U. S. EPA. Office of Solid Waste and Emergency Response. [Report to Congress]. “Management of Wastes from the Exploration, Development, and Production of Crude Oil, Natural Gas, and Geothermal Energy.” EPA/530-SW-88-003. December 8, 1987.

Report cites example of water well contamination by hydraulic fracturing fluids, and importantly states that investigation of other suspected cases of contamination was thwarted by the sealing of legal settlements between landowners and drilling companies.

N.B.: 1987 report had been buried and forgotten until an Environmental Working Group report published August 3, 2011, in conjunction with a New York Times story.

• Horwitt, Dusty. Environmental Working Group. “Cracks in the facade: 25 years ago, EPA linked ‘fracking’ to water contamination.” August 3, 2011.
• Urbina, Ian. “A tainted water well, and concern there may be more.” New York Times. August 3, 2011.

Link to copy of 1987 EPA report, hosted by The New York Times.