07-2201. Ambient Air Monitoring Regulations: Correcting and Other Amendments

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Direct final rule.

SUMMARY:

The EPA is taking direct final action on “Ambient Air Monitoring Regulations: Correcting and Other Amendments” to correct and clarify parts of a recent final rule published on October 17, 2006, that amended the ambient air monitoring requirements for criteria pollutants. These errors included several instances where the wording in the preamble and regulatory text were not completely consistent, several regulatory text passages that contained some imprecise language, two instances of regulatory text omission, an outdated address reference, and numerous publication errors in tables and equations. EPA is also amending the monitoring rule to allow EPA Regional Administrators to approve departures from the minimum number of PM₁₀ monitors otherwise specified in the rule.

The October 17, 2006, final rule revised requirements for reference and equivalent method determinations, modified requirements for general monitoring network design, and modified other requirements pertaining to quality assurance, annual network plans and assessments, data reporting, monitoring methodology, and probe and monitor siting criteria. All other preamble and regulatory text printed in the October 17, 2006, final rule is correct.

DATES:

This rule is effective on September 10, 2007, without further notice, unless EPA receives adverse comment by July 12, 2007. If we receive adverse comment, we will publish a timely withdrawal in the Federal Register informing the public that some or all of the amendments in this rule will not take effect.

ADDRESSES:

Submit your comments, identified under Docket ID No. EPA-HQ-OAR-2004-0018 by one of the following methods:

• www.regulations.gov. Follow the on-line instructions for submitting comments.
• E-mail: [e-mail].
• Fax: [phone].
• Mail: Ambient Air Monitoring Regulations: Correcting and Other Amendments, Environmental Protection Agency, Mailcode: 6102T, 1200 Pennsylvania Avenue, NW., Washington, DC 20460. Please include a total of 2 copies.
• Hand Delivery: EPA Docket Center, 1301 Constitution Avenue, NW., Room 3334, Washington, DC. Such deliveries are only accepted during the Docket's normal hours of operation, and special arrangements should be made for deliveries of boxed information.

Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-2004-0018. The EPA's policy is that all comments received will be included in the public docket without change and may be made available online at: www.regulations.gov including any personal information provided, unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through www.regulations.gov or e-mail. The www.regulations.gov website is an “anonymous access” system, which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an e-mail comment directly to EPA without going through www.regulations.gov,, your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the internet. If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses.

Docket: All documents in the docket are listed in the www.regulations.gov index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in www.regulations.gov or in hard copy at the Revisions to the Ambient Air Monitoring Regulations Docket, EPA/DC, EPA West, Room 3334, Constitution Ave., NW., Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is [phone], and the telephone number for the Air Docket is [phone].

FOR FURTHER INFORMATION CONTACT:

Mr. Lewis Weinstock, Air Quality Assessment Division (C304-06), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: [phone]; fax number: [phone]; e-mail address: [e-mail].

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Why Is EPA Using a Direct Final Rule?

II. Does This Action Apply to Me?

III. Judicial Review

IV. Authority

V. Overview of the October 17, 2006 Rule Changes

VI. This Action

A. Correction to Special Purpose Monitors

B. Clarification to Requirement for Collocating Required Continuous Fine Particle (PM_2.5) Monitors

C. Clarification to Operating Schedule Requirements for Filter-Based Manual PM_2.5 Samplers

D. Standard versus Daylight Savings Time Reference

E. Corrections to Regulatory Text on Particulate Matter (PM₁₀) Network Design Criteria

F. Additional Regional Administrator Flexibility in Applying PM₁₀ Minimum Monitoring Requirements

G. Correction to Division Name and Address Reference

H. Clarification to Conditions for Waiving Regional Administrator Comment Period on Submitted Annual Monitoring Network Plans

I. Typographical Corrections

VII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

B. Paperwork Reduction Act

C. Regulatory Flexibility Act

D. Unfunded Mandates Reform Act

E. Executive Order 13132: Federalism

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

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

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

I. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use

J. National Technology Transfer Advancement Act

K. Congressional Review Act

I. Why Is EPA Using a Direct Final Rule?

The EPA is publishing this rule without a prior proposed rule because we view this as a non-controversial action and anticipate no adverse comment. None of the proposed changes creates additional regulatory requirements on affected entities compared to those that were promulgated in the final rule that was published in the Federal Register on October 17, 2006. However, in the “Proposed Rules” section of this Federal Register, we are publishing a separate document that will serve as the proposed rule to make corrections to the Ambient Air Monitoring Regulations if relevant adverse comments are received on one or more of the amendments in this direct final rule as described in sections VI.A. through VI.I of this preamble. We will not institute a second comment period on this action. Any parties interested in commenting must do so at this time. For further information about commenting on this rule, see the ADDRESSES section of this document. If EPA receives relevant adverse comment on one or more of the amendments included in this rulemaking, we will publish a timely withdrawal in the Federal Register indicating which amendment or amendments we are withdrawing. The provisions that are not withdrawn will become effective on the date set out above, notwithstanding any relevant adverse comment on any other provision.

II. Does This Action Apply to Me?

Categories and entities potentially regulated by this action include:

Category	NAICS code 1	Examples of regulated entities
Industry	334513 541380	Manufacturer, supplier, distributor, or vendor of ambient air monitoring instruments; analytical laboratories or other monitoring organizations that elect to submit an application for a reference or equivalent method determination under 40 CFR part 53.
Federal Government	924110	Federal agencies (that conduct ambient air monitoring similar to that conducted by States under 40 CFR part 58 and that wish EPA to use their monitoring data in the same manner as State data) or that elect to submit an application for a reference or equivalent method determination under 40 CFR part 53.
State/territorial/local/tribal government	924110	State, territorial, and local air quality management programs that are responsible for ambient air monitoring under 40 CFR part 58 or that elect to submit an application for a reference or equivalent method determination under 40 CFR part 53 or for an approved regional method approved under 40 CFR part 58 appendix C. The proposal also may affect Tribes that conduct ambient air monitoring similar to that conducted by States and that wish EPA to use their monitoring data in the same manner as State monitoring data.
1 North American Industry Classification System.

This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by this action. This table lists the types of entities that EPA is now aware could potentially be regulated by this action. Other types of entities not listed in the table could also be regulated. To determine whether your facility or Federal, State, local, tribal, or territorial agency is regulated by this action, you should carefully examine the requirements for reference or equivalent method determinations in 40 CFR part 53, subpart A (General Provisions) and the applicability criteria in 40 CFR 51.1 of EPA's requirements for State Implementation Plans (SIPs). If you have questions regarding the applicability of this action to a particular entity, consult the person listed in the preceding FOR FURTHER INFORMATION CONTACT section.

III. Judicial Review

Under section 307(b)(1) of the Clean Air Act (CAA), judicial review of the direct final rule amendments is available only by filing a petition for review in the U.S. Court of Appeals for the District of Columbia by August 13, 2007. Under section 307(d)(7)(B) of the CAA, only an objection to the direct final rule amendments that was raised with reasonable specificity during the period for public comment can be raised during judicial review. Moreover, under section 307(b)(2) of the CAA, the requirements established by the direct final rule amendments may not be challenged separately in any civil or criminal proceedings brought by EPA to enforce these requirements.

IV. Authority

The EPA rules for ambient air monitoring are authorized under sections 110, 301(a), and 319 of the CAA. Section 110(a)(2)(B) of the CAA requires that each SIP provide for the establishment and operation of devices, methods, systems, and procedures needed to monitor, compile, and analyze data on ambient air quality and for the reporting of air quality data to EPA. Section 103 authorizes, among others, research and investigations relating to the causes, effects, extent, prevention and control of air pollution. Section 301(a) of the CAA authorizes EPA to develop regulations needed to carry out EPA's mission and establishes rulemaking requirements. Uniform criteria to be followed when measuring air quality and provisions for daily air pollution index reporting are required by CAA section 319.

V. Overview of the October 17, 2006 Rule Changes

On October 17, 2006 (71 FR 61236), EPA amended the rules for ambient air monitoring of criteria pollutants. The rule amendments established limited ambient air monitoring requirements for particles between 2.5 and 10 micrometers (μm) in diameter (PM_10-2.5) to support continued research into these particles' distribution, sources, and health effects. The rule amendments required each State to operate one to three “NCore” monitoring stations that will take an integrated, multipollutant approach to ambient air monitoring. In addition, the rule amendments modified the general monitoring network design requirements for minimum numbers of ambient air monitors to focus on populated areas with air quality problems and to reduce significantly the requirements for criteria pollutant monitors that have measured ambient air concentrations well below the applicable National Ambient Air Quality Standards. The rule amendments also revised certain provisions regarding monitoring network descriptions and periodic assessments, quality assurance, and data certifications. A number of the amendments related specifically to monitoring of fine particles (referring to particles less than or equal to 2.5 μm in diameter, PM_2.5), revising the requirements for reference and equivalent method determinations (including specifications and test procedures) for fine particle monitors.

