Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Large Municipal Waste Combustors Voluntary Remand Response and Five-Year Review

Federal RegisterMar 10, 2026

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 60

[EPA-HQ-OAR-2017-0183; FRL-5120-04-OAR]

RIN 2060-AO18

Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Large Municipal Waste Combustors Voluntary Remand Response and Five-Year Review

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule.

SUMMARY:

The U.S. Environmental Protection Agency (EPA) is finalizing new source performance standards (NSPS) and emission guidelines (EG) for the large municipal waste combustion (MWC) source category. This final rule responds to a voluntary remand of the preceding rule for this source category and announces the results of the non-discretionary review at five-year intervals required by Clean Air Act (CAA) section 129(a)(5), fulfilling the requirements of a consent decree for the source category. The final rule revises the remanded emission limits for cadmium, lead, particulate matter, polychlorinated dibenzodioxins and dibenzofurans, mercury, hydrogen chloride, and sulfur dioxide for all sources subject to the NSPS and EG and the remanded emission limits for nitrogen oxides and carbon monoxide for some sources subject to the EG and all sources subject to the NSPS. This final rule also removes certain startup, shutdown, and malfunction (SSM) exclusions and exemptions. In addition, the EPA is taking this opportunity to streamline regulatory language; revise recordkeeping and reporting requirements; establish electronic notification; reestablish new and existing source applicability dates; eliminate title V requirements for air curtain incinerators that burn only wood waste, yard waste, and clean lumber; close a 2007 proposed reconsideration action; and make certain typographical and technical corrections and clarifications. The EPA estimates this final rule will result in 3,269 tpy reduction in regulated pollutants from existing sources through implementation of the final emission limits.

DATES:

This final rule is effective on May 11, 2026. The incorporation by reference (IBR) of certain publications listed in the rule is approved by the Director of the

Federal Register

as of May 11, 2026.

ADDRESSES:

The EPA has established a docket for this action under Docket ID No. EPA-HQ-OAR-2017-0183. All documents in the docket are listed at

https://www.regulations.gov.

Although listed, some information is not publicly available,

e.g.,

Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. The EPA does not place certain other material, such as copyrighted material, on the internet; this material is publicly available only as Portable Document Format (PDF) versions accessible only on the EPA computers in the docket office reading room. The public cannot download certain databases and physical items from the docket but may request these items by contacting the docket office at 202-566-1744. The docket office has 10 business days to respond to such requests. With the exception of such material, publicly available docket materials are available electronically at

https://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT:

For information about this final rule, contact Ms. Noel Cope, Natural Resources Division, 109 T.W. Alexander Drive, P.O. Box 12055, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-2128; and email address:

Cope.Noel@epa.gov.

SUPPLEMENTARY INFORMATION:

Preamble acronyms and abbreviations.

Throughout this notice the use of “we,” “us,” or “our” refers to the EPA. We use multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, the EPA defines the following terms and acronyms here:

ANSI American National Standards Institute

APCD air pollution control device

ASME American Society of Mechanical Engineers

ASNCR advanced selective noncatalytic reduction

ATSDR Agency for Toxic Substances and Disease Registry

BSER Best system of emission reduction

CAA Clean Air Act

CBI Confidential Business Information

Cd cadmium

CDX Central Data Exchange

CEDRI Compliance and Emissions Data Reporting Interface

CEMS continuous emissions monitoring system

CFBS circulating fluidized bed scrubber

CFR Code of Federal Regulations

CISWI Commercial and Industrial Solid Waste Units

CO carbon monoxide

CRA Congressional Review Act

DCOT digital camera opacity technique

Dscm dry standard cubic meter

EAV equivalent annualized value

EG emission guidelines

EPA Environmental Protection Agency

ERT Electronic Reporting Tool

HAP hazardous air pollutant(s)

HCl hydrogen chloride

Hg mercury

HMIWI hospital, medical, and infectious waste incinerators

ICR Information Collection Request

Low NO

LPL lower predictive limit

MACT maximum achievable control technology

MB/RC mass burn rotary combustor

MB/WW mass burn water wall

mg milligram

MSW municipal solid waste

MWC municipal waste combustor

NAAQS National Ambient Air Quality Standards

NAICS North American Industry Classification System

ng nanogram

oxides of nitrogen (nitrogen oxides)

NRDC Natural Resources Defense Council

NSPS new source performance standards

NTTAA National Technology Transfer and Advancement Act

Ozone

OCAP Office of Clean Air Programs

OTR Ozone Transport Region

OMB Office of Management and Budget

Pb lead

PCDD/PCDF polychlorinated dibenzodioxins and dibenzofurans (dioxins/furans)

PDF portable document format

PM particulate matter

ppm parts per million

ppmvd parts per million by volume, dry basis

PRA Paperwork Reduction Act

PV present value

QRO Certification for Municipal Solid Waste Combustion Facilities Operator

RATA relative accuracy test audit

RDL representative detection level

RDF/FBC refuse-derived fuel fluidized bed combustor

RDF/S refuse-derived fuel stoker combustor

RDF/SS refuse-derived fuel semi-suspension or spreader stoker wet process conversion combustor

RFA Regulatory Flexibility Act

RIA Regulatory Impact Analysis

SCR selective catalytic reduction

SNCR selective noncatalytic reduction

SO2 sulfur dioxide

SSM startup, shutdown, and malfunction

tpd tons per day

tpy tons per year

µg microgram

UMRA Unfunded Mandates Reform Act of 1995

UPL upper prediction limit

VCS voluntary consensus standards

WTEA Waste to Energy Association

XML Extensible Markup Language

Table of Contents

I. General Information

A. Executive Summary

B. Does this action apply to me?

C. Where can I get a copy of this document and other related information?

D. Judicial Review and Administrative Reconsideration

II. Background

A. What is the statutory authority for this action?

B. What is the regulatory background for the large MWC source category, and how do the NSPS and EG regulate emissions from the source category?

C. What changes did we propose for the large MWC source category in our January 23, 2024, proposal?

D. What outreach did we conduct following the proposal?

III. What is included in these final rules?

A. What are the final rule amendments based on the five-year review and response to the voluntary MACT floor remand for the large MWC source category?

B. What are the final rule amendments addressing emissions during periods of startup, shutdown, and malfunction?

C. What are the final rule amendments addressing other changes to the large MWC EG and NSPS?

D. What are the effective and compliance dates of the standards?

E. Severability

IV. What is the rationale for our final decisions and amendments for the large MWC source category?

A. Five-Year Review and Response to the Voluntary MACT Floor Remand for the Large MWC Source Category

B. Startup, Shutdown, and Malfunction

C. Other Changes to the Large MWC EG and NSPS

V. Summary of Cost, Environmental, Economic Impacts, and Additional Analyses Conducted

A. What are the affected facilities?

B. What are the air quality impacts?

C. What are the cost impacts?

D. What are the economic impacts?

E. What are the benefits?

F. What analysis of children's environmental health did we conduct?

VI. Statutory and Executive Order Reviews and 1 CFR Part 51

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review

B. Executive Order 14192: Unleashing Prosperity Through Deregulation

C. Paperwork Reduction Act (PRA)

D. Regulatory Flexibility Act (RFA)

E. Unfunded Mandates Reform Act (UMRA)

F. Executive Order 13132: Federalism

G. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

H. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

I. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use

J. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR Part 51

K. Congressional Review Act (CRA)

I. General Information

A. Executive Summary

In December 1995, the EPA adopted emissions guidelines (EG) (40 CFR part 60, subpart Cb) and new source performance standards (NSPS) (40 CFR part 60, subpart Eb) for large municipal waste combustors (MWC), which have a combustion capacity of greater than 250 tons per day (tpd) of municipal solid waste (MSW), pursuant to Clean Air Act (CAA) section 129.

CAA section 129(a)(5) requires review of these standards at 5-year intervals and, in 2006, the EPA promulgated amendments to the 1995 standards, revising the emission limits and compliance testing provisions to reflect the actual performance achieved by existing MWCs and improvements in CEMS data performance and reliability.

Note that on February 11, 1991, Subpart Ea was promulgated that applies Standards of Performance to MWCs which commenced construction after December 20, 1989, and on or before September 20, 1994.

71 FR 27324 (May 10, 2006).

Following promulgation of the 2006 rulemaking, environmental groups filed a petition for review in the D.C. Circuit challenging the rulemaking. The petitioners challenged the emission limits which the EPA promulgated in 1995. In light of then-recent precedents casting doubt on the soundness of emission limits derived in part from state-issued air permits as the 1995 emission limits for large MWCs were, the EPA sought a voluntary remand of the 2006 rule.

In its remand motion, the EPA announced its intention to grant the environmental groups' administrative petition to revisit the 1995 emission limits and reevaluate the 2006 rule as necessary to comport with any revisions. The D.C. Circuit issued an order granting the EPA's request for a remand in 2008, which directed the EPA to review its 2006 rulemaking.

Specifically, the petitioners pointed to a 2004 decision from the D.C. Circuit, which remanded MACT floors established for existing small MWCs derived from state-issued permit limits because the Court found the EPA did not fulfill the requirement of CAA section 129(a)(2) in setting the floors.

See Northeast Maryland Waste Disposal Authority

EPA,

358 F.3d 936 (D.C. Cir. 2004). Additionally, the EPA noted in its motion for a voluntary remand that since the time the EPA finalized the 2006 rulemaking, the D.C. Circuit issued three decisions that were relevant to rules promulgated under sections 112 and 129 of the CAA, since the floor setting requirements in section 129 are essentially equivalent to those under section 112.

See Sierra Club

EPA,

479 F.3d 875 (D.C. Cir. Mar. 13, 2007) (vacating the EPA's regulations setting national emission standards for brick and clay ceramics kilns under Section 112);

Natural Resources Defense Council

EPA,

489 F.3d 1250 (D.C. Cir. June 8, 2007) (vacating the EPA's regulations setting national emission standards under section 112 for hazardous air pollutants from industrial, commercial, and institutional boilers and process heaters and the EPA's regulations under section 129 defining the term “commercial and industrial solid waste incineration unit”);

Natural Resources Defense Council

EPA,

489 F.3d 1364 (D.C. Cir. June 19, 2007) (vacating portions of an EPA rule promulgated under CAA section 112 regulating hazardous air pollutants from the manufacture of plywood and composite wood products).

Order,

Sierra Club

EPA,

No. 06-1250 (D.C. Cir. filed Feb. 15, 2008).

In 2024, the EPA proposed to revise the NSPS and EG under CAA section 129 for large MWCs by amending existing standards for the large MWC source category.

The Agency sought comment on additional data, including data on the number of facilities that would require retrofit to meet any emission limits and data to inform the EPA's projections of air pollution control device (ACPD) use by large MWCs. In addition, the EPA sought comment on developments in practices, processes, and control technologies that reduce pollutant emissions.

89 FR 4243 (Jan. 23, 2024).

In 2025, the Agency reopened the comment period for an additional four months to gather additional information on the proposed amendments to the large MWC regulations.

Specifically, the EPA sought additional information and documentation on verifiable historic pollutant emission concentration information (

e.g.,

stack test reports, waste characterization reports and continuous emission monitor records) for large MWCs so that we could further assess the proposed maximum achievable control technology (“MACT”) requirements, including operation of the control technologies over time.

90 FR 4708 (Jan. 8, 2025).

In this final rule, the EPA is revising the remanded emission limits for cadmium, lead, particulate matter, polychlorinated dibenzodioxins and dibenzofurans, mercury, hydrogen chloride, and sulfur dioxide for all sources subject to the NSPS and EG and the remanded emission limits for nitrogen oxides and carbon monoxide for some sources subject to the EG and all sources subject to the NSPS. The EPA is also finalizing the following amendments: removal of SSM exclusions and exemptions; streamlined regulatory language; revisions to recordkeeping and reporting requirements; addition of electronic reporting requirements; reestablishment of new and existing source applicability dates; elimination of title V requirements for air curtain incinerators that burn only wood waste, yard waste, and clean lumber and are not located at a major source or subject to title V for

other reasons; closing the 2007 proposed reconsideration action; and other technical, typographical, and clarifying corrections to certain provisions in the NSPS and EG.

Following consideration of comments and additional information received on the proposed rule and the reopened comment period, the EPA is revising its reassessment of the MACT floor limits for the EG and NSPS. The EPA is finalizing an approach similar to that in the proposed rule, using separate methodologies for pollutants with stack test data (Cd, Pb, Hg, PM, HCl, and PCDD/PCDF) and pollutants with CEMS data (or CEMS pollutants) (CO, NO

, and SO

). The final limits incorporate new data submitted during the reopened comment period for years 1990 to 1995 in addition to the 2000 to 2009 compliance dataset that the EPA used for the proposed limits.

The EPA estimates that this final rule will result in present value costs of $330 million at a three percent discount rate and $210 million at a seven percent discount rate over the 2030 to 2049 time frame, with equivalent annualized values of $25 and $28 million per year, respectively (in 2024 dollars, discounted to 2025).

B. Does this action apply to me?

Regulated entities.

This final action applies to large MWCs that combust more than 250 tons per day (tpd) of municipal solid waste (MSW) as defined under CAA section 129(a)(1)(B), to be regulated under title 40 of the Code of Federal Regulations (CFR) part 60, new subparts VVVV and WWWW. Table 1 of this preamble presents categories and entities that this action potentially regulates.

Table 1—Industrial Source Categories Affected by This Final Action

Category

NAICS * code

Solid Waste Combustors and Incinerators

562213

Administration of Air and Water Resource and Solid Waste Management Programs

924110

The EPA does not intend Table 1 of this preamble to be exhaustive but rather to provide a guide for readers regarding entities that this final action likely affects. To determine whether this action affects your facility, you should examine the applicability criteria found in title 40 of the Code of Federal Regulations (CFR), 40 CFR 60.5690 of subpart VVVV and 40 CFR 60.6300 of subpart WWWW. If you have questions regarding the applicability of any aspect of the final subparts to a particular entity, please contact the appropriate person listed in the preceding

FOR FURTHER INFORMATION CONTACT

section of this preamble.

C. Where can I get a copy of this document and other related information?

In addition to the docket, an electronic copy of this final action will be available on the internet. In accordance with 5 U.S. Code (U.S.C.) 553(b)(4), a brief summary of this rule may be found at

https://www.regulations.gov,

Docket ID No. EPA-HQ-OAR-2017-0183. Following signature by the Administrator, the EPA will post a copy of this final action at

https://www.epa.gov/stationary-sources-air-pollution/large-municipal-waste-combustors-lmwc-new-source-performance.

Following publication in the

Federal Register

, the EPA will post the

Federal Register

version and key technical documents at this same website.

D. Judicial Review and Administrative Reconsideration

Under CAA section 307(b)(1), judicial review of this final action is available only by filing a petition for review in the U.S. Court of Appeals for the D.C. Circuit (“D.C. Circuit”) by May 11, 2026. CAA section 307(b)(2) prohibits a party from challenging this final action separately in any civil or criminal proceedings for enforcement.

CAA section 307(d)(7)(B) further provides that only an objection to a rule or procedure that was raised with reasonable specificity during the period for public comment (including any public hearing) may be raised during judicial review. This section also requires the EPA to reconsider the rule if the person raising an objection can demonstrate to the Administrator that it was impracticable to raise such objection within the period for public comment or if the grounds for such objection arose after the period for public comment (but within the time specified for judicial review) and if such objection is of central relevance to the outcome of the rule. Any person seeking to make such a demonstration should submit a Petition for Reconsideration to the Office of the Administrator, U.S. EPA, Room 3000, WJC South Building, 1200 Pennsylvania Ave., NW, Washington, DC 20460, with a copy to both the person(s) listed in the preceding

FOR FURTHER INFORMATION CONTACT SECTION

and the Associate General Counsel for the Air and Radiation Law Office, Office of General Counsel (Mail Code 2344A), U.S. EPA, 1200 Pennsylvania Ave. NW, Washington, DC 20460.

