This article appears in the Autumn 2022 issue of Tanks and Terminals magazine, a copyrighted publication of Palladian Publications.
On June 10, 2022, the US Environmental Protection Agency (EPA) proposed revisions to emission standards for the gasoline distribution industry.[1] These standards affect storage tanks, loading racks, and equipment components in gasoline service at thousands of gasoline distribution terminals, bulk plants, and pipeline stations.[2] The proposed revisions include several important increases in stringency, such as lower numeric emission limits, additional monitoring, and shorter averaging periods.
Background
The EPA has regulated Volatile Organic Compound (VOC) emissions from the gasoline distribution sector under its New Source Performance Standards (NSPS) regulatory program since the 1983 promulgation of “Standards of Performance for Bulk Gasoline Terminals,” Subpart XX.[3] The NSPS requires most new and modified gasoline truck loading racks to meet an emission standard of 35 milligrams of Total Organic Compounds (TOC) per liter of gasoline loaded (mg/L TOC).[4] The NSPS requires monthly monitoring of loading rack equipment for leaks, by Audio, Visual, and Olfactory (AVO), or “sight/sound/smell” means.[5] NSPS XX also introduced vapor tightness requirements for gasoline tank trucks.[6]
In 1994, the EPA promulgated an emission standard regulating Hazardous Air Pollutant (HAP) emissions from major source gasoline terminals and pipeline breakout stations: “National Emission Standards for Gasoline Distribution Facilities (Bulk Gasoline Terminals and Pipeline Breakout Stations),” Subpart R.[7] This subpart required gasoline truck and rail loading racks to meet 10 mg/L TOC.[8] It required gasoline storage vessels (storage tanks) to install an Internal Floating Roof (IFR) meeting most requirements of the storage tank NSPS,[9] and to retrofit certain deck fittings on existing gasoline storage vessels with External Floating Roofs (EFRs).[10] Subpart R required monthly AVO leak inspections, but the scope included all gasoline-service equipment at the terminal or breakout station.
Subpart R only affected larger terminals and breakout stations, those that met the EPA’s HAP major source threshold. By 1999, the EPA had indicated its intent to regulate gasoline distribution facilities that did not rise to the HAP major source threshold.[11] In 2008, EPA promulgated “National Emission Standards for Hazardous Air Pollutants for Source Category: Gasoline Distribution Bulk Terminals, Bulk Plants, and Pipeline Facilities,” Subpart BBBBBB (Subpart 6B).[12] Subpart 6B contained different sets of requirements for four source categories: bulk gasoline terminals, bulk gasoline plants (a throughput of less than 20,000 gallons per day [gpd]), pipeline pump stations, and pipeline breakout stations. Table 1 presents some key requirements of Subpart 6B.
Summary of Revisions
EPA is required to review NSPS, such as Subpart XX, and National Emission Standards for Hazardous Air Pollutants (NESHAP), such as Subparts R and 6B, at least every eight years.[13] If needed, the EPA must revise the subparts to reflect the best demonstrated system of emission reduction (for NSPS) or to take developments in control technology into account (for NESHAP, a “technology review”). Table 2 presents the EPA’s key proposed revisions of the three subparts. New or more stringent requirements for loading racks, storage tanks, and gasoline-service equipment are proposed. Finalized rule revisions, which may differ from the proposed revisions, are expected on or about June 2023. A three-year time frame to reach compliance with Part 63 rules means that the Part 63, Subparts R and 6B changes would apply on or about June 1, 2026. Performance testing would occur within 180 days from that date.[14]
Certain aspects of the revisions to 40 CFR Part 60, Subpart XX and 40 CFR Part 63, Subpart 6B merit further discussion.
Subpart XXa Applicability Date
Subpart XXa proposes much more stringent requirements for emission control devices on gasoline loading racks than the current Subpart XX. When such NSPS rules are revised, existing facilities come into compliance with the new rule only after the first time they are modified, or reconstructed, after the rule proposal date. Under NSPS rules, most changes to a facility that cause emissions to increase are “modification,” and most changes that are more than 50% of the cost of an equivalent new facility are “reconstruction.”[15] Most importantly, since EPA published the proposed Subpart XXa on June 10, 2022, a loading rack project that takes place after this date may cause the loading rack to become subject to the final rule text of Subpart XXa, even though the rule is not yet final at present. Terminal operators should carefully consider the effects and schedules of capital projects affecting their loading racks, to assess if those projects will cause the racks to be subject to Subpart XXa’s stringent new standards.
Instrument Monitoring
Each of the proposed revised rules includes an instrument monitoring program to detect leaks from equipment in gasoline service. None of the current rules for gasoline distribution facilities require instrument monitoring. Even bulk gasoline plants with throughput less than 20,000 gpd would be required to conduct instrument monitoring.[16]
The proposed program includes two options. One option is a Leak Detection and Repair (LDAR) program using EPA Method 21 to detect leaks as is common at petroleum refineries or chemical plants. The other option is to use Optical Gas Imaging (OGI) to detect leaks. OGI technology creates images of hydrocarbon gases, such as gasoline vapors. The proposed rules only differ in frequency of monitoring, as shown in Table 2.
