Tuesday, 

November 1, 2005 

Part II 

Environmental 

Protection Agency 

40 CFR Parts 51 and 52 

Proposed Rule To Implement the Fine 

Particle National Ambient Air Quality 

Standards; Proposed Rule 

65984 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 51 and 52 

[FRL–7969–1] 

RIN 2060–AK74 

Proposed Rule To Implement the Fine 

Particle National Ambient Air Quality 

Standards 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rulemaking. 

SUMMARY: This proposed rule and 

preamble describe the requirements that 

States and Tribes must meet in their 

implementation plans for attainment of 

the fine particle (PM2.5) national 

ambient air quality standards (NAAQS). 

The health effects associated with 

exposure to PM2.5 are serious, including 

premature death, aggravation of heart 

and lung disease, and asthma attacks. 

Those particularly sensitive to PM2.5

exposure include older adults, people 

with heart and lung disease, and 

children. 

The EPA designated areas not 

attaining the PM2.5 standards on 

December 17, 2004. The PM 

designations notice was published in 

the Federal Register on January 5, 2005 

(70 FR 944) and became effective on 

April 5, 2005. On this same date, the 

Administrator signed a supplemental 

notice making certain changes to the 

designations based on 2002–2004 air 

quality data. The supplemental notice 

was published in the Federal Register 

on April 14, 2005 (70 FR 19844). A total 

of 39 areas with a population of 90 

million were designated as 

nonattainment. 

Within 3 years, each State having a 

nonattainment area must submit to EPA 

an attainment demonstration (and 

associated air quality modeling), 

adopted State regulations to reduce 

emissions of PM2.5 and its precursors, 

and other supporting information 

demonstrating that the area will attain 

the standards as expeditiously as 

practicable. In order to address PM2.5

problems, EPA believes that States 

should implement a balanced program 

to reduce emissions from regional 

sources [such as power plants emitting 

sulfur dioxide (SO2) and nitrogen oxides 

(NOX)] and local sources (such as cars, 

trucks, industrial sources, and various 

other combustion or burning-related 

activities). States should take into 

account national, State, and local 

emission reduction programs that are 

already in place and projected to 

provide future air quality benefits. 

DATES: The comment period on this 

proposal ends on January 3, 2006. 

Comments must be postmarked by the 

last day of the comment period and sent 

directly to the Docket Office listed in 

ADDRESSES (in duplicate form if 

possible). 

One public hearing will be held prior 

to the end of the comment period. The 

dates, times and locations will be 

announced separately. Please refer to 

SUPPLEMENTARY INFORMATION for 

additional information on the comment 

period and public hearings. 

ADDRESSES: Comments may be 

submitted by mail to: Air Docket, 

Environmental Protection Agency, Mail 

code: 6102T, 1200 Pennsylvania Ave., 

NW., Washington, DC 20460, Attention 

Docket ID No. OAR–2003–0062. 

Comments may also be submitted 

electronically, by facsimile, or through 

hand delivery/courier. Follow the 

detailed instructions provided under 

SUPPLEMENTARY INFORMATION. 

Documents relevant to this action are 

available for public inspection at the 

EPA Docket Center, located at 1301 

Constitution Avenue, NW., Room B102, 

Washington, DC between 8:30 a.m. and 

4:30 p.m., Monday through Friday, 

excluding legal holidays. A reasonable 

fee may be charged for copying. 

FOR FURTHER INFORMATION CONTACT: 

Regarding PM2.5 implementation issues, 

contact Mr. Richard Damberg, U.S. 

Environmental Protection Agency, 

Office of Air Quality Planning and 

Standards, Mail Code C504–02, 

Research Triangle Park, NC 27711, 

phone number (919) 541–5592 or by email at: damberg.rich@epa.gov. 

Regarding NSR issues, contact Mr. Raj 

Rao, U.S. Environmental Protection 

Agency, Office of Air Quality Planning 

and Standards, Mail Code C339–03, 

Research Triangle Park, NC 27711, 

phone number (919) 541–5344 or by email at: rao.raj@epa.gov. 

SUPPLEMENTARY INFORMATION: Section I 

of the preamble provides an overview of 

the PM2.5 standards, health effects 

associated with PM2.5, legal history, and 

EPA’s overall strategy for reducing PM2.5

pollution. Section II provides an 

overview of the pollutants and complex 

atmospheric chemistry that lead to 

PM2.5 formation, the sources of 

emissions, and a discussion of policy 

options for addressing PM precursors in 

the PM2.5 implemention program and 

the new source review (NSR) program. 

Section III of the preamble describes 

the various core elements of the PM2.5

implementation program, based 

primarily on the subpart 1 requirements 

of section 172 of the Clean Air Act 

(CAA). Important topics discussed in 

section III include attainment dates, 

attainment demonstrations and 

modeling, local emission reduction 

measures [reasonably available control 

technology (RACT) and reasonably 

available control measures (RACM)], 

and reasonable further progress (RFP). 

Section III also includes a subsection 

describing options for revising the NSR 

program to specifically address PM2.5. A 

number of other topics are presented for 

informational purposes in section III, 

including innovative program guidance, 

emission inventory requirements, 

addressing PM2.5 under the 

transportation conformity program, 

stationary source test methods for PM2.5, 

and approaches for reducing emissions 

through improved monitoring 

techniques. 

Section IV addresses the various 

statutory requirements and executive 

orders applicable to this rule. The final 

section contains proposed regulatory 

text for implementation of the PM2.5

NAAQS, in the form of a proposed 

subpart Y amending 40 CFR part 51. 

Public Hearing 

The EPA will hold one public hearing 

on today’s proposal during the comment 

period. The details of the public 

hearing, including the time, date, and 

location will be provided in a future 

Federal Register notice and announced 

on EPA’s PM2.5 implementation Web 

site at http://www.epa.gov/ttn/naaqs/ 

pm/pm25_index.html. 

The public hearing will provide 

interested parties the opportunity to 

present data, views, or arguments 

concerning the proposed rule. The EPA 

may ask clarifying questions during the 

oral presentations, but will not respond 

to the presentations or comments at that 

time. Written statements and supporting 

information submitted during the 

comment period will be considered 

with the same weight as any oral 

comments and supporting information 

presented at a public hearing. 

How Can I Get Copies of This 

Document and Other Related 

Information? 

Docket. The EPA has established an 

official public docket for this action 

under Docket ID No. OAR–2003–0062. 

The official public docket consists of the 

documents specifically referenced in 

this action, any public comments 

received, and other information related 

to this action. Although a part of the 

official docket, the public docket does 

not include Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

The official public docket is the 

collection of materials that is available 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 65985 

for public viewing at the Air Docket in 

the EPA Docket Center, (EPA/DC) EPA 

West, Room B102, 1301 Constitution 

Ave., NW., Washington, DC. The EPA 

Docket Center Public Reading Room is 

open from 8:30 a.m. to 4:30 p.m., 

Monday through Friday, excluding legal 

holidays. The telephone number for the 

Public Reading Room is (202) 566–1744, 

and the telephone number for the Air 

Docket is (202) 566–1742. A reasonable 

fee may be charged for copying. 

Electronic Access. You may access 

this Federal Register document 

electronically through the EPA Internet 

under the ‘‘Federal Register’’ listings at 

http://www.epa.gov/fedrgstr/. 

An electronic version of the public 

docket is available through EPA’s 

electronic public docket and comment 

system, EPA Dockets. You may use EPA 

Dockets at http://www.epa.gov/edocket/ 

to submit or view public comments, 

access the index listing of the contents 

of the official public docket, and to 

access those documents in the public 

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Once in the system, select ‘‘search,’’

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Certain types of information will not 

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Information claimed as CBI and other 

information whose disclosure is 

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will not be available for public viewing 

in EPA’s electronic public docket. The 

EPA’s policy is that copyrighted 

material will not be placed in EPA’s 

electronic public docket but will be 

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the official public docket. To the extent 

feasible, publicly available docket 

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whether the document is available for 

viewing in EPA’s electronic public 

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materials may be available 

electronically, you may still access any 

of the publicly available docket 

materials through the docket facility 

identified above. The EPA intends to 

work towards providing electronic 

access to all of the publicly available 

docket materials through EPA’s 

electronic public docket. 

For public commenters, it is 

important to note that EPA’s policy is 

that public comments, whether 

submitted electronically or in paper, 

will be made available for public 

viewing in EPA’s electronic public 

docket as EPA receives them and 

without change, unless the comment 

contains copyrighted material, CBI, or 

other information whose disclosure is 

restricted by statute. When EPA 

identifies a comment containing 

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a reference to that material in the 

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EPA’s electronic public docket. The 

entire printed comment, including the 

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Public comments submitted on 

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For additional information about 

EPA’s electronic public docket, visit 

EPA Dockets online or see 67 FR 38102; 

May 31, 2002. 

How and To Whom Do I Submit 

Comments? 

You may submit comments 

electronically, by mail, by facsimile, or 

through hand delivery/courier. To 

ensure proper receipt by EPA, identify 

the appropriate docket identification 

number, OAR–2003–0062, in the subject 

line on the first page of your comment. 

Please ensure that your comments are 

submitted within the specified comment 

period. Comments received after the 

close of the comment period will be 

marked ‘‘late.’’ The EPA is not required 

to consider these late comments. If you 

wish to submit CBI or information that 

is otherwise protected by statute, please 

follow the instructions below under, 

‘‘How Should I submit CBI to the 

Agency?’’ Do not use EPA Dockets or email to submit CBI or information 

protected by statute. 

Electronically. If you submit an 

electronic comment as prescribed 

below, EPA recommends that you 

include your name, mailing address, 

and an e-mail address or other contact 

information in the body of your 

comment. Also include this contact 

information on the outside of any disk 

or CD ROM you submit, and in any 

cover letter accompanying the disk or 

CD ROM. This ensures that you can be 

identified as the submitter of the 

comment and allows EPA to contact you 

in case EPA cannot read your comment 

due to technical difficulties or needs 

further information on the substance of 

your comment. The EPA’s policy is that 

EPA will not edit your comment, and 

any identifying or contact information 

provided in the body of a comment will 

be included as part of the comment that 

is placed in the official public docket, 

and made available in EPA’s electronic 

public docket. If EPA cannot read your 

comment due to technical difficulties 

and cannot contact you for clarification, 

EPA may not be able to consider your 

comment. 

EPA Dockets. Your use of EPA’s 

electronic public docket to submit 

comments to EPA electronically is 

EPA’s preferred method for receiving 

comments. Go directly to EPA Dockets 

at http://www.epa.gov/edocket, and 

follow the online instructions for 

submitting comments. To access EPA’s 

electronic public docket from the EPA 

Internet Home Page, select ‘‘Information 

Sources,’’ ‘‘Dockets,’’ and ‘‘EPA 

Dockets.’’ Once in the system, select 

‘‘search,’’ and then key in Docket ID No. 

OAR–2003–0062. The system is an 

‘‘anonymous access’’ system, which 

means EPA will not know your identity, 

e-mail address, or other contact 

information unless you provide it in the 

body of your comment. 

Electronic mail. Comments may be 

sent by e-mail to A-and-RDocket@epa.gov, Attention Docket ID 

No. OAR–2003–0062. In contrast to 

EPA’s electronic public docket, EPA’s email system is not an ‘‘anonymous 

access’’ system. If you send an e-mail 

comment directly to the Docket without 

going through EPA’s electronic public 

docket, EPA’s e-mail system 

automatically captures your e-mail 

address. The e-mail addresses that are 

automatically captured by EPA’s e-mail 

system are included as part of the 

comment that is placed in the official 

public docket, and made available in 

EPA’s electronic public docket. 

Disk or CD ROM. You may submit 

comments on a disk or CD ROM that 

you mail to the mailing address 

identified under Docket above. These 

electronic submissions will be accepted 

in WordPerfect or ASCII file format. 

Avoid the use of special characters and 

any form of encryption. 

By Mail. Send your comments to Air 

Docket (in duplicate if possible), 

Environmental Protection Agency, Mail 

code: 6102T, 1200 Pennsylvania Ave., 

NW., Washington, DC, 20460, Attention 

Docket ID No. OAR–2003–0062. 

By Hand Delivery or Courier. Deliver 

your comments to: Air Docket, 

Environmental Protection Agency, 1301 

Constitution Avenue, NW., Room B108, 

Mail code: 6102T, Washington, DC 

20004, Attention Docket ID No. OAR–

2003–0062. Such deliveries are only 

accepted during the Docket’s normal 

hours of operation as identified above 

under Docket. 

65986 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

By Facsimile. Fax your comments to 

(202) 566–1741, Attention Docket ID. 

No. OAR–2003–0062. 

How Should I Submit CBI to the 

Agency? 

Do not submit information that you 

consider to be CBI electronically 

through EPA’s electronic public docket 

or by e-mail. Send or deliver 

information identified as CBI only to the 

following address: Roberto Morales, 

U.S. EPA, Office of Air Quality Planning 

and Standards, Mail Code C404–02, 

Research Triangle Park, NC 27711, 

telephone (919) 541–0880, e-mail at 

morales.roberto@epa.gov, Attention 

Docket ID No. OAR–2003–0062. You 

may claim information that you submit 

to EPA as CBI by marking any part or 

all of that information as CBI (if you 

submit CBI on disk or CD ROM, mark 

the outside of the disk or CD ROM as 

CBI and then identify electronically 

within the disk or CD ROM the specific 

information that is CBI). Information so 

marked will not be disclosed except in 

accordance with procedures set forth in 

40 CFR part 2. 

In addition to one complete version of 

the comment that includes any 

information claimed as CBI, a copy of 

the comment that does not contain the 

information claimed as CBI must be 

submitted for inclusion in the public 

docket and EPA’s electronic public 

docket. If you submit the copy that does 

not contain CBI on disk or CD ROM, 

mark the outside of the disk or CD ROM 

clearly that it does not contain CBI. 

Information not marked as CBI will be 

included in the public docket and EPA’s 

electronic public docket without prior 

notice. If you have any questions about 

CBI or the procedures for claiming CBI, 

please consult the person identified in 

the FOR FURTHER INFORMATION CONTACT

section. 

What Should I consider as I Prepare 

My Comments for EPA? 

You may find the following 

suggestions helpful for preparing your 

comments: 

1. Explain your views as clearly as 

possible. 

2. Describe any assumptions that you 

used. 

3. Provide any technical information 

and/or data you used that support your 

views. 

4. If you estimate potential burden or 

costs, explain how you arrived at your 

estimate. 

5. Provide specific examples to 

illustrate your concerns. 

6. Offer alternatives. 

7. Make sure to submit your 

comments by the comment period 

deadline identified. 

8. To ensure proper receipt by EPA, 

identify the appropriate docket 

identification number in the subject line 

on the first page of your response. It 

would also be helpful if you provided 

the name, date, and Federal Register 

citation related to your comments. 

Timing 

In a number of places, this document 

refers to time periods (e.g., x number of 

years) after designation or after the 

designation date. By this, we mean the 

number of years after the effective date 

of PM2.5 designations (April 5, 2005). 

Table of Contents 

I. What Is the PM2.5 Problem and EPA’s 

Strategy for Addressing It? 

A. What are the fine particle standards and 

the health effects they address? 

B. What is the legal history of the PM2.5

standards? 

C. What was the process for designating 

PM2.5 attainment and nonattainment 

areas? 

D. What is the geographic extent of the 

PM2.5 problem? 

E. What is EPA’s overall strategy for 

reducing PM2.5 pollution? 

1. The State implementation plan (SIP) 

system 

2. National rules 

II. Fine Particles: Overview of Atmospheric 

Chemistry, Sources of Emissions, and 

Ambient Monitoring Data 

A. Introduction 

B. Concentration, composition and sources 

of fine PM 

C. The role of ammonia in sulfate, nitrate 

& secondary organic aerosol formation 

D. Regional patterns of carbon, sulfate and 

nitrate, and indications of transport 

E. Policy for addressing PM2.5 precursors 

1. Legal Authority to Regulate Precursors 

2. Proposed policy options for addressing 

PM2.5 precursors in nonattainment plan 

programs. 

III. What Are the Specific Elements of EPA’s 

PM2.5 Implementation Program? 

A. What classification options are under 

consideration for PM2.5 nonattainment 

areas? 

1. Background 

2. Proposed options for PM2.5

classifications 

a. No classification system based on design 

values 

b. Two-tiered classification system 

c. Rural transport classification 

B. When are PM2.5 attainment 

demonstrations and SIPs due, and what 

requirements must they address? 

C. What are the attainment dates for PM2.5

nonattainment areas? 

1. Background 

2. Consideration of existing measures in 

proposing an attainment date 

3. Areas may qualify for two 1-year 

attainment date extensions 

4. Areas may submit a SIP demonstrating 

that it is impracticable to attain by the 

5-year attainment date 

5. Areas that fail to attain or do not qualify 

for an attainment date extension 

6. Determining attainment for the PM2.5

standards 

7. How do attainment dates apply to Indian 

country? 

D. What are the incentives for achieving 

early reductions of PM2.5 and its 

precursors? 

E. How should the States and EPA balance 

the need to address long-range transport 

of fine particle pollution with the need 

for local emissions reductions when 

implementing the PM2.5 standards? 

1. Clean Air Act provisions for achieving 

local and regional emissions reductions 

2. Regional emission reduction strategies 

3. The role of local and State emission 

reduction efforts in reducing health risks 

and achieving the PM2.5 standards 

4. Addressing regionally transported 

emissions in local area attainment 

demonstrations 

F. How will EPA address requirements for 

modeling and attainment demonstration 

SIPs when implementing the 24-hour 

and annual average PM2.5 standards? 

1. Introduction 

2. Areas that need to conduct modeling 

3. Modeling guidance 

4. Modeled attainment test 

5. Multi-pollutant assessments and oneatmosphere modeling 

6. Which future year(s) should be 

modeled? 

7. Mid-course review 

G. What requirements for RFP apply under 

the PM2.5 implementation program? 

1. Background 

2. What is the baseline year from which 

States will track emission reductions for 

meeting RFP requirements? 

3. How does EPA propose to address the 

pollutants associated with PM2.5 in these 

RFP requirements? 

4. What areas must submit an RFP plan? 

a. Areas projected to attain within 5 years 

of designation 

b. Areas projected to attain more than 5 

years from the date of designation must 

submit a 2008 RFP plan 

i. For purposes of the 2008 RFP plan, how 

should a nonattainment area define its 

emission reduction milestones? 

ii. For what pollutants must States reduce 

emissions? 

iii. How should States assess the 

equivalence of alternative combinations 

of pollutant emissions reductions? 

iv. How would RFP be evaluated for a 

sample 2008 RFP plan? 

v. What potential RFP requirements could 

apply for ‘‘serious’’ areas under the twotiered classification option? 

5. Other RFP issues 

a. How should States account for regional 

control strategies in evaluating RFP? 

b. What geographic area should States 

address in RFP plans? 

c. How should RFP be addressed in multistate nonattainment areas? 

d. How should States compile emission 

inventories for RFP plans? 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 65987 

e. What RFP requirements apply in Tribal 

areas? 

f. What must States submit to show 

whether they have met RFP milestones? 

H. What requirements for contingency 

measures should apply under the PM2.5

implementation program? 

I. What requirements should apply for 

RACM and RACT for PM2.5

nonattainment areas? 

1. General background 

2. Background for RACT 

3. Emissions inventory analysis supporting 

RACT options 

4. Which PM2.5 precursors must be 

addressed by States in establishing 

RACT requirements? 

5. What are the proposed options for 

implementing the RACT requirement? 

6. What factors should States consider in 

determining whether an available control 

technology is technically feasible? 

7. What factors should States consider in 

determining whether an available control 

technology is economically feasible? 

8. How should condensable emissions be 

treated in RACT determinations? 

9. What are the required dates for 

submission and implementation of 

RACT measures? 

10. Under the PM2.5 implementation 

program, does a State need to conduct a 

RACT determination for an applicable 

source that already has a RACT 

determination in effect? 

11. What policies affect compliance with 

RACT for electric generating units? 

12. Is EPA developing PM2.5 controlled 

technique guidelines? 

13. Background for RACM 

14. What is the proposed approach for 

implementing RACM? 

15. What factors should States consider in 

determining whether control measures 

are reasonably available? 

16. What specific source categories and 

control measures should a State evaluate 

when determining RACM for a 

nonattainment area? 

17. What criteria should be met to ensure 

effective regulations or permits to 

implement RACT and RACM? 

J. What guidance is available to States and 

Tribes for implementing innovative 

programs to address the PM2.5 problem? 

K. What aspects of transportation 

conformity and the PM2.5 standard are 

addressed in this proposal? 

1. What is transportation conformity? 

2. Why does transportation conformity 

apply to PM2.5? 

3. Why is EPA discussing transportation 

conformity in this proposal? 

4. What revisions have been made to the 

transportation conformity rule to address 

the PM2.5 standard? 

5. Does EPA plan to revoke the PM10

standard? 

6. Will some areas be demonstrating 

conformity for both PM10 and PM2.5 at 

the same time? 

7. When does transportation conformity 

apply to PM2.5 nonattainment areas? 

8. How does the 1-year grace period apply 

in metropolitan areas? 

9. How does the 1-year grace period apply 

in ‘‘donut’’ areas? 

10. How does the 1-year grace period apply 

in isolated rural areas? 

L. What requirements for general 

conformity should apply to the PM2.5

standards? 

1. What is the purpose of the general 

conformity regulations? 

2. How is the general conformity program 

currently structured? 

3. Who runs the general conformity 

program? 

4. How does an agency demonstrate 

conformity? 

5. General conformity regulation revisions 

for the PM2.5 standards 

a. What de minimis emission levels will be 

set for pollutants that contribute to PM2.5

concentrations? 

b. What impact will the implementation of 

the PM2.5 standards have on a State’s 

general conformity SIP? 

c. Are there any other impacts on the SIPs 

related to general conformity based on 

implementation of the PM2.5 standards? 

6. Is there a 1-year grace period which 

applies to general conformity 

determinations for the purposes of the 

PM2.5 standards? 

M. How will the NSR program address 

PM2.5 and its precursors? 

1. Background 

2. What are the principal elements of the 

proposed major NSR program for PM2.5? 

3. Should precursors to the formation of 

ambient concentrations of PM2.5 be 

subject to regulation under NSR? 

a. Background 

b. Should NSR cover precursor emissions 

in addition to direct emissions of PM2.5? 

4. What is a major stationary source (major 

source) under the major NSR program for 

PM2.5? 

a. Background 

b. Proposed option 

c. What is the effect of this proposed 

option? 

5. What should the significant emissions 

rate be for direct emissions of PM2.5? 

a. Background 

b. Proposed options 

6. What should be the significant emissions 

rates for PM2.5 precursors? 

a. Background 

b. Proposed options 

7. What is the role of condensible 

emissions in determining major NSR 

applicability? 

8. What are the requirements of the 

Prevention of Significant Deterioration 

(PSD) program for attainment areas? 

9. How should BACT be implemented? 

10. What is EPA’s plan for preventing 

significant deterioration of air quality for 

PM2.5? 

11. How will the air quality analysis 

required under section 165(a)(3) be 

implemented? 

12. How should the PSD pre-construction 

monitoring requirement be implemented 

for PM2.5? 

a. Background 

b. Options for PSD preconstruction 

monitoring 

13. Nonattainment New Source Review 

(NA NSR) requirements 

14. What are the offset requirements for NA 

NSR? 

a. What is the required offset ratio for PM2.5

direct emissions? 

b. Which precursors shall be subject to the 

offset requirement? 

c. What is the required offset ratio for PM2.5

precursors? 

d. Should EPA allow interprecursor trading 

to comply with the offset requirement? 

15. What are the implementation and 

transition issues associated with this 

rule? 

16. Implementation of PSD provisions 

during the SIP Development period 

a. Background 

b. Proposed options 

c. Rationale 

17. Implementation of the nonattainment 

NSR provisions during the SIP 

development period 

a. Background 

b. Implementation of NSR under the 

Emissions Offset Interpretative Ruling 

(40 CFR part 51, Appendix S) with 

revisions. 

c. Legal basis for requiring States to issue 

nonattainment NSR permits during the 

SIP-development period 

18. NSR applicability to precursors during 

the interim period 

19. Are there any Tribal concerns? 

20. What must a State or local agency do 

about minor sources of PM2.5? 

21. Supplemental program option: rural 

transport areas 

a. What flexible implementation options 

should be available for Transport areas? 

b. Which nonattainment areas would be 

eligible for the transport program? 

c. What would be the basic requirements 

of a transport nonattainment NSR 

program? 

N. How will EPA ensure that the 8-hour 

ozone standard will be implemented in 

a way which allows an optimal mix of 

controls for PM2.5, ozone, and regional 

haze? 

1. Could an area’s PM2.5 strategy affect its 

8-hour ozone and/or regional haze 

strategy? 

2. What guidance has EPA provided 

regarding ozone, PM2.5 and regional haze 

interaction? 

3. What is EPA proposing? 

O. What emission inventory requirements 

should apply under the PM2.5 NAAQS? 

P. What stationary source test methods 

should States use under the PM2.5

implementation program? 

1. Will the existing stationary source test 

methods for particulate matter (PM) be 

acceptable for use in PM2.5 SIPs? 

2. Why are the existing stationary source 

test methods for PM deficient? 

3. If the stationary source test methods are 

changed, will the existing emission 

limitations incorporated in SIPs need to 

be changed? 

4. The existing PM test methods and the 

emission limits based upon these 

methods have been acceptable since 

1971, why do they need to be changed 

for PM2.5? 

5. What methods are available for 

measuring PM size and condensable PM 

from stationary sources? 

6. Why is a new dilution-based test method 

being developed by EPA? 

65988 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

1 In the 1997 PM NAAQS revision, EPA also 

revised the standard for particles with a nominal 

aerodynamic diameter of 10 micrometers or less 

(also known as PM10). The original PM10 standard 

was established in 1987. The revised PM10 standard 

was later vacated by the court, and thus the 1987 

PM10 standard remains in effect. Today’s proposed 

implementation rule and guidance does not address 

PM10. 

2Environmental Protection Agency. (1996) Air 

Quality Criteria for Particulate Matter. Research 

Triangle Park, NC: National Center for 

Environmental Assessment-RTP Office; report no. 

EPA/600/P–95/001aF-cF. 3v. 

7. What types of sources should use the 

new dilution-based test method? 

8. What are the main features of the new 

test method? 

9. What is the schedule for finalization of 

the new test method? 

10. How will use of this new method affect 

an areas emissions inventory and the 

emissions inventory for individual 

sources? 

11. How will use of this new method affect 

a State’s implementation program more 

broadly? 

Q. How can potentially inadequate source 

monitoring in certain SIP rules be 

improved? 

1. How does improved PM2.5 monitoring 

relate to title V monitoring? 

2. Are instrumental techniques more 

appropriate than visual emissions (VE) 

techniques for monitoring compliance 

with PM emissions limits, for some 

situations and applications? 

3. What constitutes improved monitoring? 

R. What guidance should be provided that 

is specific to Tribes? 

S. Are there any additional requirements 

related to enforcement and compliance? 

T. What requirements should apply to 

emergency episodes? 

U. What ambient monitoring requirements 

will apply under the PM2.5 NAAQS? 

IV. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

B. Paperwork Reduction Act 

C. Regulatory Flexibility Act 

D. Unfunded Mandates Reform Act 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation 

and Coordination with Indian Tribal 

Governments 

G. Executive Order 13045: Protection of 

Children from Environmental Health and 

Safety Risks 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

I. National Technology Transfer 

Advancement Act 

J. Executive Order 12898: Federal Actions 

to Address Environmental Justice in 

Minority Populations and Low-Income 

Populations 

I. What Is the PM2.5 Problem and EPA’s 

Strategy for Addressing It? 

A. What Are the Fine Particle Standards 

and the Health Effects They Address? 

Fine particles in the atmosphere are 

made up of a complex mixture of 

components. Common constituents 

include: Sulfate (SO4); nitrate (NO3); 

ammonium; elemental carbon; a great 

variety of organic compounds; and 

inorganic material (including metals, 

dust, sea salt, and other trace elements) 

generally referred to as ‘‘crustal’’

material, although it may contain 

material from other sources. Airborne 

particulate matter (PM) with a nominal 

aerodynamic diameter of 2.5 

micrometers or less (a micrometer is 

one-millionth of a meter, and 2.5 

micrometers is less than one-seventh the 

average width of a human hair) are 

considered to be ‘‘fine particles,’’ and 

are also known as PM2.5. ‘‘Primary’’

particles are emitted directly into the air 

as a solid or liquid particle (e.g., 

elemental carbon from diesel engines or 

fire activities, or condensable organic 

particles from gasoline engines). 

‘‘Secondary’’ particles (e.g., sulfate and 

nitrate) form in the atmosphere as a 

result of various chemical reactions. 

(See section II for a more detailed 

technical discussion on PM2.5, its 

precursors, formation processes, and 

emissions sources.) 

The health effects associated with 

exposure to PM2.5 are significant. 

Epidemiological studies have shown a 

significant correlation between elevated 

PM2.5 levels and premature mortality. 

Other important effects associated with 

PM2.5 exposure include aggravation of 

respiratory and cardiovascular disease 

(as indicated by increased hospital 

admissions, emergency room visits, 

absences from school or work, and 

restricted activity days), lung disease, 

decreased lung function, asthma attacks, 

and certain cardiovascular problems. 

Individuals particularly sensitive to 

PM2.5 exposure include older adults, 

people with heart and lung disease, and 

children. On July 18, 1997, we revised 

the NAAQS for particulate matter to add 

new standards for fine particles, using 

PM2.5 as the indicator. We established 

health-based (primary) annual and 24- 

hour standards for PM2.5 (62 FR 38652).1

The annual standard is a level of 15 

micrograms per cubic meter, based on 

the 3-year average of annual mean PM2.5

concentrations. The 24-hour standard is 

a level of 65 micrograms per cubic 

meter, based on the 3-year average of the 

98th percentile of 24-hour 

concentrations. The EPA established the 

standards based on significant evidence 

and numerous health studies 

demonstrating that serious health effects 

are associated with exposures to 

elevated levels of PM2.5. Estimates show 

that attainment of the PM2.5 standards 

would be likely to result in tens of 

thousands fewer premature deaths each 

year, would be likely to prevent tens of 

thousands of hospital admissions each 

year, and would be likely to prevent 

hundreds of thousands of doctor visits, 

absences from work and school, and 

respiratory illnesses in children 

annually. The research on which EPA 

based the 1997 standards did not 

identify a specific threshold 

concentration below which individuals 

have no PM-related health effects, 

meaning that emissions reductions 

resulting in reduced concentrations 

below the level of the standards may 

continue to provide additional health 

benefits to the local population.2 At the 

time we established the primary 

standards in 1997, we also established 

welfare-based (secondary) standards 

identical to the primary standards. The 

secondary standards are designed to 

protect against major environmental 

effects of PM2.5 such as visibility 

impairment, soiling, and materials 

damage. The EPA also established the 

regional haze regulations in 1999 for the 

improvement of visual air quality in 

national parks and wilderness areas 

across the country. Because regional 

haze is caused primarily by light 

scattering and light absorption by fine 

particles in the atmosphere, EPA is 

encouraging the States to integrate their 

efforts to attain the PM2.5 standards with 

those efforts to establish reasonable 

progress goals and associated emission 

reduction strategies for the purposes of 

improving air quality in our treasured 

natural areas under the regional haze 

program. 

The scientific assessment that 

resulted in the establishment of the 

PM2.5 standards included a scientific 

peer review and public comment 

process. We developed scientific 

background documents based on the 

review of hundreds of peer-reviewed 

scientific studies. The Clean Air 

Scientific Advisory Committee, a 

congressionally mandated group of 

independent scientific and technical 

experts, provided extensive review of 

these assessments, and found that EPA’s 

review of the science provided an 

adequate basis for the EPA 

Administrator to make a decision. More 

detailed information on health effects of 

PM2.5 can be found on EPA’s Web site 

at: http://www.epa.gov/air/urbanair/ 

pm/index.html. Additional information 

on EPA’s scientific assessment 

documents supporting the 1997 

standards is available at: http:// 

www.epa.gov/ttn/oarpg (see headings 

for ‘‘Staff Papers’’ and ‘‘Criteria 

Documents’’). 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 65989 

3Whitman v. American Trucking Assoc., 121 

S.Ct. 903, 911–914 (2001) (Whitman). 

4The 1998 Tribal Authority Rule (TAR) (40 CFR 

part 49), which implements section 301(d) of the 

CAA, provides for Tribes to be treated in the same 

manner as a State in implementing 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. See section III.Q. for further discussion of 

Tribal issues. 

5When the term ‘‘State’’ is used hereafter, it will 

refer to States, local air agencies, and Tribal 

governments electing to be treated as States for the 

purposes of implementing the CAA. 

6The CAA requires EPA to set ambient air quality 

standards and requires States to submit plans 

designed to attain those standards. 

7See ‘‘Designations for the Fine Particle National 

Ambient Air Quality Standard,’’ memorandum from 

Jeffrey R. Holmstead, Assistant Administrator, to 

EPA Regional Administrators, April 1, 2003. 

Available at: http://www.epa.gov/pmdesignations/ 

guidance.htm. 

8See ‘‘Additional Guidance on Defining Area 

Boundaries for PM2.5 Designations,’’ memorandum 

from Lydia N. Wegman, Director of Air Quality 

Strategies and Standards Division, EPA Office of 

Air Quality Planning and Standards, to EPA Air 

Division Directors, February 12, 2004. Available at: 

http://www.epa.gov/pmdesignations/guidance.htm. 

9The Consolidated Appropriations Bill for 

FY2004 (Pub. L. 108–199), signed by President 

Bush on January 23, 2004, codifies the required 

State submittal date (February 15, 2004) and the 

date for EPA to finalize PM2.5 designations 

(December 31, 2004) that were originally included 

in EPA’s April 2003 guidance on PM2.5

designations. 

B. What Is the Legal History of the PM2.5

Standards? 

After EPA promulgated the PM2.5 and 

8-hour ozone standards in July 1997, 

several industry organizations and State 

governments challenged EPA’s action in 

the U.S. Court of Appeals for the District 

of Columbia Circuit (the DC Circuit). 

This action initiated a long legal 

process, ending with a March 2002 

decision by the DC Circuit upholding 

the standards and the authority on 

which they were established. 

On May 14, 1999, the three-judge 

panel of the DC Circuit held in a split 

decision that the CAA, as applied by 

EPA in setting the 1997 standards for 

PM and ozone, was unconstitutional as 

an improper delegation of legislative 

authority to EPA. The ruling did not 

question the science or decision-making 

process used to establish the standards. 

The Court remanded the PM2.5

standards to EPA but did not vacate 

them. In June 1999, the Department of 

Justice (DOJ) and EPA petitioned the 

Court for a rehearing en banc with the 

entire DC Circuit Court. On October 29, 

1999, the Court denied the petition for 

rehearing. 

The DOJ and EPA then filed a petition 

for certiorari with the United States 

Supreme Court in December 1999 to 

appeal the decision of the DC Circuit, 

and the Supreme Court issued its 

decision to hear the appeal in November 

2000. The Supreme Court issued its 

decision on the merits of the appeal on 

February 27, 2001.3 In that decision, the 

Supreme Court held that EPA’s 

approach to setting the NAAQS in 

accordance with the CAA did not 

constitute an unconstitutional 

delegation of authority. The Supreme 

Court unanimously affirmed the 

constitutionality of the CAA provision 

that authorizes the Agency to set 

national air quality standards, stating 

that this provision ‘‘fits comfortably 

within the scope of discretion permitted 

by our precedent.’’ The Supreme Court 

also affirmed that the CAA requires EPA 

to set standards at levels necessary to 

protect the public health and welfare, 

without considering the economic costs 

of implementing the standards. The 

Supreme Court remanded several other 

issues back to the DC Circuit, including 

the issue of whether EPA acted 

arbitrarily and capriciously in 

establishing the specific levels of the 

standards. 

The DC Circuit heard arguments in 

this remanded case in December 2001, 

and issued its decision on March 26, 

2002. The DC Circuit found that the 

Agency had ‘‘engaged in reasoned 

decision making,’’ rejecting the claim 

that the Agency had acted arbitrarily 

and capriciously in setting the levels of 

the standards. This last decision by the 

DC Circuit gave EPA a clear path to 

move forward with implementation of 

the PM2.5 standards. 

The implementation rule we are 

proposing today provides specific 

requirements for State, local, and 

Tribal 4 air pollution control agencies to 

address as they prepare implementation 

plans required by the CAA to attain and 

maintain the PM2.5 standards.5 Each 

State with an area that is not attaining 

the PM2.5 NAAQS will have to develop, 

as part of its State implementation plan 

(SIP), emission limits for appropriate 

sources and other requirements to attain 

the NAAQS within the timeframes set 

forth in the CAA.6 Tribes with 

jurisdiction over Indian country that is 

not attaining the PM2.5 NAAQS could 

voluntarily submit a Tribal 

implementation plan (TIP) but are not 

required to do so. However, in cases 

where Tribes elect not to submit a TIP, 

EPA, working with the Tribes, has the 

responsibility for developing an 

implementation plan in those areas. 

C. What Was the Process for Designating 

PM2.5 Attainment and Nonattainment 

Areas? 

We issued guidance in April 2003 7

and February 2004 8 on the process for 

designating attainment and 

nonattainment areas for PM2.5 and on 

factors for States and Tribes to consider 

in defining boundaries for 

nonattainment areas. The guidance 

states that EPA believes the presumptive 

boundaries for nonattainment areas 

should be equal to the 1999 Office of 

Management and Budget (OMB) 

definitions of the combined 

metropolitan statistical area, where 

applicable, or the metropolitan 

statistical area. We also recognized the 

fact that in June 2003, OMB released 

updated definitions of combined 

statistical areas and core-based 

statistical areas. We communicated to 

the States and Tribes that in evaluating 

potential nonattainment area 

boundaries, they should include any 

additional counties that were added in 

2003 to the 1999 metro area definitions, 

plus adjacent counties, in their review 

of data associated with the nine 

technical factors discussed in EPA 

guidance. 

States were required to submit their 

recommendations to EPA by February 

15, 2004.9 Tribes were encouraged, but 

not required, to submit designation 

recommendations to EPA for their 

reservations or other areas under their 

jurisdiction. In general, the 

recommendations were based on the 

most recent 3 years of air quality data 

available (e.g. 2001–2003). On June 29, 

we sent letters to the Governors and 

Tribal leaders notifying them of any 

modifications we intended to make to 

their recommendations. After 

considering additional comments and 

information from States and Tribes, EPA 

issues final PM2.5 designations on 

December 17, 2004. They were 

published in the Federal Register on 

January 5, 2005 (70 FR 944). 

The nonattainment designation for an 

area starts the process whereby a State 

or Tribe must develop an 

implementation plan that includes, 

among other things, a demonstration 

showing how it will attain the ambient 

standards by the attainment dates 

required in the CAA. Under section 

172(b), States have up to 3 years after 

EPA’s final designations to submit their 

SIPs to EPA. These SIPs will be due in 

April 2008, three years from the 

effective date of the designations. 

D. What Is the Geographic Extent of the 

PM2.5 Problem? 

The PM2.5 ambient air quality 

monitoring data for the 2001–2003 

period suggest that areas violating the 

standards are located across much of the 

eastern half of the United States and in 

much of central and southern California. 

65990 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

10A listing of counties and associated PM2.5 3- 

year annual average concentrations, or ‘‘design 

values,’’ is available on EPA’s Web site at: http:// 

www.epa.gov/airtrends/values.html. 

11The PM2.5 design value for a nonattainment 

area is the highest of the 3-year average 

concentrations calculated for the monitors in the 

area, in accordance with 40 CFR part 50, appendix 

N. 

12National Acid Precipitation Assessment 

Program. Acid Deposition: State of the Science and 

Technology. Washington, DC. 1991. See also: 

Environmental Protection Agency. (2004) Air 

Quality Criteria for Particulate Matter. Research 

Triangle Park, NC: Office of Research and 

Development; report no. EPA/600/P–99/002a,bF. 

October. The 2004 PM criteria document is 

available at: http://www.epa.gov/ttn/naaqs/ 

standards/pm/s_pm_cr_cd.html. 13NARSTO (2004) Particulate Matter Assessment 

for Policy Makers: A NARSTO Assessment. P. 

McMurry, M. Shepherd, and J. Vickery, eds. 

Cambridge University Press, Cambridge, England. 

ISBN 0 52 184287 5. For more information, see 

http://www.cgenv.com/NARSTO. See also 

supporting technical information for the Clear Skies 

Act, http://www.epa.gov/clearskies/, and for the 

Clean Air Interstate Rule, http://www.epa.gov/ 

cleanairinterstaterule. 

A total of 47 areas comprised of 224 

counties and the District of Columbia 

were designated as nonattainment in 

December 2004. In April 2005, EPA 

issued a supplemental notice which 

changed the designation status of eight 

areas (with 17 counties) from 

nonattainment to attainment based on 

newly updated 2002–2004 air quality 

data. In addition, four areas previously 

designated as unclassifiable were 

changed to attainment in this notice. 

The population of the 39 PM2.5

nonattainment areas is significant—

about 90 million, or more than 30% of 

the U.S. population. Most areas violate 

only the annual standard, but a few 

violate both the annual and 24-hour 

standards. The 2001–2003 data show 

that no area violates just the 24-hour 

standard.10

The distribution of the 2001–2003 

design values 11 for the 39 

nonattainment areas is shown in the 

table below: 

Design value range 

for PM2.5 nonattainment areas 

(in μg/m3) 

Number of 

areas 

Percent of 

all areas 

(percent) 

15.1–16.0 .............. 10 26 

16.1–17.0 .............. 12 31 

17.1–18.0 .............. 12 31 

18.1–19.0 .............. 1 3 

19.1 + ................... 4 10 

Total ............... 39 100 

More than 40% of the nonattainment 

areas, including many major 

metropolitan areas, have design values 

that are 2 μg/m3 or more above the 

annual standard. 

The EPA believes the PM2.5 problem 

has a substantial regional component 

because the formation and transport of 

secondarily formed particles, such as 

sulfates and nitrates, extends over 

hundreds of miles. The regional nature 

of PM2.5 is in contrast to the more 

localized nature of PM10. 

In addition, data suggests that 

ambient PM2.5 concentrations tend to 

rise and fall in a consistent manner 

across very large geographic areas. The 

transport phenomena associated with 

PM2.5 and its precursors has been welldocumented for many years. For 

example, one significant source of 

information on long-range transport is 

the National Acid Precipitation 

Assessment Program (NAPAP) research 

from the 1980’s and its associated 

reports published in 1991.12 Additional 

studies and air quality modeling 

analyses since that time have added to 

the body of information documenting 

the regional nature of PM2.5.13 Since the 

emissions from one State may 

contribute significantly to PM2.5

violations in several other States, we 

believe that plans to attain the PM2.5

standards will need to include a 

combination of national, regional, and 

local emission reduction strategies. 

E. What Is EPA’s Overall Strategy for 

Reducing PM2.5 Pollution? 

Our overall strategy for achieving the 

PM2.5 standards is based on the 

structure outlined in the CAA. The CAA 

outlines important roles for State and 

Tribal governments and for EPA in 

implementing national ambient air 

quality standards. 

States have primary responsibility for 

developing and implementing SIPs that 

contain local and in-State measures 

needed to achieve the air quality 

standards in each area. We assist States 

and Tribes by providing technical tools, 

assistance and guidance, including 

information on control measures. In 

addition, we set national emissions 

limits for some sources such as new 

motor vehicles, certain categories of 

major new sources, and existing 

stationary sources of toxic air 

pollutants. Where upwind sources (such 

as coal-fired power plants) contribute to 

downwind problems in other States or 

Tribes, we can also ensure that the 

upwind States address these 

contributing emissions, or we can put in 

place Federal regulations in situations 

where the upwind States fail to address 

these sources. We intend to work 

closely with States and Tribes to use an 

appropriate combination of national, 

regional, and local pollution reduction 

measures to meet the standards as 

expeditiously as practicable, as required 

by the CAA. 

1. The State Implementation Plan (SIP) 

System 

A SIP is the compilation of 

regulations and programs that a State 

uses to carry out its responsibilities 

under the CAA, including the 

attainment, maintenance, and 

enforcement of NAAQS. (Only certain 

air quality programs and regulations 

implemented by States are required to 

be part of the SIP, however.) States use 

the SIP process to identify the emissions 

sources that contribute to the 

nonattainment problem in a particular 

area, and to select the emissions 

reduction measures most appropriate for 

that area, considering technical and 

economic feasibility, and a variety of 

local factors such as population 

exposure, enforceability, and economic 

impact. Under the CAA, SIPs must 

ensure that areas reach attainment as 

expeditiously as practicable. These 

plans need to take into consideration 

emission reductions resulting from 

national programs (such as mobile 

source regulations, the acid rain 

program, or maximum achievable 

control technology (MACT) standards 

for air toxics) as well as from State or 

local programs not directly mandated 

under the CAA. 

The SIP system for nonattainment 

areas is an important component of the 

CAA’s overall strategy for meeting the 

PM2.5 standards, but it is not the only 

component. As noted below, the CAA 

also includes requirements for national 

rules or programs that will reduce 

emissions and help achieve cleaner air. 

2. National Rules 

For the States to be successful in 

developing local plans showing 

attainment of standards, we must do our 

part to develop standards and programs 

to reduce emissions from sources that 

are more effectively and efficiently 

addressed at the national level. We also 

have the responsibility to ensure that 

interstate transport is addressed through 

SIPs or other means. As outlined below, 

we have issued final regulations that 

will achieve important emissions 

reductions from power plants, onroad 

and nonroad engine sources, and other 

sources that may enable some areas to 

meet the PM2.5 standards in the near 

term and make it easier for others to 

attain. 

The acid rain program, authorized 

under title IV of the 1990 CAA 

amendments, was projected to reduce 

annual SO2 emissions by 10 million 

tons from 1980 levels by 2010, and to 

reduce annual NOX emissions by 2 

million tons from 1980 levels by 2010. 

The EPA has implemented the acid rain 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 65991 

14For more information on the proposed Clear 

Skies Act, see EPA’s website: http://www.epa.gov/ 

clearskies/. 

15See http://www.epa.gov/cair. 

16See 64 FR 35714, July 1, 1999. 

17See Tier II emission standards at 65 FR 6698, 

February 10, 2000. 

18See heavy-duty diesel engine regulations at 66 

FR 5002, January 18, 2001. 

19For more information on the proposed nonroad 

diesel engine standards, see EPA’s website: http:// 

www.epa.gov/nonroad/. 

program in two phases: Phase I for SO2

began in 1995 and targeted the largest 

and highest-emitting coal-fired power 

plants. Phase I for NOX began in 1996. 

Phase II for both pollutants began in 

2000 and sets restrictions on Phase I 

plants as well as many additional 

smaller coal-, gas-, and oil-fired plants. 

Over 2,000 sources (mostly electricity 

generating facilities) are now affected by 

the Acid Rain Program. The acid rain 

emissions trading system had a cap of 

8.95 million tons on the total amount of 

SO2 that may be emitted by power 

plants nationwide, about half the 

amount emitted in 1980. Sulfate 

particles formed from SO2 emissions 

and nitrate particles formed from NOX

emissions contribute significantly to 

total PM2.5 mass in the eastern U.S. 

(ranging from 30–50 percent), so the 

reductions already achieved under the 

Acid Rain Program have led to 

improvements in PM2.5 concentrations 

across the region. 

Additional reductions in NOX

emissions from power plants and large 

industrial sources were required by May 

2004 under our rules to reduce 

interstate transport of ozone pollution in 

the eastern U.S. These rules are known 

as the NOX SIP Call, published October 

27, 1998 (63 FR 57356), and the Section 

126 Rule, published May 25, 1999 (64 

FR 28250). We estimate that when fully 

implemented, this program will result 

in the reduction of more than one 

million tons of summertime NOX. While 

this program was established primarily 

to address the ground-level ozone 

problem in the East, it will also result 

in reduced ambient levels of nitrate, one 

of the main components of PM2.5. 

The Administration has proposed 

nationwide legislation—the Clear Skies 

Act 14—to address health and 

environmental concerns associated with 

power plant emissions of sulfur dioxide, 

nitrogen oxides, and mercury. However, 

because passage of the CSA legislation 

is not assured, EPA has established the 

Clean Air Interstate Rule (CAIR),15 a 

regulatory approach to address 

interstate transport of pollution under 

section 110 of the CAA. Section 110 

gives EPA the authority to require SIPs 

to ‘‘prohibit * * * any source or other 

type of emission activity within the 

State from emitting any air pollutant in 

amounts which will contribute 

significantly to nonattainment in, or 

interfere with maintenance by, any 

other State with respect to’’ any 

NAAQS, and to prohibit sources or 

emission activities from emitting 

pollutants in amounts which will 

interfere with measures required to be 

included in State plans to prevent 

significant deterioration of air quality or 

to protect visibility (such as the 

protection of 156 mandatory Federal 

class I areas under the regional haze 

rule 16). 

CAIR, issued by EPA on March 10, 

2005, employs the same emissions 

trading approach used to achieve costeffective emission reductions under the 

acid rain program. It outlines a twophase program with declining power 

plant emissions caps for 28 eastern 

states and the District of Columbia: SO2

caps of 3.6 million tons in 2010, and 2.5 

million in 2015; NOX caps of 1.5 in 2009 

and 1.3 in 2015; and NOX ozone season 

caps of 580,000 tons in 2009 and 

480,000 tons in 2015. Emission caps are 

divided into State SO2 and NOX

budgets. By the year 2015, the Clean Air 

Interstate Rule will result in: 

—$85 to $100 billion in annual health 

benefits, annually preventing 17,000 

premature deaths, millions of lost 

work and school days, and tens of 

thousands of non-fatal heart attacks 

and hospital admissions. 

—Nearly $2 billion in annual visibility 

benefits in southeastern national 

parks, such as Great Smoky and 

Shenandoah. 

—Significant regional reductions in 

sulfur and nitrogen deposition, 

reducing the number of acidic lakes 

and streams in the eastern U.S. 

Current emissions standards for new 

cars, trucks and buses are reducing 

motor vehicle emissions of volatile 

organic compounds (VOCs, also referred 

to as hydrocarbons), NOX, and direct 

PM emissions (such as elemental 

carbon) as older vehicles are retired and 

replaced. Other existing rules are 

reducing emissions from several 

categories of nonroad engines. The Tier 

2 motor vehicle emission standards, 

together with the associated 

requirements to reduce sulfur in 

gasoline, will provide additional 

benefits nationally beginning in 2004.17

When the new tailpipe and sulfur 

standards are fully implemented, 

Americans will benefit from the cleanair equivalent of removing 164 million 

cars from the road. 

These new standards require 

passenger vehicles to have emissions 77 

to 95 percent cleaner than those on the 

road today and reduce the sulfur 

content of gasoline by up to 90 percent. 

In addition, the 2001 heavy-duty diesel 

engine regulations 18 will lead to 

continued emissions reductions as older 

vehicles in that engine class are retired 

and fleets turn over. New emission 

standards will begin to take effect in 

model year 2007 and will apply to 

heavy-duty highway engines and 

vehicles. These standards are based on 

the use of high-efficiency catalytic 

exhaust emission control devices or 

comparably effective advanced 

technologies. Because these devices are 

damaged by sulfur, the level of sulfur in 

highway diesel fuel will be reduced by 

97 percent by mid-2006. We project a 

2.6 million ton reduction of NOX

emissions in 2030 when the current 

heavy-duty vehicle fleet is completely 

replaced with newer heavy-duty 

vehicles that comply with these 

emission standards. By 2030, we 

estimate that this program will reduce 

annual emissions of hydrocarbons by 

115,000 tons and PM by 109,000 tons. 

These emissions reductions are on par 

with those that we anticipate from new 

passenger vehicles and low sulfur 

gasoline under the Tier 2 program. 

EPA also finalized national rules in 

May 2004 to significantly reduce PM2.5

and NOX emissions from nonroad 

diesel-powered equipment.19 These 

nonroad sources include construction, 

agricultural, and industrial equipment, 

and their emissions constitute an 

important fraction of the inventory for 

direct PM2.5 emissions (such as 

elemental carbon and organic carbon), 

and NOX. The EPA estimates that 

affected nonroad diesel engines 

currently account for about 44 percent 

of total diesel PM emissions and about 

12 percent of total NOX emissions from 

mobile sources nationwide. These 

proportions are even higher in some 

urban areas. The diesel emission 

standards will reduce emissions from 

this category by more than 90 percent, 

and are similar to the onroad engine 

requirements implemented for highway 

trucks and buses. Because the emission 

control devices can be damaged by 

sulfur, EPA also established 

requirements to reduce the allowable 

level of sulfur in nonroad diesel fuel by 

more than 99 percent by 2010. In 2030, 

when the full inventory of older 

nonroad engines has been replaced, the 

nonroad diesel program will annually 

prevent up to 12,000 premature deaths, 

one million lost work days, 15,000 heart 

attacks and 6,000 children’s asthmarelated emergency room visits. 

65992 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

20Environmental Protection Agency. (2004) Air 

Quality Criteria for Particulate Matter. Research 

Triangle Park, NC: Office of Research and 

Development; report no. EPA/600/P–99/002a,bF. 

October. The 2004 PM criteria document is 

available at: http://www.epa.gov/ttn/naaqs/ 

standards/pm/s_pm_cr_cd.html. 

II. Fine Particles: Overview of 

Atmospheric Chemistry, Sources of 

Emissions, and Ambient Monitoring 

Data 

A. Introduction 

Particulate matter is a chemically and 

physically diverse mixture of discrete 

solid particles and liquid droplets. It 

exists in the air in a range of particle 

sizes, from submicrometer to more than 

30 micrometers in size. The 

composition of particles varies 

throughout this range of sizes, 

depending on the age of the particle, the 

nature of the source of pollutant 

emissions, and the source’s operating 

characteristics. 

This regulation focuses on reducing 

ambient concentrations of the PM2.5 size 

fraction of PM. The term PM2.5 is used 

to describe the fraction of particles 

whose nominal aerodynamic diameter is 

less than or equal to 2.5 micrometers. 

PM2.5 in the ambient air is defined 

operationally as the set of particles 

measured (and associated 

concentration) by the Federal Reference 

Method sampling device. Since the cut 

point of this sampling device is not 

perfectly sharp, some particles smaller 

than 2.5 micrometers are not retained 

and some particles larger than 2.5 

micrometers are captured by sampling 

devices. This is important because there 

are two relevant modes to the PM size 

distribution, fine PM (nominally PM2.5) 

and coarse PM (nominally from 2.5 to 

10 micrometers aerodynamic diameter). 

These modes overlap slightly, but they 

are generally associated with distinctly 

different source types and formation 

processes. 

Fine particles emitted directly into 

the air in a stable solid or liquid 

chemical form are referred to as 

‘‘primary’’ particles. Particles formed 

near their source by condensation 

processes in the atmosphere are also 

considered to be primary particles. 

PM2.5 that is formed by chemical 

reactions of gases in the atmosphere is 

considered to be ‘‘secondarily’’ formed 

particulate matter. 

PM2.5 in the atmosphere is composed 

of a complex mixture of constituents: 

Sulfate; nitrate; ammonium; particlebound water; black carbon (also known 

as elemental carbon); a great variety of 

organic compounds; and miscellaneous 

inorganic material (sometimes called 

‘‘crustal material,’’ which includes 

geogenic dust and metals). Atmospheric 

PM2.5 also contains a large number of 

elements in various compounds and 

concentrations. Some organic materials 

such as pollen, spores, and plant 

detritus are also found in both the fine 

and coarse particle modes but from 

different sources or mechanisms. 

Crustal materials such as calcium, 

aluminum, silicon, magnesium, and 

iron are found predominately in coarse 

mode particles. Nitrate is generally 

found in the fine particle mode, but it 

is also found in the coarse mode 

particles, coming primarily from the 

reaction of gas-phase nitric acid with 

preexisting coarse particles. 

Primary coarse particles are usually 

formed by mechanical processes. This 

includes material emitted from such 

sources as wind-blown dust, road dust, 

and particles formed by abrasion, 

crushing, and grinding. Some 

combustion-generated particles such as 

fly ash and soot also are found in the 

coarse mode. Primary PM2.5 includes 

soot from diesel engines, a wide variety 

of organic compounds condensed from 

incomplete combustion or cooking 

operations, and compounds such as 

arsenic, selenium, and zinc that 

condense from vapor formed during 

combustion or smelting. The 

concentration of primary PM2.5 in the air 

depends on source emission rates, 

transport and dispersion, and removal 

rate from the atmosphere. 

Secondary PM is formed by chemical 

reactions of gas-phase precursors in the 

atmosphere. These reactions form 

condensable vapors that either form 

new particles or condense onto other 

particles in the air. Most of the sulfate 

and nitrate and a portion of the organic 

compounds in the atmosphere are 

formed by such chemical reactions. 

Secondary PM formation depends on 

numerous factors including the 

concentrations of precursors; the 

concentrations of other gaseous reactive 

species such as ozone, hydroxyl 

radicals, peroxy radicals, or hydrogen 

peroxide; atmospheric conditions 

including solar radiation, temperature, 

and relative humidity (RH); and the 

interactions of precursors and preexisting particles with cloud or fog 

droplets or in the liquid film on solid 

particles. Several atmospheric aerosol 

species, such as ammonium nitrate and 

certain organic compounds, are 

semivolatile and are found in both gas 

and particle phases. Given the 

complexity of PM formation processes, 

new information from the scientific 

community continues to emerge to 

improve our understanding of the 

relationship between sources of PM 

precursors and secondary particle 

formation. 

Certain particles, such as sulfates, 

nitrates, and certain organics, readily 

take up water and are considered to be 

hygroscopic. As a result of the 

equilibrium of water vapor with liquid 

water in hygroscopic particles, many 

ambient particles contain some amount 

of liquid water. When filter samples are 

weighed at lower relative humidity 

levels according to the PM2.5 Federal 

reference method specifications, the 

filters are desiccated and much of this 

water is removed, but some particlebound water will be measured as a 

component of the particle mass. 

Particle-bound water in the ambient air 

increases with higher relative 

humidities. This phenomenon is 

important because it affects the size of 

certain particles, and in turn, their 

properties of light scattering and 

aerodynamics. Differences in relative 

humidity can result in different 

measured particle size distributions, 

mass concentrations, and resulting 

visibility impairment levels. Regional 

emission reduction strategies to reduce 

PM2.5, particularly hygroscopic particles 

such as sulfates and nitrates, should 

also provide significant visibility 

improvements, both in urban areas and 

in federal class I areas (national parks 

and wilderness areas). 

The following discussion elaborates 

on the relationship between source 

types and the composition of PM2.5. 

More information and references on the 

composition of PM may be found in the 

EPA 2004 PM Air Quality Criteria 

Document.20

B. Concentration, Composition and 

Sources of Fine PM 

The relative contribution of PM2.5

components varies significantly by 

region of the country. Data on PM2.5

composition primarily in urban areas is 

available from the EPA Speciation 

Trends Network beginning in 2001. 

PM2.5 composition data for primarily 

rural areas (e.g. national parks and 

wilderness areas) is available from the 

IMPROVE visibility monitoring network 

beginning in 1988. Speciation data from 

September 2001 to August 2002 are 

summarized for urban and rural areas in 

nine regions in table 2. 

BILLING CODE 6560–50–U 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 65993 

21 V. Rao, N. Frank, A. Rush, F. Dimmick, 

‘‘Chemical Speciation of PM2.5 in Urban and Rural 

Areas,’’ In the Proceedings of the Air & Waste 

Management Association Symposium on Air 

Quality Measurement Methods and Technology, 

San Francisco, November 13–15, 2002. 

BILLING CODE 6560–50–C 

This discussion focuses on the eastern 

U.S. and California since most 

nonattainment areas will be located in 

those regions. In general, urban areas 

have higher annual average PM2.5

concentrations than nearby rural areas. 

In the eastern U.S. urban areas, 

ammonium sulfate and total carbon 

(comprised of black carbon and organic 

carbon) are the dominant species, each 

accounting for 30–40 percent of total 

reconstructed mass in most locations. 

(Reconstructed mass is the PM mass 

calculated by adding together the mass 

from each of the main components of 

PM as obtained from chemical 

composition monitoring.) Nitrate plus 

associated ammonium ion is a more 

significant component of PM mass in 

northern regions, such as the midwest 

and east coast, but is a less significant 

fraction in the southeast. In California, 

the main species contributing to urban 

PM2.5 mass are ammonium nitrate (35–

40 percent) and total carbon (43 

percent), while sulfate and associated 

ammonium accounts for approximately 

10–15 percent. 

Table 3 compares chemical 

composition data for 13 pairs of urban 

and nearby non-urban sites in order to 

identify the primary components that 

make up the ‘‘urban increment.’’ To 

conduct this analysis, for each species 

the PM2.5 mass in the rural location is 

subtracted from the species mass for the 

urban location. The amount by which 

the urban site exceeds the nearby rural 

site is the ‘‘urban increment.’’ 21


EP01NO05.000</GPH>
65994 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

22USEPA, National Air Quality and Emissions 

Trends Report: 2003 Special Studies Edition, Report 

Number EPA–454/R–03–005, Research Triangle 

Park, NC, September 2003. USEPA, National Air 

Pollutant Emissions Trends, Report Number EPA–

454/R–00–002, Research Triangle Park, NC, March 

2000. See also: http://www.epa.gov/ttn/chief/ 

trends/. 

TABLE 3.—URBAN INCREMENT ANALYSIS FOR 13 URBAN/RURAL PAIRS

[All values in micrograms per cubic meter] 

Chemical species 

West 

(3 site pairs) 

East 

(10 site pairs) 

Min. Max. Avg. Min. Max. Avg. 

Sulfate .................................................................................................................. 0.2 0.7 0.5 ¥0.5 1.1 0.3 

Est. Ammonium .................................................................................................... 0.2 2.2 1.2 0.1 0.8 0.4 

Nitrate ................................................................................................................... 0.6 6.9 3.7 0.4 1.4 0.8 

Total Carbon ........................................................................................................ 4.8 9.8 6.6 2.1 5.3 3.1 

Crustal .................................................................................................................. 0.1 0.6 0.4 ¥0.1 0.8 0.3 

Total Excess ................................................................................................. 5.8 20.1 12.4 2.0 9.4 4.8 

Carbonaceous mass is the largest 

contributor to urban increments in all 

regions of the country. In east coast and 

midwestern urban areas, carbon can 

account for as much as 70–90 percent of 

the total urban increment. The highest 

local increment of carbon as calculated 

from available data appears to be about 

10 μg/m3 in Fresno, CA. Nonroad diesel, 

onroad diesel, gasoline highway 

vehicles, and fire related activities are 

regarded to be important major 

contributors to this urban excess of 

carbon. The relative amounts of primary 

versus secondary organic compounds in 

the ambient air vary with location and 

time of year. While it is difficult to 

generalize, it is clear that both primary 

and secondary organic compounds are 

significant contributors to ambient PM2.5

mass in many parts of the country. 

The urban increment for sulfate, on 

the other hand, appears to be fairly low 

in most locations. Rural and urban 

sulfate levels are often very similar, 

indicating that sulfate is a regional 

pollutant that can be transported long 

distances. This is consistent with the 

fact that power plants are the principal 

sources of SO2, the precursor to sulfate, 

and in general, these plants are located 

outside urban core areas. In some 

eastern cities, the small estimated urban 

excess (up to 0.5 μg/m3) may be 

attributed to a range of source types, 

including power plants located within 

the metro area, the combustion of 

sulfur-laden fuel oil used for 

commercial or institutional heating, and 

fuel combustion by diesel and gasoline 

motor vehicles. 

Excess nitrate concentrations are 

observed predominantly in northern, 

midwestern, and western locations, 

comprising a larger local contribution 

than sulfate or crustal material. Nitrate 

is particularly high in the winter time 

partly because it is less volatile at colder 

temperatures and partly because SO2 is 

less prone to react preferentially with 

ammonium in the winter as opposed to 

the summer. Local sources of NOX

leading to excess urban nitrate likely 

include mobile sources and other types 

of fuel combustion. 

Some locations also show a small 

urban excess of crustal material (e.g. 

inorganic material including metals, 

dust, sea salt, and other trace elements). 

The estimation procedure used in the 

IMPROVE protocol includes the 

measurement of iron and other trace 

elements. Therefore, this difference also 

reflects oxidized particulate metals, 

some of which may be attributed to road 

dust or industrial sources in urban 

areas. 

We have developed a National 

Emissions Inventory (NEI) inventory for 

use in analyzing trends in emissions, 

conducting various regulatory analyses 

for PM, and for use in regional scale 

modeling.22 The NEI covers all 50 States 

plus some of the U.S. territories, and 

includes point, area, onroad and 

nonroad mobile sources, biogenic, and 

geogenic emissions. Large stationary 

sources are located individually in the 

inventory while county tallies are used 

for smaller stationary sources, and area 

and mobile source category groups. 

Spatial, temporal and compositional 

profiles are used to allocate these 

emissions to time-resolved grids for 

chemical transport modeling. The 

inventory includes emissions of SO2, 

NOX, VOC, NH3, PM10, and PM2.5. A 

brief discussion of each particle type, 

their principal sources (based on the 

NEI), formation mechanisms, and 

spatial and temporal patterns follows. 

Primary PM (Crustal and 

Carbonaceous). This section addresses 

inorganic and organic forms of primary 

PM. The main anthropogenic sources of 

inorganic (or crustal) particles are: 

Entrainment by vehicular traffic on 

unpaved or paved roads; mechanical 

disturbance of soil by highway, 

commercial, and residential 

construction; and agricultural field 

operations (tilling, planting and 

harvesting). However, much of these 

emissions are coarse PM rather than fine 

PM. 

Industrial processes such as quarries, 

minerals processing, and agricultural 

crop processing can also emit crustal 

materials, but their influence is most 

important close to the source and they 

are not generally significant contributors 

to regional scale PM problems. Even so, 

during certain high wind events, fine 

crustal PM has been shown to be 

transported over very long distances. 

Satellite data and other studies have 

shown that dust has been transported 

into the U.S. as a result of Asian or 

African dust storms. 

Emission estimates of mechanically 

suspended crustal PM from sources 

within the U.S. are often quite high. 

However, this PM is often released very 

close to the ground, and with the 

exception of windblown dust events, 

thermal or turbulent forces sufficient to 

lift and transport them very far from 

their source are not usually present. 

Thus, as shown in table 1, crustal 

material is only a minor part of PM2.5

annual average concentrations. 

Primary carbonaceous particles are 

largely the result of incomplete 

combustion of fossil or biomass fuels. 

This incomplete combustion usually 

results in emissions of both black 

carbon and organic carbon particles. 

High molecular weight organic 

molecules (i.e., molecules with 25 or 

more carbon atoms) are either emitted as 

solid or liquid particles, or as gases that 

rapidly condense into particle form. 

These heavy organic molecules 

sometimes are referred to as volatile 

organic compounds, but because their 

characteristics are most like direct PM 

emissions, they will be considered to be 

primary emissions for the purposes of 

this regulation. Primary organic carbon 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 65995 

23USEPA, 2003. Air Quality Criteria for 

Particulate Matter (Fourth External Review Draft). 

