20586 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 51 

[EPA–HQ–OAR–2003–0062; FRL–8295–2] 

RIN 2060–AK74 

Clean Air Fine Particle Implementation 

Rule 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: This final action provides 

rules and guidance on the Clean Air Act 

(CAA) requirements for State and Tribal 

plans to implement the 1997 fine 

particle (PM2.5) national ambient air 

quality standards (NAAQS). Fine 

particles and precursor pollutants are 

emitted by a wide range of sources, 

including power plants, cars, trucks, 

industrial sources, and other burning or 

combustion-related activities. Health 

effects that have been associated with 

exposure to PM2.5 include premature 

death, aggravation of heart and lung 

disease, and asthma attacks. Those 

particularly sensitive to PM2.5 exposure 

include older adults, people with heart 

and lung disease, and children. 

Air quality designations became 

effective on April 5, 2005 for 39 areas 

(with a total population of 90 million) 

that were not attaining the 1997 PM2.5

standards. By April 5, 2008, each State 

having a nonattainment area must 

submit to EPA an attainment 

demonstration and adopted regulations 

ensuring that the area will attain the 

standards as expeditiously as 

practicable, but no later than 2015. This 

rule and preamble describe the 

requirements that States and Tribes 

must meet in their implementation 

plans for attainment of the 1997 fine 

particle NAAQS. (Note that this rule 

does not include final PM2.5

requirements for the new source review 

(NSR) program; the final NSR rule will 

be issued at a later date.) 

DATES: This rule is effective on May 29, 

2007. 

ADDRESSES: The EPA has established a 

docket for this action under Docket ID 

EPA–HQ–OAR–2003–0062. All 

documents relevant to this action are 

listed in the Federal docket management 

system at www.regulations.gov. 

Although listed in the index, some 

information is not publicly available 

(e.g. Confidential Business Information 

or other information whose disclosure is 

restricted by statute). Certain other 

material, such as copyrighted material, 

is not placed on the Internet and will be 

publicly available only in hard copy 

form. Publicly available docket 

materials are available either 

electronically through 

www.regulations.gov or in hard copy 

format at the EPA Docket Center, EPA/ 

DC, EPA West, Room 3334, 1301 

Constitution Avenue, NW., Washington, 

DC. The Public Reading Room is open 

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

through Friday, excluding legal 

holidays. The telephone number for the 

Public Reading Room is (202) 566–1744, 

and the telephone number for the Office 

of Air and Radiation Docket and 

Information Center is (202) 566–1742. A 

variety of information and materials 

related to the fine particle NAAQS and 

implementation program are also 

available on EPA’s Web site: http:// 

www.epa.gov/air/particles. 

FOR FURTHER INFORMATION CONTACT: For 

general information, contact Mr. 

Richard Damberg, U.S. Environmental 

Protection Agency, Office of Air Quality 

Planning and Standards, Mail Code 

C539–01, Research Triangle Park, NC 

27711, phone number (919) 54l–5592 or 

by e-mail at: damberg.rich@epa.gov. 

SUPPLEMENTARY INFORMATION: 

General Information 

A. Does this action apply to me? 

Entities potentially regulated by this 

action are State and local air quality 

agencies. 

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 at http:// 

www.epa.gov/particles/actions.html. 

C. How is the preamble organized? 

I. Background 

II. Elements of the Clean Air Fine Particle 

Implementation Rule 

A. Precursors and Pollutants Contributing 

to Fine Particle Formation 

B. No Classification System 

C. Due Dates and Basic Requirements for 

Attainment Demonstrations 

D. Attainment Dates 

E. Modeling and Attainment 

Demonstrations 

F. Reasonably Available Control 

Technology and Reasonably Available 

Control Measures 

G. Reasonable Further Progress 

H. Contingency Measures 

I. Transportation Conformity 

J. General Conformity 

K. Emission Inventory Requirements 

L. Condensable Particulate Matter Test 

Methods and Related Data Issues 

M. Improving Source Monitoring 

N. Guidance Specific to Tribes 

O. Enforcement and Compliance 

P. Emergency Episodes 

Q. Ambient Monitoring 

III. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

B. Paperwork Reduction Act 

C. Regulatory Flexibility Act 

D. Unfunded Mandates Reform Act 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

I. National Technology Transfer 

Advancement Act 

J. Executive Order 12898: Federal Actions 

To Address Environmental Justice in 

Minority Populations and Low-Income 

Populations 

K. Congressional Review Act 

L. Petitions for Judicial Review 

M. Judicial Review 

IV. Statutory Authority 

I. Background 

Fine particles in the atmosphere are 

comprised of a complex mixture of 

components. Common constituents 

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

ammonium; elemental carbon; a great 

variety of organic compounds; and 

inorganic material (including metals, 

dust, sea salt, and other trace elements) 

generally referred to as ‘‘crustal’’ 

material, although it may contain 

material from other sources. Airborne 

particles generally less than or equal to 

2.5 micrometers in diameter are 

considered to be ‘‘fine particles’’ (also 

referred to as PM2.5). (A micrometer is 

one-millionth of a meter, and 2.5 

micrometers is less than one-seventh the 

average width of a human hair.) 

‘‘Primary’’ particles are emitted directly 

into the air as a solid or liquid particle 

(e.g., elemental carbon from diesel 

engines or fire activities, or condensable 

organic particles from gasoline engines). 

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

nitrate) form in the atmosphere as a 

result of various chemical reactions. 

(Section II of the proposed rule included 

detailed technical discussion on PM2.5, 

its precursors, formation processes, and 

emissions sources.) 

The EPA established air quality 

standards for PM2.5 based on evidence 

from numerous health studies 

demonstrating that serious health effects 

are associated with exposures to 

elevated levels of PM2.5. 

Epidemiological studies have shown 

statistically significant correlations 

between elevated PM2.5 levels and 

premature mortality. Other important 


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Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 20587 

1The original annual and daily standards for 

particles generally less than or equal to 10 

micrometers in diameter (also referred to as PM10) 

were established in 1987. In the 1997 PM NAAQS 

revision, EPA also revised the standards for PM10, 

but these revised PM10 standards were later vacated 

by the court, and the 1987 PM10 standards remained 

in effect. In the 2006 NAAQS revision, the 24-hour 

PM10 standard was retained but the annual standard 

was revoked. Today’s implementation rule and 

guidance does not address PM10. 

2Environmental Protection Agency. (2004a). Air 

Quality Criteria for Particulate Matter. Research 

Triangle Park, NC: National Center for 

Environmental Assessment—RTP, Office of 

Research and Development, U.S. Environmental 

Protection Agency, Research Triangle Park, NC 

27711; report no. EPA/600/P–99/002aF and EPA/ 

600/P–99/002bF. October 2004. 

3The revised fine particle NAAQS were 

published on October 17, 2006 (71 FR 61144). See 

EPA’s Web site for additional information: http:// 

www.epa.gov/pm/index.html. 

4Regulatory Impact Analysis for Particulate 

Matter National Ambient Air Quality Standards 

(September 2006), page ES–8. The mortality range 

includes estimates based on the results of an expert 

elicitation study, along with published 

epidemiological studies. 

effects associated with PM2.5 exposure 

include aggravation of respiratory and 

cardiovascular disease (as indicated by 

increased hospital admissions, 

emergency room visits, absences from 

school or work, and restricted activity 

days), changes in lung function and 

increased respiratory symptoms, as well 

as new evidence for more subtle 

indicators of cardiovascular health. 

Individuals particularly sensitive to 

PM2.5 exposure include older adults, 

people with heart and lung disease, and 

children. 

On July 18, 1997, we revised the 

NAAQS for particulate matter (PM) to 

add new standards for fine particles, 

using PM2.5 as the indicator. We 

established health-based (primary) 

annual and 24-hour standards for PM2.5

(62 FR 38652).1 The annual standard 

was set at a level of 15 micrograms per 

cubic meter, as determined by the 3-year 

average of annual mean PM2.5

concentrations. The 24-hour standard 

was set at a level of 65 micrograms per 

cubic meter, as determined by the 3-year 

average of the 98th percentile of 24-hour 

concentrations. 

Attainment of the 1997 PM2.5

standards is estimated to lead to 

reductions in health impacts, including 

tens of thousands fewer premature 

deaths each year, thousands fewer 

hospital admissions and emergency 

room visits each year, hundreds of 

thousands fewer absences from work 

and school, and hundreds of thousands 

fewer respiratory illnesses in children 

annually. The EPA’s evaluation of the 

science concluded that there was not 

sufficient information to either support 

or refute the existence of a threshold for 

health effects from PM exposure.2

We subsequently completed in 

October 2006 another review of the 

NAAQS for PM. With regard to the 

primary standards, the 24-hour PM2.5

standard was strengthened to a level of 

35 micrograms per cubic meter, based 

on the 3-year average of the 98th 

percentile of 24-hour concentrations, 

and the level of the annual standard 

remained unchanged.3 Attainment of 

the 2006 PM2.5 standards is estimated to 

lead to additional reductions in health 

impacts, including approximately 1,200 

to 13,000 fewer premature deaths each 

year, 1,630 fewer hospital admissions 

and 1,200 fewer emergency room visits 

for asthma each year, 350,000 fewer 

absences from work and school, and 

155,300 fewer respiratory illnesses in 

children annually.4

In both 1997 and 2006 EPA 

established welfare-based (secondary) 

standards identical to the levels of the 

primary standards. The secondary 

standards are designed to protect against 

major environmental effects of PM2.5

such as visibility impairment, soiling, 

and materials damage. The EPA also 

established the regional haze regulations 

in 1999 for the improvement of visual 

air quality in national parks and 

wilderness areas across the country. 

Because regional haze is caused 

primarily by light scattering and light 

absorption by fine particles in the 

atmosphere, EPA is encouraging the 

States to integrate their efforts to attain 

the PM2.5 standards with those efforts to 

establish reasonable progress goals and 

associated emission reduction strategies 

for the purposes of improving air quality 

in our treasured natural areas under the 

regional haze program. 

The scientific assessments used in the 

development of the PM2.5 standards 

included a scientific peer review and 

public comment process. We developed 

scientific background documents based 

on the review of hundreds of peerreviewed scientific studies. The Clean 

Air Scientific Advisory Committee, a 

congressionally mandated group of 

independent scientific and technical 

experts, provided extensive review of 

these assessments, and found that EPA’s 

review of the science provided an 

adequate basis for the EPA 

Administrator to make a decision. More 

detailed information on health effects of 

PM2.5 can be found on EPA’s Web site 

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

pm/index.html. Additional information 

on EPA’s scientific assessment 

documents supporting the 1997 

standards are available at http:// 

www.epa.gov/ttn/oarpg/t1cd.html; 

additional scientific assessment 

information on the 2006 standards is 

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

naaqs/standards/pm/s_pm_cr_cd.html. 

The EPA issued final PM2.5

designations for areas violating the 1997 

standards on December 17, 2004. They 

were published in the Federal Register 

on January 5, 2005 (70 FR 944). On 

April 5, 2005, EPA issued a 

supplemental notice which changed the 

designation status of eight areas from 

nonattainment to attainment based on 

newly updated 2002–2004 air quality 

data (70 FR 19844; published in the 

Federal Register on April 14, 2005). A 

total of 39 areas were designated as 

nonattainment for the 1997 PM2.5

standards. The population of these areas 

is estimated at about 90 million (or more 

than 30% of the U.S. population). Most 

of these areas only violate the annual 

standard, but a few violate both the 

annual and 24-hour standards. 

The nonattainment designation for an 

area starts the process whereby a State 

or Tribe must develop an 

implementation plan that includes, 

among other things, a demonstration 

showing how it will attain the ambient 

standards by the attainment dates 

required in the CAA. Under section 

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

EPA’s final designations to submit their 

SIPs to EPA. These SIPs will be due on 

April 5, 2008, 3 years from the effective 

date of the designations. 

