On March 6, 2024, the United States Environmental Protection Agency (USEPA) announced their final rulemaking to decrease the allowable annual standard of fine particulates (PM_2.5) from 12 micrograms per cubic meter (ug/m3) to 9 ug/m3. The limits for the 24-hour PM_2.5 standard (35 ug/m3), the annual PM_2.5 standard (15 ug/m3), and the PM₁₀ standard (150 ug/m3) remain the same.

Within two years of the final rule, USEPA must designate areas as either meeting (attainment) or not meeting (nonattainment) the standards. States and local agencies will then need to evaluate means to reduce pollution to meet these standards in nonattainment areas, if necessary, or maintain the attainment status for other areas. New major sources or sources undertaking major modifications at existing facilities that exceed specified emission thresholds in areas meeting the standards when the new rule takes effect will need to obtain Prevention of Significant Deterioration (PSD) construction permits. These permitting requirements will include the need to conduct air dispersion modeling and evaluation of Best Available Control Technology (BACT) among other application components. For areas not meeting the standards, Nonattainment New Source Review (NNSR) construction permits will be required for new major sources or major modifications, either upon designation or afterwards. The NNSR application process includes the evaluation of Lowest Achievable Emission Rate (LAER) requirements as well as obtaining emission offsets for the proposed project.

The data that USEPA published for projected nonattainment for PM_2.5 currently includes Brooke County and Marshall County in West Virginia based on 2019-2021 air monitoring data. The final designations will be based on the most recent three-year available data set of monitoring data. West Virginia Division of Air Quality (WVDAQ) has indicated that they are currently working on an exceptional events demonstration, as the Agency believes that the Canadian Wildfires incident during the 2023 calendar year has skewed the emissions monitoring data used to complete the attainment demonstrations. As a result, WVDAQ intends to evaluate the impact of the wildfires and petition the USEPA to disregard the data for those particular days.

USEPA also issued the Supplement to the Guidance on Significant Impact Levels for Ozone and Fine Particles in the Prevention of Significant Deterioration Permitting Program memo on April 30, 2024.

This memo from USEPA outlines the reassessed significant impact levels (SILs) for the 24-hour PM_2.5 and 8-hour ozone NAAQS and PSD increments that the Agency recommends States to use in the PSD permitting program based on new ambient air quality data and the PM_2.5 NAAQS revision. USEPA has developed new SILs for the primary annual PM_2.5 NAAQS and PSD increments and has recommended that the values for ozone and 24-hour PM_2.5 be retained. 

The updated annual PM_2.5 standard and SILs will impact new major construction projects or modifications to existing major facilities in West Virginia. Additional details can be found in Trinity’s recent EHS Quarterly publication. Trinity is continuing to track the impacts of these changes in West Virginia, the Ohio Valley area, as well as attainment and nonattainment designations nationwide. Trinity has the expertise in air quality permitting, dispersion modeling, and ambient air quality to assist you with navigating through the impacts to current and planned projects. 

Contact Melissa Hatfield-Atkinson for additional information.