Fine Particulate Matter National Ambient Air Quality Standards: State Implementation Plan Requirements

Federal RegisterAug 24, 2016

Ask Donna

What actually matters in this document.

Text

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 50, 51, and 93

[EPA-HQ-OAR-2013-0691; FRL-9946-36-OAR]

RIN 2060-AQ48

Fine Particulate Matter National Ambient Air Quality Standards: State Implementation Plan Requirements

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule.

SUMMARY:

The Environmental Protection Agency (EPA) is finalizing requirements that state, local and tribal air agencies would have to meet as they implement the current and future national ambient air quality standards (NAAQS) for fine particulate matter (PM

2.5

). Specifically, this document provides details on meeting the statutory state implementation plan (SIP) requirements that apply to areas designated nonattainment for any PM

2.5

NAAQS, such as: General requirements for attainment plan due dates and attainment dates; emissions inventories; attainment demonstrations; provisions for demonstrating reasonable further progress; quantitative milestones; contingency measures; and nonattainment New Source Review (NNSR) permitting programs, among other things. This rule clarifies the specific attainment planning requirements that apply to PM

2.5

NAAQS nonattainment areas based on their classification (either Moderate or Serious), and the process for reclassifying Moderate areas to Serious. Additionally, in this document the EPA is revoking the 1997 primary annual standard for areas designated as attainment for that standard because the EPA revised the primary annual standard in 2012. The EPA first established the PM

2.5

NAAQS in 1997, completed a review and revision of those standards in 2006, and most recently completed a review and revision of the PM

2.5

NAAQS on December 14, 2012.

DATES:

This final rule is effective on October 24, 2016.

ADDRESSES:

The EPA has established a docket for this action, identified by Docket ID No. EPA-HQ-OAR-2013-0691. All documents in the docket are listed in the

http://www.regulations.gov

Web site. Although listed in the index, some information is not publicly available,

e.g.,

Confidential Business Information or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the Internet and will be publicly available only in hard copy. Publicly available docket materials are available either electronically in

http://www.regulations.gov

FOR FURTHER INFORMATION CONTACT:

For general information on this rule, contact Mr. Rich Damberg, Office of Air Quality Planning and Standards, U.S. EPA, by phone at (919) 541-5592 or by email at

damberg.rich@epa.gov

; or Mr. Patrick Lessard, Office of Air Quality Planning and Standards, U.S. EPA, by phone at (919) 541-5383 or by email at

lessard.patrick@epa.gov

. For information on the Information Collection Request (ICR), contact Mr. Butch Stackhouse, Office of Air Quality Planning and Standards, U.S. EPA, by phone at (919) 541-5208 or by email at

stackhouse.butch@epa.gov

SUPPLEMENTARY INFORMATION:

I. General Information

A. Preamble Glossary of Terms and Acronyms

The following are abbreviations of terms used in the preamble.

AERR Air Emissions Reporting Requirements

BACM Best Available Control Measures

BACT Best Available Control Technology

BART Best Available Retrofit Technology

BC Black Carbon

CAA Clean Air Act

CAIR Clean Air Interstate Rule

CAMx Comprehensive Air Quality Model with Extensions

CBI Confidential Business Information

CBSA Core-based Statistical Area

CDD Clean Data Determination

CFR Code of Federal Regulations

CMAQ Community Multi-Scale Air Quality Model

CSAPR Cross-State Air Pollution Rule

CSN Chemical Speciation Network

DOD Department of Defense

DOT Department of Transportation

EC Elemental Carbon

EGU Electric Generating Unit

EPA Environmental Protection Agency

Fe Iron

FEM Federal Equivalent Method

FIP Federal Implementation Plan

FRM Federal Reference Method

HCl Hydrogen Chloride

ICR Information Collection Request

LAER Lowest Achievable Emission Rate

MACT Maximum Achievable Control Technology

MATS Mercury and Air Toxics Standards

MSM Most Stringent Measures

MPO Metropolitan Planning Organization

NAAQS National Ambient Air Quality Standards

NAICS North American Industry Classification System

NAPAP National Acid Precipitation Assessment Program

NEI National Emissions Inventory

NESHAP National Emissions Standard for Hazardous Air Pollutants

Ammonia

Ammonium

Ammonium Nitrate

HSO

Ammonium Bi-Sulfate

(NH

)

Ammonium Sulfate

NNSR Nonattainment New Source Review

Nitrogen Oxides

Nitrate

NSPS New Source Performance Standards

Ozone

OM Organic Mass

OMB Office of Management and Budget

PM Particulate Matter

2.5

Particulate Matter Equal to or Less than 2.5 Microns in Diameter (Fine Particulate Matter)

Particulate Matter Equal to or Less than 10 Microns in Diameter

PRA Paperwork Reduction Act

PSD Prevention of Significant Deterioration

RACM Reasonably Available Control Measures

RACT Reasonably Available Control Technology

RFP Reasonable Further Progress

RICE Reciprocating Internal Combustion Engines

SIP State Implementation Plan

SOA Secondary Organic Aerosols

Sulfur Dioxide

Sulfate

TAR Tribal Authority Rule

TIP Tribal Implementation Plan

TIP Transportation Improvement Program

TSP Total Suspended Particles

μm Micrometer (Micron)

VMT Vehicle Miles Traveled

VOC Volatile Organic Compounds

B. Entities Affected by This Rule

Entities potentially affected directly by this final rule include state, local and tribal governments and air pollution control agencies responsible for attainment and maintenance of the NAAQS. Entities potentially affected indirectly by this final rule as regulated sources include owners and operators of sources that emit PM

2.5

, sulfur dioxide (SO

), oxides of nitrogen (NO

), volatile organic compounds (VOC) and/or ammonia (NH

). Parties affected by the conformity-related elements include state and local transportation and air quality agencies, metropolitan planning organizations (MPOs), and all federal agencies including the U.S. Department of Transportation, the U.S. Department of Defense, the U.S. Department of Interior and the U.S. Department of Agriculture. Others potentially affected indirectly by this final rule include members of the general public who live, work, or recreate in areas affected by elevated ambient PM

2.5

levels in areas designated nonattainment for a PM

2.5

NAAQS.

C. Obtaining a Copy of This Document and Other Related Information

In addition to being available in the docket, an electronic copy of this

Federal Register

document will be posted at

http://www3.epa.gov/airquality/particlepollution/actions.html

D. Organization of This Federal Register Document

The information presented in this document is organized as follows:

I. General Information

A. Preamble Glossary of Terms and Acronyms

B. Entities Affected by This Rule

C. Obtaining a Copy of This Document and Other Related Information

D. Organization of This

Federal Register

Document

II. Background

A. Introduction

B. Overview of PM

2.5

NAAQS and Implementation

C. Atmospheric Chemistry of PM

2.5

and Its Precursors

III. Requirements With Respect to the Treatment of PM

2.5

Precursors in Attainment Plans and the NNSR Program

A. Background

B. Summary of Proposal

C. Final Rule

IV. Requirements for PM

2.5

Moderate Nonattainment Area Plans

A. Plan Due Dates

B. Emissions Inventory Requirements

C. Pollutants To Be Addressed in the Plan

D. Attainment Plan Control Strategy

E. Modeling for Attainment Demonstrations

F. RFP Requirements

G. Quantitative Milestones

H. Contingency Measures

I. Attainment Dates

J. Attainment Date Extensions

V. Reclassification of a PM

2.5

Moderate Nonattainment Area to Serious

A. Discretionary Authority

B. Mandatory Duty

VI. Requirements for PM

2.5

Serious Nonattainment Area Plans

A. Plan Due Dates

B. Emissions Inventory Requirements

C. Pollutants To Be Addressed in the Plan

D. Attainment Plan Control Strategy

E. Modeling for Attainment Demonstrations

F. RFP Requirements

G. Quantitative Milestones

H. Contingency Measures

I. Attainment Dates

J. Attainment Date Extensions

VII. Requirements Under CAA Section 189(d) for PM

2.5

Serious Areas That Fail To Attain the NAAQS by the Applicable Attainment Date

A. Plan Due Dates

B. Emissions Inventory Requirements

C. Pollutants To Be Addressed in the Plan

D. Attainment Plan Control Strategy

E. Modeling for Attainment Demonstrations

F. RFP Requirements

G. Quantitative Milestones

H. Contingency Measures

I. Attainment Dates

VIII. NNSR Requirements for PM

2.5

Nonattainment Areas

A. Background

B. What are the final NNSR requirements for PM

2.5

C. Transition Provisions for Major Source Permitting in PM

2.5

Nonattainment Areas

IX. Other Requirements and Considerations for PM

2.5

Nonattainment Areas

A. Waivers Under Section 188(f)

B. Conformity Requirements

C. Clean Data Policy

D. Section 179B/International Border Areas

E. Enforcement and Compliance

F. Multi-Pollutant Considerations

G. Measures To Ensure Appropriate Protections for Overburdened Populations

H. Tribal Issues

I. Voluntary Programs for Reducing Ambient PM

2.5

J. Improved Stationary Source Emissions Monitoring

K. Stationary Source Test Methods for Emissions of Condensable PM

2.5

X. Revocation of the 1997 Primary Annual PM

2.5

NAAQS

A. Background

B. History of Revocation of Other NAAQS

C. Requirements for Revocation and Related Anti-Backsliding Requirements for the 1997 Primary Annual PM

2.5

NAAQS

XI. Environmental Justice Considerations

XII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review

B. Paperwork Reduction Act (PRA)

C. Regulatory Flexibility Act (RFA)

D. Unfunded Mandates Reform Act (UMRA)

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 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use

I. National Technology Transfer and Advancement Act

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

K. Congressional Review Act (CRA)

L. Determination Under Section 307(d)

M. Judicial Review

XIII. Statutory Authority

II. Background

A. Introduction

Ambient, or outdoor, air can contain a variety of pollutants, including particulate matter (PM). Airborne PM can be comprised of either solid or liquid particles, and can be a complex mixture of particles in both solid and liquid form. The most common constituents of airborne PM include the following: Sulfate (SO

); nitrate (NO

); ammonium (NH

); elemental carbon (EC); organic mass (OM); and inorganic material, generally referred to as “crustal” material, which can include metals, dust, sea salt and other trace elements. Airborne PM can be of different sizes, commonly referred to as “coarse” and “fine” particles. Fine particles, in general terms, are PM with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers (µm). For this reason, particles of this size are referred to as PM

2.5

. PM

2.5

particles commonly include “primary” particles and “secondary” particles. Primary particles, or direct PM

2.5

, are emitted by sources directly into the air as solid or liquid particles (

e.g.,

elemental carbon from diesel engines or wildfires, or condensable organic particles from gasoline engines). Secondary particles are formed in the atmosphere as a result of chemical reactions between specific pollutants known as PM

2.5

precursors (

e.g.,

reactions between NO

and SO

emissions from mobile and stationary sources combined with ammonia to form ammonium nitrate and ammonium sulfate).

The human health effects associated with long or short-term exposure to PM

2.5

are significant and include premature mortality, aggravation of respiratory and cardiovascular disease (as indicated by increased hospital admissions and emergency room visits) and development of chronic respiratory disease. In addition, welfare effects associated with elevated PM

2.5

levels include visibility impairment as well as effects on sensitive ecosystems, materials damage and soiling and climatic and radiative processes.

For a complete discussion of the human health and welfare effects associated with exposure to elevated concentrations of particulate matter,

see generally

“Integrated Science Assessment for Particulate Matter.” U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment—RTP Division, February 10, 2010. EPA/600/R-08/139F. Available at:

http://www3.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_isa.html

See

Chapter 2.

