Port Authority of Allegheny County said Thursday that one of its bridges likely shifted last week because water penetrated a portion of its concrete support structure and then expanded when temperatures plummeted below freezing.
The Port Authority closed the Saw Mill Run Boulevard Bridge that carries light-rail cars and buses between Beechview and Mount Washington after the bridge shifted slightly and was deemed unsafe for travel. Port Authority employees first noticed the shift on Feb. 4.
The bridge is stable, but will remain closed for several weeks as repairs are made, Port Authority said.
Motorists traveling under the bridge will not be affected by the closure, but light-rail passengers have been impacted. The bridge closure has caused all Red Line rail cars to travel via the Blue Line. Before the pandemic, the Red Line carried about 10,000 passengers a day.
The bridge was built in 1977, and was last inspected in October 2020 and its condition deemed satisfactory.
To accommodate impacted riders, the authority is operating a rail shuttle between Overbrook Junction and Potomac Station, and a bus shuttle is operating between Potomac Station and Station Square. Both are running approximately every 20 to 30 minutes, and neither are collecting fares.
