64864 Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 51 and 52 

[EPA–HQ–OAR–2006–0605; FRL–9210–9] 

RIN 2060–AO24 

Prevention of Significant Deterioration 

(PSD) for Particulate Matter Less Than 

2.5 Micrometers (PM2.5)—Increments, 

Significant Impact Levels (SILs) and 

Significant Monitoring Concentration 

(SMC) 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: The EPA is amending the 

requirements for particulate matter less 

than 2.5 micrometers (PM2.5) under the 

Prevention of Significant Deterioration 

(PSD) program by adding maximum 

allowable increases in ambient pollutant 

concentrations (‘‘increments’’) and two 

screening tools, known as the 

Significant Impact Levels (SILs) and a 

Significant Monitoring Concentration 

(SMC) for PM2.5. The SILs for PM2.5 are 

also being added to two other New 

Source Review (NSR) rules that regulate 

the construction and modification of 

any major stationary source locating in 

an attainment or unclassifiable area, 

where the source’s emissions may cause 

or contribute to a violation of the 

national ambient air quality standards 

(NAAQS). 

DATES: This final rule is effective on 

December 20, 2010. 

ADDRESSES: The EPA has established a 

docket for this action under Docket ID 

No. EPA–HQ–OAR–2006–0605. All 

documents in the docket are listed on 

the http://www.regulations.gov Web 

Site. Although listed in the index, some 

information may not be publicly 

available, e.g., Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the Internet and will be publicly 

available only in hard copy form. 

Publicly available docket materials are 

available either electronically through 

http://www.regulations.gov or in hard 

copy at the Air Docket, EPA/DC, EPA 

West, Room 3334, 1301 Constitution 

Avenue, Northwest, Washington, DC. 

The Public Reading Room is open from 

8:30 a.m. to 4:30 p.m., Monday through 

Friday, excluding legal holidays. The 

telephone number for the Public 

Reading Room is (202) 566–1744, and 

the telephone number for the Air Docket 

is (202) 566–1742. 

FOR FURTHER INFORMATION CONTACT: Mr. 

Dan deRoeck, Air Quality Policy 

Division, Office of Air Quality Planning 

and Standards (C504–03), U.S. 

Environmental Protection Agency, 

Research Triangle Park, North Carolina 

27711, telephone number: (919) 541– 

5593, facsimile number: (919) 541–5509, 

e-mail address: deroeck.dan@epa.gov. 

SUPPLEMENTARY INFORMATION: The 

information in this Supplementary 

Information section of this preamble is 

organized as follows: 

I. General Information 

A. Does this action apply to me? 

B. Where can I get a copy of this document 

and other related information? 

II. Purpose 

III. Overview of Final PM2.5 PSD Regulations 

A. Increments 

B. Significant Impact Levels 

C. Significant Monitoring Concentration 

IV. Background 

A. PSD Program 

B. History of Particulate Matter (PM) 

NAAQS 

1. Total Suspended Particulate (TSP) and 

PM10 NAAQS 

2. PM2.5 NAAQS 

3. Revised PM2.5 and PM10 NAAQS 

C. Implementation of NSR for PM2.5

D. Increments Under the PSD Program 

E. Historical Approaches for Developing 

Increments 

1. Congressional Enactment of Increments 

for PM and SO2

2. EPA’s Promulgation of Increments for 

NO2 and PM10

a. Increments for NO2 Using the 

‘‘Contingent Safe Harbor’’ Approach 

Under Section 166(a) of the Act 

b. Increments for PM10 Using ‘‘Equivalent 

Substitution’’ Approach Under Section 

166(f) of the Act 

V. Final Action on PM2.5 Increments 

A. Decision To Establish PM2.5 Increments 

Using ‘‘Contingent Safe Harbor 

Approach’’ Under Section 166(a) 

B. Rationale for the Applicability of 

Section 166(a) 

C. EPA’s Interpretation of the 

Requirements Under Sections 166(a)–(d) 

of the Act 

1. Regulations as a Whole Should Fulfill 

Statutory Requirements 

2. Contingent Safe Harbor Approach 

3. The Statutory Factors Applicable Under 

Section 166(c) 

4. Balancing the Factors Applicable Under 

Section 166(c) 

5. Authority for States To Adopt 

Alternatives to Increments 

D. Framework for Pollutant-Specific PSD 

Regulations for PM2.5

1. Increment System 

2. Area Classifications 

3. Permitting Procedures 

4. AQRV Review by Federal Land Manager 

(FLM) and Reviewing Authority 

5. Additional Impacts Analysis 

6. Installation of BACT 

E. Final PM2.5 Increments 

1. Identification of Safe Harbor Increments 

2. Data Used by EPA for the Evaluation of 

the Safe Harbor Increments for PM2.5

3. Scope of Effects Considered 

4. Evaluation of the Health and Welfare 

Effects of PM2.5

a. Health Effects 

b. Welfare Effects 

5. Fundamental Elements of Increments 

6. Evaluation of the Safe Harbor Increments 

7. Compliance Determinations for the 

PM2.5 Increments 

a. Modeling Compliance With PM2.5

Increments 

b. Condensable PM 

c. PM2.5 Precursors 

F. Final Action on Trigger and Baseline 

Dates for PM2.5 Increments 

G. Definition of ‘‘Baseline Area’’ for PM2.5

H. No Final Action With Respect to the 

Proposed Revocation of PM10 Annual 

Increments 

I. Other Comments on Increments 

VI. Final Action on PM2.5 SILs 

A. EPA’s Determination on SILs for PM2.5

B. Response to Comments Concerning the 

SILs 

1. Legal Basis for SILs 

2. Levels of the SILs 

a. Class I SILs 

b. Class II and III SILs 

3. Relationship Between SILs and AQRVs 

4. Form of the SILs 

5. SILs for Other Pollutants 

VII. Final Action on the PM2.5 SMC 

A. EPA’s Determination on the PM2.5 SMC 

B. Response to Comments Concerning the 

SMC 

1. Legal Issues 

2. Level of the SMC 

C. Correction of Cross Reference in PSD 

Ambient Monitoring Requirements 

VIII. Dates Associated With Implementation 

of the Final Rule 

A. Effective Date of the Final Rule 

1. State PSD Programs 

2. Federal PSD Program 

B. Transition Period 

C. SILs and SMC for PM2.5

IX. Other Regulatory Changes 

X. 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 and 

Advancement Act 

J. Executive Order 12898—Federal Actions 

To Address Environmental Justice in 

Minority Populations and Low-Income 

Populations 

K. Congressional Review Act 

XI. Judicial Review 

XII. Statutory Authority 


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Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 64865 

I. General Information 

A. Does this action apply to me? 

Entities affected by this rule include 

sources in all industry groups. The 

majority of sources potentially affected 

are expected to be in the following 

groups: 

Industry group NAICSa

Electric services ................................................................................................................................................... 221111, 221112, 221113, 221119, 

221121, 221122 

Petroleum refining ............................................................................................................................................... 32411 

Industrial inorganic chemicals ............................................................................................................................. 325181, 32512, 325131, 325182, 

211112, 325998, 331311, 

325188 

Industrial organic chemicals ................................................................................................................................ 32511, 325132, 325192, 325188, 

325193, 32512, 325199 

Miscellaneous chemical products ........................................................................................................................ 32552, 32592, 32591, 325182, 

32551 

Natural gas liquids ............................................................................................................................................... 211112 

Natural gas transport ........................................................................................................................................... 48621, 22121 

Pulp and paper mills ............................................................................................................................................ 32211, 322121, 322122, 32213 

Paper mills ........................................................................................................................................................... 322121, 322122 

Automobile manufacturing ................................................................................................................................... 336111, 336112, 336712, 336211, 

336992, 336322, 336312, 

33633, 33634, 33635, 336399, 

336212, 336213 

Pharmaceuticals .................................................................................................................................................. 325411, 325412, 325413, 325414 

a North American Industry Classification System. 

Entities affected by this rule also 

include State and local permitting 

authorities, and tribal authorities that 

implement these regulations. 

B. Where can I get a copy of this 

document and other related 

information? 

In addition to being available in the 

docket, an electronic copy of this final 

rule will also be available on the World 

Wide Web. Following signature by the 

EPA Administrator, a copy of this final 

rule will be posted in the regulations 

and standards section of our NSR home 

page located at http://www.epa.gov/nsr. 

II. Purpose 

The purpose of this rulemaking is to 

finalize certain program provisions 

under the regulations to prevent 

significant deterioration of air quality 

due to emissions of PM2.5 (i.e., under the 

PM2.5 PSD regulations). This final rule 

supplements the final implementation 

rule for PM2.5, known as the Clean Air 

Fine Particle Implementation Rule 

(CAFPIR) that we promulgated on April 

25, 2007 (72 FR 20586), and the PM2.5

NSR Implementation Rule that we 

promulgated on May 16, 2008 (73 FR 

28321). Together, these three rules 

encompass the elements necessary for 

implementation of a PM2.5 program in 

any area. This final rule is important 

because it establishes increments, SILs, 

and an SMC for PM2.5 to facilitate 

ambient air quality monitoring and 

modeling under the PSD regulations for 

areas designated attainment or 

unclassifiable for PM2.5. 

III. Overview of Final PM2.5 PSD 

Regulations 

A. Increments 

This rulemaking establishes 

increments for PM2.5 pursuant to the 

legal authority contained in section 

166(a) of the Clean Air Act (CAA or Act) 

for pollutants for which NAAQS are 

promulgated after 1977. The final PM2.5

increments were identified as Option 1 

in the 2007 Notice of Proposed 

Rulemaking (NPRM) for this action, and 

are as follows: 

Averaging period NAAQS 

(μg/m3) 

Increments (μg/m3) 

Class I Class II Class III 

Annual .............................................................................................................................. 15 1 4 8 

24-hour ............................................................................................................................. 35 2 9 18 

As discussed in more detail in 

sections V.F and VIII, the increments for 

PM2.5 will become applicable on 

October 20, 2011 in order to comply 

with section 166(b) of the Act 

(providing that regulations under 

section 166(a) ‘‘shall become effective 

one year after the date of 

promulgation’’). 

This final rule does not revoke the 

annual increments for particulate matter 

less than 10 micrometers (PM10) as 

proposed under Option 1 in the 2007 

NPRM. Thus, we are retaining the 24- 

hour and annual PM10 increments in 

addition to adding PM2.5 increments. 

This outcome is discussed in greater 

detail in section V.H of this preamble. 

B. Significant Impact Levels 

This rule establishes SILs for PM2.5 for 

evaluating the impact a proposed new 

source or modification may have on the 

NAAQS and PSD increments for PM2.5. 

The SILs for PM2.5 were developed by 

scaling the existing PM10 SILs using a 

PM2.5-to-PM10 NAAQS ratio. The final 

SILs were identified as Option 3 in the 

2007 NPRM, and are as follows: 


emcdonald on DSK2BSOYB1PROD with RULES3
64866 Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 

1We have delegated our authority to some states 

to implement the Federal PSD program. The EPA 

remains the reviewing authority in non-delegated 

states lacking SIP-approved programs and in Indian 

country. 

Averaging period 

SILs (μg/m3) 

Class I Class II Class III 

Annual ...................................................................................................................................................... 0.06 0.3 0.3 

24-hour ..................................................................................................................................................... 0.07 1.2 1.2 

These values will be added to the 

State implementation plan (SIP) 

provisions for PSD at 40 CFR 51.166 (as 

an optional screening tool) and the 

Federal PSD program at 40 CFR 52.21, 

as well as under the preconstruction 

review permit requirements at 40 CFR 

51.165(b) and part 51, Appendix S. See 

a more detailed discussion of the SILs, 

as well as the relevant comments and 

our responses to them, in section VI of 

this preamble. The SILs for PM2.5 are 

incorporated into the Federal PSD 

program as well as into the regulations 

for State-implemented PSD programs, 

although they are regarded as optional 

for State programs. The effective date for 

implementing the SILs under the 

Federal PSD program is the effective 

date of this final rule. See section VIII 

of this preamble for further discussion 

of the effective date. 

C. Significant Monitoring Concentration 

This final rule establishes the SMC for 

PM2.5 as 4 μg/m3 PM2.5 (24-hour 

average). This value has been developed 

pursuant to proposed Option 1; 

however, it should be noted that the 

value being established in this final rule 

is lower than the proposed value of 10 

μg/m3 that was originally developed 

under Option 1. A more detailed 

discussion of the proposed SMC is 

presented in section VII of this 

preamble, describing the rationale for 

altering the proposed SMC, and the 

relevant comments on the proposed 

SMC and our responses to them. The 

SMC for PM2.5 is incorporated into the 

Federal PSD program as well as into the 

regulations for State-implemented PSD 

programs, although they are regarded as 

optional for State programs. As with the 

SILs for PM2.5, the effective date for 

implementing the SMC under the 

Federal PSD program is the effective 

date of this final rule. See section VIII 

of this preamble for further discussion 

of the effective date. 

IV. Background 

A. PSD Program 

The NSR provisions of the Act are a 

combination of air quality planning and 

air pollution control technology 

program requirements for new and 

modified stationary sources of air 

pollution. In brief, section 109 of the 

Act requires us to promulgate primary 

NAAQS to protect public health and 

secondary NAAQS to protect public 

welfare. Once we have set these 

standards, states must develop, adopt, 

and submit to us for approval SIPs that 

contain emission limitations and other 

control measures to attain and maintain 

the NAAQS and to meet the other 

requirements of section 110(a) of the 

Act. Part C of title I of the Act contains 

the requirements for a component of the 

major NSR program known as the PSD 

program. This program sets forth 

procedures for the preconstruction 

review and permitting of new and 

modified major stationary sources of air 

pollution locating in areas meeting the 

NAAQS (‘‘attainment’’ areas) and areas 

for which there is insufficient 

information to classify an area as either 

attainment or nonattainment 

(‘‘unclassifiable’’ areas). Most states have 

SIP-approved preconstruction permit 

(major NSR) programs. The Federal PSD 

program at 40 CFR 52.21 applies in 

some states that lack a SIP-approved 

permit program, and in Indian country.1

The applicability of the PSD program to 

a major stationary source must be 

determined in advance of construction 

and is a pollutant-specific 

determination. Once a major source is 

determined to be subject to the PSD 

program (PSD source), among other 

requirements, it must undertake a series 

of analyses to demonstrate that it will 

use the best available control technology 

(BACT) and will not cause or contribute 

to a violation of any NAAQS or 

increment. For the latter demonstration, 

the PSD regulations generally require 

sources to submit for review and 

approval a source impact analysis and 

an air quality analysis. 

The source impact analysis is 

primarily a modeling analysis designed 

to show that the allowable emissions 

increase from the proposed project, in 

conjunction with other emissions 

increases from existing sources, will not 

result in a violation of either the 

NAAQS or increments. In cases where 

the source’s emissions may adversely 

affect an area classified as a Class I area, 

additional review is conducted to 

protect the increments and special 

attributes of such an area defined as ‘‘air 

quality related values’’ (AQRVs). 

The air quality analysis must assess 

the ambient air quality in the area that 

the proposed project would affect. For 

this analysis, the owner or operator of 

the proposed project must submit as 

part of a complete permit application air 

quality monitoring data that represent 

the air quality in the area affected by the 

proposed source for the 1-year period 

preceding receipt of the application. 

Where data may already exist to 

represent existing air quality, it may be 

used by the applicant; otherwise, the 

source owner or operator is responsible 

for the installation and operation of 

monitors to collect the necessary data. 

Historically, EPA has allowed the use 

of several types of screening tools to 

facilitate implementation of the 

preconstruction review process to 

reduce the permit applicant’s burden 

and streamline the permitting process 

for de minimis circumstances. These 

tools include a significant emissions 

rate (SER), SILs, and a SMC. The SER, 

defined in tons per year (tpy) for each 

regulated pollutant, is used to determine 

whether the emissions increase from 

any proposed source or modification 

can be excluded from review on the 

grounds that the increase of any 

particular pollutant is de minimis. An 

emission increase for a particular 

pollutant that is greater than the SER 

defined in the NSR regulations for that 

pollutant is considered to be a 

significant increase. 

The SIL, expressed as an ambient 

pollutant concentration (micrograms per 

cubic meter (μg/m 3)), is used to 

determine whether the ambient impact 

of a particular pollutant (once it is 

determined to be emitted in significant 

amounts) is significant enough to 

warrant a complete source impact 

analysis involving modeling the 

collective impacts of the proposed 

project and emissions from other 

existing sources. 

The PSD regulations generally require 

each PSD applicant to collect 1 year of 

continuous air quality monitoring data 

for any pollutant determined to be 

subject to preconstruction review as part 

of complete PSD permit application. 

Using the SMC as a screening tool, 

expressed as an ambient pollutant 

concentration (μg/m3), sources may be 

able to demonstrate that the modeled air 


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Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 64867 

2The basic monitoring exemption provision is 

part of the original monitoring requirements 

adopted in the 1980 PSD rulemaking. 45 FR 52676, 

52710, August 7, 1980. 

quality impact of emissions from the 

new source or modification, or the 

existing air quality level in the area 

where the source would construct, is 

less than the SMC, i.e., de minimis, and 

may be allowed to forego the 

preconstruction monitoring requirement 

for a particular pollutant at the 

discretion of the reviewing 

authority.2See 40 CFR 51.166(i)(5) and 

52.21(i)(5). 

When the reviewing authority reaches 

a preliminary decision to authorize 

construction of a proposed major new 

source or major modification, it must 

provide notice of the preliminary 

decision and an opportunity for 

comment by the general public, 

industry, and other persons that may be 

affected by the emissions of the 

proposed major source or major 

modification. After considering these 

comments, the reviewing authority may 

issue a final determination on the 

construction permit in accordance with 

the PSD regulations. 

B. History of Particulate Matter (PM) 

NAAQS 

1. Total Suspended Particulate (TSP) 

and PM10 NAAQS 

The EPA initially established NAAQS 

for PM in 1971, measured by the TSP 

indicator. Based on the size of the 

particles collected by the ‘‘high-volume 

sampler,’’ which at that time was the 

reference method for determining 

ambient concentrations, TSP included 

all PM up to a nominal size of 25 to 45 

micrometers. We established both 

annual and 24-hour NAAQS for TSP. 

On July 1, 1987, we revised the 

NAAQS for PM and changed the 

indicator from TSP to PM10; the latter 

indicator includes particles with a mean 

aerodynamic diameter less than or equal 

to 10 micrometers. The PM10 particles 

are the subset of inhalable particles 

small enough to penetrate to the 

thoracic region (including the 

tracheobronchial and alveolar regions) 

of the respiratory tract (referred to as 

thoracic particles). We established 

annual and 24-hour NAAQS for PM10, 

and revoked the NAAQS for TSP. (52 FR 

24634). 

2. PM2.5 NAAQS 

On July 18, 1997, we again revised the 

NAAQS for PM in several respects. 

While we determined that the NAAQS 

should continue to focus on particles 

less than or equal to 10 micrometers in 

diameter, we also determined that the 

fine and coarse fractions of PM10 should 

be considered separately. We 

established new annual and 24-hour 

NAAQS using PM2.5 (referring to 

particles with a nominal mean 

aerodynamic diameter less than or equal 

to 2.5 micrometers) as the indicator for 

fine particles. The 1997 NAAQS rule 

also modified the PM10 NAAQS for the 

purpose of regulating the coarse fraction 

of PM10 (referred to as thoracic coarse 

particles or coarse-fraction particles; 

generally including particles with a 

nominal mean aerodynamic diameter 

greater than 2.5 micrometers and less 

than or equal to 10 micrometers, or 

PM10–2.5); however, this part of the 

rulemaking was vacated during 

subsequent litigation, leaving the preexisting 1987 PM10 NAAQS in place (62 

FR 38652). 

3. Revised PM2.5 and PM10 NAAQS 

On October 17, 2006, we promulgated 

revisions to the NAAQS for PM2.5 and 

PM10 with an effective date of December 

18, 2006 (71 FR 61144). We lowered the 

24-hour NAAQS for PM2.5 from 65 μg/ 

m3 to 35 μg/m3, and retained the 

existing annual PM2.5 NAAQS of 15 μg/ 

m3. In addition, we retained the existing 

PM10 24-hour NAAQS of 150 μg/m3, and 

revoked the annual PM10 NAAQS (set at 

50 μg/m3). 

C. Implementation of NSR for PM2.5

After we established new annual and 

24-hour NAAQS based on PM2.5 as the 

indicator for fine particles in July 1997, 

we issued a guidance document titled 

‘‘Interim Implementation for the New 

Source Review Requirements for PM2.5,’’ 

John S. Seitz, Director, Office of Air 

Quality Planning and Standards, EPA, 

October 23, 1997. As noted in that 

guidance, section 165 of the Act implies 

that certain 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 

increment or 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. These 

difficulties included 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. 

On April 5, 2005, we issued a 

guidance document entitled 

‘‘Implementation of New Source Review 

Requirements in PM–2.5 Nonattainment 

Areas,’’ Stephen D. Page, Director, Office 

of Air Quality Planning and Standards, 

EPA. This memorandum provided 

guidance on the implementation of the 

nonattainment major NSR provisions in 

PM2.5 nonattainment areas in the 

interim period between the effective 

date of the PM2.5 NAAQS designations 

(April 5, 2005) and when we promulgate 

regulations to implement nonattainment 

major NSR for the PM2.5 NAAQS. In 

addition to affirming the continued use 

of the John S. Seitz guidance memo in 

PM2.5 attainment areas, this memo 

recommended that, until we 

promulgated the PM2.5 major NSR 

regulations, states should use a PM10

nonattainment major NSR program as a 

surrogate to address the requirements of 

nonattainment major NSR for the PM2.5

NAAQS. 

On November 1, 2005, we proposed a 

rule to implement the PM2.5 NAAQS, 

including proposed revisions to the NSR 

program. For those states with EPAapproved PSD programs, we proposed 

to continue the 1997 NSR guidance to 

use PM10 as a surrogate for PM2.5, but 

only during the SIP development 

period. We also indicated in that 

proposal that we would be developing 

increments, SILs, and an SMC in a 

separate rulemaking, i.e., this final rule. 

Since there was an interim surrogate 

NSR program in place, i.e., the PM10

Surrogate Policy, EPA decided to first 

promulgate the non-NSR part of the 

implementation rule (including 

attainment demonstrations, 

designations, control measures, etc.). 

This rule was promulgated as the 

CAFPIR on April 25, 2007 (72 FR 

20586). 

The NSR part of the implementation 

rule was issued separately as a final rule 

on May 16, 2008 (73 FR 28321), and 

included sets of NSR regulations for 

both attainment (PSD) and 

nonattainment areas (nonattainment 

NSR) for PM2.5. In the May 16, 2008 rule 

we added one of the important 

screening tools—the SER—for PM2.5. 

The SER for PM2.5 is defined as an 

emissions rate of 10 tpy for direct PM2.5

emissions. We also listed sulfur dioxide 

(SO2) and nitrogen oxides (NOX) as 

precursors of ambient PM2.5 and defined 

‘‘significant’’ as 40 tpy or more of either 

precursor pollutant. States were allowed 

up to 3 years from the date of 

publication in the Federal Register to 


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64868 Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 

3Baseline dates are pollutant specific. That is, a 

complete PSD application establishes the baseline 

date only for those regulated NSR pollutants that 

are projected to be emitted in significant amounts 

(as defined in the regulations) by the applicant’s 

new source or modification. Thus, an area may have 

different baseline dates for different pollutants. 

revise their SIPs and submit their 

revised NSR programs to EPA for 

approval. 

D. Increments Under the PSD Program 

Under section 165(a)(3) of the Act, a 

PSD permit applicant must demonstrate 

that emissions from the proposed 

construction and operation of a facility 

‘‘will not cause, or contribute to, air 

pollution in excess of any (A) maximum 

allowable increase or maximum 

allowable concentration for any 

pollutant * * *.’’ The ‘‘maximum 

allowable increase’’ of an air pollutant 

that is allowed to occur above the 

applicable baseline concentration for 

that pollutant is known as the PSD 

increment. By establishing the 

maximum allowable level of ambient 

pollutant concentration increase in a 

particular area, an increment defines 

‘‘significant deterioration’’ of air quality 

in that area. 

For PSD baseline purposes, a baseline 

area for a particular pollutant emitted 

from a source includes the attainment or 

unclassifiable area in which the source 

is located, as well as any other 

attainment or unclassifiable area in 

which the source’s emissions of that 

pollutant are projected (by air quality 

modeling) to result in a significant 

ambient pollutant increase. See, e.g., 40 

CFR 52.21(b)(15)(i). Once the baseline 

area is established, subsequent PSD 

sources locating in that area need to 

consider that a portion of the available 

increment may have already been 

consumed by previous emissions 

increases. 

In general, the submittal date of the 

first complete PSD permit application in 

a particular area is the operative 

‘‘baseline date.’’ 3 On or before the date 

of the first complete PSD application, 

emissions generally are considered to be 

part of the baseline concentration, 

except for certain emissions from major 

stationary sources, as explained in the 

following discussion of baseline dates. 

Most emissions increases that occur 

after the baseline date will be counted 

toward the amount of increment 

consumed. Similarly, emissions 

decreases after the baseline date restore 

or expand the amount of increment that 

is available. 

In practice, three dates related to the 

PSD baseline concept are important in 

understanding how to calculate the 

amount of increment consumed— 

(1) Trigger date; (2) major source 

baseline date; and (3) minor source 

baseline date. The first relevant date is 

the trigger date. The trigger date, as the 

name implies, triggers the overall 

increment consumption process 

nationwide. Specifically, this is a fixed 

date, which must occur before the minor 

source baseline date can be established 

for the pollutant-specific increment in a 

particular attainment area. See, 40 CFR 

51.166(b)(14)(ii) and 52.21(b)(14)(ii). For 

PM (regulated as TSP) and SO2, 

Congress defined the applicable trigger 

date as August 7, 1977—the date of the 

1977 amendments to the Act when the 

original statutory increments were 

established by Congress. For nitrogen 

dioxide (NO2), we selected the trigger 

date as February 8, 1988—the date on 

which we proposed increments for NO2. 

See 53 FR 40656, 40658; October 17, 

1988. In this final rule, as described 

later, we are establishing a separate 

trigger date for purposes of 

implementing the PM2.5 increments. See 

section V.F of this preamble for 

additional discussion of the trigger date 

for PM2.5. 

The two remaining dates—‘‘minor 

source baseline date’’ and ‘‘major source 

baseline date’’—as described later, are 

necessary to properly account for the 

emissions that are to be counted toward 

the amount of increment consumed 

following the national trigger date, in 

accordance with the statutory definition 

of ‘‘baseline concentration’’ in section 

169(4) of the Act. The statutory 

definition provides that the baseline 

concentration of a pollutant for a 

particular baseline area is generally the 

air quality at the time of the first 

application for a PSD permit in the area. 

Consequently, any increases in actual 

emissions occurring after that date (with 

some possible exceptions that we will 

discuss later) would be considered to 

consume the applicable PSD increment. 

However, the statutory definition in 

section 169(4) also provides that 

‘‘[e]missions of sulfur oxides and 

particulate matter from any major 

emitting facility on which construction 

commenced after January 6, 1975, shall 

not be included in the baseline and 

shall be counted in pollutant 

concentrations established under this 

part.’’ 

To make this distinction between the 

date when emissions resulting from the 

construction at a major stationary source 

consume the increment and the date 

when emissions changes in general (i.e., 

from both major and minor sources) 

begin to consume the increment, we 

established the terms ‘‘major source 

baseline date’’ and ‘‘minor source 

baseline date,’’ respectively. See 40 CFR 

51.166(b)(14) and 52.21(b)(14). 

Accordingly, the ‘‘major source baseline 

date,’’ which precedes the trigger date, is 

the date after which actual emissions 

increases associated with construction 

at any major stationary source consume 

the PSD increment. In accordance with 

the statutory definition of ‘‘baseline 

concentration,’’ the PSD regulations 

define a fixed date to represent the 

major source baseline date for each 

pollutant for which an increment exists. 

Congress defined the major source 

baseline date for the statutory 

increments for PM and SO2 as January 

6, 1975. For the NO2 increments, which 

we promulgated in 1988 under our 

authority to establish an increment 

system under section 166(a) of the Act, 

the major source baseline date we 

selected was February 8, 1988—the date 

on which we proposed increments for 

NO2. 53 FR 40656. In both instances, the 

major source baseline date for the 

individual increments was set as a date 

which preceded the date on which the 

regulations pertaining to those 

increments were issued. In this final 

rule, as described later, we are 

establishing a separate major source 

baseline date for implementing the 

PM2.5 increments. See section V.F of this 

preamble for further discussion of the 

major source baseline date for PM2.5. 

The ‘‘minor source baseline date’’ is 

the earliest date after the trigger date on 

which a source or modification submits 

the first complete application for a PSD 

permit in a particular area. After the 

minor source baseline date, any increase 

in actual emissions (from both major 

and minor sources) consumes the PSD 

increment for that area. 

Once the minor source baseline date 

is established, the new emissions 

increase from that major source 

consumes a portion of the increment in 

that area, as do any subsequent actual 

emissions increases that occur from any 

new or existing source in the area. 

When the maximum pollutant 

concentration increase defined by the 

increment has been reached, additional 

PSD permits cannot be issued until 

sufficient amounts of the increment are 

‘‘freed up’’ via emissions reductions that 

may occur voluntarily, (e.g., via source 

shutdowns) or by mandatory control 

requirements imposed by the reviewing 

authority. Moreover, the air quality in a 

region cannot deteriorate to a level in 

excess of the applicable NAAQS, even 

if all the increment in the area has not 

been consumed. Therefore, new or 

modified sources located in areas where 

the air pollutant concentrations are near 

the level allowed by the NAAQS may 

not have full use of the amount of 


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4See EPA’s ‘‘Guideline on Air Quality Models’’ at 

40 CFR part 51, Appendix W. 

pollutant concentration increase 

allowed by the increment. 

Under EPA guidance, the actual 

increment analysis that a proposed new 

or modified source undergoing PSD 

review must complete depends on the 

area impacted by the source’s new 

emissions. We have provided approved 

air quality models and guidelines for 

sources to use to project the air quality 

impact of each pollutant (over each 

averaging period) for which an 

increment analysis must be done.4 In 

addition, we established SILs for each 

pollutant under the permit requirements 

applicable to new and modified major 

stationary sources locating in attainment 

areas that would cause or contribute to 

a violation of any NAAQS. See 40 CFR 

51.165(b) and part 51, Appendix S, 

section III.A. These SILs have also been 

used for implementing the PSD program 

to identify levels below which the 

source’s modeled impact of a particular 

pollutant is regarded as de minimis. In 

this final rule, we are establishing SILs 

(24-hour and annual) for PM2.5 that are 

being added to the aforementioned 

regulations containing SILs for other 

pollutants, as well as to the PSD 

regulations in 40 CFR 51.166 and 52.21. 

See further discussion of the SILs for 

PM2.5 in section VI of this preamble. 

In the event that a source’s modeled 

impacts of a particular pollutant are 

below the applicable SIL at all ambient 

air locations modeled, i.e., de minimis 

everywhere, EPA’s policy for PSD 

provides that no further modeling 

analysis is required for that pollutant. 

Our longstanding policy under the PSD 

program is that when a preliminary 

screening analysis based on the SIL is 

sufficient to demonstrate that the 

source’s emissions throughout the area 

modeled will not cause or contribute to 

a violation of the increment, there is no 

need for a comprehensive source impact 

analysis involving a cumulative 

evaluation of the emissions from the 

proposed source and other sources 

affecting the area. 

Within the impact area of a source 

subject to PSD, that is, the area within 

which the proposed project’s emissions 

increase does have a significant impact, 

increment consumption is calculated 

using the source’s proposed emissions 

increase, along with other actual 

emissions increases or decreases of the 

particular pollutant from any sources in 

the area, which have occurred since the 

minor source baseline date established 

for that area. In addition, the emissions 

increases or decreases from any major 

source that has commenced 

construction since the major source 

baseline date (which precedes the minor 

source baseline date) will consume or 

expand increment. Thus, an emissions 

inventory of sources whose emissions, 

in whole or in part, of a particular 

pollutant consume or expand the 

available increment in the area must be 

compiled. The inventory of incrementconsuming emissions includes not only 

sources located directly in the impact 

area, but sources outside the impact area 

that affect the air quality for the 

particular pollutant within the impact 

area. 

The inventory of incrementconsuming emissions includes 

emissions from increment-affecting 

sources at two separate time periods— 

the baseline date and the current period 

of time. For each source that was in 

existence on the relevant baseline date 

(major source or minor source), the 

inventory includes the source’s actual 

emissions on the baseline date and its 

current actual emissions. The change in 

emissions over these time periods 

represents the emissions that consume 

increment (or, if emissions have gone 

down, expand the available increment). 

For sources constructed since the 

relevant baseline date, all their current 

actual emissions consume increment 

and are included in the inventory. 

When the inventory of incrementconsuming emissions has been 

compiled, computer modeling is used to 

determine the change in ambient 

concentration that will result from these 

emissions when combined with the 

proposed emissions increase from the 

new major source or major modification 

that is undergoing PSD review. The 

modeling has generally been guided by 

the ‘‘Guideline on Air Quality Models’’ 

(40 CFR part 51, Appendix W), which 

includes provisions on air quality 

models and the meteorological data 

input into these models. The model 

output (expressed as a change in 

concentration) for each relevant 

averaging period is then compared to 

the corresponding allowable PSD 

increment. 

E. Historical Approaches for Developing 

Increments 

1. Congressional Enactment of 

Increments for PM and SO2

Congress established the first 

increments defining significant 

deterioration of air quality in the 1977 

Amendments to the Act. These 

amendments, among other things, added 

part C to title I, setting out the 

requirements for PSD. In section 163, 

Congress included numerical 

increments for PM and SO2 for Class I, 

II, and III areas. 