On December 14, 2012, the EPA made revisions to the suite of the NAAQS for PM to provide requisite protection of public health and welfare with an adequate margin of safety. The EPA also made corresponding revisions to the data handling conventions for PM and the ambient air monitoring, reporting and network design requirements for PM. Specifically, the agency revised the primary annual PM

2.5

standard by lowering the level from 15.0 to 12.0 μg/

to provide increased protection against health effects associated with long- and short-term PM

2.5

exposures. The EPA did not revise the secondary annual PM

2.5

standard, which remains at 15.0 μg/m

The EPA eliminated spatial averaging as part of the form of the PM

2.5

annual standards to avoid potential disproportionate impacts on at-risk populations. In addition, the EPA retained the level and form of the primary and secondary 24-hour PM

2.5

standards to continue to provide supplemental protection against health effects associated with short-term PM

2.5

exposures. Although not directly relevant to this rulemaking with respect to implementation of the PM

2.5

NAAQS, it should be noted that in December 2012, the EPA also did not revise the level or form of the primary and secondary 24-hour PM

NAAQS, which remain at 150 μg/m

78 FR 3086 (January 15, 2013).

This final rulemaking applies to implementation of the PM

2.5

NAAQS. For the PM

NAAQS, states and the EPA will continue to implement those NAAQS in accordance with the applicable statutory requirements of the CAA and the EPA's existing guidance in the “The General Preamble for Implementation of Title I of the Clean Air Act (CAA) Amendments,” 57 FR 13498 (April 16, 1992); and “State Implementation Plans for Serious PM-10 Nonattainment Areas: Addendum to the General Preamble for the Implementation of Title I of the Clean Air Act (CAA) Amendments,” 59 FR 41998 (August 16, 1994). Throughout this preamble, these documents will be referred to as the “General Preamble” and the “Addendum,” respectively.

Estimates show that attainment of the primary PM

2.5

standards will result in hundreds fewer premature deaths each year, prevent tens of thousands of hospital admissions each year and prevent hundreds of thousands of doctor visits, absences from work and school and respiratory illnesses in children annually.

Attainment of the primary PM

2.5

standards will have welfare co-benefits in addition to direct human health benefits. The term “welfare co-benefits” covers both environmental and societal benefits of reducing pollution, such as reductions in visibility impairment, materials damage and ecosystem damage.

“Regulatory Impact Analysis for the Final Revisions to the National Ambient Air Quality Standards for Particulate Matter.” U.S. Environmental Protection Agency, Office of Air Quality and Planning Standards, Health and Environmental Impacts Division, February 28, 2013. EPA-452/R-12-005.

See

http://www3.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_ria.html

Ibid.

B. Overview of PM

2.5

NAAQS and Implementation

1. General Background

Sections 108 and 109 of the Clean Air Act (CAA or Act) govern the establishment, review and revision, as appropriate, of the NAAQS for widespread pollutants emitted from numerous and diverse sources considered harmful to public health and the environment. The CAA requires two types of NAAQS: (i)

Primary

standards, which set limits to protect public health, including the health of at-risk populations; and (ii)

secondary

standards, which set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation and buildings.

The CAA also establishes important roles both for state and tribal governments and for the EPA in implementing the NAAQS. In accordance with the principle of cooperative federalism, both state and tribal governments and the EPA have respective authorities and responsibilities under the CAA. At the outset, the EPA has the authority and responsibility to promulgate the NAAQS. In turn, state, local and tribal air pollution control agencies (“air agencies”) have the authority and primary responsibility for developing and implementing attainment plans that contain emission control measures needed to achieve the air quality standards in a timely manner in each nonattainment area, consistent with the requirements of the CAA. The EPA often assists states by promulgating regulations or providing guidance for meeting implementation requirements and by providing technical tools, including information on control measures.

6 7

It is important to note that the EPA does not have a mandatory duty to promulgate an implementation rule for the PM

2.5

NAAQS, and the obligations of state and tribal air agencies to develop and submit an attainment plan are independent obligations and not conditioned upon the EPA promulgating an implementation rule for the PM

2.5

NAAQS.

When the term “state” is used hereafter, it will refer generically to states, local air agencies, and tribal governments electing to be treated as states for the purposes of implementing the CAA. Of additional note is that the 1998 Tribal Authority Rule (TAR), which is found in 40 CFR part 49, which implements section 301(d) of the CAA, provides that tribes be treated in the same manner as a state when implementing certain sections of the CAA. It gives tribes the option of developing tribal implementation plans (TIPs), but unlike states, tribes are not required to develop implementation plans. Section IX.I of this preamble provides further discussion of tribal issues.

The EPA also promulgates nationally applicable control requirements and emission limits for many sources such as new motor vehicles, certain categories of new and modified major stationary sources and existing stationary sources of toxic air pollutants. These federal actions assist states by achieving emissions reductions from certain categories of sources nationwide, which can help with local attainment needs in a given nonattainment area. The EPA also has authority to provide funding, technical assistance, and guidance to states to support implementation of the NAAQS. In addition, the EPA has authority to address interstate transport of pollutants, in the event that states fail to do so. Through this authority, the EPA has addressed regional transport of pollutants from upwind states to downwind states, and has previously done so for purposes of the PM

2.5

NAAQS.

In addition, the EPA has the authority and responsibility to review and take action to approve or disapprove attainment plans submitted by states based upon whether they meet applicable statutory and regulatory requirements and to initiate the process for imposition of sanctions and/or issue federal implementation plans (FIPs) when states fail to fulfill their CAA obligations.

See

76 FR 48208 (August 8, 2011).

2. History of PM

2.5

NAAQS Implementation

The EPA first promulgated annual and 24-hour NAAQS for PM

2.5

in July 1997.

Prior to that time, the EPA had addressed ambient PM through other means, first by regulating “total suspended particles” (TSP) and then later by regulating PM

10.

After protracted litigation, the 1997 NAAQS for PM

2.5

were upheld by the U.S. Court of Appeals for the District of Columbia Circuit in March 2002.

The EPA subsequently promulgated designations for the 1997 PM

2.5

NAAQS nationwide, designating a number of areas as nonattainment for the 1997 PM

2.5

NAAQS, effective April 2005.

In April 2007, the EPA issued a detailed implementation rule to assist states with the development of SIP submissions to meet attainment plan requirements for the 1997 NAAQS (the “2007 PM

2.5

Implementation Rule”).

In May 2008, the EPA issued another rule to assist states with SIP submissions to meet the specific requirements for permitting programs for NNSR purposes in designated nonattainment areas (the “2008 PM

2.5

NSR Rule”).

The EPA premised both the 2007 PM

2.5

Implementation Rule and the 2008 PM

2.5

NSR Rule on the EPA's interpretation of the statute that

nonattainment areas for the PM

2.5

NAAQS were subject solely to the general attainment plan requirements of subpart 1, part D of title I of the CAA (“subpart 1”).

62 FR 38652 (July 18, 1997).

For a complete summary of legal challenges and related court decisions on the PM NAAQS,

see generally

78 FR 3086 (January 15, 2013).

70 FR 944 (January 5, 2005).

72 FR 20583 (April 25, 2007).

73 FR 28231 (May 16, 2008).

Section 109(d)(1) of the CAA requires the EPA periodically to review the science upon which the standards are based and the standards themselves, and to revise the standards as may be appropriate. In October 2006, the EPA promulgated revisions to the suite of the NAAQS for PM, and in particular the EPA revised the 24-hour PM

2.5

standards.

In accordance with section 107(d), the EPA subsequently designated a number of areas as nonattainment for the revised 2006 24-hour PM

2.5

standards, effective December 2009.

In March 2012, the EPA issued a guidance document specifically to aid states in preparing their SIP submissions to meet attainment plan requirements for the 2006 24-hour PM

2.5

NAAQS in designated nonattainment areas.

The EPA's guidance for the 2006 PM

2.5

NAAQS was based, in large part, on the requirements finalized in the 2007 PM

2.5

Implementation Rule, which the EPA based solely upon the statutory requirements of subpart 1.

71 FR 61144 (October 17, 2006).

74 FR 58688 (November 13, 2009).

Memorandum of March 2, 2012 (withdrawn June 6, 2013), from Stephen D. Page, Director, Office of Air Quality Planning and Standards, to the EPA Regional Air Directors, Regions I-X, “Implementation Guidance for the 2006 24-Hour Fine Particle (PM

2.5

) National Ambient Air Quality Standards (NAAQS).” Available at:

http://www3.epa.gov/ttn/naaqs/aqmguide/collection/cp2/20120302_page_implement_guidance_2006-24-hr_pm2.5_naaqs.pdf.

The EPA initiated a review of the PM

2.5

NAAQS in June 2007, proposing revisions to the primary and secondary PM

2.5

NAAQS on June 29, 2012.

The EPA issued its final rule on December 14, 2012, in which it lowered the primary annual PM

2.5

standard from 15.0 μg/m

to 12.0 μg/m

to provide increased protection against health effects associated with long- and short-term fine particle exposures.

The EPA also eliminated spatial averaging as part of the form of the annual standard to avoid potential disproportionate impacts on at-risk populations.

The EPA retained the level (35 μg/m

) and form (98th percentile, averaged over 3 years) of the primary 24-hour PM

2.5

standard, as revised in 2006, to provide supplemental protection against health effects associated with short-term PM

2.5

exposures, especially in areas with high peak PM

2.5

concentrations.

This suite of primary PM

2.5

standards provides increased public health protection, including the health of at-risk populations which include children, older adults, persons with pre-existing health and lung disease and persons of lower socioeconomic status, against a broad range of PM

2.5

-related effects that include premature mortality, increased hospital admissions and emergency department visits and development of chronic respiratory disease.

With regard to the secondary (welfare-based) standards, the EPA retained the existing annual PM

2.5

standard of 15.0 μg/m

and the existing 24-hour PM

2.5

standard of 35 μg/m

to protect against PM-related non-visibility welfare effects including ecological effects, effects on materials and climate impacts. In addition, the secondary 24-hour PM

2.5

standard provides protection for PM-related visibility impairment.

77 FR 38890 (June 29, 2012).

78 FR 3086 (January 15, 2013).

Spatial averaging of monitored ambient air quality data was a feature of the prior PM

2.5

NAAQS monitoring regulations which had the potential for masking particularly high PM

2.5

concentrations at certain monitored locations within nonattainment areas.

71 FR 61144 (October 17, 2006).

General information regarding the health effects associated with PM

2.5

exposures is available at:

http://www3.epa.gov/airquality/particlepollution/health.html.

Additional information, such as the EPA's technical documents supporting the latest review of the standards, is available at:

http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_index.html.

On January 4, 2013, shortly after the EPA promulgated the 2012 revisions to the suite of PM NAAQS, the D.C. Circuit issued its decision in a challenge to the 2007 PM

2.5

Implementation Rule and the 2008 PM

2.5

NSR Rule. In

NRDC

EPA,

the court held that the EPA erred in implementing the 1997 PM

2.5

NAAQS pursuant only to the general implementation requirements of subpart 1, rather than also to the implementation requirements specific to particulate matter (PM

) in subpart 4, part D of title I of the CAA (“subpart 4”).

The court reasoned that the plain meaning of the CAA requires implementation of the 1997 PM

2.5

NAAQS under subpart 4 because PM

2.5

particles fall within the statutory definition of PM

and thus implementation of the PM

2.5

NAAQS is subject to the same statutory requirements as the PM

NAAQS. In addition, although the court stated that its decision that the EPA must implement the PM

2.5

NAAQS pursuant to subpart 4 requirements meant that it did not have to reach decisions on other issues concerning the regulation of precursors to PM

2.5

, the court nonetheless noted that subpart 4 has specific requirements with respect to regulation of such precursors. As a result, the court remanded to the EPA both the 2007 PM

2.5

Implementation Rule and the 2008 PM

2.5

NSR Rule, both of which were premised on the EPA's interpretation of the statute that subpart 1 was the only applicable subpart for the implementation of the 1997 PM

2.5

NAAQS in nonattainment areas. The court instructed the EPA “to repromulgate these rules pursuant to subpart 4 consistent with this opinion.” Given the D.C. Circuit's opinion in

NRDC

EPA,

the EPA withdrew its 2012 guidance document for the 2006 24-hour PM

2.5

NAAQS in June 2013. Because the court had concluded that the EPA and states must implement the PM

2.5

NAAQS consistent with the statutory requirements of subpart 4, the EPA's 2012 guidance for attainment plans for the 2006 PM

2.5

NAAQS premised solely upon subpart 1 requirements was no longer appropriate.

NRDC

EPA,

706 F.3d 428 (D.C. Cir. 2013).

The EPA issued a notice of proposed rulemaking (NPRM) on March 23, 2015 (80 FR 15340) titled, “Fine Particulate Matter National Ambient Air Quality Standards: State Implementation Plan Requirements” (PM

2.5

SIP Requirements Rule) to meet a number of objectives. This final rule accomplishes those objectives. It clarifies how states should meet the statutory SIP requirements that apply to areas designated nonattainment for any PM

2.5

NAAQS under subparts 1 and 4. It does so by establishing regulatory requirements and providing guidance that will be applicable to attainment plans for the 2012 PM

2.5

NAAQS and any future revisions of the PM

2.5

NAAQS, subject to revisions that may be necessary for implementation purposes in the future. In addition, this action responds to the D.C. Circuit's remand of the 2007 PM

2.5

Implementation Rule and the 2008 PM

2.5

NSR Rule. As a result, the requirements of the rule will also govern future actions associated with states' ongoing implementation efforts for the 1997 and 2006 PM

2.5

NAAQS.

