Contributed by Ned Coleman, Senior Project Manager, PPM Consultants
On October 15, 2024, the final version of EPA’s new storage tank rule was published in the Federal Register. New Source Performance Standards (NSPS) Subpart Kc applies to storage tanks with capacity greater than 20,000 gallons that store volatile organic liquids (VOL) if they were constructed, reconstructed, or modified after October 4, 2023.
The final rule is largely the same as the draft rule that was published in late 2023. Storage tanks triggering this rule will be subject to more stringent requirements than those that fall under the older NSPS Subpart Kb rule. Below is a summary of some of the major requirements that haven’t changed since the rule was originally proposed:
- The maximum true vapor pressure (MTVP) thresholds that trigger emission control requirements have been reduced when compared to Subpart Kb, meaning tanks that would not have triggered control requirements under the prior rule will now require control measures.
- Internal Floating Roofs (IFR) and External Floating Roofs (EFR) subject to Subpart Kc must comply with more stringent requirements on the types of rim seals and roof fittings that can be employed when compared to Subpart Kb floating roof requirements.
- Control devices for tanks storing VOL with a MTVP greater than 11.1 must now achieve 98% control, rather than the 95% control required under Subpart Kb, and additional operational and monitoring requirements apply to these control systems.
- IFR tanks will be required to undergo annual Lower Explosivity Limit (LEL) measurements in the space between the floating roof and fixed roof to assess seal performance.
- Tanks with a capacity of 1 million gallons or greater storing VOL with MTVP greater than 1.5 psia will be required to control emissions during tank degassing.
So what has changed when you compare the final rule to last year’s proposed rule? In addition to numerous minor clarifications, additional definitions, and corrections, there are two big changes that were made in the final rule. The first is a revision to EPA’s new interpretation on tank modifications, and the second is adding an exemption for tanks storing very low vapor pressure products.
The draft rule included a revision to EPA’s interpretation of what constitutes a “modification” of a storage tank. EPA’s original wording was that a tank that changes service “to store VOL that has a greater MTVP than the VOL previously stored” is considered to have undergone modification. The wording in the draft rule was extremely vague, and it could be interpreted that an existing tank could easily trigger this “modification” criteria, meaning it would have to come into compliance with the more stringent Subpart Kc standards. In the final rule, EPA revised their interpretation to clarify that a tank is only considered to have undergone modification if it changes service “to store VOL that has a greater MTVP than all VOL historically stored or permitted.” The updated rule language provided much needed clarification on tank “modification” and industry personnel probably breathed a sigh of relief as compared to the impact the original rule may have had.
Additionally, in the draft rule, any new, reconstructed, or modified VOL tank that is 20,000 gallons or larger would have been subject to the rule. While control requirements would have only applied for tanks larger than 40,000 gallons storing VOL with a MTVP greater than 0.5 psia, or tanks between 20,000- and 40,000-gallons storing VOL with a MTVP greater than 1.5 psia, tanks storing heavy VOLs such as diesel would still have been subject to certain recordkeeping requirements under the proposed rule. In the final rule, EPA added a minimum vapor pressure of 0.25 psia to the rule. This means that tanks storing VOL with a MTVP below the 0.25 psia threshold will be exempt from the rule and not have an additional regulatory burden.
We’ve seen a lot of rule updates coming out of EPA in the past couple of years, so it’s more important than ever to stay on top of all these changes and make sure you are ready for the next generation of environmental compliance requirements. Whether you have questions on this new storage tank rule, or one of the many other regulations that EPA has recently promulgated, PPM Consultants can help you plan and prepare for the future. Please do not hesitate to reach out to me directly at ned.coleman@ppmco.com to discuss any air quality related questions you may have.