First-time implementation of an instrument monitoring LDAR program requires advance consideration of several factors. Inspection logs required under current rules must be replaced with detailed, individually identified components. Typically, component identifiers and monitoring results are stored in a dedicated LDAR compliance tool. A decision must also be made between selecting a contractor or training a terminal’s staff to provide routine monitoring. This decision would consider availability of contractors and of monitoring equipment.
Loading Rack Emission Control Device Changes
The EPA’s proposed emission standard revisions to Subpart 6B are substantial for loading racks and associated vapor control systems at gasoline distribution facilities. According to the EPA, there are presently more than 9,250 facilities in the US that are subject to Subpart 6B provisions.[17]
The current Subpart 6B specifies that bulk gasoline terminals loading racks with gasoline throughput of 250,000 gallons per day or greater must reduce the emissions of TOC to less than or equal to 80 mg/L TOC. This emission standard is the same regardless of the type of vapor control system used. The standard excludes methane and ethane from TOC measurement.[18]
By contrast, the proposed Subpart 6B specifies that such bulk gasoline terminals will need to reduce emissions of TOC to the levels listed below, depending on the type of vapor control system used. And the revised standard does not explicitly exclude methane and ethane.
- Thermal Oxidation System Other than a Flare (e.g., Vapor Combustion Unit): Reduce emissions of TOC to less than or equal to 35 mg/L TOC, to be operated as specified in the proposed 40 CFR 63.11092(e)(2).
- Flare: Achieve at least 98% reduction in emissions of TOC by weight, to be operated as specified in the proposed 40 CFR 60.502a(c)(3).
- Vapor Recovery System: Reduce emissions of TOC to less than or equal to 19,200 parts per million by volume (ppmv) as propane, determined on a 3-hour rolling average.
Alternative Monitoring Changes
Gasoline distribution facility operators may face several potential challenges when complying with the proposed Subpart 6B standards. One potential challenge is related to the removal of alternative monitoring provisions in the current Subpart 6B rule for a thermal oxidation system other than a flare, such as a Vapor Combustion Unit (VCU). Presently, monitoring of the presence of a thermal oxidation system pilot flame is allowed as an alternative to measuring the firebox temperature to demonstrate compliance with the monitoring requirements of Subpart 6B.[19] Gasoline vapors combust readily; for instance, butane has a Net Heating Value (NHV) of 2,985 British thermal units per standard cubic foot (Btu/scf).[20]
The proposed rules disallow pilot flame monitoring as a compliance option. New loading racks subject to the proposed Subpart XXa would be required to monitor firebox temperature continuously.[21] Loading racks subject to Subpart XXa due to modification or reconstruction, as well as racks subject to Subpart 6B, would have an additional option to monitor the NHV of the gases fed to the VCU. Such VCUs would follow rules for open flares at petroleum refineries.[22]
A temperature monitoring method could result in the need to combust additional auxiliary fuel during periods of low gasoline loading, to maintain the firebox temperature at or above the level determined during the performance test. Furthermore, some facilities use a VCU as a backup vapor control system to their primary vapor recovery system for when the primary vapor control system is down. If the backup VCU is required to combust additional auxiliary fuel to maintain the firebox temperature, operation of the backup vapor control system may become cost prohibitive.
Facility operators should begin to develop their compliance approaches for thermal oxidation systems such as VCUs. From the more limited options available in the proposed rules, facilities should select a vapor control and compliance demonstration approach that achieves compliance in a cost-effective manner.
Averaging Period Changes
The proposed rules also reduce the duration of averaging periods for loading rack emission control devices, creating another potential compliance challenge. For thermal oxidation systems other than a flare, the EPA is proposing that combustion zone temperature be maintained at or above the level determined during the performance test on a 3-hour rolling average basis. Similarly, the EPA is proposing a 3-hour rolling average monitoring period for the ppmv emission standards for vapor recovery systems. The current averaging period for performance testing for either type of control device is 6 hours. The change from a 6-hour to a 3-hour rolling average would impact design and operation of control devices.
In thermal oxidation systems such as VCUs, firebox temperature is related to the volume of gasoline vapors combusted at a given time. At most facilities, loading activities do not occur at a uniform rate throughout the day but are, rather, characterized by periods of higher or lower gasoline demand. On a shorter, 3-hour average, facilities would record greater variability in the VCU temperature. Changes in temperature due to varying gasoline vapor generation rate would not necessarily correlate with control device efficacy. Even so, operators would have a compliance need to stay above the required temperature minimum, such as by adding assist gas, shortening periods of higher loading rates, or smoothing periods of peak and low demand. This compliance need could result in capital costs, truck waiting time, and/or delivery delays.
In vapor recovery systems, a limit expressed as ppmv on a 3-hour basis is more stringent than the same limit expressed on a 6-hour basis. Facilities’ existing vapor recovery systems may need to be redesigned to be able to accommodate the proposed emission limit of 19,200 ppmv as propane on a 3-hour rolling average basis.