The public comment period for the proposed PM

2.5

SIP Requirements Rule closed on May 29, 2015, and the EPA received 56 comments during that period. The preamble to this final rule includes discussion of the most significant comments received on the proposal and how the EPA considered them in developing the agency's final action concerning the specific nonattainment planning requirements. The Response to Comments document that accompanies this final rule provides more detailed responses to the significant comments received. The public comments received on the NPRM and the EPA's Response to Comment

document are posted in the docket at

http://www.regulations.gov

(Docket ID No. EPA-HQ-OAR-2013-0691).

C. Atmospheric Chemistry of PM

2.5

and Its Precursors

1. Overview

In order to determine how to regulate sources of direct PM

2.5

and PM

2.5

precursors to attain the PM

2.5

NAAQS in a given nonattainment area, it is necessary to understand the basic chemical processes that cause or contribute to the formation of ambient PM

2.5

. Accordingly, an understanding of these processes is necessary to design appropriate regulations for implementation of the PM

2.5

NAAQS.

As noted earlier, the term PM

2.5

refers to particles of solid and liquid material less than 2.5 microns in aerodynamic diameter.

“Primary” PM

2.5

is emitted directly from emissions sources or activities, such as from diesel fuel combustion, wood burning, construction activities, and unpaved roads, and it includes both filterable and condensable particles.

“Secondary” PM

2.5

is formed as a result of emissions of certain precursor gases that undergo chemical reactions in the atmosphere. The principal precursor gases that contribute to secondary PM

2.5

formation are SO

, from the combustion of coal or other high sulfur fuels; NO

, from many types of fossil fuel combustion; VOC, from certain fuels, solvents and industrial processes; and ammonia, from sources such as animal feeding operations, wastewater treatment and fertilizer. To illustrate the types of sources that emit relevant pollutants, Table 1 provides National Emissions Inventory (NEI) data for 2011 that represent nonattainment area anthropogenic and wildfire emissions estimates for direct PM

2.5

and the four main PM

2.5

precursor gases from major source sectors.

The regulatory definition of PM

2.5

includes particles with an upper 50 percent cut-point of 2.5μm aerodynamic diameter (the 50 percent cut-point diameter is the diameter at which the sample collects 50 percent of the particles and rejects 50 percent of the particles). PM

2.5

particles have a penetration curve as measured by a reference method based on Appendix L of 40 CFR part 50 and designated in accordance with 40 CFR part 53, by an equivalent method designed in accordance with 40 CFR part 53, or by an approved regional method designated in accordance with Appendix C of 40 CFR part 58.

Certain commercial or industrial activities involving high temperature processes (

e.g.,

fuel combustion, metal processing, cooking operations) emit gaseous pollutants into the ambient air that rapidly condense into particle form. These “condensable” PM emissions exist almost entirely in the 2.5 or less micron range and can consist of organic material, sulfuric acid and metals.

Table 1—Total Emissions of PM

2.5

and Precursors for Major Sectors in PM

2.5

Nonattainment Areas

[In tons/year]

Source: 2011 National Emissions Inventory (Version 2)

See also Sierra Club

EPA,

294 F.3d 155 (D.C. Cir. 2002).

See

Section IV of this preamble for a thorough discussion of past policy and guidance on reasonably available control measures (RACM) and reasonably available control technology (RACT). Section IV of this preamble discusses the EPA's final policy that under subpart 4, for Moderate areas that demonstrate that attainment by the statutory attainment date is impracticable, RACM and RACT would constitute all those technologically and economically feasible measures available for sources in the area that can be implemented within 4 years of designation, but they would not constitute the complete set of measures required to

demonstrate attainment as expeditiously as practicable.

In light of the court's decision in

NRDC

EPA,

the EPA considers it necessary to describe how states must address regulation of PM

2.5

precursors in attainment plans and NNSR programs for the PM

2.5

NAAQS. The court's decision made clear that appropriate regulation of all precursors in designated nonattainment areas is presumptively required under the CAA, and the regulation of precursors in general is a critical issue for attainment of the PM

2.5

NAAQS because secondarily formed particles are a substantial component of PM

2.5

concentrations in most nonattainment areas of the United States.

For the purposes of this rule, the EPA considers that for all PM

2.5

nonattainment areas, the PM

2.5

precursors for regulatory purposes are the four scientific precursors that the EPA has previously identified: SO

, NO

, VOC and ammonia. This rule does not include any national presumption that would allow a state to exclude, without a demonstration, sources of emissions of a particular precursor from further analysis for attainment plan or NNSR control requirements in a PM

2.5

nonattainment area. However, the EPA's interpretation of subpart 4 requirements with respect to precursors in attainment plans for PM

, as set out in the General Preamble, contemplates that the state may develop an attainment plan that regulates only those precursors that are necessary to control for purposes of timely attainment in the nonattainment area,

i.e.,

states may determine that only certain precursors need to be regulated in a particular PM

2.5

nonattainment area for attainment purposes.

Courts have upheld this approach to the requirements of subpart 4 for PM

The EPA believes that application of a similar approach to PM

2.5

precursors under subpart 4 is appropriate and reasonable.

See

the

Federal Register

published on April 16, 1992 (57 FR 13498, 13540 and 13541).

See, e.g., Assoc. of Irritated Residents

EPA, et al.,

423 F.3d 989 (9th Cir. 2005).

The EPA interprets the CAA to require states to inventory emissions and adopt control measures as appropriate for direct PM

2.5

and all PM

2.5

precursors. This interpretation is based on CAA section 302(g), which defines an air pollutant as including precursors contributing to the formation of that pollutant; the EPA's identification of the four main scientific PM

2.5

precursors; and the CAA provisions requiring adoption of all control measures (

i.e.,

RACM and RACT) needed in order to attain the standard as expeditiously as practicable. CAA section 189(e) explicitly requires that the control requirements applicable for major stationary sources of direct PM

2.5

emissions must also apply to major stationary sources of PM

2.5

precursors, unless the state provides a showing that emissions of a particular precursor from major stationary sources do not contribute significantly to levels that exceed the standard in the nonattainment area of concern. Thus, the statute generally requires control of all PM

2.5

precursors in a nonattainment area, but it provides an express exception applicable to major stationary sources in such areas if an appropriate demonstration is made.

The EPA also notes that CAA section 189(e) contains certain ambiguities that require interpretation. For example, CAA section 189(e) does not specify the precise method by which a state or the EPA should determine whether precursor emissions from major stationary sources do not “contribute significantly” to levels which exceed the standard in a given nonattainment area. Subpart 4 also does not explicitly address whether it would be appropriate to include a potential exemption from precursor controls for all source categories under certain circumstances, because a specific exemption from precursor controls is expressly made available in the statute only for major stationary sources. These issues are addressed in this final rule.

B. Summary of Proposal

In the proposal, the EPA sought comment on how states could focus regulatory efforts on the appropriate PM

2.5

precursors in each area. Rather than simply requiring each state to regulate direct PM

2.5

and all PM

2.5

precursors without regard to whether that would be appropriate and necessary for expeditious attainment of the NAAQS, EPA took comment on different approaches for states to focus regulatory efforts on the appropriate pollutants. Thus, in the proposal, the EPA sought comment on three options by which a state could demonstrate that emission control requirements for a particular PM

2.5

precursor or precursors would not be required for sources in a particular nonattainment area.

The proposed “precursor demonstration” options outlined procedures and technical analyses a state could elect to perform to demonstrate that control requirements for sources of a particular precursor are not needed for expeditious attainment, or that a particular PM

2.5

precursor does not significantly contribute to PM

2.5

concentrations in the area. The proposal indicated that if the EPA were to approve such a precursor demonstration, then it would not be necessary for the state to adopt control requirements for sources of the precursor or precursors in the PM

2.5

attainment planning process generally and/or in the NNSR permitting process for that particular area. The EPA requested comment on whether the final rule should include one or more precursor demonstration approaches, and whether it would be appropriate to combine specific elements from different options.

The three proposed options were: (1) Option 1—two independent analyses consisting of an attainment planning analysis showing that control measures for a particular precursor are not needed for expeditious attainment and an optional NNSR analysis showing that major stationary sources of a particular precursor do not contribute significantly to levels that exceed the PM

2.5

standard, (2) Option 2—a single analysis (for purposes of attainment planning and NNSR) showing that all emissions of a particular precursor do not contribute significantly to levels that exceed the PM

2.5

standard, and (3) Option 3—a single analysis (for purposes of attainment planning and NNSR) showing that control measures for all sources for a particular precursor are not needed for expeditious attainment.

The EPA also described three technical issues associated with any such precursor demonstration and sought comment on the following: (1) The appropriate geographic scope of the analysis; (2) whether specific types of technical analyses (such as evaluating the contribution of the precursor to total PM

2.5

concentrations, or evaluating the sensitivity of the area to decreases or increases of the precursor) should be required for a precursor demonstration; and (3) whether the EPA should establish a bright-line ambient air quality threshold (

e.g.,

3 percent of the level of the relevant NAAQS in the area) to define an air quality change below which a precursor contribution should not be considered to be significant, thereby establishing that control of sources of the precursor is unnecessary in the area.

Lastly, the EPA indicated in the proposal that if a state had an approved precursor demonstration for a particular precursor in a Moderate area and the EPA later reclassifies the area to Serious, then the state would be required to develop an updated precursor demonstration if the state were again interested in having the precursor treated as insignificant for purposes of the Serious area plan. An updated precursor demonstration is necessary because many factors (

e.g.,

emissions, air quality and fine particle concentrations) could have changed substantially since the original

demonstration for the Moderate area attainment plan.

For more information on the proposed precursor demonstration options,

see

80 FR 15340, at 15350-15362.

C. Final Rule

The EPA received many comments on the three proposed precursor demonstration approaches. Most commenters supported the inclusion of some kind of optional precursor demonstration in the final rule. Some commenters suggested that states should have the flexibility to develop any of the types of demonstrations that the EPA described in the three proposed options. One group of commenters opposed any option that would exempt a particular precursor from control measures even if the state could demonstrate it could expeditiously attain the standard by the attainment date without controls on sources of the precursor. Another group of commenters suggested that if only one option is finalized, it should allow a state to rely on a sensitivity analysis to show that changes in emissions of a particular precursor would not have a substantial contribution to PM

2.5

concentrations in the area.

The EPA agrees with commenters who suggested that states should have the flexibility to conduct different types of precursor demonstrations appropriate to the area in question. Regardless of the type of precursor demonstration, the state will still need to provide adequate technical support and that demonstration will be subject to EPA approval. Thus, the EPA concludes that the specific form of the demonstration is not as crucial as its content and adequacy, in light of the facts and circumstances in the area. The EPA disagrees with commenters who argued that a state should not be able to determine insignificance for a precursor based on an attainment planning analysis showing expeditious attainment in the area without adopting new emissions reduction measures for the precursor in question. This approach has been upheld under subpart 4 with respect to implementation of the PM

NAAQS, and the EPA finds that it is reasonable to allow for a similar policy when implementing the PM

2.5

NAAQS.

See, e.g., Assoc. of Irritated Residents

EPA, et al.,

423 F.3d 989 (9th Cir. 2005).

After consideration of the numerous comments received on this issue, the EPA has decided to adopt a final approach that allows exclusion of certain precursor sources from certain SIP requirements, provided that states make the appropriate demonstrations. However, the EPA has revised the details of the specific types of demonstrations based on further evaluation of the comments received. Section III.C.1 of this preamble describes the expeditious attainment demonstration, in which a state shows that control requirements for a particular precursor are not needed for expeditious attainment by the Moderate area attainment date. Section III.C.2 of this preamble describes the three types of optional precursor demonstrations a state may submit to the EPA to establish that emissions of a precursor do not contribute significantly to PM

2.5

levels in a particular nonattainment area: (a) Comprehensive precursor demonstration; (b) major stationary source precursor demonstration; and (c) NNSR precursor demonstration. Each option is described in detail in the following subsections.

