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The United States Environmental Protection Agency (US EPA) has completed the Residual Risk and Technology Reviews (RTRs) for Refinery MACT I and II (40 CFR 63, Subparts CC and UUU) in December 2015, and now the HCl MACT (40 CFR 63, Subpart VVVVV) in February 2019. The proposed amendments for these source categories closely resemble each other - making modifications to the same general sections of each regulation.

While these amendments are by no means "one-size-fits-all" and amendments must be tailored to fit the needs of each source category, these changes to the Refinery MACT and the HCl MACT clearly foreshadow what we can expect US EPA to propose for the upcoming chemical industry RTRs.1 As such, the chemical industry can expect similar source category specific modifications as outlined in each of the below general sections.

Control Standards Now Apply During Startup, Shutdown and Malfunction

Universally, US EPA has been overhauling how the NESHAP standards address emissions during startup, shutdown and malfunction events as follows:

  • Startup, Shutdown and Malfunction (SSM) blanket exemptions from emission control standards have been removed and sources are expected to comply with emission limits during all emission generating periods of source operation. The Refinery MACT revisions did include some specific alternative operating limits for SSM Events, however the recent HCl MACT proposals did not, as US EPA determined, for that source category, that it was not overly burdensome to expect compliance with the control standards during such events.
  • The requirement for SSM Plans are completely removed, along with associated SSM recordkeeping and reporting, but are replaced with requirements to maintain detailed records surrounding each failure to meet an applicable standard.
  • In the Refinery MACT, sources must now monitor atmospheric relief of pressure relief devices (PRDs) during release events and implement measures to prevent releases to the atmosphere, such as staged relief systems where lower pressure releases vent to a flare or other control device. Root cause analyses of releases are also required, with potential deviations if the same PRD vents more than once in a 3-year period.

US EPA is expected to make similar changes in all remaining RTR source categories; removing the current SSM framework and exemptions, expecting compliance with the applicable standards at all times and requiring enhanced recordkeeping and root cause analyses surrounding PRD events and other standard deviations.

Maintenance and Analyzer Emissions Have Been Specifically Addressed

With the removal of the SSM Exemptions, US EPA is placing separate requirements for maintenance venting of equipment into the RTR amendments in response to comments received from industry.

For example:

  • The Refinery MACT now specifies conditions that must be met before opening equipment for maintenance; if the criteria is not met, then that opening is subject to miscellaneous process vent control requirements.
  • The HCl MACT proposal does not yet provide requirements for maintenance vents, and instead is requesting comments on how to properly address these sources - either through a similar work practice standard, or through compliance with the existing control standards or a new "maintenance specific" control standard.  HCl MACT regulated sources should expect maintenance vents to be addressed in the final rule.
  • Refinery MACT redefined the definition of "miscellaneous process vent" to no longer exclude in-situ sampling systems, such that analyzer exhaust gases are now regulated - although the most likely result will be classification of these vents as Group 2 exempt from controls.

New Monitoring and Procedural Requirements for Flares

New requirements for flares, serving as both primary and "back-up" or "SSM" control devices include:

  • Daily visible observations or continuous monitoring to confirm no visible emissions (VE),
  • Continuous monitoring of vent gas and assist gasses to confirm minimum net heating value of the combustion zone and maximum stack tip velocity,
  • Feed forward control of assist and supplemental fuel gases to maintain the required net heating value of the combustion zone,
  • Root cause analysis required for certain exceedances (e.g., when VE observed).

The US EPA is expected to incorporate enhanced flare requirements into the future RTR amendments for the remaining chemical source categories, with little to no variation from the Refinery MACT requirements.

Electronic Reporting (CEDRI) Incorporated into All Amended Regulations

With almost all recent regulatory actions, including the recent RTR amendments, US EPA is incorporating requirements for electronic data submittal through US EPA's Compliance and Emissions Data Reporting Interface (CEDRI). Such reporting requirements thus far have included:

  • Submittal of NESHAP Performance Test Reports
  • Submittal of Fenceline Monitoring Reports
  • Semiannual NESHAP Initial and Semi-Annual Compliance Reports

All proposed RTR amendments, across all source categories, are incorporating some level of CEDRI reporting, and NESHAP regulated sources can expect to eventually use CEDRI for all US EPA reporting submittals.

Trinity's Chemical Sector Services (CSS) Group is well versed in helping chemical and refining industry personnel navigate their way through the RTR process. If you would like assistance assessing potential regulatory implications these RTRs may bring to your facility, please contact CSS at (713) 552-1371 Ext. 209.


1 Per court order, US EPA must complete RTRs for thirty-three (33) source categories with upcoming due dates. RTRs for seven (7) of those source categories were completed. RTRs for twenty-six (26) more chemical source categories must be completed, spread out over three (3) due dates - March 13, 2020, June 30, 2020, and October 1, 2021. with RTRs for twenty-six (26) source categories remaining.