Determination of Attainment by the Attainment Date and Clean Data Determination for the 2012 Annual Fine Particulate Standard; Plumas County, California
The Environmental Protection Agency (EPA) is proposing to determine that the Portola nonattainment area in Plumas County, California, attained the 2012 annual fine particulate m...
The Environmental Protection Agency (EPA) is proposing to determine that the Portola nonattainment area in Plumas County, California, attained the 2012 annual fine particulate matter (“PM2.5
”) national ambient air quality standard (NAAQS or “standard”) by the December 31, 2025 “Serious” area attainment date. This proposed determination is based on ambient air quality monitoring data from 2023 through 2025. We are also proposing to make a clean data determination (CDD) based on the 2023 through 2025 data. If we finalize this CDD, certain Clean Air Act (CAA) requirements that apply to the Portola nonattainment area will be suspended for so long as the area continues to meet the 2012 annual PM2.5
NAAQS. The area would remain designated nonattainment for the 2012 annual PM2.5
NAAQS, unless and until the State submits, and EPA approves, a redesignation request and maintenance plan for the area. We are taking comments on this proposal and plan to follow with a final action.
DATES:
Comments must be received on or before June 15, 2026.
ADDRESSES:
Submit your comments, identified by Docket ID No. EPA-R09-OAR-2026-2608 at
https://www.regulations.gov.
For comments submitted at
Regulations.gov, follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from
( printed page 27225)
Regulations.gov. The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission (
i.e.,
on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the
FOR FURTHER INFORMATION CONTACT
section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit
https://www.epa.gov/dockets/commenting-epa-dockets.
If you need assistance in a language other than English or if you are a person with a disability 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:
Lindsay Wickersham, Planning Section (AIR-2-1), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105; telephone number: (415) 947-4192; email address:
wickersham.lindsay@epa.gov.
SUPPLEMENTARY INFORMATION:
Throughout this document, “we,” “us,” and “our” refer to the EPA.
Table of Contents
I. Background
A. The 2012 Annual PM2.5
NAAQS
B. CAA Requirements for PM2.5
Nonattainment Areas
C. Portola Nonattainment Area Designation for the 2012 PM2.5
NAAQS and SIP Actions
D. CAA Requirement for a Determination of Attainment
E. The EPA's Clean Data Policy
II. Proposed Determination of Attainment
A. Applicable Statutory and Regulatory Provisions
B. Monitoring Network Review, Quality Assurance, and Data Completeness
H. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks
I. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use
J. National Technology Transfer and Advancement Act (NTTAA)
I. Background
A. The 2012 Annual PM2.5
NAAQS
Under section 109 of the CAA, the EPA has established NAAQS for certain pervasive air pollutants (referred to as “criteria pollutants”) and conducts periodic reviews of the NAAQS to determine whether they should be revised or whether new NAAQS should be established. The EPA established these standards after considering substantial evidence from numerous health studies demonstrating that serious adverse health effects are associated with exposures to these criteria pollutants.[1]
Particulate matter includes particles with diameters that are generally 2.5 microns or smaller (PM2.5), and particles with diameters that are generally 10 microns or smaller (PM10). PM2.5
can be emitted by sources directly into the atmosphere as a solid or liquid particle (“primary PM2.5
” or “direct PM2.5
”) or can be formed in the atmosphere (“secondary PM2.5
”) as a result of various chemical reactions among precursor pollutants such as nitrogen oxides, sulfur dioxide, volatile organic compounds, and ammonia.[2]
Epidemiological studies have shown statistically significant correlations between elevated PM2.5
levels and detrimental effects to human health and the environment. The health effects associated with PM2.5
exposure include changes in lung function resulting in the development of respiratory symptoms, aggravation of existing respiratory conditions, and cardiovascular disease (as indicated by increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days), and premature mortality. Individuals particularly sensitive to PM2.5
exposure include older adults, people with heart and lung disease, and children.[3]
Elevated PM2.5
levels also have adverse secondary effects such as visibility impairment and damage to vegetation and ecosystems.