Section III.C.3 of this preamble highlights various technical issues associated with precursor demonstrations, including the appropriate geographic scope of the analyses, thresholds for characterizing an insignificant air quality change, and different analytical methods for assessing precursor contributions. Section III.C.4 of this preamble discusses certain procedural issues associated with precursor demonstrations. Section III.C.5 of this preamble addresses other relevant comments and responses.

1. Expeditious Attainment Demonstration

As noted earlier, the EPA's interpretation of subpart 1 and 4 requirements with respect to precursors in attainment plans for PM

has been that a state may develop an attainment plan that regulates only those precursors that are necessary to control for purposes of timely attainment in the area. The EPA believes that a similar policy approach for PM

2.5

precursors is also appropriate.

Under the expeditious attainment demonstration, a state may be able to determine through its identification of RACM/RACT for existing sources in an area whether expeditious attainment could be achieved without new control measures for a particular PM

2.5

precursor. It is important to note that this approach is available to a state only if the demonstration for the area (1) ensures attainment by the Moderate area attainment date (

i.e.,

the end of the sixth calendar year after designation), and (2) ensures that the area could not advance the attainment date by at least 1 year if it were to adopt reasonable control measures for the precursor in question. If the state determines that the area cannot practicably attain by the relevant Moderate area attainment date, then the state still would have the option of developing one of the precursor demonstrations described in Sections III.C.2.a-c of this preamble for showing that the precursor contribution is not significant. The expeditious attainment option is not available for Serious nonattainment areas because BACM/BACT measures for Serious areas are not solely limited to those measures needed for expeditious attainment under this final rule. (

See

further discussion of this issue in Section VI.D of this preamble, Serious Area Attainment Plan Control Strategies.)

For the expeditious attainment demonstration, the required analysis is what is already needed for a Moderate area attainment demonstration: The identification of reasonably available control measures that provide for expeditious attainment by the attainment date, and a determination that attainment cannot be advanced through the imposition of other reasonable measures (

i.e.

RACM/RACT and other reasonable measures that are identified for the area but not necessary for the area to attain within 6 years).

See

40 CFR 51.1006(a). After a comprehensive emissions inventory has been developed, the state should then identify potential control measures and assess factors related to technological feasibility, economic feasibility, and time needed for implementation for all types of sources in the area (

i.e.,

stationary, area, mobile) and all precursors emitted by such sources as included in the emissions inventory.

After identifying the set of control measures that are economically and technologically feasible for all precursors, the state may be able to show (using best available information on emissions, control options, technologies, and costs, along with appropriate air quality modeling) that those measures that could be identified as RACM/RACT and additional reasonable measures would not need to include new control measures for sources of a given precursor.

The state could show this by demonstrating that one set of control measures to be adopted into the plan would provide for attainment by the statutory attainment date; and that an additional set of potential control measures (including measures for the precursor in question, and remaining measures for all other contributing pollutants)

collectively

would not advance the attainment date by at least 1 year (

i.e.,

enable the area to attain 1 year earlier). Under these circumstances, the state would not need to adopt the second set of measures (including measures for the particular precursor) because they would not expedite attainment of the NAAQS in the area.

See

Section IV.D.1 of this preamble, Background for Attainment Plan Control Strategy, for further discussion of “additional reasonable measures.”

If the attainment planning demonstration shows that the area can attain the NAAQS expeditiously without new emission reduction measures for a particular precursor, the state would be required to adopt control measures for only a subset of the four PM

2.5

precursors as part of the attainment plan for the area, and existing sources in the nonattainment area would not be required to adopt new control measures for the particular precursor. Accordingly, the state would not need to address the precursor in the reasonable further progress plan, in quantitative milestones and associated reports, or be required to adopt contingency measures to reduce the precursor.

See

40 CFR 51.1009(a)(4)(i). (Note that for purposes of meeting the contingency measure requirement, however, the state would still have the discretion to adopt control measures as contingency measures for a precursor that would otherwise not be subject to RACM/RACT requirements.)

It also should be noted that development of an approvable attainment plan that does not include new control measures for a particular precursor would not exempt the state from the requirements to address the same precursor with respect to the NNSR program, nor would it excuse the state from reconsidering the significance of the precursor to the PM nonattainment problem in any subsequent Serious area SIPs that could be required for the nonattainment area.

2. Optional Precursor Demonstrations

Comprehensive Precursor Demonstration.

In line with the EPA's proposal for precursor insignificance demonstrations, the EPA is finalizing an option whereby a state may submit a comprehensive precursor demonstration as part of any Moderate or Serious area attainment plan. The use of the term “comprehensive” here refers to the fact that the demonstration covers all existing stationary, area, and mobile sources, rather than major sources alone. Note, however, that the comprehensive precursor demonstration does not affect precursor requirements for future new sources. Under this comprehensive precursor demonstration, the state would need to show that emissions of a particular precursor from all existing stationary, area, and mobile sources located in the nonattainment area do not contribute significantly to PM

2.5

levels that exceed the standard in the area. The state would first need to evaluate the contribution of all existing source emissions of the particular precursor to PM

2.5

concentrations that exceed the PM

2.5

standard (described in Section III.C.2 of this preamble). If the state cannot demonstrate via the concentration-based precursor demonstration that sources of a particular precursor have an insignificant contribution to PM

2.5

levels in an area,, then the state could still demonstrate that the precursor's contribution is insignificant by conducting a sensitivity analysis to evaluate the sensitivity of ambient PM

2.5

concentrations in the nonattainment area to decreases in the precursor emissions in the area (

e.g.,

whether a given decrease is insignificant) as discussed further in Section III.C.2.c of this preamble.

If a comprehensive precursor demonstration for a precursor is approved, the state would not establish a motor vehicle emissions budget for the relevant precursor, and regional emissions analyses for the precursor would not be required to be included in transportation conformity determinations. This is consistent with the transportation conformity rule's provisions concerning PM

2.5

precursors. (

See

40 CFR 93.102(b)(2)(iv) and (v)). Separately, states may continue to determine that on-road emissions of PM

2.5

precursors are insignificant even if emissions of a given precursor from other sources are significant. (

See

40 CFR 93.102(b)(2)(iv) and (v) and 93.109(f)). With regard to general conformity, if a state precursor demonstration is approved for one or more precursors, federal agencies would not be required to address the affected precursor(s) in general conformity determinations.

If a comprehensive precursor demonstration is approved by the EPA, then in developing the attainment plan for the area, the state would not be required to adopt control measures (

e.g.,

RACM/RACT) for the precursor for any existing stationary, area, or mobile sources in the nonattainment area. The attainment plan also would not be required to address the relevant precursor in meeting the RFP or quantitative milestone requirements, or in adopting contingency measures because these requirements commonly apply to pollutants that are the subject of emission reduction measures in the attainment plan. (Note that for purposes of meeting the contingency measure requirement, however, the state would still have the discretion to adopt emission reduction requirements on the precursor in question, in conjunction with emission reduction requirements on other pollutants.) The state would still need to include the precursor in all nonattainment area emission inventory submissions.

It also should be noted that development of an approvable attainment plan that does not include new control measures for a particular precursor would not exempt the state from the requirements to address that precursor with respect to the NNSR program, nor would it excuse the state from reevaluating the significance of the precursor to the PM nonattainment problem in any subsequent Serious area SIPs that could be required for the nonattainment area.

Major Stationary Source Precursor Demonstration.

The state has the option of submitting a major stationary source precursor demonstration as part of any Moderate or Serious area plan, consistent with CAA section 189(e). This demonstration differs from the comprehensive demonstration in that it only evaluates existing major sources, and therefore may only be used to justify the exclusion of existing major sources from the control requirements for the applicable precursor. Although the EPA expects that most states making precursor demonstrations will opt for comprehensive demonstrations, this option is provided to offer additional flexibility. The requirements for a stationary source precursor demonstration are nearly identical to those of the comprehensive precursor demonstration, except the state would only need to show that a particular precursor from all existing

major stationary sources

located in the nonattainment area do not contribute significantly to PM

2.5

levels that exceed the standard in the area. Similar to the comprehensive demonstration, the state must first evaluate the contribution of major stationary source emissions of the particular precursor to PM

2.5

levels that exceed the PM

2.5

standard (pursuant to section III.C.3.c of this preamble). If the state cannot demonstrate via the concentration-based precursor demonstration that sources of a particular precursor have an insignificant contribution to PM

2.5

levels in an area, then the state could still try to demonstrate that the precursor is insignificant by conducting a sensitivity analysis to evaluate the sensitivity of PM

2.5

levels in the nonattainment area to a reduction in major stationary source

emissions in the area (pursuant to Section III.C.3.d of this preamble).

If such a demonstration is approved by the EPA, then in developing the attainment plan for the area, the state would not be required to adopt control measures for the precursor for existing major stationary sources in the nonattainment area. The attainment plan also would not be required to address the emissions of the relevant precursor from major stationary sources in meeting the RFP or quantitative milestone requirements, or in adopting contingency measures. (Note that for purposes of meeting the contingency measure requirement, however, the state would still have the discretion to adopt emission reduction requirements on the precursor in question, in conjunction with emission reduction requirements on other pollutants.) The state would still need to include stationary source emissions of the precursor in all nonattainment area emission inventory submissions.

Note that a state might consider developing a major stationary source demonstration to avoid the requirement to adopt nonattainment planning control measures for a particular precursor emitted from existing major stationary sources in the area if the state does not believe that it could comprehensively demonstrate that the precursor does not have a significant contribution, and if major stationary source emissions of the precursor do not make up a very large percentage of the emissions inventory in the area. For example, it might be possible that in a particular area the overwhelming amount of emissions of a certain precursor could originate from mobile or area sources, or both, but not from existing major stationary sources. If the EPA approves a major stationary source precursor demonstration, the attainment plan would still need to evaluate and potentially impose control requirements for the relevant precursor for existing non-major stationary sources, area sources and mobile sources in order to demonstrate expeditious attainment.

It also should be noted that development of an approvable attainment plan that does not include new control measures for a particular precursor would not exempt the state from the requirements to address that precursor with respect to the NNSR program, nor would it excuse the state from the requirement to evaluate and adopt control measures for the precursor in any subsequent Serious area SIPs that could be required for the nonattainment area.

NNSR Precursor Demonstration.

The state also has the option of submitting a NNSR precursor demonstration as part of any Moderate or Serious area plan. This specific type of precursor demonstration is the only one of the three demonstrations described in this section that if approved would exempt new and modified major stationary sources of a precursor from regulation under the NNSR permitting program.

Under the NNSR precursor demonstration, the state would need to conduct an analysis to evaluate the sensitivity of PM

2.5

levels in the nonattainment area to an increase in emissions of a particular precursor in the area, simulating the response of the atmosphere (and associated PM

2.5

concentrations) to the addition of one or more new or modified stationary sources in the nonattainment area (

see

Section III.C.3.d of this preamble). Section III.C.3 of this preamble addresses additional issues related to technical analyses for precursor demonstrations.

The EPA believes that this approach to interpreting CAA section 189(e) of the statute as it applies to control requirements for the NNSR program is appropriate because (1) an analysis that evaluates the sensitivity of the atmosphere in an area to increases in emissions would most closely replicate the scenario of concern, where precursor emissions from new major stationary sources or major modifications are

added

to the existing inventory for the area; and (2) this approach would take into consideration the specific atmospheric chemistry and emissions profile that varies from area to area. For example, one nonattainment area may have low emissions of a particular precursor from all existing sources (and corresponding low current ambient contributions from the precursor), but the introduction of a new major stationary source of emissions of that particular precursor could in some cases significantly contribute to the ambient PM

2.5

levels in the area because other pollutants with which the precursor reacts in the atmosphere could be relatively abundant.

For purposes of the NNSR precursor demonstration, the state is not required to first evaluate the contribution of existing major sources to PM

2.5

levels that exceed the standard in the area, as would be required by the comprehensive and major stationary source demonstrations. Since NNSR permitting requirements do not apply to existing sources (unless such sources engage in a major modification), the EPA does not believe it is necessary or reasonable to require evaluation of current emissions from existing major stationary sources as it would not inform the question of whether increases in emissions would significantly contribute to PM

2.5

levels in the area. Note, however, that the NNSR precursor demonstration is used only to justify an exclusion of sources of the precursor from the NNSR control requirements in the area. A state would need to pair the NNSR precursor demonstration with another type of precursor demonstration to address control requirements beyond NNSR, as described previously for each type of demonstration.