II. Background

A. What is the statutory authority for this action?

CAA section 129 provides the statutory authority for this action. CAA section 129(a)(1) requires the EPA to establish NSPS and EG pursuant to CAA sections 111 and 129 for new and existing solid waste incineration units, including “incineration units with capacity greater than 250 tons per day combusting municipal waste.”

This final rule includes a reevaluation of the first-stage technology-based standards established in 1995 pursuant to CAA section 129(a)(2) in response to a voluntary remand by the D.C. Circuit. In addition, this action includes a review of the reevaluated standards pursuant to CAA section 129(a)(5), which requires that the EPA, at five-year intervals review and, “in accordance with [section 129 and section 111],”

revise the standards and the requirements promulgated for a category solid waste incineration units, including large MWC units.

42 U.S.C. 7429(a)(1)(A)-(B).

Id.

7429(a)(5).

CAA section 129(a)(2) provides that standards “applicable to solid waste incineration units promulgated under [section 111] and this section shall reflect the maximum degree of reduction in emissions of [certain listed air pollutants] that the Administrator, taking into consideration the cost of achieving such emission reduction and any non-air quality health and environmental impacts and energy requirements, determines is achievable for new and existing units in each category.”

This level of control is referred to as a maximum achievable control technology (MACT) standard. CAA section 129(a)(4) further directs the EPA to set numeric emission limits for certain pollutants: cadmium (Cd),

mercury (Hg), lead (Pb), particulate matter (PM), hydrogen chloride (HCl), sulfur dioxide (SO

), polychlorinated dibenzodioxins and dibenzofurans (PCDD/PCDF), carbon monoxide (CO), and oxides of nitrogen (NO

In addition, the standards “shall be based on methods and technologies for removal or destruction of pollutants” before, during, and after combustion according to CAA section 129(a)(3).

The EPA has discretion to distinguish among classes, types, and sizes of incinerator units within a category when setting standards.

Id.

7429(a)(2).

Id.

7429(a)(4).

Id.

7429(a)(3).

Id.

7429(a)(2).

In promulgating a MACT standard, the EPA must calculate the minimum stringency levels for new and existing solid waste incineration units in a category based on levels of emissions control achieved in practice by the subject units. The minimum level of stringency is called the MACT floor. Different approaches exist for determining the MACT floors for new and existing sources. For new, modified, and reconstructed sources, CAA section 129(a)(2) provides that the “degree of reduction in emissions that is deemed achievable . . . shall not be less stringent than the emissions control that is achieved in practice by the best controlled similar unit, as determined by the Administrator.”

Emissions standards for existing units may be less stringent than standards for new units, provided that the standards “shall not be less stringent than the average emissions limitation achieved by the best performing 12 percent of units in the category.”

The MACT floors are the minimum standards that the EPA may consider for a source category. As a part of the “beyond-the-floor” evaluation, however, the EPA may consider standards more stringent than the MACT floor, taking into account the costs, non-air quality health and environmental impacts, and energy requirements of the more stringent controls.

Id.

The MACT analysis involves assessing emissions from the best performing units in a source category. The EPA can base this assessment on actual emissions data and other information, such as State regulatory requirements, that enable the EPA to estimate the performance of the regulated units. For each source category, the assessment involves a review of available emissions data and information with an appropriate accounting for emissions variability. The EPA can use other methods of estimating emissions, provided that the methods can be shown to provide reasonable estimates of the actual emissions performance of a source or sources in practice. Where there is more than one method or technology to control emissions, the analysis may result in several potential regulatory options, one of which the EPA selects as the MACT for each pollutant. Each regulatory option must be at least as stringent as the minimum-stringency floor requirements. The EPA also examines, but is not required to adopt, more stringent beyond-the-floor regulatory options to select the MACT. Based on the EPA's consideration of the factors outlined in CAA section 129(a)(2), including the costs, any non-air quality health and environmental impacts, and energy requirements, the EPA selects either the MACT floor level of control or a beyond-the-floor level of control as the MACT standard.

CAA section 129(a)(5) requires the EPA to review the NSPS and EG at five-year intervals and, in accordance with CAA sections 129 and 111, revise the NSPS and EG.

CAA section 111 contains a similar periodic “review and revise” provision. Specifically, CAA section 111(b)(1)(B) requires that the EPA, except in specified circumstances, review NSPS promulgated under CAA section 111 every eight years and revise the standards if the EPA determines that it is “appropriate” to do so.

In light of the explicit reference in CAA section 129(a)(5) to CAA section 111, which directs the EPA to review and revise standards previously promulgated only “if appropriate,” the EPA interprets CAA section 129(a)(5) to likewise require that the EPA review and, if appropriate, revise CAA section 129 standards.

Id.

7429(a)(5).

Id.

7411(b)(1)(B).

CAA section 129 provides guidance on the criteria relevant to determining whether revising a CAA section 129 standard is “appropriate.” Specifically, CAA section 129(a)(3) states that standards for solid waste incineration units under CAA sections 111 and 129 “shall be based on methods and technologies for removal or destruction of pollutants before, during and after combustion.”

This section's reference to methods and “technologies” supports the inference that the EPA should consider advances in technology, both in terms of effectiveness and costs, as well as the availability of new technologies when determining whether revising a CAA section 129 standard is “appropriate.” This is the same general approach that the EPA takes in periodically reviewing NSPS promulgated under CAA section 111(b)(1)(B).

Id.

7429(a)(3).

CAA section 111(b)(1)(B) directs the EPA to “review and, if appropriate, revise [section 111 NSPS] following the procedure required by this subsection for promulgation of such standards.”

Such standards, as defined in section 111(a)(1), are based on “the best system of emission reduction” or BSER, “which (taking into account the cost of achieving such reduction, and any non-air quality and health and environmental impacts and energy requirements) the Administrator determines has been adequately demonstrated.” Because the BSER is generally based on the degree of emission limitation achievable by some type of control technology, in reviewing section 111 NSPS, the EPA evaluates advances in existing control technologies, both in terms of performance and cost, as well as the availability of new technologies. Based on this evaluation, the EPA then determines whether it is appropriate to revise the standard. Similarly, in conducting CAA section 129(a)(5) reviews, the EPA assesses the performance and variability associated with control measures affecting emissions performance at sources in the subject source category (including the installed emissions control equipment), along with developments in practices, processes and control technologies. In addition, associated costs of control technologies are assessed to determine whether it is appropriate to revise the NSPS and EG.

Id.

7411(b)(1)(B).

The EPA does not interpret CAA section 129(a)(5), together with CAA section 111, as requiring the Agency to recalculate MACT floors in connection with this periodic review.

CAA section 129(a)(5) does not state that the EPA must conduct a MACT floor analysis every five years when reviewing standards promulgated under CAA sections 129 and 111. Had Congress intended the EPA to conduct a new MACT floor analysis every five years, Congress could have said so expressly, either by directly incorporating such a requirement into CAA section 129(a)(5) or by referring to CAA section 129(a)(2) specifically rather than broadly to “this section” (

i.e.,

CAA

section 129)

and CAA section 111. Moreover, reading CAA section 129(a)(5) to require the EPA to recalculate MACT floors would be inconsistent with Congress' direction that the EPA should revise CAA section 129 standards in accordance with CAA section 111, which provides that such revision should occur only if the EPA determines that it is “appropriate” to do so. This approach would effectively read the reference to CAA section 111 out of CAA section 129(a)(5). Requiring the EPA to recalculate MACT floors would eviscerate the EPA's ability to base revisions to CAA section 129 standards on a determination that it is “appropriate” to revise such standards, as the EPA's only discretion would be in deciding whether to establish a standard that is more stringent than the recalculated floor. The EPA believes that depriving the Agency of any meaningful discretion in this manner is at odds with what Congress intended.

71 FR 27324, 27327-28 (May 10, 2006); 73 FR 72962, 72971-72 (Dec. 1, 2008); 76 FR 15704, 15708 (Mar. 21, 2011); 85 FR 54178, 54182 (Aug. 31, 2020).

The scope of CAA section 129 further demonstrates why it would be unreasonable to assume that Congress intended the EPA to revise standards at five-year intervals based on a specific standard-setting provision like CAA section 129(a)(2) as opposed to a more general appropriateness standard. For example, CAA section 129(h)(3) separately requires the EPA to promulgate standards to address residual risk (which, unlike MACT, is not a technology-based analysis) if doing so would be required under CAA section 112(f). 42 U.S.C. 7412(h)(3). This review is required eight years after the initial promulgation of CAA section 129 standards.

Id.

7412(f)(2). An interpretation of “this section” in CAA section 129(a)(5) that incorporates the requirements of all standard-setting provisions in CAA section 129, whether technology-based or risk-based or subject to their own separate review schedule, would benonsensical.

The EPA believes that CAA section 129(a)(5) is best read as conferring discretion to revise as “appropriate” taking into consideration all relevant factors.

The D.C. Circuit's ruling regarding periodic review of hazardous air pollutant (HAP) standards under CAA section 112(d)(6) supports this view.

Like CAA section 129(a)(2), CAA section 112(d)(2) requires that the initial HAP standards not be less stringent than the MACT floor, and CAA section 112(d)(6) requires that the EPA “review, and revise as necessary” the HAP standards every eight years. The D.C. Circuit has repeatedly rejected arguments that CAA section 112(d)(6) imposes a duty to recalculate the MACT floor

and held that the EPA may take into account factors other than the “non-exhaustive list of considerations” in section 112(d)(6) when deciding whether revision to existing standards is “necessary.”

The Court's rulings on section 112(d)(6) are consistent with our interpretation of sections 129(a)(5) and 111 as providing the EPA discretion to revise, “as appropriate,” MACT standards established under sections 129(a)(2) and 111.

See Michigan

EPA,

576 U.S. 743, 752 (2015) (emphasizing that “ `appropriate' is `the classic broad and all-encompassing term that naturally and traditionally includes consideration of all the relevant factors' ”).

NRDC

EPA,

529 F.3d 1077, 1084 (D.C. Cir. 2008).

Id.; see also Ass'n of Battery Recyclers

EPA,

716 F.3d, 667, 673-74 (D.C. Cir. 2013);

Nat'l Ass'n for Surface Finishing

EPA,

795 F.3d 1, 8, 11 (D.C. Cir. 2015).

La. Envtl. Action Network (LEAN)

EPA,

955 F.3d 1088, 1097 (D.C. Cir. 2020).

For these reasons, the EPA does not recalculate the MACT floor in a section 129(a)(5) review. Rather, as directed by section 129(a)(5), the EPA follows the guidance in sections 111 and 129 and assesses advances in existing control technologies, both in terms of performance and cost, as well as the availability of new technologies, and then, on the basis of this evaluation, the EPA determines whether it is appropriate to revise the NSPS and EG.

B. What is the regulatory background for the large MWC source category, and how do the NSPS and EG regulate emissions from the source category?

In December 1995, the EPA promulgated EG and NSPS for large MWC units pursuant to CAA section 129.

As stated in section II.A of this preamble, these standards apply to large MWC units that have a combustion capacity greater than 250 tpd of MSW.

Both the EG and NSPS require compliance with emission limitations that reflect the maximum degree of emissions reductions for specific pollutants (Cd, CO, PCDD/PCDF, HCl, Pb, Hg, NO

, PM, and SO

). The 1995 NSPS apply to new large MWC units that commenced construction, were modified, or were reconstructed after September 20, 1994. The 1995 EG apply to existing large MWC units that commenced construction on or before September 20, 1994. The 1995 EG required that owners or operators of affected sources complete emission control retrofits by December 2000. The EPA calculated the impact of floors based, in part, on State issued air permits. These timely completed retrofits at existing large MWC units were highly effective in reducing emissions of most CAA section 129 pollutants from these units. Compared to a 1990 baseline of emissions, the 1995 EG reduced organic emissions (PCDD/PCDF) by more than 99 percent, metal emissions (Cd, Pb, and Hg) by more than 93 percent, and acid gas emissions (HCl and SO

) by more than 91 percent.

While the 1995 EG and NSPS also regulate NO

, the emissions reductions for NO

were relatively modest compared to those of the other CAA section 129 pollutants.

40 CFR part 60, subpart Cb (EG); 40 CFR part 60, subpart Eb (NSPS).

In 1991, the EPA promulgated 40 CFR part 60, subpart Ea, applying standards of performance to MWCs that commenced construction after December 20, 1989, and on or before September 20, 1994. 56 FR 5507 (Feb. 11, 1991).

See

memorandum entitled

Emissions from Large MWC Units at MACT Compliance,

June 20, 2002. Walt Stevenson to Docket A-90-45, entered as item A-90-45, VIII-B-11. Available online as Docket ID EPA-HQ-OAR-2003-0072-0048.

Id.

In 2006, the EPA promulgated amendments to the 1995 standards after completing a periodic review under CAA section 129(a)(5). The EPA increased the stringency of the Cd and Hg NSPS emission limits based on new compliance test data showing that large MWC units operating with a full set of controls could comply with more stringent limits; similar data were not available when the EPA previously set the NSPS emission limits. The EPA also revised the PCDD/PCDF, Hg, and NO

EG emission limits and compliance testing provisions to more accurately reflect the actual performance achieved by existing MWCs and their control technologies and to reflect improvements in continuous emissions monitoring system (CEMS) data performance and reliability based on large MWC compliance test data.

The EPA projected that all large MWCs could meet the 2006 EG emission limits without installing any new control technology.

71 FR 27324 (May 10, 2006).

Id.

Following promulgation of the 2006 final rule, environmental groups challenged the MACT floor limits that the EPA promulgated in 1995 in connection with their challenge to the revised standards, citing a then-recent decision questioning the legality of MACT floors derived in part from State-issued air permits.

In light of this decision and several other relevant decisions regarding the calculation of MACT floors under CAA section 112, the EPA sought a voluntary remand of the 2006 final rule.

In its remand

motion, the EPA announced its intention to grant the environmental groups' administrative petition to revisit the 1995 MACT floors and reevaluate the 2006 final rule as necessary to comport with any revisions.

The D.C. Circuit granted the EPA's request for a remand in February 2008.

Specifically, petitioners pointed to a 2004 decision from the D.C. Circuit, which remanded MACT floors established for existing small MWCs derived from state-issued permit limits after finding that the EPA did not fulfill the requirement of CAA section 129(a)(2).

See Ne. Md. Waste Disposal Auth.

EPA,

358 F.3d 936 (D.C. Cir. 2004).

See Sierra Club

EPA,

479 F.3d 875 (D.C. Cir. 2007) (vacating the EPA's regulations setting national emission standards for brick and clay ceramics kilns under CAA section 112);

NRDC

EPA,

489 F.3d 1250 (D.C. Cir. 2007) (vacating the EPA's regulations setting national emission

standards under CAA section 112 for hazardous air pollutants from industrial, commercial, and institutional boilers and process heaters and the EPA's regulations under CAA section 129 defining the term “commercial and industrial solid waste incineration unit”);

NRDC

EPA,

489 F.3d 1364 (D.C. Cir. 2007) (vacating portions of an EPA rule promulgated under CAA section 112 regulating hazardous air pollutants from the manufacture of plywood and composite wood products).

In its motion for a voluntary remand, the EPA explained that it intended to “re-analyze the floors in the 1995 rule” and “revisit the data and information used in the 1995 rule, as well as obtain additional data, to determine whether the 1995 floors need to be revised.” EPA Motion for Voluntary Remand at 8,

Sierra Club

EPA,

No. 06-1250 (D.C. Cir. filed Nov. 9, 2007).

Order,

Sierra Club

EPA,

No. 06-1250 (D.C. Cir. filed Feb. 15, 2008).

In December 2021, another environmental group petitioned in the D.C. Circuit for a writ of mandamus related to the 2008 order granting voluntary remand.

