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Final Reconsideration Rules for Chemicals and Refineries

Posted: March 28th, 2024

Authors: Philip C. 

The U.S. Environmental Protection Agency (U.S. EPA) is finalizing changes to petroleum and chemical sector rules in response to petitions for reconsideration following recent risk and technology review (RTR) rulemakings. These rules include the National Emission Standards for Hazardous Air Pollutants for Ethylene Production (EMACT), Organic Liquids Distribution (Non-Gasoline) (OLD), Miscellaneous Organic Chemical Manufacturing (MON), and Petroleum Refineries source categories.

U.S. EPA issued a proposed reconsideration rule on April 27, 2023 and Administrator Regan signed the final rule on March 15, 2023. This article provides a summary of the significant changes to each rule as described in the pre-publication version of the final rule posted to U.S. EPA’s website.

Force Majeure Allowance Removed

First, U.S. EPA is removing the force majeure allowance from the atmospheric pressure relief device (PRD) release and emergency flaring work practices in the EMACT, MON, and Petroleum Refineries rules. These work practices include specific criteria defining what events constitute a violation of the standard. Previously, atmospheric PRD releases and emergency flaring resulting from a force majeure event (i.e., an event outside of the facility’s control) were not considered when determining whether a release or set of release events constituted a violation. Moving forward, force majeure events must be considered when determining whether a release qualifies as a violation under the work practice standards. In the preamble to the final rule, U.S. EPA states that the Agency will “continue to evaluate violations on a case-by-case basis and determine whether an enforcement action is appropriate.” U.S. EPA further indicates that sources may raise defenses to an enforcement action as part of court proceedings. In addition to removing the force majeure allowance, U.S. EPA is finalizing electronic reporting requirements for atmospheric PRD releases and emergency flaring events.

Storage Vessel Degassing and Maintenance Vent Requirements Clarified

For EMACT, OLD, and MON, U.S. EPA is finalizing work practice standards for storage vessel degassing. U.S. EPA did not include degassing standards in the proposed rules during the RTR process but promulgated work practices in the 2020 final rules. This resulted in a notice and comment issue. To address the notice and comment issue, U.S. EPA re-proposed the work practice standards in 2023. The standards allow storage vessels to vent to the atmosphere once liquids have been removed to the extent practicable and the vapor concentration inside the storage vessel is 10% of the lower explosive limit (LEL). U.S. EPA also addressed petitioners’ concerns that floating roof storage vessels could not meet the vapor concentration requirement without opening the storage vessel to attach temporary control devices. U.S. EPA is finalizing the degassing requirements as proposed, including an allowance for floating roof storage vessels to be opened in preparation for degassing. U.S. EPA is also providing two important clarifications in the preamble to the final rule: 1) emissions from breathing losses after landing a floating roof while preparing for degassing are not considered a bypass or a deviation of the standards, and 2) the MON and OLD overlap provisions for storage tanks do not apply to the new degassing standards (i.e., if a facility is using the overlap provisions under the MON or OLD, they are still required to comply with the degassing requirements).

Also, for EMACT, OLD, MON, and Petroleum Refineries, U.S. EPA is clarifying the use of the term LEL in context of storage vessel degassing and maintenance vent provisions. These rules previously required facilities to measure and reduce the LEL inside equipment and storage vessels prior to opening; however, commenters noted that LEL is a physical property and not something that can be altered by purging equipment. Thus, U.S. EPA is revising the rules to clarify the intent, i.e., that the vapor concentration inside the equipment or storage vessel is measured and compared to the LEL.

Ethylene Cracking Furnace Work Practices

Under EMACT, U.S. EPA is addressing work practices for ethylene cracking furnaces by finalizing a change that allows furnace operators to delay repair of burners until the next planned decoking operation or complete shutdown (whichever occurs first) if the repair cannot occur during normal operations. U.S. EPA is finalizing another change to the furnace work practices to allow furnace operators to wait to rectify isolation valve issues until after the furnace has been decoked if the operator determines that the furnace would be damaged if the repair was attempted before decoking and/or shut down of the furnace.

Heat Exchange Systems Monitoring

U.S. EPA is finalizing changes to heat exchange system monitoring in the MON by allowing the use of monitoring methods under 40 CFR § 63.104(b) in lieu of the Modified El Paso Method if 99% by weight or more of the organic compounds that could potentially leak into the cooling tower water are water soluble and have a Henry’s Law Constant of 5.0E-06 or less (at 25°C). With some qualifications, 40 CFR § 63.104(b) allows the use of any U.S. EPA-approved method listed in 40 CFR Part 136.

Ethylene Oxide Emissions

U.S. EPA is clarifying in the MON that sites are required to monitor the scrubber liquid-to-gas ratio, the scrubber liquid pH, and the temperature of the scrubber liquid (as opposed to “water”) entering the column if a scrubber with a reactant tank is used to control ethylene oxide emissions. If the scrubber does not use a reactant tank, the facility must establish site-specific operating parameters during the performance test to demonstrate ongoing compliance.

U.S. EPA is also finalizing revisions to allow calculations and site-specific data when determining the concentration of ethylene oxide in storage vessels.

Despite requests from commenters, the Agency is maintaining that delay of repair provisions are not available for pumps and connectors in ethylene oxide service, except in the instance that the equipment can be isolated from the process and it does not remain in ethylene oxide service.


Under the MON, U.S. EPA is clarifying applicability for several provisions related to adsorbers that cannot be regenerated or that are regenerated off-site. The Agency is also requiring facilities to submit a supplement to the notification of compliance status (NOCS) to describe the adsorber characteristics as they relate to the initial and ongoing compliance demonstrations. The Agency is also finalizing updates to the recordkeeping requirements for these types of adsorbers to align with the design standard and monitoring requirements that were promulgated under the RTR. Also under the MON, U.S. EPA is finalizing the requirement to submit NOCS reports electronically.


In the Petroleum Refineries rule, U.S. EPA is finalizing requirements for pressure assisted flares. These are similar to the requirements promulgated for EMACT and MON. The Agency is also finalizing provisions to allow for the use of mass spectrometry to determine flare gas composition, along with clarifications on the associated quality assurance/quality control (QA/QC) requirements.


In addition to the revisions described above, U.S. EPA is promulgating changes to address typographical errors and other minor clarifications in each rule. With the exception the removal of the force majeure allowance and the changes outlined above for flares under the Petroleum Refineries rule, the revisions included in this rulemaking will be effective when the final rule is published in the Federal Register. The removal of the force majeure allowance and the flare amendments will come into effect 60 days following publication. Facilities should review the rules for changes affecting their operations. Please reach out to me or your ALL4 project manager with any questions on the new changes.


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