EPA/600/P–99/002aD and bD. U.S. Environmental 

Protection Agency, Office of Research and 

Development, National Center For Environmental 

Assessment, Research Triangle Park Office, 

Research Triangle Park, NC. June 2003. Available 

electronically at http://cfpub.epa.gov/ncea/cfm/ 

partmatt.cfm. 

24North American Research Strategy for 

Tropospheric Ozone and Particulate Matter 

(NARSTO) (2004) Particulate Matter Assessment for 

Policy Makers: A NARSTO Assessment. P. 

McMurry, M. Shepherd, and J. Vickery, eds. 

Cambridge University Press, Cambridge, England. 

ISBN 0 52 184287 5. For more information, see 

http://www.cgenv.com/NARSTO. See also 

supporting technical information for the Clear Skies 

Act, http://www.epa.gov/clearskies/, and for the 

Clean Air Interstate Rule, http://www.epa.gov/ 

cleanairinterstaterule. 

25Sievering, H., Boatman, J., Gorman, E., Kim, Y., 

Anderson, L., Ennis, G., Luria, M., Pandis, S.N., 

1992. Removal of sulfur from the marine boundary 

layer by ozone oxidation in sea-salt. Nature 360, 

571–573. 

26McHenry, J.N., Dennis, R.L., 1994. The relative 

importance of oxidation pathways and clouds to 

atmospheric ambient sulfate production as 

predicted by the Regional Acid Deposition Model. 

Journal of Applied Meteorology 33, 890–905. Also: 

Langner, J., Rodhe, H., 1991. A global three 

dimensional model for the tropospheric sulfur 

cycle. Journal of Atmospheric Chemistry 13, 225–

263. 

also can be formed by condensation of 

semi-volatile compounds on the surface 

of other particles. 

The main combustion sources 

emitting carbonaceous PM2.5 are mobile 

sources (both onroad and nonroad), 

managed burning, wildland fires, open 

burning of waste, residential wood 

combustion, certain industrial 

processes, and coal and oil-burning 

boilers (utility, commercial and 

industrial). Certain organic particles 

also come from natural sources such as 

decomposition or crushing of plant 

detritus. Most combustion processes 

emit more organic particles than black 

carbon particles. A notable exception to 

this are diesel engines, which typically 

emit more black carbon particles than 

organic carbon. Because photochemistry 

is typically reduced in the cooler winter 

months for much of the country, studies 

indicate that the carbon fraction of PM 

mass in the winter months is likely 

dominated by direct PM emissions as 

opposed to secondarily formed organic 

aerosol. 

Particles from the earth’s crust may 

contain a combination of metallic 

oxides and biogenic derived organic 

matter. The combustion of surface 

debris will likely entrain some soil. 

Additionally, emissions from many 

processes and from the combustion of 

fossil fuels contain elements that are 

chemically similar to soil. Thus, a 

portion of the emissions from 

combustion activities may be classified 

as crustal in a compositional analysis of 

ambient PM2.5. 

Secondary PM. Although some sulfate 

and nitrate salts (i.e. calcium sulfate, 

calcium nitrate) and acids (i.e. sulfuric 

acid, nitric acid) are directly emitted by 

sources under certain circumstances, 

sulfates and nitrates are predominately 

formed as a result of chemical reactions 

with ammonia and other compounds in 

the atmosphere. (See next sections for 

more detail.) During combustion, very 

small combustion nucleation particles 

(ultrafine particles, less than 0.1μm) are 

produced. These small particles act as 

nucleation sites where gases, water 

vapor, and other nucleation particles 

can condense or coagulate and therefore 

cause particle growth in both particle 

size and particle mass. Ammonium 

sulfate, ammonium nitrate, and 

secondarily formed organic aerosols, as 

well as agglomerating fine particles, all 

may use these ultrafine particles in their 

formation and growth in the 

atmosphere. The secondary organic 

aerosol (SOA) component of PM2.5 is a 

complex mixture of perhaps thousands 

of organic compounds. A brief 

discussion of the sources of SO2, NOX, 

NH3, and organic gases (including VOC 

and semi-volatile compounds), and the 

formation of sulfate, nitrate and 

secondary organic aerosol follows. More 

detailed discussions of the formation 

and characteristics of secondary 

particles can be found in the U.S. EPA 

Criteria Document,23 and in the 

NARSTO Fine Particle Assessment,24 on 

which much of the following discussion 

is based. 

Sulfate. SO2 is emitted mostly from 

the combustion of fossil fuels in boilers 

operated by electric utilities and other 

industry. Less than 20 percent of SO2

emissions nationwide are from other 

sources, mainly from other industrial 

processes including oil refining and 

pulp and paper production. 

The formation of sulfuric acid from 

the oxidation of SO2 is an important 

process for most areas in North 

America. There are three different 

pathways for this transformation. First, 

gaseous SO2 can be oxidized by the 

hydroxyl radical (OH) to create sulfuric 

acid. This gaseous SO2 oxidation 

reaction occurs slowly and only in the 

daytime. The hydroxl radical is an 

important product of the atmospheric 

chemistry process that forms ozone 

through the oxidation of NOX to form 

nitric acid. It is also involved in the 

formation of secondary organics. 

Second, SO2 can dissolve in cloud 

water (or fog or rain water), and there it 

can be oxidized to sulfuric acid by a 

variety of oxidants, or through catalysis 

by transition metals such as manganese 

or iron. If ammonia is present and taken 

up by the water droplet, then 

ammonium sulfate will form as a 

precipitant in the water droplet. After 

the cloud changes and the droplet 

evaporates, the sulfuric acid or 

ammonium sulfate remains in the 

atmosphere as a particle. This aqueousphase production process involving 

oxidants can be very fast; in some cases 

all the available SO2 can be oxidized in 

less than an hour. 

Third, SO2 can be oxidized in 

reactions in the particle-bound water in 

the aerosol particles themselves. This 

process takes place continuously, but 

only produces appreciable sulfate in 

alkaline (dust, sea-salt) coarse 

particles.25 Oxidation of SO2 has been 

also observed on the surfaces of black 

carbon and metal oxide particles. 

During the last twenty years, much 

progress has been made in 

understanding the first two major 

pathways, but some important questions 

still remain about the smaller third 

pathway. Models indicate that more 

than half of the sulfuric acid in the 

eastern United States and in the overall 

atmosphere is produced in clouds.26

The sulfuric acid formed from the 

above pathways reacts readily with 

ammonia to form ammonium sulfate, 

(NH4)2SO4. If there is not enough 

ammonia present to fully neutralize the 

produced sulfuric acid (one molecule of 

sulfuric acid requires two molecules of 

ammonia), part of it exists as 

ammonium bisulfate, NH4HSO4 (one 

molecule of sulfuric acid and one 

molecule of ammonia) and the particles 

are more acidic than ammonium sulfate. 

In extreme cases (in the absence of 

sufficient ammonia for neutralization), 

sulfate can exist in particles as sulfuric 

acid, H2SO4. Sulfuric acid often exists 

in the plumes of stacks where SO2, SO3, 

and water vapor are in much higher 

concentrations than in the ambient 

atmosphere, but these concentrations 

become quite small as the plume is 

cooled and diluted by mixing. 

Nitrate. The main sources of NOX are 

combustion of fossil fuel in boilers and 

onroad mobile sources. Together they 

account for more than 60 percent of 

NOX emissions in PM2.5 nonattainment 

areas (based on 2001 emission inventory 

information), with stationary and 

mobile source fuel combustion each 

accounting for about half of these 

emissions. Nitrates are formed from the 

oxidation of oxides of nitrogen into 

nitric acid either during the daytime 

65996 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

27Wayne, R.P., et al., 1991. The nitrate radical: 

physics, chemistry and the atmosphere. 

Atmospheric Environment 25A, 1–203. 

28Seinfeld, J.H., Pandis, S.N., 1998. Atmospheric 

Chemistry and Physics: From Air Pollution to 

Climate Change. J. Wiley, New York. 

29 29 As discussed earlier, high molecular weight 

organic molecules (i.e., molecules with 25 or more 

carbon atoms) are either emitted directly as 

particles or as liquids that rapidly condense onto 

existing particles. Because these condensable 

emissions act primarily as direct PM emissions, 

they are to be regulated as direct PM2.5 emissions, 

not as VOC precursors, for the purposes of this 

regulation. 30 Jang, M.; Czoschke, N.; Lee, S.; Kamens, R. 

Heterogenous Atmospheric Aerosol Production by 

Acid-Catalyzed Particle-Phase Reactions, Science, 

vol. 298, p. 814–817, October 25, 2002. 

31 Grosjean, D., Seinfeld, J.H., 1989. 

Parameterization of the formation potential of 

secondary organic aerosols. Atmospheric 

Environment 23, 1733–1747. 

32Odum, J.R., Jungkamp, T.P.W., Griffin, R.J., 

Flagan, R.C., Seinfeld, J.H., 1997. The atmospheric 

aerosol-forming potential of whole gasoline vapor. 

Science 276, 97–99. 

(reaction with OH) or during the night 

(reactions with ozone and water).27

Nitric acid continuously transfers 

between the gas and the condensed 

phases through condensation and 

evaporation processes in the 

atmosphere. However, unless it reacts 

with other species (such as ammonia, 

sea salt, or dust) to form a neutralized 

salt, it will volatize and not be measured 

using standard PM2.5 measurement 

techniques.28 The formation of aerosol 

ammonium nitrate is favored by the 

availability of ammonia, low 

temperatures, and high relative 

humidity. Because ammonium nitrate is 

not stable in higher temperatures, 

nitrate levels are typically lower in the 

summer months and higher in the 

winter months. The resulting 

ammonium nitrate is usually in the submicrometer particle size range. 

Reactions with sea-salt and dust lead to 

the formation of nitrates in coarse 

particles. Nitric acid may be dissolved 

in ambient aerosol particles. 

Secondary Organic Aerosol (SOA). 

The organic component of ambient 

particles is a complex mixture of 

hundreds or even thousands of organic 

compounds. These organic compounds 

are either emitted directly from sources 

(i.e. primary organic aerosol) or can be 

formed by reactions in the ambient air 

(i.e. secondary organic aerosol, or SOA). 

Volatile organic compounds29 are key 

precursors in both the SOA and ozone 

formation processes. The lightest 

organic molecules (i.e., molecules with 

six or fewer carbon atoms) occur in the 

atmosphere mainly as vapors and 

typically do not directly form organic 

particles at ambient temperatures due to 

the high vapor pressure of their 

products. However, they participate in 

atmospheric chemistry processes 

resulting in the formation of ozone and 

certain free radical compounds (such as 

the hydroxyl radical [OH]) which in 

turn participate in the oxidation of 

semivolatile organic compounds to form 

secondary organic aerosols, sulfates and 

nitrates. These VOCs include all alkanes 

with up to six carbon atoms (from 

methane to hexane isomers), all alkenes 

with up to six carbon atoms (from 

ethene to hexene isomers), benzene and 

many low-molecular weight carbonyls, 

chlorinated compounds, and 

oxygenated solvents. The relative 

importance of organic compounds in the 

formation of organic particles varies 

from area to area, depending upon local 

emissions sources, atmospheric 

chemistry, and season of the year. 

Intermediate weight organic molecules 

(i.e., compounds with 7 to 24 carbon 

atoms) often exhibit a range of 

volatilities and can exist in both the gas 

and aerosol phase. For this reason they 

are also referred to as semivolatile 

compounds. Semivolatile compounds 

react in the atmosphere to form 

secondary organic aerosols. These 

chemical reactions are accelerated in 

warmer temperatures, and studies show 

that SOA typically comprises a higher 

percentage of carbonaceous PM in the 

summer as opposed to the winter. 

The production of SOA from the 

atmospheric oxidation of a specific VOC 

depends on four factors: Its atmospheric 

abundance, its chemical reactivity, the 

availability of oxidants (O3, OH, HNO3), 

and the volatility of its products. In 

addition, recent work by Jang and others 

suggests that the presence of acidic 

aerosols may lead to an increased rate 

of SOA formation.30

Aromatic compounds such as toluene, 

xylene, and trimethyl benzene are 

considered to be the most significant 

anthropogenic SOA precursors and have 

been estimated to be responsible for 50 

to 70 percent of total SOA in some 

airsheds.31 As organic gases such as 

aromatics are oxidized in the gas phase 

by species such as the hydroxyl radical 

(OH), ozone (O3), and the nitrate radical 

(NO3) their oxidation products 

accumulate. Some of these products 

have low volatility and condense on 

available particles in an effort to 

establish equilibrium between the gas 

and condensed phases. Man-made 

sources of aromatics gases are mobile 

sources, petrochemical manufacturing 

and solvents. The experimental work of 

Odum and others 32 showed that the 

secondary organic aerosol formation 

potential of gasoline could be accounted 

for solely in terms of its aromatic 

fraction. 

Some of the biogenic hydrocarbons 

emitted by trees are also considered to 

be important precursors of secondary 

organic particulate matter. Terpenes (aand b-pinene, limonene, carene, etc.) 

and the sesquiterpenes are expected to 

be major contributors to SOA in areas 

with significant vegetation cover, but 

isoprene is not. Terpenes are very 

prevalent in forested areas, especially in 

the southeastern U.S. The rest of the 

anthropogenic hydrocarbons (higher 

alkanes, paraffins, etc.) have been 

estimated to contribute 5–20 percent to 

the SOA concentration depending on 

the area. 

TABLE 4.—ROLE OF ORGANIC GASES IN SECONDARY ORGANIC AEROSOL FORMATION

SOA-forming organic gases Non SOA-forming organic gases 

Anthropogenic ...................... —Aromatics (esp. toluene, xylenes, trimethyl-benzenes) 

—Higher alkanes (>6 C atoms) ......................................

—Lower alkanes <6 C atoms, (ethane to hexane isomers). 

—Benzene. 

—Lower MW carbonyls, chlorinated compounds & 

oxygenated solvents. 

Biogenic ............................... —Terpenes (esp. a- and b-pinene, limonene, carene) ..

—Sesquiterpenes ............................................................

—Isoprene. 

The contribution of the primary and 

secondary components of organic 

aerosol to the measured organic aerosol 

concentrations remains a controversial 

issue. Most of the research performed to 

date has been done in southern 

California, and more recently in central 

California, while fewer studies have 

been completed on other parts of North 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 65997 

33Hildemann, L.M., Cass, G.R., Mazurek, M.A., 

Simoneit, B.R.T., 1993. Mathematical modeling of 

urban organic aerosol properties measured by high 

resolution gas-chromatography. Environmental 

Science and Technology 27, 2045–2055. 

34Turpin, B.J., Lim, H.J., 2000. Species 

contributions to PM mass concentrations: Revisiting 

common assumptions for estimating organic mass, 

Aerosol Science and Technology, vol. 35, no. 1, p. 

602–610. 

35Anderson, N., R. Strader, and C. Davidson 

(2003) Airborne reduced nitrogen: Ammonia 

emissions from agriculture and other sources, 

Environment International, 29: 277–286. 

36Seinfeld, J.H., Pandis, S.N., 1998. Atmospheric 

Chemistry and Physics: From Air Pollution to 

Climate Change. J. Wiley, New York. 

37NARSTO, 2003. Particulate Matter Science for 

Policy Makers—A NARSTO Assessment. Parts 1 

and 2. NARSTO Management Office (Envair), Pasco, 

Washington. http://www.cgenv.com/NARSTO. 

38 Ibid, at S–31 (table S.4). 

America. Early studies suggested that 

the majority of the observed organic 

particulate matter was secondary in 

nature. Later investigators focusing on 

the emissions of primary organic 

material proposed that 80 percent or so 

of the organic aerosol in Southern 

California on a monthly basis resulted 

from direct organic particle emissions.33

More recent studies suggest that the 

primary and secondary contributions 

are highly variable even during the same 

day. Studies of pollution episodes 

indicated that the contribution of SOA 

to the organic particulate matter varied 

from 20 percent to 80 percent during the 

same day.34

Despite significant progress that has 

been made in understanding the origins 

and properties of SOA, it remains the 

least understood component of PM2.5. 

The reactions forming secondary 

organics are complex and the number of 

intermediate and final compounds 

formed is voluminous. Some of the best 

efforts to unravel the chemical 

composition of ambient organic aerosol 

matter have been able to quantify the 

concentrations of hundreds of organic 

compounds representing only 10–20 

percent of the total organic aerosol 

mass. For this reason, SOA continues to 

be a significant topic of research and 

investigation. 

C. The Role of Ammonia in Sulfate, 

Nitrate & Secondary Organic Aerosol 

Formation 

Ammonia (NH3) is a gaseous pollutant 

that is emitted by natural and 

anthropogenic sources. Emissions 

inventories for ammonia are considered 

to be among the most uncertain of any 

species related to PM. One recent 

estimate shows, however, that livestock 

(73 percent) and fertilizer application 

(17 percent) are the two primary sources 

of emissions.35 (Note that these 

estimates do not include natural 

emissions from soil, which can be 

significant.) 

Ammonia serves an important role in 

neutralizing acids in clouds, 

precipitation and particles. In 

particular, ammonia neutralizes sulfuric 

acid and nitric acid, the two key 

contributors to acid deposition (acid 

rain). Deposited ammonia also can be an 

important nutrient, contributing to 

problems of eutrophication in water 

bodies.36 Ammonia would not exist in 

particles, if not for the presence of 

acidic species with which it can 

combine to form a particle. In the 

eastern U.S., sulfate, nitrate, and the 

ammonium associated with them can 

together account for between roughly 30 

percent and 75 percent of the PM2.5

mass. The ammonium itself roughly 

accounts for between 5 percent and 20 

percent of the PM2.5.37

The NARSTO Fine Particle 

Assessment indicates that sulfates form 

preferentially over nitrates and that 

particle nitrate formation is affected by 

a number of factors, including the 

availability of sulfates, NOX, ammonia, 

nitric acid and VOCs. The report also 

notes that implementing decreasing 

ammonia emissions where sulfate 

concentrations are high can reduce 

PM2.5 mass concentrations, but may also 

increase particle and precipitation 

acidity.38 As noted above, this 

acidification of particles may result in 

an increase in the formation of 

secondary organic compounds. 

Moreover, the relationship between 

ammonia and sulfate-nitrate equilibrium 

may also impact SOA formation, 

although this link is not well 

understood. Recent studies of ammonia 

sources and possible emission reduction 

measures indicate that ammonia 

controls are a maturing science, but that 

ongoing research will greatly improve 

our understanding of such control 

measures. 

The same can be said of our 

understanding of the role of ammonia in 

aerosol formation. Based on the above 

information and further insights gained 

from the NARSTO Fine Particle 

Assessment, it is apparent that the 

formation of sulfate, nitrate and SOA 

compounds is a complex, nonlinear 

process. The control techniques for 

ammonia and the analytical tools to 

quantify the impact of reducing 

ammonia emissions on atmospheric 

aerosol formation are both evolving 

sciences. Also, there are indications that 

there may be considerable ambiguity 

concerning the results of reducing 

ammonia emissions and in some cases, 

there may be undesired consequences of 

ammonia reductions. Therefore, based 

on our current understanding of 

ammonia’s role in these complex 

precursor interactions and emission 

reduction processes, it seems prudent to 

continue research on ammonia control 

technologies and the ammonia—

sulfate—nitrate—SOA equilibrium 

before one undertakes broad national 

programs to reduce ammonia emissions. 

However, as States and EPA develop a 

greater understanding over the coming 

years about the potential air quality 

effects of reducing ammonia emissions 

in specific nonattainment areas, it may 

be appropriate for ammonia reduction 

strategies to be included in future SIPs. 

At this time, however, we believe that 

reducing SO2 and NOX will allow us to 

move with greater certainty toward 

achieving our nation’s air quality goals. 

We encourage you to provide comments 

on the resolution of this issue. 

D. Regional Patterns of Carbon, Sulfate 

and Nitrate, and Indications of 

Transport 

Table 2 above shows that much of the 

eastern U.S., both urban and non-urban 

areas alike, is subject to high PM2.5

concentrations, with the highest 

concentrations occurring in urban areas. 

Table 3 above compares the urban and 

rural concentrations of sulfate, nitrate, 

and carbon particles. The data show that 

there are high concentrations of sulfate 

across the region and that sulfate at 

urban monitoring sites is only slightly 

higher than at nearby non-urban sites. In 

contrast, the carbon mass at urban sites 

is significantly higher than at the nearby 

non-urban sites. This seems to indicate 

that sulfate is present on a much more 

regional scale and likely is associated 

with significant pollutant transport. On 

the other hand, a sizeable fraction of the 

carbonaceous mass seems to be more 

associated with urban sources. Mobile 

sources are much more concentrated in 

urban areas and may explain much of 

the elevated urban carbon 

concentrations. However, black carbon 

and organic aerosols still make up a 

large percentage of the non-urban air 

quality composition, indicating that 

there is a regional background level of 

carbon that is enhanced in urban areas 

by local sources. 

The atmospheric lifetimes of particles 

and thus the distances they can be 

transported vary with particle size. The 

regional nature of PM2.5 reflects the fact 

that fine particles can be transported 

over long distances. Ultra-fine and fine 

particles rapidly grow in size into a 

relatively stable size range, generally 

less than 2 μm. These fine particles are 

kept suspended by normal air motions 

and have very low deposition rates to 

surfaces. They can be transported 

65998 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

39See the final transportation conformity rule (69 

FR 40004; July 1, 2004); the conformity rule 

amendments addressing PM2.5 precursors (70 FR 

24280; May 6, 2005); and transportation conformity 

regulations at 40 CFR Parts 51 and 93. 

40The final transportation conformity rule on 

PM2.5 precursors was published in the Federal 

Register on May 6, 2005 at 70 FR 24280. 

thousands of kilometers and remain in 

the atmosphere for a number of days. 

Thus, they are important when 

considering regional PM transport. 

Coarse particles can settle rapidly from 

the atmosphere within hours and 

normally travel only short distances. 

However, when mixed high into the 

atmosphere, as in some dust storms, the 

smaller-sized coarse-mode particles may 

have longer lives and travel greater 

distances. 

Meteorology also plays a role in the 

size and characteristics of particles. 

High temperatures increase reaction 

rates, which may explain why sulfate 

concentrations are generally greatest in 

the summer. Conversely, lower 

temperatures result in a greater fraction 

of nitrates being in the particle phase. 

Fine particles, especially particles with 

a hygroscopic component, grow as the 

relative humidity increases, serve as 

cloud condensation nuclei, and grow 

into cloud droplets. If the cloud droplets 

grow large enough to form rain, the 

particles are removed in the rain. 

Falling rain drops impact coarse 

particles and remove them. Very fine 

particles are small enough to diffuse to 

the falling drop, be captured, and be 

removed in rain. However, falling rain 

drops are not nearly as effective in 

removing PM2.5 as the cloud processes 

mentioned above. Sulfuric acid, 

ammonium nitrate, ammonium sulfates, 

and organic particles also are deposited 

on surfaces by dry deposition. 

Therefore, reductions in SO2 and NOX

emissions will decrease both acidic 

deposition and PM concentrations. 

E. Policy for Addressing PM2.5

Precursors 

1. Legal Authority To Regulate 

Precursors 

The Clean Air Act authorizes the 

Agency to regulate criteria pollutant 

precursors. The term ‘air pollutant’’ is 

defined in section 302(g) to include 

‘‘any precursors to the formation of any 

air pollutant, to the extent the 

Administrator has identified such 

precursor or precursors for the 

particular purpose for which the term 

’air pollutant’ is used.’’’ The first clause 

of this second sentence in section 302(g) 

explicitly authorizes the Administrator 

to identify and regulate precursors as air 

pollutants under other parts of the Act. 

In addition, the second clause of the 

sentence indicates that the 

Administrator has discretion to identify 

which pollutants should be classified as 

precursors for particular regulatory 

purposes. Thus, we do not necessarily 

construe the Act to require that EPA 

identify a particular precursor as an air 

pollutant for all regulatory purposes 

where it can be demonstrated that 

various Clean Air Act programs address 

different aspects of the air pollutant 

problem. Likewise, we do not interpret 

the Act to require that EPA treat all 

precursors of a particular pollutant the 

same under any one program when 

there is a basis to distinguish between 

such precursors. For example, in a 

recent rule addressing PM2.5 precursors 

for purposes of transportation 

conformity, we chose to adopt different 

approaches for some precursors based 

on the degree to which the various 

precursors emitted by transportationrelated sources contributed to the PM2.5

air quality problem. 70 FR 24280 (May 

6, 2005). 

Other provisions of the Act reinforce 

our reading of section 302(g) that 

Congress intended precursors to 

NAAQS pollutants to be subject to the 

air quality planning and control 

requirements of the Act, but also 

recognized that there may be 

circumstances where it is not 

appropriate to subject precursors to 

certain requirements of the Act. Section 

182 of the Act provides for the 

regulation of NOX and VOCs as 

precursors to ozone in ozone 

nonattainment areas, but also provides 

in Section 182(f) that major stationary 

sources of NOX (an ozone precursor) are 

not subject to emission reductions 

controls for ozone where the State 

shows through modeling that NOX

reductions do not decrease ozone. 

Section 189(e) provides for the 

regulation of PM10 precursors in PM10

nonattainment areas, but also recognizes 

that there may be certain circumstances 

where it is not appropriate to apply 

control requirements to PM10

precursors. In providing that the Agency 

was to issue guidelines for the control 

of PM10 precursors, the legislative 

history of Section 189(e) recognized the 

complexity behind the science of 

precursor transformation into PM10

ambient concentrations and the need to 

harmonize the regulation of PM10

precursors with other provisions of the 

Act: 

The Committee notes that some of these 

precursors may well be controlled under 

other provisions of the Act. The Committee 

intends that * * * the Administrator will 

develop models, mechanisms, and other 

methodology to assess the significance of the 

PM10 precursors in improving air quality and 

reducing PM10. Additionally, the 

Administrator should consider the impact on 

ozone levels of PM10 precursor controls. The 

Committee expects the Administrator to 

harmonize the PM10 reduction objective of 

this section with other applicable regulations 

of this Act regarding PM10 precursors, such 

as NOX. 

See H. Rpt. 101–490, Pt. 1, at 268 (May 

17, 1990), reprinted in S. Prt. 103–38, 

Vol. II, at 3292. 

In summary, section 302(g) of the Act 

clearly calls for the regulation of 

precursor pollutants, but the Act also 

identifies circumstances when it may 

not be appropriate to regulate precursors 

and gives the Administrator discretion 

to determine how to address particular 

precursors under various programs 

required by the Clean Air Act. Due to 

the complexities associated with 

precursor emissions and their variability 

from location to location, we believe 

that in certain situations it may not be 

effective or appropriate to control a 

certain precursor under a particular 

regulatory program or for EPA to require 

similar control of a particular precursor 

in all areas of the country. 

In the following section II.E.2, we 

discuss our proposal for how States 

should address PM2.5 precursors for the 

majority of the nonattainment program 

issues in PM2.5 implementation plans, 

such as RACT, RACM, reasonable 

further progress and most of the other 

issues discussed in section III. This 

discussion is linked to related 

discussions of precursor issues in the 

NSR section of this package (see section 

III.M.), the transportation conformity 

program (see section III.K. of this 

package, and the conformity 

regulations 39), and the general 

conformity program (see section III.L. of 

this package. All of these programs take 

effect prior to approval of SIPs for 

attaining the PM2.5 NAAQS. In the case 

of NSR, the program applies on the 

effective date of the nonattainment area 

designation. In the case of 

transportation conformity and general 

conformity, the program takes effect one 

year from the effective date of 

designation of the nonattainment area 

(i.e., April 5, 2006). Thus, for each of 

these programs there is an interim 

period between the date the program 

becomes applicable to a given 

nonattainment area and the date the 

State receives EPA approval of its 

overall PM2.5 implementation plan. 

Options for addressing PM2.5 precursors 

in the NSR program are discussed in 

section III.M. below. For the 

transportation conformity program, 

precursor policies are addressed in the 

final rule on PM2.5 precursors.40

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 65999 

41As stated in the May 6, 2005 (70 FR 24282) 

final transportation conformity rule on PM2.5

precursors, on-road emissions of sulfur dioxide 

would only be addressed in conformity 

determinations if the state air agency or EPA 

Regional Administrator found that the on-road 

emissions are a significant contributor to the area’s 

PM2.5 problem or if the area’s SIP established a 

motor vehicle emissions budget for sulfer oxides. 

42As stated in the May 6, 2005 (70 FR 24282) 

final transportation conformity rule on PM2.5

precursors, on-road emissions of ammonia would 

also be addressed in conformity determinations 

before a SIP is submitted and budgets are found 

adequate or approved if the state air agency or EPA 

Regional Administrator found that the on-road 

emissions of ammonia are a significant contributor 

to the area’s PM2.5 problem. 

2. Proposed Policy Options for 

Addressing PM2.5 Precursors in 

Nonattainment Plan Programs 

This section discusses potential 

options for addressing the PM2.5

precursors SO2, ammonia, NOX and 

volatile organic compounds in PM2.5

nonattainment plan programs other than 

NSR and transporation conformity. 

Several other preamble sections in 

today’s notice, including those on RFP, 

RACT, RACM, and modeling and 

attainment demonstrations refer the 

reader to this overall section. Our 

approach to precursors of PM2.5 in these 

areas will be decided after consideration 

of comments through this rulemaking 

process and our policy for PM2.5

precursors will be stated in the final 

rule. 

As an initial matter, it is helpful to 

clarify the terminology we use 

throughout this notice to discuss 

precursors. We recognize NOX, SO2, 

VOCs, and ammonia as precursors of 

PM2.5 in the scientific sense because 

these pollutants can contribute to the 

formation of PM2.5 in the ambient air. 

However, the degree to which these 

individual precursors and pollutants 

contribute to PM2.5 formation in a given 

location is complex and variable. This 

requires that we further consider in this 

action how States should address these 

PM2.5 precursors in their PM2.5

nonattainment plan programs. Thus, 

where we believe that all states should 

address a given precursor of PM2.5 under 

a specific PM2.5 nonattainment plan 

requirement, we refer to it more 

specifically as a ‘‘PM2.5 nonattainment 

plan precursor, transportation 

conformity precursor, or NSR precursor. 

We request comment on all aspects of 

the proposed options set forth below. 

Sulfur dioxide. We believe the 

previous technical discussion and 

analysis of speciated air quality data 

provides an appropriate basis for 

requiring States to address sulfur 

dioxide as a PM2.5 nonattainment plan 

precursor in all areas.41 The fact that 

sulfate is a significant contributor (e.g. 

ranging from 9 percent to 40 percent) to 

PM2.5 nonattainment and other air 

quality problems in all regions of the 

country is a critical piece of evidence 

supporting this approach. The EPA 

requests comments on the requirement 

that SO2 is a PM2.5 nonattainment plan 

precursor in all nonattainment areas. 

Ammonia. In regard to ammonia, 

however, we believe there is sufficient 

uncertainty about emissions inventories 

and about the potential efficacy of 

control measures from location to 

location such that the most appropriate 

approach for proposal is a case-by-case 

approach. Ammonia reductions may be 

appropriate in selected locations, but in 

others such reductions may lead to 

increased atmospheric acidity, 

exacerbating acidic deposition 

problems. Each State should evaluate 

whether reducing ammonia emissions 

would lead to PM2.5 reductions in their 

specific PM2.5 nonattainment areas. 

Under this proposed policy, however, 

States are not required to address 

ammonia as a PM2.5 nonattainment plan 

precursor, unless the State or EPA 

makes a technical demonstration that 

ammonia emissions from sources in the 

State significantly contribute to the 

PM2.5 problem in a given nonattainment 

area or to other downwind air quality 

concerns. As noted above, ammonia 

reductions may be effective primarily in 

areas where nitric acid is in abundance 

and ammonia is the limiting factor to 

ammonium nitrate formation. Where the 

State or EPA has determined that 

ammonia is a significant contributor to 

PM2.5 formation in a nonattainment 

area, the State would address ammonia 

emissions in its nonattainment SIP due 

in 2008. From that point in time, the 

implementation of the PM program and 

other associated programs (e.g. the NSR 

program and transportation conformity 

program) in that area would proceed in 

accordance with this determination.42

Ammonia will be addressed under the 

transportation conformity program if the 

SIP establishes a budget specifically for 

on-road ammonia emissions. The EPA 

requests comments on this approach to 

addressing ammonia emissions under 

the PM2.5 program. 

Nitrogen oxides. Based on a review of 

speciated monitoring data analyses, it is 

apparent that nitrate concentrations 

vary significantly across the country. 

For example, in some southeastern 

locations, annual average nitrate levels 

are in the range of 6 to 8 percent of total 

PM2.5 mass, whereas nitrate comprises 

40 percent or more of PM2.5 mass in 

certain California locations. Nitrate 

formation is favored by the availability 

of ammonia, low temperatures, and high 

relative humidity. It is also dependent 

upon the relative degree of nearby SO2

emissions because ammonia reacts 

preferentially with SO2 over NOX. 

The sources of NOX are numerous and 

widespread, including motor vehicles, 

power plants, and many other 

combustion activities. We believe the 

previous technical discussion and 

analysis of speciated air quality data 

provides an appropriate basis for 

presuming that states must evaluate and 

implement reasonable controls on 

sources of NOX in all nonattainment 

areas. Under this policy, States are 

required to address NOX under all 

aspects of the program, unless the State 

and EPA makes a finding that NOX

emissions from sources in the State do 

not significantly contribute to the PM2.5

problem in a given area or to other 

downwind air quality concerns. An 

additional consideration is that the 

majority of potential PM2.5

nonattainment areas are already 

designated as nonattainment for the 8- 

hour ozone standard. For PM2.5 areas 

that are also violating the 8-hour ozone 

standard, strategies to reduce NOX

emissions will help address both air 

pollution problems. The EPA requests 

comments on this approach to 

addressing NOX emissions under the 

PM2.5 program. 

Volatile Organic Compounds (VOC). 

Section II.B. discusses the main 

categories of organic compounds with 

varying degrees of volatility: Highly 

reactive, volatile compounds with six or 

fewer carbon atoms which indirectly 

contribute to PM formation through the 

formation of oxidizing compounds such 

as the hydroxyl radical and ozone; and 

semivolatile compounds with between 

seven and 24 carbon atoms which can 

exist in particle form and can readily be 

oxidized to form other low volatility 

compounds. High molecular weight 

organic compounds (with 25 carbon 

atoms or more and low vapor pressure) 

are emitted directly as primary organic 

particles and exist primarily in the 

condensed phase at ambient 

temperatures. For this reason, these 

organic compounds will be regulated as 

primary PM2.5 emissions and not VOCs 

for the purposes of the PM2.5

implementation program. 

Current scientific and technical 

information clearly shows that 

carbonaceous material is a significant 

fraction of total PM2.5 mass in most 

areas, and that certain aromatic VOC 

emissions such as toluene, xylene, and 

trimethyl-benzene are precursors to the 

formation of secondary organic aerosol. 

Further, analyses of ambient data 

66000 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

indicate that a considerable fraction of 

the total carbonaceous material is likely 

from local as opposed to regional 

sources. 

However, while significant progress 

has been made in understanding the 

role of gaseous organic material in the 

formation of organic PM, this 

relationship remains complex. We 

recognize that further research and 

technical tools are needed to better 

characterize emissions inventories for 

specific VOC compounds, and to 

determine the extent of the contribution 

of specific VOC compounds to organic 

PM mass. 

In light of the factors discussed above, 

EPA proposes that States are not 

required to address VOC’s as PM2.5

nonattainment plan precursors, unless 

the state or EPA makes a finding that 

VOC’s significantly contribute to a PM2.5

nonattainment problem in the State or 

to other downwind air quality concerns. 

In proposing this policy, we are mindful 

of the fact that a majority of areas that 

have been designated as nonattainment 

for PM2.5 are already designated as 

nonattainment for the 8-hour ozone 

standard. Thus, these areas will already 

be required to evaluate VOC control 

measures for ozone purposes. (The 

inventory of VOC as defined here, 

including gaseous organic compounds, 

is essentially identical to the inventory 

of VOC for ozone control purposes.) The 

few PM2.5 areas not designated as 

nonattainment for the 8-hour ozone 

standard will not be required to regulate 

VOC emissions sources unless the State 

or EPA makes a relevant technical 

finding. We request comments 

accompanied by detailed technical 

supporting information on this 

proposed policy approach for 

addressing VOC’s under the PM2.5

implementation program. 

In general. Any State or EPA technical 

demonstration to modify the 

presumptive policy approach for 

ammonia, NOX, or VOC should be 

developed well in advance of the SIP 

submittal date. In addition, the 

development of such a technical 

demonstration should include 

consultation with appropriate State, 

local, and EPA technical representatives 

representing air quality and 

transportation agencies. 

III. What Are the Specific Elements of 

EPA’s PM2.5 Implementation Program? 

A. What classification options are under 

consideration for PM2.5 nonattainment 

areas? 

1. Background 

Section 172 of subpart 1 contains the 

general requirements for SIPs for all 

nonattainment areas. Section 172(a)(1) 

states that on or after the date of 

designation, the Administrator may 

classify the area for the purpose of 

applying an attainment date or for some 

other purpose. Thus, a classification 

system is allowed under section 172, 

but is not required for the purposes of 

implementing a national ambient air 

quality standard. 

If we choose to establish a 

classification system, the Act states that 

we may consider certain factors in doing 

so, such as the severity of 

nonattainment in such areas, and the 

availability and feasibility of the 

pollution control measures that may be 

needed to achieve attainment. We must 

publish a notice in the Federal Register 

announcing any classifications and 

provide for at least 30 days for written 

comment. Classifications are not subject 

to notice and comment rulemaking 

requirements, however, nor are they 

subject to judicial review until we take 

any action on plan submissions (under 

sections 110(k) or 110(l)), or sanctions 

in cases where the State fails to submit 

a plan (under section 179). 

2. Proposed Options for PM2.5

Classifications 

This section describes two 

implementation approaches for 

classifying or not classifying PM2.5

nonattainment areas. The first and 

preferred option is to not have any 

classification system. The second option 

would have a two-tiered classification 

system, with areas classified as 

‘‘moderate’’ or ‘‘serious’’ based on 

specific criteria. These options are 

discussed below. 

a. No Classification System Based on 

Design Values 

In today’s notice, our preferred option 

is to not have any system for classifying 

PM2.5 nonattainment areas or assigning 

attainment dates and control strategy 

requirements based on the severity of 

the nonattainment problem (e.g. the 

area’s design value). We believe that an 

advantage of this approach is that it will 

provide a relatively simple 

implementation structure for state 

implementation of the PM2.5 standards. 

This approach also will allow flexibility 

to determine attainment dates and 

control strategies appropriate for each 

area under Clean Air Act requirements. 

We believe that with the variable mix 

of sources contributing to PM2.5

concentrations in various regions of the 

country and the variable set of 

appropriate control measures, it may not 

be advantageous to have a classification 

system which automatically requires a 

longer list of control strategies, and 

allows a later attainment date, for areas 

with higher current levels of PM2.5

pollution. 

Under our proposed approach, the 

State will be required to submit an 

attainment demonstration for each 

nonattainment area proposing an 

attainment date that is as expeditious as 

practicable for each area. (Attainment 

date issues are discussed in more detail 

in section III.C.) In determining what 

attainment date is considered ‘‘as 

expeditious as practicable,’’ the State 

will need to demonstrate that it is 

achieving RFP (see section III.G.), and it 

will have to adopt rules to implement 

the RACT and RACM requirements 

within the nonattainment area (see 

section III.I.) in order to attain the 

standard as expeditiously as practicable. 

In determining an expeditious 

attainment date, the State will need to 

take into consideration the air quality 

improvements that are expected due to 

other emission reduction programs at 

the national level (e.g. Tier II vehicle 

standards, heavy-duty diesel program, 

etc.), regional level reductions (e.g. NOX

SIP call), any additional regional SO2 or 

NOX reductions that may be achieved 

under a legislative or regulatory 

approach, and State level (e.g. Clean 

Smokestacks legislation in North 

Carolina). 

b. Two-Tiered Classification System 

Another option on which we are 

seeking comment is a two-tiered 

classification system. Under this 

approach, areas with higher PM2.5 levels 

(i.e. design values) would qualify for an 

attainment date extension beyond April 

2010 to no later than April 2015. In 

return, consistent with the approach in 

subpart 2, part D of Title I for ozone, 

such areas would be required to include 

certain mandatory measures in their 

SIPs. 

Definition of serious and moderate 

areas. This option would establish two 

nonattainment classification categories: 

‘‘moderate’’ and ‘‘serious.’’ These 

categories could be based on the 

severity of nonattainment (e.g., serious 

areas would be those with a design 

value above a specific threshold), the 

attainment date for the area (e.g., serious 

areas would be those with attainment 

dates after April 2010), or some other 

measure. We invite comment on 

appropriate ways to define moderate 

and serious areas and request that any 

recommended approach be 

accompanied by adequate supporting 

information. 

Under a potential two-tiered 

classification system, all areas not 

classified as ‘‘serious’’ would be 

classified as ‘‘moderate.’’ However, any 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66001 

43Under this approach, attaining by April 2010 

means that the design value for 2007–2009 would 

attain the standards. 

moderate area that needed an 

attainment date longer than five years 

would be reclassified to serious. This 

would ensure that areas with a more 

persistent PM2.5 problem are subject to 

more stringent requirements, even if 

they are not one of the areas with the 

highest current design values. For such 

areas, the state would be required to 

request reclassification and ensure that 

the 2008 attainment SIP submission for 

the area includes all measures needed to 

meet serious area requirements. 

Serious area requirements. Serious 

areas would be required to meet RACM 

and RACT requirements described 

elsewhere in this notice. The attainment 

date would be as expeditiously as 

practicable, but no later than 10 years 

after designation, depending on the year 

in which the area would be projected to 

attain considering existing control 

requirements and the effect of RACM, 

RACT and RFP. 

Various approaches can be considered 

for outlining additional requirements for 

serious areas beyond those required for 

all areas by subpart 1. More stringent 

requirements for serious areas could be 

established for RFP, RACT, and/or 

RACM. 

For RFP, one approach could involve 

setting a more prescriptive or higher 

RFP requirement for serious areas from 

the 2002 base year to the attainment 

year. For example, the required rate 

could be a specific annual percentage 

reduction in direct PM2.5 and all PM2.5

precursors, analogous to the 3% per 

year reduction requirement for the 1- 

hour ozone program in section 182 of 

the Act. This approach is described 

among the options in the RFP section of 

this proposal (see section III.G.5). 

Progress would be evaluated in 2008 

and every 3 years thereafter. An 

alternative could be to require a specific 

weighted average annual reduction in 

direct PM2.5 and all precursors, based 

upon the PM2.5 speciation profile for the 

relevant urban area. 

An additional requirement for serious 

areas could be to define a lower 

emissions threshold for major sources 

for purposes of determining 

applicability for RACT than would 

apply in moderate areas. Note that the 

option of a lower threshold for RACT is 

consistent with only options 1 and 3 

proposed in the RACT section of this 

notice (see section III.I.5). A discussion 

of possible thresholds is included in 

that section. 

Moderate area requirements. Under 

this option, ‘‘moderate’’ areas would 

constitute all areas that are not 

categorized as ‘‘serious.’’ They would be 

required to submit 2008 plans that 

demonstrate attainment of the standards 

as expeditiously as practicable, but not 

later than April 2010.43 Attainment 

would be based on implementation of 

existing measures (e.g. CAIR, mobile 

source rules, previously adopted state 

and local measures) and any other 

measures necessary to meet the RACT, 

RACM, RFP, and expeditious attainment 

requirements. (The scope of these 

requirements will be determined based 

on which options for these program 

elements are adopted in the final rule.) 

The area would be required to provide 

a demonstration that it had adopted all 

reasonable controls to ensure 

expeditious attainment, and that there 

was no additional collection of 

reasonable controls (i.e. RACM and 

RACT) available in the area that would 

advance the attainment date by at least 

one year. EPA seeks comment on what 

would constitute adequate information 

provided by the State to show that a 

moderate area has met the RACT, 

RACM, and RFP requirements and 

cannot advance the attainment date. 

Failure to attain. Under the general 

authority in section 172(a)(1) to 

establish a classification system, EPA 

proposes a process here that is similar 

to the PM10 process included in subpart 

4 for addressing areas that fail to attain. 

With this approach, EPA would have 

the authority to make a finding of failure 

to attain within 6 months for any 

moderate area that fails to attain the 

standards by April 2010. Once EPA 

issues such a finding, the area would be 

automatically ‘‘bumped-up’’ to the 

serious category. The area would then 

have one year to develop a revised 

implementation plan and RFP plan in 

order to attain the standards as 

expeditiously as practicable, but no later 

than April 2015. 

Any serious area that fails to attain by 

its attainment date would be subject to 

the requirements of sections 179(c) and 

(d) of the Act. EPA would make a 

finding of failure to attain no later than 

6 months after the attainment date and 

publish a notice in the Federal Register. 

The state would be required to submit 

an implementation plan revision within 

one year after publication of the Federal 

Register notice pursuant to section 

179(d)(2) of the Act. 

Voluntary Bump-Up. Under this 

option, any area wishing to reclassify 

from moderate to serious may do so. 

The Administrator shall publish a 

notice in the Federal Register of any 

such request and of the action by the 

Administrator granting the request. 

c. Rural Transport Classification 

The 8-hour ozone implementation 

program includes a ‘‘rural transport 

classification’’ for subpart 1 

nonattainment areas. In this section we 

discuss whether an area classification of 

this type would be appropriate for the 

PM2.5 implementation program in light 

of the fact that no currently designated 

PM2.5 nonattainment area could meet 

criteria similar to those that apply to 

rural transport areas under the ozone 

implementation program. 

Under this potential concept, a PM2.5

nonattainment area would qualify for 

the ‘‘rural transport’’ classification if it 

met criteria similar to those specified for 

rural transport areas for the 1-hour 

ozone standard under section 182(h). 

Section 182(h) defines ‘‘rural transport’’

areas as those areas that do not include, 

and are not adjacent to, any part of a 

Metropolitan Statistical Area (MSA) or, 

where one exists, a Consolidated 

Metropolitan Statistical Area (CMSA). 

Because OMB issued revised 

metropolitan area definitions in 2003, 

EPA suggests that if PM2.5 rural 

transport areas are made possible under 

the final rule, this geographic criterion 

would be revised for PM2.5 such that a 

rural transport area could not include or 

be adjacent to any part of a core-based 

statistical area (CBSA) or a consolidated 

statistical area (CSA). Section 182(h) 

further limits the category to those areas 

whose own emissions do not make a 

significant contribution to pollutant 

concentrations in those areas, or in 

other areas. 

In the event the ozone approach is 

followed, a State with a PM2.5 ‘‘rural 

transport’’ area would need to (1) 

demonstrate that the area meets the 

above criteria, (2) demonstrate using 

EPA approved attainment modeling that 

the nonattainment problem in the area 

is due to the ‘‘overwhelming transport’’

of emissions from outside the area, and 

(3) demonstrate that sources of PM2.5

and its precursor emissions within the 

boundaries of the area do not contribute 

significantly to PM2.5 concentrations 

that are measured in the area or in other 

areas. Because this is a proposed rule, 

EPA currently has not developed any 

modeling guidance for PM2.5 rural 

transport demonstrations. 

An area which qualifies for the ‘‘rural 

transport’’ classification would only be 

required to adopt local control measures 

sufficient to demonstrate that the area 

would attain the standard by its 

attainment date ‘‘but for’’ the 

overwhelming transport of emissions 

emanating from upwind States. RFP 

requirements under subpart 1 would 

66002 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

44The Agency is also considering the 

development of a separate proposed rule on flexible 

implementation of nonattainment NSR for any areas 

where transport is the primary cause of the area’s 

nonattainment for any criteria pollutant. Such a 

proposal would not be dependent on the 

incorporation of a transport classification in a 

classification system for a NAAQS. 

45More information on the Clean Air Interstate 

Rule is available at: http://www.epa.gov/cair. 

still apply to these areas (see section E 

of this notice). 

As with other nonattainment areas, 

rural transport nonattainment areas 

would be subject to NSR, transportation 

conformity, and general conformity 

requirements. However, in section M of 

today’s notice, we are soliciting 

comment on whether it would be 

appropriate to establish less 

burdensome NSR requirements in the 

event that a classification for rural 

transport areas is adopted in the final 

rule.44 Regarding transportation 

conformity, EPA has issued revised 

conformity regulations to address the 8- 

hour ozone and PM2.5 standards in 

separate actions. In general under the 

current program, nonattainment areas 

not part of a metropolitan planning 

organization subject to transportation 

conformity already have less 

burdensome requirements. For example, 

areas without a metropolitan planning 

organization do not need to conduct 

emissions analyses for conformity 

purposes until the time that a federal 

highway or transit project is proposed 

within the area (see further discussion 

of transportation conformity issues in 

section III.K. of this notice). 

Under this potential approach, a State 

applying for a rural transport 

classification for an area would need to 

develop an attainment demonstration 

that takes into consideration projected 

emissions reductions from the 

implementation of local, regional, and 

national control measures in order to 

show that it would reach attainment as 

expeditiously as practicable. Because 

such an area would need to rely on 

national or regional reductions to some 

degree, the State or Tribe should take 

into consideration the attainment date 

of contributing nonattainment areas that 

contribute to the affected area’s air 

quality problem, and the 

implementation schedule for any 

regional reduction strategy (such as a 

regulation to address transported 

emissions of SO2 and NOX), in 

developing its attainment 

demonstration. The issues related to 

interstate transport are also discussed 

elsewhere in this proposed rulemaking. 

In reviewing the currently designated 

PM2.5 nonattainment areas, it appears 

that all areas are within or adjacent to 

a CBSA or CSA, and thus would not 

meet the criteria discussed above. 

Because of this fact, EPA requests 

comment on whether this type of 

classification option is needed at all 

under the PM2.5 implementation 

program. 

B. When are PM2.5 attainment 

demonstrations and SIPs due, and what 

requirements must they address? 

Part D of Title I of the Act sets forth 

the requirements for SIPs needed to 

attain the national ambient air quality 

standards. Part D includes a general 

subpart 1 which applies to all NAAQS 

for which a specific subpart does not 

exist. Because the PM standards were 

not established until 1997, the 

nonattainment plan provisions found in 

section 172 of subpart 1 apply. 

Section 172(b) of the Act requires that 

at the time the Agency promulgates 

nonattainment area designations, the 

EPA must also establish a schedule for 

states to submit SIPs meeting the 

applicable requirements of section 

172(c) and of section 110(a)(2) of the 

Act. Nonattainment area designations 

were finalized in December 2004, and a 

supplemental notice was issued in April 

2005. Consistent with section 172(b) of 

the Act, section 51.1002 of the proposed 

rule requires the State to submit its 

attainment demonstration and SIP 

revision within three years, or by April 

2008. 

Section 51.1006 of the proposed rule 

addresses the situation in which an area 

is initially designated as attainment/ 

unclassifiable but is later designated as 

nonattainment based on air quality data 

after the 2001–2003 period. Under such 

circumstances, the SIP submittal date 

would be three years from the effective 

date of the redesignation, and the 

attainment date would be as 

expeditiously as practicable but no later 

than five years from the effective date of 

the redesignation. 

The section 172(c) requirements that 

States are to address under section 

172(c) (including RACT, RACM, RFP, 

contingency measures, emission 

inventory requirements, and NSR) are 

discussed in later sections of this notice. 

Section 110(a)(2) of the Act requires all 

States to develop and maintain a solid 

air quality management infrastructure, 

including enforceable emission 

limitations, an ambient monitoring 

program, an enforcement program, air 

quality modeling, and adequate 

personnel, resources, and legal 

authority. Section 110(a)(2)(D) also 

requires State plans to prohibit 

emissions from within the State which 

contribute significantly to 

nonattainment or maintenance areas in 

any other State, or which interfere with 

programs under part C to prevent 

significant deterioration of air quality or 

to achieve reasonable progress toward 

the national visibility goal for federal 

class I areas (national parks and 

wilderness areas). In order to assist 

States in addressing their obligations 

regarding regionally transported 

pollution, EPA has finalized the CAIR to 

reduce SO2 and nitrogen oxide 

emissions from large electric generating 

units (see section I.E.2. for further 

discussion).45

To date, few states have submitted a 

SIP revision addressing the section 

110(a) requirements for the purposes of 

implementing the PM standards. The 

EPA recognizes that this situation is due 

in part to the fact that there were a series 

of legal challenges to the PM standards 

which were not resolved until March 

2002, at which time the standards and 

EPA’s decision process were upheld 

(see section I.B. for further discussion of 

past legal challenges to the standards). 

To address the States’ continuing 

obligation to address the requirements 

of section 110(a), however, section 

51.1002 of the proposed rule also 

requires each State to address the 

required elements of section 110(a)(2) of 

the Act in its nonattainment plan SIP 

revision, if it has not already done so. 

C. What are the attainment dates for 

PM2.5 nonattainment areas? 

1. Background 

Section 172(a)(2)(A) states that the 

attainment date for a nonattainment area 

must be ‘‘as expeditiously as 

practicable, but no later than 5 years 

from the date of designation for the 

area.’’ Since PM2.5 designations were 

promulgated in December 2004 and 

have an effective date of April 2005, the 

initial attainment date for PM2.5 areas 

would be no later than April 2010. For 

an area with an attainment date of April 

2010, EPA would determine whether it 

had attained the standard by evaluating 

air quality data from the three previous 

calendar years (i.e. 2007, 2008, and 

2009). 

Section 172 also states that if EPA 

deems it appropriate, the Agency may 

extend the attainment date for an area 

for a period not greater than 10 years 

from the date of designation, taking into 

account the severity of the 

nonattainment problem in the area, and 

the availability and feasibility of 

pollution control measures. (See further 

discussion of attainment date extensions 

in section III.C.4.) For any areas that are 

granted the full five year attainment 

date extension, the attainment date 

would be no later than April 2015. For 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66003 

46See section 51.1005 of the proposed regulation. 

such areas, EPA would determine 

whether they have attained the standard 

by evaluating air quality data from 2012, 

2013, and 2014. Section 51.1004 of the 

proposed regulations addresses the 

attainment date requirement. 

2. Consideration of Existing Measures in 

Proposing an Attainment Date 

As part of their attainment 

demonstrations, States will need to 

assess the effect of implementation of 

existing national and State programs 

already in place (e.g. partial 

implementation of the CAIR rule, final 

Acid Rain Program, motor vehicle tier II 

standards and heavy-duty diesel engine 

standards, NOX SIP call, State 

legislation such as Clean Smokestacks 

bill in North Carolina), plus the 

implementation of RACT and RACM in 

the nonattainment area, to determine 

what is the most expeditious attainment 

date for the area. States in this situation 

will need to first project the emissions 

reductions expected by 2009 due to 

national standards, State regulations, 

and any local measures already being 

implemented, and then conduct localscale modeling to project the estimated 

level of air quality improvement in 

accordance with EPA’s modeling 

guidance. These assessments and any 

needed State emission reduction 

programs will need to be part of the 

State’s 2008 attainment demonstration. 

3. Areas May Qualify for Two 1-Year 

Attainment Date Extensions 

Subpart 1 provides for States to 

request 2 one-year extensions of the 

attainment date for a nonattainment area 

under limited circumstances. Section 

172(a)(2)(C) of the Act provides that 

EPA initially may extend an area’s 

attainment date for one year, provided 

that the State has complied with all the 

requirements and commitments 

pertaining to the area in the applicable 

implementation plan, and provided that 

the area has had no more than a 

minimal number of ‘‘exceedances’’ of 

the relevant standard in the preceding 

year. Because the PM2.5 standards do not 

have exceedance-based forms but are 

based on 3-year averaging periods, we 

interpret the air quality test in section 

51.1005 to mean that the area would 

need to have ‘‘clean data’’ for the third 

of the three years that are to be 

evaluated to determine attainment.46 By 

this we mean that for the third year, the 

air quality for all monitors in the area 

as analyzed in accordance with 

Appendix N to 40 CFR Part 50 each 

must have an annual average of 15.0 μg/ 

m3 or less, and a 98th percentile of 24- 

hour monitoring values of 65 μg/m3 or 

less in order to qualify for a 1-year 

extension. (Given the rounding 

provisions specified in 40 CFR Part 50, 

Appendix N, these criteria would be 

satisfied if the concentrations before 

final rounding are less than an annual 

average of 15.05 μg/m3 and a 24-hour 

value of 65.5 μg/m3.) 

For example, suppose an area in 

violation of the annual standard has an 

attainment date of April 2010, and its 

annual average for 2007 was 15.8 and 

for 2008 was 15.6. If the annual average 

for the area in 2009 is 14.9, then the 3- 

year average would be 15.4, and it 

would not have attained the standard. 

We interpret section 172(a)(2)(C) as 

allowing the area to submit a request to 

EPA for a one-year extension of its 

attainment date to 2013 (provided the 

State has also complied with its 

requirements and commitments) since 

the 14.9 ambient air quality value in the 

third year (2009) met the test of being 

at or below 15.0. Section 51.1005(a) of 

the proposed regulation addresses the 

initial one-year attainment date 

extension. 

The air quality measured in 2010 in 

conjunction with prior data will 

determine if the area attains the 

standard, qualifies for a second one-year 

extension, or does not attain the 

standard. For example, if the area’s 

annual average for 2011 is 14.3, then its 

3-year average for 2009–2011 would be 

14.9 and it would have met the annual 

standard. 

If the area’s annual average for 2011 

is 14.9, however, then its 3-year average 

for 2009–2011 would be 15.1. In this 

situation the area would not have 

attained the standard, but the area 

would meet the air quality test for the 

second of the 1-year extensions allowed 

under section 172(a)(2)(C), because the 

2011 annual average was at or below 

15.0. Section 51.1005(b) of the proposed 

rule addresses the second one-year 

attainment date extension. After 

obtaining a second one-year extension, 

the State would evaluate whether the air 

quality values in 2012, in conjunction 

with 2010 and 2011 data, bring the area 

into attainment. 

Pursuant to section 172(a)(2)(C), 

States must submit additional 

information to EPA to demonstrate that 

they have complied with applicable 

requirements, commitments, and 

milestones in the implementation plan. 

This information is needed in order for 

EPA to make a decision on whether to 

grant a 1-year attainment date extension. 

The EPA will not be inclined to grant 

a 1-year attainment date extension to an 

area unless the State can demonstrate 

that it has met important requirements 

contained in the area’s implementation 

plan. States must demonstrate that: (1) 

Control measures have been submitted 

in the form of a SIP revision and 

substantially implemented to satisfy the 

requirements of RACT and RACM for 

the area, (2) the area has made 

emissions reductions progress that 

represents reasonable further progress 

(RFP) toward attainment of the NAAQS, 

and (3) trends related to recent air 

quality data for the area indicate that the 

area is in fact making progress toward 

attainment of the standard. Any 

decision made by EPA to extend the 

attainment date for an area will be based 

on facts specific to the nonattainment 

area at issue, and will only be made 

after providing notice in the Federal 

Register and an opportunity for the 

public to comment. 

If an area fails to attain the standard 

by the attainment date, EPA would 

publish a finding to this effect in 

accordance with section 179 of the Act. 

The area then would be required, within 

1 year of publication of this finding, to 

develop a revised SIP containing 

additional emission reduction measures 

needed to attain the standard as 

expeditiously as practicable. See section 

III.C.5. below for further discussion. 

4. Areas May Submit a SIP 

Demonstrating That It Is Impracticable 

To Attain by the 5-Year Attainment Date 

As stated previously, under section 

172(a)(2)(A), EPA may grant an area an 

extension of the initial attainment date 

for a period of one to five years. States 

that request an extension of the 

attainment date under this provision of 

the Act must submit a SIP in 2008 that 

includes, among other things, an 

attainment demonstration showing that 

attainment within 5 years of the 

designation date is impracticable. It 

must also show that the area will attain 

the standard by an alternative date that 

is as expeditiously as practicable, but in 

no case later than 10 years after the 

designation date for the area (i.e. by 

April 2015 for an area with an effective 

designation date of April 2005). An 

appropriate extension in some cases 

may be only 1 or 2 years—a five-year 

extension is not automatic upon request. 

The attainment demonstration must 

provide sufficient information to show 

that attainment by the initial attainment 

date is impracticable due the severity of 

the nonattainment problem in the area, 

the lack of available or feasible control 

measures, and any other pertinent 

information which shows that 

additional time is required for the area 

to attain the standard. States requesting 

an extension of the attainment date 

must also demonstrate that all local 

66004 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

control measures that are reasonably 

available and technically feasible for the 

area are currently being implemented to 

bring about expeditious attainment of 

the standard by the alternative 

attainment date for the area. The State’s 

plan will need to project the emissions 

reductions expected due to federally 

enforceable national standards, State 

regulations, and local measures such as 

RACT and RACM, and then conduct 

modeling to project the level of air 

quality improvement in accordance 

with EPA’s modeling guidance. The 

EPA will not grant an extension of the 

attainment date beyond the initial five 

years required by section 172(a)(2)(A) 

for an area if the State has not 

thoroughly considered the 

implementation of all RACM and RACT 

local control measures for the area (see 

section III.I for a more detailed 

discussion of RACT and RACM). EPA 

also will examine whether the State has 

adequately considered measures to 

address intrastate transport of pollution 

from sources within its jurisdiction. In 

attainment planning, States have the 

obligation and authority to address the 

transport of pollution from one area of 

the state to another. Any decision made 

by EPA to extend the attainment date for 

an area beyond its original attainment 

date will be based on facts specific to 

the nonattainment area at issue and will 

only be made after providing notice in 

the Federal Register and an opportunity 

for the public to comment. 

5. Areas That Fail To Attain or Do Not 

Qualify for an Attainment Date 

Extension 

Section 179 of the Act requires that 

EPA publish a finding in the Federal 

Register for areas that fail to attain by 

their attainment dates, or that fail to 

qualify for an attainment date extension. 

Within one year of EPA’s determination 

that the area failed to attain, the State is 

then required to submit a SIP revision 

providing for attainment of the standard 

as expeditiously as practicable in 

accordance with section 172(a)(2) of the 

Act. Section 179(d)(3) provides that the 

SIP revision must include any specific 

additional measures as may be 

prescribed by EPA, including ‘‘all 

measures that can be feasibly 

implemented in the area in light of 

technological achievability, costs, and 

any nonair quality and other air qualityrelated health and environmental 

impacts.’’ The EPA believes that in 

considering the factors above, States 

that fail to attain the standard initially 

should give greater weight to 

technologically feasible measures 

despite the fact that these measures may 

be more costly than those implemented 

under the previous plan. 

6. Determining Attainment for the PM2.5

Standards 

The EPA has the responsibility for 

determining whether a nonattainment 

area has attained the standard by its 

applicable attainment date. Section 

179(c)(1) of the Act requires EPA to 

make determinations of attainment no 

later than 6 months following the 

attainment date for the area. Under 

section 179(c)(2), EPA must publish a 

notice in the Federal Register 

identifying those areas which failed to 

attain by the applicable attainment date. 

The statute further provides that EPA 

may revise or supplement its 

determination of attainment for the 

affected areas based upon more 

complete information or analysis 

concerning the air quality for the area as 

of the area’s attainment date. 

Section 179(c)(1) of the Act provides 

that the attainment determination for an 

area is to be based upon an area’s ‘‘air 

quality data as of the attainment date.’’

The EPA will make the determination of 

whether an area’s air quality is meeting 

the PM2.5 NAAQS by the applicable 

attainment date primarily based upon 

data gathered from the air quality 

monitoring sites which have been 

entered into EPA’s Air Quality System 

(AQS) database. No special or additional 

SIP submittal will be required from the 

State for this determination. 

A PM2.5 nonattainment area’s air 

quality status is determined in 

accordance with appendix N of 40 CFR 

part 50. To show attainment of the 24- 

hour and annual standards for PM2.5, the 

most recent three consecutive years of 

data prior to the area’s attainment date 

must show that three-year average PM2.5

concentrations are at or below the levels 

of the standards. A complete year of air 

quality data, as described in part 50, 

Appendix N, is comprised of all 4 

calendar quarters with each quarter 

containing data from at least 75 percent 

of the scheduled sampling days. The 

annual standard for PM2.5 is attained 

when the 3-year average annual mean 

concentration is less than or equal to 

15.0 μg/m3. The 24-hour standard for 

PM2.5 is met when the average of 98th 

percentile values for three consecutive 

calendar years at each monitoring site is 

less than or equal to 65 μg/m3. 

The EPA will begin processing and 

analyzing data related to the attainment 

of PM2.5 areas immediately after the 

applicable attainment date for the 

affected areas. Current EPA policy, 

under 40 CFR part 58, sets the deadline 

for submittal of air quality data into the 

AQS database for no later than 90 days 

after the end of the calendar year. 

While EPA may determine that an 

area’s air quality data indicates that an 

area may be meeting the PM2.5 NAAQS 

for a specified period of time, this does 

not eliminate the State’s responsibility 

under the Act to adopt and implement 

an approvable SIP. If EPA determines 

that an area has attained the standard as 

of its attainment date, the area will 

remain classified as nonattainment until 

the State has requested, and EPA has 

approved, redesignation to attainment 

for the area. 

In order for an area to be redesignated 

as attainment, the State must comply 

with the five requirements listed under 

section 107(d)(3)(E) of the Act. Among 

other things, section 107(d)(3)(E) 

requires that EPA determine that an area 

has met the PM2.5 NAAQS and that the 

State has submitted a SIP for the area 

which has been approved by EPA. 

7. How Do Attainment Dates Apply to 

Indian Country? 

The Tribal Authority Rule (TAR) at 40 

CFR 49.9 provides guidelines by which 

Tribes may implement air quality 

programs in a similar manner as States. 

However, Tribes choosing to implement 

their own air quality programs are not 

required to meet the same schedules 

and deadlines that apply to States, 

including attainment dates for NAAQS. 

In situations where a Tribe chooses to 

not implement its own air quality 

program or any element thereof, EPA is 

required under the TAR to develop a 

Federal Implementation Plan (FIP) as 

necessary and appropriate. 40 CFR 

49.11. Because public health 

considerations are of utmost concern, 

we believe that any FIP for tribal lands 

should provide for an attainment date 

that is as expeditious as practicable. 

Therefore, EPA will work in 

consultation with the Tribes to ensure 

that implementation of the standards is 

conducted as soon as possible taking 

into consideration the needs of the 

Tribes, and to ensure that attainment in 

other jurisdictions is not adversely 

affected. 

D. What Are the Incentives for 

Achieving Early Reductions of PM2.5

and Its Precursors? 

There are significant regulatory 

incentives for achieving early local area 

emissions reductions. Areas with design 

values just over the level of the standard 

may be able to achieve reductions in the 

local area or in the State so that, when 

their effect is considered in combination 

with reductions achieved under 

national programs, they may be 

sufficient to attain the standards before 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66005 

47Memorandum of December 14, 2004, from 

Steve Page, Director, EPA Office of Air Quality 

Planning and Standards to EPA Air Division 

Directors, ‘‘Clean Data Policy for the Fine Particle 

National Ambient Air Quality Standards.’’ This 

document is available at: http://www.epa.gov/ 

pmdesignations/guidance.htm. 