In January 2022, the same organization also filed a citizen suit under CAA section 304(a)(2), alleging that the EPA failed to carry out a nondiscretionary duty to timely review and, if appropriate, revise emissions standards for large MWCs pursuant to the five-year review provision in CAA section 129(a)(5).

On November 9, 2023, the D.C. Circuit entered a consent decree requiring the EPA to sign a proposed rule by December 31, 2023, and a final rule by November 30, 2024, to satisfy the EPA's obligations in the citizen suit and mandamus action (

i.e.,

to complete the five-year review and MACT floor reevaluation). The parties later filed a joint stipulation to extend the consent decree deadline for the final rule to December 22, 2025.

In re E. Yard Cmtys. for Envtl. Justice,

No. 21-1271 (D.C. Cir. filed Dec. 21, 2021).

E. Yard Cmtys. for Envtl. Justice

EPA,

No. 22-cv-0094 (D.C. Cir. filed Jan. 13, 2022).

Notice of Lodging of Proposed Consent Decree,

E. Yard Cmty. for Envtl. Justice

EPA,

No. 22-cv-0094 (D.C. Cir., filed May 23, 2023).

C. What changes did we propose for the large MWC source category?

On January 23, 2024, the EPA proposed revisions to the NSPS and EG for large MWCs to reflect the results of the EPA's reevaluation of the MACT floors, pursuant to the 2008 voluntary remand, and the results of the EPA's five-year review, pursuant to CAA section 129(a)(5).

The EPA proposed the following with respect to 40 CFR part 60, subparts Cb and Eb:

89 FR 4243 (Jan. 23, 2024).

• Revisions to all existing-source emission limits in the EG, except the existing CO and NO

limits for two subcategories of combustors, and revisions to all new-source emission limits in the NSPS. With the exception of proposed changes to the NO

limits, the proposed revisions resulted from the EPA's reevaluation of the MACT floors in response to the 2008 voluntary remand.

• Simultaneously, the EPA conducted a five-year review as required by CAA section 129(a)(5). Based on this review, the EPA proposed NO

standards that were more stringent than the reevaluated MACT floor emissions limits for NO

and that were consistent with the recently promulgated Good Neighbor Plan, which set ozone season standards for a significant portion of the large MWC source category.

88 FR 36654 (June 5, 2023).

• Removal of the alternative percent reduction standards to establish a consistent approach to compliance for all facilities and removal of the NO

emissions averaging allowance for existing sources.

• Removal of the SSM exclusions and exemptions and significant revisions to the monitoring provisions during these periods. For NO

, SO

, and CO, where a CEMS continuously measures the pollutant concentration, we proposed to eliminate the exclusions of periods of SSM from CEMS data averaging calculations present in the 1995 large MWC standards and instead require a monitoring and compliance demonstration approach used in the more recent CAA section 129 rulemaking for commercial and industrial solid waste units (CISWI) NSPS and EG.

81 FR 40956 (June 23, 2016).

• Conversion of the 1995 large MWC regulatory text describing emission standards and performance testing requirements from paragraphs into tables to facilitate easier implementation and understanding of the requirements.

• Requiring source owners and operators to submit electronic copies of required performance test reports, performance evaluation reports, semiannual compliance reports, and annual reports through the EPA's Central Data Exchange (CDX), using the Compliance and Emissions Data Reporting Interface (CEDRI), to increase the usefulness of the data contained in those reports and to improve availability and transparency of data.

• Reestablishing new and existing source applicability so that large MWC units currently subject to the 2006 NSPS would become “existing” sources under the proposed amended standards and would be required to meet the revised EG by the applicable compliance date for the revised guidelines. Large MWC units that commence construction after the date of the proposal or commence a modification on or after the date six months after promulgation of the amended standards would be “new” units subject to the more stringent NSPS emission limits.

• Eliminating the regulatory title V permitting requirement for air curtain incinerators that burn only wood waste, yard waste, and clean lumber and are not located at a major source or subject to title V for other reasons.

• Other technical amendments, including closing a 2007 proposed reconsideration action, correcting certain typographical errors, making certain technical corrections, and clarifying certain provisions in the NSPS and EG.

72 FR 13016 (Mar. 20, 2007).

D. What outreach did we conduct following the proposal?

In developing this final rule, the EPA conducted post-proposal outreach activities with communities, States, local governments, industry, and Tribes. On January 11, 2024, the EPA emailed a consultation letter to Tribal nations explaining how to comment on the proposed rulemaking and how to request consultation with the EPA. The EPA participated in the National Tribal Air Association monthly meeting on January 25, 2024. On January 16, 2024, the EPA presented details of the large MWC proposal to members of interested communities and environmental organizations. Additionally, the EPA held an informational webinar with air pollution control agencies on February 29, 2024. The EPA's outreach activities also included meetings with the following: Waste-to-Energy Association (WTEA) to discuss varying aspects of the proposal, including waste variability, Reworld Waste (formerly Covanta) to discuss their concerns about the proposed emission limits, compliance implications, and costs of the proposal, and a coalition of community representatives and organizations to discuss their concerns about the rulemaking and impacts of air pollution near large industrial facilities. The EPA subsequently reopened the comment period on the proposed amendments to the large MWC regulations for an additional 4 months, from January 16, 2025, to May 30, 2025,

to gather additional information and documentation.

III. What is included in these final rules?

In this action, we are finalizing decisions and revisions for the NSPS and EG for large MWC units. We discuss the significant comments on the proposal and changes the EPA made to the final NSPS and EG in more detail in section IV of this preamble. A comment summary and the EPA's responses are available in the docket.

Summary of Public Comments and Responses for Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Large Municipal Waste Combustors Voluntary Remand Response and 5-year Review

(“Comment Response Document”), Docket ID No. EPA-HQ-OAR-2017-0183.

This final rule sets out the EPA's determinations resulting from our reevaluation of the 1995 MACT floor standards for large MWCs pursuant to the 2008 voluntary remand and from our five-year review of large MWC standards under CAA section 129(a)(5), as well as the final amendments to the large MWC NSPS and EG based on those determinations. This action also finalizes other changes to the NSPS and EG largely as proposed, including the following: removal of SSM exclusions and exemptions; streamlined regulatory language; revisions to recordkeeping and reporting requirements; addition of electronic reporting requirements; reestablishment of new and existing source applicability dates; elimination of title V requirements for air curtain incinerators that burn only wood waste, yard waste, and clean lumber and are not located at a major source or subject to title V for other reasons; closing the 2007 proposed reconsideration action; and other technical, typographical, and clarifying corrections to certain provisions in the NSPS and EG.

The EPA is finalizing the amendments as new subparts VVVV (Standards of Performance for Large Municipal Waste Combustors) and WWWW (Emissions Guidelines and Compliance Times for Large Municipal Waste Combustors That are Constructed on or Before January 23, 2024), in lieu of revising existing subparts Cb (Emissions Guidelines and Compliance Times for Large Municipal Waste Combustors That are Constructed on or Before September 20, 1994) and Eb (Standards of Performance for Large Municipal Waste Combustors for Which Construction is Commenced After September 20, 1994 or for Which Modification or Reconstruction is Commenced After June 19, 1996). As proposed, we are reserving (removing without replacing) subpart Ea (NSPS limits for units constructed after December 20, 1989, and on or before September 20, 1994). Although we proposed to promulgate amendments as revisions to subparts Cb and Eb, the EPA has determined that creating new subparts will lessen confusion for affected sources and implementing agencies. Therefore, we have created new subparts for the NSPS and EG at 40 CFR part 60, subparts VVVV and WWWW, respectively, which will replace subparts Cb, Ea, and Eb once facilities are required to comply with the new subparts. The revised standards and new subparts will become effective May 11, 2026. For the EG, States must submit revised State plans to the EPA within one year after promulgating the amendments, by March 10, 2027. Existing large MWC units must demonstrate compliance with the updated standards as expeditiously as practicable after approval of a State plan, but no later than three years after the date of approval of a State plan or five years after promulgation of the revised standards, whichever is earlier. For NSPS, new sources must be in compliance with the updated standards within six months from promulgation, by September 10, 2026, or upon startup, whichever is later.

By incorporating these amendments as new subparts, we hope to alleviate confusion that may arise from significant amendments to the current subpart Cb and subpart Eb regulatory text. For example, to support making the format and structure of the regulations more understandable based on Federal Plain Language Guidelines, we are moving the requirements in subparts Cb and Eb to subparts VVVV and WWWW. Additionally, by creating new subparts VVVV and WWWW, we can omit transitional regulatory requirement language and have a single applicability date (

i.e.,

January 23, 2024) for the new subparts, upon which applicability of subparts Cb, Ea, and Eb ends and a single subpart, WWWW, apply to all the current, operating large MWCs. (We provide additional information on the effective and compliance dates of the final rule in section III.D of this preamble.) Finally, to better accommodate potential future updates to the regulations, in subparts VVVV and WWWW, we are numbering sections in increments of five to support adequate numeric spacing to revise or add new regulatory text sections if needed.

A. What are the final rule amendments based on the response to the voluntary MACT floor remand and five-year review for the large MWC source category?

1. Emission Limits

In the proposed rule, the EPA presented amendments resulting from its reevaluation of the 1995 large MWCs MACT standards undertaken pursuant to the D.C. Circuit's 2008 voluntary remand and the EPA's five-year review of large MWC standards, undertaken pursuant to CAA section 129(a)(5). Based on the EPA's reevaluation of the MACT floors and beyond-the-floor options and review of the standards and requirements, the EPA proposed revised limits at the MACT floor for all covered pollutants except for NO

, for which the EPA proposed to implement more stringent emission standards as a result of the five-year review.

Following consideration of comments, input from stakeholder meetings, and additional data received post-proposal, the EPA revised its initial reevaluation of the 1995 MACT floors and is finalizing recalculated emission limits.

Specifically, for the EG, the EPA is finalizing newly revised emission limits for all pollutants, except for the CO and NO

limits for two categories and subcategories of combustors, respectively. The revised limits reflect the MACT floor reevaluation results rather than the results of the five-year review. For the NSPS, the EPA is finalizing revised reevaluated MACT emission limits for all pollutants except NO

, which will retain the proposed five-year review limit for new sources.

As explained in sections IV.A.3 and IV.A.4 of this preamble, the EPA received additional emissions test data from the 1990-1995 period during the original comment period and the supplemental 2025 comment period that bolstered the dataset available for reanalysis of the MACT floors.

See section IV of this preamble for rationale for these revisions and summarized comments and responses on this topic.

Tables 2 and 3 of this preamble present the final EG and NSPS emission limits for large MWCs, respectively. For comparison, the table presents current emission limits (from the 2006 rule) for both existing and new units as well. The EPA assessed NO

and CO limits by subcategories, determined based on combustor type, including mass burn waterwall (MB/WW), mass burn rotary combustor (MB/RC), refuse-derived fuel stoker (RDF/S), RDF spreader stoker fixed floor/100 percent coal capable and RDF semi-suspension/wet RDF process

conversion (RDF/SS), and RDF/fluidized bed combustion (RDF/FBC).

The EG contain CO emission limits for two additional subcategories of units that are not found in the NSPS. More recent installations have not used these designs, and the EPA expects that most new large MWCs will likely be MB/WW.

Table 2—Comparison of Existing Source Limits for 2006 Large MWC Rule and the Final Emission Limits for Existing Sources

Pollutant

Units

(@7 percent O

)

2006 EG

(current)

limits

Final subcategory EG limits

MB/WW

MB/RC

RDF/S

RDF/SS

RDF/FBC

μg/dscm

400

mg/dscm

μg/dscm

PCDD/PCDF

ng/dscm (total mass basis)

30/35

HCl

ppmvd

180-250

205

150

160

180

ppmvd

50-250

100

110

250

110

30 ng/dscm for fabric filter equipped MWC units and 35 ng/dscm for electrostatic precipitator-equipped MWC units.

Range in limits based on combustor type. MB/WW (205); RDF (250); MB/RC (210); RDF/FBC (180).

Range in limits based on combustor type. MB/WW (100); MB/RC (250); RDF/S (200); RDF/SS (250); RDF/FBC (200); modular starved air or modular excess air (50).

Reevaluated MACT floor limit was less stringent than current limit, so current limit was retained.

Table 3—Comparison of New Source Limits for 2006 Large MWC Rule and the Final Emission Limits for New Sources

Pollutant

Units

(@7 percent O

)

2006 NSPS

(current)

limits

Final subcategory NSPS limits

RDF

μg/dscm

2.3

μg/dscm

140

mg/dscm

5.1

μg/dscm

PCDD/PCDF

ng/dscm (total mass basis)

HCl

ppmvd

7.2

ppmvd

150

ppmvd

50-150

100

limit based on 50 ppm (24 hour) permitted limit for units currently equipped with selective catalytic reduction (SCR) control devices.

Range in limits based on combustor type. MB/WW (100); RDF/S (150); Modular starved air or modular excess air (50).

2. MACT Floor Assessment

This final rule fulfills the EPA's reevaluation of the 1995 MACT floors for the large MWC source category pursuant the D.C. Circuit's 2008 voluntary remand of the 2006 large MWC rule, as discussed in section II.B of this preamble. In response to the remand, the EPA explained at proposal that the Agency lacked sufficient data from the time period of the 1995 large MWC rulemaking to now characterize the performance of all units needed to reassess the original MACT floors. The EPA proposed to recalculate the MACT floors for large MWCs based on compliance data from 2000 through 2009 reported for the population of units that were operating at the time of the original EG development (1990), adjusted to account for the installation of air pollution control devices (APCD) and other improvements that sources made to meet the 1995 standards. The EPA subsequently ranked the best performing units in the source category for each covered pollutant based on the adjusted emissions, analyzed the data to determine the average performance of those units, considered beyond-the-floor options, and established MACT floor emission limits.

See discussion in section III.A.3 of this preamble.

Following consideration of comments and additional information received on the proposed rule, the EPA is revising its reassessment of the MACT floor limits for the EG and NSPS. The EPA is finalizing a similar approach as that in the proposed rule, using separate methodologies for pollutants having stack test data (Cd, Pb, Hg, PM, HCl, and PCDD/PCDF) and pollutants having CEMS data (or CEMS pollutants) (CO, NO

, and SO

). However, the final limits incorporate new data submitted for years 1990 to 1995 for unit ranking and UPL determinations, in addition to the 2000 to 2009 compliance dataset that the EPA used for the proposed limits. Considering the unique situation of the MACT reevaluation, the EPA's limited ability to gather multiple years of tests for the top performers from several decades ago, and the high variability of waste that these sources use as fuel, the EPA also has revised the NSPS methodology to account for additional intra-source variability in top performers, instead of relying on a singular test from the 1990s. For each stack test pollutant, the EPA performed a statistical analysis on the annual test averages from the 1990 to 1995 dataset

and adjusted averages from the 2000 to 2009 dataset to determine an upper prediction limit (UPL).

For EG limits, the EPA used average annual run data corresponding to the top 12 percent of units, and for NSPS limits, the EPA used run data for the single top performer. For NSPS limits, the EPA also assessed the distribution and variance of 2000 to 2009 test averages for the top performer incorporated this data into the UPL calculation.

For a more detailed discussion, see section IV.A.4 of this preamble.

