EPA Proposes Updates to MACT Y for Marine Tank Vessel Loading Operations

On March 4, 2026, EPA proposed updates to MACT Y for marine tank vessel loading operations (MTVLO) (91 FR 10559). The proposal stems from EPA’s technology review under Clean Air Act (CAA) section 112(d)(6) and represents the first substantive revision to the MTVLO NESHAP since the 2011 risk and technology review (RTR). The public comment period closed April 20, 2026 (Docket EPA-HQ-OAR-2025-0207). Industry trade associations submitted comments addressing the proposal’s technical assumptions, cost analyses, and compliance feasibility. A detailed analysis of the rule and summary of key issues is available in the International Liquid Terminals Association (ILTA) comments. as well as comments jointly submitted by the American Petroleum Institute (API), the American Fuels and Petrochemical Manufacturers (AFPM), and ILTA.

EPA’s proposed revisions center on four key thrusts:

1. enhanced flare monitoring requirements aligned with the 2015 Refineries Rule;
2. periodic performance testing for non-flare control devices, including annual relative accuracy test audits (RATAs) for VOC continuous emissions monitoring systems (CEMS);
3. removal of startup, shutdown, and malfunction (SSM) exemptions consistent with Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008); and
4. mandatory electronic reporting through EPA’s Compliance and Emissions Data Reporting Interface (CEDRI).

Notably, EPA did not propose tightening any Hazardous Air Pollutant (HAP) control efficiency thresholds, expanding the Leak Detection and Repair (LDAR) requirements to liquid components, or lowering the leak definition.

EPA is currently obliged to issue a final rule in March of 2027 under the consent decree that led to this proposal. (Envt’l Integrity Project et al. v. Regan, No. 1:20-cv-03119-TNM (D.D.C. Oct. 29, 2020; as amended Jan. 8, 2021), Order Approving Consent Decree (entered Aug. 24, 2022))

MACT Y Applicability

MACT Y applies only to MTVLO at major sources of HAP. Within those facilities, requirements are tiered by MTVLO emissions and throughput:

• MACT control standards. Apply to MTVLO at new major sources of HAP, and to MTVLO with emissions of either ≥ 10 tpy of any individual HAP or ≥ 25 tpy aggregate HAP (considering only MTVLO emissions) at existing major sources.
• RACT standards (CAA § 183(f)). Apply where aggregate 24-month average marine loading throughput is ≥ 10 million barrels per year (MMbbl/yr) gasoline or ≥ 200 MMbbl/yr crude oil.
• Submerged fill (MACT floor). Applies where MTVLO emissions fall below the 10/25 tpy MACT threshold at a major source, and to existing offshore loading terminals.

No changes were proposed to the categorization, control requirements, or applicability threshold values associated with these affected facility groupings. EPA does propose to add the word “permitted” to its emission estimation procedure at § 63.565(l), for MTVLO that emit less than the 10- and 25-ton thresholds but which do not have a performance test. EPA’s stated intent is to require that MTVLO “with pre-controlled emissions of 10- or 25-tons HAP should comply with the control provisions in the MTVLO NESHAP or have enforceable, permitted control requirements to ensure emissions remain below 10- and 25-tons HAP at all times.” (91 FR 10565) However, the proposed rule text change would appear not to affect every MTVLO source less than 10 and 25 tons, only those that cannot base their emission estimates on “test data,” and it would appear not to change the post-control nature of §63.565(l) calculations “based on test data.” Notably, while EPA proposes to remove the word “actual” from the exemption thresholds in §63.561, EPA does not propose to remove the word “actual” from the phrase, “actual throughputs by commodity,” in the emission exemption recordkeeping requirement at §63.567(j)(4). The proposal thus appears not to move fully to a Potential To Emit (PTE) approach to the 10- and 25-ton thresholds.

Enhanced Flare Monitoring

EPA asserts that the existing requirements (initial performance test plus pilot flame monitoring at §63.564(f)) do not ensure ongoing compliance with the 95%, 97%, and 98% control efficiencies. Under the proposed amendments, flares used for MTVLO control would be obliged to meet the operating limits for petroleum refinery flares in §63.670 and the monitoring requirements in §63.671, with MTVLO-specific accommodations:

• Cumulative liquid loading rate as an alternative to waste gas flow monitoring (§ 63.670(i)).
• 14-grab-sample NHV demonstration may be collected over fewer days, with at least 60 minutes between samples.
• One-time flare tip velocity assessment based on maximum cumulative loading rate, in lieu of 15-minute block monitoring under § 63.670(k)(2).