VI. This Action

EPA is taking the following actions:

• Correcting a statement in the regulatory text pertaining to the potential comparability of data collected from Special Purpose Monitors (SPM) with approved alternative quality assurance plans to the National Ambient Air Quality Standards (NAAQS).
• Correcting a statement in the preamble with regard to the requirement for collocating required continuous PM_2.5 monitors and clarifying associated regulatory text.
• Clarifying several ambiguous regulatory text passages pertaining to operating schedules for manual PM_2.5 samplers.
• Correcting a reference regarding standard versus daylight savings time.
• Restoring two instances of regulatory text that were inadvertently omitted from the network design for monitoring particles less than or equal to 10 μm in diameter (PM₁₀).
• Adding authority for the Regional Administrator, consistent with the authority that already exists for PM_2.5 and ozone, to allow monitoring agencies to deviate from PM₁₀ monitoring requirements.
• Updating an organizational address reference within regulatory text pertaining to quality assurance requirements.
• Clarifying the conditions when the EPA Regional Administrator is not required to offer a public comment opportunity prior to approving a State's annual monitoring network plan.
• Correcting numerous typographical errors in tables and equations.

A. Correction to Special Purpose Monitors

The intent of 40 CFR 58.20(c) (published at 71 FR 61302) was to describe the conditions when data from an SPM using a Federal reference method (FRM), Federal equivalent method (FEM), or Approved Regional Method (ARM) which has operated for more than 24 months is eligible for comparison to the relevant NAAQS. The rule text states that all data from an SPM is eligible for comparison to the relevant NAAQS unless the data from the particular monitor came from a period when the requirements of appendix A to part 58 (Quality Assurance Requirements for SLAMS, SPMs, and PSD Air Monitoring) or an approved alternative, appendix C to part 58 (Ambient Air Quality Monitoring Methodology), or appendix E to part 58 (Probe and Monitoring Path Siting Criteria for Ambient Air Monitoring) were not met in practice. This text does not reflect EPA's actual intention. Instead, as discussed in the preamble (71 FR 61253), the intention of the October 17, 2006, final rule was that if the Regional Administrator approved an alternative quality assurance plan in place of the requirements of appendix A to part 58, the data from the affected SPM would not be eligible for comparison to the relevant NAAQS. The unintentional inclusion in the rule text of the phrase “or an approved alternative” implied that data from SPMs operating during a period when approved alternative quality assurance requirements were in effect, rather than appendix A requirements, would still be eligible for comparison to the relevant NAAQS.

The EPA provided the Regional Administrator with the authority to approve an alternative to the requirements of appendix A to part 58 with respect to SPM sites when meeting those requirements would be physically and/or financially impractical due to physical conditions at the monitoring site and the requirements were not essential to achieving the intended data objectives of the SPM site.

Therefore, EPA is clarifying the regulatory text by deleting the aforementioned words referencing alternative quality assurance plans. The corrected rule text 40 CFR 58.20(c) reads: “All data from an SPM using an FRM, FEM, or ARM which has operated for more than 24 months is eligible for comparison to the relevant NAAQS, subject to the conditions of § 58.30, unless the air monitoring agency demonstrates that the data came from a particular period during which the requirements of appendix A, appendix C, or appendix E to this part were not met in practice.”

B. Clarification to Requirement for Collocating Required Continuous Fine Particle (PM_2.5) Monitors

The regulatory text in 40 CFR part 58, appendix D (Network Design Criteria for Ambient Air Quality Monitoring), section 4.7.2 (71 FR 61322) describes the minimum requirements for operating continuous PM_2.5 analyzers.^[1] The text requires States to operate a minimum number of continuous PM_2.5 analyzers equal to at least one-half (round up) the minimum required FRM/FEM/ARM PM_2.5 sites listed in Table D-5 of appendix D to part 58. At least one required FRM/FEM/ARM PM_2.5 monitor in each MSA must be collocated with a continuous analyzer. For example, if a MSA had three required FRM/FEM/ARM PM_2.5 monitors, then two continuous monitors are required, and at least one of those continuous monitors must be collocated (placed at the same site) with one of the FRM/FEM/ARM PM_2.5 monitors. The second required continuous monitor could be collocated with one of the remaining two required FRM/FEM/ARM PM_2.5 monitors at another site, or be located at a separate site based on monitoring objectives. The EPA did not intend that the continuous analyzers required under section 4.7.2 be required to be collocated with each other.

The October 17, 2006, rule text matches our intended meaning. However, when referencing this rule requirement in the preamble (71 FR 61263), EPA incorrectly stated that the collocation requirement was adopted to address concerns about whether required continuous monitors needed to be collocated with a matching second continuous monitor, and that the final rule only required one of all the required PM_2.5 continuous monitors in each MSA to have “such a collocated match.” This unintentional statement could be construed as a requirement for collocating two continuous monitors with each other, in addition to the requirement for collocation with at least one required FRM/FEM/ARM monitor, leading to the conclusion that EPA was requiring three PM_2.5 monitors (two continuous, one filter-based) at the first required site, subject to the requirements of section 4.7.2. Moreover, it was not our intention to require a second continuous monitor be sited with an FEM or ARM that itself provides continuous data.

Therefore, EPA is clarifying the regulatory text to make clear the intentions described above. The EPA is also clarifying that an associated reference to quality assurance/quality control procedures refers to the continuous monitoring requirement by adding the words “for these required continuous analyzers.” The corrected provision of 40 CFR part 58, appendix D, section 4.7.2 now reads: “Requirement for Continuous PM_2.5 Monitoring. The State, or where appropriate, local agencies must operate continuous PM_2.5 analyzers equal to at least one-half (round up) the minimum required sites listed in Table D-5 of this appendix. At least one required continuous analyzer in each MSA must be collocated with one of the required FRM/FEM/ARM monitors, unless at least one of the required FRM/FEM/ARM monitors is itself a continuous FEM or ARM monitor, in which case no collocation requirement applies. State and local air monitoring agencies must use methodologies and quality assurance/quality control (QA/QC) procedures approved by the EPA Regional Administrator for these required continuous analyzers.”

C. Clarification to Operating Schedule Requirements for Filter-Based Manual PM_2.5 Samplers

The regulatory text in 40 CFR 58.12(d) (71 FR 61299) describes the required sampling frequency for manual filter-based PM_2.5 samplers. Manual PM_2.5 samplers at SLAMS stations must operate on at least a 1-in-3 day schedule at sites which do not also have a collocated continuously operating PM_2.5 monitor. For SLAMS PM_2.5 sites with both manual and continuous PM_2.5 monitors operating, other than NCore stations, monitoring agencies may request approval from the EPA Regional Administrator for a reduction to 1-in-6 day PM_2.5 sampling or for seasonal sampling. The EPA Regional Administrator may grant sampling frequency reductions after consideration of factors including, but not limited to, the historical PM_2.5 data quality assessments, the location of current PM_2.5 design value sites, and the regulatory data needs of States and EPA. The regulatory text provides specific criteria under which a manual PM_2.5 sampler at a SLAMS station cannot be exempted by the Regional Administrator from at least 1-in-3 day sampling, and also includes a separate provision describing when a daily sampling schedule is required. The textual length of 40 CFR 58.12(d)(1) as well as the specific wording of certain statements could create difficulty in understanding the intended operating schedule requirements for manual PM_2.5 samplers. Therefore, EPA is clarifying 40 CFR 58.12(d)(1) as described below.

The first sentence of 40 CFR 58.12(d)(1) stated that: “Manual PM_2.5 samplers at SLAMS stations other than NCore stations must operate on at least a 1-in-3 day schedule at sites without a collocated continuously operating PM_2.5 monitor.” This statement could be construed as meaning that manual PM_2.5 samplers at NCore stations were not required to maintain at least a 1-in-3 day schedule. The rule in fact does require manual PM_2.5 samplers at NCore stations to maintain at least a 1-in-3 day sampling schedule, as later noted in 40 CFR 58.12(d)(2), and these samplers are not eligible for sampling frequency relief. Therefore, EPA is clarifying the rule text by deleting the phrase “other than NCore stations” from first sentence of 40 CFR 58.12(d)(1).

Another potential ambiguity regarding the 1-in-3 day sampling frequency provision of 40 CFR 58.12(d)(1) is its geographic applicability. Since the regulatory language did not specify that the 1-in-3 day sampling frequency requirement be applied only in areas in which PM_2.5 monitoring is required, this requirement could be interpreted as applying to any manual PM_2.5 sampler within a State that recorded the highest design value “in an area” whether or not any PM_2.5 monitors were even required in that area according to 40 CFR part 58, appendix D. The EPA is concerned that such an interpretation would create a disincentive to monitoring by potentially requiring States that operated discretionary SLAMS monitors to sample on a 1-in-3 day frequency even though the monitor was in excess of minimum monitoring requirements. Therefore, the first sentence of 40 CFR 58.12(d)(1)(i) is amended to read: “Manual PM_2.5 samplers at required SLAMS stations without a collocated continuously operating PM_2.5 monitor must operate on at least a 1-in-3 day schedule.” In this rule text, “required SLAMS stations” refers to minimum monitoring requirements as specified in 40 CFR part 58, appendix D, section 4.7. It does not include SPMs; therefore SPMs are not required to sample on a 1-in-3 day schedule.