For CEMS pollutants (CO, NO

, and SO

), the EPA reevaluated MACT floor limits by averaging annual peak CEMS data corresponding to the top performers for each pollutant and applicable subcategory. For NO

and CO, the EPA calculated separate NSPS limits for only two subcategories, MB (as reflected by MB/WW combustor technology) and RDF. In cases where results were greater (less stringent) than the current large MWC EG limit, the EPA proposed to retain the existing regulatory limit as the MACT floor limit. While the methodology has not changed from proposal, based on comments and evaluation of the data from the units identified as best performers for CO at proposal, we performed a paired t-test analysis on the best performers for CO and determined that the data reported for Wheelabrator Bridgeport Units #1, #2, and #3 exhibit a different population characteristic from the remainder of the source category,

i.e.,

statistically, there is a significant difference in the CO data reported by the Wheelabrator Bridgeport facility from the CO data reported by all other facilities that is outside the variation we would expect of CO emissions from large MWCs. This indicates that the owner or operator of these units may have reported the data in a different way than requested based on a different understanding of the reporting requirement, resulting in reported CO numbers that were much lower than all other facilities not because of better operation and lower emissions but because of differently understood reporting requirements. As a result, the EPA removed the CEMS data for these units from the CEMS pollutant calculations. The removal results in a new NSPS CO limit of 76 ppmvd from the proposed NSPS CO limit of 16 ppmvd and an EG SO

limit of 22 ppmvd from the proposed EG SO

limit of 20 ppmvd. Further discussion of this change from proposal is in section IV of this preamble.

Table 4 of this preamble presents the UPL results and the derived final EG and NSPS MACT floor limits for stack test pollutants. Tables 5 and 6 of this preamble summarize the averages and subsequent MACT floor EG and NSPS limits, respectively, for CEMS pollutants. Additional discussion of the methodology, detailed results, and a copy of the UPL template are available in the docket for this rulemaking.

See

memorandum entitled

MACT Floor Calculations for Large Municipal Waste Combustor Units—Final Rule,

Docket ID No. EPA-HQ-OAR-2017-0183.

Table 4—Large MWC MACT Floor EG and NSPS Limits for Stack Test Pollutants

Pollutant

Units

(@7 percent O

)

EG MACT floor calculations

UPL result

MACT floor limit

NSPS MACT floor calculations

UPL result

MACT floor limit

μg/dscm

9.99

0.577

2.3

μg/dscm

67.86

5.33

mg/dscm

19.05

5.06

5.1

μg/dscm

52.67

31.60

PCDD/PCDF

ng/dscm

13.88

10.61

HCl

Ppmvd

9.82

7.103

7.2

Calculated UPL result was less than three times the representative detection level (RDL), so MACT Floor limit set at the 2 dscm 3*RDL value (2.3 ug/dscm for Cd, 23 ug/dscm for Pb).

Table 5—Large MWC MACT Floor EG Limits for CEMS Pollutants

Pollutant

Units

(@7 percent O

)

EG MACT floor calculations

Average of annual peak CEMS data

MB/WW

MB/RC

RDF

RDF/SS

RDF/FBC

MACT floor limit

MB/WW

MB/RC

RDF

RDF/SS

RDF/FBC

ppmvd

21.26

ppmvd

226.52

142.25

157.29

290.83

205

150

160

180

ppmvd

221.44

109.92

102.14

818.90

101.40

100

110

250

110

Calculated limit was less stringent than current limit so kept at current limit.

Table 6—Large MWC MACT Floor NSPS Limits for CEMS Pollutants

Pollutant

Units

(@7 percent O

)

NSPS MACT floor calculations

Average of annual peak CEMS data

RDF

MACT floor limit

RDF

ppmvd

13.96

ppmvd

130.50

154.46

140

150

ppmvd

75.71

99.03

100

The MB/RC, RDF/SS, and RDF/FBC subcategories are representative of unique facilities that likely will not be a design used in any future large MWC units. For the NSPS purposes, it is assumed the overarching MB or RDF subcategories will represent performance of any units built in the future.

These values represent limits that would have resulted if the EPA had selected the MACT floor as its basis for the NSPS NO

limits; however, the EPA is finalizing the proposed 50 ppmvd NO

limit for all subcategories based on units currently equipped with SCR control devices.

Calculated limit was less stringent than current limit, so current limit would have been retained if the MACT floor were selected.

3. Beyond-the-Floor and Five-Year Review Results and Selection of Emission Limits

Following consideration of comments received on the proposed rule, the EPA is not finalizing the beyond-the-floor and five-year review assessments for the EG as proposed. The final rule uses the MACT floor calculations to establish EG and NSPS limits for existing and new units for all pollutants except for NO

(which reflect the results of the MACT floor calculations for the EG as well as the results of the five-year review for the NSPS).

For its proposed assessment of beyond-the-floor in the reevaluation of the 1995 standards, the EPA assumed that the beyond-the-floor option for existing sources is the new source MACT floor (emissions control achieved in practice by the best controlled similar unit, as required by CAA section 129(a)(2)) which is more stringent than the existing source MACT floor (an average of a broader range of best performing units, also as required by CAA section 129(a)(2)). To assess additional, currently in-use control options as part of the five-year review pursuant to CAA section 129(a)(5), the EPA evaluated the performance of control measures at large MWC sources (including the installed emissions control equipment), and recent developments in practices, processes, and control technologies, including the recently finalized Good Neighbor Plan rulemaking. The EPA proposed NO

control technologies consistent with those discussed in the Good Neighbor Plan as five-year review options for consideration. For the other covered pollutants, there are some controls that have been demonstrated on non-MWC combustion sources that could potentially be applied to large MWCs; however, the technical feasibility and cost-effectiveness of these controls when used on large MWCs are highly uncertain at this time.

Following its evaluation of these scenarios, the EPA proposed a 110 ppmvd (24-hour) NO

limit (which was consistent with the NO

limit finalized under the Good Neighbor Plan), as the five-year review option for existing units based on the application of advanced selective noncatalytic reduction (ASNCR) or Covanta LN

technologies. The EPA also proposed a NO

NSPS limit of 50 ppmvd (24-hour), based on the permitted NO

limit for the only facility currently using selective catalytic reduction (SCR) technology with an air-to-air heat exchanger providing flue gas reheat prior to entering the SCR reactor to represent the five-year technology review standard for new sources.

Based on the consideration of several factors, including the stay of the Good Neighbor Plan,

the EPA is not finalizing the five-year review limit for NO

emissions from existing units as proposed. First, the total compliance costs for existing sources to meet the proposed 110 ppmvd NO

limit is significantly higher than the EPA's estimate in the proposed rule. At proposal, the EPA excluded units expected to be covered by the Good Neighbor Plan from the $257 million capital cost estimate. Inclusion of the compliance costs for those units significantly increases the total estimated capital cost to $412 million. These large capital expenditures likely will pose a significant challenge to the large MWC industry. The EPA recognizes that this is a unique industry providing essential public services, with many facilities owned and operated by State or local governments. These large capital expenditures could hinder government funded municipalities' ability to continue to utilize large MWCs for the public MSW disposal needs.

See Ohio

EPA,

603 U.S. 279 (2024) (staying the Good Neighbor Plan as likely arbitrary and capricious).

Second, at the same time, emission reductions from the proposed 110 ppmvd NO

limit likely are much lower than the EPA's estimate at proposal. The EPA estimated baseline NO

emissions using the average of the available annual peak 24-hour CEMs data from 2000 through 2007. Using the peak values likely overestimates annual emissions by about 30% compared to the 2008 National Emissions Inventory and, in turn, likely overestimates the amount of emission reductions and therefore the cost effectiveness of the proposed NO

limit.

2008 National Emissions Inventory (

https://www.epa.gov/air-emissions-inventories/2008-national-emissions-inventory-nei-data

For these reasons, the EPA is not finalizing the 110 ppmvd limit for NO

for existing sources and is instead promulgating the re-evaluated MACT floor limits for existing sources discussed in section III.A.2 of this preamble. The EPA is finalizing the 50 ppmvd NO

limit for new sources as proposed, as there are units operating that have cost-effectively used SCR to perform at this level for several years, and the EPA sees no technical or economic barriers to future sources doing likewise.

B. What are the final rule amendments addressing emissions during periods of startup, shutdown, and malfunction?

The EPA is finalizing, as proposed, revisions to the SSM provisions of the NSPS and EG in response to the D.C. Circuit's decision in

Sierra Club

EPA.

This final rule removes the exemption for SSM periods contained in the 1995 large MWC rule so that the emission standards apply at all times. The EPA is not finalizing a separate emission standard for large MWC units during periods of startup and shutdown.

551 F.3d 1019 (D.C. Cir. 2008).

See the rationale in section IV.B of this preamble.

The EPA notes that on September 5, 2025, the D.C. Circuit held in

SSM Litigation Group

EPA

that although the EPA has no authority under the CAA to “create a regulatory `defense' that limits the remedial authority granted by Congress to the Federal courts,” a “complete affirmative defense, like the one at issue [in that case], is permissible because it relates to the antecedent question of liability and therefore does not impinge on the judiciary's authority to award `appropriate civil penalties.' ”

The EPA is not addressing

SSM litigation Group

in this action because the LMWC NSPS and EG do not contain affirmative defense provisions. However, the EPA may in an appropriate future action request comment on whether and how we should establish affirmative defense provisions within section 129 regulations in response to the D.C. Circuit's

SSM Litigation Group

decision. As proposed, the emission standards that the EPA is finalizing do not factor emissions that occur during periods of malfunction into the development of the standards. This is consistent with the D.C. Circuit's decision in

U.S. Sugar Corp.

EPA,

as explained further below.

150 F.4th 593, 599 (D.C. Cir. 2025) (quoting CAA section 304(a), 42 U.S.C. 7604(a)).

830 F.3d 579, 606-10 (D.C. Cir. 2016).

The EPA is also finalizing, as proposed, revisions to eliminate the exclusions of periods of warmup, startup, and shutdown from CEMS data averaging calculations and to replace

them with a monitoring and compliance demonstration approach. The final rule requires that affected sources collect CEMS data and use this data to determine compliance when the large MWC unit is operating. While the large MWC unit is warming up, starting up, or shutting down, CEMS data must be flagged as warmup, startup, or shutdown period data. The final rule requires that affected sources use the CEMS data to calculate rolling or block averages and to average the data as measured instead of applying a seven percent oxygen diluent cap for the warmup period and an allowance of up to three hours of startup or shutdown time per occurrence. Under the final rule, a deviation occurs when an operating combustor does not record monitoring data due to monitor malfunctions.

C. What are the final rule amendments addressing other changes to the large MWC EG and NSPS?

1. Changes to the Applicability Date of the Large MWC EG and NSPS

As noted earlier in section III of this preamble, the EPA is finalizing the amendments as 40 CFR part 60, subparts VVVV (Standards of Performance for Large Municipal Waste Combustors) and WWWW (Emissions Guidelines and Compliance Times for Large Municipal Waste Combustors That are Constructed on or Before January 23, 2024), in lieu of revising existing subparts Cb (Emissions Guidelines and Compliance Times for Large Municipal Waste Combustors That are Constructed on or Before September 20, 1994) and Eb (Standards of Performance for Large Municipal Waste Combustors for Which Construction is Commenced After September 20, 1994 or for Which Modification or Reconstruction is Commenced After June 19, 1996).

The EPA is finalizing, as proposed, that large MWC units currently subject to the NSPS are existing sources with respect to the emission standards promulgated in this final rule. Under this final rule, large MWC units that currently are subject to the NSPS at 40 CFR part 60, subparts Ea and Eb will be subject to the revised EG standards at 40 CFR part 60, subpart WWWW through meeting requirements of the relevant approved State or Federal plans. Those sources will continue to be NSPS units subject to the current large MWC NSPS until the sources come into compliance with the requirements of the revised EG standards. The revised EG standards are as stringent as, or more protective than, the 1995 large MWC new source emission limits, as revised in 2006, with the sole exception of PCDD/PCDF. For the PCDD/PCDF limit, large MWC units that are subject to NSPS subpart Eb but are existing sources under the new EG subpart WWWW remain new sources under NSPS subpart Eb and, as such, must continue to comply with the more stringent NSPS limit (

i.e.,

13 ng/dscm total mass basis at seven percent oxygen) in NSPS subpart Eb.

Under the final rule, large MWC units that commence construction after January 23, 2024, and units that are modified or reconstructed after September 10, 2026 are new units subject to the NSPS emission limits. Large MWC units that commence construction, reconstruction, or modification prior to those dates would be existing units subject to the revised EG standards under 40 CFR part 60, subpart WWWW. Under the final rule, any large MWC unit that commenced construction on or before January 23, 2024, or that is reconstructed or modified prior to September 10, 2026, remains subject to 40 CFR part 60 subparts Cb, Ea, or Eb, as appropriate, until the unit comes into compliance with the relevant approved State or Federal plan to implement and enforce the revised EG. Large MWC units that commence construction after January 23, 2024, or that are reconstructed or modified on or after September 10, 2026 must meet the revised NSPS emission limits in 40 CFR part 60, subpart VVVV by September 10, 2026, or upon startup, whichever is later.

As stated in the proposal, the EPA intends to “reserve” 40 CFR part 60, subpart Ea NSPS standards once the revised EG emission limits are implemented. Due to the resetting of the “new” and “existing” definitions, any units that meet 40 CFR part 60, subpart Ea applicability would become existing units subject to the new 40 CFR part 60, subpart WWWW once implemented through a relevant State or Federal plan. Additionally, based on changes the EPA has made since proposal to introduce the new subparts to 40 CFR part 60 for large MWC regulations, once all existing units are in compliance with the requirements of 40 CFR part 60, subpart WWWW through a State or Federal plan, subparts Cb and Eb will no longer be necessary. Therefore, we intend to reserve all three subparts (40 CFR part 60 subparts Cb, Ea, and Eb) in a future action for potential use in a future rulemaking once all large MWC units are in compliance with the requirements of 40 CFR part 60, subpart WWWW through either a State or Federal plan.

2. Changes to Alternative Percent Reduction Standards for Hg, HCl, and SO

and Removal of Emissions Averaging Allowance for NO

The EPA is not finalizing, as proposed, the removal of the alternative percent reduction standards, including the 85 percent reduction allowed for Hg (NSPS and EG), the 95 percent allowed for HCl (NSPS and EG), and the 80 percent (NSPS) and 75 percent (EG) allowed for SO

. Instead, after considering public comments and upon further review, we are finalizing recalculated alternative percent reduction standards based on additional removal efficiency data from the years 1990 to 1995 for the best performing units used in the reevaluated MACT standards for Hg, HCl and SO

The EPA is finalizing, as proposed, the removal of the NO

emissions averaging alternative provided in 40 CFR 60.33b(d)(1) of the existing EG regulation and will not include this provision in subpart WWWW. Once implementation of subpart WWWW occurs, sources will no longer be able to comply with applicable requirements using NO

emissions averaging.

See the rationale in section IV.C of this preamble.

3. Changes for Optional Continuous Monitoring

The EPA is finalizing, as proposed, the incorporation of new performance specifications for the optional use of PM CEMS, HCl CEMS or Hg CEMS in place of stack testing and for the optional use of multi-metal, PCDD/PCDF CEMS in place of stack tests after promulgation of a performance specification or approval of a site-specific monitoring plan. As discussed in the preamble to the proposed rule, in the 2006 final amendments to the large MWC requirements, the EPA revised the PM and Hg compliance testing requirements to allow the optional use of a PM CEMS or Hg CEMS in place of stack testing and the optional use of multi-metal, HCl, PCDD/PCDF CEMS in place of stack tests after promulgation of performance specifications for these CEMS.

This final rule incorporates promulgated performance specifications (PS), including PS-11 (PM), PS-12A (Hg), and PS-12B (Hg).

These updates do not require a facility that already has an approved site-specific monitoring plan to incorporate these optional CEMS or to obtain reapproval of that plan on that basis. If owners and operators use these optional CEMS for compliance

demonstration purposes, owners and operators must submit these data to the EPA in the same manner as data for the required CEMS pollutants (CO, NO

and SO

89 FR 4257 (Jan. 23, 2024); 71 FR 27326 (May 10, 2006).

Appendix B to Part 60, Title 40.

