On January 8, 2025, the U.S. Environmental Protection Agency (EPA) signed a pre-publication of the proposed amendments to the
National Emission Standards for Hazardous Air Pollutants (NESHAP) for Chemical Manufacturing Area Sources (CMAS). The CMAS rule is part of the Area Source Program under the Urban Air Toxics Strategy, under which greater than 90 percent of emissions of the 30 HAP designated as urban air toxics must be subject to regulation. Under the current CMAS rule EPA designates 15 urban air toxics as Table 1 HAP and triggers
applicability for chemical manufacturing process unit (CMPUs) with a feedstock, in-process, or product/byproduct stream containing CMAS Table 1 HAP at 1.0/0.1 wt%. With this proposal EPA is implementing recommendations from the 2021 Office of Inspector General Report and adding a new HAP to the CMAS Table 1 HAP list, ethylene oxide (EtO), along with new, stringent requirements for any CMPU that contains EtO. In addition to the regulation
of EtO EPA also proposed several revisions to the CMAS rule based on its once every eight (8) year required technology review of the Generally Available Control Technology (GACT) standards.

New Ethylene Oxide Standards

With the addition of EtO as a CMAS Table 1 HAP, EPA has proposed new applicability triggers and enhanced controls for EtO emissions. Under the new applicability criteria, presence of EtO at concentrations levels as low as 1 ppmv in process vents or certain
liquid streams could trigger applicability. Once applicability is triggered, sources will be required to meet stringent requirements incorporated by reference from the HON (40 CFR 63, Subparts, F/G/H). These obligations include but are not limited
to the following:

• Identifying equipment in EtO service, including mandatory testing/sampling for any process vents or wastewater streams that may contain EtO to confirm applicability or non-applicability;
• Stringent control and monitoring standards for process vents and storage tanks at 99.9% Destruction Removal Efficiency (DRE) or to an outlet concentration of 1 ppmv;
• Enhanced Leak Detection and Repair (LDAR) standards; 
• More frequent monitoring for leaks from heat exchangers in EtO service;
• New wastewater treatment standards;
• Updated flare standards to comply 40 CFR Subpart CC, including requirements for flare monitoring systems and management plans; and
• Fenceline monitoring for EtO.

A quick review of costs presented by EPA in the proposal preamble indicates that EPA may be underestimating the number of sources impacted by these new requirements and may be using a limited dataset for estimating costs. Table 1 presents the average
cost per facility based on EPA’s cost estimates for compliance with the EtO requirements. EPA’s cost estimates are based on industry averages and can significantly underestimate the cost associated with site-specific factors. These estimates
may also underestimate beyond the rule compliance costs, such as near source monitoring needed to identify the source of emissions observed by fenceline monitoring. Facilities should review the data provided by EPA and, if found to be not representative,
comment should be made during the public comment period to ensure the basis for these new requirements is correct.

Table 1. EPA Average Estimated Compliance Cost

Technology and Other Review 

For the technology and other review portions of the CMAS rule amendments, EPA has included many of the recent amendments proposed in other chemical manufacturing rules. These updates include, but are not limited to, the following:

• Pressure vessel LDAR monitoring and routing of releases, including PRDs, to controls;
• Pressure release management standards for PRDs;
• Removal of some bypass exemptions and identifying each bypass as a violation;
• Annual Method 21 LDAR monitoring, in lieu of current visual inspections;
• Heat Exchange Systems monitoring using the Modified El Paso Method;
• Removal the 50 ppmv exemption for metal HAP process vents;
• Removal of the Affirmative Defense and added General Duty Clause;
• Removal of design evaluations and engineering assessment options and requiring performance testing once every five (5) years for compliance with process vent limits for batch and continuous process vents and storage tanks;
• The Administrator can require performance testing during periods of startup or shutdown;
• Enhanced recordkeeping and reporting for deviations, including emissions details;
• Added NSPS Subparts VVa, VVb, IIIa, NNNa, and RRRa to the overlap provisions; and
• Added reporting requirements to EPA through CEDRI and removed skip periods from
  semiannual reporting.

Timeline

Based on the timing of EPA’s consent order, a final rule is required to be published no later than January
15, 2026. As proposed, compliance with EtO obligations is required within 2 years (e.g., early 2028) and all other non-EtO obligations are required within 3 years (i.e., early 2029). 

There are narrow allowances to request a 1-to-2-year extension to the above timeline for certain provisions of the rule. However, facilities need to do their homework early. Approval is based on specific need (e.g., supplier time to deliver a thermal
oxidizer) and must be due to circumstances beyond the reasonable control of the facility. The earlier and more detailed a request is made, the more likely it will be to be approved. In addition, the request for a 2-year extension must be submitted
within 90 days of the effective date of the final rule (i.e., early 2026) and must provide justification for why compliance with a specific relevant standard is infeasible. 

Comment Period

The public comment period for the proposed rule ends 60 days after final publication in the Federal Register, and the EPA is required to consider and respond to each comment received. While the incoming Trump EPA administration may be more receptive to
facility comments, the final rule must ultimately be supported by information included in the docket. Notably, several of the proposed CMAS non-EtO requirements align closely with those in the MON RTR, which was issued under the prior Trump EPA.

In development of the CMAS amendments, EPA heavily relied on recent data collection for other chemical manufacturing rules (e.g., HON MACT and MON MACT). EPA’s general assumption is that all chemical
manufacturing sources are similar, stating in the proposed rule background document:

There are generally no discernible differences between the processes at area and major chemical manufacturing sources excepting size. In fact, major and area sources use similar, if not identical, control technologies and practices to manage process emissions. Therefore, the control technologies used by chemical manufacturing major sources are generally available for CMAS.

This may be a valid assumption for many area sources but may not be true for all given the nature and small size of CMAS facilities operations. Since the CMAS is an area source GACT with a high percentage of regulated facilities being small entities,
comments can carry a heavier weight than in a lot of recent major source rulemaking. If your facility has unique circumstances, it is crucial to submit detailed technical and/or economic comments demonstrating the burden applied to smaller sources
by the proposed standards.

Next Steps

Although several years for compliance can seem far off, based on Trinity’s experience with the MON and HON compliance, the CMAS proposed timeline is very tight. Any potentially impacted CMAS facility should be reviewing applicability and understanding
the impacts. A high-level gap assessment, technical feasibility, and estimated implementation cost analysis should be front loaded and completed as soon as practical. Where it is technically infeasible and/or prohibitively expensive to comply,
public comments should be submitted. This front load work is especially important for any potential EtO CMAS affected sources that have a short compliance timeline, complex compliance logistics, and relatively large capital cost. 

Trinity will be hosting a webinar on
January 29, 2024 to review all aspects of the proposed CMAS amendments. If you’re interested in a more detailed review of the specific technical aspects of the rule or need any help with your facility, please contact Inaas Darrat, PE, at 713.552.1371 or Gena Driscoll at 251.391.5789.