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

States to attain the standards as 

expeditiously as practicable but within 

5 years of designation (i.e. attainment 

date of April 2010 based on air quality 

data for 2007–2009), or within up to 10 

years of designation (i.e. to April 2015) 

if the EPA Administrator extends an 

area’s attainment date by 1–5 years 

based upon the severity of the 

nonattainment problem or the feasibility 

of implementing control measures. 

Virtually all nonattainment problems 

appear to result from a combination of 

local emissions and transported 

emissions from upwind areas. The 

structure of the CAA requires EPA to 

develop national rules for certain types 

of sources which are also significant 

contributors to local air quality 

problems, including motor vehicles and 

fuels. It also provides for States to 

address emissions sources on an areaspecific basis through such 

requirements as RACT, RACM, and RFP. 

We believe that to attain the PM2.5

standards, it is important to pursue 

emissions reductions simultaneously on 

the local, regional, and national levels. 

The EPA issued the Clean Air Interstate 


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20588 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

5See http://www.epa.gov/cair. 

6See 64 FR 35714, July 1, 1999. 

7See Tier II emission standards at 65 FR 6698, 

February 10, 2000. 

8See heavy-duty diesel engine regulations at 66 

FR 5002, January 18, 2001. 

9For more information on the proposed nonroad 

diesel engine standards, see EPA’s Web site: 

http://www.epa.gov/nonroad/. 

Rule (CAIR) 5 on March 10, 2005 to 

address the interstate transport of sulfur 

dioxide and nitrogen oxide emissions 

primarily from power plants. Section 

110 gives EPA the authority to require 

SIPs to ‘‘prohibit * * * any source or 

other type of emission activity within 

the State from emitting any air pollutant 

in amounts which will contribute 

significantly to nonattainment in, or 

interfere with maintenance by, any 

other State with respect to’’ any 

NAAQS, and to prohibit sources or 

emission activities from emitting 

pollutants in amounts which will 

interfere with measures required to be 

included in State plans to prevent 

significant deterioration of air quality or 

to protect visibility (such as the 

protection of 156 mandatory Federal 

class I areas under the regional haze 

rule 6). CAIR employs the same 

emissions trading approach used to 

achieve cost-effective emission 

reductions under the acid rain program. 

It outlines a two-phase program with 

increasingly tighter power plant 

emissions caps for 28 eastern states and 

the District of Columbia: SO2 caps of 3.6 

million tons in 2010, and 2.5 million in 

2015; NOX caps of 1.5 in 2009 and 1.3 

in 2015; and NOX ozone season caps of 

580,000 tons in 2009 and 480,000 tons 

in 2015. Emission caps are divided into 

State SO2 and NOX budgets. By the year 

2015, the Clean Air Interstate Rule is 

estimated to result in: 

—$85 to $100 billion in annual health 

benefits, including preventing 17,000 

premature deaths, millions of lost 

work and school days, and tens of 

thousands of non-fatal heart attacks 

and hospital admissions annually. 

—Nearly $2 billion in annual visibility 

benefits in southeastern national 

parks, such as Great Smoky and 

Shenandoah. 

—Significant regional reductions in 

sulfur and nitrogen deposition, 

reducing the number of acidic lakes 

and streams in the eastern U.S. 

Over the past several years, EPA has 

also issued a number of regulations 

addressing emissions standards for new 

cars, trucks and buses. These standards 

are providing reductions in motor 

vehicle emissions of volatile organic 

compounds (VOCs, also referred to as 

hydrocarbons), NOX, and direct PM 

emissions (such as elemental carbon) as 

older vehicles are retired and replaced. 

Other existing rules are designed to 

reduce emissions from several 

categories of nonroad engines. The Tier 

2 motor vehicle emission standards, 

together with the associated 

requirements to reduce sulfur in 

gasoline, are estimated to provide 

additional benefits nationally beginning 

in 2004.7 When the new tailpipe and 

sulfur standards are fully implemented, 

Americans are estimated to benefit from 

the clean-air equivalent of removing 164 

million cars from the road. These new 

standards require passenger vehicles to 

have emissions 77 to 95 percent cleaner 

than those on the road today and require 

fuel manufacturers to reduce the sulfur 

content of gasoline by up to 90 percent. 

In addition, the 2001 heavy-duty diesel 

engine regulations 8 will lead to 

continued emissions reductions as older 

vehicles in that engine class are retired 

and fleets turn over. New emission 

standards began to take effect for model 

year 2007 and apply to heavy-duty 

highway engines and vehicles. These 

standards are based on the use of highefficiency catalytic exhaust emission 

control devices or comparably effective 

advanced technologies. Because these 

devices are damaged by sulfur, the level 

of sulfur in highway diesel fuel was to 

be reduced by 97 percent by mid-2006. 

We project a 2.6 million ton reduction 

of NOX emissions in 2030 when the 

current heavy-duty vehicle fleet is 

completely replaced with newer heavyduty vehicles that comply with these 

emission standards. By 2030, we 

estimate that this program will reduce 

annual emissions of hydrocarbons by 

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

These emissions reductions are on par 

with those that we anticipate from new 

passenger vehicles and low sulfur 

gasoline under the Tier 2 program. 

The EPA also finalized national rules 

in May 2004 to reduce significantly 

PM2.5 and NOX emissions from nonroad 

diesel-powered equipment.9 These 

nonroad sources include construction, 

agricultural, and industrial equipment, 

and their emissions constitute an 

important fraction of the inventory for 

direct PM2.5 emissions (such as 

elemental carbon and organic carbon), 

and NOX. The EPA estimates that 

affected nonroad diesel engines 

currently account for about 44 percent 

of total diesel PM emissions and about 

12 percent of total NOX emissions from 

mobile sources nationwide. These 

proportions are even higher in some 

urban areas. The diesel emission 

standards will reduce emissions from 

this category by more than 90 percent, 

and are similar to the onroad engine 

requirements implemented for highway 

trucks and buses. Because the emission 

control devices can be damaged by 

sulfur, EPA also established 

requirements to reduce the allowable 

level of sulfur in nonroad diesel fuel by 

more than 99 percent by 2010. In 2030, 

when the full inventory of older 

nonroad engines has been replaced, the 

nonroad diesel program will annually 

prevent up to 12,000 premature deaths, 

one million lost work days, 15,000 heart 

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

The EPA expects the implementation 

of regional and national emission 

reduction programs such as CAIR and 

the suite of mobile source rules 

described above to provide significant 

air quality improvements for PM2.5

nonattainment areas. At the same time, 

analyses for the final CAIR rule indicate 

that without implementation of local 

measures, a number of PM2.5 areas are 

projected to remain in nonattainment 

status in the 2010–2015 timeframe. 

Thus, EPA believes that local and State 

emission reduction efforts will need to 

play an important role in addressing the 

PM2.5 problem as well. The EPA will 

work closely with States, Tribes, and 

local governments to develop 

appropriate in-state pollution reduction 

measures to complement regional and 

national strategies to meet the standards 

expeditiously and in a cost-effective 

manner. States will need to evaluate 

technically and economically feasible 

emission reduction opportunities and 

determine which measures can be 

reasonably implemented in the near 

term. Local and regional emission 

reduction efforts should proceed 

concurrently and expeditiously. 

The promulgation of a revised 24- 

hour PM2.5 standard effective on 

December 18, 2006 has initiated another 

process of State recommendations, and 

the eventual designation by EPA of 

areas not attaining the revised standard. 

The additional designations are to be 

completed within two years from the 

effective date, although EPA may take 

an additional year to complete the 

designations if it determines it does not 

have sufficient information. State plans 

to attain the 24-hour standard would 

then be due within three years of the 

final designations. A number of areas, 

including some that are already 

designated as not attaining the 1997 

standards, may be exceeding the revised 

24-hour standard. The EPA encourages 

State and local governments to be 

mindful of the strengthened 24-hour 

standard as they adopt emission 

reduction strategies to attain the 1997 

standards. Such steps may help with 


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Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 20589 

10See: U.S. EPA 2006. Regulatory Impact 

Analysis for the Particulate Matter National 

Ambient Air Quality Standards. Air Benefits and 

Cost Group, Office of Air Quality Planning and 

Standards, Research Triangle Park, N.C. October 6, 

2006. Appendix A provides an analysis of estimated 

benefits and costs of attaining the 1997 PM NAAQS 

standards in 2015. 

future attainment efforts, or even help 

some areas avoid a nonattainment 

designation for the 24-hour standard in 

the first place. 

The public health benefits of meeting 

the PM2.5 standards are estimated to be 

significant. Even small reductions in 

PM2.5 levels may have substantial health 

benefits on a population level. For 

example, in a moderate-sized 

metropolitan area with a design value of 

15.5 μg/m3, efforts to improve annual 

average air quality down to the level of 

the standard (15.0 μg/m3) are estimated 

to result in as many as 25–50 fewer 

mortalities per year due to air pollution 

exposure. In a smaller city, the same air 

quality improvement from 15.5 to 15.0 

μg/m3 still are estimated to result in a 

number of avoided mortalities per year. 

These estimates are based on EPA’s 

standard methodology for calculating 

health benefits as used in recent 

rulemakings.10 In addition, because 

many different precursors contribute to 

the formation of fine particles, 

reductions in pollutants that contribute 

to PM2.5 also can provide concurrent 

benefits in addressing a number of other 

air quality problems—such as groundlevel ozone, regional haze, toxic air 

pollutants, and urban visibility 

impairment. 

In order to assist States in developing 

effective plans to address the local 

component of the PM2.5 nonattainment 

problem, EPA is issuing this final fine 

particle implementation rule. The EPA 

is issuing this rule to implement the 

1997 PM2.5 NAAQS in accordance with 

the statutory requirements of the CAA 

set forth in Subpart 1 of Part D of Title 

1, i.e., sections 171–179B of the Act. 

The EPA believes that the CAA directs 

the Agency to implement new or revised 

NAAQS in nonattainment areas solely 

in accordance with Subpart 1, unless 

another Subpart of the Act also applies 

to the particular NAAQS at issue. In this 

case, EPA has concluded that Congress 

did not intend the Agency to implement 

particulate matter NAAQS other than 

those using PM10 as the indicator in 

accordance with Subpart 4 of Part D of 

Title 1, i.e., sections 188–190 of the 

CAA. Moreover, EPA believes that 

implementation of the PM2.5 NAAQS 

under the provisions of Subpart 1 is 

more appropriate, given the inherent 

nature of the PM2.5 nonattainment 

problem. In contrast to PM10, EPA 

anticipates that achieving the NAAQS 

for PM2.5 will generally require States to 

evaluate different sources for controls, 

to consider controls of one or more 

precursors in addition to direct PM 

emissions, and to adopt different control 

strategies. As a result, EPA has 

concluded that the provisions of 

Subpart 1 will allow States and EPA to 

tailor attainment plans so that they can 

be based more specifically upon the 

facts and circumstances of each 

nonattainment area. 

The proposed clean air fine particle 

implementation rule was issued on 

November 1, 2005 (70 FR 65984). About 

100 comments were received from 

private citizens and parties representing 

industry, state and local governments, 

environmental groups, and federal 

agencies. Section II of this document 

describes the primary elements of the 

fine particle implementation program. 

Each section summarizes the relevant 

policies and options discussed in the 

proposed rule, discusses the final policy 

set forth by EPA in the final rule, and 

provides responses to the major 

comments received on each issue. 

II. Elements of the Clean Air Fine 

Particle Implementation Rule 

A. Precursors and Pollutants 

Contributing to Fine Particle Formation 

1. Introduction 

The main precursor gases associated 

with fine particle formation are SO2, 

NOX, volatile organic compounds 

(VOC), and ammonia. This section 

provides technical background on each 

precursor, discusses the policy 

approach for addressing each precursor 

under the PM2.5 implementation 

program, and responds to key issues 

raised in the public comment process. A 

subsection is also included on direct 

PM2.5 emissions to address key 

comments received on this issue as 

well. 

