SUPPLEMENTARY INFORMATION:

Throughout this document, the use of “we,” “us,” or “our” is intended to refer 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:

CAA Clean Air Act

CBI confidential business information

CEMS continuous emissions monitoring system

CFR Code of Federal Regulations

COMAR Code of Maryland Regulations

CTG control technique guidelines

CRA Congressional Review Act

EPA Environmental Protection Agency

lbs/hr pounds per hour

MCRRF Montgomery County Resource Recovery Facility

MDE Maryland Department of the Environment

MWC municipal waste combustor

NAAQS National Ambient Air Quality Standards

NO_X  oxides of nitrogen (nitrogen oxides)

NPRM notice of proposed rulemaking

OTC Ozone Transport Commission

OTR Ozone Transport Region

ppm parts per million

ppmv parts per million by volume

ppmvd parts per million by volume, dry basis

PRA Paperwork Reduction Act

PTE potential to emit

RACM reasonably available control measures

RACT reasonably available control technology

RFA Regulatory Flexibility Act

SCR selective catalytic reduction

SIP state implementation plan

U.S.C United States Code

VOC volatile organic compound(s)

Wheelabrator Wheelabrator Baltimore, Inc. facility

Table of Contents

I. Background

II. Summary of Maryland's SIP Submittals

III. The EPA's Evaluation of Maryland's Submittals

IV. The EPA's Response to Comments Received

V. Final Action

VI. Incorporation by Reference

VII. Statutory and Executive Order Reviews

I. Background

On April 29, 2026, the EPA published a notice of proposed rulemaking (NPRM) for the State of Maryland.^[1] In the NPRM, the EPA proposed approval of a portion of Maryland's SIP submittal from July 27, 2018 and the State's full SIP submittal from July 17, 2020. The EPA's action proposed that Maryland had met the CAA's major source NO_X RACT requirement for MWCs for both the 2008 ozone NAAQS and the 2015 ozone NAAQS.

The CAA requires States to address emissions of NO_X and volatile organic compound(s) (VOC) from certain sources in certain parts of the country to limit photochemical reactions that result in ozone formation. RACT is an important strategy for reducing NO_X and VOC emissions from major stationary sources. For purposes of implementing the ozone NAAQS, a “major source” is defined based on the source's potential to emit (PTE) NO_X , VOC, or both pollutants.^[2] The applicable thresholds differ based on the classification of the nonattainment area in which the source is located.

Areas designated nonattainment for the ozone NAAQS are subject to the general nonattainment area planning requirements of CAA section 172.^[3] CAA section 172(c)(1) provides that SIPs for nonattainment areas must include reasonably available control measures (RACM), including emissions reductions from existing sources through adoption of RACT.

RACT is defined as the lowest emission limitation that a particular source is capable of meeting by the application of control technology that is reasonably available considering technological and economic feasibility.^[4] CAA sections 182(b)(2) and 182(f)(1) require States with Moderate or higher (Serious, Severe, or Extreme) ozone nonattainment areas to implement RACT controls for any source covered by a control technique guidelines (CTG) document issued by the EPA and for all major sources of VOC and NO_X emissions located in the area.

CAA section 184(a) established the Ozone Transport Region (OTR) comprised of all or portions of 12 eastern states, including all of Maryland. CAA section 184(b)(1)(B) requires RACT to be implemented on all sources in the OTR that are covered by a CTG. Further, CAA section 184(b)(2) requires that any source in the OTR with a PTE of at least 50 tons per year (tpy) of VOC “be considered a major stationary source and subject to the requirements which would be applicable to major stationary sources if the area were classified as a Moderate nonattainment area.” As such, RACT applies to all sources of VOC in the OTR with a PTE of at least 50 tpy.

In accordance with both CAA sections 182 and 184, Maryland is required to submit to the EPA revisions to its SIP that demonstrate how it meets RACT ( printed page 64283) requirements under the 2008 and 2015 ozone NAAQS, including requirements for major stationary sources of NO_X located within the State boundaries.

