One small piece of a vast network of makeshift mine shafts collapsed on a construction site not far from Penn Hills High School this morning creating a 30 foot deep sinkhole, Penn Hills construction manager Denny Russo said.
The section collapsed about 10 a.m. 100 feet from the new school building and 15 feet away from a retaining wall supporting the school's bus roadway.
"We're working here with the Pittsburgh coal seam," Mr. Russo said. "It dates back in the '20s and '30s. People would individually mine that seam."
Construction crews sealed some of these underground mines before building the new Penn Hills High School, but the site of this sinkhole wasn't sealed because it wasn't close enough to the construction site.
Mr. Russo said just a year earlier, heavy machinery rolled over the site of the sinkhole without incident.
"Obviously, all of the rain we took in last night puts enough pressure on the roof of that shaft to cave in the structure," Mr. Russo said. "It's typical of Western Pennsylvania. There are sinkholes everywhere."
Mr. Russo said crews are already in the process of filling in the hole and "all structural concerns have been put to rest."
Alex Zimmerman: firstname.lastname@example.org or 412-263-3909.