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Federal Register / Vol. 86, No. 173 / Friday, September 10, 2021 / Rules and Regulations section 3134 advanced or paid on or after July 1, 2021.

MDAQMD or District portion of the California State Implementation Plan SIP. This revision concerns oxides of nitrogen NOX emissions from stationary internal combustion engines.
Under the authority of the Clean Air Act CAA or the Act, this action approves a local rule that regulates these emission sources into the federally-enforceable SIP, thereby strengthening the SIP, while identifying deficiencies with the rule that must be corrected by the MDAQMD in order for the EPA to grant full approval of the rule.

Douglas W. ODonnell, Deputy Commissioner for Services and Enforcement.
Approved: August 18, 2021.
Mark J. Mazur, Acting Assistant Secretary of the Treasury Tax Policy.
FR Doc. 202119524 Filed 9821; 4:15 pm BILLING CODE 483001P

ENVIRONMENTAL PROTECTION
AGENCY

DATES:

40 CFR Part 52

ADDRESSES:

This rule will be effective on October 12, 2021.

EPAR09OAR20210333; FRL860902
R9

Air Plan Limited Approval and Limited Disapproval, California; Mojave Desert Air Quality Management District Environmental Protection Agency EPA.
ACTION: Final rule.
AGENCY:

The Environmental Protection Agency EPA is finalizing a limited approval and limited disapproval of a revision to the Mojave Desert Air Quality Management Districts
SUMMARY:

The EPA has established a docket for this action under Docket No.
EPAR09OAR20210333. All documents in the docket are listed on the https www.regulations.gov website. Although listed in the index, some information is not publicly available, e.g., Confidential Business Information CBI or other information whose disclosure is restricted by statute.
Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form.
Publicly available docket materials are available through https

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www.regulations.gov, or please contact the person identified in the FOR FURTHER
INFORMATION CONTACT section for additional availability information. If you need assistance in a language other than English or if you are a person with disabilities who needs a reasonable accommodation at no cost to you, please contact the person identified in the FOR
FURTHER INFORMATION CONTACT section.
FOR FURTHER INFORMATION CONTACT:

Kevin Gong, EPA Region IX, 75
Hawthorne St., San Francisco, CA
94105. By phone: 415 9723073 or by email at gong.kevin@epa.gov.
SUPPLEMENTARY INFORMATION:
Throughout this document, we, us and our refer to the EPA.

Table of Contents I. Proposed Action II. Public Comments and EPA Responses III. EPA Action IV. Incorporation by Reference V. Statutory and Executive Order Reviews
I. Proposed Action On June 1, 2021 86 FR 29227, the EPA proposed a limited approval and limited disapproval of the following rule that was submitted for incorporation into the California SIP.

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TABLE 1SUBMITTED RULE
Rule

Rule title
1160

Internal Combustion Engines

We proposed a limited approval because we determined that this rule improves the SIP and is largely consistent with the relevant CAA
requirements. We simultaneously proposed a limited disapproval because some rule provisions conflict with section 110 and part D of the Act. The following 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
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enforceable emission limitation, control measure, means or technique, as required under section 110a2 of the Act. Furthermore, the rule leaves the approval of the NOX emission reduction alternative to the District without EPA
review or approval of the alternative into the SIP. Because the rule is not clear with respect to how to calculate the baseline emission rate, and the approval of an alternative limit lies solely with the District, this provision allows for overbroad discretion on the part of the Director to modify requirements of the SIP without the procedures required under section 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.
Additionally, the alternative limits have not been justified as meeting the reasonably available control technology RACT requirement.
2. Under section C2bv, the alternative emission reduction option
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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 emissions aggregation constitutes an economic incentive program EIP under the EPAs 2001 EIP
guidance.1 As discussed in the proposed rule, 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 therefore 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 1 Improving Air Quality with Economic Incentive Programs EPA452/R01001, January 2001.

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