48Memorandum of November 18, 2002, from 

Lydia Wegman and Peter Tsirigotis, ‘‘2002 Base 

Year Emission Inventory SIP Planning: 8-hr Ozone, 

PM2.5 and Regional Haze Programs.’’ This document 

is available at the following web site: http:// 

www.epa.gov/ttn/oarpg/t1/memoranda/ 

2002bye_gm.pdf. 

49USEPA, 2002. Health Assessment Document 

for Diesel Engine Exhaust. The EPA/600/8–90/057F. 

01 May 2002. U.S. Environmental Protection 

Agency, Office of Research and Development, 

National Center for Environmental Assessment, 

Washington, DC. Available on EPA’s Web site: 

http://cfpub.epa.gov/ncea/. 

SIPs are due in 2008. For example, if 

monitoring in a nonattainment area 

shows that the air quality for 2004–2006 

meets the standards, then the area may 

be subject to reduced regulatory 

requirements and be redesignated as 

‘‘attainment.’’ EPA issued a ‘‘Clean 

Data’’ policy memorandum in December 

2004 describing possible reduced 

regulatory requirements for areas that 

attain the standards early, but have not 

yet been redesignated as attainment.47

For example, the area also would be 

relieved of the requirements to 

implement the nonattainment NSR 

program otherwise required for 

nonattainment areas, and instead would 

implement the PSD program. 

Another regulatory incentive for early 

emissions reductions is credit toward 

RFP requirements. We issued a 

guidance memorandum designating 

2002 as the base year for emissions 

inventories for PM2.5 and 8-hour ozone 

attainment plans and for regional haze 

implementation plans.48 For PM2.5, 

States therefore can take credit for 

emissions reductions achieved after 

2002 in meeting their requirements for 

RFP. In addition, when developing 

attainment demonstrations, States 

should account for these reductions 

when establishing baseline control 

scenarios for assessing what additional 

reductions might be needed to attain the 

standards. 

Examples of possible early reduction 

programs include efforts to reduce 

diesel engine emissions (e.g. Clean 

School Bus USA, retrofits for trucks, 

locomotives, construction equipment, 

and marine vessels such as ferries, and 

diesel idling emissions programs); 

programs to reduce auto emissions 

through reduced vehicle miles traveled 

and improving maintenance of high 

emitting vehicles; implementation and 

enforcement of regulations to reduce 

emissions from burning activities (such 

as smoke management programs, wood 

stove retrofit programs, and ordinances 

to ban open burning of waste or debris 

from land clearing); energy conservation 

programs that can reduce demand from 

power plants; improved emission 

controls on stationary sources; and 

improved compliance assurance 

monitoring to ensure that stationary 

source emissions are maintained at the 

levels demonstrated during emissions 

performance tests. Additional 

discussion of possible emission 

reduction strategies which could be 

introduced early is included in section 

III.I. on RACM and RACT. 

E. How Should the States and EPA 

Balance the Need To Address LongRange Transport of Fine Particle 

Pollution With the Need for Local 

Emissions Reductions When 

Implementing the PM2.5 Standards? 

1. Clean Air Act Provisions for 

Achieving Local and Regional 

Emissions Reductions 

Section I provides background on 

PM2.5 monitoring data, the geographic 

distribution of potential nonattainment 

areas, and the estimated population 

affected. It also includes a discussion of 

the regional nature of the PM2.5

problem. 

Section 172(a)(2) of the Act requires 

States to attain the standards as 

expeditiously as practicable but within 

five years of designation (i.e. attainment 

date of April 2010 based on air quality 

data for 2007–2009), or within up to ten 

years of designation (i.e. to 2015) if the 

EPA Administrator extends an area’s 

attainment date by 1–5 years based 

upon the severity of the nonattainment 

problem and/or the feasibility of 

implementing control measures. 

Virtually all nonattainment problems 

appear to result from a combination of 

local emissions and transported 

emissions from upwind areas. The 

structure of the CAA requires EPA to 

develop national rules for certain types 

of sources which are also significant 

contributors to local air quality 

problems, including motor vehicles and 

fuels. It also provides for States to 

address emissions sources on an areaspecific basis through such 

requirements as RACT, RACM, and RFP. 

We believe that to attain the PM2.5

standards, it is important to pursue 

emissions reductions simultaneously on 

the local, regional, and national levels. 

As discussed in more detail in section 

III.I. on RACM and RACT requirements, 

States will need to evaluate technically 

and economically feasible emission 

reduction opportunities at the local 

level and determine which measures 

can be reasonably implemented within 

the nonattainment area. Local and 

regional emission reduction efforts 

should proceed concurrently and 

expeditiously. 

In addition, reductions in pollutants 

that contribute to PM2.5 can provide 

concurrent benefits in addressing a 

number of air quality problems—such as 

ozone, regional haze, urban visibility, 

and toxic air pollutant problems—by 

reducing common pollutants. Such is 

the case with programs to reduce diesel 

emissions, for example. While diesel 

engines collectively are large sources of 

NOX and direct PM emissions, they also 

emit significant amounts of toxic air 

pollutants.49 Similarly, many sources 

and activities which lead to direct 

emissions of organic and elemental 

carbon (such as open burning and 

residential wood combustion) also are 

key sources of toxic air pollutants (i.e. 

polycyclic aromatic hydrocarbon 

emissions), and contribute to regional 

haze as well. Thus, programs and 

strategies designed to reduce local 

emissions of PM and its precursors can 

help reach attainment for the PM2.5

standards and provide other air quality 

benefits as well. 

2. Regional Emission Reduction 

Strategies 

As stated earlier in section II, the 

principal regional pollutants 

contributing to downwind PM2.5

concentrations in the eastern U.S. are 

SO2 and NOX. Sulfate formed from SO2

accounts for about 30–50 percent of 

PM2.5 mass in most eastern locations, 

while ammonium nitrate formed from 

NOX accounts for 6 percent to more than 

20 percent in some locations. The EPA 

implemented phase II of the Acid Rain 

Program in 2000, setting an emissions 

cap of 8.95 million tons of SO2 and 

bringing the average emission rate for 

power plants to a level of 1.2 lbs per 

mmBTU. However, EPA analyses have 

shown that sulfate and nitrate 

contribute to nonattainment problems 

significantly and will remain a large 

percentage of PM2.5 concentrations in 

the eastern U.S. even after full 

implementation of the Acid Rain 

Program. In order to address health and 

environmental problems associated with 

PM2.5, ozone, and mercury deposition, 

the President has proposed the Clear 

Skies Act. [The Clear Skies Act of 2003 

was introduced in the U.S. House of 

Representatives (H.R. 999) and the U.S. 

Senate (S. 485) on February 27, 2003.] 

It is designed to achieve significant 

reductions in SO2, NOX, and mercury 

emissions from power plants. (For more 

information, see section I.E.1. above.) 

66006 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

50See discussion of local control measures in the 

proposed CAIR, 69 FR 4596–4599, and associated 

supporting information (docket #OAR–2003–0053, 

item #OAR–2003–0053–0162, Technical Support 

Document for the CAIR, Modeling Analyses). 

51These estimates are based on the relative risk 

for all-cause mortality from the Pope et al. 2002 

analysis of the American Cancer Society cohort. 

The EPA standard methodology for estimating 

health benefits has been used in developing 

regulatory impact analyses for a number of 

regulations. Most recently, this methodology was 

used in support of the CAIR (docket #OAR–2003–

0053, item #OAR–2003–0053–0175, Benefits of the 

Proposed CAIR, January 2004). 52U.S. EPA, 2005. Regulatory Impact Analysis for 

the Clean Air Interstate Rule. EPA 452/–03–001. 

Prepared by Office of Air and Radiation. Available 

at: http://www.epa.gov/interstateairquality/ 

tsd0175.pdf. See also: U.S. Environmental 

Protection Agency, 2004. Final Regulatory Analysis: 

Control of Emissions from Nonroad Diesel Engines. 

EPA420–R–04–007. Prepared by Office of Air and 

Radiation. Available at http://www.epa.gov/ 

nonroad-diesel/2004fr/420r04007.pdf. 

Because it is uncertain whether the 

CSA will be enacted, EPA established 

the CAIR under the existing CAA to 

achieve regional reductions of SO2 and 

NOX. (See section I.E.2. for a discussion 

of CAIR.) The CAA requires States to 

develop SIPs that provide for attainment 

by deadlines in the CAA and requires 

States to have implementation plans 

that prohibit emissions that contribute 

significantly to nonattainment in other 

States. As described in the Federal 

Register actions for the NOX SIP call 

and section 126 rulemakings, EPA 

believes it has the authority under the 

CAA to define what States need to do 

to address the interstate transport 

requirements of section 110 in advance 

of the submission of nonattainment area 

SIPs. The CAIR program will help many 

cities throughout the region meet the 

PM2.5 standards or make significant 

progress toward attainment. 

Air quality modeling analyses in 

support of the final CAIR rule show that 

of the 36 areas currently designated 

nonattainment for PM2.5 in the eastern 

United States, 17 areas are projected to 

attain the standards by 2010 with 

implementation of CAIR and other 

existing federal and state measures. By 

2015, 22 areas are projected to attain the 

standards. While the air quality benefits 

from implementation of CAIR and other 

programs are significant, it is also 

evident that in some areas local 

emission reduction measures will serve 

an important role in addressing the 

PM2.5 nonattainment problem. 

3. The Role of Local and State Emission 

Reduction Efforts in Reducing Health 

Risks and Achieving the PM2.5

Standards 

As discussed above, the 

implementation of regional and national 

strategies (such as CAIR and various 

mobile source programs) are expected to 

provide significant air quality 

improvements for PM2.5 nonattainment 

areas. At the same time, analyses for the 

final CAIR rule indicate that without 

implementation of local measures, 

approximately 14 to 19 areas would be 

projected to remain in PM2.5

nonattainment status in the 2010–2015 

timeframe. Thus, EPA believes that local 

and State emission reduction efforts will 

need to play an important role in 

addressing the PM2.5 problem as well. 

EPA intends to work closely with States, 

Tribes, and local governments to 

develop appropriate in-state pollution 

reduction measures to complement 

regional and national strategies to meet 

the standards expeditiously and in a 

cost-effective manner. 

Many types of emissions sources 

contribute to the PM problem, and in 

many cases cost-effective measures are 

available to reduce their emissions. 

Examples of possible local measures are 

discussed in the previous section III.D. 

on early reductions, as well as in section 

III.I. on RACT and RACM. The EPA has 

also provided grant funding to STAPPA/ 

ALAPCO to develop a ‘‘menu of 

options’’ document to provide State and 

local agencies and the general public 

with additional information on sources 

of emissions, potential control 

measures, and their associated costs and 

air quality benefits. 

EPA encourages States to implement 

technologically available and 

economically feasible local measures 

expeditiously. States can adopt a 

number of programs now, or expand 

their level of implementation of existing 

programs, in order to achieve local area 

emissions reductions in the near term. 

While regional emissions reductions 

may have a lower cost per ton of 

emissions reduced than many local 

reductions, local reduction 

opportunities may be more readily 

available, they may be more feasible to 

implement in a shorter period of time 

than a broad regional emissions trading 

program, and they may have high 

benefits per ton of emission reduction. 

In addition, local emissions reductions 

can be especially beneficial in reducing 

exposure to air pollution for dense 

urban populations. Thus, by taking 

action in advance of the date that 

regional reductions may be achieved, 

local communities can enjoy the 

benefits of improved public health 

(including a reduction in health care 

costs). 

Preliminary EPA analyses 50 show 

that if local emissions reductions (e.g., 

including SO2 and other local 

emissions) were obtained only from 

sources located within metro areas 

projected to be nonattainment, the 

average air quality improvement in 

these cities would be 1.26 μg/m3, and 

the number of counties projected to 

have violating monitors in 2010 would 

decrease from 61 to 26. These analyses 

also show that if local emissions 

reductions were limited to pollutants 

other than SO2, the average air quality 

improvement in these cities would be 

0.37 μg/m3, and the number of counties 

projected to have violating monitors in 

2010 would decrease from 61 to 48. 

Thus, these analyses support the 

conclusion that emissions reductions 

due to regional and national programs 

such as CAIR and recently promulgated 

national rules for mobile sources will 

make important contributions to 

attainment for many eastern 

nonattainment areas. In the absence of 

regional controls on upwind sources, 

downwind States would be forced to 

obtain greater emissions reductions, and 

incur greater costs, to offset the 

transported pollution from upwind 

sources. At the same time, this 

preliminary analysis also illustrates that 

local emissions reductions can be 

beneficial, and have the potential to 

bring a number of metropolitan areas 

into attainment. 

EPA believes that expeditiously 

achieving the PM2.5 reductions that are 

available from reasonable local controls 

is important because, as discussed in 

section I.A., the effects of PM2.5 on 

public health are serious. Estimates 

suggest that each year tens of thousands 

of people die prematurely from 

exposure to PM2.5, and many hundreds 

of thousands more people experience 

significant respiratory or cardiovascular 

effects. Even small reductions in PM2.5

levels may have substantial health 

benefits on a population level. For 

example, in a moderate-sized 

metropolitan area with a design value of 

15.5 μg/m3, efforts to improve annual 

average air quality down to the level of 

the standard (15.0 μg/m3) may be 

expected to result in as many as 25–50 

fewer mortalities per year due to air 

pollution exposure. In a smaller city, the 

same air quality improvement from 15.5 

to 15.0 μg/m3 still may be expected to 

result in a number of avoided 

mortalities per year. These estimates are 

based on EPA’s standard methodology 

for calculating health benefits as used in 

recent rulemakings.51

The benefits of PM2.5 control also are 

significant in dollar terms. Depending 

on the particular emission controls on 

sources of PM2.5 precursor emissions, 

EPA has estimated that the monetized 

health benefits of reducing emissions of 

pollutants that lead to PM2.5 formation 

exceed the costs by 3 to over 30 times.52

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66007 

53 ‘‘Estimated NOX, SO2, and PM Emissions 

Health Damages for Heavy-duty Vehicle 

Emissions.’’ April 22, 2002. Memorandum by Bryan 

Hubbell, EPA Office of Air Quality Planning and 

Standards, to docket A–2000–01, docket item IV–

A–146. 

54USEPA, ‘‘Interim Air Quality Policy on 

Wildland and Prescribed Fires,’’ memorandum from 

Richard Wilson, Acting Assistant Administrator for 

Air and Radiation, to Regional Administrators, May 

15, 1998. 

As discussed in more detail in section 

III.I. on RACM and RACT requirements, 

States will need to evaluate technically 

and economically feasible emission 

reduction opportunities at the local 

level and determine which measures 

can be reasonably implemented within 

the nonattainment area. To avoid the 

public health consequences of delayed 

improvements in PM2.5 concentrations, 

we believe that local and regional 

emission reduction efforts should 

proceed concurrently and expeditiously. 

Although direct emissions may 

appear relatively small in tonnage 

terms, States should not overlook 

reductions of direct local emissions, 

particularly carbonaceous emissions. 

Monitoring data show that many urban 

areas have higher levels of carbonaceous 

PM2.5 than rural areas. Based on 

information developed by EPA in 

support of regulations on diesel engines, 

the population weighted impact per ton 

of direct PM diesel emissions reduced is 

estimated to be about 9–14 times more 

effective in reducing health effects as 

compared to SO2 and NOX reductions 

from the same sources.53 This analysis 

reflects the fact that by definition, all of 

the direct fine particle emissions 

contribute to PM2.5 concentrations, but 

only a fraction of the SO2 and NOX

emissions undergo reactions in the 

atmosphere to become PM2.5. 

In addressing a nonattainment area 

having military training, testing and 

operational activities occurring within 

it, the State should not need to target 

these activities for emission reductions. 

Regarding prescribed burning activities, 

EPA intends to continue 

implementation of the Interim Air 

Quality Policy on Wildland and 

Prescribed Fires.54

4. Addressing Regionally Transported 

Emissions in Local Area Attainment 

Demonstrations 

As discussed in section III.C., the 

CAA requires States with PM2.5

nonattainment areas to attain the 

standards as expeditiously as 

practicable, but no later than within five 

years of designation (e.g., April 2010). If 

the State provides an adequate 

demonstration showing that it cannot 

attain the standards within five years, 

based on the severity of the area’s 

problem, the availability of control 

measures, and the feasibility of 

implementing controls, then EPA may 

grant the area an attainment date 

extension of one to five years. 

Now that the multi-state CAIR 

emission reduction program has been 

adopted well before the PM2.5 SIPs are 

due, it will be important for affected 

States to take into account the 

incremental projected emissions 

reductions resulting from that program 

in assessing the degree of air quality 

improvement that can be expected in 

the State and the projected timetable for 

those reductions to be realized. 

Experience with implementation of 

the cap-and-trade and emissions 

banking provisions of the Acid Rain 

Program has shown that certain sources 

likely will take steps to reduce 

emissions and ‘‘bank’’ emissions 

allowances prior to the date that 

compliance with the initial emissions 

cap is required. 

Under a trading program with an 

emissions banking provision, we 

estimate that SO2 emissions will be 

reduced on a steadily decreasing 

glidepath rather than a stair step 

pattern. By 2009, the last year prior to 

the 2010 attainment year, a portion of 

the total regional SO2 emissions 

reductions expected under CAIR would 

be realized. In developing their SIPs, 

States should use existing projections of 

the geographic distribution and 

magnitude of early emissions reductions 

that are expected to be achieved by 2009 

using existing information from the IPM 

emissions projection model. They 

should also assess the associated impact 

of these reductions on air quality by 

using a regional air quality model. We 

encourage the States to use existing 

analyses to the extent possible to project 

interim air quality improvements from 

regional emissions reduction strategies, 

and we commit to working with the 

States and regional planning 

organizations to evaluate the expected 

air quality improvements from CAIR. In 

addition, states must assess the effect of 

potential RACM, including RACT, in 

determining an appropriate attainment 

date. We will work with the States as 

they develop attainment demonstrations 

and SIPs designed to attain the 

standards as expeditiously as 

practicable, taking into account 

emissions reductions from broad 

regional programs (such as the CAIR 

and NOX SIP Call); national measures 

such as new emissions standards for 

cars and trucks; and other cost effective 

State and local strategies which may 

advance the attainment date. 

F. How Will EPA Address Rrequirements 

for Modeling and Attainment 

Demonstration SIPs When 

Implementing the 24-Hour and Annual 

Aaverage PM2.5 Standards? 

1. Introduction 

Section 172(c) requires States with 

nonattainment areas to submit an 

attainment demonstration. An 

attainment demonstration consists of: 

(1) Technical analyses that locate, 

identify, and quantify sources of 

emissions that are contributing to 

violations of the PM2.5 NAAQS; (2) 

analyses of future year emissions 

reductions and air quality improvement 

resulting from already-adopted national 

and local programs, and from potential 

new local measures to meet the RACT, 

RACM, and RFP requirements in the 

area; (3) adopted emission reduction 

measures with schedules for 

implementation; and (4) contingency 

measures required under section 

172(c)(9) of the CAA. with a 

nonattainment area will have to submit 

a SIP with an attainment demonstration 

that includes analyses supporting the 

State’s proposed attainment date. The 

State must show that the area will attain 

the standards as expeditiously as 

practicable, and it must include an 

analysis of whether implementation of 

reasonably available measures will 

advance the attainment date. 

2. Areas That Need To Conduct 

Modeling 

Some areas having design values close 

to the standard may be projected to 

come into attainment within five years 

based on modeling analyses of national 

and regional emission control measures 

that are scheduled to occur through 

2009. Regional scale modeling for 

national rules such as the Tier II motor 

vehicle standards, the Heavy-duty 

Engine standards and the Nonroad 

Engine standards indicate major 

reductions in PM2.5 by 2010. A portion 

of these benefits will occur in the 2004–

2009 PM2.5 attainment timeframe. 

Experience with past ozone 

attainment demonstrations has shown 

that the process of performing detailed 

photochemical grid modeling to develop 

an attainment demonstration can be 

very resource intensive for States. The 

EPA believes that it would be 

appropriate for States to leverage 

resources by collaborating on modeling 

analyses to support SIP submittals, or by 

making use of recent modeling analyses 

that have already been completed. For 

this reason, EPA proposes that States 

may use in a PM2.5 attainment 

demonstration certain local, regional 

and/or national modeling analyses that 

66008 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

55 ‘‘DRAFT Guidance for Demonstrating 

Attainment of Air Quality Goals for PM2.5 and 

Regional Haze’’ can be found at: http:// 

www.epa.gov/scram001/guidance/guide/ 

draft_pm.pdf. 

56The unmonitored area attainment test will be 

limited to locations which are appropriate to allow 

the comparison of predicted PM2.5 concentrations to 

the NAAQS, based on PM2.5 monitor siting 

requirements and recommendations. 

have been developed to support Federal 

or local emission reduction programs, 

provided the modeling meets the 

attainment modeling criteria set forth in 

EPA’s modeling guidance (described 

below). As with all SIPs under subpart 

1, the State must demonstrate that the 

area will attain the PM2.5 standards as 

expeditiously as practicable. As part of 

this demonstration, the State must 

evaluate those technically and 

economically feasible measures in the 

nonattainment area in order to 

determine whether, if implemented 

together, these measures would advance 

the attainment date. (This evaluation of 

local measures may or may not involve 

additional modeling.) The EPA proposes 

that if the State can rely on existing 

modeling analyses as part of its 

attainment demonstration, it should 

reference appropriate reports on that 

modeling which are readily available, or 

include the modeling documentation in 

its submittal. In such situations, the 

State must provide an explanation 

describing how it meets the criteria for 

attainment-level modeling, and why the 

existing modeling is appropriate for use 

as part of the attainment demonstration. 

The EPA requests comment on this 

proposed approach for using existing air 

quality modeling analyses in attainment 

demonstrations, where appropriate. 

Nonattainment areas would be 

required to submit an attainment 

demonstration SIP that includes new 

modeling showing attainment of the 

standards as expeditiously as 

practicable. The new modeling will 

need to include additional emissions 

controls or measures in order to 

demonstrate attainment. 

3. Modeling Guidance 

Section 110(a)(2)(K)(i) states that SIPs 

must contain air quality modeling as 

prescribed by the Administrator for the 

purpose of predicting the effect of 

emissions on ambient air quality. The 

procedures for modeling PM2.5 as part of 

an attainment SIP are contained in 

EPA’s ‘‘DRAFT Guidance for 

Demonstrating Attainment of Air 

Quality Goals for PM2.5 and Regional 

Haze.’’ 55 The EPA welcomes public 

comments on the guidance at any time 

and will consider those comments in 

any future revision of the document. 

Comments submitted on the modeling 

guidance document should be identified 

as such and will not be docketed as part 

of this rulemaking, nor will a comment/ 

response summary of these comments 

be a part of the final PM2.5

implementation rule since they will not 

affect the rule itself. The final version of 

the guidance is scheduled for release in 

2005 and will be posted on EPA’s web 

site (http://www.epa.gov/ttn/scram/). 

The draft modeling guidance 

describes how to estimate whether a 

control strategy to reduce emissions of 

particulate matter and its precursors 

will lead to attainment of the annual 

and 24-hour PM2.5 NAAQS. Part I of the 

guidance describes a ‘‘modeled 

attainment test’’ for the annual and 24- 

hour PM2.5 NAAQS. Both tests are 

similar. The output of each is an 

estimated future design value consistent 

with the respective forms of the 

NAAQS. If the future design value does 

not exceed the concentration of PM2.5

specified in the NAAQS, the test is 

passed. The modeled attainment test 

applies to locations with monitored 

data. 

A separate test is recommended to 

examine projected future year PM2.5

concentrations in unmonitored 

locations.56 Interpolated PM2.5 ambient 

data combined with modeling data can 

be used to predict PM2.5 concentrations 

in unmonitored areas. The details of 

such an analysis will be contained in 

the final modeling guidance. 

States may use other analyses in 

addition to the modeled attainment test 

and hot spot analysis to estimate 

whether future attainment of the 

NAAQS is likely. Attainment is likely if 

a preponderance of evidence suggests 

so. This procedure is called a ‘‘weight 

of evidence determination.’’

Reliability of recommended tests for 

estimating future attainment depends on 

having reliable data bases. The guidance 

identifies and prioritizes key data 

gathering activities and analytical 

capabilities which will increase 

credibility of analyses used to estimate 

if the air quality goals for PM2.5 will be 

met. 

Part II of the guidance describes how 

to apply air quality models to generate 

results needed by the modeled tests for 

attainment. This includes developing a 

conceptual description of the problem 

to be addressed; developing a modeling/ 

analysis protocol; selecting an 

appropriate model to support the 

demonstration; selecting appropriate 

meteorological episodes or time periods 

to model; choosing an appropriate area 

to model with appropriate horizontal/ 

vertical resolution; generating 

meteorological and air quality inputs to 

the air quality model; generating 

emissions inputs to the air quality 

model; evaluating performance of the air 

quality model; and performing 

diagnostic tests. After these steps are 

completed, the model is used to 

simulate effects of candidate control 

strategies. 

EPA is not recommending a specific 

model for use in the attainment 

demonstration for the PM2.5 NAAQS. At 

present, there is no single model which 

has been extensively tested and shown 

to be clearly superior to other available 

models. The current modeling 

guideline, 40 CFR part 51, appendix W 

does not identify a ‘‘preferred model’’

for use in attainment demonstrations of 

the NAAQS for PM2.5. Thus, States may 

choose from several alternatives. The 

EPA’s draft modeling guidance provides 

a set of general requirements which an 

air quality model should meet to qualify 

for use in an attainment demonstration 

for the PM2.5 NAAQS. These include 

having received a scientific peer review, 

being applicable to the specific 

application on a theoretical basis, and 

having an adequate data base to support 

its application. 

In some cases, multiple models may 

need to be applied in the attainment 

demonstration. In most cases, a 

photochemical grid model is needed to 

treat secondary particulate matter. 

Photochemical grid models can also be 

used to treat primary particulate. In high 

concentration areas of primary 

particulate, however, a Gaussian plume 

model or puff model may also be 

needed to more accurately represent 

steep concentration gradients. The 

modeling guidance provides details and 

recommendations on using multiple 

models. 

The application of air quality models 

requires a substantial effort by State 

agencies and EPA. Therefore, States 

should work closely with the 

appropriate U.S. EPA Regional Offices 

in executing each step of the modeling 

process. By doing so, it will increase the 

likelihood of EPA approval of the State 

demonstration submitted at the end of 

the modeling and overall SIP 

development process. 

4. Modeled Attainment Test 

The two modeled attainment tests for 

the annual and 24-hour standards use 

monitored data to estimate current air 

quality. The attainment test for a given 

standard is applied at each monitor 

location within or near a designated 

nonattainment area for that standard. 

There is also an additional attainment 

test to be performed in unmonitored 

areas. Models are used in a relative 

sense to estimate the response of 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66009 

57Certain VOCs (especially aromatic compounds) 

with >6 carbon atoms may form secondary organics 

aerosols. 

measured air quality to future changes 

in emissions. Future air quality is 

estimated by multiplying current 

monitored values times modeled 

responses to changes in emissions. 

Because PM2.5 is a mixture of chemical 

components, States should use current 

observations and modeled responses of 

major components of PM2.5 to estimate 

future concentrations of each 

component. The predicted future 

concentration of PM2.5 is the sum of the 

predicted component concentrations. 

Direct application of the modeled 

attainment tests requires speciated PM2.5

ambient data co-located with FRM sites. 

However, there will not be speciation 

monitors at every FRM site. In fact, 

speciation monitors are only located at 

approximately 20 percent of the FRM 

monitoring sites. Therefore EPA is 

developing a refinement of the modeled 

attainment test that uses interpolated 

ambient speciation data to calculate 

current values of PM2.5 species at all of 

the FRM monitoring sites. Gridded 

spatial fields of interpolated speciated 

PM2.5 data are created in order to 

estimate the species fractions at each 

FRM site. This information, combined 

with modeling results, may be used to 

calculate future air quality at each FRM 

monitoring site. 

An application of this methodology 

was employed and documented as part 

of EPA’s Clean Air Interstate Rule 

(CAIR). The final modeling guidance 

will contain default recommendations 

for the disaggregation and treatment of 

PM2.5 species for the purpose of 

applying the modeled attainment test. 

5. Multi-Pollutant Assessments and 

One-Atmosphere Modeling 

A multi-pollutant assessment, or oneatmosphere modeling, is conducted 

with a single air quality model that is 

capable of simulating transport and 

formation of multiple pollutants 

simultaneously. For example, this type 

of model simulates the formation and 

deposition of PM2.5, ozone, and regional 

haze components, and it includes 

algorithms simulating gas phase 

chemistry, aqueous phase chemistry, 

aerosol formation, and acid deposition. 

Multipollutant assessments are 

recommended for PM2.5 attainment 

demonstrations because the formation 

and transport of PM2.5 is closely related 

to the formation of both regional haze 

and ozone. The components of PM2.5

account for the vast majority of visibility 

impairment associated with regional 

haze. For any given mass, fine particles 

are more efficient at scattering light than 

particles larger than 2.5 micrometers in 

diameter, and certain components of 

PM2.5 are more efficient at scattering or 

absorbing light than others. The most 

efficient light-scattering particle types 

are secondary particulate species such 

as sulfates and nitrates. Primary 

particles composed of crustal and other 

inorganic material are less efficient at 

scattering light. Secondary particulate 

matter comprises a significant fraction 

of measured PM2.5 in most parts of the 

country, and therefore is a significant 

contributor to regional haze. The impact 

of fine particles on visibility is 

enhanced still further by high relative 

humidity, which is especially relevant 

in the Eastern U.S., because sulfates and 

nitrates commonly absorb water and 

grow to sizes comparable to the 

wavelengths of visible light. 

There is often a positive correlation 

between measured ozone and secondary 

particulate matter. Many of the same 

factors affecting concentrations of ozone 

also affect concentrations of secondary 

particulate matter. For example, 

similarities exist in sources of 

precursors for ozone and secondary 

particulate matter. Emissions of NOX

may lead to formation of nitrates as well 

as ozone. Sources of VOC may be 

sources or precursors for both ozone and 

organic particles. Presence of ozone 

itself may be an important factor 

affecting secondary particulate 

formation. For example, as ozone builds 

up, hydroxyl (OH) radicals do also as a 

result of equilibrium reactions between 

ozone, water and OH in the presence of 

sunlight. Hydroxyl (OH) radicals are 

instrumental in oxidizing gas phase SO2

to sulfuric acid, which is eventually 

absorbed by liquid aerosol and 

converted to particulate sulfate in the 

presence of ammonia. SO2 also reacts 

with ozone and hydrogen peroxide (a 

byproduct of photochemistry), in the 

aqueous phase, to form particulate 

sulfate. Hydroxyl radicals and NO are 

also precursors for gas phase nitric acid, 

which is absorbed by liquid aerosol and, 

in the presence of ammonia, leads to 

particulate nitrate. 

Strategies to reduce ozone can also 

affect formation of secondary PM. 

Reducing VOC emissions could reduce 

ozone, OH, and/or hydrogen peroxide. If 

sulfate or nitrate production is limited 

by lack of availability of oxidizing 

agents, the ozone reduction strategy 

could also reduce secondary PM. Recent 

research has also shown increased 

secondary organic aerosol 

concentrations in the presence of acid 

aerosols. Reductions in oxidizing agents 

may lead to lower concentrations of 

sulfate and/or nitrate which may lead to 

reduced levels of secondary organic 

aerosols. Control of certain VOCs 57 may 

also reduce secondary organic aerosols 

by reducing their semi-volatile 

precursors. Reducing NOX emissions 

diminishes one of the precursors for 

nitric acid (i.e., NO2 which results from 

NO). Therefore, in the presence of 

sufficient ammonia, reducing NOX

emissions could reduce particulate 

nitrate concentrations. There are also 

more subtle interfaces between 

strategies to reduce ozone and to reduce 

secondary particulate matter. For 

example, reducing NOX in the presence 

of substantial particulate sulfates and 

lack of sufficient ammonia could in 

some cases exacerbate the particulate 

sulfate problem, or reducing SO2 in the 

presence of substantial NOX and 

ammonia could in some cases 

exacerbate the particulate nitrate 

problem. 

Therefore, models and data analysis 

intended to address PM2.5 should also 

address visibility impairment. These 

models also need to be capable of 

simulating transport and formation of 

ozone. At a minimum, modeling should 

include previously implemented or 

planned measures to reduce ozone, PM, 

and visibility impairment. An integrated 

assessment of the impact controls have 

on ozone, PM2.5, and regional haze 

provides safeguards to ensure that 

optimal emission reduction strategies 

are developed for the three programs to 

the extent possible. States that 

undertake multi-pollutant assessments 

as part of their attainment 

demonstration should assess the impact 

of their PM2.5 strategies on visibility and 

ozone, or perform a consistent analysis 

for PM2.5,visibility, and ozone. To 

facilitate such an effort, EPA encourages 

States to work closely with established 

regional haze Regional Planning 

Organizations (RPOs) and the 

jurisdictions responsible for developing 

ozone implementation plans. 

6. Which Future Year(s) Should be 

Modeled? 

The concept of simultaneously 

modeling control impacts on PM2.5, 

regional haze, and ozone may be further 

facilitated by the alignment of the 

implementation process for ozone, 

regional haze, and PM2.5. To the extent 

that dates for attainment demonstration 

SIPs coincide, the practicality of using 

common data bases and analysis tools 

for all three programs becomes more 

viable and encourages efficient use of 

resources. 

66010 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

58Memorandum of March 28, 2002, from Lydia N. 

Wegman and J. David Mobley, re: ‘‘Mid-Course 

Review Guidance for the 1-Hour Ozone 

Nonattainment Areas that Rely oin Weight-ofEvidence for Attainment Demonstration.’’ Located 

at URL: http://www.epa.gov/scram001/guidance/ 

guide/policymem33d.pdf. 

59EPA issued general guidance for moderate 

PM10 nonattainment areas in the General Preamble 

on CAA Title I provisions, published April 16, 

1992, at 57 FR 13498. (See 57 FR 13539). Further 

guidance by EPA (published August 16, 1994 at 59 

In some cases the attainment dates for 

areas that are classified as 

nonattainment for both the 8-hour ozone 

NAAQS and the PM2.5 NAAQS will 

coincide. In other cases they may differ 

by one or more years. The choice of the 

future modeling year should take into 

account the local attainment dates for 

PM2.5 and ozone as well as the 

attainment dates of nearby 

nonattainment areas within the State 

and/or nearby areas or regions. Where 

possible, future modeling years should 

be coordinated so that a single year can 

be used for both PM2.5 and ozone 

modeling. This coordination will help 

to reduce resources expended for 

individual modeling applications for 

PM2.5 and ozone and will facilitate 

simultaneous evaluation of ozone and 

PM impacts. 

Although there is some flexibility in 

choosing the future year modeling time 

periods, unless the State believes it 

cannot attain the standards within five 

years of the date of designation and 

must request an attainment date 

extension, the choice of modeling years 

for PM2.5 cannot go beyond the initial 

five year attainment period. For 

example, if a nonattainment area has an 

ozone nonattainment date that is 

beyond the 5 year PM2.5 period, the area 

cannot show attainment of the PM2.5

NAAQS by modeling the later ozone 

attainment date. In this case, the State 

could model an earlier year for both 

PM2.5 and ozone. 

Attainment date extensions will only 

be granted under certain circumstances. 

Among other things, the State must 

submit an attainment demonstration 

showing that attainment within 5 years 

of the designation date is impracticable. 

Section III.C. includes further 

discussion on attainment date issues. 

Further details on choosing future 

modeling years is contained in EPA’s 

draft modeling guidance. Further 

revisions to the guidance are expected 

to address the needed flexibility in 

choosing future modeling years. 

7. Mid-Course Review 

A MCR is a process by which the 

State assesses whether a nonattainment 

area is or is not making sufficient 

progress toward attainment of the PM2.5

standards, as predicted in its attainment 

demonstration. Such a review would 

evaluate the most recent monitoring and 

other data to assess whether the control 

measures relied on in a State’s 

attainment demonstration have resulted 

in adequate improvement in air quality. 

In reviewing each attainment 

demonstration, EPA will assess on a 

case-by-case basis whether a MCR 

would be needed. EPA will consider a 

number of factors in making this 

determination, including: The length of 

time to the proposed attainment date; 

the supporting information provided in 

the attainment demonstration; and 

uncertainties associated with future 

projections of pollutant emissions, air 

quality levels, and related information. 

Where EPA finds that a MCR would 

be required, the approval of the 

demonstration would be contingent on 

a commitment from the State to conduct 

the MCR. For such cases, the EPA 

believes that a commitment to perform 

a MCR is a critical element in an 

attainment demonstration that employs 

a long-term projection period. Because 

of the uncertainty in long term 

projections, EPA believes such 

attainment demonstrations should 

contain provisions for periodic review 

of monitoring, emissions, and modeling 

data to assess the extent to which 

refinements to emission control 

measures are needed. 

In reviewing individual attainment 

demonstrations, EPA will give 

particular consideration to requiring a 

MCR for areas that are granted an 

extension of their attainment date of two 

years or more beyond the first five year 

period. For areas where the effective 

date of designations is April 2005, the 

MCR requirement would then apply to 

areas with attainment date extensions to 

April 2012 to April 2015. The EPA 

would require submittal of the MCR 

within five years of the effective date of 

designations. 

The procedure for performing a MCR 

contains three basic steps: (1) 

Demonstrate whether the appropriate 

emission limits and emission reduction 

programs that were approved as part of 

the original attainment demonstration 

and SIP submittal were adopted and 

implemented; (2) analyze available air 

quality, meteorology, emissions and 

modeling data and document relevant 

findings; and (3) document conclusions 

regarding whether progress toward 

attainment is being made using a weight 

of evidence determination. This 

determination may or may not include 

new modeling analyses. 

The EPA does not request that States 

commit in advance to adopt new control 

measures as a result of the MCR process. 

Based on the MCR, however, if EPA 

determines that sufficient progress has 

not been made, EPA would determine 

whether additional emissions 

reductions are necessary from the State 

or States in which the nonattainment 

area is located, or from upwind States, 

or both. The EPA would then require 

the appropriate State or States to adopt 

and submit the new measures within a 

specified period. The EPA anticipates 

that these findings would be made as 

calls for SIP revisions under section 

110(k)(5), and therefore the period for 

submission of the measures would be no 

longer than 18 months after the EPA 

finding. Thus, States must complete the 

MCR three or more years before the 

applicable attainment date to ensure 

that any additional controls that may be 

needed can be adopted in sufficient 

time to reduce emissions by the 

attainment year. 

A number of States previously 

participated in a consultative process 

with EPA which resulted in the 

development of the 1-hour ozone MCR 

guidance.58 If a MCR will be required 

for certain PM2.5 nonattainment areas, 

separate PM2.5 MCR guidance will be 

written to address the specific 

requirements of PM2.5 nonattainment 

areas. 

G. What Requirements for RFP Apply 

Under the PM2.5 Implementation 

Program? 

1. Background 

Section 172(c)(2) provides that 

nonattainment area plans ‘‘shall require 

reasonable further progress.’’ Section 

171(1) defines ‘‘reasonable further 

progress,’’ as ‘‘such annual incremental 

reductions in emissions of the relevant 

air pollutant as are required by this part 

or may reasonably be required by the 

Administrator for the purpose of 

ensuring attainment of the applicable 

national ambient air quality standard by 

the applicable date.’’ This section 

presents how EPA will implement the 

RFP requirement, and it proposes the 

criteria by which EPA will judge State 

submittals addressing this requirement. 

The approaches proposed here should 

ensure emissions reductions on a path 

towards attainment which will yield an 

incremental improvement in air quality, 

while being sufficiently flexible to 

accommodate the range of control 

strategies necessary to address the 

complex mixtures of pollutants 

comprising PM2.5 in different areas. 

EPA has previously described its 

interpretation of RFP requirements 

applicable to particles with a nominal 

aerodynamic diameter of 10 

micrometers and smaller (PM10).59 The 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66011 

FR 41997) described RFP requirements for serious 

PM10 nonattainment areas. (See 59 FR 42015.) 

60Memorandum of November 18, 2002, from 

Lydia Wegman and Peter Tsirigotis, ‘‘2002 Base 

Year Emission Inventory SIP Planning: 8-hr Ozone, 

PM2.5 and Regional Haze Programs.’’ This document 

is available at the following web site: http:// 

www.epa.gov/ttn/oarpg/t1/memoranda/ 

2002bye_gm.pdf. 

61Section 172(a)(2)(A) allows EPA to provide 

extensions of 1 to 5 years based on an adequate 

demonstration by the State. Attainment deadline 

extensions under section 172(a)(2)(C), which extend 

the attainment deadline by up to a total of 2 

additional years to confirm preliminary monitoring 

data indicating attainment, would not trigger the 

requirement for the second RFP plan. 

guidance for serious PM10

nonattainment areas included extensive 

discussion of the need for incremental 

reductions to provide RFP. According to 

the criteria described in that guidance, 

PM10 nonattainment areas are expected 

to implement an ongoing series of 

measures providing steady progress 

toward attainment. It is important that 

reductions needed to attain the 

standards not be achieved only in the 

last year or two prior to the attainment 

date. The EPA believes that these 

principles should also apply in 

achieving RFP for the PM2.5 standards. 

2. What Is the Baseline Year From 

Which States Will Track Emission 

Reductions for Meeting RFP 

Requirements? 

EPA issued a memorandum 

identifying 2002 as the appropriate 

emission inventory base year for 

purposes of addressing the RFP and SIP 

planning requirements under the 

implementation programs for the 8-hour 

ozone and the PM2.5 standards.60 The 

EPA selected 2002 as the appropriate 

inventory base year for RFP and 

attainment demonstration purposes for 

several reasons. First, the inventory for 

2002 will be the most recently available 

consolidated emissions inventory 

available at the time EPA promulgates 

PM2.5 designations. Under the 

‘‘Consolidated Emissions Reporting 

Rule’’ (June 10, 2002, 67 FR 39602), 

emissions inventories are required every 

three years, including the years 2002 

and 2005. 

Second, with a 2002 base year, States 

will receive credit for reductions from 

the 2002 base year forward. The policy 

provides an incentive for State and local 

agencies to achieve early emissions 

reductions, and it gives appropriate 

credit for projected future reductions 

from certain already-adopted national, 

regional, and local measures. Third, 

EPA designated nonattainment areas 

based on air quality data for the 2001 to 

2003 period. Emissions inventories for 

2002 should be representative of the 

period on which States and EPA 

establish nonattainment area 

designations. For all these reasons, EPA 

proposes that the base year inventory for 

attainment and RFP planning should be 

2002. 

3. How Does EPA Propose to Address 

the Pollutants Associated With PM2.5 in 

these RFP Requirements? 

Ambient PM2.5 is a complex mixture 

containing multiple components. In 

many areas more than half of the PM2.5

mass collected by speciation monitors 

arises not from direct particle emissions 

but rather from emissions of precursors 

that undergo atmospheric 

transformation into particles. Section 

II.E. takes comment on options for 

addressing PM2.5 precursors, and the 

pollutants required to be addressed in 

RFP plans will be determined in the 

final rule. As proposed, the pollutants 

that are to be addressed in all RFP plans 

for PM2.5 are direct PM2.5 (including 

organic carbon, elemental carbon, and 

crustal material), sulfur dioxide, and 

nitrogen oxides. Ammonia and/or VOCs 

should be addressed in the RFP plan if 

ammonia and/or VOC emission 

reduction strategies are included in the 

attainment demonstration. 

4. What Areas Must Submit an RFP 

Plan? 

Under this proposed RFP approach, 

an area’s RFP requirement would be 

considered to be met if its attainment 

demonstration (due by April 2008) 

shows that the area will attain the 

standards within 5 years of its 

nonattainment designation (i.e. by April 

2010). An area submitting an attainment 

demonstration indicating that it will not 

attain by April 2010 must submit an 

RFP plan by April 2008 along with its 

attainment demonstration. The RFP 

plan must show how the area will make 

reasonable progress toward attainment 

with periodic 3-year milestones. 

Subsection (a) discusses areas projected 

to attain by April 2010. Subsection (b) 

discusses areas projected to attain after 

April 2010. 

a. Areas Projected To Attain Within 5 

Years of Designation 

Under this option, an area that the 

State projects will attain within five 

years of designation (i.e. April 2010) 

will be considered to have met the RFP 

requirement through submission of all 

regulations and emissions reductions 

necessary to demonstrate attainment as 

expeditiously as practicable. For such 

areas, attainment-level emissions must 

be achieved during 2009. It would be 

assumed that adequate interim progress 

is already being made in the area since 

the area would be projected to attain 

within a relatively short period of 

time—only two years from the date of 

SIP submittal. This option provides a 

flexible interpretation of RFP (‘‘annual 

incremental emission reductions’’) in 

order to minimize additional regulatory 

burden on State and local agencies. It is 

consistent with the approach taken for 

‘‘subpart 1 areas’’ in the implementation 

rule for the 8-hour ozone program. How 

a State projects that an area will attain 

the standards within five years is a 

critical issue in implementing this 

approach and one on which EPA seeks 

comment. For example, should State 

projections of attainment be based on 

regional modeling conducted for major 

regulatory analyses (such as for CAIR), 

or should State projections only be 

based on local modeling analyses 

performed with a finer grid resolution 

and more refined local emission 

inventory inputs? EPA proposes that 

States must follow the Agency’s most 

recent modeling guidance for PM2.5

implementation in developing such 

projections. Section III.F. includes an 

in-depth discussion about modeling 

guidance and attainment 

demonstrations, and it requests 

comment on a number of related issues. 

b. Areas Projected To Attain More Than 

5 Years From the Date of Designation 

Must Submit a 2008 RFP Plan 

Under this approach, EPA proposes 

that for any area for which the State 

submits an attainment demonstration in 

April 2008 requesting an attainment 

deadline extension beyond April 

2010,61 the state also must submit an 

RFP plan along with the area’s 

attainment plan. This 2008 RFP plan 

must show that the area will achieve 

generally linear progress according to 

emission reduction milestones the State 

establishes for 2010 and every 3 years 

thereafter until the attainment year. Just 

as attainment is determined by 

evaluating air quality data for previous 

years, compliance with an RFP 

milestone would be determined by 

evaluating emissions from the previous 

year. Thus, any reference to an RFP 

milestone in this section refers to 

annual emissions levels achieved during 

the previous year and prior to January 

1 of the milestone year. 

The following sections III.G.4.b.i. 

through III.G.4.b.iv. describe the 

proposed 2008 RFP plan option under a 

scenario where there is no classification 

system. Section III.G.4.b.v. discusses a 

potential 2008 RFP plan approach for 

‘‘serious’’ areas under a two-tiered 

classification system. As described in 

66012 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

section III.A., a serious area would be 

one that could not demonstrate that it 

would attain the standards within the 

first five years after designation, or one 

with a design value above a particular 

threshold. 

i. For purposes of the 2008 RFP plan, 

how should a nonattainment area define 

its emission reduction milestones? 

The deadline for submittal of the 2008 

RFP plan is the same as the deadline for 

submittal of the attainment plan, i.e. 

three years after designations. In 

developing their RFP plans and 

emission reduction targets for specific 

nonattainment areas, States should use 

the emission inventories and air quality 

modeling they have completed for 

attainment planning purposes. EPA 

expects the attainment plan would 

define several elements of the 2008 RFP 

plan. First, the attainment plan will 

define the pollutants that are to be 

reduced for attaining the standards. 

Second, the attainment plan will define 

the relationship between emissions 

reductions and air quality improvement, 

including identifying the emissions 

reductions by pollutant which are 

needed to attain the standard. Third, the 

attainment plan will define the expected 

attainment year, thereby defining the 

number of years over which the 

reductions leading to attainment must 

occur. 

EPA proposes that the 2008 RFP plan 

must provide emission reduction and 

program implementation milestones to 

be achieved by January 1, 2010 (based 

on the 2009 emissions year), and, if 

necessary, milestones to be achieved by 

January 1, 2013 (based on the 2012 

emissions year). As part of the plan, the 

State also should include a motor 

vehicle emissions budget for each 

milestone year. The motor vehicle 

emissions budget should only apply to 

emissions attributed to vehicles in the 

nonattainment area. (See section III.K. 

for further discussion of transportation 

conformity issues.) 

Under Section 172(a)(2)(A), EPA may 

extend the attainment deadline to as late 

as April 2015 (for areas where the 

effective date of designations is April 

2005), based on an acceptable 

demonstration. Thus, 2014 is the latest 

year in which attainment level 

emissions are to be achieved. The EPA 

proposes to define RFP as emissions 

reductions that would be estimated to 

provide generally linear progress toward 

attainment from the 2002 base year 

emissions to the emissions year prior to 

the attainment date. The States have 

flexibility in meeting RFP goals with 

alternative emission reduction and air 

quality improvement scenarios. 

An important element of establishing 

appropriate RFP milestones for 

addressing PM2.5 is establishing the 

relative degrees of control of various 

pollutants. The following subsection 

describes how EPA proposes to assure 

that the plans provide for the necessary 

air quality improvement and yet provide 

flexibility for addressing a variety of 

situations of relative feasibility and 

significance of controlling various 

pollutants. 

ii. For what pollutants must States 

reduce emissions? 

One approach for achieving RFP is to 

address all pollutants, including direct 

PM and all precursors, on the same 

timetable. However, EPA recognizes that 

different control measures address 

different pollutants, and States can 

implement some measures more quickly 

than others. Therefore, EPA’s proposal 

for 2008 RFP plan requirements 

includes two components: (1) A 

benchmark set of pollutant reductions 

that establish the overall level of control 

that the 2010 milestones must provide; 

and (2) an equivalency process that 

allows States the flexibility to address 

different pollutants according to 

different schedules so long as the EPA 

finds the net air quality improvements 

to be equivalent. 

The RFP benchmark reflects 

reductions only for those pollutants that 

the State intends to reduce in the 

attainment plan, subject to EPA 

approval. Pollutants that are not subject 

to control measures in the attainment 

plan, either because of insignificant 

benefits in reducing ambient PM2.5

concentrations or because of availability 

or feasibility of control, are not included 

in the RFP benchmark for 2008 RFP 

plan purposes. 

EPA proposes that States should 

define RFP benchmark emission 

reduction levels in each area to reflect 

generally linear progress toward 

attainment. Consider an example for a 

particular area in which the State 

proposes an April 2013 attainment date 

and thus would need to achieve 

attainment level emissions in 2012. If 

the attainment plan calls for a 20 

percent reduction in SO2 emissions 

from 2002 levels and a 10 percent 

reduction in PM2.5 direct emissions, 

then the RFP benchmark for SO2 would 

reflect roughly a 2 percent reduction in 

SO2 emissions per year, and the 

benchmark level for PM2.5 would be 

roughly a 1 percent reduction per year. 

The 2010 milestones in this example 

would be about a 14 percent reduction 

in annual SO2 emissions and a 7 percent 

reduction in PM2.5 direct emissions to 

be achieved during 2009 (the emissions 

year prior to the January 1, 2010 

milestone date). 

EPA proposes that States must 

provide 2010 RFP milestones that 

provide air quality improvement 

equivalent to this RFP benchmark. The 

next subsection describes the process 

EPA is proposing to use to assess 

whether alternative timetables for 

controlling various pollutants are 

equivalent. 

iii. How should States assess the 

equivalence of alternative combinations 

of pollutant emissions reductions? 

EPA proposes to judge an alternative 

combination of pollutant emissions 

reductions as being at least equivalent to 

the RFP benchmark (e.g., emissions 

reductions to be achieved from 2002 to 

the January 1, 2010 milestone) if the 

State makes an adequate showing that 

the alternative will provide estimated 

air quality improvements that are 

roughly the same as those that the 

benchmark emission reductions would 

provide. If the State elects to follow this 

approach, it must provide in its 2008 

RFP plan the information necessary to 

assess whether an alternative set of 

emissions reductions is generally 

equivalent to the RFP benchmark 

reduction levels. The attainment plan 

will define a set of emissions reductions 

and analyze the corresponding expected 

air quality improvements. For example, 

attainment plans that include 

reductions in SO2 emissions will 

include modeling and an attainment 

demonstration which assess the 

corresponding reduction in sulfate 

concentrations. States should use this 

information to evaluate the equivalence 

of alternative combinations of pollutant 

emissions reductions. 

EPA recommends that States estimate 

air quality improvements associated 

with intermediate emission control 

levels by assuming that the same 

relationship between emissions and air 

quality applies at intermediate levels as 

would apply at attainment plan levels. 

For the purpose of developing their 

2010 RFP milestones, States should 

assume that by January 1, 2010, a given 

fraction of the emissions reductions in 

the attainment plan (i.e. the fraction 

being the percent of reductions to be 

achieved by the 2010 milestone) will 

achieve the same fraction of the 

associated air quality benefits in the 

attainment plan. An example in the next 

section further explains this point. 

EPA recognizes that because 

atmospheric processes are quite 

complex, a specific percent change in 

emissions typically does not lead to an 

equivalent percent change in air quality. 

This non-linear relationship introduces 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66013 

uncertainties as to whether alternate 

RFP plans will in fact achieve 

equivalent benefits. Nevertheless, EPA 

believes that it is important to provide 

the flexibility to address different 

pollutants on different timetables so 

long as the plan can reasonably be 

expected to achieve the intended air 

quality benefits at the RFP benchmark 

level. In general, EPA does not intend to 

require dispersion modeling specifically 

to assess whether an alternative 

approach to meeting RFP provides 

equivalent air quality benefits as the 

benchmark definition. The attainment 

plan modeling addresses the 

nonlinearities at attainment levels, and 

EPA believes for RFP plan purposes that 

the relationship between emissions and 

air quality at attainment levels provides 

an adequate approximation of the 

relationship at RFP levels. 

EPA anticipates that RFP plans will 

generally only control pollutants that 

are also controlled in the attainment 

plan. Therefore, EPA expects the 

attainment plan to include information 

on the emissions-air quality relationship 

for all pollutants included in the RFP 

plan. If a case arises where the RFP plan 

reduces emissions for a pollutant that is 

not reduced in the attainment plan, the 

State may need to conduct additional 

modeling to assess the air quality 

benefit of the relevant component of the 

RFP plan to support its demonstration 

of equivalence with the RFP benchmark. 

iv. How would RFP be evaluated for a 

sample 2008 RFP plan? 

As an example, suppose that the 

attainment plan for ‘‘Kleenare City’’

projects that the area will attain the 

standards with a 20 percent reduction in 

SO2 emissions, 20 percent reduction in 

nitrogen oxide emissions, and a 10 

percent reduction in direct PM2.5

emissions. (For the purpose of 

simplifying this example, assume that 

direct PM2.5 emissions are principally 

comprised of organic and elemental 

carbon.) The area’s plan projects that, 

consistent with the requirement to 

attain as expeditiously as practicable, 

the area would attain by April 2013 

based on reductions achieved during 

2012. Under EPA’s proposal, the RFP 

benchmark levels should reflect roughly 

1⁄10 of the emission reduction for each 

pollutant each year. Thus, for the ten 

year period from 2002–2012, this 

roughly equates to a 2.0 percent annual 

reduction in SO2 emissions, 2.0 percent 

annual reduction in nitrogen oxide 

emissions, and 1.0 percent annual 

reduction in direct PM2.5 (carbon) 

emissions per year. The January 1, 2010 

milestones should then include 7⁄10 of 

the progress from 2002 conditions 

through 2009 (the emissions year prior 

to the milestone). Thus, the 2010 RFP 

benchmark would have emission levels 

reflecting a 14 percent reduction of SO2

emissions, a 14 percent reduction of 

nitrogen oxide emissions, and a 7 

percent reduction of direct PM2.5

(carbon) emissions. 

Unless the State sets RFP emission 

reduction milestones for 2010 identical 

to (or greater than) the RFP benchmark, 

the next step is to assess the air quality 

improvement estimated for the RFP 

benchmark and the air quality 

improvement estimated for the State’s 

alternative milestones. Both assessments 

would rely on the relationship between 

emissions reductions and air quality 

improvement for the various pollutants 

addressed in the attainment plan. 

This example assumes that Kleenare 

City has the concentrations of PM2.5

constituents described in the above 

example, the attainment plan described 

in the paragraph above, and the 

expectation of achieving attainment 

level emissions by 2012 (i.e., a 2013 

attainment deadline). Thus, the design 

value for the area is 17.0 μg/m3, 

consisting of 7.0 μg/m3 of ammonium 

sulfate, 6.0 μg/m3 of carbonaceous PM 

(e.g. organic and elemental carbon), and 

4.0 μg/m3 of ammonium nitrate. Assume 

further that the attainment plan as 

described just above demonstrates 

relative reduction factors which indicate 

the following impacts: The 20 percent 

SO2 emission reduction is expected to 

reduce ammonium sulfate 

concentrations by 1.2 μg/m3; the 10 

percent reduction in direct PM2.5

emissions is expected to reduce direct 

PM2.5 concentrations (assume this 

component is primarily organic and 

elemental carbon) by 0.4 μg/m3; and the 

20 percent NOX emission reduction is 

expected to reduce nitrate 

concentrations by 0.6 μg/m3. 

As calculated above, the RFP 

benchmark levels for 2010 would 

include 7⁄10 of the emissions reductions 

planned through 2012, which would be 

expected to achieve at least 7⁄10 of the 

associated air quality improvement 

expected in the attainment plan. Thus, 

the 2010 RFP benchmark levels would 

be expected to reflect the following 

estimated air quality improvement: the 

20 percent SO2 emission reduction 

would yield an estimated [1.2 * (14 

percent / 20 percent)] or 0.84 μg/m3

ammonium sulfate reduction, the 8 

percent direct PM2.5 (carbon) emission 

reduction would yield an estimated [0.4 

* (7 percent / 10 percent)] or 0.28 μg/ 

m3 carbon particle reduction, and the 20 

percent NOX emission reduction would 

yield an estimated [0.6 * (14 percent / 

20 percent)] or 0.42 μg/m3 ammonium 

nitrate reduction. The total air quality 

improvement of this 2010 benchmark 

plan would be estimated as (0.84 + 0.28 

+ 0.42), or 1.54 μg/m3. Thus, for this 

example, the target air quality level for 

the 2007–9 period would be 

approximately 15.5 μg/m3 (17.0 ¥ 1.54 

= 15.46). 

Now suppose that the State is 

considering phasing in emission 

reduction strategies such that by the 

2010 milestone date, SO2 emissions 

would be reduced by only 10 percent, 

direct organic and elemental carbon 

particle emissions would be reduced by 

the full 10 percent (as included in the 

attainment plan), and NOX emissions 

would be reduced by the full 20 percent. 

This alternative would be estimated to 

achieve air quality improvement that 

includes [1.2 * (10 percent / 20 percent)] 

or 0.6 μg/m3 ammonium sulfate 

reduction, [0.4 * (10 percent / 10 

percent)] or 0.4 μg/m3 carbon particle 

reduction, and [0.6 * (20 percent / 20 

percent)] or 0.6 μg/m3 ammonium 

nitrate reduction. The total air quality 

improvement of this 2010 milestone 

alternative would be estimated to be (0.6 

+ 0.4 + 0.6) or 1.6 μg/m3 reduction in 

PM2.5 concentrations. Since this 

estimated air quality improvement 

exceeds the improvement estimated for 

the 2010 RFP benchmark level, EPA 

would judge this set of milestones to be 

considered equivalent to the 2010 RFP 

benchmark levels. 

v. What potential RFP requirements 

could apply for ‘‘serious’’ areas under 

the two-tiered classification option? 

As described in section III.A. on 

classification options, a serious area 

would be one that could adequately 

demonstrate that attainment of the 

standards ‘‘as expeditiously as 

practicable’’ would not be within the 

first five years after designation, and 

therefore would receive an attainment 

date extension of 1 to 5 years. Under the 

two-tiered classification option, a 

serious area would be subject to more 

stringent requirements in return for the 

attainment date extension. The 

classifications section III.A. takes 

comment on possible ‘‘more stringent’’ 

requirements for serious areas, 

including prescriptive RFP 

requirements and/or lower thresholds 

for RACT review (under one RACT 

option presented in section III.I.5 of this 

package). 

One possible RFP approach 

contemplated in the classifications 

discussion is a fixed percentage 

reduction of the emissions of direct 

PM2.5 and regulated PM2.5 precursors to 

be achieved in specified milestone years 

between the 2002 base year and the 

66014 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

62Memorandum of December 29, 1997 from 

Richard D. Wilson to Regional Administrators, 

Regions I–X re ‘‘Guidance for Implementing the 1- 

Hour Ozone and Pre-Existing PM10 NAAQS.’’

Located at URL: http://www.epa.gov/ttn/oarpg/t1/ 

memoranda/iig.pdf-. This policy recognized that 

VOC emissions up to 100 km and NOX emissions 

up to 200 km from the nonattainment area could be 

relied on for RFP. The specified distances resulted 

from discussions of the FACA Subcommittee on 

Ozone, PM, and Regional Haze Implementation 

Programs. Because some stakeholders have 

expressed concerns about this policy, EPA is in the 

process of subjecting this policy to a technical 

review and may revise it in light of that review. 

attainment year proposed in the 

attainment demonstration. This 

approach would be patterned after the 

rate of progress requirement in section 

182 for ozone, which requires a 3 

percent per year average emission 

reduction of VOC for certain areas, with 

emission reduction targets to be met 

every three years (i.e., a 9 percent 

reduction over three years). The EPA 

could formulate this alternative either 

with the same 3 percent average annual 

emission reduction as specified in 

section 182 or with some other more 

appropriate percentage. Use of a fixed 

percentage reduction target would be 

consistent with the congressional intent 

behind the section 182 requirement to 

require additional emission reduction 

actions in areas with more serious air 

quality problems. 

This approach could require a strict 

percentage reduction of each pollutant, 

or it could allow the States flexibility to 

employ a different mix of pollutant 

reduction percentages in order to 

achieve an equivalent air quality 

improvement as would be achieved 

under the fixed percentage approach. 

Section III.G.5.b.iii. above provides 

guidance on how to demonstrate 

equivalency in this type of situation. 

Under this option, RFP plans would 

be submitted in April 2008 along with 

attainment plans. RFP milestones would 

be established for 2010 and, in the case 

of areas with later attainment dates, 

2013. The application of the percent 

reduction concept is relatively straight 

forward. For example, under a 3 percent 

per year RFP emission reduction 

requirement for an area with an 

attainment date extension to 2015, the 

area’s 2010 emission reduction 

milestone would reflect a 21% 

reduction (i.e. 3% per year × 7 years 

from 2002 through 2009) in emissions of 

regulated PM2.5 pollutants. For a 2013 

milestone (e.g. reductions through 

2012), a 30% emission reduction would 

be required (3% per year × 10 years 

from 2002 to 2012). The requirement for 

RFP between 2013 and the attainment 

date would be satisfied by the 

reductions needed for attainment. 

As with the basic RFP approach 

proposed above, all emissions 

reductions since 2002 from federal, 

regional, state and local measures would 

be creditable toward meeting the RFP 

targets. These would include, for 

example, substantial reductions from 

CAIR, federal motor vehicle emissions 

standards and other federal rules. 

Overall, we believe there would be 

merit in establishing a more stringent 

RFP requirement under any option for 

serious areas. An advantage of the fixed 

percentage approach may be that it 

would be easier to implement and 

communicate to the public. EPA 

requests comment on the use of a fixed 

percentage requirement for serious areas 

and on what is an appropriate annual 

percentage reduction rate for PM2.5 and 

associated precursors. 

5. Other RFP Issues 

a. How should States account for 

regional control strategies in evaluating 

RFP? 

States should consider all adopted, 

enforceable control programs in 

evaluating whether RFP is being 

achieved, including national measures, 

regional measures, and local measures. 

National programs established by EPA 

include the Clean Air Interstate Rule 

addressing SO2 and NOX emissions in 

the eastern U.S., eastern NOX reductions 

from power plants and other sources to 

address the ozone standards (the ‘‘NOX

SIP call’’), and a variety of motor vehicle 

limitations, including the phase-in of 

emission limits as new vehicles replace 

older vehicles through fleet turnover. 

More recent mobile source rules include 

limits for new heavy-duty diesel engines 

starting in 2004, considerably more 

stringent diesel engine limits starting in 

2007, emission limits for new gasoline 

vehicles (‘‘Tier II’’) starting in 2004, 

limits on the sulfur content of gasoline 

and diesel starting in 2004 and 2006, 

respectively, and limits on nonroad 

vehicle emissions. Expressed more 

generally, States should base the 

evaluation of RFP simply on the 

enforceable emissions for the area, 

regardless of what mix of adopted 

control programs and other influences 

lead to the applicable emissions level. 

The guidance for PM2.5 differs 

somewhat in this respect from the 

guidance for ozone. For ozone, CAA 

section 182(b)(1)(D) specifies several 

types of measures that may not be 

credited toward achievement of the 

ozone rate of progress requirements. 

These restrictions are only mandated by 

the statute with respect to pre-1990 

controls for ozone. The Act does not 

provide any such requirement with 

respect to controls for PM. 

b. What geographic area should States 

address in RFP plans? 

Another important issue is the 

geographic area to be addressed in the 

RFP plan. As discussed above, EPA 

believes the CAA RFP provision 

requires emissions reductions that will 

provide steady improvement in air 

quality in the nonattainment area prior 

to its attainment date. This suggests that 

RFP requirements should apply within 

a geographic area from which emissions 

substantially affect air quality in the 

nonattainment area. This geographic 

area may differ for different pollutants 

that contribute to PM2.5 levels. The EPA 

also envisions approaching this issue 

differently for the reasons described 

below. 

EPA proposes an approach based on 

EPA’s views of the typical emissions 

area that most strongly correlates with 

associated components of urban PM2.5

concentrations. Since different 

prospective nonattainment areas have 

different types of PM2.5 problems, some 

areas may warrant use of different 

geographic areas from the defaults 

presented here. For example, a 

mountain valley area in which 

concentrations are dominated by local 

emissions regularly trapped in 

inversions should address all pollutants 

on a nonattainment area basis and not 

on a statewide basis. 

EPA is proposing default areas of 

consideration for emissions of direct 

PM2.5, NOX, and SO2. For direct PM2.5

emissions, including emissions of 

elemental carbon, organic particles and 

inorganic particles such as metals and 

crustal material, emissions from within 

the nonattainment area should be 

considered for tracking compliance with 

RFP milestones. Particles that originate 

from direct PM2.5 emissions tend to be 

dominated by nearby emissions. While 

the greatest impact at a monitoring 

location may arise from sources within 

a few kilometers, a nonattainment areawide approach assures that the entire 

area is achieving RFP. A nonattainment 

area-wide approach also will generally 

be easier to administer in conjunction 

with other requirements such as RACT 

and RACM. EPA does not believe that 

direct PM2.5 emissions from sources 

outside the nonattainment area should 

be considered for RFP purposes. 