After stating the 1-in-3 day sampling requirement, the rule text at 40 CFR 58.12(d)(1)(ii) goes on to allow the Regional Administrator to grant a reduction of this schedule to 1-in-6 day for SLAMS PM_2.5 sites with both manual and continuous PM_2.5 monitors operating. In this context, the rule text contains a duplicated reference to SLAMS PM_2.5 sites; the second reference, “at SLAMS stations,” is removed in the corrected rule language since the opening part of the sentence already states the applicability of the provision to SLAMS PM_2.5 sites. The text goes on to describe two situations in which a manual PM_2.5 sampler at a required SLAMS station could not be granted sampling frequency relief by the Regional Administrator from the minimum 1-in-3 day sampling schedule. In the first situation, the phrase: “Sites that have design values that are within plus or minus 10 percent of the NAAQS” could be construed as applying to all sites within a particular area that have design values that are within plus or minus 10 percent of the NAAQS, when the intention was to apply the provision only to the site with the highest value in a particular area calculated in accordance with 40 CFR part 50, appendix N (Interpretation of the National Ambient Air Quality Standards for PM_2.5).^[2] In the second situation, the phrase: “and sites where the 24-hour values exceed the NAAQS for a period of 3 years are required to maintain at least a 1-in-3 day sampling frequency” created ambiguity about whether the provision was applicable in situations where a single 24-hour value exceeded the NAAQS at a particular site during only 1 or 2 years of a 3-year period. The EPA's intention was that at least one 24-hour value had to exceed the NAAQS in each of the years comprising the 3-year period situation for the provision to apply.

Also, the regulatory text could be construed as requiring 1-in-3 day manual PM_2.5 sampling at all sites within a particular area that have design values within the plus or minus 10 percent criteria, regardless of whether the site is required and regardless of the potential availability of continuous PM_2.5 FEM or ARM monitors which inherently would provide every-day data eligible for comparison to the NAAQS. The EPA anticipates the increasing availability of approved FEM and ARM methods over the next few years, and expects that many such approved continuous monitors will be deployed at sites formerly dedicated to manual filter-based FRM or FEM PM_2.5 samplers, including design value sites subject to the plus or minus 10 percent criteria when compared with the 24-hour PM_2.5 NAAQS. The EPA supports the deployment of approved FEM or ARM continuous PM_2.5 methods to meet appropriate monitoring objectives as such monitors become available, and thus we did not intend to require 1-in-3 day sampling utilizing manual PM_2.5 methods at design value sites, or any other sites, where monitoring agencies have deployed an approved continuous FEM or ARM.

The clarified language of the restriction related to being within plus or minus 10 percent of the NAAQS now reads: “Required SLAMS stations whose measurements determine the design value for their area and that are within plus or minus 10 percent of the NAAQS, and all required sites where one or more 24-hour values have exceeded the NAAQS each year for a consecutive period of at least 3 years, are required to maintain at least a 1-in-3 day sampling frequency. A continuously operating FEM or ARM PM_2.5 monitor satisfies this requirement.”

At the end of 40 CFR 58.12(d)(1), EPA specified that manual PM_2.5 samplers at sites that have a design value within plus or minus 5 percent of the daily PM_2.5 NAAQS must have an FRM or FEM operate on a daily schedule. As with the previously discussed phrasing in the context of the 1-in-3 day sampling requirement, this text could be construed as applying to all sites within a particular area that have design values that are within plus or minus 5 percent of the NAAQS, when the intention was to apply the provision only to the required SLAMS site with the highest value in a particular area. Also, the above described concern regarding the acceptability of continuous PM_2.5 analyzers applies in the case of this plus or minus 5 percent criterion, and a similar clarification to the rule text is appropriate.

Therefore, EPA is clarifying 40 CFR 58.12(d)(1) and for purposes of clarity is adding subparagraph (iii). It will read: “Required SLAMS sites whose measurements determine the design value for their area and that are within plus or minus 5 percent of the daily PM_2.5 NAAQS must have an FRM or FEM operate on a daily schedule. A continuously operating FEM or ARM PM_2.5 monitor satisfies this requirement.”

The EPA notes that only population-oriented monitors are subject to the previously described percent-dependent sampling frequency requirements. In 40 CFR 58.30 (Special Considerations for Data Comparisons to the NAAQS), sites must be population-oriented to be comparable to either the annual or daily PM_2.5 NAAQS. By implication, design value sites must be NAAQS comparable, therefore non-population oriented sites would not be affected by the plus or minus 10 percent or plus or minus 5 percent provisions.

As previously mentioned, EPA is aware that the length of 40 CFR 58.12(d)(1) creates the potential for ambiguity in the applicability of individual provisions related to sampling frequency requirements. To clarify the applicability of such provisions, EPA has restructured 40 CFR 58.12(d)(1) to create distinct paragraphs encompassing the previously described amended language applicable to SLAMS sites without continuously operating PM_2.5 monitors (now numbered 40 CFR 58.12(d)(1)(i)), SLAMS sites with both manual and continuous PM_2.5 monitors (now numbered 40 CFR 58.12(d)(1)(ii)), and design value sites within plus or minus 5 percent of the daily PM_2.5 NAAQS (now numbered 40 CFR 58.12(d)(1)(iii)).

In 40 CFR 58.12(d)(3), manual PM_2.5 speciation samplers at required Speciation Trends Network (STN) stations are required to operate on a1-in-3 day sampling frequency. The EPA intended the 1-in-3 day sampling frequency to be a minimum sampling frequency and not to imply a prohibition against a more frequent sampling frequency, such as a daily sampling frequency, if such a frequency is appropriate for specific monitoring objectives. Consistent with the phraseology of sampling frequency requirements elsewhere in the regulatory text, EPA is correcting the aforementioned phrase to read: “Manual PM_2.5 speciation samplers at STN stations must operate on at least a1-in-3 day sampling frequency.”

D. Standard versus Daylight Savings Time Reference

40 CFR 58.12(e) requires that the operating schedule for PM₁₀ samplers must be a 24-hour sampling period taken from midnight to midnight (local time) to ensure national consistency. In a 1999 EPA memorandum,^[3] the use of standard time versus daylight savings time is discussed in the context of sample collection for particulate matter monitors, concluding with the recommendation that monitoring agencies operate their particulate matter sampler clocks on standard time to avoid the semi-annual time-shift issues associated with conversion between standard time and daylight savings time. Monitoring agencies have generally adopted the practice of keeping their particulate matter sampler clocks on standard time since the issuance of the 1999 memorandum. It was EPA's intention to codify the practice of keeping particulate matter clocks on standard time in the October 17, 2006, Revisions to the Ambient Monitoring Regulations; however, the codifying rule text was inadvertently omitted for PM₁₀.^[4] If the aforementioned 40 CFR 58.12(e) reference to PM₁₀ operating schedule is left uncorrected, this could create inconsistent interpretation of the standard versus daylight savings time issue among monitoring agencies causing unnecessary confusion in the interpretation of the air quality data.

Therefore, EPA is correcting the reference to PM₁₀ operating schedules in 40 CFR 58.12(e) to read as follows: “For PM₁₀ samplers, a 24-hour sample must be taken from midnight to midnight (local standard time) to ensure national consistency.”

E. Corrections to Regulatory Text on Particulate Matter (PM₁₀) Network Design Criteria

In the preamble to the final monitoring rule (71 FR 61240), EPA stated an intention to retain the pre-existing minimum monitoring network design requirements for PM₁₀, which are based on the population of an MSA and its historical PM₁₀ air quality. The EPA's intention in finalizing the regulatory text in section 4.6, Particulate Matter (PM₁₀) Design Criteria, of 40 CFR part 58, appendix D (Network Design Criteria for Ambient Air Quality Monitoring) (71 FR 61320) was to retain all PM₁₀-relevant portions of the pre-existing regulatory text beginning with section 3.7, Particulate Matter Design Criteria for NAMS (see 62 FR 38820, July 18, 1997), with only minor changes necessary to maintain consistency of monitor type terminology (e.g., to eliminate obsolete references to National Air Monitoring Stations (NAMS)). The EPA inadvertently omitted several passages from the pre-existing regulatory text in section 3.7 referencing PM₁₀ network design criteria. If left uncorrected, these omissions could lead to misinterpretation of PM₁₀ monitoring network design requirements. Three specific textual corrections are detailed below.

First, in Table D-4, PM₁₀ Minimum Monitoring Requirements (Number of Stations per MSA), the word “Approximate” which had appeared in the title of the pre-existing Table 4 was omitted. Therefore, in order to retain the earlier language EPA is revising the title of Table D-4 to read: “PM₁₀ Minimum Monitoring Requirements (Approximate Number of Stations Per MSA).”

Second, the first footnote contains some words (“within the ranges shown in this table”) that were not part of the corresponding footnote to the pre-existing Table 4. Therefore, the first footnote is revised to read: “Selection of urban areas and actual numbers of stations per area will be jointly determined by EPA and the State Agency.”