Gas-phase precursors SO2, NOX, VOC, 

and ammonia undergo chemical 

reactions in the atmosphere to form 

secondary particulate matter. Formation 

of secondary PM depends on numerous 

factors including the concentrations of 

precursors; the concentrations of other 

gaseous reactive species; atmospheric 

conditions including solar radiation, 

temperature, and relative humidity 

(RH); and the interactions of precursors 

with preexisting particles and with 

cloud or fog droplets. Several 

atmospheric aerosol species, such as 

ammonium nitrate and certain organic 

compounds, are semivolatile and are 

found in both gas and particle phases. 

Given the complexity of PM formation 

processes, new information from the 

scientific community continues to 

emerge to improve our understanding of 

the relationship between sources of PM 

precursors and secondary particle 

formation. 

As an initial matter, it is helpful to 

clarify the terminology we use 

throughout this notice to discuss 

precursors. We recognize NOX, SO2, 

VOCs, and ammonia as precursors of 

PM2.5 in the scientific sense because 

these pollutants can contribute to the 

formation of PM2.5 in the ambient air. In 

section II.K on emission inventory 

issues, we make the point that because 

of the complex and variable interaction 

of multiple pollutants and precursors in 

the formation of fine particles, it is 

important for States and EPA to 

continue to characterize and improve 

the emissions inventories for all PM2.5

precursors. The States and EPA need to 

use the best available information 

available in conducting air quality 

modeling and other assessments. At the 

same time, the refinement of emissions 

inventories, the overall contribution of 

different fine particle precursors to 

PM2.5 formation, and the efficacy of 

alternative potential control measures 

will vary by location. This requires that 

we further consider in this action how 

States should address these PM2.5

precursors in their PM2.5 attainment 

plan programs. Thus, we require 

emission inventories to include the best 

available information on all pollutants 

and precursors that contribute to PM2.5

concentrations, and at same time we use 

the term ‘‘PM2.5 attainment plan 

precursor’’ to describe only those 

precursors that are required to be 

evaluated for control strategies in a 

specific PM2.5 nonattainment area or 

maintenance area plan. 

In this rule, EPA has not made a 

finding that all precursors should be 

evaluated for possible controls in each 

specific nonattainment area. The policy 

approach in the rule instead requires 

sulfur dioxide to be evaluated for 

control measures in all areas, and 

describes general presumptive policies 

for NOX, ammonia, and VOC for all 

nonattainment areas. The rule provides 

a mechanism by which the State and/or 

EPA can make an area-specific 

demonstration to reverse the general 

presumption for these three precursors. 

States must also consider any relevant 

information brought forward by 

interested parties in the SIP planning 

and development process. (See section 

II.A.8 for additional discussion on these 

issues.) 

In the following sections, we discuss 

how States must evaluate PM2.5

precursors for nonattainment program 

issues in PM2.5 implementation plans, 


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20590 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

including issues such as RACT, RACM, 

and reasonable further progress. This 

discussion in the final rule is linked to 

precursor policies for the 

implementation of the new source 

review program, the transportation 

conformity program, the general 

conformity program, and the regional 

haze program. All of these programs 

take effect prior to approval of SIPs for 

attaining the PM2.5 NAAQS. In the case 

of NSR, the program applies on the 

effective date of the nonattainment area 

designation. In the case of 

transportation conformity and general 

conformity, the program takes effect 1 

year from the effective date of 

designation of the nonattainment area 

(i.e., April 5, 2006 for areas designated 

nonattainment effective April 5, 2005). 

Thus, for each of these programs there 

is an interim period between the date 

the program becomes applicable to a 

given nonattainment area and the date 

the State receives EPA approval of its 

overall PM2.5 implementation plan. 

2. Legal Authority to Regulate 

Precursors 

a. Background 

The CAA authorizes the Agency to 

regulate criteria pollutant precursors. 

The term ‘‘air pollutant’’ is defined in 

section 302(g) to include ‘‘any 

precursors to the formation of any air 

pollutant, to the extent the 

Administrator has identified such 

precursor or precursors for the 

particular purpose for which the term 

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

of this second sentence in section 302(g) 

explicitly authorizes the Administrator 

to identify and regulate precursors as air 

pollutants under other parts of the CAA. 

In addition, the second clause of the 

sentence indicates that the 

Administrator has discretion to identify 

which pollutants should be classified as 

precursors for particular regulatory 

purposes. Thus, we do not necessarily 

construe the CAA to require that EPA 

identify a particular precursor as an air 

pollutant for all regulatory purposes 

where it can be demonstrated that 

various CAA programs address different 

aspects of the air pollutant problem. 

Likewise, we do not interpret the CAA 

to require that EPA treat all precursors 

of a particular pollutant the same under 

any one program when there is a basis 

to distinguish between such precursors. 

For example, in a rule addressing PM2.5

precursors for purposes of the 

transportation conformity program, we 

chose to adopt a different approach for 

one precursor based on the limited 

emissions of that precursor from onroad 

mobile sources and the degree to which 

it contributes to PM2.5 concentrations. 

(70 FR 24280; May 6, 2005). 

Other provisions of the CAA reinforce 

our reading of section 302(g) that 

Congress intended precursors to 

NAAQS pollutants to be subject to the 

air quality planning and control 

requirements of the CAA, but also 

recognized that there may be 

circumstances where it is not 

appropriate to subject precursors to 

certain requirements of the CAA. 

Section 182 of the CAA provides for the 

regulation of NOX and VOCs as 

precursors to ozone in ozone 

nonattainment areas, but also provides 

in section 182(f) that major stationary 

sources of NOX (an ozone precursor) are 

not subject to emission reductions 

controls for ozone where the State 

shows through modeling that NOX

reductions do not decrease ozone. 

Section 189(e) provides for the 

regulation of PM10 precursors in PM10

nonattainment areas, but also recognizes 

that there may be certain circumstances 

(e.g. if precursor emission sources do 

not significantly contribute to PM10

levels) where it is not appropriate to 

apply control requirements to PM10

precursors. The legislative history of 

Section 189(e) recognized the 

complexity behind the science of 

precursor transformation into PM10

ambient concentrations and the need to 

harmonize the regulation of PM10

precursors with other provisions of the 

CAA: 

The Committee notes that some of these 

precursors may well be controlled under 

other provisions of the CAA. The Committee 

intends that * * * the Administrator will 

develop models, mechanisms, and other 

methodology to assess the significance of the 

PM10 precursors in improving air quality and 

reducing PM10. Additionally, the 

Administrator should consider the impact on 

ozone levels of PM10 precursor controls. The 

Committee expects the Administrator to 

harmonize the PM10 reduction objective of 

this section with other applicable regulations 

of this CAA regarding PM10 precursors, such 

as NOX. See H. Rpt. 101–490, Pt. 1, at 268 

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

Vol. II, at 3292. 

In summary, section 302(g) of the 

CAA clearly calls for the regulation of 

precursor pollutants, but the CAA also 

identifies circumstances when it may 

not be appropriate to regulate precursors 

and gives the Administrator discretion 

to determine how to address particular 

precursors under various programs 

required by the CAA. Due to the 

complexities associated with precursor 

emissions and their variability from 

location to location, we believe that in 

certain situations it may not be effective 

or appropriate to control a certain 

precursor under a particular regulatory 

program or for EPA to require similar 

control of a particular precursor in all 

areas of the country. 

b. Final Rule 

The final rule maintains the same 

legal basis for regulating precursors as 

was described in the proposal and in the 

background section above. We also 

include a clarification of the term 

‘‘significant contributor.’’

In the proposal, when considering the 

impacts of the precursors NOX, VOC 

and ammonia on ambient 

concentrations of particulate matter, we 

referred to the possibility of reversing 

the presumed approach for regulating or 

not regulating a precursor if it can be 

shown that the precursor in question is 

or is not a ‘‘significant contributor’’ to 

PM2.5 concentrations within the specific 

nonattainment area. ‘‘Significant 

contribution’’ in this context is a 

different concept than that in Section 

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

prohibits States from emitting air 

pollutants in amounts which 

significantly contribute to 

nonattainment or other air quality 

problems in other states. Consistent 

with the discussion of sections 189(e) 

and 302(g) above, we are clarifying that 

the use in this implementation rule of 

the term ‘‘significant contribution’’ to 

the nonattainment area’s PM2.5

concentration means that a significant 

change in emissions of the precursor 

from sources in the state would be 

projected to provide a significant change 

in PM2.5 concentrations in the 

nonattainment area. For example, if 

modeling indicates that a reduction in a 

state’s NOX emissions would reduce 

ambient PM2.5 levels in the 

nonattainment area, but that a reduction 

in ammonia emissions would result in 

virtually no change in ambient PM2.5

levels, this would suggest that NOX is a 

significant contributor but that ammonia 

is not. The EPA in this rule is not 

establishing a quantitative test for 

determining whether PM2.5 levels in a 

nonattainment area change significantly 

in response to reductions in precursor 

emissions in a state. However, in 

considering this question, it is relevant 

to consider that relatively small 

reductions in PM2.5 levels are estimated 

to result in worthwhile public health 

benefits. 

This approach to identifying a 

precursor for regulation reflects 

atmospheric chemistry conditions in the 

area and the magnitude of emissions of 

the precursor in the area or State. 

Assessments of which source categories 

are more cost effective or technically 

feasible to control should be part of the 

later RACT and RACM assessment, to 


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Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 20591 

11NARSTO (2004) (Particulate Matter 

Assessment for Policy Makers: A NARSTO 

Assessment. P. McMurry, M. Shepherd, and J. 

Vickery, eds. Cambridge University Press, 

Cambridge, England. ISBN 0 52 184287 5. 

occur after the basic assessment of 

which precursors are to be regulated is 

completed. 

In the proposed regulatory text, the 

provisions for reversing presumptions 

for NOX, VOC and ammonia included 

consideration of whether the precursor 

would significantly contribute to ‘‘other 

downwind air quality concerns.’’ In the 

final rule we have removed that 

language to clarify that identification of 

attainment plan precursors involves 

evaluation of the impact on PM2.5 levels 

in a nonattainment area of precursor 

emissions from sources within the 

state(s) where the nonattainment area is 

located. Other parts of the Act, notably 

section 110(a)(2)(D) and section 126, 

focus on interstate transport of 

pollutants. 

c. Comments and Responses 

Comment: The EPA received several 

comments supporting EPA’s 

interpretation of 302(g) to determine the 

appropriate regulatory status of each 

precursor pollutant. 

Response: The EPA agrees with the 

commenters. In establishing section 

302(g), Congress intended that 

precursors to NAAQS pollutants be 

subject to the air quality planning and 

control requirements of the CAA. 

However, the CAA also recognizes that 

there may be circumstances where it is 

not appropriate to subject precursors to 

certain requirements of the CAA. 

Comment: The EPA received several 

comments regarding the applicability of 

section 189(e), noting that it requires 

states to presumptively control sources 

of PM10 precursors except where the 

EPA ‘‘determines that such sources [of 

precursors] do not significantly 

contribute to PM10 levels which exceed 

the standard in the area.’’ Several 

commenters stated that EPA does not 

have the legal authority to regulate 

PM2.5 precursors in a different manner. 

Several commenters maintained that all 

PM2.5 precursors presumptively should 

be subject to regulation unless 

demonstrated by the State as not a 

significant contributor to PM2.5

concentrations in a specific area. 

