Concern is growing in Westchester over a controversial practice of extracting natural gas from a prehistoric layer of shale a mile beneath the earth's surface.

More than 35 people, including local representatives, turned out Wednesday night to hear a Sierra Club sponsored presentation on hydrofracking, a method of drilling for natural gas that many speculate could come to the Catskills and put Westchester's water in jeopardy.

"There is a lot of potential damage and it's disconcerting," said Marc Sussman, 58, a former Air America radio host who also works in finance and traveled from New York City to the Greenburgh Nature Center in Scarsdale for the presentation.

Chris W. Burger, chairman of the Broome County Energy Commission in Binghamton, NY gave a thorough 90-minute presentation on hydrofracking weighing its environmental costs verses economic benefits.

Hydrofracking involves drilling into Marcellus Shale, a layer of earth 400 million years old around a mile beneath the earth's surface.

A vast swath of the natural gas rich shale lies underneath much of the eastern seaboard stretching from New York to West Virginia.

Utilizing relatively new technology, companies are able to drill down and horizontal into Marcellus Shale, then pump in a high-pressure brew of water, sand and chemicals that then force natural gas toward pump spigots on the surface.

However, the method utilizes millions of gallons of water per well and dredges up toxic heavy metals as well as radioactive material. Many fear that should hydrofracking come to the Catskills, reservoirs from which Westchester and New York City get drinking water could be polluted.

"Am I worried about it? Of course I am," said Gerri Currall, 58, a Scarsdale resident and member of the Sierra Club who helped organize the presentation.

Yancy Roy, a spokesman for the state Department of Environmental Conservation, said there have been 58 applications to hydrofrack in New York State, none of them in the watershed in which Westchester and New York City get their water. He added that there are more than 13,000 traditional oil and gas wells, those that go straight down and use relatively little water, already in New York State.

The Department of Conservation is currently working on a Supplemental Generic Environmental Impact Statement on hydrofracking. No permits can be issued until its completion.

"We're still doing a review and we don't have a timeline," Roy said

Even though hydrofracking in the Catskills may not be imminent, some Westchester leaders are still very concerned.

"Just because there are not permits at this juncture in the watershed doesn't mean there won't be," said Peter B. Harckham, who was at the presentation and serves on the Westchester County Board of Legislators.

Westchester county legislator Judy Meyers, a representative from Senator Andrea Stewart-Collins office and Michael Kaplowitz, a state senate candidate, were also in attendance.

John Senn, a spokesman for the Environmental Protection Agency, said the federal government is also studying hydrofracking.

Meanwhile, the New York City Department of Environmental Protection has spoken out against potential hydrofracking in the Catskills.

"We don't feel there is a way to allow for drilling in the watershed without posing significant risks to our water supply because our water supply is unfiltered and we invested an incredible amount of resources and money into keeping it that way," said Farrell Sklerov, spokesman for the DEP. "We think this could put all that at risk."

"Scarsdale Village Director Alfred Gatta said he was alarmed by
potential Catskill hydrofracking.

"In order to protect my village and protect my residents and everyone else who uses the water from the Catskills, a rational, analytical discussion needs to be had in regards to the impacts to our drinking water," he said.

Bart Hamlin, who serves on the Scarsdale Environmental Advisory Council, said the potential for polluted water is "a very serious issue."

In his presentation, Burger showed several ways in which polluted water could make its way to the aquifer. They included dredge pond leaks, polluted water working up to the aquifer through natural cracks, deterioration of gas wells over time and truck spills.

Many pictures in the presentation were of neighboring Pennsylvania, where hydrofracking has gone on since 2007.

Marcellus gas drilling, though not directly hydrofracking, was determined the culprit in polluted water wells near Dimock, PA, and some believe that it was also to blame for a fish kill along miles of Dunkard Creek.

Carl S. Kirby, a professor of geology at Bucknell University in Lewisburg, PA, said the pros and cons of hydrofracking are not black and white.

"With any extractive industry there are going to be some environmental costs and benefits," he said. "Society is having a real hard time deciding."

At the conclusion of his presentation, Burger said the future of hydrofracking in New York is "in a holding pattern" as the state DEC works through more than 14,000 comments it received on its initial Environmental Impact Statement.

"It's very much in the air where this is going to go, but the track record is not good," he said. "This is going to be a tough fight, there are powerful forces on each side, but if anybody can do it, New York can do it."