`[Federal Register Volume 89, Number 244 (Thursday, December 19, 2024)]
[Rules and Regulations]
[Pages 103652-103657]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-29223]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 50 and 58

[EPA-HQ-OAR-2015-0072; FRL-8635.1-02-OAR]
RIN 2060-AW48


Reconsideration of the National Ambient Air Quality Standards for 
Particulate Matter; Correction

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule; correction and correcting amendment.

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SUMMARY: The Environmental Protection Agency (EPA) is correcting a 
final rule published in the Federal Register on March 6, 2024, that 
became effective on May 6, 2024. The final rule revised the primary 
annual PM2.5 standard by lowering the level from 12.0 
[micro]g/m\3\ to 9.0 [micro]g/m\3\, retained the current primary 24-
hour PM2.5 standard and the primary 24-hour PM10 
standard, retained the secondary 24-hour PM2.5 standard, 
secondary annual PM2.5 standard, and secondary 24-hour 
PM10 standard, and finalized revisions to the Air Quality 
Index (AQI) and monitoring requirements for the national ambient air 
quality standards for particulate matter (PM NAAQS). After publication, 
the EPA became aware of an error in the preamble text regarding the due 
date for infrastructure State implementation plan (infrastructure SIP) 
submissions for the 2024 p.m. NAAQS. With this action, the EPA is 
clarifying the due date for infrastructure SIP submissions for the 2024 
p.m. NAAQS. The EPA is also correcting inadvertent errors in the 
PM2.5 monitoring regulatory text. These corrections do not 
include any substantive changes to the final rule.

DATES: This correction is effective on December 19, 2024.

ADDRESSES: The EPA has established a docket for the final rule under 
Docket ID No. EPA-HQ-OAR-2015-0072. All documents in the docket are 
listed on the www.regulations.gov website. Although listed in the 
index, some information is not publicly available, e.g., confidential 
business information 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. Publicly available docket materials are available 
electronically through www.regulations.gov.

FOR FURTHER INFORMATION CONTACT: Mr. Tim Hanley, Air Quality Assessment 
Division, Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Mail Code C304-06, Research Triangle 
Park, NC 27711; telephone: (919) 541-4417; email: [email protected].

SUPPLEMENTARY INFORMATION:

I. General Information

A. What is the authority for this action?

    The EPA is correcting the deadline for infrastructure SIP 
submissions under its authority provided in section 110(a)(1) of the 
Clean Air Act (CAA) (42 U.S.C. 7410), which directs the States to 
submit their implementation plans within 3 years after promulgation of 
a primary or secondary NAAQS.
    The EPA is also acting under the authority provided by CAA sections 
103, 105, 110, 114, 301, 311, 314, and 319, which direct the EPA to 
develop and implement measures to conduct ambient air quality 
surveillance. Under this authority, this action implements minor, non-
substantive typographical and technical corrections to conform the 40 
CFR part 58 regulatory text to the rule's preamble and remedies 
regulatory text formatting errors.

B. What corrective action is the Agency taking?

Correction to Preamble of March 6 Final Rule
    In the proposed rule published on January 27, 2023 (88 FR 5558), 
the preamble states that ``Under CAA sections 110(a)(1), all states are 
required to make these infrastructure SIP submissions within 3 years 
after promulgation of a new or revised primary standard.'' However, in 
the final rule published on March 6, 2024 (89 FR 16202), the preamble 
incorrectly and inadvertently states that ``Under CAA section 
110(a)(1), all States are required to make these infrastructure SIP 
submissions within three years after the effective date of a new or 
revised primary standard. While the CAA authorizes the EPA to set a 
shorter time for States to make these SIP submissions, the EPA is 
requiring submission of infrastructure SIPs within three years of the 
effective date of this revised primary annual PM2.5 NAAQS.''
    Pursuant to CAA section 110(a)(1), infrastructure SIP submissions 
are not

