10K bridges similar to Pittsburgh one that collapsed should be checked for corrosion, report says

Investigators looking into the collapse of a Pittsburgh bridge want transportation officials nationwide to examine more than 10,000 other bridges with similar construction to ensure they don’t have the same kind of corrosion that was found on the bridge that collapsed.

The National Transportation Safety Board said in a report Thursday that drainage problems on the weathered steel bridge that failed allowed the metal legs to deteriorate over time. It determined Pennsylvania neglected for years to perform the maintenance needed to clear the debris, dirt and leaves that was causing the problem 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 collapsed on Jan. 28, 2022. Work was done in 2009 to clear the debris clogging the bridge’s drainage system, but that wasn’t repeated in the years since even after inspectors said in every report between 2011 and 2021 that the drains had become clogged again.

Officials at the Pennsylvania Department of Transportation didn’t immediately respond to questions about the NTSB recommendations. They issued a bulletin last fall focused on the maintenance issues with these steel bridges in response to the NTSB’s preliminary findings.

The Pittsburgh bridge span that fell last year dropped a bus and four cars some 100 feet (30 meters) into a ravine, injuring several people hours before President Joe Biden visited the city to promote a massive infrastructure law. The span carried Forbes Avenue over Frick Park, Fern Hollow Creek and Tranquil Trail.

A new bridge opened to traffic in December after design and construction were fast-tracked.

The NTSB said that these kind of steel-frame bridges can last for decades if they are properly maintained. But in the Pittsburgh case, the drainage issues kept the steel from developing a protective patina that would have kept the corrosion at bay. Investigators looked at ten similar bridges in Pennsylvania and found similar maintenance problems although none were as severe as the Fern Hollow Bridge.

It’s not clear how widespread these issues are nationwide, but the NTSB wanted to urgently call them to bridge owners’ attention even though it hasn’t completed its investigation of the Pittsburgh bridge collapse.

The NTSB said in its report that it’s critical for bridge owners, usually cities and states, to clear “accumulation of water and debris on bridges with weathering steel components.”

The agency wants the Federal Highway Administration to help owners identify similar problems and complete the needed bridge safety work.