Water and winter cold likely caused Pittsburgh’s Saw Mill Run Boulevard bridge to shift, the Port Authority said Thursday. A rapid freeze-thaw cycle allowed water to enter part of the bridge’s support structure, and when temperatures dropped, it forced the structure to shift by “several inches.”
The agency closed the bridge on the morning of Feb. 4 after an employee noticed that part of the bridge’s surface seemed to have expanded. While engineers and a bridge consultant deemed the bridge in stable condition, bus and rail traffic were suspended immediately.
The 1,052-foot bridge carries the South Busway over Saw Mill Run Boulevard. The Port Authority is still developing a timeline for its repair.
Since its closure last week, all travelers on the Red Line have been routed along the Blue Line. Bus and rail shuttles run every 20 to 30 minutes — a rail shuttle between Overbrook Junction and Potomac station, and a bus shuttle from Potomac Station and Station Square — and can be ridden for free.
Port Authority officials said the bridge’s last inspection took place in October 2020 and it was found to be in satisfactory condition.