Third, in paragraph (a) of section 4.6, the regulatory text notes that State, and where applicable local, agencies must operate the minimum number of required PM₁₀ SLAMS sites listed in Table D-4 of appendix D. In the October 17, 2006, rulemaking, EPA intended to retain all of the pre-existing regulatory text in the pre-existing paragraph 3.7.1 (as last promulgated on July 18, 1997, at 62 FR 38850) in new paragraph (a) of new section 4.6, to explain in words the flexibility in minimum PM₁₀ monitoring requirements as provided in the pre-existing Table 4 which had listed ranges of required numbers (rather than a single number) of monitors for each of the categories of MSA population and historical PM₁₀ range. This regulatory text was inadvertently omitted. Therefore, EPA is restoring the omitted text and correcting paragraph (a) of section 4.6 to read: “Table D-4 indicates the approximate number of permanent stations required in MSAs to characterize national and regional PM₁₀ air quality trends and geographical patterns. The number of PM₁₀ stations in areas where MSA populations exceed 1,000,000 must be in the range from 2 to 10 stations, while in low population urban areas, no more than 2 stations are required. A range of monitoring stations is specified in Table D-4 because sources of pollutants and local control efforts can vary from one part of the country to another and, therefore, some flexibility is allowed in selecting the actual number of stations in any one locale.”

F. Additional Regional Administrator Flexibility in Applying PM₁₀ Minimum Monitoring Requirements

We are amending the monitoring rule to allow EPA Regional Administrators to approve departures from the minimum number of PM₁₀ monitors otherwise specified in the rule.

In the January 17, 2006, proposed monitoring rule (71 FR 2802), EPA proposed minimum network design monitoring requirements for PM_10-2.5. In paragraph (b) of section 4.8.1 of 40 CFR part 58, appendix D, (Network Design Criteria for Ambient Air Quality Monitoring), EPA proposed that modifications from the PM_10-2.5 monitoring requirements must be approved by the Regional Administrator. The proposed regulatory language providing the Regional Administrator flexibility to modify the PM_10-2.5 monitoring requirements was consistent with similar language proposed for PM_2.5 that read: “Deviations from these PM_2.5 monitoring requirements must be approved by the EPA Regional Administrator” (71 FR 2801, paragraph (b) of section 4.7.1). Similar regulatory language was proposed for ozone monitoring requirements (71 FR 2798, paragraph (b) of section 4.1): “Deviations from the above O₃ requirements are allowed if approved by the EPA Regional Administrator.” The EPA finalized the Regional Administrator authority to modify the PM_2.5 and ozone monitoring requirements in the October 17, 2006, rule following a public comment period in which no adverse comments were received about the specific provisions concerning Regional Administrator flexibility in applying these regulations.

The EPA did not adopt the proposed PM_10-2.5 minimum monitoring network design including the Regional Administrator flexibility language. The EPA notes, however, that no adverse comments were received specifically addressing the proposed Regional Administrator authority to modify PM_10-2.5 monitoring network requirements although voluminous comment was received on other proposed provisions of the PM_10-2.5 monitoring network design and accompanying suitability test.

The EPA also proposed and adopted requirements for “NCore” multipollutant monitoring sites, including a provision allowing the Administrator to approve modifications from these requirements. Again, no adverse comment was received on this modification provision. Finally, specific requirements in the rule for photochemical assessment monitoring stations (PAMS) have always been modifiable by the Administrator.

Thus, EPA notes that under the current 40 CFR part 58, appendix D network design requirements, PM₁₀ is the only pollutant with minimum monitoring requirements not subject to modification based on either Administrator or Regional Administrator evaluation and approval. Such flexibility, already finalized for ozone and PM_2.5, can prove useful in particular cases where a State demonstrates that meeting the minimum monitoring requirements, for an individual MSA for example, may be impractical or contrary to the optimum use of monitoring resources.

The EPA believes it is appropriate to allow the Regional Administrator to modify PM₁₀ monitoring requirements, for the same reasons such authority was finalized for PM_2.5 and ozone monitoring requirements. Such authority allows for specific local factors and information can be considered in order to make the PM₁₀ monitoring network more economical while still meeting program data needs. In light of the absence of any comments of concern regarding very similar Administrator or Regional Administrator authority for other pollutants, we do not expect any adverse comment on this action. Therefore, EPA is amending paragraph (a) of section 4.6 quoted in the section above and adding the following sentence so it now reads: “Modifications from these PM₁₀ monitoring requirements must be approved by the Regional Administrator.” See also section VI.E of this preamble for a clarifying amendment which also affects section 4.6 of appendix D to part 58 by restoring inadvertently omitted text.

G. Correction to Division Name and Address Reference

The October 17, 2006, final rule provided an address reference in paragraph 2.4 of 40 CFR part 58 appendix A, to assist with communications regarding the National Performance Evaluation Programs. Monitoring agencies were advised to contact either the appropriate EPA Regional Quality Assurance (QA) Coordinator at the appropriate EPA Regional Office location, or the NPAP Coordinator, Emissions Monitoring and Analysis Division (D205-02), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. Due to a reorganization within the Office of Air Quality Planning and Standards and subsequent physical relocation within the North Carolina facility, the provided address mail code (D205-02) is no longer correct for quality assurance related communications. Additionally, the Emissions Monitoring and Analysis Division has been renamed to the Air Quality Assessment Division, as part of the same reorganization. Due to the possibility of future address changes, EPA believes a more general reference to quality assurance contact information is appropriate for inclusion in regulatory language. Updated contact information for all air monitoring program leads is maintained on the Ambient Monitoring Technology Information Center (AMTIC) Web site http://www.epa.gov/​ttn/​amtic/​contacts.html. This website is well publicized and frequently accessed by all monitoring agencies; therefore, specific address entries in the rule are unnecessary and potentially misleading. Accordingly, EPA is amending the regulatory text in paragraph 2.4 to read: “For clarification and to participate, monitoring organizations should contact either the appropriate EPA Regional Quality Assurance (QA) Coordinator at the appropriate EPA Regional Office location, or the NPAP Coordinator at the Air Quality Assessment Division, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency in Research Triangle Park, North Carolina.”

H. Clarification to Conditions for Waiving Regional Administrator Comment Period on Submitted Annual Monitoring Network Plans

The regulatory text in 40 CFR 58.10(a)(2) (71 FR 61298) describes the approval process for State-submitted annual monitoring network plans that propose SLAMS network modifications. Such plans are subject to the approval of the Regional Administrator, including a new requirement for the Regional Administrator to provide opportunity for public comment during the 120-day period allowed for approval or disapproval. The rule permits the Regional Administrator to waive the separate public comment opportunity if the State or local agency has already provided a public comment opportunity on its plan and has made no changes to the plan subsequent to that comment opportunity.

Implied but not explicitly stated in the regulatory language is that the Regional Administrator may forgo public comment only if the State or local agency submitted the full text of public comments received on its annual monitoring network plan to the Regional Administrator, because only the availability of such detailed comments would make a separate comment period by the Regional Administrator redundant.

The EPA believes that the aforementioned regulatory language should be clarified to avoid ambiguity about what situations would require the Regional Administrator to provide a public comment opportunity on submitted annual monitoring network plans that contain SLAMS network modifications. The EPA notes that the clarification does not modify the minimum requirements for State and local agencies to make their plans available for public inspection for at least 30 days prior to submission to EPA.

Accordingly, the clarified regulatory text in the second sentence of 40 CFR 58.10(a)(2) reads: “If the State or local agency has already provided a public comment opportunity on its plan and has made no changes subsequent to that comment opportunity, and has submitted the received comments together with the plan, the Regional Administrator is not required to provide a separate opportunity for comment.”

Such comments could be transmitted to the Regional Administrator in hard-copy or electronic format, and at a minimum, would include all relevant information supplied to the State or local agency by the commenters. Monitoring agencies would not be expected to provide comment summaries or comment responses, although those submissions could optionally be provided to the Regional Administrator in addition to the actual text of the received comments.

I. Typographical Corrections

The Federal Register printing of the October 17, 2006, final rule contained typographical errors in equations, tables, and figures. These errors, as explained below and listed by Federal Register page reference and CFR section number, are corrected in this rulemaking.