3. Technical Issues Associated With Precursor Demonstrations

Geographic Area.

The proposal indicated that the emissions inventory to be used as the starting point for the comprehensive, major stationary source, and NNSR precursor demonstrations should represent emissions from sources located in the nonattainment area, and the final rule remains unchanged. The EPA believes that limiting the emissions inventory for these analyses to sources in the nonattainment area is appropriate based on the statutory construction of CAA section 189(e), in which the relevant test is whether “such sources contribute significantly to [PM

2.5

] levels which exceed the standard in the area.” The EPA believes that a reasonable interpretation is that this provision applies to sources in the nonattainment area.

Significance Threshold.

The proposal described the concept of including a bright-line threshold of 3 percent of the relevant NAAQS in the rule for precursor demonstrations other than the expeditious attainment approach, such that if an air quality contribution was found not to exceed the threshold amount, then it would not be considered significant. The proposal also included an option for no bright-line threshold in the final rule, based on the recognition that all nonattainment area situations are different.

Some commenters supported the bright-line threshold concept, but they suggested thresholds across a broad range, from less than 1 percent of the relevant NAAQS, to up to 5 percent. Some commenters stated that inclusion of a bright-line threshold of 3 percent of the relevant NAAQS was preferred because without such a threshold, states would be unsure about whether their proposed precursor assessment would be acceptable. Other commenters supported having no bright line threshold because the circumstances of each area are unique, and for that reason

each area should be considered on a case-by-case basis.

The EPA found merit in comments supporting both proposed options. The EPA agrees that an insignificance threshold can help avoid situations where lack of clarity may lead to delays in the EPA assessment of precursor demonstrations. At the same time, the EPA understands that PM

2.5

nonattainment problems are complex and vary greatly based on the facts and circumstances of each area.

After considering the range of comments on this issue and the complexity of the types of analyses that may be conducted for precursor demonstrations, the EPA has decided that the best approach is for the final rule to codify the availability and basic requirements for precursor demonstrations, but to provide technical details (such as a recommended approach for assessing whether a particular air quality concentration threshold can be considered to be insignificant in a given area) in guidance supporting this final rule.

c. Concentration-based Contribution Analysis.

The first type of analysis required for the comprehensive precursor demonstration (or, less commonly, the major stationary source precursor demonstration) is an existing source contribution analysis that would demonstrate whether emissions of a particular precursor from all existing sources (or, for a major source precursor demonstration, emissions from existing major sources) in the nonattainment area do not significantly contribute to PM

2.5

concentrations that exceed the standard in the area. The state should use technically credible approaches for estimating the ambient contribution of emissions of a particular precursor to total PM

2.5

concentration in the nonattainment area. The EPA anticipates that the forthcoming technical guidance will discuss the possible use of advanced air quality modeling tools to estimate precursor contributions to total PM

2.5

concentrations in an area. For example, several photochemical air quality models (

e.g.,

Community Multi-Scale Air Quality Model (CMAQ) and the Comprehensive Air Quality Model with Extensions (CAMx)) can be used to quantify the contributions of precursor emissions to PM

2.5

concentrations in the area.

For more information on CMAQ,

see http://www.epa.gov/air-research/community-multi-scale-air-quality-cmaq-modeling-system-air-quality-management.

For more information on CAMx,

see http://www.camx.com/.

Other techniques such as the analysis of chemical speciation data and emissions inventories also may be appropriate for determining the contribution of a particular precursor to PM

2.5

concentrations. For example, SO

emissions and measured sulfate concentrations (in the form of ammonium sulfate or other forms) may be small in a particular nonattainment area. A simple analysis of measured species concentrations (attributable to a particular precursor) combined with nonattainment area emissions and other relevant data analyses may be sufficient to show that a precursor does not contribute significantly to PM

2.5

concentrations in the area.

d. Sensitivity-based Contribution Analysis.

A second type of analysis may also be used in developing comprehensive precursor demonstrations (or, less commonly, major source precursor demonstrations). This type of analysis is a sensitivity-based contribution analysis that would demonstrate the degree to which concentrations in the nonattainment area are sensitive to decreases of a precursor. Changes in PM

2.5

concentrations at a particular location often will not be linear with respect to changes in PM

2.5

precursor emissions; therefore, sensitivity analyses are useful for better understanding the complexity and variability of the atmospheric chemistry affecting PM

2.5

concentrations in different areas across the country. A sensitivity-based contribution analysis evaluating the effect of precursor emissions reductions could be used in the event the state cannot demonstrate via the concentration-based analysis that sources of a particular precursor have an insignificant contribution to PM

2.5

levels in an area.

The EPA also requires a sensitivity-based analysis as the means for conducting the NNSR precursor demonstration. In this case, in contrast to the assessment of decreases described for the comprehensive (or major source) precursor demonstration for existing sources, the appropriate sensitivity analysis is one that evaluates the impact of precursor emissions

increases

—without the need for a separate evaluation of existing source contribution to PM

2.5

concentrations. This analysis is clearly most appropriate for NNSR, which is a program that governs emissions increases. Thus, the final rule requires that such an analysis must be used if a state chooses to submit a NNSR precursor demonstration.

The EPA states in the final rule that a sensitivity-based analysis is an appropriate approach for understanding whether emissions of a precursor make an insignificant contribution to PM

2.5

levels in an area. Several main components of PM

2.5

are secondarily formed in the atmosphere and are the result of chemical reactions between various PM

2.5

precursors. In some areas, one precursor may be abundant while a second precursor, with which it primarily reacts, may be less abundant. In such cases, a sensitivity analysis may find that reducing emissions of the second, less abundant precursor (the “limiting” precursor) may be generally more effective for reducing PM

2.5

concentrations. It may also find that increasing emissions of the less abundant precursor may be more effective at increasing PM

2.5

concentrations than a comparable tonnage increase of a more abundant precursor.

In another type of area, the PM

2.5

concentrations that exceed the standard may be commonly dominated by primary PM

2.5

emissions rather than by secondarily formed PM

2.5

. In such an area, a sensitivity analysis may be able to demonstrate that sources of a particular precursor in the nonattainment area do not contribute significantly to PM

2.5

levels that exceed the standard, and that the potential air quality improvement from reducing emissions of the precursor in the area may be limited.

Thus, the most effective precursor strategies for reducing PM

2.5

concentrations as part of attainment planning will vary from area to area, depending upon which specific precursors play a role in forming or limiting PM

2.5

formation in the particular area. The EPA therefore believes that it is a reasonable interpretation of the statute to allow a precursor to be excluded from control requirements if the PM

2.5

concentration in the area is insensitive to decreases of that precursor.

For states that choose to develop an optional precursor demonstration, the final rule provides that in addition to the basic requirement to do a concentration-based contribution analysis, the state may choose to develop a sensitivity-based contribution analysis evaluating potential emissions reductions for either a comprehensive precursor demonstration or a major stationary source demonstration intended to show that emissions reductions of the particular precursor are not effective in reducing PM

2.5

levels that exceed the standard in the area. As noted previously, the EPA expects to recommend approaches for assessing whether a particular air quality concentration threshold can be considered to be insignificant in a given area. If a concentration-based contribution analysis conducted for

either a comprehensive precursor demonstration or a major stationary source precursor demonstration shows that the contribution from a precursor is less than a particular threshold which may be considered insignificant at each PM

2.5

monitor in the area, then the EPA could approve the concentration-based contribution analysis. However, if a concentration-based contribution analysis cannot be approved (

e.g.,

shows that the contribution of a precursor to PM

2.5

levels in the area is not less than such a threshold at one or more monitors), then the overall precursor demonstration still could be approved, but only if the state also provides an appropriate sensitivity-based contribution analysis. If the sensitivity-based contribution analysis shows that the reduction in PM

2.5

concentration at each PM

2.5

monitor resulting from an emission reduction level that would not exceed such a threshold, then the EPA could approve the overall precursor demonstration, and the state would not be required to adopt control requirements for the precursor or address the precursor for attainment planning purposes.

In evaluating whether it would be appropriate to exclude sources of any precursors from NNSR regulation in a nonattainment area, it is important to understand the sensitivity of the atmosphere to potential increases in precursor emissions that could result from major source growth (from both new sources and major modifications at existing major sources) in the nonattainment area. For example, in some circumstances, adding a few hundred tons of a “less abundant” precursor to an area could result in a significant increase in PM

2.5

concentrations even if there are currently very few existing major sources of the precursor in the area. In contrast to the emissions reduction analyses described for attainment planning purposes, sensitivity analyses that consider the effect of potential emissions increases of a particular precursor in the nonattainment area will help the state and the EPA to understand the potential response of PM

2.5

concentrations to increased emissions in the area in order to assess whether the contribution from such increases is not significant under CAA section 189(e). In assessing whether a state precursor demonstration (

i.e.,

for attainment planning or for NNSR) can be approved, the EPA will consider the air quality changes estimated in the state's technical sensitivity analyses, their relationship to thresholds developed under any EPA-recommended approaches (including any thresholds that EPA may recommend), and any other information presented by the state.

4. Procedural Considerations

a. Consultation and Public Review.

The EPA anticipates that a state's development of an approvable PM

2.5

precursor demonstration will require a substantial level of effort and consultation with the EPA. Such a demonstration by the state would likely involve technically rigorous and complex analyses, such as air quality modeling and ambient data analyses. Accordingly, the EPA strongly recommends that any state that is considering limiting the applicability and associated control strategy decisions only to specific precursors, either for the attainment plan, for the NNSR permitting program, or for both, should develop a precursor demonstration early in the attainment plan development process. The EPA is committed to consulting with states on designing technically appropriate precursor demonstrations consistent with EPA technical guidance. If a state chooses to develop a precursor demonstration, it must be submitted to the appropriate EPA regional office no later than the date of submission of the relevant attainment plan or NNSR program revision; an earlier submission is preferable. For example, if a state submits the Moderate area plan elements no later than 18 months from the date of designation (as discussed in Section IV.A of the preamble), it should submit any precursor demonstration no later than this same date. In its review of any precursor demonstration provided by a state, the EPA will consider all relevant information.

The critical first step in any precursor analysis is the development of a comprehensive inventory of all precursor emissions in the nonattainment area. A state will not be able to reasonably determine whether reductions of a given PM

2.5

precursor are needed for expeditious attainment, or whether sources of such precursor are insignificant contributors to PM

2.5

levels above the standard in an area, unless the state has adequately accounted for all nonattainment area emissions in its emissions inventory. (

See

section IV.B of this preamble for more details on emission inventory requirements.)

In the preamble to proposed rule, we indicated that if a state developed a precursor demonstration as part of its draft attainment plan or NNSR program submission, then in accordance with the state rulemaking process, the demonstration would be subject to public review at the state level. We also stated that, as required under any rulemaking process, the state had to consider and provide a response in the rulemaking record to any information or evidence brought forward by commenters during the state's SIP planning, development and review process. By ensuring that this important issue was explicitly addressed and supported in any attainment plan or NNSR program revision submitted to the EPA, the EPA could better evaluate the precursor demonstration in accordance with its obligations under the CAA. The EPA believes these are sound procedural steps for a state rulemaking process, and the final rule includes similar language requiring public review of any proposed precursor demonstration.

If a state chooses to develop a comprehensive precursor demonstration or major stationary source precursor demonstration for a nonattainment area, it must submit a concentration-based contribution analysis and, if applicable, a sensitivity-based contribution analysis conducted for the area. In cases where a sensitivity-based analysis was developed the concentration-based analysis must also still be submitted. Although the rule clearly provides that the precursor demonstration requirement may still be satisfied in such cases, the information in the concentration-based analysis will help inform review of the overall demonstration by the EPA. Similarly, the data from the concentration-based analysis should be available in the public record because it will help inform the review of the overall precursor demonstration by the public.

See

40 CFR 51.1006(b).

b. Precursor Demonstration to be Reevaluated for Each New State Implementation Plan.

There may be situations where the EPA approved a Moderate area plan that excluded a precursor from regulation from one or more requirements based on an approvable precursor demonstration, and then the area is reclassified as a Serious area, triggering an additional plan submission requirement. (Section V of this preamble provides additional detail on reclassification of areas from Moderate to Serious under subpart 4.) In addition, an area that had been reclassified as Serious later may be required to submit one or more additional SIPs if it obtains an extension of the Serious area attainment date, or if it fails to attain the standard by the end of the tenth year after designation. For a state seeking to continue a precursor exclusion in a subsequent attainment plan or NNSR program

submission, the final rule requires the state to assess the appropriateness of continuing the exclusion by providing a new precursor demonstration updated to reflect the type of plan and the conditions in effect when the new plan is submitted.

