The push to find clean domestic energy has zeroed the country in on one resource it has plenty of: natural gas. Vast deposits large enough to supply the country for decades have become the focus of a drilling boom stretching across 31 states. But water contamination has also been reported in more than a thousand cases where that drilling is taking place, raising questions about the primary drilling method being used to get to the gas.

That drilling technique, called hydraulic fracturing, shoots large amounts of water, sand and toxic chemicals into the ground to break up rock and release the gas. The Environmental Protection Agency has declared the process to be safe despite warnings from several of its own scientists that it is not. The gas companies are exempt from federal laws protecting the nation’s water supplies, and are allowed to conceal the identities of their chemicals as trade secrets. Together these things have made it difficult for scientists and investigators to determine the exact cause of the contamination that is occurring in water supplies.

That’s why lawmakers in Congress and in several states are pushing for deeper study of the impact of drilling and for closer oversight of the gas industry. The U.S. House and Senate are considering legislation to reverse the federal exemptions, and New York state is considering a partial ban on drilling anywhere near New York City’s watershed. The industry -- in the form of millions of dollars spent on lobbying, a slew of court cases, and a robust public relations campaign -- is pushing back.