Response: As stated above, EPA 

believes that section 302(g) allows the 

Administrator to presumptively not 

require certain precursors to be 

addressed in PM2.5 implementation 

plans generally, while allowing the 

State or EPA to make a finding for a 

specific area to override the general 

presumption. In the following pollutantspecific sections of this preamble, EPA 

finds that at this time there is sufficient 

uncertainty regarding whether certain 

precursors significantly contribute to 

PM2.5 concentrations in all 

nonattainment areas such that the 

policy set forth in this rule does not 

presumptively require certain 

precursors (ammonia, VOC) to be 

controlled in each area. However, the 

State or EPA may reverse the 

presumption and regulate a precursor if 

it provides a demonstration showing 

that the precursor is a significant 

contributor to PM2.5 concentrations in 

the area. In addition, if in the State’s SIP 

planning and adoption process a 

commenter provides additional 

information suggesting an alternative 

policy for regulating a particular 

precursor, the State will need to 

respond to this information in its 

rulemaking action. 

3. Policy for Ammonia 

[Section II.E.2 of November 1, 2005 

proposed rule (70 FR 65999); sec. 

51.1002 in draft and final regulatory 

text.] 

a. Background 

Ammonia (NH3) is a gaseous pollutant 

that is emitted by natural and 

anthropogenic sources. Emissions 

inventories for ammonia are considered 

to be among the most uncertain of any 

species related to PM. Ammonia serves 

an important role in neutralizing acids 

in clouds, precipitation and particles. In 

particular, ammonia neutralizes sulfuric 

acid and nitric acid, the two key 

contributors to acid deposition (acid 

rain). Deposited ammonia also can 

contribute to problems of eutrophication 

in water bodies, and deposition of 

ammonium particles may effectively 

result in acidification of soil as 

ammonia is taken up by plants. The 

NARSTO Fine Particle Assessment 11

indicates that reducing ammonia 

emissions where sulfate concentrations 

are high may reduce PM2.5 mass 

concentrations, but may also increase 

the acidity of particles and 

precipitation. An increase in particle 

acidity is suspected to be linked with 

human health effects and with an 

increase in the formation of secondary 

organic compounds. Based on the above 

information and further insights gained 

from the NARSTO Fine Particle 

Assessment, it is apparent that the 

formation of particles related to 

ammonia emissions is a complex, 

nonlinear process. 

Though recent studies have improved 

our understanding of the role of 

ammonia in aerosol formation, ongoing 

research is required to better describe 

the relationships between ammonia 

emissions, particulate matter 

concentrations, and related impacts. 

The control techniques for ammonia 

and the analytical tools to quantify the 

impacts of reducing ammonia emissions 

on atmospheric aerosol formation are 

both evolving. Also, area-specific data 

are needed to evaluate the effectiveness 

of reducing ammonia emissions on 

reducing PM2.5 concentrations in 

different areas, and to determine where 

ammonia decreases may increase the 

acidity of particles and precipitation. 

The proposal showed consideration 

for the uncertainties about ammonia 

emissions inventories and about the 

potential efficacy of ammonia control 

measures by providing for a case-bycase approach. It was recommended that 

each State should evaluate whether 

reducing ammonia emissions would 

lead to PM2.5 reductions in their specific 

PM2.5 nonattainment areas. The 

proposed policy did not require States 

to address ammonia as a PM2.5

attainment plan precursor, unless a 

technical demonstration by the State or 

EPA showed that ammonia emissions 

from sources in the State significantly 

contribute to PM2.5 concentrations in a 

given nonattainment area or to other 

downwind air quality concerns. Where 

the State or EPA has determined that 

ammonia is a significant contributor to 

PM2.5 formation in a nonattainment 

area, the State would be required to 

evaluate control measures for ammonia 

emissions in its nonattainment SIP due 

in 2008, in the implementation of the 

PM program, and in other associated 

programs in that area. 

b. Final Rule 

In the final rule, ammonia is 

presumed not to be a PM2.5 attainment 

plan precursor, meaning that the State is 

not required to address ammonia in its 

attainment plan or evaluate sources of 

ammonia emissions for reduction 

measures. This presumption can be 

reversed based on an acceptable 

technical demonstration for a particular 

area by the State or EPA. If a technical 

demonstration by the State or EPA 

shows that ammonia emissions from 

sources in the State significantly 

contribute to PM2.5 concentrations in a 

given nonattainment area, the State 

must then evaluate and consider control 

strategies for reducing ammonia 

emissions in its nonattainment SIP due 

in 2008, in the implementation of the 

PM2.5 program. Technical 

demonstrations on ammonia should also 

consider the potential for atmospheric 

and particle acidity to increase with 

ammonia reductions. Further discussion 

about technical demonstrations to 


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20592 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

support reversing a PM2.5 precursor 

presumption is included in section 

II.A.8 below. 

This approach was retained from the 

proposal because of continued 

uncertainties regarding ammonia 

emission inventories and the effects of 

ammonia emission reductions. 

Ammonia emission inventories are 

presently very uncertain in most areas, 

complicating the task of assessing 

potential impacts of ammonia emissions 

reductions. In addition, data necessary 

to understand the atmospheric 

composition and balance of ammonia 

and nitric acid in an area are not widely 

available across PM2.5 nonattainment 

areas, making it difficult to predict the 

results of potential ammonia emission 

reductions. Ammonia reductions may 

be effective and appropriate for 

reducing PM2.5 concentrations in 

selected locations, but in other locations 

such reductions may lead to minimal 

reductions in PM2.5 concentrations and 

increased atmospheric acidity. Research 

projects continue to expand our 

collective understanding of these issues, 

but at this time EPA believes this caseby-case policy approach is appropriate. 

In light of these uncertainties, we 

encourage States to continue efforts to 

better understand the role of ammonia 

in its fine particle problem areas. 

c. Comments and Responses 

Comment: One commenter stated that 

scientific understanding of the 

complexities of PM formation from 

ammonia is limited. The commenter 

claimed that the reduction of ammonia 

will not reduce PM in many areas, and 

speciated PM data to investigate the 

potential decrease in PM from ammonia 

emissions reductions is not available in 

all areas. 

Response: The final rule takes these 

uncertainties into consideration by 

allowing ammonia to be addressed on a 

case-by-case basis. For any area about 

which enough information is available 

to determine that ammonia emission 

reductions would lead to a beneficial 

reduction in PM2.5, the State can 

develop a technical demonstration 

justifying the control of ammonia. If the 

State chooses to develop such a 

demonstration, preferably it should be 

completed as part of the SIP 

development process and prior to the 

adoption of control measures, in 

consultation with the appropriate EPA 

regional office. 

Comment: Some commenters claimed 

that requiring no action on some 

precursors is counter to the requirement 

in sections 172(a)(2) and 188 to attain 

the NAAQS as expeditiously as 

practicable. They also asserted that 

presuming that ammonia is not a PM2.5

attainment plan precursor violates 

302(g) by improperly delegating 

authority to the States. 

Response: In many areas, reducing 

ammonia emissions could have little 

effect on PM2.5 concentrations and could 

lead to the potentially harmful effect of 

increased atmospheric acidity. While 

States are not required to take action on 

ammonia sources under this policy, 

States would be required to address 

information on ammonia brought to 

their attention during the planning and 

rule adoption process. Under this 

approach, States should assess whether 

ammonia reductions would lead to 

reduced PM2.5 concentrations in specific 

nonattainment areas. If the State decides 

that ammonia reductions could yield 

beneficial reductions in PM2.5, the State 

should complete a technical 

demonstration supporting a reversal of 

the presumption. The EPA does not 

believe that this approach improperly 

delegates authority to the States. It 

establishes a general presumption for all 

areas through this rulemaking process, 

and allows for the presumption to be 

modified by the State or EPA on a caseby-case basis. EPA still retains the 

ability to make a technical 

demonstration for any area if 

appropriate to reverse the presumption 

and require ammonia to be addressed in 

its attainment plan. 

Comment: Some commenters stated 

that the results of a large study on air 

emissions from concentrated animal 

feeding operations (CAFOs) should be 

evaluated before requiring control of 

ammonia in areas where agriculture is 

alleged to be a major source. 

Response: The $15 million national 

CAFO consent agreement study 

coordinated by Purdue University will 

greatly improve ammonia and VOC 

emissions inventories and our 

understanding of the impacts of 

agricultural emissions on particle 

formation. The EPA recognizes that the 

agricultural emissions study is expected 

to provide data for future planning 

purposes, and we expect that some of 

the results of the study will not be 

available in time to be considered in the 

development of PM2.5 State 

Implementation Plans dues in April 

2008. However, if a State believes it has 

sufficient technical information to 

warrant regulation of ammonia 

emissions in their 2008 implementation 

plans, it may include in its plan a 

demonstration to reverse the 

presumption as well as emission 

reduction measures. The EPA will 

review each submittal on a case-by-case 

basis. 

Comment: A presumption to not 

address ammonia will impede certain 

states (i.e. those that have provisions 

requiring their regulations to be ‘‘no 

stricter than Federal’’ provisions) from 

regulating ammonia. 

Response: This presumptive approach 

to ammonia will not restrict States from 

addressing ammonia in their PM2.5

attainment plans. If a State has 

information indicating that reductions 

in ammonia emissions would cause 

beneficial reductions in PM2.5

concentrations, the State can make a 

technical demonstration to reverse the 

presumption. In such cases, inclusion of 

ammonia as a PM2.5 attainment plan 

precursor would not be considered 

stricter than Federal requirements. 

Under the policy in the final rule, the 

Federal government or the State may 

assess the impact of ammonia in a 

particular area and determine whether 

the presumption of insignificance is 

appropriate or whether ammonia is in 

fact a significant contributor to the PM2.5

problem in the area. 

4. Policy for VOC 

[Section II.E.2 of November 1, 2005 

proposed rule (70 FR 65999); sec. 

51.1002 in draft and final regulatory 

text.] 

a. Background 

The VOC policy in this rule addresses 

volatile and semivolatile organic 

compounds, generally up to 24 carbon 

atoms. High molecular weight organic 

compounds (typically 25 carbon atoms 

or more) are emitted directly as primary 

organic particles and exist primarily in 

the condensed phase at ambient 

temperatures. Accordingly, high 

molecular weight organic compounds 

are to be regulated as primary PM2.5

emissions for the purposes of the PM2.5

implementation program. 

The organic component of ambient 

particles is a complex mixture of 

hundreds or even thousands of organic 

compounds. These organic compounds 

are either emitted directly from sources 

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

formed by reactions in the ambient air 

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

Volatile organic compounds are key 

precursors in the formation processes 

for both SOA and ozone. The relative 

importance of organic compounds in the 

formation of secondary organic particles 

varies from area to area, depending 

upon local emissions sources, 

atmospheric chemistry, and season of 

the year. 

The lightest organic molecules (i.e., 

molecules with six or fewer carbon 

atoms) occur in the atmosphere mainly 

as vapors and typically do not directly 


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Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 20593 

12The policy is the same as proposed, with the 

clarification regarding downwind areas discussed 

above (Section A.2.b). 

form organic particles at ambient 

temperatures due to the high vapor 

pressure of their products. However, 

they participate in atmospheric 

chemistry processes resulting in the 

formation of ozone and certain free 

radical compounds (such as the 

hydroxyl radical [OH]) which in turn 

participate in oxidation reactions to 

form secondary organic aerosols, 

sulfates, and nitrates. These VOCs 

include all alkanes with up to six 

carbon atoms (from methane to hexane 

isomers), all alkenes with up to six 

carbon atoms (from ethene to hexene 

isomers), benzene and many lowmolecular weight carbonyls, chlorinated 

compounds, and oxygenated solvents. 

Intermediate weight organic 

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

carbon atoms) often exhibit a range of 

volatilities and can exist in both the gas 

and aerosol phase at ambient 

conditions. For this reason they are also 

referred to as semivolatile compounds. 