[[Page 103653]]

due within three years of the effective date, but within three years of 
the promulgation of a new or revised NAAQS. The EPA has traditionally 
held that ``promulgation'' means the signature and widespread 
dissemination of a final rulemaking in the context of the NAAQS. Per 
this standard practice, because the EPA promulgated (signed and made 
available on the EPA's website) the reconsideration of the 
PM2.5 NAAQS on February 7, 2024, infrastructure SIP 
submissions are due by no later than February 7, 2027.
    To be consistent with the CAA and the proposed rule, the EPA is 
correcting the last two sentences of the first paragraph of B. Section 
110(a)(1) and (2) Infrastructure SIP Requirements in the final rule 
preamble.
Correction
    In FR Doc. 2024-02637, at 89 FR 16202 in the Federal Register of 
March 6, 2024, on page 16367, in the second column, the last two 
sentences of the first paragraph of B. Section 110(a)(1) and (2) 
Infrastructure SIP Requirements are corrected to read as follows:
    ``Under CAA section 110(a)(1), all States are required to make 
these infrastructure SIP submissions within three years after the 
promulgation date of a new or revised primary standard. While the CAA 
authorizes the EPA to set a shorter time for States to make these SIP 
submissions, the EPA is requiring submission of infrastructure SIPs 
within three years of the promulgation date of this revised primary 
annual PM2.5 NAAQS.''
Correcting Amendments to 40 CFR Parts 50 and 58
    The EPA is also making several corrections to inadvertent errors in 
the PM2.5 monitoring regulatory text as described below.
    After publication, it was realized that the EPA did not add 
promulgated Sec.  50.20 to the 40 CFR 50.3 list of sections containing 
PM2.5 standards, which was inconsistent with past NAAQS 
regulations. Therefore, in 40 CFR 50.3, the EPA is adding Sec.  50.20 
to its list of sections containing PM2.5 standards to be 
consistent with all existing PM2.5 standards and methods.
    The EPA proposed to adjust the minimum value required by appendix 
A, section 3.2.4, to be considered valid sample pairs for the 
PM2.5 Performance Evaluation Program (PEP) from 3 [micro]g/
m\3\ to 2 [micro]g/m\3\ (88 FR 5665, January 27, 2023). In section 
3.2.4 of appendices A and B to part 58, the EPA finalized 2 [micro]g/
m\3\ for the quality assurance program that assesses PM2.5 
network bias. However, in the final rule, section 4(c)(5) in appendix A 
and section 4(b)(5) and (c) in appendix B, which provides the 
PM2.5 limit for use in bias assessments, was not updated to 
reflect the finalized 2 [micro]g/m\3\ for PM2.5 and instead 
states the previous 3 [micro]g/m\3\, which is inconsistent with section 
3.2.4 in the two appendices. Within the PM NAAQS, the same criteria 
should be used for PM2.5 for consistency. Therefore, the EPA 
is correcting section 4(c)(5) of appendix A and section 4(b)(5) and (c) 
of appendix B to part 58 to be consistent with section 3.2.4 of 
appendices A and B to part 58.
    In the PM NAAQS Reconsideration proposed rule (88 FR 5665, January 
27, 2023), the EPA proposed to revise equation 6 in section 4.2.1 of 
appendices A and B to part 58. The proposed equation 6 had a plus sign 
in the denominator. However, in the final rule, the EPA inadvertently 
published equation 6 with a minus sign in the denominator instead of a 
plus sign. Therefore, the EPA is correcting the denominator in equation 
6 of section 4.2.1 in appendices A and B by changing the minus sign to 
a plus sign, which is consistent with what was proposed.
    In section 2.2.2 in appendix C to part 58, the EPA is correcting a 
typo by replacing ``multijusinstincional'' with 
``multijurisdictional.''
    Appendix C to part 58 of the final rule's regulatory text had an 
incorrect instruction to remove and reserve sections 2.4 and 2.4.1 and 
remove sections 2.4.1. through 2.4.1.7. The EPA's intention was to 
reserve all of section 2.4, which includes sections 2.4.1 through 2.4.6 
and their subsections, and to remove sections 2.4.1.1 through 2.4.1.7. 
However, due to the EPA's confusing instructions, only sections 2.4 and 
2.4.1 were reserved. To correct this issue, the EPA is reserving 
sections 2.4.2 through 2.4.6 of appendix C to part 58, including their 
subsections, so that all of section 2.4 is reserved as intended.
    Also, when the EPA reserved section 2.4 in appendix C to part 58, 
the EPA revoked language associated with Approved Regional Methods 
(ARMs). However, after publication, several mentions of the revoked 
term ``ARM'' and references to the reserved section 2.4 were left in 
appendices A and C to part 58. To correct this issue, the EPA is 
removing the revoked term ``ARM'' and references to the reserved 
section 2.4 from section 3.2.4.2 in appendix A to part 58 and sections 
2.7.1, 2.8.4, 2.7.6, 2.8.1, 2.8.5, and 3.1 in appendix C to part 58.
    Lastly, after publication of the final rule, the EPA became aware 
that, in the finalized tables E-3 and E-6 of appendix E to part 58, 
several merged cells were inadvertently unmerged, resulting in 
misalignment of the data presented for each pollutant-specific row in 
the tables. The EPA is correcting this error by providing reformatted 
tables E-3 and E-6 so that each pollutant-specific row and the 
information in each column is displayed correctly.