• 71 FR 61284. Subpart C of Part 53—§ 53.35(d)(4), Calculation of mean concentrations. Equation 12: The “n” over the summation symbol is replaced with “m.”
• 71 FR 61284. Subpart C of Part 53—§ 53.35(e) and § 53.35(f), Tests for reference method and candidate method precision. Equations 13 and 15: 100% is moved to be outside the square root symbol.
• 71 FR 61284. Subpart C of Part 53—§ 53.35(g), Test for additive and multiplicative bias (comparative slope and intercept). Equation 17: Left part of equation is changed to be R̄ not R̄ _j.
• 71 FR 61284. Subpart C of Part 53—§ 53.35(h), Tests for comparison correlation. Equation 21: Radical sign in the denominator is extended to cover both summation signs.
• 71 FR 61285. Table C-1 to Subpart C of Part 53, Test Concentration Ranges, Number of Measurements Required, and Maximum Discrepancy Specification. The four occurrences of “Total” in the first column are moved to the second column.
• 71 FR 61285. Table C-1 to Subpart C of Part 53, Test Concentration Ranges, Number of Measurements Required, and Maximum Discrepancy Specification. Two entries of “18” are moved 3 columns left to appear in the “Second Set” column rather than as shown in the right-most column.
• 71 FR 61285. Table C-4 to Subpart C of Part 53—Test Specifications for PM₁₀, PM_2.5 and PM_10-2.5 Candidate Equivalent Methods. An erroneous “R” character in the table title is removed so that the title reads—Test Specifications for PM₁₀, PM_2.5 and PM_10-2.5 Candidate Equivalent Methods.
• 71 FR 61286. Table C-4 to Subpart C of Part 53—Test Specifications for PM₁₀, PM_2.5 and PM_10-2.5 Candidate Equivalent Methods. In the column header for the last 2 columns, the “PM_10-2.5” is corrected to be “PM_10-2.5”.
• 71 FR 61286. Table C-4 to Subpart C of Part 53—Test Specifications for PM₁₀, PM_2.5 and PM_10-2.5 Candidate Equivalent Methods. The horizontal line under “R_j > 60 μg/m3” in the table is removed.
• 71 FR 61286. Table C-4 to Subpart C of Part 53—Test Specifications for PM₁₀, PM_2.5 and PM_10-2.5 Candidate Equivalent Methods. In the first column, in the “Precision of replicate reference method measurements * * *” entry, the “prime” symbols are removed from “RP_Rj” and “PM_10-2.5”.
• 71 FR 61286. Table C-4 to Subpart C of Part 53—Test Specifications for PM₁₀, PM_2.5 and PM_10-2.5 Candidate Equivalent Methods. An unintended period is removed at the end of the entry in the last column, Intercept row, and at the end of the second footnote.
• 71 FR 61286. Table C-4 to Subpart C of Part 53—Test Specifications for PM₁₀, PM_2.5 and PM_10-2.5 Candidate Equivalent Methods. Values for correlation of reference method and candidate method measurements for PM_2.5 Class II and III, and PM_10-2.5 Class II and III are added to all four columns:
• ≥0.93 for CCV≤0.4;
• ≥0.85 + 0.2×CCV for 0.4≤CCV≤0.5;
• ≥0.95 for CCV≥0.5.
• 71 FR 61287. Figure C-1 to Subpart C of Part 53—Suggested Format for Reporting Test Results for Methods for SO₂, CO, O₃, NO₂. Title and the first lines of content are repositioned from being section text to being proper parts of Figure C-1.
• 71 FR 61287. Figures C-2 and C-3 to Subpart C of Part 53—Illustration of the Slope and Intercept Limits for Class II and Class III PM_2.5 Candidate Equivalent Methods and Illustration of the Slope and Intercept Limits for Class II and Class III PM_10-2.5 Candidate Equivalent Methods. “PM_2.5” is changed to “PM_2.5,” “PM_10-2.5” is changed to “PM_10-2.5,” “μg/m3” is changed to “μg/m³.” Also, the “Class II” and “Class III” labels are related by arrows to the outline of the hexagons rather than the area inside, to be consistent with the title, which indicates “Acceptance Limits.”
• 71 FR 61289. Figure C-4 to Subpart C of Part 53—Illustration of the Minimum Limits for Correlation Coefficient for PM_2.5 and PM_10-2.5 Class II and III methods. In the axes labels, the commas are deleted and the “r” and the “CCV” are placed within parentheses.
• 71 FR 61293. Subpart E of Part 53—§ 53.58(g), Operational field precision and blank test. Equation 26: the symbol “C_1,j” is corrected to “C_i,j.”
• 71 FR 61294. Table E-1 to Subpart E of Part 53—Summary of Test Requirements for Reference and Class I Equivalent Methods for PM_2.5 and PM_10-2.5. In the 3rd column, row identified as “§ 53.56* * *,” a comma is added after “16.67 ± 5%” and before “L/min.”
• 71 FR 61294. Table E-1 to Subpart E of Part 53—Summary of Test Requirements for Reference and Class I Equivalent Methods for PM_2.5 and PM_10-2.5. In the 3rd column, row identified as “§ 53.57* * *,” one of the two periods at the end of item 3 is removed.
• 71 FR 61294. Table E-1 to Subpart E of Part 53—Summary of Test Requirements for Reference and Class I Equivalent Methods for PM_2.5 and PM_10-2.5. In the fourth column, row identified as “§ 53.57* * *,” item (c) is changed to read “Solar flux of 1000 ± 50 W/m²” not “Solar flux of 1000 ? 50 W/m².”
• 71 FR 61294. Table E-1 to Subpart E of Part 53—Summary of Test Requirements for Reference and Class I Equivalent Methods for PM_2.5 and PM_10-2.5. Spurious “?” characters throughout the table are removed.
• 71 FR 61294. Table E-1 to Subpart E of Part 53—Summary of Test Requirements for Reference and Class I Equivalent Methods for PM_2.5 and PM_10-2.5. § 53.56 cell reference, Barometric pressure effect test, Sample flow rate performance specification, value is changed to be 16.67 (versus 16.6).
• 71 FR 61296. Table F-1 to Subpart F of Part 53—Performance Specifications for PM_2.5 Class II Equivalent Samplers. In the last column, row identified as “§ 53.64,” “Dp₅₀ = 2.5 μm ? 0.2 μm” is changed to be “Dp₅₀ = 2.5 μm ± 0.2 μm.”
• 71 FR 61296. Table F-1 to Subpart F of Part 53—Performance Specifications for PM_2.5 Class II Equivalent Samplers. In the last column, last row, a comma is added after “0.15mg” and before “r ≥0.97.”
• 71 FR 61296. Table F-1 to Subpart F of Part 53—Performance Specifications for PM_2.5 Class II Equivalent Samplers. Spurious “?” characters throughout the table are removed.
• 71 FR 61300. Figure 1 to Subpart B of Part 58—Ratio to Standard for PM₁₀ Operating Schedule. A missing value (1.4) is added on the X axis.
• 71 FR 61309. Appendix A of Part 58—Quality Assurance Requirements for SLAMS, SPMs, and PSD Air Monitoring. Equation 7: A missing “•” character is added so that the equation reads: Lower Probability Limit = m-1.96 • S.
• 71 FR 61309. Appendix A of Part 58—Quality Assurance Requirements for SLAMS, SPMs, and PSD Air Monitoring. A missing minus sign is added in caption below Equation 11 so that it reads: a chi-squared distribution with n-1 degrees of freedom.
• 71 FR 61310. Appendix A of Part 58—Quality Assurance Requirements for SLAMS, SPMs, and PSD Air Monitoring. Equation 12: missing ellipsis is added in caption so that it reads: where, n_j is the number of pairs and d₁, d₂, * * * dn_j are the biases for each of the pairs to be averaged.
• “PM_10C”, where it appears in Part 53 without a subscripted “C”, is replaced with “PM_10c.”

VII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

Under Executive Order 12866 (58 FR 51735, October 4, 1993), this action is a “significant regulatory action” because it may raise novel legal policy issues arising out of legal mandates, the President's priorities, or the principles set forth in the Executive Order. Accordingly, EPA submitted this action to the Office of Management and Budget (OMB) for review under Executive Order 12866 and any changes made in response to OMB recommendations have been documented in the docket for this action.

B. Paperwork Reduction Act

This action does not impose any new information collection, as it only corrects printing errors, provides clarifications, and provides new flexibility for PM₁₀ monitoring on a case-by-case basis. However, the OMB has previously approved the information collection requirements contained in the existing regulations for 40 CFR part 53 and 40 CFR part 58 under the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq., and has assigned OMB control number 2060-0084, EPA ICR number 0940.20. A copy of the OMB approved Information Collection Request (ICR) may be obtained from Susan Auby, Collection Strategies Division, U.S. Environmental Protection Agency (2822T), 1200 Pennsylvania Ave., NW., Washington, DC 20460 or by calling [phone]. This action does not impose any new information collection burden beyond the already-approved ICR.

Burden means the total time, effort, or financial resources expended by persons to generate, maintain, retain, or disclose or provide information to or for a Federal agency. This includes the time needed to review instructions; develop, acquire, install, and utilize technology and systems for the purposes of collecting, validating, and verifying information, processing and maintaining information, and disclosing and providing information; adjust the existing ways to comply with any previously applicable instructions and requirements; train personnel to be able to respond to a collection of information; search data sources; complete and review the collection of information; and transmit or otherwise disclose the information. An agency may not conduct or sponsor, and a person is not required to respond to a collection of information unless it displays a currently valid OMB control number. The OMB control numbers for EPA's regulations in 40 CFR are listed in 40 CFR part 9.

C. Regulatory Flexibility Act

The Regulatory Flexibility Act (RFA) generally requires an agency to prepare a regulatory flexibility analysis of any rule subject to notice and comment rulemaking requirements under the Administrative Procedure Act or any other statute unless the agency certifies that the rule will not have a significant economic impact on a substantial number of small entities. Small entities include small businesses, small organizations, and small governmental jurisdictions.

For purposes of assessing the impacts of today's rule on small entities, small entity is defined as: (1) A small business defined by the Small Business Administration's (SBA) regulations at 13 CFR 121.201; (2) a small governmental jurisdiction that is a government of a city, county, town, school district or special district with a population of less than 50,000; and (3) a small organization that is any not-for-profit enterprise which is independently owned and operated and is not dominant in its field.