Semivolatile compounds react in the 

atmosphere to form secondary organic 

aerosols. These chemical reactions are 

accelerated in warmer temperatures, 

and studies show that SOA typically 

comprises a higher percentage of 

carbonaceous PM in the summer as 

opposed to the winter. The production 

of SOA from the atmospheric oxidation 

of a specific VOC depends on four 

factors: Its atmospheric abundance, its 

chemical reactivity, the availability of 

oxidants (O3, OH, HNO3), and the 

volatility of its products. In addition, 

recent work suggests that the presence 

of acidic aerosols may lead to an 

increased rate of SOA formation. 

Aromatic compounds such as toluene, 

xylene, and trimethyl benzene are 

considered to be the most significant 

anthropogenic SOA precursors and have 

been estimated to be responsible for 50 

to 70 percent of total SOA in some 

airsheds. Man-made sources of 

aromatics gases include mobile sources, 

petrochemical manufacturing and 

solvents. Some of the biogenic 

hydrocarbons emitted by trees are also 

considered to be important precursors of 

secondary organic particulate matter. 

Terpenes (and b-pinene, limonene, 

carene, etc.) and the sesquiterpenes are 

expected to be major contributors to 

SOA in areas with significant vegetation 

cover, but isoprene is not. Terpenes are 

very prevalent in areas with pine 

forests, especially in the southeastern 

U.S. The rest of the anthropogenic 

hydrocarbons (higher alkanes, paraffins, 

etc.) have been estimated to contribute 

5–20 percent to the SOA concentration 

depending on the area. 

The contribution of the primary and 

secondary components of organic 

aerosol to the measured organic aerosol 

concentrations remains a complex issue. 

Most of the research performed to date 

has been done in southern California, 

and more recently in central California, 

while fewer studies have been 

completed on other parts of North 

America. Many studies suggest that the 

primary and secondary contributions to 

total organic aerosol concentrations are 

highly variable, even on short time 

scales. Studies of pollution episodes 

indicate that the contribution of SOA to 

the organic particulate matter can vary 

from 20 percent to 80 percent during the 

same day. 

Despite significant advances in 

understanding the origins and 

properties of SOA, it remains probably 

the least understood component of 

PM2.5. The reactions forming secondary 

organics are complex, and the number 

of intermediate and final compounds 

formed is voluminous. Some of the best 

efforts to unravel the chemical 

composition of ambient organic aerosol 

matter have been able to quantify the 

concentrations of hundreds of organic 

compounds representing only 10–20 

percent of the total organic aerosol 

mass. For this reason, SOA continues to 

be a significant topic of research and 

investigation. 

Current scientific and technical 

information clearly shows that 

carbonaceous material is a significant 

fraction of total PM2.5 mass in most 

areas, that certain VOC emissions are 

precursors to the formation of secondary 

organic aerosol, and that a considerable 

fraction of the total carbonaceous 

material is likely from local as opposed 

to regional sources. However, while 

significant progress has been made in 

understanding the role of gaseous 

organic material in the formation of 

organic PM, this relationship remains 

complex. We recognize that further 

research and technical tools are needed 

to better characterize emissions 

inventories for specific VOC 

compounds, and to determine the extent 

of the contribution of specific VOC 

compounds to organic PM mass. 

In light of these factors, the proposed 

rule did not require States to address 

VOCs as PM2.5 attainment plan 

precursors and evaluate them for control 

measures, unless the State or EPA 

makes a finding that VOCs significantly 

contribute to a PM2.5 nonattainment 

problem in the State or to other 

downwind air quality concerns. Many 

PM2.5 nonattainment areas are also 

nonattainment areas for the 8-hour 

ozone standard; control measures for 

VOCs will be implemented in some of 

these areas, potentially providing a cobenefit for PM2.5 concentrations. 

b. Final Rule 

The final rule maintains the same 

policy as proposed.12 States are not 

required to address VOC in PM2.5

implementation plans and evaluate 

control measures for such pollutants 

unless the State or EPA makes a 

technical demonstration that emissions 

of VOCs from sources in the State 

significantly contribute to PM2.5

concentrations in a given nonattainment 

area. Technical demonstrations are 

discussed in section II.A.8 below. If a 

State chooses to make a technical 

demonstration, it should be developed 

in advance of the attainment 

demonstration. 

c. Comments and Responses 

Comment: One commenter stated that 

our understanding of the complexities 

of PM2.5 formation from VOCs is 

limited, that speciated PM data are not 

available in all areas, and that VOC 

reductions will not reduce PM2.5 in 

many areas. 

Response: The EPA acknowledges the 

uncertainties regarding the role of VOC 

in secondary organic aerosol formation. 

For this reason the final rule does not 

presumptively include VOC as a 

regulated pollutant for PM planning. 

However, if available data demonstrates 

that control of VOC would reduce PM2.5

concentrations in an area, the State or 

EPA may include VOC as an attainment 

plan precursor. 

Comment: One commenter stated that 

the rationale that VOC should not be 

considered a PM2.5 attainment plan 

precursor because most PM areas are 

also ozone areas is not appropriate 

because many ozone areas will attain 

soon and VOC reductions will still be 

needed for PM. 

Response: The primary rationale for 

not including VOC as a PM2.5 attainment 

plan precursor in every nonattainment 

area is the uncertainty regarding the 

contribution of anthropogenic VOCs to 

the formation of the organic carbon 

portion of fine particles. In certain areas, 

EPA expects that VOC control measures 

will have some co-benefits in the 

reduction of fine particulates. However, 

this reason should not be considered the 

principal reason for the policy in the 

final rule that VOCs presumptively 

should not be considered PM2.5

attainment plan precursors. If a State or 

EPA determines that VOCs do 

contribute significantly to PM2.5

concentrations in an area, the State will 

be required to evaluate control measures 

for VOC as a PM2.5 attainment plan 


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20594 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

13The policy is the same as proposed, with the 

clarification regarding downwind areas discussed 

above (Section A.2.b). 

precursor for that area. This approach 

will provide for regulation of VOCs in 

locations where it is most appropriate. 

Comment: One commenter suggested 

that EPA wait for the results of the 

pending agricultural emissions study 

before requiring control of VOCs in 

agricultural areas. 

Response: The $15 million national 

CAFO consent agreement study 

coordinated by Purdue University will 

greatly improve ammonia and VOC 

emissions inventories and our 

understanding of the impacts of 

agricultural emissions on particle 

formation. The EPA recognizes that the 

agricultural emissions study is expected 

to provide data for future planning 

purposes, and we expect that some of 

the results of the study will not be 

available in time to be considered in the 

development of PM2.5 State 

Implementation Plans dues in April 

2008. However, if a State believes it has 

sufficient technical information to 

warrant regulation of VOC emissions in 

their 2008 implementation plans, it may 

include in its plan a demonstration to 

reverse the presumption as well as 

emission reduction measures. The EPA 

will review each submittal on a case-bycase basis. 

5. Policy for NOX

[Section II.E.2 of November 1, 2005 

proposed rule (70 FR 65999); sec. 

51.1002 in draft and final regulatory 

text.] 

a. Background 

The sources of NOX are numerous and 

widespread. The combustion of fossil 

fuel in boilers for commercial and 

industrial power generation and in 

mobile source engines each account for 

approximately 30 percent of NOX

emissions in PM2.5 nonattainment areas 

(based on 2001 emission inventory 

information). Nitrates are formed from 

the oxidation of oxides of nitrogen into 

nitric acid either during the daytime 

(reaction with OH) or during the night 

(reactions with ozone and water). Nitric 

acid continuously transfers between the 

gas and the condensed phases through 

condensation and evaporation processes 

in the atmosphere. However, unless it 

reacts with other species (such as 

ammonia, sea salt, or dust) to form a 

neutralized salt, it will volatilize and 

not be measured using standard PM2.5

measurement techniques. The formation 

of aerosol ammonium nitrate is favored 

by the availability of ammonia, low 

temperatures, and high relative 

humidity. Because ammonium nitrate is 

semivolatile and not stable in higher 

temperatures, nitrate levels are typically 

lower in the summer months and higher 

in the winter months. The resulting 

ammonium nitrate is usually in the submicrometer particle size range. 

Reactions with sea salt and dust lead to 

the formation of nitrates in coarse 

particles. Nitric acid may be dissolved 

in ambient aerosol particles. 

Based on a review of speciated 

monitoring data analyses, it is apparent 

that nitrate concentrations vary 

significantly across the country. For 

example, in some southeastern 

locations, annual average nitrate levels 

are in the range of 6 to 8 percent of total 

PM2.5 mass, whereas nitrate comprises 

40 percent or more of PM2.5 mass in 

certain California locations. Nitrate 

formation is favored by the availability 

of ammonia, low temperatures, and high 

relative humidity. It is also dependent 

upon the relative degree of nearby SO2

emissions because ammonia reacts 

preferentially with SO2 over NOX. NOX

reductions are expected to reduce PM2.5

concentrations in most areas. However, 

it has been suggested that in a limited 

number of areas, NOX control would 

result in increased PM2.5 mass by 

disrupting the ozone cycle and leading 

to increased oxidation of SO2 to form 

sulfate particles, which are heavier than 

nitrate particles. Because of the above 

factors, the proposed rule presumed that 

States must evaluate and implement 

reasonable controls on sources of NOX

in all nonattainment areas, but allowed 

for the State and EPA to develop a 

technical demonstration to reverse this 

presumption. 

b. Final Rule 

The EPA is retaining the proposed 

approach in the final rule.13 Under this 

policy, States are required to address 

NOX as a PM2.5 attainment plan 

precursor and evaluate reasonable 

controls for NOX in PM2.5 attainment 

plans, unless the State and EPA make a 

finding that NOX emissions from 

sources in the State do not significantly 

contribute to PM2.5 concentrations in the 

relevant nonattainment area. This 

presumptive policy is consistent with 

other recent EPA regulations requiring 

NOX reductions which will reduce fine 

particle pollution, such as the Clean Air 

Interstate Rule and a number of rules 

targeting onroad and nonroad engine 

emissions. 

Technical demonstrations that would 

reverse the presumption should be 

developed in advance of the attainment 

demonstration and are discussed in 

section II.A.8 below. 

c. Comments and Responses 

Comment: Most commenters generally 

agreed with the proposed inclusion of 

NOX as a presumptive PM2.5 attainment 

plan precursor. 

Response: The EPA agrees with these 

commenters. 

Comment: Some commenters 

requested guidance on what would 

constitute an acceptable demonstration 

to reverse the presumption that NOX is 

a PM2.5 attainment plan precursor. 

Response: Guidance on technical 

demonstrations to reverse the 

presumptive inclusion of NOX in all 

state implementation plans is discussed 

in section II.A.8 below. 

Comment: One commenter raised 

concerns that the proposed policy for 

NOX would allow a State to find NOX

to be an insignificant contributor to an 

area’s PM2.5 nonattainment problem and 

effectively keep the State from 

controlling the area’s NOX emissions for 

other purposes, such as to address 

interstate transport under section 110 of 

the CAA. Section 110 requires SIPs to 

prohibit emissions within the State that 

would contribute significantly to 

another State’s nonattainment problem 

or interfere with another State’s 

maintenance plan. 

Response: The identification of 

precursors for regulation under this rule 

is for purposes of PM2.5 nonattainment 

and maintenance plans under Part D of 

the CAA. The PM2.5 implementation 

rule does not prevent a State from 

regulating NOX sources under any other 

Federal or State rule, including 

interstate transport rules under Section 

110. 

6. Policy for SO2

[Section II.E.2 of November 1, 2005 

proposed rule (70 FR 65999); sec. 

51.1002 in draft and final regulatory 

text.] 

a. Background 

Sulfur dioxide is emitted mostly from 

the combustion of fossil fuels in boilers 

operated by electric utilities and other 

industry. Less than 20 percent of SO2

emissions nationwide are from other 

sources, mainly other industrial 

processes such as oil refining and pulp 

and paper production. The formation of 

sulfuric acid from the oxidation of SO2

is an important process affecting most 

areas in North America. There are three 

different pathways for this 

transformation. 

