Three-dimensional laser scan image showing remaining section on bottom of northwest leg (pictured rotated on its side) of the Fern Hollow Bridge post collapse. (NTSB image)
Investigators looking into the 2022 collapse of a Pittsburgh bridge want transportation officials nationwide to examine more than 10,000 other spans in the United States with similar construction to ensure they do not have the same kind of corrosion that was found on that city's Fern Hollow Bridge.
The National Transportation Safety Board (NTSB) said in a report released May 18 that drainage problems on the weathered steel bridge that failed allowed the metal legs to deteriorate over time. It also found that for years maintenance needed to clear the debris, dirt and leaves that were causing the problem at the Fern Hollow Bridge site was not properly done, the Associated Press reported, even though inspectors noted the issue.
Rust that caused the deterioration of the Pittsburgh bridge's steel legs and allowed holes to form in the structure was noted on every inspection done since 2005, including one completed just four months before the Fern Hollow Bridge fell into a ravine on Jan. 28, 2022.
Work was done in 2009 to clear the debris clogging the bridge's drainage system, but that was not repeated in the years since even after inspectors noted on all reports between 2011 and 2021 that the drains had become clogged again.
Pennsylvania Department of Transportation (PennDOT) spokesperson Alexis Campbell said in a statement that the agency is still reviewing the NTSB report, and the state will continue cooperating with the investigation. Last fall, PennDOT issued a safety bulletin focused on the maintenance issues with these steel bridges in response to the NTSB's preliminary findings.
"Safe, reliable infrastructure is a top priority of the [Gov. Josh] Shapiro administration, and we are committed to ensuring Pennsylvanians and all motorists can travel across the Commonwealth safely," Campbell said. "To that end, PennDOT remains proactive in its review, analysis and maintenance of its bridges."
Feds Urge States to Properly Maintain Steel Bridges
The Pittsburgh bridge span that fell last year dropped a bus and four cars some 100 ft. into a ravine, injuring several people just hours before President Joe Biden was scheduled to visit the city to promote his massive infrastructure law. The span carried Forbes Avenue over Frick Park, Fern Hollow Creek and Tranquil Trail.
A new bridge opened to traffic last December after its design and construction were fast-tracked.
The NTSB said that these types of steel-frame bridges can last for decades if they are properly maintained.
In the Pittsburgh case, however, the drainage issues prevented the steel from developing a protective patina that would have kept the corrosion at bay. The federal agency's investigators looked at 10 other steel-framed bridges in Pennsylvania and found similar maintenance problems, although none were as severe as what was discovered at the Fern Hollow Bridge.
It is unclear how widespread these issues are nationwide, but the NTSB wanted to urgently call them to bridge owners' attention even though it has not completed its investigation of the Pittsburgh bridge collapse.
The NTSB said in its report that it is critical for bridge owners — usually cities and states — to clear any "accumulation of water and debris on bridges with weathering steel components."
The agency wants the Federal Highway Administration (FHWA) to help bridge owners identify similar problems and complete the needed bridge safety work. In addition, the FHWA will review the NTSB recommendations and work with bridge owners to carefully study inspection reports to decide what needs to be done.
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