On July 18, 1997, the EPA first established annual and 24-hour NAAQS for PM2.5
.[4]
The annual primary and secondary standards were set at 15.0 micrograms per cubic meter (µg/m[3]
) based on a 3-year average of annual mean PM2.5
concentrations. Then, on January 15, 2013, the EPA promulgated a more stringent annual PM2.5
NAAQS, revising the primary standard to 12.0 µg/m[3]
based on a 3-year average of annual mean PM2.5
concentrations, while retaining the secondary standard at 15.0 µg/m[3]
.[5]
B. CAA Requirements for PM2.5
Nonattainment Areas
The CAA requires states to develop state implementation plan (SIP) revisions that provide generally for the attainment, maintenance, and enforcement of the NAAQS. In addition, the CAA requires states to make a specific type of SIP submittal, a nonattainment plan submittal, that imposes additional controls for purposes of attaining the PM2.5
NAAQS, to achieve reductions of PM2.5
and PM2.5
precursor emissions.
The general CAA part D nonattainment area planning requirements are found in subpart 1 and the nonattainment area planning requirements specific to particulate matter are found in subpart 4. The subpart 1 statutory requirements for attainment plans include the following: the section 172(c)(1) requirements for reasonably available control measures, including reasonably available control technology (RACM/RACT), and attainment demonstrations; the section 172(c)(2) requirement to demonstrate reasonable further progress (RFP); the section 172(c)(3) requirement for emissions inventories; the section 172(c)(5) requirements for a nonattainment new source review (NNSR) permitting program; and the section 172(c)(9) requirement for contingency measures.
The more specific subpart 4 statutory requirements for Moderate PM2.5
( printed page 27226)
nonattainment areas include the following: the section 189(a)(1)(A) NNSR permit program requirements; the section 189(a)(1)(B) requirements for attainment demonstrations; the section 189(a)(1)(C) requirements for RACM/RACT; the section 189(c) requirements for RFP and quantitative milestones; and the section 189(e) requirement for controls on sources of particulate matter precursors.
Under subpart 4, states with Moderate PM2.5
nonattainment areas must provide for attainment in the area as expeditiously as practicable but no later than the end of the sixth calendar year after designation. For the 2012 PM2.5
annual NAAQS, this date was December 31, 2021. In addition, under subpart 4, direct PM2.5
and all precursors to the formation of PM2.5
are subject to control unless the EPA approves a demonstration from the state establishing that a given precursor does not contribute significantly to PM2.5
levels that exceed the PM2.5
NAAQS in the area.[6]
To implement the PM2.5
NAAQS, the EPA has also promulgated the “Fine Particle Matter National Ambient Air Quality Standard: State Implementation Plan Requirements; Final Rule” (“PM2.5
Implementation Rule”).[7]
The PM2.5
Implementation Rule provides additional regulatory requirements and guidance applicable to attainment plan submittals for the PM2.5
NAAQS, including the 2012 annual PM2.5
NAAQS at issue in this action.
C. Portola Nonattainment Area Designation for the 2012 PM2.5
NAAQS and SIP Actions
Following promulgation of new or revised NAAQS, the EPA is required under CAA section 107(d) to designate regions throughout the nation as attaining or not attaining these NAAQS. Those regions found not to be attaining the NAAQS are also given a classification that reflects the degree of nonattainment. Under subpart 4 of part D of title I of the CAA, the EPA designates areas found to be violating the PM2.5
NAAQS, and areas that contribute to such violations, as nonattainment and classifies them initially as Moderate nonattainment areas.
Effective January 15, 2015, the EPA designated the Portola nonattainment area [8]
for the 2012 PM2.5
NAAQS based on ambient monitoring data that showed the area was above the 12.0 µg/m[3]
primary standard for the three-year 2011-2013 monitoring period.[9]
For this 2011-2013 monitoring period, the annual PM2.5
design value [10]
for the Portola nonattainment area was 12.8 µg/m[3]
at the Portola PM2.5
monitoring site.[11]
This Moderate nonattainment designation and classification required the state of California to submit an attainment plan for the Portola nonattainment area, in accordance with the requirements of CAA sections 172(c) and 189(a), (c), and (e), demonstrating attainment of the NAAQS as expeditiously as practical but no later than the end of the sixth calendar year following the designation, or December 31, 2021.
