Independent Analysis: Real-time Air Quality Monitoring at Natural Gas Development Sites
Data presented from 15 sites across Southwestern PA
October 10, 2024
By Guest Contributor CleanAir Engineering
Natural gas is an important and abundant resource produced in the U.S. primarily via unconventional gas development involving hydraulic fracturing of shale rock formations. One of the major shale gas regions in the U.S. is the Appalachian Basin, which contains the Marcellus and Utica shale formations.
In response to recent observational epidemiological studies in communities across Southwestern Pennsylvania with unconventional natural gas development, CNX Resources Corporation (CNX) has taken a proactive approach to directly monitor air and water quality at unconventional natural gas sites and provide public access to the full dataset.
Preliminary results of these efforts were presented as a poster at the 2024 National Ambient Air Monitoring Conference in New Orleans, Louisiana (August 12-15, 2024).
Initially, fifteen natural gas facilities, including natural gas compressor stations and well sites in various stages of development, such as site construction, drilling, hydraulic fracturing, and production, were selected for a program to provide data for CNX’s ongoing operation.
For the measurement of PM2.5 (particulates with an aerodynamic diameter of less than 2.5 micrometer), each facility was equipped with real-time Federal Equivalent Method (FEM) monitors at representative upwind and downwind locations at the facility fence line. Each monitoring station was operated according to Environmental Protection Agency (EPA) guidelines for State and Local Ambient Air Monitoring Stations (SLAMS) for at least six months. In addition to PM2.5, each facility was equipped with four passive samplers to determine benzene, toluene, ethylbenzene, and xylenes (BTEX) concentrations around each site via EPA Method 325.
Radical Transparency Ambient Air Quality Preliminary Results_8.8.2024.pdf
PDF - 3.4 Mb
The poster presentation introduced the program objectives and experimental design and summarized results from ongoing operations, highlighting efforts at sites with data sets of more than six months in duration. Analysis of the preliminary program data set allowed for the following conclusions:
- There was no exceedance of the 24-hour National Ambient Air Quality Standard for PM2.5 (35 micrograms per cubic meter of air)
- Daily PM2.5 concentrations were similar to nearby regional air quality stations operated by the Pennsylvania Department of Environmental Protection
- Downwind stations show minor PM2.5 enhancements compared to upwind monitoring stations during short-lived drilling and completion site activities
- All benzene observations were near regional background levels and well below the inhalation minimum risk levels (Acute MRL: 9 ppb)
- At compressor stations, BTEX concentrations remained at or below method reporting limits and close to regional background levels
- Highest observed BTEX concentrations at a compressor station were linked to emissions from vehicular traffic based on compound concentration ratios
- Downwind stations did not show enhancement in benzene concentrations above the background at compressor stations or at well pads when in the production phase
- There was a less than 0.1 ppb average enhancement above background benzene levels at well pads during short-lived well pad drilling and completion activities
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