The three area classes are part of the 

increment system originally established 

by Congress. Congress designated Class 

I areas (including certain national parks 

and wilderness areas) as areas of special 

national concern, where the need to 

prevent deterioration of air quality is the 

greatest. Consequently, the allowable 

level of incremental change is the 

smallest relative to the other area 

classes, i.e., most stringent, in Class I 

areas. The increments of Class II areas 

are larger than those of Class I areas and 

allow for a moderate degree of 

emissions growth. For future 

redesignation purposes, Congress 

defined a ‘‘Class III’’ classification to 

allow the redesignation of any existing 

Class II area for which a State may 

desire to promote a higher level of 

industrial development (and emissions 

growth). Thus, Class III areas are 

allowed to have the greatest amount of 

pollutant increase of the three area 

classes while still achieving the 

NAAQS. To date, there have been no 

redesignations made to establish a Class 

III area. 

In establishing these PSD increments, 

Congress used the then-existing NAAQS 

for those pollutants as the benchmark 

for determining what constitutes 

‘‘significant deterioration.’’ Congress 

established the increments for PM as a 

percentage of the then-existing PM 

NAAQS. At the time the Act was 

amended in 1977, the NAAQS for PM 

were expressed in terms of ambient 

concentrations of TSP. Thus, EPA 

interpreted the statutory increments for 

PM using the same ambient TSP 

‘‘indicator.’’ 

2. EPA’s Promulgation of Increments for 

NO2 and PM10

Congress also provided authority for 

EPA to promulgate additional 

increments and to update the original 

PM increments created by statute. The 

EPA has promulgated two regulations 

pursuant to this authority. 

a. Increments for NO2 Using the 

‘‘Contingent Safe Harbor’’ Approach 

Under Section 166(a) of the Act 

Based on section 166(a) of the Act, on 

October 17, 1988, EPA promulgated 

increments for NO2 to prevent 

significant deterioration of air quality 

due to emissions of NOX (53 FR 40656). 

The EPA based these increments on 

percentages of the NAAQS in the same 

way that Congress derived the statutory 

increments for PM and SO2. Those NO2

increments were challenged in 1988 by 

the Environmental Defense Fund (EDF) 

when EDF filed suit in the U.S. Court of 


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5The term ‘‘air quality related values’’ is not 

defined in the Act, but the legislative history 

provides language saying that ‘‘The term ‘air quality 

related values’ of Federal lands designated as Class 

I includes the fundamental purposes for which such 

lands have been established and preserved by the 

Congress and the responsible Federal agency. For 

example, under the 1916 Organic Act to establish 

the National Park Service (16 U.S.C. 1), the purpose 

of such national park lands ‘is to conserve the 

scenery and the natural and historic objects and the 

wildlife therein and to provide for the enjoyment 

of the same in such manner and by such means as 

will leave them unimpaired for the enjoyment of 

future generations.’ ’’ S. Rep. No. 95–127 at 36 

(1977). 

6Under the 2005 NOX regulation, states can adopt 

measures other than increments as long as they can 

demonstrate that the measures selected comply 

with the same criteria and goals of sections 166(c) 

and (d) of the Act that must be met for increments. 

Appeals for the District of Columbia 

Circuit against the Administrator 

(Environmental Defense Fund, Inc. v. 

Reilly, No. 88–1882). The EDF 

successfully argued that we failed to 

sufficiently consider certain provisions 

in section 166 of the Act. The court 

remanded the case to EPA ‘‘to develop 

an interpretation of section 166 that 

considers both subsections (c) and (d), 

and if necessary to take new evidence 

and modify the regulations.’’ See 

Environmental Defense Fund v. EPA, 

898 F.2d 183, 190 (D.C. Cir. 1990) (EDF 

v. EPA). Section 166(c) of the Act 

requires the PSD regulations to, among 

other things, meet the goals and 

purposes set forth in sections 101 and 

160 of the Act. Section 166(d) requires 

these regulations be at least as effective 

as the increments established for PM (in 

the form of TSP) and SO2 in section 163 

of the Act. The court considered the 

NO2 increment values determined using 

the percentage-of-NAAQS approach as 

‘‘safe harbor’’ increments which met the 

requirements of section 166(d) of the 

Act. However, the court also determined 

that EPA’s reliance on such increment 

levels was contingent upon our 

completing the analyses required under 

section 166(c), which provided that the 

final increment values must address the 

goals of sections 101 and 160 of the Act 

to protect public health and welfare, 

parks, and AQRVs 5 and to insure 

economic growth. 

In response to the court’s decision, we 

proposed rulemaking on increments for 

NO2 on February 23, 2005 (70 FR 8880) 

and finalized the rule on October 12, 

2005 (70 FR 59582). In the final rule, we 

established our policy on how to 

interpret and apply the requirements of 

sections 166(c) and (d) of the Act. In 

accordance with the court ruling, we 

conducted further analyses (considering 

the health and welfare effects of NOX) 

and concluded that the existing NO2

increments were adequate to fulfill the 

requirements of section 166(c). See 70 

FR 59586 for our detailed analysis of 

how pollutant regulations satisfy the 

requirements of section 166 of the Act. 

Hence, we retained the existing NO2

increments along with other parts of the 

existing framework of pollutant-specific 

NO2 increment regulations. We also 

amended the PSD regulations under 40 

CFR 51.166 to make it clear that states 

may seek EPA approval of SIPs that 

utilize a different approach than EPA 

used to establish these NO2 increments. 

To receive our approval of an alternative 

program, a State must demonstrate that 

its program satisfies the requirements of 

sections 166(c) and 166(d) of the Act 

and prevents significant deterioration of 

air quality from emissions of NOX.6

b. Increments for PM10 Using 

‘‘Equivalent Substitution’’ Approach 

Under Section 166(f) of the Act 

On October 5, 1989, we proposed 

PM10 increments. See 54 FR 41218. 

Although section 163 did not expressly 

define the existing statutory increments 

for PM in terms of a specific indicator, 

EPA reasoned that Congress’ knowledge 

that TSP was the indicator for the PM 

NAAQS, and that the TSP standards 

were the starting point for the 

increments levels when the increments 

were established in 1977, meant that 

TSP was also the appropriate measure 

for the PM increments in section 163. 

As a consequence, EPA believed that the 

statutory PM increments could not 

simply be administratively redefined as 

PM10 increments, retaining the same 

numerical values, following the revision 

of the PM NAAQS. Rather, we stated 

our belief that with the promulgation of 

the PM10 NAAQS, EPA had both the 

responsibility and the authority under 

sections 166 and 301 of the Act to 

promulgate new increments for PM to 

be measured in terms of PM10. We 

further concluded that promulgating 

PM10 increments to replace, rather than 

supplement, the statutory TSP 

increments under section 163 

represented the most sensible approach 

for preventing significant deterioration 

with respect to PM. See 54 FR 41220– 

41221. 

We promulgated PM10 increments to 

replace the then-existing TSP 

increments on June 3, 1993 (58 FR 

31622). In the interim between proposal 

and promulgation, Congress enacted the 

1990 CAA Amendments. As part of 

these amendments, Congress amended 

section 166 to add a new section 166(f). 

This section specifically authorized EPA 

to substitute PM10 increments for the 

existing section 163 PM increments 

based on TSP, provided that the 

substituted increments are ‘‘of equal 

stringency in effect’’ as the section 163 

increments. 

Thus, we were able to replace the TSP 

increments under section 163 of the Act 

using PM10 increments based directly on 

the newly enacted authority under 

section 166(f) of the Act. In the PM10

rule, we maintained the existing 

baseline dates and baseline areas for PM 

that had been previously established 

using the TSP indicator. Also, as 

proposed, we promulgated PM10

increments based on an approach we 

called the ‘‘equivalent to statutory 

increments’’ approach. Under this 

approach, we used the original TSP 

increments as a benchmark for 

calculating the PM10 increments, 

thereby retaining roughly the same 

limitations on future deterioration of air 

quality as was allowed under the TSP 

increments. 

In using this approach, we considered 

the historical consumption of TSP 

increment by a sample population of 

permitted PSD sources, and then 

determined the PM10 increments for 

each area classification and averaging 

time that would provide approximately 

the same percentage of PM10 increment 

consumption, on average, by the same 

population of sources. Then, all future 

calculations of increment consumption 

after the PM10 implementation date 

would be based on PM10 emissions. See 

58 FR 31622 and 31625. 

V. Final Action on PM2.5 Increments 

In this section of the preamble, we 

will summarize the considerations that 

went into our proposed action and 

describe the final action being taken 

regarding new regulations for 

preventing significant deterioration of 

PM2.5 air quality—including PM2.5

increments (sections V.A through V.E, 

baseline dates and other permit 

requirements for PM2.5 (section V.F), 

baseline areas for PM2.5 (section V.G), 

and PM10 increments (section V.H). 

A. Decision To Establish PM2.5

Increments Using ‘‘Contingent Safe 

Harbor Approach’’ Under Section 166(a) 

The EPA’s 2007 NPRM contained 

three options for developing numerical 

PM2.5 increments. Option 1 used the 

authority of section 166(a) of the Act to 

establish increments for PM2.5 as a new 

pollutant for which NAAQS were 

established after August 7, 1977, and 

established 24-hour and annual PM2.5

increments (Class I, II, and III) based on 

the ‘‘contingent safe harbor’’ approach. 

Options 2 and 3 used the contingent 

safe harbor approach under section 

166(a) to only develop 24-hour PM2.5

increments (Class I, II, and III), while 

using the ‘‘equivalent substitution’’ 


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approach under section 166(f) of the Act 

to develop annual PM2.5 increments. 

Each of these options is discussed in 

detail in the 2007 NPRM. 72 FR 54123– 

54138. In addition, significant 

comments on each of the three options, 

and our responses to them, are provided 

in this section V of this preamble. 

In this final rule, after considering the 

available information and comments 

from interested parties, EPA has 

decided to select Option 1 and establish 

increments for PM2.5 using the 

‘‘contingent safe harbor’’ approach in 

accordance with the authority provided 

in section 166(a) of the Act. 

This final rule establishes increments 

for PM2.5 at the following levels: 

Averaging period NAAQS 

(μg/m3) 

Increments (μg/m3) 

Class I Class II Class III 

Annual .............................................................................................................................. 15 1 4 8 

24-hour ............................................................................................................................. 35 2 9 18 

B. Rationale for the Applicability of 

Section 166(a) 

In the 2007 NPRM, we expressed our 

belief that it is permissible to interpret 

section 166(a) to apply to PM2.5. Section 

166(a) requires EPA to develop 

regulations to prevent the significant 

deterioration of air quality due to 

emissions of certain named pollutants, 

and to develop such regulations for any 

pollutants for which NAAQS are 

subsequently promulgated. Although 

EPA has generally characterized the 

NAAQS for PM2.5 as a NAAQS for a new 

indicator of PM, EPA did not replace the 

PM10 NAAQS with the NAAQS for 

PM2.5 when the latter NAAQS were 

promulgated in 1997. Rather, EPA 

retained the annual and 24-hour PM10

NAAQS (retaining PM10 as an indicator 

of coarse particulate matter), and 

established new annual and 24-hour 

NAAQS for PM2.5 as if PM2.5 was a new 

pollutant, even though EPA had already 

developed air quality criteria for PM 

generally. Thus, for purposes of section 

166(a), the promulgation of a NAAQS 

for PM2.5 established a NAAQS for an 

additional pollutant after 1977. 

Nine commenters supported our 

proposed Option 1, although only three 

of these explicitly expressed support for 

the use of section 166(a) authority to 

promulgate PM2.5 increments. Ten other 

commenters specifically opposed the 

use of section 166(a) authority and/or 

supported the use of section 166(f) 

authority (on which the annual 

increments under Options 2A and 2B 

were based). 

One of the commenters who explicitly 

agreed with our proposed use of section 

166(a) authority stated that it is the only 

option that is legally available. This 

commenter asserted that section 166(a) 

plainly applies to PM2.5 because PM2.5 is 

a pollutant for which NAAQS were 

promulgated after August 7, 1977. This 

commenter held that EPA’s rulemaking 

duty under section 166(a) is not 

confined to ‘‘new pollutants,’’ but is 

triggered by post-1977 NAAQS 

promulgations, regardless of whether for 

new or previously regulated pollutants. 

On the other hand, this commenter 

noted that by its terms, section 166(f) is 

limited to authorizing the adoption of 

PM10 increments as a substitute for the 

statutory TSP increments and does not 

provide for substitution of PM2.5

increments for TSP or PM10 increments. 

The opposing commenters did not 

believe that section 166(a) provides a 

legal basis for EPA to promulgate PM2.5

increments. One of these commenters 

stated that section 166(a) can only be 

used for a new pollutant, and PM2.5 is 

not a new pollutant. 

Another commenter who opposed the 

use of section 166(a) authority argued 

that nothing in section 166(a) of the Act 

can be interpreted to allow it to be used 

as the basis of increments when EPA 

revises an existing NAAQS. The 

commenter explained that, on its face, 

section 166(a) can only be interpreted to 

apply to pollutants other than PM and 

SO2 since increments for these 

pollutants were enacted by Congress in 

section 163 of the Act. The commenter 

added that it can be argued that 

Congress intended to have section 

166(a) apply to the four other pollutants 

specifically listed there. 

This commenter found unpersuasive 

our argument that we are not 

‘‘substituting’’ increments (as section 

166(f) requires for PM10) but rather 

adding PM2.5 increments to the existing 

PM10 increments, and that only section 

166(a) allows such an approach (72 FR 

54121). The commenter asserted that if 

EPA had defined a coarse fraction to the 

particulate matter standards, then that 

fraction, together with the PM2.5

standards, would form the set of 

‘‘substituted’’ new standards for the 

existing PM10 standards, and, thus, the 

increments. 

The commenter also disagreed with 

EPA’s argument that it can treat PM2.5 as 

a new pollutant under section 166(a) of 

the Act since it has been demonstrated 

that sub-PM2.5 particles have distinctly 

different health and welfare effects than 

the other forms of PM (i.e., coarse or 

PM10). The commenter indicated that 

just as EPA replaced the TSP standards 

by PM10 as a better indicator of health 

effects, ongoing research has led to 

establishment of the PM2.5 standards as 

a better indicator of certain health 

effects, and it is the natural outcome of 

such research that has enabled EPA to 

separate the effect of total particulate 

matter into two fractions with distinct 

effects. The commenter added that given 

that the definition of particulate matter 

includes a vast conglomeration of solids 

and liquids, the finding of differing 

effects should not come as a surprise. 

The commenter explained that as is the 

case of different pollutants having 

similar effects that are, nonetheless, 

treated as separate pollutants, the same 

concept should apply to a range or 

fraction of particulate matter found to 

have different effects in establishing it 

as another indicator and not a different 

pollutant. 

The commenter did not disagree with 

the specific numerical increments 

proposed by EPA under Option 1, but 

did have concerns with the potential 

consequences of the section 166(a) 

approach. The commenter’s primary 

concern was the proposal to allow states 

to substitute other measures in the place 

of uniform national increments for 

PM2.5. (This is discussed further in 

section V.C.5 of this preamble.) Another 

commenter also expressed this concern. 

Another commenter who opposed the 

section 166(a) approach believes that 

the legal and congressional history 

regarding the establishment of PM 

increments shows that Congress added 

section 166(f) to the Act based on the 

conviction that without it, EPA had no 

authority to revise the PM increments 

for PM10 (citing and quoting from S. 

Rep. No. 228, 101st Cong., 2nd Sess. 75 

(1990), reprinted in 1990 U.S.C.C.A.N. 

3385, 3461). The commenter concluded 

that EPA did not have authority in 1987 

under section 166(a) to adopt PM10

increments, and does not have authority 

now under section 166(a) to adopt PM2.5

increments. 

We read section 166(a) to authorize 

EPA to promulgate pollutant-specific 

PSD regulations meeting the 


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7We also believe that we sufficiently described 

how section 166(f) might provide alternative 

authority for establishing increments for PM2.5 (see, 

e.g., 72 FR 54120–54121), but will not address that 

in detail here because the increments in this rule 

are not based on section 166(f) authority. 

requirements of sections 166(c) and 

166(d) for any pollutant for which EPA 

promulgates a NAAQS after 1977. Most 

of the pollutants identified in section 

166(a) (NOX, photochemical oxidants, 

carbon monoxide) are pollutants for 

which EPA had established NAAQS in 

1977 when Congress adopted section 

166 of the Act. There was no need for 

Congress to list other criteria pollutants, 

SO2 and PM, in section 166(a) because 

Congress had already established 

increments for these pollutants in 

section 163 of the Act. In addition to 

requiring regulations for the enumerated 

pollutants, we conclude that under 

section 166 of the Act Congress 

intended to authorize EPA to establish 

additional pollutant-specific PSD 

regulations, potentially containing 

increments, for any additional 

pollutants for which EPA promulgated a 

NAAQS under section 109 of the Act. 

Furthermore, because the Act refers to 

pollutants for which EPA promulgates 

NAAQS after 1977, and does not use the 

phrase ‘‘additional pollutants,’’ section 

166(a) provides authority for EPA to 

promulgate new increments after 

revising an existing NAAQS (including 

NAAQS first promulgated before 1977), 

when we find that such action is 

appropriate. 

Moreover, any new increments 

developed pursuant to section 166(a) 

have no effect on existing increments, as 

there is no indication therein that an 

existing increment should be revoked or 

replaced when additional increments 

are promulgated. This was the situation 

following the promulgation of new 

NAAQS for PM in 1987 when EPA 

replaced the old NAAQS based on TSP 

with new ones based on PM10. Had 

Congress not added new section 166(f) 

in 1990, increments for PM10 could have 

been developed pursuant to section 

166(a) of the Act, but such increments 

would have had no effect on the original 

statutory increments for PM (based on 

TSP). Consequently, seeing no basis for 

retaining the original increments, 

Congress added section 166(f) which 

explicitly provides for the replacement 

of the existing increments with PM10

increments. 

One commenter asserted that if EPA 

establishes increments for PM2.5 under 

the authority of section 166(a) on the 

basis that PM2.5 is a new pollutant, then 

it must also establish PM10 increments 

under section 166(a) because (according 

to the commenter’s analysis) PM10 is 

also a new pollutant. In the same 

analysis, the commenter concluded that 

EPA must adopt new measures to 

prevent significant deterioration from 

coarse PM based on section 166(a). 

In this final rule, EPA is not setting or 

amending any increments for PM10 or 

otherwise taking action with respect to 

PM10 increments. The preexisting 

annual and 24-hour increments for PM10

are being retained. See section V.H. 

Similarly, EPA is not taking any action 

with respect to coarse PM in this rule. 

For these reasons, the commenter’s 

arguments on what authority must be 

used to set increments for PM10 and/or 

coarse PM, and that EPA has some 

obligation to take action with respect to 

coarse PM, are not on point for this rule. 

Thus, no substantive response to this 

comment is needed. Nevertheless, as 

mentioned earlier, Congress provided 

explicit authority under section 166(f) of 

the Act to address increments for PM10,

because it intended for such increments 

to be substitute increments for the 

original statutory increments for PM 

measured as TSP. Thus, the PM10

increments legally supersede the 

original statutory increments for PM. 

Had the PM10 increments been 

developed under section 166(a), which 

prior to the 1990 Act Amendments was 

the only authority available for 

developing new increments, then the 

original statutory PM increments would 

have remained in effect in addition to 

the PM10 increments. 

One commenter expressed general 

objections to EPA’s legal rationale for 

the PM2.5 increments proposal, asserting 

that we failed to expressly state and 

support our legal authority for the PM2.5

increments, offering two possible 

sources of authority (‘‘contingent safe 

harbor,’’ ‘‘equivalent substitution,’’ or 

possibly a combination of the two) but 

never stating our legal position with 

clarity. The commenter agreed with 

EPA’s assessment that the PM2.5

increments should and must fulfill the 

legal requirements of the Act (72 FR 

54121), and added that it is the 

government’s burden of proof to 

establish its legal authority for action. 

The commenter stated that it would be 

arbitrary and capricious to promulgate 

these regulations for which EPA has not 

stated legal authority. 

We do not disagree that the 2007 

NPRM described two different legal 

authorities for the two different options 

for establishing increments, but we 

disagree that these discussions did not 

clearly present the alternative legal 

bases that the Agency was considering 

for taking action in this rule. In 

particular, we clearly described our 

legal authority for developing the 24- 

hour and annual PM2.5 increments 

under section 166(a) of the Act, which 

is the basis on which we are taking final 

action in this rule.7 First, we expressly 

stated that Option 1 was based on the 

statutory authority of section 166(a) of 

the Act. See 72 FR 54123 (Under the 

first option, ‘‘we would use the authority 

of section 166(a) of the Act to develop 

new increments for PM2.5’’). Second, we 

provided a discussion of this authority 

both in general (see 72 FR 54118–54119 

and 54120–54123), and how it would be 

applied to establish increments for 

PM2.5 (see 72 FR 54119–120 and 54123– 

136). 

We now believe that section 166(a) 

provides the most straightforward 

approach for developing increments for 

a pollutant or pollutant indicator for 

which no increments have yet been 

established. Our position is also 

consistent with the comments we 

received which supported the delay in 

implementation of the PM2.5

increments, opposed the potential for 

two sets of definitions for ‘‘major source 

baseline date’’ and ‘‘trigger date’’ for the 

PM2.5 increment system, and 

highlighted the complexities involved 

with having to establish and maintain 

two sets of emissions inventories for the 

24-hour and annual PM2.5 increments. 

(See further description of relevant 

comments in section VIII of this 

section.) 

C. EPA’s Interpretation of the 

Requirements Under Sections 166(a)–(d) 

of the Act 

In section 166(a) of the Act, Congress 

directed EPA to develop pollutantspecific regulations to prevent 

significant deterioration of air quality. 

Congress further specified that such 

regulations meet specific requirements 

set forth in sections 166(c) and 166(d) of 

the Act. We stated in the 2007 NPRM 

that because we believed that section 

166(a) could be applied to the 

development of increments for PM2.5, 

we would follow the interpretation of 

sections 166(a)–(d) that the Agency 

adopted in its most recent NO2

increments rule. 70 FR 59582, October 

12, 2005. That particular interpretation 

and application was upheld in 

Environmental Defense v. EPA, 489 F.3d 

1320 (D.C. Cir. 2007). 

The EPA’s interpretation of these 

provisions is grounded on five 

principles and conclusions. First, we 

read section 166 of the Act to direct EPA 

to conduct a holistic analysis that 

considers how a complete system of 

regulations will collectively satisfy the 


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applicable criteria, rather than 

evaluating one individual part of a 

regulatory scheme in isolation. Second, 

we use a ‘‘contingent safe harbor’’ 

approach which calls for EPA to first 

determine an increment that is at least 

as effective as the increments in section 

163 of the Act, as required under section 

166(d) and then to conduct further 

analysis to determine if additional 

measures are necessary to fulfill the 

requirements of section 166(c). Third, 

we interpret section 166(c) of the Act to 

identify eight statutory factors that EPA 

must apply when promulgating 

pollutant-specific regulations to prevent 

significant deterioration of air quality. 

Fourth, where these factors are at odds 

with each other, we interpret the statute 

to require EPA to use its judgment to 

balance the conflicting factors. Fifth, we 

recognize that the requirements of 

section 166 may be satisfied by adopting 

other measures besides an increment 

and that EPA may allow states to 

demonstrate that alternatives to 

increments contained in a SIP meet the 

requirements of sections 166(c) and 

166(d). Below is a brief discussion of 

each of these five principles and 

conclusions. A more detailed 

description of each of these is contained 

in the 2007 NPRM at 72 FR 54121– 

54123. 

1. Regulations as a Whole Should Fulfill 

Statutory Requirements 

Section 166(a) of the Act directs EPA 

to develop pollutant-specific regulations 

to prevent the significant deterioration 

of air quality. Sections 166(c) and 166(d) 

provide detail on the contents of those 

regulations, but do not necessarily 

require the same type of increment 

system Congress created in section 163 

of the Act. The EPA interprets section 

166 to require that the entire system of 

PSD regulations (the framework and 

details, as described in section V.D of 

this preamble) for a particular pollutant 

must, as a whole, satisfy the criteria in 

sections 166(c) and 166(d) of the Act. 

2. Contingent Safe Harbor Approach 

Section 166(c) of the Act describes the 

kinds of measures to be contained in the 

regulations to prevent significant 

deterioration of air quality called for in 

section 166(a) and specifies that these 

regulations are to ‘‘fulfill the goals and 

purposes’’ set forth in sections 160 and 

101 of the Act. Section 166(d) of the Act 

directs EPA to ‘‘fulfill such goals and 

purposes’’ by providing ‘‘specific 

measures at least as effective as the 

increments established in section 163 

* * *.’’ Thus, EPA reads section 166(d) 

to require that the Agency identify ‘‘safe 

harbor’’ pollutant-specific PSD 

regulations adopted under section 166. 

The EPA reads section 166(c) to 

require that the Agency conduct further 

review to determine whether, based on 

the criteria in section 166(c), EPA’s 

pollutant-specific PSD regulations 

under section 166 should contain 

measures that are different from the 

‘‘safe harbor’’ identified under section 

166(d). The EPA construes section 

166(d) to require that the measures be 

‘‘at least as effective’’ as the statutory 

increments set forth in section 163. 

To apply the ‘‘contingent safe harbor’’ 

approach for PM2.5, we first identified 

‘‘safe harbor’’ increments for each area 

classification (Class I, II, or III), using: 

(1) Equivalent percentages of the 

NAAQS as the percentages used for 

developing the statutory increments; (2) 

the same pollutant as the NAAQS, i.e., 

PM2.5, and (3) the same time (averaging) 

periods as were used for the PM2.5

NAAQS. We concluded that this 

approach would ensure that the 

increments would be ‘‘at least as 

effective as the increments established 

in section 163,’’ as required by section 

166(d). Second, EPA conducted further 

review to determine whether the ‘‘safe 

harbor’’ increments, in conjunction with 

existing elements of the PSD program or 

additional measures proposed under 

section 166 to augment the increments, 

sufficiently fulfill the criteria in 

subsection (c) of section 166. 

In this review, we weighed and 

balanced the criteria set forth in 

subsection (c) (and, as provided in 

subsection (c), the incorporated goals 

and purposes of the Act in section 101 

and the PSD program in section 160) to 

determine whether additional measures 

might be needed to satisfy the criteria in 

subsection (c). See section V.E.6 of this 

preamble for further discussion of our 

evaluation, comments on the evaluation, 

and our response to them. 

3. The Statutory Factors Applicable 

Under Section 166(c) 

The EPA interprets section 166(c) of 

the Act to establish eight factors to be 

considered in the development of PSD 

regulations for the pollutants covered by 

this provision. These eight factors 

included the three criteria stated in 

section 166(c) and the five goals and 

purposes identified in section 160 of the 

Act (which, as noted below, also cover 

the goals and purposes set forth in 

section 101). The three stated criteria in 

section 166(c) indicate that PSD 

regulations for specific pollutants 

should provide: (1) Specific numerical 

measures for evaluating permit 

applications; (2) a framework for 

stimulating improved control 

technology, and (3) protection of air 

quality values. The five goals and 

purposes in section 160 are 

incorporated into the analysis by virtue 

of the fourth criterion in section 166(c), 

which directs that EPA’s pollutantspecific PSD regulations ‘‘fulfill the 

goals and purposes’’ set forth in sections 

160 and 101 of the Act. We construed 

the term ‘‘fulfill the goals and purposes,’’ 

as used in section 166(c), to mean that 

EPA should apply the goals and 

purposes listed in section 160 as factors 

applicable to pollutant-specific PSD 

regulations established under section 

166. The Agency’s view is that PSD 

measures that satisfy the specific goals 

and purposes of section 160 also satisfy 

the more general purposes and goals 

identified in section 101 of the Act. See 

72 FR 54122. 

One commenter disagreed with our 

interpretation that the goals and 

purposes of section 160 also satisfy all 

of those in section 101. This commenter 

asserted that although there is some 

overlap between the two sections, they 

are not identical. As an example, the 

commenter noted that section 101 

expressly states that a primary goal of 

the Act is to promote pollution 

prevention—a goal not stated in section 

160. The commenter asserted that, 

although the proposed increments 

would limit some pollution increases, 

there was no provision in the proposal 

that would require or promote pollution 

prevention. 

We disagree with the commenter and 

continue to believe that measures that 

satisfy the specific goals and purposes 

of section 160 also satisfy the more 

general purposes and goals identified in 

section 101 of the Act. As we stated in 

the 2005 NO2 increment rulemaking, the 

overall goals and purposes of the Act 

listed in sections 101(b) and 101(c) are 

general goals regarding protecting and 

enhancing the nation’s air resources and 

controlling and preventing pollution. 

Because these broad goals are given 

more specific meaning in section 160, 

EPA does not believe it is necessary to 

consider them in detail when evaluating 

whether PSD regulations satisfy the 

criteria in section 166(c). 70 FR 59587 

FN 3. 

Regarding pollution prevention 

specifically, we believe that this general 

goal is encompassed in, and given more 

specific meaning by, sections 160(1), 

160(2), and 160(4) of the Act. These 

sections spell out the specific purposes 

under the PSD program for the general 

section 101 goals of controlling and 

preventing pollution. We believe that 

any requirement to limit or reduce 

emissions serves to promote pollution 

prevention, which is often the most cost 


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effective means of lowering pollutant 

emissions. 

In addition to citing the purposes set 

out in section 160, section 166(c) 

includes the criterion that pollutantspecific PSD regulations should provide 

a framework for stimulating improved 

control technology. As discussed 

subsequently in sections V.D.1 and 

V.D.6 of this preamble, we believe that 

this criterion is fulfilled by the system 

of increments for PM2.5 and by the 

requirement for PSD permittees to apply 

BACT to minimize PM2.5 emissions. In 

stimulating improved control 

technology generally, these elements of 

the PSD program also promote pollution 

prevention. As noted previously, 

pollution prevention is often the most 

cost effective means of control, 

particularly for new sources and new 

process lines at existing sources. In 

addition, because BACT is a case-bycase determination that considers cost 

and collateral environmental impacts, 

pollution prevention, where technically 

feasible, often fairs well in BACT 

analyses because it is typically free from 

the negative environmental impacts that 

result from the use of add-on air 

pollution control devices. 

4. Balancing the Factors Applicable 

Under Section 166(c) 

While the eight factors in section 

166(c) are generally complementary, 

there are circumstances where some of 

the objectives may be in conflict with 

each other. In these situations, some 

degree of balance or accommodation is 

inherent in the requirement to establish 

regulations that satisfy all of these 

factors. As first discussed in our 2005 

NO2 increments rulemaking (70 FR 

59582 at 59587), we believe this 

balancing test derives primarily from 

the third goal and purpose set forth in 

section 160: To insure economic growth 

consistent with the preservation of 

existing clean air resources. A more 

detailed discussion of how the 

balancing of factors should be 

interpreted is contained in the 2007 

NPRM at 72 FR 54122–54123. 

One commenter claimed that EPA 

‘‘incorrectly and repeatedly asserts’’ that 

a goal of section 160 of the Act is to 

insure economic growth. The 

commenter claimed that neither section 

160 nor section 101 of the Act uses 

language to support a goal of promoting 

or maximizing opportunities for 

economic growth. Instead, the 

commenter asserted that both sections 

state only that any growth that does 

occur must be consistent with 

protection of air quality. The commenter 

concluded that ‘‘EPA’s notion that the 

need to satisfy the other requirements of 

Section 166 and other goals and 

purposes in Sections 101 and 160 can 

never preclude additional emissions 

from economic growth unlawfully 

elevates such growth over all other 

statutory factors.’’ 

The language in section 160(3) 

provides that one of the purposes of the 

PSD program is ‘‘to insure that economic 

growth will occur in a manner 

consistent with the preservation of 

existing clean air resources.’’ The 

commenter suggests that this language 

can only be read as if the statutory 

phrase ‘‘economic growth’’ actually said 

‘‘any economic growth that does occur’’ 

such that section 160(3) says ‘‘to insure 

that any economic growth that does 

occur will occur in a manner consistent 

with the preservation of existing clean 

air resources.’’ We disagree; the phrasing 

used by Congress is ‘‘to insure that 

economic growth will occur.’’ Thus, we 

believe the plain language of the statute 

supports EPA’s reading that section 

160(3) requires a balancing of the goals 

of (1) economic growth and (2) 

preservation of existing clean air 

resources. At a minimum, if the 

language were to be considered 

ambiguous enough to allow the 

commenter’s reading, then the Agency’s 

interpretation is also a reasonable 

reading of the statutory language. 

5. Authority for States To Adopt 

Alternatives to Increments 

While section 166 of the Act 

authorizes EPA to promulgate 

increments for pollutants listed under 

section 166(a), we have also interpreted 

the section to allow states to employ 

approaches other than increments to 

prevent significant deterioration of air 

quality, so long as such an approach 

otherwise meets the requirements of 

sections 166(c) and 166(d). This 

interpretation was explained in the 2005 

NO2 increment rulemaking (70 FR 

59611–59612), in which we amended 

the PSD regulations at 40 CFR 51.166 by 

adding new paragraph (c)(2) to codify 

this statutory authority. Under the 

existing provision in 40 CFR 

51.166(c)(2), states may seek EPA 

approval of SIPs that use an alternative 

approach to increments if the State can 

demonstrate that the alternative 

program satisfies the requirements of 

sections 166(c) and 166(d). However, 

the current language at paragraph (c)(2) 

states the authority for states to adopt 

alternative measures only with respect 

to increments for NO2. To clarify our 

interpretation that the authority to adopt 

alternative measures covers any 

pollutant listed in section 166(a), we are 

revising 40 CFR 51.166(c)(2) to make it 

inclusive to all applicable pollutants 

rather than just NO2. 

Two commenters supported our 

proposal to revise paragraph (c)(2) to 

include PM2.5, while four State/local 

agency commenters expressed 

opposition. An environmental 

commenter agreed that the Act allows 

for other approaches, but believes that 

such approaches must be in addition to 

the national increments. Specifically, 

this commenter stated that ‘‘although 

EPA can provide for states to adopt 

approaches in addition to increments in 

order to fulfill the statutory purposes, 

the agency must make clear that states 

cannot adopt approaches that are less 

protective that the national increments.’’ 

