NYC demands drilling ban

They also want to wrest more regulatory control from state officials.

New York City is one of just four major cities in the United States with a special permit allowing its drinking water to go unfiltered. And that pristine water comes from a network of reservoirs and rivers throughout five counties. If the special permit were revoked, the city would have to build a treatment facility that could cost it nearly $10 billion, according to Walter Mugden, an official at the U.S. Environmental Protection Agency.

That's roughly what the state estimated it would earn from natural gas development over the next decade.

In a letter from the New York City Department of Environmental Protection to state officials, obtained by ProPublica, Commissioner Emily Lloyd said she was not satisfied with state assurances that the environment would be protected from drilling in the Marcellus Shale, a layer of rock that dives 7,000 to 9,000 feet below much of the Appalachian East, including south central New York state.

The letter doesn't offer specifics on how drilling might taint the city's water or explain the basis for a one-mile buffer, but it made clear that as guardians of New York City's water, city officials view drilling as a serious threat.

Lloyd asked that a state, city and federal working group be formed to reassess regulations in the watershed. She also called for the city to be given a say in the state's permit review process, and for the public to be allowed to comment on each well permit, something that is not guaranteed now.

"If you are ranking areas of concern that need extremely careful protection (the New York watershed) would have to be at the top of anybody's list," said Mugden, director of the division of environmental planning and protection at the Environmental Protection Agency, region two. "More than half the state depends on that watershed on a daily basis."

The Marcellus Shale is among several large new natural gas reserves in the United States that are becoming economically viable in a time of record oil and gas prices. Recovering the gas involves a process called hydrofracking -- shooting millions of gallons of water and drilling chemicals at explosive pressure deep underground to break up the rock. Hydrofracking requires more water than most other types of drilling, and the identity of the chemicals, which are sometimes toxic, is protected as a trade secret, making it difficult to assess how waste water can be safely treated and discharged.