State investigating methane in water near Dimock Twp.

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By Laura Legere (Staff Writer)
Published: April 28, 2012

State environmental regulators are investigating a possible case of methane migrating into water supplies just north of the 9-square-mile box in Dimock Township where the state halted a gas driller’s operations because of methane contamination in 2010.

Regulators with the state Department of Environmental Protection emphasized that they have not determined the source of elevated methane discovered in two Susquehanna County water wells and whether it is caused by Marcellus Shale drilling or a natural occurrence of gas in the aquifer.

One focus of the investigation is Cabot Oil and Gas Corp.’s Greenwood 1 well, where the company recently squeezed additional cement between steel barriers that are meant to seal off gas and fluids from the aquifer.

The work in late March was an effort to stop the problem, DEP spokesman Kevin Sunday said, even though inspectors have not pinpointed the well as the cause.

“The next step is to determine the effectiveness of the remediation work and to continue water well sampling,” he said.

Regulators began investigating the elevated methane levels in August 2010 after a resident complained about water quality.

The gas wells being evaluated are less than 400 feet from the northern boundary of a section of Dimock where Cabot’s drilling and hydraulic fracturing operations have been on hold since April 2010, when state regulators blamed faulty Cabot wells for allowing shallow methane to channel into 18 private water wells. Cabot disputes the state’s findings in that case.

The current investigation is separate from the ongoing review of Cabot’s wells in the off-limits area.

Cabot spokesman George Stark said Friday that the company “always investigates landowners’ concerns as they are brought to our attention. Cabot has been working closely with the Department of Environmental Protection on this matter and will continue to do so with the best interest of our landowners in mind.”

Neither of the two water wells involved in the current investigation has been vented because one well is buried and has not been located and inspections of the other have not found gas trapped in the open space above the water in the well, Sunday said.

Methane in drinking water is not known to cause any health risks, but at high concentrations it can seep out of water into the air and create an explosion hazard in enclosed spaces.

The state has not reached a determination 20 months into the investigation because a number of factors need to be considered, including the construction of nearby gas wells and identifying features of the methane, DEP spokeswoman Colleen Connolly said.

“It’s not different from any case,” she said. “There are just many issues to deal with.”

The Greenwood 1 well was the first Marcellus Shale well drilled by Cabot in Dimock, in September 2007, according to state records.

Three horizontal wells later drilled on the same pad in November 2009 and May 2010 were among the top-producing wells in the state early last year.

Those wells, the Greenwood 6, 7 and 8, have also been evaluated as part of the investigation. Cabot was cited by DEP for a “failure to case and cement” the three wells “to prevent migrations into fresh groundwater” in January 2011 but Cabot has argued in a letter to the state that the wells were properly constructed and the violations should be rescinded.

Connolly said that DEP is addressing the violations with Cabot. The defects cited by the department “could have been a means of allowing methane to migrate into the fresh groundwater, but that doesn’t necessarily mean the water supply has been impacted,” she said.

llegere@timesshamrock.com