This commenter further stated that ‘‘to 

the extent that EPA is suggesting that it 

can allow states to adopt PSD programs 

that do not include the minimum 

Federal increments, that position is 

contrary to the statute.’’ 

As in the 2005 NO2 increment 

rulemaking, we are codifying the basic 

principle that states can seek to use 

alternative measures without defining 

any specific type of alternative program 

that would be approved or otherwise 

creating standards beyond the 

requirements of sections 166(c) and 

166(d). Instead, we plan to make 

determinations on a case-by-case basis 

when a State submits a specific 

alternative approach for EPA to approve 

as part of a SIP. In making those 

determinations, we will address the 

specific alternative measures as states 

propose them to the Agency in light of 

the requirements of sections 166(c) and 

166(d), including whether the 

alternative program is ‘‘at least as 

effective as the increments established 

in section 163,’’ as required in section 

166(d). 

The four State/local agency 

commenters opposing the revision to 40 

CFR 51.166(c)(2) expressed the 

importance of using uniform national 

increments for PM2.5. One commenter 

argued that a nationally inconsistent 

approach to PM2.5 in attainment areas 

could result in a patchwork of State PSD 

regulations—and the exact kinds of 

economic repercussions that Congress 

wished to avoid. The same commenter 

argued that varying incrementequivalent measures could also result in 

an uneven playing field for industry and 

could exacerbate difficulties between 

states experiencing transport problems. 

Another opposing commenter was 

concerned that allowing states to adopt 

alternatives to increments would likely 

lead to a ‘‘mish-mash’’ of State 

approaches which defeats the intention 

of Congress that there be uniformity in 

PSD rules to avoid economic 


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dissimilarities from State to State that 

could allow interstate competition for 

industry based upon which State offers 

the best (least expensive) environmental 

compliance regulations. Another 

commenter objected to allowing the use 

of alternatives to increments by stating 

that such alternative allowances 

undermine the desired national 

consistency, and EPA has failed to even 

identify any Act programs which would 

benefit from this approach. 

While we acknowledge the potential 

problems identified by the commenters 

associated with allowing states to adopt 

alternative approaches to the numerical 

increments that we are establishing, we 

also note that section 166(d) expressly 

gives EPA some latitude in 

promulgating regulations that will be at 

least as effective as the increments in 

section 163, by stating that such 

regulations ‘‘may contain air quality 

increments, emission density 

requirements, or other measures.’’ Thus, 

EPA is authorized to provide that states 

may consider alternatives to the 

increments established in this rule. That 

said, the statutory authority is not a 

blank check for states to do as they 

please, but enables states to consider 

options that may provide a meaningful 

way for them to manage their air 

resources within the framework allowed 

by the statutory PSD requirements. 

D. Framework for Pollutant-Specific 

PSD Regulations for PM2.5

In the 2007 NPRM, we proposed to 

apply the same basic framework for 

pollutant-specific PSD regulations for 

PM2.5 that we used in our 2005 NO2

increments regulations. Specifically, we 

proposed adopting an increment and 

area classification system for PM2.5 and 

applying the statutory AQRV review 

process to PM2.5 as well. We also 

indicated that while some of the factors 

applicable under section 166(c) are 

fulfilled by using this type of framework 

for pollutant-specific PSD regulations 

under section 166(a) of the Act, this 

framework of regulations also needs to 

satisfy the other applicable factors. 

Thus, the details of our regulations 

(such as the characteristics of the 

increments themselves) are important, 

and we evaluated the effectiveness of 

the framework in conjunction with more 

detailed elements of our regulations. As 

discussed in the following subsections, 

we believe our obligations under section 

166(c) of the Act are satisfied when the 

PSD regulations collectively satisfy the 

factors applicable under 166(c) of the 

Act. 

1. Increment System 

An increment-based program satisfies 

the requirements under 166(c) to 

provide ‘‘specific numerical measures 

against which permit applications may 

be evaluated.’’ An increment is the 

maximum allowable level of ambient 

pollutant concentration increase that is 

allowed to occur above the applicable 

baseline concentration in a particular 

area. As such, an increment defines 

‘‘significant deterioration.’’ Establishing 

an increment system for PM2.5 will 

fulfill two of the factors applicable 

under section 166(c): (1) Providing 

specific numerical measures to evaluate 

permit applications, and (2) stimulating 

improved control technology. 

First, under section 165(a)(3) of the 

Act, a permit applicant must 

demonstrate that emissions from the 

proposed construction and operation of 

a facility ‘‘will not cause, or contribute 

to, air pollution in excess of any (A) 

maximum allowable increase or 

maximum allowable concentration for 

any pollutant * * *.’’ Once the baseline 

date associated with the application for 

the first new major stationary source or 

major modification in an area is 

established, the new emissions from 

that source consume a portion of the 

increment in that area, as do any 

subsequent emissions increases that 

occur from any source in the area. When 

the maximum pollutant concentration 

increase defined by the increment has 

been reached, additional PSD permits 

cannot be issued until sufficient 

amounts of the increment are ‘‘freed up’’ 

via emissions reductions that may be 

required by the reviewing authority. 

Thus, an increment is a quantitative 

value that establishes a ‘‘maximum 

allowable increase’’ for a particular 

pollutant. It functions, therefore, as a 

specific numerical measure that can be 

used to evaluate whether an applicant’s 

proposed project will cause or 

contribute to air pollution in excess of 

allowable levels. 

Increments also satisfy the second 

factor in section 166(c) by providing ‘‘a 

framework for stimulating improved 

control technology.’’ Increments 

establish an incentive to apply 

improved control technologies in order 

to avoid violating the increment and to 

‘‘free up’’ available increment to promote 

continued economic growth. These 

control technologies may become the 

basis of BACT determinations 

elsewhere, as the technologies become 

more commonplace and the costs tend 

to decline. 

One commenter stated that, although 

increments may encourage the use of 

existing control technologies, EPA has 

not cited any evidence that increments 

actually stimulate the development of 

improved technologies. Moreover, the 

commenter asserted that even if 

increments provide the incentive 

asserted by EPA, any encouragement of 

improved control technology is wholly 

incidental and hardly amounts to a 

‘‘framework’’ whose purpose is to 

stimulate such technology. 

We continue to believe that the total 

program, encompassing increments and 

BACT, does provide an appropriate 

framework to stimulate BACT in such a 

way that it is not simply ‘‘wholly 

incidental,’’ as the commenter claims. 

The fact that economic growth in an 

area must occur within a defined 

amount of allowable air quality 

deterioration should logically lead to 

the application of improved pollution 

control technology as the amount of 

deterioration increases, and should not 

be regarded as an incidental 

consequence. As stated in the 2007 

NPRM, Congress envisioned that the 

increments they originally established 

would serve as an incentive: ‘‘The 

incremental ceiling should serve as an 

incentive to technology, as a potential 

source may wish to push the frontiers of 

technology in a particular case to obtain 

greater productive capacity with the 

limits of the increments.’’ S. Rep. 95– 

127 at 18, 30 (3 LH at 1392, 1404). We, 

too, believe that as the available 

increment in an area becomes smaller, 

and as states try to preserve some of the 

remaining increments for future growth, 

it will be necessary to require sources to 

install more stringent controls in that 

area. Such levels of control ultimately 

must be considered in subsequent BACT 

evaluations in other PSD areas 

throughout the country. Admittedly, the 

increasing stringency of control 

technologies over time, as observed in 

EPA’s BACT/Lowest Achievable 

Emission Rate (LAER) Clearinghouse, 

supports but cannot in itself 

conclusively demonstrate that the PSD 

program has already stimulated 

development of improved control 

technology; there are undoubtedly a 

number of factors that could cause such 

trends. Nevertheless, even the need to 

require a more stringent BACT 

determination in only a few PSD areas 

(due to dwindling increment 

availability) necessitates consideration 

of that level of control for all other PSD 

sources wherever they may decide to 

locate. In any event, while the 

commenter generally questions the 

effectiveness of the increments as an 

incentive for tightening BACT, they 

provided no evidence that more 

stringent BACT is not related to the 


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increment system established as an 

integral part of the PSD program. 

2. Area Classifications 

In this final rule, EPA is establishing 

the same three-tiered area classification 

system for PM2.5 that is applicable to the 

increments for NO2 and other pollutants 

under the PSD program and the Act. 

Accordingly, areas that are currently 

Class I for other pollutants will also be 

Class I for PM2.5 and all other areas will 

be Class II for PM2.5 unless we 

redesignate the area based on a request 

by a State or tribe pursuant to the 

process in section 164 of the Act and 

EPA’s regulations at 40 CFR 51.166(g) 

and 52.21(g). 

As explained earlier in section IV.E.1, 

Class I areas are areas where very clean 

air is most desirable. In contrast, Class 

III areas are designed as those areas in 

which a State wishes to permit the 

highest relative level of industrial 

development, and thus allow the largest 

incremental increase in pollution. Areas 

that are not especially sensitive and 

where states have not provided for a 

higher level of industrial growth are 

classified as Class II. When Congress 

established this three-tiered scheme for 

SO2 and PM, it intended that Class II 

areas be subject to an increment that 

allows ‘‘moderately large increases over 

existing pollution.’’ H.R. Rep. 95–294, 4 

LH at 2609. 

Establishing increments at different 

levels for each of the three area 

classifications helps to fulfill two of the 

factors applicable under section 166(c) 

of the Act. First, establishing the 

smallest increments in Class I areas 

helps fulfill EPA’s obligation to 

establish regulations that ‘‘preserve, 

protect, and enhance the air quality’’ in 

parks and special areas. Class I areas are 

primarily the kinds of parks and special 

areas covered by section 160(2) of the 

Act. Second, by providing for two 

additional area classifications with 

increment levels that are higher but still 

protective, the area classification system 

helps satisfy the goal in section 160(3) 

of the Act that EPA ‘‘insure that 

economic growth will occur in a manner 

consistent with preservation of clean air 

resources.’’ In those areas where clean 

air resources may not require as much 

protection, more growth is allowed. By 

employing an intermediate level (Class 

II areas) and higher level (Class III 

areas), this classification scheme helps 

ensure that growth can occur where it 

is needed (Class III areas) without 

putting as much pressure on existing 

clean air resources in other areas where 

some growth is still desired (Class II 

areas). 

By requesting that EPA redesignate an 

existing Class II area to Class III, states 

may accommodate economic growth 

and air quality in areas where the Class 

II increment is too small to allow the 

siting of new or modified sources. The 

procedures specified by the Act for such 

a redesignation require a commitment 

by the State government to create such 

an area, extensive public review, local 

government participation in the SIP area 

redesignation process, and a finding that 

the redesignation will not result in the 

applicable increment being exceeded in 

a nearby Class I or Class II area. See 

sections 164(a) and (b) of the Act. (No 

State has yet requested a Class III 

redesignation.) The EPA believes that 

the three-tiered classification system has 

allowed for economic growth, consistent 

with the preservation of clean air 

resources. 

However, an area classification 

system alone may not completely satisfy 

the factors applicable under section 

166(c) of the Act. The increment that is 

employed for each class of area is also 

relevant to an evaluation of whether the 

area classification system achieves the 

goals of the PSD program. We briefly 

discuss the characteristics of increments 

in section V.E.5. 

One commenter took issue with our 

assessment of the two factors that we 

believe a classification system helps to 

fulfill. As discussed previously in 

section V.C.4, the commenter asserted 

that EPA has unlawfully interpreted 

section 160(3) of the Act to elevate 

economic growth over all other statutory 

factors. As explained in greater detail in 

section V.C.4, we disagree that our 

interpretation elevates economic growth 

over other factors, and believe that the 

plain language of the statute supports 

EPA’s reading that section 160(3) 

requires a balancing of the goals of (1) 

economic growth and (2) preservation of 

existing clean air resources. 

The commenter also stated that EPA 

has failed to demonstrate that the 

classification system and safe harbor 

increments, in combination with the 

other elements of the regulatory 

framework, will ‘‘preserve, protect, and 

enhance the air quality’’ in parks and 

special areas as required under section 

160(2) of the Act. These comments and 

our response to them are found in 

section V.E.6 of this preamble where we 

discuss our evaluation of the safe harbor 

increments. 

3. Permitting Procedures 

Two of the factors applicable under 

section 166(c) are fulfilled by the caseby-case permit review procedures that 

are built into our existing PSD 

regulations. The framework of our 

existing PSD regulations employs the 

preconstruction permitting system and 

procedures required under section 165 

of the Act. These requirements are 

generally reflected in 40 CFR 51.166 and 

52.21 of EPA’s PSD regulations. These 

permitting and review procedures, 

which apply to construction of new 

major sources and to major 

modifications, fulfill the goals set forth 

in sections 160(4) and 160(5) of the Act. 

These goals require that PSD programs 

in one State not interfere with the PSD 

programs in other states and that PSD 

programs assure that any decision to 

permit increased air pollution is made 

after careful evaluation and public 

participation in the decision-making 

process. For the same reasons discussed 

in our proposal for the pollutantspecific NO2 increments regulations (70 

FR 8896, February 23, 2005), we believe 

these factors are also fulfilled for PM2.5

by employing the permit review 

procedures. 

4. AQRV Review by Federal Land 

Manager and Reviewing Authority 

In this final rule, we apply the 

existing requirements to evaluate 

impacts on AQRVs in Class I areas (see 

existing 40 CFR 51.166(p) and 52.21(p)) 

to PM2.5. The existing requirements for 

an AQRV review, which Congress 

applied to SO2 and TSP, provide 

Federal land managers (FLMs) with the 

responsibility to review source impacts 

on site-specific AQRVs in Class I areas 

and to bring any alleged adverse 

impacts to the attention of the reviewing 

authority. Under an increment 

approach, we consider this review to be 

an additional measure that helps satisfy 

the factors in sections 166(c) and 160(2) 

which require EPA’s pollutant-specific 

PSD regulations to protect (1) air quality 

values, and (2) parks and other special 

areas, respectively. 

Two State/local agency commenters 

supported our proposal to apply the 

requirements to evaluate impacts on 

AQRV in Class I areas to PM2.5 review. 

However, one commenter indicated that 

FLM review does not and cannot assure 

the prevention of all significant PM2.5- 

related deterioration because it applies 

only to the construction or modification 

of very large stationary sources (e.g., 

factories and power plants) affecting 

Class I areas. This commenter pointed 

out that Class I areas do not include 

Bureau of Land Management wilderness 

and wilderness study areas 

(encompassing more than 15 million 

acres), 341 of the nation’s 390 national 

park units (only 49 national parks are 

Class I), and many U.S. Forest Service 

lands (including a number of wilderness 

areas). The commenter added that FLM 


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8Even if such a waiver of the Class I increment 

is allowed upon a finding of no adverse impact, the 

source must comply with such emissions 

limitations as may be necessary to ensure that 

alternative increments specified in the rules for SO2

or PM are not exceeded. The alternative increments 

are generally at the level of the Class II increments, 

with the lone exception being a more restrictive 3- 

hour increment for SO2. Section 165(d)(2)(C)(iv). 

The EPA made this provision applicable to the PSD 

provisions for NOX at the level of the NO2 Class II 

increment (53 FR 3704; 53 FR 40656) and 

substituted the PM10 Class II increments for the 

statutory alternative PM increments, which were 

based on TSP (58 FR 31622). This final rule 

expands this provision to include the PM2.5 Class 

II increments as well. See 40 CFR 51.166(p)(4) and 

52.21(p)(5). 

9 In response to concerns that Class I increment 

would hinder growth in areas surrounding the Class 

I area, Congress established Class I increments as a 

means of determining where the burden of proof 

should lie for a demonstration of adverse effects on 

AQRVs. See Senate Debate, June 8, 1977 (3 LH at 

725). 

10See S. Rep. 95–127, at 12, reprinted at 3 LH at 

1386, 1410 (describing the goal of protecting ‘‘air 

quality values’’ in ‘‘Federal lands—such as national 

parks and wilderness areas and international 

parks,’’ and in the next paragraph and subsequent 

text using the term ‘‘air quality related values’’ to 

describe the same goal); id. at 35, 36 (‘‘The bill 

charges the Federal land manager and the 

supervisor with a positive role to protect air quality 

values associated with the land areas under the 

jurisdiction of the [FLM]’’ and then describing the 

statutory term as ‘‘air quality related values’’). H.R. 

Report 95–564 at 532 (describing duty of 

Administrator to consider ‘‘air quality values’’ of the 

tribal and State lands in resolving an appeal of a 

tribal or State redesignation, which is described in 

the final bill as ‘‘air quality related values’’). 

review does not help to fulfill section 

160(2)’s goal of preserving and 

protecting air quality in ‘‘other areas of 

special national or regional natural, 

recreational, scenic, or historic value,’’ 

such as State and local parks, wildlife 

refuges, recreation areas, lakes, and 

historic areas, none of which are Class 

I areas. In addition, the commenter 

noted that FLM review does not apply 

to emissions increases from sources of 

PM2.5 and precursor pollution other 

than major stationary sources, such as 

motor vehicles and non-major industrial 

sources (which are sources that emit 

substantial amounts of PM2.5 and 

precursors). Alabama Power v. Costle, 

636 F.2d 323, 362 (D.C. Cir. 1979) 

(Alabama Power) (expressly recognizing 

that ‘‘[s]ignificant deterioration may 

occur due to increased emissions from 

unregulated minor sources.’’). 

The commenter also asserted that 

FLM review is of limited reach even 

where it does apply. Under the current 

PSD regulations, a State must consider 

an FLM’s objections and must justify its 

decision in writing when it disagrees 

with those objections, but the State can 

still issue a PSD permit over those 

objections unless emissions are 

predicted to cause an exceedance of the 

applicable increment. The commenter 

believes that, given these limitations, 

EPA cannot plausibly claim that the 

existing provision for FLM review 

ensures the preservation, protection, 

and enhancement of air quality for parks 

and natural areas throughout the nation 

as required by section 160(2) of the Act. 

In our rulemakings addressing PSD 

for NOX, EPA extended the AQRV 

review procedures set forth in 40 CFR 

51.166(p) and 52.21(p) to cover NO2. 

These AQRV review procedures were 

established based on section 165(d) of 

the Act, and they were originally 

applied only in the context of the 

statutory increments for PM and SO2. 

However, because they also address 

many of the factors applicable under 

section 166(c) of the Act, EPA also 

applied them to NOX through 

regulation. In this final rule, we are 

amending the existing PSD regulations 

to extend, as proposed, the AQRV 

review procedures to include PM2.5 by 

explicitly including PM2.5 in the 

regulatory text that now simply 

references ‘‘particulate matter.’’ See new 

40 CFR 51.166(p)(4) and 52.21(p)(5). 

Section 165(d) creates a scheme in 

which the FLM and reviewing authority 

must review the impacts of a proposed 

new or modified source’s emissions on 

AQRVs. The Act assigns to the FLM an 

‘‘affirmative responsibility’’ to protect 

the AQRVs in Class I areas. This is in 

notable contrast to the reviewing 

authority’s responsibility for protecting 

the increments—including Class I 

increments. The FLM may object to or 

concur in the issuance of a PSD permit 

based on the impact, or lack thereof, 

that new emissions may have on any 

affected AQRV that the FLM has 

identified and for which information is 

available to the general public. If the 

proposed source’s emissions are shown 

not to cause or contribute to a violation 

of a Class I increment, the FLM may still 

prevent issuance of the permit by 

demonstrating to the satisfaction of the 

reviewing authority that the source or 

modification will have an adverse 

impact on AQRVs. Section 165(d)(2)(C). 

On the other hand, if the proposed 

source is shown to cause or contribute 

to a violation of a Class I increment, the 

reviewing authority (State or EPA) shall 

not issue the permit unless the owner or 

operator demonstrates to the satisfaction 

of the FLM that there will be no adverse 

impact on AQRVs.8 Thus, the showing 

of compliance with the increment 

determines whether the FLM or the 

permit applicant has the burden of 

satisfactorily demonstrating whether or 

not the proposed source’s emissions 

would have an adverse impact on 

AQRVs.9 In any event, the FLM plays an 

important and material role by raising 

these issues for consideration by the 

reviewing authority, which in the 

majority of cases will be the State. 

Extending the AQRV review 

procedures of the PSD regulations to 

PM2.5 helps to provide protection with 

respect to potential adverse effects from 

PM2.5 for parks and special areas (which 

are generally the Class I areas subject to 

this review) not afforded by the 

increment system alone. As discussed 

later, we believe the factors applicable 

under section 166(c) of the Act can be 

fulfilled when the review of AQRVs is 

applied in conjunction with increments 

and other aspects of our PSD 

regulations. In those cases where the 

increment is not violated and the 

reviewing authority agrees that a 

proposed project will adversely affect 

AQRVs, the parks and other special 

areas will be protected by denying 

issuance of the permit or by requiring 

the applicant to modify the project to 

alleviate the adverse impact. 

We read the legislative history to 

show that Congress intended the AQRV 

review provisions of section 165(d) to 

provide a special layer of protection, 

beyond that provided by increments. 

The Senate committee report stated the 

following: 

A second test of protection is provided in 

specified Federal land areas (Class I areas), 

such as national parks and wilderness areas; 

these areas are also subjected to a review 

process based on the effect of pollution on 

the area’s air quality related values.’’ 

S. Rep. 95–127, at 17, 4 LH at 1401. 

As we stated in the NO2 increment 

rule, we believe the term ‘‘air quality 

values’’ should be given the same 

meaning as ‘‘air quality related values.’’ 

Legislative history indicates that the 

term ‘‘air quality value’’ was used 

interchangeably with the term ‘‘air 

quality related value’’ (AQRV) regarding 

Class I lands.10

The commenter is correct that the 

FLM (or AQRV) review applies only to 

Class I areas, and not to other ‘‘special’’ 

areas such as the numerous State and 

local parks and some other areas that 

could be seen as being covered by the 

protective purposes of section 160(2) of 

the Act. This level of coverage by FLM 

review to protect AQRVs was 

established by Congress when it enacted 

the PSD program, including the 

purposes set out in section 160(2). Thus, 

we conclude that Congress believed that 

the special areas not designated as Class 

I areas were properly addressed by the 

other elements of the PSD program. As 

discussed further in the next section, 

one such element is the requirement for 

sources to conduct an ‘‘additional 

impacts analysis,’’ which includes an 


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analysis of the impacts on visibility, 

soils, and vegetation of the proposed 

source and associated growth, regardless 

of the classification of the area impacted 

by the source. Note also that states have 

the option under the Act of designating 

additional areas as Class I areas and 

providing for AQRV review for these 

State Class I areas if they believe that 

there are areas within their borders that 

merit such protection. 

The commenter is not correct in 

saying that the review to protect AQRVs 

does not apply to emissions increases 

from sources other than major stationary 

sources. While it is generally true that 

a major stationary source may trigger the 

analysis as part of the required PSD 

review for new major stationary sources 

and major modifications where such 

source’s emissions increase may affect a 

Class I area, the review itself includes 

the impacts on an AQRV of other 

emissions in the area, including 

emissions from non-major sources. In 

addition, states may adopt requirements 

in their State implementation plans to 

require certain minor sources seeking a 

permit to undergo an AQRV analysis if 

they choose to do so. 

We agree with the commenter that the 

AQRV review has certain limitations in 

that a State can, under some 

circumstances, issue a PSD permit over 

the objection of the FLM. Here again, 

Congress enabled this outcome when it 

provided that a permit would not be 

issued when the FLM demonstrates ‘‘to 

the satisfaction of the State’’ that the 

source will have an adverse impact on 

AQRVs in a Class I area. Section 

165(d)(2)(C)(ii). We read this provision 

to reflect Congress’s judgment on the 

appropriate balance between State and 

FLM discretion in the reach of AQRV 

review. That said, when a reviewing 

authority declines to follow a 

determination of adverse impact by the 

FLM, the reviewing authority is 

expected to provide a rational basis for 

doing so, and a reviewing authority’s 

rejection of an FLM’s finding may not be 

arbitrary and capricious. As stated by 

EPA’s Environmental Appeals Board in 

In the Matter of: Hadson Power 14— 

Buena Vista, 4 E.A.D. 258, 1992 WL 

345661 (October 5, 1992)(in Section 

II.A): 

States do not have unfettered discretion to 

reject an FLM’s adverse impact 

determination. If a State determines that an 

FLM has not satisfactorily demonstrated an 

adverse impact on AQRVs from the proposed 

facility, the State must provide a ‘‘rational 

basis’’ for such a conclusion, ‘‘given the 

FLMs’ affirmative responsibility and 

expertise regarding the Class I areas within 

their jurisdiction.’’ 50 FR 28549, July 12, 

1985. Arbitrary and capricious rejections of 

adverse impact determinations are not 

sustainable. (citations omitted). 

In sum, the commenter correctly 

enumerated some of the limitations of 

the AQRV review under the Act. 

However, such review is only one 

element of the full PSD program, which 

must be evaluated against the statutory 

requirements in their entirety. We 

continue to believe, as previously 

stated, that under an increment 

approach, FLM review for AQRV 

impacts is an additional measure that 

helps satisfy the factors in sections 

166(c) and 160(2) of the Act (which 

require EPA’s pollutant-specific PSD 

regulations to protect (1) air quality 

values, and (2) parks and other special 

areas, respectively) in balance with the 

other statutory factors. We add that the 

AQRV review requirements of the 

existing regulations mirror these 

requirements in the Act, which reflect 

Congress’ judgment of how AQRV 

review should properly be used to 

promote the purposes of the program as 

set out in section 160 of the Act. 

5. Additional Impacts Analysis 

The ‘‘additional impacts analysis’’ 

requirements set forth in our part 51 and 

52 PSD regulations also help fulfill the 

criteria and goals and purposes in 

sections 166(c) and 160. The additional 

impacts analysis involves a case-by-case 

review of potential harm to visibility, 

soils, and vegetation in Class II and III 

areas that could occur from the 

construction or modification of a PSD 

source. 

Sections 51.166(o)(1) and 52.21(o)(1) 

of the PSD regulations require that a 

permit provide the following analysis: 

An analysis of the impairment to visibility, 

soils and vegetation that would occur as a 

result of the source or modification and 

general commercial, residential, industrial 

and other growth associated with the source 

or modification. The owner or operator need 

not provide an analysis of the impact on 

vegetation having no significant commercial 

or recreational value. 

This requirement was based on 

section 165(e)(3)(B) of the Act, which 

provides that EPA establish regulations 

that require ‘‘an analysis of the ambient 

air quality, climate and meteorology, 

terrain, soils and vegetation, and 

visibility at the site of the proposed 

major emitting facility and in the area 

potentially affected by emissions from 

such facility * * *.’’ 

As mentioned in the previous section, 

one commenter argued that the 

provisions for protection of Class I areas 

are of no help in fulfilling the goal set 

forth in section 160(2) of the Act to 

preserve and protect air quality in the 

countless ‘‘other areas of special 

national or regional natural, 

recreational, scenic, or historic value’’ 

such as State and local parks, wildlife 

refuges, recreation areas, lakes and 

historic areas, none of which were 

originally defined by Congress as Class 

I areas. 

We acknowledge that the special 

provisions for protecting Class I areas 

are not applicable for protecting areas 

that are not designated as ‘‘Class I.’’ 

However, we believe that the 

‘‘additional impacts analysis’’ provisions 

are especially helpful for satisfying the 

requirements of section 166(c) in Class 

II and Class III areas, including the types 

of areas described by the commenter, 

that are not Class I areas but are worthy 

of special protection beyond what might 

be provided by the NAAQS and 

increments. 40 CFR 51.166(o) and 

52.21(o). These areas are not subject to 

the special AQRV review that applies 

only in Class I areas. While the 

additional impacts analysis is not as 

intensive a review as the AQRV analysis 

required in Class I areas, the 

requirement to consider impairments to 

visibility, soils, and vegetation through 

the additional impacts analysis 

contributes to satisfying the factors 

applicable under section 166(c) of the 

Act in all areas, including Class II and 

Class III areas. 

6. Installation of BACT 

The requirement that new sources and 

modified sources subject to PSD apply 

BACT is an additional measure that 

helps to satisfy the factors in sections 

166(c), 160(1), and 160(2) of the Act. 

This requirement, based on section 

165(a)(4) of the Act, is already included 

in EPA’s PSD regulations for all 

pollutants generally and thus, in the 

2007 NPRM we considered it to be a 

part of the regulatory framework for the 

Agency’s pollutant-specific regulations 

for PM2.5. 40 CFR 51.166(j) and 52.21(j). 

Our existing regulations define ‘‘best 

available control technology’’ as ‘‘an 

emission limitation * * * based on the 

maximum degree of reduction for each 

pollutant subject to regulation under the 

Act * * * which the Administrator, on 

a case-by-case basis, taking into account 

energy, environmental, and economic 

impacts and other costs, determines is 

achievable for such source through 

application of production processes or 

available methods, systems, and 

techniques * * *.’’ 40 CFR 

51.166(b)(12) and 52.21(b)(12). This 

pollutant control technology 

requirement, in practice, has required 

significant reductions in the pollutant 

emissions increases from new and 

modified sources while also stimulating 

the on-going improvement of control 


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11We have paraphrased these factors here and in 

other sections to facilitate the explanation of our 

reasoning. However, we recognize, as we did in our 

regulation for NOX, that the statutory language is 

broader than the shorthand we use here for 

convenience. 

12Note that the PM10 increment may still be more 

limiting in areas where much of that increment has 

already been consumed. 

13The 24-hour PM2.5 NAAQS (35 μg/m3) is about 

23 percent of the 24-hour PM10 NAAQS (150 μg/ 

m3). 

technology. The control of PM2.5

emissions through the application of 

BACT helps to protect air quality 

values, public health and welfare, and 

parks and other special areas. 

E. Final PM2.5 Increments 

Based on our evaluation of the effects 

of PM2.5 and a balancing of the criteria 

in section 166(c) of the Act (and the 

incorporated goals and purposes of the 

Act contained in section 101 and the 

statutory PSD program in section 160 of 

the Act), EPA has concluded that the 

‘‘safe harbor’’ increments for PM2.5

(which satisfy section 166(d) of the Act) 

are sufficient to fulfill the criteria in 

section 166(c) when combined with the 

other measures described earlier that we 

apply to PM2.5. Since several of the eight 

factors applicable under section 166(c) 

are satisfied by adopting the framework 

and other measures described earlier, 

our development of these increments for 

PM2.5 was guided by the four remaining 

factors that may not be fully satisfied by 

the framework and other measures: (1) 

Protecting AQRVs; (2) protecting the 

public health and welfare from 

reasonably-anticipated adverse effects; 

(3) protecting the air quality in parks 

and special areas, and (4) insuring 

economic growth.11 In accordance with 

the ‘‘contingent safe harbor’’ approach, 

to determine the specific characteristics 

of the proposed increments, we first 

established safe harbor increments 

representing the level of effectiveness 

necessary to satisfy the ‘‘at least as 

effective as’’ requirement in section 

166(d) of the Act and then conducted 

further analysis to determine if 

additional measures are necessary to 

fulfill the requirements of section 

166(c). 

1. Identification of Safe Harbor 

Increments 

Using the percentage-of-NAAQS 

approach under proposed Option 1, as 

explained in section V.C.2 of this 

preamble, we derived the following safe 

harbor increments for PM2.5: 

Averaging period NAAQS 

(μg/m3) 

Increments (μg/m3) 

Class I Class II Class III 

Annual .............................................................................................................................. 15 1 4 8 

24-hour ............................................................................................................................. 35 2 9 18 

The table shows PM2.5 NAAQS levels 

(primary and secondary NAAQS) at 15 

μg/m3 for the annual averaging time and 

35 μg/m3 for the 24-hour averaging time. 

See 40 CFR 50.7. From these NAAQS 

levels, we calculated the safe harbor 

increments based on the same 

percentages that were used by Congress 

to establish the original PM increments 

(measured as TSP) in section 163 of the 

Act, i.e., 6.6 percent of the NAAQS for 

Class I areas, 25 percent of the NAAQS 

for Class II areas, and 50 percent of the 

NAAQS for Class III areas. We have 

concluded that increments with these 

characteristics are sufficient to satisfy 

the requirement in section 166(d) that 

we adopt increments (or other PSD 

regulations) that are ‘‘at least as effective 

as’’ the increments established in section 

163 of the Act. See EDF v. EPA, 898 

F.2d at 188, 190. 

Nine commenters supported proposed 

Option 1, either explicitly or implicitly 

supporting our method of calculating 

the safe harbor increments used to 

develop increments for PM2.5. One of 

these commenters, while agreeing with 

the safe harbor increment approach 

under Option 1, disagreed with our 

analysis of the adequacy of the safe 

harbor increments, as discussed in other 

sections of this preamble. One 

commenter who opposed Option 1 

(based on the belief that section 166(a) 

of the Act is not the appropriate basis 

for PM2.5 increments) nevertheless 

supported the percentage-of-NAAQS 

approach for developing PM2.5

increments under the statutory authority 

at section 166(f). 

A commenter who opposed our 

proposal to calculate increments using 

percentages of the NAAQS argued that 

this approach for setting the PM2.5

increments is not scientifically 

supported. This commenter indicated 

that basing the PM2.5 increments on the 

same percentage of the NAAQS that 

were used to set PM10 increments based 

on the TSP NAAQS ignores the 

relationship between PM10 and PM2.5

emissions, which may be much different 

than the relationship between TSP and 

PM10 emissions. The commenter argued 

that, because the ratio of PM2.5 to PM10

emissions is 0.8, it appears that using 

the percentages proposed by EPA would 

indirectly restrict PM10/TSP emissions 

and air quality impacts to 

proportionally lower levels than the 

PM10 increments in order to avoid 

exceeding the PM2.5 increments. The 

commenter conceded that using the 0.8 

factor to set PM2.5 increments may seem 

too high, but asserted that using the safe 

harbor approach would set increments 

for PM2.5 that are too low. 