4. Changes To Streamline Regulatory Text Within the Large MWC EG and NSPS

The EPA is finalizing, with revisions, proposed changes to the regulatory format of the large MWC standards. The final rule converts text describing emission standards and performance testing requirements to tables to facilitate easier implementation and understanding of the requirements. As noted throughout this section of the preamble, the EPA is finalizing the large MWC NSPS and EG as new subparts VVVV (Standards of Performance for Large Municipal Waste Combustors) and WWWW (Emissions Guidelines and Compliance Times for Large Municipal Waste Combustors That are Constructed on or Before January 23, 2024), in lieu of revising existing subparts Cb and Eb. The EPA has converted the proposed streamlining changes to the new subparts to reduce potential confusion for affected sources and implementing agencies. The EPA also developed the new final subparts VVVV and WWWW to update the format and structure of the regulations to be more accessible, based on Federal Plain Language Guidelines, and establish section-numbering increments of five to allow for adequate numeric spacing to revise or add new regulatory text sections, if needed, in the future.

Federal Plain Language Guidelines:

https://digital.gov/guides/plain-language.

5. Closing the 2007 Proposed Reconsideration of the Large MWC EG and NSPS

In 2007, the EPA announced that the Agency would reconsider three aspects of the 2006 final rule in response to requests by stakeholders: (1) operator stand-in provisions, (2) data requirements for continuous monitors, and (3) the status of operating parameters during the two weeks prior to Hg and PCDD/PCDF testing.

In both 2007 and 2024, the EPA proposed that no changes were necessary to resolve the 2007 reconsideration.

As we received no adverse comments on our proposed approach, we are now completing action on this reconsideration by making no changes to these three aspects of the rule.

72 FR 13016 (Mar. 20, 2007).

72 FR 13016 (Mar. 20, 2007); 89 FR 4257 (Jan. 23, 2024).

6. Updating Operator Training Examination Requirements

The final rule updates the citation to and incorporates by reference the American Society of Mechanical Engineers (ASME) Standard for the Qualification and Certification of Resource Recovery Facility Operators (QRO) to reflect 2005 updates made to the QRO by ASME. The rule and text of 40 CFR 60.17(g), 60.5865, and 60.6420 update the citation to this document and incorporate it by reference as QRO-1-2005.

7. Revisions to Title V Permitting Requirements for Air Curtain Incinerators Burning Only Wood Waste, Clean Lumber, and Yard Waste

For air curtain incinerators that burn only wood waste, clean lumber, yard waste and that are not located at a major source or subject to title V for other reasons, the EPA is finalizing, as proposed, removal of the requirement in the 1995 large MWC final rule that air curtain incinerators that burn only wood waste, clean lumber, and yard waste and comply with the opacity limits established under CAA section 129(g)(1)(C)) must apply for and obtain a title V operating permit.

CAA section 129(e), which requires title V permits for “solid waste incineration units,”

does not apply to these ACI because, as noted in the proposed rule, the definition of “solid waste incineration unit” in CAA section 129(g)(1) “does not include (C) air curtain incinerators [that] only burn wood wastes, yard wastes and clean lumber” and comply with applicable opacity limits.

CAA section 502(a)

and the EPA's regulations at 40 CFR 70.3 identify the types of sources that must obtain a title V permit for operation. In particular, title V permitting applies to any major source as defined in 40 CFR 70.2 without exceptions, including ACI that are not solid waste incineration units under CAA section 129(g)(1) but are themselves major sources. Based on available data, ACI that burn exclusively wood waste, clean lumber, and yard waste are commonly located at facilities that are not major sources and would not otherwise require a title V operating permit, such as land clearing operations on public or private land. Further, to the EPA's knowledge, no large MWC facility operates an ACI that burns exclusively wood waste, clean lumber, and yard waste on its premises. This final rule clarifies the applicability of title V permitting requirements for ACIs that burn exclusively wood waste, clean lumber, and yard waste or a combination of these materials and comply with the applicable CAA section 129 opacity limitations and related requirements.

60 FR 65387 (Dec. 19, 1995).

42 U.S.C. 7429(e).

89 FR 4258 (Jan. 23, 2024) (quoting 42 U.S.C. 7429(g)(1)).

42 U.S.C. 7661a(a).

8. Electronic Reporting

The EPA is finalizing, as proposed, a requirement that owners and operators of large MWC units submit electronic copies of required performance test reports, performance evaluation reports, semiannual compliance reports, annual reports, and certain notifications through the EPA's CDX using CEDRI. Owners or operators must submit performance test results collected using test methods that the EPA's Electronic Reporting Tool (ERT) supports, as listed on the ERT website at the time of the test, and in the format generated through the use of the ERT or an electronic file consistent with the XML schema on the ERT website. Owners or operators must submit other performance test results in PDF format using the attachment module of the ERT.

Owners or operators must submit performance evaluation results of CEMS measuring relative accuracy test audit (RATA) pollutants in the format generated through the use of the ERT or an electronic file consistent with the XML schema on the ERT website, and must submit performance evaluation results in PDF format using the attachment module of the ERT. Owners or operators must submit certain other notifications in CEDRI. For semiannual and annual reports, the final rule requires that owners and operators use the appropriate spreadsheet template to submit information to CEDRI.

See

ERT Tool:

https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert.

The final rule also provides extensions for electronic reporting in two specific circumstances: (1) outages of the EPA's CDX or CEDRI which preclude an owner or operator from accessing the system and submitting required reports, and (2) force majeure events, which the rule defines as events that have been caused by circumstances beyond the control of the affected facility, its contractors, or any entity controlled by the affected facility that prevent an owner or operator from complying with the requirement to submit a report electronically.

In both circumstances, the decision to accept

the request for additional time to report is within the discretion of the Administrator, and reporting should occur as soon as possible.

See

40 CFR 63.2 (definition of force majeure).

9. Technical and Implementation Corrections

The EPA is finalizing corrections and clarifications to the NSPS and EG that the Agency and stakeholders identified during implementation of the previous regulations as proposed, with minimal revisions to accommodate the new subparts.

Specifically, the EPA includes the proposed clarifications and corrections in the final new subparts VVVV and WWWW and has updated citations and cross-references accordingly.

See

memorandum entitled

Proposed Regulation Edits for 40 CFR part 60, subparts Cb and Eb: Review of the Emission Guidelines for Existing Sources and New Source Performance Standards: Large Municipal Waste Combustors Voluntary Remand Response and 5-year Review,

Docket ID No. EPA-HQ-OAR-2017-0183.

D. What are the effective and compliance dates of the standards?

The revisions to the NSPS and EG standards that the EPA is promulgating in this action are effective on May 11, 2026.

The EPA is finalizing the compliance dates of the NSPS and EG as proposed. Under the final EG and consistent with CAA section 129(b)(2), revised State plans containing the revised existing source emission limits and other requirements in the proposed amendments are due within one year after promulgation of the amendments. States must submit revised plans to the EPA by March 10, 2027.

The final EG allow existing large MWC units to demonstrate compliance with the amended standards as expeditiously as practicable after approval of a State plan, but no later than three years after the date of approval of a State plan or five years after promulgation of the revised standards, whichever is earlier. Consistent with CAA section 129(b)(2), the EPA expects States to require compliance as expeditiously as practicable. Because we anticipate that several large MWC units will need to retrofit existing emission control equipment and/or install additional emission control equipment to meet the final revised limits, the EPA anticipates that some States may choose to provide the three-year compliance period allowed by CAA section 129(f)(2).

CAA section 129 does not require or authorize the EPA to specify the control technology sources must use to meet a numeric emission limit. The costs are based on assumptions of air pollution control device retrofits, new equipment, or increased use of sorbent that may be needed to comply with the emission limits, but owners will evaluate and use the controls that they determine are necessary for their source.

In revising the standards in a State plan, a State may have two options, depending on the performance of the large MWC units in that State. First, a State could include both the 2006 large MWC standards and the new standards in its revised State plan, which would allow a phased approach for applying the new emissions limits. The State plan would clarify that the standards in the 2006 large MWC final rule remain in effect for large MWC units and apply until the compliance date of the revised existing source standards (as defined in the State plan).

Second, a State with existing large MWC units that do not need to improve performance to meet the revised standards could replace the 2006 large MWC final rule standards with the standards in this final rule; follow the procedures in 40 CFR part 60, subpart B and submit a revised State plan to the EPA for approval. If the revised State plan contains only the revised standards (

i.e.,

does not retain the 2006 large MWC final rule standards), the revised standards must be effective immediately for units subject to the 2006 large MWC final rule.

All sources currently subject to the 1995 large MWC EG or NSPS will become existing sources once the final revised large MWC standards are in place. See section III.B of this preamble for further discussion.

The EPA will revise or replace the existing Federal plan to incorporate changes to the existing source emission limits and other requirements that the EPA is promulgating in this action.

The Federal plan applies to large MWC units in any State without an approved State plan. The final amendments to the EG allow existing large MWC units subject to the Federal plan a maximum of five years after promulgation of the revised standards to demonstrate compliance with the amended standards, as required by CAA section 129(b)(3).

See

40 CFR part 62, subpart FFF—Federal Plan Requirements for Large Municipal Waste Combustors Constructed on or before September 20, 1994.

For new sources, the final NSPS requires compliance within six months after promulgation of this final rule, or upon startup of the new MWC, whichever is later. This compliance timeline for new sources is consistent with the requirements of CAA section 129(f)(1).

E. Severability

This final action contains several discrete components, which the EPA views as severable as a practical matter—

i.e.,

they are functionally independent and operate in practice independently of the other components. These discrete components are generally delineated by the section headings within this section (section III) and section IV of this preamble. For example, the recalculated MACT floor standards, calculated using 1990's data, are severable from the 5-year review standard.

Further, each new or existing source standard for a specific pollutant is severable from the new or existing source standard for any other pollutant. The final rule also includes other revisions to the LMWC NSPS and EG that generally function independently of one another (

e.g.,

changes to startup, shutdown malfunction provisions, alternative percentage reduction standards).

As discussed in section IV.A.4, the EPA is finalizing one standard (50 ppmvd NO

limit for new sources) as a result of the 5-year review.

IV. What is the rationale for our final decisions and amendments for the large MWC source category?

For each issue, this section describes what we proposed and what we are finalizing, the EPA's rationale for the final decisions and amendments, and a summary of key comments and responses. The EPA solicited comment on the proposed rule from January 23, 2024, to March 25, 2024. Specifically, we gathered general comments, additional data, and information regarding developments in practices, processes, and control technologies that reduce pollutant emissions as well as associated costs, feasibility concerns, and other drawbacks. The EPA subsequently reopened the comment period on the proposal for an additional four months, from January 16, 2025, to May 30, 2025. Specifically, we then gathered additional information and documentation on verifiable historic pollutant emission concentration information (

e.g.,

stack test reports, waste characterization reports and continuous emission monitor records) for the source category so we could further assess the proposed MACT requirements, including operation of the control technologies over time. For all comments that this preamble does not discuss, comment summaries and our responses are available in the comment summary and response document in the docket.

Docket ID No. EPA-HQ-OAR-2017-0183.

A. Five-Year Review and Response to the Voluntary MACT Floor Remand for the Large MWC Source Category

1. What did we propose based on the five-year review and voluntary MACT floor remand for the large MWC source category?

a. Emission Limits

In developing the proposed standards, the EPA considered four scenarios for setting new EG and NSPS emission limits and conducted the five-year review under CAA section 129(a)(5). In the first scenario, we considered the MACT floor limits established by the best performing units for each covered pollutant. In a second scenario, we considered the appropriateness of additional beyond-the-floor controls for each covered pollutant. In a third scenario, we evaluated a combination of MACT floor emission limits for some covered pollutants and limits based on technology innovations identified in the five-year review for others. In the fourth scenario, we evaluated a combination of beyond-the-floor emission limits for some covered pollutants and limits based on technology innovations identified in the five-year review for others. As part of the EPA's reevaluation of the MACT floors established in 1995, we first considered the best performing units to establish MACT floor limits and then further considered whether beyond-the-floor controls are appropriate, including by evaluating improvements in pollution controls and associated costs and other drawbacks. Following its reevaluation, the EPA proposed standards resulting from the third scenario, which includes the MACT floor limits (as assessed and described in section IV.A.1.b of this preamble) for all covered pollutants except for NO

, for which the EPA proposed to implement more stringent emission standards as a result of the five-year review. Tables 2 and 3 of the preamble to the proposed rule present the proposed emission limits.

89 FR 4251 (Jan. 23, 2024).

b. MACT Floor Assessment

As discussed in sections II.B and III.A.2 of this preamble, the EPA sought and received a voluntary remand of the 2006 revisions to the large MWC regulations to reevaluate the 1995 MACT floors. In this rulemaking, the EPA proposed to recalculate the large MWC MACT floors from its initial analysis in 1995.

Id.

While reviewing the data and information originally used to calculate the 1995 MACT floors, the EPA determined that it did not have sufficient data from that time period to characterize the performance of all units necessary to re-evaluate MACT floors. Accordingly, the EPA proposed to base the calculation of the MACT floors on additional emissions data from sources in the large MWC source category. The EPA also proposed to reevaluate the MACT floors based on the state of the industry at the time the EPA first calculated limits for large MWCs in 1995. The EPA proposed using 1990-1995 performance levels to reestablish MACT floor requirements to acknowledge the steps that large MWC facilities took to reduce emissions following the promulgated 1995 standards and to meet the EPA's obligation to correctly set MACT floor standards for each source category regulated under CAA section 129.

In other words, the EPA accounted for the fact that the 1995 regulations resulted in changes to the operation and APCDs of many large MWCs in a manner that altered the characteristics of the “best” performing units. As explained in the proposed rule, the composition of the industry remained relatively stable between the promulgation of the 1995 MACT floors and the time of our reevaluation. The EPA thus proposed to recalculate the MACT floors for large MWCs based on the population of units operating at the time of the original EG development (

i.e.,

approximately 1990), taking into account the installation of APCDs and other improvements sources made to meet the 1995 standards as based on compliance data reported for the same units from 2000 through 2009. Specifically, the EPA adjusted the initial MACT floors by assigning default control efficiencies to each APCD configuration for each covered pollutant, back-calculated an “uncontrolled” emissions value from the post-retrofit data, and then applied the control efficiencies corresponding to pre-retrofit configurations to estimate emissions that would more accurately represent the performance level of units operating in 1990. The EPA subsequently ranked the best performing units within the source category for each covered pollutant based on the adjusted emissions; analyzed the data to determine the average performance of those units, with appropriate accounting for emissions variability; and proposed MACT floor emission limits.

In calculating MACT floors, for existing sources, CAA section 129(a)(2) requires that MACT reflect the average emissions limitation achieved by the best performing twelve percent of units in the source category; for new sources, MACT limits most be no less stringent that the emissions control achieved by the best performing similar unit.

The EPA proposed separate methodologies for pollutants having stack test data (Cd, Pb, Hg, PM, HCl, and PCDD/PCDF) and pollutants having CEMS data (CO, NO

, and SO

) due to inherent differences in the data (

i.e.,

test run data vs. hourly averages). For each stack test pollutant, we performed a statistical analysis on annual averages of screened run data from the 2000 to 2009 dataset to determine UPL, based on the EPA's most recent UPL template (January 2022). For EG limits, we used average annual test data corresponding to the top 12 percent of units, and for NSPS limits, we used average annual run data for the single best performer in the UPL calculations.

The EPA used the most recent UPL template to conduct the analysis and then rounded up UPL results to two significant figures.

For PCDD/PCDF, the top performing unit only had enough reported data to derive two annual averages. In this case, because the UPL template can only accommodate data sets of n ≥ 3, the EPA used unit run data instead of the test average in the UPL calculation.

