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© UnknownOhio
Akron - Millions of gallons of drilling waste have been injected underground in Ohio, leading some to worry about possible ties to earthquakes.

The drilling practice known as hydraulic fracturing uses chemically-laced water to free oil and gas from underground shale formations. Ohio has 181 wells to inject waste fluid underground.

The Akron Beacon Journal reported that nearly 50 percent of the drilling waste comes from Pennsylvania, which last year banned shipment of the liquid to state water treatment plants.

In contrast to Ohio, Pennsylvania only has eight injection wells, due to its underground geology.

In Pennsylvania, a drilling boom into the Marcellus shale is under way. Ohio drillers worry that the flood of waste fluid from Pennsylvania will crowd out space for Ohio waste as drilling into the potentially-lucrative Marcellus and Utica shale spreads, Tom Stewart, executive director of the 1,500-member Ohio Oil & Gas Association, told the newspaper.

Ohio cannot ban shipments from other states, as they are protected under the U.S. Constitution.

Between 2007 and 2010, Ohio injected nearly 1.2 billion gallons of waste underground. The liquids spread out in the rock layers, making it impossible to predict how much more can be stored. However, it is unlikely the ground can store an extensive amount, as the drilling industry in Ohio has been using injection wells since the 1930s.

Geologists suspect that the drilling fluid can trigger earthquakes along geological fault lines by allowing rocks to flow more easily past one another.

Injection wells for drilling waste were banned in an earthquake-prone area of central Arkansas after more than 1,000 small earthquakes hit the area over the last year. Arkansas has about 500 injection wells, compared with Ohio's 181.

Injection well operators say there is no clear link between earthquakes and fluid being pumped underground. No operating Ohio wells have been linked to earthquakes, but a now-closed well in Ashtabula County was.

The operation, run by Resource Environmental Services Inc. from 1986 to 1994, was linked to numerous small earthquakes between 1987 and 2003, Michael Hansen, state geologist and director of the Ohio Seismic Network, told the newspaper.

West Virginia, Colorado and Texas have also raised questions about earthquakes and injection wells.