The National Transportation Safety Board won’t officially determine until Wednesday why the Fern Hollow Bridge collapsed two years ago, but state, local and federal officials already have made a series of changes about how bridges are inspected and maintained.
Those include the state updating inspection procedures to better flag bridges with evidence of continuing deterioration, Pittsburgh expanding its division that oversees bridge maintenance and hiring a consultant to recommend maintenance schedules and prioritize work on the city’s 147 bridges, and adding federal recommendations about how states care for bridges made with uncoated weathering steel such as the old Fern Hollow structure.
The changes are all interim steps agencies and officials have taken after Fern Hollow — it had been continuously rated in poor condition for more than 10 years — collapsed from Forbes Avenue in Squirrel Hill into Frick Park underneath it about 6:40 a.m. Jan. 28, 2022. Nine people were injured when six vehicles, including a Pittsburgh Regional Transit bus, fell into the ravine.
The NTSB will release its findings Wednesday, but in many cases, officials didn’t need to wait for the final cause to know changes should be made.
Nearly 6,000 pages of investigation documents released by the NTSB last month include inspection reports on the bridge over more than 15 years, transcripts of interviews with front-line bridge inspectors and contractors, reports from state and local officials charged with monitoring the condition of bridges across the state, and technical reports from experts who examined the ruins.
NTSB investigators collected the information as part of their effort to reach a definitive conclusion on why Fern Hollow collapsed.
The documents also outline procedural changes agencies have made as a result of shortcomings identified during the two-year investigation.
“I’d say [Pennsylvania Department of Transportation] has done a really good job of taking the lessons from the collapse and the federal government, too,” said Roberto Leon, a construction engineering professor at Virginia Tech University who has followed the bridge investigation.
“The speed with which these changes have occurred testifies to the importance of this failure. Turning around a big ship only happens when you have a big problem.”
New inspection guidelines
At the state level, the Pennsylvania Department of Transportation issued a “technical bulletin” on Nov. 22, 2022, to the agency’s 11 maintenance districts. That 31-page document outlines a series of changes in how inspectors should review more than 26,000 bridges and how state officials should handle those completed inspections.
Michael C. Kaiser, acting deputy secretary for highway administration at the time but now retired, wrote that the bulletin was developed after the Fern Hollow collapse following an “in-depth review” of its procedures. Although the bridge is owned by the city of Pittsburgh and inspections are frequently done by private engineering firms, PennDOT reviews those inspections and files them with the Federal Highway Administration.
As a result of the review, the agency made a series of procedural changes designed to collect and report the best information about the condition of bridges, and then present it in inspection reports so that state oversight engineers who review them can easily determine whether additional action should be taken. With Fern Hollow, field inspectors had identified deteriorating conditions over more than 10 years, but they never changed the condition rating or called for a review of the 26-ton load limit on the bridge.
Those deteriorating conditions included holes in support legs growing from about 2 inches by 2 inches to about 12 inches by 12 inches, among other problems.
PennDOT reviewers, who could have asked questions or called for more work based on what was in the reports, instead routinely approved them. In an August 2022 interview with NTSB investigators, Rich Runyan, assistant chief bridge engineer, said he considered it unusual that the department didn’t question inspectors.
“It is surprising to see, you know, comments, sketches, a number of things in the report pointing to increased — and noting increased deterioration — and yet that never crossed over to the load rating, is very surprising,” Runyan, who is now the department’s chief engineer, told investigators.
“… To go several inspections and note the increased loss and that not result in a new load rating is one of the head scratchers, in my opinion, of this whole thing. That never — nobody in that chain of, you know, whether it be our reviewers or the city, or even, you know, the inspectors didn’t see that as enough to populate new numbers and possibly lower the [weight limit] posting.”
As a result of the Fern Hollow incident, the department changed a series of inspection policies immediately with the technical bulletin.
