Michele Hallowell contributed to this post.

Recent earthquakes near Youngstown, Ohio are alleged to have been caused by the increased underground injection of wastewater produced in the hydraulic fracturing boom in the Marcellus and Utica region. After reports that the wells may have been sited on a geologic fault line, environmentalists have been quick to use the quakes to call for broader federal regulation and drilling moratoriums.

Like other oil and gas drilling techniques, hydraulic fracturing produces brine wastewater that must be treated and appropriately disposed. Publicly owned treatment works (POTW) treat many kinds of wastewater, but concerns have been raised about the POTWs’ ability to adequately treat wastewater from fracking operations. In response, certain states, like Pennsylvania, have imposed moratoriums on the treatment of fracking wastewater at POTW’s. The alternative, and EPA-preferred method of disposal, has long been injection into underground wells.

Underground injection has been used for wastewater disposal in oil and gas operations since the 1930’s. It is ubiquitous throughout the Western states, where the geology is favorable. While injection is virtually impossible in most of the Marcellus due to impervious rock layers, it is possible in parts of Ohio overlaying the Utica. Ohio currently has 178 Class II injection wells, which accept fracking and other drilling wastewater—some of it from nearby Marcellus states like Pennsylvania where injection is impossible and POTW disposal is virtually illegal.

In response to the recent Ohio earthquakes―including a 4.0 magnitude earthquake on December 31, 2011―NRDC has argued the quakes may not have occurred if wastewater had been injected into Class I wells as opposed to Class II wells. Class I well regulations require a seismicity determination prior to permitting and also expressly prohibit wells in areas where earthquakes could compromise the integrity of the injection zone or endanger groundwater. Federal Class II well requirements do not require the same measures.

Whether the quakes were caused by the injection has yet to be determined. And the consequences of these events are difficult to predict (last Wednesday, the Youngstown City Council approved a moratorium on oil and gas drilling and underground injection, raising legal issues regarding the scope of Youngstown’s home rule authority. It could be that EPA—which sets the federal standards under the UIC program—will bolster the seismic requirements for Class II wells. Indeed, in a potentially related move, EPA officials have asked as many as 26 states for information on how "produced water" and other drilling wastes are currently managed under the Resource Conservation and Recovery Act (RCRA). It could also be that the injections are not determined to have caused the quakes, or that the overall seismic risk from disposal of oil and gas wastewater into Class II wells remains nominal, despite these incidents.

For the time being, however, it is critical to make clear that the facts of this case pertain only to underground injection and not the hydraulic fracturing process itself—which most experts agree does not transfer enough energy from the deep depths of a typical fracture to present an appreciable seismic risk. As concerns flare, industry should anticipate heightened scrutiny and likely additional regulation under the EPA’s underground injection program.