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Delaware Transportation Secretary Shailen Bhatt says it could be weeks or months before the I-495 bridge over the Christine River can be reopened. Engineers are still trying to determine what caused four of the bridge's support piers to tilt as much as four degrees off their vertical axis. Markings shown in photos of the bridge's upper section show it has shifted up to 18 inches from where it should be.

DelDOT engineers suspect a huge mound of soil dumped piled alongside the bridge may be responsible. They say the weight of the pile, which is said to up to two stories high and the length of a football field, may have compressed the ground beneath it, causing a shift in the sediment surrounding the pier footings.

Published reports say cracks have been discovered across the width of at least two concrete footings, and the steel piles in the bridge's foundation are deformed. Engineers have ruled out the possibility that steel piles supporting the structure had been weakened by corrosion.

Geotechnical experts say the lateral movement of the steel piles supporting I-495 over the Christina River is consistent with a force caused by seismic activity, or the weight of a massive dirt pile compressing soils on the east side of the leaning piers, suggests a story on DelawareOnline.

The website notes an earthquake hasn't been ruled out, but there has been no evidence of seismic activity in the past year anywhere within 250 miles of the bridge.

Transportation Secretary Anthony Foxx has pledged $2 million in emergency federal aid to help assess and repair the damaged bridge. Delaware Gov. Jack Markell said in a press briefing the funds would help fast-track repairs.

Mary F. Ridgeway, regional administrator for the Federal Highway Administration, has indicated the emergency relief funds will pay 100 percent of costs of work needed to stabilize the structure, prevent further damage and restore traffic for up to 180 days. The federal share would drop to 90% afterward.

Meanwhile, the closure is causing massive delays for travelers. The bridge is a key north-south artery for motorists traveling between southern Delaware and New Jersey/Philadelphia areas.

Lee Derrickson, director of the Delaware Motor Transport Association, was quoted by DelawareOnline as saying some truck-dependent industries have had to "pay a heavy penalty in tolls" while diverting along New Jersey toll roads.

"I spoke with someone from one of the poultry companies yesterday," Derrickson was quoted by the paper. On some routes, "instead of running 95 all the way out through Philadelphia and across the river into Trenton, they're taking the New Jersey Turnpike. It's certainly going to add to their transportation costs."

Speaking at a press briefing earlier this week, Secretary Bhatt said engineers are still trying to define what has caused the pilings to shift. Once they have, they will have to come up with a way to repair it. That will take time, he said, emphasizing the time the bridge will remain closed will be not be days but "weeks or months."