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Federal Register / Vol. 86, No. 103 / Tuesday, June 1, 2021 / Proposed Rules
C. What is the purpose of the submitted rule revision?

requirements for the applicable criteria pollutants include the following:

Emissions of NOX contribute to the production of ground-level ozone, smog and particulate matter, which harm human health and the environment.
Section 110a of the CAA requires states to submit regulations that control NOX emissions. Rule 1160 regulates NOX emissions from stationary internal combustion engines. In the Districts reasonably available control technology RACT SIP for the 2008 National Ambient Air Quality Standards NAAQS, the District concluded that Rule 1160 did not meet current RACT
and acknowledged the need to revise the rule, primarily the limits for NOX, in order to implement RACT.1 The submitted rule revisions are intended to strengthen the rule by, among other things, strengthening the NOX limits in the rule, in order to implement current RACT. The EPAs technical support document TSD has more information about this rule.

1. Issues Relating to VOC Regulation Cutpoints, Deficiencies, and Deviations, EPA, May 25, 1988 the Bluebook, revised January 11, 1990.
2. Guidance Document for Correcting Common VOC & Other Rule Deficiencies, EPA Region 9, August 21, 2001 the Little Bluebook.
3. Improving Air Quality with Economic Incentive Programs EPA452/R01001, January 2001.
4. Alternative Control Techniques DocumentNOX Emissions from Stationary Reciprocating Internal Combustion Engines EPA453/R93032, July 1993.

II. The EPAs Evaluation and Action A. How is the EPA evaluating the rule?

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Rules in the SIP must be enforceable see CAA section 110a2, must not interfere with applicable requirements concerning attainment and reasonable further progress or other CAA
requirements see CAA section 110l, and must not modify certain SIP control requirements in nonattainment areas without ensuring equivalent or greater emissions reductions see CAA section 193.
Generally, SIP rules must require RACT for each major source of NOX in ozone nonattainment areas classified as moderate or above see CAA sections 182b2 and 182f. The MDAQMD
regulates an ozone nonattainment area classified as Severe-15 for the 2008
8-hour ozone NAAQS and the 2015
8-hour ozone NAAQS 40 CFR 81.305, and Rule 1160 regulates multiple major sources of NOX in the nonattainment area. Therefore, this rule must implement RACT.
Guidance and policy documents that we use to evaluate enforceability, revision/relaxation and rule stringency 1 The EPA conditionally approved the Districts RACT SIPs for major NOX sources, based on the Districts commitment to remedy deficiencies in a set of different NOX rules, including Rule 1160. 83
FR 5921 February 12, 2018. The District has also submitted revisions to the other NOX rules subject to the conditional approval. Because the EPA has not yet acted on these other rules, we intend to address our conditional approval of the major NOX
RACT source category in a separate rulemaking once we have taken action on all of the applicable NOX rules.

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B. Does the rule meet the evaluation criteria?
Rule 1160 improves the SIP by establishing more stringent NOX
emission limits and by clarifying monitoring, recording and recordkeeping provisions. The revised rule also requires an additional ten percent reduction in allowed emissions for facilities opting to use emissions aggregation as part of an economic incentive program EIP, consistent with the EPAs guidance on such provisions.
The rule is largely consistent with CAA
requirements and relevant guidance regarding enforceability, and RACT, except for the provisions described below. The rule is also consistent with the EPAs requirements on SIP
revisions, except for the provisions described below. Rule provisions that do not meet the evaluation criteria are summarized below and discussed further in the TSD.
C. What are the rule deficiencies?
These provisions do not satisfy the requirements of section 110 and part D
of title I of the Act and prevent full approval of the SIP revision.
1. MDAQMD Rule 1160 section C2b allows for engines to comply with an alternative emission reduction provision instead of the concentrationbased emission limits for NOX.
Specifically, this alternative provision allows for owners or operators of applicable equipment to submit a plan for alternative emissions reduction that would achieve an 80% or 90%
reduction of emissions from a baseline emission rate. Because the rule does not clearly specify how to calculate the baseline emission rate, the rule is not sufficiently clear to constitute an enforceable emission limitation, control measure, means or technique, as required under 110a2 of the Act.
The rule leaves the approval of the NOX
emission reduction alternative to the District. Because the rule is not clear with respect to how to calculate the
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baseline emission rate, and the approval of an alternative limit is left to the District, this provision allows for overbroad discretion on the part of the Director to modify requirements of the SIP without the procedure required under 110 of the Act. In addition, the ambiguous alternative emission reduction provision could allow many units to emit more than the concentration limit in the rule by, in some cases, more than two times. These alternative limits have not been justified as meeting the RACT requirement.
2. Under section C2bv, the alternative emission reduction option also allows for units operating at the same facility to aggregate their emissions in order to comply with the percentage reduction. This type of provision constitutes an EIP under the EPAs 2001 policy referenced above.
The rule provisions do not meet the criteria for EIP integrity because they fail to require that any excess emission reductions credited through the provision be surplus i.e., not required by any other federally enforceable provision. This omission could allow reductions that are otherwise federally required to be aggregated and used to allow greater emissions at other units.
3. The compliance determination requirements described in section E1c do not require adequate source testing for emission units without emission control equipment. The requirements do not specify any frequency for testing beyond the initial compliance test, and do not specify what criteria must be met for certified manufacturer emission rates to be evidence of compliance.
D. Proposed Action and Public Comment As authorized in sections 110k3
and 301a of the Act, the EPA is proposing a limited approval and limited disapproval of the submitted MDAQMD Rule 1160. We will accept comments from the public on this proposal until July 1, 2021. If finalized, this action would incorporate the submitted rule into the SIP, including those provisions identified as deficient.
The submitted rule would replace the existing SIP-approved version of MDAQMD Rule 1160, which would be removed from the SIP. This approval is limited because the EPA is simultaneously proposing a limited disapproval of the rule under section 110k3.
If we finalize this disapproval, CAA
section 110c would require the EPA to promulgate a federal implementation plan within 24 months of the effective date of our final action unless we
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