Thousands of Ohio, Pennsylvania and West Virginia residents live within one city block of highly pressurized underground natural gas storage wells, according to new research from Harvard University.

The study, published this week in the journal Environmental Health, found more than 20,000 homes and an estimated 53,000 people across six states are living within 650 feet of an underground gas storage well. 

“Our results were somewhat surprising in that a lot of these wells are in residential suburban areas, which in terms of the entire natural gas supply chain is definitely a unique kind of land use conflict,” said Drew Michanowicz, a research associate at the Center for Climate, Health and Global Environment at the Harvard T.H. Chan School of Public Health and lead author of the study. 

To store natural gas, companies often inject natural gas into repurposed decades-old oil and gas wells. The practice gained national attention in 2015, when a well in Aliso Canyon, California, failed, leaking natural gas for 118 days. Nearby residents were evacuated and reported suffering from headaches, nosebleeds and rashes. 

The leak released almost 100,000 metric tons of the potent greenhouse gas methane into the atmosphere, equivalent to the emissions created by 530,000 cars in a year. 

Following the Aliso Canyon disaster, the Harvard team in 2017 set out to map the location of natural gas storage wells. 

The new study aims to show what the consequences to human life would look like if another Aliso Canyon-type disaster were to occur. Residents living near underground storage facilities are at risk of possible explosions and exposure to chemicals contained in natural gas. 

“We wanted to know where are the potential worst-case scenarios if something were to go wrong,” Michanowicz said. “ So, where do the most people live? Who’s the most vulnerable?”

Researchers used a combination of census data, satellite data, land use data and addresses to pinpoint homes located near more than 9,000 underground gas storage wells in Ohio, Pennsylvania, West Virginia, New York, Michigan and California. Their mapping model estimates 10,000 more people live near underground natural gas storage wells than previous models found. 

Michanowicz said one of the most striking findings is that in many instances, underground gas storage wells are located within “setback” zones. Many states have laws that set limits on how close industrial activity can occur to homes. 

Companies often use older wells built before setback laws were put in place to store natural gas. In West Virginia, the study found half of the state’s underground storage facilities have at least one well that is near at least one home within the state’s 200-foot setback zone. 

Overall, the researchers found across the six states that 41 percent of underground storage wells are located within one city block of at least one home.

In Ohio, more than half of the state’s underground storage wells are located within one block of a residence affected an estimated 12,000 Ohio homes and over 30,000 residents.

This article was originally published by West Virginia Public Broadcasting.