For CEMS pollutants (CO, NO

, and SO

), the EPA proposed that the reported CEMS data already accounted for emissions variability because the available data consisted of the reported annual peak 24-hour or four-hour average selected from the year's CEMS data and represents only the highest end of readings for the year. We therefore reevaluated limits for CEMS pollutants by averaging annual peak CEMS data corresponding to the top performers for each pollutant and applicable subcategory. For NO

and CO, we calculated separate NSPS limits for only two subcategories, MB/WW and RDF. For NSPS purposes, the EPA assumed that the overarching MB or RDF subcategories will represent performance of any units built in the future. We rounded up the resulting averages for CEMS pollutants to two significant figures. In cases where results were greater (less stringent) than the current large MWC EG limit, we proposed to retain the current limit as the MACT floor limit.

The proposed EG and NSPS MACT floor limits for stack test pollutants and CEMS pollutants and additional information regarding the EPA's MACT floor assessment are available in section III.A.2 of the preamble to the proposed rule.

Id.

c. Beyond-the-Floor and Five-Year-Review Results

For assessing beyond-the-floor options in the reevaluation of the 1995 standards, in conjunction with addressing the remand of the original rule's MACT floors, the EPA proposed to represent the beyond-the-floor emission limits for existing sources numerically by assuming that the beyond-the-floor option for existing sources is the new source MACT floor (emissions control achieved in practice by the best controlled similar unit, as required by CAA section 129(a)(2)) which is more stringent than the existing source MACT floor (an average of a broader range of best performing units, also as required by CAA section 129(a)(2)).

As part of the five-year review pursuant to CAA section 129(a)(5), to assess additional control options, the EPA evaluated the performance of, and variability associated with control measures affecting emissions performance at large MWC sources (including the installed emissions control equipment) and recent developments in practices, processes, and control technologies along with associated costs and other drawbacks. As part of this review, the EPA considered at proposal developments from the Good Neighbor Plan rulemaking, which found cost-effective advances in NO

control technologies that are available for the large MWC sector.

The EPA proposed NO

standards, consistent with those finalized in the Good Neighbor Plan as the CAA section 129(a)(5) five-year review options for consideration combined with either the MACT floor or beyond-the-floor controls for the other covered pollutants. Specifically, the EPA's third scenario consisted of evaluating MACT floor emission limits for all covered pollutants except NO

, which the EPA proposed as a five-year review emission limit. The EPA's fourth scenario consisted of evaluating beyond-the-floor emission limits for all pollutants except NO

, which the EPA proposed as a five-year review emission limit. Based on the EPA's analyses and the findings of the Good Neighbor Plan, the EPA selected at proposal the MACT floor plus five-year review approach (scenario three) as the most cost-effective means to maximize emissions reductions.

88 FR 36654 (June 5, 2023).

In the proposed rule, the EPA found that the 14,200 tpy emissions reductions achieved by the third scenario (the combination of MACT floors for all covered pollutants except for NO

, which the EPA proposed updating per the five-year review) are significantly greater than the reductions achieved by the first scenario (updates to the MACT floors alone), by approximately 5,020 tpy. The 16,800 tpy emissions reductions achieved by the fourth scenario (the combination of beyond-the-floor limits with the updated NO

standard under the five-year review) equal 2,600 tpy in incremental emissions reduction above those achieved by scenario three. In reviewing the cost effectiveness of the third and fourth scenarios, the EPA found that the third scenario included a cost effectiveness of approximately $7,000 per ton emissions reduction of regulated pollutants, while the fourth scenario resulted in a cost effectiveness of approximately $35,000 per ton emissions reduction of regulated pollutants. As such, the EPA proposed that the third scenario—reevaluated MACT floor limits coupled with the five-year review for NO

standards—provided the most cost-effective means to maximize emissions reductions and was therefore the most appropriate set of emission standards.

In the proposal, through selection of the third scenario, the combination of MACT floor emission limits for all covered pollutants except for NO

with the five-year review emission limit, the EPA recognized that owners or operators have retrofitted most sources with APCDs that were state of the art for MWCs in the 1990s (

i.e.,

spray dryers, fabric filters, and activated carbon injection) for covered pollutants other than NO

. The EPA also believed that the NO

control retrofits that are currently available—but were not in the 1990s—for most existing large MWCs appear to be cost-effective (approximately $5,000 to $6,000 per ton) and technically feasible for several existing large MWC units currently operating in the U.S. More details on the cost effectiveness of the options considered are in the memorandum entitled

Compliance Cost Analyses for Large MWC Final Rule Amendments

in the docket for this rulemaking.

The EPA proposed the 110 ppmvd (24-hour) NO

limit consistent with the NO

limit finalized under the Good Neighbor Plan based on the application of ASNCR or Covanta LN

technology, finding that this limit was cost effective for existing units outside of the Ozone Transport Region that the Good Neighbor Plan did not cover; separately, in the Good Neighbor Plan, the EPA found that the limit was cost-effective for units inside of the Ozone Transport Region.

Unlike the Good Neighbor Plan, the EPA did not propose a mechanism for existing large MWCs to request a case-by-case emission limit based on a demonstration that application of ASNCR and Covanta's LN

Technology or any other NO

emission reduction technologies or measures is not technically feasible.

Id.

For all new units, the EPA proposed a NSPS NO

limit of 50 ppmvd (measured in 24-hour period). The EPA based this limit on the permitted NO

limit for the only facility currently using SCR technology with an air-to-air heat exchanger providing flue gas reheat prior to entering the SCR reactor to represent the five-year review standard for new sources. The EPA determined that owners or operators only reasonably can apply this design during construction of the unit, so retrofitting SCRs to other existing units would be technically infeasible and/or very costly if provision of reheat requires use of a supplemental burner.

Although the EPA considered other potential improvements that could be technically feasible for large MWCs as part of the five-year review, including circulating fluidized bed scrubbers (CFBS) for acid gas control and oxidation catalysts for CO control, we did not propose standards based on the performance improvements these technologies might yield. The EPA determined that retrofitting existing large MWC units with CO oxidation catalysts would be prohibitively costly, as accommodating an entirely new piece of equipment in the APCD system would require new facility footprint space and flue gas routing. For CFBS, the EPA acknowledged that although theoretically owners or operators could replace existing acid gas control devices with a CFBS to achieve slightly better acid gas control, the EPA lacked data demonstrating technical feasibility for new or existing MWC units.

2. How did the proposed emission limits and MACT floor assessment change for the large MWC source category?

As introduced in section III.A of this preamble, the EPA has revised its MACT floor assessment for the EG and NSPS in response to new data and associated comments since the proposal. The EPA is finalizing the same fundamental analytical approach as proposed, specifically using separate methodologies for pollutants with stack test data (Cd, Pb, Hg, PM, HCl, and PCDD/PCDF) and pollutants with CEMS data (CO, NO

, and SO

). For each stack

test pollutant, the EPA performed a statistical analysis on annual averages of screened run data to determine a UPL. For CEMS pollutants, we averaged peak annual values, maintaining its stance that the data in this form already account for emissions variability. For EG limits, we used data corresponding to the top 12 percent of units, and for NSPS limits, we used data for the single top performer, consistent with CAA section 129(a)(2).

The emissions test data that the EPA used for the UPL analyses for stack test pollutants includes the 2000 through 2009 compliance data and newly received data from 1990 through 1995. The EPA made minor revisions to the 2000 through 2009 data set based on comments received. The 1990s data came from test reports and related documents submitted via email to the EPA in 2024 and 2025 by the WTEA or from attachments to comments submitted to the docket. The EPA assessed the performance of large MWCs operating in 1990 primarily based on the 1990s data. However, these data accounted for 75% of units operating in 1990, so we filled data gaps, where possible, based on adjusted emissions data from the 2000s dataset. Similar to the approach used at proposal, we accounted for performance improvement over time by adjusting the 2000 through 2009 emissions data to reflect 1990s performance. In the revised analysis, the EPA used paired 1990s and 2000s data to inform its adjustment factor development based on combustor/APCD combinations rather than relying on default APCD efficiencies alone, as the EPA did at proposal.

For the NSPS analysis for stack test pollutants, the EPA revised the UPL approach to address variability concerns raised by commenters regarding the limited number of data points available for the top performers. For every stack test pollutant, only one test was available for the top performer. To account both for more recent operational practices and waste characteristics that a single test from the 1990s may not sufficiently characterize and for the fact that we could not obtain additional years of data from the early 1990s, we assessed the distribution and variance of 2000s test averages (

i.e.,

data from several years) for the same performer. In all cases, the 2000s data distribution matched the 1990s distribution, and the EPA combined variance of the 2000s data with the variance of the 1990s data in the UPL calculation.

For CEMS pollutants, the EPA made no changes to the MACT floor calculation methodology; however, revisions to the dataset as described in this section yielded a new EG limit for SO

and a new NSPS limit for CO for mass burn waterwall units. Further details regarding the revised MACT floor assessment are provided in the LMWC MACT Floor memorandum for the final rule.

See

memorandum entitled

MACT Floor Calculations for Large Municipal Combustor Units—Final Rule,

available at Docket ID No. EPA-HQ-OAR-2017-0183.

For the five-year review and beyond-the-MACT floor approaches, the EPA is not finalizing our determinations as proposed for existing units, meaning that the EPA is not basing the NO

standard on the findings of our five-year review. Tables 2 and 3 of this preamble present the resulting final emission limits.

3. What key comments did we receive on the emissions limits, MACT floor assessment, beyond-the-floor, and five-year review, and what are our responses?

Comment:

The EPA received numerous comments on the proposed control factor adjustment approach to emulate data from large MWCs that were operating in 1990 for reevaluating the original MACT floor. Commenters suggested that the EPA's proposed approach did not adequately characterize operational and waste composition differences from the 2000-2009 timeframe to the early 1990s and urged the EPA to use actual data from the 1990s to better inform any adjustments or calculations. Several commenters provided emission tests, spreadsheets, or test report summaries with emissions test information for a portion of the large MWC units in operation in 1990, as well as for some units that came into operation after that time but had performance data from the early 1990s. These industry commenters also provided some emissions test summary data from units within the 2000-2009 timeframe, consisting mainly of test averages for years and units for which we did not already have data in the 2000-2009 database. Other commenters argued that the EPA should not adjust the emissions data to reflect less protective performance and should not limit the reevaluation of the MACT floor to units operating in 1990, stating that this approach ignores better equipment and performance exhibited by newer large MWCs and that the five-year review requires use of newer units' data.

Response:

The EPA agrees with commenters' arguments that adjusting post-compliance data based purely on expected APCD performance may not adequately reflect differences in waste composition or operational improvements from the 1990s to the 2000-2009 compliance data in the EPA's database. The EPA therefore reopened the comment period for commenters to compile and submit available data from the 1990s. The data received during the additional comment period significantly increased the amount of information available to evaluate performance in the 1990s, especially in cases where no data was available for a unit. The additional data also allowed the development of a more robust adjustment factor to apply to 2000-2009 compliance data.

The EPA assessed the performance of large MWCs operating in 1990 primarily based on the 1990s data. However, these data accounted for 75% of units operating in 1990, so the EPA filled data gaps, where possible, based on adjusted emissions data from the 2000s dataset. Similar to the approach used in the proposal, the EPA accounted for performance improvement over time by adjusting the 2000s emissions data to reflect 1990s performance. In the revised analysis, we used paired 1990s and 2000s data to inform its adjustment factor development on combustor/APCD combinations rather than relying on default APCD control efficiencies alone, as we did at proposal.

For the NSPS analysis for stack test pollutants, the EPA revised the UPL approach to address variability concerns that commenters raised regarding the limited number of data points available for the top performers. For every stack test pollutant, only one test was available for the top performer. To account both for more recent operational practices and waste characteristics that a single test from the 1990s may not sufficiently characterize and for the fact that we could not obtain additional years of data from the early 1990s, we assessed the distribution and variance of 2000s test averages (

i.e.,

data from several years) for the same performer. In all cases, the 2000s data distribution matched the 1990s distribution, and we combined the variance of the 2000s data with the variance of the 1990s data in the UPL calculation.

For CEMS pollutants, the EPA made no changes to the MACT floor calculation methodology; however, revisions to the dataset yielded a new EG limit for SO

and a new NSPS limit for CO for mass burn waterwall units.

The EPA disagrees with some commenters' argument that using data from more recently constructed units to

establish the MACT floor is appropriate here, as that suggested approach would characterize best performers that were already in compliance with the existing MACT standards. The goal of the remand is not to calculate MACT on top of the existing MACT but to reevaluate the original standards to ensure they appropriately reflect MACT when initially promulgated.

Thus, the analysis continues to reflect only units that were operating in 1990 because the EPA is reevaluating this original MACT floor as part of this rulemaking. Further, we have not changed our approach to using the UPL for calculating stack test pollutant emission limits and the average of the highest annual values for the best performers for the CEMS pollutants (CO, NO

, SO

), although we have reevaluated the data for the units identified in the proposal as best performers.

Additional specific comments on various aspects of the emission limit calculation approach, such as use of the UPL, subcategorization and other approaches to addressing variability are in section 4.0 of the Comment Response Document in the docket for this rulemaking.

See U.S. Sugar Corp.,

113 F.4th 984 (upholding the EPA's decision to rely on original dataset to correct prior MACT standards errors and recalculate MACT floor during remand);

cf. Med. Waste Inst. Energy Recovery Council

EPA,

645 F.3d 420 (D.C. Cir. 2011) (holding that the EPA was reasonable in its decision to use post-compliance data to reset MACT floor during remand after concluding that the prior dataset was flawed).

See comment and response below on NSPS CO emission limit for further discussion.

Comment:

Commenters argued that the proposed new source limits do not consider the variability of waste streams from different communities as well as seasonal variation within a community. One commenter proposed that the EPA base the variance on the top 12% of units identified for development of the MACT floors for existing units to provide a more representative estimate of variability, given the lack of actual data. Other commenters stated that the EPA's UPL approach for stack test pollutants limits the data set to only a handful of tests and leads to an extremely high calculation of variability under the extreme (99th percentile) UPL employed. These commenters asserted that in the past, the EPA has instead set “beyond-the-floor” limits for units where the 99th percentile UPL for the single “best” unit was less stringent than the UPL for the average of the top 12 percent.

Response:

The EPA recognizes that there is some merit to the argument that a single emissions test taken more than 30 years ago may not accurately characterize waste and operational variability that a large MWC unit may see on a day-to-day basis. Further, we acknowledge that, after extensive industry efforts to collect legacy emissions data from the 1990s, the best performing units each only have a single emissions test reflecting performance at that time, and there are not additional tests from that timeframe available that we could use to gauge waste variability impacts in the 1990s. To address these commenters' concerns, we have reviewed the available 2000-2009 data for the best performing units, for which several years of data are available. The EPA compared the variance observed for the best performing units' 1990s data and 2000s data and found them to be the same distribution type and so we replaced the variance from the single 1990s emissions test with the variance observed from the multiple year 2000s data set available for the best performer in the UPL calculation. The resulting limits therefore incorporate variance observed over multiple years, which presumably would incorporate waste variance, and apply this variance to the UPL calculation using 1990s emissions data. The resulting limits are more stringent than the reevaluated EG MACT floors, so beyond-the-floor emission limits suggested by commenters are not necessary for the stack test pollutant limits calculated using UPL methodology.

To represent beyond-the-floor emission limits numerically, we assumed the new source MACT floor (

i.e.,

emissions control achieved in practice by the best controlled similar unit) as the emission limit applied to existing sources. From a cost-effectiveness viewpoint, the beyond-the-floor/5-year review scenario was five times more costly with less incremental emissions reductions of regulated pollutants. For further discussion of the rationale, see section III.A.3 of the preamble to the proposed rule.

Comment:

Commenters questioned the data that the EPA used to calculate the NSPS CO emission limit for MB/WW units and questioned the validity of the low CO emissions reported for the Wheelabrator Bridgeport large MWC. Commenters added that the proposed 16 ppmvd emission limit is unachievable.

