The Port Authority of Allegheny County says a shift in a portion of the Saw Mill Run Boulevard bridge discovered Feb. 4 was likely caused by a combination of water infiltration and freezing temperatures. In an update published on its website, the Port Authority said its engineers and consultants determined “water that penetrated a portion of the concrete support structure of the Saw Mill Run Boulevard Bridge and expanded when temperatures plummeted below freezing is likely what caused the span to shift several inches.”
Transit operations on the bridge, which hosts seven Port Authority bus and Red Line trains, was suspended and detoured when the shift was discovered. An employee noticed a joint on the deck of the bridge appeared to have expanded. The Port Authority is working with third-party contractors on repairing the bridge and says a timeline for repairs is expected next week. The Port Authority will keep the bridge closed, but reiterates it is stable.