First, gaseous SO2 can be oxidized by 

the hydroxyl radical (OH) to create 

sulfuric acid. This gaseous SO2

oxidation reaction occurs slowly and 

only in the daytime. Second, SO2 can 


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dissolve in cloud water (or fog or rain 

water), and there it can be oxidized to 

sulfuric acid by a variety of oxidants, or 

through catalysis by transition metals 

such as manganese or iron. If ammonia 

is present and taken up by the water 

droplet, then ammonium sulfate will 

form as a precipitate in the water 

droplet. After the cloud changes and the 

droplet evaporates, the sulfuric acid or 

ammonium sulfate remains in the 

atmosphere as a particle. This aqueous 

phase production process involving 

oxidants can be very fast; in some cases 

all the available SO2 can be oxidized in 

less than an hour. Third, SO2 can be 

oxidized in reactions in the particlebound water in the aerosol particles 

themselves. This process takes place 

continuously, but only produces 

appreciable sulfate in alkaline (dust, sea 

salt) coarse particles. Oxidation of SO2

has also been observed on the surfaces 

of black carbon and metal oxide 

particles. During the last 20 years, much 

progress has been made in 

understanding the first two major 

pathways, but some important questions 

still remain about the smaller third 

pathway. Models indicate that more 

than half of the sulfuric acid in the 

eastern United States and in the overall 

atmosphere is produced in clouds. 

The sulfuric acid formed from the 

above pathways reacts readily with 

ammonia to form ammonium sulfate, 

(NH4)2SO4. If there is not enough 

ammonia present to fully neutralize the 

produced sulfuric acid (one molecule of 

sulfuric acid requires two molecules of 

ammonia), part of it exists as 

ammonium bisulfate, NH4HSO4 (one 

molecule of sulfuric acid and one 

molecule of ammonia) and the particles 

are more acidic than ammonium sulfate. 

In certain situations (in the absence of 

sufficient ammonia for neutralization), 

sulfate can exist in particles as sulfuric 

acid, H2SO4. Sulfuric acid often exists in 

the plumes of stacks where SO2, SO3, 

and water vapor are in much higher 

concentrations than in the ambient 

atmosphere, but these concentrations 

become quite small as the plume is 

cooled and diluted by mixing. 

Because sulfate is a significant 

contributor (e.g. ranging from 9 percent 

to 40 percent) to PM2.5 concentrations in 

nonattainment areas and to other air 

quality problems in all regions of the 

country, EPA proposed that States 

would be required to address sulfur 

dioxide as a PM2.5 attainment plan 

precursor in all areas. 

b. Final Rule 

The final rule includes the same 

policy for sulfur dioxide as in the 

proposal. States are required to address 

sulfur dioxide as a PM2.5 attainment 

plan precursor and evaluate SO2 for 

possible control measures in all areas. 

Sulfate is an important precursor to 

PM2.5 formation in all areas, and has a 

strong regional impact on PM2.5

concentrations. This policy is consistent 

with past EPA regulations, such as the 

CAIR, the Clean Air Visibility Rule, the 

Acid Rain rules, and the Regional Haze 

rule, that require SO2 reductions to 

address fine particle pollution and 

related air quality problems. 

Under the transportation conformity 

program, sulfur dioxide is not required 

to be addressed in transportation 

conformity determinations before a SIP 

is submitted unless either the state air 

agency or EPA regional office makes a 

finding that on-road emissions of sulfur 

dioxide are significant contributors to 

the area’s PM2.5 problem. Sulfur dioxide 

would be addressed after a PM2.5 SIP is 

submitted if the area’s SIP contains an 

adequate or approved motor vehicle 

emissions budget for sulfur dioxide. 

EPA based this decision on the de 

minimis level of sulfur dioxide 

emissions from on-road vehicles 

currently, and took into consideration 

the fact that sulfur dioxide emissions 

from on-road sources will decline in the 

future due to the implementation of 

requirements for low sulfur gasoline 

(which began in 2004) and for low 

sulfur diesel fuel (beginning in 2006). 

For more information, see the May 6, 

2005 transportation conformity rule on 

PM2.5 precursors at 70 FR 24283. 

c. Comments and Responses 

Comment: Most commenters agreed 

with the proposed policy for SO2. One 

commenter stated, ‘‘* * * requiring 

states to address sulfur dioxide in 

attainment planning in all areas is 

consistent with the science of PM2.5

formation and essential to effective 

implementation of the PM2.5 NAAQS.’’

Another commenter concluded that 

EPA’s proposal ‘‘* * * is justified based 

on the fact that SO2 has been found to 

be a significant contributor to PM2.5

nonattainment in all areas.’’

Response: The EPA agrees with these 

comments. 

Comment: Some commenters believe 

States should be able to make a 

demonstration that SO2 not be 

addressed as an attainment plan 

precursor. The commenters claim that 

the urban increment of sulfate is 

generally small, and SO2 control will 

not matter in many areas. Commenters 

also note that a large percentage of the 

SO2 emission inventory is being 

reduced and will be reduced further 

through existing programs, and that if 

attainment can be demonstrated without 

additional SO2 controls, a State should 

be allowed to make that demonstration 

in its SIP. One commenter stated that 

whether SO2 emissions from a given 

source located in a nonattainment area 

in fact contribute significantly to 

ambient concentrations of sulfate and 

PM2.5 in that nonattainment area likely 

will depend on a range of factors, 

including source type, stack height, 

location, and meteorology. The 

commenter asserted that sulfate forms 

over significant geographic distances 

from the source of the SO2 emissions 

and may not form significant 

concentrations of PM2.5 in the local 

nonattainment area. 

Response: As in the proposal, the 

final rule requires SO2 to be considered 

a PM2.5 attainment plan precursor in all 

cases. Sulfate is a significant fraction of 

PM2.5 mass in all nonattainment areas 

currently, and although large SO2

reductions are projected from electric 

generating units with the 

implementation of the CAIR program, 

sulfate is still projected to be a key 

contributor to PM2.5 concentrations in 

the future. SO2 emissions also lead to 

sulfate formation on both regional and 

local scales. The EPA agrees that the 

extent of the contribution from a 

particular source in a nonattainment 

area to PM2.5 concentrations in the area 

will depend on a number of factors, and 

that at times the reaction of SO2

emissions in the atmosphere to form 

sulfate particles may occur less rapidly 

and extend over a significant distance. 

However, at other times the conversion 

of SO2 to sulfate can occur rapidly and 

local impacts from a particular source 

can be more significant. States are 

required to develop plans to attain as 

expeditiously as practicable through the 

identification of technically and 

economically feasible control measures 

from the full range of source categories 

contributing to PM2.5 nonattainment 

areas. In developing these plans, each 

State will need to consider whether 

controls on local SO2 sources would be 

cost-effective and would be needed to 

attain expeditiously. 

7. Policy for Direct PM 

[Section II.E.2 of November 1, 2005 

proposed rule (70 FR 65999); sec. 

51.1002 in draft and final regulatory 

text.] 

a. Background 

This section addresses inorganic and 

organic forms of directly emitted PM. 

Although these direct emissions are by 

definition not precursors to PM2.5, this 

section is included to provide 

information on the full range of 


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components that commonly make up 

fine particulate matter. 

The main anthropogenic sources of 

inorganic (or crustal) particles are: 

entrainment by vehicular traffic on 

unpaved or paved roads; mechanical 

disturbance of soil by highway, 

commercial, and residential 

construction; and agricultural field 

operations (tilling, planting and 

harvesting). Industrial processes such as 

quarries, minerals processing, and 

agricultural crop processing can also 

emit crustal materials. While much of 

these emissions are coarse PM, the size 

distribution can have a tail of particles 

smaller than PM2.5. 

In general, coarse PM is most 

important close to the source, and not 

generally a significant contributor to 

regional scale PM problems. Even so, 

during certain high wind events, fine 

crustal PM has been shown to be 

transported over very long distances. 

Emission estimates of mechanically 

suspended crustal PM from sources 

within the U.S. are often quite high. 

However, this PM is often released very 

close to the ground, and with the 

exception of windblown dust events, 

thermal or turbulent forces sufficient to 

lift and transport these particles very far 

from their source are not usually 

present. Thus, crustal material is only a 

minor part of PM2.5 annual average 

concentrations. 

Primary carbonaceous particles are 

largely the result of incomplete 

combustion of fossil or biomass fuels. 

This incomplete combustion usually 

results in emissions of both black 

carbon and organic carbon particles. 

High molecular weight organic 

molecules (i.e., molecules with 25 or 

more carbon atoms) are either emitted as 

solid or liquid particles, or as gases that 

rapidly condense into particle form. 

These heavy organic molecules 

sometimes are referred to as volatile 

organic compounds, but because their 

characteristics are most like direct PM 

emissions, they will be considered to be 

primary emissions for the purposes of 

this regulation. Primary organic carbon 

also can be formed by condensation of 

semi-volatile compounds on the surface 

of other particles. 

The main combustion sources 

emitting carbonaceous PM2.5 are certain 

industrial processes, managed burning, 

wildland fires, open burning of waste, 

residential wood combustion, coal and 

oil-burning boilers (utility, commercial 

and industrial), and mobile sources 

(both onroad and nonroad). Certain 

organic particles also come from natural 

sources such as decomposition or 

crushing of plant detritus. Most 

combustion processes emit more organic 

particles than black carbon particles. A 

notable exception to this is diesel 

engines, which typically emit more 

black carbon particles than organic 

carbon. Because photochemistry is 

typically reduced in the cooler winter 

months for much of the country, studies 

indicate that the carbon fraction of PM 

mass in the winter months is likely 

dominated by direct PM emissions as 

opposed to secondarily formed organic 

aerosol. 

Particles from the earth’s crust may 

contain a combination of metallic 

oxides and biogenic organic matter. The 

combustion of surface debris will likely 

entrain some soil. Additionally, 

emissions from many processes and 

from the combustion of fossil fuels 

contain elements that are chemically 

similar to soil. Thus, a portion of the 

emissions from combustion activities 

may be classified as crustal in a 

compositional analysis of ambient 

PM2.5. The proposed rule required that 

States address the direct emissions of 

particulate matter in their PM2.5

attainment plans. During the comment 

period, EPA received several comments 

regarding the definition of what should 

be regulated as ‘‘direct PM2.5.’’

b. Final Rule 

This rule defines direct PM2.5

emissions as ‘‘air pollutant emissions of 

direct fine particulate matter, including 

organic carbon, elemental carbon, direct 

sulfate, direct nitrate, and miscellaneous 

inorganic material (i.e. crustal 

material).’’ Development of attainment 

plans will include direct PM2.5

emissions and specific PM2.5 attainment 

plan precursors. 

c. Comments and Responses 

Comment: A few commenters noted 

that 40 CFR 51.1000 of the proposed 

rule includes definitions for both 

‘‘direct PM2.5 emissions’’ and for ‘‘PM2.5

direct emissions.’’ They recommend 

including just one definition in the final 

rule. 

Response: The EPA acknowledges this 

oversight and has included in the final 

rule a single definition for ‘‘direct PM2.5

emissions.’’ It reads: ‘‘Direct PM2.5

emissions means solid particles emitted 

directly from an air emissions source or 

activity, or gaseous emissions or liquid 

droplets from an air emissions source or 

activity which condense to form 

particulate matter at ambient 

temperatures. Direct PM2.5 emissions 

include elemental carbon, directly 

emitted organic carbon, directly emitted 

sulfate, directly emitted nitrate, and 

other inorganic particles (including but 

not limited to crustal material, metals, 

and sea salt).’’

8. Optional Technical Demonstrations 

for NOX, VOC, and Ammonia 

[Section II.E.2 of November 1, 2005 

proposed rule (70 FR 65999); sec. 

