WILMINGTON, Del. (AP) -- The bridge carrying the Interstate 495 bypass over the Christina River in Wilmington has been closed since Monday because four huge support columns are tilting, leading to ongoing traffic problems on I-95, the critical north-south artery that goes through the city's downtown. Here's what we know and don't know about the bridge closure.
-- WHAT CAUSED THE COLUMS TO TILT? Officials haven't said definitively, but they suspect that a mountain of dirt, about two stories high and 100 yards long, caused the soil beneath the columns to shift. The dirt was dumped next to the bridge by a contractor who had permission to use the land, although some of the pile was on state property. The contractor is working with the state to remove the dirt, which wasn't there in 2012, the last time the bridge was inspected.
-- HOW LONG WILL IT TAKE TO FIX, AND HOW MUCH WILL IT COST? There's no price tag on repairs, and officials have said it will take weeks for engineers to design a system to shore up and brace the bridge. The Federal Highway Administration has pledged to cover 90 percent of the cost of permanent repairs because I-495 is an interstate highway, and the agency has already pledged $2 million in emergency funds.
-- WHEN DID THE PROBLEM BEGIN? It's not clear when the bridge started tilting, but the owner of an automotive body shop called 911 in April 15 to report that the cement Jersey barriers dividing the northbound and southbound lanes were separating. Charles Allen Jr. said he also reported the problem to the state transportation department, and that a department official told him someone would look at the bridge. However, it's not clear that the department took any action, and transportation Secretary Shailen Bhatt said he was unaware of Allen's call.
-- WHAT PROMPTED THE DEPARTMENT TO ACT? A private engineer emailed the department on May 29 to report that the bridge appeared to be tilting. The email reached senior managers on May 30, and inspectors were sent to the bridge on Monday, the same day Bhatt was informed. The bridge was closed that day.
-- WAS THE BRIDGE IN DANGER OF COLLAPSE? State officials and outside experts say a collapse was not imminent before the bridge was closed. No one was injured, and Bhatt said the department closed the bridge "in time." However, officials believe the condition of the bridge deteriorated rapidly. Dave Charles, the geotechnical engineer who reported the problem last week, said he returned to the bridge on Tuesday and saw that the columns had shifted even farther.
Nuckols reported from Washington.
Follow Ben Nuckols on Twitter at https://twitter.com/APBenNuckols.
Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.