When an area is reclassified to Serious, existing sources of all PM

2.5

precursors in the area are again presumptively subject to evaluation for BACM/BACT control measures and potential future control requirements, unless a new precursor demonstration is developed and approved as part of the Serious area plan. As noted in the discussion of the provisions for excluding sources of precursors from certain Moderate area requirements based on an expeditious attainment demonstration, this option is not available for Serious areas. Accordingly, if the state seeks to submit an updated precursor demonstration for a Serious area, at this stage it must submit a comprehensive, major stationary source, or NNSR precursor demonstration. Regardless of the type of demonstration(s) provided in the Moderate area plan, the final rule requires that the state must submit a reevaluated and updated precursor demonstration for the Serious area plan. The reason for this is that the Serious area plan would be due several years after the submission of a state's original precursor demonstration, and over that period, substantial emissions changes could have occurred that might call into question the basis of the previous precursor demonstration. In addition, because the area failed to attain by the Moderate area attainment date, it is reasonable and appropriate to require the state to reconsider and update its prior precursor demonstration. The final rule also requires similar updates for each successive plan beyond the initial Serious area plan (such as a revised Serious area plan for an area that fails to attain by the end of the tenth calendar year after designation). The EPA recommends that in developing a revised precursor demonstration, the state should consider changes in a number of factors, including: Changes in emissions inventory levels due to implementation of control programs, growth in emissions, and changes in emission estimation methodologies; recent ambient air quality concentrations; fine particle composition and the sensitivity of the atmosphere to increases and decreases of different precursors; advances in technical tools and modeling techniques to assess the effectiveness of precursor reductions; and advances in control technologies and emission reduction programs.

5. Comments and Responses.

Comment:

With regard to whether the existing source contribution analysis or the sensitivity-based contribution analyses should be required if a state opts to submit a precursor demonstration, a number of commenters supported only the sensitivity analysis because they believed the analysis would help identify the control measures that are most effective at reducing PM

2.5

concentrations. Some commenters noted that conducting a “zero-out” analysis (

i.e.,

simulating the change in atmospheric chemistry and PM

2.5

concentrations due to a hypothetical removal of 100 percent of the emissions of a precursor from the inventory) is not appropriate for a sensitivity analysis because the response of the photochemical grid model is highly non-linear under such circumstances.

Another group of commenters supported requiring only the concentration-based existing source contribution analysis because only that analysis would address the question alluded to in the statute, which is whether sources of the precursor contribute significantly to levels which exceed the standard in the area. These commenters stated that sensitivity-based analyses reflect localized conditions and do not represent a consistent effect across an air basin. The commenters suggested that sensitivity analyses might be considered to inform what pollutants are most cost-effective to control, but believed that this is dubious because the fact that certain pollutants are very abundant is likely the result of a history of under-regulation. They suggested that it actually may be cheaper to control the more abundant pollutant than the less abundant pollutant in order to achieve an equal amount of air quality improvement.

Response:

The EPA agrees with commenters who suggested that the rule should closely align with the statutory language in CAA section 189(e) of subpart 4 and include provisions for evaluating the contribution of existing sources to PM

2.5

levels which exceed the standard in the area. For this reason, the final rule states that the existing source contribution analysis should be required for any comprehensive precursor demonstration or major stationary source precursor demonstration seeking to exempt a precursor from attainment planning requirements.

The EPA also believes that a sensitivity-based contribution analysis is consistent with the language and intent of CAA section 189(e). As applied to attainment plans, CAA section 189(e) allows states to evaluate whether PM

2.5

precursors significantly contribute to levels which exceed the standard in the area. The intent of CAA section 189(e) in applying control requirements to PM

2.5

precursors is to ensure expeditious attainment of the standard. However, if conditions in a particular area are such that control of sources of one or more precursors does not reduce PM

2.5

concentrations in the area, then those controls will not help the area attain (expeditiously or otherwise). Therefore, the EPA disagrees with commenters who argue that sensitivity-based contribution analyses are not appropriate for determining if precursors do not significantly contribute to PM

2.5

levels in the area. The EPA believes that sensitivity-based contribution analyses can be useful for determining whether adoption of control requirements for sources of a particular precursor would be effective in reducing PM

2.5

concentrations, and can be useful for determining whether potential emissions increases under the NNSR program would lead to insignificant air quality changes. For this reason, the final rule allows states to conduct sensitivity-based contribution analyses for the comprehensive, major stationary source, and NNSR precursor demonstrations.

Comment:

Some commenters expressed support for the precursor option from the proposal (

i.e.,

Option 3) that would have allowed for an expeditious attainment precursor demonstration to be deemed to demonstrate under CAA section 189(e) that emissions of the precursor do not need to be addressed for all major stationary source requirements, such as the NNSR program.

Response:

Upon further consideration of this potential approach, the EPA decided that it would not be appropriate to include such an approach in the final rule. The reason for this is that an expeditious attainment planning analysis on its own would determine that the area could attain the standard by the Moderate area attainment date without new control requirements for sources of a particular precursor, but it would not address the potential impact of increased emissions of the precursor in the area due to new or modified sources, as is reasonably needed under the NNSR precursor demonstration. The evaluation of controls required for expeditious attainment does not consider what happens if new sources move into an area. Thus, while a state might be able to show that controlling existing sources of a precursor does not

advance attainment, the analysis would not determine whether a new major source of that precursor might have a significant contribution to air quality. The EPA believes it is important for purposes of CAA section 189(e) and our overall environmental goal under the NNSR program to evaluate emissions increases. Consequently, the EPA has revised the details of the specific types of demonstrations to include a specific stand-alone demonstration for purposes of exempting new major stationary sources and major modifications of a precursor from regulation under the NNSR permitting program.

IV. Requirements for PM

2.5

Moderate Nonattainment Area Plans

Sections 189(a), (c), and (e) of the CAA require that Moderate area attainment plans contain the following: (i) An approved permit program for construction of new and modified major stationary sources (CAA section 189(a)(1)(A)); (ii) a demonstration that the plan provides for attainment by no later than the applicable Moderate area attainment date or a demonstration that attainment by that date is impracticable CAA (section 189(a)(1)(B)); (iii) provisions for the implementation of RACM and RACT no later than 4 years after designation (CAA section 189(a)(1)(C)); (iv) quantitative milestones that will be used to evaluate compliance with the requirement to demonstrate reasonable further progress (RFP) (CAA section 189(c)); and, (v) evaluation and regulation of PM

2.5

precursors (in general to meet RACM and RACT and other attainment planning requirements, and as specifically provided for major stationary sources under CAA section 189(e)). In addition, subpart 1 requirements for attainment plans continue to apply to PM

2.5

nonattainment areas unless they are superseded by subpart 4 provisions and include the following: (i) A description of the expected annual incremental reductions in emissions that will demonstrate RFP (CAA section 172(c)(2)); (ii) emissions inventories, as necessary (CAA section 172(c)(3)); (iii) other control measures (besides RACM and RACT) needed for attainment (CAA section 172(c)(6)); and, (iv) contingency measures (CAA section 172(c)(9)). The EPA notes that its longstanding guidance on interpreting these statutory requirements is embodied in the General Preamble and the Addendum.

The preamble for the proposed rule presented several interpretations of these provisions, and further explained where its proposal varies from past EPA guidance and the reasons for the variance. The following sections of this preamble explain the EPA's final approach and, where different from the proposal, also explain EPA's reasons for finalizing an amended approach. This final rule reflects our careful consideration of the numerous thoughtful comments we received from air agencies, who are responsible under the CAA for these implementation activities, and a variety of other stakeholders.

See

57 FR 13498, 13536, 13537, 13538, 13539, 13540, 13541, 13542, 13543, 13544 and 13545 (April 16, 1992); and 59 FR 41988 (August 16, 1994).

A. Plan Due Dates

1. Summary of Proposal

The EPA proposed to require that all Moderate area plan elements for a nonattainment area be submitted by the state no later than 18 months from the effective date of designation. The attainment plan submission would thus include all necessary plan elements required under CAA subparts 1 and 4.

2. Final Rule

The final regulations at 51.1003(a) require all Moderate nonattainment area elements to be submitted by no later than 18 months from the date of designation, as proposed. Section 189 of the CAA specifies the schedule by which states must submit attainment plans for the PM

2.5

NAAQS. Specifically, CAA section 189(a)(2)(B) requires states to submit an attainment plan that meets Moderate area attainment plan requirements no later than 18 months from the date of nonattainment designation.

While subpart 1 of the CAA could potentially be interpreted to authorize the EPA to provide up to 3 years after designation for states to submit certain attainment plan elements, the EPA believes that such an interpretation would be inconsistent with the specific deadlines that Congress imposed in subpart 4. The EPA concludes that all subpart 1 and subpart 4 nonattainment area requirements should be considered together in order to facilitate state development, and EPA review, of a comprehensive plan to attain the PM

2.5

NAAQS in a given nonattainment area. In fact, the EPA finds that meeting key subpart 1 requirements within the 18-month timeframe of subpart 4 is fundamentally necessary for the state to develop an approvable plan. For example, the state must develop an emissions inventory (or inventories) either before or at the same time as the other attainment plan elements due under subpart 4 because the information contained in the emissions inventory is critical for development of other elements of the Moderate area attainment plan, such as its precursor analysis, analysis of RACM and RACT and additional reasonable measures, and attainment demonstration modeling. The EPA's ability to evaluate the submitted attainment plan therefore will be impaired if the state does not submit all the required plan elements at the same time.

The EPA notes that Congress provided different statutory deadlines for submission of attainment plans under subpart 1 and subpart 4. Under section 172(b) of the CAA, the EPA is directed to establish the date for the attainment plan submission, but it can extend no later than 3 years from the date of a nonattainment designation. By contrast, under CAA section 189(a)(2)(B), the statute provides that states must make the attainment plan submissions within 18 months after designation. Due to the December 2013 court decision in

NRDC

EPA,

however, the EPA promulgated an alternative submission date of December 31, 2014, for attainment plans for the 1997 PM

2.5

and 2006 PM

2.5

NAAQS in order to provide a reasonable, prospective due date for attainment plans that must comply with subpart 4 requirements and to clarify the requirements that a state must meet prior to redesignation of a PM

2.5

nonattainment area.

See

79 FR 31566 (June 2, 2014).

3. Comments and Responses

Comment:

Commenters suggested that the EPA should interpret the statute to allow more time for states to develop and submit contingency measures.

Response:

As discussed earlier in this section, the EPA believes that it would be inconsistent with the specific deadlines that Congress imposed in subpart 4 to allow contingency measures to be submitted later than the other elements of the attainment plan. Contingency measures need to be adopted and ready for rapid and timely implementation in the event a nonattainment area fails to meet RFP requirements or fails to attain the PM

2.5

NAAQS by the applicable attainment date. The state's evaluation of what emissions controls are appropriate to meet the contingency measure requirement is closely related to other aspects of the attainment plan, such as the pollutants and sources to be addressed in meeting the RACM/RACT requirements, and the amount of emissions reductions that the contingency measures should achieve, based upon the facts and circumstances of the attainment plan for the area. The same types of facts and analyses that are necessary for the other elements of an attainment plan are directly relevant to the development of contingency measures.

Although nothing in the CAA prohibits states from making separate attainment plan submissions to meet the

individual required elements for attainment plans in advance of the required date, the EPA presumes that development and submission of all of the attainment plan elements simultaneously will be most efficient, both for the state and for the EPA in reviewing the state's submission. A Moderate area implementation plan with a single SIP submission due date will be less administratively burdensome than a program with two SIP submission due dates. Under an approach with two submissions, the state would likely need to issue two sets of proposed regulations, hold two sets of public hearings, and respond to two sets of public comments, rather than dealing with all of these requirements in one comprehensive action. Likewise, the EPA would have two separate submissions to review and two sets of proposed and final actions to publish in the

Federal Register

for every Moderate nonattainment area. Thus, for the reasons outlined earlier, the final rule includes a single Moderate area attainment plan submission deadline of 18 months after designation. Accordingly, the areas designated as nonattainment for the 2012 PM

2.5

NAAQS (with an effective date of April 15, 2015) are required to submit Moderate area attainment plans to the EPA no later than October 15, 2016.