51.1002 in draft and final regulatory 

text.] 

a. Background 

The proposed rule required States to 

evaluate and consider control strategies 

for sources of SO2 and direct PM2.5

emissions in all nonattainment areas. 

For the precursors NOX, VOC, and 

ammonia, the proposed rule included 

presumptive policies that could be 

reversed with an acceptable technical 

demonstration by the State or EPA. (The 

policy in the proposal presumptively 

required that NOX emissions must be 

addressed in all areas, and that VOC and 

ammonia emissions do not need to be 

addressed in all areas.) A number of 

commenters requested additional 

guidance on the criteria for an 

acceptable technical demonstration. 

b. Final Rule 

The final rule retains provisions for 

the State or EPA to conduct a technical 

demonstration to reverse the 

presumptive inclusion of NOX or to 

reverse the presumptive exclusions of 

ammonia and VOC as PM2.5 attainment 

plan precursors. Demonstrations to 

reverse the presumptions for ammonia, 

VOC, or NOX are to be based on the 

weight of evidence of available 

information, and any demonstration by 

the State must be approved by EPA. The 

State must demonstrate that based on 

the sum of available technical and 

scientific information, it would be 

appropriate for a nonattainment area to 

reverse the presumptive approach for a 

particular precursor. The demonstration 

should include information from 

multiple sources, including results of 

speciation data analyses, air quality 

modeling studies, chemical tracer 

studies, emission inventories, or special 

intensive measurement studies to 

evaluate specific atmospheric chemistry 

in an area. 

Because of the variation among 

nonattainment areas in terms of such 

factors as local emissions sources, 

growth patterns, topography, and 

severity of the nonattainment problem, 

EPA believes that it would not be 

appropriate to define a prescriptive set 

of analyses that must be included in all 

PM2.5 precursor technical 

demonstrations. The key criterion is that 

any technical demonstration must fairly 

represent available information. 

In developing the implementation 

plan for a nonattainment area, the State 

should use all relevant information 


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available (from EPA, the State, or other 

sources) to determine the scientifically 

most appropriate approach to regulating 

NOX, ammonia, and VOC emissions in 

the area. As required under any State 

rulemaking process, the State must 

consider and provide a response in the 

record to any information or evidence 

brought forward by commenters during 

the SIP planning, development and 

review process which indicates that the 

presumption for a precursor should be 

reversed. In its review of the 

forthcoming State implementation plan 

submittal, EPA will review the State’s 

proposed precursor policies in light of 

all currently available information. If 

information brought forward by 

commenters or the State in the SIP 

development process shows that the 

presumption in this rule for ammonia, 

VOC or NOX is not technically justified 

for a particular nonattainment area, the 

State must conduct a technical 

demonstration to reverse the 

presumption. In the case of ammonia or 

VOC, the State then would evaluate 

control measures and implement those 

measures that are technically and 

economically feasible and that will 

contribute to expeditious attainment of 

the standards. 

In the section below we suggest 

examples of the types of analyses that 

would be appropriate to use in 

developing such a demonstration. States 

are encouraged to consult with EPA in 

formulating appropriate technical 

demonstrations. 

i. Emission Inventory Information: An 

analysis might show that a precursor 

composes a significant fraction of the 

emissions inventory in an area and 

therefore requires greater consideration. 

Example: Several stationary sources 

emitting particular VOCs known to 

contribute to SOA formation make up a 

significant portion of the area’s VOC 

inventory. This analysis may be useful in 

conjunction with other analyses included in 

a weight of evidence demonstration. 

ii. Speciation Data Information: 

Analysis of data from speciation 

networks might lead a State to 

determine the relative importance of a 

precursor to seasonal or yearly average 

PM concentrations. Individual 

precursors require different approaches. 

Collection of new data could be used to 

understand the impacts of precursors in 

an area. 

Example: Nitrate ion is a large portion of 

winter average PM2.5 mass. Nitrate ion is a 

major portion of PM2.5 mass on the 10 highest 

PM2.5 days in winter in the past 3 years. The 

days with the highest mass concentrations 

might be indicative of inversion conditions 

and/or local impacts, rather than large-scale 

transport processes. For these reasons, nitrate 

should be addressed in the PM2.5 attainment 

plan. 

Example: Ammonium ion data combined 

with total calculated nitrate data indicates 

that reductions in ammonia would reduce 

PM concentrations without a sharp related 

increase in particle acidity. PM speciation 

data shows that PM in the area is generally 

within 10% of calculated neutralization. In 

places for which the needed atmospheric 

data are available to determine whether 

increased acidity is estimated to lead to 

negative environmental effects, analysis 

showing that increased acidity of particles 

and precipitation would likely result from 

ammonia reductions would support the 

presumption against ammonia regulation. 

Analysis showing that ammonia reductions 

would be unlikely to increase the acidity of 

particles and precipitation, and that potential 

reductions in ammonia would significantly 

reduce PM2.5 levels, would support a 

technical demonstration to reverse the 

presumption. 

iii. Modeling Information: Results of 

atmospheric modeling may help a State 

characterize the impacts of potential 

precursor emission reductions on PM2.5

concentrations in an area. 

Example: Modeling of SO2, NOX, and VOC 

emission reductions result in lower sulfate 

and nitrate levels but not lower secondary 

organic aerosol levels. This likely indicates 

that VOC reductions are not as vital as 

reductions of the other precursors. 

Example: Modeled reductions of NOX

show a potential increase in sulfate formation 

through disruption of the ozone cycle. SO2

reductions may be a better choice than NOX

reductions. 

Example: Modeled ammonia reductions 

show a projected reduction in PM2.5

concentrations in selected areas. Although 

dependant on good quality inventory data, 

this type of an analysis would indicate that 

the area is ammonia-limited and that 

ammonia reductions may be beneficial. 

Example: Modeling shows that reductions 

in SO2 in the absence of NOX reductions in 

an area will not result in a significant PM2.5

reduction because more nitrate particles form 

when less SO2 is available for particle 

formation. However, PM2.5 reductions are 

significant when both SO2 and NOX are 

reduced concurrently. This analysis would 

indicate that NOX reductions should be 

included in the PM2.5 attainment plan for the 

area. 

iv. Monitoring, Data Analysis, or 

Other Special Studies: Could include 

monitoring of gases and compounds not 

typically monitored under the PM2.5

speciation network, receptor modeling 

analysis, or special monitoring studies. 

Example: Data from specialized monitoring 

studies can provide insights about 

concentrations of ammonia gas and nitric 

acid in an area and whether the area is 

ammonia-limited or not. Ammonia 

reductions in ammonia-limited areas 

typically yield reductions in PM2.5

concentrations. Specialized monitoring and 

laboratory studies can also assess the relative 

concentrations of organic compounds and 

provide insights into the contributions of 

different anthropogenic and biogenic VOCs 

to secondary organic aerosol formation. 

Example: Receptor modeling and statistical 

analysis PM2.5 speciation monitoring data 

can indicate relative contributions to PM2.5

mass from sources with different chemical 

‘‘fingerprints.’’

Example: Additional analysis of organic 

compounds on filters collected through 

speciation monitoring may reveal insights 

about the relative degree of carbonaceous 

material considered to be from fossil fuel 

combustion as opposed to combustion of 

‘‘modern’’ material (such as wood or 

biomass). 

c. Comments and Responses 

Comment: A number of commenters 

requested that the final rule include 

guidance on acceptable technical 

demonstrations. 

Response: The above section includes 

examples designed to help States 

formulate appropriate demonstrations. 

Prescribing specific technical indicators 

to be used in all areas would ignore the 

scientific uncertainty inherent in the 

relationships between precursor 

emissions and the responses of 

atmospheric concentrations of PM2.5. 

Therefore, States are encouraged to 

review available information and 

consult with EPA in formulating 

technical demonstrations appropriate to 

a particular area. 

B. No Classification System 

1. No Classification System 

a. Background 

Section 172 of subpart 1 contains the 

general requirements for SIPs for all 

nonattainment areas. Section 172(a)(1) 

states that on or after the date of 

designation, the Administrator may 

classify an area for the purpose of 

applying an attainment date or for some 

other purpose. Thus, a classification 

system is allowed under section 172 of 

the CAA, but is not required for the 

purposes of implementing a national 

ambient air quality standard. The CAA 

also states that EPA may consider 

certain factors in making a decision 

concerning classification for areas, such 

as the severity of nonattainment in such 

areas, and the availability and feasibility 

of the pollution control measures that 

may be needed to achieve attainment. In 

the proposed rule, EPA provided two 

implementation approaches for 

classifying PM2.5 nonattainment areas. 

Under the first approach, there would 

be no classification system. Under the 

second approach, a two-tiered 

classification system would apply, with 

areas classified as either ‘‘moderate’’ or 

‘‘serious’’ based on specific criteria. 


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For example, the two classification 

tiers could be based on the severity of 

nonattainment (e.g., serious areas would 

be those with a design value above a 

specific threshold), or on the attainment 

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

would be those with attainment dates 

after April 2010). However, any 

moderate area that needs an attainment 

date longer than 5 years would be 

reclassified as serious. This would 

ensure that areas with a more persistent 

PM2.5 problem are subject to more 

stringent requirements, even if they are 

not one of the areas with the highest 

current design values. For such areas, 

the State would be required to request 

reclassification for an area and ensure 

that the 2008 attainment SIP submission 

for the area includes all measures 

needed to meet the serious area 

requirements. Under the two tiered 

classification approach, we proposed 

that serious PM2.5 nonattainment areas 

would be required to meet the more 

stringent requirements than moderate 

areas that would be defined in this 

rulemaking action (e.g., lower 

thresholds for RACT, fixed percentage 

reduction for RFP, etc.). For serious 

areas, the attainment date would be as 

expeditious as practicable, but no later 

than 10 years after designation, 

depending on the year in which the area 

would be projected to attain considering 

existing control requirements and the 

effect of RACM, RACT and RFP. 

b. Final Rule 

The EPA believes that in the case of 

PM2.5, the no-classification approach is 

the most appropriate approach. An 

advantage of this approach is that it 

provides a relatively simple 

implementation structure for State 

implementation of the PM2.5 standards, 

and avoids the need to define a 

classification system and determine 

classifications for each area. Without 

classifications, this rule still requires 

that that SIPs include all reasonable 

measures that contribute to achieving 

attainment as expeditiously as 

practicable. (Further detail is provided 

in sections D. and F. below.) Because of 

differences in the nature and sources of 

the PM2.5 problem in different parts of 

the country, EPA did not find it 

appropriate to establish a tiered 

classification system with increasing 

control measure requirements. The noclassifications approach provides States 

with greater flexibility to determine the 

control strategies that will be most 

effective and efficient in bringing 

specific areas into attainment as 

expeditiously as practicable. In 

addition, EPA believes that States 

requesting additional time to attain the 

standard beyond the initial 5 year 

attainment date, provided for under 

Subpart I, will need to adopt additional 

or more stringent measures to meet their 

obligations for RACT, RACM and 

attainment that is as expeditious as 

practicable. We believe that this 

addresses the main concerns of those 

commenters who contend that a two 

tiered classification system should be 

implemented. 

c. Comments and Responses 

Comment: The majority of the 

commenters who commented on this 

issue stated that they agreed with EPA’s 

preferred no classification approach. 

These commenters generally stated that 

they believed that EPA has the authority 

not to establish a classification system 

for PM2.5 nonattainment areas. Some 

commenters stated that it would also be 

unreasonable, at this point in the 

process, for EPA to implement a 

classification scheme for the PM2.5

standard. Many commenters support the 

no classification approach because it 

provides for a simple implementation 

structure and/or allows greater 

implementation flexibility to States, 

including flexibility to address specific 

problems related to individual 

nonattainment areas in the most costeffective and expeditious manner, rather 

than through a one size fits all 

approach. Other commenters stated that 

they believe that a classification system 

is not needed because nonattainment 

areas in the Eastern United States are 

likely to attain the standard within a 

timeframe that is consistent with the 

timeframe established under Subpart 1. 