The proposed approach for 

considering NOX and SO2 emissions for 

RFP under the PM2.5 program is similar 

to the approach for addressing NOX

emissions in past guidance for 1-hour 

ozone rate of progress plans.62 The 

ozone guidance provides that in their 

RFP baseline inventories, States at a 

minimum are required to include all 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66015 

63Under this option, sources outside the 

nonattainment area would exclude on-road sources 

since under the transportation conformity program, 

motor vehicle emissions budgets apply only within 

the nonattainment area. 

sources of NOX and VOC emissions 

from within the nonattainment area. 

The ozone guidance also provides that 

States may include in RFP plans certain 

NOX sources located up to 200 

kilometers outside of an ozone 

nonattainment area and certain VOC 

sources located 100 kilometers outside 

of an ozone nonattainment area and take 

credit for emission reductions from 

these sources for RFP purposes. EPA 

believes that for the PM2.5 program, it 

would be appropriate to allow for the 

possibility of crediting SO2 and NOX

reductions outside the nonattainment 

area because numerous technical 

studies have generally demonstrated the 

long-range transport of sulfates and 

nitrates. (See section II on the technical 

characterization of PM2.5.) As with 

ozone, EPA believes that ambient 

particle concentrations reflect a 

combination of effects from local as well 

as regional NOX and SO2 emissions, 

justifying an approach that focuses on 

nonattainment area NOX and SO2

emissions but also gives incentive for 

reductions outside the nonattainment 

area. 

However, because of various concerns 

expressed about such a policy for RFP 

purposes, any State proposing to take 

credit for reductions by any NOX or SO2

source located within 200 kilometers of 

the nonattainment area will need to 

include with its SIP submittal 

appropriate documentation 

demonstrating that emissions from the 

sources outside the nonattainment area 

contribute to fine particle 

concentrations within the 

nonattainment area. Because of the 

uncertainty associated with VOC 

contributions to PM2.5 concentrations, 

we do not believe it would be 

appropriate to extend the policy to VOC 

sources located 100 kilometers outside 

of a PM2.5 nonattainment area. If the 

State or EPA finds that VOC are a 

significant contributor to an area’s PM2.5

problem, RFP credit for VOC will be 

granted for reductions achieved within 

the nonattainment area only. 

As discussed earlier, the RFP plan 

should include a motor vehicle 

emissions budget for each milestone 

year. Because the transportation 

conformity program applies only within 

the nonattainment area, the RFP plan 

cannot take credit for motor vehicle 

direct PM2.5 and applicable PM2.5

precursor emissions reductions 

achieved outside of the nonattainment 

area. (See section III.K. for further 

discussion of transportation conformity 

issues.) 

The EPA expects that analyses 

conducted as part of the attainment 

demonstration will help identify the 

most appropriate geographic range of 

interest for each pollutant. EPA believes 

that if an area concludes that controls 

for a specific pollutant on an alternate 

geographic scale are more appropriate 

for reaching attainment, the area should 

use that same alternate geographic scale 

in assessing RFP. In particular, for each 

pollutant addressed, the same 

geographic scale must be used in 

analyzing the 2002 inventory, the 

attainment year inventory, and any RFP 

milestone year inventories, in order to 

assure that the milestones in fact 

represent RFP on a path to timely 

attainment. 

EPA solicits comments on other 

alternatives for the geographic coverage 

of NOX and SO2 inventories. The 

principal alternatives of interest are to 

be either more or less inclusive. EPA 

takes comment on (1) an approach that 

would allow the State to include a 

broader set of sources 63 located within 

200 kilometers of the nonattainment 

area, and (2) an approach including all 

nonattainment area sources but no 

additional sources outside the 

nonattainment area. 

c. How should RFP be addressed in 

multi-state nonattainment areas? 

In general, EPA seeks to ensure that 

nonattainment areas that include more 

than one State meet RFP requirements 

as a whole. States that share a 

nonattainment area should consult to 

assure that the collective set of emission 

reduction milestones provide for 

adequate emissions reductions to 

represent RFP for the area as a whole. 

The States should work with the EPA 

region or regions that oversee the SIPs 

for those States to confirm that their 

collective approach is acceptable for 

RFP. 

d. How should States compile emission 

inventories for RFP plans? 

In general, States should prepare 

emission inventories for RFP plans 

according to the same guidance that 

applies to emission inventories for 

attainment plans. Similar guidance on 

assessment of allowable emissions 

resulting from a new emission limit 

applies in both cases. Emission 

inventories for RFP plans should be 

adequate to track progress in meeting 

the annual standard in all areas. States 

should also develop inventories 

adequate to ensure progress in meeting 

the 24-hour standard for those areas that 

violate or are close to violating this 

standard. 

e. What RFP requirements apply in 

Tribal areas? 

Under the Tribal Authority Rule (40 

CFR 49.4), EPA found that it was not 

appropriate to treat Tribes in a manner 

similar to a State with regard to SIP 

schedules. This flexibility extends to 

submittal of plans for the RFP 

requirement. Because there are typically 

limited emissions in Tribal areas, this 

flexibility on RFP should not have 

significant impact on surrounding 

jurisdictions in most instances. 

However, the TAR also acknowledges 

that where the Tribes are unable to meet 

the requirements of the CAA, EPA will 

implement the program where it is 

‘‘necessary and appropriate’’. Therefore, 

in the event that flexibility in the RFP 

deadline for Tribes jeopardizes RFP in 

surrounding jurisdictions, EPA will 

work with the Tribes to ensure that 

emissions on Tribal lands are 

appropriately addressed. 

EPA guidance for nonattainment areas 

that include both State and Tribal lands 

is similar to guidance for multi-State 

nonattainment areas. States and Tribes 

that share a nonattainment area should 

consult to assure that the collective set 

of emission reduction milestones for the 

nonattainment area as a whole satisfy 

the requirements described above and 

thus provide for the steady air quality 

improvement intended under the CAA. 

f. What must States submit to show 

whether they have met RFP milestones? 

The establishment of milestones 

implies subsequent reporting 

demonstrating whether these milestones 

have been met. For example, the 

establishment in a 2008 RFP plan of 

milestones reflecting 2009 emissions 

implies reporting in 2010 whether these 

milestones were met. However, 

emissions for a given year are 

commonly not known until well after 

the year has ended. The EPA is 

evaluating alternative approaches to this 

issue and plans to issue guidance on 

this issue at a later date. 

H. What requirements for contingency 

measures should apply under the PM2.5

implementation program? 

For PM2.5, under Subpart I of the 

CAA, all nonattainment areas must 

include in their SIPs contingency 

measures consistent with section 

172(c)(9). Contingency measures are 

additional control measures to be 

implemented in the event that an area 

fails to meet RFP or fails to attain the 

standards by its attainment date. These 

contingency measures must be fully 

66016 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

64Under the TAR, requirements for RACT and 

RACM may be considered to be severable elements 

of implementation plan requirements for Tribes. 

65 In the context of the PM10 NAAQS, EPA has 

concluded, based upon the annual form of the 

standard, that ‘‘advancement of the attainment 

date’’ should mean an advancement of at least one 

calendar year. See: State Implementation Plans; 

General Preamble for the Implementation of Title I 

of the CAA Amendments of 1990; Proposed Rule.’’

April 16, 1992 (57 FR 13498). See also Sierra Club 

v. EPA, 294 F.3d 155 (DC Cir. 2002). 

adopted rules or control measures that 

are ready to be implemented quickly 

upon failure to meet RFP or failure of 

the area to meet the standard by its 

attainment date. The SIP should contain 

trigger mechanisms for the contingency 

measures, specify a schedule for 

implementation, and indicate that the 

measures will be implemented without 

significant further action by the State or 

EPA. The contingency measures should 

consist of other control measures for the 

area that are not included in the control 

strategy for the SIP. 

The April 16, 1992 General Preamble 

provided the following guidance: 

‘‘States must show that their 

contingency measures can be 

implemented with minimal further 

action on their part and with no 

additional rulemaking actions such as 

public hearings or legislative review. In 

general, EPA will expect all actions 

needed to affect full implementation of 

the measures to occur within 60 days 

after EPA notifies the State of its 

failure.’’ (57 FR at 13512.) This could 

include Federal measures and local 

measures already scheduled for 

implementation. 

The EPA has approved numerous SIPs 

under this interpretation—i.e., that use 

as contingency measures one or more 

Federal or local measures that are in 

place and provide reductions that are in 

excess of the reductions required by the 

attainment demonstration or RFP plan. 

(62 FR 15844, April 3, 1997; 62 FR 

66279, December 18, 1997; 66 FR 30811, 

June 8, 2001; 66 FR 586 and 66 FR 634, 

January 3, 2001.) The key is that the 

statute requires extra reductions that are 

not relied on for RFP or attainment and 

that are in the demonstration in order to 

provide a cushion while the plan is 

revised to meet the missed milestone. In 

other words, contingency measures are 

intended to achieve reductions over and 

beyond those relied on in the attainment 

and RFP demonstrations. Nothing in the 

statute precludes a State from 

implementing such measures before 

they are triggered. In fact, a recent court 

ruling upheld contingency measures 

that were previously required and 

implemented where they were in excess 

of the attainment demonstration and 

RFP SIP. See LEAN v. EPA, 382 F.3d 

575 5th Circuit, 2004. 

One basis EPA recommends for 

determining the level of reductions 

associated with contingency measures is 

the amount of actual PM2.5 emissions 

reductions required by the control 

strategy for the SIP to attain the 

standards. The contingency measures 

are to be implemented in the event that 

the area does not meet RFP, or attain the 

standards by the attainment date, and 

should represent a portion of the actual 

emissions reductions necessary to bring 

about attainment in area. Therefore, the 

emissions reductions anticipated by the 

contingency measures should be equal 

to approximately one year’s worth of 

emissions reductions necessary to 

achieve RFP for the area (See section 

III.G. for more detail on RFP 

requirements.) 

As stated previously, EPA believes 

that contingency measures should 

consist of other available control 

measures beyond those required to 

attain the standards, and may go beyond 

those measures considered to be RACM 

for the area. It is, however, important 

that States make decisions concerning 

contingency measures in conjunction 

with their determination of RACM for 

the area, and that all available measures 

needed in order to demonstrate 

attainment of the standards must be 

considered first; all remaining measures 

should then be considered as candidates 

for contingency measures. It is 

important not to allow contingency 

measures to counteract the development 

of an adequate control strategy 

demonstration. 

Contingency measures must also be 

implemented immediately after EPA 

determines that the area has either 

failed to meet RFP, or attain the 

standard by its attainment date. The 

purpose of the contingency measure 

provision is to ensure that corrective 

measures are put in place automatically 

at the time that EPA makes its 

determination that an area has either 

failed to meet RFP or failed to meet the 

standard by its attainment date. The 

EPA is required to determine within 90 

days after receiving a State’s RFP 

demonstration, and within 6 months 

after the attainment date for an area, 

whether these requirements have been 

met. The consequences for states which 

fail to attain or to meet RFP are 

described in section 179 of the Act. 

I. What requirements should apply for 

RACM and RACT for PM2.5

nonattainment areas? 

1. General Background 

Subpart 1 of section 172 of the Act 

includes general requirements for all 

designated nonattainment areas. Section 

172(c)(1) requires that each 

nonattainment area plan ‘‘provide for 

the implementation of all reasonably 

available control measures as 

expeditiously as practicable (including 

such reductions in emissions from 

existing sources in the area as may be 

obtained through the adoption, at a 

minimum, of reasonably available 

control technology), and shall provide 

for attainment of the national primary 

ambient air quality standards.’’ States 

are required to implement RACM and 

RACT in order to attain the standards 

‘‘as expeditiously as practicable.’’ 64 A 

RACM demonstration should show that 

there are no additional reasonable 

measures available that would advance 

the attainment date by at least one year 

or contribute to RFP for the area.65

This section first discusses issues 

associated with RACT, traditionally 

considered to be an independent 

stationary source control requirement, 

and then addresses issues associated 

with RACM. 

2. Background for RACT 

EPA’s historic definition of RACT has 

been the lowest emissions limitation 

that a particular source is capable of 

meeting by the application of control 

technology that is reasonably available, 

considering technological and economic 

feasibility. Because RACT is a control 

technology requirement and modeling 

techniques were not precise in the past, 

RACT has been considered to be 

independent of the need to demonstrate 

attainment. 

Section 172 (subpart 1) does not 

include specific applicability thresholds 

for the size of sources that should be the 

minimum starting point for RACT 

analysis, as are provided in subpart 2 

(ranging from 100 to 10 tons per year for 

ozone, depending on the level of 

nonattainment) or subpart 4 (either 100 

or 70 tons per year for PM10 depending 

on the level of nonattainment). Subpart 

1 also does not include a specific list of 

stationary source categories for which 

control techniques guidelines are to be 

developed. For PM10, the Act provided 

particular emphasis for specific sources 

of area emissions, but did not highlight 

specific stationary sources for the 

purposes of RACT. (Section 190 of the 

Act required EPA to develop RACM 

guidance documents for residential 

wood combustion, prescribed burning 

for forest management and agricultural 

activities, and for urban fugitive dust 

control.) Under subpart 2 for ozone, 

EPA has more specifically identified 

RACT for certain source categories 

through issuance of a number of control 

techniques guidelines (CTGs) and 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66017 

66Note that States are required to implement 

RACT only within the nonattainment area while it 

is proposed elsewhere in today’s proposal that 

States may use reductions from selected sources 

outside the nonattainment area to meet RFP 

milestones. 

alternative control techniques (ACTs) 

documents. 

3. Emissions Inventory Analysis 

Supporting RACT Options 

As supporting information for 

developing options for RACT for PM2.5, 

we have reviewed the 2001 National 

Emissions Inventory to examine both 

the size range of stationary sources and 

the types of sources that emit PM2.5 and 

its precursors. Because the statutory 

requirements for both PM10 and ozone 

are such that the RACT applicability 

threshold cannot be higher than a 

potential to emit 100 tons per year, we 

began our analysis by evaluating the 

national emissions inventory to identify 

sources of PM2.5 or any precursor which 

exceeded this threshold. Because 

information in the national emission 

inventory is expressed in terms of actual 

emissions rather than ‘‘potential’’

emissions, we used actual emissions 

information in this analysis as a 

surrogate for potential emissions 

thresholds. 

Our analysis of the national emissions 

inventory indicates that the mix of 

source categories responsible for PM2.5

and precursor emissions in potential 

PM2.5 nonattainment areas varies 

greatly. Contributing sources include 

stationary sources such as electricity 

generating units, industrial boilers, and 

oil refineries, as well as smaller mobile 

and area sources, such as diesel engines, 

solvent usage, and various types of 

burning activities. 

The analysis of point source 

emissions for stationary sources located 

in PM2.5 nonattainment areas shows that 

for each of the five main pollutants 

associated with PM2.5 (direct PM2.5, SO2, 

NOX, VOC, and ammonia), individual 

facilities with actual emissions greater 

than 100 tons per year of one of these 

pollutants account for a significant 

amount of the total emissions for all 

facilities in these areas. When the 

potential 70 and 50 ton per year 

thresholds are compared to the 100 ton 

per year threshold, the additional 

emissions coverage increases by 2 

percent or less for PM2.5, NOX, SO2, and 

ammonia. For VOC, the emissions 

coverage increases modestly, by about 9 

percent. 

In contrast, the number of facilities 

potentially covered at the 70 and 50 ton 

thresholds increase more significantly. 

When the number of facilities exceeding 

the 100 ton threshold for each pollutant 

is compared to the number of facilities 

exceeding the 70 ton threshold, the 

numbers of facilities increase from 10 

percent (ammonia) to 44 percent (VOC). 

When the number of facilities exceeding 

the 100 ton threshold for each pollutant 

is compared to the number of facilities 

exceeding the 50 ton threshold, the 

numbers of facilities increase by 24 

percent (SO2) to 90 percent (VOC). 

4. Which PM2.5 precursors must be 

addressed by States in establishing 

RACT requirements? 

As discussed earlier in this section on 

RACT and RACM and in the technical 

overview section, the precursors of 

PM2.5 are SO2, NOX, VOC, and 

ammonia. In section II.E., we discuss 

options for addressing these precursors 

under the PM implementation program. 

The EPA will finalize its precursor 

policy for PM implementation after 

considering public comment received 

on this proposal. 

5. What are the proposed options for 

implementing the RACT requirement? 

This section describes the approaches 

EPA is considering for implementation 

of the RACT requirement of section 

172(c)(1), to insure that States consider 

and adopt RACT measures for stationary 

sources in a way that is consistent with 

the overarching requirement to attain 

the standards as expeditiously as 

practicable, yet provides flexibility for 

States to focus regulatory resources on 

those sources of emissions that 

contribute most to local PM2.5

nonattainment. The RACT requirement 

will apply both to sources of direct 

PM2.5 emissions and to sources of PM2.5

precursors in the given nonattainment 

area. The EPA will require States to 

demonstrate that they have adopted all 

appropriate RACT measures in the 

attainment demonstrations that States 

must submit to EPA in early 2008. 

EPA is proposing three basic 

approaches to implementing the RACT 

requirement. The first alternative would 

simply require States to conduct a 

RACT analysis and require reasonably 

available controls for all affected 

stationary sources in the nonattainment 

area, comparable to the implementation 

of RACT provided in subpart 4 

governing implementation of the PM10

NAAQS and subpart 2 governing 

implementation of the 1-hour ozone 

NAAQS. Under this alternative for 

RACT, EPA is also proposing to limit 

the universe of sources for which States 

must conduct a RACT analysis and 

impose RACT controls, based upon the 

amount of emissions potentially emitted 

by the sources. (See discussion later in 

this section on potential emissions 

thresholds applicable under the first 

alternative.) The second alternative 

would likewise require States to 

conduct a RACT analysis and require 

reasonably available controls on 

stationary sources, but would allow 

States to decline to impose controls that 

would not otherwise be necessary to 

meet RFP requirements or to attain the 

PM2.5 NAAQS as expeditiously as 

practicable.66

The third alternative would be a 

combination of the first two and is 

consistent with the RACT approach 

adopted in the final implementation 

rule for the 8-hour ozone program. It 

would require States to conduct a RACT 

analysis and require reasonably 

available controls for all affected 

stationary sources in the nonattainment 

area only for areas with attainment dates 

more than five years from the date of 

designation. For areas with an 

attainment date within five years of 

designation (e.g. by April 2010 for areas 

designated in late 2004), RACT would 

be required as under the second 

alternative, in which States could 

decline to impose controls that would 

not otherwise be necessary to meet RFP 

requirements or to attain the PM2.5

NAAQS as expeditiously as practicable. 

The EPA seeks comment on the three 

alternative approaches for RACT 

discussed below, and on the options 

presented for a RACT source emissions 

threshold applicable under the first and 

third options. 

First proposed alternative for RACT. 

Under the first alternative, EPA would 

require States to conduct RACT 

determinations and require RACT 

controls for all stationary sources 

located in nonattainment areas, subject 

to any size threshold as discussed in the 

options below. In this approach, 

covered sources would be required to 

apply technically and economically 

feasible controls and there would be no 

opportunity for States to excuse major 

stationary sources from control on the 

basis that the emissions reductions from 

those controls would not be necessary 

for RFP or to expedite attainment. The 

EPA believes that this first alternative 

would be consistent with the approach 

set forth in the CAA in subpart 4 

governing PM10 nonattainment areas 

and in subpart 2 governing 1-hour ozone 

nonattainment areas wherein all 

stationary sources with at least a given 

amount of potential annual emissions 

are subject to RACT controls. The logic 

behind requiring RACT for all such 

sources in subpart 2 and subpart 4 was 

presumably that large stationary sources 

are a significant source of emissions in 

nonattainment areas and that States 

66018 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

67A stationary source, as defined in various EPA 

regulations, is any building, structure, facility or 

installation which emits or may emit any pollutant 

regulated under the CAA, and for which all of the 

pollutant-emitting activities belong to the same 

industrial grouping, are located on one or more 

contiguous or adjacent properties, and are under the 

control of the same person (or persons under 

common control). 

necessarily need to control them as part 

of an effective SIP. 

EPA believes that requiring RACT for 

all large sources may also be appropriate 

for implementation of the RACT 

requirement for PM2.5 for a number of 

reasons. First, as with ozone problem 

areas, sources located across a broad 

region appear to contribute to PM2.5

nonattainment problems. As such, 

implementing the RACT requirement for 

all major sources located in 

nonattainment areas will ‘‘level the 

playing field’’ from one area to another. 

Controls on sources subject to RACT 

will improve air quality in the 

nonattainment area in which the facility 

is located, and in many cases will also 

improve air quality in nearby 

nonattainment areas. 

Second, like ozone and to a lesser 

extent PM10, PM2.5 nonattainment in 

many areas appears to be largely a 

product of secondarily formed particles 

that result from emissions of precursors 

that react in the atmosphere. While we 

understand the basic processes and 

mechanisms that cause PM2.5 formation, 

we likewise recognize that sorting out 

the various sources and their impacts on 

local and regional nonattainment is a 

difficult and resource intensive process, 

subject to some uncertainty. Requiring 

RACT controls for all large stationary 

sources under subpart 2 (for ozone) and 

subpart 4 (for PM10) greatly simplified 

the SIP development process by 

requiring the analysis for and 

imposition of RACT controls for these 

sources, and thereby foreclosed the need 

to divert State resources to demonstrate 

conclusively the need for RACT controls 

for large stationary sources or to explore 

plan options that would permit 

excusing certain sources from control, 

perhaps at the cost of regulating other 

smaller sources less central to the 

nonattainment problem. 

Third, EPA notes that the rule to 

implement the new 8-hour ozone 

NAAQS also sought comment on an 

option that would require RACT for all 

large stationary sources in subpart 1 

areas with design values greater than 91 

parts per billion (ppb). Given that some 

of the PM2.5 and 8-hour ozone 

nonattainment areas will overlap and 

that PM and ozone have common 

precursors, EPA anticipates that many 

of the same large stationary sources will 

be subject to RACT in connection with 

the ozone NAAQS in any case. Thus, 

requiring RACT on all large sources will 

also ‘‘level the playing field’’ among 

sources located in ozone or PM2.5

nonattainment areas, and will help to 

alleviate unintended consequences of an 

inconsistent approach. 

Notwithstanding the practical and 

policy arguments in favor of requiring 

RACT for all large stationary sources, 

EPA recognizes that in other contexts 

concerning other NAAQS, RACT has 

been interpreted alternatively as a 

component of the general RACM 

requirement in section 172(c)(1). 

Nevertheless, EPA believes that the 

health impacts of PM2.5 nonattainment 

and the similarities between the PM2.5, 

PM10, and ozone problems (e.g., cause 

by many and various sources, regional 

in nature) may justify consideration of 

a comparable RACT approach. The EPA 

specifically solicits comment on this 

alternative in which RACT is required 

for all large sources above a particular 

tonnage threshold, without regard to 

RFP or attainment needs. 

Options for a RACT emissions 

threshold under the first proposed 

alternative. Under the first proposed 

alternative in which States are required 

to impose RACT controls on stationary 

sources, EPA recognizes that it may not 

be reasonable for States to require RACT 

controls regardless of the amount of the 

emissions from the individual sources 

in question. Section 172(c)(1) does not 

provide an explicit cutoff for the size of 

sources that States should subject to 

RACT controls, but there are such 

cutoffs elsewhere in the statute. 

For example, in section 182(b)(2) 

governing nonattainment areas for the 

one-hour ozone NAAQS, the CAA 

requires RACT for those sources covered 

by preexisting control techniques 

guidelines or for other ‘‘major stationary 

sources,’’ i.e., those sources with 

emissions above a specified number of 

tons per year, which varies depending 

upon the area’s nonattainment 

classification. In subpart 4 governing 

PM10 nonattainment areas, section 

189(b)(3) defines a ‘‘major source’’ as 

one stationary source (or a group of such 

sources contiguously located and under 

common control) that emits or has the 

potential to emit at least 70 tons of PM10

per year, thereby altering the otherwise 

applicable 100 ton definition of major 

source in ‘‘moderate’’ PM10

nonattainment areas and imposing 

greater control requirements on smaller 

sources in areas that are ‘‘serious’’

nonattainment for PM10. The logic 

behind such emissions thresholds is 

presumably that requiring RACT 

controls for small sources may not 

achieve the same degree of reductions 

that may be possible through focusing 

regulatory resources on relatively larger 

sources. 

Given the significance of the health 

impacts that result from PM2.5

nonattainment, EPA considered 

proposing that there should be no size 

threshold for sources that States must 

address in a RACT analysis, thereby 

considering even small emissions 

sources for RACT controls and 

implementing those controls as 

appropriate. Ultimately, however, EPA 

has concluded that under the first 

proposed alternative for RACT, 

requiring RACT analyses for all 

stationary sources, regardless of the 

amount of annual potential emissions, 

may divert resources and attention from 

the necessary RACT analyses for larger, 

more significant sources of direct PM2.5

and PM2.5 precursors. Moreover, EPA 

expects States to consider controls for 

smaller stationary sources as part of the 

RACM analysis discussed below, so 

EPA does not anticipate that the 

creation of a RACT threshold based 

upon the amount of emissions will serve 

to exempt smaller stationary sources 

completely from all consideration of 

controls. 

In short, EPA finds that under the first 

proposed alternative, it may not be 

reasonable to require RACT controls for 

all stationary sources regardless of size, 

and EPA is proposing to interpret 

section 172(c)(1) to allow EPA to define 

the universe of sources for which States 

should consider the need to impose 

RACT, based upon the potential annual 

emissions of the sources affected. For 

the first overall RACT alternative 

discussed above, EPA is proposing three 

sub-options for thresholds for 

implementing the RACT requirement 

that would limit the universe of sources 

for which States must conduct a RACT 

analysis, based upon the potential 

emissions from each source. 

The first sub-option would require 

States to conduct RACT determinations, 

at a minimum, for all existing stationary 

sources 67 located in nonattainment 

areas and which have the potential to 

emit 100 tons per year or more of direct 

PM2.5 or any individual precursor to 

PM2.5. (See the following subsection for 

a more detailed discussion of precursor 

emissions covered under RACT.) A 

source would be subject to this 

requirement if its plant-wide potential 

emissions exceeded the 100 ton 

threshold for PM2.5 or any individual 

precursor in the baseline year of 2002 or 

later. We would require States to adopt 

RACT rules covering those sources 

above this threshold for which control 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66019 

68This approach is consistent with EPA’s 

historical RACT policy outlined in the 1992 general 

preamble (57 FR 13541). 

69Subpart 1 of part D of the CAA includes the 

general provision that States must adopt plans for 

nonattainment areas which require implementation 

of RACM and RACT. The EPA has interpreted the 

provision to require States to include RACM and 

RACT measures to the extent that such measures 

will meet RFP requirements and will expedite 

attainment. In Subpart 2 specifically governing onehour ozone nonattainment areas, however, the Act 

requires States to implement RACT on certain 

stationary sources independent of the emissions 

reductions needed to attain the applicable standard. 

70A recent decision by the U.S. Court of Appeals 

for the District of Columbia has upheld this 

interpretation for RACM. The Court agreed with 

EPA’s view that the statute does not require a State 

to adopt reasonably available control measures 

without regard to whether they would facilitate RFP 

or would expedite attainment. See Sierra Club v. 

EPA, 294 F.3d 155 (DC Cir. 2002). 

71 ‘‘State Implementation Plans; General Preamble 

for the Implementation of Title I of the CAA 

Amendments of 1990; Proposed Rule.’’ April 16, 

1992 (57 FR 13498). See also Sierra Club v. EPA, 

294 F.3d 155 (DC Cir. 2002). 

measures are technically and 

economically feasible. As discussed in 

the previous section, the number of 

sources with emissions over 100 tons 

per year of direct PM2.5 or any precursor 

pollutant make up a fairly small 

percentage of all stationary sources, but 

on a pollutant-by-pollutant basis, they 

are responsible for 70–90+ percent of 

the emissions in many nonattainment 

areas. Thus, this proposed approach to 

RACT would provide a mechanism by 

which States can address large 

emissions sources in all contributing 

source categories while evaluating a 

relatively small number of sources for 

consideration of RACT and 

implementation of RACT, as compared 

to the entire inventory of emissions 

sources. 

Under the second proposed suboption on emissions thresholds, we 

would require States to conduct RACT 

determinations for all existing stationary 

sources located in nonattainment areas 

which have potential emissions of 50 

tons per year or more of direct PM2.5 or 

any individual precursor to PM2.5. 

Under this option, States would conduct 

RACT determinations for a larger 

universe of stationary sources 

responsible for a larger fraction of direct 

PM2.5 and precursor emissions. This 

sub-option would provide a lower 

threshold for RACT that would require 

States to address smaller sources and a 

broader range of sources under the 

RACT requirement. 

As a third suboption for a RACT 

emissions threshold under the first 

alternative, EPA is considering creation 

of a scaled RACT threshold based upon 

the severity of pollution in the 

nonattainment area. Under this 

approach, most PM areas would have a 

100-ton threshold, but areas with a more 

serious PM problem would have a 50- 

ton threshold. As a variation, another 

tier (e.g., 25 tons or 10 tons) could be 

created for areas with the highest PM 

levels. 

The CAA imposes a tiered RACT 

approach for ozone in subpart 2, and 

EPA believes that the approach has been 

helpful to assure more expeditious 

attainment of the ozone NAAQS. The 

EPA has not yet determined what design 

values might be appropriate as cut 

points for lower thresholds, and we 

specifically request comments and 

supporting analyses on this issue, as 

well as on the overall approach in 

general. 

Under all three sub-options for the 

RACT threshold, the specified potentialto-emit threshold would be the 

minimum starting point for RACT 

analyses. The EPA would not preclude 

a State from conducting an analysis to 

assess the suitability of RACT controls 

for sources with emissions below the 

applicable threshold, particularly in 

areas having more serious air quality 

problems, in order to apply available 

control technology to those existing 

sources in the nonattainment area that 

are reasonable to control in light of the 

attainment needs of the area and the 

feasibility of installing such controls.68

For example, States may find that 

selected source categories can apply 

controls cost-effectively at smaller 

sources than EPA’s baseline 

applicability threshold. 

Second proposed alternative for 

RACT. Under the second proposed 

alternative for RACT, EPA also would 

require States to conduct a RACT 

analysis and to require RACT for 

stationary sources, but would allow 

States to decline to impose controls that 

would otherwise be required as RACT if 

they are not necessary to meet RFP 

requirements or to attain the PM2.5

NAAQS as expeditiously as practicable. 

In connection with other NAAQS, EPA 

has previously interpreted section 

172(c)(1) to provide that a State must 

adopt at a minimum those RACM 

measures that are necessary for the 

nonattainment areas in that State to 

meet RFP requirements and to attain the 

standards as expeditiously as 

practicable. Under this second proposed 

alternative, the imposition of RACT 

controls on stationary sources would 

derive from the same statutory provision 

and impose the same requirement.69

The EPA has also interpreted section 

172(c)(1) to allow a State to decline to 

adopt certain technically and 

economically feasible measures, if 

adoption of those measures would not 

advance the attainment date by at least 

a year for the nonattainment area. Under 

this alternative interpretation, EPA 

would take the position that the RACT 

requirement for the PM2.5 standards 

should be subject to that limitation as 

well.70

In the context of the PM10 NAAQS, 

EPA has concluded, based upon the 

annual form of the standard, that 

‘‘advancement of the attainment date’’

should mean an advancement of at least 

one calendar year.71 Similarly, given 

that the annual PM2.5 standard is 

considered to be the ‘‘controlling’’

standard (as opposed to the 24-hour 

standard), and the fact that all sites 

violating the PM2.5 standards are 

violating the annual standard rather 

than only the 24-hour standard, EPA 

believes that, under this option, 

advancement of the attainment date by 

at least one calendar year is likewise the 

proper test for assessing whether RACM 

(including RACT under this option) 

would advance the attainment date for 

purposes of the PM2.5 NAAQS. 

EPA’s second proposed RACT 

alternative, therefore, would require that 

all States must adopt such RACT 

measures for stationary sources as are 

necessary to meet RFP requirements and 

to attain the PM2.5 standards as 

expeditiously as practicable. Under this 

approach, determination of RACT 

would be part of the broader RACM 

analysis and identification of all 

measures—for stationary, mobile, and 

area sources—that are technically and 

economically feasible, and that would 

collectively contribute to advancing the 

attainment date. Because RACT and 

RACM are considered together under 

this alternative, we are not proposing 

emissions threshold options for 

evaluation of stationary source RACT as 

are included under the first proposed 

alternative. In addition, under the 

second alternative, areas cannot avoid 

the imposition of either available RACT 

or RACM measures without a 

demonstration showing that there is no 

combination of such declined RACT 

and RACM measures that would 

advance the date of attainment by one 

year. 

EPA presumes that many States with 

PM2.5 nonattainment areas will 

conclude that RACT standards are 

necessary for many of the major 

stationary sources of emissions within 

the boundaries of such nonattainment 

areas in order to meet RFP and to 

expedite attainment of the standards. 

Nevertheless, there may be 

nonattainment areas in which a 

requirement for RACT controls on 

certain stationary sources would not 

66020 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

72EPA must initially rely on the States to provide 

the necessary analysis and documentation to show 

whether RACT measures would advance the 

attainment date at least one year. It should be noted 

that although the court upheld EPA’s interpretation 

of § 172(c)(1) in Sierra Club v. EPA, supra, the court 

also concluded in that case that neither the local 

government authority nor EPA had provided an 

adequate analysis to support the determination that 

certain control measures were not in fact capable 

of advancing the attainment date for that area. 

advance attainment by at least one year. 

For example, there may be 

nonattainment areas that are within a 

few tenths of a microgram of the 

standard and the State may determine 

that other local measures are adequate 

to bring the area into attainment as 

expeditiously as practicable, and that 

the absence of such controls will not 

significantly impact downwind States. 

In such areas, EPA believes that it might 

be reasonable to forego the requirement 

of RACT controls on certain stationary 

sources. Under this second alternative, 

each State would make that 

determination through its own fact 

specific RACT analysis in the 

attainment demonstration it submits to 

the Agency. EPA proposes that the 

RACT analysis under this option would 

not need to be a source-specific 

analysis, and instead could be 

conducted on a source-category basis. 

This alternative would provide greater 

flexibility for States to design local 

control programs for such areas.72 EPA 

requests comment on all aspects of the 

second proposed option for RACT. 

Third proposed alternative for RACT. 

The third proposed alternative for RACT 

would be a combination of the first two 

and is consistent with the RACT 

approach adopted in the final 

implementation rule for the 8-hour 

ozone program. Because of the 

importance EPA places on providing 

consistent policies between the ozone 

and PM2.5 implementation programs, we 

propose this alternative as our preferred 

option. 

The third proposed alternative would 

require States to conduct a RACT 

analysis and impose reasonably 

available controls for all affected 

stationary sources in the nonattainment 

area, only for those nonattainment areas 

with attainment dates more than five 

years from the date of designation. The 

same proposed suboptions with respect 

to the size of sources for consideration 

discussed under the first alternative 

would be included under this 

alternative as well. 

For areas with an attainment date 

within five years of designation (e.g. by 

April 2010 for areas designated in late 

2004), RACT would be required as 

described under the second alternative, 

in which States could decline to impose 

controls that would not otherwise be 

necessary to meet RFP requirements or 

to attain the PM2.5 NAAQS as 

expeditiously as practicable. 

EPA believes that this alternative, 

which is in effect a ‘‘hybrid’’ of the first 

two, provides important policy 

advantages. First, it recognizes that 

certain areas are projected to attain the 

standards within five years of 

designations predominantly due to 

federal emission reduction programs. 

This alternative enables such areas to 

decline to impose controls on certain 

categories of sources if their 

implementation would not provide for 

an advancement of the attainment date. 

Second, it recognizes that those areas 

that need an attainment date extension 

due to more serious nonattainment 

problems should be required to impose 

RACT controls on affected sources in 

return for receiving the extension. This 

alternative is consistent with the overall 

approach taken in the 1990 Clean Air 

Act amendments, such as subpart 2 for 

ozone, under which areas with more 

severe air quality problems are required 

to implement a broader range of control 

requirements, in conjunction with 

attainment dates that are farther into the 

future. EPA requests comment on all 

three proposed RACT alternatives 

presented above. 

Factors to consider in determining 

RACT. States should consider a number 

of factors in analyzing whether or not 

RACT controls will help a given area to 

meet RFP requirements or to attain the 

standard as expeditiously as practicable, 

and in determining what would 

constitute RACT for a given source 

category. First, our understanding of 

PM2.5 formation indicates that ambient 

pollutant levels are the result of 

emissions from a large number of varied 

sources of direct PM2.5 and PM2.5

precursors. Accordingly, each State 

should examine closely the universe of 

emissions sources in each 

nonattainment area and evaluate 

carefully whether RACT controls are 

appropriate for some or all of these 

sources, given the specific nature of the 

nonattainment problem in such area. 

We anticipate that States may decide 

upon RACT controls that differ from 

State to State, but that are the most 

effective given the relevant mixture of 

sources and potential controls in the 

respective nonattainment areas. So long 

as each State can adequately 

demonstrate that its chosen RACT 

approach will provide for meeting RFP 

requirements and for attainment of the 

NAAQS as expeditiously as practicable, 

we anticipate approving plans that may 

elect to control a somewhat different 

mix of sources or to implement 

somewhat different controls as RACT. 

Nevertheless, States should consider 

and address RACT measures developed 

for other areas or other States as part of 

a well reasoned RACT analysis. The 

EPA’s own evaluation of State SIPs for 

compliance with the RACT and RACM 

requirements will include comparison 

of measures considered or adopted by 

other States. 

Second, implementation of the PM2.5

NAAQS is in its initial stages, and many 

of the designated PM2.5 nonattainment 

areas are not current or former PM10

nonattainment areas. Thus, some 

existing stationary sources in these areas 

may currently be uncontrolled or 

undercontrolled for PM or PM 

precursors. Further, emissions controls 

for existing sources in these areas may 

focus primarily on particulate matter 

that is filterable at stack temperatures 

and thus may not adequately control 

condensable emissions. In addition, 

States should bear in mind that the 

controlled sources may have installed 

emission controls 15 years ago or more, 

and now there may be cost-effective 

opportunities available to reduce 

emissions further through more 

comprehensive and improved emissions 

control technologies, or through 

production process changes that are 

inherently lower in emissions. 

Moreover, improved monitoring 

methods may enhance the ability of 

sources to maintain the effectiveness of 

installed emissions controls and to 

reduce emissions by detecting 

equipment failures more quickly. For 

example, State imposition of 

requirements for more frequent 

monitoring (e.g., continuous opacity 

monitors, PM continuous emissions 

monitors, etc.) may provide greater 

assurance of source compliance and 

quicker correction of inadvertent upset 

emissions conditions than existing 

approaches. 

Third, even in former or current PM10

nonattainment areas, existing 

requirements for controlling direct PM 

emissions (e.g., with a baghouse or 

electrostatic precipitator) may not have 

been revised significantly since the 

1970’s. When EPA established the PM10

standards in 1987, we stated in the 

General Preamble that it was reasonable 

to assume that control technology that 

represented RACT for total suspended 

particulates (TSP) should satisfy the 

requirement for RACT for PM10. The 

rationale for this provision was that 

controls for PM10 and TSP would both 

be focused on reducing coarse 

particulate matter, and specifically that 

fraction of particulate matter that is 

solid (rather than gaseous or 

condensable) at typical stack 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66021 

73For example, see past EPA guidance on PM2.5

control technologies: Stationary Source Control 

Techniques Document for Fine Particulate Matter 

(EPA–452/R–97–001), EPA Office of Air Quality 

Planning and Standards, October 1998. 

74Stationary Source Control Techniques 

Document for Fine Particulate Matter (EPA–452/R–

97–001), EPA Office of Air Quality Planning and 

Standards, October 1998. See also: Controlling SO2

Emissions: A Review of Technologies (EPA/600/R–

00/093), EPA Office of Research and Development, 

November 2000. 

75See EPA’s website for more information: 

http://www.epa.gov/ttn/emc/monitor.html. 

temperatures. However, emission 

controls to capture coarse particles in 

some cases may be less effective in 

controlling PM2.5. For this reason, there 

may be significant opportunities for 

sources to upgrade existing control 

technologies 73 and compliance 

monitoring methods to address direct 

PM emissions contributing to fine 

particulate matter levels with 

technologies that have advanced 

significantly over the past 15 years. 

Fourth, it will be important for States 

to conduct RACT determinations for 

stationary sources of PM2.5 precursors as 

well as direct PM2.5 emissions. A 

significant fraction of PM2.5 mass in 

most areas violating the standards is 

attributed to secondarily-formed 

components such as sulfate, nitrate, and 

carbonaceous PM, and EPA believes that 

certain stationary sources of these 

precursors in nonattainment areas 

currently may be poorly controlled. 

Accordingly, to address these 

precursors, States should review 

existing sources for emission controls or 

process changes that could be 

reasonably implemented to reduce 

emissions from activities such as fuel 

combustion, industrial processes, and 

solvent usage. 

Finally, EPA believes that the proper 

and timely implementation of RACT by 

the States is a relevant criterion in 

assessing State requests for any 

attainment date extension of the 

applicable attainment date. Because 

EPA anticipates that most States will 

conclude that RACT controls are 

appropriate and consistent with meeting 

RFP requirements and with expeditious 

attainment of the standards, EPA 

assumes that States will include a 

detailed RACT analysis in connection 

with any extension request. The EPA 

proposes that any State that seeks an 

attainment date extension of 1 to 5 years 

beyond the initial 5-year attainment 

date provided in section 172(a)(2) must, 

among other things, submit a 

demonstration satisfactory to EPA 

showing that the State has implemented 

all RACT for the appropriate sources in 

that State in order to meet RFP 

requirements and to provide for 

attainment of the PM2.5 standards as 

expeditiously as practicable. 

EPA requests comment on all aspects 

of the proposed alternatives and 

guidance for implementing the RACT 

requirement discussed above. 

6. What factors should States consider 

in determining whether an available 

control technology is technically 

feasible? 

The technological feasibility of 

applying an emission reduction method 

to a particular source should consider 

factors such as the sources’s process and 

operating procedures, raw materials, 

physical plant layout, and any other 

environmental impacts such as water 

pollution, waste disposal, and energy 

requirements. For example, the process, 

operating procedures, and raw materials 

used by a source can affect the 

feasibility of implementing process 

changes that reduce emissions and the 

selection of add-on emission control 

equipment. The operation of, and 

longevity of, control equipment can be 

significantly influenced by the raw 

materials used and the process to which 

it is applied. The feasibility of 

modifying processes or applying control 

equipment also can be influenced by the 

physical layout of the particular plant. 

The space available in which to 

implement such changes may limit the 

choices and will also affect the costs of 

control. 

Reducing air emissions may not 

justify adversely affecting other 

resources by increasing pollution of 

bodies of water, creating additional 

solid waste disposal problems or 

creating excessive energy demands. An 

otherwise available control technology 

may not be reasonable if these other 

environmental impacts cannot 

reasonably be mitigated. For analytic 

purposes, a State may consider a PM2.5

control measure technologically 

infeasible if, considering the availability 

(and cost) of mitigative adverse impacts 

of that control on other pollution media, 

the control would not, in the State’s 

reasoned judgment, provide a net 

benefit to public health and the 

environment. In many instances, 

however, PM2.5 control technologies 

have known energy penalties and 

adverse effects on other media, but such 

effects and the cost of their mitigation 

are also known and have been borne by 

owners of existing sources in numerous 

cases. Such well-established adverse 

effects and their costs are normal and 

assumed to be reasonable and should 

not, in most cases, justify rejection of 

the potential PM2.5 control technology. 

The costs of preventing adverse water, 

solid waste and energy impacts will also 

influence the economic feasibility of the 

PM2.5 control technology. 

EPA recommends that States evaluate 

alternative approaches to reducing 

emissions of particulate matter by 

reviewing existing EPA guidance 74 and 

other sources of control technology 

information. In EPA’s 1998 guidance, 

the design, operation and maintenance 

of general particulate matter control 

systems such as electrostatic 

precipitators, fabric filters, and wet 

scrubbers are presented. The filterable 

particulate matter collection efficiency 

of each system is discussed as a 

function of particle size. Information is 

also presented regarding energy and 

environmental considerations and 

procedures for estimating costs of 

particulate matter control equipment. 

Secondary environmental impacts are 

also discussed. Because control 

technologies and monitoring approaches 

are constantly being improved, the State 

should also consider more updated or 

advanced technologies not referenced in 

this 1998 guidance when conducting a 

RACT determination. Emissions 

reductions may also be achieved 

through the application of monitoring 

and maintenance programs that use 

critical process and control parameters 

to verify that emission controls are 

operated and maintained so that they 

more continuously achieve the level of 

control that they were designed to 

achieve.75

7. What factors should States consider 

in determining whether an available 

control technology is economically 

feasible? 

Economic feasibility considers the 

cost of reducing emissions and the 

difference between the cost of the 

emissions reduction approach at the 

particular source and the costs of 

emissions reduction approaches that 

have been implemented at other similar 

sources. Absent other indications, EPA 

presumes that it is reasonable for similar 

sources to bear similar costs of emission 

reduction. Economic feasibility for 

RACT purposes is largely determined by 

evidence that other sources in a source 

category have in fact applied the control 

technology or process change in 

question. 

The capital costs, annualized costs, 

and cost effectiveness of an emission 

reduction technology should be 

considered in determining its economic 

feasibility. The EPA Air Pollution 

66022 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

76EPA Air Pollution Control Cost Manual—Sixth 

Edition (EPA 452/B–02–001), EPA Office of Air 

Quality Planning and Standards, Research Triangle 

Park, NC, Jan 2002. 

77U.S. EPA, 2003 Technical Support Package for 

Clear Skies; U.S. EPA, 2003. See also: Draft 

Regulatory Impact Analysis: Control of Emissions 

from Nonroad Diesel Engines. United States 

Environmental Protection Agency Office of Air and 

Radiation EPA420-R–03–008, April 2003. 

78The consolidated emissions reporting rule was 

published in the Federal Register on June 10, 2002, 

pages 39602–39616. 

Control Cost Manual 76 describes 

procedures for determining these costs 

for stationary sources. The above costs 

should be determined for all 

technologically feasible emission 

reduction options. 

States may give substantial weight to 

cost effectiveness in evaluating the 

economic feasibility of an emission 

reduction technology. The cost 

effectiveness of a technology is its 

annualized cost ($/year) divided by the 

emissions reduced (i.e., tons/year) 

which yields a cost per amount of 

emission reduction ($/ton). Cost 

effectiveness provides a value for each 

emission reduction option that is 

comparable with other options and 

other facilities. 

In considering what level of control is 

reasonable, EPA is not proposing a fixed 

dollar per ton cost threshold for RACT. 

We believe that what is considered to be 

a reasonable control level should vary 

based on the severity of the 

nonattainment problem in the area. In 

addition, we believe that in determining 

what are appropriate emission control 

levels, the State should also consider 

the collective health benefits that can be 

realized in the area due to projected 

improvements in air quality. The health 

benefits associated with reducing PM2.5

levels are significant. Using estimation 

techniques reviewed and deemed 

reasonable by the National Academy of 

Sciences, national monetized health 

benefits resulting from reductions in PM 

concentrations are estimated to exceed 

emission control costs by a factor of 

three to thirty times, depending on the 

particular controls on sources of PM 

precursor emissions.77 This approach is 

consistent with EPA’s view that RACT 

may be related to what is needed for 

attainment. That is, for options where 

RACT is met where an area 

demonstrates timely attainment and 

areas with more severe air quality 

problems typically will need to adopt 

more stringent controls, RACT level 

controls in such areas will require 

controls at higher cost effectiveness 

levels ($/ton) than areas with less severe 

air quality problems. 

Areas with more serious air quality 

problems typically will need to obtain 

greater levels of emissions reductions 

from local sources than areas with less 

serious problems, and it would be 

expected that their residents could 

realize greater health benefits. For this 

reason, we believe that it will be 

reasonable and appropriate for areas 

with more serious air quality problems 

and higher design values to impose 

emission reduction requirements with 

generally higher costs per ton of 

reduced emissions than the cost of 

emissions reductions in areas with 

lower design values. 

If a source contends that a sourcespecific RACT level should be 

established because it cannot afford the 

technology that appears to be RACT for 

other sources in its source category, the 

source should support its claim with 

such information regarding the impact 

of imposing RACT on: 

1. Fixed and variable production costs 

($/unit), 

2. Product supply and demand 

elasticity, 

3. Product prices (cost absorption vs. 

cost pass-through), 

4. Expected costs incurred by 

competitors, 

5. Company profits, and 

6. Employment costs. 

8. How should condensable emissions 

be treated in RACT determinations? 

Certain commercial or industrial 

activities involving high temperature 

processes (fuel combustion, metal 

processing, cooking operations, etc.) 

emit gaseous pollutants into the ambient 

air which rapidly condense into particle 

form. The constituents of these 

condensed particles include, but are not 

limited to, organic material, sulfuric 

acid, and metals. In general, 

condensable emissions are taken into 

account wherever possible in emission 

factors used to develop national 

emission inventories, and States are 

required under the consolidated 

emissions reporting rule (CERR) 78 to 

report condensable emissions in each 

inventory revision. Currently, some 

States have regulations requiring 

sources to quantify condensable 

emissions and to implement control 

measures for them, and others do not. In 

1990, EPA promulgated Method 202 in 

Appendix M of 40 CFR Part 51 to 

quantify condensable particulate matter 

emissions. 

EPA is in the process of developing 

detailed guidance on a new test method 

which quantifies and can be used to 

characterize the constituents of the 

PM2.5 emissions including both the 

filterable and condensable portion of the 

emissions stream. (See section III.P for 

more information.) When a source 

implements either of these test methods 

addressing condensable emissions, the 

State will likely need to revise the 

source’s emissions limit to account for 

those emissions that were previously 

unregulated. For the purposes of 

determining RACT applicability and 

establishing RACT emission limits, EPA 

intends to require the State to adopt the 

new test method once EPA issues its 

detailed guidance for use by all sources 

within a PM2.5 nonattainment area that 

are required to reduce emissions as part 

of the area’s attainment strategy. The 

EPA requests comment on this proposal 

with respect to addressing condensable 

emissions in PM2.5 RACT 

determinations. 

9. What are the required dates for 

submission and implementation of 

RACT measures? 

States must submit adopted RACT 

rules to EPA within three years of 

designation, at the same time as the 

attainment demonstration due in April 

2008. States should also implement any 

measures determined to be RACT 

expeditiously, as required by section 

172. Implementation of RACT measures 

should start no later than the beginning 

of the final year of the three-year period 

on which attainment is to be assessed. 

(See section I.11. for a discussion of 

RACT for sources subject to CAIR.) For 

example, if an area has an attainment 

date of April 2010, then any required 

RACT measures should be in place and 

operating no later than the beginning of 

2009, so that their effect will be 

reflected in the air quality levels for 

calendar year 2009. (See relateddiscussion in section I.11. on the 

interaction of CAIR and RACT.) If the 

area has recorded air quality levels 

above 15.1 μg/m3 for the first two years 

of the three-year period, then it is 

possible that implementation of the 

emission controls in the third year 

could enable the area to have improved 

air quality below 15.1 and thereby be 

eligible to receive a one-year attainment 

date extension. 

While EPA expects that States will 

implement required RACT controls by 

January 2009 in most situations, there 

may be cases where additional 

implementation time is needed to 

implement an innovative control 

measure or to achieve a greater level of 

reduction through a phased approach. If 

an area has provided an adequate 

demonstration showing that an 

attainment date extension would be 

appropriate, then the area may consider 

phasing-in certain RACT controls after 

January 2009. Implementation of 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66023 

79However, there are some MACT categories for 

which it may not be possible to determine the 

Continued 

selected RACT controls after January 

2009 would only be allowable if the 

state can show why additional time is 

needed for implementation, and still 

would need to be on a schedule that 

provides for expeditious attainment. In 

no event could the area wait to 

implement RACT controls until the last 

few years prior to the attainment date. 

EPA requests comments on this 

approach for RACT implementation. 

10. Under the PM2.5 implementation 

program, does a State need to conduct 

a RACT determination for an applicable 

source that already has a RACT 

determination in effect? 

In PM2.5 nonattainment areas, States 

are required to implement the RACT 

requirement to reduce emissions of 

direct PM2.5 and PM2.5 precursors from 

applicable sources. Under this proposal, 

RACT would need to be addressed for 

emissions of SO2 and NOX in all areas. 

For VOC and ammonia, this proposal 

would require RACT to be addressed 

only in those areas for which EPA or the 

State provides a determination that the 

pollutant is a significant contributor to 

the local PM2.5 problem. 

The sources subject to RACT in a 

particular nonattainment area will 

depend on which RACT option 

described in section III.I.5 is adopted in 

the final rule. Under EPA’s preferred 

option, an area projected to attain 

within five years after designations (by 

April 2010) according to the attainment 

demonstration would need to impose 

RACT controls only on those sources as 

necessary to attain as expeditiously as 

practicable. An area projected to attain 

in more than five years would be 

required to conduct RACT 

determinations for all sources exceeding 

a particular emissions threshold. 

EPA anticipates that for a number of 

sources located in a PM2.5

nonattainment area, the State would 

have previously conducted RACT 

determinations for VOC or NOX under 

the 1-hour ozone standard, or for direct 

PM10 emissions under the PM10

standards. Some of the RACT 

determinations established under these 

other programs would have been made 

more recently, while other 

determinations will be more than ten 

years old. In some cases, a new RACT 

determination would call for the 

installation of similar control 

technology as the initial RACT 

determination because the relevant 

pollutant was addressed, the same 

emission points were reviewed, and the 

same fundamental control techniques 

would still have similar costs. In other 

cases, a new RACT analysis could 

determine, for example, that better 

technology has become available, and 

that cost-effective emission reductions 

are achievable. 

For these reasons, EPA recommends 

that the State should closely review any 

existing RACT determinations 

established under another NAAQS 

program. We believe States must 

consider new information that has 

become available since the original 

RACT determination. EPA proposes that 

where major sources or source 

categories were previously reviewed 

and sources subsequently installed 

controls to meet the RACT requirement 

for the pollutant(s) in question, States 

would be allowed to accept the initial 

RACT analysis as meeting RACT for 

purposes of the PM2.5 program, provided 

that the State submits as part of its SIP 

revision a certification with appropriate 

supporting information that it 

previously met the RACT requirement 

for these sources as part of its prior SIP 

revision, and that the previous 

determination currently represents an 

appropriate RACT level of control for 

PM2.5. In the alternative, the State 

should revise the SIP to reflect a 

modified RACT requirement for specific 

sources or source categories. 

In any case where additional 

information on updated control 

technologies is presented as part of 

notice-and-comment rulemaking, 

including a RACT SIP submittal for 

sources previously controlled, States 

(and EPA) must consider the additional 

information as part of that rulemaking. 

In cases where the State’s RACT 

analysis previously concluded that no 

additional controls were necessary, we 

propose that a new RACT determination 

is required for that source. The new 

RACT determination is needed to take 

into account that newer, cost-effective 

control measures may have become 

available for sources that were not 

previously regulated. EPA believes it 

may not always be sufficient for a State 

to rely on technology guidance that is 

several years old in conducting new 

RACT determinations. States should 

take into account appropriate 

information about updated control 

technologies as well as any additional 

information obtained through public 

comments when conducting RACT 

determinations for PM2.5. 

EPA requests comment on the policy 

approach described above for taking 

existing RACT determinations into 

account, and on the following questions: 

(1) Should new RACT determinations be 

required for all existing determinations 

that are older than a specified amount 

of time (such as 10 years old)?; (2) what 

supporting information should a state be 

required to submit as part of its 

certification to demonstrate that a 

previous RACT analysis meets the 

RACT requirement currently for 

purposes of the PM2.5 program? 

Prior BACT/LAER/MACT 

determinations. In many cases, but not 

all, best available retrofit technology 

(BACT) or lowest achievable emission 

rate (LAER) provisions for new sources 

would assure at least RACT level 

controls on such sources. The BACT/ 

LAER analyses do not automatically 

ensure compliance with RACT since the 

regulated pollutant or source 

applicability may differ and the 

analyses may be conducted many years 

apart. States may, however, rely on 

information gathered from prior BACT 

or LAER analyses for the purposes of 

showing that a source has met RACT to 

the extent the information remains 

valid. We believe that the same logic 

holds true for emissions standards for 

municipal waste incinerators under 

CAA section 111(d) and NSR/PSD 

settlement agreements. Where the State 

is relying on these standards to 

represent a RACT level of control, the 

State should present their analysis with 

their determination during the SIP 

adoption process. 

In situations where the State has 

determined VOC to be a significant 

contributor to PM2.5 formation in an 

area, compliance with MACT standards 

may be considered in VOC RACT 

determinations. For VOC sources 

subject to MACT standards, States may 

streamline their RACT analysis by 

including a discussion of the MACT 

controls and relevant factors such as 

whether VOCs are well controlled under 

the relevant MACT air toxics standard, 

which units at the facility have MACT 

controls, and whether any major new 

developments in technologies or costs 

have occurred subsequent to the MACT 

standards. We believe that there are 

many VOC sources that are well 

controlled (e.g., through add-on controls 

or through substitution of non-VOC 

non-HAP materials for VOC HAP 

materials) because they are regulated by 

the MACT standards, which EPA 

developed under CAA section 112. Any 

source subject to MACT standards must 

meet a level that is as stringent as the 

best-controlled 12 percent of sources in 

the industry. Examples of these HAP 

sources that may effectively control 

VOC emissions include organic 

chemical plants subject to the hazardous 

organic NESHAP (HON), 

pharmaceutical production facilities, 

and petroleum refineries.79 We believe 

66024 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

degree of VOC reductions from the MACT standard 

without additional analysis; for example, the 

miscellaneous metal parts and products (40 CFR 

part 60, subpart MMMM) due to the uncertainty of 

the compliance method that will be selected. 

80Under CAIR, states may allow other units to opt 

into the trading program. 

that, in many cases, it will be unlikely 

that States will identify emission 

controls more stringent than the MACT 

standards that are not prohibitively 

expensive and thus unreasonable. We 

believe this will allow States, in many 

cases, to rely on the MACT standards for 

purposes of showing that a source has 

met VOC RACT. 

Year-round controls. In some cases, 

sources subject to NOX RACT for PM 

will also be subject to controls under the 

NOX SIP Call. We proposed in the 8- 

hour ozone implementation rule that 

certain sources which have installed 

emission controls to comply with the 

NOX SIP call would be deemed to meet 

NOX RACT for the purposes of the 8- 

hour ozone implementation program. 

Some of these sources subject to the 

NOX SIP call may choose to control NOX

emissions only or primarily during the 

ozone season. For purposes of PM, 

however, EPA believes that the 

operation of emission controls only or 

primarily during the ozone season 

would not constitute RACT for PM 

purposes. Instead, EPA believes that 

RACT for PM should be year-round 

operation of controls because PM 

concentrations are a year-round problem 

and NOX emissions have a more 

significant role in PM formation in 

cooler temperatures. 

As described above, the PM RACT 

determination is made on a case-by-case 

basis. For sources subject to both the 

NOX SIP call and NOX RACT for PM, we 

believe that, in most cases, the 

additional costs of running the NOX SIP 

call controls year-round would be 

feasible and the cost effectiveness 

would be lower than the average cost 

effectiveness for many other sources 

subject to PM RACT. For example, if a 

source that has installed selective 

catalytic reduction to comply with the 

NOX SIP call extends operation of the 

control equipment from just during the 

ozone season to year-round, it would 

only incur additional operating costs 

but would achieve substantial 

additional emissions reductions. Thus, 

where sources have installed controls to 

meet the NOX SIP call, we believe that 

in most cases, RACT for PM would 

require running the emission controls 

year-round. 

11. What policies affect compliance 

with RACT for electric generating units? 

Overview. The Clean Air Interstate 

Rule (CAIR) (70 FR 25162) provides for 

a cap-and-trade mechanism that States 

may choose to use to achieve the 

emissions reductions required by CAIR. 

Under the cap-and-trade program, 

electric generating units (EGUs) 80 must 

collectively reduce their emissions of 

SO2 and NOX across a multi-state area 

in order to comply with emissions caps 

for these pollutants. A source subject to 

a cap-and-trade program such as the 

CAIR trading program generally has the 

option of installing emissions control 

technology, adopting some other 

strategy (such as using lower sulfur 

coal) to control its emissions, or 

purchasing emissions allowances and 

thereby effectively paying another 

source covered by the cap to reduce its 

emissions. The initial CAIR NOX cap is 

effective in 2009, and the initial CAIR 

SO2 cap is effective in 2010. However, 

EPA analysis shows that sources 

covered by the SO2 trading program will 

make significant reductions in their SO2

emissions well before 2010 because they 

are able to ‘‘bank’’ these early 

reductions. EPA also expects some early 

NOX reductions due to the opportunity 

for states to use their portion of the 

compliance supplement pool to award 

credit for early annual NOX reductions. 

Although we expect that many EGUs 

that will be subject to mandatory 

requirements under the cap-and-trade 

program under CAIR will not be located 

in PM2.5 nonattainment areas, some of 

these units will be located in 

nonattainment areas and thus will be 

subject to RACT requirements for large 

stationary sources. As discussed 

elsewhere in this section, RACT is one 

of the basic subpart 1 control 

requirements for nonattainment areas. 

Under the Clean Air Act, a source 

subject to CAIR that is located within a 

nonattainment area is also subject to the 

nonattainment RACT provisions for 

emissions of PM2.5 and nonattainment 

plan precursors (including SO2 and, in 

the absence of a finding that NOX is not 

a significant contributor, NOX). 

In this rulemaking, EPA is proposing 

to determine that in states that fulfill 

their CAIR emission reductions entirely 

through emission reductions from 

EGUs, CAIR would satisfy SO2 RACT 

requirements for EGU sources in eastern 

PM2.5 nonattainment areas covered by 

CAIR. EPA is proposing a similar 

finding for NOX RACT for EGUs, subject 

to a requirement that existing SCRs in 

those nonattainment areas be operated 

year-round beginning in 2009. The EPA 

believes that the SIP provisions for 

those sources meet the ozone Nox RACT 

requirement. A State that is relying on 

this conclusion for the affected sources 

should document this reliance in its 

RACT SIP. 

SO2 RACT. As stated elsewhere in this 

proposal, RACT controls in PM2.5

nonattainment areas should be in place 

and operational by the beginning of 

2009 unless an attainment date 

extension is obtained. As discussed 

more fully in the CAIR final rulemaking 

notice, EPA has set the 2009 and 2010 

CAIR caps at a level that will require 

EGUs to install emission controls on the 

maximum total capacity on which it is 

feasible to install emission controls by 

those dates. Although the actual SO2

cap does not become effective until 

2010, we have designed ‘‘banking’’

provisions in CAIR so that covered 

EGUs will begin to reduce their SO2

emissions almost immediately after 

CAIR is finalized, and will continue 

steadily to reduce their emissions in 

anticipation of the 2010 cap and the 

more stringent cap that becomes 

effective in 2015. The 2015 SO2 and 

NOX caps are specifically designed to 

eliminate all SO2 and NOX emissions 

from EGUs that are highly cost effective 

to control (the first caps represent an 

interim step toward that end). In 

general, we expect that the largestemitting sources will be the first to 

install SO2 and NOX control technology 

and that such control technology will 

gradually be installed on progressively 

smaller-emitting sources until the 

ultimate cap is reached. 

We do not believe that requiring 

source-specific RACT controls on EGUs 

in nonattainment areas will reduce total 

SO2 and NOX emissions from sources 

covered by CAIR below the levels that 

would be achieved under CAIR alone. In 

fact, if states chose to require smalleremitting sources in nonattainment areas 

to meet source-specific RACT 

requirements by 2009, they would likely 

use labor and other resources that 

would otherwise be used for emission 

controls on larger sources. Because of 

economies of scale, more boiler-makers 

may be required per megawatt of power 

generation for smaller units than larger 

units. In this case, the imposition of 

source-specific RACT on smaller 

emitting sources by 2009 could actually 

reduce the amount of ‘‘banking’’ that 

would otherwise occur and result in 

higher SO2 emissions in 2009 as 

compared to the level that would result 

from CAIR alone. 

In any event, the imposition of 

source-specific control requirements on 

a limited number of sources also 

covered by a cap-and-trade program 

would not reduce the total emissions 

from sources subject to the program. 

Under a cap-and-trade program such as 

CAIR, there is a given number of 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66025 

allowances that equals a given emission 

level. Source-specific control 

requirements may affect the temporal 

distribution of emissions (by reducing 

banking and thus delaying early 

reductions) or the spatial distribution of 

emissions (by moving them around from 

one place to another), but it does not 

affect total emissions. If source-specific 

requirements were targeted at the units 

that can be controlled most costeffectively, then the imposition of 

source-specific controls would likely 

achieve the same result as the cap-andtrade program. If not, however, the 

imposition of source-specific 

requirements would make any given 

level of emission reduction more costly 

than it would be under the cap-andtrade program alone. Thus, the 

imposition of source-specific RACT on 

EGUs covered by CAIR would not 

reduce total emissions, but would likely 

achieve the same total emission 

reductions in a more costly way. 

We recognize that the RACT 

provisions are an important tool to help 

nonattainment areas come into 

attainment. However, neither EPA nor 

the States have determined what would 

constitute SO2 and NOX RACT on EGUs 

for the purpose of the PM2.5

implementation program. Therefore, it 

is not possible to determine at this time 

whether, for any particular PM2.5

nonattainment area, CAIR or the 

imposition of RACT on EGUs located in 

that area would achieve greater 

emissions reductions from those 

specific EGUs. We are confident, 

however, that CAIR will provide 

substantial SO2 emissions reductions in 

most nonattainment areas in the CAIR 

region, as well as substantial SO2

reductions in attainment areas, which 

together will substantially improve air 

quality in PM2.5 nonattainment areas in 

the CAIR region. EPA requests comment 

on this option in which EGUs located 

within PM2.5 nonattainment areas would 

be considered to meet their SO2 RACT 

requirements through participation in 

the CAIR trading program. 

NOX RACT. With respect to NOX, we 

propose to find that, for EGUs subject to 

CAIR SIPs, CAIR satisfies NOX RACT in 

PM2.5 nonattainment areas, except that 

in addition, the state’s SIP must ensure 

that any source that has selective 

catalytic reduction (SCR) technology for 

summertime NOX control will operate 

the SCR year-round, starting by the 

beginning of 2009. In the CAIR final 

rulemaking notice, EPA found that the 

operation of existing SCRs on a yearround basis, instead of operating them 

only during the ozone season, could 

achieve NOX reductions at low cost 

relative to other available NOX controls 

for EGUs or for other sectors. EPA 

projected that power generators would 

employ this control measure for CAIR 

compliance. Based on this control 

opportunity, EPA estimated the average 

cost of non-ozone-season NOX control at 

$500/ton. These considerations support 

a finding that RACT should include 

year-round operation of existing SCRs 

that are located in PM2.5 nonattainment 

areas. ‘‘Existing’’ SCR would be defined 

to include those in place by the date of 

proposal of this rule; using the proposal 

date rather than the final rule date 

would avoid creating a potential 

incentive to delay installation of new 

SCR. Because all areas violate the 

annual form of the PM2.5 standard and 

public health can be affected by high 

PM2.5 levels in the winter as well as the 

summer, we believe that year-round 

operation of existing SCR in 

nonattainment areas will provide 

additional health benefits for relatively 

low dollar cost per ton of pollutant 

reduced. 

