Del. closes I-495 bridge because of column tilt

AP News
Posted: Jun 02, 2014 9:11 PM
Del. closes I-495 bridge because of column tilt

DOVER, Del. (AP) — Delaware officials on Monday ordered the emergency closure of the Interstate 495 bridge over the Christina River in Wilmington after discovering that four support columns are tilting.

The 4,800-foot bridge normally carries about 90,000 vehicles a day on I-495, which diverts traffic around the city of Wilmington and toward the Port of Wilmington. The route parallels Interstate 95, which runs through downtown Wilmington.

"We understand that there will be a significant impact to the traveling public," said state Transportation Secretary Shailen Bhatt.

He added that he doesn't know how long the bridge will be closed. "It could be a day; it could be significant amount of time," he said.

Officials said the four columns on the south bank of the river are tilted by as much as 2.4 degrees, or 4 percent, from vertical. The bridge will be closed in both directions until officials can determine what caused the tilt and what must be done to address it.

"The whole bridge will be re-inspected," said Rob McCleary, chief engineer for the Delaware Department of Transportation.

Workers placed sensors on the four columns Monday to help engineers determine whether they are still shifting. "By tomorrow early afternoon we should have some data that will tell us, 'Is the bridge continuing to move or has it stopped?'" Bhatt said.

Crews also excavated around some columns where they tie into concrete footers to make sure there was no separation between the footers and columns. Bhatt also said soil borings have been taken to look at pilings and check the soil beneath the columns.

"I've got more questions than answers right now," he said.

Delaware transportation officials said the agency received a report late Friday from an engineering firm working on an unrelated project about a possible problem with the bridge. The department sent out 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 I-495 will be closed northbound at Terminal Avenue, which leads to the port, and that local northbound traffic can stay on I-495 to Terminal Avenue. Southbound traffic on I-495 will be closed at the Pennsylvania state line, with traffic diverted onto I-95 southbound. Southbound port traffic is being directed to Interstate 295 east and then to Delaware 9 north to the port.

Bhatt warned that closing the bridge and shifting traffic onto Interstate 95, which already is congested during the morning and afternoon rush hours, will have a significant impact for motorists.

"We get a lot of traffic on 95 through here," he said. "You can't take 90,000 vehicles and just shift them onto 95 and not expect to have an impact."

Delaware officials are working with counterparts in surrounding states to advise motorists and trucking companies of the closure.

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.

"The main span is not what's in question here," McCleary said.

The bridge was built in 1974 and is scheduled for inspection every two years. It was last inspected in October 2012.