New Tank Regulations

On September 30th, 2022, the United States Environmental Protection Agency (EPA) published its Limited Approval, Limited Disapproval of the California Air Plan Revisions issued by the California Air Resources Board (CARB). The EPA has rejected CARB’s demonstrations of reasonably available control technology (RACT) for the 2008 and 2015 ozone National Ambient Air Quality Standards (NAAQS) for tanks subject to U.S. EPA’s 2016 Oil and Gas Control Techniques Guidelines (CTG). The demonstrations relied on South Coast AQMD Rules 463 – Organic Liquid Storage and 1178 – Further Reductions of VOC Emissions from Storage Tanks at Petroleum Facilities to demonstrate compliance. However, RACT deficiencies were identified in both rules with respect to their alignment with the U.S. EPA’s Oil and Gas CTG.

By Foster Voelker II, Director of Engineering – Williams Valves

Regulations 463 and 1178 establish lim­its on volatile organic compound (VOC) emissions from above-ground storage tanks utilized in storing organic liquids and petroleum products. Rule 463 per­tains to storage tanks with a design capacity exceeding 19,815 gallons or tanks within the range of 251 to 19,815 gallons specifically designed for gaso­line storage. The regulation mandates floating roofs with seals or fixed roofs with 95% emission control for tanks exceeding 39,630 gallons used to store organic liquids possessing a true vapor pressure (TVP) of 0.5 pound per square inch absolute (psia) or higher, and for tanks of 19,815 gallons capacity utilized for storing organic liquids with a TVP of 1.5 psia or greater.

Focused on petroleum facilities, Rule 1178 applies to storage tanks with a design capacity of at least 19,815 gallons storing materials with a TVP greater than 0.1 psia, and it requires more rigorous controls on all roof components for facilities that have higher emission levels.

Conversely, the Oil and Gas CTG for RACT requires a 95% emission control standard for storage tanks that have a potential to emit six tons or more per year and that are used in the oil and natural gas sector. However, Rules 463 and 1178 govern storage tanks based on their design capacity and the true va­por pressure of the liquid stored, not on the potential to emit. As a result, these rules may not cover all tanks subject to the Oil and Gas CTG. The Proposed Amended Rule 463 (PAR 463) and Pro­posed Amended Rule 1178 (PAR 1178) have been proposed to address this RACT deficiency by bringing the appli­cability of each rule in line with that of the Oil and Gas CTG.

Proposed Changes

PAR 463 and PAR 1178 are currently un­dergoing public review, which includ­ed a public workshop held on March 1, 2023. During this workshop, staff pre­sented the proposed amended rules to the general public and stakeholders and gathered feedback. Draft versions of the rule language in PAR 463 and PAR 1178, specifically addressing the RACT deficiency, were presented by the staff. Furthermore, regarding PAR 1178, additional language was pro­posed based on the results of a ‘best available retrofit control technology’ (BARCT) assessment for leak detection and emission reduction technologies.

Figure 1: Proposed Amended Rule 463 modified to include tanks subject to EPA 2016 CTG.

The discussion on the proposed amendments to Rule 1178 included a variety of requirements, such as dom­ing, seals, emission control systems, optical gas imaging (OGI) inspections, recordkeeping, and reporting. Stake­holders have expressed the need for additional time to collaborate with staff on the proposed requirements concerning the BARCT assessment for PAR 1178.

The February iteration of the proposed amended PAR 1178 included several requirements for storage tanks. One significant change, applicable to all floating roof tanks, is more stringent gap requirements for primary seals on floating roof tanks. Primary seal gaps greater than 1/2 inch cannot exceed 10% of tank circumference, while gaps great­er than 1/8 inch cannot exceed 30% of tank circumference. This is a reduction from 30% and 60% of allowable tank circumference, respectively. Internal floating roof tanks are also subjected to a compliance schedule for the installa­tion of a secondary seal when the tank is next emptied and degassed, no later than ten years after the adoption date.

Figure 2: Proposed Amended Rule 1178 98% emission control and Free of Visible Vapors.
Figure 3: Proposed Amended Rule 1178 Reporting/Record Keeping for OGI Inspections.

The February proposal outlined ad­ditional requirements for fixed roof tanks, including requirements for emis­sion control systems to meet 98% by weight control efficiency and that tanks are maintained in a condition free of Visible Vapors as determined by an optical gas imaging inspection. There are compliance schedules for installing domes crude oil tanks, defining specific requirements for tanks subject to dom­ing upon adoption and those subject to doming after adoption.

Lastly, there are requirements for OGI inspections and recording. The pro­posed rule would require component inspections for floating roof tanks to be conducted at specific intervals. Compliance with certain requirements must be demonstrated within 24 hours of visible vapors being detected, or the storage tank is considered non-compli­ant.

Moreover, OGI inspections require detailed reporting and recordkeeping, which includes notifying South Coast AQMD of nonconformance or visible vapor detection during tank inspec­tions, recordkeeping requirements for each type of inspection, and digital re­cording requirements for OGI devices.

However, the changes outlined in Fig­ure 3, driven by the BARCT assessment, were removed from the April iteration of the proposed rule. CARB has instruct­ed South Coast AQMD to revise Rules 463 and 1178 by June 2023 to address the RACT issue. The current proposed amendments to PAR 463 and PAR 1178, which solely aim to rectify the RACT de­ficiency, will be presented to the South Coast AQMD Governing Board at a Pub­lic Hearing on May 5th, 2023.

The amendments proposed will be lim­ited to remedying the RACT deficiency, excluding the additional requirements proposed to address the BARCT assess­ment issues in order to provide stake­holders with more time to collaborate with staff on the remaining additional amendments to Rule 1178. The BARCT-based requirements will be presented at a separate public hearing tentatively scheduled for August 4th, 2023.


The proposed revisions seek to address the RACT shortfall by aligning the appli­cability of each regulation with that of the 2016 Oil and Gas CTG. Although the current proposal does not encompass the alterations outlined for Rule 1178, it is anticipated that these modifica­tions will be integrated in due course. The stipulations comprise proficient control and monitoring approaches for tanks, encompassing gap requirements for floating roof tanks, vapor recovery for fixed roof tanks, secondary seal requirements for internal and domed external floating roof tanks, doming requirements for external floating roof tanks, OGI monitoring requirements for all tanks, and updated protocols for recordkeeping and reporting. Any facilities impacted by these proposals may want to participate in the ongoing public review process.


  1. scaqmd-rule-book/proposed-rules/rule-1178
ABOUT THE AUTHOR: Foster Voelker II attended the University of Houston, receiving a degree in Mechanical Engineering. After graduation, Foster Voelker began his career as a valve engineer for a large commodity valve manufacturer. He is the Director of Engineering for William E. Williams Valve Corporation.
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