The Act requires RACT to be 

implemented as expeditiously as 

practicable (and, in the case of areas 

without an attainment date extension, 

no later than 2009). EPA has considered 

the following factors in proposing 

January 1, 2009, as the compliance date 

for year-round operation of existing 

SCR. Depending on the source, yearround operation of existing SCR 

involves either no alteration or 

relatively minor alteration of existing 

equipment. For EGUs where these 

alterations are needed, we expect the 

work to be conducted during a routine 

outage at a unit, which typically occurs 

one or more times a year. Finally, a 

year-round operation requirement 

would not be legally applicable to 

individual sources until the RACT SIP 

is adopted. We note that all EGUs in 

PM2.5 nonattainment areas would be on 

notice from the date this rule is 

finalized that RACT SIPs must require 

year-round operation of existing SCRs. 

Taking these factors into account, EPA 

believes that a January 1, 2009, 

implementation date would provide 

ample lead time to enable existing SCRs 

in PM2.5 nonattainment areas to be 

operated year-round, including those 

SCRs for which physical alterations are 

necessary. EPA requests comment on 

the proposal to find that for an EGU 

located in a PM2.5 nonattainment area in 

the CAIR region and having selective 

catalytic reduction control technology to 

reduce NOX emissions, compliance with 

CAIR satisfies NOX RACT, provided the 

State’s SIP ensures that the source 

operates the SCR year-round, starting no 

later than the beginning of 2009. 

RACT for sources in states requiring 

non-EGU reductions for CAIR 

compliance or allowing non-EGUs to 

‘‘opt into’’ CAIR. Under CAIR, a State 

may elect to meet its state caps for SO2

and NOX emissions by requiring 

emissions reductions from SO2 and NOX

sources that are not electric generating 

units. A second, separate option 

allowed under CAIR is that the state 

may elect to allow non-EGU sources to 

voluntarily enter the EPA-administered 

CAIR trading program through an opt-in 

provision in the CAIR model rule. If 

only part of a state’s CAIR reductions 

are achieved by EGUs, and the balance 

of the reductions obtained from nonEGU sources, then the stringency of 

CAIR EGU control would be diminished 

to some extent (an amount that cannot 

be determined until the State submits a 

SIP indicating which sources are 

participating in the program). Therefore, 

in these cases, the above rationale for 

our judgment that CAIR satisfies RACT 

would not apply. For this reason, a state 

selecting either of the above non-EGU 

options in implementing CAIR would 

need to conduct RACT analyses for 

EGUs in its PM2.5 nonattainment areas 

(either on an individual basis, or using 

the averaging approach within the 

nonattainment area) to determine 

whether the lesser EGU reductions 

satisfy RACT. 

For clarity, it should be noted that a 

State has authority to conduct its own 

RACT analysis for any source. Also, the 

proposed approach to CAIR and RACT 

would not prevent a state from requiring 

beyond-RACT controls to provide for 

expeditous attainment. 

RACT averaging concept. In addition 

to the option above relating to EGU 

compliance with CAIR and RACT for 

PM2.5, we propose to provide states with 

a nonattainment area RACT averaging 

option for EGU’s previously available in 

the ozone program. We also propose to 

make this option available to non-EGU 

categories for which accountability of an 

averaging system could be assured. 

The EPA’s NOX RACT guidance (NOX

General Preamble at 57 FR 55625) under 

the ozone program encourages States to 

develop NOX RACT programs for EGU’s 

that are based on ‘‘areawide average 

emission rates.’’ Thus, EPA’s 1992 

policy for ozone RACT provides for 

States to submit a demonstration as part 

of their RACT submittal showing that 

the weighted average emission rate from 

EGU sources in the nonattainment area 

subject to RACT—including sources 

reducing emissions to meet the NOX SIP 

Call or CAIR NOX requirements—meet 

RACT requirements. Under this 

approach, emission reductions within 

the nonattainment area must be at least 

66026 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

81Economic incentive program guidance, 

‘‘Improving Air Quality With Economic Incentive 

Programs,’’ January 2001. 

82Controlling Particulate Matter Under the Clean 

Air Act: A Menu of Options, STAPPA/ALAPCO, 

July 1996. 

83See EPA’s website at http://www.epa.gov/ttn/ 

catc for the Clean Air Technology Center and 

RACT/BACT/LAER Clearinghouse. 

84Available at: http://www.epa.gov/air/caaac/ 

aqm.html#library in response to the recent National 

Research Council report on Air Quality 

Management in the United States (January 2004) 

[available for sale; individual pages available for 

viewing at http://www.nap.edu/books/0309089328/ 

html]. 

equivalent to the emission reductions 

that would result from collective 

application of source-specific RACT 

within the nonattainment area. 

We envision that the state would first 

identify presumptive RACT for a set of 

emissions sources, as EPA has not 

issued guidance on RACT for PM2.5

purposes. The state would then propose 

a program that would assure collective 

emissions reductions equivalent or 

greater than the emissions reductions 

that would be achieved if the 

presumptive RACT level were met by 

each individual source. 

EPA proposes that the approach 

described above be available as a way 

for states to show that EGUs in PM2.5

nonattainment areas comply with RACT 

for NOX and SO2. Similarly, EPA 

proposes that this option be available to 

non-EGUs. As with other economic 

incentive programs, an approvable 

program would be required to ensure 

emissions reductions that are 

quantifiable, surplus, enforceable and 

permanent, and provide an 

environmental benefit.81

We generally solicit comment on 

whether RACT averaging should be 

permitted in PM2.5 areas for EGUs and 

non-EGUs, and which non-EGU source 

categories have adequate monitoring 

methods available to provide for 

accountability in an emissions trading 

program. In addition, we solicit 

comment on the following topics: 

• Whether RACT averaging in PM2.5

nonattainment areas, if permitted for 

both EGUs and non-EGUs, should be 

separate for EGUs and for non-EGUs, or 

whether averaging among EGUs and 

non-EGUs should be permitted 

• Whether a collective approach to 

RACT should be implemented through 

a rate-based approach (mass of 

emissions per activity level) involving 

weighted average emission rates (e.g., 

pounds of NOX per MMBtu of heat 

input), or through a cap-and-trade 

approach that controls total emissions 

regardless of activity level. 

• The appropriate averaging period 

for showing compliance with RACT for 

PM2.5 purposes 

12. Is EPA developing PM2.5 control 

techniques guidelines for specific 

source categories? 

To date, EPA has not developed a 

series of control techniques guidelines 

for specific source categories for the 

purposes of PM2.5 implementation. 

However, there are a number of sources 

of information on recent control 

technologies and other approaches for 

reducing PM2.5 and precursor emissions 

from stationary sources that are 

available to States and Tribes and can be 

helpful in making RACT determinations 

on a source category or source-specific 

basis. These sources of information 

include EPA’s 1998 guidance document 

on stationary source control measures, a 

1996 particulate matter ‘‘Menu of 

Options’’ document by STAPPA/ 

ALAPCO,82 and the EPA’s Clean Air 

Technology Center website.83 The Clean 

Air Technology Center website includes 

a wide variety of control technology 

information, including summaries of 

previous RACT determinations for other 

NAAQS programs, as well as 

assessments for best available control 

technology (BACT) and lowest 

achievable emissions rate (LAER) under 

the NSR and prevention of significant 

deterioration programs. 

Under the implementation program 

for the 1-hour ozone standard, a number 

of control techniques guidance (CTG) 

and alternative control technology 

(ACT) documents have been developed 

for sources of NOX and VOC over the 

past 25 years. (CTGs include a 

presumptive RACT level while ACTs do 

not. However, ACTs are intended to 

help States in making RACT 

determinations.) Over a five year period, 

1991–94, EPA issued nine alternative 

control technique guideline documents 

for large stationary sources of NOX. In 

2000, updates to the NOX ACT 

documents were completed for 

stationary internal combustion engines 

and cement kilns. In addition, EPA 

issued a number of CTGs in the 1980’s 

for various source categories of NOX and 

VOC. 

As discussed in section III.I.10 above, 

EPA recognizes that control technology 

guidance for certain source categories 

has not been updated for many years. 

Section 183(c) of the CAA, which 

addresses control technologies to 

address ozone nonattainment problems, 

requires EPA to ‘‘revise and update such 

documents as the Administrator 

determines necessary.’’ As new or 

updated information becomes available 

States should consider the new 

information in their RACT 

determinations. A State should consider 

the new information in any RACT 

determinations or certifications that 

have not been issued by the State as of 

the time such updated information 

becomes available.84

In addition, EPA is considering 

related recommendations from the Air 

Quality Management Work Group to the 

Clean Air Act Advisory Committee 

(CAAAC) dated January 2005. One of 

the recommendations to the CAAAQ is 

that ‘‘for the SIPs States are required to 

submit over the next several years, EPA 

and States, locals, and Tribes should 

promote the consideration of 

multipollutant impacts, including the 

impacts of air toxics, and where there is 

discretion, select regulatory approaches 

that maximize benefits from controlling 

key air toxics, as well as ozone, PM2.5

and regional haze.’’ As part of this 

effort, EPA intends in the future to 

develop updated technology guidance 

with respect to source categories 

emitting multiple pollutants in large 

amounts. At this time, however, we 

think it is unlikely that updated 

technology guidance will be available 

prior to 2006. The EPA also intends to 

maintain an updated list of references 

for new PM2.5 control technology 

options. We request that commenters 

submit any additional references for 

PM2.5 control technology information 

that may be useful for state program 

implementation efforts. 

We also have provided STAPPA/ 

ALAPCO with funding to update its 

1996 Particulate Matter Menu of 

Options document with additional 

information regarding control measures 

to reduce PM2.5 and its precursors. 

STAPPA/ALAPCO will be able to draw 

on the information and experience of its 

broad national membership in 

developing this updated guidance 

document for PM2.5. While we 

anticipate that this guidance document 

will provide very useful updated 

information for regulatory agencies and 

affected sources, the specifications in 

this privately-issued document will not 

be binding on States, sources, or EPA. 

13. Background for RACM 

The proposed approach for 

implementing the RACM requirement 

for PM2.5 is generally consistent with the 

approach followed under other NAAQS 

implementation programs. Under this 

approach, the State is required to 

provide a demonstration in its SIP that 

it has adopted all reasonably available 

measures needed to meet RFP and to 

attain the standard as expeditiously as 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66027 

practicable. The demonstration should 

show that there are no additional 

reasonable measures available that 

would advance the attainment date by at 

least one year or contribute to RFP for 

the area. Reasonable measures are those 

measures that are technologically and 

economically feasible within the 

nonattainment area. 

Under section 172, the attainment 

date for a nonattainment area is 

presumed to be within five years or less 

after the effective date of designation of 

the area (e.g., no later than April 2010 

for the final designations December 

2004). Each State is required to evaluate 

all RACM in the area to determine if any 

such measures could contribute to RFP 

or attainment as expeditiously as 

practicable. If this evaluation of all 

RACM finds that the State will not be 

able to demonstrate attainment within 

five years of designation based on the 

severity of the problem or the 

availability or feasibility of 

implementing controls, then the State 

may request an attainment date 

extension. The EPA may extend the 

attainment date for a period of 1 to 5 

years, provided the State has presented 

an adequate demonstration showing 

they will implement all RACT and 

RACM as expeditiously as practicable, 

and still need additional time to attain. 

14. What is the proposed approach for 

implementing RACM? 

The State should begin the process of 

determining RACM by identifying all 

available control measures in the 

nonattainment area. RACM can apply to 

mobile sources, area sources, and 

stationary sources not already subject to 

PM2.5 RACT requirements. If the State 

receives substantive public comment 

demonstrating through appropriate 

documentation that other specific 

control measures may be available for 

existing emissions sources or activities 

in the area, then the State or local 

agency must also closely review those 

additional control measures and 

determine if they are reasonably 

available for the area in light of local 

circumstances. 

After the universe of available 

measures have been identified for the 

sources in the area, the State should 

evaluate them to determine whether 

implementation of such measures is 

technically and economically feasible, 

and whether the measure will 

contribute to advancing the attainment 

date. The State should consider the 

feasibility of partial implementation of 

certain measures when ‘‘full’’

implementation would be infeasible. 

For example, if a State is considering 

diesel retrofits of school buses to be 

RACM for an area, it may not be feasible 

to retrofit all school buses in the 

nonattainment area, but it may be 

feasible to retrofit buses for specific 

school districts. The burden is with the 

State to provide a demonstration to EPA 

containing the justification and 

supporting documentation describing 

which measures it has determined to be 

RACM, and which it has not. 

Because the local circumstances for 

each area (e.g., design value, variety of 

emissions sources, contribution of each 

PM2.5 precursor to overall PM2.5 mass) 

will be different, the set of measures 

that constitute RACM are expected to 

vary from area to area. We anticipate 

that what may be considered RACM in 

one area may not be considered RACM 

in another. For example, certain 

transportation control measures, such as 

high occupancy vehicle (HOV) lanes, 

may be appropriate in a densely 

populated urban area with a significant 

commuting population, whereas HOV 

lanes may not be appropriate in a less 

densely populated suburban county. 

In any case, the State or local agency 

will have the initial responsibility for 

demonstrating to EPA that the area has 

adopted all reasonably available 

measures so that the area will achieve 

RFP and attain the standards as 

expeditiously as practicable, in 

accordance with applicable policy and 

guidance for attainment demonstrations 

and modeling. In reviewing the State’s 

selection of measures for RACM, or 

determination that certain measures are 

not RACM, EPA may supplement the 

rationale of the State or provide an 

alternative reason for reaching the same 

conclusion as the State, where 

appropriate. 

In the past under other SIP programs, 

there have been instances where a State 

proposed to reject a single measure 

under consideration as RACM because 

the emission reduction benefits from 

that measure alone would not advance 

the attainment date by one year. The 

EPA does not believe this approach is 

appropriate under section 172. In the 

past, EPA has historically interpreted 

the RACM requirement as requiring the 

collective evaluation of measures and 

the assessment of whether they will 

advance the attainment date when taken 

together. EPA believes this approach is 

appropriate for implementing the PM2.5

program. 

In a RACM assessment, the State 

should not reject an individual measure 

unless the State can show that it has 

evaluated the collective effect of that 

measure plus all other available control 

measures to determine whether 

implementing those measures together 

would advance the attainment date. The 

State’s analysis should provide a 

reasoned justification for rejecting any 

available control measures. The 

supporting information must show why 

each rejected measure, including any 

measure raised as part of the State’s 

public hearing or public comment 

process, is infeasible or unreasonable, or 

will not contribute to advancing 

attainment by one year. 

If, for example, a State determines 

that there are six available control 

measures that are technically and 

economically feasible, yet when 

implemented together they would not 

contribute to RFP or advance the 

attainment date, then the state would 

not be required to adopt the measures as 

RACM. On the other hand, suppose a 

State determines that there are ten 

available control measures that are 

technically and economically feasible 

and collectively these measures would 

advance the attainment date by more 

than a year but less than two years. If 

the State determines that the collective 

implementation of only seven of the 

measures would still advance the 

attainment date by at least one year, 

then the state only would be required to 

adopt the seven measures and not all 

ten. 

EPA emphasizes the importance for 

States to provide credible and thorough 

RACM analyses as part of their SIP 

demonstrations, complete with adequate 

supporting information and rationale 

supporting the State’s inclusion or 

rejection of control measures. Recent 

experience with other SIP programs has 

shown that members of the public may 

bring legal challenges against the State 

if the State fails to provide an adequate 

technical analysis and supporting 

information for RACM. We believe it is 

essential that the public have the benefit 

of reviewing credible State RACM 

analyses in order to be sure that 

emissions reductions will be achieved 

expeditiously and all requirements for 

RFP and timely attainment will be 

achieved. 

In the CAIR rulemaking (May 12, 2005 

(70 FR at 25221 et seq.), EPA found that 

the control installations projected to 

result from the CAIR NOX and SO2 caps 

in 2009 and 2010 would be as much as 

feasible from EGUs across the CAIR 

region by those dates. EPA concluded 

that the CAIR compliance dates 

represent an aggressive schedule that 

reflects the limitations of the labor pool, 

and equipment/vendor availability, and 

need for electrical generation reliability 

for installation of emission controls. 

States should recognize these 

constraints in developing their own 

compliance schedules for emission 

controls in meeting their CAIR and 

66028 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

RACT responsibilities. However, the 

CAIR trading program did not specify 

which sources should install emissions 

control equipment or reduce emissions 

rates to a specific level in order to meet 

the SO2 and NOX caps under CAIR. 

Based on our experience developing 

the NOX SIP call, CAIR, and the 

proposed Clear Skies legislation, we 

believe that many power companies will 

develop their strategies for complying 

with CAIR based, in part, on 

consultations with air quality officials 

in the areas in which their plants are 

located. Because power plants are 

generally major emission sources, the 

operators of those plants typically have 

ongoing relationships with state and 

local officials that will be involved in 

developing air quality plans. We are 

aware that, in the past, companies have 

worked with air quality officials to meet 

their emission control obligations under 

a cap-and-trade approach such as the 

NOX SIP call while also addressing the 

concerns of air quality officials about 

the air quality impacts of specific 

plants. This has led to controlling 

emissions from power plants located in 

or near specific ozone nonattainment 

areas. A number of companies have 

indicated that such collaboration will be 

even more important as the States where 

they are located address multiple air 

quality goals (e.g., visibility, interstate 

air pollution, local attainment). 

EPA expects similar consultations 

between States and power sector 

companies on the location of plants to 

be controlled under CAIR, considering 

local PM2.5 and ozone attainment needs 

in planning for CAIR compliance. This 

consultation might reveal opportunities 

to provide improved air quality earlier 

for large numbers of people. Power 

companies may identify economic 

advantages in situating CAIR controls to 

help the local area attain; for example, 

it might need to control fewer facilities 

for the area to reach attainment. These 

benefits may outweigh any additional 

marginal costs the company might incur 

by forgoing controls on another more 

distant plant. In any event, the intent of 

these consultations would not be to 

upset market behavior or incentives. 

Rather, we anticipate that these 

consultations will affect individual 

control decisions for certain PM2.5 areas. 

In this regard, EPA notes that CAIR SIPs 

will be due in 2006, while local 

attainment plans are proposed to be due 

in April 2008. EPA suggests that 

consultations on location of CAIR 

controls would be timely during state 

development of the CAIR SIP. 

15. What factors should States consider 

in determining whether control 

measures are reasonably available? 

Once the State has identified 

measures that are available for 

implementation in the nonattainment 

area, then it must evaluate those 

measures to determine whether 

implementation of such measures 

would be technically and economically 

feasible, and would collectively advance 

attainment. Many of the factors that the 

State should take into consideration in 

determining technical and economic 

feasibility are described earlier in 

sections 6 and 7 for RACT. Since RACM 

applies to area and mobile sources as 

well as stationary sources, the State 

should consider other factors as well in 

conducting its RACM analysis. For 

example, in many cases obtaining 

emissions reductions from area and 

mobile sources is achieved not by 

adding control technology to a specific 

emissions source, but by reducing the 

level of activity of a fleet of vehicles or 

by modifying a type of commercial 

process. In these situations, the State 

should also consider issues such as the 

social acceptability of the measure; local 

circumstances such as infrastructure, 

population, or workforce; and the time 

needed to implement the measure in 

light of the attainment date. 

In regard to economic feasibility, EPA 

is not proposing a fixed dollar per ton 

cost threshold for RACM, just as it is not 

doing so for RACT. We believe that 

what is considered to be a reasonable 

emission reduction level can vary based 

on the severity of the nonattainment 

problem in the area and existing control 

measures in place. Where the severity of 

the nonattainment problem makes 

reductions more imperative or where 

essential reductions are more difficult to 

achieve, the acceptable cost of achieving 

those reductions could increase. In 

addition, we believe that in determining 

what are economically feasible emission 

reduction levels, the State should also 

consider the collective health benefits 

that can be realized in the area due to 

projected improvements in air quality. 

Areas with more serious air quality 

problems typically will need to obtain 

greater levels of emissions reductions 

from local sources than areas with less 

serious problems, and it would be 

expected that their residents could 

realize greater health benefits from such 

reductions. For this reason, we believe 

that it will be reasonable and 

appropriate for areas with more serious 

air quality problems and higher design 

values to impose emission reduction 

requirements with generally higher 

costs per ton than the cost of emissions 

reductions in areas with lower design 

values. In areas with existing control 

measures in place for the purpose of 

attaining the PM10 standards, the RACM 

analysis should evaluate the costeffectiveness of additional control 

measures beyond those already being 

implemented. 

Some nonattainment areas with 2001–

2003 design values relatively close to 

the standard may be able to demonstrate 

through existing modeling analyses that 

they are projected to attain the standard 

within five years of the date of 

designation, based on the 

implementation of existing federally 

enforceable national and State measures 

alone (e.g., CAIR, national mobile 

source measures such as Tier II 

standards). 

EPA believes that while areas 

projected to attain within five years of 

designation as a result of existing 

national measures should still be 

required to conduct a RACM analysis, 

such areas may be able to conduct a 

limited RACM analysis that does not 

involve additional air quality modeling. 

A limited analysis of this type could 

involve the review of available 

reasonable measures, the estimation of 

potential emissions reductions, and the 

evaluation of the time needed to 

implement these measures. If the State 

could not achieve significant emissions 

reductions by the beginning of 2008 due 

to time needed to implement reasonable 

measures or other factors, then it could 

be concluded that reasonably available 

local measures would not advance the 

attainment date. In lieu of conducting 

air quality modeling to assess the 

impact of potential RACM measures, 

existing modeling information could be 

considered in determining the 

magnitude of emissions reductions that 

could significantly affect air quality and 

potentially result in earlier attainment. 

If the State, in consultation with EPA, 

determines from this initial, more 

limited RACM analysis that the area 

may be able to advance its attainment 

date through implementation of 

reasonable measures, then the State 

must conduct a more detailed RACM 

analysis, involving air quality modeling 

analyses, to assess whether it can 

advance the attainment date. 

16. What specific source categories and 

control measures should a State 

evaluate when determining RACM for a 

nonattainment area? 

Section 172 does not provide a 

specific list of source categories and 

control measures that must be evaluated 

for RACM for PM2.5. In order to provide 

further guidance to States in the form of 

a starting list of source categories to 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66029 

85 ‘‘Emission inventory analysis for 39 PM2.5

Nonattainment Areas,’’ memo by Richard Damberg 

to docket OAR–2003–0062. 

86See Clean School Bus USA program at http:// 

www.epa.gov/cleanschoolbus/. See also: ‘‘What You 

Should Know About Diesel Exhaust and School Bus 

Idling’’, (June 2003, EPA420–F–03–021) at http:// 

www.epa.gov/otaq/retrofit/documents/f03021.pdf. 

87See EPA’s voluntary diesel retrofit program 

web site at http://www.epa.gov/otaq/retrofit/ 

overfleetowner.htm. 

88See EPA’s voluntary diesel retrofit program 

web site at http://www.epa.gov/otaq/retrofit/ 

idling.htm. 

89See EPA’s website on transportation control 

measures at http://www.epa.gov/otaq/transp/ 

traqtcms.htm. 

90See EPA’s web site on nonroad engines, 

equipment, and vehicles at http://www.epa.gov/ 

otaq/nonroad.htm. 

consider in a RACM analysis, we 

reviewed 2001 national emission 

inventory information for the more than 

200 counties comprising PM2.5

nonattainment areas. We have identified 

the detailed stationary, mobile, and area 

source categories that are major 

contributors to total emissions of PM2.5

and its precursors in these counties.85

Based on our review of this emission 

inventory data and air quality 

monitoring data from the speciation 

trends network, we recognize that a 

wide variety of source categories 

contribute to PM2.5 concentrations in 

nonattainment areas across the country. 

We have also reviewed a wide variety of 

information sources to identify available 

control measures for many of these 

categories. Based on this analysis, a list 

of potential RACM measures is included 

at the end of this section. 

Emission reduction measures 

constituting RACM should be 

determined on an area-by-area basis. We 

believe that a State should consider 

each of the measures listed in this 

section to determine if each measure is 

reasonably available in the applicable 

nonattainment area. However, under 

current EPA policy we do not presume 

that each of these measures is 

reasonably available in each 

nonattainment area. 

We propose that each State use the 

list of source categories in this section 

as a starting point for identifying 

potentially available control strategies 

for a nonattainment area. States are 

encouraged and expected to add other 

potentially available measures to the list 

based on its knowledge of the particular 

universe of emissions sources in the 

area and comments from the general 

public. We expect that, depending on 

the potential measure being analyzed, 

the State’s degree of evaluation will vary 

as appropriate. 

Stationary Source Measures 

—Stationary diesel engine retrofit, 

rebuild or replacement, with 

catalyzed particle filter 

—New or upgraded emission control 

requirements for direct PM2.5

emissions at stationary sources (e.g., 

installation or improved performance 

of control devices such as a baghouse 

or electrostatic precipitator; revised 

opacity standard; improved 

compliance monitoring methods) 

—New or upgraded emission controls 

for PM2.5 precursors at stationary 

sources (e.g., SO2 controls such as wet 

or dry scrubbers, or reduced sulfur 

content in fuel) 

—Energy efficiency measures to reduce 

fuel consumption and associated 

pollutant emissions (either from local 

sources or distant power providers) 

Mobile Source Measures 

—Onroad diesel engine retrofits for 

school buses 86 and trucks using EPAverified technologies 

—Nonroad diesel engine retrofit, rebuild 

or replacement, with catalyzed 

particle filter 87

—Diesel idling programs for trucks, 

locomotive, and other mobile 

sources 88

—Transportation control measures 

(including those listed in section 

108(f) of the CAA as well as other 

TCMs), as well as other transportation 

demand management and 

transportation systems management 

strategies 89

—Programs to reduce emissions or 

accelerate retirement of high emitting 

vehicles, boats, and lawn and garden 

equipment 

—Emissions testing and repair/ 

maintenance programs for onroad 

vehicles 

—Emissions testing and repair/ 

maintenance programs for nonroad 

heavy-duty vehicles and equipment 90

—Programs to expand use of clean 

burning fuels 

—Prohibitions on the sale and use of 

diesel fuel that exceeds a high sulfur 

content 

—Low emissions specifications for 

equipment or fuel used for large 

construction contracts, industrial 

facilities, ship yards, airports, and 

public or private vehicle fleets 

—Opacity or other emissions standards 

for ‘‘gross-emitting’’ diesel equipment 

or vessels 

—Reduce dust from paved and unpaved 

roads 

Area Source Measures 

—New open burning regulations and/or 

measures to improve program 

effectiveness 

—Smoke management programs to 

minimize emissions from forest and 

agricultural burning activities 

—Programs to reduce emissions from 

woodstoves and fireplaces 

—Controls on emissions from 

charbroiling or other commercial 

cooking operations 

—Reduced solvent usage or solvent 

substitution (particularly for organic 

compounds with 7 carbon atoms or 

more, such as toluene, xylene, and 

trimethyl benzene) 

—Reduce dust from construction 

activities and vacant disturbed areas 

We request comment on the specific 

sources and potential control measures 

recommended for RACM analysis on 

this list. Commenters supporting the 

inclusion or exclusion of measures for 

this list should provide detailed 

supporting information as part of their 

comments. 

17. What criteria should be met to 

ensure effective regulations or permits 

to implement RACT and RACM? 

After the State has identified a RACT 

or RACM measure for a particular 

nonattainment area, it must then 

implement that measure through a 

legally enforceable mechanism (e.g., 

such as a regulation or a permit 

provision). The regulation or permit 

provision should meet four important 

criteria. 

First, the baseline emissions from the 

source or group of sources and the 

future year projected emissions should 

be quantifiable so that the projected 

emissions reductions from the sources 

can be attributed to the specific 

measures being implemented. It is 

important that the emissions from the 

source category in question are 

accurately represented in the baseline 

inventory so that emissions reductions 

are properly calculated. In particular, it 

is especially important to ensure that 

both the filterable and condensable 

components of PM2.5 are accurately 

represented in the baseline since 

traditional Federal and State test 

methods have not included the 

condensable component of particulate 

matter emissions and have not required 

particle sizing of the filterable 

component. 

Second, the control measures must be 

enforceable. This means that they must 

specify clear, unambiguous, and 

measurable requirements. When 

feasible, the measurable requirements 

for larger emitting facilities should 

include periodic source testing to 

establish the capability of such facilities 

to achieve the required emission level. 

Additionally, to verify the continued 

performance of the control measure, 

66030 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

91 ‘‘Incorporating Emerging and Voluntary 

Measures in a State Implementation Plan,’’ EPA 

Office of Air Quality Planning and Standards, Air 

Quality Strategies and Standards Division, Research 

Triangle Park, NC, September 2004. For further 

information, see: http://www.epa.gov/ttn/oarpg/t1/ 

memoranda/evm_ievm_g.pdf. 

92 ‘‘Guidance on Incorporating Voluntary Mobile 

Source Emission Reduction Programs in State 

Implementation Plans (SIPs),’’ memorandum from 

Richard D. Wilson, Acting Assistant Administrator 

for Air and Radiation, to EPA Regional 

Administrators, October 24, 1997. For further 

information, see http://www.epa.gov/otaq/transp/ 

vmweb/vmpoldoc.htm. 

specific monitoring programs 

appropriate for the type of control 

measure employed and the level of 

emissions must be included to verify the 

continued performance of the control 

measure. The control measures and 

monitoring program must also have 

been adopted according to proper legal 

procedures. 

Third, the measures should be 

replicable. This means that where a rule 

contains procedures for interpreting, 

changing, or determining compliance 

with the rule, the procedures are 

sufficiently specific and nonsubjective 

so that two independent entities 

applying the procedures would obtain 

the same result. 

Fourth, the control measures should 

be accountable. This means, for 

example, that source-specific emission 

limits should be permanent and must 

reflect the assumptions used in the SIP 

demonstration. It also means that the 

SIP must contain a mechanism (such as 

a title V operating permit) to track 

emission changes at sources and 

provide for corrective action if 

emissions reductions are not achieved 

according to the plan. 

J. What guidance is available to States 

and Tribes for implementing innovative 

programs to address the PM2.5 problem? 

EPA recognizes that, in order to 

address their fine particle problems, 

States, Tribes, and local agencies may 

need to approach certain categories of 

contributing emissions sources in nontraditional and innovative ways. EPA 

has developed several guidance 

documents on innovative programs and 

policies that may be useful to States and 

Tribes in developing implementation 

plans for attaining the PM2.5 standards, 

and these are available at http:// 

www.epa.gov/ttn/airinnovations/ 

policy.html. 

Many of these guidance documents 

and policies provide information on 

approaches that could be used for 

achieving reductions in emissions of 

PM2.5 and its precursors. In 2001, EPA 

released guidance on the development 

and implementation of nontraditional 

measures. This guidance, entitled 

‘‘Improving Air Quality with Economic 

Incentive Programs,’’ provides factors to 

use to select the right emissions control 

program, as well as guidance on writing 

nontraditional regulations that can be 

approved into a SIP. 

EPA has also developed policy 

documents that provide guidance on 

attaining credit in SIPs for voluntary 

measures which reduce emissions from 

stationary sources 91 and from mobile 

sources.92 Current SIP policy requires 

that, in order for an emission reduction 

measure to be approved, the emissions 

reductions must be quantifiable, surplus 

to other program requirements, 

enforceable, and permanent. These 

‘‘voluntary measures’’ policies address 

situations in which reductions will be 

achieved despite the lack of any directly 

enforceable requirement on the sources 

of emissions. Under these policies, the 

State would receive credit toward its 

SIP obligations, and it would be 

responsible for assuring that the 

emissions reductions credited in the SIP 

actually occur. The State would make 

an enforceable commitment to monitor, 

assess and report on the emissions 

reductions resulting from the voluntary 

measures, and to remedy any shortfalls 

from forecasted emissions reductions in 

a timely manner. An example of 

stationary source measures that could be 

considered under this policy are noburn days for wood stoves, voluntary 

woodstove change-out programs, or 

energy conservation programs. 

Examples of voluntary mobile source 

measures include ozone action plans, 

reduced switchboard locomotive idling, 

and trip reduction strategies. 

The emerging and voluntary measures 

policy also addresses situations where 

quantification of projected emissions 

reductions from certain measures may 

be difficult to assess. The policy enables 

a State to receive provisional credit for 

implementing hard-to-quantify 

measures and sets forth procedures by 

which the State should evaluate 

program effectiveness. 

Request for Comment on the 

Integrated Local Emission Reduction 

Program Concept. While significant 

environmental gains will be achieved 

through the Title IV SO2 Acid Rain 

Program, the NOX SIP Call Program, the 

Mobile Source Control Program, and 

future implementation of the Clean Air 

Interstate Rule (CAIR), they are not 

designed to solve every nonattainment 

problem. Residual nonattainment areas 

will continue to exist after 

implementation of these programs, and 

EPA believes that it may be useful to 

provide incentives that would stimulate 

innovative programs to focus additional 

emission reduction efforts designed to 

help bring these remaining 

nonattainment areas into attainment. 

In particular, it may be useful to 

provide real incentives for the 

emissions-generating community to 

help design additional approaches on 

their own initiative that could achieve 

further environmental benefits outside 

of the sources and emissions subject to 

these rules. 

EPA is interested in ideas that could 

create a system which satisfies regional 

reduction obligations through targeted 

reduction strategies for designated 

nonattainment areas. These ideas and 

incentives could be designed and 

administered by individual States, or 

groups of States to be incorporated as 

part of their State and local attainment 

planning process for developing SIPs. 

We believe that, for any such program 

to be successful, it would need to 

balance accountability and flexibility, as 

well as respond to the needs and 

concerns of air pollution control 

agencies and regulated sources. 

To support the concept of the ILERP, 

EPA solicits comment on the 

development and application of factors 

or criteria for the States and the 

emissions-generating community that 

would take into account the unique 

needs of specific nonattainment areas. 

We also seek comment on approaches 

that would provide incentives for 

improved monitoring and 

characterization of emissions, e.g., using 

different factors based on the technical 

rigor and reliability of emissions 

verification methods. 

Potential mechanisms could range 

from basic financial incentives to more 

aggressive and innovative approaches. 

In its simplest form, the emissionsgenerating community could choose to 

complement or expand existing control 

measures, or perhaps fund new ones. 

Under the latter approach, a specific 

value could be applied to a ton of local 

emissions to be reduced depending on 

one or more specific criteria such as: 

The accuracy and technical validity of 

emissions monitoring used to 

characterize emissions or demonstrate 

compliance, seasonal timing or location 

of the reductions, population exposure, 

or other considerations. 

For example, reducing PM2.5 from a 

sector in a nonattainment area might 

receive a greater value than reductions 

from a sector that is upwind of the 

nonattainment area most of the year, 

due to the relative effectiveness of the 

measures at reducing population 

exposure and monitoring of PM2.5. 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66031 

93 69 FR 72140 (December 13, 2004). 

Another example could be one in which 

the emissions-generating facility 

receives an incentive in exchange for 

reductions in other pollutants causing 

PM2.5, based on using technically 

appropriate air quality models to 

demonstrate superior environmental 

results. 

We seek comment, consistent with the 

philosophy of State implementation 

planning, on various approaches that 

could incorporate these ideas to allow 

the States to implement such a program 

that would result in greater emissions 

reductions and greater environmental 

results beyond the reductions achieved 

by the aforementioned existing 

programs. 

K. What aspects of transportation 

conformity and the PM2.5 standard are 

addressed in this proposal? 

1. What is transportation conformity? 

Transportation conformity is required 

under section 176(c) of the CAA (42 

U.S.C. 7506(c)) to ensure that federally 

supported highway and transit project 

activities are consistent with (‘‘conform 

to’’) the purpose of a SIP. Conformity to 

the purpose of the SIP means that 

transportation activities will not cause 

new air quality violations, worsen 

existing violations, or delay timely 

attainment of the NAAQS. 

Transportation conformity applies in 

nonattainment areas and maintenance 

areas. The EPA’s transportation 

conformity rule, 40 CFR part 93, 

establishes the criteria and procedures 

for determining whether transportation 

activities conform to the State air 

quality plan. It also establishes criteria 

and procedures for determining whether 

transportation activities conform in 

areas where no SIP containing mobile 

source emissions budgets yet exists. 

EPA first published the transportation 

conformity rule on November 24, 1993 

(58 FR 62188) and has amended the rule 

several times. On August 15, 1997, a 

comprehensive set of amendments was 

published that clarified and streamlined 

language from the 1993 transportation 

conformity rule (62 FR 43780). On July 

1, 2004 the rule was amended to address 

conformity requirements in 8-hour 

ozone and PM2.5 nonattainment and 

maintenance areas (69 FR 40004). The 

July 1, 2004 final rule also incorporated 

revisions related to a March 1999 court 

decision and further clarified and 

streamlined language in the previous 

version of the rule. On May 6, 2005, 

EPA finalized a rule on requirements for 

addressing PM2.5 precursors in 

transportation conformity 

determinations (70 FR 24280). These 

rulemakings, as well as other relevant 

conformity materials such as guidance 

documents, policy memoranda, the 

complete text of the conformity rule, 

and conformity research can be found at 

EPA’s transportation conformity Web 

site, at http://www.epa.gov/otaq/ 

transp.htm (once at the site, click on 

‘‘Transportation Conformity.’’) 

2. Why does transportation conformity 

apply to PM2.5? 

Transportation conformity will apply 

to PM2.5 because EPA has evidence to 

indicate that motor vehicle emissions 

are significant contributors to the air 

quality problem in most, if not all, PM2.5

nonattainment areas. Gasoline and 

diesel vehicles emit fine particulate 

matter as well as PM2.5 precursors such 

as volatile organic compounds (VOCs), 

NOX, sulfur oxides (SO2) and ammonia 

(NH3). Travel on paved and unpaved 

roads results in re-entrained road dust 

which may contribute to measured 

PM2.5 violations. Also, in some areas 

transportation-related construction 

activities may also result in the creation 

of significant amounts of dust. 

3. Why is EPA discussing transportation 

conformity in this proposal? 

We are not proposing changes to the 

transportation conformity rule in 

today’s proposal. Instead, we are 

discussing transportation conformity in 

this notice in order to provide affected 

parties with information on when 

transportation conformity will be 

implemented under the PM2.5 standard. 

Affected parties may include State and 

local transportation and air quality 

agencies, metropolitan planning 

organizations (MPOs) and the U.S. 

Department of Transportation (DOT). To 

determine whether this discussion 

affects your organization, you should 

carefully examine the applicability 

requirements in 40 CFR 93.102 of the 

transportation conformity rule. 

4. What revisions have been made to the 

transportation conformity rule to 

address the PM2.5 standard? 

The July 1, 2004, transportation 

conformity rule revisions contain a 

number of provisions that apply to 

PM2.5 nonattainment and maintenance 

areas. For example, the July 1, 2004, 

rule contains requirements for: regional 

conformity tests in PM2.5 areas; 

considering direct emissions of PM2.5

(i.e., exhaust, brake and tire wear and reentrained dust) in regional emissions 

analyses; considering re-entrained road 

dust and construction-related fugitive 

dust in regional emissions analyses and 

compliance with PM2.5 SIP control 

measures. 

In addition to the July 1, 2004 rule, 

EPA published a final rule on May 6, 

2005 (70 FR 24280) that established 

requirements for addressing PM2.5

precursors in regional emissions 

analyses. EPA also published a 

supplemental notice of proposed 

rulemaking 93 requesting comment on a 

number of options for consideration of 

localized emissions impacts of 

individual transportation projects in 

PM2.5 nonattainment and maintenance 

areas. We intend to finalize 

requirements for localized emissions 

analyses in PM2.5 nonattainment and 

maintenance areas as expeditiously as 

possible. 

5. Does EPA plan to revoke the PM10

standard? 

No, we are not planning to revoke the 

PM10 standards at this time. We are in 

the process of reviewing the PM 

NAAQS, and as part of that process we 

are considering whether the current 

scientific literature would support the 

establishment of coarse particle 

standards. (Coarse particles are those 

which have an aerodynamic diameter 

between 2.5 and 10 micrometers.) 

6. Will some areas be demonstrating 

conformity for both PM10 and PM2.5 at 

the same time? 

Yes, since the PM10 standard is being 

retained, a small number of areas will be 

required to determine conformity to 

both air quality standards. PM10

nonattainment and maintenance areas 

should continue to make PM10

conformity determinations according to 

the conformity regulation. By the end of 

the one-year grace period, conformity of 

metropolitan plans and transportation 

improvement programs (TIPs) must be 

determined, reflecting the metropolitan 

area and any associated donut areas 

(defined below). 

7. When does transportation conformity 

apply to PM2.5 nonattainment areas? 

Transportation conformity applies to 

PM2.5 nonattainment areas one year after 

the effective date of an area’s 

designation. This one-year grace period 

is found in the CAA at 42 U.S.C. 

7506(c)(6). Specifically, this section of 

the CAA provides areas, when they are 

first designated nonattainment for a 

given air quality standard, with a oneyear grace period before the conformity 

regulation applies with respect to that 

standard. Since the PM2.5 standard is a 

different standard from the PM10

standard, every area that is designated 

nonattainment for the PM2.5 standard 

will have a one-year grace period before 

66032 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

94When used only in this section on 

transportation conformity, the acronym ‘‘TIP’’ refers 

to ‘‘transportation improvement program.’’ In all 

other sections of this preamble, the acronym ‘‘TIP’’

stands for ‘‘tribal implementation plan.’’

conformity applies for the PM2.5

standard, regardless of whether 

conformity applies in the area for the 

PM10 standard. 

For more information, please see the 

proposed and final rulemaking entitled, 

‘‘Transportation Conformity Rule 

Amendments: Minor Revision of 18- 

Month Requirement for Initial SIP 

Submissions and Addition of Grace 

Period for Newly Designated 

Nonattainment Areas,’’ published 

October 5, 2001, (66 FR 50954), and 

August 6, 2002, (67 FR 50808), 

respectively for additional discussion of 

the one-year grace period for newly 

designated areas. (The proposed and 

final rule can be found on EPA’s 

transportation conformity website 

mentioned above.) 

8. How does the 1-year grace period 

apply in metropolitan areas? 

A one-year grace period for 

implementation of the conformity 

program applies in metropolitan areas 

that have an established metropolitan 

planning organization (MPO) that is 

responsible for transportation planning 

per 23 U.S.C. 134. In these areas, the 

one-year grace period means that, one 

year after the effective date of an area’s 

designation as nonattainment for the 

PM2.5 standard, the area must have a 

conforming transportation plan and 

transportation improvement program 

(TIP) 94 in place to fund or approve 

transportation projects. (For the 

discussion of which projects can 

proceed after the end of the grace period 

if a conformity determination has not 

been made by the MPO and U.S. DOT, 

please see the July 1, 2004 final rule (69 

FR 40037), DOT’s January 2, 2002, 

guidance, published February 7, 2002, 

at 67 FR 5882; and EPA’s May 14, 1999, 

conformity guidance. All of these 

documents can be found on EPA’s 

transportation conformity Web site.) 

9. How does the 1-year grace period 

apply in ‘‘donut’’ areas? 

For the purposes of conformity, a 

donut area is the geographic area 

outside a metropolitan planning area 

boundary, but inside the boundary of a 

designated nonattainment/maintenance 

area. The conformity requirements for 

donut areas are generally the same as 

those for metropolitan areas, and the 

MPO would include any projects 

occurring in the donut area in its 

analysis of the metropolitan 

transportation plan and TIP. A donut 

area is not an isolated rural area for the 

purposes of the conformity process. 

Therefore, the one-year grace period 

applies to donut areas in much the same 

way that it applies to metropolitan 

areas. That is, within one year of the 

effective date of an area’s designation, a 

donut area’s projects must be included 

in an MPO’s conformity determination 

for the metropolitan plan and TIP for 

those projects to be funded or approved. 

If, at the conclusion of the one-year 

grace period, the donut area’s projects 

have not been included in the MPO’s 

conformity determination, new 

‘‘nonexempt’’ projects and project 

phases could not be approved in the 

metropolitan area or the donut area. 

10. How does the 1-year grace period 

apply in isolated rural areas? 

For the purposes of conformity, 

isolated rural nonattainment and 

maintenance areas are areas that do not 

contain or are not part of any 

metropolitan planning area designated 

under the transportation planning 

regulations. Isolated rural areas do not 

have federally required metropolitan 

transportation plans or TIPs and do not 

have projects that are part of the 

emissions analysis of any MPO’s 

transportation plan or TIP. Isolated rural 

areas are distinguished from ‘‘donut’’

areas which are geographic areas 

outside a metropolitan planning area 

boundary, but inside the boundary of a 

nonattainment or CAA section 175A 

maintenance plan area that is 

dominated by a metropolitan area(s). 

Because isolated rural areas do not 

have federally required metropolitan 

transportation plans and TIPs, a 

conformity determination need only be 

done in an isolated rural area when that 

area has a transportation project or 

projects that need approval. Therefore, 

isolated rural areas also have a one-year 

grace period before conformity applies 

under the PM2.5 standard, but at the end 

of that grace period, the area does not 

have to have made a conformity 

determination. An isolated rural area 

would be required to do conformity 

only at the point when a new 

transportation project needs approval. 

This point may occur significantly after 

the one-year grace period has ended. 

(Conformity requirements for isolated 

rural areas can be found at 40 CFR 

93.109(g).) 

L. What requirements for general 

conformity should apply to the PM2.5

standards? 

1. What is the purpose of the general 

conformity regulations? 

Section 176(c) of the CAA requires 

that before a Federal entity takes an 

action, it must make a determination 

that the proposed action will not 

interfere with the SIP or the State’s 

ability to attain and maintain the 

NAAQS. In November 1993, EPA 

promulgated two sets of regulations to 

implement section 176(c). One set, 

known as the Transportation 

Conformity Regulations (described 

above) deals with approval and funding 

of highway and mass transit project. The 

other set, known as the general 

conformity regulations, deals with all 

other Federal activities. Besides 

ensuring that Federal actions will not 

interfere with the SIP, the general 

conformity program also fosters 

communications with State/local air 

quality agencies, allows for public 

participation in the review of air quality 

impacts from Federal actions, and 

allows for air quality review of 

individual projects. In 1995, Congress 

limited the application of section 176(c) 

to nonattainment and maintenance areas 

only. 

2. How is the general conformity 

program currently structured? 

Due to the very broad definition of 

‘‘Federal action’’ in the statute and the 

number of Federal agencies subject to 

the conformity requirement, the number 

of individual conformity decisions 

could have been on the order of a 

thousand or more per day. To avoid 

creating an unreasonable administrative 

burden, EPA established de minimis 

emissions levels and exempted certain 

actions. In addition, the regulations 

allow Federal agencies to develop their 

own list of actions which are presumed 

to conform. For non-exempt actions that 

increase emissions above the de 

minimis levels, the Federal agency must 

demonstrate that the action will 

conform with the SIP or will not cause 

or contribute to any new violation of 

any standard in any area; interfere with 

provisions in the applicable SIP for 

maintenance of any standard; increase 

the frequency or severity of any existing 

violation of any standard; or delay 

timely attainment of any standard or 

any required interim emissions 

reductions or other milestone. We are 

currently reviewing the general 

conformity program and, in a separate 

action, may revise the regulations as 

appropriate, with respect to the PM2.5

standards. 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66033 

95See 68 FR 32843. 

96See section 42 U.S.C. 7506(c)(6). 

97The Act uses the terms ‘‘major emitting 

facility’’ to refer to sources subject to the PSD 

program, and ‘‘major stationary source’’ to refer to 

sources subject to Nonattainment NSR. CAA 

Sections 169 and 302(j). For ease of reference, we 

use the term ‘‘major source’’ to refer to both terms. 

98 In addition, the PSD program applies to most 

noncriteria regulated pollutants. 

3. Who runs the general conformity 

program? 

Each Federal agency is responsible for 

determining if the action it takes is 

subject to the conformity regulations 

and, if so, whether the action conforms 

to the SIP. Each Federal agency’s 

approach to the conformity evaluation 

differs depending upon the actions 

being taken. Agencies that permit or 

fund actions subject to the conformity 

rules generally require the applicant to 

develop the technical support for the 

conformity determination, although 

some agencies undertake the complete 

evaluation themselves. 

4. How does an agency demonstrate 

conformity? 

Depending upon the pollutant and the 

specific situation, Federal agencies have 

several options for demonstrating 

conformity. For actions in PM2.5

nonattainment and maintenance areas, 

the Federal agency can demonstrate that 

the project/action is specifically 

identified and accounted for in the SIP, 

obtain documentation from the State 

that the emissions are included in the 

SIP, have the State commit to include 

the emissions in the SIP, or mitigate the 

emissions or offset the emissions from 

emissions reductions within the same 

nonattainment or maintenance area. 

5. General Conformity Regulation 

Revisions for the PM2.5 Standards 

a. What de minimis emission levels will 

be set for pollutants that contribute to 

PM2.5 concentrations? 

As discussed in the technical 

overview section, the key pollutants 

contributing to PM2.5 concentrations in 

the atmosphere are direct PM2.5

emissions, SO2, NOX, VOC, and 

ammonia. Section II.E. proposes policy 

options for addressing each of these 

precursors under the PM2.5

implementation program. After 

consideration of public comment, EPA 

will finalize precursor requirements for 

the PM2.5 implementation program. 

When finalized, these precursor 

requirements will also apply under the 

general conformity program. 

In another rulemaking action, we will 

propose to establish de minimis 

emission levels for federal projects or 

actions covered by the general 

conformity program. It is expected that 

the proposed levels will be identical to 

the nonattainment area major source 

levels for the NSR program. Under this 

approach, PM2.5 nonattainment areas 

would have de minimis emission levels 

for general conformity purposes of 100 

tons per year for all PM2.5 pollutants. 

These levels are also consistent with the 

levels proposed for VOC and NOX

emissions in subpart 1 areas under the 

8-hour ozone implementation strategy.95

b. What impact will the implementation 

of the PM2.5 standards have on a State’s 

general conformity SIP? 

Since we are not now proposing to 

make specific revisions to the general 

conformity regulations in this proposal, 

States should not need to revise their 

general conformity SIPs, unless they 

need to do so to ensure the regulations 

apply in the appropriate areas. 

c. Are there any other impacts on the 

SIPs related to general conformity based 

on implementation of the PM2.5

standards? 

Currently, we are developing a 

revision to the general conformity 

regulations through a separate 

rulemaking action, but we are not 

proposing any general conformity 

revisions in today’s action. However, as 

areas develop SIPs for the PM2.5

standards, we recommend that State and 

local air quality agencies work with 

major facilities which are subject to the 

general conformity regulations (e.g., 

commercial airports and large military 

bases) to establish an emission budget 

for each facility in order to facilitate 

future conformity determinations. Such 

a budget could be used by Federal 

agencies in determining conformity or 

identifying mitigation measures. 

6. Is there a 1-year grace period which 

applies to general conformity 

determinations for the purposes of the 

PM2.5 standards? 

Yes, the 1-year grace period for 

implementation of conformity 

requirements after area designations are 

completed applies to both 

transportation and general conformity.96

Therefore, the general conformity 

requirements would not apply to federal 

actions or projects in newly designated 

nonattainment areas until 1 year after 

the effective date of the PM2.5 area 

designation. The effective date of the 

PM2.5 designations was April 2005. 

Thus, general conformity requirements 

would apply in April 2006. As 

discussed earlier, the PM2.5 standards 

are new and the grace period applies to 

all the areas designated nonattainment 

for that standard. The general 

conformity regulations specify 

requirements for actions/projects in 

areas without an approved SIP. Those 

requirements would apply to PM2.5

nonattainment areas until the SIP is 

approved by EPA. 

M. How will the NSR program address 

PM2.5 and its precursors? 

1. Background 

The existing regulations require both 

major and minor New Source Review 

(NSR) programs to address any pollutant 

for which there is a national ambient air 

quality standard (NAAQS) and any 

precursors to the formation of that 

pollutant when identified for regulation 

by the Administrator. We are proposing 

to amend the NSR regulations to clarify 

how States, local agencies and Tribes 

must implement NSR for the PM2.5

standard. This proposal also explains 

how the existing rules will be 

implemented with respect to PM2.5

during the State Implementation Plan 

(SIP) development period. 

The NSR program is a preconstruction 

permitting program that applies when a 

source is constructed or modified. The 

NSR program is composed of three 

different programs: 

• Prevention of Significant 

Deterioration (PSD); 

• Nonattainment NSR (NA NSR); and, 

• Minor NSR. 

We often refer to the PSD and 

Nonattainment NSR program as the 

major NSR program because these 

programs regulate only major sources.97

The PSD program applies when a 

major source, that is located in an area 

that is designated as attainment or 

unclassifiable for any criteria pollutant, 

is constructed or undergoes a major 

modification.98 The NA NSR program 

applies when a major source that is 

located in an area that is designated as 

nonattainment for any criteria pollutant 

is constructed or undergoes a major 

modification. The minor NSR program 

addresses both major and minor sources 

that undertake construction or 

modification activities that do not 

qualify as major, and it applies 

regardless of the designation of the area 

in which a source is located. 

The national regulations that apply to 

each of these programs are located in 

the Code of Federal Regulations (CFR) 

as shown below: 

66034 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

Applicable regulations 

PSD ........... 40 CFR 52.21, 40 CFR 51.166, 

40 CFR 51.165(b). 

NA NSR ..... 40 CFR 52.24, 40 CFR 51.165, 

40 CFR Part 51, Appendix S. 

Minor NSR 40 CFR 51.160–164. 

The PSD requirements include but are 

not limited to: 

• Installation of Best Available 

Control Technology (BACT), 

• Air quality monitoring and 

modeling analyses to ensure that a 

project’s emissions will not cause or 

contribute to a violation of any NAAQS 

or maximum allowable pollutant 

increase (PSD increment), 

• Notification of Federal Land 

Manager of nearby Class I areas, and 

• Public comment on the permit. 

Nonattainment NSR requirements 

include but are not limited to: 

• Installation of Lowest Achievable 

Emissions Rate (LAER) control 

technology, 

• Offsetting new emissions with 

creditable emissions reductions, 

• Certification that all major sources 

owned and operated in the State by the 

same owner are in compliance with all 

applicable requirements under the Act, 

• An alternative siting analysis 

demonstrating that the benefits of the 

proposed source significantly outweigh 

the environmental and social costs 

imposed as a result of its location, 

construction, or modification, 

• Public comment on the permit. 

Minor NSR programs must meet the 

statutory requirements in Section 

110(a)(2)(c) of the Act which requires 

‘‘* * *regulation of the modification 

and construction of any stationary 

source* * * as necessary to assure that 

the [NAAQS] are achieved.’’

This proposed rule on the 

implementation of NSR for PM2.5 does 

not supersede existing PM10 NSR 

requirements. EPA is not planning to 

revoke the original PM10 standards at 

this time. Accordingly, sources are 

subject to NSR for both PM10 and PM2.5. 

2. What are the principal elements of 

the proposed major NSR program for 

PM2.5? 

The table below summarizes the main 

elements of the existing major NSR 

program that EPA is proposing to 

address for PM2.5 as a regulated NSR 

pollutant. The EPA’s proposal for each 

element, or where appropriate, 

explanation of implementation under 

existing regulations, is explained in 

detail in the referenced sections of this 

preamble. 

Major NSR program element EPA proposal Section 

PSD Major Source Threshold .................................................... 100/250 TPY (no change) ........................................................ IV.M.4. 

NA NSR Major Source Threshold ............................................. 100 TPY (no change) ............................................................... IV.M.4. 

Significant Emissions Rate ........................................................ PM2.5 Direct Emissions—10 TPY; SO2—40 TPY .................... IV.M.5 & 6. 

If other precursors are included:.

NOX—40 TPY (no change).

VOC & Ammonia—determined by SIP.

Control technology: BACT and LAER ....................................... Applies for PM2.5 direct, SO2 and other precursors, if included.IV.M.9 & 13. 

Air quality impact analysis ......................................................... Applies for PM2.5 ...................................................................... IV.M.11. 

Preconstruction monitoring ........................................................ Applies for PM2.5. .....................................................................

Proposing five options to address. ..........................................

IV.M.12. 

NA NSR Statewide compliance ................................................. Applies for PM2.5 direct and precursors, if included ................ IV.M.13. 

NA NSR offsets ......................................................................... Applies for PM2.5 direct ............................................................

Considering for precursor emissions .......................................

IV.M.14. 

Interprecursor Offsetting ............................................................ Allowed with modeling demonstration (no change) ................. IV.M.14.c. 

Transition for PSD ..................................................................... Continues to apply with limited provisions for use of PM10 as 

a surrogate.

IV.M.16. 

Transition for NA NSR ............................................................... Applies at designation through an approved SIP or through 

40 CFR part 51, appendix S.

IV.M.17. 

Minor NSR ................................................................................. Clarifies that State and local regulatory programs must include PM2.5 requirements for minor sources.IV.M.20. 

NSR Transport Option ............................................................... Flexible implementation for areas granted a transport classification.IV.M.21. 

The proposed provisions of the PM2.5

major NSR program will be codified in 

the regulatory text as revisions to 40 

CFR 51.165; 51.166; 52.21; and 40 CFR 

part 51, Appendix S. We have made two 

assumptions in developing the proposed 

regulatory text for this rule. 

The first assumption is that the ozone 

phase II rule will be promulgated prior 

to the promulgation of this proposed 

PM2.5 rule. Thus, this proposed PM2.5

rule includes language related to ozone 

precursors and offsets that make the 

format of the ozone rule consistent with 

the PM2.5 language. The ozone 

provisions contained in the regulatory 

text set forth below are consistent with 

what we expect to finalize in the ozone 

rule, and this PM2.5 proposal is not 

intended to alter the substance of the 

ozone phase II rule. To the extent there 

are changes to the ozone phase II 

regulatory language when promulgated 

or the ozone rule is not promulgated 

prior to the final PM2.5 rule, we would 

need to make changes to the proposed 

regulatory text in this PM2.5 rule at 

promulgation. 

The paragraphs in the revisions to 

appendix S of this proposed PM2.5 rule 

have not been numbered at this time, 

based on the second assumption that 

both of the appendix S rule revisions, 

appendix S changes in the ozone phase 

II rule (incorporating the 1990 

amendments) and the revisions to 

appendix S (incorporating NSR reform), 

will be promulgated prior to the final 

PM2.5 rule. Depending on the status of 

these appendix S rule revisions at the 

time of promulgation of the PM2.5 rule, 

the paragraphs would be numbered 

accordingly. 

3. Should precursors to the formation of 

ambient concentrations of PM2.5 be 

subject to regulation under NSR? 

a. Background 

Certain NAAQS pollutants such as 

ozone and PM2.5, are partially or entirely 

formed by precursors. Precursors are 

currently regulated under parts C and D 

of the Act based on either statutory 

presumptions or a scientific 

determination that the pollutants must 

be regulated to achieve attainment. The 

following table shows precursors that 

we have identified for regulation under 

the NSR program because of their ability 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66035 

99We have proposed to amend the PSD 

regulations to expressly include NOx as an ozone 

precursor. 68 FR 32802 (June 2, 2003). 

to cause or contribute to violations of 

the ozone NAAQS. 

Criteria pollutant Precursor pollutants 

Ozone: 

Nonattainment Areas ......................................................................... Volatile Organic Compounds (VOC) and Nitrogen Oxides (NOX). 

Attainment Areas ............................................................................... VOC 99. 

Individual SIPs may identify additional 

precursors as regulated NSR pollutants. 

Scientific research has shown that 

various pollutants can contribute to 

ambient PM2.5 concentrations, including 

the following: 

• PM2.5 (direct emissions) 

• SO2 (as a precursor) 

• NOX (as a precursor) 

• VOC (as a precursor) 

• Ammonia (as a precursor) 

b. Should NSR cover precursor 

emissions in addition to direct 

emissions of PM2.5? 

Contribution of precursors to PM2.5

nonattainment. As discussed in Section 

II, precursors contribute significantly to 

ambient PM2.5 concentrations, 

producing approximately half of the 

concentration. In most areas of the 

country, PM2.5 precursor emissions are 

the major contributors to ambient PM2.5

concentrations. However, it is 

technically difficult to determine 

impacts of source-specific precursor 

emissions on ambient air quality levels. 

The relative contribution to ambient 

PM2.5 concentrations from each of these 

pollutants varies by area. The relative 

effect of reducing emissions of these 

pollutants is also highly variable. 

PM2.5 precursors already addressed 

under NSR. Some PM2.5 precursors are 

already subject to major NSR under 

other NAAQS as shown below: 

PM2.5 precursor ........................................................................................ Existing Program coverage for major NSR applicability. 

NOX .......................................................................................................... NA NSR for NO2 and Ozone PSD for NO2. 

SO2 ............................................................................................................ NA NSR and PSD for SO2. 

VOC .......................................................................................................... NA NSR and PSD for Ozone. 

Ammonia .................................................................................................. No coverage for NSR (Some areas regulate ammonia for other air 

quality purposes.) 

The PM2.5 NSR program could include 

some, all or none of these precursors of 

PM2.5. 

Legal Authority. As discussed earlier 

in section II.E. of this preamble, we 

interpret the Clean Air Act to provide 

explicit authority for EPA to regulate 

precursors but also to grant the 

Administrator discretion to determine 

how to address precursors for particular 

regulatory purposes. This reading is 

based on section 302(g) of the Clean Air 

Act which defines the term ‘‘air 

pollutant’’ to include ‘‘any precursors to 

the formation of any air pollutant, to the 

extent the Administrator has identified 

such precursor or precursors for the 

particular purpose for which the term 

‘air pollutant’ is used.’’ The 

Administrator’s discretion to determine 

how to address precursors under 

specific programs is also supported by 

the language in sections 182(f) and 

189(e) which identifies circumstances 

where the Administrator may determine 

that it is not appropriate to regulate 

certain precursors. We discuss these 

provisions in more detail in section II.E. 

Thus, we interpret section 302(g) of 

the Act to require that the Administrator 

consider how to address precursors 

under the NSR program. The term ‘‘air 

pollutant’’ is incorporated into the NSR 

provisions for various purposes. 

Sections 182(f) and 189(e) apply to State 

implementation plan provisions and 

control requirements, which include 

NSR programs. 

With regard to PSD, Section 165(a)(3) 

of the Act states that new or modified 

major sources must demonstrate that 

emissions ‘‘will not cause, or contribute 

to, air pollution in excess of any * * * 

NAAQS in any air quality control 

region.’’ A source could not reasonably 

make this demonstration without 

considering precursors that the Agency 

has identified for this purpose. Section 

165(a)(4) of the Act states that a new or 

modified source must apply the Best 

Available Control Technology (BACT) 

‘‘for each pollutant subject to regulation 

under this Act emitted from, or which 

results from, such facility.’’ The phrase 

‘‘emitted from, or which results from’’

indicates that the statute is not limited 

to direct emissions, but rather extends 

to precursors as well. 

With regard to nonattainment NSR, 

Sections 172(c)(4) and 173 require 

States to demonstrate, among other 

things, that emissions from new or 

modified major sources are consistent 

with the achievement of ‘‘reasonable 

further progress.’’ Reasonable further 

progress is further defined as reductions 

of the relevant air pollutant, which is 

defined in Section 302(g) to include 

precursors identified by the Agency as 

subject to regulation for that purpose. 

Treatment of Precursors for Purposes of 

NSR. As discussed in section II.E., 

where there is a basis to do so, we 

believe EPA may treat precursors of the 

same pollutant differently under the 

same program. In this action, we 

propose different approaches for 

addressing the individual precursors to 

PM2.5 under the Act’s NSR provisions. 

Generally, where the scientific data and 

modeling analyses provide reasonable 

certainty that the pollutant’s emissions 

from stationary sources are a significant 

contributor to ambient PM2.5

concentrations, we believe that 

pollutant should be identified as a 

‘‘regulated NSR pollutant’’ and subject 

to the PM2.5 NSR provisions. 

Conversely, where the effect of a 

pollutant’s emissions from stationary 

sources on ambient PM2.5

concentrations is subject to substantial 

uncertainty, such that in some 

circumstances, the pollutant may not 

result in formation of PM2.5, or control 

of the pollutant may have no effect or 

may even aggravate air quality, we 

generally believe it is unreasonable to 

establish a nationally-applicable 

presumption that the pollutant is a 

regulated NSR pollutant subject to the 

requirements of NSR for PM2.5. We also 

request comment on whether, despite 

reasonable scientific certainty 

associated with the effect of a 

66036 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

pollutant’s emissions from stationary 

sources on ambient PM2.5

concentrations, there are circumstances 

that would support a finding that the 

Administrator should not identify the 

pollutant as a precursor for the purposes 

of the NSR program even if the pollutant 

is so identified for other programs. 

For the purposes of the NSR program, 

the EPA proposes the following options 

for addressing SO2, NOX, VOCs, and 

ammonia as precursors to PM2.5, and 

requests comment on these options. 

Commenters should provide detailed 

technical information supporting their 

comments. Sulfur Dioxide. We are 

proposing to regulate SO2 as a precursor 

to PM2.5 for purposes of NSR in all 

attainment, unclassifiable and 

nonattainment areas. We believe that 

the technical discussion and analysis of 

speciated air quality data described in 

Section II provide an appropriate basis 

for requiring States to address SO2 as a 

precursor to PM2.5 for NSR purposes. 

The fact that sulfate is a significant 

contributor (e.g. ranging from 9 percent 

to 40 percent) to PM2.5 nonattainment 

and other air quality problems in all 

regions of the country is a critical piece 

of evidence supporting this approach. 

Additionally, sulfates are a major 

contributor to ambient PM2.5

concentrations in the Eastern United 

States, roughly equaling the 

concentration of carbonaceous particles. 

EPA does not believe that regulating 

SO2 as a precursor to PM2.5 is likely to 

add a major burden to sources as SO2 is 

already regulated in these programs as 

part of the NSR program for the SO2

NAAQS. The EPA requests comments 

on this approach to regulate SO2 as a 

precursor to PM2.5 and a ‘‘regulated NSR 

pollutant’’ for purposes of NSR in all 

attainment, unclassifiable and 

nonattainment areas¿ Nitrogen Oxides. 

We are proposing to regulate NOX as a 

precursor to PM2.5 for the NSR program. 

Under this approach, a State or EPA 

would presume that NOX is a significant 

contributor to an area’s ambient PM2.5

concentration. This presumption is 

warranted based on the well-known 

transformation of NOX into nitrates, as 

discussed in more detail in Section II. 

Nitrates are a significant component of 

PM2.5 mass in northern regions, such as 

the Midwest and East Coast, and are a 

main contributor to urban PM2.5 mass in 

California (35–40 percent). However, as 

described in Section II, nitrate 

concentrations vary significantly in 

other regions of the country. 