Under state law, the local air district with the primary responsibility for developing a plan to attain the 2012 annual PM2.5
NAAQS in this area is the Northern Sierra Air Quality Management District (NSAQMD or “District”). The District worked with the California Air Resources Board (CARB) in preparing the plan. On February 28, 2017, California submitted the “Portola Fine Particulate Matter (PM2.5) Attainment Plan” (“Portola PM2.5
Plan”) to address the CAA's Moderate nonattainment area requirements for the 2012 annual PM2.5
NAAQS. On March 25, 2019, the EPA fully approved the Portola PM2.5
Plan, except for the contingency measure elements.[12]
California later submitted a revision to the Portola PM2.5
Plan (“PM2.5
Plan Revision”), which included a contingency measure adopted in an ordinance by the City of Portola.
On April 2, 2021, the EPA took final action to approve the PM2.5
Plan Revision.[13]
We also found that the contingency measure element of the Portola PM2.5
Plan, as revised and supplemented by the PM2.5
Plan Revision, satisfied the requirements for contingency measures in CAA section 172(c)(9) and 40 CFR 51.1014 for purposes of the 2012 PM2.5
NAAQS in the Portola nonattainment area.[14]
On December 29, 2022, the EPA determined that the Portola nonattainment area did not attain the 2012 annual PM2.5
NAAQS by its applicable Moderate area attainment date of December 31, 2021.[15]
Pursuant to CAA section 188(b)(2), the Portola nonattainment area was reclassified as a Serious PM2.5
nonattainment area effective January 30, 2023.
On December 24, 2024, CARB submitted the “Portola Fine Particulate Matter (PM2.5) Serious State Implementation Plan” to address the Serious area requirements for the Portola nonattainment area.
D. CAA Requirement for a Determination of Attainment
Sections 179(c) and 188(b)(2) of the CAA require that within six months following the applicable attainment date, the EPA shall determine whether a nonattainment area attained the standard by that date. The Serious attainment date for the 2012 PM2.5
NAAQS in the Portola nonattainment area was December 31, 2025. Therefore, the determination of whether the area attained by the Serious attainment date is based on the 2023-2025 design value. Section 179(c)(2) of the CAA requires the EPA to publish the determination in the
Federal Register
no later than 6 months after the attainment date, that is, in the case of the Portola nonattainment area, by June 30, 2026.
E. The EPA's Clean Data Policy
Under the EPA's longstanding Clean Data Policy, which was codified in the PM2.5
Implementation Rule at 40 CFR 51.1015, when an area has attained the relevant PM2.5
standard(s), the EPA may issue a CDD (also sometimes referred to as a determination of attainment for the purposes of the Clean Data Policy) after notice and comment rulemaking determining that a specific area is attaining the relevant standard(s). A CDD is not linked to any particular attainment deadline and is not necessarily equivalent to a determination that an area has attained the standard by its applicable attainment deadline (
i.e.,
a DAAD).
The effect of a CDD for a Serious PM2.5
nonattainment area is to suspend the requirements for the area to submit an attainment demonstration, RFP plan, quantitative milestones and quantitative milestone reports, and contingency measures for as long as the area continues to attain the standard.[16]
A
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CDD does not suspend the requirements for an emissions inventory, for new source review, or for BACM/BACT in a Serious PM2.5
nonattainment area.