II. Rulemaking Procedures

    Section 553(b)(B) of the Administrative Procedure Act (APA), 5 
U.S.C. 553(b)(B), provides that when an agency for good cause finds 
that public notice and comment procedures are impracticable, 
unnecessary, or contrary to the public interest, the agency may issue a 
rule without providing notice and an opportunity for public comment. 
The EPA has determined that there is good cause for making this 
correction final without prior proposal. In this instance, notice and 
opportunity for comment is unnecessary because this action implements 
minor, non-substantive typographical and technical corrections that 
correct preamble language in one instance, conform the regulatory text 
to the rule's preamble, and remedy formatting errors.
    Moreover, EPA has determined that there is good cause for making 
this final rule effective less than 30 days after publication in the 
Federal Register. Section 553(d)(3) of the APA, 5 U.S.C. 553(d)(3), 
provides that final rules shall not become effective until 30 days 
after publication in the Federal Register ``except . . . as otherwise 
provided by the agency for good cause found and published with the 
rule.'' ``In determining whether good cause exists, an agency should 
`balance the necessity for immediate implementation against principles 
of fundamental fairness which require that all affected persons be 
afforded a reasonable amount of time to prepare for the effective date 
of its ruling.'' Omnipoint Corp. v. Fed. Commc'n Comm'n, 78 F.3d 620, 
630 (D.C. Cir. 1996) (quoting United States v. Gavrilovic, 551 F.2d 
1099, 1105 (8th Cir. 1977)). This action adjusts a deadline that will 
not apply for at least two years (from May 6, 2027, to February 7, 
2027) and makes only minor technical and typographical corrections to 
the monitoring provisions that are not connected to immediate 
regulatory obligations.
    For these reasons, the Agency finds that good cause exists under 
APA section 553(d)(3) to make this rule effective on December 19, 2024.

[[Page 103654]]

III. Statutory and Executive Orders Reviews

    Additional information about these statutes and Executive orders 
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 14094: Modernizing Regulatory Review

    This action is not a significant regulatory action as defined by 
Executive Order 12866, as amended by Executive Order 14094 and was, 
therefore, not subject to a requirement for Executive Order 12866 
review.

