PIKE & WAYNE COUNTIES — Well-water tested in Pike and Wayne counties contains low-to-moderate concentrations of naturally occurring methane, according to new studies by the U.S. Geological Survey (USGS).

The Pike and Wayne county samples were collected in 2012 and 2013 to assess baseline groundwater quality in areas underlain by the Marcellus Shale, but where no extensive shale-gas development has occurred. Both Wayne and Pike counties are within the Delaware River Basin, where a moratorium on shale-gas drilling is in place.

The Pike County Conservation District cooperated in the Pike study, and Director Sally Corrigan told the county commissioners on November 19 that a new $295,000 state/federal grant will expand Pike’s ongoing baseline testing from 20 to up to 80 private water wells.

Corrigan said the $188,000 state portion is the only baseline water-quality study currently being funded by the state.

Commissioners Chair Rich Caridi said that “with these studies we’ll have a baseline. If we have contamination, we’ll have protection.”

“It’s not just fracking,” he added. “We don’t know what is going down the interstate every day.”

Methane is the primary component of natural gas produced from the Marcellus Shale in Pennsylvania. One of the concerns with “unconventional gas production,” which makes use of hydraulic fracturing, or fracking, is the possible migration of methane into drinking water aquifers because it can be flammable or explosive. These studies show that naturally occurring methane can be found in drinking water wells in areas where no unconventional natural gas development is occurring.

Pike County

Data on occurrence of methane and other constituents potentially related to shale-gas development were not available or were limited in Pike County, according to USGS Scientist Lisa Senior, who led the Pike study.

She said that the Pike study included sampling four wells monthly over the course of one year because “little is known about variability in groundwater quality through time, but this variability is important in interpreting baseline assessments. Many baseline assessments consist of one-time sampling.”

In the Pike study, about 80%, or 16 of 20 tested wells, contained detectable concentrations of methane, with two wells having methane concentrations greater than 1 milligram per liter and as high as 5.8 milligrams per liter. The concentrations of dissolved methane in about 10 percent of well-water samples in both studies were high enough to allow for isotopic analysis to identify the type of natural gas in the water.

In Pike County, the isotopic composition of two methane samples indicated that methane was predominantly microbial in origin, typical of methane produced by microbial activity at or near the surface such as in marshes or in alluvial deposits.

Wayne County

“Water-quality data were lacking in Wayne County,” said USGS scientist Ronald Sloto, who led the Wayne study. “Without baseline water-quality data, it would be difficult to determine whether a relationship exists between gas production activities and the well-water chemistry in the area. This study provides a pre-gas-well-drilling groundwater-quality baseline for Wayne County. Although the number of water samples was small, the analytical results show the presence of naturally occurring methane in some private drinking water wells.”

In Wayne County, about 65%, or 22 of the 34 private drinking-water supply wells tested, contained concentrations of dissolved methane high enough to detect in laboratory testing, but most methane concentrations were low, less than 0.1 milligrams per liter. Three, or about 10%, of the 34 tested wells in Wayne County produced groundwater with dissolved methane concentrations near or greater than 1 milligram per liter and as high as 3.3 milligrams per liter; these relatively elevated concentrations are at least 10 times greater than methane concentrations in the other well-water samples.

In Wayne County, the isotopic composition of three methane samples indicated a thermogenic origin (typical of shale-gas methane) and (or) a mixture of microbial and thermogenic types.

Sampling to continue

According to the USGS, none of the water tested in these two studies exceeded the Pennsylvania Department of Environmental Resources (DEP) action level of seven milligrams per liter for methane in well water. The DEP recommends periodic monitoring for wells with detectable methane up to seven milligrams per liter. Corrective action, such as well venting, is recommended for wells with methane concentrations equal to or greater than 7 milligrams per liter.

The studies also provide background information on other aspects of groundwater quality, such as arsenic, barium, chloride and radon concentrations that may be of concern in areas of shale-gas development. All of the well owners were notified of the results.

The number of samples in Wayne and Pike counties was relatively small. In addition to the new Pike grant, USGS says additional sampling will be necessary, to provide a broader picture of naturally occurring methane in the region. USGS is continuing to collect data on baseline groundwater quality in areas in Pennsylvania underlain by the Marcellus Shale, by conducting an expanded study in Wayne County in cooperation with the Wayne Conservation District.

There will also be a new study in Lycoming County in the north-central part of the state, done in cooperation with Lycoming County. The results will be available online at the USGS National Water Information System website.

The Wayne County study was conducted by USGS in cooperation with the Pennsylvania Department of Conservation and Natural Resources, Bureau of Topographic and Geological Survey.