The National Transportation Safety Board (NTSB) recently recommended that federal and state authorities review inspection reports and identify incomplete follow-up actions for bridges made of uncoated weathering steel.
The recommendation is part of the ongoing investigation of the Jan. 28, 2022, collapse of the 447-foot-long Fern Hollow bridge in Pittsburgh.
The bridge experienced structural failure and fell approximately 100 feet. Six vehicles were on or near the bridge at the time.
NTSB investigators found corrosion, deterioration, and section loss on all the bridge’s legs, some resulting in holes.
Prior inspections performed on behalf of the Pennsylvania Department of Transportation identified problems with drainage, but maintenance was not regularly performed.
NTSB investigators found other Pennsylvania bridges with similar issues. The agency asked the Federal Highway Administration to develop a process for bridge owners to perform follow-up actions on bridges with uncoated weathering steel components.
Debris, dirt, and leaves blocked the Fern Hollow Bridge’s drainage systems, allowing water to drain where it wasn’t intended and preventing a protective oxide coating, or patina, from forming. Periods of dryness are required for a patina to form on uncoated weathering steel. The patina helps the steel resist corrosion over time.
The final investigative report will be released later this year.