B. Paperwork Reduction Act (PRA)

    This action does not impose any new information collection burden 
under the PRA. The EPA is clarifying the due date for infrastructure 
SIP submissions for the 2024 PM NAAQS and correcting inadvertent errors 
in the PM2.5 monitoring regulatory text. However, the Office 
of Management and Budget (OMB) has previously approved the information 
collection activities contained in the existing regulations and has 
assigned OMB control number 2060-0084.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities. Rather, this 
action corrects inadvertent errors in the final rule's preamble and 
regulatory text.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate of $100 million or 
more as described in the Unfunded Mandates Reform Act (UMRA), 2 U.S.C. 
1531-1538, and does not significantly or uniquely affect small 
governments. This action corrects inadvertent errors in the final 
rule's preamble and regulatory text.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the National Government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

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

    This action does not have Tribal implications, as specified in 
Executive Order 13175. It does not have a substantial direct effect on 
one or more Indian Tribes as Tribes are not obligated to adopt or 
implement any NAAQS. In addition, Tribes are not obligated to conduct 
ambient monitoring for PM or to adopt the ambient monitoring 
requirements of 40 CFR part 58. Thus, Executive Order 13175 does not 
apply to this action.

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

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive order. This action is not subject to 
Executive Order 13045 because it does not concern an environmental 
health risk or safety risk. This action corrects inadvertent errors in 
the final rule's preamble and regulatory text.

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

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act (NTTAA)

    The final rule involved environmental monitoring or measurement. 
The PM NAAQS final rule maintained the use of the existing indicators 
for fine (PM2.5) and coarse (PM10) particles. The 
indicator for fine particles is measured using the Reference Method for 
the Determination of Fine Particulate Matter as PM2.5 in the 
Atmosphere (appendix L to 40 CFR part 50), which is known as the 
PM2.5 FRM, and the indicator for coarse particles is 
measured using the Reference Method for the Determination of 
Particulate Matter as PM10 in the Atmosphere (appendix J to 
40 CFR part 50), which is known as the PM10 FRM. To the 
extent feasible, the EPA employs a Performance-Based Measurement System 
(PBMS), which does not require the use of specific, prescribed analytic 
methods. The PBMS is defined as a set of processes wherein the data 
quality needs, mandates or limitations of a program or project are 
specified and serve as criteria for selecting appropriate methods to 
meet those needs in a cost-effective manner. It is intended to be more 
flexible and cost effective for the regulated community; it is also 
intended to encourage innovation in analytical technology and improved 
data quality. This action corrects inadvertent errors in the monitoring 
regulatory text for parts 50 and 58.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    The EPA believes that this correction does not concern human health 
or environmental conditions and, therefore, cannot be evaluated with 
respect to potentially disproportionate and adverse effects on people 
of color, low-income populations and/or indigenous peoples. This action 
corrects inadvertent errors in the final rule's preamble and regulatory 
text.
    Although this action does not concern human health or environmental 
conditions, the EPA identified and addressed environmental justice 
concerns in the underlying final rule in sections II.A.2, II.B.3.a, 
II.B.3.c, II.B.2, and II.B.4. of the final rule preamble and also in 
the 2019 Integrated Science Assessment, Supplement to the 2019 
Integrated Science Assessment, and 2022 Policy Assessment.

K. Congressional Review Act (CRA)

    This action is subject to the CRA, and the EPA will submit a rule 
report to each House of the Congress and to the Comptroller General of 
the United States. The CRA allows the issuing agency to make a rule 
effective sooner than otherwise provided by the CRA if the agency makes 
a good cause finding that notice and comment rulemaking procedures are 
impracticable, unnecessary or contrary to the public interest (5 U.S.C. 
808(2)). The EPA has made a good cause finding for this rule as 
discussed in the SUPPLEMENTARY INFORMATION section. The EPA has 
determined that there is good cause for making this correction final 
without prior proposal. In this instance, notice and opportunity for 
comment is unnecessary because this action implements minor, non-
substantive typographical and technical corrections that conform the 
regulatory text to the rule's preamble and remedy formatting errors.

[[Page 103655]]

List of Subjects

40 CFR Part 50

    Environmental protection, Air pollution control, Particulate 
matter.