After considering the economic impacts of today's final rule on small entities, I certify that this action will not have a significant economic impact on a substantial number of small entities.

This final rule will not impose any requirements on small entities. None of the corrections and clarifications creates additional regulatory requirements on affected entities compared to those that were promulgated in the final rule that was published in the Federal Register on October 17, 2006. The rule changes being made only correct printing errors, provide clarifications, and provides new flexibility for PM₁₀ monitoring on a case-by-case basis.

D. Unfunded Mandates Reform Act

Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public Law 104-4, establishes requirements for Federal agencies to assess the effects of their regulatory actions on State, local, and tribal governments and the private sector. Under section 202 of the UMRA, EPA generally must prepare a written statement, including a cost-benefit analysis, for proposed and final rules with “Federal mandates” that may result in expenditures to State, local, and Tribal governments, in the aggregate, or to the private sector, of $100 million or more in any one year. Before promulgating an EPA rule for which a written statement is needed, section 205 of the UMRA generally requires EPA to identify and consider a reasonable number of regulatory alternatives and adopt the least costly, most cost-effective or least burdensome alternative that achieves the objectives of the rule. The provisions of section 205 do not apply when they are inconsistent with applicable law. Moreover, section 205 allows EPA to adopt an alternative other than the least costly, most cost-effective or least burdensome alternative if the Administrator publishes with the final rule an explanation why that alternative was not adopted. Before EPA establishes any regulatory requirements that may significantly or uniquely affect small governments, including Tribal governments, it must have developed under section 203 of the UMRA a small government agency plan. The plan must provide for notifying potentially affected small governments, enabling officials of affected small governments to have meaningful and timely input in the development of EPA regulatory proposals with significant Federal intergovernmental mandates, and informing, educating, and advising small governments on compliance with the regulatory requirements.

The EPA has determined that this final rule does not contain a Federal mandate that may result in expenditures of $100 million or more for State, local, and tribal governments, in the aggregate, or the private sector in any one year, because the changes being made are merely clarifications and corrections. Thus, today's rule is not subject to the requirements of sections 202 and 205 of the UMRA.

The EPA has determined that this final rule contains no regulatory requirements that might significantly or uniquely affect small governments. None of the changes creates additional regulatory requirements on affected entities compared to those that were promulgated in the final rule that was published in the Federal Register on October 17, 2006. The rule changes being made only correct printing errors, provide clarifications, and provide some new flexibility for PM₁₀ monitoring on a case-by-case basis. Therefore, this final rule is not subject to the requirements of section 203 of the UMRA.

E. Executive Order 13132: Federalism

Executive Order 13132 (64 FR 43255, August 10, 1999), requires EPA to develop an accountable process to ensure “meaningful and timely input by State and local officials in the development of regulatory policies that have federalism implications.” “Policies that have federalism implications” is defined in the Executive Order to include regulations that 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.”

This final rule does not have federalism implications because 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, as specified in Executive Order 13132. This is because the changes being made only correct printing errors, provide clarifications, and provides some new flexibility for PM₁₀ monitoring on a case-by-case basis. Thus, Executive Order 13132 does not apply to this final rule.

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

Executive Order 13175, entitled “Consultation and Coordination with Indian Tribal Governments” (65 FR 67249, November 9, 2000), requires EPA to develop an accountable process to ensure “meaningful and timely input by tribal officials in the development of regulatory policies that have tribal implications.” This final rule does not have tribal implications, as specified in Executive Order 13175. The EPA consulted with tribal officials early in the process of developing the October 17, 2006, rule to permit them to have meaningful and timely input into its development. Although tribal governments may elect to conduct ambient air monitoring, none of the changes in today's rule apply directly to tribal governments. Thus, Executive Order 13175 does not apply to this rule.

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

Executive Order 13045 “Protection of Children from Environmental Health Risks and Safety Risks” (62 FR 19885, April 23, 1997) applies to any rule that: (1) Is determined to be “economically significant” as defined under EO 12866, and (2) concerns an environmental health or safety risk that EPA has reason to believe may have a disproportionate effect on children. If the regulatory action meets both criteria, the Agency must evaluate the environmental health or safety effects of the planned rule on children, and explain why the planned regulation is preferable to other potentially effective and reasonably feasible alternatives considered by the Agency.

EPA interprets EO 13045 as applying only to those regulatory actions that concern health or safety risks, such that the analysis required under section 5-501 of the EO has the potential to influence the regulation. This final rule is not subject to EO 13045 because it does not establish an environmental standard intended to mitigate health or safety risks.

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

Executive Order 12898 (59 FR 7629, February 16, 1994) establishes federal executive policy on environmental justice. Its main provision directs Federal agencies, to the greatest extent practicable and permitted by law, to make environmental justice part of their mission by identifying and addressing, as appropriate, disproportionately high and adverse human health or environmental effects of their programs, policies, and activities on minority populations and low-income populations in the United States.

EPA has determined that this final rule will not have disproportionately high and adverse human health or environmental effects on minority or low-income populations because it does not affect the level of protection provided to human health or the environment. The rule merely amends the October 17, 2006, final monitoring rule (71 FR 61236) by correcting printing errors, providing clarifications, and providing some new flexibility for PM₁₀ monitoring on a case-by-case basis.

I. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use

This rule is not a “significant energy action” as defined in Executive Order 13211, “Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution or Use” (66 FR 28355, May 22, 2001) because it is not likely to have a significant adverse effect on the supply, distribution, or use of energy. No significant change in the use of energy is expected because the total number of monitors for ambient air quality measurements will not increase above present levels. Further, we have concluded that this rule is not likely to have any adverse energy effects.

J. National Technology Transfer Advancement Act

Section 12(d) of the National Technology Transfer and Advancement Act of 1995 (“NTTAA”), Public Law No. 104-113, 12(d) (15 U.S.C. 272 note) directs EPA to use voluntary consensus standards in its regulatory activities unless to do so would be inconsistent with applicable law or otherwise impractical. Voluntary consensus standards are technical standards (e.g., materials specifications, test methods, sampling procedures, and business practices) that are developed or adopted by voluntary consensus standards bodies. The NTTAA directs EPA to provide Congress, through OMB, explanations when the Agency decides not to use available and applicable voluntary consensus standards.

This action does not involve technical standards, other than to make corrections and clarifications. Therefore, EPA did not consider the use of any voluntary consensus standards.

K. Congressional Review Act

The Congressional Review Act, 5 U.S.C. 801, et seq., as added by the Small Business Regulatory Enforcement Fairness Act of 1996, generally provides that before a rule may take effect, the agency promulgating the rule must submit a rule report, which includes a copy of the rule, to each House of Congress and to the Comptroller General of the United States. EPA will submit a report containing this rule and other required information to the U.S. Senate, the U.S. House of Representatives, and the Comptroller General of the United States prior to publication of the rule in the Federal Register. A major rule cannot take effect until 60 days after it is published in the Federal Register. This action is not “major rule” as defined by 5 U.S.C. 804(2). This final rule will not have an annual effect on the economy of $100 million or more, will not result in a major increase in costs or prices for State or local agencies, and will not affect competition with foreign-based enterprises in domestic and export markets. The final amendments will be effective on September 10, 2007.

List of Subjects in 40 CFR Parts 53 and 58

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

Dated: April 30, 2007.

Stephen L. Johnson,

Administrator.

For the reasons stated in the preamble, title 40, chapter I, parts 53 and 58 of the Code of Federal Regulations are amended as follows:

PART 53—[AMENDED]

1. The authority citation for part 53 continues to read as follows:

Authority: Section 301(a) of the Clean Air Act (42 U.S.C. sec. 1857g(a)), as amended by sec. 15(c)(2) of Pub. L. 91-604, 84 Stat. 1713, unless otherwise noted.

Subpart C—[Amended]

2. Section 53.35 is amended by:

a. Revising Equation 12 of paragraph (d)(4),

b. Revising Equation 13 of paragraph (e)(1),

c. Revising Equation 15 of paragraph (f)(1),

d. Revising Equation 17 of paragraph (g)(1), and

e. Revising Equation 21 of paragraph (h)(1) to read as follows:

§ 53.35

Test procedure for Class II and Class III methods for PM _2.5 and PM_10-2.5.

* * * * *

(d) * * *

(4) * * *

Where:

C_j = The mean concentration measured by the candidate method for the measurement set;

C_i,j = The measurement of the candidate method sampler or analyzer i on test day j; and

m = The number of valid candidate method measurements in the measurement set (normally 3).

