In its third regional report over the past year, the Pennsylvania Department of Environmental Protection (DEP) found compounds of natural gas constituents near natural gas operations in Bradford, Lycoming and Tioga counties, but none at any level that would trigger health issues.

"The results show there are no emission levels that would be of concern to the health of residents living and working near these operations," DEP Secretary Michael Krancer said, noting that the report does not address the potential cumulative impacts of air emissions.

DEP conducted the sampling at four Marcellus Shale sites between August and December 2010 -- two compressor stations, a well site during flaring operations and an active drilling site -- as well as a fifth location away from drilling activities used to measure background emissions levels. The air quality sampling took place during the weeks of Aug. 30, Nov. 15 and Dec. 6, with an evening sampling event on Nov. 17.

The surveys were conducted near Talisman Energy's Thomas Compressor Station in Bradford County, East Energy's Shaw Compressor Station and nearby Chicken Hawk well in Tioga County, and Anadarko Petroleum's Hagemeyer well in Lycoming County. The background sampling took place in late August at the Sones Pond parking lot in Loyalsock State Forest, in Sullivan County.

The DEP set up mobile laboratories downwind of each site to screen for 48 volatile organic compounds (VOC), including methane and benzene. Sampling took place from 5 a.m. to noon and from 5 p.m. to midnight, times when the DEP said it gets the most complaints about Marcellus exploration activities. The surveys found methane, ethane, propane and butane -- the main constituents of natural gas -- as well as "low levels" of the gasoline additive methyl tertiary butyl ether, carbon monoxide and the odorous methyl mercaptan, but none at concentrations likely to trigger health issues, the DEP said.

Although the sampling detected benzene, the DEP said it measured at levels below those found in widely publicized studies by the Texas Commission on Environmental Quality in the Barnett Shale in 2010 (see Shale Daily, Feb. 16; Nov. 24, 2010).

The DEP previously studied air quality in Washington and Greene counties in southwestern Pennsylvania in April through July 2010, and in Sullivan and Susquehanna counties in northeastern Pennsylvania in August through October 2010 (see Shale Daily, Feb. 2; Nov. 3, 2010). Combined, the three studies collected samples over 12 weeks from 15 sites -- six compressor stations, six well sites and two background sites. All three reports reached similar conclusions.

"The elevated methane results at the sampling sites would seem to confirm that the natural gas production infrastructure in general, from well sites to condensate tank farms to compressor stations, is a source of pollutant emissions through fugitive and/or direct means," the report said. But at individual operations, the sampling did not find that these emissions were enough to make "acute adverse health impacts" likely.

The DEP plans to compare the three regional studies, particularly in regard to any differences between wet gas operations in southwestern Pennsylvania and dry gas operations in northeastern and north central Pennsylvania, before deciding whether to launch a longer-term study. The DEP, though, said it would continue to respond "on a case-by-case basis to reported air pollution episodes" in the Marcellus.

Looking at cumulative impacts could reignite questions about what facilities are and are not exempt from permitting. Upon taking office earlier this year Krancer rescinded a policy document that guided how the DEP could bundle small but related sources of emissions into a larger source.

"The department thinks that there are a number of potentially interrelated air quality topics regarding gas exploration and extraction activities within the Marcellus Shale which should be considered together," Krancer wrote in his notice rescinding the policy (see Shale Daily, March 1).

The DEP is taking comments on those air quality issues through Thursday (May 26).