Response:

Acknowledging differences in the reporting method for the Wheelabrator Bridgeport data from the data submitted for other sources, the EPA assessed whether it was appropriate to consider the Wheelabrator Bridgeport data as part of the larger dataset that included other submissions. The EPA performed a paired t-test analysis, using ProUCL software, of the three Wheelabrator Bridgeport units against the rest of the best performers in order to determine whether these units are in fact representative of the best performers or whether they are a statistically distinct dataset. The paired t-test indicates that, at the 99.9 percent confidence coefficient, there are two distinct populations of data—those from Wheelabrator and those for the other units. Figure 1 depicts the two distinct data sets.

Figure 1. Probability Distribution Function of Adjusted Raw CO 1990 Data

ER10MR26.124

There are no known operational differences that would cause the Wheelabrator Bridgeport units to be distinct from the rest of the best performers. Wheelabrator Bridgeport did not report emissions that occurred during SSM, which is inconsistent with the new standard (which includes periods of SSM), while other units included SSM data. While emissions of covered pollutants are typically low during periods of startup and shutdown because no waste has been added to the large MWC, this is not always true of CO because low emissions of CO in a combustor is an indicator of good combustion efficiency. The goal of warmup and startup in a combustor is to establish steady-state, maintainable good combustor efficiency to begin normal operations; before the combustor reaches steady-state, the CO emissions can vary widely with the changes in the combustion environment characteristic of warmup, startup, and shutdown. For large MWCs, annual maximum average CO emission concentrations frequently occur during periods of SSM.

The EPA finds it most likely that the low reported concentrations in data from the Wheelabrator Bridgeport units exclude emissions during periods of SSM, which other facilities include in their reported data. We attribute this likely exclusion to the reporting requirements of the applicable rule. Specifically, although the NSPS and EG, subparts Eb and Cb only require regulated facilities to report the maximum average during the year, some State and local agencies require the reporting of all periods of operation, and others require reporting only during normal operations. Because the EPA therefore determined that the Wheelabrator Bridgeport data from the CEMS dataset are nonrepresentative and not appropriately comparable to data from units whose reported emissions data included SSM periods, we removed the Wheelabrator Bridgeport data from the dataset and redetermined the best performers and the associated MACT floor. This approach resulted in a NSPS CO emission limit of 76 ppmvd and an EG SO

emission limit of 22 ppmvd, because the EPA had identified the Wheelabrator Bridgeport units as the best performer for CO and within the top 12 percent of best performers for SO

at proposal and these data were excluded from the dataset in this final rule.

This is why we are finalizing that CEMS data collected during warmup, startup, or shutdown periods will be averaged at stack oxygen content and not corrected to seven percent oxygen, as are data during normal operations.

Comment:

Commenters both supported and criticized the five-year review finding that there are cost-effective methods such as ASNCR technology and Covanta's LN

Technology, available for existing units to meet a 110 ppmvd emission limit for NO

Some commenters suggested a more stringent NO

limit based on the application of hybrid selective noncatalytic reduction (SNCR) and SCR.

Response:

The EPA is not finalizing the proposed NO

emission limit of 110 ppmvd for existing large MWCs due primarily to the large capital expense (more than $412 million) that the EPA reasonably anticipates for the existing large MWC source category as a whole. As noted previously, the stay of the Good Neighbor Plan means costs to comply with this standard would be higher than previously estimated and the emissions reductions estimates are more uncertain than previously believed. At proposal, the EPA excluded units that we expected the Good Neighbor Plan to cover from the capital cost estimate, which was $257 million for the remaining units. The inclusion of those previously excluded units increases the total estimated capital cost to $412 million. The EPA recognizes that this industry provides public services, and these large capital expenditures on the industry could be challenging, especially for municipalities that own large MWCs or parent companies that operate multiple large MWC facilities.

In addition, the EPA recognizes significant uncertainty in the emission reductions and cost effectiveness estimates from proposal, based on a likely overestimation when using the average of peak 24-hour CEMs data to calculate baseline NO

emissions. We are, however, maintaining the proposed 50 ppmvd NO

limit for new sources within the NSPS based on the availability and continued operation of a large MWC unit equipped with SCR controls.

Regarding SNCR-SCR hybrid

technologies, limited information is available about application of these technologies, and no information is available about long-term performance of these controls applied to municipal waste combustors. However, the final standards do not specify the controls that owners and operators must use to meet the emission limits for NO

, and owners or operators may investigate whether an SNCR-SCR hybrid system is a viable option for their emission control needs.

See

memorandum entitled

Clean Air Act Section 129(a)(5) 5-Year Review for the Large Municipal Waste Combustor Source Category,

available in docket EPA-HQ-OAR-2017-0183. Also note that the Good Neighbor Plan supporting documentation came to similar conclusion: “[T]he study concluded that there are significant space considerations with SCR system installation which can be managed in a cost effective way in a new development, but which make retrofit installation very costly and complex.”

Municipal Waste Combustor Workgroup Report

(Revised May 2023), Ozone Transport Commission Stationary and Area Sources Committee:

https://otcair.org/upload/Documents/Reports/OTC%20MWC%20report%20revised%205_2023.pdf.

4. What is the rationale for our final approach?

The underlying approach to and premise for our reevaluation of the 1995 MACT floors as described in the proposed rule remains the same. As discussed in sections II.B and III.A of this preamble and in the proposed rule, the EPA has recalculated the large MWC MACT floors using actual 1990-1995 test data in order to correct the EPA's 1995 analysis of MACT floors to account for case law questioning standards based on State-issued permit levels without evidence that the permit levels reflect the performance of the best performing sources. In recalculating the 1995 MACT floors to correct errors in our initial analysis, the EPA is assessing the state of the industry at the time that we first calculated limits for large MWCs. Given the history of limited data availability of this source category, the EPA views this approach as appropriate to establish MACT floors that reflect the emission levels actually achieved by the best performing sources using the MACT before sources in the category first complied with the 1995 standards. The EPA determined that utilizing 1990s performance levels to reestablish MACT floor requirements appropriately balances competing interest in this rulemaking, by recognizing on one hand that large MWC facilities have taken steps to reduce emissions since the EPA first promulgated 1995 standards, and on the other hand the EPA's obligation to correctly set MACT floor standards for each source category regulated under CAA section 129. At proposal, the EPA determined that it did not have sufficient data from the 1990s to characterize the performance of all units during that time period and that it was necessary to utilize a different dataset to recalculate new MACT floors from the one used to set the initial MACT floors in 1995. Emissions data received during the public comment periods allowed the EPA to develop a 1990-1995 data set, which the EPA used in conjunction with the 2000-2009 compliance data to better reflect 1990s performance when reevaluating the MACT floors for the final rule.

The EPA further notes that this approach is consistent with the congressional design of CAA section 129, which envisioned the calculation and implementation of MACT floors for this source category through rulemaking by 1990.

See

42 U.S.C. 7429(a)(1)(B).

In the related context of hospital, medical, and infectious waste incinerators (HMIWI) also regulated under CAA section 129, the EPA issued a rule on remand from the D.C. Circuit to further explain our reasoning in determining MACT floors for new and existing HMIWI.

In that situation, after the original MACT floors went into effect for HMIWI, approximately 94 percent of HMIWI units shut down, and an additional three percent of units obtained exemptions from the regulations.

Because of these significant changes in the regulated industry, we were not confident in using much of the same data used to set the original MACT floors, in part because data were unavailable from the many units that shut down following promulgation of the original standards. The EPA instead found “the best course of action [was] to re-propose a response to the remand based on data from the 57 currently operating HMIWI.”

Subsequently, in reviewing the EPA's recalculated MACT floors for HMIWI, the D.C. Circuit found that “[w]hen the EPA determined that its regulation rested on unreliable data and that it had to reset the floors, the Agency was functionally regulating on a blank slate even though the regulation continued to remain on the books.”

74 FR 51368 (Oct. 6, 2009).

72 FR 5510, 5518 (Feb. 6, 2007).

73 FR 72962, 72970 (Dec. 1, 2008).

Med. Waste Inst. & Energy Recovery Council,

645 F.3d 420.

The EPA is also functionally establishing new MACT floors for large MWCs on a blank slate because the 1995 MACT floors were originally calculated using a data set—state air permitting levels—that was not appropriate absent evidence of actual emissions. Unlike in the HMIWI rulemaking, however, there have not been significant retirements in the large MWC industry since we first introduced standards in 1995, and the industry today consists largely of the same units that were operating before the original MACT floors went into effect. Instead of retirements, the majority of the industry installed APCD and made other improvements to meet the 1995 standards. Because the industry today consists of largely the same units that were operating in 1995, we are able, as proposed, to calculate revised MACT floors for large MWCs that are appropriate for the current fleet, based on the industry's 1995 performance level.

Sections III.A.2 and IV.A.2 of this preamble explain the data and methodology the EPA used to reevaluate the MACT floors for large MWCs. In general, the EPA has used the 1990s emissions data to the fullest extent possible considering the documentation available for the data. For example, the EPA used emissions concentration data extracted from emission test reports, test report executive summaries, and State-provided compliance data that contained sufficient information to convert the data into useable and consistent units of measure (

i.e.,

mg/dscm at seven percent O

) for use in the UPL calculations in lieu of adjusting 2000-2009 data, as done at proposal. In calculating the MACT floors, we did not use data that was provided in the form of emission factors (

e.g.,

lb/ton MSW) or emission rates (

e.g.,

lb/hr) and that lacked sufficient supporting test data to convert to consistent units of measure without use of default F-factors or heat input rates. Recognizing that 1990s data were unavailable for some of the units in operation in 1990, the EPA filled data gaps by adjusting the 2000-2009 data for each of the units as necessary using data adjustment factors. Unlike at proposal, the EPA used paired 1990s-2000s data for similar combustor types and APCD configurations to develop the data adjustment factors. These factors thus reflect all differences in waste and operational methods from the 1990s and 2000s, and the EPA was able to better adjust the 2000s data accordingly to approximate performance in the 1990s when earlier data are unavailable for specific units.

The EPA did not change the UPL calculation methodology for the EG MACT floor standards from proposal, but recognized that the best performers used for calculating the NSPS standards for stack test pollutants only had one test available from the 1990s. The EPA acknowledged that municipal waste streams are a uniquely variable fuel source with numerous factors that can directly impact emissions (such as seasonal changes in waste composition or consumer habits), and one stack test

may not sufficiently reflect this inherent waste variability. Considering that sources collected these data three decades ago and that obtaining additional data from the 1990s to evaluate variability at the unit over that time period was not possible, we reviewed the 2000-2009 data available for the best performers. The EPA compared the variance and population distribution of the sole 1990s test data to the multiple years of data available from the 2000s for the best performers and found them to be of the same distribution type. Therefore, to ensure that longer-term waste variability is adequately addressed in this unique situation, we incorporated the variance data from the 2000s data for the best performers into the UPL equations, using the 1990s emissions data to develop the NSPS MACT floor emission limits.

Likewise, the EPA analyzed the data from the CO best performer at proposal (CEMS data from Wheelabrator Bridgeport units) and, as described in section III.A.2 of this preamble, determined that these data are statistically unique from the remainder of the large MWC fleet's data due to the probable non-reporting of data during SSM. Therefore, the EPA has excluded the Wheelabrator Bridgeport CEMS data from the CEMS pollutant MACT calculations.

Finally, after review of comments and considering the stay of the Good Neighbor Plan, the EPA is not finalizing the results of our five-year review as proposed. Mainly, the EPA is setting the emission standards for NO

at the reevaluated MACT floor level instead of the 110 ppmvd limit based on the five-year review proposed for large MWCs in light of the then-effective Good Neighbor Plan and the performance observed by some existing large MWC units operating in the U.S. currently. While the standards do not prescribe a particular control technology, as we discuss in the preamble to the proposed rule, existing sources have used ASNCR and Covanta's LN

technologies to achieve the 110 ppmvd performance. We evaluated the costs associated with this performance level,

and we have the following concern: application of these controls to the remaining population of existing large MWCs would result in an expected $411.6 million capital expenditure by the large MWC sector, which in turn owners or operators potentially would pass forward, resulting in tipping fee increases or potential unit closures for municipalities that utilize large MWCs for the MSW disposal needs.

See

memorandum entitled

Compliance Cost Analyses for Large MWC Final Rule Amendments,

Docket ID No. EPA-HQ-OAR-2017-0183.

See id.

The EPA does not see this situation for large MWC sources that have yet to commence construction. As noted at proposal, a facility designed with SCR NO

controls has been operating successfully for several years. Nothing in the comments suggests that future large MWC unit construction could not do the same. Therefore, we are maintaining the proposed 50 ppmvd NO

limit for NSPS units. Specific comments on and associated responses to comments on the emission limit calculation and 5-year review methodology and results are provided in the Comment Response Document in the docket for this rulemaking.

B. Startup, Shutdown, and Malfunction

1. What did we propose pursuant to SSM provisions for the large MWC source category?

The EPA proposed revisions to the SSM provisions of the large MWC NSPS and EG to ensure that these provisions are consistent with the D.C. Circuit's decision in

Sierra Club.

In that decision, the court vacated an SSM exemption in a CAA section 112 regulation after concluding that, pursuant to the definition of “emission standard” and “emission limitation” in CAA section 302(k), emissions standards or limitations under CAA section 112 must apply continuously and that the SSM exemption violated the CAA's requirement.

The EPA proposed that the reasoning in

Sierra Club

applies equally to CAA section 129 because the definition of “emission standard” in CAA section 302(k) also applies to emission standards and limitations established pursuant to CAA section 129.

551 F.3d 1028 (vacated the SSM exemptions that were codified at 40 CFR 63.6(e)(1), (f)(1) and (h)(1)).

The EPA did not propose a separate emission standard for large MWC units during periods of startup and shutdown. We determined that large MWC units would be able to meet the emission limits during periods of warmup and startup because most units use natural gas or clean distillate oil to warm up the unit and do not add waste until the unit has reached combustion temperatures during a brief startup period. Emissions from burning natural gas or distillate fuel oil would generally be significantly lower than from burning solid wastes, for most pollutants, specifically those where owners or operators measure compliance by using stack tests (

e.g.,

Cd, Pb, Hg, PM, PCDD/PCDF, and HCl). Further, because we accounted for emissions variability and proposed appropriate averaging times to determine compliance with the revised MACT standards, we believed we adequately addressed any minor variability that may occur during startup or shutdown.

The EPA also proposed to eliminate the exclusions of periods of warmup, startup, and shutdown from CEMS data averaging calculations present in the 1995 large MWC rules for NO

, SO

, and CO and replace them with a monitoring and compliance demonstration approach used in the more recent CAA section 129 rulemaking for CISWI NSPS and EG.

We proposed that owners or operators must collect and report CEMS data whenever the large MWC unit is operating. Periods when the combustor is operating but owners or operators are not recording monitoring data due to monitor malfunctions may be considered deviations.

We proposed that owners or operators flag CEMS data collected while the large MWC unit is warming up, starting up, and shutting down as warmup, startup, or shutdown period data. We proposed that owners or operators must use the CEMS data for the warmup period and up to three hours of allowable startup or shutdown time per occurrence to calculate rolling or block average values but average these at stack oxygen content instead of at a seven percent O

diluent cap. We requested comment on whether we should adopt a 30-day hourly rolling average for demonstrating compliance for pollutants measured using continuous monitoring, similar to provisions that the EPA has promulgated in many recent combustion standards, such as in CISWI, the Mercury Air Toxics Standards, and the National Emission Standards for Hazardous Air Pollutants for Major Sources: Industrial, Commercial and Institutional Boilers and Process Heaters.

84 FR 15846 (Apr. 16, 2019).

This excludes periods of system breakdowns, repairs, and required routine monitor calibrations or quality assurance/quality control periods, according to 40 CFR 60.13(e).

Mercury Air Toxics Standards (40 CFR part 63, subpart UUUU); Commercial and Institutional Boilers and Process Heaters (40 CFR part 63, subpart DDDDD).

