State environmental officials are investigating new instances of methane contaminating private residential water wells and bubbling up in a northern Pennsylvania stream near a Marcellus Shale natural gas drilling operation.
The Department of Environmental Protection found the flammable gas in seven water wells in Lycoming County and gas bubbling into the nearby Little Muncy Creek, prompting XTO Energy Inc., a subsidiary of energy giant ExxonMobil Corp., to voluntarily stop operations in the county and provide the water well owners with bottled water for drinking.
The company collected some data on the water wells before it began drilling and has given that information to the department, spokesman Dan Spadoni said Friday. However, he said the agency has not determined the source of the methane.
"The investigation is complex and will take time to resolve," he told the Williamsport Sun-Gazette.
Isotopic testing to determine the source of the methane _ whether it is from natural decomposition of living matter or likely from a shale formation _ could take two to four weeks, he said.
Methane is not considered toxic to drink, but officials say it could ignite and explode if allowed to build up in an enclosed space.
The homes are near Lairdsville. Investigators have not found methane building up in homes or harming aquatic life in the creek, Spadoni said.
Fort Worth, Texas-based XTO Energy has vented the wells to prevent gas from building up and will screen other nearby homes and wells within 4,000 feet of its three well pads in the area, Spadoni said. XTO or a contractor connected water tankers to the homes with polluted well water, he said.
Another DEP official, spokeswoman Katy Gresh, said the agency is investigating other instances of methane contamination in wells or waterways near Marcellus Shale drilling sites, but she said the agency couldn't disclose details because they are active investigations.
Last month, the DEP fined Oklahoma City-based Chesapeake Energy Corp. more than $1 million in part for methane contaminating wells in nearby Bradford County, although Chesapeake did not assume blame for the methane contamination.
In another case, Houston-based Cabot Oil & Gas Corp. agreed in December to pay residents of Dimock in Susquehanna County $4.1 million, install whole-house gas mitigation systems in 19 affected homes and pay DEP $500,000. The DEP accused Cabot of contaminating the wells with methane gas, but Cabot denied responsibility for the pollution.
In Lycoming County, the DEP initially received a report of bubbling well water on May 17. The home is about 2,300 feet from a pad where XTO Energy has drilled and hydraulically fractured three wells, Spadoni said.
The agency then received a report about bubbling water in the creek on June 9, he told the Sun-Gazette.
XTO spokesman Jeffrey Neu said methane was in water samples the company collected within 4,000 feet of some of its Lycoming County well sites before it began drilling.
"In general, the gas levels that were detected after drilling was completed were similar to the pre-drilling samples we studied," he said.
However, Neu said he was unsure as to whether XTO took samples from water wells near the drilling site in question.