II. Proposed Determination of Attainment
A. Applicable Statutory and Regulatory Provisions
Sections 179(c)(1) of the CAA requires the EPA to determine whether a nonattainment area attained by the applicable attainment date, based on the area's air quality “as of the attainment date.” [17]
Generally, this determination of whether an area's air quality meets the PM2.5
standard(s) is based upon the most recent three years of complete, certified data gathered at eligible monitoring sites in accordance with 40 CFR part 58.[18]
The requirements of 40 CFR part 58 include quality assurance procedures for monitor operation and data handling, siting parameters for instruments or instrument probes, and minimum ambient air quality monitoring network requirements. State, local, or Tribal agencies operating air monitoring sites, in accordance with 40 CFR part 58, must enter the ambient air quality data and associated quality assurance data from these sites into the EPA's Air Quality System (AQS) database.[19]
These monitoring agencies certify annually that these data are accurate to the best of their knowledge, taking into consideration the quality assurance findings.[20]
Accordingly, the EPA relies primarily on AQS data when determining the attainment status of an area. In determining whether data are suitable for regulatory determinations, the EPA uses a “weight of evidence” approach, considering the requirements of 40 CFR part 58, appendix A “in combination with other data quality information, reports, and similar documentation that demonstrate overall compliance with 40 CFR part 58.” [21]
The 2012 primary annual PM2.5
standard is met when the three year average of the annual arithmetic mean concentration, as determined in accordance with 40 CFR part 50, appendix N, is less than or equal to 12.0 µg/m[3]
at each eligible monitoring site.[22]
For the annual PM2.5
standard, eligible monitoring sites are those monitoring stations that meet the criteria specified in 40 CFR 58.11 and 58.30, and thus are approved for comparison to the annual PM2.5
NAAQS.[23]
Three years of valid annual means are required to produce a valid annual PM2.5
NAAQS design value.[24]
Data completeness requirements for a given year are met when at least 75 percent of the scheduled sampling days for each quarter have valid data.[25]
B. Monitoring Network Review, Quality Assurance, and Data Completeness
The Portola monitoring site (AQS ID: 06-063-1010) is the only regulatory PM2.5
monitoring site in the Portola nonattainment area and is operated by the District. CARB serves as the primary quality assurance organization (PQAO) and submits annual monitoring network plans to the EPA documenting the status of CARB's air monitoring network, including monitors operated by NSAQMD and other local air districts, as required under 40 CFR 58.10.[26]
The EPA reviews these annual network plans for compliance with specific requirements in 40 CFR part 58. With respect to the Portola nonattainment area, we have found that the annual network plans submitted by CARB meet these requirements under 40 CFR part 58, including minimum monitoring requirements.[27]
In accordance with 40 CFR 58.15, the District certifies annually that the previous year's ambient concentration and quality assurance data are completely submitted to AQS and that the ambient concentration data are accurate to the best of their knowledge, taking into consideration the quality assurance findings.[28]
Along with the certification letters, the District submits a summary of the precision and accuracy data for all ambient air quality data.[29]
The Design Value Report also includes a validity indicator that reflects whether the design value is valid (
i.e.,
calculated using data that meet the applicable completeness criteria). For the purposes of this proposal, we reviewed the certified ambient data for the 2023-2025 monitoring period for completeness and determined that the PM2.5
data collected by the District met the 75 percent completeness criterion for all 12 quarters at the Portola monitoring site.
Finally, the EPA conducts regular technical systems audits (TSAs) of state and local ambient air monitoring programs to assess compliance with applicable regulations concerning the collection, analysis, validation, and reporting of ambient air quality data. Additionally, CARB conducts regular TSAs of local ambient air monitoring programs within their PQAO. For the purposes of this proposal, we reviewed the findings from the EPA's 2022 TSA of CARB's ambient air monitoring program.[30]
None of the findings from the 2022 TSA were cause for invalidation of any data from the Portola PM2.5
monitoring site.[31]
We also reviewed the findings of CARB's TSA of the District in May 2024.[32]
The results of the TSA do not preclude the EPA from using the data for determining whether the Portola nonattainment area has attained the 2012 annual PM2.5
NAAQS.
In summary, based on the relevant annual monitoring network plans, certifications, and 2022 TSA, we propose to find that the PM2.5
data collected at the Portola monitoring site are suitable for determining whether the Portola nonattainment area attained the 2012 annual PM2.5
NAAQS by the applicable attainment date.
C. The EPA's Evaluation of Attainment
Table 1 provides the PM2.5
design value from the regulatory monitor within the Portola nonattainment area, expressed as a single design value representing the average of the annual
( printed page 27228)
mean values from the 2023-2025 period; the annual mean for each individual year is also listed. The PM2.5
data show that the design value at the Portola monitoring site was 11.3 µg/m3
, which meets the 2012 annual PM2.5
NAAQS of 12.0 µg/m3
. Consequently, the EPA proposes to determine based upon three years of complete, quality-assured and certified data from 2023 through 2025, that the Portola nonattainment area attained the 2012 annual PM2.5
NAAQS by the applicable Serious attainment date of December 31, 2025.
