There is a recent report that EPA is conducting a "multi-media" investigation into the environmental impacts from Marcellus Shale operations in Washington County, Pennsylvania. The agency is looking for environmental damage that violates federal regulations.
I've visited natural gas operations in Washington County. The county is home to almost 700 Marcellus Shale wells and at least 11 compressor stations. Given the recent news from PennEnvironment that oil and gas companies violated the law 3,355 times between 2008 and 2011 in Pennsylvania, it's safe to assume that some of these operations in Washington County have not been in complete compliance with all applicable rules.
By "multi-media," the agency means they are investigating impacts from air, water and hazardous materials impacts. This approach makes enormous sense. Oil and gas production operations are extremely complex and can impact land, groundwater, surface water, or air--crossing the authorities of various laws. For example, take fracking. Chemicals and fracking waste are stored on the surface, and can spill onto land. Fracking waste may be stored in open air pits that allow toxic air pollutants to evaporate into the atmosphere. These pits can also allow waste to seep into groundwater or run off into surface waters. And there are concerns that subsurface fracking activity has also harmed groundwater. All of these activities are inter-connected, and the EPA is doing the right thing by looking at them in a holistic way.