more about the timeline in a few weeks. “Could it get better? It could,” he said of the project’s speed. “Could it get worse? It could.”

Bhatt emphasized that his department was moving quickly. For example, he said, instead of taking many weeks to fabricate certain items needed for the project, such as cages to reinforce concrete shafts, the team located pieces that were already made.

On Thursday, the U.S. Department of Transportation made $2 million in federal emergency funding immediately available for the project. The first phase of construction is estimated to cost $20 million, and the total cost of a permanent fix is unknown, the Delaware Transportation Department said in a news release. Construction is to be performed by J.D. Eckman Inc.

What caused the columns to tilt is not yet known, said Greg Layton, a spokesman for the state Transportation Department. One theory involves a pile of dirt, about the size of a football field, placed next to the bridge by a contractor. Layton said the pile appears to have compressed the soil beneath it, which may have caused the bridge’s movement. The pile has been removed, he said.  

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