Thus, a State could exempt NOX from 

its PM2.5 NSR program in a specific area 

by demonstrating to the Administrator’s 

satisfaction that NOX emissions from 

stationary sources in that area are not a 

significant contributor to that area’s 

ambient PM2.5 concentrations and the 

area is not in a State identified by EPA 

as a source of a PM2.5 interstate 

transport problem. Hence, for such an 

area, the State would not need to 

regulate construction and modification 

of stationary sources that increase 

emissions of NOX in that area to assure 

that these emissions do not interfere 

with reasonable further progress or the 

ability of that area to attain or maintain 

the PM2.5 NAAQS. Otherwise, this 

option would make NOX a precursor for 

the PSD, NA NSR and minor source 

programs for PM 2.5. EPA does not 

believe that this is likely to add a major 

burden to sources as NOX is already a 

regulated NSR pollutant. This is because 

NOX is an identified precursor for the 

ozone NAAQS and an indicator for the 

NO2 NAAQS. 

Volatile Organic Compounds. The 

consideration of VOC for NSR 

applicability is complicated by the 

variations in reactions of the different 

species of VOC in the atmospheric 

transformation into PM2.5. Scientific 

analysis demonstrates that, while the 

transformation of VOC into particles is 

a complex and uncertain process, all 

VOC potentially play a role in the 

formation of PM2.5. However some 

specific compounds play a more direct 

role than others. These transformations 

are discussed in Section II. In light of 

the complexity in assessing the role of 

VOC in PM 2.5 formation, we are not 

proposing to regulate VOC as a 

precursor to PM2.5 for the NSR program. 

However, if a State demonstrates to 

the Administrator’s satisfaction that 

VOC emissions from stationary sources 

in a specific area are a significant 

contributor to that area’s ambient PM2.5

concentrations, then the State would 

regulate VOC (or a subset of VOC) as a 

PM2.5 precursor for the NSR program in 

that area. Therefore, for such an area, 

the State would need to regulate 

construction and modification of 

stationary sources that increase 

emissions of VOC in that area to assure 

that these emissions do not interfere 

with reasonable further progress or the 

ability of that area to attain or maintain 

the PM2.5 NAAQS. Under either 

scenario, as discussed in Section II, we 

would still regulate high molecular 

weight VOC (with 25 carbon atoms or 

more and low vapor pressure) as PM2.5

direct emissions because they are 

emitted directly as primary organic 

particles and exist primarily in the 

condensed phase at ambient 

temperatures. 

Ammonia. As discussed in section 

II.E., in some areas of the country, 

ammonia plays a significant role in the 

formation of ambient PM2.5

concentrations. In other areas, ammonia 

plays a less significant role. Our 

understanding of emissions inventories, 

and the impact that reducing ammonia 

emissions has on ambient PM2.5

concentrations, is evolving. In some 

cases, undesired consequences may 

result from reductions of ammonia, such 

as increased acidity levels for particles 

and deposition. For these reasons, EPA 

proposes that ammonia would only be 

identified as a precursor to PM2.5

NAAQS in a nonattainment area for 

purposes of NSR on a case-by-case basis. 

If the State demonstrates to the 

Administrator’s satisfaction that 

ammonia emissions from stationary 

sources in a specific nonattainment area 

are a significant contributor to that 

area’s ambient PM2.5 concentrations, 

then the State would regulate ammonia 

as a PM2.5 precursor under the NSR 

program in that nonattainment area. 

Therefore the State would need to 

regulate construction and modification 

of stationary sources that increase 

emissions of ammonia in that area to 

assure that these emissions do not 

interfere with reasonable further 

progress or the ability of that area to 

attain or maintain the PM2.5 NAAQS. 

However, in other nonattainment areas, 

we would not require States to include 

ammonia in their NSR programs. We are 

not proposing to identify ammonia as a 

regulated NSR pollutant for purposes of 

PSD in any attainment or unclassifiable 

areas. 

The EPA requests comments on this 

approach for addressing ammonia 

emissions under the NSR programs. 

4. What is a major stationary source 

(major source) under the major NSR 

program for PM2.5? 

a. Background 

The major NSR program applies to 

construction of major stationary sources 

and major modifications at major 

stationary sources. A stationary source 

is a ‘‘major source’’ if its actual 

emissions or its potential to emit for a 

specific pollutant equals or exceeds the 

major source threshold for that pollutant 

established in the CAA. Different 

pollutants are not summed to determine 

applicability. 

b. Proposed Option 

Sections 169 and 302(j) of the Act 

contain definitions of ‘‘major emitting 

facility’’ and ‘‘major stationary source’’

that apply to programs implemented 

under part C and subpart 1 of part D of 

the Act. Accordingly, we are proposing 

to follow these definitions for purposes 

of defining a major emitting facility or 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66037 

100For additional background on EPA’s 

interpretation of modification and rationale for 

including significant emissions rates in defining 

major modifications, see 61 FR 38253–54 (Dec. 31, 

2002). 

major stationary source that would be 

subject to major NSR based on direct 

PM2.5 emissions or emissions of 

pollutants identified as PM2.5 precursors 

for the NSR program. This approach is 

also consistent with how we treat other 

criteria pollutants that are covered by 

subpart 1 of part D of the Clean Air Act 

and thus are not subject to a tiered 

classification system such as the one 

required for ozone nonattainment areas 

under subpart 2 of the Clean Air Act. 

EPA does not interpret subpart 4 of part 

D of the Act (creating ‘‘serious’’ and 

‘‘moderate’’ classifications for PM10

nonattainment areas) to apply to PM2.5. 

This means the major source 

thresholds would be: 

PSD ......... 100 tpy for source categories 

listed in 40 CFR 

51.166(b)(1)(i)(a) and 

52.21(b)(1)(i)(a). 

250 tpy for all other source categories. 

NA NSR .. 100 tpy for all source categories. 

Thus, no regulatory change would be 

required. See §§ 51.165(a)(1)(iv)(a); 

51.166(b)(1)(i); 52.21(b)(1)(i); Appendix 

S, Section II.A.4. 

We request comment on this approach 

for establishing the major source 

threshold for purposes of the major NSR 

program for the PM2.5 NAAQS. We also 

request comment on whether the 

definitions in Section 169 and 302(j) are 

controlling for purposes of establishing 

the definition of major stationary source 

for the PM2.5 NAAQS, which is being 

implemented under part C and subpart 

1 of part D of the Act. 

c. What is the effect of this proposed 

option? 

Although our proposed approach is 

consistent with Sections 169 and 302(j) 

and Subpart 1 of part D of the Act, this 

approach results in a higher major 

source threshold in PM2.5

nonattainment areas than the major 

source threshold that applies in some 

PM10 nonattainment areas under 

Subpart 4 of part D of the Act. This is 

because Section 189(b) of the Act 

establishes a 70 tpy major source 

threshold for ‘‘serious’’ PM10

nonattainment areas while ‘‘moderate’’

PM10 nonattainment areas apply a 100 

tpy major source threshold based on the 

definition in section 302(j). We do not 

believe the Act gives us the discretion 

to promulgate a lower major source 

threshold for pollutants such as PM2.5

that are only subject to Subpart 1 of part 

D of the Act. 

Nevertheless, we do not believe this 

situation will adversely impact 

attainment of the PM2.5 NAAQS. Data 

from EPA’s emissions inventory 

indicate that a significant number of 

sources have actual PM2.5 emissions in 

the 100 to 250 tpy range. Additionally, 

the more current inventory data shows 

that the number of sources that would 

be covered as major sources by a lower 

major source threshold would not 

increase substantially unless the 

threshold were lowered to 20 tpy or 

below. Thus, even if EPA had the 

discretion to adopt a 70 tpy major 

source threshold for PM2.5

nonattainment areas, we do not believe 

that many additional sources would be 

subject to the major NSR program in 

PM2.5 nonattainment areas. 

States should consider this 

information in developing their own 

SIP-approved NSR programs. For 

example, if construction of PM2.5

sources emitting 99 tpy with no major 

NSR controls and without mitigation 

would undermine a State’s ability to 

achieve reasonable further progress or 

attain the PM2.5 NAAQS, then the State 

should consider imposing emissions 

controls or other requirements on these 

sources through the State’s minor NSR 

program. 

5. What should the significant emissions 

rate be for direct emissions of PM2.5? 

a. Background 

The determination of what should be 

classified as a modification subject to 

major NSR is based, in part, on a 

significant emissions rate.100 The NSR 

regulations define this term as a rate 

above which a net emissions increase 

will trigger major NSR permitting 

requirements if such increase results 

from a major modification. Sources are 

exempt from major NSR requirements if 

an emissions increase resulting from a 

modification is below this rate because 

EPA considers such lower emissions 

increase to be de minimis for purposes 

of the NSR program. The significant 

emissions rates for criteria pollutants 

are given below: 

Criteria 

pollutant Significant emissions rate (tpy) 

Ozone ...... VOC: Any increase—40 tpy (dependent on NA classification). 

NOX: Any increase—40 tpy (dependent on NA classification). 

NO2 .......... NOX: 40 tpy. 

PM10 ........ 15 tpy. 

CO ........... 100 tpy. 

SO2 .......... 40 tpy. 

Lead ......... .6 tpy. 

The significant emissions rates listed 

in the above table apply to the direct 

and precursor pollutants listed in the 

table in section III.M.3.a. Significant 

emissions rates for additional pollutants 

that are subject to the PSD program are 

contained in the following provisions of 

our regulations: 

• 40 CFR 51.166(b)(23) and 

• 40 CFR 52.21(b)(23) 

The EPA performed some preliminary 

modeling analyses to determine an 

appropriate significant emissions rate 

for direct emissions of PM2.5. Several 

typical stack heights (ranging from 5 to 

200 meters in height) were modeled 

using meteorological data from 

Pittsburgh and Oklahoma City. 

Modelers ran ISCST (Industrial Source 

Complex Short Term model) to assess 

the impact of emissions increases on 

ambient PM2.5 concentrations. EPA ran 

models for a variety of source types with 

varying meteorology, release heights, 

building shapes, and receptor locations. 

The modeling produced the following 

results that we considered further in 

developing the options below: 

• Shorter stacks had much more 

impact in the local area than taller 

stacks. 

• Increases of about 5 tons per year 

from facilities with short stacks were 

shown to cause a measurable increase in 

ambient PM2.5 concentrations. 

• Emissions increases from tall 

stacks, 100 meters or greater, were 

associated with a small increase in 

ambient PM2.5 concentrations in the 

immediate area. 

b. Proposed Options 

Preferred option 1: For direct 

emissions of PM2.5, EPA is proposing to 

define the significant emissions rate as 

10 tons per year. This proposal is based 

fundamentally on the same approach as 

we used in setting the significant 

emissions rate for total suspended 

particulate matter (TSP) and PM10. 

Historically, the significant emissions 

rate for TSP (equal or exceeding 25 tons 

per year) was set by analyzing the 

source size that would be unlikely to 

cause impacts above 4 percent of the 

standard (4 percent of 260 μg/m3 or 10.4 

μg/m3 as a 24-hour average). Although a 

range of source configurations can yield 

a wide range of impacts per ton per year 

of emissions, EPA reviewed typical 

configurations of major TSP sources and 

concluded that a major modification 

that increased emissions by 25 tons per 

year or more would be unlikely to 

increase 24-hour average TSP 

concentrations by more than 10.4 μg/m3. 

When EPA set the significant 

emissions rate for PM10, we first 

determined the ratio between the 

66038 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

controlling standards for PM10 and TSP, 

i.e. (150 μg/m3)/(260 μg/m3) or about 3/ 

5. Both of these standards are based on 

a year’s second highest 24-hour average 

concentration. The EPA then set the 

PM10 significant emissions rate at about 

3/5 of 25 tons per year, which (with 

rounding) is 15 tons per year. This 

reflects the fact that a source emitting 25 

tons of TSP per year that has an impact 

of 4 percent of the TSP standard would 

show an impact from 15 tons PM10 per 

year of approximately 4 percent of the 

PM10 standard (i.e., 6 μg/m3). 

Conceptually, EPA is proposing a 

significant emissions rate for PM2.5

based on the same approach. However, 

the comparison of the PM2.5 standard 

with earlier particulate matter standards 

is complicated by the difference in the 

averaging times of the controlling 

standards, which are 24-hour average 

values for TSP and PM10 but an annual 

average value for PM2.5. Because the 

annual standard is the generally 

controlling standard for lowering both 

short-term and long-term ambient PM2.5

concentrations (62 FR at 38669), EPA 

proposes using the annual standard to 

determine the significant emissions rate. 

We conducted additional modeling 

using the ISC3 model to compare annual 

average and 24-hour average impacts of 

a fixed emissions rate for a variety of 

source configurations. Several typical 

stack heights (ranging from 5 to 200 

meters in height) were modeled using 

meteorological data from Pittsburgh and 

Oklahoma City and both with and 

without downwash from different 

building types. 

Our analysis of these modeling results 

shows that a major modification that 

increases direct PM2.5 emissions by less 

than 10 tons per year would be unlikely 

to increase annual average ambient 

PM2.5 concentrations by more than 4 

percent of the annual PM2.5 standard. 

This finding relies on EPA’s comparison 

of annual average versus 24-hour 

average concentrations. As noted above, 

EPA previously concluded that a source 

that increases PM10 emissions by 15 

tons per year would likely cause an 

increase in the 24-hour average PM10

concentration by 6 μg/m3 or less. Based 

on the ratios between annual and 24- 

hour average concentrations found in 

EPA’s recent modeling, a source having 

that impact would typically increase 

annual average PM10 concentrations by 

about 0.8 μg/m3 or less. The EPA is 

using a target PM2.5 impact of 4 percent 

of the annual PM2.5 standard or 0.6 μg/ 

m3. This target impact is (0.6 μg/m3)/(0.8 

μg/m3) or 3/4 of the potential impact of 

a 15 ton per year emissions increase. 

This suggests a significant emissions 

rate of 3/4 of 15 tons per year. By 

rounding the result, we determined that 

an emissions increase below 10 tons per 

year increase in direct PM2.5 emissions 

would be unlikely to increase ambient 

PM2.5 concentrations by more than 4 

percent of the annual PM2.5 standard. 

Option 2: The EPA recognizes that a 

range of source configurations can have 

a range of impacts, that the PM2.5 source 

population differs in some respects from 

the TSP and PM10 source population 

and that the acceptable stationary 

source impact on ambient PM2.5

concentrations may warrant being 

defined differently from the acceptable 

impact for TSP or PM10. The EPA 

specifically solicits comments on a 

range of potential thresholds ranging 

from 5 to 15 tons per year for the 

significant emissions rate for PM2.5

direct emissions. The upper bound is a 

set rate of 15 tons per year because that 

is the significant emissions rate for 

PM10. The lower bound is a set rate of 

5 tons per year because our modeling 

indicates that an increase in ambient 

PM2.5 concentrations above the target de 

minimis impact level can occur where 

facilities with short stacks have PM2.5

emissions increases of about 5 tons per 

year. 

We solicit comments on the proposed 

significant emissions rate level and on 

any other approaches for determining 

this value. 

6. What should be the significant 

emissions rates for PM2.5 precursors? 

a. Background 

It is difficult to determine the ambient 

air quality effects that result from a 

single source of emissions of PM2.5

precursors. There are conservative 

screening models for predicting impacts 

of large NOX and SO2 sources on 

ambient PM2.5 concentrations. We 

conducted a range of modeling analyses 

to determine the amount of PM2.5

precursor emissions needed to show an 

increase in ambient PM2.5

concentrations. These analyses showed 

that precursor emissions probably have 

some localized impacts, but that most 

impact is farther downwind as 

precursors have the time to convert to 

PM2.5. In addition, the modeling 

available at this time does not provide 

sufficient information to estimate 

impacts of single source emissions of 

ammonia and VOC on ambient PM2.5

concentrations. 

Although we have not finally 

determined which pollutants (if any) 

will be regulated as PM2.5 precursors 

under the NSR program, we are 

proposing significant emissions rates in 

the event that the precursors under 

consideration are identified as such for 

the major NSR program. In the event 

that EPA adopts an ‘‘opt-in’’ approach—

that is, the presumption that a precursor 

is not subject to NSR unless a State 

demonstrates to the Administrator’s 

satisfaction that it should be included—

the State opting in would be required to 

adopt the significant emissions rate for 

the precursor as set forth below, in the 

absence of demonstrating that another 

significant emissions rate is more 

appropriate. 

b. Proposed Options 

Preferred Option 1: The EPA proposes 

the use of existing significant emissions 

rates for those pollutants already 

included in major NSR programs as 

shown below: 

Pollutant Significant emissions rate 

(equal or exceeding) 

NOX ......... 40 tpy. 

SO2 .......... 40 tpy. 

VOC ......... 40 tpy. 

The use of existing significant 

emission rates where the PM2.5

precursor is also regulated under NSR 

for a separate criteria pollutant 

harmonizes the NSR program for PM2.5

with the NSR programs for those other 

criteria pollutants. This enables a source 

to determine the NSR impacts of 

proposed modifications by reference to 

a single significant emissions rate for 

each pollutant, and enables streamlining 

of determinations regarding the 

applicable control technology and 

analysis of air quality impacts into a 

single and comprehensive decision 

making process for both PM2.5 and other 

criteria pollutants that also cover PM2.5

precursors. This also follows precedent. 

When ozone became a criteria pollutant 

EPA used the NOX significant emissions 

rate from the NO2 program. 

EPA has never set a significant 

emissions rate for ammonia to 

determine major NSR applicability. A 

necessary component of our approach to 

NSR applicability for ammonia is that 

those States who determine in their SIPs 

that control of ammonia is necessary 

will set the significant emissions rate for 

ammonia based on the information 

presented in each attainment 

demonstration. 

Option 2: Set the precursor levels at 

the same level as the significant 

emission rate for PM2.5 direct emissions, 

that is, 10 TPY. This would make more 

modifications subject to PM2.5

permitting requirements and therefore 

could provide more protection to the 

environment. This does not, however, 

follow the precedent in the ozone NSR 

program. Having several different 

significant emissions rates for the same 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66039 

101Memo. from Thompson G. Pace, Acting Chief, 

Particulate Matter Programs Branch, to Sean 

Fitzsimmons, Iowa Department of Natural 

Resources, (Mar. 31, 1994) (copy avaiable at 

http://www.epa.gov/Region7/programs/artd/air/ 

nsr.nsrmemos/cpm.pdf). 

pollutant would add additional 

complexity to an already complex 

program without necessarily providing 

additional environmental benefits. 

We request comment on the options 

listed above and on any other 

approaches for establishing precursor 

significant emissions rates. 

7. What is the role of condensible 

emissions in determining major NSR 

applicability? 

Condensible emissions commonly 

make up a significant component of 

PM2.5 emissions. As discussed in 

Sections IV.I. and IV.P, certain sources 

utilizing high temperature processes 

emit gaseous pollutants into the ambient 

air which rapidly condense into particle 

form. The constituents of these 

condensed particles include, but are not 

limited to, organic material, sulfuric 

acid, nitrates, and metals. 

The EPA has issued guidance 

clarifying that PM10 includes 

condensible particles and that, where 

condensible particles are expected to be 

significant, States should use methods 

that measure condensible emissions.101

States are already required under the 

consolidated emissions reporting rule to 

report condensible emissions in each 

inventory revision (see 67 FR 39602, 

June 10, 2001), and Method 202 in 

Appendix M of 40 CFR part 51 

quantifies condensible particulate 

matter. 

However, because of the flexibility 

incorporated into EPA’s approach to the 

issue and the inconsistent 

implementation of the existing 

guidance, there have been some 

misconceptions as to whether 

condensible emissions must be included 

in a source’s PM10 emissions under the 

PM10 standard in determining NSR 

applicability. The rules at 40 CFR 

51.100 define ‘‘PM emissions’’ and 

‘‘PM10 emissions’’ by reference to the 

PM measured by applicable reference 

methods, an equivalent or alternative 

method specified in part 51, or by a test 

method specified in an approved SIP. 

See 40 CFR 51.100(pp), (rr), and § 52.01 

(incorporating § 51.100 definitions by 

default). As discussed in Section III.P., 

different test methods measure 

condensible emissions with varying 

levels of accuracy. In addition, sources 

often project their emissions increases 

from new construction and 

modifications based on emissions 

factors, such as AP–42 factors, that in 

some cases have not accounted for 

condensible emissions. Sources have 

used other methods to project their PM 

emissions that do not account for 

condensible emissions (e.g., projecting 

PM10 impacts based on an analysis of 

existing TSP limits without adding 

condensible emissions). 

We are proposing to clarify in this 

rule that condensible emissions must be 

included when determining whether a 

source is subject to the major NSR 

program. The inclusion of condensible 

emissions in a source’s PM2.5 emissions 

is of increasing importance with the 

change in the indicator for particulate 

matter to PM2.5. Condensible emissions 

are essentially fine particles, and thus 

are a larger fraction of PM2.5 emissions 

than of TSP or PM10 emissions. 

Condensible emissions commonly make 

up a significant component of PM2.5

emissions, and the failure to include 

them may result in adverse 

consequences to the environment. 

While EPA has always included 

condensible emissions in its definition 

of particulate matter emissions, insofar 

as these emissions are measured by 

applicable test methods or included in 

emissions factors, we believe that the 

greater significance of condensible 

emissions in addressing PM2.5 warrants 

greater emphasis on including these 

emissions in implementing the major 

NSR program. A key aspect of this issue 

is the development of the new test 

method discussed in Section III.P., 

which quantifies and can be used to 

characterize the constituents of PM2.5

emissions, including both the filterable 

and condensible portion of the 

emissions stream. 

8. What are the requirements of the 

Prevention of Significant Deterioration 

(PSD) program for attainment areas? 

Background. Sources subject to PSD 

must: 

• Install Best Available Control 

Technology (BACT), 

• Conduct air quality modeling 

analyses to ensure that the project’s 

emissions will not cause or contribute 

to: 

• A violation of any NAAQS or 

maximum allowable pollutant increase 

(PSD increment), 

• Any impact on any Class I area air 

quality related value, and 

• As required, perform 

preconstruction monitoring. 

Each of these elements is discussed 

below. 

9. How should BACT be implemented? 

We are not proposing any change to 

our current policy for implementing 

BACT requirements at a major source 

that is subject to the requirements of the 

PSD program. Accordingly, if a physical 

or operational change at the source will 

result in a significant emissions increase 

and a significant net emissions increase 

of a regulated NSR pollutant, then the 

major source must apply BACT (for that 

pollutant) to the emissions unit(s) that 

will be physically or operationally 

changed as a part of that project. Under 

the PM2.5 major NSR program, BACT 

will be required at an emissions unit if 

a physical or operational change at the 

unit causes a significant emissions 

increase and significant net emissions 

increase of PM2.5 direct emissions, or a 

PM2.5 precursor, if applicable at the 

major stationary source. 

10. What is EPA’s plan for preventing 

significant deterioration of air quality 

for PM2.5? 

Background. The PSD provisions of 

the CAA limit the degradation of 

ambient air concentrations of certain 

pollutants. The CAA does not dictate 

the mechanism to achieve this result for 

pollutants other than PM10 and SO2. 

One mechanism involves a system of 

‘‘increments’’ and area classifications 

that define significant deterioration for 

individual pollutants. The PSD 

increments are the maximum allowable 

increase in ambient air concentrations 

above a baseline concentration for a 

criteria pollutant. The current 

increments are: 

Pollutant/averaging time Class I Class II Class III 

PM10

Annual average ................................................................................................................................ 4 μg/m3 17 μg/m3 34 μg/m3

8-Hour average ................................................................................................................................ 8 μg/m3 30 μg/m3 60 μg/m3

SO2

Annual average ................................................................................................................................ 2 μg/m3 20 μg/m3 40 μg/m3

24-hour average ............................................................................................................................... 5 μg/m3 91 μg/m3 182 μg/m3

3 Hour Average ................................................................................................................................ 25 μg/m3 512 μg/m3 700 μg/m3

66040 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

Pollutant/averaging time Class I Class II Class III 

NO2—Annual Average ..................................................................................................................... 2.5 μg/m3 25 μg/m3 50 μg/m3

We are in the process of developing 

an approach for preventing significant 

deterioration of air quality which may 

include PM2.5 increments. The EPA has 

placed this action on a separate 

administrative track due to the 

additional time necessary to fully 

develop any potential proposal. In the 

interim period, States must continue to 

implement the PM10 increments in 40 

CFR 51.166, 52.21 and/or their SIPs, as 

applicable. 

11. How will the air quality analysis 

required under section 165(a)(3) be 

implemented? 

Scope of the Requirement. All sources 

subject to PSD review must perform an 

ambient air quality impact analysis to 

show that the emissions from the source 

do not cause or contribute to a PSD 

increment or NAAQS violation. See 

CAA Section 165(a)(3); 40 CFR 

51.166(k), 52.21(k). Accordingly, 

sources will be required to perform this 

analysis for the PM2.5 NAAQS. Such 

analyses would consider how a source 

impacts air quality at existing PM2.5

monitor locations as well as at other 

locations which are appropriate to allow 

the comparison of predicted PM2.5

concentrations to the NAAQS, based on 

PM2.5 monitor siting requirements and 

recommendations. 

Sources also will remain under an 

obligation to perform the air quality 

impact analysis for the PM10 increments 

and the PM10 NAAQS. 

Plan for Development of Significant 

Impact Levels for PM2.5. The Agency has 

had a practice of exempting sources 

from the cumulative air quality impact 

analyses where their level of 

contribution is below a significant 

impact level (SIL). If the maximum 

ambient impacts from the proposed 

project are less than a SIL, the source 

• Is presumed to not cause or 

significantly contribute to a PSD 

increment or NAAQS violation, and 

• Is not required to perform multiple 

source cumulative impact assessments. 

The EPA has long interpreted the 

‘‘significant contribution’’ test set forth 

in § 51.165(b)(2) to apply to the PSD 

program since the provision applies to 

major new sources and major 

modifications located in attainment and 

unclassifiable areas. We have proposed 

codifying this exemption in the PSD 

regulations in a separate Federal 

Register notice. See 61 FR 38249, 38293 

(July 23, 1996). This exemption is based 

on the de minimis nature of the source’s 

contribution. 

The SIL (in μg/m3) have been 

established for other criteria pollutants 

with PSD increments and are given 

below: 

Criteria pollutant Averaging time 

Class I SIL μg/ 

m3

(proposed 7/23/ 

96, not promulgated) 

Class II and III SIL 

μg/m3

SO2 ............................................... 3 hour ................................................................................................. 1.0 25 .0 

24-hour ............................................................................................... .2 5 .0 

Annual ................................................................................................. .1 1 .0 

CO ................................................ 1 hour .................................................................................................

8 hours ................................................................................................

N/A 

N/A 

2000 

500 

NO2 ............................................... Annual ................................................................................................. .1 1 .0 

PM10 .............................................. 24-hour ............................................................................................... .3 5 .0 

Annual ................................................................................................. .2 1 .0 

Because the SIL benefits the NSR 

permitting program by exempting 

sources with de minimis impacts from 

the cumulative air quality analysis, EPA 

is considering establishing PM2.5 SIL for 

emissions of PM2.5 direct. This would 

enable sources with impacts below the 

SIL to avoid the cumulative air quality 

impact analysis with respect to their 

potential contribution to a PM2.5

NAAQS violation, and create a de 

minimis ‘‘cause or contribute’’

definition for violations. Direct PM2.5

emissions can be evaluated with current 

models. Therefore, the development of 

SIL for impact evaluations of direct 

PM2.5 emissions is technically 

achievable. The EPA is soliciting 

comments on this question and on 

methods for the development of PM2.5

SIL. 

The limited capabilities of existing 

models make it difficult to establish and 

implement SIL for PM2.5 precursors. 

Current models are only able to 

accurately address individual source 

impacts associated with direct PM2.5

emissions and, to a lesser degree, SO2

and NOX. They can not accurately 

predict single source impacts on 

ambient PM2.5 concentrations from 

other precursors. Without including 

formation of PM2.5 from precursor 

emissions, the complete impact cannot 

be assessed. 

EPA solicits comments and ideas on 

the direction to take and possible 

approaches to setting PM2.5 SIL for 

direct and precursor emissions. The 

EPA intends to use these comments in 

developing SIL on a separate 

administrative track. 

12. How should the PSD preconstruction monitoring requirement be 

implemented for PM2.5? 

EPA solicits comment on what 

preconstruction monitoring 

requirements should be required by the 

PM2.5 PSD program. 

a. Background 

Sources subject to PSD are subject to 

pre-construction ambient air quality 

monitoring requirements. See Sections 

165(a)(7) and 165(e) of the CAA and 40 

CFR 51.166(m), § 52.21(m). The PSD 

permitting requirements currently 

provide that continuous preconstruction ambient air quality 

monitoring must be conducted for any 

criteria pollutant emitted in significant 

amounts. Under 40 CFR 51.166(i)(5), 

and 40 CFR 52.21(i)(5) the reviewing 

authority has the discretion to exempt 

an applicant from this monitoring 

requirement if: 

• The maximum modeled 

concentration for the applicable 

averaging period caused by the 

proposed significant emissions increase 

(or net emissions increase) is less than 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66041 

the prescribed significant monitoring 

concentration (SMC); or 

• The existing monitored ambient 

concentrations are less than the 

prescribed SMC. The following are the 

SMC for criteria pollutants: 

Pollutants 

Ambient 

concentration 

(μg/m3) 

Averaging 

period 

CO .............. 575 8 hours. 

NO2 ............. 14 Annual. 

SO2 ............. 13 24 hours. 

PM10 ............ 10 24 hours. 

A source may also use existing data as 

a surrogate for pre-construction 

monitoring if the existing monitored 

data record is determined to be 

representative of the project’s location. 

For information on representative 

monitoring see ‘‘Ambient Monitoring 

Guideline for Prevention of Significant 

Deterioration (PSD),’’ EPA–450/4–87–

007. Under the current regulatory 

approach, the need for pre-construction 

monitoring by an applicant depends on 

the spatial and temporal coverage of the 

current monitoring program. The 

expected gradients of concentration 

between existing monitors also need to 

be considered in deciding whether there 

is a need for pre-construction ambient 

monitoring. 

The PM2.5 ambient monitoring data 

are used in the PSD program to: 

• Establish current PM2.5 NAAQS 

compliance status in the project’s 

impact area; 

• Determine a representative 

background ambient PM2.5

concentration which will be included 

with modeled estimates to assess 

NAAQS compliance. 

The PM2.5 ambient monitoring 

measurements include particulate 

matter from PM2.5 direct emissions and 

those formed by PM2.5 precursors. If 

required of a particular source, preconstruction monitoring could add one 

year to the permitting process and 

increase the cost of the permit. Such a 

requirement could have the effect of 

delaying or preventing sources from 

undertaking environmentally beneficial 

projects. Accordingly, today, we are 

reconsidering our current approach for 

satisfying the pre-construction 

monitoring requirements for the 

purposes of the PM2.5 standard. While 

we are proposing to retain the current 

approach, we are also soliciting 

comments on innovative options that 

could provide better solutions for 

satisfying the preconstruction 

monitoring requirements. 

b. Options for PSD Preconstruction 

Monitoring 

Preferred Option 1: Require 

preconstruction monitoring for all major 

sources of PM2.5 direct and the 

precursors identified as regulated NSR 

pollutants for PM2.5, but on a case-bycase basis allow sources to satisfy this 

requirement by demonstrating the 

existing PM2.5 network is sufficient. 

This option will provide information on 

effects of new construction on the PM2.5

NAAQS and increments. This option 

would not require a change to the 

preconstruction monitoring regulations. 

Concerns about this option include: 

• It is challenging to find an 

appropriate location for any monitor 

because PM2.5 direct emissions typically 

affect nearby locations while precursor 

emissions affect areas farther away. 

• The existing monitors can either 

measure total PM2.5 mass or can provide 

data on the mass of different PM2.5

components. The latter type, a 

speciation monitor, is more expensive to 

operate but provides useful information 

on the contribution of sources of 

precursor and PM2.5 direct emissions. 

In cases where ambient PM2.5

concentration gradients between 

existing monitors are small with little 

likelihood of local site-specific ‘‘hot 

spots,’’ interpolation between existing 

monitored values may be appropriate 

for determining that the existing PM2.5

monitoring network is sufficient. We 

request comment on this approach. 

Option 2: Exempt all PM2.5 sources 

from doing monitoring by determining 

the existing PM2.5 network is sufficient. 

The use of the acquired PM2.5

monitored data record in place of 

applicant performed pre-construction 

monitoring would follow the current 

trend in PSD permitting activities. This 

procedure would have the advantage of 

reducing the time required for permit 

preparation and reduce the costs of the 

permit application. If ambient PM2.5

concentration gradients between 

monitoring stations are small there may 

be little need for additional monitoring 

data. The need to make discretionary 

decisions on whether to perform preconstruction monitoring would be 

eliminated. 

However, EPA favors the continued 

use of the case-by-case determination as 

to the need to perform ambient PM2.5

pre-construction monitoring because of 

the following limitations to using the 

existing PM2.5 monitoring data record: 

• The PM2.5 monitoring data record 

would require spatial interpolation 

between monitors for the determination 

of appropriate concentrations at the 

project’s location. 

• Use of existing monitored data will 

not increase the PM2.5 monitoring data 

record to confirm or contradict 

conventional perceptions. 

• The PM2.5 monitoring data record 

assumes that local hot spots of high 

PM2.5 concentrations do not exist or are 

already being monitored, which may not 

be true in all cases. 

• Automatic acceptance of existing 

measurements does not follow EPA’s 

current policy that a case-by-case 

determination needs to be made to 

determine whether pre-construction 

ambient monitoring is necessary. 

• When used with the impact 

modeling, separate concentrations of 

direct and precursor formed particulate 

matter is needed. 

Because of these limitations, existing 

PM2.5 monitoring data must be reviewed 

for applicability and representativeness 

before being judged appropriate for use 

in lieu of project acquired ambient data. 

The current PM2.5 network may not be 

sufficient for all applicants. The EPA is 

soliciting comments and suggestions on 

this issue. 

Option 3: Use Significant Monitoring 

Concentrations (SMC) to exempt sources 

from pre-construction monitoring 

requirements. The reviewing authority 

has the discretion to exempt an 

applicant from the pre-construction 

monitoring requirement if the modeled 

impacts from the proposed source are 

less than the prescribed SMC. 

Similar to the significant impact 

levels used in modeled impact analysis, 

the PSD process will become simpler 

through the use of SMC. It provides a 

definitive means for applicants with 

little impact to opt out of the resource 

intensive, costly, and time consuming 

pre-construction ambient air quality 

monitoring requirement. Therefore, it is 

an important component of the PSD 

program. 

The form of the SMC will be defined 

by the form of the impact modeling. 

SMC must be developed for direct PM2.5

emissions if the impact modeling only 

addresses direct emissions of PM2.5. 

This may require different direct and 

precursor SMC. 

Because of the advantages SMC 

provide to the NSR permitting program, 

EPA is considering the development of 

PM2.5 SMC. The EPA is soliciting 

comments on the development and use 

of PM2.5 SMC in the PSD program. This 

option could be used in combination 

with the other options described. 

Option 4: Use of the available large 

PM10 data record, combined with the 

recent PM2.5 acquired ambient 

measurements, may provide a 

monitoring data base that is sufficiently 

distributed to provide representative 

66042 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

102These sections actually cross-reference the list 

at § 51.166(i)(8)(i) and 52.21(i)(8)(i), however we 

renumbered those sections to subsection (i)(5)(i) of 

those provisions in December 2002 and 

inadvertently overlooked correcting the crossreferences in subsections (i)(5)(ii) and (i)(5)(iii). See 

67 FR 80186. It is apparent from the rule as 

originally promulgated in 1980 that subsection 

(i)(5)(i) is now the correct cross-reference. See 45 FR 

52676, 52739 (Aug. 7, 1980). We propose to correct 

this misnumbering and others in this section when 

we finalize today’s proposal. 

ambient measurements for most 

applicants. This would alleviate the 

need for pre-construction monitoring 

and make the PSD program less 

burdensome. This would also provide 

an interim means to estimate ambient 

PM2.5 concentrations until more 

extensive monitoring data record can be 

developed. 

However, the differences in 

characteristics between PM2.5 and PM10, 

and our limited understanding of their 

relationships, presents a problem. 

• PM10 conversion factors may not 

sufficiently reflect important industry 

specific and spatially related 

characteristics of PM2.5. 

• Removing the obligation to provide 

pre-construction ambient monitoring 

data would eliminate industry’s 

contribution to the ambient PM2.5 data 

record. 

This may not be a viable substitute to 

satisfy the need to provide 

representative PM2.5 ambient 

measurements. The EPA requests 

comments on these options on preconstruction monitoring. 

Option 5: Existing § 52.21(i)(5)(ii) and 

§ 51.166(i)(5)(iii) could be interpreted to 

allow a reviewing authority to exempt 

an applicant from pre-construction 

monitoring for any pollutant for which 

we have not established a SMC. These 

provisions state that a source may be 

exempted from preconstruction 

monitoring ‘‘if * * * the pollutant is 

not listed in’’ the list of pollutants for 

which SMC have been set.102 The 

original rationale for this exemption is 

based on the lack of adequate methods 

for measuring ambient concentrations of 

pollutants not on the list. 45 FR at 

52709, 52723–52724. We request 

comment on this interpretation and any 

other legal or policy rationale that could 

support applying the text of these 

provisions to exempt sources from 

preconstruction monitoring if we do not 

define a SMC for PM2.5. 

13. Nonattainment New Source Review 

(NA NSR) Requirements 

Background. Sources subject to NA 

NSR must: 

• Install Lowest Achievable 

Emissions Rate (LAER) control 

technology; 

• Offset new emissions with 

creditable emissions reductions. 

• Certify that all sources owned and 

operated by the same owner within the 

State are in compliance; and, 

• Conduct an alternative siting 

analysis demonstrating that the benefits 

of the proposed source significantly 

outweigh the environmental and social 

costs. 

14. What are the offset requirements for 

NA NSR? 

Background. Under Section 173 of the 

Act, all major sources and major 

modifications at existing sources within 

a nonattainment area must obtain 

emissions reductions to offset any 

emissions increases resulting from the 

project in an amount that is at least 

equal to the emissions increase, and that 

is consistent with reasonable further 

progress towards attainment. In 

addition, these offsets must be: 

• From the same nonattainment area 

or a different nonattainment area that 

impacts the area where the source is 

located (as long as the other area has the 

same or higher classification); 

• Federally enforceable; and 

• Affect air quality in the area where 

the emissions increases from the new 

major source or modification are 

occurring. 

We refer to the proportional 

difference between the amount of the 

required offsets to the amount of 

emissions increase as the ‘‘offset ratio.’’

The offset ratios for the other criteria 

pollutants are: 

Pollutant Offset ratio 

Ozone ...... At least 1:1 to 1.5:1 depending 

on ozone nonattainment classification. 

PM10 ........ At least 1:1. 

NOX ......... At least 1:1. 

SO2 .......... At least 1:1. 

Lead ........ At least 1:1. 

CO ........... At least 1:1. 

a. What is the required offset ratio for 

PM2.5 direct emissions? 

The Act specifies an offset ratio for 

several situations. In ozone 

nonattainment areas subject to subpart 

2, the ratio is set between 1.1:1 and 1.5:1 

depending on the area’s level of 

classification pursuant to subpart 2 of 

the Act. For other nonattainment areas, 

the Act establishes a minimum offset 

ratio of 1:1 pursuant to Subpart 1 of the 

Act. Since the PM2.5 program is being 

implemented under subpart 1, the 

applicable ratio is at least 1:1 on a mass 

basis. We request comment on 

establishing a required offset ratio of at 

least 1:1, and on any other option for 

establishing the required offset ratio for 

PM2.5 direct emissions. 

b. Which precursors shall be subject to 

the offset requirement? 

If we identify a precursor as a 

regulated NSR pollutant in our final 

action, then that pollutant will be 

subject to the offset requirement. 

Accordingly, consistent with our 

preferred approach for identifying SO2

as a national precursor and NOX as a 

presumptive national precursor, we 

propose that SO2 and NOX would be 

subject to the offset requirement. VOCs 

and ammonia would be subject to the 

offset requirement if we designated 

these pollutants as PM2.5 precursors for 

the purposes of major NSR. If we adopt 

an approach under which the precursors 

are presumptively excluded from major 

NSR unless and until a State NA NSR 

program specifically includes such a 

pollutant, then the precursor would not 

be subject to the offset requirement until 

such time. 

c. What is the required offset ratio for 

PM2.5 precursors? 

The Act requires that a source obtain 

offsets for emissions increases that 

occur in a nonattainment area. As with 

PM2.5 direct emissions, the minimum 

offset ratio permitted under the Act 

would be at least 1:1. We believe this 

ratio should apply where a source seeks 

to offset an increase in emissions of a 

PM2.5 precursor with creditable 

reductions of the same precursor. We 

request comment on requiring an offset 

ratio of at least 1:1 for any precursor 

identified by the Administrator as a 

regulated NSR pollutant for PM2.5

nonattainment areas. We also request 

comment on whether this mandatory 

offset ratio should apply to any other 

precursor identified by a State for 

regulation through its SIP-approved 

nonattainment major NSR program, or 

whether the State should have the 

option to establish a different offset ratio 

for such pollutant. 

d. Should EPA allow interprecursor 

trading to comply with the offset 

requirement? 

Because several different pollutants 

contribute to ambient PM2.5

concentrations, we are proposing to 

allow flexibility in how major sources 

may satisfy the offset requirement. 

Specifically, we are proposing to allow 

increases in emissions of direct PM2.5 to 

be offset by a decrease in PM2.5

precursor emissions; and we are 

proposing to allow an increase in a 

PM2.5 precursor to be offset by a 

decrease in emissions of a different 

PM2.5 precursor or with PM2.5 direct 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66043 

103See ‘‘Interim Implementation for New Source 

Review Requirements for PM2.5,’’ J. Seitz, EPA (Oct. 

23, 1997). 

104We note that we requested that States submit 

certifications that their SIPs were adequate with 

respect to certain infrastructure elements, including 

PSD, for the PM2.5 NAAQS, by July 2000, consistent 

with Section 110(a)(1) and (2). See Re-issue of the 

Early Planning Guidance for the Revised Ozone and 

Particulate Matter (PM) National Ambient Air 

Continued 

emissions. However, such trades would 

only be permissible if the State shows 

that the trade is beneficial in reducing 

overall ambient concentrations of PM2.5, 

and the Administrator approves of the 

trade. 

This additional flexibility might make 

it difficult to ensure that the ambient air 

concentration of PM2.5 continues to 

decrease. It may also be administratively 

difficult to manage. Nonetheless, we are 

proposing to allow interprecursor 

trading to generate creditable emissions 

reductions for use as offsets, because we 

believe that reductions of a different 

PM2.5 precursor may have an equal or 

better impact in reducing ambient PM2.5

concentrations if an appropriate offset 

ratio is determined. Additionally, 

interprecursor trading may provide a 

reliable source of offset emissions in 

areas where availability may otherwise 

be limited. 

There are several ways in which 

interprecursor trading for offsets could 

be implemented. Under one approach, a 

State would develop its own 

interprecursor trading rule for inclusion 

in its SIP, based on a modeling 

demonstration for a specific 

nonattainment area. The EPA would 

review a State interprecursor trading 

rule during the SIP approval process. 

Once approved, the State could follow 

this approach on all future NSR permits 

issued. Another approach would be to 

review individual trades as part of the 

major NSR permitting process. The EPA 

and the public would have an 

opportunity to comment on whether the 

modeling or other technical evidence 

presented by a particular State is 

sufficient to support interprecursor 

offsets for that specific permit 

application. Under either approach, a 

State could not allow interprecursor 

trading without EPA approval. The EPA 

is requesting comment on whether, 

States should be required to 

demonstrate the adequacy of offset 

ratio(s) using modeling as part of a State 

rule, in demonstrations for specific 

nonattainment areas, and/or on a 

permit-by-permit basis, and/or on some 

other basis. While EPA believes that 

such interprecursor trading flexibility is 

more appropriate for offsets which are 

statutorily required, we are seeking 

comment on whether this flexibility 

should also apply to netting analysis for 

a source. 

15. What are the implementation and 

transition issues associated with this 

rule? 

Implementation. Implementation of 

NSR for PM2.5 is dependent on: 

• Who implements the program and 

• What regulations are used to 

implement NSR. 

The components of the NSR programs 

are implemented by the following: 

• PSD: States or EPA 

• Nonattainment NSR: State or EPA 

• Minor NSR: States only 

• NSR in Indian country: Tribes or 

EPA 

Transition. The requirements 

applicable to NSR SIPs for and the 

obligation to subject sources to NSR 

permitting for PM2.5 direct and 

precursor emissions are codified in the 

existing federal regulations, and can be 

implemented without specific 

regulatory changes. The existing 

regulations require NSR for any NAAQS 

pollutant for which an area is 

designated attainment or nonattainment. 

See 40 CFR 51.160(b); 51.165(a)(2)(i); 

51.166(a)(7); 52.21(a)(2); 52.24(k); 40 

CFR part 51, Appendix S, Section IV. A. 

Thus, the obligation to implement PSD 

for the NAAQS was triggered upon the 

effective date of the NAAQS, as 

explained in prior guidance.103 (In that 

guidance, EPA also explained that PSD 

permitting for PM10 would be accepted 

as a surrogate approach for this 

obligation, as discussed in more detail 

below.) For nonattainment areas, 

permits must comply with the 

nonattainment NSR requirements for 

PM2.5, either in a State’s approved part 

D program or, where that is lacking, as 

set forth in 40 CFR part 51, Appendix 

S, pursuant to § 52.24(k). To clarify how 

these requirements are to be 

implemented for PM2.5, we are 

proposing to add provisions to: 

• 40 CFR 51.166—implementation 

plan requirements for major new or 

modified sources in attainment or 

unclassifiable areas; 

• 40 CFR 51.165—implementation 

plan requirements for addressing major 

new or modified sources in 

nonattainment areas and sources located 

in attainment or unclassifiable areas that 

would impact a nonattainment area; 

• 40 CFR 52.21—the federal 

implementation plan for areas lacking 

an approved SIP or TIP program to 

regulate construction or modification of 

major stationary sources in an 

attainment or unclassifiable area. 

• 40 CFR part 51, Appendix S—

provisions for issuing permits before a 

State has an approved implementation 

plan regulating construction or 

modification of major stationary 

sources. 

16. Implementation of PSD provisions 

during the SIP Development period 

a. Background 

On October 23, 1997, we issued a 

guidance document entitled ‘‘Interim 

Implementation for the New Source 

Review Requirements for PM2.5,’’ John 

Seitz, EPA. As noted in that guidance, 

Section 165 of the Act suggests that PSD 

requirements become effective for a new 

NAAQS upon the effective date of the 

NAAQS. Section 165(a)(1) of the Act 

provides that no new or modified major 

source may be constructed without a 

PSD permit that meets all of the Section 

165(a) requirements with respect to the 

regulated pollutant. Moreover, Section 

165(a)(3) provides that the emissions 

from any such source may not cause or 

contribute to a violation of any NAAQS. 

Also, Section 165(a)(4) requires BACT 

for each pollutant subject to PSD 

regulation. The 1997 guidance stated 

that sources would be allowed to use 

implementation of a PM10 program as a 

surrogate for meeting PM2.5 NSR 

requirements until certain difficulties 

were resolved, primarily the lack of 

necessary tools to calculate the 

emissions of PM2.5 and related 

precursors, the lack of adequate 

modeling techniques to project ambient 

impacts, and the lack of PM2.5

monitoring sites. As discussed in this 

preamble, those difficulties have been 

resolved in most respects, and where 

they have not been, the proposal 

contains appropriate provisions to 

account for it. These issues will be 

finally resolved by the Agency upon 

promulgation of these proposed 

revisions. When final, these revisions 

will take effect immediately on the 

effective date in States that issue 

permits under a delegation from EPA. 

However, States with a SIP-approved 

PSD program requiring amendments to 

incorporate these rule changes will need 

additional time to incorporate the final 

NSR rule change for PM2.5 into their 

SIPs. For example, a State may need to 

amend their existing regulations to add 

the specific significant emissions rate 

for PM2.5 or a designated precursor. We 

propose to require that States with SIPapproved PSD programs submit revised 

PSD programs for PM2.5 at the same time 

that they must submit nonattainment 

NSR programs for PM2.5 (April 5, 

2008).104 However, during the SIPVerDate Aug<31>2005 16:37 Oct 31, 2005 Jkt 208001 PO 00000 Frm 00061 Fmt 4701 Sfmt 4700 E:\FR\FM\01NOP2.SGM 01NOP2
66044 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

Quality Standards (NAAQS) (June 16, 1998). In 

accordance with a Consent Decree in 

Environmental Defense and American Lung Ass’n 

v. Johnson, No. 1:05CV00493 (D.D.C. June 15, 

2005), EPA must determine by October 4, 2008 

whether each State has submitted SIP revisions for 

PM2.5 required under section 110(a)(2) of the Clean 

Air Act. 

development period, the PM2.5 NAAQS 

must still be protected under the PSD 

program in such States. 

b. Proposed Options 

Upon promulgation of this rule, States 

that accept delegation would implement 

the PM2.5 program in 40 CFR 52.21 from 

the effective date of this rule. However, 

for SIP-approved States, we seek 

comment on the following options to 

address implementation of the PSD 

program from the time this rule is final 

until EPA approves a State’s PSD 

program for PM2.5: 

Option 1—Continue Implementing the 

1997 Guidance To use PM10 Program as 

a Surrogate for PM2.5

We are proposing that if a SIPapproved State is unable to implement 

a PSD program for the PM2.5 NAAQS 

upon promulgation of these proposed 

revisions, then the State may continue 

to implement a PM10 program as a 

surrogate to meet the PSD program 

requirements for PM2.5 pursuant to the 

1997 guidance mentioned above. 

However, to assure that use of PM10 is 

protective of the PM2.5 NAAQS, the 

State must assure that two requirements 

are met. First, States must require 

sources to demonstrate that emissions 

from construction or operation of the 

facility will not cause or contribute to a 

violation of the PM2.5 NAAQS. We 

believe that States have the authority to 

implement this requirement through 

existing SIP-approved programs. 

Second, States will be required to 

include condensible particulate matter 

emissions in determining major NSR 

applicability and control requirements. 

As discussed elsewhere, PM10 already 

includes condensible emissions, but 

many States have not regulated 

condensible emissions in implementing 

the PM10 NAAQS because EPA has not 

consistently implemented its guidance 

on this issue. Because condensible 

emissions are essentially fine particles 

and a larger fraction of PM2.5 emissions 

in comparison to PM10, EPA believes 

inclusion of condensible emissions 

during the SIP development period for 

PSD programs is necessary to ensure 

that the PM10 indicator acts as an 

adequate surrogate for PM2.5. 

Option 2—Update the 1997 Guidance to 

Include Proposed Provisions of this 

Rule or Amend 40 CFR part 51, 

Appendix S to State That 40 CFR 52.21 

Would Apply 

Another option would be to update 

the 1997 guidance to reflect the 

provisions in this proposed rule and 

allow States to run a PM2.5 program 

pursuant to this updated guidance. 

Alternatively, we would amend 

Appendix S and 40 CFR 52.24 so that 

the PSD requirements of 40 CFR 52.21 

would govern the issuance of major NSR 

permits during the period between the 

time we finalize this implementation 

rule and when we approve changes to 

the State’s PSD program to include 

PM2.5 as a regulated NSR pollutant. This 

provision would not apply to sources 

located in Indian Country because they 

are already directly subject to the 

requirements of 40 CFR 52.21. 

If a State does not believe it has the 

authority to issue PSD permits 

consistent with Appendix S, then EPA 

would issue the permit. We specifically 

seek comment on whether we should 

update the 1997 guidance or amend 

Appendix S to allow States to run a PSD 

program for PM2.5 in attainment areas 

during the SIP development period. 

Option 3—State Requests Delegation of 

40 CFR 52.21 

A third option would be for EPA to 

allow a State to request delegation of 

just the federal PM2.5 program (reflected 

in § 52.21 of our regulations) in that 

State. A State that otherwise has a SIPapproved PSD program could request 

delegation for PM2.5 by informing EPA 

that it does not intend to submit a PSD 

SIP for PM2.5 in the immediate future. 

After promulgation of a new NAAQS, 

EPA may allow States up to three years 

to submit a State implementation plan 

containing a PSD program for that 

pollutant. 42 U.S.C. 7410(a). EPA’s PSD 

regulation at § 51.166 gives SIPapproved States up to three years to 

submit a revision to their PSD program 

after EPA amends § 51.166. 

(§ 51.166(a)(6)). Under section 110(c) of 

the Act, EPA must promulgate a federal 

implementation plan (FIP) upon finding 

that a State has failed to make a required 

plan submission or that a required 

submission is inadequate. 

If a State notifies EPA prior to the 

close of the customary three-year period 

that the State does not intend to submit 

a PSD SIP for PM2.5 in the immediate 

future and requests delegation, we 

believe EPA could find that the State 

has failed to submit the requisite PSD 

SIP for PM2.5, promulgate a PSD FIP for 

PM2.5 based on 40 CFR 52.21, and 

delegate implementation of the federal 

PSD program to the State. The State 

would then be able to implement a PSD 

program for PM2.5 in accordance with 

the terms of section 52.21, as amended 

in this rulemaking action. However, 

such a State would still have the option 

to obtain EPA approval of a PSD SIP for 

PM2.5 if it submitted the SIP revision at 

a later date. 

c. Rationale 

We believe option 1 is reasonable for 

the following reasons. First, PM10 will 

act as an adequate surrogate for PM2.5 in 

most respects, because all new major 

sources and major modifications that 

would trigger PSD requirements for 

PM2.5 would also trigger PM10

requirements because PM2.5 is a subset 

of PM10. The one situation where this 

would not be true is where a source 

emitted significant amounts of 

condensible emissions that would not 

otherwise be counted under a State’s 

PM10 PSD program. This is the reason 

EPA would ensure that States include 

condensible emissions in determining 

major NSR applicability as a condition 

of using PM10 as a surrogate. Second, 

both of the precursors proposed for 

regulation in this preamble—SO2 and 

NOX—are already regulated under State 

NSR programs for other criteria 

pollutants. Thus, those precursors will 

be subject to NSR through those other 

programs. Third, requiring immediate 

implementation of the Section 165(a)(3) 

air quality analysis for the PM2.5

NAAQS will adequately cover the 

remaining gap that results from using 

PM10 as a surrogate for PM2.5. 

Upon promulgation of these rules, 

except in SIP-approved States which 

would be running a PM10 program as a 

surrogate for a PM2.5 program as stated 

in option 1 above, a PM2.5 program 

would apply in attainment areas of 

delegated States and in nonattainment 

areas. Hence to avoid this imbalance, we 

are seeking comment on option 2 which 

addresses whether there is a need to 

update the 1997 interim policy to reflect 

these rules in SIP-approved States or 

whether we should amend Appendix S 

to allow these States to run a PM2.5

program for PSD based on the 

requirements of 40 CFR 52.21 during the 

SIP development period in attainment 

areas. 

Option 3 would also address this 

imbalance by allowing a State to request 

delegation of only the PSD program for 

PM2.5 prior to the deadline for 

submitting a PSD SIP for PM2.5. (April 

5, 2008 as discussed in the background 

discussion of section M16.) Because we 

need to allow a State enough time to 

submit a PSD SIP for PM2.5, we do not 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66045 

105 In a separate Federal Register notice, we will 

be revising Appendix S to incorporate changes that 

conform Appendix S with the minimum 

requirements for implementation plans that are set 

forth in 40 CFR 51.165. 

106EPA has interpreted this requirement to 

require States to issue permits that are consistent 

with the requirements in Appendix S. We believe 

that many States have the authority to issue permits 

that are consistent with Appendix S for example, 

Continued 

believe we can unilaterally issue a FIP 

for the PSD PM2.5 program right away. 

However, if a State informs EPA prior to 

April 5, 2008 that it does not intend to 

submit a PM2.5 SIP, we would then have 

cause to issue a FIP addressing the PSD 

program for PM2.5 and then delegate that 

program to the State. 

17. Implementation of the 

Nonattainment NSR Provisions During 

the SIP Development Period 

a. Background 

EPA interprets section 172(c)(5) of the 

Clean Air Act to require that States issue 

major NSR permits for construction and 

major modifications of major stationary 

sources in any nonattainment area. 

Thus, since the PM2.5 nonattainment 

designations became effective on April 

5, 2005, States are now required to issue 

major NSR permits that address the 

Section 173, nonattainment major NSR 

requirements for PM2.5. On the date that 

the PM2.5 non-attainment designations 

took effect (April 5, 2005), we issued a 

guidance to address implementation of 

the NA NSR program pending the 

completion of this action to develop 

implementation rules for PM2.5. See 

memorandum from Stephen D. Page, 

Director, Office of Air Quality Planning 

and Standards to Regional Air Directors, 

‘‘Implementation of New Source Review 

Requirements in PM2.5 Nonattainment 

Areas’’ (Apr. 5, 2005). 

Our current guidance permits States 

to implement a PM10 nonattainment 

major NSR program as a surrogate to 

address the requirements of 

nonattainment major NSR for the PM2.5

NAAQS. A State’s surrogate major NSR 

program in PM2.5 nonattainment areas 

may consist of either the 

implementation of the State’s SIPapproved nonattainment major NSR 

program for PM10 or implementation of 

a major NSR program for PM10 under 

the authority in 40 CFR part 51, 

Appendix S. Appendix S generally 

applies where a State lacks a 

nonattainment major NSR program 

covering a particular pollutant. 

Once this PM2.5 implementation rule 

is finalized, States will have the 

necessary tools to implement a major 

NSR program for PM2.5 States will no 

longer be permitted to implement a 

nonattainment major NSR program for 

PM10 as a surrogate for the PM2.5

nonattainment major NSR program. 

Most States will then need to implement 

a transitional PM2.5 nonattainment 

major NSR program under Appendix S 

(as amended in this rulemaking action) 

until EPA approves changes to a State’s 

SIP-approved major NSR program to 

reflect the requirements of this rule. 

The NA NSR provisions in a State’s 

existing SIP-approved NA NSR program 

would only apply in areas designated 

nonattainment for the PM2.5 NAAQS if 

the SIP-approved regulations contain a 

generic requirement to issue part D 

permits in areas designated as 

nonattainment for any criteria pollutant 

and do not otherwise need to be 

amended to incorporate the changes 

proposed in this rule. In the situations 

described below, the States will need to 

revise their NA NSR regulations and 

submit them to EPA for incorporation 

into the SIP by the date the new 

implementation plans for PM2.5 are due 

(April 5, 2008): 

• States that have nonattainment 

regulations that need to be amended to 

incorporate the new PM2.5 requirements. 

• States that have newly designated 

nonattainment areas for PM2.5 and 

nonattainment NSR regulations that 

specifically list the areas in which NA 

NSR applies (i.e., the list does not 

include the newly designated areas). 

• States that currently have no 

nonattainment areas but have newly 

designated nonattainment areas for 

PM2.5. 

States in the categories listed above 

will have to implement a transitional 

major NSR permitting program for PM2.5

pursuant to 40 CFR 52.24(k) and 

Appendix S until their existing part D 

SIPs are revised to meet these new PM2.5

NSR regulations. 

b. Implementation of NSR Under the 

Emissions Offset Interpretative Ruling 

(40 CFR part 51, Appendix S) With 

Revisions 

In general, Appendix S requires new 

or modified major sources to meet LAER 

and obtain sufficient offsetting 

emissions reductions to assure that a 

new major source or major modification 

of an existing major source will not 

interfere with the area’s progress toward 

attainment. Readers should refer to 40 

CFR part 51, Appendix S for a complete 

understanding of these and other 

existing Appendix S requirements. In 

this action, we propose to revise 

Appendix S to include provisions 

necessary to implement a transitional 

major NSR program for PM2.5, including 

significant emissions rates applicable to 

major modifications for PM2.5 and, as 

appropriate, precursors.105

As currently written, Appendix S 

applies directly to major stationary 

sources. In accordance with the 

requirements of Section 110(a)(2)(c) of 

the Act, we believe that the majority of 

States have the legal authority to issue 

permits consistent with these 

requirements under an existing SIPapproved permitting program. 

Nonetheless, at least one State has 

reported that it lacks the legal authority 

to issue permits implementing the 

requirements of Appendix S under its 

existing permitting rules. If a State is 

unable to apply the requirements of 

Appendix S, EPA will act as the 

reviewing authority for the relevant 

portion of the permit. 

We believe that it is appropriate for 

EPA to issue the pre-construction 

permits in such circumstances. As 

discussed earlier, Congress amended the 

Act in 1990 to remove the requirements 

that would have applied a construction 

ban in area’s that lacked a SIP-approved 

part D permit program. Thus, we believe 

that it is consistent with Congressional 

intent that either the State or EPA issue 

permits to construct during the interim 

period. 

c. Legal Basis for Requiring States To 

Issue Nonattainment NSR Permits 

During the SIP-Development Period 

Section 110(a)(2)(C) of the CAA 

establishes a general duty on States to 

include a program in their SIP that 

regulates the modification and 

construction of any stationary source as 

necessary to assure that NAAQS are 

achieved. This general duty exists 

during all periods, including before a 

State has an approved NA NSR permit 

program. 

Section 110(a)(2)(c) of the Act does 

not define specific requirements States 

must follow for issuing major source 

permits during the period between 

nonattainment designation and EPA 

approval of a nonattainment NSR SIP 

(the ‘‘SIP-development’’ period). 

However, EPA has historically 

recognized that the SIP development 

period provided under Section 172(b) of 

the CAA leaves a gap in part D major 

NSR permitting and has determined that 

this gap is to be filled, in general, with 

a transitional major NSR program that 

includes the LAER and offset 

requirements from part D. 57 FR 18070, 

18076 (Apr. 28, 1992). This transitional 

NSR program has been implemented, to 

date, through the Emissions Offset 

Interpretative Ruling at 40 CFR part 51, 

Appendix S. The EPA’s regulations at 

40 CFR 52.24(k) require that Appendix 

S govern permitting during this time.106

66046 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

through State minor NSR permit programs. 

However, if a State lacks authority to issue a permit, 

then EPA will issue the permit. 

107See Alabama Power Co. v. Costle, 636 F.3d 

323, 346–047 (DC Cir. 1980) (discussing Sierra Club 

v. Ruckelshaus, 344 F. Supp. 253 (D.D.C. 1972), 

aff’d per curiam 4 ERC 1815 (DC Cir. 1972), aff’d 

by an equally divided court, sub nom Fri v. Sierra 

Club, 412 U.S. 541 (1973). 

108The actual language at 40 CFR 52.24(k) 

arguably allows States to issue permits under 

Appendix S for a maximum period of 18 months 

after designation. After this time, if the 

nonattainment area does not have an approved NA 

NSR permit program, a construction ban would 

apply. However, in 1990, Congress altered the 

provisions of the construction ban such that it 

would not apply when a State/Local lacked an 

approved NA NSR permit program in the future. 

The EPA believes that Congress’ removal of the 

construction ban from the Act supersedes the 

regulatory language at 52.24(k) and EPA has 

reinterpreted this language to allow States to issue 

permits under Appendix S from designation until 

the SIP is approved even if this exceeds 18 months. 

See 1991 memo, ‘‘New Source Review (NSR) 

program Transitional Guidance, John S. Seitz, 

March 11, 1991. The EPA anticipates revising the 

language at section 52.24(k) to properly reflect this 

interpretation. 

109 109 Letter from Bill Grantham, National Tribal 

Environmental Council, to docket 2003–0079, 

providing comments on the proposed 8-hour ozone 

implementation rule (66 FR 32802). 

In addition, Congress indicated in the 

1977 CAA Amendments that major NSR 

permitting should apply during the SIP 

development period. See Public Law 

95–95, section 129(a), 91 Stat. 685 

(1977). Specifically, in 1977, when 

Congress enacted a moratorium on 

construction in any area lacking an 

approved part D SIP, with a delayed 

effective date of July 1, 1979, Congress 

directed that Appendix S govern 

permitting of sources constructing in 

such areas prior to that date. Id. section 

108(b), section 129(a). 

The EPA subsequently codified the 

use of Appendix S as the transitional 

major NSR program in 40 CFR 52.24(k), 

reasoning (in the context of 

implementing a delay in the 

construction ban for then-recently 

designated nonattainment areas) that 

Congress had directed that Appendix S 

remain in effect to protect air quality 

while State plans were being designed. 

45 FR 91604 (Oct. 2, 1980). When 

Congress removed the construction ban 

(except as provided in Section 

110(n)(3)), it left 40 CFR 52.24(k) in 

place, implementing the transitional 

major NSR program under Appendix S. 

The continued application of 

appendix S through § 52.24(k) is also 

supported by one of the purposes of the 

Clean Air Act ‘‘to protect and enhance 

the quality of the Nation’s air resources 

so as to promote the public health and 

welfare and the productive capacity of 

its population.’’ 42 U.S.C. 7401(b)(1). 

This provision was the basis for the 

original judicial finding that the Act 

imposed an obligation to prevent 

significant deterioration in areas that 

meet the NAAQS, prior to Congress’

enactment of the PSD program at part C 

of the Act.107 This policy of 

nondegradation applies with even 

greater force in areas that fail to meet 

the NAAQS. Thus, we believe that an 

interim major NSR program for the SIP 

development period—as codified at 

appendix S and updated to reflect CAA 

amendments and the promulgation of 

the PM2.5 NAAQS—is supported by 

section 110(a)(2)(C), section 101(b)(1), 

Congressional intent, and our gap-filling 

authority under section 301(a). 

Although EPA omitted § 52.24(k) from 

the regulatory text accompanying a 

proposed rulemaking in 1996 (see 61 FR 

38250, 38305 (July 23, 1996)), the 

preamble indicated that the change was 

intended only to update and clarify the 

regulation with regard to the changes to 

the construction ban made by the 1990 

Amendments.108 The proposal did not 

in any manner indicate that EPA 

believed that NSR permits complying 

with Appendix S, or otherwise 

satisfying Section 110(a)(2)(C), were not 

required during the interim period. We 

have discussed the continued 

applicability of § 52.24(k) and Appendix 

S in implementation of the 8-hour ozone 

NAAQS. 68 FR at 32846. 

18. NSR Applicability to Precursors 

During the Interim Period 

As discussed in Section M.2, EPA has 

proposed several options for NSR 

applicability to the potential PM2.5

precursors (SO2, NOX, VOC, and 

ammonia). EPA has proposed that SO2

is a national precursor to PM2.5. EPA has 

also proposed that if NOX emissions are 

subject to NSR as PM2.5 precursor, States 

could exempt NOX from its PM2.5 NSR 

program in a specific area by 

demonstrating that NOX emissions from 

stationary sources in that area are not a 

significant contributor to that area’s 

ambient PM2.5 concentrations and the 

area is not in a State identified by EPA 

as a source of a PM2.5 interstate 

transport problem. However, during the 

SIP development period, States face 

substantial hurdles in making such a 

demonstration because they are in the 

initial stages of gathering information 

and analyses necessary to prepare their 

attainment demonstrations. Thus, 

during this period, a presumption that 

a precursor is a regulated NSR pollutant 

for PM2.5 may amount to an irrebuttable 

presumption for many States. Because 

of the challenges posed by the SIP 

development period, EPA is considering 

whether NSR applicability to precursors 

should be stayed for one or more 

precursors during the SIP development 

period. The EPA is soliciting comments 

on the applicability of NSR to 

precursors during the SIP development 

period. 

