HARRISBURG, Pa. (AP) — State environmental regulators said Thursday they misfired in a bid to catalog chemicals used by the drilling industry to extract natural gas from the rich Marcellus Shale reserve.
Department of Environmental Protection spokesman Tom Rathbun said a list of chemicals provided to The Associated Press shortly after a blowout at a natural-gas well inadvertently included all chemicals used at well sites, not just those injected into wells.
"It was an effort to be transparent and give complete public disclosure, and unfortunately it didn't work out that way," Rathbun said.
A blowout at a well in a remote area about 90 miles northeast of Pittsburgh on June 3 shot explosive gas and polluted water as high as 75 feet into the air before crews were able to tame it more than half a day later. The gas never caught fire, and no injuries were reported, but state officials had worried about an explosion before the well could be controlled.
The AP wrote about the list of chemicals earlier this week.
Rathbun said the list includes chemicals that have other purposes, such as cleaning drilling equipment. Some are considered harmful to human health in large enough quantities, even though many are present in consumer products.
The department will continue to try to assemble a list of chemicals that are being injected underground, based on information the drilling companies are required to provide, Rathbun said.
Chemicals used in a drilling process called hydraulic fracturing are injected underground at high pressure to break up the shale some 5,000 to 8,000 feet down and prop open the cracks to allow the gas trapped inside to flow up the well to the surface.
Environmental advocates worry the chemicals are poisoning underground drinking water sources. However, department officials say they know of no examples in Pennsylvania or elsewhere.
Industry officials say the chemicals are heavily diluted by water, accounting for less than 1 percent of the fluid that is blasted underground.
The chemicals are used to reduce friction, kill microorganisms and break down mineral deposits in the wells. Various well services firms make different proprietary blends of the solutions and supply them to drilling companies, which blend them with water at the well sites before pumping them underground.
The companies typically keep the recipes of those solutions secret, but Rathbun said the department is seeking the approval of a new regulation it says would force the companies to disclose those recipes to the agency.
Among the chemicals on the list are naphthalene, toluene and xylene — although various industry representatives said this week that they are not aware of the chemicals' use in drilling.
The U.S. Environmental Protection Agency classifies naphthalene as a possible human carcinogen. Toluene and xylene are linked by the federal government to central nervous system depression.
A list of 260 hydraulic fracturing chemicals compiled by the New York state Department of Environmental Conservation and included in the agency's proposed permitting requirements for drilling in the Marcellus Shale includes all three. The New York list was made public last September.
Some geologists believe the Marcellus Shale reserve, a hotly pursued gas formation primarily under Pennsylvania, West Virginia, New York and Ohio, could become the nation's most productive natural-gas field. There are more than 1,000 Marcellus Shale wells in Pennsylvania alone, some of them within view of homes, farmhouses and public roads.
Associated Press writer Mary Esch in Albany, N.Y., contributed to this report.