"The Pennsylvania Department of Environmental Protection (PA DEP) is working to regulate salt discharges that result from natural-gas drilling. The move is a response to a statewide increase in drilling and to water pollution in the fall of 2008 that affected a 70-mile stretch of the Monongahela River, the drinking-water source for more than 300,000 people living near Pittsburgh. High levels of total dissolved solids (TDS), including chloride and sulfate, threaten many other Pennsylvania waterways, according to PA DEP. But many gas and business interests say the proposal is a poorly targeted overreaction.
Pennsylvania is at the heart of the latest natural-gas boom. In 2008, the state issued permits for more than 500 deep natural-gas wells, and drilling companies are leasing mineral rights for hundreds more. The Marcellus Shale, which lies about one mile underneath most of Pennsylvania and parts of New York, West Virginia, and Ohio, is estimated to be the third-largest natural-gas field in the world ...."