A five-week air quality study found no air contaminant emission levels indicating problems for residents living near Marcellus Shale natural gas operations in southwestern Pennsylvania’s Greene and Washington counties, the state’s Department of Environmental Protection (DEP) said last week.

“This short-term study only provides a snapshot of the air contaminants we found at surveyed sites, but the data shows no emission levels that would constitute a concern to the health of residents living near these operations,” DEP Secretary John Hanger said. The report did not assess the potential cumulative effects from natural gas operations, he noted.

“These results only provide preliminary information about the type of pollutants released to the atmosphere. Drilling activity continues to increase at a rapid pace across the state, so this study provides us with good information as part of our ongoing effort to gauge the impact these operations have on our air quality, public health and the environment. Needless to say, we plan to conduct more of these types of air-sampling exercises moving forward.”

DEP’s assessment focused on concentrations of volatile organic compounds, including benzene, toluene and xylene, which are typically found in petroleum products. The department also sampled for other pollutants, including carbon monoxide (CO) and nitrogen dioxide (NO2), near gas extraction and processing sites.

The agency gathered samples to provide background data at its monitoring station in Florence Township, Washington County.

The air monitoring surveys near gas operations were conducted at a wastewater impoundment, tank farm and two compressor stations. The surveys detected the main constituents of natural gas, which include methane, ethane, propane and butane, as well as low levels of associated compounds, including benzene and n-hexane, which were detected ” infrequently” at the tank farm and at a compressor station. Higher concentrations of the main constituents of gas were detected mostly near the compressor stations.

Methyl mercaptan, a gas with a penetrating odor similar to rotten eggs, also was detected at concentrations that generally produce odors at each location where samples were taken. That threshold is about one part/billion, DEP noted.

The air sampling surveys conducted for CO, NO2 and ozone precursor emissions did not detect levels above national ambient air quality standards at any of the surveyed sites, the department noted. “However, DEP has not yet determined if the potential cumulative emissions of these air contaminants will cause or contribute to violations of the national ambient air quality standards.”

DEP is conducting similar air monitoring studies near gas facilities in the Dimock area of Susquehanna County, as well as in the north-central region of the state, to determine if there is a “consistent statewide emissions profile for air contaminants near natural gas operations.” All studies are expected to be complete in January.

The air quality report is available at www.depweb.state.pa.us. Click first on “Regional Resources,” followed by the “Southwest Region” link and finally on the “Community Information” link.

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