Skip to main content
Press Release

The U.S. Government and Pennsylvania Settle With MarkWest for Air Emission Violations at Natural Gas Facilities

For Immediate Release
Office of Public Affairs

The Department of Justice, the U.S. Environmental Protection Agency, and the Pennsylvania Department of Environmental Protection announced a settlement today with MarkWest Liberty Midstream Resources, LLC and Ohio Gathering Company, LLC (MarkWest), which is expected to reduce emissions of volatile organic compounds (VOCs) by more than 700 tons per year from company facilities in eastern Ohio and western Pennsylvania. The settlement addresses alleged violations of the Clean Air Act and the Pennsylvania Air Pollution Control Act for failure to obtain permits and keep records associated with maintenance activities that resulted in VOC emissions. As part of the settlement, MarkWest will also perform three supplemental environmental projects (SEPs) and pay a $610,000 civil penalty.

Under the terms of the settlement, MarkWest is expected to spend approximately $2.6 million to install and operate technologies that minimize VOC emissions at its facilities throughout eastern Ohio and western Pennsylvania in the Utica and Marcellus shale formations. MarkWest will also implement two SEPs involving the installation and operation of ambient air monitoring stations located upwind and downwind of MarkWest compressor stations in eastern Ohio and western Pennsylvania; one SEP requiring the dissemination and demonstration of a proprietary MarkWest technology for reducing VOC emissions; and one community environmental project for emissions monitoring equipment under an agreement between MarkWest and the commonwealth of Pennsylvania. The total value of the SEPs under this settlement is more than $2.4 million.

“This Clean Air Act settlement will reduce harmful emissions from facilities located across western Pennsylvania and eastern Ohio,” said Acting Assistant Attorney General Jeffrey H. Wood of the Department of Justice’s Environment and Natural Resources Division. “Today’s action also demonstrates our commitment to working with federal, state and local partners to ensure the health and safety of the American people.”

“Our legacy to future generations will be defined, in part, by our commitment to protecting the environment,” said U.S. Attorney Scott W. Brady of the Western District of Pennsylvania. “This settlement agreement with MarkWest demonstrates the commitment of the U.S. Attorney’s Office to improving the quality of the environment and ensuring cleaner air for the residents of western Pennsylvania.”

“I’m pleased to announce that through this agreement, MarkWest will make improvements to more than 300 facilities in western Pennsylvania and eastern Ohio,” said EPA’s Assistant Administrator Susan Bodine for the Office of Enforcement and Compliance Assurance. “We estimate that these improvements will reduce VOC emissions from these facilities by more than 90 percent, helping bring cleaner air to surrounding communities.” 

“Research, monitoring data, and compliance information help DEP refine and improve the effectiveness of our oversight, craft stronger regulations, and focus on minimizing air contaminants,” said Secretary Patrick McDonnell for the Pennsylvania Department of Environmental Protection. “The new methodology to measure emissions from pigging developed through this case will help us work with all operators in Pennsylvania to reduce emissions.”

MarkWest operates facilities in eastern Ohio and western Pennsylvania designed to gather and transport natural gas and natural gas condensates through pipelines. As part of regular maintenance activities, MarkWest uses devices called “pigs,” which are sent through the gathering pipeline to remove debris and push through accumulated liquids, in an operation known as “pigging.” Pigging a pipeline involves inserting and removing pigs from the pipeline, which requires the operator to depressurize and vent pipeline gas from equipment designed to launch and receive pigs. MarkWest is alleged to have failed to apply for, and comply with, the required permits and/or recordkeeping requirements under the Clean Air Act and the Pennsylvania Air Pollution Control Act for venting activities that released VOC emissions.

VOCs include a variety of chemicals that may produce adverse health effects such as eye, nose, and throat irritation, headaches, nausea, and damage to the liver, kidney, and the central nervous system. VOCs also contribute to the formation of ground level ozone, which is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen and volatile organic compounds in the presence of sunlight. Breathing ozone can trigger a variety of health problems, particularly for children, the elderly, and anyone with lung diseases such as asthma. Ground level ozone can also have harmful effects on sensitive vegetation and ecosystems.

This settlement is part of the EPA’s National Enforcement Initiative (NEI): Ensuring Energy Extraction Activities Comply with Environmental Laws. 

The consent decree has been lodged with the U.S. District Court for the Western District of Pennsylvania and is subject to public comment for a period of at least 30 days. Notice of the lodging of the consent decree will appear in the Federal Register allowing for a 30-day public comment period before the consent decree can be entered by the court as final judgment. The consent decree will available for viewing at

For more information on the settlement, please visit: 

Updated April 5, 2024

Press Release Number: 18-526