You may have been walking over hollow ground before. There are mines scattered throughout Pennsylvania. Especially near Freedom, New Sewickley, and Conway. All of these mines used room-and-pillar mining, which was the common, modern mining style for when they were in operation. All mines in Pennsylvania were  iron, zinc, lead, clay, and most of them were coal.

In this case, we have clay mines under the schools. There are no mineshafts documented underneath the school, however there is sinking prevalent, just at a very low rate. The sinking is not as rapid as it used to be. There have been mineshafts that were filled in to achieve this slow rate.

“After eight years of fighting to obtain funding and putting up with the noise and dust caused by drilling, the end is near for the Freedom Area School District’s mine subsidence problem,”  Beaver County Times on June 10, 1985. The article later comments on how there were multiple issues with water lines due to the majority of mines being undocumented, and the Department of Environmental Resource’s Abandoned Mine Reclamation Bureau (DER) had to experimentally drill to find mineshafts. The first mine in Pennsylvania was in Pittston, PA, and at that time no records were made. If some maps were made, they were difficult to preserve.

“An evacuation plan has been developed by the district, Extensometers- devices which measure any vertical or lateral movement- have been installed on the buildings. If movement occurs, it will set off an alarm in the superintendent’s office,” the same article indicates. There are still extensometers implanted on the building today, so if there was any dramatic change in the level of ground evacuation would happen immediately.

“As the director of building and grounds, I have a lot of information on the mines. I’m the one who would be alerted if the extensometer went off, but for now we have nothing to worry about because the mines are mostly filled in.” Gary Mortimer says, and he is correct. The mines were filled in and there has not been any significant sinking, so as of now the infrastructure of the school is in safe hands.