II. Summary of Maryland's SIP Submittals

On July 27, 2018, the Maryland Department of the Environment (MDE) submitted to the EPA a SIP revision (#18-04) which was intended to satisfy certain statewide RACT requirements for sources of NO_X emissions for the 2008 ozone NAAQS, including those related to MWCs.^[5] Following that submittal, MDE adopted updated emission limits as RACT for MWCs for the 2008 and 2015 ozone NAAQS and these updated emission limits were submitted to the EPA as a revision to Maryland's SIP on July 17, 2020 (#20-10).

Through the MWC portion of SIP revision #18-04 and SIP revision #20-10, MDE adopted new NO_X RACT standards and requirements for the two large MWCs in Maryland, including individual NO_X 24-hour block average emission rates and 30-day rolling average emission rates. Under MDE's regulations, the Montgomery County Resource Recovery Facility (MCRRF) must meet a NO_X 24-hour block average emission rate of 140 parts per million volume (ppmv) and a 30-day rolling average rate of 105 ppmv. The Wheelabrator Baltimore, Inc. facility must meet a NO_X 24-hour block average emission rate of 150 ppmv and a 30-day rolling average rate of 145 ppmv. The 24-hour block average and the 30-day rolling average emission rates are mathematically adjusted so that the volumetric gas flow rate from the stack is corrected to seven percent oxygen, dry basis. During periods of startup and shutdown, MCRRF must meet a facility-wide NO_X emission limit of 202 pounds per hour (lbs/hr) timed average mass loading over a 24-hour period and the Wheelabrator Baltimore, Inc. facility must meet a facility-wide NO_X emission limit of 252 lbs/hr timed average mass loading over a 24-hour period. The duration of startup and shutdown procedures for a large MWC are not to exceed three hours per occurrence, and the NO_X 24-hour mass emission limits apply during these times. Large MWCs must continuously monitor NO_X emissions with a continuous emissions monitoring system (CEMS) and submit quarterly reports to MDE.

Additionally, under MDE's regulations, small MWCs that were constructed on or before August 30, 1999, will not be in violation of the provisions of 40 Code of Federal Regulations (CFR) part 62 subpart JJJ.^[6]

III. The EPA's Evaluation of Maryland's Submittals

The EPA reviewed Maryland's July 27, 2018 and July 17, 2020 SIP submissions containing regulations establishing RACT for MWCs for the 2008 and 2015 ozone NAAQS, and proposed to approve the portions of the submissions in our April 29, 2026 NPRM. A full discussion of the EPA's rationale for proposing approval of the full July 17, 2020 SIP submission and a portion of the July 27, 2018 SIP submission is available in the NPRM, which is in the docket for the action.^[7]

IV. The EPA's Response to Comments Received

The initial public comment period for this action was originally scheduled to close on May 29, 2026.^[8] On May 28, 2026, the EPA extended the comment period by two weeks to June 12, 2026.^[9] The EPA received two sets of comments. All comments received have been placed in the docket for this action.

A summary of the relevant commentsand the EPA's responses thereto are provided below.

Comment 1: One commenter was supportive of the proposed revisions. They note the consistency of the Maryland regulation with other States' MWC regulations as well as with CAA requirements.

Response 1: The EPA thanks the commenter for this supportive comment.

Comment 2: One commenter believes that the EPA should issue a limited approval to incorporate the proposed MWC limits into the Maryland SIP, and simultaneously issue a limited disapproval that would direct Maryland to establish for both large MWCs a 24-hour NO_X average emission limit of 110 parts per million by volume, dry basis (ppmvd) and a 30-day NO_X rolling emission limit of 105 ppmvd, corrected to seven percent oxygen. The commenter notes that the two large MWCs in Maryland are equipped with pollution control technology that the EPA and the Ozone Transport Commission (OTC) have recognized enable such facilities to meet a NO_X 24-hour average of 110 ppm. The commenter states that each facility's actual NO_X emissions are well below what the EPA proposed and that by “definition . . . the proposed limits submitted by Maryland cannot constitute RACT.” The commenter asserts that, since in “every case RACT should represent the toughest controls considering technological and economic feasibility . . .”, Maryland's proposed RACT for large MWCs fails to comply with CAA requirements.^[10] Additionally, the commenter states that since the time of MDE's SIP submission, multiple states have adopted 24-hour 110 ppm and lower limits.