We conclude that the commenter is 

mistaken in saying that the PM2.5

increments use the same percentage of 

the NAAQS that were used to set the 

PM10 NAAQS. We adopted the PM10

increments using the ‘‘equivalent 

substitution’’ approach set forth under 

section 166(f) of the Act. Under that 

approach, rather than calculating the 

PM10 increments as specific percentages 

of the PM10 NAAQS (using the same 

percentages that Congress used for 

setting the statutory increments for PM 

and SO2), EPA determined the levels of 

the PM10 increments that could 

represent an equivalent amount of 

increment consumed, as if the TSP 

increments were still in effect. See 58 

FR 31622, June 3, 1993, at 31626–31627. 

Nevertheless, the commenter is correct 

that, in cases where the ratio of PM2.5 to 

PM10 emissions is 0.8 for an individual 

source, the source may have to reduce 

its PM10 emissions more than would 

otherwise be necessary to meet the PM10

increments in order to control its PM2.5

emissions sufficiently to meet the safe 

harbor PM2.5 increments.12 This is 

because the safe harbor PM2.5

increments are less than 80 percent of 

the PM10 increments. For example, the 

Class II 24-hour PM2.5 safe harbor 

increment (9 μg/m3) is only 30 percent 

of the corresponding PM10 increment 

(30 μg/m3). 

The underlying reason that the safe 

harbor PM2.5 increments are so much 

less than the PM10 increments is that the 

PM2.5 NAAQS are much less than the 

PM10 NAAQS.13 This is the result of the 

evolution in our knowledge about the 

health and welfare effects of PM, in 

particular the effects of the fine PM 


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14The review completed in 2006 updated the 

previous review, which began in 1994 and resulted 

in revised standards for PM in 1997. 

represented by PM2.5. We believe that it 

is fitting for PM2.5 increments to reflect 

our greater knowledge about PM2.5

effects (as embodied in the NAAQS), 

rather than to simply maintain the 

control level required by the PM10

increments as suggested by the 

commenter. If this results in PM2.5

increments that are more limiting than 

PM10 increments, we believe that this 

outcome is appropriate in light of our 

statutory requirement to prevent 

significant deterioration of air quality as 

it relates to PM2.5. 

2. Data Used by EPA for the Evaluation 

of the Safe Harbor Increments for PM2.5

We evaluated whether measures other 

than the safe harbor increments are 

necessary by analyzing primarily the 

scientific and technical information on 

the health and welfare effects of PM2.5

contained in the June 2005 OAQPS Staff 

Paper which accompanied the last full 

review of the PM NAAQS completed in 

2006.14

Section 166(a) of the Act provides that 

EPA establish pollutant-specific PSD 

regulations, such as increments, after 

the establishment of a NAAQS for the 

applicable pollutants. The Act provides 

that EPA will promulgate new PSD 

regulations under section 166, including 

new increments if appropriate, within 2 

years from the promulgation of any 

NAAQS after 1977. Within that time 

frame, the health and welfare 

information used for the setting of the 

NAAQS would also be ‘‘current’’ for 

purposes of establishing pollutantspecific PSD regulations. We believe 

this timing reflects congressional intent 

that EPA consider the same body of 

information concerning a pollutant’s 

health and welfare effects when it 

promulgates the NAAQS and 

subsequent PSD increments (or other 

measures) defining significant air 

quality deterioration for the same 

pollutant. However, when we used that 

same information as the basis for our 

proposed pollutant-specific PSD 

regulations, we evaluated that 

information under the legal criteria in 

section 166 of the Act rather than the 

criteria in section 109 applicable to the 

promulgation of NAAQS. See EDF v. 

EPA, 898 F.2d at 190. 

At the time of our proposal of PM2.5

increments, we had just completed a 

review of the PM2.5 NAAQS. Thus, the 

information used in the NAAQS review 

was current and timely for purposes of 

establishing pollutant-specific PSD 

regulations for PM2.5. On October 17, 

2006, based primarily on considerable 

new data on the air quality and human 

health effects for PM2.5 directly, EPA 

revised the primary and secondary 

NAAQS to provide increased protection 

of public health and welfare by 

retaining the level of the annual 

standard and tightening the level of the 

24-hour standard from 65 to 35 μg/m3

while retaining the 24-hour PM10

NAAQS and revoking the annual PM10

NAAQS. The information contained in 

both the 2004 Criteria Document and 

2005 Staff Paper that was used for the 

latest review of the PM NAAQS was 

also considered for the purpose of 

evaluating the PM2.5 increments that we 

have established in this final rule. 

The 2004 Criteria Document and 2005 

Staff Paper are the products of a 

rigorous process that is followed to 

validate and interpret the available 

scientific and technical information, 

and provided the basis for 

recommending the PM2.5 NAAQS. In 

accordance with the Act, the NAAQS 

process begins with the development of 

‘‘air quality criteria’’ under section 108 

for air pollutants that ‘‘may reasonably 

be anticipated to endanger public health 

or welfare’’ and that come from 

‘‘numerous or diverse’’ sources. Section 

108(a)(1). For each NAAQS review, the 

Administrator must appoint ‘‘an 

independent scientific review 

committee composed of seven members 

of the National Academy of Sciences, 

one physician, and one person 

representing State air pollution control 

agencies,’’ known as the Clean Air 

Scientific Advisory Committee 

(CASAC). Section 109(d)(2)(A). The 

CASAC is charged with recommending 

revisions to the criteria document and 

NAAQS, and advising the Administrator 

on several issues, including areas in 

which additional knowledge is required 

to appraise the adequacy and basis of 

existing, new, or revised NAAQS. 

Section 109(d)(2)(B),(C). 

‘‘Air quality criteria’’ must reflect the 

latest scientific knowledge on ‘‘all 

identifiable effects on public health or 

welfare’’ that may result from a pollutant 

presence in the ambient air. Section 

108(a)(2). The scientific assessments 

constituting air quality criteria generally 

take the form of a ‘‘criteria document,’’ 

a rigorous review of all pertinent 

scientific studies and related 

information. The EPA also develops a 

‘‘staff paper’’ to ‘‘bridge the gap’’ between 

the scientific review and the judgments 

the Administrator must make to set 

standards. See Natural Resources 

Defense Council v. EPA (‘‘NRDC ’’), 902 

F.2d 962, 967 (D.C. Cir. 1990). Both 

documents undergo extensive scientific 

peer review as well as public notice and 

comment. See, e.g., 62 FR 386542. 

3. Scope of Effects Considered 

The effects of ambient PM2.5

concentrations may include effects from 

secondarily-formed PM2.5. Thus, when 

we analyzed the data in this rulemaking, 

we evaluated the health and welfare 

effects of both direct PM2.5 and 

secondarily-formed PM2.5 that may 

result from the transformation of other 

pollutants such as SO2 and NOX. This 

was consistent with the approach we 

described for addressing these effects in 

the review of our pollutant-specific NO2

increments regulations. 70 FR 59590. 

4. Evaluation of the Health and Welfare 

Effects of PM2.5

Airborne PM is not a specific 

chemical entity, but rather is a mixture 

of liquid and solid particles from 

different sources and of different sizes, 

compositions, and properties. Particle 

size distributions show that atmospheric 

particles exist in two classes: Fine 

particles and coarse particles. The 

indicator for fine particles is PM2.5, 

which represents that population of 

particles that is mostly less than 2.5 

micrometers in size. The indicator for 

thoracic coarse particles is ‘‘PM10–2.5,’’ 

which represents particles sized 

between 2.5 and 10 micrometers. In the 

last two reviews of the PM NAAQS, 

EPA concluded that these two 

indicators, because of their different 

sources, composition, and formation 

processes, should be treated as separate 

subclasses of PM pollution for purposes 

of setting ambient air quality standards. 

Fine PM is derived directly from 

combustion material that has volatilized 

and then condensed to form primary PM 

or from precursor gases, such as SO2

and NOX, reacting in the atmosphere to 

form secondary PM. Major components 

of fine particles are sulfates, strong acid, 

ammonium nitrate, organic compounds, 

trace elements (including metals), 

elemental carbon, and water. Primary 

and secondary fine particles have long 

lifetimes in the atmosphere (days to 

weeks) and travel long distances 

(hundreds to thousands of kilometers). 

They tend to be uniformly distributed 

over urban areas and larger regions, 

especially in the eastern United States. 

As a result, they are not easily traced 

back to their individual sources. 

a. Health Effects 

The EPA reported important progress 

since the last PM NAAQS review in 

advancing our understanding of 

potential mechanisms by which ambient 

PM2.5, alone and in combination with 

other pollutants, is causally linked to a 


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15 It should be noted, however, that an increment 

does not allow air pollution levels in an area to 

increase beyond the ambient concentration of a 

pollutant that would exceed the level allowed by 

the NAAQS. 

number of key health effects. The more 

extensive and stronger body of evidence 

used by EPA to study the health effects 

of PM2.5 in our latest review identified 

a broader range of effects than those 

previously documented, involving 

premature mortality and indices of 

morbidity (including respiratory 

hospital admissions and emergency 

room visits, school absences, work loss 

days, restricted activity days, effects on 

lung function and symptoms, 

morphological changes, and altered host 

defense mechanisms) associated with 

both long-term and short-term exposure 

to PM2.5. A more detailed discussion of 

the health effects associated with PM2.5

is contained in the 2007 NPRM. 72 FR 

54127–54128. In addition, an overview 

of the scientific and technical evidence 

considered in the 2004 Criteria 

Document and 2005 Staff Paper can be 

found in our proposed rule for revising 

the NAAQS for PM (71 FR 2619, January 

17, 2006). 

b. Welfare Effects 

Ambient PM alone, and in 

combination with other pollutants, can 

have a variety of effects on public 

welfare. While visibility impairment is 

the most noticeable effect of fine 

particles present in the atmosphere, 

both fine and coarse particles can have 

other significant welfare-related effects, 

including effects on vegetation and 

ecosystems, materials (e.g., soiling and 

corrosion), and climate change 

processes. 

In reaching our decision in 2006 to 

revise the suite of PM secondary 

standards, EPA factored in several key 

conclusions from the scientific and 

technical information contained in the 

2004 Criteria Document and 2005 Staff 

Paper. These conclusions included the 

following: (1) PM-related visibility 

impairment is principally related to fine 

particle levels, and most directly related 

to instantaneous levels of visual air 

quality associated with short-term 

averaging periods; (2) PM2.5

concentrations can be used as a general 

surrogate for visibility impairment in 

urban areas; (3) any secondary NAAQS 

for visibility protection should be 

considered in conjunction with the 

regional haze program as a means of 

achieving appropriate levels of 

protection against PM-related visibility 

impairment in urban, non-urban, and 

Class I areas nationwide; (4) the 

available evidence is not sufficient to 

support distinct secondary standards for 

fine or coarse particles for any nonvisibility related welfare effects; and (5) 

the secondary standards should be 

considered in conjunction with 

protection afforded by other programs 

intended to address various aspects of 

air pollution effects on ecosystems and 

vegetation, such as the acid deposition 

program and other regional approaches 

to reducing pollutants linked to nitrate 

or acidic deposition. 

In this rulemaking, EPA has reviewed 

the scientific and technical information 

concerning welfare related effects 

considered in the 2004 Criteria 

Document and 2005 Staff Paper to 

determine whether there is any basis for 

modifying the safe harbor increments 

developed for PM2.5 to satisfy the 

criteria under sections 166(c) and 160 of 

the Act. Our review included 

information on visibility impairment, 

and effects on vegetation and other 

ecosystem components, materials and 

soiling, and climate changes. A detailed 

discussion of the various welfare effects 

we considered for evaluating the safe 

harbor increments for PM2.5 is contained 

in the 2007 NPRM. 72 FR 54128–54133. 

5. Fundamental Elements of Increments 

As we have previously noted, under 

the model established in the Act and 

prior EPA regulations, the function of an 

increment is not like that of the NAAQS 

in that an increment is not intended to 

set a uniform ambient pollutant 

concentration ‘‘ceiling’’ across the 

United States. See 70 FR 59600. Instead, 

while both increments and NAAQS 

generally serve to limit ambient air 

pollution levels, increments are 

designed to allow a uniform amount of 

pollutant concentration increase for 

each area in the United States having a 

particular classification, i.e., Class I, II, 

or III. The amount of the allowable 

increase is measured against a baseline 

air quality level that is typically 

different for each particular area.15

Because the baseline air quality level 

varies from one location to another, and 

is not established for a particular area 

until a source proposing to construct in 

that area submits a complete PSD permit 

application, it is not possible to 

determine what the maximum ambient 

pollutant concentration attainable will 

be for a given area (to be used to 

determine the protection afforded by an 

increment against potential adverse 

environmental effects) until the specific 

baseline air quality level is known. 

For the reasons described in our NO2

increments rule, our objective is to 

establish uniform increments, consistent 

with the increments for SO2 and PM 

originally established by Congress, that 

allow the same level of deterioration for 

each area of the country having the 

same classification. 70 FR 59601. It is 

important to understand that increments 

are not intended to reduce ambient 

concentrations of an air pollutant below 

existing baseline levels in each area, but 

rather to define a level of allowable 

increase in pollutant concentrations 

above baseline levels, and to identify 

the level at which ‘‘significant’’ 

deterioration occurs for each area, in 

accordance with its specific 

classification. 70 FR 59600. 

6. Evaluation of the Safe Harbor 

Increments 

As indicated earlier (in section V.E.2 

of this preamble), mindful of the 

considerations made about the 

fundamental characteristics of the 

increments, we reviewed the scientific 

and technical evidence available for the 

2005 review of the NAAQS for PM in 

order to determine whether, and to what 

extent, the ‘‘safe harbor’’ increments 

might need to be modified in order to 

protect air quality values, health and 

welfare, and parks while insuring 

economic growth consistent with the 

preservation of clean air resources in 

accordance with sections 166(c) and 160 

of the Act. As we did in our evaluation 

of the safe harbor NO2 increments (70 

FR 59603–59606), we relied on an 

approach that evaluates how protective 

the safe harbor PM2.5 increments are by 

comparing the marginal pollutant 

concentration increases allowed by the 

safe harbor increment levels against the 

pollutant concentrations at which 

various environmental responses occur. 

We analyzed the available evidence 

from both a quantitative and qualitative 

perspective to reach a decision about 

whether we should modify the 

contingent safe harbor PM2.5 increments 

and whether we have sufficient 

information to select a specific 

alternative level, averaging time, or 

pollutant indicator for the increments. 

As a result of our analysis, we proposed 

to conclude that it was not necessary to 

modify the safe harbor increments to 

protect human health, address nonvisibility welfare effects, or further 

protect visibility. This analysis is 

described in detail in the 2007 NPRM. 

After considering the comments on 

our evaluation of the safe harbor 

increments and the conclusions we 

reached in the 2007 NPRM (summarized 

in the following paragraphs), we 

continue to believe that the safe harbor 

increments for PM2.5 (which satisfy 

section 166(d) of the Act) are sufficient 

to fulfill the criteria in section 166(c) of 

the Act (and the incorporated goals and 

purposes of the Act in section 101 and 

the PSD program in section 160) when 


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16 Docket No. EPA–HQ–OAR–2006–0605 can be 

accessed on line at http://www.regulations.gov. 

17 In the 2005 OAQPS Staff Paper reviewing the 

NAAQS for PM, EPA cited the following accepted 

definition of ‘‘critical load’’: ‘‘quantitative estimate 

of an exposure to one or more pollutants below 

which significant harmful effects on specified 

sensitive elements of the environment do not occur 

according to present knowledge.’’ See page 6–45. 

combined with the other measures 

described earlier that we apply to PM2.5. 

Consequently, this final rule establishes 

the PM2.5 increments at the level of the 

proposed safe harbor increments. 

An environmental group submitted 

extensive comments arguing that the 

PM2.5 safe harbor increments are not 

sufficient to meet the Act’s requirements 

for PSD and that our analysis was 

inadequate, and two other commenters 

submitted more narrowly targeted 

comments in this area. A summary of 

the major comments, along with our 

responses, follows. A more detailed 

treatment of the comments can be found 

in the Response to Comments document 

for this rulemaking, which is available 

in the rulemaking docket.16

The environmental group commenter 

stated that EPA has not complied with 

section 166(c) of the Act because the 

Agency has not made a finding or 

demonstrated that the PM2.5 PSD rules 

will (as required by section 160(2) of the 

Act) preserve, protect, and enhance the 

air quality in parks and special areas. 

The commenter asserted that EPA 

offered only vague assertions that the 

proposed increments would ‘‘satisfy’’ the 

statutory factors and that they, along 

with other programs, would ‘‘help’’ to 

fulfill the statutory purposes. The 

commenter went on to argue that EPA 

sought to excuse its failure to show 

fulfillment of the statutory purposes by 

asserting that it cannot develop a 

uniform, quantitative, dose-response 

relationship between fine particle levels 

and certain ecosystem impacts (citing 72 

FR 54134), but that, even if true, such 

a claim does not excuse the agency from 

satisfying its statutory duty under 

section 166(c). 

We conclude that the 2007 NPRM 

demonstrated that the safe harbor 

increments, in combination with the 

other aspects of the regulatory 

framework, fulfill the statutory 

requirements despite the scientific 

uncertainties. We reiterate that finding 

today. The fact that we did not, in the 

2007 NPRM, explicitly state this as a 

finding does not diminish the 

demonstration made there and 

reiterated in this preamble. 

The environmental group commenter 

believes that the relationship between 

PM2.5 and adverse effects can be 

quantified to a greater extent than stated 

by EPA. Regarding acid rain and other 

adverse ecological impacts, the 

commenter asserted that critical loads 

can be established as a way of 

quantifying and limiting the PM2.5

contribution to degradation, and noted 

that critical loads are now used by 

authorities in Europe, have been 

endorsed by leading North American 

scientists, and have been used by 

Federal land management agencies. To 

comply with section 166(c), the 

commenter believes that EPA must 

establish a mechanism to supplement 

the nationally uniform increments with 

additional measures, including a 

requirement to establish area-specific 

critical loads or equally protective 

limits, where necessary to protect and 

enhance air quality in specific parks and 

natural areas. 

With regard to the critical load 

concept, we agree conceptually with the 

commenter that critical loads could be 

used to supplement the existing 

increments, especially as a means of 

protecting the known sensitive 

ecosystems within Class I areas. While 

we disagree that the critical loads 

concept can be used as an effective 

replacement to increments for limiting 

air quality degradation, we believe that 

the concept offers considerable promise 

in helping to protect sensitive receptors 

in specific Class I areas. However, we do 

not believe that it would be appropriate 

at this time to establish a requirement 

for area-specific critical loads under the 

PSD program. In our 2005 PSD rule for 

NO2 increments, we indicated that 

states could propose using information 

on critical loads as part of their 

approach for managing air quality in 

their individual SIP-approved PSD 

programs, but sufficient information 

was not yet available for EPA to 

incorporate the use of critical loads into 

the national PSD program. See 70 FR 

59613. 

The concept of critical loads is useful 

for estimating how much pollution a 

particular ecosystem can experience on 

a prolonged basis without showing 

adverse effects. In addition to 

addressing the opportunity for using 

critical loads under its NO2 increment 

rule, EPA has addressed the concept of 

critical loads in the last review of the 

PM NAAQS and currently in the 

secondary NO2/SO2 NAAQS review.17

To date in the United States, critical 

loads have had their primary 

application in the area of atmospheric 

deposition of sulfur (S) and nitrogen 

(N). In the last review of the PM 

NAAQS, EPA found that ambient PM 

was contributing to the total load of 

pollutants entering the U.S. ecosystem 

annually. However, the review also 

concluded that there were ‘‘insufficient 

data for the vast majority of U.S. 

ecosystems that differentiate the PM 

contribution to total N [nitrate] or S 

[sulfate] deposition to allow for 

practical application of this approach as 

a basis for developing national 

standards to protect sensitive U.S. 

ecosystems from adverse effects related 

to PM deposition.’’ The 2005 Staff Paper 

for the PM NAAQS, in reaching this 

conclusion, addressed various 

important factors, including (1) the lack 

of a long-term, historic database of 

annual speciated PM deposition rates to 

establish relationships between PM 

deposition and ecosystem responses; 

(2) uncertainty in predicting the amount 

of PM deposited to sensitive receptors 

from measured concentrations of PM in 

the ambient air; and (3) the unique 

nature of each ecosystem and the 

current inability to extrapolate with 

confidence any effect from one 

ecosystem to another. The 2005 Staff 

Paper recommended that EPA give 

serious attention to the critical load 

concept and recommended the 

collection of data from a ‘‘greater variety 

of ecosystems over longer time scales to 

determine how ecosystems respond to 

different loading rates over time.’’ 2005 

Staff Paper at page 7–19. 

The review of the secondary NAAQS 

for NOX and sulfur oxides (SOX), which 

is currently underway, is evaluating 

ecological effects due to the atmospheric 

deposition of NOX and SOX. The two 

main targeted effects are acidification 

and nutrient enrichment in both aquatic 

and terrestrial ecosystems. This review 

is attempting to use critical loads to 

evaluate the impact of current 

depositional loads and alternative loads 

in several case study areas. However, as 

mentioned earlier, the estimation of 

ecosystem critical loads expressed in 

terms of PM requires long-term 

ecosystem-level data on speciated PM 

deposition rates for which an adequate 

database is currently lacking for most 

sites in the United States. 

The environmental group commenter 

also asserted that the safe harbor 

increments would allow PM2.5 air 

quality to deteriorate to the level of the 

NAAQS in many locations. According 

to the commenter’s analysis, at 55 

percent of the locations with PM2.5

monitors that were not already 

exceeding the PM2.5 NAAQS, 24-hour 

PM2.5 concentrations would be allowed 

to increase up to the level of the 

NAAQS. In addition, the analysis 

showed that for 84 percent of locations 

not already exceeding the NAAQS, the 

24-hour PM2.5 concentrations would be 

allowed to increase to a level of 30 μg/ 


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18The commenter cited http://www.nps.gov/ 

shen/naturescience/visibility_and_haze.htm for 

historic visibility in national parks. 

m3 or more. The commenter believes 

that allowing such levels would not be 

protective of public health, given that 

we stated in the 2007 NPRM that we 

had previously found that PM2.5

concentrations less than a range of 30– 

35 μg/m3 (24-hour average) were 

protective of public health (citing 72 FR 

54128). 

The environmental group 

commenter’s analysis showed similar 

results for the proposed annual PM2.5

increments. The commenter asserted 

that PM2.5 concentrations would be 

allowed to increase up to the level of the 

annual NAAQS in 55 percent of the 

locations that are currently in 

attainment, and that 87 percent of these 

sites would be allowed PM2.5

concentrations of 12 μg/m3 or higher. 

Again, the commenter believes that 

allowing annual concentrations at or 

above 12 μg/m3 would not be protective 

of public health, based on our statement 

in the 2007 NPRM that we had 

previously found that PM2.5

concentrations less than a range of 12– 

15 μg/m3 (annual average) were 

protective of public health (citing 72 FR 

54128). 

We do not believe that increments 

must be set at levels that ensure that the 

full amount of increment will be 

available in all locations. The statutory 

provisions in the PSD program have 

always been clear that a source must 

demonstrate that it will comply with 

both the NAAQS and increments for any 

pollutant. Consistent with congressional 

intent, the PSD program does not allow 

a source to violate the NAAQS just 

because its emissions will not cause the 

increments to be exceeded. If the 

increments were to be developed in 

such a way that all areas, taking into 

account current ambient air quality 

status, would be able to utilize the full 

amount of increment, then the 

increment levels would have to be 

unnecessarily stringent in areas that are 

substantially cleaner than levels 

allowed by the NAAQS. 

Congress recognized that all areas of 

the country might not be able to utilize 

the full amount of increment when they 

provided provisions within the Act 

requiring that both the NAAQS and 

increments must continue to be met at 

all times. In areas where the full amount 

of increment is not available due to 

levels of pollution approaching the 

NAAQS, states may need to require 

emissions reductions at existing sources 

to accommodate the desired amount of 

economic growth. Hence, we do not 

believe it is reasonable to unduly 

restrict economic growth in cleaner 

areas by setting more restrictive 

increments to help maintain air quality 

levels below the NAAQS in areas which 

are currently only marginally 

attainment. 

In addition, we disagree with the 

commenter’s assertion that the 

increments will not protect public 

health. In setting the PM2.5 NAAQS at 

35 μg/m3 (24-hour) and 15 μg/m3

(annual), EPA concluded that these 

levels protect public health with an 

adequate margin of safety. Regardless of 

the level at which the increments are 

set, no source is permitted to cause the 

NAAQS to be exceeded. That is, as 

noted previously, the upper bound on 

the permissible concentration of PM2.5 is 

determined by the increment or the 

NAAQS, whichever is more restrictive 

in each particular case. Thus, the entire 

framework of the PM2.5 regulations, 

including the safe harbor increments, is 

protective of public health. In asserting 

otherwise, the commenter has 

misconstrued our statements in this 

regard. 

In the 2007 NPRM section on the 

health effects of PM2.5 (72 FR 54127– 

54128), we discussed the fact that we 

considered setting the 24-hour NAAQS 

in the range of 30 to 35 μg/m3 and the 

annual NAAQS in the range of 12 to 15 

μg/m3. However, we concluded in 

setting the NAAQS that 35 μg/m3 (24- 

hour) and 15 μg/m3 (annual) are 

protective of public health with an 

adequate margin of safety. We did not 

say, nor do we believe, that PM2.5

concentrations must be below 30 μg/m3

(24-hour average) or 12 μg/m3 (annual 

average) to protect public health. 

The environmental group commenter 

believes that there is a quantifiable 

relationship between visibility 

impairment and PM2.5 levels, citing the 

2007 NPRM discussion (72 FR 54135) as 

well as the most recent Criteria 

Document and Staff Paper for PM2.5. The 

commenter pointed out that in the 2007 

NPRM (72 FR 54135), EPA observed that 

the proposed Class II short-term safe 

harbor increment of 9 μg/m3, if 

combined with the estimated daily 

background levels in most areas (i.e., 10 

μg/m3), would be below the minimum 

values recommended in the 2005 Staff 

Paper for the secondary short-term 

standard for PM2.5 (which was 20 μg/ 

m3). Rather than supporting the 

adequacy of 9 μg/m3 as an increment 

level to protect visibility, the 

commenter believes that this shows that 

the safe harbor increment is inadequate 

because consumption of an increment of 

9 μg/m3 combined with background 

levels alone would cause an area to 

reach within 1 μg/m3 of the staffrecommended value of 20 μg/m3. The 

commenter added that most areas would 

have PM2.5 pollution from motor 

vehicles and stationary sources in 

concentrations substantially greater than 

background levels, easily placing these 

areas above 20 μg/m3 (citing the 2005 

Staff Paper at 2–77). 

The environmental group commenter 

went on to assert that the safe harbor 

PM2.5 increments will not be sufficient 

to protect visibility in parks and other 

natural areas. In the 2007 NPRM, we 

stated that a 24-hour average PM2.5

concentration of 20 μg/m3 correlates to 

a visual range of approximately 25 to 35 

kilometers. 72 FR 54129. The 

commenter asserted that this visual 

range distance falls far short of what the 

National Park Service considers to be 

good visibility for national parks, 

adding that the National Park Service 

has stated that visibility used to be 90 

miles (145 km) on average in eastern 

parks, and 140 miles (225 km), on 

average in western parks.18 The 

commenter stated that the safe harbor 

increments would allow parks and other 

natural areas to experience PM2.5

pollution that is correlated with a 

25–35 km visual range. 

The visibility impairment issue is 

more complex than suggested by the 

environmental group commenter. In 

addition to predicting what the 

maximum ambient change in air quality 

is for a particular area, a visibility 

impairment assessment considers such 

things as the frequency, magnitude, and 

duration of visibility impacts in order to 

conclude that an adverse impact will 

occur. 

In addition, the environmental group 

commenter misconstrued the 

illustration we included in the 2007 

NPRM. We noted that the lowest level 

we considered as a secondary PM2.5

NAAQS was 20 μg/m3, which was 

considered to address visibility issues in 

urban areas. We also noted that in most 

areas, the estimated 98th percentile of 

daily background concentrations is less 

than 10 μg/m3. In adding the Class II 

safe harbor increment (9 μg/m3) to the 

98th percentile of background levels, we 

were simply showing that even in the 

worst case, the combination of the safe 

harbor increment and background PM2.5

would not exceed the most stringent 

level we considered for the secondary 

PM2.5 NAAQS. The commenter 

presented this rough, worst-case 

calculation as if it represented the 

typical situation that would result from 

the safe harbor increments. In addition, 

the environmental group commenter’s 

statements do not apply to parks and 

special areas that are classified as Class 


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64884 Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 

I areas because the safe harbor 

increments for such areas are much 

lower. 

Another commenter stated that the 

proposed 24-hour Class I increment (2 

μg/m3) would not be protective of 

AQRVs, particularly visibility. This 

commenter noted that the National Park 

Service uses a 5 percent change in light 

extinction from estimated natural 

conditions as the threshold for ‘‘adverse 

impacts’’ to Class I visibility. The 

commenter indicated that depending on 

the constituents of the ambient PM2.5

and the humidity, a concentration of 2 

μg/m3 in a typical Class I area would 

result in a change in light extinction 

ranging from 13 to 80 percent in the 

Western United States and from 8 to 50 

percent in the Eastern United States 

and, therefore, would likely constitute 

‘‘adverse impacts’’ to Class I visibility. 

While acknowledging that the FLM may 

still determine that the visibility in the 

Class I area is adversely affected by an 

increase in concentration that is less 

than the increment, this commenter 

pointed out that we stated in the 2007 

NPRM that ‘‘generally speaking an 

increment should not be so large that it 

routinely results in substantially more 

pollution in Class I areas than is 

generally acceptable under the AQRV 

approach’’ (citing 72 FR 54135). The 

commenter concluded that the proposed 

24-hour PM2.5 increment does not meet 

this test and recommended that EPA set 

a lower PM2.5 24-hour increment. 

This commenter appears to have 

identified a worst-case scenario in terms 

of increment concentrations, and 

although we agree with the visibility 

impacts related to those concentrations 

discussed in the comment, we do not 

believe the proposed increment level 

compromises the protection of visibility 

or other AQRVs. Although the ‘‘AQRV 

test’’ uses 5 percent light extinction as 

a screening threshold, the determination 

of adverse impact is made on a case-bycase basis taking into account the 

geographic extent, intensity, duration, 

frequency, and time of visibility 

impairment and how these factors 

correlate with visitation to the Class I 

area. The suggestion that the 5 percent 

threshold is routinely exceeded by PSD 

sources or that an absolute worst-case 

scenario is occurring to the geographic 

extent, intensity, duration, and 

frequency that would warrant an 

adverse impact determination is 

unsupported, especially considering the 

relatively few adverse impact 

determinations that have been made in 

the past. It is, however, important to 

note that the AQRV analysis is 

independent of the PSD increment 

analysis; whether or not the increment 

is projected to be exceeded does not 

determine the need for an AQRV 

analysis. The determination that a 

facility does or does not cause an 

adverse impact on a Class I area is not 

solely contingent upon the PSD 

increment, so we do not believe that 

lowering the proposed increment is 

necessarily more protective of the 

AQRV. 

With respect to these two 

commenters’ concerns about visibility 

protection, we continue to believe that 

the increments cannot be expected to be 

the sole means of protecting various 

welfare concerns. In the 2007 NPRM, we 

stated that ‘‘visibility protection in Class 

I areas is more adequately provided by 

the AQRV process.’’ Congress defined 

AQRVs to specifically include visibility 

and left it for the FLMs to define other 

special attributes of Class I areas that 

warranted special protection. We also 

noted that Congress has established 

several visibility programs that target 

emissions reductions to achieve desired 

visibility benefits. See 72 FR 54135. 

Collectively, these protective programs, 

along with the totality of the PSD 

program, offer an effective means of 

addressing unique local problems that 

cannot be addressed solely by uniform 

national increments. 

However, the environmental group 

commenter asserted that these other 

programs will not fulfill the statutory 

purposes. As discussed previously in 

sections V.D.4 and 5, the commenter 

does not believe that FLM review in the 

AQRV process and the air quality 

impacts analysis required by section 

165(a) of the Act are adequate. We 

disagree; see sections V.D.4 and 5 for 

more detail on the comments and our 

responses. 

The environmental group commenter 

also noted that we cited the regional 

haze program as a justification for 

adopting less protective PSD rules 

(referring to 72 FR 54135), but the 

commenter pointed out that the haze 

program applies only to Class I areas 

and does not apply at all to the majority 

of the nation, which is Class II. The 

commenter further noted that we stated 

in the 2007 NPRM that ‘‘some State and 

local governments have also developed 

programs to improve visual air quality 

in specific urban areas’’ (citing 72 FR 

54135), and pointed out that we gave no 

specific information on such programs, 

nor any information about the visibility 

protection that they provide beyond that 

provided by the proposed increments. 

The commenter asked that we identify 

the specific State and local programs, 

and that we specify how much visibility 

protection such programs are providing. 

The commenter is correct that the 

regional haze program directly 

addresses only Class I areas. As we have 

discussed before, these are the areas that 

Congress defined as deserving of the 

most protection under PSD, including 

the visibility protection provisions in 

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

which is the statutory basis for the 

regional haze program. While Class I 

areas are the target for the regional haze 

program, we believe that many areas of 

the nation will receive collateral 

visibility benefits from this program. As 

emissions of the pollutants that cause 

regional haze are reduced, many areas 

in the paths of transport will benefit. In 

addition, as discussed previously in 

section V.D.5 of this preamble, PSD 

applicants must prepare an analysis of 

‘‘other impacts,’’ including visibility 

impacts, in areas other than Class I 

areas. 

Regarding State and local visibility 

programs, in the 2005 Staff Paper EPA 

described several existing programs to 

improve visual air quality in urban 

areas. These programs were located in 

Denver, CO; Phoenix, AZ; and Lake 

Tahoe, CA. Also, the states of California 

and Vermont have each established 

standards to protect visibility. See the 

2005 Staff Paper, pages 6–17 through 

6–23. 

