PA Bridge Replacement Plans, Design Announced

FRIDAY, MARCH 11, 2022

On Tuesday (March 8), the Pennsylvania Department of Transportation announced design and construction plans to replace the Fern Hollow Bridge in Pittsburgh after it collapsed in January. The plans are in collaboration with City of Pittsburgh officials and the Federal Highway Administration.

“With the Fern Hollow Bridge seeing more than 14,000 cars daily, we knew it was critical to act quickly to reconstruct,” said Pennsylvania Governor Tom Wolf. “This reconstruction will allow commerce to continue without further interruptions to the lives of community members.”

PennDOT reports that it has selected HDR Inc. and Swank Construction Company to design and construct the new bridge. The Design Build partnership plans to take environmental complexities into account regarding its location with Frick Park.

“We are extremely thankful for our partners at PennDOT,” said Mayor Ed Gainey. “Because of their leadership we have been able to move efficiently to begin the process so we can safely restore this critical piece of our infrastructure to our city. We are encouraged by the progress being made and are looking forward to this next phase of the project to reconnect this critical roadway for our city.” 

According to the release, the team determined after evaluating several options that a three-span continuous composite prestressed concrete I-beam with integral abutments would be the best structure type. Material availability, cost, design concerns and delivery time, along with supply chain concerns, were factored into the decision.

The new structure will reportedly remain along the same roadway alignment and width, but plans to include four 10-foot-wide travel lanes, two-foot-wide shoulders on both sides, a five-foot-wide sidewalk and a 10-foot 5-inch-wide shared use path on the southern side of the bridge.

Currently, field work including survey, core borings and lab testing as part of a geotechnical investigation and an environmental assessment are currently underway. Erosion and sediment controls have also been implemented and monitored by the county’s Conservation District.

Demolition and cleanup of the old bridge is being continued in assistance with the National Transportation Safety Board’s ongoing investigation.

PennDOT expects construction to begin in late April, pending proposed materials being available in a timely manner, with most of the construction taking place this year. Gov. Wolf has announced that $25.3 million in federal funding has been made available for the project, which is a direct result of funds made available in Federal Fiscal Year 2022 from the bipartisan infrastructure law.

“We’re going to build from the bottom up, starting with the substructure,” said Cheryl Moon-Sirianni, PennDOT’s District Executive. “With this design-build approach, we can still be putting the finishing touches on [the design for] the top while we’re working on the substructure.”

Moon-Sirianni added that a shortage of steel “absolutely” played a role in choosing precast concrete, with specialty steel potentially adding 18 months to two years to construction. “It would have taken substantially longer to get steel and even longer to get specialty steel,” she said.

Aesthetic treatments planned include treatments to the concrete pier columns and bridge barriers, painting of the beams, a stream restoration plan, ornamental bridge lighting and a site restoration plan with tree plantings to restore damaged areas. PennDOT is consulting with Pittsburgh Parks Conservancy and the Pittsburgh History and Landmarks Foundation and seeking public input on these elements.

Emergency declarations issued following the collapse reportedly allowed the city and PennDOT to manage construction and design for the project immediately, while also using emergency procurement procedures through the FHWA to being work within seven days of the collapse. According to the release, these emergency procedures have allowed the replacement to occur two to three years earlier than would have been possible using typical design and construction methods.

What Happened

On Friday, Jan. 28 around 6:40 a.m., the Allegheny County Police Department was notified about a partial bridge collapse over Frick Park. Emergency crews arrived at Forbes Avenue Bridge, also referred to as the Fern Hollow Bridge, around Forbes and Braddock avenues.

An articulated Port Authority bus and four passenger vehicles were on the bridge at the time of the collapse, along with a fifth passenger vehicle that drove off the east bridge abutment following the collapse. First responder crews rappelled 100 to 150 feet to reach victims, while others formed a “human chain” to rescue people from the bus.

Authorities reported 10 “minor injuries,” with four people being transported to the hospital. Of the four, one individual was released from the hospital later that day, and one was reported to be a first responder. None of the injuries were life-threatening, said Pittsburgh Fire Department Chief Darryl Jones.

Urban Search and Rescue crews drilled holes into the bridge deck, utilizing search cameras “just to make sure everyone is accounted for.” Search dogs were also on the scene.

“We were fortunate” that no one was killed, Pittsburgh Mayor Ed Gainey said from the scene of the collapse, where he was joined by Allegheny County Executive Rich Fitzgerald, Pennsylvania Lt. Gov. John Fetterman and others.

Initial reports from witnesses described a loud noise and hissing sound, along with a strong smell of natural gas in the area. Responders later confirmed that the collapse caused a gas line to break, prompting an evacuation of homes in the surrounding area. Authorities were eventually able to off the gas line, but a few hours later service was restored and families were permitted to return to homes, according to Jones.

President Biden was briefed on the collapse and spoke with state and local officials prior to his arrival in the city. Biden visited the bridge site around 1:30 p.m. that day ahead of his previously scheduled trip to Carnegie Mellon University’s Mill 19 research and development center to talk about infrastructure, the economy and supply chain issues.