19. Are there any Tribal concerns? 

We expect that some Tribal areas will 

be designated as nonattainment in part 

because of pollution that is transported 

from surrounding State lands. Tribal 

representatives have advocated for 

additional flexibility to address 

nonattainment problems caused by 

transported pollution, such as the 

provision of NSR offset set-asides 

(which we expect would come from 

State offset pools or banks), because 

they have limited ability to generate 

offsets on their own. Tribal 

representatives have raised these and 

other concerns in discussions on 

implementation of the 8-hour ozone and 

PM2.5 standards, and in comments on 

the 8-hour ozone implementation 

rule.109 We request comment on 

whether emissions offset set-asides, 

possibly generated by innovative 

measures to promote additional 

emissions reductions, are an appropriate 

method to help level the playing field 

for the Tribes and support economic 

development in Tribal areas. We also 

request comment on ways in which 

States may help provide the Tribes 

access to offsets from non-Tribal areas. 

In addition, to address these and other 

issues related to implementation of the 

NSR program in Indian country, EPA is 

evaluating the impact of the NSR 

program on Tribes in Indian country. 

The EPA plans to address these 

concerns in a future Tribal NSR rule. 

20. What must a State or local agency 

do about minor sources of PM2.5? 

Pursuant to Section 110(a)(2)(C), 

States must have a minor source 

permitting program. This applies to new 

and modified stationary sources that are 

not considered major for a criteria 

pollutants or a precursor for a criteria 

pollutant. At this time States must 

include the following pollutants in their 

minor NSR program: 

• VOC, 

• SO2, 

• NOX, 

• CO, 

• PM10, and 

• Lead (Pb) 

States must now amend their minor 

source programs to include 

• PM2.5 direct emissions, and 

• Precursor emissions as included in 

PM2.5 major NSR. 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66047 

21. Supplemental Program Option: 

Rural Transport Areas 

a. What flexible implementation options 

should be available for Transport areas? 

EPA is considering flexible 

implementation for Nonattainment NSR 

for areas that qualify for the transport 

classification. These areas are 

designated nonattainment due to 

overwhelming transport, for example, 

areas where pollution is from 

surrounding jurisdictions but where 

there are few or no sources of PM2.5 in 

the area. Under the current program no 

flexibility is available under NA NSR for 

sources in these areas overwhelmed by 

transport. As mentioned earlier, in this 

rule, we are proposing a transport 

classification to provide some flexibility 

to address some of the fairness issues 

associated with transport. This transport 

classification can be used by States and 

Tribes if they meet the criteria discussed 

below. If there is no transport 

classification then this option will not 

be available in the near-term. However, 

EPA intends to develop a separate 

proposed rule on flexible 

implementation of nonattainment NSR 

for areas designated nonattainment for 

any criteria pollutant, where transport is 

the primary cause of the area’s 

nonattainment. Such a proposal would 

not be dependent on the incorporation 

of a transport classification in a 

classification system for a NAAQS. 

b. Which nonattainment areas would be 

eligible for the transport program? 

In order to be eligible for the transport 

option the State/Local with jurisdiction 

over a nonattainment area must: 

(1) Have submitted an attainment plan 

which demonstrates, through modeling, 

that the area is designated 

nonattainment due to overwhelming 

transport from an upwind area(s); and 

(2) Have submitted an attainment plan 

containing any additional local control 

measures needed for attainment of the 

PM2.5 standard; and 

(3) Have submitted the attainment 

plan that commits the State/Local to 

implement a program that meets the 

requirements for transport areas 

discussed below. 

As described earlier in the 

classification section, an area will not be 

reclassified as a ‘‘transport’’ area until 

after the SIP is approved by the Regional 

Office. A transport area could apply for 

single or multi-state/Local 

nonattainment areas. Such areas will 

not be able to implement the 

nonattainment NSR transport program 

until the area is reclassified as a 

‘‘transport’’ area. Until an area is 

reclassified, States must continue to 

apply the nonattainment NSR program. 

c. What would be the basic 

requirements of a transport 

nonattainment NSR program? 

EPA is requesting comment on what 

type of regulatory flexibility would be 

beneficial for transport areas while 

providing equal environmental 

protection. Specific examples of needed 

flexibility for areas which the 

commenter suggests would qualify as 

transport areas would be helpful. As 

noted above, we anticipate proposing a 

separate rulemaking on the details of the 

NSR requirements. 

N. How will EPA ensure that the 8-hour 

ozone standard will be implemented in 

a way which allows an optimal mix of 

controls for PM2.5, ozone, and regional 

haze? 

1. Could an area’s PM2.5 strategy affect 

its 8-hour ozone and/or regional haze 

strategy? 

Based on current data, many areas are 

violating both the 8-hour ozone and the 

PM2.5 NAAQS. Thus, many cities will 

have ozone and PM2.5 nonattainment 

areas with overlapping boundaries. 

Requirements for regional haze apply to 

all areas. Each State is responsible for 

developing SIP revisions to meet all the 

requirements relevant to each 

nonattainment area for each pollutant as 

well as developing a regional haze plan. 

In some cases, ozone control measures 

may also be useful for a PM2.5 control 

strategy or a regional haze plan. 

Similarly, controls for PM2.5 may lead to 

reductions in ozone or regional haze. 

For example, considered in isolation, a 

metropolitan area’s ozone strategy might 

be based on additional VOC emissions 

reductions; if the area needs NOX

reductions for PM2.5 attainment, 

however, an optimal approach might 

include a more complex ozone strategy 

using both NOX and VOC reductions. 

We believe integration of ozone and 

PM2.5 attainment planning will reduce 

overall costs of meeting multiple air 

quality goals. 

Many of the factors affecting 

concentrations of ozone also affect 

concentrations of PM2.5. Emissions of 

NOX and/or VOC will lead to formation 

of organic particles and the precursors 

of particulate nitrate, as well as ozone. 

The presence of ozone is an important 

factor affecting PM2.5 formation; as 

ozone builds up, so do hydroxyl (OH¥) 

radicals which are instrumental in 

oxidizing gas phase SO2 to sulfuric acid. 

The sulfuric acid may be converted to 

sulfate particles, increasing the PM2.5

concentration. Further, the local ozone 

concentrations may be decreased by the 

reaction of ozone with nitric oxide; 

thus, in some large urban areas, a 

decrease in local NOX emissions can 

result in higher local ozone 

concentrations, leading to higher OH 

radical concentrations and increases in 

secondary PM2.5. Because the precursors 

for ozone and PM2.5 may be transported 

hundreds of kilometers, regional scale 

impacts must also be considered. 

2. What guidance has EPA provided 

regarding ozone, PM2.5 and regional 

haze interaction? 

States must develop 8-hour ozone and 

PM2.5 attainment demonstrations for 

most nonattainment areas. General 

criteria for attainment demonstrations 

are contained in 40 CFR part 51, 

appendix W (i.e., ‘‘EPA’s Guideline on 

Air Quality Models’’). The EPA’s May 

1999 draft ‘‘Guidance on the Use of 

Models and Other Analyses in 

Attainment Demonstrations for the 8- 

Hour Ozone NAAQS’’ provides a set of 

general requirements that an air quality 

model should meet to qualify for use in 

an attainment demonstration for the 8- 

hour ozone NAAQS. The draft guidance 

encourages States to integrate PM2.5

control strategies with strategies 

designed to attain the 8-hour ozone 

NAAQS and to meet reasonable progress 

goals for regional haze. In addition, the 

draft guidance presents some modeling/ 

analysis principles to help States 

develop databases and capabilities for 

considering joint effects of control 

strategies for ozone, PM2.5 and regional 

haze. Because emissions and 

meteorological conditions vary 

seasonally, the guidance recommends 

assessing the effects of an ozone control 

strategy on annual PM2.5 concentrations 

by estimating effects on mean PM2.5 for 

each season and using the resulting 

information to estimate annual impacts. 

Emission estimates for VOC, NOX, 

primary PM2.5, SO2 and ammonia will 

be needed. In addition, the modeling 

should separately estimate the effects of 

the ozone strategy on the major 

components of PM2.5: Mass associated 

with sulfates, nitrates, organic carbon, 

elemental carbon, and all other species. 

We believe that this approach is 

adequate to ensure that the 8-hour 

ozone standard will be implemented by 

States in a way that allows an optimal 

mix of controls for ozone, PM2.5, and 

regional haze. 

Similarly, EPA’s draft attainment 

demonstration guidance for PM2.5 and 

regional haze states that models 

intended to address secondary PM 

problems should also be capable of 

simulating ozone formation and 

transport (January 2, 2001 (draft), 

66048 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

110As in the past, EPA will provide sufficient 

time for state and local agencies to transition to any 

new motor vehicle emissions factor model, if one 

becomes available during the development of PM2.5

SIPs. 

111Emissions Inventory Guidance for 

Implementation of Ozone and Particulate Matter 

National Ambient Air Quality Standards (NAAQS) 

and Regional Haze Regulations,’’ EPA–454/R–05–

001, August 2005. 

‘‘Guidance for Demonstrating 

Attainment of Air Quality Goals for 

PM2.5 and Regional Haze’’). The 

formation and transport of secondary 

PM are closely related to processes that 

are important in the formation and 

transport of ozone. Thus, it makes sense 

for programs designed to control ozone 

to be cognizant of programs to reduce 

PM2.5 and improve visibility and vice 

versa. The PM2.5 guidance suggests 

conducting a ‘‘mid-course review’’ of an 

approved PM2.5 plan to review changes 

in air quality resulting from 

implementation of plans to reduce 

PM2.5, regional haze, and ozone (see 

section E). 

3. What is EPA proposing? 

Today, we propose to continue the 

policy of encouraging each State with a 

PM2.5 nonattainment area which 

overlaps, is near to, or otherwise affects 

an 8-hour ozone nonattainment area to 

take all reasonable steps to coordinate 

the required control measures needed to 

attain the standards in nonattainment 

areas and meet reasonable progress 

goals for regional haze. Specifically, 

States conducting modeling analyses for 

PM2.5 should evaluate the concurrent 

effects of control strategies on estimated 

ozone levels. In addition, we encourage 

States conducting modeling analyses for 

ozone to estimate separately the effects 

of ozone control strategies on PM2.5 and 

its precursors. 

O. What emission inventory 

requirements should apply under the 

PM2.5 NAAQS? 

Emission inventories are critical for 

the efforts of State, local, tribal and 

federal agencies to attain and maintain 

the NAAQS that EPA has established for 

criteria pollutants including PM2.5. 

Pursuant to its authority under section 

110 of Title I of the CAA, EPA has long 

required States to submit emission 

inventories containing information 

regarding 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. 

The 1990 CAAA 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 emission 

inventory requirements applicable to 

certain areas that were designated 

nonattainment for certain pollutants. In 

the case of particulate matter, the 

emission inventory provisions are in the 

general provisions under Section 

172(c)(3). 

In June 2002, EPA promulgated the 

Consolidated Emissions Reporting Rule 

(CERR)(67 FR 39602, June 10, 2002). 

The CERR consolidates the various 

emissions reporting requirements that 

already exist into one place in the CFR, 

establishes new reporting requirements 

for PM2.5 and ammonia, and establishes 

new requirements for the statewide 

reporting of area source and mobile 

source emissions. 

The CERR establishes two types of 

required emission inventories: 

• Annual inventories 

• 3-year cycle inventories 

The annual inventory requirement is 

limited to reporting statewide emissions 

data from the larger point sources. For 

the 3-year cycle inventory, States will 

need to report data from all of their 

point sources plus all of the area and 

mobile sources on a statewide basis. A 

special case exists for the first 3-year 

cycle inventory for the year 2002 which 

is due on June 1, 2004. The EPA has 

designated 2002 as the new Base Year 

for 8-hour ozone, PM2.5 and regional 

haze (November 18, 2002 EPA 

memorandum ‘‘2002 Base Year 

Emission Inventory SIP Planning: 8- 

Hour Ozone, PM2.5 and Regional Haze 

Programs’’ http://www.epa.gov/ttn/ 

chief/eidocs/ 

2002baseinven_102502new.pdf). 

States would estimate mobile source 

emissions by using the latest emissions 

models and planning assumptions 

available at the time the SIP is 

developed. The latest approved version 

of the MOBILE model should be used to 

estimate emissions from on-road 

transportation sources, in combination 

with the latest available estimates of 

vehicle miles traveled (VMT). The 

current version of the MOBILE model, 

MOBILE6.2, is used for areas outside 

California.110 The model EMFAC2002 is 

used for California. The latest 

information on MOBILE6.2 is available 

at: http://www.epa.gov/otaq/m6.htm. 

The NONROAD model is currently 

available in draft form and can be used 

for estimates of non-road mobile source 

emissions: http://www.epa.gov/otaq/ 

nonrdmdl.htm. By merging the 

information on point sources, area 

sources and mobile sources into a 

comprehensive emission inventory, 

State, local and Tribal agencies may do 

the following: 

• Set a baseline for SIP development. 

• Measure their progress in reducing 

emissions. 

• Have a tool to support future 

trading programs. 

• Answer the public’s request for 

information. 

EPA uses the data submitted by the 

States to develop the National Emission 

Inventory (NEI). The NEI is used by EPA 

to show national emission trends, as 

modeling input for analysis of potential 

regulations, and other purposes. 

Most importantly, States need these 

inventories to help nonattainment areas 

develop and meet SIP requirements to 

attain the annual and 24-hour PM2.5

NAAQS. There is a special situation 

regarding emission inventories from 

Tribal areas that should be considered. 

In the past, there have been instances 

where portions of tribal areas have been 

included in designated nonattainment 

areas, but when the baseline emission 

inventory was prepared, emissions from 

the tribal lands were not included. This 

has had the effect of preventing the 

tribes from generating emissions 

reductions from existing sources to 

develop emission offsets, as well as 

impairing the ability of the State to 

model as accurately as possible. We are 

encouraging the States and Tribes to 

work together to ensure that the 

information used in developing the 

baseline emission inventory is inclusive 

of all emissions from the nonattainment 

area. 

In April 1999, EPA published the 

‘‘Emissions Inventory Guidance for 

Implementation of Ozone and 

Particulate Matter National Ambient Air 

Quality Standards (NAAQS) and 

Regional Haze Regulations,’’ EPA–454/ 

R–99–006. The EPA updated this 

guidance in August 2005.111 The current 

version of this guidance is available at: 

http://www.epa.gov/ttn/chief/eidocs/ 

eiguid/index.html. The EPA developed 

this guidance document to complement 

the CERR and to provide specific 

guidance to State and local agencies and 

Tribes on how to develop emissions 

inventories for 8-hour ozone, PM2.5, and 

regional haze SIPs. While the CERR sets 

forth requirements for data elements, 

EPA guidance complements these 

requirements and indicates how the 

data should be prepared for SIP 

submissions. The SIP inventory also 

must be approved by EPA as a SIP 

element and is subject to public hearing 

requirements where the CERR is not. 

Because of the regulatory significance of 

the SIP inventory, EPA will need more 

documentation on how the SIP 

inventory was developed by the State as 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66049 

opposed to the documentation required 

for the CERR inventory. In addition, the 

geographic area encompassed by some 

aspects of the SIP submission inventory 

will be different from the statewide area 

covered by the CERR emissions 

inventory. If a State’s 2005 emission 

inventory (or a later one) becomes 

available in time to use for an area 

subsequently redesignated 

nonattainment, then that inventory 

should be used. We also encourage the 

cooperation of the Tribes and the State 

and local agencies in preparing their 

emissions inventories. 

Therefore, the basis for EPA’s 

emission inventory program is specified 

in the CERR and the related guidance 

document. The EPA is interested in 

receiving comments on whether or not 

additional emission inventory 

requirements or guidance are needed to 

implement the PM2.5 NAAQS. For 

example, do any of the following issues 

need to be defined through additional 

requirements or guidance? 

• An important difference between 

inventories submitted in response to the 

CERR and SIP inventories is the issue of 

approvability. While it is likely that an 

inventory submitted under the CERR 

would be identical to the inventory 

submitted as part of a SIP, the SIP 

inventory will need to go through public 

hearing and formal approval by EPA as 

a SIP element. This approval process 

can be combined with other SIP 

elements. Should EPA specify an 

inventory approval process? 

• Are the data elements specified 

within the CERR sufficient to develop 

adequate SIPs? For example, in the 

determination of RACT should more 

information on existing control devices 

be required? 

• Currently the CERR requires the 

reporting of SO2, VOC, NOX, CO, Pb, 

PM10, PM2.5, and NH3. VOC and PM are 

speciated by the emissions processing 

models based on speciation profiles for 

specific source categories. Is this 

approach sufficient, or should EPA 

require more specific emission 

component reporting such as specific 

organic compounds or groups of 

compounds or reporting of elemental 

carbon and organic carbon? 

• The CERR allows states to adopt 

EPA developed emission estimates from 

area and mobile sources in lieu of 

making these estimates themselves if 

they accept these estimates for their 

emission inventory. Since 2002 has 

been designated as the new base year, 

should EPA require that States develop 

their own estimates for area and mobile 

sources? 

• Are there other inventory issues 

that EPA should define through either 

regulation or guidance? 

P. What stationary source test methods 

should States use under the PM2.5

implementation program? 

1. Will the existing stationary source 

test methods for particulate matter (PM) 

be acceptable for use in PM2.5 SIPs? 

We believe that states that need to 

adopt local control measures for 

primary particulate matter in 

nonattainment areas will need to revise 

their stationary source test methods. 

However, the acceptability of existing 

stationary source test methods for PM2.5

SIPs depends upon what is measured 

under the State’s current test methods 

for particulate matter. Information 

available to the Agency indicates that 

the majority of existing SIPs currently 

specify the use of stationary source test 

methods that quantify only filterable 

particulate matter. We believe that test 

methodologies that measure only 

filterable particulate matter would be 

acceptable in areas where no additional 

reductions of primary PM2.5 and 

particulate precursor emissions are 

required to project attainment of the 

PM2.5 NAAQS. The use of these existing 

stationary source test methods provide 

verification that PM2.5 emissions are 

consistent with the levels emitted as a 

result of existing applicable 

requirements for filterable particulate 

matter. However, for areas where 

additional local control of primary 

particulate matter emissions are 

required as part of the attainment 

demonstration, we believe that existing 

test methodologies that measure only 

filterable particulate matter would not 

be acceptable. The use of existing source 

test methods potentially would limit the 

control measures available for 

developing cost effective strategies to 

achieve attainment of the PM2.5 NAAQS. 

In addition, the existing test methods 

may not be acceptable for demonstrating 

compliance with emission limitations to 

achieve the PM2.5 NAAQS under certain 

circumstances: 

(1) Where the attainment 

demonstration includes control 

methodologies for PM precursors which 

are likely to result in a significant 

increase in the direct emissions of fine 

particulate matter (for example, 

ammonia injection to reduce NOX

emissions). 

(2) Where the attainment 

demonstration includes control 

methodologies for PM precursors which 

are likely to result in a significant 

decrease in the direct emissions of fine 

particulate matter (for example, alkaline 

scrubbers to reduce SO2 emissions) and 

incorporate these direct emissions 

reductions in their attainment 

demonstration or allow for the use of 

these reductions as credits for other 

programs. 

2. Why are the existing stationary source 

test methods for PM deficient? 

Most stationary source test methods 

specified in State rules do not 

adequately quantify either total PM 

emissions or PM2.5 emissions. 

Additionally, some of the current 

stationary source test methods will not 

adequately provide a uniform indication 

of the sources’ performance in 

controlling PM2.5 emissions. Most 

source test methods referenced in SIPs 

provide a measurement of the 

particulate matter that is solid or liquid 

at a temperature specified in the method 

or applicable standard. Filtration 

temperatures of 250 °F and 320 °F are 

typical although other temperatures may 

be specified in a few test methods or 

applicable standards. Generally, these 

filterable particulate matter test methods 

are either identical or very similar to 

one of the ten Federal test methods 

published in Appendix A of 40 CFR Part 

60 and used to determine compliance 

with New Source Performance 

Standards (NSPS). These test methods 

are adequate to evaluate the compliance 

status of a source for emissions of that 

component of particulate matter 

evaluated when the applicable rule was 

developed. However, these test methods 

do not provide a measurement of total 

particulate matter emissions, or PM2.5

emissions. 

The test method proposed to 

determine compliance with the first 

group of NSPS (36 FR 15713) 

determined the sum of the mass of 

material collected on or prior to the 

filters maintained at 250 °F and the 

material collected in the cooled 

impingers that followed the filter. While 

the material collected prior to the filter 

provided a measure of the filterable 

particulate material, the material 

collected in the impingers was stated to 

measure vapors in the stack that would 

become particulate matter at 70 °F (36 

FR 15495). When combined, the method 

provided a measurement of the total 

particulate matter emissions from the 

facility tested. The promulgated test 

method (36 FR 24888) did not include 

the analysis of the impinger portion of 

the sampling train. To accommodate the 

change in the test method, EPA made 

adjustments in the promulgated 

emission limits to reflect the change in 

the test method. The EPA made 

adjustments of up to 50 percent in the 

promulgated emission limitations to 

66050 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

reflect the measurement of only the 

filterable portion of the emissions. 

EPA recognized in setting several 

subsequent NSPS that the source test 

method used to determine compliance 

with the particulate matter emissions 

limits measured only part of the total 

particulate matter emitted by the 

applicable sources. This recognition was 

published on October 6, 1975, in the 

promulgated Revisions to Performance 

Testing Methods (40 FR 46250). 

Similarly, EPA acknowledged this in the 

proposal preamble to Subpart CC—

Standards of Performance for Glass 

Manufacturing Plants (6/15/79) in the 

section ‘‘Selection of Performance Test 

Methods: The use of EPA Reference 

Method 5—Determination of Particulate 

Emissions from Stationary Sources.’’

In developing the NSPS emission 

limitations, it is evident that only a 

portion of the particulate matter 

emissions were considered. As a result, 

the test methods that EPA selected for 

determining compliance with these 

emission limitations measured only that 

same portion of the particulate matter 

emissions. It was recognized that these 

test methods were not suitable for 

quantifying the total emissions to the 

atmosphere and that the impinger 

portion of the sampling train contained 

the missing portion of the particulate 

matter emissions. 

On December 17, 1990, EPA 

promulgated Method 202 in Appendix 

D of 40 CFR Part 51 (56 FR 65433) to 

provide a method for States to use to 

analyze the impinger (or ‘‘back half’’) 

content of PM emissions and provide a 

measure of the condensable particulate 

emissions. The principal procedures in 

Method 202 improved upon the original 

Method 5 back half analysis proposed in 

1971. In developing this measurement 

method, EPA consulted with several 

State and local agencies and 

incorporated several options to simplify 

or accommodate existing policies and 

source testing methodologies for 

condensable particulate matter. We 

believe that by excluding the optional 

components, the use of EPA Method 

202, combined with EPA Method 5 or 

EPA Method 17, provides a reasonable 

indication of total particulate matter 

emissions for the majority of stationary 

emission sources. 

However, the combination of EPA 

Method 5 and Method 202 measures 

particulate matter that is larger than 2.5 

micrometers in aerodynamic diameter, 

and will not provide a reasonable 

measurement of the emissions of PM2.5. 

Methods are available that can separate 

particulate matter by aerodynamic size. 

On April 17, 1990, EPA promulgated 

EPA Method 201 and Method 201A to 

provide a source test method that 

separated filterable particulate matter 

greater than 10 micrometers from 

filterable particulate matter equal or 

smaller than 10 micrometers. The single 

cyclone used in these methods replaced 

the nozzle of EPA Method 17 to separate 

the two size classes of filterable 

particulate. This method allows sources 

to determine their emissions of filterable 

PM10 when there are size specific 

emission limits or when there is a need 

for size specific emission inventories. 

With the addition of a second smaller 

cyclone following the single cyclone of 

EPA Method 201A, the filterable 

particulate can be separated into three 

size classifications. These classifications 

include filterable particulate matter 

greater than 10 micrometers, filterable 

particulate matter equal or smaller than 

10 micrometers but greater than 2.5 

micrometers, and filterable particulate 

matter equal or smaller than 2.5 

micrometers. This method is posted as 

Conditional Method 40 (CTM 40) on 

EPA’s Emission Measurement Centers 

web page at http://www.epa.gov/ttn/ 

emc/ctm.html. Of the methods 

mentioned previously, the most reliable 

measurement of total direct PM2.5

emissions would combine the use of 

Conditional Method 40 with EPA 

Method 202. 

Conditional Method 40 has been used 

at several facilities in the U.S. and the 

hardware required to implement this 

method has been readily available since 

the mid-1980’s. The acceptability of a 

source using the existing SIP test 

methods for filterable particulate matter 

as an indication of the source’s relative 

performance in controlling PM2.5

emissions would depend on the source’s 

level of condensable particulate matter 

emissions in relation to filterable PM 

emissions, the proportion of filterable 

particulate matter that is smaller than 

2.5 micrometers, the add-on PM control 

device effectiveness, and the need to 

consider limiting the emissions of the 

condensable material. In areas where 

there is no need to reduce stationary 

source particulate matter emission 

levels to demonstrate attainment of the 

PM2.5 NAAQS, the use of total filterable 

particulate test methods may be 

adequate to insure that existing levels of 

PM control are being maintained. 

However, in areas where a reduction of 

stationary source particulate matter 

emissions is incorporated into the 

attainment demonstration, the use of a 

test method that measures total PM2.5

emissions would be more appropriate 

than existing test methods that measure 

only total filterable PM. 

3. If the stationary source test methods 

are changed, will the existing emission 

limitations incorporated in SIPs need to 

be changed? 

Changes in the source test method 

will require reevaluations of the 

emission limitations. The reevaluation 

will need to consider the interrelated 

impacts due to differences in the test 

method, characteristics of the 

particulate matter emissions from the 

sources, and intended changes in the 

stringency of the emission limitations. 

The following three examples provide a 

range of the relationships that can occur 

between the source test method and the 

characteristics of the particulate matter 

emissions. For sources with no 

condensable particulate matter 

emissions, a change from a total 

particulate matter test method (using the 

same particle size cutoff) to a PM2.5 test 

method will result in lower measured 

emissions. The difference in mass 

measured by the two test methods 

depends on the size distribution of the 

filterable particulate matter emissions 

from the source. For sources with 

condensable particulate matter 

emissions, a change from a filterable 

particulate matter test method to a total 

particulate matter test method will 

result in higher measured emissions. 

The difference in mass measured by the 

two test methods depends on the 

relative emissions of filterable and 

condensable emissions from the source. 

For sources with condensable 

particulate matter emissions, a change 

from a total filterable particulate matter 

test method to a total PM2.5 test method 

may increase or decrease the measured 

emissions. The increase or decrease and 

the magnitude of any change would 

depend on the particle size distribution 

of the filterable particulate matter and 

the magnitude of the condensable 

particulate matter emission. 

As can be inferred from these three 

examples, the application of a single 

multiplier to convert existing emission 

limitations to a total PM2.5 emission 

limitation would result in a variable 

change in the stringency of emission 

limitation. The use of a single multiplier 

would result in unplanned and variable 

changes in the stringency in the existing 

emission limitations. These changes 

may create unintended consequences 

for the affected sources and result in 

poorly understood and quantified 

estimates of the benefits. 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66051 

112The significance of the condensable fraction of 

PM2.5 is illustrated using the original supporting 

data for the Subpart D NSPS cited previously. The 

promulgated standard was reduced by 50% because 

about half the emissions were filterable PM and the 

other half were condensable PM. However, only 

about 29 percent of the filterable particulate matter 

is filterable PM2.5 (based upon the particle size 

distribution presented in Table 1.1–6 of AP–42). 

Therefore, about 78 percent of the total PM2.5

emissions would be condensable PM {Total PM = 

0.5 filterable + 0.5 condensable, Total PM2.5 = (0.5 

filterable × .29) + 0.5 condensable = 0.645, 

condensable PM2.5 = 0.5/0.645 = 78%}. 

4. The existing PM test methods and the 

emission limits based upon these 

methods have been acceptable since 

1971, why do they need to be changed 

for PM2.5? 

Several changes have occurred over 

the last 30 years that have gradually 

eroded the predictive capabilities of 

particulate matter source test methods 

used in most SIPs to evaluate the 

sources performance in controlling the 

pollutant measured by the ambient air 

quality test method. In the 1970’s and 

early 1980’s, the ambient air quality test 

method quantified the total particulate 

matter suspended in the ambient air. At 

the beginning of this period, particulate 

matter control measures were relatively 

poor. Additionally, most of particulate 

matter control measures applied over 

the last 30 years have focused on 

filterable particulate matter. While some 

control measures for other air pollutants 

also resulted in collateral reductions in 

condensable particulate and particulate 

precursor emissions, these reductions 

were relatively small. As a result, the 

relative amount of sulfates, nitrates and 

condensed organic matter in the 

ambient air particulate matter was 

proportionally greater in the 1980’s than 

it was in the 1970’s. The promulgation 

of the PM10 NAAQS in 1987 resulted in 

further reductions in filterable PM from 

sources, but there were few nonattainment areas where control of the 

condensable constituents of PM10 was 

required in order to achieve attainment. 

As a result, stationary source control 

measures that addressed only the 

filterable component of particulate 

matter were generally adequate to 

achieve the PM10 NAAQS. 

With the promulgation of the PM2.5

NAAQS in 1997 and associated ambient 

air quality monitoring, speciation 

analyses of PM2.5 show that a substantial 

portion of PM2.5 consists of sulfates, 

nitrates and organic carbon. These 

constituents are also a substantial 

portion of the condensable particulate 

matter collected from stationary sources. 

With the increased application of 

increasingly efficient filterable 

particulate matter control measures, 

condensable emissions have become a 

larger percentage of overall PM2.5

emissions for several stationary source 

categories. 

Based upon the particle size 

distribution presented in Table 1.1–6 of 

AP–42, about 29 percent of the total 

filterable particulate matter is filterable 

PM2.5. As a result, about 78 percent of 

the total PM2.5 emissions would be 

condensable PM.112 Since filterable 

particulate matter emissions controls 

have improved since 1971 and since 

most sources achieve substantially 

lower emissions than required by State 

and Federal emissions limitations, and 

condensable emissions have generally 

not been significantly reduced, the 

significance of the condensable 

emissions as a proportion of direct PM2.5

emissions may be greater than indicated 

above. A test method that measures total 

filterable particulate matter, commonly 

including mostly particles larger than 

PM2.5 and yet excluding condensable 

emissions, is a poor indicator of source 

performance at reducing PM2.5

emissions. 

5. What methods are available for 

measuring PM size and condensable PM 

from stationary sources? 

EPA has adopted one of several 

methods that are available for 

classifying particulate matter by 

aerodynamic diameter. The method 

adopted is based upon the use of 

centrifugal forces created in cyclones to 

separate particulate matter into two 

aerodynamic size classifications. The 

cyclone specified in EPA Method 201 

and 201A separates particulate matter 

with a nominal aerodynamic diameter 

greater than 10 micrometers from the 

remaining particulate matter. The 

addition of a second smaller cyclone 

following the EPA Method 201A 

cyclone as is specified in EPA Method 

CTM 40 separates the particulate matter 

that has an aerodynamic diameter 

greater than 2.5 micrometers from the 

remaining particulate matter. A filter 

follows the final cyclone of these 

particle sizing methods to collect the 

smaller material. Under EPA’s source 

test methods to separate PM based on 

particle size, both of the cyclones and 

the filter are maintained at the flue gas 

temperature. Therefore, any material 

that is in a vapor state in the flue gas 

but would be condensed as a result of 

dilution and cooling when released to 

the ambient air will not be measured by 

these particle sizing methods. 

Vapors that would condense to form 

particulate matter in the ambient air can 

be quantified by EPA Method 202. The 

EPA Method 202 is intended for use in 

conjunction with a filterable particulate 

matter test method such as Method 

201A or CTM 40. Impingers containing 

cold water are used by most methods to 

condense water vapor for determining 

the flue gas moisture content. Besides 

condensing water vapor in the flue gas, 

organic and inorganic chemical vapors 

are also condensed in these impingers. 

In EPA Method 202, the organic and 

inorganic vapors condensed in the 

impingers are separated with an organic 

solvent and weighed after evaporating 

the water and organic solvent used for 

separation. 

As recommended by the National 

Academy of Sciences, EPA and others 

are developing dilution based source 

test methods for collecting and 

analyzing PM2.5. Rather than 

condensing vapors in chilled water, cool 

filtered dilution air condenses the 

vapors prior to collection on filters. In 

the new method developed by EPA, 

particulate matter is sized using the 

same cyclones used in CTM 40. 

However, the in-stack filter used in 

CTM 40 is removed so that all of the 

PM2.5 particulate matter is collected at 

near ambient temperature on the filters. 

6. Why is a new dilution-based test 

method being developed by EPA? 

The use of dilution-based particulate 

matter sampling offers several 

advantages over the combination of EPA 

Method CTM 40 and Method 202. One 

advantage is that the vapors are 

condensed and chemical reactions occur 

in a manner similar to when stack gas 

is released to the atmosphere. As a 

result, the potential for particulate 

matter formation that may occur in 

water but would not occur in air is 

eliminated. Another advantage is that 

the potential for losing particulate 

matter during the evaporation of the 

impinger water is eliminated. With the 

use of multiple filter types, the use of 

dilution sampling methods will allow 

for the speciation of the collected PM2.5

by the same methods used for speciation 

of ambient air particulate matter. 

Additionally, dilution-based methods 

allow for the measurement of the 

particle size distribution of the 

particulate matter smaller than 2.5 

micrometers. This can be accomplished 

by modifying the hardware of the 

sampling equipment to extend the 

residence time of the sampled 

particulate matter. The extra residence 

time allows the ultrafine particulate 

matter initially formed during vapor 

condensation to grow toward its 

ultimate particle size distribution. 

66052 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

7. What types of sources should use the 

new dilution-based test method? 

The new dilution-based test method 

would be appropriate for most sources. 

Sources with very complex flue gas 

characteristics (e.g., having several 

acidic and alkali gases with semivolatile organic matter) and those 

sources that want to generate a 

speciation profile specific to their 

facility should use the new dilution test 

method. Sources with very low PM2.5

emission concentrations and low SO2

and NOX emission concentrations also 

may wish to use the new dilution 

method. However, the more complex 

operation and increased size of the 

equipment associated with the new 

method may persuade some sources to 

use an alternative method. Sources 

where the flue gas is near ambient 

temperature or where the sampled gas 

can be cooled to near ambient 

temperature could use CTM 40 or its 

equivalent to quantify PM2.5 emissions. 

Sources with less complex flue gas 

characteristics may want to use CTM 40 

combined with EPA Method 202. 

8. What are the main features of the new 

test method? 

The main features of the new test 

method are in the areas of sample 

extraction, particle sizing, sample flow 

rate measurement, dilution air 

conditioning, dilution air flow rate 

measurement, sample mixing with 

dilution air and sample filtration. An 

additional major feature, where 

particulate speciation is desired, is the 

method of extracting an aliquot of the 

diluted sample. Flue gas is extracted 

isokinetically at a flow rate that 

produces particulate matter sizing at 10 

and 2.5 micrometers by the two in-stack 

cyclones. The sampled flue gas and the 

PM2.5 particulate matter is extracted 

from the stack prior to dilution and 

cooling with ambient air that has been 

conditioned by removing excess 

moisture and ambient particulate matter 

with a HEPA filter. The objective of all 

the methods is to achieve complete 

mixing prior to filtration and to 

minimize sample losses on the internal 

surfaces of the hardware. The PM2.5 is 

removed from the diluted sample gas by 

a Teflon filter. The PM2.5 deposited on 

the internal surfaces of the hardware is 

quantitatively recovered with acetone. 

Both the Teflon filter and the PM2.5

recovered from the internal surfaces of 

the sampler are weighed. When 

speciation of the PM2.5 is desired, 

aliquots of the diluted sample gas are 

extracted for collection on filters. The 

ambient air speciation criteria are 

followed with respect to the filter media 

used and analytical finish of the three 

filters. 

9. What is the schedule for finalization 

of the new test method? 

We have posted the dilution-based 

PM2.5 source test method on the TTN 

web as ‘‘Conditional Test Method 39’’

and expect that this method will 

provide the basis for a 40 CFR Part 51, 

Appendix M method to be proposed at 

a later date. Beyond proposing the EPAdeveloped dilution test method, we may 

identify the use of a source test method 

developed by a national voluntary 

consensus standard setting organization. 

Public Law 104–113, also known as the 

National Technology Transfer and 

Advancement Act (NTTAA), requires 

that we use technical standards that are 

developed or adopted by voluntary 

consensus standards bodies as a means 

to carry out policy objectives where 

appropriate. The law also requires us to 

consult with such bodies when it is in 

the public interest to participate with 

them in the development of technical 

standards. Recently, the ASTM Source 

and Ambient Atmospheres Committee 

developed a PM2.5 source test method 

similar to the method we have 

developed. We believe that it is in the 

interest of the public and the Agency to 

participate in the ASTM process of 

developing a PM2.5 source test method. 

While we cannot predict when an 

ASTM standard will be available and 

whether it will be a suitable test method 

for EPA to specify for use in SIPs, we 

expect to make a decision on the final 

test method in the near future. We are 

aware of two manufacturers which have 

commercially available equipment 

meeting the specifications of CTM–39 

and the draft ASTM certification. 

10. How will use of this new method 

affect an areas emissions inventory and 

the emissions inventory for individual 

sources? 

We do not expect that particulate 

matter emissions inventories will be 

significantly affected by the use of this 

new test method. The stationary source 

emissions of PM2.5 are based upon 

existing filterable particulate matter size 

distributions and filterable and 

condensable particulate matter emission 

factors. The emission factor information 

is supported by source test data similar 

to that available from EPA Method 

CTM–40 and Method 202. However, it 

is unclear how the use of the new 

dilution sampling method will affect the 

PM2.5 emission inventory for any 

particular source category. Source 

categories for which emission estimates 

for condensable particulate matter are 

not available or are under estimated 

may find that the inventoried emissions 

are significantly higher. As indicated 

previously, the addition of the 

condensable portion of PM2.5 to 

filterable PM2.5 may increase direct 

PM2.5 emissions by a factor of five or 

more. Source categories for which the 

condensable particulate matter emission 

factor is based on EPA Method 202 test 

data that excludes the nitrogen purge 

may find that their emissions are 

somewhat lower. The significance of 

this lower mass of condensable 

particulate matter depends on the mass 

of filterable and condensable particulate 

matter compared to the mass of 

particulate artifact formed by the 

dissolved SO2 that was not removed 

from the impinger water by the nitrogen 

purge. 

11. How will use of this new method 

affect a State’s implementation program 

more broadly? 

The use of this new dilution method 

(or the use of EPA Method CTM 40 

combined with Method 202) to obtain 

measured source specific emissions of 

PM2.5 will improve the quality of the 

emissions inventory for stationary 

sources and will aid in the development 

of a more reliable attainment strategy. In 

addition, we expect the use of the 

speciation capabilities of this new 

source test method will expand the 

information available to formulate 

attainment demonstration strategies and 

to justify the most effective strategy. For 

example, this new source-specific 

speciation data may allow the State to 

identify additional local control 

measures for consideration. The 

combined information from the ambient 

air speciation network and individual 

source category speciation data will aid 

in developing the most efficient 

attainment strategies. In addition, after 

initial attainment strategies are 

implemented, speciation profiles for the 

most significant sources of direct PM2.5

combined with data from the ambient 

monitoring network may enable States 

to make important mid-course revisions 

to attainment strategies as needed. 

Q. How can potentially inadequate 

source monitoring in certain SIP rules 

be improved? 

1. How Does Improved PM2.5

Monitoring Relate to Title V 

Monitoring? 

Two provisions of EPA’s State and 

federal operating permits program 

regulations require that title V permits 

contain monitoring requirements. The 

‘‘periodic monitoring’’ rules, 40 CFR 

70.6(a)(3)(i)(B) and 71.6(a)(3)(i)(B), 

require that: 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66053 

113The term ‘‘applicable requirements’’ includes, 

but is not limited to: monitoring required under the 

compliance assurance monitoring (CAM) rule, 40 

CFR part 64, where it applies; monitoring required 

under federal rules such as new source performance 

standards (NSPS) in 40 CFR part 60, national 

emissions standards for hazardous air pollutants 

(NESHAP) in 40 CFR part 61, maximum achievable 

control technology (MACT) standards in 40 CFR 

part 63, and the acid rain program rules in 40 CFR 

parts 72 through 75; and monitoring required in 

EPA-approved SIP, TIP and FIP rules. 

‘‘[w]here the applicable requirement does 

not require periodic testing or instrumental 

or noninstrumental monitoring (which may 

consist of recordkeeping designed to serve as 

monitoring), [each title V permit must 

contain] periodic monitoring sufficient to 

yield reliable data from the relevant time 

period that are representative of the source’s 

compliance with the permit, as reported 

pursuant to [§ 70.6(a)(3)(iii) or 

§ 71.6(a)(3)(iii)]. Such monitoring 

requirements shall assure use of terms, test 

methods, units, averaging periods, and other 

statistical conventions consistent with the 

applicable requirement. Recordkeeping 

provisions may be sufficient to meet the 

requirements of [§ 70.6(a)(3)(i)(B) and 

§ 71.6(a)(3)(i)(B)].’’

The ‘‘umbrella monitoring’’ rules, 

§§ 70.6(c)(1) and 71.6(c)(1), require that 

each title V permit contain, 

‘‘[c]onsistent with paragraph (a)(3) of 

this section, compliance certification, 

testing, monitoring, reporting, and 

recordkeeping requirements sufficient to 

assure compliance with the terms and 

conditions of the permit.’’

In a final rule entitled ‘‘Revisions to 

Clarify the Scope of Certain Monitoring 

Requirements for Federal and State 

Operating Permits Programs’’ (69 FR 

3202, January 22, 2004), EPA 

announced a four-step strategy for 

improving existing monitoring where 

necessary through rulemaking or other 

programmatic actions, while reducing 

resource-intensive, case-by-case 

monitoring reviews and so-called ‘‘gapfilling’’ in title V operating permits. 

Improved PM2.5 monitoring, as 

discussed in this preamble and to be 

addressed in future guidance, is part of 

that strategy. 

In the first step, the ‘‘umbrella 

monitoring’’ rule (69 FR 3202, January 

22, 2004), EPA decided not to adopt 

proposed revisions to the regulatory text 

of §§ 70.6(c)(1) and 71.6(c)(1) (67 FR 

58561, September 17, 2002) and instead 

ratified the text of those rules without 

making any changes. The EPA also 

announced that notwithstanding the 

recitation in §§ 70.6(c)(1) and 71.6(c)(1) 

of monitoring as a permit element, EPA 

has determined that these provisions do 

not establish a separate regulatory 

standard or basis for requiring or 

authorizing review and enhancement of 

existing monitoring independent of any 

review and enhancement as may be 

required under §§ 70.6(a)(3) and 

71.6(a)(3). The EPA explained that 

§§ 70.6(c)(1) and 71.6(c)(1) require that 

title V permits contain: (1) Monitoring 

required by ‘‘applicable requirements’’

under the Act, as that term is defined in 

§§ 70.2 and 71.2 113; and (2) such 

monitoring as may be required under 

§§ 70.6(a)(3)(i)(B) and 71.6(a)(3)(i)(B). 

See Appalachian Power Co. v. EPA, 208 

F.3d 1015 (DC Cir. 2000). Thus, for 

monitoring, EPA explained, §§ 70.6(c)(1) 

and 71.6(c)(1) constitute ‘‘umbrella 

provisions’’ that direct permitting 

authorities to include monitoring 

required under existing statutory or 

regulatory authorities in title V permits. 

Based on EPA’s interpretation of the 

Act, the plain language and structure of 

§§ 70.6(c)(1) and 71.6(c)(1) and the 

policy reasons described in the 

preamble to the umbrella monitoring 

rule (see 69 FR at 3204), EPA concluded 

that where the periodic monitoring rules 

do not apply, §§ 70.6(c)(1) and 71.6(c)(1) 

do not require or authorize a new and 

independent type of monitoring in 

permits in order for the permits to 

contain monitoring to assure 

compliance as required by the Act. 

In the ‘‘umbrella monitoring’’ rule, 

EPA also announced plans to address 

monitoring in three related rulemaking 

actions. First, EPA announced plans to 

encourage States to improve potentially 

inadequate monitoring in certain SIP 

rules through this preamble and 

specifically through separate guidance 

to be developed later in connection with 

this rulemaking. The guidance is 

expected to describe methods of 

improving monitoring frequency or 

adopting more appropriate monitoring 

for States to consider in developing 

their PM2.5 SIPs and to illustrate the 

amount of credit that States could 

receive in PM2.5 SIPs for adopting such 

improved monitoring. In particular, the 

guidance is expected to address the 

widespread practice of using visual 

techniques, such as visible emissions 

checks, to show compliance with 

particulate matter limits. As discussed 

in section Q.2 below, we are concerned 

that visible emissions techniques may 

be inadequate to detect PM2.5 emissions 

in some circumstances. To the extent 

that States implement this PM2.5

guidance and revise their SIPs to adopt 

improved monitoring, then further 

actions by the State or EPA to bring an 

area into attainment may be 

unnecessary. 

In addition, EPA announced plans to 

identify and consider improving 

potentially inadequate monitoring in 

certain federal rules or in SIP rules not 

addressed in connection with the PM2.5

implementation guidance or rulemaking 

over a longer time frame. Specifically, 

EPA announced its intent to publish an 

advance notice of proposed rulemaking 

requesting comment on what inadequate 

monitoring may exist in federal 

applicable requirements and seeking 

suggestions as to the ways in which 

inadequate monitoring in such rules 

could be improved. EPA also 

announced its intent to request 

comment on inadequate monitoring that 

may exist in other rules, such as SIP 

rules not addressed in connection with 

this PM2.5 rulemaking and guidance. 

The EPA indicated that comments 

received on the ANPR will inform its 

decision as to what steps to take next, 

such as whether to undertake national 

rulemakings to revise federal rules such 

as NSPS or NESHAP. Finally, EPA 

announced plans to publish a separate 

proposed rule to address what 

monitoring constitutes ‘‘periodic’’

monitoring under §§ 70.6(a)(3)(i)(B) and 

71.6(a)(3)(i)(B) and what types of 

monitoring should be created under 

§§ 70.6(a)(3)(i)(B) and 71.6(a)(3)(i)(B). 

Together with the umbrella monitoring 

rule, these three related rulemaking 

actions comprise EPA’s four-step 

strategy for improving existing 

monitoring where necessary on a 

programmatic basis. 

2. Are Instrumental Techniques More 

Appropriate Than Visual Emissions 

(VE) Techniques for Monitoring 

Compliance With PM Emissions Limits, 

for Some Situations and Applications? 

We have a concern about the reliance 

on VE techniques (which are based on 

observations of visible emissions or 

opacity) for monitoring compliance with 

particulate matter emissions limits, in 

certain situations. For example, in 

situations where a facility has a low 

margin of compliance with its emission 

limit [e.g., the emission limit is 25 

milligrams of PM2.5 per dry standard 

cubic meter (mg/dscm) and actual 

emissions are 22.5 mg/dscm, leaving a 

margin of compliance of 2.5 mg/dscm], 

VE monitoring may not provide the 

level of sensitivity necessary to monitor 

compliance. We also have a concern 

about the infrequency of the monitoring 

sometimes associated with the use of 

these VE monitoring techniques. 

Although visible emissions and the 

opacity of visible emissions are 

indicators of a change in PM emissions 

levels, we believe the use of available 

instrumental monitoring technologies 

that provide a more direct measure of 

the pollutant of concern, PM2.5, 

constitute improved monitoring 

techniques and are the more appropriate 

66054 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

114 ‘‘Impact of Improved Monitoring on PM2.5

Emissions,’’ memorandum from L. Barr and K. 

Schaffner, RTI International, to B. Parker, U.S. 

Environmental Protection Agency. December 2003. 115 Ibid. 

method in many cases. These 

instrumental techniques include bag 

leak detectors (BLD), and particulate 

matter continuous emissions monitoring 

systems (PM CEMS). In this proposal, 

we are encouraging States to adopt 

improved monitoring techniques for 

PM2.5 in their SIPs, and we plan to 

show, via separate guidance, how States 

can improve emissions reductions and 

therefore increase credits in their SIPs if 

they adopt the improved monitoring for 

selected sources. See the discussion 

above in section I.17 for potential ways 

to obtain emissions reductions through 

improved monitoring or controls. Note 

that the improved monitoring 

techniques may also be appropriate for 

sources with PM10 emissions. 

With respect to the frequency of VE 

monitoring, we believe more frequent 

monitoring will reduce the potential for 

excess emissions to occur unnoticed 

and, thus, will minimize the duration of 

excess emissions periods. An example is 

the monitoring of VE from a fabric filter 

control device utilizing weekly visual 

observations. The potential exists for 

excess emissions to occur during the 

entire period between observations, or 

up to seven days. Increasing the 

frequency of observations to a daily 

basis significantly reduces the potential 

duration of any excess emissions period. 

For example, consider an emissions unit 

controlled with a fabric filter that emits 

15 tons per year PM2.5 (filterable), and 

has no visible emissions during normal 

operation. For the baseline condition, 

assume an excess emissions rate of 5 

percent. By increasing the frequency of 

observations from a weekly to a daily 

basis, the exceedences are observed and 

corrective action and repair are taken in 

a more timely manner; the resulting 

emissions reduction ranges from 11 to 

13 tons per year filterable PM2.5, or 37 

to 81 percent reduction of the potential 

excess emissions.114 If the potential 

emissions reduction for filterable PM10

also is considered, the PM reductions 

would include an additional 6.3 to 8.0 

tons per year depending on the 

calculation method used. 

With respect to improved monitoring 

techniques for PM2.5, we believe 

currently available instrumental 

techniques are more capable of 

detecting changes in performance of the 

control device than visual observations 

or COMS, in some applications, such as 

at low emissions levels sometimes 

required for compliance with PM2.5

emissions limits. Furthermore, unlike 

periodic visual observations, these 

instrumental techniques provide 

information on a continuous basis. 

Consequently, we believe use of these 

instrumental techniques can reduce the 

occurrence of excess emissions because 

(1) they are capable of sensing a change 

in performance that might not be sensed 

by a visual technique and (2) when 

excess emissions occur, the duration of 

excess emissions will be reduced as a 

result of the frequency of monitoring. 

An example of an improved monitoring 

technique is the use of a BLD to monitor 

PM2.5 emissions from a fabric filter 

control device in lieu of weekly visual 

observations. Consider a model 

emissions unit emitting 15 tons per year 

PM2.5 (filterable). For the baseline 

condition, assume an excess emissions 

rate of 5 percent. By using a continuous 

instrumental technique, such as a BLD, 

rather than weekly visual observations, 

the emissions from potential excess 

emissions events would be reduced by 

11 to 14 tons per year of filterable PM2.5. 

If the potential emissions reduction for 

filterable PM10 also is considered, the 

PM reductions would be an additional 

6.8 to 8.5 tons per year.115

Use of a PM CEMS is another 

improved monitoring technique. PM 

CEMS technology provides the 

opportunity to quantitatively monitor 

PM emissions levels (concentration or 

emissions rates). This provides the 

source owner/operator with an 

additional level of information that can 

be useful for understanding and 

operating the process and air pollution 

control device. Furthermore, this 

technology will provide the State with 

quantitative information on actual PM 

emissions, which will help improve the 

inventory and achieve compliance with 

the NAAQS for PM2.5. 

To inform our guidance development, 

we are asking for comment, information, 

and relevant data on these monitoring 

issues. Specifically: 

(1) In certain instances or 

applications, are we correct in our belief 

that improved monitoring techniques 

are available and are more appropriate 

to use than VE techniques for 

monitoring compliance with PM2.5

emissions? Based on your experience, in 

which cases do you believe improved 

monitoring techniques are more 

appropriate than VE techniques for 

monitoring compliance with PM2.5 (or 

PM, in general) emissions limits, and 

what monitoring techniques would you 

recommend? Based on your experience, 

are BLD and PM CEMS reliable, costeffective methods that are more 

sensitive then VE techniques for 

monitoring compliance with PM 

emissions? 

(2) Will increasing the frequency of 

VE observations resolve the issue of 

applicability of VE techniques for 

monitoring compliance with PM2.5

emissions? In other words, are there 

situations in which increased VE 

frequency (i.e., daily versus weekly) 

would be expected to have no impact on 

compliance with PM2.5 emission limits? 

If so, please provide relevant data and 

explanation of such situations. 

(3) Do we need to mandate through 

rulemaking a move away from VE 

techniques for monitoring compliance 

with PM2.5 and PM emissions limits, in 

certain situations and applications? If 

so, in what cases? 

(4) Should our effort with regard to 

the use of improved monitoring 

techniques in lieu of VE monitoring be 

focused on applicable requirements 

established/relied upon for compliance 

with the PM2.5 standard, or should we 

more broadly address other applicable 

requirements where VE techniques are 

commonly used (e.g., TSP, PM10)? 

In addition, we also request comment, 

information, and relevant data on any 

other issues relating to the use of VE 

techniques for monitoring compliance 

with particulate matter emission limits. 

3. What constitutes improved 

monitoring? 

Additional Reductions from Existing 

Rules. We request comment on the 

following approach that States may 

choose to implement to reduce 

emissions through the improved 

monitoring of emission controls at 

stationary sources. An improved 

monitoring control measure would 

increase emissions reduction for 

existing rules. These emissions 

reductions would be achieved by 

increasing the monitoring frequency or 

improving the monitoring technique of 

the add-on air pollution control device 

operation and the process operation 

above the level currently required in 

existing rules. The increased frequency 

or improved technique would allow 

owners or operators to achieve greater 

emissions reductions by identifying and 

correcting periods of excess emissions. 

State, local, and Tribal agencies could 

use the improved monitoring control 

measure option to reduce emission 

levels and receive credits. As described 

in the docket, State, local, and Tribal air 

pollution agencies who have source 

owners/operators increase monitoring 

frequency at their facilities could 

achieve emissions reductions up to 13 

percent, and those who improve the 

monitoring technique could achieve 

emissions reductions up to 15 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66055 

116 ‘‘Impact of Improved Monitoring on PM2.5

Emissions,’’ memorandum from L. Barr and K. 

Schaffner, RTI International, to B. Parker, U.S. 

Environmental Protection Agency. December 2003. 

percent.116 Nonattainment areas where 

additional reductions are needed to help 

the area achieve compliance with the 

NAAQS could implement an improved 

monitoring measure. State, local, and 

Tribal air pollution agencies could set a 

size cutoff or other criteria that would 

define which facilities would be subject. 

State, local, and Tribal agencies could 

receive SIP credits because enforceable 

improved monitoring or voluntary 

programs meeting EPA’s voluntary 

policies for SIP credit could achieve 

additional emissions reductions for 

facilities in the area. 

Improved monitoring could come in 

the form of (1) conducting the currently 

required monitoring more frequently 

(i.e., increased monitoring frequency), 

(2) changing the monitoring technique 

to a parameter more closely related to 

PM2.5 and its precursors (i.e., an 

improved monitoring technique), (3) 

changing the technique to monitoring 

PM2.5 and its precursors, or (4) a 

combination of these improvements. 

These types of monitoring 

improvements could be conducted for 

both controlled and uncontrolled 

emission units. The improved 

monitoring control measure would 

require facilities to pay more attention 

to the operation of add-on air pollution 

control devices and the process 

operation. The additional attention will 

reduce excess emission periods and 

increase emissions reductions for 

existing rules. 

For the purposes of discussion today, 

we are focusing on two scenarios. The 

first scenario involves increased 

monitoring frequency for controlled 

emission units. The second scenario 

incorporates improved monitoring 

techniques that include upgrading to a 

bag leak detector (BLD) monitoring 

device and upgrading to a PM 

continuous emissions monitoring 

system (CEMS) for controlled emission 

units. 

As an example of improved 

monitoring, consider a facility that 

currently monitors for visible emissions 

once per day voluntarily increasing its 

monitoring frequency of visible 

emissions to once per hour, or installing 

a BLD system that continuously 

monitors the control device. Under the 

improved monitoring control measure, 

the source owners/operators would be 

more likely to detect the presence of a 

problem and to correct it more quickly. 

Expedient detection and correction of 

problems will result in reduced periods 

of excess emissions and, consequently, 

lower emissions. The increased 

monitoring frequency works to reduce 

the time between equipment failure and 

its discovery by plant personnel. The 

underlying assumption is, of course, 

that faster discovery leads to faster 

correction. 

The improved monitoring technique 

provides more certainty in detecting the 

presence of a problem that may have 

gone unnoticed with the previous 

technique. For example, consider a 

facility that monitors opacity with a 

COMS as a surrogate for particulate 

matter. The facility’s opacity, as 

measured by the COMS, is consistently 

at 10 percent. However, emissions test 

data have shown that, when a new BLD 

monitoring system is applied, the 

facility can be exceeding its PM limit at 

an opacity less than 10 percent. In this 

example, application of an improved 

monitoring technique provides a more 

direct and more sensitive measurement 

of the pollutant of concern (PM vs. 

opacity) and allows the facility to better 

track performance of the control device 

and its emissions levels. 

In addition to the improved 

monitoring measures, there are other 

ways to achieve significant PM2.5

emissions reductions, including 

requiring add-on air pollution controls 

for uncontrolled emissions units that are 

capable of being controlled. In this type 

of approach, State, local, and Tribal 

agencies could require large 

uncontrolled emission units to be 

controlled with new air pollution 

control devices. Fabric filters would 

control filterable PM2.5 emissions while 

other control devices such as scrubbers 

would control both filterable and 

condensable PM2.5 emissions. In one 

example for a large uncontrolled unit, 

PM2.5 emissions (filterable) may be 

reduced by 131 tons per year when a 

fabric filter achieving 99 percent control 

efficiency is installed. The cost 

effectiveness to install this new control 

device would be determined based on 

the annualized cost of operating the 

fabric filter and the emission reduction 

of PM2.5 achieved by the device. If cocontrolled pollutants are included in the 

analysis, e.g., PM10 filterable emissions, 

then the emissions reductions achieved 

by the new fabric filter would include 

an additional 260 tons per year. The 

total emission reduction for this source 

would be 390 tons per year; the costeffectiveness values with collateral 

benefits included will be even lower. 

The fabric filter in this example would 

be monitored with a BLD system on a 

continuous basis (at least four times per 

hour). 

What are the Assumptions Used to 

Determine the Reductions? We 

estimated the emissions reductions that 

can be achieved by implementation of 

the improved monitoring measures. 

Consistent with the baseline excess 

emissions rate established in the 

compliance assurance monitoring 

(CAM) rule (40 CFR part 64) analysis, 

we assumed an initial excess emissions 

rate of five percent each year. Under the 

NSPS and other federal rules, an excess 

emissions rate greater than five percent 

is a trigger for increased reporting, and 

facilities generally ensure that they do 

not exceed this threshold level of excess 

emissions to avoid increased reporting. 

Of course, there may be exceptions to 

this assumption, where facilities have 

excess emissions rates greater than 5 

percent. The percentage of excess 

emissions represents a period of 

noncompliance when emissions are 

likely to be above the allowable 

emissions rates. Increased frequency 

monitoring will help owners or 

operators of facilities to maintain the 

effectiveness of emissions controls by 

identifying excursions early and 

repairing or adjusting the control device 

immediately. The length of time that an 

emissions unit is experiencing excess 

emissions is directly related to the level 

of excess emissions from the source. 

Reducing the amount of time the 

emission unit operates in this mode will 

reduce its actual emissions to the 

atmosphere. 

In this study, we made two 

assumptions regarding the control 

efficiency of the add-on air pollution 

control device during excess emissions 

periods. In one method, we assumed the 

control device fails catastrophically; 

that is, its control efficiency is zero 

percent. We realize that some add-on air 

pollution control devices fail 

catastrophically during malfunctions, 

while others operate at some efficiency 

less than optimal but greater than zero. 

For the purposes of the study and for 

simplification, we made the assumption 

of zero percent control in this method. 

The control efficiency could also be 

estimated at some value between zero 

and the design control efficiency. In an 

alternative method, the control 

efficiency during excess emissions 

periods was estimated to be 80 percent 

of the design efficiency. 

The potential emissions reductions 

examined here mostly address direct, 

filterable PM2.5 and also address 

condensable PM2.5 only where the 

control device was likely to achieve 

reductions for condensable emissions. 

Additional emissions reductions may 

also be achieved for co-pollutants 

emitted from the emissions units. We 

66056 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

117 In the six metropolitan statistical areas 

reviewed for this study, 100 percent rule 

effectiveness and 100 percent rule penetration was 

shown in the 1999 NEI version 3 for all facilities. 

believe that control for these other 

pollutants, e.g., PM10, TSP, and HAP, 

may also be improved by the monitoring 

measures. However, these 

improvements are not accounted for 

here. Improved monitoring, i.e., 

increased frequency for existing 

monitoring instruments or improved 

monitoring techniques, could also be 

applied to the precursors of PM2.5 to 

achieve additional potential reductions. 

The improved monitoring control 

measure would increase emissions 

reductions for existing rules. The 

emissions reduction achieved would not 

necessarily be reflected in future 

emissions inventory data but rather 

would be reflected in lower ambient air 

monitoring concentrations.117 In 

assessing emissions from a particular 

facility, we generally assume 100 

percent compliance for 100 percent of 

the operating time. However, excess 

emissions occur as a result of less than 

full compliance with standards, rules, 

and regulations. For example, a facility 

with an air pollution control device 

designed to achieve a 95 percent control 

efficiency will achieve the design 

efficiency if maintained and operated 

properly. Currently, the owner or 

operator of such a facility would 

conduct a prescribed monitoring 

technique (control device parameter, 

process parameter, or pollutant 

concentration) at a prescribed 

frequency. Operation outside of limits 

set for the monitored parameter(s) is an 

excursion for CAM rule purposes (and 

may be an exceedance for other rules) 

and may be an indication of excess 

emissions. 

In accordance with CAM rule 

requirements, we assumed that facilities 

are currently required to monitor add-on 

control devices of applicable emission 

units at least once per day. With this 

approach, we ensure that the emissions 

reductions achieved by the CAM rule 

are not double-counted. We determined 

previously during the CAM rule 

development that the detection of a 

problem with an add-on air pollution 

control device that is monitored once 

per day could take up to 12 hours to 

detect. After the problem has been 

detected, it may take an additional 24 

hours to conduct the repair, during 

which time the process may be emitting 

above the emissions limit. The entire 

excess emissions period could last up to 

36 hours. By increasing the frequency of 

monitoring and conducting diligent 

repair, the time required to detect a 

problem will decrease, and the time a 

unit operates in excess emission mode 

or malfunction will decrease. 

Examples of the Emissions 

Reductions that Can Be Achieved. In a 

six-metropolitan statistical area (MSA) 

mini-study, we reviewed the PM2.5

emissions data (filterable and some 

condensable) from the 1999 NEI version 

3 for all emission points at stationary 

sources located in the MSAs. We 

applied the improved monitoring 

control measures to only those emission 

points in the MSA that are controlled 

with fabric filters, electrostatic 

precipitators, and scrubbers. This subset 

included a total of 689 emission points 

at 128 facilities. 

Based on review of emission points 

with add-on air pollution control 

devices, we found that PM2.5 emissions 

(filterable/some condensable) can be 

reduced from 0.25 percent up to 13 

percent following the application of a 

requirement to conduct more frequent 

monitoring. Potential PM2.5 emissions 

reductions ranged from 89 tons per year 

to 4,600 tons per year with increased 

monitoring frequency. We also found 

that PM2.5 emissions (filterable/some 

condensable) can be reduced from 2.5 

percent to 15 percent by requiring an 

improved monitoring technique such as 

a PM CEMS (and a corollary increased 

frequency). The potential PM2.5

emissions reductions ranged from 810 to 

5,300 tons per year. We analyzed the 

emissions reductions achievable by 

reducing the excess emission rate from 

the nominal 5 percent excess emissions 

to an excess emissions rate of 2.5 

percent (half of the nominal excess 

emission rate), 0.46 percent (represents 

one week of excess emissions each year, 

40 hours out of 8760), and 0 percent (no 

excess emissions). As mentioned 

previously, there may be some facilities 

with an excess emissions rate even 

greater than 5 percent; in these 

instances, the potential emissions 

reductions due to improved monitoring 

may be even greater. The emissions 

reduction calculation for application of 

an improved monitoring control 

measure included a certainty factor 

related to detecting excess emission 

periods and assurance of emissions 

levels. The certainty factor for PM 

CEMS was 1.0, the factor for BLD was 

0.95, and the factor for parametric 

monitoring was 0.90. The certainty 

factor for visual emissions and COMS 

when used to monitor PM was also 0.90. 

In another example of an improved 

monitoring technique, a BLD monitoring 

system was applied only to the subset 

of emission units in the six MSA area 

that are controlled with fabric filters. A 

total of 102 facilities were affected by 

this option. In this scenario, the 

emission reduction (filterable PM2.5

only) was determined to be 0.78 to 12 

percent, or 280 to 4,100 tons per year. 

Costs to conduct monitoring at an 

increased frequency included the cost to 

develop the more frequent monitoring 

approach and the incremental annual 

costs for recordkeeping, reporting, and 

certification related to the improved 

monitoring. Costs to implement an 

improved monitoring technique 

included the total annual cost for the 

new monitoring equipment, including 

the recordkeeping and reporting costs 

associated with the new monitoring. We 

anticipate that changes to monitoring 

would be incorporated into individual 

facility permits at permit renewal, to 

help minimize costs to air agencies and 

source owners/operators; costs related 

to incorporating the improved 

monitoring into permits on a quicker 

basis than regular permit renewal have 

not been assessed. The cost algorithms 

for the six-MSA study are delineated in 

the ‘‘Improved Monitoring’’

memorandum. The cost-effectiveness 

values include the emissions reductions 

for PM2.5 filterable and some 

condensable. When reduction of copollutants are included in the costeffectiveness analysis, the costeffectiveness values are even lower. 

States can compare the cost 

effectiveness for improved monitoring 

to the cost effectiveness of other PM2.5

control measures when selecting the 

mix of measures for their 

implementation plans. 

The methods for estimating emission 

reductions and cost effectiveness ranges 

for the six-city study discussed in this 

section are based on the best technical 

information we had available. We 

recognize that commenters may have 

suggestions for ways to improve these 

estimates. Thus, to inform our guidance 

development, we solicit your comments 

on a number of issues. We solicit your 

comments on these control measures for 

increased frequency of monitoring and 

improved monitoring technique. We 

also request your comments on the 

feasibility of co-pollutant control due to 

improved monitoring measures. We also 

solicit submission of developed 

examples of improved monitoring, 

including a description of the measure, 

monitoring data, etc., if available. 

Finally, we encourage submission of 

methodologies—complete with 

equations and explanations—for 

estimating emissions reductions due to 

improved monitoring other than those 

referenced here. 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66057 

118See 40 CFR 49.4(a). In addition, EPA 

determined it was not appropriate to treat tribes 

similarly to states with respect to provisions of the 

CAA requiring as a condition of program approval 

the demonstration of criminal enforcement 

authority or providing for the delegation of such 

criminal enforcement authority. See 40 CFR 49.4(g). 

