NTSB urges bridge owners to fix drainage, corrosion problems that plagued Fern Hollow

Year after year, a devastating mixture of dirt, debris, leaves and water conspired to clog drains and severely corrode the special steel used to build critical components of the Fern Hollow Bridge a half-century ago, federal investigators announced Thursday.

But a report issued by the National Transportation Safety Board didn’t blame only poor drainage for wreaking havoc on the legs of the span, which broke apart last year in a spectacular pre-dawn collapse that sent vehicles tumbling into a 100-foot-deep gorge in Frick Park, injured drivers and passengers and shook the confidence of the motoring public.

It also fingered another culprit for the calamitous conditions: a head-scratching failure to heed simple yet urgent maintenance chronically flagged by inspectors to improve drainage and prevent corrosion.

“Maintenance activities to address these issues were called for in numerous inspection reports but were not completed,” the safety board wrote.

Who was responsible for following up on inspectors’ recommendations and why maintenance was not addressed remain part of the agency’s ongoing investigation.

The City of Pittsburgh, which owned the defunct bridge, refused to comment on the report’s findings, claiming it could not because it is a party to the safety board’s probe. But a lawyer representing a driver severely injured in the disaster had no trouble firing broadsides at the city.

“Hopefully, the NTSB recommendation will underscore the importance of bridge inspections and bridge maintenance and prompt bridge owners, like the City of Pittsburgh, to do their job and fix problems rather than ignore them once problems are discovered,” said Jason Matzus, attorney for Clinton Runco, a Squirrel Hill dentist who broke his neck, ribs and sternum when his Toyota Corolla soared into the ravine on Jan. 28, 2022.

In its report, the agency went far beyond addressing problems with the Fern Hollow Bridge. It also sounded an urgent alarm about more than 10,000 other spans in the U.S. built from the same type of alloy – uncoated weathering steel.

The safety board raised the prospect that other bridges built from a similar material might not have been maintained properly and deemed it “critical” that bridge owners – including municipalities, counties and states — prevent water and debris from building up.

While investigators don’t know how widespread or severe the problem might be, they cited a dire need for proper maintenance and called on the Federal Highway Administration to develop a plan for state transportation and others to deal with the issue.

In Fern Hollow’s case, year after year inspectors flagged drainage problems and degradation so severe that gaping holes were left in the bridge’s legs.

Inspectors not only wrote about their findings but included alarming pictures of the worst damage – flaking steel, severe corrosion and sections of the 447-foot-span that had been eaten away.

Clogs led water, deicing salts and other contaminants to end up in spots not designed to handle the flow, such as the bridge legs.

The problem was chronic.

In 2009, Fern Hollow’s downspouts had to be replaced, Its drains were cleared. But two years later, the safety board said, an inspection report noted that some drains were clogged again.

For a decade, inspectors continually flagged backed-up drains on the Fern Hollow Bridge and the need to clear them, according to the agency.

But that didn’t regularly happen.

“Clogged drains and the need for associated maintenance work were continually identified in the inspection reports between 2011 and 2021,” the report said. “Reports dating to 2005 and as recent as September 2021 — four months before the collapse — documented corrosion and deterioration of the bridge legs.”

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The Fern Hollow Bridge was built from something called uncoated weathering steel – a kind of alloy used in places that experience wet and dry phases. The steel is designed to not need painting because the passage of time and exposure to weather are supposed to form a protective oxide coating.

But there’s a catch. The steel must be able to dry.

“The dry periods are critical to the steel forming a protective oxide coating, or patina, that resists corrosion over time,” the report said. “The presence of ponding water and debris buildup can trap water on and around the bridge structure, prevent the steel from drying, and preclude the formation of the protective patina, which in turn enables corrosion and deterioration to occur and reduces the safety and service life of the uncoated weathering steel.”

Hota GangaRao, an engineering professor at West Virginia University, said the report indicates that the calamity could have been avoided.

“That’s one part,” he said. “The other part is they should have corrected this situation as they were finding the corrosion is eating into the steel.”

Over the past 16 months, federal investigators and engineers examined 10 bridges in Pennsylvania with steel frames similar to Fern Hollow’s. Some were built from uncoated weathering steel.

“Although not as severe as on the Fern Hollow Bridge, the examinations revealed maintenance problems that allowed the buildup of debris on and around bridge legs, improper drainage, and associated corrosion,” the report said.

The upshot, according to the safety board: “the problem of incomplete maintenance — where maintenance was identified as needed in inspection reports but not completed — was not unique to the Fern Hollow Bridge.”

Thursday’s report isn’t the agency’s final say. Another report, expected within several months, will pinpoint the probable cause of the bridge failure mere hours before President Joe Biden arrived to tout a $1.2 trillion infrastructure plan.