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The Day The Mine Collapsed Jump to map

Homes over an underground coal mine that closed nearly a century ago were damaged in Mt Oliver Borough, PA in July, 2013 when the abandoned mine subsided.

The ground around Frederick Street shifted & sank following heavy rain. Houses buckled. Porches detached. Five homes were declared unsafe to live in. Two were unoccupied at the time. Gas & electric to their homes were shut off. “Do Not Enter” signs were posted.

People who lived in the five impacted houses were told to grab what they could at once. They got out with what they could carry. The American Red Cross arranged food & shelter to adults & children affected by the evacuation. At first, they didn’t know when they could return to collect the rest of their belongings. None of them had purchased mine subsidence insurance to underwrite repairs caused by a closed mine operated by a company that no longer exists.

More widespread damages were discovered as an investigation continued. Foundations & brickwork had cracked, walls bulged, & doors wouldn’t open & close right in seven additional residences. The damages weren’t severe enough to require evacuations. Families could continue to live in those homes.

Mt Oliver Borough residents converged on the next Borough Council meeting. People wanted answers about the mine subsidence & twelve damaged homes. They were told that residents couldn’t return to the five original homes, which were condemned, until the danger was past. Although the PA Department of Environmental Protection (DEP) determined the cause of the houses being damaged was mine subsidence, residents pointed to heavy rainfall or a suspected old water line break as culprits. Borough officials promised to help the affected people to the extent they could.

DEP officials studied old maps of long-abandoned mines. They captured core samples to assess the extent of the problem. A core sample is obtained by drilling into the ground with a hollow tube. A largely intact sample is pushed into the tube. The sample is studied to determine what things look like deep underground – in this case, to see how shaky or widespread a deteriorated mine is. Officials put together a report. They rushed a request for federal funding to stabilize the land as quickly as possible.

Within weeks, work started on the fix. Once homeowners approved the operation, holes were drilled into the ground of each yard where a house was damaged. A mix of sand, concrete & fly ash – also called grout – was pumped into the century old mine to fill it up. With the void filled, ground could no longer subside. Houses were again well-supported.

Stopping the subsidence of the land above the abandoned mine took two months & cost more than $1 million. It was paid for from taxes paid by operating coal mines.

Most of South Pittsburgh & southern Allegheny County is at risk of mine subsidence following hundreds of years of underground mining in the area. The coalfields here, & spread across many states, are the largest in the country. The coal was dug from underground mines using a room & pillar system. Rooms of ore are excavated. Pillars of material are left behind to support the roof. Over time, the pillars decay. They can collapse. If they collapse, the roof may fall, leading to mine subsidence if the mine was shallow enough.

Repairs to land damaged by mine subsidence is paid for by the state.

Repairs to structures damaged by mine subsidence are paid for by the landowners. Cracks in foundations caused by sliding land can be expensive to fix. Homeowners insurance usually doesn’t cover mine subsidence damages.

Mine Subsidence Insurance (MSI) from the DEP pays homeowners for losses caused by mine subsidence. It covers buildings & incidental losses. It costs about 55 cents a year for every $1,000 of coverage.

Since the Mt Oliver mine subsidence of 2013 – where none of the owners of the five severely damaged houses had purchased MSI – the DEP has been sending notifications to people who own property in areas that are at risk for mine subsidence. The DEP estimates that one million buildings have been constructed above abandoned mines. About 60,000 of those buildings are covered by MSI. Everyone else will have to pay for the own repairs if a mine subsistence problem damages their property.

Map marker placements are approximate