See

40 CFR 51.1003(a).

B. Emissions Inventory Requirements

1. Summary of Proposal

In the proposal, the EPA proposed for both Moderate and Serious areas to require both a “base year inventory for the nonattainment area” and an “attainment projected inventory for the nonattainment area.” The proposal spelled out a list of requirements for each of these inventories. The proposal also specified, based on the timing requirements of CAA section 172(b), that the emissions inventories required for a Moderate area must be submitted within 18 months after the effective date of the designation of the nonattainment area.

The EPA proposed that the base year inventory for the nonattainment area: (a) Be required to represent one of the 3 years used for designations or another technically appropriate year; (b) include actual emissions of all sources within the nonattainment area; (c) be annual total or average-season-day emissions in accordance with the NAAQS violation(s) (annual and/or 24-hour); (d) include direct PM

2.5

(filterable and condensable) as well as all scientific PM

2.5

precursors; (e) follow the Air Emissions Reporting Requirements (AERR), 40 CFR part 51, subpart A for the emissions thresholds for point sources; (f) use the level of detail as prescribed by the AERR; and (g) still meet the public review requirements even if submitted as a separate plan.

The EPA further proposed that the attainment projected inventory for the nonattainment area (a) be required to represent projected emissions in the first year for which attainment is demonstrated by the modeled attainment demonstration; (b) include projected emissions of the same sources included in the base year inventory for the nonattainment area; (c) use the same temporal period as the base year inventory (annual or average-season-day); (d) include the same pollutants as the base year inventory; (e) report as point sources the same sources treated as point sources in the base year inventory; (f) be consistent in inventory detail with the base year inventory; and (g) still meet the public review requirements even if submitted as a separate plan.

2. Final Rule

The final regulations at 51.1008 provide the inventory requirements for Moderate areas. The EPA received a number of comments on the emissions inventory requirements for Moderate areas. Commenters both supported the provisions of the proposed rule and objected to some aspects of the inventory requirements. The EPA is finalizing all of the proposed Moderate area requirements with some modifications based on comments. Specifically, the definition of what can constitute a seasonal inventory has been made more flexible to accommodate certain cases, as explained in Section IV.B.2.c of this preamble.

Pursuant to its authority under section 110 of title I of the CAA, the EPA has long required states to submit inventories of the emissions of criteria pollutants and their precursors. The EPA codified these requirements in 40 CFR part 51, subpart Q in 1979 and amended them in 1987. Additionally, the 1990 CAA Amendments revised many of the provisions of the CAA related to attainment of the NAAQS and the protection of visibility in mandatory Class I federal areas (certain national parks and wilderness areas). These revisions established new emissions inventory requirements applicable to areas that were designated nonattainment for certain pollutants. In the case of PM, Congress did not create a specific emissions inventory requirement in subpart 4 that would supersede the emissions inventory requirement under subpart 1. Thus, the CAA section 172 (c)(3) emissions inventory requirements continue to apply, and that provision explicitly requires “a comprehensive, accurate, and current inventory of actual emissions of the relevant pollutants” in the nonattainment area. In addition, the specific attainment plan requirements for the PM

2.5

NAAQS set forth in CAA section 189(a) and associated modeling requirements make an accurate and up-to-date emissions inventory a critical element of any viable attainment plan. Because of the nature of PM

2.5

, the EPA concludes that the statutory requirements for emissions inventories need further elaboration through additional regulatory requirements as described later.

Emissions inventory data serve as the foundation for various types of analyses performed by states and by the EPA. For example, these data enable states to evaluate the degree to which different emissions sources contribute to the nonattainment problem in a given nonattainment area and enable states to estimate the air quality improvement that can be achieved through different control measures. States should use the best available, current emissions inventory information for attainment plan development, because high quality emissions inventory data are essential for the development of an effective control strategy. To assist states in preparing complete, high quality inventories, the EPA provides guidance for developing emissions inventories called “Emissions Inventory Guidance for Implementation of Ozone and Particulate Matter National Ambient Air Quality Standards (NAAQS) and Regional Haze,” which is available from

https://www.epa.gov/air-emissions-inventories/emissions-inventory-guidance-documents.

This guidance is commonly called the “SIP Emissions Inventory Guidance.” The EPA recommends that states consult this guidance while developing the emissions inventories to meet statutory and regulatory requirements.

a. Inventory Requirements.

As explained in the proposed rule, CAA section 172(c)(3) requires states to submit an emissions inventory and periodic revisions thereof with an attainment plan. 80 FR at 15363. In addition, pursuant to CAA section 301, the EPA has authority to promulgate regulations as necessary for the implementation of the PM

2.5

NAAQS, including requirements pertaining to emissions inventories. In this final action, the EPA is establishing several different inventory requirements that the agency has determined are necessary

for the proper implementation of the PM

2.5

NAAQS in attainment plans.

There are three key facets of the emissions inventory requirements, as described later: (i) The type of inventories required; (ii) the timing of submission of these inventories; and (iii) the content of these inventories. These content requirements are described in this section; however, the EPA's rationale for these content requirements is in some cases further described in subsequent sections of this document.

First, states must submit at least two separate and distinct nonattainment area emissions inventories as elements of an attainment plan. The first emissions inventory is relevant for assessing the current or base year emissions from sources located in the nonattainment area; the second emissions inventory is a projected inventory relevant for assessing emissions in the target attainment year in the nonattainment area. The first type of inventory is called the “base year inventory for the nonattainment area,” and the second type of inventory is called the “attainment projected inventory for the nonattainment area.”

See

40 CFR 51.1000. The base year inventory for the nonattainment area is necessary for development and evaluation of various elements of the attainment plan, such as the determination of appropriate pollutants, sources, and emission controls addressed in other elements of the attainment plan for the nonattainment area. The attainment projected inventory is necessary to implement the attainment demonstration requirement of CAA section 189(a)(1)(B), and it also may be used as part of meeting the RFP requirement (

see

Section IV.F of this preamble). The need for the attainment projected inventory also stems from the need for both the EPA and the public to be able to compare, during their reviews of the attainment plan, the base year inventory against the attainment projected inventory for the nonattainment area. For these reasons, this rule establishes a regulatory requirement at 51.1008 that Moderate area attainment plans must include a base year inventory for the nonattainment area and an attainment projected inventory for the nonattainment area.

Second, as noted in Section IV.A of this preamble, to meet the statutory requirements for submission of certain attainment plan elements required under subpart 4, the EPA believes that states must meet the same submission schedule for emissions inventories as for the other elements of an attainment plan,

i.e.,

within 18 months after the effective date of the designation of the nonattainment area. This schedule must apply to both of these emissions inventories because they are necessary for effective evaluation of the attainment plan as a whole. Consequently, under the authority of CAA section 172(b), this rule establishes a regulatory requirement for Moderate areas that states must submit the required base and projected emissions inventories by 18 months after designation.

Third, the EPA is establishing specific requirements for both the base year inventory for the nonattainment area and for the attainment projected inventory for the nonattainment area in order to implement the PM

2.5

NAAQS most effectively. Accordingly, this final rule requires that the base year inventory for Moderate nonattainment areas must meet the following minimum criteria 1 through 7:

(1) The inventory year must be one of the 3 years used for designations for the relevant PM

2.5

NAAQS or another technically appropriate inventory year. Another inventory year may be chosen under specific circumstances (

e.g.,

to account for a change in sources in the nonattainment area, changes in nonattainment area boundaries, to allow the base year to be consistent with the base year needed for the conformity rule, or significant time lag between designations and preparation of the inventory) with consultation from the appropriate EPA Regional Office. This requirement is intended to ensure that the inventory will adequately represent the emissions sources that contributed to the nonattainment designation for the area.

See

40 CFR 51.1008(a)(1)(i).

(2) The inventory must include actual emissions of all sources within the nonattainment area. This requirement stems directly from the language in CAA section 172(c)(3). Sources outside of the nonattainment area are explicitly not included in the section 172(c)(3) requirement with the words “in such area.” Furthermore, the EPA interprets the Act requirement for “actual emissions from all sources” in CAA section 172(c)(3) as intending to include all emissions that may contribute to the formation of PM

2.5

within the nonattainment area. This means that the inventory must include point sources, stationary nonpoint sources,

mobile sources, prescribed fires and wildfires. The EPA encourages states and tribes to work together to ensure that the information used in developing the base year inventory for the nonattainment area is inclusive of all emissions from the designated nonattainment area, including emissions from sources in tribal areas located therein.

See

40 CFR 51.1008(a)(1)(ii).

Point sources are the same as major stationary sources, and the term indicates sources that must be reported at an individual facility with process-level details. Nonpoint sources are all other stationary sources, and the term indicates sources that are reported as a county total. The definitions for this rule (

see

51.1000) refer to the definitions in the AERR (40 CFR part 51, subpart A). Nonpoint sources include minor sources, synthetic minor sources, and area sources such as residential heating and other sources where it is not realistic to estimate emissions from each emissions point.

(3) The emissions must be reported as annual total emissions, average-season-day emissions, or both, as appropriate for the relevant PM

2.5

NAAQS. The rationale for the type(s) of emissions provided must be included as part of the attainment plan. When seasonal emissions are included, the rationale for the seasonal period must also be included as part of the attainment plan. A discussion of the EPA's rationale for including the option of seasonal or annual inventories is provided in Section IV.B.2.c of this preamble.

See

40 CFR 51.1008(a)(1)(iii).

(4) As discussed earlier and consistent with past implementation rule requirements, the inventory must include emissions of direct PM

2.5

(both filterable PM

2.5

and condensable PM

2.5,

provided as separate components), as well as all scientific PM

2.5

precursors (SO

, NO

, VOC and ammonia). A discussion of the EPA's rationale for including this requirement is provided in Section IV.B.2.d of this preamble.

See

40 CFR 51.1008(a)(1)(iv).

(5) States must follow the Air Emissions Reporting Requirements (AERR), 40 CFR part 51, subpart A criteria for emissions thresholds for states to use to determine which emissions sources must be reported as point sources. This requirement is consistent with past implementation rules and is needed to specify whether emissions must be submitted as specific major source stationary facilities with detailed emissions processes or whether emissions can be provided as county totals (

i.e.,

area sources, also called nonpoint sources). A discussion of the use of 40 CFR part 51, subpart A for the emissions thresholds is provided in Section IV.B.2.e of this preamble.

See

40 CFR 51.1008(a)(1)(v).

(6) The level of detail of the emissions included in the inventory must be consistent with the detail required by 40 CFR part 51, subpart A. For example, all emissions must be subdivided to individual emissions processes within a facility or county. While these details should underlie the emissions

inventory, this information can be summarized for other elements of the attainment plan. This requirement is consistent with the remanded 2007 PM

2.5

Implementation Rule and is needed to define the data reporting elements (

i.e.,

how they are reported) as opposed to the emissions values (

i.e.,

how much emissions derive from each source or source category) of the emissions inventories submitted to the EPA.

See

40 CFR 51.1008(a)(1)(vi).

(7) If the base year inventory for the nonattainment area is submitted to the EPA as a separate plan submission (

i.e.,

severed from the overall attainment plan and provided separately), the inventory must still meet the notice and public hearing requirements of CAA sections 110(a)(1) and 110(a)(2).

For the attainment projected inventory for Moderate nonattainment areas, this final rule also establishes specific requirements necessary to implement the PM

2.5

NAAQS effectively. Accordingly, the attainment projected inventory must meet the following minimum criteria 1 through 7:

(1) The year of the projected inventory must be the most expeditious year for which projected emissions show modeled PM

2.5

concentrations below the level of the NAAQS, consistent with the requirement for expeditious attainment by no later than the applicable deadlines provided in the statute.

See

40 CFR 51.1008(a)(2)(i).

(2) The emissions must be projected emissions from the same sources included in the base year inventory for the nonattainment area and any new sources projected to locate within the boundaries of the nonattainment area. The projected emissions should be the best available representation of expected emissions, and thus should take into account emissions growth and contraction, facility closures, new facilities, new controls and other changes in emissions forecast to occur between the base year and the attainment year. In deciding what factors are relevant, states should consider factors affecting projected emissions that could significantly alter the conclusions of the modeled attainment demonstration.