Response 2: The EPA disagrees with the commenter that we should issue both a limited approval and a limited disapproval of the submittals. We believe that what Maryland has provided in its SIP submittals meets the major NO_X RACT requirements for large MWCs for the 2008 ozone NAAQS and the 2015 ozone NAAQS and therefore a full approval is appropriate. The EPA does not agree with the commenter's suggestion that we should, at this time, direct Maryland to establish a 24-hour NO_X average emission limit of 110 ppmvd and a 30-day NO_X rolling emission limit of 105 ppmvd for both of its large MWCs. While the EPA agrees that the Wheelabrator facility is currently operating technology that can meet these limits, the facility upgraded its control technology after the State completed its RACT analysis and adopted the regulations referred to in this SIP action into State law, and submitted this SIP revision to the EPA. The commenter acknowledged this as they stated in their comment letter that Maryland “submitted its proposed SIP revisions in 2018 and 2020 and that [the submissions] predate technological advancements and upgrades which now enable the two facilities at issue to meet lower NO_X emissions.” ^[11] As for MCRRF, which uses proprietary Covanta “Low NO_X ” technology in addition to selective non-catalytic reduction (SNCR) technology, 105 ppmvd is currently the State's 30-day average RACT requirement for the facility. According to the OTC's revised 2023 “Stationary and Area Sources Committee's Municipal Waste Combustor Workgroup Report,” MCRRF has been able to typically control its average 24-hour NO_X rate to less than 100 ppm, however there are some periodic spikes in excess of those values ( printed page 64284) caused by process variations that are outside operator control. The OTC Report also refers to a previous publication that concluded that an emissions limitation of 140 ppmvd at seven percent oxygen for a 24-hour average emissions limit, MCRRF's current RACT 24-hour average RACT limit, is reasonable and can be met with good ammonia slip control.^[12]

The commenter also indicates that since Maryland's SIP submission, multiple States have adopted 24-hour 110 ppm and lower average limits and the State's MWC RACT determination fails to comply with CAA requirements since it does not represent the “toughest controls.” The commenter points to the Virginia Department of Environmental Quality's determination in 2019 that the 110 ppm 24-hour average emissions limit is RACT for two Covanta facilities in the Commonwealth. However, these facilities use proprietary technology to obtain this limit. As such, this technology is unavailable to Wheelabrator. Also, the other States that the commenter provides as examples do not yet have the limits the commenter refers to adopted into a SIP as RACT for their large MWC's or the limits at the facilities are not yet effective. Additionally, the EPA expects States to consider recent information, including controls that have been achieved in practice by other similar sources, at the time they are making RACT determinations.^[13] Since the EPA evaluates RACT SIPs based on the information available at the time they were developed, it would be unreasonable for the EPA to expect that the State should have known the information cited by the commenters when it was developing its RACT SIP. However, the EPA's approach to RACT SIPs is not only long-established but also makes sense: a State cannot anticipate each new technological advancement, nor would it be reasonable to expect that their RACT determinations could keep up when technology is evolving so quickly. If the EPA adopted the commenter's approach, then it could result in a situation where the State's SIP submittal could never be approvable as RACT if technology continued to advance. In the EPA's view, it is necessary to have a point in time by which to judge the adequacy of a RACT SIP submittal, rather than requiring States to meet a moving target in terms of technological advancements. Further, RACT is an iterative process. Each time a State is determining RACT under a different ozone standard, if required, the public will have the opportunity to submit to States specific information about controls that are alleged to be reasonably available in light of technological and economic feasibility at that time. States also have the discretion to adopt more stringent limits and controls ( i.e., beyond-RACT reductions) in addition to RACT when considering what emissions reductions of NO_X and VOC are necessary for timely attainment of the ozone NAAQS. Overall, we disagree that Maryland's RACT determination, at the time of its SIP submittal, is insufficient for meeting RACT under the 2008 ozone NAAQS and the 2015 ozone NAAQS. Current regulatory proposals in other States are not relevant to the sufficiency of Maryland's RACT determination, because Maryland's determination was based on EPA guidance, regulations, and other information that were available when the RACT SIP was being developed.