40 CFR Part 58

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Intergovernmental relations, Reporting and 
recordkeeping requirements.

Michael S. Regan,
Administrator.

    Accordingly, 40 CFR parts 50 and 58 are corrected by making the 
following correcting amendments:

PART 50--NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY 
STANDARDS

0
1. The authority citation for part 50 continues to read as follows:

    Authority: 42 U.S.C. 7401, et seq.


0
2. Revise Sec.  50.3 to read as follows:


Sec.  50.3  Reference conditions.

    All measurements of air quality that are expressed as mass per unit 
volume (e.g., micrograms per cubic meter) other than for particulate 
matter (PM2.5) standards contained in Sec. Sec.  50.7, 
50.13, 50.18, and 50.20, and lead standards contained in Sec.  50.16 
shall be corrected to a reference temperature of 25 (deg) C and a 
reference pressure of 760 millimeters of mercury (1,013.2 millibars). 
Measurements of PM2.5 for purposes of comparison to the 
standards contained in Sec. Sec.  50.7, 50.13, 50.18, and 50.20, and of 
lead for purposes of comparison to the standards contained in Sec.  
50.16 shall be reported based on actual ambient air volume measured at 
the actual ambient temperature and pressure at the monitoring site 
during the measurement period.

PART 58--AMBIENT AIR QUALITY SURVEILLANCE

0
3. The authority citation for part 58 continues to read as follows:

    Authority:  42 U.S.C. 7403, 7405, 7410, 7414, 7601, 7611, 7614, 
and 7619.


0
4. Amend appendix A to part 58 by revising sections 3.2.4.2 and 4(c)(5) 
and equation 6 in section 4.2.1 to read as follows:

Appendix A to Part 58--Quality Assurance Requirements for Monitors Used 
in Evaluations of National Ambient Air Quality Standards

* * * * *
    3.2.4.2 Have all FRM and FEM samplers subject to a PEP audit at 
least once every 6 years, which equates to approximately 15 percent 
of the monitoring sites audited each year.
* * * * *
    4. * * *
    (c) * * *
    (5) PM2.5: 2 [micro]g/m\3\.
* * * * *
    4.2.1 * * *

Equation 6 to Section 4.2.1 of Appendix A
[GRAPHIC] [TIFF OMITTED] TR19DE24.014

* * * * *

0
5. Amend appendix B to part 58 by revising section 4(b)(5) and (c) and 
equation 6 in section 4.2.1 to read as follows:

Appendix B to Part 58--Quality Assurance Requirements for Prevention of 
Significant Deterioration (PSD) Air Monitoring

* * * * *
    4. * * *
    (b) * * *
    (5) PM2.5: 2 [micro]g/m\3\.
    (c) The PM2.5 2 [micro]g/m\3\ limit for the 
PM2.5-PEP may be superseded by mutual agreement between 
the PSD PQAO and the PSD reviewing authority as specified in section 
3.2.4 of this appendix and detailed in the approved QAPP.
* * * * *
    4.2.1 * * *

Equation 6 to Section 4.2.1 of Appendix B
[GRAPHIC] [TIFF OMITTED] TR19DE24.015

* * * * *

0
6. Amend appendix C to part 58 by:
0
a. Revising section 2.2.2; and
0
b. Removing and reserving sections 2.4.2 through 2.4.6; and
0
c. Revising sections 2.7.1, 2.7.4, 2.7.6, 2.8.1, 2.8.5, and 3.1.
    The revisions read as follows:

Appendix C to Part 58--Ambient Air Quality Monitoring Methodology

* * * * *
    2.2.2 A request to update a designated methods calibration may 
be initiated by the instrument manufacturer of record or the EPA 
Administrator. State, local, Tribal, and multijurisdictional 
organizations of these entities may work with an instrument 
manufacture to update a designated method calibration.
* * * * *
    2.7.1 Requests for approval under section 2.2, 2.6.2, or 2.8 of 
this appendix must be submitted to: Director, Center for 
Environmental Measurement and Modeling, Reference and Equivalent 
Methods Designation Program (MD-D205-03), U.S. Environmental 
Protection Agency, P.O. Box 12055, Research Triangle Park, North 
Carolina 27711.
* * * * *
    2.7.4 To the extent that such incorporation by reference 
provides data or information required by this section (2.7) or by 
section 2.5 or 2.6 of this appendix, independent data or duplicative 
information need not be submitted.
* * * * *
    2.7.6 If the Administrator determines, on the basis of any 
available information, that any of the determinations or statements 
on which approval of a request under this section was based are 
invalid or no longer valid, or that the requirements of section 2.5 
or 2.6, as applicable, have not been met, he/she may withdraw the 
approval after affording the person who obtained the approval an 
opportunity to submit information and arguments opposing such 
action.
* * * * *
    2.8.1 Except as otherwise provided in this section, no reference 
method or equivalent method may be used in a SLAMS network if it has 
been modified in a manner that could significantly alter the 
performance characteristics of the method without prior approval by 
the Administrator. For purposes of this section, ``alternative 
method'' means an analyzer, the use of which has been approved under 
section 2.5 or 2.6 of this appendix or some combination thereof.
* * * * *
    2.8.5 A temporary modification that could alter the performance 
characteristics of a reference or equivalent may be made without 
prior approval under this section if the method is not functioning 
or is malfunctioning, provided that parts necessary for repair in 
accordance with the applicable operation manual cannot be obtained 
within 45 days. Unless such temporary modification is later approved 
under section 2.8.4 of this appendix, the temporarily modified 
method shall be repaired in accordance with the applicable operation 
manual as quickly as practicable but in no event later than 4 months 
after the temporary modification was made, unless an extension of 
time is granted by the Administrator. Unless and until the temporary 
modification is approved, air quality data obtained with the method 
as temporarily modified must be clearly identified as such when 
submitted in accordance with Sec.  58.16 and must be accompanied by 
a report containing the information specified in section 2.8.3 of 
this appendix. A request that the Administrator approve a temporary 
modification may be submitted in accordance with sections 2.8.1 
through 2.8.4 of this appendix. In such cases, the request will be 
considered as if a request for prior approval had been made.
* * * * *
    3.1 Methods employed in NCore multipollutant sites used to 
measure SO2, CO, NO2, O3, 
PM2.5, or PM10-2.5 must be reference or 
equivalent methods as defined in Sec.  50.1 of this chapter for any 
monitors

[[Page 103656]]

intended for comparison with applicable NAAQS.
* * * * *

0
7. Amend appendix E to part 58 by revising table E-3 to section 2.7 and 
table E-6 to section 3.8 to read as follows:

Appendix E to Part 58--Probe and Monitoring Path Siting Criteria for 
Ambient Air Quality Monitoring