Those changes include conducting a load review every 10 years even if conditions haven’t changed appreciably; requiring photos, detailed sketches and precise measurements showing areas that have deteriorated, including measuring the thickness of the remaining metal; and brushing away rusted areas to show the actual condition of the remaining metal.
“Such cleaning and documentation of section losses is essential in determining the load carrying capacity of bridges, tunnels and other structures and to the decision-making process for maintenance recommendations to maintain safety of highway systems within the Commonwealth,” the bulletin said.
In addition, inspection reports — they can run hundreds of pages — now must have a summary sheet on the front identifying changes from the previous report so that oversight engineers can quickly identify whether a bridge might need additional attention.
The new requirements will be part of a new Best Practices Load Rating Manual that is under development.
Kent Harries, a professor of civil and environmental engineering at the University of Pittsburgh, said more thorough inspection reports are only valuable if agencies have the resources to follow their recommendations.
“Certainly, more detail is better detail, but what good is it if the resources aren’t there to do the work?” he said. “This is the issue. [The U.S.] left things go for a long time. You have to prioritize bridges to take care of the worst ones first.”
More city attention
The Fern Hollow incident was a rude welcoming for Pittsburgh Mayor Ed Gainey’s administration, occurring less than a month after he took the oath of office.
The early morning collapse focused a spotlight on serious problems with a series of major bridges among 147 the city owns. For years, the city had done minimal work on many of its bridges, to the point where last February it closed the Charles Anderson Bridge that carries the Boulevard of the Allies into Schenley Park until it can be rehabilitated.
Almost immediately after Fern Hollow, the city hired engineering consultant WSP Inc. to evaluate all of its bridges, determine what work was needed and prioritize which projects should be done first. The consultant also looked at routine maintenance needs for the bridges because recommendations for routine items at Fern Hollow such as cleaning drains and repairing holes never were performed.
Last March, the consultant identified 66 bridges that needed high-priority repairs over the next two years at an estimated cost of $11.7 million.
For major rehabilitation work such as Charles Anderson, the city also has started working more closely with the Southwestern Pennsylvania Commission. That agency reviews road and bridge projects for a 10-county area to set priorities for federal funding, but the city hadn’t pushed the agency for help for more than a decade.
That renewed relationship led to SPC working with the city to fast-track the estimated $48 million Charles Anderson rehabilitation, which hadn’t been scheduled for major work yet despite being rated in poor condition since 2012.
The city also has beefed up the staff for its bridge division in the Department of Mobility and Infrastructure. In 2023, the city hired three engineers, including a chief engineer for bridges and structures, a bridge maintenance supervisor and a project manager.
This year’s budget calls for adding a bridge maintenance foreman and three bridge maintenance workers.
Special bridge review
The Fern Hollow Bridge that collapsed was built with uncoated, weatherizing steel, which will form its own protective layer known as patina if it goes through wet and dry periods. Investigators learned early on that despite repeated inspection recommendations to clear drains to allow the bridge to dry, the city left the drains clogged, and the protective layer never formed, leading to deterioration that contributed to the collapse.
Investigators reviewed reports on 10 other uncoated bridges in Pennsylvania and found that problem wasn’t unique to Fern Hollow.
As a result, in May 2023, the NTSB issued an interim report on Fern Hollow that recommended owners of about 10,000 bridges that used weatherizing steel across the country pay special attention to proper drainage. It called on the Federal Highway Administration to develop proper procedures for state departments of transportation to provide the best care for those bridges.
The FHWA’s Joseph L. Hartman, director of the office of bridges and structures, issued those recommendations in July.
“FHWA continues to work closely with the NTSB to support its investigation of the January 2022 Fern Hollow Bridge collapse in Pittsburgh and will work expeditiously to address any recommendations NTSB issues to ensure the safety for all our nation’s bridges,” the agency said in a statement last week.
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Ed covers transportation at the Pittsburgh Post-Gazette, but he's currently on strike. Email him at eblazina@unionprogress.com.