Hundreds of people on both sides gathered Monday for what are expected to be contentious public hearings on a federal environmental study of a natural gas drilling technique aimed at tapping a rich formation beneath much of the Northeast.

Opponents of the process — hydraulic fracturing, or fracking — carried signs saying "Kids can't drink gas" and "Protect our water. Stop fracking America." Supporters, including union workers eager for jobs, carried signs that said "Yes to science, no to paranoia" and chanted "Pass gas now!"

The Environmental Protection Agency is holding four-hour hearings in Binghamton beginning at noon and again at 6 p.m. Two more sessions are scheduled for Wednesday.

The EPA is considering how broadly to construct its study of fracking, ordered last year by Congress after the agency's 2004 study that declared the technology safe was widely criticized as flawed. That study had enabled passage of 2005 energy legislation exempting fracking from federal regulation under the Safe Drinking Water Act.

The drilling technique involves blasting millions of gallons of chemical-laced water mixed with sand into the ground and then horizontally to release natural gas from rock formations thousands of feet underground. Opponents say the process can poison drinking water but the industry, strongly opposed to federal regulation, contends there's no proof that fracking chemicals have contaminated drinking water.

The hearings come as a gas rush barely two years old is under way in Pennsylvania and West Virginia, with drilling companies tapping into the vast and lucrative Marcellus Shale region underlying those states, New York and Ohio. Some geologists estimate the Marcellus might contain more than 500 trillion cubic feet of natural gas, of which 50 trillion cubic feet might be recoverable by fracking — enough to supply the entire East Coast for 50 years.

The proximity of the gas stores to the large East Coast energy market makes it particularly valuable. But its location brings drilling to a densely populated region and fears of water contamination of the Delaware River watershed that provides drinking water for 17 million people from Philadelphia to New York City.

"There's no way this can be done safely. It will toxify the air, water and soil," said protester Kathy Shimberg, 73, of Mount Vision, N.Y., wearing a T-shirt that read "Love N.Y.? Don't frack it up."

"Gas is not a clean fuel and the extraction process is massively unclean," she said.

New York's Department of Environmental Conservation has upheld issuing drilling permits until it draws regulations to govern the process. Complaints of wellwater contamination and surface spills of post-fracking water have forced revision of state rules in Pennsylvania, where more than 1,600 wells have already been drilled in the Marcellus Shale and more than 4,000 permits have been granted.

Drilling companies have used fracking to release natural gas from other shale reserves around the country. EPA earlier held hearings in Colorado, Texas and Pennsylvania.

The two sides gathered for the Binghamton hearings were kept at either end of a street on Monday, separated by a long neutral zone and observed by a heavy police presence.

Alex Parillo, representing about 1,000 workers at Laborers Local 785, said allowing the drilling would bring much needed jobs to the economically struggling region.

"It's a big jobs issue for us," Parillo said. "We see industries coming into New York with their hands out, looking for tax abatements and bringing in out of state workers. Here we have an industry, they don't have their hands out. They embrace the local work force. They just want guidelines to do it right. The DEC will have the strictest regulations in the world."

Parillo said local laborers have a stake in safeguarding the environment.

"We're going to be on the front lines and make sure it's done right," he said.

Claude Crispell of Burdette has been working on pipelines all his life and said it's one of the safest jobs he's ever had.

"I don't see a problem with drilling here," he said. "The DEC has studied it for three years and says it's safe."