State inspectors are investigating what caused a 125-ton (109 t) concrete overpass to fall onto Interstate 70 the evening of Dec. 27.
Pennsylvania Department of Transportation (PennDOT) officials said the Lake View Drive Bridge was last inspected in March 2004, and it was visually inspected again in August. The bridge collapsed the same day a news article in the Patriot-News of Harrisburg reported that four out of every 10 bridges in Pennsylvania are structurally deficient or functionally obsolete.
The state owns and maintains approximately 25,000 bridges. Six thousand others are owned by counties and municipalities. Approximately 25 percent of state-owned bridges show significant deterioration to their decking, piers or other integral parts, according to the Federal Highway Administration (FHWA). Engineers have lowered weight limits on more than 700 bridges and closed 50 of them, according to the Patriot-News.
“Bridges must be inspected bridges every two years,” said Jeff Breen, PennDOT’s maintenance chief in Washington County. The next inspection was slated for March 2006.
Michael Baker Corporation of Moon Township, PA, is conducting forensic diagnostic tests on the samples of concrete removed from the scene. Investigators are trying to determine whether overweight truck traffic on the bridge was to blame, or if oversized vehicles colliding with the base of the bridge could have caused the collapse. Road salt and anti-skid run-off could be another factor. PennDOT does not have an estimate on how long the testing will take.
Early speculation also pointed the finger at possible mine subsidence beneath the overpass, but the Pennsylvania Department of Environmental Protection (DEP) has since ruled this out.
“This region of Pennsylvania is very active in longwall coal mining,” said District 12 PennDOT Spokesperson Valerie Petersen. “The DEP tested the site and determined that the Lake View Drive Bridge was not a mining area.”
“There are no active deep mines under I-70 at this time,” said Betsy Mallison, spokeswoman of the state Department of Environmental Protection. Mallison went on to say that mining was detected 15 ft. from the bridge but that did not affect the bridge in any way.
The concrete fell between vehicles passing underneath approximately 5:45 p.m., authorities said. Small pieces of debris fell on a passenger car before the rest of the abutment from the Lakeview Drive Bridge crashed onto I-70 in South Strabane Township, approximately 20 mi. south of Pittsburgh, not far from the highway’s south junction with Interstate 79. The driver and passenger of the car on which debris fell were not injured, police said.
Two large concrete sections formed a “V” when they fell onto the roadway. A minivan driven by Vickie Scott Barber, of Cincinnati, and carrying her two small children, hit the fallen concrete, state police said.
Barber and her 22-month-old son were treated at a local hospital. Her 6-year-old daughter was flown by helicopter to Children’s Hospital of Pittsburgh to be treated for a possible leg injury, police said.
“This could’ve been a major catastrophic occurrence,” Breen said.
Gaylord Plants was nearby when he heard a loud boom and screeching tires. He dialed 911 and then went to investigate, stopping his truck on the bridge.
“I said, ’Holy cow, the whole side of the bridge is gone. We’d better get the heck off of here,’” he said.
With an average daily traffic (ADT) of more than 20,000 vehicles on I-70, PennDOT crews had to work fast to clear the debris and re-open the interstate.
“The westbound lanes were open by 6:15 p.m. on the December 28, followed by the eastbound lanes later that evening at 10 p.m. Emergency bids will be let soon to have the overpass razed,” said Petersen.
The ADT on Lake View Drive is only approximately 400 and the detour is short, but PennDOT said that it will be replacing the bridge in the future. Bids for rebuilding the bridge have not yet been let.
“Our first priority is to remove the bridge and ensure the safety of motorists,” said Petersen. CEG