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The Latest on Startup, Shutdown, and Malfunction (SSM) Provisions in Air Quality Regulations

Posted: November 29th, 2022

Authors: Lindsey K. 

There has been a lot of activity regarding Startup, Shutdown, and Malfunction (SSM) provisions in state and federal regulations over the last few years. Namely, exemptions from emissions standards during SSM events are being removed from the regulations. The fundamental issue being addressed by these activities is that U.S. EPA determined (sometimes in response to court decisions from legal challenges) that exemptions from emissions standards during periods of SSM are not consistent with the Clean Air Act (CAA), and therefore the affected regulations must be revised to require that some emissions standard (either numeric or work practice standard) applies at all times, including periods of SSM. This position can be challenging for the regulated community; the exemptions have existed because emissions during periods of SSM may exceed emissions standards developed based on normal operations, but the SSM events are often outside of the operator’s control. The following sections provide updates on recent SSM activities in three types of regulations: National Emission Standards for Hazardous Air Pollutants (NESHAPs), State Implementation Plans (SIPs), and New Source Performance Standards (NSPS).

National Emission Standards for Hazardous Air Pollutants

The SSM exemptions in the 40 Code of Federal Regulations (CFR) Part 63 NESHAP General Provisions were vacated in December 2008 as a result of a decision by the U.S. Court of Appeals for the District of Columbia Circuit. However, the amendments to the NESHAP General Provisions were only published in the Federal Register in March 2021. In the years between 2008 and 2021, U.S. EPA revised individual NESHAP regulations to remove SSM exemptions, either by eliminating specific exemptions in the specific regulation or eliminating references to the outdated General Provisions. The removal of specific SSM provisions often occurred when the rules were being amended in response to scheduled risk and technology (RTR) reviews, so many rules already reflected the court decision by the time the General Provisions were updated.

State Implementation Plans

The SSM exemption provisions in SIPs have been contested since 2015, when U.S. EPA issued a SIP Call requiring states with SIPs containing SSM exemptions to eliminate those exemptions. However, U.S. EPA’s enforcement of the 2015 SIP Call was lacking until a September 2021 memo was issued reestablishing its 2015 position. As a result, it is common to see at least one action in the Federal Register every few weeks pertaining to the removal of SSM exemptions from the SIPs for various states. You can read more about the September 2021 memo here, but of note for purposes of today’s update is that U.S. EPA had withdrawn the SIP Calls for Iowa, North Carolina, and Texas prior to the September 2021 memo. During a September 2022 presentation at the Association of Air Pollution Control Agencies (AAPCA) fall conference, U.S. EPA indicated that they would be reestablishing the SIP Calls for those three states. There are ongoing challenges to the legality of prohibiting SSM exemptions in SIPs, based on the premise that the logic applied in December 2008 for the NESHAP regulations under section 112 of the CAA should not be applied to SIP regulations under section 110 of the CAA.

New Source Performance Standards

While most of the recent activity related to the elimination of SSM exemptions has pertained to NESHAPs and SIPs, another set of regulations may soon be added to that list: the Standards of Performance for New Stationary Sources, commonly referred to as NSPS. On September 13, 2022, several environmental groups petitioned U.S. EPA to remove SSM exemption provisions from the NSPS regulations. At the forefront of the petition’s basis is Environmental Justice (EJ); namely, the impact that SSM events could have on communities located nearby and/or downwind from industrial facilities that experience them. Indeed, the petition outlines numerous statistical observations regarding the cumulative impacts of SSM events on disadvantaged communities. The petition goes on to explain that not only are these SSM events often during or due to environmental disasters like hurricanes (which may be becoming stronger and more frequent due to climate change), but the affected communities may also already be disproportionally impacted by the environmental disasters themselves.

The petition also references the aforementioned U.S. EPA positions regarding SSM exemptions in the NESHAP regulations and SIPs, in particular concluding that the same logic for the CAA section 112 NESHAP regulations can be applied to the CAA section 111 NSPS regulations. The key provision of the CAA at issue for the NESHAP regulations was section 302(k), which defines emissions standards as applying “on a continuous basis.” The petition presents the position that for the NSPS regulations, CAA section 302 defines “standard of performance” as “a requirement of continuous emission reduction,” and therefore the same connection can be made as for the NESHAP regulations. The petition acknowledges that, like the NESHAP regulations, U.S. EPA has already addressed SSM exemptions in some NSPS regulations as they are amended for other reasons; however, the petition calls on U.S. EPA to promulgate a single rulemaking to eliminate all remaining SSM exemptions in the NSPS regulations.


While U.S. EPA acknowledged EJ as a factor when it reestablished its position on SSM exemptions in SIPs in its September 2021 memo, EJ was not addressed in detail. However, it seems likely that U.S. EPA’s response to the petition on SSM exemptions in NSPS will more thoroughly address EJ, as the petition specifically focuses on EJ and references the Biden administration’s commitment to addressing EJ. It also seems that eventually no air quality regulations will allow for exemptions from emissions standards during periods of SSM. To address SSM exemptions, rules may be revised to state that emissions standards that have historically applied during normal operations now apply at all times, or they may be revised to apply alternative standards during periods of startup and shutdown (separate standards for malfunction periods are not likely). Be sure to monitor rulemaking activity at the federal, state, and local levels and participate in the rulemaking process to understand how your applicable requirements and associated methods of compliance may change. Please contact me at lkroos@all4inc.com with any questions.


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