Table 1—2023-2025 Annual PM
2.5
Design Value for the Portola Nonattainment Area
Monitoring site
AQS site ID #
Annual weighted mean
(µg/m3
)
2023-2025
annual design
value
(µg/m3
)
2023
2024
2025
Portola
06-063-1010
11.9
11.3
10.7
11.3
Source: EPA AQS Design Value Report, AMP480, dated March 31, 2026. (Report Request ID: 2367374).
III. Proposed Clean Data Determination
As described in section I.E of this document, when an area has attained the relevant PM2.5
standard(s), the EPA may issue a CDD after notice and comment rulemaking determining that a specific area is attaining the relevant standard.[33]
As described in section II.C, based on complete, quality-assured, and certified data for 2023-2025, the Portola nonattainment area meets the 2012 annual PM2.5
standard. Consequently, the EPA is proposing to issue a CDD under 40 CFR 51.1015(b).
If we finalize this proposed CDD, the requirements for the State to submit an attainment demonstration, an RFP plan, quantitative milestones and quantitative milestone reports, and contingency measures for the area will be suspended until such time as: (1) the area is redesignated to attainment, after which such requirements are permanently discharged; or, (2) the EPA determines that the area has re-violated the 2012 PM2.5
NAAQS, after which time the state shall submit such attainment plan elements for the Serious nonattainment area by a future date to be determined by the EPA and announced through publication in the
Federal Register
at the time the EPA determines the area is violating the 2012 PM2.5
NAAQS.[34]
The requirements to submit emissions inventories and an NNSR permitting program for the Serious nonattainment area will remain in effect.
IV. The EPA's Proposed Action
For the reasons discussed in this document, the EPA is proposing to determine, based on the most recent three years (2023-2025) of complete, quality-assured, and certified data that the Portola nonattainment area attained the 2012 annual PM2.5
NAAQS by its December 31, 2025 attainment date. This action, when finalized, will fulfill the EPA's statutory obligation to determine whether the Portola nonattainment area attained the NAAQS by the attainment date.
We are also proposing a CDD under 40 CFR 51.1015(b). If the EPA finalizes this proposal, the requirements for this area to submit an attainment demonstration, RFP plan, quantitative milestones and quantitative milestone reports, and contingency measures, for the 2012 annual PM2.5
NAAQS, will be suspended so long as this area continues to meet the standard. This CDD does not constitute a redesignation to attainment. The Portola nonattainment area will remain designated nonattainment for the 2012 annual PM2.5
NAAQS until such time as the EPA determines, pursuant to sections 107 and 175A of the CAA, that the Portola nonattainment area meets the CAA requirements for redesignation to attainment, including an approved maintenance plan showing that the area will continue to meet the standard for 10 years.
This action is not a significant regulatory action and was therefore not submitted to the Office of Management and Budget (OMB) for review. This action proposes to issue a DAAD and CDD for the Portola nonattainment area.
This action does not impose an information collection burden under the PRA. This action proposes to determine that the Portola nonattainment area is attaining the 2012 PM2.5
NAAQS. Thus, this proposed action does not impose additional requirements beyond those imposed by state law.
D. 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 beyond those imposed by state law. The proposed DAAD and CDD do not create any new requirements and does not directly regulate any entities.
E. Unfunded Mandates Reform Act (UMRA)
This action does not contain any unfunded mandate as described in UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect small governments. This action does not impose additional requirements beyond those imposed by state law. Accordingly, no additional costs to state, local, or Tribal governments, or to the private sector, will result from this action.
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. Pursuant to the CAA, this action proposes a DAAD and CDD.