The environmental group commenter 

cited the 2007 NPRM (72 FR 54135) 

where we said that the use of ‘‘distinct 

PM increments for visibility protection 

is not the most effective means of 

addressing the visibility problem.’’ The 

commenter believes that this claim is 

based on false premises, including the 

idea (discussed previously) that other 

programs effectively protect visibility 

nationwide, and the idea that the only 

option is a ‘‘distinct’’ PM increment for 

visibility protection. As to the latter, the 

commenter stated that EPA can 

strengthen the safe harbor increment to 

ensure visibility protection and need 

not adopt a separate ‘‘visibility’’ 

increment. In addition, the commenter 

asserted that EPA has ignored the 

statutory mandate that the PSD rules 

fulfill the statutory goals and purposes, 

and that we cannot shirk that statutory 

duty merely because we claim some 

other type of action would be ‘‘more 

effective.’’ 

We continue to believe that Class I 

area visibility protection under the PSD 

program is appropriately addressed via 

the AQRV process. As mentioned 

previously, Congress explicitly included 

‘‘visibility’’ as an AQRV for which FLMs 

would have an affirmative responsibility 

to protect in Class I areas under their 

jurisdictions. Where the FLM 

successfully demonstrates that there 


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would be an adverse impact on the 

AQRV (e.g., visibility), a State cannot 

issue a PSD permit, even when the 

source’s emissions do not violate the 

PM2.5 increments. In addition, we 

continue to believe that the analysis of 

other impacts, including visibility, in 

non-Class I areas is the appropriate 

means of addressing visibility 

protection in these areas, as envisioned 

by Congress when it enacted the PSD 

provisions of the Act. 

As a result, we do not believe it is 

necessary to create a distinct increment 

(e.g., with a different averaging period) 

or to lower the safe harbor increments 

to protect visibility in urban, non-urban, 

or Class I areas across the United States. 

We reach this conclusion in proper 

consideration of the other, more direct 

approaches being used to address 

visibility problems in the United States. 

The primary such approach, the 

regional haze program, is within the 

PSD framework for PM2.5. Note that part 

C of title I of the Act, ‘‘Prevention of 

Significant Deterioration of Air Quality,’’ 

includes subpart 2, which is the 

statutory basis for the regional haze 

program. Regarding our consideration of 

other State and local visibility 

protection measures that are outside the 

PSD framework, we do not believe it is 

reasonable to disregard these areaspecific measures that focus on the 

preferences of individual communities 

where a uniform national increment for 

visibility protection generally cannot. 

The environmental group commenter 

also stated that the proposed PSD rules 

fail to ensure fulfillment of the 

‘‘enhancement goal’’ set out in the Act. 

The commenter noted that section 

101(a) states as the Act’s first purpose: 

‘‘to protect and enhance the quality of 

the Nation’s air resources,’’ while 

section 160(2) states that the purpose of 

the PSD program is to ‘‘preserve, protect, 

and enhance’’ air quality in parks and 

other special areas. The commenter 

asserted that the proposed rule did not 

address these enhancement 

requirements or explain how the 

proposed increments would fulfill those 

requirements. 

This same issue was raised in the 

2005 PSD rule affirming the NO2

increments. At that time we expressed 

our belief that the goal to enhance air 

quality in national parks and wilderness 

areas is implemented through the 

regional haze program while the PSD 

program focuses on preserving and 

protecting air quality in these areas. 

However, when a PSD increment 

violation is identified, we agree that 

EPA may require a State to revise its SIP 

to correct the violation. See 40 CFR 

51.166(a)(3). Otherwise, we do not 

interpret these PSD provisions to 

authorize us to direct states in their SIPs 

to achieve reductions in emissions from 

existing sources for PSD purposes. 

We recognized at that time, and 

continue to believe, that the growth 

management goals of PSD may also be 

fulfilled when the states adopt controls 

on existing sources that would reduce 

emissions and allow growth from new 

sources and major modifications to 

existing sources without causing 

significant deterioration. Under the 

increment approach, we have 

interpreted the PSD rules to allow states 

to require reductions from existing 

sources in order to expand the allowable 

increments and, thereby, allow for more 

growth under the PSD program. 

However, we have never required states 

to do so because, in the absence of an 

increment violation, we do not believe 

section 166 and other provisions in part 

C of title I of the Act give us the legal 

authority to mandate such reductions 

for PSD purposes. 

Another commenter stated that the 

PM2.5 increments should be twice the 

recommended levels because scientific 

studies do not support the need for such 

low levels for protection of health and 

welfare. The commenter believes that 

increments at the proposed levels would 

jeopardize the goal of providing 

opportunities for economic growth. The 

commenter expressed concern over 

EPA’s use of epidemiologic studies and 

questioned the ability of such studies to 

provide a reliable evaluation of health 

risks. The commenter claimed that 

epidemiologic studies are capable of 

finding association between a substance 

or exposure and a health effect but 

rarely capable of determining if there is 

causation, while toxicological studies 

using randomized trials are specifically 

designed to determine causation. The 

commenter added that other factors 

providing evidence for causation 

include dose-response relationships, 

consistency, and repeatability of 

studies, which the commenter said are 

not present in the studies cited by EPA. 

The commenter specifically referred to 

two studies, acknowledged by EPA to 

show no evidence of a dose-response 

relationship gradient between PM2.5 and 

specific health related effects. 

We disagree with the commenter’s 

recommendation that the increments 

should be twice the proposed (and final) 

levels. The scientific studies to which 

the commenter referred pertain to 

studies that EPA used to determine the 

health-based NAAQS for PM2.5, and we 

do not believe it is relevant to this rule 

to respond to comments related to the 

setting of the NAAQS. The NAAQS are 

designed to protect public health and 

welfare; increments then are intended to 

insure that air quality in clean areas is 

not allowed to deteriorate significantly, 

and the PSD regulations insure that any 

such deterioration does not lead to air 

pollution levels that exceed the levels 

defined by the NAAQS. 

As discussed previously, we are 

finalizing this rulemaking using the safe 

harbor approach under section 166(a) of 

the Act. Using this approach, we 

calculated the ‘‘safe harbor’’ increments 

as percentages of the NAAQS 

comparable to the percentages that 

Congress used to establish the original 

statutory increments for PM and SO2. 

These values represent the level of 

effectiveness necessary to satisfy section 

166(d) of the Act, and could be 

tightened if necessary based on further 

analysis to determine if additional 

measures are necessary to fulfill the 

requirements of section 166(c) of the 

Act. Thus, under this approach and on 

this record, we do not conclude that it 

is appropriate to finalize increments at 

levels any less stringent than the safe 

harbor increments, as the commenter 

recommends. 

7. Compliance Determinations for the 

PM2.5 Increments 

a. Modeling Compliance With PM2.5

Increments 

Section 163(a) of the Act provides that 

‘‘In the case of any maximum allowable 

increase * * * for a pollutant based on 

concentrations permitted under the 

national ambient air quality standards 

for any period other than an annual 

period, such regulations shall permit 

such maximum allowable increase to be 

exceeded during one such period per 

year [emphasis added].’’ Accordingly, 

the existing PSD rules allow one 

exceedance per year of each short-term 

increment defined by the rules. See 40 

CFR 51.166(c) and 52.21(c). With the 

addition of the PM2.5 increments to the 

list of maximum allowable 

concentrations in the PSD rules, the 

existing provision allowing one 

exceedance per year applies equally to 

the 24-hour PM2.5 increments as well. 

Thus, when modeling increment 

compliance, the highest value of the 

second-highest modeled increase in 

estimated PM2.5 concentrations at each 

model receptor for the 24-hour 

averaging time should be less than or 

equal to the maximum allowable 

increase for PM2.5. For the annual 

increments, the modeled annual 

averages should not exceed the annual 

maximum allowable increase for PM2.5. 

See EPA’s ‘‘Guideline on Air Quality 

Models’’ at 40 CFR part 51 appendix W, 

section 10.2.3.3. 


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19We proposed test methods for measuring PM10

and PM2.5, including condensable PM emissions, 

from stationary sources on March 25, 2009 (74 FR 

12970). In the same notice, we sought comments on 

whether to end the NSR transition period for 

condensable PM earlier than January 1, 2011. We 

anticipate publication of a final rule announcing 

our decision on the NSR transition period in July 

2010. 

We did not expressly state in the 2007 

NPRM the implications of adding PM2.5

increments to the existing list of 

increments in 40 CFR 51.166(c) and 

52.21(c) of the PSD regulations. 

Nevertheless, it should have been clear 

at the time that, in the absence of 

alternative language for PM2.5, the 

existing provision allowing one 

exceedance for the short-term 

increments would apply to the 

increments for PM2.5 along with the 

increments already listed. We did not 

receive any comments either supporting 

or opposing these methods for 

determining compliance with the PM2.5

increments. 

We recognize that the above approach 

for determining compliance with the 24- 

hour PM2.5 increments differs from the 

approach contained in guidance that we 

provided in a March 23, 2010 memo 

titled ‘‘Modeling Procedures for 

Demonstrating Compliance with PM2.5

NAAQS,’’ which sets forth a procedure 

designed to demonstrate compliance 

with a statistically based standard that 

is met when the 98th percentile 24-hour 

concentration is less than or equal to 

35 ug/m3. A similar dichotomy exists for 

the 24-hour PM10 increments and 

NAAQS, where compliance with the 24- 

hour PM10 NAAQS is based on an 

expected exceedance form of the 

standard. 

b. Condensable PM 

Initially, the EPA will not require PSD 

applicants under the Federal PSD 

program to consider condensable PM in 

emissions calculations to determine 

whether a proposed project is subject to 

the PSD requirements. In addition, we 

will not require the condensable portion 

to be considered in the required PM2.5

air quality analyses. In our May 2008 

PM2.5 NSR Implementation Rule, we 

announced that we would not require 

that states address condensable PM in 

establishing enforceable emissions 

limits for either PM10 or PM2.5 in NSR 

permits until the completion of a 

transition period. Further, we indicated 

that the transition period would end 

January 1, 2011 unless EPA advanced 

the date through the rulemaking 

process. We also indicated that such 

rulemaking would involve the 

assessment and possible revision of test 

methods for measuring condensable 

emissions and taking comment on an 

earlier closing date for the transition 

period in the NSR program if we are on 

track to meet our expectations to 

complete the test methods rule much 

earlier than January 1, 2011.19 In 

addition, states that have developed the 

necessary tools are not precluded from 

acting to include condensable PM 

emissions in NSR permit actions prior 

to the end of the transition period, 

especially if it is required in an 

applicable SIP. See 73 FR 28334–28336. 

c. PM2.5 Precursors 

In the 2007 NPRM, we proposed to 

add SILs for PM2.5 to the PSD 

regulations at 40 CFR 51.166 and 52.21. 

(The SILs are described more fully in 

section VI of this preamble.) 

Accompanying these SILs, we proposed 

to add a new paragraph to the 

regulations explaining that the 

requirements for a source impact 

analysis for PM2.5 would be considered 

to be satisfied, without further air 

quality modeling, if it were to be shown 

that the increase in direct PM2.5

emissions from the source or 

modification will cause air quality 

impacts less than the prescribed SILs for 

PM2.5. The reasoning at the time was 

that state-of-the-art modeling would not 

be available to adequately account for 

secondary PM2.5 impacts resulting from 

emissions of precursors of PM2.5, e.g., 

SO2 and NOX. Nevertheless, the existing 

PSD rules currently define potential 

precursors of PM2.5. Based on the 

proposed language, the required 

compliance demonstration for the PM2.5

NAAQS and the PM2.5 increments 

(when promulgated) would be limited 

by regulation to an analysis of direct 

PM2.5 emissions, and would not include 

consideration of emissions of PM2.5

precursors for comparing the modeled 

source impacts to the prescribed SILs 

for PM2.5. 

The impacts of PM2.5 precursors on 

ambient concentrations of PM2.5 cannot 

be determined from the dispersion 

models that EPA has currently approved 

for modeling individual PSD sources. 

Such models are not designed to 

consider chemical transformations that 

occur in the atmosphere after the 

precursor emissions have been released 

from the source. Consideration of these 

transformations is necessary to be able 

to add precursor impacts into the total 

modeled ambient PM2.5 concentrations 

for comparison to the SILs for PM2.5. 

The technical tools needed to 

complete a comprehensive analysis of 

all emissions that contribute to ambient 

concentrations of PM2.5 are only in the 

developmental stage; nevertheless, we 

believe that it would be inappropriate to 

restrict the regulatory language in such 

a way that future regulatory 

amendments would be required to 

enable the inclusion of precursor 

impacts in the PM2.5 analysis as the 

necessary technical tools become 

available. Estimating techniques are 

being developed that will be able to be 

applied to the PM2.5 analysis in the near 

future, which could not be required if 

the regulatory language precluded them. 

We acknowledge the concerns that have 

been expressed by some commenters 

about the shortcomings of not 

considering the impacts of PM2.5

precursors under the PM2.5 air quality 

analyses. Accordingly, we believe that 

the new provision for applying the SILs 

for PM2.5 to the required analyses for the 

NAAQS and increments should not be 

self-limiting by specifying the use of 

only direct PM2.5 emissions. Instead, the 

new provision contained in this final 

rule provides that the test will be based 

on whether ‘‘the emissions increase 

* * * would cause * * * air quality 

impacts less than [the PM2.5 SILs].’’ See 

new 40 CFR 51.166(k)(2) and 

52.21(k)(2). We believe that it would be 

more effective to rely on interim policy 

and guidance as appropriate to help 

determine the best methods available to 

make the required assessment of source 

impacts on ambient PM2.5 resulting from 

any emissions. 

F. Final Action on Trigger and Baseline 

Dates for PM2.5 Increments 

In the 2007 NPRM, we proposed as 

part of Option 1 to require the 

implementation of the PM2.5 increment 

system (annual and 24-hour increments) 

with new baseline areas, baseline dates, 

and trigger date. Specifically, we 

proposed that the major source baseline 

date and trigger date, both fixed dates, 

would be defined as the effective date 

of the final rule and would reflect a date 

1 year from the date of promulgation, in 

accordance with section 166(b) of the 

Act. In contrast, under Option 2 (both 

2A and 2B), we proposed to establish 

new baseline dates for the 24-hour PM2.5

increments, but to retain the existing 

baseline areas and dates for the annual 

PM2.5 increments because the annual 

increments would be equivalent 

substitutes for the existing annual PM10

increments. 

In light of the then-current and 

expected trends in PM2.5 concentrations, 

our judgment was that starting with new 

baseline dates on or after the effective 

date of this rule would make the PSD 

increments for PM2.5 more protective. 

We proposed that any emissions 

reductions occurring prior to the 

effective date of this rule would lower 


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Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 64887 

the baseline concentration rather than 

be used for expanding the PM2.5

increment. If a retroactive baseline date 

were to apply, emissions reductions 

occurring prior to the effective date of 

this rule would serve to expand the 

available increments, enabling more 

new pollution than would otherwise be 

allowed to occur. 

We also expressed our belief that 

starting with different baseline dates to 

implement increments for PM2.5 would 

be appropriate because Option 1 treats 

PM2.5 essentially as a ‘‘new’’ pollutant 

for purposes of PSD and section 166 of 

the Act. We continue to believe that 

establishing a new baseline also 

overcomes significant implementation 

concerns that would otherwise exist if 

the existing PM baseline were 

maintained. In particular, if we were to 

require sources and reviewing 

authorities to conduct PM2.5 increment 

analyses based on the minor source 

baseline dates previously established 

years or even decades ago under the 

TSP or PM10 program, they would have 

to attempt to recreate the PM2.5

emissions inventory as of the minor 

source baseline date in order to 

determine the baseline PM2.5

concentration for the area. For early 

minor source baseline dates in 

particular (e.g., 1976 in some areas of 

the United States), establishing the 

emissions inventory for PM2.5 would be 

extremely difficult, cumbersome, and 

potentially inaccurate because historic 

emissions inventories did not include 

PM2.5 emissions. For all of these 

reasons, we proposed Option 1 as our 

preferred option and requested 

comment on this contingent safe harbor 

approach for annual and 24-hour PM2.5

increments under Option 1. 

Under Option 1, we proposed that the 

PM2.5 increments would be subjected to 

a 1-year delay consistent with the 

procedures under section 166(b) of the 

Act, which provides in general that 

these rules ‘‘shall become effective one 

year after the date of promulgation.’’ 

Alternatively, we sought comment on a 

60-day delay as part of our proposal 

under Option 1. In the proposal we 

requested comment on the argument 

that, while the Act includes a 1-year 

implementation delay for new 

increments, the same provision calls for 

EPA to promulgate new increments 

within 2 years of the promulgation of 

the NAAQS. Given that these PM2.5

increments are being promulgated more 

than 2 years after promulgation of the 

NAAQS, we expressed our belief that 

the overall congressional intent 

reflected in section 166 of the Act could 

possibly be met by setting the effective 

date of the PM2.5 increments earlier than 

the ‘‘one year after the date of 

promulgation’’ provided in section 

166(b) of the Act. 

Twelve commenters supported our 

proposal under Option 1 to establish 

new trigger and baseline dates for PM2.5, 

regardless of the particular increment 

option that they otherwise supported. 

These commenters generally saw new 

dates as being the best approach because 

of various problems that would result 

from retaining existing trigger and 

baseline dates. Some commenters 

claimed that it would be technically 

difficult to try to reconstruct old 

inventories to determine the amount of 

PM2.5 emitted by sources in the past. 

One commenter stated that 

establishing PM2.5 increment 

inventories using existing PM10 baseline 

dates would be ‘‘extremely difficult, 

cumbersome, and necessarily inaccurate 

and unreliable as historic emissions did 

not speciate PM2.5 emissions.’’ A State/ 

local agency commenter said that it 

would be ‘‘virtually impossible for 

States to calculate the PM2.5 component 

of previously consumed PM10

increments because data on the fine and 

coarse fractions of source emissions are 

largely unavailable.’’ 

Yet another commenter claimed that 

‘‘resurrecting PM2.5 inventories based on 

the PM10 baseline dates would be 

insurmountable.’’ Similar comments 

were echoed by several commenters 

who supported the use of legal authority 

set forth in section 166(f) (‘‘equivalent 

substitution’’ approach) for developing 

the numerical values for the PM2.5

increments. One of these commenters 

stated that he did not ‘‘believe the 

establishment of new baseline dates for 

PM2.5 would abandon past cases of 

increment consumption for PM10, 

because the 24-hour PM10 increments 

would still be in effect * * *.’’ 

One commenter suggested that ‘‘EPA 

establish the trigger date as of the date 

when it officially established the nonattainment and attainment areas for 

PM2.5; that is, April 5, 2005.’’ The 

commenter explained that this approach 

is consistent with the PSD regulations 

from their inception and partially 

mitigates EPA’s delays in implementing 

the PSD program for PM2.5. The 

commenter believes ‘‘that States should 

be required to use the baseline areas 

previously established for their PSD 

program, unless the process for 

redefining these areas strictly follow 

procedures in the PSD regulations and 

EPA policy.’’ The commenter claimed, 

‘‘this will minimize any inconsistent 

applications of the regulations for 

PM2.5.’’ 

One commenter noted that our 

proposed PM2.5 increments were very 

low and ‘‘facilities may find themselves 

immediately out of compliance with the 

PM2.5 increments upon promulgation of 

the rule, based on a January 1975 or 

1977 baseline date.’’ 

One commenter indicated that the 

historic TSP/PM10 baseline dates should 

be retained. This commenter favored the 

equivalent substitution approach under 

section 166(f) and, consistent with that 

approach, retention of the existing 

baseline dates. 

Having considered all the comments, 

we believe that the most reasonable 

approach for addressing the relevant 

dates associated with the PM2.5

increments is to start anew with the 

baseline date concept. As already 

mentioned, the commenters have 

identified difficulties that would occur 

if the PM2.5 emissions inventory for 

increment analyses had to be created for 

an earlier period of time, and the 

existence of these difficulties supports 

the approach under Option 1 to 

establish new dates for implementing 

the PM2.5 increments. Also, these new 

baseline dates for PM2.5 increments will 

not undo the current protection 

provided by the existing increments for 

PM because we are not revoking the 24- 

hour or annual PM10 increments under 

this new rule. Accordingly, this final 

rule establishes independent PM2.5

increments using a ‘‘trigger date’’ and 

‘‘major source baseline date’’ that are 

separate from the dates defined for the 

PM10 increments. Consequently, new 

minor source baseline dates and the 

corresponding baseline areas will be 

used for the annual and 24-hour PM2.5

increments, and will be established 

when a source applies for a PSD permit 

any time on or after the new trigger date 

for PM2.5. (See also the discussion about 

changes to the definition of ‘‘baseline 

area’’ in section V.G of this preamble.) 

The ‘‘major source baseline date’’ for 

PM2.5 is being set as October 20, 2010— 

the date of publication of this final rule. 

The setting of this date differs from 

previous major source baseline dates 

which were set as the date of 

publication of the proposed rule, but is 

similar to the major source baseline date 

set for the other increments in that the 

date precedes the effective date for 

implementing the increments, and 

thereby requires that certain major 

source emissions increases that occur 

before the trigger date retroactively 

count toward the amount of increment 

consumed. 

The ‘‘trigger date’’ is being set at 

October 20, 2011, which is 1 year after 

the date of promulgation of this final 

rule. We are using this approach to 

define the date on which the PM2.5

increments become effective as 1 year 


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64888 Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 

20 ‘‘A source will be considered to impact an area 

if it has an impact of 1 μg/m3 or more of SO2 or 

PM on an annual basis. This figure has been 

selected because it corresponds to levels of 

significance used in previous Agency 

determinations for SO2 and PM. 45 FR 52716. 

from the date of publication, consistent 

with the 1-year delay required under 

section 166(b) of the Act. This date for 

the ‘‘trigger date’’ separates the 

applicability date of the PM2.5

increments from the effective date of 

this final rule in general, but also 

ensures that the ‘‘minor source baseline 

date’’ for PM2.5 for any particular PM2.5

attainment or unclassifiable area cannot 

be established until after the increments 

become effective in this final rule. The 

implementation of these dates as part of 

the PM2.5 increment system is discussed 

in greater detail in section VIII of this 

preamble. 

We recognize that some may still have 

a concern about our decision to set the 

major source baseline date as the date of 

publication of this final rule in light of 

the fact that the PM2.5 NAAQS have 

been in place since 1997; however, we 

believe that the selection of possible 

earlier dates would require states to 

retroactively establish PM2.5 emissions 

inventories for increment analyses 

during a period when sources were 

generally not required to conduct PM2.5

air quality analyses. Hence, given the 

lack of information, and considering the 

technical difficulties in doing so, we do 

not believe that it would be appropriate 

to require states and sources to 

retroactively account for PM2.5

increment consumption by setting the 

major source baseline date at an earlier 

date than the date we have selected. 

G. Definition of ‘‘Baseline Area’’ for 

PM2.5

No changes were proposed with 

respect to the definition of ‘‘baseline 

area’’ for PM2.5 increments. One 

commenter, however, noted that fact in 

claiming that we did not adequately 

account for significant impacts of PM2.5

for purposes of defining the ‘‘baseline 

area’’ for the PM2.5 increments. Under 

the existing regulations, the 

establishment of a baseline area for any 

PSD increment results from the 

submittal of the first complete PSD 

application, and is based on both the 

location of the proposed source and the 

impact of the source’s emissions on the 

area. In accordance with the definition, 

the attainment or unclassifiable area in 

which the proposed source would 

construct is always part of the baseline 

area in which the minor source baseline 

date is established and the increment 

analysis is conducted. In addition, the 

definition provides that any 

surrounding attainment or 

unclassifiable area in which the 

proposed source’s impact is greater than 

1 μg/m3, annual average, would also 

become part of the baseline area, 

assuming the area had not already been 

established as a baseline area by a 

previous application for a PSD permit. 

See 40 CFR 51.166(b)(15) and 

52.21(b)(15). 

As explained in the preamble for the 

1980 PSD regulations, EPA selected an 

impact of 1 μg/m3, annual average, for 

the definition of ‘‘baseline area’’ because 

that value was considered the level of 

significance for both SO2 and PM when 

the definition was originally 

established.20 There was no mandate at 

that time that a 1 μg/m3 impact be used 

to determine the baseline area for 

increments for other pollutants; 

however, the use of a 1 μg/m3 impact in 

the definition of ‘‘baseline area’’ was not 

changed when EPA developed 

increments for NO2 in 1988 because 

EPA also defined ‘‘significant’’ for NO2

using the same annual average 

concentration of 1 μg/m3. The EPA has 

determined, however, that ‘‘significant’’ 

for PM2.5 ambient impacts should be 

considered to occur at a lower 

concentration than 1 μg/m3. Elsewhere 

in this preamble, we have indicated that 

the SIL for PM2.5 in this final rule is 0.3 

μg/m3, annual average. Consequently, 

although no change to the definition of 

‘‘baseline area’’ was proposed in this 

rule, we believe it is necessary and 

appropriate to define in this final rule 

a level of significance of 0.3 μg/m3, 

annual average, for establishing a new 

baseline area for purposes of PM2.5

increments. See revised 40 CFR 

51.166(b)(15)(i) and 52.21(b)(15)(i). 

Had we established the SIL at 

1 μg/m3, annual average, as proposed 

under Option 1 for SILs, then the 

definition of ‘‘baseline area’’ would not 

need to be revised. However, the revised 

definition in this final rule is consistent 

with our decision to establish a SIL of 

0.3 μg/m3, annual average, for PM2.5. We 

consider this action to be a logical 

outgrowth of our decision to establish a 

SIL for PM2.5 and the comment 

concerning the effect of that action on 

the definition of ‘‘baseline area.’’ Thus, 

we believe that our failure to initially 

propose this change to the definition of 

‘‘baseline area,’’ based on the possibility 

of selecting Option 3 for defining the 

SIL for PM2.5, does not warrant a 

reproposal. 

H. No Final Action With Respect to the 

Proposed Revocation of PM10 Annual 

Increments 

In the 2007 NPRM, we proposed to 

either revoke or replace the annual 

increments (Class I, II, and III) for PM10

to conform to the earlier revocation of 

the annual PM10 NAAQS. We proposed 

to revoke the annual increments, based 

on the same technical evidence that led 

us to revoke the annual PM10 NAAQS, 

if we decided to use Option 1 for 

adopting PM2.5 increments, and 

discussed our authority and rationale 

for doing so. 72 FR 54136. 

As an alternative, under Options 2A 

and 2B we proposed to replace the 

existing annual PM10 increments with 

equivalent substitute PM2.5 increments 

using the authority under section 166(f) 

of the Act. After further analysis and 

consideration of the comments on this 

issue, we have decided not to take any 

final action on our proposal to revoke 

the existing increments for PM10 as part 

of this rulemaking. The effect of not 

taking final action with respect to the 

PM10 annual increments is to leave 

those increments in place and 

unchanged. 

Three commenters agreed with EPA’s 

proposal to ‘‘adopt the 24-hour and 

annual PM2.5 increments and to revoke 

the annual PM10 increments.’’ One 

commenter stated, ‘‘counting and 

tracking increment is confusing enough 

without adding the confusion of 

potentially overlapping PM standards.’’ 

The commenter noted that the ‘‘cleanest 

approach is to establish a single new 

PM2.5 increment and work from there.’’ 

The commenter suggested that EPA first 

‘‘develop a coarse fraction increment, 

once EPA establishes coarse PM 

NAAQS.’’ The commenter added that 

the removal of the PM10 annual 

increment is supported by the removal 

of the ‘‘health based standard for annual 

PM10.’’ 

One of the commenters agreed, ‘‘it 

makes no sense for EPA’s regulations to 

contain an annual increment for PM10

even though an annual PM10 NAAQS no 

longer exists.’’ The commenter added, 

‘‘EPA is without authority under Section 

166(f) to retain the PM10 annual 

increment if it adopts a PM2.5 annual 

increment.’’ This commenter explained, 

‘‘EPA is compelled by law to eliminate 

the PM10 annual increment.’’ 

We agree with this commenter that 

section 166(f) is a ‘‘substitution’’ 

approach; however, as we stated in our 

2007 NPRM, we expressed some 

concern about using section 166(f) to 

substitute PM2.5 increments for PM10

increments. In fact, some commenters 

challenged our authority under section 

166(f) to replace the PM10 increments. In 

our response to the following 

comments, we address the legal issues 

that we believe prevent us from simply 

revoking the PM10 increments. 


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One environmental commenter 

claimed, ‘‘the agency has no authority to 

repeal an existing PM10 increment 

without at the same time restoring the 

corresponding TSP increment.’’ The 

commenter noted, ‘‘Congress established 

the TSP increments by statute and gave 

EPA no authority to revoke them,’’ and 

‘‘instead, Congress gave EPA only 

limited authority to substitute PM10

increments for TSP increments under 

the conditions specified in Section 

166(f).’’ The commenter explained, ‘‘EPA 

cannot revoke the annual PM10

increments, either by ‘‘replacing’’ them 

with PM2.5 increments or otherwise, 

unless EPA at the same time restores the 

annual TSP increment.’’ The commenter 

noted, ‘‘retention of the PM10 annual 

increment is also entirely compatible 

with the statutory purposes, 

notwithstanding EPA’s revocation of the 

annual PM10 NAAQS.’’ The commenter 

further noted the following examples/ 

evidence that retention of the annual 

PM10 increments is important to 

achieving the goals of the Act’s PSD 

provisions: 

• ‘‘While EPA attributes the visibility 

impairing impacts of PM pollution 

primarily to elevated short term fine 

particle concentrations, EPA recognizes 

that PM10 plays a significant role in the 

other welfare related impacts of PM 

pollution.’’ 72 FR 54136. 

• ‘‘EPA also states that the most 

significant PM-related ecosystem-level 

effects result from long term cumulative 

deposition * * * that exceeds the 

natural buffering or storage capacity of 

the ecosystem and/or affects the 

nutrient status of the ecosystem.’’ 72 FR 

54131. 

Five State/local agency commenters 

opposed the revocation of PM10 annual 

increments ‘‘until EPA makes a 

determination on a PM-coarse NAAQS’’ 

and/or ‘‘establishes equivalent 

increments for PM-coarse.’’ One of these 

commenters added, ‘‘it is prudent to 

maintain the PM10 increments until EPA 

makes a determination on the health 

and environmental effects of the coarse 

fraction of PM.’’ The commenter claimed 

that, ‘‘if EPA retains the annual PM10

increments’’ ‘‘then the determination of 

PM2.5 increments can complement the 

continuation of PM10 increment 

determinations without any 

discontinuities or unwanted 

degradation concerns.’’ 

Another one of these commenters 

stated, ‘‘the basis for dismissing the 

annual PM10 NAAQS by the substitution 

of fine particle NAAQS to address 

certain health and welfare effects does 

not provide a basis for dismissing a PSD 

increment which is meant to stop 

significant degradation of air quality.’’ 

The commenter noted, ‘‘as refinements 

are made to estimation of fine particle 

emissions or in instances where these 

are deemed not to be a major component 

of particulate emissions, the PM10

annual increment could prevent long 

term deterioration of air quality 

associated with the coarse component.’’ 

One State/local agency commenter 

noted, ‘‘EPA also proposes to replace the 

PM10 annual increment with the 

corresponding PM2.5 increment under 

the Section 166(f) options 2A and 2B as 

well, but does not provide a substantive 

basis for such an action.’’ The 

commenter does ‘‘not see the tension 

noted by EPA between Sections 166(a) 

and (f) with respect to reaching a 

holistic solution if EPA views PM2.5 as 

a new indicator of PM, as we believe it 

can.’’ The commenter explained, ‘‘under 

this approach, if EPA determines that 

coarse particle levels are necessary to 

protect the public from certain 

exposures not addressed by PM2.5, then 

it will be appropriate for EPA to define 

complementary increments for coarse 

particulates as another indicator of PM.’’ 

The commenter also asserted that the 

24-hour increments for PM2.5 must be 

based on section 166(f) authority, but 

believes that the PM2.5 increment need 

not replace the PM10 increment for this 

averaging period. 

One commenter requested that EPA 

‘‘keep the PM10 PSD program (especially 

the increments) in place until the full 

PM2.5 program is adopted and in place.’’ 

One commenter ‘‘does not support 

revoking the annual PM10 increments,’’ 

because the commenter feels that ‘‘there 

are too many uncertainties regarding 

PM2.5.’’ The commenter provided the 

following example: ‘‘The program has 

been dragging for years, analytical 

methods are not formulated, the NSR 

part of the implementation rule has not 

issued, condensables are not yet 

included, and the impact of precursors 

has not been definitively explored.’’ The 

commenter explained that ‘‘under these 

conditions, nothing concerning PM10

should be revoked until the reasons for 

doing so are clearly understood and the 

overall impact on ensuring clean air and 

the public health and welfare have been 

fully explored.’’ The commenter 

suggested, ‘‘PM10 increments and 

NAAQS should remain in effect until 

these issues have been resolved to the 

satisfaction of the Administrator.’’ This 

commenter believed that Options 2A 

and 2B must be based entirely on 

section 166(f) of the Act, but that the 

presence of increments for both PM10

and PM2.5 can be supported under this 

section because the two sets of 

increments complement each other. The 

commenter indicated that the problem 

will be resolved when sufficient data are 

available to revoke the PM10 NAAQS 

and increments and/or PM10 is replaced 

by PM10–2.5. 

One State/local agency association 

commenter recommended that ‘‘EPA can 

and should continue both the 24-hour 

and annual average PM10 PSD increment 

program until PM10¥2.5 standards are 

promulgated.’’ The commenter 

explained that ‘‘EPA has the discretion 

to accomplish this under CAA § 166(f)’’ 

and ‘‘at a minimum, the agency should 

continue the 24-hour PM10 increments 

in conjunction with the continuation of 

the 24-hour PM10 NAAQS.’’ 

