EPA Hits MPLX With US$2 Million Fine For Violating The Clean Air Act

    MPLX To Strengthen Air Pollution Controls At Seven Natural Gas Processing Plants And 10 Compressor Stations

    The US Environmental Protection Agency (EPA), US Department of Justice (DOJ), the State of North Dakota, and the State of Wyoming announced a settlement agreement with MPLX LP (MPLX) that will strengthen air pollution controls at seven natural gas processing plants and 10 compressor stations located in North Dakota, Wyoming, and on the Uintah and Ouray Reservation in Utah.

    MPLX LP is a master limited partnership formed by Marathon Petroleum Corporation to own and operate midstream energy infrastructure assets. Of relevance to this settlement, MPLX’s assets include multiple natural gas processing plants that extract natural gas liquid products such as ethane, propane, butane, isobutane, and natural gasoline and compressor station facilities that gather natural gas, natural gas condensate, and produced water from an incoming natural gas pipeline.


    The United States, the State of North Dakota, and the State of Wyoming have filed a complaint against MPLX for violations of the Clean Air Act and analogous state air pollution control laws at natural gas processing plants and compressor stations located in North Dakota, Wyoming, and on the Uintah and Ouray Reservation in Utah.

    At the gas plants, MPLX failed to comply with multiple volatile organic compound (VOC) emissions control requirements under several new source performance standards (NSPS) applicable to natural gas processing plants, including failure to comply with leak detection and repair (LDAR) requirements. At the compressor stations, MPLX failed to comply with National Emissions Standards for Hazardous Air Pollutants (NESHAP) for large glycol dehydration units and engines, NSPS requirements for combustion engines, and Title V permit requirements.

    Injunctive Relief

    MPLX has agreed to the following elements of injunctive relief for seven natural gas processing plants: comply with NSPS Subpart OOOOa at all process units; implement a LDAR program that will bring facilities into compliance with LDAR regulations, and which includes measures to mitigate the environmental harm caused by alleged noncompliance; install technological fixes for pilot-operated pressure relief valves to prevent pilot-escaping emissions from being vented directly to the atmosphere; comply with NSPS Subpart NNN applicable to synthetic organic chemical manufacturing distillation units; implement fugitive leak monitoring for fin fan heat exchangers and covered equipment using optical gas imaging (OGI) instrumentation; improve LDAR monitoring associated with pressure relief devices; comply with NSPS Dc requirements applicable to process heaters at MPLX facilities; and submit applications for non-Title V permit amendments to incorporate consent decree requirements that will survive termination of the decree.

    MPLX has agreed to the following elements of injunctive relief for nine compressor stations and the Robinson Lake Gas Plant: develop and implement enhanced catalyst operations and maintenance procedures, conduct more frequent performance testing on engines, and install and operate an automatic shutdown on the glycol dehydrator at the Wonsits Valley Compressor Station in Utah and the Robinson Lake Gas Plant in North Dakota to prevent emissions during flare downtime.

    Also, MPLX has agreed to mitigate past excess emissions by installing control equipment at the Flat Rock Compressor Station in Utah; conducting enhanced monitoring of all equipment in residue gas service at the gas plants; conducting enhanced monitoring of compressor stations at sites in North Dakota, Wyoming, and Utah; installing pig ramps and high-low jumpers at various sites; and plugging and remediating four abandoned wells in North Dakota.

    The EPA said the injunctive relief and mitigation under this settlement is valued at approximately US$4.5 million.

    Pollutant Impacts

    When fully implemented, the EPA estimates that the new controls, requirements, and mitigation projects will reduce ozone-producing air pollution by an estimated 95 tons (86 tonnes) per year and greenhouse gases by 3850 tons (3493 tonnes) per year of carbon dioxide equivalent, including methane.

    Health Effects And Environmental Benefits 

    VOCs are a key component in the formation of ground-level ozone, a pollutant that irritates the lungs, exacerbates diseases such as asthma, and can increase susceptibility to respiratory illnesses such as pneumonia and bronchitis. Some of the oil and gas facilities covered by this settlement are in the Uinta Basin, an area that does not meet National Ambient Air Quality Standards established under the Clean Air Act for ground-level ozone.

    The primary HAPs associated with oil and natural gas include benzene, toluene, ethyl benzene, mixed xylenes (collectively referred to as BTEX) and n-hexane. Exposure to these chemicals has been demonstrated to cause adverse health effects including irritation to skin and eyes, blood disorders, reproductive issues, cancer, nervous system effects, and in high concentrations death.