The Pennsylvania Department of Environmental Protection (DEP) said Monday it has launched its fourth study in about two years to monitor air quality and determine potential impacts of Marcellus Shale activities, this time in the southwestern part of the state.

The DEP said all of the testing sites for its long-term, one-year study will be in Washington County, the primary one being downwind of MarkWest Energy Partners LP’s Houston Processing Facility, which is in Chartiers Township. The agency said it will monitor for ground-level ozone, particulate matter (PM-10), carbon monoxide (CO), nitrogen oxides (NOx), hydrogen sulfide (H2S) and methane at the site. It also plans to test the ambient air for more than 60 volatile organic compounds (VOC) and continuously collect meteorological data.

“We operate on facts and sound science, and this study will provide us with data on long-term air quality in an area of active natural gas extraction,” DEP Secretary Mike Krancer said. “There has been a documented downward trend in airborne pollutants across the state over the past 10 years, and Marcellus Shale development holds the promise of emissions benefits from the use of this cleaner-burning fuel in the transportation and electricity generation sectors.”

The DEP said it will also monitor VOCs and continuously collect meteorological data from two additional test sites in Chartiers — one upwind of the Houston plant and one downwind of MarkWest’s Brigich compressor station — and from one test site in Mount Pleasant Township downwind of MarkWest’s Stewart compressor station.

“The data from the study will allow [us] to assess any potential long-term impact of air emissions from unconventional natural gas operations to nearby communities, and it will help [us] address the cumulative impact of the operations in the Marcellus Shale region,” the DEP said, later adding that it “intends to collect at least one year of data and compare those results to national ambient air quality standards, then conduct a long-term risk analysis.

“The Washington County results and risk analysis will aid in determining the need for any further long-term sampling in other regions of the state.”

Josh Hallenbeck, vice president of finance and treasurer for MarkWest, told NGI’s Shale Daily the Denver-based company supports the DEP’s efforts.

“MarkWest supported DEP’s short-term, 2010 study in Washington County that clearly showed our operations are conducted in a way that protects the environment and meets all regulatory requirements,” Hallenbeck said Tuesday. “Likewise, we support longer-term studies designed and conducted with valid methods and standards. We absolutely believe that science and fact-based data should guide these important studies and form the basis for regulations and policy.”

Kathryn Klaber, president of the Marcellus Shale Coalition, echoed that sentiment.

“Our industry is eager to assist DEP in every way that we can throughout this important analysis,” Klaber told NGI’s Shale Daily on Tuesday. “Technological advancements, pioneered by our industry, and common sense regulations continue to make certain that natural gas production is undertaken in a way that safeguards our environment. As more natural gas is used to power our transportation and electricity needs, we continue to realize broad-based environmental benefits, particularly from an air quality standpoint.”

The DEP has conducted three air quality studies near various Marcellus Shale facilities in different parts of the state since 2010, but it found no emission levels that would trigger health concerns. Companies that owned the facilities tested included Anadarko Petroleum Corp., Cabot Oil & Gas Corp., East Energy, Stone Energy Corp. and Talisman Energy Inc.

Tests were conducted in Bradford, Lycoming and Tioga counties between August and December 2010 (see Shale Daily, May 24, 2011), in Sullivan and Susquehanna counties between August and October 2010 (see Shale Daily, Feb. 2, 2011), and in Washington and Greene counties between April and July 2010 (see Shale Daily, Nov. 3, 2010).

MarkWest’s Houston facility has a processing capacity of 355 MMcf/d and is to tie-in to the proposed Mariner West NGL Pipeline project (see Shale Daily, March 24, 2011).