As stated previously, in this rule we 

are taking no final action on our 

proposal to revoke the annual PM10

increments even though the annual 

PM10 NAAQS has been revoked. Based 

on comments and our own legal 

analysis of the PM10 increments, we 

have concluded that there is a strong 

legal basis for not revoking the annual 

increments at this time. The PM10

increments were promulgated on June 3, 

1993 (58 FR 31622) as replacement 

increments for the then existing 

statutory increments for PM measured 

as TSP. The fact that EPA promulgated 

the PM10 increments as ‘‘equivalent’’ 

replacements for the TSP increments 

under the authority of section 166(f) of 

the Act is important in that EPA does 

not have authority to simply remove the 

TSP increments that were explicitly 

defined within the PSD program 

requirements in the Act. Accordingly, 

we believe that the annual TSP 

increments would be restored by default 

should we decide to revoke the annual 

PM10 increments as proposed. However, 

even if the original annual TSP 

increments were not restored, there is 

no basis for automatically revoking the 

annual PM10 increments simply because 

we have revoked the annual PM10

NAAQS, because annual increments are 

not contingent upon the existence of 

annual NAAQS. This is clear from the 

court’s decision in the earlier NO2

increment litigation stating that 

increments for a particular pollutant do 

not necessarily need to match the 

averaging periods that have been 

established for NAAQS for the same 

pollutant. EDF v. EPA, at 189–190 

(‘‘* * * the ‘goals and purposes’ of the 

PSD program, set forth in § 160, are not 

identical to the criteria on which the 

ambient standards are based.’’). 

I. Other Comments on Increments 

Ten commenters (including State/ 

local agencies and industry 

commenters) supported section 166(f) of 

the Act as the basis for PM2.5

increments. These commenters typically 


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voiced the belief that when Congress 

enacted section 166(f), it authorized 

EPA to update PM increments when 

another indicator was defined, and that 

section 166(f) allows EPA to continue 

do so as long as these increments are of 

equal stringency to the prior increments. 

Some of these commenters believe that 

section 166(f) is the only legitimate 

approach under the Act, while others 

indicated simply that it is preferable to 

section 166(a). Some of the commenters 

believe that section 166(f) authority can 

be used to add PM2.5 increments to the 

existing PM10 increments. Others 

believe that PM2.5 increments finalized 

under section 166(f) must fully replace 

the existing PM10 increments, and 

recommended doing so. 

For the reasons discussed previously 

in this preamble, EPA has decided to 

finalize the PM2.5 increments under the 

authority of section 166(a) of the Act. 

With respect to the potential creation of 

PM2.5 increments under section 166(f) 

(as discussed in the 2007 NPRM at 72 

FR 54120–54121), we have not reached 

any final conclusion as to whether that 

approach is authorized by the statute, 

but believe that such an approach raises 

significant legal issues. Because the 

Agency is not relying on section 166(f) 

in this rulemaking, we do not address 

these issues in this preamble, though 

some additional discussion is included 

in the Response to Comments document 

for this rule. 

One industry association that 

supported the Option 1 approach based 

on section 166(a) authority also 

acknowledged that EPA is authorized to 

use the Option 2 approach based on 

section 166(f) authority. An industry 

commenter indicated that 2007 NPRM’s 

arguments regarding the alternative 

legal authorities under section 166(a) 

and (f) were not compelling; the 

commenter recommended setting the 

PM2.5 increments at the levels proposed 

as Option 2B because they would have 

the lowest economic impact. 

As noted previously, we have decided 

to finalize Option 1 based on section 

166(a) authority because we believe that 

provision provides the clearest statutory 

authority for purposes of developing 

increments based on PM2.5. We would 

point out, however, that any conclusion 

as to which option would yield 

increments that ‘‘have the lowest 

economic impact’’ must include a 

consideration of not only the levels of 

the increments but also the associated 

baseline dates that define when 

emissions changes must be considered 

to affect the amount of increment 

consumed. Under Options 2 and 3, the 

PM2.5 increments would be regarded as 

replacement increments for the PM10

increments and, as such, would include 

amounts of increment (based upon the 

PM2.5 component) already consumed 

under the existing PM10 increment 

system. Thus, portions of the substitute 

PM2.5 increments could have already 

been consumed by previous PSD 

sources that emit PM. If, in fact, a 

portion of the PM2.5 increments had 

already been consumed by the prior 

PM10 increment consumption process, 

than there would be a basis to conclude 

that less additional economic growth 

would be allowed under a set of 

replacement PM2.5 increments as 

compared to PM2.5 increments based on 

separate, independent baseline dates. 

One industry commenter suggested 

that EPA develop geographic areaspecific increments (and SILs and 

SMCs) that take local conditions into 

account. The commenter pointed out 

that PM2.5 levels in PSD areas proximate 

to international borders may be elevated 

by sources outside the legal and 

practical control of the United States 

and State authorities. The commenter 

also noted that PM2.5 levels may be 

elevated by natural conditions, such as 

drought, fires, geologic formations 

(sandy or fine-grained surface features), 

high winds, etc., leading to excessively 

dusty ambient conditions over which 

the local area has no control. The 

commenter indicated that local area 

baselines must reflect these PM 

emissions, though they are not reflected 

in the local area’s emissions inventory. 

The commenter urged EPA not to 

penalize such PSD areas by imposing 

uniform national PSD increments (or 

SILs or SMCs) where the conditions of 

concern are not capable of control. 

As previously discussed, this final 

rule establishes an area classification 

system with prescribed, uniform PM2.5

increments for each class. We do not 

believe that it is necessary to develop 

different increments (or SILs or SMC) 

for different areas of the country. 

Emissions from natural conditions such 

as those described by the commenter 

would not consume increment due to 

their natural and temporary nature. In 

addition, if a State wishes to disregard 

new emissions from sources outside the 

United States, the State’s PSD program 

may provide that such emissions do not 

consume increment (see 40 CFR 

51.166(f)(1)(iv)). 

VI. Final Action on PM2.5 SILs 

A. EPA’s Determination on SILs for 

PM2.5

It is EPA’s longstanding policy to 

allow the use of the SILs as de minimis 

thresholds under the NSR programs at 

40 CFR 51.165(b) and part 51, Appendix 

S, to determine whether the predicted 

ambient impact resulting from the 

emissions increase at a proposed major 

new stationary source or modification is 

considered to cause or contribute to a 

violation of the NAAQS. We have also 

allowed the SILs under the PSD 

program to determine: (1) When a 

proposed source’s ambient impacts 

warrant a comprehensive (cumulative) 

source impact analysis; (2) the size of 

the impact area within which the air 

quality analysis is completed, and (3) 

whether the emissions increase from a 

proposed new major stationary source 

or major modification is considered to 

cause or contribute to a violation of any 

NAAQS. 

We proposed three separate options 

for setting SILs for PM2.5. The first 

option relied upon the same approach 

we proposed for PM10 in the 1996 NSR 

Reform proposal. This set included 

Class I SILs set at 4 percent of the Class 

I PM2.5 increments. For class II and III 

areas, we proposed to codify the SIL 

values that already existed for PM10, i.e., 

1.0 μg/m3 (annual) and 5.0 μg/m3 (24- 

hour). Options 2 and 3 relied on scaling 

the PM10 SILs, as codified in 40 CFR 

51.165(b), by a particular ratio. 

Specifically, for Option 2, the multiplier 

was the emissions ratio of PM2.5 to PM10

for point sources in the 1999 NEI; for 

Option 3 the multiplier was the ratio of 

the PM2.5 NAAQS to the PM10 NAAQS. 

The resulting SILs were proposed as 

follows: 

Option 

Proposed SILs (μg/m3) 

Class I Class II Class III 

Annual 24-hr Annual 24-hr Annual 24-hr 

1 ....................................................................................................................................... 0.04 0.08 1.0 5.0 1.0 5.0 

2 ....................................................................................................................................... 0.16 0.24 0.8 4.0 0.8 4.0 

3 ....................................................................................................................................... 0.06 0.07 0.3 1.2 0.3 1.2 


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21We note that, under the 2007 NPRM, we 

proposed that the SILs for PM2.5 would not be 

treated as a minimum program element for State 

PSD programs; however, the proposed regulatory 

language at 40 CFR 51.166(k)(2) incorrectly stated 

the ‘‘the plan shall provide that,’’ which would 

indicate that the use of the SILs for PM2.5 was 

required in the State plan. This final rule corrects 

this error. 

We have decided to finalize the PM2.5

SILs proposed under Option 3. As 

explained earlier, these values will be 

used in the Federal PSD preconstruction 

review process consistent with our 

proposal. See 72 FR 54138–41 and 

54143. 

States are not required to adopt SILs 

in their NSR or PSD programs; the 

analyses for PM2.5 required by each 

applicable regulation can be carried out 

without using a SIL.21 Therefore, we do 

not intend for any specific deadlines to 

apply under the regulations at 40 CFR 

51.165(b), 51.166, or part 51, Appendix 

S for states to submit SILs for PM2.5, 

should they choose to do so, as part of 

their revisions to incorporate the final 

rules for PM2.5 into SIPs. Nonetheless, 

we believe that the availability of SILs 

as a screening tool greatly improves PSD 

program implementation by 

streamlining the permit process and 

reducing labor hours necessary to 

submit and review a complete permit 

application where the projected impact 

of the proposed source is de minimis in 

the relevant area. For these reasons, we 

are including the PM2.5 SILs in the 

Federal PSD regulations at 40 CFR 52.21 

to screen proposed projects concerning 

the need for a cumulative source impact 

analysis for PM2.5. 

B. Response to Comments Concerning 

the SILs 

The primary purpose of the SILs is to 

identify a level of ambient impact that 

is sufficiently low relative to the 

NAAQS or increments that such impact 

can be considered trivial or de minimis. 

Hence, the EPA considers a source 

whose individual impact falls below a 

SIL to have a de minimis impact on air 

quality concentrations that already 

exist. Accordingly, a source that 

demonstrates that the projected ambient 

impact of its proposed emissions 

increase does not exceed the SIL for that 

pollutant at a location where a NAAQS 

or increment violation occurs is not 

considered to cause or contribute to that 

violation. In the same way, a source 

with a proposed emissions increase of a 

particular pollutant that will have a 

significant impact at some locations is 

not required to model at distances 

beyond the point where the impact of its 

proposed emissions is below the SILs 

for that pollutant. When a proposed 

source’s impact by itself is not 

considered to be ‘‘significant,’’ EPA has 

long maintained that any further effort 

on the part of the applicant to complete 

a cumulative source impact analysis 

involving other source impacts would 

only yield information of trivial or no 

value with respect to the required 

evaluation of the proposed source or 

modification. 

While some commenters opposed all 

of the proposed options for PM2.5 SILs, 

most commenters generally supported 

the use of a SIL as a screening tool for 

PM2.5 air quality analyses. Commenters 

who supported one of the proposed 

options for the SILs were divided as to 

their support of a particular approach 

for selecting the SIL value, with each 

option receiving some support. 

Commenters also tended to agree that 

the SILs should not be used for 

determining significant impacts on 

AQRVs in Class I areas. 

Those commenters supporting the 

concept of the SILs, yet opposing all 

proposed options, believed that all 

options yielded SILs that were too low. 

Another commenter, an environmental 

group, presented extensive legal and 

policy arguments against the SILs 

concept in general. Some of the 

significant comments and our responses 

to them are addressed herein, while 

others are covered in the Response to 

Comments document which we have 

placed in the docket for this rulemaking. 

1. Legal Basis for SILs 

One commenter opposed all three 

proposed options on both legal and 

policy grounds claiming that EPA has 

no legal authority to promulgate SILs 

and that the de minimis doctrine 

endorsed by the court does not apply to 

increment analyses, where Congress has 

expressly directed that the letter of the 

law applies in all circumstances, as it 

has in this case. (The commenter’s 

policy concerns about SILs are 

discussed later in this section of this 

preamble.) The commenter stated that 

‘‘Congress codified increments in 

section 163 of the Act, directing that 

SIPs contain measures assuring that the 

increments shall not be exceeded.’’ 

According to the commenter, ‘‘The Act 

plainly provides that no major source 

may be constructed unless it meets this 

requirement, and may not contribute to 

an exceedance ‘for any pollutant in any 

area.’ ’’ The commenter further stated 

that ‘‘the de minimis doctrine is 

inapplicable because it applies only 

where the regulations will yield a gain 

that is demonstrably trivial or zero.’’ 

We disagree with this commenter’s 

claim that there is no legal basis for 

SILs. As stated in the 2007 NPRM, the 

concept of a SIL is grounded on the de 

minimis principles described by the 

court in Alabama Power at 323, 360. In 

this case reviewing EPA’s 1978 PSD 

regulations, the court recognized that 

‘‘there is likely a basis for an implication 

of de minimis authority to provide 

exemption when the burdens of 

regulation yield a gain of trivial or no 

value.’’ Alabama Power at 360. See the 

2007 NPRM for more on how we have 

applied the de minimis principle in the 

past. See also, Sur Contra La 

Contaminacion v. EPA, 202 F.3d 443, 

448–49 (1st Cir. 2000) (upholding EPA’s 

use of SILs to allow permit applicant to 

avoid full impact analysis.) 

2. Levels of the SILs 

Several commenters opposed all three 

proposed options on the grounds that all 

yielded levels of SILs that are too low. 

One of these commenters argued that 

the proposed SILs ‘‘imply a level of 

monitoring and modeling sophistication 

that is currently absent in our regulatory 

scheme.’’ This commenter 

recommended that EPA ‘‘rethink the 

level of the proposed SILs and select 

concentrations less likely to be within 

the level of error inherent in current 

monitoring and modeling methods.’’ 

We disagree with these commenters’ 

concerns about all the proposed SILs 

being too low. While we did not select 

the Option 1 levels, the Class II and III 

SILs for PM2.5 under that option were 

the same ambient concentration levels 

that are used for the SILs for the other 

criteria pollutants under 40 CFR 

51.165(b), and those existing SILs values 

are associated with NAAQS that are 

considerably higher than the NAAQS 

for PM2.5. Clearly, it would have been 

inappropriate to select Class II and III 

SILs for PM2.5 that represent relatively 

higher values than the existing SIL 

values for other pollutants in light of the 

more stringent NAAQS levels that exist 

for PM2.5. We also disagree that the SILs 

should be consistent with current 

monitoring capabilities for PM2.5. The 

SILs are a screening tool used in 

comparison with modeled predictions— 

not monitored concentrations—of PM2.5. 

Monitoring accuracy is not a relevant 

concern in predicting with air quality 

dispersion models the concentrations of 

a pollutant that a source will cause if its 

construction and operation are allowed 

to occur. 

Two commenters expressed concern 

about national de minimis values. One 

stated that ‘‘the idea that a single 

national number can define ‘trivial’ is 

flawed, given that even very small 

impact can be of great significance in an 

area that is close to an increment or 

NAAQS.’’ The other commenter 


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22See ‘‘Information Collection Request (ICR) for 

the Prevention of Significant Deterioration for 

PM2.5-Increments, Significant Impact Levels and 

Significant Monitoring Concentration,’’ Docket No. 

EPA–HQ–OAR–2007–0628. 

recommended that EPA ‘‘develop 

geographic area-specific * * * levels 

that take local conditions into account.’’ 

This commenter reasoned that some 

PSD areas ‘‘should not be ‘penalized’ by 

a single, national PSD increment, 

significant impact levels and significant 

monitoring level, where the conditions 

of concern are not capable of control.’’ 

With regard to the first of these 

commenters, our longstanding policy 

has been that when a source has a de 

minimis impact on an existing air 

quality problem, that source should not 

necessarily be required to bear the 

burden of addressing its small 

contribution to a problem caused 

primarily by other sources. However, 

notwithstanding the existence of a SIL, 

permitting authorities should determine 

when it may be appropriate to conclude 

that even a de minimis impact will 

‘‘cause or contribute’’ to an air quality 

problem and to seek remedial action 

from the proposed new source or 

modification. 

We do not agree with the second of 

these comments concerning the 

development of regional SILs based on 

a concern that some amounts of PM2.5 in 

a particular area are ‘‘not capable of 

control.’’ The PM2.5 SILs define a 

threshold level for determining whether 

a predicted ambient impact by a 

proposed major stationary source or 

major modification of PM2.5 needs to 

undergo a more thorough analysis of the 

PM2.5 NAAQS or increments. This value 

is not directly affected by the total 

amounts of PM2.5 that may exist in an 

area or by what causes the existing 

PM2.5 concentrations, rather by the 

impact of a single source relative to the 

levels of the NAAQS and increments 

that must be protected. Therefore, we do 

not see why the SILs should be 

influenced by the geographic area of 

concern, or how different levels of SILs 

for the same pollutant and averaging 

period would be necessary. 

With regard to the commenters that 

supported at least one of the proposed 

SILs options, they generally did not 

prefer the entire suite of SILs (Class I, 

II, and III SILs) from a single option, but 

instead supported parts of different 

options, primarily divided by drawing a 

distinction between the Class I SILs and 

the SILs for Class II and III areas. 

Consistent with the way that 

commenters addressed the Class I, II, 

and III SILs, we will address the 

comments separately herein as well. 

a. Class I SILs 

Support and opposition for the 

proposed PM2.5 SILs for Class I areas 

was fairly evenly divided. The PM2.5

SILs for Class I areas proposed under 

Option 2 received the support of some 

commenters, but also received an equal 

amount of opposition. Option 1, which 

yielded the lowest (most restrictive) 

values for the Class I area SILs for PM2.5

(annual and 24-hour averages), was 

supported by some commenters, 

including a Federal agency that serves 

as a FLM for Federal Class I areas under 

the PSD program, but was equally 

opposed. Finally, comments supporting 

the Class I SILs proposed under Option 

3 (from which we derived the values 

included in the final rules) were 

matched by comments that opposed the 

Class I SILs under Option 3. 

One commenter opposing the Option 

3 SILs for Class I areas said that the 

values ‘‘appear to be unrealistically low 

and, if selected, would point to the need 

for EPA to conduct an economic impact 

analysis.’’ We disagree that adopting the 

Option 3 SILs for Class I areas (and 

Class II and III areas) will result in 

economic impacts significant enough to 

warrant an economic impact analysis. 

Under the Paperwork Reduction Act, 

EPA is required to analyze, and receive 

approval from the Office of Management 

and Budget (OMB) for, the 

recordkeeping and reporting burden 

imposed by its regulations (referred to 

as the ‘‘Information Collection Request’’ 

or ‘‘ICR’’ for the regulation). For the PSD 

program, this includes the burden 

associated with the entire permitting 

process, including any required 

modeling analyses. In our analysis for 

this rulemaking, we have concluded 

that the number of PSD permits issued 

annually will be unchanged (at an 

estimated 274 per year), while the total 

burden across all PSD permit applicants 

of adding PM2.5 analyses will increase 

by a total of approximately 29,000 hours 

per year at a cost of approximately $2.8 

million per year. This total annual 

impact on industry is a small fraction of 

the threshold ($100 million per year) 

that is considered ‘‘significant’’ under 

Executive Order 12866 (Regulatory 

Planning and Review) and the 

Unfunded Mandates Reform Act. See 

sections X.B and X.D of this preamble 

for more on the Paperwork Reduction 

Act and the Unfunded Mandates Reform 

Act, respectively. Our analysis of the 

recordkeeping and reporting burden of 

this rulemaking can be found in the 

docket for this ICR.22

Another commenter stated that the 

use of a NAAQS-based ratio under 

Option 3 for the proposed SILs does not 

‘‘translate back to the emissions point 

level when comparing PM10 and PM2.5.’’ 

This commenter continued, ‘‘this is an 

invalid method of proceeding because 

EPA has not shown that there is a 

correlation between the NAAQS and 

direct PM2.5 since there is no accounting 

for precursors and EPA does not have a 

quantifiable sense of the portion of 

PM2.5 that is condensable for various 

industries.’’ 

We disagree with the commenter’s 

concern that the use of NAAQS-based 

ratios is an invalid method for 

developing the PM2.5 SILs. The purpose 

of using the NAAQS ratio with the PM10

SILs to develop PM2.5 SILs is to 

establish values that have a comparable 

relationship between ambient 

concentrations of PM10 and PM2.5 and 

their respective NAAQS levels. Whether 

a particular ambient concentration of 

PM2.5 results from direct PM2.5

emissions or from precursor emissions 

is not relevant to this particular 

approach. The PM2.5 SILs in this final 

rule are intended to be compared to the 

ambient concentrations of PM2.5 that are 

predicted by modeling the emissions of 

a proposed new project. Ambient 

concentrations of PM2.5 can be the result 

of direct PM2.5 emissions, which may 

include condensable particulate matter, 

as well as precursor emissions, e.g., SO2

and NOX. 

We note that the 2007 NPRM 

included proposed regulatory language 

providing that demonstrations of 

whether the air quality impact of a 

major new source or modification 

would be less than the PM2.5 SILs be 

based on direct PM2.5 emissions from 

the proposed project. The intent of this 

was to recognize the technical 

limitations associated with modeling 

precursor emissions to predict ambient 

PM2.5 impacts. However, in this final 

rule we have removed that limitation by 

removing the reference to ‘‘direct’’ PM2.5

emissions. 

One commenter, who did not support 

any of the proposed SILs options, was 

especially critical of the Class I SILs for 

PM2.5 under Option 1, stating that 

multiplying the proposed PM2.5

increment by 4 percent is without legal 

or practical merit. The commenter 

stated that just because ‘‘4 percent may 

have been a reasonable multiplier to use 

in establishing a significant emission 

rate threshold does not mean that the 

multiplier should be used for a 

completely different regulatory 

purpose.’’ The commenter added that if 

the PM2.5 SILs for Class I areas under 

Option 1 were codified, emissions from 

even the most well-controlled coal-fired 

electric generating station located as far 

away as 300 km from a Class I area 

could well exceed the threshold. 


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In contrast, the Federal agency 

commenter supporting the PM2.5 SILs 

for Class I areas under Option 1 

explained that they analyzed the 

effectiveness of the three sets of 

proposed SILs by modeling four 

different coal-fired power plant 

scenarios using an EPA-approved longrange transport model. The modeled 

plants included a large 1,500 megawatt 

(MW) facility, a moderate-sized 500 MW 

facility, and two medium 800 MW 

facilities. Based on this modeling 

analysis, the commenter concluded that 

the proposed levels of the Class I 24- 

hour SILs based on Option 1 and Option 

3 are ‘‘more appropriately protective of 

the proposed Class I PM2.5 increment 

and impacts to visibility than the level 

obtained under Option 2.’’ This 

commenter supported the consistency of 

using 4 percent of the Class I increments 

that was used by EPA in proposing 

Class I SILs for SO2, NOX, and PM10 in 

1996. 

We chose the Class I SILs under 

Option 3 because we believe that this 

option yields the most appropriate 

combination of SILs for all area 

classifications. Whether a particular 

source will have a significant impact on 

an area is determined to some extent by 

the amount of its emissions, but also by 

other factors such as the height of 

release, pollutant transport distance, 

terrain features, and meteorological 

factors. Thus, we did not select SILs 

values to address a certain size source 

or the degree of control of that source, 

but the ambient impact of that source 

relative to the NAAQS and increments 

that will result from the source’s 

emissions. While the annual Class I SIL 

under Option 3 represents a level that 

is somewhat greater than 4 percent of 

the PM2.5 annual increment for Class I 

areas, it is sufficiently close (as derived 

from a ratio of the PM2.5 NAAQS to the 

PM10 NAAQS) so as to provide a 

reasonable threshold for defining de 

minimis for purposes of conducting a 

Class I increment analysis. We had 

proposed the use of 4 percent of the 

existing Class I increments to develop 

SILs for pollutants in the 1996 NSR 

Reform proposal; however, that 

particular component of the proposal 

was never finalized. See 61 FR 38250 

beginning at 38291. We will further 

discuss our rationale for selecting the 

SILs under Option 3 in the discussion 

which follows for the Class II and III 

SILs. 

b. Class II and III SILs 

While many commenters tended to 

favor Option 2 with regard to the 

proposed Class I increments, they 

tended clearly to support Option 1 for 

defining Class II and III SILs for PM2.5. 

These particular SILs for PM2.5 were 

proposed so as to be equal to the 

existing Class II and III SILs for the 

existing pollutants. In all, six 

commenters supported Option 1. One of 

these commenters stated that Option 1 

SILs for Class II and III areas are 

‘‘sufficiently stringent and fully 

consistent with the de minimis 

justification for SILs.’’ The commenter 

added that ‘‘when conducting an air 

quality impact analysis * * * most 

applicants assume all coarse PM10 to be 

PM2.5.’’ The commenter claimed that 

this assumption is conservative and 

‘‘overestimates the amount of fine 

particles being emitted and renders the 

effective SIL thresholds for PM2.5 lower 

than those written into the regulations.’’ 

We strongly disagree that the SILs 

proposed under Option 1 as applied to 

PM2.5 are sufficiently stringent. The 

application of such values as SILs for 

PM2.5 would result in ambient 

concentrations of PM2.5 that consume a 

much larger portion of both the PM2.5

NAAQS and increments than either of 

the other two options proposed for 

PM2.5 in light of the correspondingly 

more stringent levels of the PM2.5

NAAQS and increments than those for 

the other pollutants. We believe that of 

the 3 options proposed, the PM2.5 SILs 

based on Option 3 represent values that 

are more closely aligned percentagewise with the SILs that have been or are 

being used for other forms of PM when 

compared to their respective NAAQS 

and increments. 

We also disagree with the 

commenter’s suggestion that the 

development of the SILs for PM2.5, or 

any other pollutant, should in any way 

be influenced by the possibility that 

some sources may use conservative 

techniques for estimating a source’s 

emissions rate. Such conservative 

techniques may be needed to the extent 

that technical issues associated with the 

determination of PM2.5 emissions are 

identified, and can certainly be used at 

any time as a simplified methodology 

for estimating PM2.5 emissions. But 

when such an overly conservative 

approach fails to yield de minimis 

results, the source may find it necessary 

to rely upon more accurate techniques 

for determining the amount of PM2.5 that 

the source will emit. 

Finally, one commenter, objecting to 

all of the proposed SILs, stated that EPA 

must assure that SILs are truly de 

minimis and must also include 

limitations on the use of SILs as 

necessary to prevent air quality from 

significantly deteriorating. We 

acknowledge that we did not conduct 

any new modeling or other types of 

analyses of the proposed SILs in order 

to explicitly show that the final PM2.5

SILs values in this final rule are de 

minimis. Instead, we have relied on past 

actions regarding the setting of de 

minimis levels to illustrate that the 

PM2.5 values selected via Option 3 

represent values that are as stringent as 

the previous levels that have been 

established to define de minimis for 

PM10 and TSP. See 45 FR 52706–708 

(using modeling and representative 

data). 

Using the 24-hour and annual 

NAAQS ratios of PM2.5 to PM10, and 

multiplying them by the corresponding 

existing PM10 SILs, we conclude that the 

PM2.5 SILs define de minimis for the 

PM2.5 NAAQS in the same way as the 

PM10 SILs do for PM10 NAAQS. Using 

the increments as a basis for comparison 

provides further support for our 

conclusion. The annual and 24-hour 

PM2.5 SILs represent about 7.5 and 13 

percent of the annual and 24-hour PM2.5

increments, respectively. By 

comparison, the annual and 24-hour 

PM10 SILs represent about 5 and 17 

percent of the annual and 24-hour PM10

increments, respectively. We believe the 

PM2.5 SILs fall into a comparable 

relative range with the PM10 SILs and 

can be considered de minimis. 

In EPA’s 1980 final rule for PSD, EPA 

adopted SERs for the pollutants then 

subject to regulation under the PSD 

requirements. The SER adopted for PM 

(then measured as TSP) was 25 tpy, 

which represented an emissions rate for 

which EPA modeled impacts that 

represented about 4 percent of the TSP 

24-hour NAAQS and about 28 percent 

of the 24-hour TSP increment. Thus, 

EPA considered it acceptable under the 

de minimis assessment for PM that a 

source of particulate matter capable of 

consuming around 28 percent of the 

applicable 24-hour TSP increment could 

be exempted from the requirements to 

complete a comprehensive source 

impact analysis for the PM NAAQS and 

increments. 45 FR 52708. 

In looking at the amount of increment 

that could be consumed by a source that 

is ultimately exempted from having to 

complete a comprehensive modeling 

analysis, it should be pointed out that 

the maximum modeled concentration 

typically occurs in a relatively limited 

area, as compared to the entire modeling 

domain. In particular, for the short-term 

averaging periods, such as the 24-hour 

averaging period, modeled 

concentrations across the modeled area 

generally show that ground level 

impacts are reduced significantly from 

the peak value as the pollutant travels 

a relatively short distance from the 

source, so that the peak modeled 


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concentrations represent the source’s 

impact at only a relatively few receptors 

within the modeled area. In addition, it 

is important to note that the temporal 

and spatial conditions which lead to a 

maximum impact by one source are 

seldom the same for other sources, such 

that maximum impacts of individual 

sources do not typically occur at the 

same location or at the same time. 

Thus, in an area where several 

sources can demonstrate that their 

modeled impacts are de minimis, it 

generally should not be assumed that 

their individual maximum (albeit de 

minimis) impacts on the increment are 

additive. For example, four sources with 

de minimis PM2.5 impacts, each 

consuming 12 percent of the 24-hour 

PM2.5 increment, would not necessarily 

consume 48% of the 24-hour increment. 

Increment consumption is determined 

by the cumulative impact of source 

emissions on each individual receptor 

or modeling point in the area of impact 

within the baseline area defined for the 

affected PSD sources. 

The preamble for the 1980 final rule 

for PSD included a description of a 

modeling analysis that EPA conducted 

to illustrate that a number of major 

sources each making a de minimis 

emissions increase for SO2 could locate 

in an area (in that case, the Dayton area) 

and not cause a violation of either the 

applicable SO2 increment or NAAQS. In 

that particular case, the modeling 

indicated that the maximum aggregate 

increment consumption for 37 sources 

emitting 40 tpy of SO2 (the de minimis 

emissions rate for SO2) would have a 

cumulative impact at any location of 

less than 1.5 μg/m3 on a 24-hour basis— 

well below the NAAQS and increments 

for SO2. 45 FR 52708. 

With regard to the commenter’s 

recommendation that we place 

limitations on the use of SILs, we earlier 

provided an example of when it might 

be appropriate to require a modified 

source to mitigate its contribution to a 

violation of a NAAQS or increment even 

when the predicted ambient impact of 

the proposed emissions increase would 

result in what is normally considered to 

be de minimis. In addition, we have 

historically cautioned states that the use 

of a SIL may not be appropriate when 

a substantial portion of any NAAQS or 

increment is known to be consumed. 

We have indicated elsewhere in this 

preamble that states are not required to 

adopt the SILs for PM2.5 in this final 

rule. At their discretion they may 

choose not to rely on SILs to screen 

applicants or they may establish more 

stringent values. 

Finally, it should be noted that while 

a source having only de minimis 

impacts may not be required to 

complete a comprehensive source 

impact analysis, the emissions from 

such sources are still considered to 

consume increment and would be 

counted as part of the next increment 

analysis required to be completed by a 

PSD applicant in that same area, or by 

the State under a periodic increment 

review. 

3. Relationship Between SILs and 

AQRVs 

While commenters generally 

supported EPA’s position that the SILs 

should not be used in any way to 

determine effects of emissions increases 

on the AQRVs in a Class I area, two 

commenters urged that the de minimis 

concentration be used for analyzing 

Class I area impacts under certain 

circumstances. That is, they believed 

that the SILs should be used to 

determine the need for a Class I area air 

quality analysis when an FLM has not 

identified a specific AQRV related to the 

pollutant under evaluation or obtained 

ambient monitoring data to confirm that 

predicted concentrations from air 

dispersion models are representative of 

actual AQRV impacts in the Class I area. 

The commenters claimed that without 

this flexibility, applicants would be 

required to conduct complex and 

extensive Class I air dispersion 

modeling without any clear objective, 

and regulatory agencies would have to 

review the modeling with limited 

information to determine if the 

emissions could cause an ‘‘adverse’’ 

impact or if potentially costly controls 

should be required. 

These commenters appear to be 

suggesting that an FLM may needlessly 

call for an analysis of a particular Class 

I area, involving ‘‘complex and extensive 

Class I area dispersion modeling’’ 

despite the fact that no AQRV has been 

identified for that Class I area. We agree 

that a Class I analysis in the absence of 

any known AQRVs would be 

unnecessary because any demonstration 

of an adverse impact must be made with 

respect to a pollutant adversely affecting 

an AQRV. We believe, however, that 

such analyses would be avoided under 

the procedures set forth in section 

165(d)(2)(C) of the Act which require 

that a notice be filed alleging that a 

proposed source may cause or 

contribute to adverse effects, and 

identifying the adverse impact. Insofar 

as the FLM must also demonstrate ‘‘to 

the satisfaction of the State that 

emissions from such facility will have 

an adverse impact on the air quality 

related values,’’ it would be difficult to 

require the source to undertake any kind 

of detailed analysis in the absence of an 

AQRV on which such adverse impacts 

must be demonstrated. Thus, we have 

concluded that it is not necessary to use 

the SILs as a safeguard against 

unnecessary Class I area analyses. 

Instead, we believe that the need for a 

Class I analysis, other than the required 

analysis of the NAAQS and Class I 

increments (for both of which the SILs 

are intended to be used), should be 

based on the potential for adverse 

effects on an AQRV that the FLM has 

identified and believes could be affected 

by a pollutant that would be emitted by 

the proposed project. 

4. Form of the SILs 

One commenter stated that ‘‘the 

Proposal does not indicate how the 

proposed PM2.5 SILs are to be 

interpreted.’’ This commenter believed 

that ‘‘the form of the SILs should be 

consistent with the form of the PM2.5

NAAQS’’ adding that ‘‘the current PM2.5

NAAQS requires that compliance with 

the 24-hour and annual standards be 

determined using 3-year averaging.’’ 

Specifically, ‘‘The annual standard is 

calculated based upon the 3-year 

average of annual mean PM2.5

concentrations, and the 24-hour 

standard is based on the 3-year average 

of the 98th percentile (or highest-8th 

high value) of 24-hour concentrations.’’ 