"We saw today when a bridge is in disrepair, it literally can threaten lives,” Biden said at the event. “We're going to rebuild that bridge, along with thousands of other bridges in Pennsylvania and across the country, because it's in our interest for [our] own safety sake and it generates commerce in a way that we can't do now. That's part of how we're going to build a better America.”

Later in the afternoon, 13 members of the National Transportation Safety Board investigation team arrived at the site of the collapse. In their short time there, investigators were reportedly already able to study some of the bridge elements.

On Saturday (Jan. 29), the NTSB announced it had launched an investigation into the collapse, planning to look at the full history of the bridge, including design, construction and maintenance.

NTSB Chair Jennifer Homendy told reporters at a briefing in Pittsburgh on Jan. 29 that the investigation would be “lengthy.” Currently, the final board report on the cause of the collapse will not be issued for 12 to 18 months, but the NTSB hopes it will take less time.

Pennsylvania Gov. Tom Wolf signed a proclamation of disaster emergency for the county following the collapse, authorizing state agencies to use all available resources and personnel, as necessary, to manage this emergency situation. According to the release, time-consuming bidding and contract procedures, as well as other formalities normally prescribed by law, are also waived through the proclamation.

A similar declaration was signed by Gainey on Jan. 30. The declaration will increase the availability of federal funds, facilitate closer coordination between PennDOT and Department of Mobility and Infrastructure (DOMI) and speed up cleanup and reconstruction of the Fern Hollow Bridge.

Crews from Allegheny Crane Rental lifted the Port Authority bus from the site on Jan. 31. Utilizing a 400-ton crane, the company’s largest piece of equipment and built on site at the collapse, the bus was lifted by straps underneath it.

Bridge History, Inspections

The 447-foot, rigid steel frame bridge with three spans was built in 1970 and owned by the city. According to reports, the posted weight limit of the bridge is 26 tons and sees an average of more than 14,000 vehicles a day.

Forbes Avenue is a four-lane, non-divided roadway with two travel lanes in both directions. Sidewalks flanked the travel lanes on both sides, and at the time of the collapse, some snow had accumulated on the roadway and bridge surfaces.

The bridge goes across Frick Park, one of the city’s largest parks, over the Hot Dog Dam Dog Park and a public walking trail. The park was closed for safety reasons; parts of the park were reopened on Jan. 31.

Gainey told reporters the bridge was last inspected in September 2021, with the report from Pennsylvania Department of Transportation stating that the bridge received an overall “poor” rating and has been consistently found to be in this condition in since 2011. The deck condition and superstructure condition received poor scores, while the substructure condition gained a “satisfactory” rating.

According to PennDOT, Pennsylvania has the third-largest number of bridges in the nation and the average age of bridges in the state system is over 50 years old. PennDOT conducts approximately 18,000 inspections annually on state-owned bridges, with inspection intervals based on each bridge’s condition ratings and several other criteria. Inspection intervals reportedly range from 6 months up to a maximum of 48 months.

The “Bridge Conditions” page on the PennDOT site shows 175 bridges in Allegheny County rated as poor. $1.6 billion of funding from the infrastructure bill is expected to go towards the state’s bridge maintenance.

“We do have people go out and inspect the bridges. As you know, Pittsburgh is the city of bridges. We have a lot of them, and they’re routinely inspected,” Jones said at the time. “So, this one caught everyone by surprise this morning.” 

Preliminary NTSB Investigation

In its preliminary report, the NTSB reports that the bridge was an uncoated, weathering steel, three-span, continuous rigid “K” frame structure with two welded steel girders, welded steel floor beams and rolled steel stringers. The ends of the structure rested on reinforced concrete caps on stone masonry abutments, with each girder additionally supported by two inclined, welded and uncoated weathering steel frame legs on concrete thrust blocks.

According to the release, certain areas of the welded steel girders were identified as being fracture critical, but no primary fractures were found in those areas. Initial assessment indicates the collapse began at the west end of the bridge.

As more debris are removed and areas are more accessible, further examination is expected to be performed. The NTSB also plans to conduct forensic examination of several of the bridge’s components, as well as evaluate the design of the bridge, its condition at the time of the collapse, its maintenance and rehabilitation history and its inspection and load rating history.

Footage recovered from the seven cameras on the Port Authority bus will be analyzed for further information by a group of specialists. These cameras include one forward-facing camera, one right side aft facing camera and five interior cameras.

The initial assessment of these cameras is reportedly consistent with the initial assessment of the bridge components.

“The recovery of evidence, including extraction and documentation, is expected to be a lengthy process,” the NTSB wrote. “All aspects of the collapse remain under investigation while the NTSB determines the probable cause, with the intent of issuing safety recommendations to prevent similar events.”


Tagged categories: Accidents; Bridges; Bridges; concrete; Construction; Department of Transportation (DOT); Design; Design build; Federal Highway Administration (FHWA); Infrastructure; Infrastructure; NA; North America; Ongoing projects; Program/Project Management

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