A southbound lane of Route 28 remained closed in Harmar on Wednesday, a day after boulders the size of small cars slid from a hillside onto the busy highway’s shoulder.
PennDOT spokesman Steve Cowan said geotechnical engineers who surveyed the area said two large boulders fell from a height of about 125 feet and brought debris down with them.
After the engineers determined the hillside was stable, Cowan said crews began working to remove the rocks and debris.
It was unclear when the closed lane would reopen. The closed lane is between the Harmar (Exit 11) and RIDC Drive (Exit 10) interchanges, in the area where the two-lane highway opens up to three lanes.
The slide happened around 5 p.m. Tuesday. It’s unclear what triggered it. Just 0.03-inch of rain fell on the region throughout the day, according to the National Weather Service.
“We live in a slide-prone area,” Cowan said. “The area is susceptible to landslides and rock falls.”
That area of the Allegheny Valley Expressway has had so many rockfalls in the past that the roadway was moved away from the hillside years ago to allow for a wider rock fall zone.
The closure caused significant traffic delays. Vehicles backed up about a mile before Exit 10 on Tuesday evening.
The highway is used by about 50,000 motorists a day.
