PA Environment Digest Blog: Environmental Integrity Project: DEP Made Changes To Permit For MarkWest Harmon Creek Natural Gas Processing Plant In Washington County To Reduce Air Emissions, Improve Accountability

On May 2, 2025, the Department of Environmental Protection issued an Air Quality Plan Approval Permit covering changes to the MarkWest Liberty Midstream & Resources, LLC Harmon Creek Natural Gas Processing Plant in Smith Township, Washington County.

The Air Quality Plan Approval authorizes the construction and temporary operation of air contamination sources and air cleaning devices associated with expansion of the plant to add a third cryogenic plant and a second de-ethanization plant.

Natural gas cryogenic plants take natural gas and cool it to sub-zero temperatures-- minus 120 degrees Fahrenheit-- in order to condense and separate out liquids like butane, ethane and propane from the gas.

These natural gas liquids are then shipped via pipeline to places like the Shell Petrochemical Plant in Beaver County to make plastics and through the Mariner East Pipelines to Southeast Pennsylvania as feedstock for other petrochemical plants and export.

After receiving extensive public comments from more than a dozen local residents, the Environmental Integrity Project, PennFuture, FracTracker Alliance, Earthworks, Moms Clean Air Force, and others, DEP made significant changes to the permit in response to those comments to reduce emissions and improve accountability at the plant.

Click Here for DEP's Comment/Response Document for the permit.

Summary Of Changes

Lisa Widawsky Hallowell, lead attorney on this issue for the Environmental Integrity Project, provides this summary of the changes DEP made to the Harmon Creek Plant permit and other background information--

When MarkWest initially applied for the permit in January 2024, it estimated that the volatile organic compound (VOC) emissions from the expanded facility would be greater than 50 tons per year, exceeding the major source threshold for this pollutant and triggering specific federal “major source” permitting requirements.

In November 2024, MarkWest submitted a revised application incorporating two significant revisions: installation of the vapor recovery unit (VRU) (a system to capture and treat routine emissions so that they can be recycled rather than combusted) and an enhanced monitoring program and valve specifications to reduce emissions resulting from equipment leaks.

The revised application estimated the annual potential to emit for VOCs at 48.33 tons per year, less than 2 tons per year below the major source threshold.

DEP issued a draft permit for the plant expansion on February 10, 2025 classifying the plant as a synthetic minor source.

This means that the plant’s potential VOC emissions remain below the major source threshold as long as specific conditions and restrictions, which must be included in the permit, are met.

In this case, MarkWest is reducing emissions by incorporating the VRU (and therefore reducing potential throughput to the flare) and limiting emissions from equipment leaks by incorporating the enhanced monitoring requirements and valve specifications.

EIP, PennFuture, FracTracker Alliance, Earthworks, Moms Clean Air Force, and more than a dozen local residents submitted comments on the draft permit.

These comments resulted in several changes to the permit that will reduce pollution, including clear requirements for the enhanced leak detection and repair program for connectors and flanges, requiring low emissions specifications for new as well as existing valves, a new plant flare throughput limit, a new VOC emission limit from fugitive sources, and improved pollution reporting, recordkeeping, and monitoring requirements.

DEP revised the permit to include a throughput limit for the plant flare, the largest source of VOC emissions at the site.

This will ensure that the gases combusted in the flare do not exceed the potential maximum estimated by MarkWest.[RTC 44.2 (p 14); Final Permit p 37]

DEP revised the permit to include a VOC limit specific to emissions from leaks at piping components, the VOC source most drastically reduced in MarkWest’s revised permit application. [RTC 49 (p 15-16); Final Permit p 31]

To ensure that all valves above a certain size (one inch) meet enhanced specifications that will reduce emissions, DEP has added a requirement that not only new valves meet these “low-e” specifications, but also any replaced or reworked valves must meet those specifications. [RTC 55 (p 18-19); Final Permit p 33]

To ensure that MarkWest will meet the enhanced piping component monitoring requirements, DEP revised the permit to require that MarkWest submit a Leak Detection and Repair plan that details monitoring methods, frequencies, and minimum durations between monitoring surveys. [RTC 63 (p 22); Final Permit p 33

To ensure that the enhanced monitoring required by the permit results in the projected emission reductions from leaks at piping components, DEP revised the permit to include more frequent recordkeeping requirements for emissions from connectors and valves. [RTC 49 p 15-16; Final Permit p 31]

Read DEP's Comment/Response Document for the permit for more on the comments and changes made.

Visit DEP’s MarkWest Harmon Creek Gas Processing Plant webpage for more information.

Washington County is known as the most “fracked” county in Pennsylvania with the most shale gas wells and related gas infrastructure.

It is also the epicenter of efforts by local residents and communities to better protect themselves from the health and environmental impacts of shale gas development.

Read the Resource Links below.

Resource Links - Harmon Creek Plant:

-- Washington County Resident To DEP: Harmon Creek Natural Gas Plant Expansion Will Result In A Huge Increase In Air Pollution, It Should Be Required To Have A Major Air Quality Permit, It Is Not A ‘Minor’ Source [PaEN]

-- Community Speaks Out Against Expansion Of Harmon Creek Natural Gas Processing Plant In Washington County [PaEN]

-- Moms Clean Air Force To DEP: Families In Washington County Are Already Living In The Middle Of Major Natural Gas Industrial Sites - Do Not Expand The Harmon Creek Natural Gas Processing Plant And Make It Worse [PaEN]

-- Center For Coalfield Justice To DEP: Harmon Natural Gas Processing Plant Should Be Required To Apply For A Full Title V Air Quality Permit As They Originally Proposed In Washington County [PaEN]

-- DEP Sets March 11 Environmental Justice Office Hearing On Air Quality Permit For New Pollution Control Devices At Harmon Creek Natural Gas Processing Plant In Washington County [PaEN]

Resource Links - Washington County: [Just Read The Headlines]

-- Observer-Reporter: Explosion, Fire At Energy Transfer’s Revolution Natural Gas Cryogenic Plant Burned For Nearly 11 Hours On Christmas Day In Smith Twp., Washington County [PaEN]

-- DEP Ongoing Explosion/Fire Investigation: Energy Transfer Reported An Uncontrolled Release Of Ethane For 9.5 Hours From Its Revolution Natural Gas Processing Plant In Washington County [PaEN]

-- 3 Days That Shook Washington County: Natural Gas Plant Explosion; Pipeline Leak Of 1.1 Million Cubic Feet Of Gas; 10,000 Gallon Spill At Compressor Station [PaEN]

-- Natural Gas Pipeline Pigging Facility Malfunction Dec. 27 Released 1.1 Million Cubic Feet Of Natural Gas; Same Facility Plagued Community With Blowdowns 3 Times A Day, 7 Days A Week For Nearly 10 Years Until Criminal Charges Brought Against CNX [PaEN]