Preparing for the Changes
The EPA has proposed substantial changes to air emission standards for the gasoline distribution industry. The proposed revisions include instrument monitoring LDAR requirements, revised monitoring requirements for storage vessels, and stricter emission standards for loading racks. The proposed standards may require affected facilities to undertake capital projects, to implement new compliance demonstration programs, or to conduct internal feasibility studies for compliance planning. Gasoline distribution facilities should begin developing compliance strategies for the revised rules, especially as NSPS rules apply to facilities modified after the proposed rule date.
Harold Laurence ([email protected]), Managing Consultant at Trinity Consultants, is based out of Trinity’s Seattle office. For the past 10 years, Mr. Laurence has provided Clean Air Act consulting support to the U.S. liquid terminal and petroleum refining industries. He leads Trinity’s nationwide group of storage tank subject matter experts. Mr. Laurence earned his bachelor’s in chemical engineering from the University of Kansas and is a licensed Professional Engineer in Washington and Hawaii.
Behdad Yazdani ([email protected]), Managing Consultant at Trinity Consultants, is based out of Trinity’s Baton Rouge office. He offers his bulk petroleum liquid terminal and petroleum refinery clients 10 years of experience in environmental engineering consulting. Mr. Yazdani graduated from North Carolina State University with an M.S. degree in environmental engineering and is a licensed Professional Engineer.
[1] Docket numbers EPA-HQ-OAR-2020-0371-0062, -0063, -0064, and -0065, available at https://www.regulations.gov/docket/EPA-HQ-OAR-2020-0371. The federal register posting may be found at: https://www.federalregister.gov/documents/2022/06/10/2022-12223/national-emission-standards-for-hazardous-air-pollutants-gasoline-distribution-technology-review-and
[2] EPA’s cost calculations in the rule docket (EPA-HQ-OAR-2020-0371-0010) include a basis of 210 Hazardous Air Pollutant (HAP) major sources and over 9,250 HAP area sources.
[3] 40 CFR Part 60, Subpart XX, “Subpart XX – Standards of Performance for Bulk Gasoline Terminals,” was first promulgated on August 18, 1983 (48 FR 37590). The subpart is available online from the electronic CFR at https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-60/subpart-XX.
[4] 40 CFR 60.502(b). Paragraph (c) provides an exception for loading racks that had a vapor processing system constructed or refurbished before December 17, 1980, and that could attain 80 mg/L TOC.
[5] 40 CFR 60.502(j).
[6] 40 CFR 60.502(e)(1).
[7] 40 CFR Part 63, Subpart R, “National Emission Standards for Gasoline Distribution Facilities (Bulk Gasoline Terminals and Pipeline Breakout Stations),” was first promulgated on December 14, 1994 (59 FR 64318). The subpart is available online at the eCFR at https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-63/subpart-R.
[8] 40 CFR 63.422(b).
[9] 40 CFR 63.423(a). Some deck fitting control requirements of 40 CFR Part 60, Subpart Kb were not included in Part 63, Subpart R. Seal requirements were included, as was the requirement that deck fittings have projections below the liquid surface.
[10] 40 CFR 63.423(b).
[11] Table 3 of U.S. EPA, “National Air Toxics Program: The Integrated Urban Strategy,” July 19, 1999 (64 FR 38721), available online at https://www.govinfo.gov/content/pkg/FR-1999-07-19/pdf/99-17774.pdf.
[12] 40 CFR 63 Subpart BBBBBB, “Subpart BBBBBB – National Emission Standards for Hazardous Air Pollutants for Source Category: Gasoline Distribution Bulk Terminals, Bulk Plants, and Pipeline Facilities,” was first promulgated on January 10, 2008 (73 FR 1933). The subpart is available online from the eCFR at https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-63/subpart-BBBBBB.
[13] Clean Air Act, §§ 111(b)(1)(B) and 112(d)(6).
[14] See proposed text of 40 CFR 63.11092(e)(1) for thermal oxidation systems other than a flare, and proposed text of 40 CFR 60.503a(b)(1) for vapor recovery systems.
[15] Details are given at 40 CFR 60.14 and 40 CFR 60.15.
[16] Proposed text of 40 CFR 63.11086(c) and 40 CFR 63.11089.
[17] Federal Register, Vol. 87, No. 112/Friday, June 10, 2022/Proposed Rules: https://www.govinfo.gov/content/pkg/FR-2022-06-10/pdf/2022-12223.pdf
[18] 40 CFR 60.503(c)(6).
[19] 40 CFR 63.11092(b)(1)(iii)(B).
[20] Standard conditions of 379 scf/lbmol, an NHV of 19,466 Btu per pound (Btu/lb), and a molar mass of 58.12 lb/lbmol.
[21] Proposed 40 CFR 60.502a(b)(1)(ii) (new racks) and (c)(1)(ii) (modified or reconstructed racks).
[22] Proposed 40 CFR 63.11092(e)(2)(ii).