This action does not have Tribal implications as specified in Executive Order 13175. As there are no federally recognized Tribes within the Portola
( printed page 27229)
nonattainment area,[35]
the proposed DAAD and CDD not apply to Tribal areas, and the proposed rule would not impose a burden on Indian reservation lands or other areas where the EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction within the Portola nonattainment area. Thus, this proposed rule does not have Tribal implications and will not impose substantial direct costs on Tribal governments or preempt Tribal law as specified by Executive Order 13175.
H. 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. Therefore, this action is not subject to Executive Order 13045 because it merely proposes a DAAD and CDD. Furthermore, the EPA's Policy on Children's Health does not apply to this action.
I. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use
J. National Technology Transfer and Advancement Act (NTTAA)
Section 12(d) of the NTTAA directs the EPA to use voluntary consensus standards in its regulatory activities unless to do so would be inconsistent with applicable law or otherwise impractical. The EPA believes that this action is not subject to the requirements of section 12(d) of the NTTAA because application of those requirements would be inconsistent with the CAA.
1.
For a given air pollutant “primary” NAAQS are those determined by the EPA as requisite to protect the public health, allowing an adequate margin of safety, and “secondary” standards are those determined by the EPA as requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of such air pollutant in the ambient air. See CAA section 109(b).
4.
62 FR 38652 (July 18, 1997). In October 2006, the EPA lowered the 24-hour NAAQS for PM2.5
from 65 micrograms per cubic meter (µg/m3.
) to 35 µg/m3.
. 71 FR 61144 (October 17, 2006).
5.
78 FR 3086 (January 15, 2013) and 40 CFR 50.18. Unless otherwise noted, all references to the PM2.5
NAAQS in this document are to the 2012 annual NAAQS of 12.0 µg/m3.
, codified at 40 CFR 50.18.
10.
A design value is the three-year average NAAQS metric that is compared to the NAAQS level to determine when a monitoring site meets or does not meet the NAAQS. The specific methodologies for calculating whether the annual PM2.5
NAAQS is met at each eligible monitoring site in an area are found in 40 CFR part 50, appendix N, section 4.1.
11.
From 2000 through early 2013, the Portola PM2.5
monitoring site was located at 161 Nevada Street. In 2013, the site was relocated to 420 Gulling Street where it remains to date.
16.
40 CFR 51.1015. In the context of CDDs, the EPA distinguishes between attainment planning requirements of the CAA, which relate to the
attainment demonstration for an area and related control measures designed to bring an area into attainment for the given NAAQS as expeditiously as practicable, and other types of requirements, such as permitting requirements under the nonattainment new source review program, emissions inventory requirement, and specific control requirements independent of those strictly needed to ensure timely attainment of the given NAAQS. 81 FR 58010, 58128.
17.
See also
CAA section 188(b)(2) (“Within 6 months following the applicable attainment date for a PM-10 nonattainment area, the Administrator shall determine whether the area attained the standard by that date.”)
28.
We have included NSAQMD's annual data certifications for 2023, 2024, and 2025 in the docket for this action. We have also included our reviews of NSAQMD's annual data certifications and the correspondence transmitting these reviews in the docket.
30.
Letter dated March 14, 2024, from Matthew Lakin, Director, Air and Radiation Division, EPA Region IX, to Edie Chang, Executive Officer, CARB, with enclosure titled “Technical Systems Audit of the Ambient Air Monitoring Program: California Air Resources Board December 2021-August 2022” (Final Report dated March 2024).
32.
Letter dated April 21, 2026, from Manisha Singh, Chief, Quality Management Branch, CARB, to Julie Hunter, Air Pollution Control Officer, Northern Sierra Air Quality Management District, with enclosure titled “Technical Systems Audit of Northern Sierra Air Quality Management District” (April 2026).
Use this for formal legal and research references to the published document.
91 FR 27224
Web Citation
Suggested Web Citation
Use this when citing the archival web version of the document.
“Determination of Attainment by the Attainment Date and Clean Data Determination for the 2012 Annual Fine Particulate Standard; Plumas County, California,” thefederalregister.org (May 14, 2026), https://thefederalregister.org/documents/2026-09604/determination-of-attainment-by-the-attainment-date-and-clean-data-determination-for-the-2012-annual-fine-particulate-sta.