The tilting of a heavily-traveled interstate bridge in Delaware is a “Defcon 5” nightmare, says the state’s transportation secretary, and has prompted officials to shut down the span indefinitely.
Delaware Department of Transportation officials and engineers said on Tuesday that the Interstate 495 bridge that spans the Christina River in Wilmington can currently support itself on its own. But that opening it to traffic could cause more damage to the four piers, each made of two 50-foot tall pilings, which are tilting.
“We don’t want to put traffic back on it until we get more shoring in place,” transportation secretary Shailen Bhatt said. Asked about the magnitude of the situation, the secretary replied: "You ask me 'Am I kept up awake at night by this?' This is the sort of thing that is a sort of Defcon 5."
The 4,800 foot span, which carries an average of 90,000 vehicles around downtown Wilmington and to the Port of Wilmington, was shut down on Monday night after officials discovered the leaning. The worst of the four piers, support 12, is tilted 2 feet to the side, engineers found.
Sensors have been placed on the bridge providing real-time monitoring of any further shift in the span. Piles of soil are also being moved and tested.
“We are still trying to isolate what has caused this shift,” Bhatt said. “Until we know definitively what is causing the problem, we have to assume that everything is a possibility.”
I-495 is closed northbound at Terminal Avenue, which leads to the port. Southbound traffic ends at the Pennsylvania state line, with traffic diverted onto I-95. Southbound port traffic is being directed to I-295 east and then to Delaware 9 north to the port.
Bhatt suggested that motorists traveling south from New York may want to stay on the New Jersey Turnpike rather than getting on I-95. They should cross into Delaware over the Delaware Memorial Bridge south of Wilmington and then get back on I-95. Similarly, motorists traveling north can stay on I-95 through Wilmington or take Interstate 295 into New Jersey and bypass northern Delaware.
DelDOT first learned of the issue on Friday after an engineering firm, working on an unrelated project, spotted a possible problem. The agency sent out an inspection team on Monday and discovered the tilting.
“It didn't come to us as like an emergency call,” Bhatt said, explaining why a team wasn't sent earlier.
The 40-year-old span was last inspected in October 2012. Such movement, Bhatt said, is unusual. Bridges are usually inspected every two years.
Officials said the main span of the bridge over the water is considered “fracture critical,” meaning that failure of one element could result in failure of the entire bridge, which consists of a concrete deck on steel beams supported by 37 reinforced concrete columns. However, the tilting columns in question support a different area of the 38-span bridge.