Non-Flare Control Device Changes

Non-flare control devices must conduct performance tests at least once every 60 calendar months, with annual RATAs for VOC CEMS (Procedure 1, Method 25A or 25B as the reference method, propane calibration). Importantly, EPA proposes to require each MTVLO to conduct the first of its periodic performance tests within 180 days of the final rule effective date. (91 FR 10572) This proposed timeline will pose a significant challenge for MTVLO owners and operators, in light of the complexities and lead times of MTVLO performance testing.

Corollary proposed changes include the following three changes:

• Sunset of manufacturer-recommended baseline temperature for combustion devices. Performance tests conducted on or after the effective date would be able to determine monitored temperature only with the performance-test-based baseline (§ 63.565(f)(1)); the manufacturer option at § 63.565(f)(2) would be eliminated going forward.
• Tighter condenser/refrigeration operating window. The § 63.563(b)(7)(ii) operating limit drops from 28°C (50°F) to 5.6°C (10°F) above baseline temperature, aligning with the existing carbon adsorber requirement.
• 1,000 ppmv as a direct emission limit. The rule proposal reframes the §63.562(c)(4) gasoline loading compliance alternative, of 1,000 ppmv outlet VOC concentration, as an alternative emission limit rather than an alternative monitored operating parameter. Accordingly, EPA proposes to remove the 1,200 ppmv operational allowance for each control device type for which this option is given, including condenser/refrigeration units and carbon adsorbers. EPA also proposes to extend the option to absorbers under revisions to the existing absorber provisions at § 63.563(b)(8).

SSM Removal, LDAR, and Electronic Reporting

EPA proposes to remove maintenance allowance options and to expand the general duty clause of the rule, furthering its original changes from 2011 to meet the intent of Sierra Club v. EPA, 353 F.3d 976 (D.C. Cir. 2004). In so doing, EPA proposes that vessel compartment purging prior to connection the dock vapor control system is “inconsistent with the general duty requirement to minimize emissions.”

The rule proposal includes new CEDRI semiannual reports, which sunset the summary and excess emissions reporting at § 63.567(e) and malfunction reporting at § 63.567(m).

LDAR refinements at § 63.563(c) tighten existing practice without expanding scope: Method 21 monitoring must be coincident with loading; AVO methods replace Method 21 for difficult-to-monitor (>2 m elevation) and underwater/floating components; the 15-day repair window becomes a hard completion deadline with re-monitoring verification. The current rule proposal does not include an Optical Gas Imaging (OGI) alternative, though an OGI alternative was included for a similar LDAR standard for bulk gasoline terminals in 2024. Comments from industry stakeholders ask EPA to consider adding an OGI standard to Subpart Y.

Electronic reporting through CEDRI begins 180 days after the final rule’s publication. Periodic reports use a draft spreadsheet template (in the docket); other notifications and reports are submitted as PDF; performance test and CEMS performance evaluation results use ERT or compliant XML.

MACT Floor Source Applicability and Reporting Changes

For major sources of HAP with MTVLO emissions below the 10- and 25-tpy thresholds, EPA did not strengthen the underlying control requirements — submerged fill, recordkeeping, and reporting remain the only obligations. EPA is, however, proposing two related revisions that warrant attention:

• Annual HAP control efficiency report. The annual report under § 63.567(j)(3) must now identify the monitoring parameter(s) used to ensure the source continuously maintains HAP control efficiency while loading a regulated commodity.
• Basis for HAP status determination. EPA proposes to remove the word “actual” from the definition of “sources with [emissions] less than 10 or 25 tons” and to revise § 63.565(l) so that emission estimation procedures rely on “permitted” operating conditions rather than actual operations. This change may have meaningful permitting implications: facilities relying on uncontrolled emission estimates to stay below the 10/25 tpy threshold may need federally enforceable permit conditions reflecting the operating assumptions used in the emission estimate.

How Trinity can help

Trinity supports MTVLO and refinery clients with all aspects of MACT Y, including but not limited to compliance gap analysis, flare monitoring strategy, CPMS scoping, and CEDRI reporting readiness.

Please reach out to Harold Laurence for more information on the proposed MTVLO MACT Y amendments and how Trinity can help.