What Pittsburgh's Fern Hollow Bridge collapse can tell us about Pennsylvania bridges
The collapse of the city-owned Fern Hollow Bridge on Friday has raised concerns about the state of Pennsylvania’s thousands of bridges, nearly 20% percent of which were in poor condition as of a 2018 review by the Pittsburgh section of the American Society of Civil Engineers.
According to the Pennsylvania Department of Transportation, the Fern Hollow Bridge is just one of 175 state- or locally owned bridges in poor condition in Allegheny County alone.
Pittsburgh City Controller Michael Lamb said that given the many bridges and other infrastructure assets in the region that need attention, “it really isn’t surprising that something like this could happen.”
He urged the city and county to look at other bridges also deemed in poor condition because “there’s a good chance it could happen again.”
However, Pittsburgh ASCE past president Jonathan Shimko cautioned against panic, or thinking that “all of our infrastructure is in imminent condition of failure, because that is not the case.”
The overall rating for Fern Hollow was “poor,” but that’s because “engineers are risk-averse by nature,” said Shimko. If there’s an element of the bridge that scores poorly, that will drive the bridge’s overall score, he said.
The guidelines to evaluate a bridge are shared and applied across state and federal agencies, including PennDOT, even if an inspection is done by a third-party contractor. They use a scorecard that ranges from 0-9, with 0 being the worst, for “failed, bridge is out of service and beyond corrective action.”
The part of the Fern Hollow bridge that actually carries traffic — the deck — and the infrastructure underneath that — the superstructure — both scored a “4” under those guidelines, which means their deterioration had “advanced.” However, the structures that support those two components — the substructure — rated a “6,” or satisfactory with “minor deterioration”
While PennDOT keeps records on the state’s bridges, Fern Hollow is city-owned and city-maintained. The bridge’s last inspection was conducted in fall 2021 by a third-party contractor, said Pittsburgh City Council Corey O’Connor; he could not remember who. WESA was not immediately able to secure the most recent report. O’Connor told WESA that while the bridge was known to be in poor condition, “There was no indication that we needed to shut this down."
Both PennDOT and The U.S. Department of Transportation’s Federal Highway Administration maintain a record of bridge inspections. At the federal level, it’s called the National Bridge Inventory; it classifies various parts of the bridge — elements — as falling into four categories called “condition states.”
In 2020, four steel columns that support the Fern Hollow Bridge were classified as “condition state 4.” On the National Bridge Inventory website, that is annotated as “severe,” but a technical guide provides a prescribed set of actions rather than a description.
The Bridge Element Inspection Manual from the American Association of State Highway and Transportation Officials, AASHTO, defines condition state 4 for steel columns as possibly requiring “a structural review” to gather further information.
Neither PennDOT officials nor officials from U.S. Department of Transportation or the Federal Highway Administration responded to questions Friday about the differences between state and federal guidelines and their implications.
“The proper assessment of the condition of bridge elements is the cornerstone of sound bridge management,” the introduction to AASHTO’s manual reads.
When asked what could have contributed to the bridge’s deterioration, Shimko of ASCE said it would not be appropriate to comment immediately because the focus needs to be on securing the site. However, he noted that many infrastructure failures, such as the sinkhole that opened in Downtown Pittsburgh in 2019, result from not a single actor or event, but the culmination of a number of events.
“A lot of which are the out-of-sight, out-of-mind nature of our infrastructure,” he said. “In a bridge, there’s a lot of steel, but a lot of times it’s wrapped in concrete or its supports are covered in a lot of earth.”
That makes it difficult to predict or know what the conditions are without “money and investment to make sure we can maintain what we have built.”
Paying to fix all of the bridges of concern in Pennsylvania is an expensive proposition. President Joe Biden’s infrastructure bill will provide $1.6 billion in bridge funding to the state, and during a visit to Pittsburgh Friday he committed to “fix them all.” Still, there are more than 4,000 state- and locally-owned bridges in poor condition.
While the state has reduced the number of bridges that are structurally deficient, much of the funding that could have been used to address aging roads and bridges instead has been used to fund the State Police for much of the past decade.
The potential cost to replace Fern Hollow Bridge is unknown, and Lamb didn’t want to speculate. He was adamant, however, that the first source of funding not be the new federal pot of money.
“There are other funding sources for emergencies like this,” he said, citing programs through the U.S. Department of Transportation, the Federal Highway Administration, and PennDOT.
For now, local and state officials say they are focused on figuring out what happened to cause the Fern Hollow Bridge collapse. A response team from the National Transportation Safety Board arrived on the scene Friday afternoon, with NTSB Chair Jennifer Homendy saying the investigation will take months.
WESA’s Ariel Worthy contributed to this report.