V. Final Action

In this final rule, regarding MDE's SIP revision #18-04, the EPA is only approving statewide RACT control regulations and definitions that relate to MWCs. SIP revision #18-04 contains additional elements, including Maryland's certification that the State satisfied all required statewide RACT elements for the 2008 ozone NAAQS. The EPA is not acting on those other elements, including the certification, that comprise the remainder of MDE's SIP revision #18-04. The EPA will take separate action on those other portions of the July 27, 2018 SIP submittal at another time. The EPA approves all portions of MDE's SIP revision #20-10, submitted to the EPA on July 17, 2020. Overall, the EPA is finalizing approval of the above Maryland SIP revisions as meeting the CAA's major source NO_X RACT requirement for municipal waste combustors for both the 2008 ozone NAAQS and the 2015 ozone NAAQS. The EPA is finalizing this approval pursuant to CAA sections 110, 172, 182, and 184.

VI. Incorporation by Reference

In this document, the EPA is finalizing regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is finalizing the incorporation by reference of the Maryland Code of Maryland Administrative Regulations (COMAR) described in section II of this preamble and in the amendments to 40 CFR part 52 in this document. The EPA has made, and will continue to make, these materials generally available through www.regulations.gov and at the EPA Region III Office (please contact the person identified in the FOR FURTHER INFORMATION CONTACT section of this preamble for more information). Therefore, these materials have been approved by the EPA for inclusion in the SIP, have been incorporated by reference by the EPA into that plan, are fully federally enforceable under sections 110 and 113 of the CAA as of the effective date of the final rule of the EPA's approval, and will be incorporated by reference in the next update to the SIP compilation.^[14]

VII. Statutory and Executive Order Reviews

Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the CAA and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, the EPA's role is to approve State choices, provided that they meet the criteria of the CAA. Accordingly, this action merely approves State law as meeting Federal requirements and does not impose additional requirements beyond those imposed by State law. For that reason, this action:

• Is not a significant regulatory action subject to review by the Office of Management and Budget under ( printed page 64285) Executive Order 12866 (58 FR 51735, October 4, 1993);
• Is not anExecutive Order 14192 (90 FR 9065, February 6, 2025) regulatory action because this action is not significant under Executive Order 12866;
• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq.);
• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);
• Does not have federalism implications as specified inExecutive Order 13132 (64 FR 43255, August 10, 1999);
• Is not subject toExecutive Order 13045 (62 FR 19885, April 23, 1997) because it approves a State program;
• Is not a significant regulatory action subject toExecutive Order 13211 (66 FR 28355, May 22, 2001); and
• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the CAA.

This action is subject to the Congressional Review Act, and the EPA will submit a rule report to each House of the Congress and to the Comptroller General of the United States. This action is not a “major rule” as defined by 5 U.S.C. 804(2).

Under section 307(b)(1) of the CAA, petitions for judicial review of this action must be filed in the United States Court of Appeals for the appropriate circuit by December 7, 2026. Filing a petition for reconsideration by the Administrator of this final rule does not affect the finality of this action for the purposes of judicial review nor does it extend the time within which a petition for judicial review may be filed, and shall not postpone the effectiveness of such rule or action. This action approving NO_X RACT for large MWCs may not be challenged later in proceedings to enforce its requirements. (See section 307(b)(2).)

For the reasons stated in the preamble, the EPA amends 40 CFR part 52 as follows:

91 FR 64282