See

40 CFR 51.1008(a)(2)(ii). For prescribed and wildfire emissions, Section IV.D.3.b of this preamble describes in more detail the appropriate way to handle these sources in the attainment projected inventory.

(3) The temporal period of emissions must be the same temporal period (annual, average-season-day, or both) as the base year inventory for the nonattainment area.

See

40 CFR 51.1008(a)(2)(iii).

(4) Consistent with the base year inventory for the nonattainment area, the inventory must include all emissions of direct PM

2.5

(both filterable and condensable PM

2.5

provided as separate components), as well as all emissions of the scientific precursors (SO

, NO

, VOC and ammonia).

See

40 CFR 51.1008(a)(2)(iv).

(5) The same sources reported as point sources in the base year inventory for the nonattainment area must also be provided as point sources in the attainment projected inventory for the nonattainment area. Likewise, nonpoint and mobile source projected emissions must also be provided using the same delineations as the base year inventory.

See

40 CFR 51.1008(a)(2)(v).

(6) The detail of the emissions included must be consistent with the level of detail in the base year inventory (

i.e.,

as required by 40 CFR part 41, subpart A).

See

40 CFR 51.1008(a)(2)(vi).

(7) If the attainment projected inventory for the nonattainment area is submitted to the EPA as a separate plan submission (

e.g.,

severed from the overall attainment plan and provided separately), then the inventory must still meet all the notice and public hearing requirements of CAA sections 110(a)(1) and 110(a)(2).

Comparison to Inventory Requirements from Earlier PM

2.5

Implementation Rules.

The 2007 PM

2.5

Implementation Rule required states to submit specific emissions inventories in connection with the RFP requirements of CAA section 172(c)(2) under subpart 1. In this rule, no specific RFP related inventory is required, but the attainment projected inventory for the nonattainment area also may serve a purpose for evaluation of RFP. Past EPA guidance with respect to RFP requirements under subpart 4 has not explicitly required a separate emissions inventory for this purpose for PM

NAAQS. Through evaluation of the RFP requirement in connection with this rulemaking, however, EPA has determined that there may be circumstances in which such an approach may be appropriate. For this reason, the EPA describes this issue more fully in Section IV.F of this preamble.

The 2007 PM

2.5

Implementation Rule also required states to submit a statewide base year emissions inventory as part of the attainment plan. The EPA included the statewide emissions inventory requirement because it was relevant to evaluation of emissions reductions from sources outside of the designated nonattainment area for purposes of RFP. The EPA no longer interprets the CAA to allow such reductions for purposes of RFP, so this particular form of emissions inventory is not needed for attainment plan for the PM

2.5

NAAQS. Furthermore, statewide inventories are already required as part of the AERR (40 CFR part 51, subpart A) on a triennial basis. While these inventories do not receive the same level of scrutiny as inventories associated with attainment plans, the EPA believes that this existing statewide inventory requirement is sufficient for understanding the PM

2.5

nonattainment contributions from areas outside of the nonattainment area, which is a necessary component of modeled attainment demonstrations described in Section IV.E of this preamble.

Seasonal Inventories.

The statute does not explicitly address whether the emissions inventory required under CAA section 172(c)(3) should include emissions throughout an entire calendar year or emissions during some shorter portion of the year that may be appropriate for implementation of a particular NAAQS. In the case of the PM

2.5

NAAQS, the standards currently include both annual NAAQS and 24-hour NAAQS. With respect to the annual NAAQS, the form of the NAAQS includes monitored ambient PM

2.5

values at all times throughout the course of the year, and thus an annual emissions inventory is necessarily required for development of an appropriate attainment plan for a given area. In the case of the 24-hour NAAQS, however, the form of the NAAQS is based upon monitored values on particular days with high levels of ambient PM

2.5,

and in some nonattainment areas those days may occur only during a distinct and definable season of the year. The EPA considers it appropriate to interpret the emissions inventory requirements of the CAA in light of the specific inventory needs that are relevant for the NAAQS in question. For the PM

2.5

NAAQS, states can meet the inventory requirement with different combinations of temporal resolutions for the emissions. For the annual standard, annual emissions must be submitted. For the 24-hour standard, states must submit either an annual or an average-season-day inventory and optionally may submit both. For a nonattainment area for both the annual and 24-hour standard, states can meet the inventory requirement with only an annual inventory or with both an annual and average-season-day inventory.

In contrast with the annual PM

2.5

NAAQS, the 24-hour PM

2.5

NAAQS are designed to protect against peak exposures. Thus, for the 24-hour PM

2.5

NAAQS, there are circumstances in which the EPA believes that only seasonal emissions inventories may be useful for attainment planning purposes. This rule at 40 CFR 51.1008(a)(1)(iii) allows states to use seasonal inventories for attainment plan development for attaining the 24-hour PM

2.5

standard in areas that are designated nonattainment for only the 24-hour standard. Use of a seasonal emissions inventory will also be appropriate only if the monitored violations of the 24-hour PM

2.5

NAAQS in the area occur during an identifiable season. In the event that it is appropriate to rely on a seasonal emissions inventory, the state should confer with the EPA concerning the exact length of the season and the start and stop dates of the season. The duration and start and stop dates of the season will be an important component of the attainment plan and must be approved by the EPA along with other elements of the attainment plan for a given nonattainment area. Further, this rule requires that seasonal inventories must use average-season-day emissions values for this purpose, defined by 40 CFR 51.1000. The nature of some seasonal PM

2.5

emissions sources (

e.g.,

residential wood combustion) does not allow for only weekday emissions to be included in the inventory, therefore all days must be included. The state would need to explain the rationale for the duration of the season used for the inventory as part of the attainment plan submission. To justify the use of a seasonal emissions inventory, the state must demonstrate why a seasonal emissions inventory is appropriate for the particular PM

2.5

nonattainment area in question.

Commenters recommended that the EPA should allow episode-specific inventories, in lieu of seasonal inventories. As a result, the EPA acknowledges in this final rule that, for some source categories, it may be advisable to limit the “season” considered in calculating emissions to an episodic period to reflect periods of higher emissions during periods of high ambient PM

2.5

. Such an approach could help to ensure the nonattainment area inventory reflects the emissions conditions that led to an initial nonattainment area designation. For example, if nonattainment conditions are associated only with periods of peak emissions from residential wood combustion, then an episodic average for residential wood combustion may be more appropriate than a seasonal average. The resulting seasonal emissions inventory would then have a mix of the seasonal averages as defined by 40 CFR 51.1000 for most categories, but using a shorter period for the emissions categories that can be justified and an improvement. In such cases, in addition to the requirement to justify the seasonal period, the state must additionally justify the factual basis for the period used to calculate emissions from such categories, and this would be subject to EPA approval. While the EPA encourages using the same averaging period for all sectors for purposes of simplicity, an episodic averaging period may only be needed for a select group of sources or even for a single category of sources. Those special cases must be explained in the emissions inventory part of the state implementation plan [

see

40 CFR 51.1008(a)(1)(iii)]. For the purposes of the definitions included in this final rule, all non-annual emissions (whether seasonal or episodic) will be referred to as “seasonal” in this rule.

Pollutant Requirements.

This rule requires that states must submit emissions inventories that include all emissions of direct PM

2.5

and all emissions of scientific PM

2.5

precursors: SO

, VOC and ammonia. Furthermore, the inventories must differentiate between the condensable and filterable portions of direct PM

2.5

emissions, and states must provide this information in the emissions inventories as separate components. As described in Section IV.B.3 of this preamble, commenters disagreed with the EPA's proposal to require inclusion of ammonia emissions and to require separate reporting of condensable and filterable emissions. The approach being finalized in this rule does not differ from the EPA's proposal despite these adverse comments.

Section II.B of this preamble describes the background needed to understand the importance of including these precursors in emissions inventories for attainment plan purposes for the PM

2.5

NAAQS. Emissions information about PM

2.5

and its precursors is a necessary precondition to meeting other core attainment plan requirements, such as effective evaluation of control measures and adequate demonstration of projected future attainment of the NAAQS through modeling. The EPA notes that, with respect to requiring states to include emissions of direct PM

2.5

and PM

2.5

precursors in emissions inventories, the agency is following the requirements it established for the 2007 PM

2.5

NAAQS Implementation Rule in the past.

Section 172(c)(3) of the CAA explicitly requires states to submit a “comprehensive, accurate, current inventory of actual emissions of the relevant pollutants” and the EPA continues to believe that to meet these basic statutory requirements for the PM

2.5

NAAQS, states must address PM

2.5

and all PM

2.5

precursors in their emissions inventories.

72 FR 20647 (April 25, 2007).

The EPA requires states to use the best available methodologies for estimating emissions of PM

2.5

and its precursors.

The AERR Defines the Thresholds, Data Elements and Data Methods.

Because the provisions of the CAA do not specify the form of the emissions information to be reported to the EPA for meeting the attainment plan inventory requirement under CAA section 172(c)(3), it is necessary for the EPA to prescribe specifically the data elements of that emissions inventory and the attainment projected inventory. The EPA uses the AERR to define basic requirements/parameters of reporting emissions for all pollutants. This approach creates consistency and eases the burden for the states, because states have one basic set of rules that apply to all emissions they have to report to the EPA.

Distinct from the emissions

values

(

i.e.,

how much emissions derive from each source or source category), the emissions

elements

(

i.e.,

how they are reported) refer to the reporting definitions, data codes and required data fields. Under this final rule, states must use the emissions elements from 40 CFR part 51, subpart A in preparing their inventories to be submitted to the EPA for implementing the PM

2.5

NAAQS. It also requires that states use point source thresholds from Appendix A of the same subpart. This is consistent with past requirements for the form of emissions inventories.

In addition to defining the point source thresholds and data elements, 40 CFR part 51, subpart A also requires states to submit emissions information to the EPA. The EPA is not referring to those emissions submission requirements here, but rather to the emissions elements—the definitions, data codes and required data fields. Later, the EPA addresses the issue of whether the emissions values submitted through the AERR are relevant to the inventory requirements of this final rule (

see

Section IV.B.2.g of this preamble).

As noted earlier, the EPA recommends that states consult the SIP Emissions Inventory Guidance in preparing the inventories required by this rule. In addition to the AERR, this guidance includes definitions for data fields that are not required by the AERR, such as seasonal emissions values and

other fields that are optional in the AERR data collection system. The EPA is updating the SIP Emissions Inventory Guidance in coordination with this final rule. It provides specific guidance to states on how to develop base year inventories for the nonattainment area and attainment projected inventories for 8-hour ozone, PM

2.5

, and regional haze SIPs. While the AERR sets forth requirements for data elements and definitions, the guidance complements these requirements, defines all data elements (even those that are voluntary AERR elements), and indicates how states should prepare and document the data for attainment plan submissions.

In the case of prescribed fires and wildfires, the AERR no longer requires those categories to be submitted, but rather the emissions data can be optionally provided as an “Event” source, which is a day-specific source at a point location. For this rule as described earlier, states are required to include prescribed fires and wildfires for the base year inventory for the nonattainment area and the attainment projected inventory for the nonattainment area. For this rule, states are not expected to use the “Event” detail to meet their inventory reporting requirements. Instead, states can report these fire emissions by county as nonpoint sources are reported.

Emissions Inventories for Support of Modeled Attainment Demonstrations.

This section clarifies the difference between the inventories required to be a part of a state's Moderate area attainment plan submission (as described earlier) and other modeling inventories that are also relevant for attainment planning. While the EPA is not establishing additional modeling inventory requirements in this rule (

i.e.,

for which a state must submit an emissions inventory to the EPA), to meet the attainment demonstration requirements of CAA sections 189(a)(1) and 189(b)(1), states are required to submit either an attainment demonstration (which includes air quality modeling) to show how the area will attain the NAAQS by the applicable attainment date or a demonstration that the area cannot attain by the attainment date. The modeled attainment demonstration requirements for Moderate areas are described fully in Section IV.E of this preamble.

As part of the modeled attainment demonstration, the EPA presumes that states will need to prepare attainment demonstration modeling inventories for both a modeled base year and projected attainment year. Respectively, these are called the “base year (baseline) inventory for modeling” and the “attainment projected inventory for modeling.” These inventories contain emissions for all regions (

i.e.,

not just from sources in the nonattainment area) within the modeling domain being used for the attainment plan modeling demonstration, which typically includes counties and even states outsi

This text is long and has been trimmed here. Open the source document for the complete record.

This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.