Periods of startup, normal operations, and shutdown are predictable and routine aspects of a source's operations. Malfunctions, in contrast, are neither predictable nor routine. Instead they are, by definition, sudden, infrequent, and not reasonably preventable failures

of emissions control, process, or monitoring equipment.

The D.C. Circuit in

U.S. Sugar Corp.

upheld the EPA's position that CAA section 112 does not require the Agency to include emissions that occur during periods of malfunction when developing CAA section 112 MACT standards.

We proposed that the reasoning in

U.S. Sugar Corp.

applies equally to section CAA 129 standards given the similarities between the section 112 and 129 standard setting criteria.

See

40 CFR 63.2 (definition of malfunction).

830 F.3d at 606-10.

2. How did the proposed startup, shutdown, and malfunction provisions change for the large MWC source category?

The EPA is finalizing the proposed revisions to the SSM provisions of the NSPS and EG. We received comments both supporting and opposed to the proposed approach, but none presented sufficient information to cause us to determine that the approach proposed would be unachievable for large MWC units or otherwise as inappropriate. Moreover, in

Environmental Committee of the Florida Electric Power Coordinating Group, Inc.

EPA,

the D.C. Circuit recognized that similar to CAA section 112, CAA section 129(a)(1)(A) requires the use of “emission limitations” consistent with the CAA section 302(k) definition.

This further supports finalizing the proposed revisions to the SSM provisions consistent with the D.C. Circuit's decision in

Sierra Club.

94 F.4th 77, 103 (D.C. Cir. 2024).

We note that large MWC units operating in Florida have operating permits with practically the same requirements for startup and shutdown events as those the EPA proposed. For example, the Covanta Lake II, Inc. facility has limits that apply during startup and shutdown but “[t]hese limits do not utilize any diluent correction.”

100

Specific comments and associated responses to the SSM provision revisions are in the Comment Response Document in the docket for this rulemaking.

100

See

the Covanta Lake II, Inc. Startup-Shutdown-Malfunction Emission Limit Project, Permit No. 0690046-017-AC, Docket ID EPA-HQ-OAR-2017-0183.

C. Other Changes to the Large MWC EG and NSPS

1. Changes to the Applicability Date of the 1995 Large MWC EG and NSPS

a. What did we propose regarding applicability dates for the large MWC source category?

The EPA proposed new applicability dates for determining whether units are “existing” or “new” sources. Specifically, we proposed that large MWC units that are currently subject to the NSPS would become existing sources under the proposed amended standards and subject to the revised EG by the applicable compliance date for the revised guidelines. However, those units would continue to be NSPS units subject to the 1995 large MWC final rule until they become subject to the amended existing source EG. We proposed that large MWC units that commence construction after the date of the proposal, or for which a modification is commenced on or after the date six months after promulgation of the amended standards, would be new units subject to the NSPS emission limits. Units for which owners or operators commence construction or modification prior to those dates would be existing units subject to the proposed EG.

As discussed in section III of this preamble, the EPA proposed to reserve 40 CFR part 60, subpart Ea standards, which apply to units for which construction commenced after December 20, 1989, and on or before September 20, 1994. The EPA proposed that any units that meet subpart Ea applicability would become existing units subject to the EG once implemented through a State or Federal plan.

b. How did the proposed revisions to the applicability dates change for the large MWC source category?

The EPA did not receive comments on the proposed resetting of the applicability dates, so we are finalizing these revisions as proposed. However, as noted earlier in the preamble, we recognize that the Agency may need subparts Cb and Eb at a future date once all large MWC units are complying with the requirements of subpart WWWW through an approved State plan or the Federal Plan. Therefore, we intend to reserve all three subparts (40 CFR part 60, subparts Cb, Ea, and Eb) in a future rulemaking once all large MWC units are in compliance with the requirements of 40 CFR part 60, subpart WWWW via either State plan or Federal plan means of implementation.

2. Changes to Alternative Percent Reduction Standards for Hg, HCl, and SO

, and Removal of the Emissions Averaging Allowance for NO

a. What did we propose regarding changes to alternative percent reduction standards for the large MWC source category and emissions averaging allowances for NO

The EPA proposed to remove all alternative percent reduction standards that the original 1991 final rule allowed, including the 85 percent reduction allowed for Hg (NSPS and EG), the 95 percent allowed for HCl (NSPS and EG), and the 80 percent (NSPS) and 75 percent (EG) allowed for SO

. We proposed to remove the alternative standards based on limited data available in the large MWC emissions database to evaluate for the alternative percent reduction standards and to provide a numeric concentration limit for these pollutants, which would prevent situations where a different concentration of covered pollutants is emitted from facility to facility or unit to unit.

The EPA also proposed to remove the NO

emissions averaging alternative provided in the EG.

101

We determined that owners or operators rarely use this emissions averaging alternative and proposed that it is incompatible with the NO

emissions standards established in the Good Neighbor Plan, which were considered as part of the five-year review process as discussed in sections III.A and IV.A of this preamble.

101

40 CFR 60.33b(d)(1).

b. How did the proposed revisions to the alternative percent reduction standards change for the large MWC source category?

After considering public comments and upon further review, the EPA is not finalizing the proposed removal of the alternative percent reduction standards allowed in the existing NSPS and EG. Instead, we are finalizing recalculated alternative percent reduction standards based on additional 1990-1995 removal efficiency data for the best performing units used in the re-evaluated MACT standards for Hg, HCl and SO

. The EPA used emission reduction data and a predictive statistical interval, the lower predictive limit (LPL), to calculate alternative standards to the concentration-based emission limits for these three pollutants.

102

The EPA received comments supporting and opposing the removal of the alternative

percent reduction standards. Considering the comments, the EPA recognizes that the alternative percent reduction standards provide much-needed compliance flexibility considering the variable composition of municipal solid waste and the air pollution controls available for covered pollutants. Occasional slugs of high sulfur or chlorine-containing waste materials may cause brief spikes in acid gas content of the flue gas, to which acid gas scrubbing devices may not immediately be able to respond. Similarly, a mercury-containing item in the municipal waste stream could cause an unanticipated spike, which the activated carbon adsorbent injection system may not immediately be able to respond and which may cause noncompliance with a numeric flue gas concentration limit, although the device is still achieving a high level of Hg removal. Because large MWC owners and operators have limited control over the contents of the waste combusted in their units, this flexibility furthers the goal of leveling the playing field for large MWCs. Without the percent reduction alternative, a large MWC could have a set of air pollution controls identified as the BSER but, due to the unexpected or unusual presence of a waste with a high content of a covered pollutant or precursor to a covered pollutant, be unable to comply with the numeric flue gas concentration limit through no fault of their own. This means that even if two large MWCs have identical administrative and engineering controls, one may be able to demonstrate compliance with the standard and the other may not. That does not represent a level playing field, and only potentially subjects the compliance status of large MWCs to the whims of what the public throws in municipal waste on any given day. The percent reduction alternative standard provides for a more level playing field where two large MWCs with the same administrative and engineering controls can consistently achieve compliance regardless of the contents of the municipal waste, which they cannot completely control.

102

See

memorandum entitled

MACT Floor Calculation for Large Municipal Waste Combustor Units—Final Rule,

available in the docket for this rulemaking.

The EPA also recognizes, however, that the Agency relied heavily on engineering judgement while developing the existing alternative percent reduction standards rather than data demonstrating the performance of the best performing sources. Therefore, as discussed above, the EPA has recalculated these alternative standards based on emissions data using LPL predictive statistics. The resulting alternative percent reduction standards are generally similar to the existing standards but now reflect a standard based on actual emissions performance data. For example, the EG Hg and SO

alternative percent removal standards remain unchanged. However, the EG HCl percent reduction standard rises from 95% to 96%. Similarly, for the NSPS, the Hg percent reduction standard is unchanged at 85%. However, the HCl standard rises from 95% to 98%, while the SO

drops by a percentage point, from 80% to 79%.

The EPA is not including the NO

emissions averaging allowance in the final subpart WWWW EG although for different reasons than those stated at proposal. We conclude that existing sources will not need this allowance on two distinct factors. First, we are not aware of any units that cannot meet the revised NO

MACT floor limits without mass retrofits and additional controls. As a result, there will be no large scale retrofit needs across the fleet of large MWCs to meet the final NO

emission limits and less burden on existing sources to accomplish additional NO

emissions reductions and retrofits about which commenters expressed concerns. Because we are finalizing the reevaluated NO

MACT floor emission limits, the expected need to retrofit is limited in scope and should not result in significant limited retrofit resource availability or scheduling concerns that an averaging allowance would help alleviate.

Second, an analysis of the air pollution controls installed at large MWC facilities shows that almost all units are similarly equipped at any given facility. For NO

, this means that, with very limited exceptions, each unit at a facility employs the same NO

control device (

i.e.,

SCR, SNCR) or has a lower NO

-generating design.

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As a result, the EPA does not anticipate a need to average data from a better-controlled or performing source at a facility with that from a source without a similar control or at a lower performance to allow that lower-performing unit to operate. Specific comments on this topic and associated responses to the alternative percent reduction standards and removal of the emissions averaging allowance are in the Comment Response Document in the docket for this rulemaking.

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The only two exceptions are facilities where the owner or operator constructed a new large municipal waste combustor unit at a later date, and the new unit was subject to 40 CFR 60 subpart Eb NSPS, which does not contain an emissions averaging allowance.

3. Changes for Optional Continuous Monitoring

a. What did we propose with respect to optional continuous monitoring for the large MWC source category?

The EPA proposed to incorporate updated performance specifications for the optional use of a PM CEMS or Hg CEMS or the use of multi-metal, HCl, PCDD/PCDF CEMS in place of stack tests into the large MWC requirements. The proposed changes would update the 2006 final amendments to the large MWC rules, which revised the PM and Hg compliance testing requirements to allow the optional use of a PM CEMS or Hg CEMS in place of stack testing and allow the optional use of multi-metal, HCl, PCDD/PCDF CEMS in place of stack tests after performance specifications for these CEMS are promulgated.

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71 FR 27326 (May 10, 2006).

The EPA also requested comment on whether the use of CEMS for compliance testing requires adopting alternative emission limits. We noted that more recent combustion rulemakings have included 30-day hourly rolling averages for pollutants measured with Hg CEMS (

e.g.,

Mercury Air Toxics Standards, 40 CFR part 63, subpart UUUU) or other optional CEMS (

e.g.,

CISWI NSPS and EG, 40 CFR part 60, subparts CCCC and DDDD). We also requested comment on whether the 30-day rolling hourly average is appropriate to use in the large MWC source category.

b. How did the revisions to the optional continuous monitoring provisions change for the large MWC source category?

The EPA is finalizing the proposed changes to continue to allow the optional use of CEMS in place of stack testing after performance specifications for the CEMS are promulgated and incorporate currently available applicable performance specifications. This allows flexibility for a facility to use CEMS for which performance specifications do not yet exist through the use of site-specific performance evaluation plans. Additionally, we are not finalizing 30-day averaging times for any of the required CEMS pollutant monitoring (CO, SO

and NO

). The EPA at this time has insufficient information to assess the suitability and magnitude of a potential 30-day rolling average, as the data consists solely of the maximum four-hour or 24-hour average, recorded over the course of a reporting year. The EPA received comments mainly supporting the

allowance of CEMS for additional pollutants as an option, but some commenters urged the EPA to require monitoring using CEMS. Specific comments and associated responses to the optional use of CEMS and a 30-day hourly rolling average are in the Comment Response Document in the docket for this rulemaking.

4. Changes To Streamline Regulatory Text Within the Large MWC EG and NSPS

a. What did we propose with respect to streamlining regulatory text for the large MWC source category?

The EPA proposed changes to the regulatory format of the large MWC standards to be more accessible and easier to follow than the 1995 large MWC final rule. The proposed rule converted paragraph text describing emission standards and performance testing requirements to tables to facilitate easier implementation and understanding of the requirements. The EPA added these new tables to the ends of the subparts for these requirements, similar to the approach in other, recent CAA section 129 rulemakings.

b. How did the proposed revisions to streamline regulatory text change for the large MWC source category?

The EPA is finalizing changes to the regulatory format of the large MWC standards as proposed, with additional revisions to convert the text and tables to new subparts VVVV and WWWW, incorporate Federal Plain Language Guidelines, and establish section-numbering increments of five to allow or adequate numeric spacing to revise or add new regulatory text sections if needed in the future. The EPA received no substantive comments on streamlining the regulatory text.

5. Closing the 2007 Proposed Reconsideration of the Large MWC EG and NSPS

a. What did we propose in connection with closing the 2007 proposed reconsideration for the large MWC source category?

The EPA proposed to complete action on the March 20, 2007 reconsideration that the EPA had not finalized. In that 2007 notice, we announced our reconsideration of three aspects of the 2007 final rule based on stakeholder requests: operator stand-in provisions, data requirements for continuous monitors, and the status of operating parameters during the two weeks prior to Hg and PCDD/PCDF testing.

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We proposed that no changes to the 2007 final rule were warranted as a result of the reconsideration.

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In the proposed rule for this action, the EPA reiterated the issues raised and discussed in the 2007 notice, acknowledged that we received only one supportive comment on these issues, and proposed to finalize the 2007 reconsideration, as previously proposed, with no changes to those three aspects of the rule, if the Agency received no adverse comments during the comment period for this rulemaking.

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105

72 FR 13016 (Mar. 20, 2007).

106

Id.

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89 FR 4257 (Jan. 23, 2024). As a miscellaneous and superfluous observation, the EPA notes that the reconsideration petition issue concerning the Pb standard, which the EPA did not grant, is moot based on this final action to address the voluntary remand of the MACT floors, which results in more stringent Pb standards.

b. How did the proposed revisions change for the large MWC source category?

The EPA is making no additional changes to the final rule as a result of the proposed closing of the issues raised in the 2007 reconsideration, as recent comments received generally support closing these issues. We received comments both supporting the operator stand-in provisions as they exist and supporting revisions to the provisions to shorten the timeframe that provisionally certified operators may operate the MWC unit. Additionally, commenters supported not changing the mass carbon feed rate operating parameter provisions for PCDD/PCDF and Hg testing. Our response to these comments is in the Comment Response Document in the docket for this rulemaking.

6. Updating Operator Training Examination Requirements

a. What did we propose with respect to updating operator training exam requirements for the large MWC source category?

The EPA proposed to include and incorporate by reference the updated QRO in the final rulemaking. The 1995 large MWC final rule cited the 1994 version, QRO-1-1994. However, ASME released an updated version in 2005, identified as QRO-1-2005, which the EPA proposed to include in the regulatory text and incorporate by reference.

b. How did the proposed revisions change for the large MWC source category?

The EPA is promulgating as proposed with no additional changes to the final rule. We received one comment requesting increased training requirements for MWC operators, supervisors, and personnel. Our response to this comment is in the Comment Response Document in the docket for this rulemaking. The reference to QRO-1-2005 has been added to 40 CFR 60.17(g), 60.5865, and 60.6420.

7. Revisions to Title V Permitting Requirements for Air Curtain Incinerators Burning Only Wood Waste, Clean Lumber, and Yard Waste

a. What did we propose in connection with title V permitting requirements for air curtain incinerators for the large MWC source category?

The EPA proposed to remove a title V permitting requirement in the 1995 large MWC final rule for air curtain incinerators that only burn wood wastes, yard wastes, and clean lumber (and that comply with applicable opacity limitations) and are not at a major source or subject to title V for other reasons.

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The EPA noted in the proposed rule that CAA section 129(e), which requires title V permits for solid waste incineration units, does not apply to these ACI because they are not solid waste incineration units, as defined in CAA section 129(g)(1)(C). The proposed rule explained that the EPA nevertheless required title V permitting for these air curtain incinerators in previous rulemakings for various reasons, primarily because we believed that compliance with a title V permit was necessary to assure compliance with the opacity requirements established for such incinerators. However, we proposed to remove this requirement based on feedback from several States indicating that the title V requirements are unneces

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