June 3, 2014 at 3:54 pm

Delaware bridge tilt likely from ground shifting

DelDot crew members surround a support column holding a span of the I-495 bridge over the Christina River Monday, June 2, 2014, after it shifted four degrees to the right prompting the closure of the span. (Kyle Grantham / The Wilmington News-Journal)

Dover, Del. — Engineers say subsurface ground movement appears to have caused supporting columns on an Interstate 495 bridge in Delaware to tilt, forcing the indefinite closure of the highway that is a major East Coast artery.

Officials said Tuesday they believe the bridge over the Christina River is stable enough to support itself, but that re-opening it to traffic could overload the structure.

Four pairs of 50-foot columns have been found to be tilting, with the top of one column roughly two feet out of line with the bottom. Cars are being diverted onto the already busy I-95 causing even more traffic.

Engineers are conducting tests to determine the exact cause of the problem. No exact timetable for the bridge to reopen has been determined.

The emergency closure created heavier-than-normal traffic conditions for motorists on a major East Coast artery, Interstate 95, though no major problems were reported. The bridge normally carries about 90,000 vehicles a day, routing traffic around Wilmington and freight trucks to the port of Wilmington. The closing forces more traffic onto I-95, which runs through downtown Wilmington, and already is heavily congested during the morning and afternoon rush hours.

Delaware officials put up message boards and were working with their counterparts in surrounding states to help get the word out.

“We’re basically letting from Florida to Maine know that this issue is going on in Delaware so that trucking interests can be made aware,” Transportation Secretary Shailen Bhatt said Monday evening. “You can’t take 90,000 vehicles and just shift them onto 95 and not expect to have an impact.”

Bhatt suggested that motorists traveling south from New York 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.

Officials said 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.

Delaware transportation officials said the agency got a report late Friday from an engineering firm working on an unrelated project about a possible bridge problem and dispatched an inspection team Monday morning.

“It didn’t come to us as like an emergency call,” Bhatt said, explaining why a team wasn’t sent earlier.

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.

Built in 1974, the bridge is scheduled for inspection every two years and was last examined in October 2012.