Executive Summary:
A new HON provision ends the SSM wastewater discard exemption in July 2027. Here is what facilities need to know to prepare for this upcoming compliance date.
EPA Closes the SSM Loophole in HON Wastewater Discard Rules
The HON RTR final rule made a wide range of high-profile amendments that have gotten most of the attention, including the revocation of the startup, shutdown and malfunction (SSM) provisions. Most facilities recognize the impact of the removal of the SSM provisions on control devices and bypasses, but the ramifications of this action on HON wastewater collection, storage and treatment obligations, while quite consequential, is often overlooked.
A short addition in 40 CFR 63.132(f)(5) narrows an existing exemption from the wastewater discard prohibition. The compliance date is still a year out but understanding the implications of this change for sources without a robust HON Group 1 wastewater emissions suppression and treatment system and finding a path forward to comply will take time to implement and where necessary, upgrade existing systems.
What Section 63.132(f) Actually Requires
Section 63.132(f) is a discard prohibition. It says facilities cannot dump liquid or solid organic material containing 10,000 parts per million or more of Table 9 compounds into water or wastewater unless that stream is managed and treated as a Group 1 wastewater stream. In plain terms, if a waste stream is concentrated enough, a facility cannot simply route it to the drain and call it wastewater. It has to be treated like the regulated stream it actually is. This statement has always been there, but until these amendments, it wasn’t problematic.
EPA historically built in a handful of exemptions to that prohibition in 63.162(f)(1)-(4), including activities tied to maintenance, startup, shutdown, and malfunction (SSM) operations per 63.132(f)(2). That exemption is where 63.132(f)(5) comes in.
What’s Changing
As prescribed in 63.132(f)(5), beginning July 15, 2027, the phrase “or startup/shutdown/malfunction” is removed from the exclusions in 63.132(f)(4). After that date, SSM-related activities lose their exemption from the discard prohibition. A stream generated during a startup, shutdown, or malfunction event that hits the 10,000 ppm (1 weight percent) Table 9 threshold will need to be managed and treated as Group 1 wastewater, the same as any other prohibited discharge, rather than falling under the old SSM exemption.
This is not an isolated tweak. It fits a pattern EPA has followed across several recent NESHAP updates: closing the door on exemptions tied to startup, shutdown, and malfunction events. Other industry sectors that reference the HON have already done this same removal of the SSM exemption from the wastewater provisions (for example see 40 CFR 63.2485(q)(3) of the MON that predated the HON amendments). Additionally, any other rules that directly reference the HON that have not yet seen SSM removals, now have the same impact to their source.
This change to wastewater is not isolated, as EPA has been steadily removing SSM-related exemptions across multiple source categories as part of general regulatory updates to address court decisions made in Sierra Club v. EPA U.S. Court of Appeals for the D.C. Circuit (December 19, 2008). NESHAP wastewater provisions are simply the latest place that trend has landed.
What This Means in Practice
Liquid streams containing 1 weight percent (wt%) of Table 9 compounds have always been considered Group 1 streams, irrespective of flow rate, but no one ever considered the SSM case and now solid organic materials are also included in the mix during such times. Historically, streams generated during SSM events were either not considered at all in HON wastewater determinations, or, surges in concentrations and/or flows during such events were removed from group determinations.
Now, post HON compliance date, all streams count, and annual average concentration is not part of the equation for this prohibition. To prepare, regulated sources must reassess their wastewater PODs and ensure that at no time PODs exceed 1 wt% Table 9 compounds and are discharged to a “non-Group 1” wastewater collection and treatment system. This simple regulatory tweak could result in the upgrade of non-HON wastewater collection, storage and treatment systems to Group 1 HON compliant systems and/or containerization and off-site shipment of problematic streams to remove them from non-compliant systems.
How to Prepare
To prepare, sites need to reassess their HON wastewater points of determination, to ensure any startup, shutdown or malfunction uniquely generated PODs are accounted for and, for all PODs, review and ensure:
- Determinations are updated to reflect overall annual average concentrations and flows including SSM events,
- Identification of all PODs that could plausibly hit 1 wt% Table 9 compounds under any circumstance, irrespective of annual average concentration calculations, and
- A compliant path forward is found for any liquid or solid streams containing 1 wt% Table 9 HAP at any time, if not already discharging to a compliant HON Group 1 wastewater collection and treatment system.
Due to the nature of SSM streams, Trinity recommends process knowledge always be combined with current sampling data to make such determinations with any confidence. Facilities have never been required to sample such streams previously, so there is no current definitive knowledge basis. Sampling programs will need to be planned around actual SSM events, which are not exactly scheduled on demand, and the resulting data has to be interpreted, documented, and worked into whatever process wastewater management approaches the facility already has in place. Waiting to start that process leaves a narrow window to react if the sampling results give unexpected concentrations.
How Trinity Can Help
Facilities should treat this as a prompt to revisit their wastewater PODs and maintenance wastewater streams well before the compliance date, not after it. That means identifying every process wastewater stream that has historically been managed under the maintenance/SSM exception, pulling together whatever composition data already exists, and flagging where that data is outdated, incomplete, or simply never collected for SSM conditions specifically. For any stream where the answer is unclear, sampling now is the only way to know whether the 1 wt% Table 9 HAP threshold is a real risk or a non-issue.
Trinity’s Chemical Sector Services group has subject matter expertise focused on HON wastewater sampling and characterization, including programs structured around SSM events, and can provide engineering support, field sampling and analytical support, and if desired, turnkey services to support facilities as they walk through this process of updating wastewater POD and group determinations ahead of the 2027 compliance date.
A related pattern has already surfaced with HON fenceline monitoring, where wastewater streams turned out to be a source of fenceline concentration spikes that facilities initially attributed to LDAR. In both cases, the underlying issue is the same: wastewater streams that have not been characterized recently can behave differently than assumed once new monitoring or discard requirements take effect.
Because SSM events cannot be scheduled and sampling around them requires advance planning, facilities that begin this evaluation well ahead of 2027 will have more flexibility in designing and executing a sampling program than those that wait until closer to the compliance date.
For more information on wastewater sampling and characterization services, contact Gena Driscoll, Manager of Chemical Sector Services.
