"The U.S. Environmental Protection Agency released on Thursday the locations in five states where it will study the safety of a natural gas drilling technique some blame for polluting water.
The EPA expects the initial results from its study on hydraulic fracturing, or fracking, which was mandated by Congress, will be released by the end of next year.
The agency said it will study fracking in the Haynesville Shale formation in DeSoto Parish, Louisiana, and the Marcellus Shale in Washington County, Pennsylvania.
The EPA said it will monitor 'key aspects of the hydraulic fracturing process throughout the lifecycle of a well' at these sites.
It will also do retrospective case studies in North Dakota, Texas, Pennsylvania and Colorado. In those studies, the agency will gather information from reviews, states, industry and communities, and conduct its own field research."
Timothy Gardner reports for Reuters June 24, 2011.