(e) * * *

(1) * * *

* * * * *

(f) * * *

(1) * * *

* * * * *

(g) * * *

(1) * * *

* * * * *

(h) * * *

(1) * * *

* * * * *

3. Table C-1 to subpart C is revised to read as follows:

Table C-1 to Subpart C of Part 53—Test Concentration Ranges, Number of Measurements Required, and Maximum Discrepancy Specification

Pollutant	Concentration range, parts per million	Simultaneous measurements required				Maximum discrepancy specification, parts per million
		1-hr		24-hr
		First set	Second set	First set	Second set
Ozone	Low 0.06 to 0.10	5	6			0.02
	Med 0.15 to 0.25	5	6			.03
	High 0.35 to 0.45	4	6			.04
	Total	14	18
Carbon monoxide	Low 7 to 11	5	6			1.5
	Med 20 to 30	5	6			2.0
	High 35 to 45	4	6			3.0
	Total	14	18
Sulfur dioxide	Low 0.02 to 0.05			3	3	0.02
	Med 0.10 to 0.15			2	3	.03
	High 0.30 to 0.50	7	8	2	2	.04
	Total	7	8	7	8
Nitrogen dioxide	Low 0.02 to 0.08			3	3	0.02
	Med 0.10 to 0.20			2	3	.03
	High 0.25 to 0.35			2	2	.03
	Total			7	8

4. Table C-4 to subpart C is revised to read as follows:

Table C-4 to Subpart C of Part 53.—Test Specifications for PM₁₀, PM_2.5 and PM_10-2.5 Candidate Equivalent Methods

Specification	PM10	PM2.5			PM10-2.5
		Class I	Class II	Class III	Class II	Class III
Acceptable concentration range (Rj), μg/m3	15-300	3-200	3-200	3-200	3-200	3-200
Minimum number of test sites	2	1	2	4	2	4
Minimum number of candidate method samplers or analyzers per site	3	3	3 1	3 1	3 1	3 1
Number of reference method samplers per site	3	3	3 1	3 1	3 1	3 1
Minimum number of acceptable sample sets per site for PM10 methods:
Rj < 60 μg/m3	3
Rj > 60 μg/m3	3
Total	10
Minimum number of acceptable sample sets per site for PM2.5 and PM10-2.5 candidate equivalent methods:
Rj < 30 μg/m3 for 24-hr or Rj < 20 μg/m3 for 48-hr samples		3
Rj > 30 μg/m3 for 24-hr or Rj > 20 μg/m3 for 48-hr samples		3
Each season		10	23	23	23	23
Total, each site		10	23	23 (46 for two-season sites)	23	23 (46 for two-season sites)
Precision of replicate reference method measurements, PRj or RPRj, respectively; RP for Class II or III PM2.5 or PM10-2.5, maximum	5 μg/m3 or 7%	2 μg/m3 or 5%	10% 2	10% 2	10% 2	10% 2
Precision of PM2.5 or PM10-2.5 candidate method, CP, each site			10% 2	15% 2	15% 2	15% 2
Slope of regression relationship.	1 ± 0.10	1 ± 0.05	1 ± 0.10	1 ± 0.10	1 ± 0.10	1 ± 0.12
Intercept of regression relationship, μg/m3	0 ± 5	0 ± 1	Between: 13.55 − (15.05 × slope), but not less than −1.5; and 16.56 − (15.05 × slope), but not more than +1.5	Between: 15.05 − (17.32 × slope), but not less than −2.0; and 15.05 − (13.20 × slope), but not more than +2.0	Between: 62.05 − (70.5 × slope), but not less than −3.5; and 78.95 − (70.5 × slope), but not more than +3.5	Between: 70.50 − (82.93 × slope), but not less than −7.0; and 70.50 − (61.16 × slope), but not more than +7.0
Correlation of reference method and candidate method measurements	≥ 0.97	≥ 0.97	≥ 0.93—for CCV ≤ 0.4; ≥ 0.85 + 0.2 × CCV—for 0.4 ≤ CCV ≤ 0.5; ≥ 0.95—for CCV ≥ 0.5
1 Some missing daily measurement values may be permitted; see test procedure.
2 Calculated as the root mean square over all measurement sets.

5. Figures C-1 through C-4 to subpart C are revised to read as follows:

Figure C-1 to Subpart C of Part 53—Suggested Format for Reporting Test Results for Methods for SO ₂, CO, O ₃, NO ₂

Candidate Method

Reference Method

Applicant

☐ First Set   ☐ Second Set   ☐ Type   ☐ 1 Hour   ☐ 24 Hour

Concentration range		Date	Time	Concentration, ppm		Difference	Table C-1 spec.	Pass or fail
				Candidate	Reference
Low	1
____ ppm	2
to ____ ppm	3
	4
	5
	6
Medium	1
____ ppm	2
to ____ ppm	3
	4
	5
	6
High	1
____ ppm	2
to ____ ppm	3
	4
	5
	6
	7
	8
							Total Failures:

Subpart E—[Amended]

6. Section 53.58 is amended by revising Equation 26 of paragraph (g)(2)(i) to read as follows:

§ 53.58

Operational field precision and blank test.

* * * * *

(g) * * *

(2)(i) * * *

* * * * *

7. Table E-1 to subpart E is revised to read as follows:

Table E-1 to Subpart E of Part 53.—Summary of Test Requirements for Reference and Class I Equivalent Methods for PM_2.5 and PM_10-2.5

Subpart E procedure	Performance test	Performance specification	Test conditions	Part 50, appendix L reference
§ 53.52 Sample leak check test	Sampler leak check facility	External leakage: 80 mL/min, max Internal leakage: 80 mL/min, max	Controlled leak flow rate of 80 mL/ min	Sec. 7.4.6.
§ 53.53 Base flow rate test	Sample flow rate 1. Mean 2. Regulation 3. Meas accuracy 4. CV accuracy 5. Cut-off	1. 16.67 ± 5%, L/ min 2. 2%, max 3. 2%, max 4. 0.3% max 5. Flow rate cut-off if flow rate deviates more than 10% from design flow rate for >60 ± 30 seconds	(a) 6-hour normal operational test plus flow rate cut-off test (b) Normal conditions (c) Additional 55 mm Hg pressure drop to simulate loaded filter (d) Variable flow restriction used for cut-off test	Sec. 7.4.1. Sec. 7.4.2. Sec. 7.4.3. Sec. 7.4.4. Sec. 7.4.5.
§ 53.54 Power interruption test	Sample flow rate 1. Mean 2. Regulation 3. Meas. accuracy 4. CV accuracy 5. Occurrence time of power interruptions 6. Elapsed sample time 7. Sample volume	1. 16.67 ± 5%, L/ min 2. 2%, max 3. 2%, max 4. 0.3% max 5. ± 2 min if >60 seconds. 6. ± 20 seconds 7. ± 2%, max	(a) 6-hour normal operational test (b) Nominal conditions (c) Additional 55 mm Hg pressure drop to simulate loaded filter (d) 6 power interruptions of various durations	Sec. 7.4.1. Sec. 7.4.2. Sec. 7.4.3. Sec. 7.4.5. Sec. 7.4.12. Sec. 7.4.13. Sec. 7.4.15.4. Sec. 7.4.15.5.
§ 53.55 Temperature and line voltage test	Sample flow rate 1. Mean 2. Regulation 3. Meas. accuracy 4. CV accuracy 5. Temperature meas. accuracy 6. Proper operation.	1. 16.67 ± 5%, L/ min 2. 2%, max 3. 2%, max 4. 0.3% max 5. 2 °C	(a) 6-hour normal operational test (b) Normal conditions (c) Additional 55 mm Hg pressure drop to simulate loaded filter (d) Ambient temperature at −20 and +40 °C (e) Line voltage: 105 Vac to 125 Vac	Sec. 7.4.1. Sec. 7.4.2. Sec. 7.4.3. Sec. 7.4.5. Sec. 7.4.8. Sec. 7.4.15.1.
§ 53.56 Barometric pressure effect test	Sample flow rate 1. Mean 2. Regulation 3. Meas. accuracy 4. CV accuracy 5. Pressure meas. accuracy 6. Proper operation.	1. 16.67 ± 5%, L/ min 2. 2%, max 3. 2%, max 4. 0.3% max 5. 10 mm Hg	(a) 6-hour normal operational test (b) Normal conditions (c) Additional 55 mm Hg pressure drop to simulate loaded filter (d) Barometric pressure at 600 and 800 mm Hg	Sec. 7.4.1. Sec. 7.4.2. Sec. 7.4.3. Sec. 7.4.5. Sec. 7.4.9.
§ 53.57 Filter temperature control test	1. Filter temp. meas. accuracy 2. Ambient temp. meas. accuracy 3. Filter temp. control accuracy, sampling and non-sampling	1. 2 °C 2. 2 °C 3. Not more than 5 °C above ambient temp. for more than 30 min	(a) 4-hour simulated solar radiation, sampling (b) 4-hour simulated solar radiation, non-sampling (c) Solar flux of 1000 ± 50 W/m 2	Sec. 7.4.8. Sec. 7.4.10. Sec. 7.4.11.
§ 53.58 Field precision test	1. Measurement precision 2. Storage deposition test for sequential samplers	1. Pj < 2 μg/m3 or RPj < 5% 2. 50 μg max. average weight gain/blank filter	(a) 3 collocated samplers at 1 site for at least 10 days (b) PM2.5 conc. > 3 μg/m3 (c) 24- or 48-hour samples (d) 5- or 10-day storage period for inactive stored filters	Sec. 5.1. Sec. 7.3.5. Sec. 8. Sec. 9. Sec. 10.
The Following Requirement Is Applicable to Class I Candidate Equivalent Methods Only
§ 53.59 Aerosol transport test	Aerosol transport	97%, min. for all channels.	Determine aerosol transport through any new or modified components with respect to the reference method sampler before the filter for each channel

Subpart F—[Amended]

8. Table F-1 to subpart F is revised to read as follows:

Table F-1 to Subpart F of Part 53.—Performance Specifications for PM_2.5 Class II Equivalent Samplers

Performance test	Specifications	Acceptance criteria
§ 53.62 Full Wind Tunnel Evaluation	Solid VOAG produced aerosol at 2 km/hr and 24 km/hr	Dp50 = 2.5 μm ± 0.2 μm Numerical Analysis Results: 95% ≤ Rc ≤ 105%.
§ 53.63 Wind Tunnel Inlet Aspiration Test	Liquid VOAG produced aerosol at 2 km/hr and 24 km/hr	Relative Aspiration: 95% ≤ A ≤ 105%.
§ 53.64 Static Fractionator Test	Evaluation of the fractionator under static conditions	Dp50 = 2.5 μm ± 0.2 μm Numerical Analysis Results: 95% ≤ Rc ≤ 105%.
§ 53.65 Loading Test	Loading of the clean candidate under laboratory conditions	Acceptance criteria as specified in the post-loading evaluation test (§ 53.62, § 53.63, or § 53.64).
§ 53.66 Volatility Test	Polydisperse liquid aerosol produced by air nebulization of A.C.S. reagent grade glycerol, 99.5% minimum purity	Regression Parameters Slope = 1 ± 0.1, Intercept = 0 ± 0.15 mg, r ≥ 0.97.