To the extent a tribe is precluded from asserting 

criminal enforcement authority, the federal 

government will exercise primary criminal 

enforcement responsibility. See 40 CFR 49.8. In 

such circumstances, tribes seeking approval for 

CAA programs provide potential investigative leads 

to an appropriate federal enforcement agency. 

119See 40 CFR 70.5(c)(3)(i), 70.5(b), and 

70.7(a)(1)(i); 40 CFR 71.5(c)(3)(i), 71.5(b), and 

71.7(a)(1)(i). 

R. What guidance should be provided 

that is specific to Tribes? 

This section summarizes guidance for 

Tribes offered in various parts of this 

proposal. The 1998 Tribal Authority 

Rule (TAR) (40 CFR part 49), which 

implements section 301(d) of the CAA, 

gives Tribes the option of developing 

tribal implementation plans (TIPs). 

Specifically, the TAR provides for the 

Tribes to be treated in the same manner 

as a State in implementing sections of 

the CAA. However, Tribes are not 

required to develop implementation 

plans. The EPA determined in the TAR 

that it was inappropriate to treat Tribes 

in a manner similar to a State with 

regard to specific plan submittal and 

implementation deadlines for NAAQSrelated requirements, including, but not 

limited to, such deadlines in CAA 

sections 110(a)(1), 172(a)(2), 182, 187, 

and 191.118

If a Tribe elects to do a TIP, we will 

work with the Tribe to develop an 

appropriate schedule which meets the 

needs of the Tribe, and which does not 

interfere with the attainment of the 

NAAQS in other jurisdictions. The 

Tribe developing a TIP can work with 

the EPA Regional Office on the 

appropriateness of addressing RFP and 

other substantive SIP requirements that 

may or may not be appropriate for the 

Tribe’s situation. 

The TAR indicates that EPA is 

ultimately responsible for implementing 

CAA programs in Indian country, as 

necessary and appropriate, if Tribes 

choose not to implement those 

provisions. For example, an unhealthy 

air quality situation in Indian country 

may require EPA to develop a FIP to 

reduce emissions from sources on the 

reservation. In such a situation, EPA, in 

consultation with the Tribe and in 

consideration of their needs, would 

work to ensure that the NAAQS are met 

as expeditiously as practicable. 

Likewise, if we determine that sources 

in Indian country could interfere with a 

larger nonattainment area meeting the 

NAAQS by its attainment date, we 

would develop a FIP for those sources 

in consultation with the Tribe, as 

necessary or appropriate. 

The TAR also provides flexibility for 

the Tribe in the preparation of a TIP to 

address the NAAQS. If a Tribe elects to 

develop a TIP, the TAR offers flexibility 

to Tribes to identify and implement—on 

a Tribe-by-Tribe, case-by-case basis—

only those CAA programs or program 

elements needed to address their 

specific air quality problems. In the 

proposed Tribal rule, we described this 

flexible implementation approach as a 

‘‘modular approach.’’ Each Tribe may 

evaluate the particular activities, 

including potential sources of air 

pollution within the exterior boundaries 

of its reservation (or within nonreservation areas for which it has 

demonstrated jurisdiction), which cause 

or contribute to its air pollution 

problem. A Tribe may adopt measures 

for controlling those sources of PM2.5- 

related emissions, as long as the 

elements of the TIP are ‘‘reasonably 

severable’’ from the package of elements 

that can be included in a whole TIP. A 

TIP must include regulations designed 

to solve specific air quality problems for 

which the Tribe is seeking EPA 

approval, as well as a demonstration 

that the Tribal air agency has the 

authority from the Tribal government to 

develop and run their program, the 

capability to enforce their rules, and the 

resources to implement the program 

they adopt. In addition, the Tribe must 

receive an ‘‘eligibility determination’’

from EPA to be treated in the same 

manner as a State and to receive 

authorization from EPA to run a CAA 

program. 

EPA would review and approve, 

where appropriate, these partial TIPs as 

one step of an overall air quality plan to 

attain the NAAQS. A Tribe may step in 

later to add other elements to the plan, 

or EPA may step in to fill gaps in the 

air quality plan as necessary or 

appropriate. In approving a TIP, we 

would evaluate whether the plan 

interferes with the overall air quality 

plan for an area when Tribal lands are 

part of a multi-jurisdictional area. 

Because many of the nonattainment 

areas will include multiple 

jurisdictions, and in some cases both 

Tribal and State jurisdictions, it is 

important for the Tribes and the States 

to work together to coordinate their 

planning efforts. States need to 

incorporate Tribal emissions in their 

base emission inventories if Indian 

country is part of an attainment or 

nonattainment area. Tribes and States 

need to coordinate their planning 

activities as appropriate to ensure that 

neither is adversely affecting attainment 

of the NAAQS in the area as a whole. 

S. Are there any additional 

requirements related to enforcement 

and compliance? 

In general, for a SIP regulation to be 

enforceable, it must clearly spell out 

which sources or source types are 

subject to its requirements and what its 

requirements (e.g., emission limits, 

work practices, etc.) are. The regulation 

also needs to specify the time frames 

within which these requirements must 

be met, and must definitively state 

recordkeeping and monitoring 

requirements appropriate to the type of 

sources being regulated. The 

recordkeeping and monitoring 

requirements must be sufficient to allow 

determinations on a continuing basis 

whether sources are complying. An 

enforceable regulation must also contain 

test procedures in order to determine 

whether sources are in compliance. 

Under the Title V regulations, major 

sources have an obligation to include in 

their Title V permit applications all 

emissions for which the source is major 

and all emissions of regulated air 

pollutants. The definition of regulated 

air pollutant in 40 CFR 70.2 includes 

any pollutant for which a NAAQS has 

been promulgated, which would 

include both PM10 and PM2.5. To date, 

some permitted entities have been using 

PM10 emissions as a surrogate for PM2.5

emissions. Upon promulgation of this 

rule, EPA will no longer accept the use 

of PM10 as a surrogate for PM2.5. Thus, 

sources will be required to include their 

PM2.5 emissions in their Title V permit 

applications, in any corrections or 

supplements to these applications, and 

in applications submitted upon 

modification and renewal.119 Sources 

must continue to identify their PM10

emissions in their applications as 

described above because the original 

PM10 NAAQS remains in effect. 

T. What requirements should apply to 

emergency episodes? 

Currently, subpart H of 40 CFR part 

51 specifies requirements for SIPs to 

address emergency air pollution 

episodes and for preventing air 

pollutant levels from reaching levels 

determined to cause significant harm to 

human health. We anticipate proposing 

a separate rulemaking in the future to 

update portions of that rule to address 

the 8-hour ozone and PM2.5 NAAQS. 

66058 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

120The PM2.5 monitoring regulations are located 

at 40 CFR Part 58. 

U. What ambient monitoring 

requirements will apply under the PM2.5

NAAQS? 

States are required to monitor PM2.5

mass concentrations using Federal 

Reference Method devices to determine 

compliance with the NAAQS.120

Currently, there are more than 1200 

FRM monitors located across the 

country. States will need to maintain 

monitors in designated nonattainment 

areas in order to track progress toward 

attainment and ultimately determine 

whether the area has attained the PM2.5

standards. 

In addition to the FRM network, EPA 

and the States have also deployed more 

than 250 speciation monitoring sites 

around the country to sample for 

chemical composition of PM2.5. The data 

provided from these speciation monitors 

are invaluable in identifying 

contributing source categories and 

developing control strategies to reach 

attainment. Source apportionment and 

other receptor modeling techniques rely 

on the detailed data on species, ions, 

and other compounds obtained from 

chemical analysis. Analyses of rural 

versus urban sites to identify which 

PM2.5 components comprise the ‘‘urban 

excess’’ (urban minus rural levels) 

portion of PM2.5 mass also rely on data 

from speciation monitors. The EPA 

encourages states to expand their data 

analysis efforts using the wealth of 

information provided from the 

speciation monitoring network. 

IV. Statutory and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

Under Executive Order 12866, [58 FR 

51735 (October 4, 1993)] the Agency 

must determine whether the regulatory 

action is ‘‘significant’’ and therefore 

subject to OMB review and the 

requirements of the Executive Order. 

The Order defines ‘‘significant 

regulatory action’’ as one that is likely 

to result in a rule that may: 

(1) Have an annual effect on the 

economy of $100 million or more or 

adversely affect in a material way the 

economy, a sector of the economy, 

productivity, competition, jobs, the 

environment, public health or safety, or 

State, local, or tribal governments or 

communities; 

(2) Create a serious inconsistency or 

otherwise interfere with an action taken 

or planned by another agency; 

(3) Materially alter the budgetary 

impact of entitlements, grants, user fees, 

or loan programs or the rights and 

obligations of recipients thereof; or 

(4) Raise novel legal or policy issues 

arising out of legal mandates, the 

President’s priorities, or the principles 

set forth in the Executive Order. 

Under the terms of Executive Order 

12866, it has been determined that this 

rule is a ‘‘significant regulatory action.’’

As such, this action was submitted to 

OMB for EO 12866 review. Changes 

made in response to OMB suggestions or 

recommendations will be documented 

in the public record. 

B. Paperwork Reduction Act 

The information collection 

requirements in this rule will be 

submitted for approval to OMB under 

the Paperwork Reduction Act, 44 U.S.C. 

3501 et seq. The information collection 

requirements are not enforceable until 

OMB approves them other than to the 

extent required by statute. 

This rule provides the framework for 

the States to develop SIPs to achieve a 

new or revised NAAQS. This framework 

reflects the requirements prescribed in 

CAA sections 110 and part D, subpart 1 

of title I. In that sense, the present final 

rule does not establish any new 

information collection burden on States. 

Had this rule not been developed, States 

would still have the legal obligation 

under law to submit nonattainment area 

SIPs under part D of title I of the CAA 

within specified periods after their 

nonattainment designation for the PM2.5

standards, and the SIPs would have to 

meet the requirements of part D. 

A SIP contains rules and other 

requirements designed to achieve the 

NAAQS by the deadlines established 

under the CAA, and also contains a 

demonstration that the State’s 

requirements will in fact result in 

attainment. The SIP must meet the CAA 

requirements in subpart 1 to adopt 

RACM, RACT, and provide for RFP 

toward attainment for the period prior 

to the area’s attainment date. After a 

State submits a SIP, the CAA requires 

EPA to approve or disapprove the SIP. 

If EPA approves the SIP, the rules in the 

SIP become federally enforceable. If 

EPA disapproves the SIP (or if EPA 

finds that a State fails to submit a SIP), 

the CAA requires EPA to impose 

sanctions (2:1 offsets for major new or 

modified sources and restrictions on 

Federal highway funding) within 

specified timeframes; additionally, EPA 

must prepare and publish a SIP within 

2 years after a disapproval or finding of 

failure to submit. The SIP must be 

publicly available. States must maintain 

confidentiality of confidential business 

information, however, if used to support 

SIP analyses. The SIP is a one-time 

submission, although the CAA requires 

States to revise their SIPs if EPA 

requests a revision upon a finding that 

the SIP is inadequate to attain or 

maintain the NAAQS. The State may 

revise its SIP voluntarily as needed, but 

in doing so must demonstrate that any 

revision will not interfere with 

attainment or RFP or any other 

applicable requirement under the CAA 

(see section 110(l)). 

This rule does not establish 

requirements that directly affect the 

general public and the public and 

private sectors, but, rather, interprets 

the statutory requirements that apply to 

States in preparing their SIPs. The SIPs 

themselves will likely establish 

requirements that directly affect the 

general public, and the public and 

private sectors. 

The EPA has not yet projected cost 

and hour burden for the statutory SIP 

development obligation but has started 

that effort and will shortly prepare an 

Information Collection Request (ICR) 

request. However, EPA did estimate 

administrative costs at the time of 

promulgation of the PM2.5 standards in 

1997. See Chapter 10 of U.S. EPA 1997, 

Regulatory Impact Analyses for the 

Particulate Matter and Ozone National 

Ambient Air Quality Standards, 

Innovative Strategies and Economics 

Group, Office of Air Quality Planning 

and Standards, Research Triangle Park, 

N.C., July 16, 1997. Assessments of 

some of the administrative cost 

categories identified as a part of the SIP 

for the PM2.5 standards have already 

been conducted as a result of other 

provisions of the CAA and associated 

ICRs (e.g., emission inventory 

preparation, air quality monitoring 

program, conformity assessments, NSR, 

I/M program). 

The burden estimates in the ICR for 

this rule are incremental to what is 

required under other provisions of the 

CAA. Burden means the total time, 

effort, or financial resources expended 

by persons to generate, maintain, retain, 

or disclose or provide information to or 

for a Federal agency. This includes the 

time needed to review instructions; 

develop, acquire, install, and utilize 

technology and systems for the purposes 

of collecting, validating, and verifying 

information, processing and 

maintaining information, and disclosing 

and providing information; adjust the 

existing ways to comply with any 

previously applicable instructions and 

requirements; train personnel to be able 

to respond to a collection of 

information; search data sources; 

complete and review the collection of 

information; and transmit or otherwise 

disclose the information. 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66059 

An agency may not conduct or 

sponsor, and a person is not required to 

respond to a collection of information 

unless it displays a currently valid OMB 

control number. The OMB control 

numbers for EPA’s regulations in 40 

CFR are listed in 40 CFR part 9. When 

this ICR is approved by OMB, the 

Agency will publish a technical 

amendment to 40 CFR part 9 in the 

Federal Register to display the OMB 

control number for the approved 

information collection requirements 

contained in this final rule. However, 

the failure to have an approved ICR for 

this rule does not affect the statutory 

obligation for the States to submit SIPs 

as required under part D of the CAA. 

The information collection 

requirements associated with NSR 

permitting for ozone are covered by 

EPA’s request to renew the approval of 

the ICR for the NSR program, ICR 

1230.17, which was approved by OMB 

on January 25, 2005. The information 

collection requirements associated with 

NSR permitting were previously 

covered by ICR 1230.10 and 1230.11. 

The OMB previously approved the 

information collection requirements 

contained in the existing NSR 

regulations at 40 CFR parts 51 and 52 

under the provisions of the Paperwork 

Reduction Act, and assigned OMB 

control number 2060–0003. A copy of 

the approved ICR may be obtained from 

Susan Auby, Collection Strategies 

Division; U.S. Environmental Protection 

Agency (2822T); 1200 Pennsylvania 

Ave., NW., Washington, DC 20460 or by 

calling (202) 566–1672. 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act 

generally requires an Agency to prepare 

a regulatory flexibility analysis of any 

rule subject to notice and comment 

rulemaking requirements under the 

Administrative Procedures Act or any 

other statute unless the Agency certifies 

the rule will not have a significant 

economic impact on a substantial 

number of small entities. Small entities 

include small businesses, small 

organizations, and small governmental 

jurisdictions. 

For purposes of assessing the impacts 

of today’s proposed rule on small 

entities, small entity is defined as: (1) A 

small business that is a small industrial 

entity as defined in the U.S. Small 

Business Administration (SBA) size 

standards. (See 13 CFR part 121); (2) a 

governmental jurisdiction that is a 

government of a city, county, town, 

school district or special district with a 

population of less than 50,000; and (3) 

a small organization that is any not-forprofit enterprise which is independently 

owned and operated and is not 

dominant in its field. 

After considering the economic 

impacts of today’s proposed rule on 

small entities, I certify that this action 

will not have a significant economic 

impact on a substantial number of small 

entities. The proposed rule governing 

SIPs will not directly impose any 

requirements on small entities. Rather, 

this rule interprets the obligations 

established in the CAA for States to 

submit implementation plans in order to 

attain the PM2.5 NAAQS. 

Additionally, with respect to NSR, 

this proposed rule does not itself create 

the obligation to obtain an NSR permit 

for new major stationary sources and 

modifications resulting in emissions of 

PM2.5 and its precursors. Rather, the 

preexisting rules establish this 

obligation, and this proposed rule 

clarifies how that obligation will be 

implemented. 

We believe that the existing 

Regulatory Flexibility Screening 

Analysis (RFASA) further supports the 

conclusion that the NSR proposal will 

not have a significant economic impact 

on a substantial number of small 

entities. The RFASA, developed as part 

of a 1994 draft Regulatory Impact 

Analysis (RIA) and incorporated into 

the September 1995 ICR renewal 

analysis, showed that the changes to the 

NSR program due to the 1990 CAA 

Amendments would not have an 

adverse impact on small entities. This 

analysis encompassed the entire 

universe of applicable major sources 

that were likely to also be small 

businesses (approximately 50 ‘‘small 

business’’ major sources). Because the 

administrative burden of the NSR 

program is the primary source of the 

NSR program’s regulatory costs, the 

analysis estimated a negligible ‘‘cost to 

sales’’ (regulatory cost divided by the 

business category mean revenue) ratio 

for this source group. Currently, there is 

no economic basis for a different 

conclusion. We do not believe the 

number of ‘‘small business’’ major 

sources will increase appreciably 

because all sources who are major for 

PM2.5 or one of its precursors (SO2, NOX, 

or VOC) will already be major for PM10

or such precursor. We continue to be 

interested in the potential impacts of the 

proposed rule on small entities and 

welcome comments on issues related to 

such impacts. 

D. Unfunded Mandates Reform Act 

Title II of the Unfunded Mandates 

Reform Act of 1995 (UMRA), Public 

Law 104–4, establishes requirements for 

Federal agencies to assess the effects of 

their regulatory actions on State, local, 

and Tribal governments and the private 

sector. Under section 202 of the UMRA, 

EPA generally must prepare a written 

statement, including a cost-benefit 

analysis, for proposed and final rules 

with ‘‘Federal mandates’’ that may 

result in expenditures to State, local, 

and tribal governments, in the aggregate, 

or to the private sector, of $100 million 

or more in any 1 year. Before 

promulgating an EPA rule for which a 

written statement is needed, section 205 

of the UMRA generally requires EPA to 

identify and consider a reasonable 

number of regulatory alternatives and 

adopt the least costly, most costeffective or least burdensome alternative 

that achieves the objectives of the rule. 

The provisions of section 205 do not 

apply when they are inconsistent with 

applicable law. Moreover, section 205 

allows EPA to adopt an alternative other 

than the least costly, most cost-effective 

or least burdensome alternative if the 

Administrator publishes with the final 

rule an explanation why that alternative 

was not adopted. Before EPA establishes 

any regulatory requirements that may 

significantly or uniquely affect small 

governments, including Tribal 

governments, it must have developed 

under section 203 of the UMRA a small 

government agency plan. The plan must 

provide for notifying potentially 

affected small governments, enabling 

officials of affected small governments 

to have meaningful and timely input in 

the development of EPA regulatory 

proposals with significant Federal 

intergovernmental mandates, and 

informing, educating, and advising 

small governments on compliance with 

the regulatory requirements. 

The EPA has determined that this rule 

does not contain a Federal mandate that 

may result in expenditures of $100 

million or more for State, local, and 

Tribal governments, in the aggregate, or 

the private sector in any 1 year. The 

estimated administrative burden hour 

and costs associated with implementing 

the PM2.5 NAAQS were developed upon 

promulgation of the standard and 

presented in Chapter 10 of U.S. EPA 

1997, Regulatory Impact Analyses for 

the Particulate Matter and Ozone 

National Ambient Air Quality 

Standards, Innovative Strategies and 

Economics Group, Office of Air Quality 

Planning and Standards, Research 

Triangle Park, N.C., July 16, 1997. The 

estimated costs presented there for 

States in 1990 dollars totaled $0.9 

million. The corresponding estimate in 

1997 dollars is $1.1 million. Thus, 

today’s rule is not subject to the 

requirements of section 202 and 205 of 

the UMRA. 

66060 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

121See 62 FR 38652–38760, National Ambient Air 

Quality Standards for Particulate Matter, Final Rule; 

also 40 CFR Part 50. 

The CAA imposes the obligation for 

States to submit SIPs to implement the 

PM2.5 NAAQS. In this rule, EPA is 

merely providing an interpretation of 

those requirements. However, even if 

this rule did establish an independent 

requirement for States to submit SIPs, it 

is questionable whether a requirement 

to submit a SIP revision would 

constitute a Federal mandate in any 

case. The obligation for a State to submit 

a SIP that arises out of section 110 and 

section 172 (part D) of the CAA is not 

legally enforceable by a court of law, 

and at most is a condition for continued 

receipt of highway funds. Therefore, it 

is possible to view an action requiring 

such a submittal as not creating any 

enforceable duty within the meaning of 

section 421(5)(9a)(I) of UMRA (2 U.S.C. 

658(a)(I)). Even if it did, the duty could 

be viewed as falling within the 

exception for a condition of Federal 

assistance under section 421(5)(a)(i)(I) of 

UMRA (2 U.S.C. 658(5)(a)(i)(I)). 

In the proposal, EPA has determined 

that this proposed rule contains no 

regulatory requirements that may 

significantly or uniquely affect small 

governments, including Tribal 

governments. Nonetheless, EPA carried 

out consultations with governmental 

entities affected by this rule. 

E. Executive Order 13132: Federalism 

Executive Order 13132, entitled 

‘‘Federalism’’ (64 FR 43255, August 10, 

1999), requires EPA to develop an 

accountable process to ensure 

‘‘meaningful and timely input by State 

and local officials in the development of 

regulatory policies that have federalism 

implications.’’ ‘‘Policies that have 

federalism implications’’ is defined in 

the Executive Order to include 

regulations that have ‘‘substantial direct 

effects on the States, on the relationship 

between the national government and 

the States, or on the distribution of 

power and responsibilities among the 

various levels of government.’’

This proposed rule does not have 

federalism implications. It will not have 

substantial direct effects on the States, 

on the relationship between the national 

government and the States, or on the 

distribution of power and 

responsibilities among the various 

levels of government, as specified in 

Executive Order 13132. As described in 

section D, above (on UMRA), EPA 

previously determined the costs to 

States to implement the PM2.5 NAAQS 

to be approximately $0.9 million in 

1990 dollars. The corresponding 

estimate in 1997 dollars is $1.1 million. 

While this proposed rule considers 

options not addressed at the time the 

NAAQS were promulgated, the costs for 

implementation under these options 

would rise only marginally. This rule 

clarifies the statutory obligations of 

States in implementing the PM2.5

NAAQS. Finally, the CAA establishes 

the scheme whereby States take the lead 

in developing plans to meet the 

NAAQS. This proposed rule would not 

modify the relationship of the States 

and EPA for purposes of developing 

programs to implement the NAAQS. 

Thus, Executive Order 13132 does not 

apply to this proposed rule. 

Although section 6 of Executive Order 

13132 does not apply to this rule, EPA 

actively engaged the States in the 

development of this proposed rule. The 

EPA held a number of calls with 

representatives of State and local air 

pollution control agencies. 

In the spirit of Executive Order 13132, 

and consistent with EPA policy to 

promote communications between EPA 

and State and local governments, EPA 

specifically solicits comment on this 

proposed rule from State and local 

officials. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

Executive Order 13175, entitled 

‘‘Consultation and Coordination with 

Indian Tribal Governments’’ (65 FR 

67249, November 9, 2000), requires EPA 

to develop an accountable process to 

ensure ‘‘meaningful and timely input by 

Tribal officials in the development of 

regulatory policies that have Tribal 

implications.’’ This proposed rule does 

not have ‘‘Tribal implications’’ as 

defined in Executive Order 13175. This 

rule concerns the requirements for state 

and tribal implementation plans for 

attaining the PM2.5 air quality standards. 

The CAA provides for States to develop 

plans to regulate emissions of air 

pollutants within their jurisdictions. 

The Tribal Air Rule (TAR) under the 

CAA gives Tribes the opportunity to 

develop and implement CAA programs 

such as programs to attain and maintain 

the PM2.5 NAAQS, but it leaves to the 

discretion of the Tribe the decision of 

whether to develop these programs and 

which programs, or appropriate 

elements of a program, they will adopt. 

This proposed rule does not have 

Tribal implications as defined by 

Executive Order 13175. It does not have 

a substantial direct effect on one or 

more Indian Tribes, since no Tribe has 

implemented a CAA program to attain 

the PM2.5 NAAQS at this time. EPA 

notes that even if a Tribe were 

implementing such a plan at this time, 

while the rule might have Tribal 

implications with respect to that Tribe, 

it would not impose substantial direct 

costs upon it, nor would it preempt 

Tribal law. 

Furthermore, this rule does not affect 

the relationship or distribution of power 

and responsibilities between the Federal 

government and Indian Tribes. The 

CAA and the TAR establish the 

relationship of the Federal government 

and Tribes in developing plans to attain 

the NAAQS, and this rule does nothing 

to modify that relationship. As this rule 

does not have Tribal implications, 

Executive Order 13175 does not apply. 

Although Executive Order 13175 does 

not apply to this rule, EPA did reach out 

to Tribal leaders and environmental 

staff regarding this proposal. The EPA 

supports a national ‘‘Tribal Designations 

and Implementation Work Group’’

which provides an open forum for all 

Tribes to voice concerns to EPA about 

the designations and implementation 

process for the NAAQS, including the 

PM2.5 NAAQS. In conference calls EPA 

briefed Work Group participants and 

Tribal environmental professionals gave 

input as the rule was under 

development. Furthermore, EPA is 

sending individualized letters to all 

federally recognized Tribes about this 

proposal to give Tribal leaders the 

opportunity for consultation. EPA 

specifically solicits additional comment 

on this proposed rule from tribal 

officials. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

Executive Order 13045: ‘‘Protection of 

Children From Environmental Health 

and Safety Risks’’ (62 FR 19885, April 

23, 1997) applies to any rule that (1) is 

determined to be ‘‘economically 

significant’’ as defined under Executive 

Order 12866, and (2) concerns an 

environmental health or safety risk that 

EPA has reason to believe may have 

disproportionate effect on children. If 

the regulatory action meets both criteria, 

the Agency must evaluate the 

environmental health or safety effects of 

the planned rule on children, and 

explain why the planned regulation is 

preferable to other potentially effective 

and reasonably feasible alternatives 

considered by the Agency. 

The proposed rule is not subject to 

Executive Order 13045. Nonetheless, we 

have evaluated the environmental 

health or safety effects of the PM2.5

NAAQS on children. The results of this 

evaluation are contained in the 1997 

Federal Register notice establishing the 

PM2.5 standards.121 In a number of 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66061 

locations in that notice, children are 

identified as one of the principle subpopulations that are particularly 

sensitive to exposure to fine particle 

pollution. Today’s proposed rule 

provides the framework by which States 

will require sources to reduce pollutant 

emissions, thereby improving air quality 

and reducing the exposure of children 

and others to unhealthy levels of fine 

particle pollution. 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This proposed rule is not a 

‘‘significant energy action’’ as defined in 

Executive Order 13211, ‘‘Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use,’’ (66 FR 28355, 

May 22, 2001) because it is not likely to 

have a significant adverse effect on the 

supply, distribution, or use of energy. 

I. National Technology Transfer 

Advancement Act 

Section 12(d) of the National 

Technology Transfer Advancement Act 

of 1995 (NTTAA), Public Law 104–113, 

section 12(d) (15 U.S.C. 272 note) 

directs EPA to use voluntary consensus 

standards (VCS) in its regulatory 

activities unless to do so would be 

inconsistent with applicable law or 

otherwise impractical. Voluntary 

consensus standards are technical 

standards (e.g., materials specifications, 

test methods, sampling procedures, and 

business practices) that are developed or 

adopted by VCS bodies. The NTTAA 

directs EPA to provide Congress, 

through OMB, explanations when the 

Agency decides not to use available and 

applicable VCS. 

This proposed rulemaking does not 

involve technical standards. Therefore, 

EPA is not considering the use of any 

VCS. 

The EPA will encourage the States 

and Tribes to consider the use of such 

standards, where appropriate, in the 

development of the implementation 

plans. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

Executive Order 12898 requires that 

each Federal agency make achieving 

environmental justice part of its mission 

by identifying and addressing, as 

appropriate, disproportionate high and 

adverse human health or environmental 

effects of its programs, policies, and 

activities on minorities and low-income 

populations. 

The EPA believes that this proposed 

rule should not raise any environmental 

justice issues. The health and 

environmental risks associated with 

ozone were considered in the 

establishment of the PM2.5 NAAQS. The 

level is designed to be protective with 

an adequate margin of safety. The 

proposed rule provides a framework for 

improving environmental quality and 

reducing health risks for areas that may 

be designated nonattainment. 

Dated: September 8, 2005. 

Stephen L. Johnson, 

Administrator. 

For the reasons stated in the 

preamble, Title 40, Chapter I of the Code 

of Federal Regulations is proposed to be 

amended as follows: 

PART 51—REQUIREMENTS FOR 

PREPARATION, ADOPTION, AND 

SUBMITTAL OF IMPLEMENTATION 

PLANS 

1. The authority citation for part 51 

continues to read as follows: 

Authority: 23 U.S.C. 101; 42 U.S.C. 7401–

7671q. 

Subpart I—Review of New Sources and 

Modifications 

2. Section 51.165 is amended: 

a. By revising paragraphs (a)(1)(x), 

(a)(1)(xxxvii)(B), (a)(1)(xxxvii)(C); 

b. By adding paragraphs 

(a)(1)(xxxvii)(D) and (a)(9); and 

c. By adding and reserving paragraph 

(a)(8) to read as follows: 

§ 51.165 Permit requirements. 

(a) * * * 

(1) * * * 

(x) Significant means in reference to 

a net emissions increase or the potential 

of a source to emit any of the following 

pollutants, a rate of emissions that 

would equal or exceed any of the 

following rates: 

Pollutant Emission Rate 

Carbon monoxide: 100 tons per year 

(tpy). 

Nitrogen oxides: 40 tpy. 

Sulfur dioxide: 40 tpy. 

Ozone: 40 tpy of volatile organic 

compounds. 

Lead: 0.6 tpy. 

PM10: 15 tpy. 

PM2.5: 10 tpy of PM2.5 emissions; 40 

tpy of sulfur dioxide emissions; 40 tpy 

of nitrogen oxide emissions when 

identified as a PM2.5 precursor under 

paragraph (a)(1)(xxxvii)of this section. 

* * * * * 

(xxxvii) * * * 

(B) Any pollutant for which a national 

ambient air quality standard has been 

promulgated; 

(C) Any pollutant that is a constituent 

or precursor of a general pollutant listed 

under paragraphs (a)(1)(xxxvii)(A) or (B) 

of this section, provided that a 

constituent or precursor pollutant may 

only be regulated under NSR as part of 

regulation of the general pollutant. 

Precursors identified by the 

Administrator for purposes of NSR are 

the following: 

(1) Volatile organic compounds and 

nitrogen oxides are precursors to ozone 

in all ozone nonattainment areas. 

(2) Sulfur dioxide is a precursor to 

PM2.5 in all PM2.5 nonattainment areas. 

(3) Nitrogen oxides are presumed to 

be precursors to PM2.5 in all PM2.5

nonattainment areas, unless the State 

demonstrates to the Administrator’s 

satisfaction that emissions of nitrogen 

oxides from stationary sources in a 

specific area are not a significant 

contributor to that area’s ambient PM2.5

concentrations and the area is not in a 

State identified by the Administrator as 

a source of a PM2.5 interstate transport 

problem. 

(4) Volatile organic compounds and 

ammonia are presumed not to be 

precursors to PM2.5 in any PM2.5

nonattainment area, unless the State 

demonstrates to the Administrator’s 

satisfaction that emissions of volatile 

organic compounds or ammonia from 

stationary sources in a specific area are 

a significant contributor to that area’s 

ambient PM2.5 concentrations; or 

(D) Particulate matter (PM2.5 and 

PM10) includes gaseous emissions from 

a source or activity which condense to 

form particulate matter at ambient 

temperatures. 

* * * * * 

(8) [Reserved.] 

(9) (i) The plan shall require that in 

meeting the emissions offset 

requirements of paragraph (a)(3) of this 

section, the ratio of total actual 

emissions reductions to the emissions 

increase shall be at least 1:1 unless an 

alternative ratio is provided for the 

applicable nonattainment area in 

paragraph (a)(9)(ii) through (a)(9)(iv) of 

this section. 

(ii) The plan shall require that in 

meeting the emissions offset 

requirements of paragraph (a)(3) of this 

section for ozone nonattainment areas 

that are subject to subpart 2, part D, title 

I of the Act, the ratio of total actual 

emissions reductions of VOC to the 

emissions increase of VOC shall be as 

follows: 

(A) In any marginal nonattainment 

area for ozone—at least 1.1:1; 

(B) In any moderate nonattainment 

area for ozone—at least 1.15:1; 

(C) In any serious nonattainment area 

for ozone—at least 1.2:1; 

(D) In any severe nonattainment area 

for ozone—at least 1.3:1 (except that the 

66062 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

ratio may be at least 1.2:1 if the 

approved plan also requires all existing 

major sources in such nonattainment 

area to use BACT for the control of 

VOC); and 

(E) In any extreme nonattainment area 

for ozone—at least 1.5:1 (except that the 

ratio may be at least 1.2:1 if the 

approved plan also requires all existing 

major sources in such nonattainment 

area to use BACT for the control of 

VOC); and 

(iii) Notwithstanding the 

requirements of paragraph (a)(9)(ii) of 

this section for meeting the 

requirements of paragraph (a)(3) of this 

section, the ratio of total actual 

emissions reductions of VOC to the 

emissions increase of VOC shall be at 

least 1.15:1 for all areas within an ozone 

transport region that is subject to 

subpart 2, part D, title I of the Act, 

except for serious, severe, and extreme 

ozone nonattainment areas that are 

subject to subpart 2, part D, title I of the 

Act. 

(iv) The plan shall require that in 

meeting the emissions offset 

requirements of paragraph (a)(3) of this 

section for ozone nonattainment areas 

that are subject to subpart 1, part D, title 

I of the Act (but are not subject to 

subpart 2, part D, title I of the Act, 

including 8-hour ozone nonattainment 

areas subject to 40 CFR 51.902(b)), the 

ratio of total actual emissions reductions 

of VOC to the emissions increase of 

VOC shall be at least 1:1. 

* * * * * 

3. Section 51.166 is amended: 

a. By adding paragraph (a)(6)(iv). 

b. By revising paragraphs (b)(23)(i), 

(b)(49)(i), (b)(49)(iii), (i)(5)(ii), and 

(i)(5)(iii); 

c. By adding and reserving paragraph 

(b)(49)(v); and 

d. By adding paragraphs (b)(49)(vi) to 

read as follows: 

§ 51.166 Prevention of significant 

deterioration of air quality. 

(a) * * * 

(6) * * * 

(iv) When an implementation plan 

must be amended to address the 

prevention of significant deterioration of 

air quality for the PM2.5 national 

ambient air quality standards, the PM10

implementation plan provisions 

approved pursuant to this section may 

be used to implement a PM2.5 program 

until such amendments are approved, 

provided that: Particulate matter 

emissions shall include gaseous 

emissions from a source or activity 

which condense to form particulate 

matter at ambient temperatures for 

purposes of determining applicability of 

prevention of significant deterioration 

requirements; and the air quality 

analysis required under paragraph (m) 

of this section shall be conducted with 

respect to the PM2.5 standards. 

* * * * * 

(b) * * * 

(23) (i) Significant means, in reference 

to a net emissions increase or the 

potential of a source to emit any of the 

following pollutants, a rate of emissions 

that would equal or exceed any of the 

following rates: 

Pollutant and Emissions Rate 

Carbon monoxide: 100 tons per year 

(tpy). 

Nitrogen oxides: 40 tpy. 

Sulfur dioxide: 40 tpy. 

Particulate matter: 25 tpy of 

particulate matter emissions. 15 tpy of 

PM10 emissions. 

PM2.5: 10 tpy of PM2.5 emissions; 40 

tpy of sulfur dioxide emissions; 40 tpy 

of nitrogen oxide emissions when 

identified as a PM2.5 precursor under 

paragraph (b)(49). 

Ozone: 40 tpy of volatile organic 

compounds. 

Lead: 0.6 tpy. 

Fluorides: 3 tpy. 

Sulfuric acid mist: 7 tpy. 

Hydrogen sulfide (H2 S): 10 tpy. 

Total reduced sulfur (including H2 S): 

10 tpy. 

Reduced sulfur compounds 

(including H2 S): 10 tpy. 

Municipal waste combustor organics 

(measured as total tetra-through octachlorinated dibenzo-p-dioxins and 

dibenzofurans): 3.2 × 10–6 megagrams 

per year (3.5 × 10–6 tons per year). 

Municipal waste combustor metals 

(measured as articulate matter): 14 

megagrams per year (15 tons per year) 

Municipal waste combustor acid gases 

(measured as sulfur dioxide and 

hydrogen chloride): 36 megagrams per 

year (40 tons per year) Municipal solid 

waste landfill emissions (measured as 

nonmethane organic compounds): 45 

megagrams per year (50 tons per year). 

* * * * * 

(49) Regulated NSR pollutant, for 

purposes of this section, means the 

following: 

(i) Any pollutant for which a national 

ambient air quality standard has been 

promulgated and any constituents or 

precursors to such pollutants. 

Precursors identified by the 

Administrator for purposes of NSR are 

the following: 

(A) Volatile organic compounds and 

nitrogen oxides are precursors to ozone 

in all attainment and unclassifiable 

areas. 

(B) Sulfur dioxide is a precursor to 

PM2.5 in all attainment and 

unclassifiable areas. 

(C) Nitrogen oxides are presumed 

precursors to PM2.5 in all attainment and 

unclassifiable areas, unless the State 

demonstrates to the Administrator’s 

satisfaction that emissions of nitrogen 

oxides from stationary sources in a 

specific area are not a significant 

contributor to that area’s ambient PM2.5

concentrations and the area is not in a 

State identified by the Administrator as 

a source of a PM2.5 interstate transport 

problem. 

(D) Volatile organic compounds are 

presumed not to be precursors to PM2.5

in any attainment or unclassifiable area, 

unless the State demonstrates to the 

Administrator’s satisfaction that 

emissions of volatile organic 

compounds from stationary sources in a 

specific area are a significant 

contributor to that area’s ambient PM2.5

concentrations. 

* * * * * 

(iii) Any Class I or II substance subject 

to a standard promulgated under or 

established by title VI of the Act; 

* * * * * 

(v) [Reserved.]; 

(vi) Particulate matter (PM2.5 and 

PM10) emissions include gaseous 

emissions from a source or activity 

which condense to form particulate 

matter at ambient temperatures. 

* * * * * 

(i) * * * 

(5) * * * 

(ii) The concentrations of the 

pollutant in the area that the source or 

modification would affect are less than 

the concentrations listed in paragraph 

(i)(5)(i) of this section; or 

(iii) The pollutant is not listed in 

paragraph (i)(5)(i) of this section. 

* * * * * 

5. A new Subpart Y is added to read 

as follows: 

Subpart Y—Provisions for Implementation 

of PM2.5 National Ambient Air Quality 

Standards 

Sec. 

51.1000 Definitions. 

51.1001 Applicability of part 51. 

51.1002 Submittal of State implementation 

plan. 

51.1003 Classifications. 

51.1004 Attainment dates. 

51.1005 One-year extensions of the 

attainment date. 

51.1006 Redesignation to nonattainment 

following initial designations for the 

PM2.5 NAAQS. 

51.1007 Attainment demonstration and 

modeling requirements. 

51.1008 Emission inventory requirements 

for the PM2.5 NAAQS. 

51.1009 Reasonable further progress (RFP) 

requirements. 

51.1010 Requirements for reasonably 

available control technology (RACT) and 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66063 

reasonably available control measures 

(RACM). 

Subpart Y—Provisions for 

Implementation of PM2.5 National 

Ambient Air Quality Standards 

§ 51.1000 Definitions. 

The following definitions apply for 

purposes of this subpart. Any term not 

defined herein shall have the meaning 

as defined in 40 CFR 51.100. 

(a) Act means the Clean Air Act as 

codified at 42 U.S.C. 7401–7671q. 

(2003). 

(b) Attainment year means the final 

year of the three consecutive years 

evaluated to determine attainment with 

the PM2.5 NAAQS. 

(c) Benchmark RFP plan means the 

reasonable further progress plan that 

requires generally linear emission 

reductions from the 2002 baseline 

emissions year through the emissions 

year preceding the RFP milestone. 

(d) Date of designation means the 

effective date of the PM2.5 area 

designation as promulgated by the 

Administrator. 

(e) Direct PM2.5 emissions means air 

pollutant emissions of direct fine 

particulate matter, including organic 

carbon, elemental carbon, direct sulfate, 

direct nitrate, and miscellaneous 

inorganic material (i.e. crustal material). 

(f) Existing control measure means 

any federally enforceable national, 

State, or local control measure that has 

been approved in the SIP and that 

results in reductions in emissions of 

PM2.5 and its precursors in a 

nonattainment area. 

(g) PM2.5 NAAQS means the 

particulate matter national ambient air 

quality standards (annual and 24-hour) 

codified at 40 CFR 50.7. 

(h) PM2.5 design value for a 

nonattainment area is the highest of the 

three-year average concentrations 

calculated for the monitors in the area, 

in accordance with 40 CFR part 50, 

appendix N. 

(i) PM2.5 direct emissions means solid 

particles emitted directly from an 

emissions source or activity, or gaseous 

emissions or liquid droplets from a 

source or activity which condense to 

form particulate matter at ambient 

temperatures. PM2.5 direct emissions 

include elemental carbon, directly 

emitted organic carbon, and inorganic 

particles (including but not limited to 

crustal material, metals, and sea salt). 

(j) PM2.5 nonattainment plan 

precursor means those PM2.5 precursors 

emitted by sources in the State which 

the State must evaluate for emission 

reduction measures. 

(k) PM2.5 precursor means those 

regulated air pollutants other than PM2.5

direct emissions that contribute to the 

formation of PM2.5. PM2.5 precursors 

include SO2, NOX, volatile organic 

compounds, and ammonia. 

(l) Reasonable further progress (RFP) 

means the incremental emissions 

reductions toward attainment required 

under section 172(c)(2) and section 

171(1). 

(m) Subpart 1 means subpart 1 of part 

D of title I of the Act. 

§ 51.1001 Applicability of Part 51. 

The provisions in subparts A-X of part 

51 apply to areas for purposes of the 

PM2.5 NAAQS to the extent they are not 

inconsistent with the provisions of this 

subpart. 

§ 51.1002 Submittal of State 

Implementation Plan. 

(a) For any area designated by EPA as 

nonattainment for the PM2.5 NAAQS, 

the State shall submit a State 

implementation plan satisfying the 

requirements of section 172 of the Act 

and this subpart Y of 40 CFR part 51 to 

EPA no later than 3 years from the 

effective date of the designation. 

(b) The State must submit a plan 

consistent with the requirements of 

section 110(a)(2) of the Act unless the 

State already has fulfilled this obligation 

for the purposes of implementing the 

PM2.5 NAAQS. 

(c) Precursors of fine particles. The 

state implementation plan must identify 

and evaluate sources of PM2.5 direct 

emissions and PM2.5 nonattainment plan 

precursors in accordance with 

§§ 51.1009 and 51.1010 of this subpart. 

(1) The State must address sulfur 

dioxide as a PM2.5 nonattainment plan 

precursor and evaluate SO2 emissions 

sources for control measures. 

(2) The State must address NOX as a 

PM2.5 nonattainment plan precursor and 

evaluate sources of NOX emissions 

sources for control measures, unless the 

State and EPA provide an appropriate 

technical demonstration for a specific 

area showing that NOX emissions do not 

significantly contribute to the PM2.5

nonattainment problem in the area or to 

other downwind air quality concerns. 

(3) The State is not required to 

address VOC as a PM2.5 nonattainment 

plan precursor and evaluate sources of 

VOC emissions for control measures in 

that area, unless: 

(i) The State provides an appropriate 

technical demonstration for a specific 

area showing that VOC emissions 

significantly contribute to the PM2.5

nonattainment problem in the area or to 

other downwind air quality concerns 

and such demonstration is approved by 

EPA, or 

(ii) EPA provides such a technical 

demonstration. 

(4) The State is not required to 

address ammonia as a PM2.5

nonattainment plan precursor and 

evaluate sources of ammonia emissions 

for control measures in that area, unless: 

(i) the State provides an appropriate 

technical demonstration for a specific 

area showing that ammonia emissions 

significantly contribute to the PM2.5

nonattainment problem in the area or to 

other downwind air quality concerns 

and such demonstration is approved by 

EPA, or 

(ii) EPA provides such a technical 

demonstration. 

(5) Any technical demonstration 

referred to in paragraphs (c)(1) through 

(c)(4) of this section to modify the 

presumptive approach for any PM2.5

precursor must be considered in future 

SIP development activities. 

§ 51.1003. Classifications. 

An area designated as nonattainment 

for the PM2.5 NAAQS will not receive a 

specific classification based on design 

value. 

§ 51.1004 Attainment dates. 

(a) Consistent with section 

172(a)(2)(A) of the Act, the attainment 

date for an area designated 

nonattainment for the PM2.5 NAAQS 

shall be the date by which attainment 

can be achieved as expeditiously as 

practicable. The attainment date 

presumptively shall be 5 years or less 

from the date of designations. The 

Administrator may approve an 

attainment date extension pursuant to 

section 172(a)(2)(A). 

(b) In the SIP submittal for each of its 

nonattainment areas, the State shall 

submit an attainment demonstration 

providing detailed information 

justifying its proposed attainment date. 

For each nonattainment area, the 

Administrator will approve an 

attainment date at the same time the 

Administrator approves the attainment 

demonstration for the area, consistent 

with the attainment date timing 

provision of section 172(a)(2)(A) and 

paragraph (a) of this section. 

§ 51.1005 One-year extensions of the 

attainment date. 

(a) Pursuant to section 172(a)(2)(C)(ii) 

of the Act, a State with an area that fails 

to attain the PM2.5 NAAQS by its 

attainment date may apply for an initial 

1-year attainment date extension if the 

State has complied with all 

requirements and commitments 

pertaining to the area in the applicable 

implementation plan, and: 

(1) For an area that violates the annual 

PM2.5 NAAQS as of its attainment date, 

the annual average concentration for the 

66064 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

most recent year at each monitor is 15.0 

μg/m3 or less (calculated according to 

the data analysis requirements in 40 

CFR part 50, appendix N). 

(2) For an area that violates the 24- 

hour PM2.5 NAAQS as of its attainment 

date, the 98th percentile concentration 

for the most recent year at each monitor 

is 65 μg/m3 or less (calculated according 

to the data analysis requirements in 40 

CFR part 50, appendix N). 

(b) An area that fails to attain the 

PM2.5 NAAQS after receiving a 1-year 

attainment date extension may apply for 

a second 1-year attainment date 

extension pursuant to section 

172(a)(2)(C)(ii) if the State has complied 

with all requirements and commitments 

pertaining to the area in the applicable 

implementation plan, and: 

(1) For an area that violates the annual 

PM2.5 NAAQS as of its attainment date, 

the annual average concentration at 

each monitor, averaged over both the 

original attainment year and the first 

extension year, is 15.0 μg/m3 or less 

(calculated according to the data 

analysis requirements in 40 CFR part 50, 

appendix N). 

(2) For an area that violates the 24- 

hour PM2.5 NAAQS as of its attainment 

date, the 98th percentile concentration 

at each monitor, averaged over both the 

original attainment year and the first 

extension year, is 65 μg/m3 or less 

(calculated according to the data 

analysis requirements in 40 CFR part 50, 

appendix N). 

§ 51.1006 Redesignation to nonattainment 

following initial designations for the PM2.5

NAAQS. 

Any area that is initially designated 

‘‘attainment/unclassifiable’’ for the 

PM2.5 NAAQS may be subsequently 

redesignated to nonattainment if 

ambient air quality data in future years 

indicate that such a redesignation is 

appropriate. For any area that is 

redesignated to nonattainment for the 

PM2.5 NAAQS, any absolute, fixed date 

that is applicable in connection with the 

requirements of this part is extended by 

a period of time equal to the length of 

time between the effective date of the 

initial designation for the PM2.5 NAAQS 

and the effective date of redesignation, 

except as otherwise provided in this 

subpart. 

§ 51.1007 Attainment demonstration and 

modeling requirements. 

(a) For any area designated as 

nonattainment for the PM2.5 NAAQS, 

the State must submit an attainment 

demonstration showing that the area 

will attain the annual and 24-hour 

standards as expeditiously as 

practicable. The demonstration must 

include modeling results, inventory 

data, and emission reduction analyses 

on which the State has based its 

projected attainment date. Such 

modeling must be consistent with EPA 

guidance and must be appropriate for 

the area. The modeled strategies must be 

consistent with requirements in 

§ 51.1009 for RFP and in § 51.1010 for 

RACT and RACM. The attainment 

demonstration and supporting air 

quality modeling must be consistent 

with Appendix W of this part and EPA’s 

most recent modeling guidance in effect 

at the time the modeled attainment 

demonstration is performed. 

(b) Required timeframe for obtaining 

emissions reductions. For each 

nonattainment area, the State 

implementation plan must provide for 

implementation of all control measures 

needed for attainment as expeditiously 

as practicable, but no later than the 

beginning of the year prior to the 

attainment date. Consistent with section 

172(c)(1) of the Act, the plan must 

provide for implementation of all RACM 

and RACT as expeditiously as 

practicable. The plan also must include 

RFP milestones in accordance with 

§ 51.1009, and control measures needed 

to meet these milestones, as necessary. 

§ 51.1008 Emission inventory 

requirements for the PM2.5 NAAQS. 

(a) For purposes of meeting the 

emission inventory requirements of 

section 172(c)(3) of the Act, the State 

shall: 

(1) Submit to EPA statewide emission 

inventories for PM2.5 and its precursors 

under the Consolidated Emissions 

Reporting Rule (CERR), 40 CFR part 51, 

subpart A. 

(2) Submit any additional emission 

inventory information needed to 

support an attainment demonstration 

and RFP plan ensuring expeditious 

attainment of the annual and 24-hour 

PM2.5 standards. 

(b) A baseline emission inventory is 

required for the attainment 

demonstration required under § 51.1007 

and for meeting RFP requirements 

under § 51.1009. As determined on the 

effective date of an area’s nonattainment 

designation, the base year for this 

inventory shall be the most recent 

calendar year for which a complete 

inventory was required to be submitted 

to EPA pursuant to the Consolidated 

Emissions Reporting Rule in subpart A 

of this part. The baseline emission 

inventory for calendar year 2002 shall 

be used for attainment planning and 

RFP plans for areas initially designated 

nonattainment for the PM2.5 NAAQS. 

§ 51.1009 Reasonable further progress 

(RFP) requirements. 

(a) Consistent with section 172(c)(2) 

of the Act, State implementation plans 

for areas designated nonattainment for 

the PM2.5 NAAQS must demonstrate 

reasonable further progress as defined in 

section 171(1). 

(b) Requirements for RFP plans. 

(1) If the State submits an attainment 

plan for an area which proposes to 

attain the PM NAAQS within five years 

of the date of designation and such plan 

is approved by EPA, then compliance 

with the requirements of the attainment 

plan will be considered to also meet the 

requirements for achieving reasonable 

further progress for that area. 

(2) For any area for which the State 

proposes an attainment date of more 

than five years from the date of 

designation (i.e. attainment date 

extension), the State must submit an 

RFP plan as part of its SIP submittal. 

The SIP submittal is due to EPA within 

three years of the date of designation. 

(3) The RFP plan must require 

generally linear progress in direct PM2.5

and PM2.5 nonattainment plan precursor 

emission reductions from the 2002 base 

year through the year preceding the 

attainment date. For any area seeking an 

attainment date extension, the RFP plan 

must include RFP emission reduction 

milestones and projected air quality 

improvement to be achieved prior to 

January 1, 2010. Any area seeking an 

attainment date extension of three years 

or more must also include in its plan 

RFP emission reduction milestones and 

projected air quality improvement to be 

achieved prior to January 1, 2013. The 

State should develop these emission 

reduction milestones from attainment 

year modeling analyses and the 

projected direct PM2.5 and PM2.5

nonattainment plan precursor emission 

reduction levels presented in the 

analyses. 

(4) In its RFP plan, the State must 

define the geographic area to be covered 

by the inventories for each pollutant 

addressed in the plan. For each 

pollutant, this area shall reflect the area 

for which the emissions of that 

pollutant best corresponds with 

concentrations of the associated ambient 

species in the nonattainment area, based 

on information developed during 

attainment planning. In no case shall 

the area be less than the nonattainment 

area. All emissions sources that the 

State intends to track for RFP purposes 

must be included in the 2002 baseline 

inventory. 

(5) For any area seeking an attainment 

date extension beyond five years from 

designation, the benchmark RFP plan 

due with the area’s attainment 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66065 

demonstration shall include emission 

reduction milestones to be achieved by 

January 1, 2010 and January 1, 2013, if 

applicable. The following dates are 

defined for purposes of the benchmark 

RFP plan: 

(i) The baseline year for the 

benchmark RFP plan is the 2002 

emissions year. 

(ii) The milestone date inventory is 

the emission inventory for the year prior 

to the January 1 milestone date. 

(iii) The full implementation emission 

inventory is the emission inventory for 

the year preceding the attainment date. 

(6) The plan shall address each 

emitted pollutant that is reduced or 

otherwise affected by the control 

strategy of the PM2.5 attainment plan. 

(7) For each pollutant addressed 

pursuant to paragraph (b)(6) of this 

section, an overall tonnage reduction 

shall be calculated by subtracting the 

full implementation emission inventory 

from the baseline year inventory. 

(8) The ‘‘milestone date fraction’’ is 

the ratio of the number of years from the 

baseline year to the milestone inventory 

year divided by the number of years 

from the baseline year to the full 

implementation year. 

(9) For each pollutant addressed 

pursuant to paragraph (b)(6) of this 

section, a benchmark tonnage emission 

reduction shall be calculated by 

multiplying the full strategy tonnage 

reduction pursuant to paragraph (b)(7) 

of this section times the milestone date 

fraction pursuant to paragraph (b)(8) of 

this section. The benchmark emission 

level for each pollutant as of the 

milestone date shall be determined by 

subtracting the benchmark tonnage 

emission reduction from the baseline 

year emission level. A benchmark RFP 

plan is defined as a plan that achieves 

benchmark emission levels for each 

pollutant to be addressed pursuant to 

paragraph (b)(6) of this section. 

(10) The RFP plan due at the time of 

the attainment demonstration shall 

provide milestones that provide for 

emissions levels by January 1, 2010, to 

be either: 

(i) At levels that are roughly 

equivalent to the benchmark emission 

levels defined in paragraph (b)(8) of this 

section for all applicable pollutants; or 

(ii) At levels included in an 

alternative scenario that can be shown 

to provide generally equivalent air 

quality protection as the benchmark 

RFP plan. 

(11) The equivalence of an alternative 

scenario to the corresponding 

benchmark plan shall be determined by 

comparing the expected air quality 

benefits of the two scenarios at the 

design value monitor location. This 

comparison shall use the information 

developed for the attainment plan to 

assess the relationship between 

emissions reductions of the regulated 

pollutants and the ambient air quality 

improvement for the associated ambient 

species. The analysis of both scenarios 

may use the linear assumption that 

achievement of a given fraction of the 

emissions reductions of the attainment 

plan will achieve the same fraction of 

the associated air quality improvement 

that the attainment plan is demonstrated 

to achieve. 

§ 51.1010 Requirements for reasonably 

available control technology (RACT) and 

reasonably available control measures 

(RACM). 

(a) A PM2.5 nonattainment area that 

provides an attainment demonstration 

proposing an attainment date no later 

than five years from the date of 

designation is required to conduct 

RACT determinations for major 

stationary sources and impose RACT 

controls only to the extent that such 

controls are necessary to meet RFP or 

attain the PM2.5 standards as 

expeditiously as practicable. 

(b) A PM2.5 nonattainment area that 

provides an attainment demonstration 

proposing an attainment date of more 

than five years but no later than ten 

years from the date of designation must 

conduct a RACT determination for all 

stationary sources with the potential to 

emit 100 tons or more of any one 

pollutant associated with PM2.5 (direct 

PM2.5, SO2, and NOX). 

(c) In any source-specific RACT 

determination, the State must evaluate 

whether emission controls, process 

changes, or other emission reduction 

measures are technically and 

economically feasible in accordance 

with this rule and appropriate guidance. 

The State also must consider any 

additional information obtained through 

public comments when conducting 

RACT determinations for PM2.5. Any 

RACT emission reduction regulations 

required by the State must be included 

in the State’s SIP submittal. 

(d) For any source that installed 

controls due to a previous RACT 

determination for another NAAQS 

implementation program, the State may 

accept the previous RACT 

determination for the purposes of the 

PM2.5 program, provided it submits a 

certification with appropriate 

supporting information that the 

previous RACT determination currently 

represents an appropriate level of 

control for the PM2.5 program. 

(e) For each PM2.5 nonattainment area, 

the State shall submit with the 

attainment demonstration a SIP revision 

demonstrating that it has adopted all 

reasonably available control measures 

necessary to demonstrate attainment as 

expeditiously as practicable and to meet 

any RFP requirements. In developing its 

attainment demonstration, in 

demonstrating attainment as 

expeditiously as practicable, and in 

determining whether a particular 

emission reduction measure or set of 

measures must be adopted as RACM 

under section 172(c)(1) of the Act, the 

State must consider the cumulative 

impact of implementing the available 

measures and whether such measures 

taken together would advance the 

attainment date by one year. In 

conducting a RACM analysis, the State 

should consider control technology 

information available in EPA and State 

guidance documents, in control 

technology clearinghouses, and in any 

comments provided by the public. 

5. Appendix S to Part 51 is amended: 

a. By revising paragraph II. A. 10.; 

c. By adding paragraph II. A. 21.; and 

b. By revising paragraph IV. G. to read 

as follows: 

Appendix S to Part 51—Emission Offset 

Interpretative Ruling 

* * * * * 

II. * * * 

A. * * * 

10. Significant means, in reference to 

a net emissions increase or the potential 

of a source to emit any of the following 

pollutants, a rate of emissions that 

would equal or exceed any of the 

following rates: 

Pollutant and Emissions Rate 

Carbon monoxide: 100 tons per year 

(tpy) . 

Nitrogen oxides: 40 tpy. 

Sulfur dioxide: 40 tpy. 

Ozone: 40 tpy of volatile organic 

compounds. 

Lead: 0.6 tpy. 

Particulate matter: 25 tpy of 

particulate matter emissions. 

PM10: 15 tpy. 

PM2.5: 10 tpy of PM2.5 emissions; 40 

tpy of sulfur dioxide emissions; 40 tpy 

of nitrogen oxide emissions when 

identified as a PM2.5 precursor under 

paragraph II. A. 21. 

* * * * * 

21. Regulated NSR pollutant, for 

purposes of this section, means the 

following: 

(i) Nitrogen oxides or any volatile 

organic compounds; 

(ii) Any pollutant for which a national 

ambient air quality standard has been 

promulgated; 

(iii) Any pollutant that is a 

constituent or precursor of a general 

pollutant listed under paragraphs II. A. 

66066 Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 

21. (i) or (ii) of this section, provided 

that a constituent or precursor pollutant 

may only be regulated under NSR as 

part of regulation of the general 

pollutant. Precursors identified by the 

Administrator for purposes of NSR are 

the following: 

(a) Volatile organic compounds and 

nitrogen oxides are precursors to ozone 

in all ozone nonattainment areas. 

(b) Sulfur dioxide is a precursor to 

PM2.5 in all PM2.5 nonattainment areas. 

(c) Nitrogen oxides are presumed to 

be precursors to PM2.5 in all PM2.5

nonattainment areas, unless the State 

demonstrates to the Administrator’s 

satisfaction that emissions of nitrogen 

oxides from stationary sources in a 

specific area are not a significant 

contributor to that area’s ambient PM2.5

concentrations and the area is not in a 

State identified by the Administrator as 

a source of a PM2.5 interstate transport 

problem. 

(d) Volatile organic compounds and 

ammonia are presumed not to be 

precursors to PM2.5 in any PM2.5

nonattainment area, unless the State 

demonstrates to the Administrator’s 

satisfaction that emissions of volatile 

organic compounds or ammonia from 

stationary sources in a specific area are 

a significant contributor to that area’s 

ambient PM2.5 concentrations; or 

(iv) Particulate matter (PM2.5 and 

PM10) includes gaseous emissions from 

a source or activity which condense to 

form particulate matter at ambient 

temperatures. 

* * * * * 

IV. * * * 

G. Offset Ratios. 

1. In meeting the emissions offset 

requirements of paragraph IV. A., 

Condition 3 of this Ruling, the ratio of 

total actual emissions reductions to the 

emissions increase shall be at least 1:1 

unless an alternative ratio is provided 

for the applicable nonattainment area in 

paragraphs IV. G. 2. to IV. G. 4. 

2. In meeting the emissions offset 

requirements of paragraph IV. A., 

Condition 3 of this Ruling for ozone 

nonattainment areas that are subject to 

subpart 2, part D, title I of the Act, the 

ratio of total actual emissions reductions 

of VOC to the emissions increase of 

VOC shall be as follows: 

(i) In any marginal nonattainment area 

for ozone—at least 1.1:1; 

(ii) In any moderate nonattainment 

area for ozone—at least 1.15:1; 

(iii) In any serious nonattainment area 

for ozone—at least 1.2:1; 

(iv) In any severe nonattainment area 

for ozone—at least 1.3:1 (except that the 

ratio may be at least 1.2:1 if the State 

also requires all existing major sources 

in such nonattainment area to use BACT 

for the control of VOC); and 

(v) In any extreme nonattainment area 

for ozone—at least 1.5:1 (except that the 

ratio may be at least 1.2:1 if the State 

also requires all existing major sources 

in such nonattainment area to use BACT 

for the control of VOC); 

3. Notwithstanding the requirements 

of paragraph IV.G. 2. of this Ruling for 

meeting the requirements of paragraph 

IV. A., Condition 3 of this Ruling, the 

ratio of total actual emissions reductions 

of VOC to the emissions increase of 

VOC shall be at least 1.15:1 for all areas 

within an ozone transport region that is 

subject to subpart 2, part D, title I of the 

Act, except for serious, severe, and 

extreme ozone nonattainment areas that 

are subject to subpart 2, part D, title I 

of the Act. 

4. In meeting the emissions offset 

requirements of paragraph IV. A., 

Condition 3 of this Ruling for ozone 

nonattainment areas that are subject to 

subpart 1, part D, title I of the Act (but 

are not subject to subpart 2, part D, title 

I of the Act, including 8-hour ozone 

nonattainment areas subject to 40 CFR 

51.902(b)), the ratio of total actual 

emissions reductions of VOC to the 

emissions increase of VOC shall be at 

least 1:1. 

PART 52—APPROVAL AND 

PROMULGATION OF 

IMPLEMENTATION PLANS 

5. The authority citation for part 52 

continues to read as follows: 

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

6. Section 52.21 is amended by: 

a. Revising paragraphs (b)(23)(i), 

(b)(50)(i), (b)(50)(iii), and (i)(5)(ii); 

b. Adding and reserving paragraph 

(b)(50)(v); and 

c. Adding paragraphs (b)(50)(vi) and 

(i)(5)(iii) to read as follows: 

§ 52.21 Prevention of significant 

deterioration of air quality. 

* * * * * 

(b) * * * 

(23)(i) Significant means, in reference 

to a net emissions increase or the 

potential of a source to emit any of the 

following pollutants, a rate of emissions 

that would equal or exceed any of the 

following rates: 

Pollutant and Emissions Rate 

Carbon monoxide: 100 tons per year 

(tpy). 

Nitrogen oxides: 40 tpy. 

Sulfur dioxide: 40 tpy. 

Particulate matter: 25 tpy of 

particulate matter emissions. 

PM10: 15 tpy. 

PM2.5: 10 tpy of PM2.5 emissions; 40 

tpy of sulfur dioxide emissions; 40 tpy 

of nitrogen oxide emissions when 

identified as a PM2.5 precursor under 

paragraph (b)(50) of this section. 

Ozone: 40 tpy of volatile organic 

compounds. 

Lead: 0.6 tpy. 

Fluorides: 3 tpy. 

Sulfuric acid mist: 7 tpy. 

Hydrogen sulfide (H2 S): 10 tpy. 

Total reduced sulfur (including H2 S): 

10 tpy. 

Reduced sulfur compounds 

(including H2 S): 10 tpy. 

Municipal waste combustor organics 

(measured as total tetra-through octachlorinated dibenzo-p-dioxins and 

dibenzofurans): 3.2 × 10-6 megagrams 

per year (3.5 × 10-6 tons per year). 

Municipal waste combustor metals 

(measured as particulate matter): 14 

megagrams per year (15 tons per year). 

Municipal waste combustor acid gases 

(measured as sulfur dioxide and 

hydrogen chloride): 36 megagrams per 

year (40 tons per year). 

Municipal solid waste landfills 

emissions (measured as nonmethane 

organic compounds): 45 megagrams per 

year (50 tons per year). 

* * * * * 

(50) Regulated NSR pollutant, for 

purposes of this section, means the 

following: 

(i) Any pollutant for which a national 

ambient air quality standard has been 

promulgated and any constituents or 

precursors for such pollutants. 

Precursors identified by the 

Administrator for purposes of NSR are 

the following: 

(A) Volatile organic compounds and 

nitrogen oxides are precursors to ozone 

in all attainment and unclassifiable 

areas. 

(B) Sulfur dioxide is a precursor to 

PM2.5 in all attainment and 

unclassifiable areas. 

(C) Nitrogen oxides are presumed 

precursors to PM2.5 in all attainment and 

unclassifiable areas, unless the State 

demonstrates to the Administrator’s 

satisfaction that emissions of nitrogen 

oxides from stationary sources in a 

specific area are not a significant 

contributor to that area’s ambient PM2.5

concentrations and the area is not in a 

State identified by the Administrator as 

a source of a PM2.5 interstate transport 

problem. 

(D) Volatile organic compounds are 

presumed not to be precursors to PM2.5

in any attainment or unclassifiable area, 

unless the State demonstrates to the 

Administrator’s satisfaction that 

emissions of volatile organic 

compounds from stationary sources in a 

specific area are a significant 

Federal Register / Vol. 70, No. 210 / Tuesday, November 1, 2005 / Proposed Rules 66067 

contributor to that area’s ambient PM2.5

concentrations. 

* * * * * 

(iii) Any Class I or II substance subject 

to a standard promulgated under or 

established by title VI of the Act; 

* * * * * 

(v) [Reserved.]; 

(vi) Particulate matter (PM2.5 and 

PM10) emissions include gaseous 

emissions from a source or activity 

which condense to form particulate 

matter at ambient temperatures. 

* * * * * 

(i) * * * 

(5) * * * 

(ii) The concentrations of the 

pollutant in the area that the source or 

modification would affect are less than 

the concentrations listed in paragraph 

(i)(5)(i) of this section; or 

(iii) The pollutant is not listed in 

paragraph (i)(5)(i) of this section. 

* * * * * 

[FR Doc. 05–20455 Filed 10–31–05; 8:45 am] 

BILLING CODE 6560–50–U