* * * * *
    2.7 * * *

                                        Table E-3 to Section 2.7 of Appendix E--Summary of Probe Siting Criteria
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                             Horizontal or
                                                                             Height from   vertical distance   Distance from
                                                                              ground to     from supporting    drip line of    Distance from roadways to
                Pollutant                            Scale \9\                probe \8\      structures \1\   trees to probe      probe \8\ (meters)
                                                                              (meters)        \8\ to probe     \8\ (meters)
                                                                                             inlet (meters)
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2 \2\ \3\ \4\ \5\.....................  Middle, Neighborhood, Urban,             2.0-15              >=1.0            >=10  N/A.
                                           and Regional.
CO \3\ \4\ \6\..........................  Micro [downtown or street               2.5-3.5              >=1.0            >=10  2.0-10 for downtown areas
                                           canyon sites].                                                                      or street canyon
                                                                                                                               microscale.
CO \3\ \4\ \6\..........................  Micro [Near-Road sites]........         2.0-7.0              >=1.0            >=10  <=50 for near-road
                                                                                                                               microscale.
CO \3\ \4\ \6\..........................  Middle and Neighborhood........          2.0-15              >=1.0            >=10  See Table E-2 of this
                                                                                                                               appendix for middle and
                                                                                                                               neighborhood scales.
O3 \2\ \3\ \4\..........................  Middle, Neighborhood, Urban,             2.0-15              >=1.0            >=10  See Table E-1 of this
                                           and Regional.                                                                       appendix.
NO2 \2\ \3\ \4\.........................  Micro..........................         2.0-7.0              >=1.0            >=10  <=50 for near-road micro-
                                                                                                                               scale.
NO2 \2\ \3\ \4\.........................  Middle, Neighborhood, Urban,             2.0-15              >=1.0            >=10  See Table E-1 of this
                                           and Regional.                                                                       appendix.
PAMS \2\ \3\ \4\ Ozone precursors.......  Neighborhood and Urban.........          2.0-15              >=1.0            >=10  See Table E-1 of this
                                                                                                                               appendix.
PM, Pb \2\ \3\ \4\ \7\..................  Micro..........................         2.0-7.0  >=2.0 (horizontal            >=10  See Figure E-1 of this
                                                                                              distance only)                   appendix.
PM, Pb \2\ \3\ \4\ \7\..................  Middle, Neighborhood, Urban and          2.0-15  >=2.0 (horizontal            >=10  See Figure E-1 of this
                                           Regional.                                          distance only)                   appendix.
--------------------------------------------------------------------------------------------------------------------------------------------------------
N/A--Not applicable.
\1\ When a probe is located on a rooftop, this separation distance is in reference to walls, parapets, or penthouses located on the roof.
\2\ Should be greater than 20 meters from the dripline of tree(s) and must be 10 meters from the dripline.
\3\ Distance from sampler or probe inlet to obstacle, such as a building, must be at least twice the height the obstacle protrudes above the sampler or
  probe inlet. Sites not meeting this criterion may be classified as microscale or middle scale (see paragraphs 2.3(a) and 2.3(c) of this appendix).
\4\ Must have unrestricted airflow in a continuous arc of at least 270 degrees around the probe or sampler; 180 degrees if the probe is on the side of a
  building or a wall for street canyon monitoring.
\5\ The probe or sampler should be away from minor sources, such as furnace or incineration flues. The separation distance is dependent on the height of
  the minor source emission point(s), the type of fuel or waste burned, and the quality of the fuel (sulfur, ash, or lead content). This criterion is
  designed to avoid undue influences from minor sources.
\6\ For microscale CO monitoring sites, the probe must be >=10 meters from a street intersection and preferably at a midblock location.
\7\ Collocated monitor inlets must be within 4.0 meters of each other and at least 2.0 meters apart for flow rates greater than 200 liters/min or at
  least 1.0 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference, unless a waiver has been granted by
  the Regional Administrator pursuant to paragraph 3.3.4.2(c) of appendix A of to this part. For PM2.5, collocated monitor inlet heights should be
  within 1.0 meter of each other vertically.
\8\ All distances listed are expressed as having 2 significant figures. When rounding is performed to assess compliance with these siting requirements,
  the distance measurements will be rounded such as to retain at least two significant figures.
\9\ See section 1.2 of appendix D to this part for definitions of monitoring scales.