PART 58—[AMENDED]

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

Authority: 42 U.S.C. 7403, 7410, 7601(a), 7611, and 7619.

Subpart B—[Amended]

10. Section 58.10 is amended by revising the second sentence in paragraph (a)(2) to read as follow:

§ 58.10

Annual monitoring network plan and periodic network assessment.

(a)(1) * * *

(2) * * * If the State or local agency has already provided a public comment opportunity on its plan and has made no changes subsequent to that comment opportunity, and has submitted the received comments together with the plan, the Regional Administrator is not required to provide a separate opportunity for comment.

* * * * *

11. Section 58.12 is amended by revising paragraph (d)(1), paragraph (d)(3), and the first sentence of paragraph (e) to read as follows:

§ 58.12

Operating schedules.

* * * * *

(d) * * *

(1)(i) Manual PM_2.5 samplers at required SLAMS stations without a collocated continuously operating PM_2.5 monitor must operate on at least a 1-in-3 day schedule.

(ii) For SLAMS PM_2.5 sites with both manual and continuous PM_2.5 monitors operating, the monitoring agency may request approval for a reduction to 1-in-6 day PM_2.5 sampling or for seasonal sampling from the EPA Regional Administrator. The EPA Regional Administrator may grant sampling frequency reductions after consideration of factors, including but not limited to the historical PM_2.5 data quality assessments, the location of current PM_2.5 design value sites, and their regulatory data needs. Required SLAMS stations whose measurements determine the design value for their area and that are within plus or minus 10 percent of the NAAQS; and all required sites where one or more 24-hour values have exceeded the NAAQS each year for a consecutive period of at least 3 years are required to maintain at least a 1-in-3 day sampling frequency. A continuously operating FEM or ARM PM_2.5 monitor satisfies this requirement.

(iii) Required SLAMS stations whose measurements determine the design value for their area and that are within plus or minus 5 percent of the daily PM_2.5 NAAQS must have an FRM or FEM operate on a daily schedule. A continuously operating FEM or ARM PM_2.5 monitor satisfies this requirement.

* * * * *

(3) Manual PM_2.5 speciation samplers at STN stations must operate on at least a 1-in-3 day sampling frequency.

(e) For PM₁₀ samplers, a 24-hour sample must be taken from midnight to midnight (local standard time) to ensure national consistency. * * *

§ 58.12

[Amended]

12. Figure 1 of paragraph (e) of § 58.12 is revised to read as follows:

Subpart C—[Amended]

13. Section 58.20(c) is revised to read as follows:

§ 58.20

Special purpose monitors (SPM).

* * * * *

(c) All data from an SPM using an FRM, FEM, or ARM which has operated for more than 24 months is eligible for comparison to the relevant NAAQS, subject to the conditions of § 58.30, unless the air monitoring agency demonstrates that the data came from a particular period during which the requirements of appendix A, appendix C, or appendix E to this part were not met in practice.

* * * * *

Appendix A to Part 58—[Amended]

14. Appendix A is amended by:

a. Revising the third (last) sentence of section 2.4;

b. Revising Equation 7 of section 4.1.4;

c. Revising the definition of the symbol “ n” for Equation 11 of section 4.2.1,

d. Revising the last sentence in section 4.2.2.2, and

e. Revising the definition of the symbol “ n_j” for Equation 12 of section 4.3.2.1 to read as follows:

2. General Monitoring Requirements

* * * * *

2.4 * * * For clarification and to participate, monitoring organizations should contact either the appropriate EPA Regional Quality Assurance (QA) Coordinator at the appropriate EPA Regional Office location, or the NPAP Coordinator at the Air Quality Assessment Division, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency in Research Triangle Park, North Carolina.

* * * * *

4. Calculations for Data Quality Assessments

* * * * *

4.1.4 * * *

* * * * *

4.2.1 * * *

where, n is the number of valid data pairs being aggregated, and X²_0.1, n-1 is the 10th percentile of a chi-squared distribution with n-1 degrees of freedom. The factor of 2 in the denominator adjusts for the fact that each d_i is calculated from two values with error.

4.2.2 * * * The absolute volume bias upper bound is then calculated using equation 3 of this appendix, where n is the number of flow rate audits being aggregated; t_0.95, n-1 is the 95th quantile of a t-distribution with n-1 degrees of freedom, the quantity AB is the mean of the absolute values of the d_i's and is calculated using equation 4 of this appendix, and the quantity AS in equation 3 of this appendix is the standard deviation of the absolute values of the d_i's and is calculated using equation 5 of this appendix.

4.3.2.1 * * *

where, n_j is the number of pairs and d₁, d₂, * * *, d _nj are the biases for each of the pairs to be averaged.

* * * * *

Appendix D to Part 58—[Amended]

15. Appendix D is amended by:

a. Revising section 4.6(a);

b. Revising the title of Table D-4 and Footnote 1 to Table D-4; and

c. Revising section 4.7.2 to read as follows:

4. Pollutant-Specific Design Criteria for SLAMS Sites

* * * * *

4.6 Particulate Matter (PM₁₀) Design Criteria.

(a) Table D-4 indicates the approximate number of permanent stations required in MSAs to characterize national and regional PM₁₀ air quality trends and geographical patterns. The number of PM₁₀ stations in areas where MSA populations exceed 1,000,000 must be in the range from 2 to 10 stations, while in low population urban areas, no more than two stations are required. A range of monitoring stations is specified in Table D-4 because sources of pollutants and local control efforts can vary from one part of the country to another and therefore, some flexibility is allowed in selecting the actual number of stations in any one locale. Modifications from these PM₁₀ monitoring requirements must be approved by the Regional Administrator.

Table D-4 of Appendix D to Part 58. PM₁₀ Minimum Monitoring Requirements (Approximate Number of Stations Per MSA) ^[1]

* * * * *

4.7.2 Requirement for Continuous PM_2.5 Monitoring. The State, or where appropriate, local agencies must operate continuous PM_2.5 analyzers equal to at least one-half (round up) the minimum required sites listed in Table D-5 of this appendix. At least one required continuous analyzer in each MSA must be collocated with one of the required FRM/FEM/ARM monitors, unless at least one of the required FRM/FEM/ARM monitors is itself a continuous FEM or ARM monitor in which case no collocation requirement applies. State and local air monitoring agencies must use methodologies and quality assurance/quality control (QA/QC) procedures approved by the EPA Regional Administrator for these required continuous analyzers.

* * * * *

Footnotes

1.  In 40 CFR part 58 and in this preamble, the terms monitor, analyzer, and sampler are sometimes used interchangeably. Monitor is the more general term. Most often, analyzer means a self-contained monitor which can produce concentration data on-site. Sampler means a device that collects a sample (e.g., a filter) which must be further processed at an outside laboratory to obtain the concentration value.

2.  EPA notes that the term “design value” as defined in the final rule (40 CFR part 58.1, 71 FR 61296) is the calculated concentration of a pollutant according to the applicable appendix of part 50 for the highest monitoring site in an attainment or nonattainment area, and that EPA's usage of “design value” in the rule text was consistent with this definition.

3.  “Use of PM Reference Methods and Daylight Savings Time,” J. David Mobley; Office of Air Quality Planning and Standards, June 11, 1999. http://www.epa.gov/​ttn/​amtic/​files/​ambient/​pm25/​stdtime.pdf.

4.  The intention to base sampling on local standard time was correctly reflected in rule text applicable to PM_2.5. 40 CFR part 50, appendix N (Interpretation of the National Ambient Air Quality Standards for PM_2.5) reads: “Daily values for PM_2.5 refers to the 24-hour average concentrations of PM_2.5 calculated (averaged from hourly measurements) or measured from midnight to midnight (local standard time) that are used in NAAQS computations.”

1.  Selection of urban areas and actual numbers of stations per area will be jointly determined by EPA and the State agency.