In a March 23, 2010 EPA 

memorandum titled ‘‘Modeling 

Procedures for Demonstrating 

Compliance with PM2.5 NAAQS,’’ we 

provided guidance for using the SILs in 

conjunction with the 24-hour and 

annual PM2.5 NAAQS, which takes into 

account the statistical form of the 

NAAQS. Following promulgation of the 

PM2.5 increments in this final rule, we 

intend to provide guidance for 

interpreting the SILs for their use with 

the 24-hour and annual PM2.5

increments as well. 

5. SILs for Other Pollutants 

In proposing Option 1, we noted that 

many who commented on the 1996 NSR 

Reform proposal supported this 

approach and believed that the 

proposed PM10 SIL values would serve 

as appropriate de minimis values. In 

fact, we are aware that many states have 

been using these proposed SILs for PM10

as screening tools since 1996 or earlier. 

Regarding the proposed Class I SILs 

under Option 1, we expressed our belief 

that where a proposed source consumes 

less than 4 percent of the Class I 

increment, the source’s impact is 

sufficiently low so as not to warrant 

requiring the source to carry out a 

detailed analysis of the combined effects 

of the proposed source and all other 

increment-consuming emissions in the 


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Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 64895 

23 In 1985, the requirements now contained in 40 

CFR 51.165(b) were contained in 40 CFR 51.18(k), 

which was later part of a major restructuring of the 

part 51 SIP requirements. 

24 In the case of a NAAQS compliance analysis, 

all sources in the area are considered to contribute 

to the air quality levels; for increments, however, 

‘‘all’’ refers only to those sources whose emissions, 

in whole or in part, consume PSD increment for a 

particular pollutant. 

25The provision for the monitoring exemption 

was originally promulgated at 40 CFR 51.24(i)(8) 

and 52.21(i)(8); it should be noted, however, that 

this provision is now found at 40 CFR 51.166(i)(5) 

and 52.21(i)(5). 

area. 72 FR 54140. We previously used 

a similar rationale to establish the SERs 

for PSD applicability purposes, 

concluding in part that emissions rates 

that resulted in ambient impacts less 

than 4 percent of the 24-hour standards 

for PM and SO2 were sufficiently small 

so as to be considered de minimis. 45 

FR 52707–8. 

The original SIL values of 1.0 and 5.0 

μg/m3 for TSP and PM10 were 

interpreted by EPA as representing the 

minimum amount of ambient impact 

that is significant. This formed the basis 

for the proposed Option 1 PM2.5 SIL 

values of 1.0 and 5.0 μg/m3 for the 

annual and 24-hour averaging periods 

for Class II and III areas. 

The SILs currently appear in EPA’s 

regulations at 40 CFR 51.165(b). That 

particular NSR regulation provides that 

states must include a preconstruction 

review permit program for any new 

major stationary source or major 

modification that proposes to locate in 

an attainment or unclassifiable area and 

would cause or contribute to a violation 

of the NAAQS. These values, added to 

40 CFR 51.165(b) on July 1, 1987, have 

previously been referred to as 

‘‘significant ambient impact 

concentrations’’ and are used to enable 

a source to determine whether its 

emissions would cause or contribute to 

a NAAQS violation at ‘‘any locality that 

does not or would not meet the 

applicable national standard.’’ 52 FR 

24672, April 2, 1985, at 24688. 

In 1985, when EPA proposed to add 

‘‘significant ambient impact levels’’ for 

PM10, we also indicated that for PSD 

purposes the requirements under 

section 51.165(b) 23 ‘‘would be applied 

to all applicable PSD requirements.’’ The 

EPA has since applied these values in 

other analogous circumstances under 

the PSD program. Based on EPA 

interpretations and guidance, SILs have 

also been widely used in the PSD 

program as a screening tool for 

determining when a new major source 

or major modification that wishes to 

locate in an attainment or unclassifiable 

area must conduct a more extensive air 

quality analysis to demonstrate that it 

will not cause or contribute to a 

violation of the NAAQS or PSD 

increment in the attainment or 

unclassifiable area. The SILs are also 

used to define the extent of the 

Significant Impact Area where, using air 

dispersion models and ambient 

monitoring data, a cumulative source 

impact analysis accounting for 

emissions changes from affected sources 

is performed.24 See the 2007 NPRM for 

additional information on the history of 

EPA’s guidance related to SILs (72 FR 

54138–39). 

In the 1996 NSR Reform proposal, we 

proposed to add the SILs for PM10 and 

other pollutants already contained in 40 

CFR 51.165(b)(2) directly into the PSD 

regulations at 40 CFR 51.166 and 52.21. 

Because the SILs in 40 CFR 51.165(b) 

did not include thresholds for Class I 

areas, we proposed to set Class I SILs at 

the level of 4 percent of the respective 

Class I increments. Thus, for PM10, the 

proposed Class I SILs were 0.2 μg/m3

(annual) and 0.3 μg/m3 (24-hour), and 

the proposed Class II and III SILs were 

1.0 μg/m3 (annual) and 5.0 μg/m3 (24- 

hour). The EPA has not yet taken final 

action on the 1996 proposal on SILs for 

pollutants other than PM2.5; therefore, 

we rely upon our longstanding policy to 

use those values, as codified in 40 CFR 

51.165(b)(2), for PSD permitting. 

VII. Final Action on the PM2.5 SMC 

A. EPA’s Determination on the PM2.5

SMC 

As with the increments and SILs for 

PM2.5, we proposed three different 

options for establishing an SMC for 

PM2.5. The first option, referred to as the 

‘‘lowest detectable concentration’’ 

approach, relied on the method we used 

in 1980 to develop the SMCs for the 

pollutants then subject to PSD. This 

particular method focused on 

development of the SMC value based on 

the current capability of providing a 

meaningful measure of the pollutants. 

See relevant discussion later in this 

section and at 45 FR 52710. Options 2 

and 3, called the ‘‘PM2.5 to PM10

emissions ratio’’ and the ‘‘PM2.5 to PM10

NAAQS ratio,’’ respectively, used the 

SMC for PM10 as the base for 

multiplying the emissions and NAAQS 

ratios to derive an SMC for PM2.5. See 

72 FR 54141. The three proposed 

options yielded the following numerical 

levels for the SMC: 

• Option 1: 10 μg/m3, (24-hour 

average); 

• Option 2: 8.0 μg/m3 (24-hour 

average); and 

• Option 3: 2.3 μg/m3 (24-hour 

average). 

We are taking final action on the SMC 

for PM2.5 using the ‘‘lowest detectable 

concentration’’ approach (Option 1). 

However, we have determined that the 

SMC value that is calculated under this 

methodology is lower than the proposed 

value of 10 μg/m3 to reflect ‘‘current 

capability’’ with respect to the 

measurement and collection of ambient 

PM2.5 concentrations. The result of such 

revised calculation is that the SMC 

value in this final rule is different from 

(more stringent than) the proposed 

level. The revised value is 4 μg/m3 (24- 

hour average). Our basis for the revised 

calculation and the resulting lower 

value is described in greater detail later 

in this section. 

The EPA and its delegated reviewing 

authorities will use the PM2.5 SMC to 

determine when it may be appropriate 

to exempt a proposed new major 

stationary source or major modification 

from the ambient monitoring data 

requirements under the PSD rules. 

Similarly, states with EPA-approved 

PSD programs that adopt the SMC for 

PM2.5 may use the SMC, once it is part 

of an approved SIP, to determine when 

it may be appropriate to exempt a 

particular major stationary source or 

major modification from the monitoring 

requirements under their State PSD 

programs (see 40 CFR 51.166(i)(5)). 

B. Response to Comments Concerning 

the SMC 

1. Legal Issues 

Under the Act and EPA regulations, 

an applicant for a PSD permit is 

required to gather preconstruction 

monitoring data in certain 

circumstances. Section 165(a)(7) of the 

Act calls for ‘‘such monitoring as may be 

necessary to determine the effect which 

emissions from any such facility may 

have, or is having, on air quality in any 

areas which may be affected by 

emissions from such source.’’ In 

addition, section 165(e) of the Act 

requires an analysis of the air quality in 

areas affected by a proposed major 

facility or major modification and calls 

for gathering 1 year of monitoring data 

unless the reviewing authority 

determines that a complete and 

adequate analysis may be accomplished 

in a shorter period. These requirements 

are codified in EPA’s PSD regulations at 

40 CFR 51.166(m) and 52.21(m). 

In 1980, EPA adopted regulations that 

included pollutant-specific SMCs as a 

screening tool for sources to determine 

whether they should conduct sitespecific preconstruction ambient 

monitoring.25 We explained our 


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position that it was appropriate to 

exempt sources from preconstruction 

monitoring requirements for a pollutant 

if the source could demonstrate that its 

ambient air impact was less than a value 

known as the Significant Monitoring 

Concentration or SMC. At the time the 

SMCs were adopted, EPA described 

them as ‘‘air quality concentration de 

minimis level[s] for each pollutant [that 

were available] for the purpose of 

providing a possible exemption from 

monitoring requirements.’’ 45 FR 52676, 

52707 (August 7, 1980). The EPA 

explained that it believed there was 

‘‘little to be gained from preconstruction 

monitoring’’ where a source could show 

that its projected impact of a pollutant 

within the affected area was below the 

de minimis concentration for that 

pollutant. 45 FR at 52710. 

One commenter opposed our 

proposed establishment of any SMC for 

PM2.5, claiming that SMCs in general are 

contrary to the Act. The commenter 

stated that ‘‘in Section 165(e) Congress 

mandated a full year of continuous air 

quality monitoring for each major 

source subject to the PSD program.’’ 

With this in mind, the commenter 

indicated that there are no exceptions, 

other than the limited statutory 

provisions, discussed above, which 

allow for less than a year’s worth of 

monitoring based on a determination 

that a complete and adequate analysis of 

such purposes may be accomplished in 

a shorter period. The commenter then 

argued that ‘‘the allowance for a ‘shorter 

period’ hardly amounts to authority to 

waive monitoring entirely, which is 

what EPA’s SMC proposal would do.’’ 

As with the SMCs adopted by EPA in 

1980, the SMCs that we proposed for 

PM2.5 are supported by the de minimis 

doctrine set forth in the Alabama Power 

opinion. Like the other pollutants for 

which EPA has promulgated SMCs, EPA 

believes there is little to be gained from 

preconstruction monitoring of PM2.5

concentrations that cannot be accurately 

measured. 

Therefore, in developing the three 

proposed options for an SMC, EPA 

sought to use methods that would 

identify levels representing a de 

minimis or insignificant impact on 

PM2.5 ambient air quality that makes the 

collection of additional monitoring data 

extraneous. 

2. Level of the SMC 

As indicated earlier, the SMC for 

PM2.5 in this final rule is 4 μg/m3, 24- 

hour average. This value may be used by 

permitting authorities to determine 

when they may exempt a proposed 

major stationary source or major 

modification for PM2.5 from the air 

quality monitoring requirements for 

PM2.5 under 40 CFR 51.166. The EPA 

and its delegated State/local programs 

will also use this new value under the 

Federal PSD program at 40 CFR 52.21. 

We proposed three options for 

developing the SMC for PM2.5; each 

option yielded a different concentration 

value. In choosing between the three 

options, EPA proposed to select the 

option that reflected the degree of 

ambient impact on PM2.5 concentrations 

that could be considered truly de 

minimis and used to justify exempting 

a source from the requirement to gather 

1 year of ambient monitoring data for 

PM2.5. Ultimately, we have selected the 

‘‘lowest detectable concentration’’ 

approach (Option 1) that relies directly 

upon ambient monitoring measurement 

sensitivity and precision. That is, if 

either the predicted source impact or 

estimated existing air quality in an area 

is below a concentration that can be 

accurately measured, then it would not 

be reasonable to require a source to 

attempt to collect such ambient data. 

In 1980, EPA determined the SMCs 

based on the then current capability of 

providing a meaningful measure of 

ambient pollutant concentrations. The 

EPA promulgated values that 

represented five times the lowest 

detectable concentration in ambient air 

that could be measured by the 

instruments available for monitoring the 

pollutants. 45 FR 52710. The factor of 

‘‘five’’ took into account the 

measurement errors associated with the 

monitoring of these low pollutant levels 

or small incremental changes in 

concentration. These measurement 

errors were said to arise from various 

sources, such as sample collection, 

analytical measurement, calibration, 

and interferences. See May 20, 1980 

EPA memorandum from Rehme, K. A., 

to Warren Peters, contained in the 

docket for this rulemaking. Accordingly, 

in the 2007 NPRM for PM2.5, we voiced 

our belief that this was a reasonable 

approach, since it was also used for 

PM10 and TSP. 72 FR 54141. 

Eight commenters expressed support 

for the SMC based on Option 1, albeit 

at the higher level as originally 

proposed. In some cases, it is not clear 

whether these commenters supported 

the particular approach (i.e., an SMC 

linked to the lowest detectable level) or 

the fact that the calculated value was 

simply the highest value of the values 

proposed under the three options. 

Clearly, some of the commenters 

indicated their support for the approach 

because it is consistent with the 

approach used for setting the original 

SMCs in 1980. Two commenters 

opposed Option 1 because it resulted in 

an SMC value that was too high. These 

latter commenters noted that the SMC 

derived via Option 1 (10 μg/m3, 24-hour 

average) was greater than the proposed 

24-hour PM2.5 increment for Class II 

areas and argued that such an outcome 

is inappropriate. We believe that this 

important concern is adequately 

addressed by the level of the SMC for 

PM2.5 that is established in this 

rulemaking. 

Several commenters supported the 

levels derived from either Option 2 or 

Option 3, but were concerned that the 

justification for choosing either of these 

values would need to be further 

explained. Some of these commenters 

were specifically concerned about the 

use of a 0.8 PM2.5-to-PM10 emissions 

ratio which, they argued, relied on 

inventory data that did not adequately 

address all sources that would likely 

affect ambient concentrations of PM2.5

in an area. 

We conclude that Option 1 is the 

appropriate option for defining the SMC 

for PM2.5. The ability to accurately 

measure ambient PM2.5 concentrations 

is not related to a ratio of PM2.5 to PM10

either directly in terms of emissions or 

as expressed by the respective NAAQS, 

which were used to define the SMC for 

PM2.5 under Options 2 and 3, 

respectively. Our original concern was 

that, while Option 1 linked the SMC 

directly to the concept of a minimum 

detectable concentration (in order to 

identify de minimis monitoring 

circumstances), the value originally 

derived from that approach in the 2007 

NPRM was high in relationship to the 

concentrations of PM2.5 defined by the 

existing NAAQS and increments for 

PM2.5.

In considering the use of Option 1 for 

developing the SMC in the final rules, 

however, we recognized after 

publication of the proposed rule that it 

was necessary to re-examine the 

assumptions that we relied upon in 

1980 to develop the numerical values 

for the original SMCs so that we could 

most accurately reflect current 

monitoring techniques for PM2.5. Our reexamination for this final rule utilized 

the most current information concerning 

the physical capabilities of the PM2.5

Federal Reference Method Samplers, 

and addresses uncertainties introduced 

to the measurement of PM2.5 due to 

variability in the mechanical 

performance of the PM2.5 samplers and 

the micro-gravimetric analytical 

balances that weigh filter samples. 

The minimum detection limit (MDL) 

of 2 μg/m3, originally used in 1980 for 

the SMC for PM and promulgated for 

PM2.5 in 1997 (see 40 CFR part 50, 

Appendix L, section 3.1), has been 


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26This information is contained in a March 12, 

2009 internal EPA memorandum from Dennis 

Crumpler to Raj Rao, titled ‘‘PSD Monitoring De 

Minimis Concentration for PM2.5,’’ which has been 

placed in the docket for this rulemaking. 

reaffirmed by 9 years of field blank data 

collected by EPA through the PM2.5

Performance Evaluation Program. 

However, we found that new data exist 

to ‘‘indicate a conservative estimate of 

the aggregate uncertainty factor is no 

greater that ‘2’ at the concentration 

equal to the MDL of 2 μg/m3.’’ 26

Accordingly, the lowering of the 

uncertainty factor from ‘‘five’’ to ‘‘two’’ 

under Option 1 yields an SMC of 4 μg/ 

m3 PM2.5, 24-hour average, rather than 

the proposed concentration of 10 μg/m3. 

We conclude that the modified level 

of 4 μg/m3 PM2.5, 24-hour average, for 

the SMC under Option 1, based upon a 

more current understanding of 

monitoring precision for PM, especially 

fine PM, addresses commenter support 

for the use of a method that is consistent 

with the way other SMCs were 

developed and most directly reflects 

monitoring capability for the pollutant 

of concern, while at the same time 

responding to the concern of other 

commenters that a value in the lower 

range of proposed SMC values is most 

reasonable considering the levels of the 

NAAQS and increments for PM2.5. 

C. Correction of Cross Reference in PSD 

Ambient Monitoring Requirements 

In the 2007 NPRM, we proposed to 

take final action to correct a cross 

reference contained in paragraph (i) of 

the part 51 and 52 PSD regulations. 

Specifically, at the time of the proposal, 

paragraphs (ii) and (iii) in 40 CFR 

51.166(i)(5), and paragraph (ii) in 40 

CFR 52.21(i)(5), each referred to 

concentrations listed in paragraph 

(i)(8)(i) of both regulations. However, 

there is no paragraph (i)(8)(i) in existing 

40 CFR 51.166, and no concentration 

values are contained in existing section 

(i)(8)(i) of 40 CFR 52.21. The cross 

reference in these provisions was 

intended to reference the SMCs in 

paragraph (i)(5)(i) of the two PSD 

regulations, but EPA failed to make this 

change when the paragraphs were 

renumbered in an earlier rulemaking. 

We did not receive any comments 

concerning this proposed corrective 

action. We made the necessary 

correction as part of the May 16, 2008 

final PM2.5 NSR Implementation Rule 

(see 73 FR 28348 and 28349); therefore 

it is not necessary to take any further 

action in this final rule with regard to 

the proposed correction. 

VIII. Dates Associated With 

Implementation of the Final Rule 

This section describes the key dates 

that we have established for 

implementing the final rule. In the 2007 

NPRM, we indicated that different dates 

appeared to be appropriate for 

implementing the PM2.5 increments, 

each date depending on the legal 

authority that we relied upon to 

promulgate it. We described and took 

comment on some alternative effective 

dates for increments, as well. In 

addition, we discussed and took 

comment on potential implementation 

dates for the SILs and SMC components 

of the proposed rule, which we 

indicated were not subject to the same 

statutory considerations as the 

increments. 

We received a number of comments 

on the different proposed dates. We 

carefully considered these comments in 

selecting the dates described below for 

the final rule. Some of the significant 

comments and our responses to those 

comments are provided below. The 

remaining comments and our responses 

are contained in the Response to 

Comments document included in the 

docket for this rulemaking. 

A. Effective Date of the Final Rule 

In the 2007 NPRM, we took comment 

on the effective date of the final rule by 

presenting the different options 

available for implementing the PM2.5

increments. Under Option 1 for 

developing the increments, we stated 

that section 166(b) of the Act specifies 

that increments promulgated pursuant 

to section 166(a) are to become effective 

1 year following their promulgation. In 

contrast, there is no such 1-year delay 

or any other date prescribed for 

increments promulgated in accordance 

with section 166(f) of the Act, upon 

which we based Options 2 and 3 for the 

annual PM2.5 increments. Thus, 

increments promulgated under Option 

1, which relies on the procedural 

provisions of section 166(b) of the Act, 

would normally be subject to a 1-year 

delay in implementation, while 

increments promulgated under either 

Option 2 or 3, relying on section 166(f) 

of the Act, could follow a 30- or 60-day 

effective date, typical of the effective 

date for most new rules in general. In 

either case, our consideration of the 

effective date for the PM2.5 increments 

assumed that the selected date would 

also be the effective date of the final 

rule. 

In the 2007 NPRM, we took comment 

on some alternative approaches to 

establishing the effective date for PM2.5

increments. Specifically, while 

proposing a 1-year effective date under 

Option 1, we requested comment on 

whether we could promulgate these 

increments under section 166(a) of the 

Act with an effective date of only 60 

days. See 72 FR 54142. 

Nine commenters supported our 

proposal to establish the effective date 

of the part 51 and 52 PSD regulations for 

PM2.5 as 1 year from the date of 

publication. Alternatively, two 

commenters encouraged us to apply the 

60-day effective date, while three other 

commenters supported other effective 

dates, as described in this section. 

Seven industry and industry 

association commenters supported our 

proposal to make the final rule for PM2.5

increments effective 1 year after 

promulgation. Most of these 

commenters cited the additional time 

necessary to develop the needed PM2.5

inventories needed for implementation 

of the PM2.5 PSD program. Two of the 

commenters urged EPA to allow State 

programs sufficient time to adopt 

increments, particularly if condensable 

particulate matter is included in the 

increment and its analysis. These 

commenters stated that the Federal rule 

should not be effective for 1 year. (They 

also stated that states should have 3 

years for the associated SIP revisions.) 

These same commenters added that this 

delay would provide time for sources 

that have permits in the pipeline or are 

just about to submit an application to be 

able to complete the permitting process 

without undue delay. One of the 

commenters specifically voiced support 

for Option 1 for the effective date of the 

final rule (1 year) and Option 2B for the 

period granted for SIP revisions (3 

years). This commenter also explained 

that this additional time may give the 

Agency time to promulgate better 

measurement methods for sources of 

condensable particulate matter. 

Another of these commenters noted 

that, at the time of the proposal, the 

NSR portion of the CAFPIR had not yet 

been promulgated, and that states would 

need time to incorporate that rule as 

well as the requirements of the proposal 

into their SIPs. This commenter added 

that making the PM2.5 increments 

effective before states and sources have 

had a reasonable opportunity to begin, 

let alone complete, the SIP process for 

the two related rulemakings would 

unnecessarily complicate an alreadycomplex regulatory process. 

In contrast, the two commenters 

supporting the shorter effective date 

encouraged us to apply the 60-day 

period for the effective date under 

whatever option is finalized. One of 

these commenters urged us to take 

measures to expedite the 


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implementation of the PM2.5 final rule 

and suggested that we choose the 

shortest of the proposed effective dates 

which are allowed under any of the 

applicable regulations. This commenter 

indicated that in light of the excessive 

delay in the implementation of the 

PM2.5 PSD program since the NAAQS 

were promulgated, the 60-day effective 

date should be applied under EPA’s 

preferred option. 

In light of our decision to promulgate 

PM2.5 increments under the authority of 

section 166(a) of the Act (proposed 

Option 1), we are faced with the 

decision as to how to most effectively 

implement the long-awaited PM2.5

increments, recognizing that the Act 

provides for a 1-year implementation 

delay. We have concluded that it is most 

appropriate to follow the plain language 

of the Act which calls for a 1-year 

effective date for implementing 

increments developed under section 

166(a) of the Act. We agree with the 

commenters who suggested that a 

shortened implementation delay was 

desirable because of the substantial 

delay in the promulgation of measures 

to prevent significant air quality 

deterioration with respect to PM2.5. 

Nevertheless, we believe it would be 

inappropriate in this action to disregard 

the statutory language which plainly 

calls for a 1-year delay. Accordingly, we 

are setting the effective date of the PM2.5

increments at 1 year from the date of 

promulgation of this final rule, 

consistent with the 1-year delay 

required under section 166(b) of the Act. 

We are doing this by setting the ‘‘trigger 

date’’ for PM2.5 as October 20, 2011. See 

new 40 CFR 51.166(b)(14)(i)(c) and 

(ii)(c), and new 40 CFR 52.21(b)(14)(i)(c) 

and (ii)(c). At the same time, we are 

establishing an effective date for the 

other provisions, i.e., the SILs and SMC 

for PM2.5, in this final rule as December 

20, 2010. This will enable the 

implementation of these key elements of 

this rule under the Federal PSD program 

as soon as possible. 

1. State PSD Programs 

In this final rule, we are establishing 

the final PM2.5 increments as minimum 

program elements for all State PSD 

programs. Accordingly, states must 

submit for EPA’s approval revised SIPs 

that incorporate the final PM2.5

increments or alternative measures that 

can be demonstrated to EPA’s 

satisfaction to provide an equivalent 

level of protection as the PM2.5

increments. In accordance with section 

166(b) of the Act, we are requiring states 

to submit revised implementation plans 

to EPA for approval within 21 months 

of promulgation, that is, by July 20, 

2012. Section 166(b) also specifies that 

we must approve or disapprove these 

revisions within 25 months of 

promulgation (4 months from the 

statutory deadline for SIP submittal). 

We regard these statutory deadlines as 

maximum allowed timeframes for 

action. Moreover, we do not believe that 

the Act restricts our ability to approve 

SIP revisions requested by a State at any 

time before these deadlines. In this final 

rule, we are amending the regulatory 

provisions at 40 CFR 51.166(a)(6)(i) to 

articulate the deadline set forth by the 

statute for the SIP submittals involving 

the PM2.5 increments pursuant to 

section 166(a) of the Act. 

It is very unlikely that states will be 

able to revise their SIPs and submit 

them to EPA for approval prior to the 

applicability date of the PM2.5

increments in this final rule, which is 

October 20, 2011. Therefore, there is 

likely to be a period of time after 

October 20, 2010 when State laws will 

not require PSD applicants otherwise 

subject to PSD for PM2.5 to complete an 

increment analysis for the PM2.5

increments, even though the PM2.5

increments, major source baseline date, 

and trigger date have been established 

as a result of this final rule. Similarly, 

it is not clear whether states will have 

the authority to consider such 

applicants as having triggered the minor 

source baseline date during this interim 

period before their revised PSD rules 

containing the PM2.5 increments and 

relevant baseline dates become effective. 

The EPA does not intend to prescribe 

the implementation timeline for State 

programs; rather, each State will need to 

determine how increment consumption 

and the setting of the minor source 

baseline date for PM2.5 will occur under 

its own PSD program. Nevertheless, 

regardless of when a State begins to 

require PM2.5 increment analyses and 

how it chooses to set the PM2.5 minor 

source baseline date, the emissions from 

sources subject to PSD for PM2.5 on 

which construction commenced after 

October 20, 2010 (the major source 

baseline date) will consume PM2.5

increment and must be included in 

increment analyses occurring after the 

minor source baseline date is 

established for an area under the State’s 

revised PSD program. 

2. Federal PSD Program 

The Federal PSD regulations under 40 

CFR 52.21 apply where states do not 

have approved PSD programs and in 

Indian lands. In such cases, either EPA 

implements the PSD program or the 

State will implement it under authority 

granted by EPA through a delegation 

agreement. 

We proposed to begin implementing 

the Federal PSD program for PM2.5 on 

the effective date of the final rule, i.e., 

either 1 year from the date of 

publication in the Federal Register or 

60 days from date of publication, if we 

developed the PM2.5 increments 

pursuant to proposed Option 1. 

Alternatively, we requested comment on 

whether we should delay 

implementation of the Federal PSD 

program until 25 months after 

promulgation, which is the latest date 

by which EPA is required to approve 

State SIP revisions. This is the same 

approach we took in 1988 to implement 

the then new NO2 increments. See 53 

FR 40658. We did not propose the 24- 

month delay for the PM2.5 increments 

because of the significant delay that has 

already occurred between the time we 

promulgated the PM2.5 NAAQS and the 

time the PM2.5 increment rulemaking 

would be finalized. However, we sought 

comment on this alternative approach 

because we recognized that it might not 

be equitable to begin implementation of 

the new program requirements in those 

few areas where the Federal program 

applies before the majority of states are 

required to implement the program. 

Two commenters urged EPA to hold 

off implementation of State programs 

administered under the Federal PSD 

program in order to provide a uniform 

and consistent national approach. One 

State agency supported implementing 

the Federal PSD program with a delayed 

effective date of 1 year after the effective 

date of the final rule instead of 60 days. 

We have decided to begin 

implementing the revised Federal PSD 

program as set out previously in our 

introductory discussion of this issue in 

section VIII.A. That is, the revised 

regulations at 40 CFR 52.21 will become 

effective in 60 days, on December 20, 

2010. This will allow EPA or the 

delegated State agency to begin using 

the SILs and SMC for PM2.5 on that date, 

as described in section VIII.C of this 

preamble. However, the date established 

in the regulations for the trigger date 

will ensure that the PM2.5 increments do 

not become effective for 1 year, 

consistent with section 166(b) of the 

Act, and that the minor source baseline 

date cannot be established until the 

PM2.5 increments become effective. 

However, PSD sources subject to PM2.5

that receive their PSD permit after the 

date of publication of this final rule will 

be considered to consume PM2.5

increments by virtue of the fact that they 

will commence construction after the 

major source baseline date for PM2.5, 

which is the date of publication of this 

final rule. 


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Thus, sources in an area subject to the 

Federal PSD program for PM2.5 will be 

able to use the SILs and SMC as 

screening tools for the required PM2.5

NAAQS compliance demonstration, but 

in most cases will not be required to 

submit a PM2.5 increment analysis as 

part of a complete PSD permit 

application for a Federal PSD permit 

unless the application is submitted on 

or after October 20, 2011. On or after 

that date, when an applicant submits a 

complete PSD permit application that is 

required to address PM2.5 under the 

Federal PSD program, that first 

application will establish the minor 

source baseline date for PM2.5 in the 

applicable attainment or unclassifiable 

area. 

As with the State PSD program 

requirements, prior to the establishment 

of the minor source baseline date in an 

area, emissions increases from minor 

sources in the area will be counted 

toward the baseline concentration, 

rather than to the PM2.5 increment. As 

described earlier, the emissions from 

major stationary sources that commence 

construction after the major source 

baseline date, regardless of the date on 

which their PSD application is 

submitted, must be counted toward 

consumption of the PM2.5 increments. 

While these sources will not be required 

to submit an increment analysis for 

PM2.5 as part of their complete 

application as long as they receive their 

PSD permit before the trigger date for 

PM2.5 (see discussion that follows in 

section VIII.B), the emissions increases 

resulting from the permitting of these 

sources ultimately must be counted 

toward the PM2.5 increments when the 

first PSD permit application submitted 

after the trigger date establishes the 

minor source baseline date for the area 

of concern, and in all subsequent PM2.5

increment analyses for that area. 

B. Transition Period 

In the 2007 NPRM, we proposed a 

transition period to clarify when PSD 

permit applications must contain an 

increment analysis demonstrating 

compliance with the PM2.5 increments 

following the date the PM2.5 increments 

become effective in any State or Federal 

PSD program. Specifically, we proposed 

to establish a grandfathering provision 

to allow complete applications 

submitted before the increment effective 

date, but for which the permit had not 

yet been issued by the effective date, to 

continue being processed using the 

PM10 Surrogate Policy to satisfy the 

requirement to demonstrate compliance 

with the new PM2.5 requirements. The 

grandfathering provision for PM2.5 was 

originally proposed in the 2007 NPRM 

at 40 CFR 51.166(i)(10) and 40 CFR 

52.21(i)(11) for State and Federal PSD 

programs, respectively. See 72 FR 54149 

and 54154. 

Three commenters supported the 

proposed grandfathering provision for 

sources that submitted a complete 

application before the effective date of 

the applicable PSD rules. Another 

commenter felt that it was reasonable to 

allow states a choice between using 

PM10 or PM2.5 increments during a 

transition period including SIP 

approval, where applicable. 

During the time since the proposal of 

this rule in 2007, we have reconsidered 

the need for the proposed transition 

period in the Federal PSD program to 

effectively implement the PM2.5

increments. In light of the importance of 

preventing significant deterioration of 

PM2.5 air quality and the amount of time 

that has passed since the initial 

promulgation of the PM2.5 NAAQS, we 

do not believe that further delay is 

warranted. We expect that most permits 

issued after October 20, 2011 will be 

from sources that submitted their PSD 

applications after the major source 

baseline date for PM2.5, which is defined 

as the date of publication of this final 

rule, so that they will be incrementconsuming sources. Therefore, when 

these sources apply for their PSD 

permits, they will have had significant 

advance notice of when the PM2.5

increments will become effective, i.e., 1 

year from the date of publication of this 

final rule. The review and permitting of 

permit applications submitted prior to 

the publication date of this final rule 

should generally be completed prior to 

the effective date of PM2.5 increments 

and thus effectively have a transition 

period of 1 year to complete processing. 

Thus, we are requiring each source 

that receives its PSD permit after the 

effective date of the PM2.5 increments, 

regardless of when the application was 

submitted, to provide a demonstration 

that the source’s proposed emissions 

increase, along with other incrementconsuming emissions, will not cause or 

contribute to a violation of the PM2.5

increments. 

Under this final rule, sources 

applying for a PSD permit under the 

Federal PSD program after the major 

source baseline date for PM2.5 (i.e., after 

the date of publication of this final rule), 

but before the PM2.5 increments become 

effective (i.e., the date 1 year after 

publication of this final rule), will be 

considered to consume PM2.5 increment. 

While EPA will not require any such 

source to include a PM2.5 increment 

analysis as part of its initial PSD 

application, an increment analysis 

ultimately will be required before the 

permit may be issued if the date of 

issuance will occur after the trigger date, 

when the PM2.5 increments become 

effective under the Federal PSD 

program. 

Finally, for the same reasons that we 

are not adopting the proposed transition 

period that would have exempted PSD 

applicants with pending permit 

applications from demonstrating 

compliance with the PM2.5 increment 

requirements under the Federal PSD 

program, we have decided not to 

provide an option for states to apply a 

transition period under 40 CFR 51.166. 

We believe it is appropriate for all 

increment-consuming sources subject to 

PM2.5 to demonstrate compliance with 

the PM2.5 increments when the required 

permit is issued after the PM2.5

increments become effective in the 

State’s PSD regulations. 

C. SILs and SMC for PM2.5

In the 2007 NPRM, we explained our 

position that SILs and SMCs are not 

minimum required elements of an 

approvable SIP. While these de minimis 

values are widely considered to be 

useful components for implementing 

the PSD program, they are not 

absolutely necessary for the states to 

implement their PSD programs. That is, 

states can satisfy the statutory 

requirements for a PSD program by 

requiring each PSD applicant to submit 

air quality monitoring data and to 

conduct a comprehensive air quality 

impacts analysis for PM2.5 without using 

de minimis thresholds to exempt certain 

sources from such requirements. 