* * * * *
    3.8 * * *

                                   Table E-6 to Section 3.8 of Appendix E--Summary of Monitoring Path Siting Criteria
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                                                                                              Horizontal or
                                                                                            vertical distance   Distance from
                                                                            Height from      from supporting    trees to 90%   Distance from roadways to
               Pollutant                 Maximum monitoring path length   ground to 80% of  structures \2\ to   of monitoring   monitoring path \1\ \8\
                                                    \9\ \10\              monitoring path   90% of monitoring   path \1\ \8\            (meters)
                                                                          \1\ \8\ (meters)     path \1\ \8\       (meters)
                                                                                                 (meters)
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SO2 \3\ \4\ \5\ \6\....................  <= 300 m for Middle...........             2.0-15              >=1.0            >=10  N/A.
                                         <= 1.0 km for Neighborhood,
                                          Urban, and Regional.
CO \4\ \5\ \7\.........................  <= 300 m for Micro [downtown              2.5-3.5              >=1.0            >=10  2.0-10 for downtown areas
                                          or street canyon sites].                                                              or street canyon
                                                                                                                                microscale.
CO \4\ \5\ \7\.........................  <= 300 m for Micro [Near-Road             2.0-7.0              >=1.0            >=10  <=50 for near-road
                                          sites].                                                                               microscale.
CO \4\ \5\ \7\.........................  <= 300 m for Middle...........             2.0-15              >=1.0            >=10  See Table E-5.
CO \4\ \5\ \7\.........................  <= 1.0 km for Neighborhood....             2.0-15              >=1.0            >=10  See Table E-5.
O3 \3\ \4\ \5\.........................  <= 300 m for Middle...........             2.0-15              >=1.0            >=10  See Table E-4.
O3 \3\ \4\ \5\.........................  <= 1.0 km for Neighborhood,                2.0-15              >=1.0            >=10  See Table E-4.
                                          Urban, and Regional.
NO2 \3\ \4\ \5\........................  Between 50 m-300 m for Micro              2.0-7.0              >=1.0            >=10  <=50 for near-road micro-
                                          (Near-Road).                                                                          scale.
NO2 \3\ \4\ \5\........................  <= 300 m for Middle...........             2.0-15              >=1.0            >=10  See Table E-4 of this
                                                                                                                                appendix.
NO2 \3\ \4\ \5\........................  <= 1.0 km for Neighborhood,                2.0-15              >=1.0            >=10  See Table E-4 of this
                                          Urban, and Regional.                                                                  appendix.

[[Page 103657]]

 
PAMS \3\ \4\ \5\ Ozone precursors......  <= 1.0 km for Neighborhood and             2.0-15              >=1.0            >=10  See Table E-4 of this
                                          Urban.                                                                                appendix.
--------------------------------------------------------------------------------------------------------------------------------------------------------
N/A--Not applicable.
\1\ Monitoring path for open path analyzers is applicable only to middle or neighborhood scale CO monitoring, middle, neighborhood, urban, and regional
  scale NO2 monitoring, and all applicable scales for monitoring SO2, O3, and O3 precursors.
\2\ When the monitoring path is located on a rooftop, this separation distance is in reference to walls, parapets, or penthouses located on roof.
\3\ At least 90 percent of the monitoring path should be greater than 20 meters from the dripline of tree(s) and must be 10-meters from the dripline.
\4\ Distance from 90 percent of monitoring path to obstacle, such as a building, must be at least twice the height the obstacle protrudes above the
  monitoring path. Sites not meeting this criterion may be classified as microscale or middle scale (see text).
\5\ Must have unrestricted airflow 270 degrees around at least 90 percent of the monitoring path; 180 degrees if the monitoring path is adjacent to the
  side of a building or a wall for street canyon monitoring.
\6\ The monitoring path should be away from minor sources, such as furnace or incineration flues. The separation distance is dependent on the height of
  the minor source's emission point (such as a flue), the type of fuel or waste burned, and the quality of the fuel (sulfur, ash, or lead content). This
  criterion is designed to avoid undue influences from minor sources.
\7\ For microscale CO monitoring sites, the monitoring path must be >=10. meters from a street intersection and preferably at a midblock location.
\8\ All distances listed are expressed as having 2 significant figures. When rounding is performed to assess compliance with these siting requirements,
  the distance measurements will be rounded such as to retain at least two significant figures.
\9\ See section 1.2 of appendix D to this part for definitions of monitoring scales.
\10\ See section 3.7 of this appendix.

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[FR Doc. 2024-29223 Filed 12-18-24; 8:45 am]
BILLING CODE 6560-50-P`