Because the de minimis values for PM2.5

(and other pollutants) are not mandatory 

elements, we proposed not to establish 

specific deadlines for submitting 

revisions to incorporate the specific 

values for PM2.5 into SIPs. 

One State/local commenter agreed 

that the SILs and SMCs should not be 

a required element of the PSD SIP. 

Another State/local commenter agreed 

with our proposal, but stated that EPA 

has the authority to include SILs and 

SMCs as minimum program 

requirements per the opinion set forth 

in Alabama Power. This commenter 

added that the EPA Environmental 

Appeals Board has affirmed EPA’s 

interpretation of the Act to allow EPA 

to evaluate the significance of a source’s 

impact when determining whether the 

source’s emissions would ‘‘cause or 

contribute’’ to a NAAQS or increments 

violation under section 165(a)(3) of the 

Act. 

Two commenters disagreed with our 

proposed position and argued that SILs 

and SMCs should be mandatory 

elements of a State PSD program. One 


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of these commenters argued that the 

requirement to model without the use of 

screening models with SILs and SMCs 

is so unreasonable that EPA must 

require that states adopt the SILs and 

SMCs to meet the Purpose clause of the 

Act, which requires a balancing of 

environmental and economic 

considerations. The other opposing 

commenter stated that the increments, 

SILs, and SMCs need to be adopted as 

a single regulatory approach because the 

SILs and SMCs define when additional 

work is needed to ensure that PSD 

requirements, such as maintaining 

adequate increment, are met. This 

commenter added that there is no 

reason for sources to be placed in the 

position of conducting expensive 

modeling that can delay a project when 

it is unnecessary from an air quality 

perspective. 

We agree that the SILs and SMCs used 

as de minimis thresholds for the various 

pollutants are useful tools that enable 

permitting authorities and PSD 

applicants to screen out ‘‘insignificant’’ 

activities; however, the fact remains that 

these values are not required by the Act 

as part of an approvable SIP program. 

We believe that most states are likely to 

adopt the SILs and SMCs because of the 

useful purpose they serve regardless of 

our position that the values are not 

mandatory. Alternatively, states may 

develop more stringent values if they 

desire to do so. In any case, states are 

not under any SIP-related deadline for 

revising their PSD programs to add 

these screening tools. 

Using the SILs for PM2.5, when a 

proposed major new source or major 

modification of PM2.5 predicts (via air 

quality modeling) an impact less than 

the PM2.5 de minimis value, the 

proposed source or modification is not 

considered to have a significant air 

quality impact and would not need to 

complete a cumulative impact analysis 

involving an analysis of other sources in 

the area. Also, a source with a de 

minimis ambient impact would not be 

considered to cause or contribute to a 

violation of either the PM2.5 NAAQS or 

increments. 

The PM2.5 SILs will become effective 

under the Federal PSD program on the 

effective date of this final rule, that is, 

on December 20, 2010, when either 

EPA, or a State acting under a 

delegation of EPA’s authority, 

implements the revised PSD permitting 

requirements for PM2.5 pursuant to 40 

CFR 52.21. The SILs will be for use 

initially with the compliance 

demonstration for the PM2.5 NAAQS, 

and later for the PM2.5 increment 

analysis, under the Federal PSD 

program. We emphasize, however, that 

the PM2.5 SILs are not intended to be 

used as part of the determination of 

adverse impacts on AQRVs for PM2.5 in 

Class I areas. 

Similarly, we intend to use the PM2.5

SMC (4 μg/m3, 24-hour average) as a 

screening tool in the Federal PSD permit 

program beginning on December 20, 

2010. Accordingly, when either the 

modeled PM2.5 impact of, or the existing 

ambient air quality within the area of, 

the proposed new major source or major 

modification is less than the PM2.5 SMC, 

the reviewing authority may exempt the 

source or modification from the 

monitoring data requirements for PM2.5

under 40 CFR 52.21(m). 

IX. Other Regulatory Changes 

The Act provides that the PSD 

regulations apply to areas designated as 

‘‘attainment’’ or ‘‘unclassifiable’’ as 

defined by the Act. When the original 

regulations were written, the Act 

provisions for designating areas as 

either ‘‘attainment’’ or ‘‘unclassifiable’’ 

were contained in sections 107(d)(1)(D) 

and (E), respectively. In 1990, Congress 

revised section 107 and changed the 

relevant paragraphs defining 

‘‘attainment’’ and ‘‘unclassifiable’’ areas 

to sections 107(d)(1)(A)(ii) and (iii), 

respectively. In accordance with these 

statutory changes, we are correcting the 

references to the statutory classifications 

contained in the existing PSD rules to 

match the revised paragraphs in the Act. 

See revised 40 CFR 51.166(b)(14)(iii)(a) 

and (15)(i) and (ii), and 40 CFR 

52.21(b)(14)(iii)(a) and (15)(i) and (ii). 

In adding the SILs for PM2.5 in this 

final rule, we restructured paragraph (k) 

(‘‘Source impact analysis’’) in the 

existing PSD regulations at 40 CFR 

51.166 and 52.21. Under the 

restructuring of paragraph (k), old 

paragraph (k)(2) is now paragraph 

(k)(1)(ii). To accommodate this 

restructuring change, we are also 

revising grandfathering provisions that 

are contained in existing paragraphs 

(i)(8) and (i)(9) at 40 CFR 51.166, and 

paragraphs (i)(9) and (i)(10) at 40 CFR 

52.21, which contained references to 

requirements contained in paragraph 

(k)(2). As revised, the grandfathering 

provisions now reference new 

paragraph (k)(1)(ii). 

X. Statutory and Executive Order 

Reviews 

A. Executive Order 12866—Regulatory 

Planning and Review 

Under Executive Order 12866 (58 FR 

51735, October 4, 1993), this action is a 

‘‘significant regulatory action’’ because it 

raises novel legal or policy issues 

arising out of legal mandates, the 

President’s priorities, or the principle 

set forth in the Executive Order. 

Accordingly, EPA submitted this action 

to OMB for review under Executive 

Order 12866 and any changes made in 

response to OMB recommendations 

have been documented in the docket for 

this action. 

B. Paperwork Reduction Act 

The information collection 

requirements in this rule have been 

submitted for approval to the OMB 

under the Paperwork Reduction Act, 44 

U.S.C. 3501 et seq. The information 

collection requirements are not 

enforceable until OMB approves them. 

Pursuant to title I, part C, of the Act, 

the PSD program requires the owner or 

operator to obtain a permit prior to 

either constructing a new major 

stationary source of air pollutants or 

making a major modification to an 

existing major stationary source. The 

information collection for sources under 

PSD results from the requirement for 

owners or operators to submit 

applications for NSR permits. In some 

cases, sources must conduct 

preconstruction monitoring to 

determine the existing ambient air 

quality. For reviewing authorities, the 

information collection results from the 

requirement to process permit 

applications and issue permits, and to 

transmit associated information to EPA. 

The EPA oversees the PSD program, and 

the information collected by sources 

and reviewing authorities is used to 

ensure that the program is properly 

implemented. 

The final rule will increase the PSD 

permitting burden for owners and 

operators of major stationary sources of 

PM2.5 emissions by adding PM2.5

increments to the list of existing 

increments for which air quality impact 

analyses must be carried out to track the 

amount of increment consumed by the 

proposed source and other sources in 

the area. Over the 3-year period covered 

by the ICR, we estimate an average 

annual burden totaling about 29,000 

hours and $2.8 million for all industry 

entities that will be affected by the final 

rule. For the same reasons, we also 

expect the final rule (when fully 

implemented) to increase burden for the 

State and local authorities reviewing 

PSD permit applications. In addition, 

there will be additional burden for State 

and local agencies to revise their SIPs to 

incorporate the proposed changes. Over 

the 3-year period covered by the ICR, we 

estimate that the average annual burden 

for all State and local reviewing 

authorities will total about 7,500 hours 

and $581,000. Burden is defined at 5 

CFR 1320.3(b). 


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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. 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act (RFA) 

generally requires an agency to prepare 

a regulatory flexibility analysis of any 

rule subject to notice and comment 

rulemaking requirements under the 

Administrative Procedure Act or any 

other statute unless the Agency certifies 

that the rule will not have a significant 

economic impact on a substantial 

number of small entities. Small entities 

include small businesses, small 

organizations, and small governmental 

jurisdictions. 

For purposes of assessing the impacts 

of this rule on small entities, ‘‘small 

entity’’ is defined as: (1) A small 

business as defined by the Small 

Business Administration’s regulations at 

13 CFR 121.201; (2) a small 

governmental jurisdiction that is a 

government of a city, county, town, 

school district or special district with a 

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

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

owned and operated and is not 

dominant in its field. 

After considering the economic 

impacts of this final rule on small 

entities, I certify that this action will not 

have a significant economic impact on 

a substantial number of small entities. 

This final rule will not impose any 

requirements on small entities because 

small entities are not subject to the 

requirements of this rule. 

D. Unfunded Mandates Reform Act 

This action contains no Federal 

mandates under the provisions of Title 

II of the Unfunded Mandates Reform 

Act of 1995 (UMRA), 2 U.S.C. 1531– 

1538 for State, local, or tribal 

governments or the private sector. The 

action imposes no enforceable duty on 

any State, local or tribal governments or 

the private sector. The final rules adds 

only a relatively small number of new 

requirements to the existing permit 

requirements already in place under the 

PSD program, since states are currently 

implementing a PM10 surrogate program 

pursuant to EPA guidance. Thus, this 

action is not subject to the requirements 

of sections 202 or 205 of UMRA. 

This rule is also not subject to the 

requirements of section 203 of UMRA 

because it contains no regulatory 

requirements that might significantly or 

uniquely affect small governments. The 

final rule applies only to new major 

stationary sources and to major 

modifications at existing major 

stationary sources. 

E. Executive Order 13132—Federalism 

This final 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. The final rule 

makes relatively minor changes to the 

established PSD program, simply 

making it possible for states to 

implement PSD for PM2.5 instead of 

relying on PM10 as a surrogate. Thus, 

Executive Order 13132 does not apply 

to this rule. In the spirit of Executive 

Order 13132, and consistent with EPA 

policy to promote communications 

between EPA and State and local 

governments, EPA specifically solicited 

comment on the proposed rule from 

State and local officials. 

F. Executive Order 13175—Consultation 

and Coordination With Indian Tribal 

Governments 

This action does not have tribal 

implications, as specified in Executive 

Order 13175 (65 FR 67249, November 9, 

2000). The final rule provides the 

elements to implement a PM2.5 PSD 

program in attainment areas. The Act 

provides for states to develop plans to 

regulate emissions of air pollutants 

within their jurisdictions. The Tribal 

Air Rule (TAR) under the Act gives 

tribes the opportunity to develop and 

implement Act programs to attain and 

maintain the PM2.5 NAAQS, but leaves 

to the discretion of the tribes the 

decision of whether to develop these 

programs and which programs, or 

appropriate elements of a program, they 

will adopt. Thus, Executive Order 13175 

does not apply to this action. 

The EPA did reach out to national 

tribal organizations in 2006 to provide 

a forum for tribal professionals to 

provide input to the rulemaking. 

However, not much participation or 

input was received. 

G. Executive Order 13045—Protection of 

Children From Environmental Health 

and Safety Risks 

This action is not subject to Executive 

Order 13045 (62 FR 19885, April 23, 

1997) because it is not economically 

significant as defined in Executive 

Order 12866, and because the Agency 

does not believe the environmental 

health or safety risks addressed by this 

action present a disproportionate risk to 

children. One of the basic requirements 

of the PSD program is that new and 

modified major sources must 

demonstrate that any new emissions do 

not cause or contribute to air quality in 

violation of the NAAQS. 

H. Executive Order 13211—Actions 

That Significantly Affect Energy Supply, 

Distribution, or Use 

This action is not a ‘‘significant energy 

action’’ as defined in Executive Order 

13211 (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. Further, 

we have concluded that this rule is not 

likely to have any adverse energy 

effects. 

I. National Technology Transfer and 

Advancement Act 

Section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (NTTAA), Public Law 104– 

113, 12(d) (15 U.S.C. 272 note) directs 

EPA to use voluntary consensus 

standards in its regulatory activities 

unless to do so would be inconsistent 

with applicable law or otherwise 

impractical. Voluntary consensus 

standards are technical standards (e.g., 

materials specifications, test methods, 

sampling procedures, and business 

practices) that are developed or adopted 

by voluntary consensus standards 

bodies. The NTTAA directs EPA to 

provide Congress, through OMB, 

explanations when the Agency decides 

not to use available and applicable 

voluntary consensus standards. 

This action does not involve technical 

standards. Therefore, EPA did not 

consider the use of any voluntary 

consensus standards. 

J. Executive Order 12898—Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

Executive Order 12898 (59 FR 7629, 

Feb. 16, 1994) establishes Federal 

executive policy on environmental 

justice. Its main provision directs 

Federal agencies, to the greatest extent 

practicable and permitted by law, to 

make environmental justice part of their 

mission by identifying and addressing, 


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as appropriate, disproportionately high 

and adverse human health or 

environmental effects of their programs, 

policies, and activities on minority 

populations and low-income 

populations in the United States. 

The EPA has determined that this 

final rule will not have 

disproportionately high and adverse 

human health or environmental effects 

on minority or low-income populations 

because it does not affect the level of 

protection provided to human health or 

the environment. This final rule will 

provide regulatory certainty for 

implementing the preconstruction NSR 

permitting program for PM2.5. However, 

the requirements are similar to the 

existing requirements of the PM10

program and hence do not impact the 

human health or environmental effects. 

K. Congressional Review Act 

The Congressional Review Act, 5 

U.S.C. 801 et seq., as added by the Small 

Business Regulatory Enforcement 

Fairness Act of 1996, generally provides 

that before a rule may take effect, the 

agency promulgating the rule must 

submit a rule report, which includes a 

copy of the rule, to each House of the 

Congress and to the Comptroller General 

of the United States. The EPA will 

submit a report containing this rule and 

other required information to the U.S. 

Senate, the U.S. House of 

Representatives, and the Comptroller 

General of the United States prior to 

publication of the rule in the Federal 

Register. A major rule cannot take effect 

until 60 days after it is published in the 

Federal Register. This action is not a 

‘‘major rule’’ as defined by 5 U.S.C. 

804(2). Nevertheless, this rule needs to 

be reviewed for the PM2.5 increments 

being promulgated herein so that they 

can be scrutinized by Congress as 

intended under section 166(b) of the 

Act. Even though the PM2.5 increments 

will not become applicable for 1 year, 

the final rule will become effective 60 

days from the date of publication, that 

is, on December 20, 2010, for the 

screening tools (SILs and SMC) being 

established in this rule. 

XI. Judicial Review 

Under section 307(b)(1) of the Act, 

petitions for judicial review of this 

action must be filed in the United States 

Court of Appeals for the District of 

Columbia Circuit by December 20, 2010. 

Any such judicial review is limited to 

only those objections that are raised 

with reasonable specificity in timely 

comments. Filing a petition for 

reconsideration by the Administrator of 

this final rule does not affect the finality 

of this rule for the purposes of judicial 

review nor does it extend the time 

within which a petition for judicial 

review may be filed, and shall not 

postpone the effectiveness of such rule 

or action. Under section 307(b)(2) of the 

Act, the requirements of this final action 

may not be challenged later in civil or 

criminal proceedings brought by us to 

enforce these requirements. 

XII. Statutory Authority 

The statutory authority for this final 

action is provided by sections 101, 160, 

163, 165, 166, 301, and 307(d) of the Act 

as amended (42 U.S.C. 7401, 7470, 7473, 

7475, 7476, 7601, and 7607(d)). 

List of Subjects 

40 CFR Part 51 

Administrative practices and 

procedures, Air pollution control, 

Environmental protection, 

Intergovernmental relations. 

40 CFR Part 52 

Administrative practices and 

procedures, Air pollution control, 

Environmental protection, 

Intergovernmental relations. 

Dated: September 30, 2010. 

Lisa P. Jackson, 

Administrator. 

■ For the reasons set out in the 

preamble, title 40, chapter I of the Code 

of Federal Regulations is amended as 

follows: 

PART 51—[AMENDED] 

■ 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—[Amended] 

■ 2. Section 51.165 is amended by 

revising the table in paragraph (b)(2) to 

read as follows: 

§ 51.165 Permit requirements. 

* * * * * 

(b) * * * 

(2) * * * 

Pollutant Annual 

Averaging time (hours) 

24 8 3 1 

SO2 ............................................................................................................... 1.0 μg/m3 5 μg/m3 25 μg/m3

PM10 .............................................................................................................. 1.0 μg/m3 5 μg/m3

PM2.5 ............................................................................................................. 0.3 μg/m3 1.2 μg/m3

NO2 ............................................................................................................... 1.0 μg/m3

CO ................................................................................................................ 0.5 mg/m3 2 mg/m3

* * * * * 

■ 3. Section 51.166 is amended as 

follows: 

■ a. By revising paragraph (a)(6)(i); 

■ b. By revising paragraph (b)(14)(i)(a); 

■ c. By removing the period at the end 

of paragraph (b)(14)(i)(b) and adding ‘‘; 

and’’ in its place; 

■ d. By adding paragraph (b)(14)(i)(c); 

■ e. By revising paragraph (b)(14)(ii)(a); 

■ f. By removing the period at the end 

of paragraph (b)(14)(ii)(b) and adding ‘‘; 

and’’ in its place; 

■ g. By adding paragraph (b)(14)(ii)(c); 

■ h. By revising paragraph (b)(14)(iii)(a); 

■ i. By revising paragraph (b)(15)(i) and 

paragraph (b)(15)(ii) introductory text; 

■ j. By revising the table in paragraph 

(c)(1); 

■ k. By revising paragraph (c)(2); 

■ l. By revising paragraph (i)(5)(i)(c); 

■ m. By redesignating existing 

paragraphs (i)(5)(i)(d) through (j) as 

paragraphs (i)(5)(i)(e) through (k); 

■ n. By adding new paragraph 

(i)(5)(i)(d); 

■ o. By removing ‘‘(k)(2)’’ from 

paragraph (i)(8) and adding ‘‘(k)(1)(ii)’’ in 

its place; 

■ p. By removing in two places ‘‘(k)(2)’’ 

from paragraph (i)(9) and adding 

‘‘(k)(1)(ii)’’ in those places; 

■ q. By revising paragraph (k); 

■ r. By removing the words ‘‘particulate 

matter’’ in the last sentence of paragraph 

(p)(4) introductory text and adding in 

their place ‘‘PM2.5, PM10’’; and 

■ s. By revising the table in paragraph 

(p)(4). 

§ 51.166 Prevention of significant 

deterioration of air quality. 

(a) * * * 

(6) * * * 


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(i) Any State required to revise its 

implementation plan by reason of an 

amendment to this section, with the 

exception of amendments to add new 

maximum allowable increases or other 

measures pursuant to section 166(a) of 

the Act, shall adopt and submit such 

plan revision to the Administrator for 

approval no later than 3 years after such 

amendment is published in the Federal 

Register. With regard to a revision to an 

implementation plan by reason of an 

amendment to paragraph (c) of this 

section to add maximum allowable 

increases or other measures, the State 

shall submit such plan revision to the 

Administrator for approval within 21 

months after such amendment is 

published in the Federal Register. 

* * * * * 

(b) * * * 

(14)(i) * * * 

(a) In the case of PM10 and sulfur 

dioxide, January 6, 1975; 

* * * * * 

(c) In the case of PM2.5, October 20, 

2010. 

(ii) * * * 

(a) In the case of PM10 and sulfur 

dioxide, August 7, 1977; 

* * * * * 

(c) In the case of PM2.5, October 20, 

2011. 

(iii) * * * 

(a) The area in which the proposed 

source or modification would construct 

is designated as attainment or 

unclassifiable under section 

107(d)(1)(A)(ii) or (iii) of the Act for the 

pollutant on the date of its complete 

application under 40 CFR 52.21 or 

under regulations approved pursuant to 

40 CFR 51.166; and 

* * * * * 

(15)(i) Baseline area means any 

intrastate area (and every part thereof) 

designated as attainment or 

unclassifiable under section 

107(d)(1)(A)(ii) or (iii) of the Act in 

which the major source or major 

modification establishing the minor 

source baseline date would construct or 

would have an air quality impact for the 

pollutant for which the baseline date is 

established, as follows: Equal to or 

greater than 1 μg/m3 (annual average) 

for SO2, NO2, or PM10; or equal or 

greater than 0.3 μg/m3 (annual average) 

for PM2.5. 

(ii) Area redesignations under section 

107(d)(1)(A)(ii) or (iii) of the Act cannot 

intersect or be smaller than the area of 

impact of any major stationary source or 

major modification which: 

* * * * * 

(c) * * * 

(1) * * * 

Pollutant 

Maximum 

allowable 

increase 

(micrograms 

per cubic 

meter) 

Class I Area 

PM2.5: 

Annual arithmetic mean ................................................................................................................................................................ 1 

24-hr maximum ............................................................................................................................................................................. 2 

PM10: 

Annual arithmetic mean ................................................................................................................................................................ 4 

24-hr maximum ............................................................................................................................................................................. 8 

Sulfur dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 2 

24-hr maximum ............................................................................................................................................................................. 5 

3-hr maximum ............................................................................................................................................................................... 25 

Nitrogen dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 2.5 

Class II Area 

PM2.5: 

Annual arithmetic mean ................................................................................................................................................................ 4 

24-hr maximum ............................................................................................................................................................................. 9 

PM10: 

Annual arithmetic mean ................................................................................................................................................................ 17 

24-hr maximum ............................................................................................................................................................................. 30 

Sulfur dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 20 

24-hr maximum ............................................................................................................................................................................. 91 

3-hr maximum ............................................................................................................................................................................... 512 

Nitrogen dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 25 

Class III Area 

PM2.5: 

Annual arithmetic mean ................................................................................................................................................................ 8 

24-hr maximum ............................................................................................................................................................................. 18 

PM10: 

Annual arithmetic mean ................................................................................................................................................................ 34 

24-hr maximum ............................................................................................................................................................................. 60 

Sulfur dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 40 

24-hr maximum ............................................................................................................................................................................. 182 

3-hr maximum ............................................................................................................................................................................... 700 

Nitrogen dioxide: 


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Pollutant 

Maximum 

allowable 

increase 

(micrograms 

per cubic 

meter) 

Annual arithmetic mean ................................................................................................................................................................ 50 

* * * * * 

(2) Where the State can demonstrate 

that it has alternative measures in its 

plan other than maximum allowable 

increases as defined under paragraph 

(c)(1) of this section, that satisfy the 

requirements in sections 166(c) and 

166(d) of the Clean Air Act for a 

regulated NSR pollutant for which the 

Administrator has established 

maximum allowable increases pursuant 

to section 166(a) of the Act, the 

requirements for maximum allowable 

increases for that pollutant under 

paragraph (c)(1) of this section shall not 

apply upon approval of the plan by the 

Administrator. The following regulated 

NSR pollutants are eligible for such 

treatment: 

(i) Nitrogen dioxide. 

(ii) PM2.5. 

* * * * * 

(i) * * * 

(5) * * * 

(i) * * * 

(c) PM2.5–4 μg/m3, 24-hour average; 

(d) PM10–10 μg/m3, 24-hour average; 

* * * * * 

(k) Source impact analysis—(1) 

Required demonstration. The plan shall 

provide that the owner or operator of 

the proposed source or modification 

shall demonstrate that allowable 

emission increases from the proposed 

source or modification, in conjunction 

with all other applicable emissions 

increases or reduction (including 

secondary emissions), would not cause 

or contribute to air pollution in 

violation of: 

(i) Any national ambient air quality 

standard in any air quality control 

region; or 

(ii) Any applicable maximum 

allowable increase over the baseline 

concentration in any area. 

(2) Significant impact levels. The plan 

may provide that, for purposes of PM2.5, 

the demonstration required in paragraph 

(k)(1) of this section is deemed to have 

been made if the emissions increase 

from the new stationary source alone or 

from the modification alone would 

cause, in all areas, air quality impacts 

less than the following amounts: 

Pollutant Averaging time Class I 

area 

Class II 

area 

Class III 

area 

PM2.5 .................................................................... Annual .................................................................. 0.06 μg/m3 0.3 μg/m3 0.3 μg/m3

24-hour ................................................................. 0.07 μg/m3 1.2 μg/m3 1.2 μg/m3

* * * * * 

(p) * * * 

(4) * * * 

Pollutant 

Maximum 

allowable 

increase 

(micrograms 

per cubic 

meter) 

PM2.5: 

Annual arithmetic mean ................................................................................................................................................................ 4 

24-hr maximum ............................................................................................................................................................................. 9 

PM10: 

Annual arithmetic mean ................................................................................................................................................................ 17 

24-hr maximum ............................................................................................................................................................................. 30 

Sulfur dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 20 

24-hr maximum ............................................................................................................................................................................. 91 

3-hr maximum ............................................................................................................................................................................... 325 

Nitrogen dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 25 

* * * * * 

■ 4. Appendix S to part 51 is amended 

by revising the table in section III.A to 

read as follows: 

Appendix S to Part 51—Emission Offset 

Interpretative Ruling 

* * * * * 

III. * * * 

A. * * * 

Pollutant Annual 

Averaging time (hours) 

24 8 3 1 

SO2 ........................................................................ 1.0 μg/m3 5 μg/m3 25 μg/m3

PM10 ...................................................................... 1.0 μg/m3 5 μg/m3


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Pollutant Annual 

Averaging time (hours) 

24 8 3 1 

PM2.5 ...................................................................... 0.3 μg/m3 1.2 μg/m3

NO2 ........................................................................ 1.0 μg/m3

CO ......................................................................... 0.5 mg/m3 2 mg/m3

* * * * * 

PART 52—[AMENDED] 

■ 1. The authority citation for part 52 

continues to read as follows: 

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

Subpart A—[Amended] 

■ 2. Section 52.21 is amended as 

follows: 

■ a. By revising paragraph (b)(14)(i)(a); 

■ b. By removing the period at the end 

of paragraph (b)(14)(i)(b) and adding ‘‘; 

and’’ in its place; 

■ c. By adding paragraph (b)(14)(i)(c); 

■ d. By revising paragraph (b)(14)(ii)(a); 

■ e. By removing the period at the end 

of paragraph (b)(14)(ii)(b) and adding ‘‘; 

and’’ in its place; 

■ f. By adding paragraph (b)(14)(ii)(c); 

■ g. By revising paragraph (b)(14)(iii)(a); 

■ h. By revising paragraph (b)(15)(i) and 

paragraph (b)(15)(ii) introductory text; 

■ i. By revising the table in paragraph 

(c); 

■ j. By revising paragraph (i)(5)(i); 

■ k. By removing ‘‘(k)(2)’’ from 

paragraph (i)(9) and adding ‘‘(k)(1)(ii)’’ in 

its place; 

■ l. By removing in two places ‘‘(k)(2)’’ 

from paragraph (i)(10) and adding 

‘‘(k)(1)(ii)’’ in those places; 

■ m. By revising paragraph (k); 

■ n. By removing the words ‘‘particulate 

matter’’ in the last sentence of paragraph 

(p)(5) introductory text and adding in 

their place ‘‘PM2.5, PM10’’; and 

■ o. By revising the table in paragraph 

(p)(5). 

§ 52.21 Prevention of significant 

deterioration of air quality. 

* * * * * 

(b) * * * 

(14)(i) * * * 

(a) In the case of PM10 and sulfur 

dioxide, January 6, 1975; 

* * * * * 

(c) In the case of PM2.5, October 20, 

2010. 

(ii) * * * 

(a) In the case of PM10 and sulfur 

dioxide, August 7, 1977; 

* * * * * 

(c) In the case of PM2.5, October 20, 

2011. 

(iii) * * * 

(a) The area in which the proposed 

source or modification would construct 

is designated as attainment or 

unclassifiable under section 

107(d)(1)(A)(ii) or (iii) of the Act for the 

pollutant on the date of its complete 

application under 40 CFR 52.21 or 

under regulations approved pursuant to 

40 CFR 51.166; and 

* * * * * 

(15)(i) Baseline area means any 

intrastate area (and every part thereof) 

designated as attainment or 

unclassifiable under section 

107(d)(1)(A)(ii) or (iii) of the Act in 

which the major source or major 

modification establishing the minor 

source baseline date would construct or 

would have an air quality impact for the 

pollutant for which the baseline date is 

established, as follows: equal to or 

greater than 1 μg/m3 (annual average) 

for SO2, NO2, or PM10; or equal or 

greater than 0.3 μg/m3 (annual average) 

for PM2.5. 

(ii) Area redesignations under section 

107(d)(1)(A)(ii) or (iii) of the Act cannot 

intersect or be smaller than the area of 

impact of any major stationary source or 

major modification which: 

* * * * * 

(c) * * * 

Pollutant 

Maximum 

allowable 

increase 

(micrograms 

per cubic 

meter) 

Class I Area 

PM2.5: 

Annual arithmetic mean ................................................................................................................................................................ 1 

24-hr maximum ............................................................................................................................................................................. 2 

PM10: 

Annual arithmetic mean ................................................................................................................................................................ 4 

24-hr maximum ............................................................................................................................................................................. 8 

Sulfur dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 2 

24-hr maximum ............................................................................................................................................................................. 5 

3-hr maximum ............................................................................................................................................................................... 25 

Nitrogen dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 2.5 

Class II Area 

PM2.5: 

Annual arithmetic mean ................................................................................................................................................................ 4 

24-hr maximum ............................................................................................................................................................................. 9 

PM10: 

Annual arithmetic mean ................................................................................................................................................................ 17 

24-hr maximum ............................................................................................................................................................................. 30 

Sulfur dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 20 


emcdonald on DSK2BSOYB1PROD with RULES3
64906 Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 

Pollutant 

Maximum 

allowable 

increase 

(micrograms 

per cubic 

meter) 

24-hr maximum ............................................................................................................................................................................. 91 

3-hr maximum ............................................................................................................................................................................... 512 

Nitrogen dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 25 

Class III Area 

PM2.5: 

Annual arithmetic mean ................................................................................................................................................................ 8 

24-hr maximum ............................................................................................................................................................................. 18 

PM10: 

Annual arithmetic mean ................................................................................................................................................................ 34 

24-hr maximum ............................................................................................................................................................................. 60 

Sulfur dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 40 

24-hr maximum ............................................................................................................................................................................. 182 

3-hr maximum ............................................................................................................................................................................... 700 

Nitrogen dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 50 

* * * * * 

(i) * * * 

(5) * * * 

(i) The emissions increase of the 

pollutant from the new source or the net 

emissions increase of the pollutant from 

the modification would cause, in any 

area, air quality impacts less than the 

following amounts: 

(a) Carbon monoxide—575 μg/m3, 

8-hour average; 

(b) Nitrogen dioxide—14 μg/m3, 

annual average; 

(c) PM2.5—4 μg/m3, 24-hour average; 

(d) PM10—10 μg/m3, 24-hour average; 

(e) Sulfur dioxide—13 μg/m3, 24-hour 

average; 

(f) Ozone; 

(g) Lead—0.1 μg/m3, 3-month average; 

(h) Fluorides—0.25 μg/m3, 24-hour 

average; 

(i) Total reduced sulfur—10 μg/m3, 

1-hour average; 

(j) Hydrogen sulfide—0.2 μg/m3, 

1-hour average; 

(k) Reduced sulfur compounds— 

10 μg/m3, 1-hour average; or 

Note to paragraph (c)(50)(i)(f): No de 

minimis air quality level is provided for 

ozone. However, any net emissions increase 

of 100 tons per year or more of volatile 

organic compounds or nitrogen oxides 

subject to PSD would be required to perform 

an ambient impact analysis, including the 

gathering of ambient air quality data. 

* * * * * 

(k) Source impact analysis—(1) 

Required demonstration. The owner or 

operator of the proposed source or 

modification shall demonstrate that 

allowable emission increases from the 

proposed source or modification, in 

conjunction with all other applicable 

emissions increases or reductions 

(including secondary emissions), would 

not cause or contribute to air pollution 

in violation of: 

(i) Any national ambient air quality 

standard in any air quality control 

region; or 

(ii) Any applicable maximum 

allowable increase over the baseline 

concentration in any area. 

(2) Significant impact levels. For 

purposes of PM2.5, the demonstration 

required in paragraph (k)(1) of this 

section is deemed to have been made if 

the emissions increase from the new 

stationary source alone or from the 

modification alone would cause, in all 

areas, air quality impacts less than the 

following amounts: 

Pollutant Averaging time Class I 

area 

Class II 

area 

Class III 

area 

PM2.5 ................................................................... Annual ................................................................. 0.06 μg/m3 0.3 μg/m3 0.3 μg/m3

............................................................................. 24-hour ................................................................ 0.07 μg/m3 1.2 μg/m3 1.2 μg/m3

* * * * * (p) * * * 


emcdonald on DSK2BSOYB1PROD with RULES3
Federal Register / Vol. 75, No. 202 / Wednesday, October 20, 2010 / Rules and Regulations 64907 

(5) * * * 

Pollutant 

Maximum 

allowable 

increase 

(micrograms 

per cubic 

meter) 

PM2.5: 

Annual arithmetic mean ................................................................................................................................................................ 4 

24-hr maximum ............................................................................................................................................................................. 9 

PM10: 

Annual arithmetic mean ................................................................................................................................................................ 17 

24-hr maximum ............................................................................................................................................................................. 30 

Sulfur dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 20 

24-hr maximum ............................................................................................................................................................................. 91 

3-hr maximum ............................................................................................................................................................................... 325 

Nitrogen dioxide: 

Annual arithmetic mean ................................................................................................................................................................ 25 

* * * * * 

[FR Doc. 2010–25132 Filed 10–19–10; 8:45 am] 

BILLING CODE 6560–50–P 


emcdonald on DSK2BSOYB1PROD with RULES3