Response: The EPA agrees with these 

commenters. 

Comment: Several commenters 

disagreed with EPA’s preferred 

approach and agreed with the two tiered 

classification approach featuring a 

‘‘moderate’’ and a ‘‘serious’’ area 

classification. These commenters also 

stated that the threat of reclassification 

or ‘‘bump up’’ to a higher classification 

was a powerful incentive for areas to 

attain as expeditiously as practicable. 

Commenters also indicated that areas 

needing more time to attain the standard 

should be required to implement more 

stringent measures or mandatory 

measures. 

Response: The EPA agrees that areas 

with more severe nonattainment 

problems will need to implement more 

stringent measures to attain. However, 

EPA does not believe that a 

classification system is needed to ensure 

that such measures are implemented. 

The EPA believes that on balance the no 

classification approach is the most 

appropriate classification option for the 

implementation of the PM2.5 standard 

because of the difference in contributing 

sources from area to area. 

Comment: Several commenters stated 

that under EPA’s preferred approach, 

each State would be required to submit 

an attainment demonstration proposing 

an attainment date that is ‘‘as 

expeditious as practicable’’ for each 

area. They asserted that to allow States 

to propose their own attainment dates 

would invite delay in the process of 

cleaning up fine particle pollution. 

These commenters further stated that 

States would have no incentive to set an 

attainment date earlier than the outer 

limit set by EPA, even if it would be 

practicable to attain the NAAQS sooner. 

Response: Section 172 of the CAA 

requires SIPs to demonstrate attainment 

as expeditiously as practicable 

regardless of whether there is a 

classification system, and under this 

rule states must justify that their 

attainment date is as expeditious as 

practicable considering all reasonable 

measures. As noted above, EPA believes 

that States requesting additional time to 

attain the standard beyond the initial 5 

year attainment date will need to adopt 

additional or more stringent measures to 

meet their obligations for RACT and 

RACM and to attain as expeditiously as 

practicable. More details on the 

analytical process required for an 

attainment demonstration is included in 

section II.F. 

Comment: Several commenters stated 

that the CAA requires regulation of the 

PM2.5 standard under Subpart 4 of Part 

D. These commenters state that EPA 

takes the position that it must regulate 

PM2.5 under Subpart 1 of the CAA, 

which applies to nonattainment areas in 

general. The commenters state that 

section 7513, in Subpart 4 of Part D of 

the CAA, contains specific provisions 

for classification of particulate matter 

nonattainment areas, and that EPA must 

therefore regulate PM2.5 under Subpart 

4, which requires a moderate and 

serious area classification system. Other 

commenters argued that implementation 

of the PM2.5 standard must proceed 

under Subpart 1 of Part D of Title I of 

the CAA and cannot be governed by 

Subpart 4 of Part D, which addresses the 

implementation of the PM10 standard 

which is a different pollutant than 

PM2.5. 

Response: The EPA finds that the 

PM2.5 standard should be implemented 

under subpart I of the CAA, which is the 

general provision of the CAA related to 

NAAQS implementation. Part D of Title 

I of the CAA sets forth the requirements 

for SIPs needed to attain the national 

ambient air quality standards. Part D 

also includes a general provision under 


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Subpart I which applies to all NAAQS 

for which a specific subpart does not 

exist. Because the PM2.5 standards were 

not established until 1997, the plan 

provisions found in section 172 of 

subpart 1 pertaining to plans for 

nonattainment areas apply. The EPA 

further agrees with comments stating 

that subpart 4 on its face applies only 

to the PM10 standard. In general, the 

emphasis in subpart 4 on reducing PM10

concentrations from certain sources of 

direct PM2.5 emissions can be somewhat 

effective in certain PM2.5 nonattainment 

areas but not in all. Contributions to 

PM2.5 concentrations are typically from 

a complex mix of sources of primary 

emissions and sources of precursor 

emissions which form particles through 

reactions in the atmosphere. PM2.5 also 

differs from PM10 in terms of 

atmospheric dispersion characteristics, 

chemical composition, and contribution 

from regional transport. 

2. Rural Transport Classification Option 

a. Background 

The 8-hour ozone implementation 

program includes a ‘‘rural transport 

classification’’ for subpart 1 

nonattainment areas. In the proposal for 

this rule we discussed whether an area 

classification of this type would be 

appropriate for the PM2.5

implementation program in light of the 

fact that no currently designated PM2.5

nonattainment area met the criteria 

similar to those that apply to rural 

transport areas under the ozone 

implementation program. 

As addressed in the proposal, a PM2.5

nonattainment area would qualify for 

the ‘‘rural transport’’ classification if it 

met criteria similar to those specified for 

rural transport areas for the 1-hour 

ozone standard under section 182(h). 

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

areas as those areas that do not include, 

and are not adjacent to, any part of a 

Metropolitan Statistical Area (MSA) or, 

where one exists, a Consolidated 

Metropolitan Statistical Area (CMSA). 

Section 182(h) further limits the 

category to those areas whose own 

emissions do not make a significant 

contribution to pollutant concentrations 

in those areas, or in other areas. 

As discussed in the preamble to the 

proposed rule, potential criteria for a 

State to identify an area for a rural 

transport classification under the PM2.5

program could be similar to the criteria 

used in the ozone implementation 

program: A State with a PM2.5 ‘‘rural 

transport’’ area would need to (1) 

demonstrate that the area meets the 

above criteria, (2) demonstrate using 

EPA approved attainment modeling that 

the nonattainment problem in the area 

is due to the ‘‘overwhelming transport’’

of emissions from outside the area, and 

(3) demonstrate that sources of PM2.5

and its precursor emissions within the 

boundaries of the area do not contribute 

significantly to PM2.5 concentrations 

that are measured in the area or in other 

areas. 

An area which qualifies for the ‘‘rural 

transport’’ classification would only be 

required to adopt local control measures 

sufficient to demonstrate that the area 

would attain the standard by its 

attainment date ‘‘but for’’ the 

overwhelming transport of emissions 

emanating from upwind States. RFP 

requirements under subpart 1 would 

still apply to these areas. As with other 

nonattainment areas, rural transport 

nonattainment areas would be subject to 

NSR, transportation conformity, and 

general conformity requirements. In the 

proposal we solicited comments on 

whether it would be appropriate to 

establish less burdensome NSR 

requirements in the event that a 

classification for rural transport areas is 

adopted in the final rule. The EPA 

requested comment on whether this 

type of classification option is needed at 

all under the PM2.5 implementation 

program. 

b. Final Rule 

The final rule does not include a rural 

transport classification. This type of 

classification was included in the CAA 

for purposes of implementing the ozone 

standards because of the phenomenon 

of the formation of high ozone levels far 

downwind in very rural locations, 

including on high elevation mountain 

peaks. In reviewing the currently 

designated PM2.5 nonattainment areas, it 

appears that all areas but one are within 

or adjacent to a metropolitan area (i.e. 

core-based statistical area or 

consolidated statistical area), and thus 

would not meet the criteria discussed 

above. Although PM2.5 concentrations 

are greatly affected by long-range 

transport of air pollution, it appears that 

nonattainment areas typically are 

located in urban areas and include 

significant local pollutant sources. 

c. Comments and Responses 

Comment: Several commenters stated 

that they do not support the adoption of 

a rural transport classification because it 

is not needed. Commenters stated that 

given the criteria for the rural transport 

classification, which greatly limits its 

applicability, few if any PM2.5

nonattainment areas can qualify for the 

option. One commenter stated that EPA 

modeled the rural transport 

classification after the ‘‘rural transport 

areas’’ provision contained in subpart 2 

of the CAA, which applies only to the 

ozone standard. The commenter further 

states that neither Subpart 1 nor 4 

contain any statutory authority for such 

a classification. 

Response: The EPA believes that it 

has sufficient statutory authority under 

the CAA to establish a rural transport 

classification, but we do not believe that 

such a classification is needed. 

Comment: One commenter generally 

supported the rural transport concept 

and the proposed associated 

requirements, with the addition that 

data analysis be included as appropriate 

in the required technical 

demonstrations in addition to modeling. 

While no PM2.5 area currently meets the 

requirements for the rural transport 

classification option, several 

commenters recommended that it be 

maintained for potential cases in which 

the PM2.5 standards are made more 

stringent, or measured air quality in 

areas change in such a way that areas 

would qualify for the rural transport 

classification at a later date. 

Response: The EPA does not agree 

that a rural transport classification is 

needed. The EPA will re-evaluate the 

need for such a classification as 

appropriate. 

C. Due Dates and Basic Requirements 

for Attainment Demonstrations 

a. Background 

Part D of Title I of the CAA sets forth 

the requirements for SIPs needed to 

attain the national ambient air quality 

standards. Part D includes a general 

subpart 1 which applies to all NAAQS 

for which a specific subpart does not 

exist. The 1990 CAA Amendments do 

not include any subpart for PM2.5

because the PM2.5 standards were not 

yet established. The EPA has 

determined that for PM2.5, the 

nonattainment area plan provisions 

found in section 172 of subpart 1 apply. 

Section 172(b) of the CAA requires 

that at the time the Agency promulgates 

nonattainment area designations, the 

EPA must also establish a schedule for 

States to submit SIPs meeting the 

applicable requirements of section 

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

CAA. Nonattainment area designations 

were finalized in December 2004, and a 

supplemental notice was issued in April 

2005. Consistent with section 172(b) of 

the CAA, 40 CFR 51.1002 of the 

proposed rule requires the State to 

submit its attainment demonstration 

and SIP revision within 3 years, or by 

April 2008. 

Section 51.1006 of the proposed rule 

addresses the situation in which an area 


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20600 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

14More information on the Clean Air Interstate 

Rule (CAIR) is available at: http://www.epa.gov/ 

cair. 

is initially designated as attainment/ 

unclassifiable but is later designated as 

nonattainment based on air quality data 

after the 2001–2003 period. Under such 

circumstances, the SIP submittal date 

would be 3 years from the effective date 

of the redesignation, and the attainment 

date would be as expeditiously as 

practicable but no later than 5 years 

from the effective date of the 

redesignation. 

The section 172(c) requirements that 

States are to address under section 

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

contingency measures, emission 

inventory requirements, and NSR) are 

discussed in later sections of this 

document. Section 110(a)(2) of the CAA 

requires all States to develop and 

maintain a solid air quality management 

infrastructure, including enforceable 

emission limitations, an ambient 

monitoring program, an enforcement 

program, air quality modeling, and 

adequate personnel, resources, and legal 

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

requires State plans to prohibit 

emissions from within the State which 

contribute significantly to 

nonattainment or maintenance areas in 

any other State, or which interfere with 

programs under part C to prevent 

significant deterioration of air quality or 

to achieve reasonable progress toward 

the national visibility goal for Federal 

class I areas (national parks and 

wilderness areas). In order to assist 

States in addressing their obligations 

regarding regionally transported 

pollution, EPA has finalized the CAIR to 

reduce SO2 and nitrogen oxide 

emissions from large electric generating 

units.14

To date, few states have submitted a 

SIP revision addressing the section 

110(a)(2) requirements for the purposes 

of implementing the PM2.5 standards. 

The EPA recognizes that this situation is 

due in part to the fact that there were 

a series of legal challenges to the PM 

standards which were not resolved until 

March 2002, at which time the 

standards and EPA’s decision process 

were upheld (see section I.B. for further 

discussion of past legal challenges to the 

standards). To address the States’

continuing obligation to address the 

requirements of section 110(a), 40 CFR 

51.1002 of the proposed rule also 

required each State to address the 

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

the CAA as part of the SIP revision 

adopting its attainment plan, if it has 

not already done so. On March 10, 2005, 

EPA entered into a consent decree with 

Environmental Defense and American 

Lung Association concerning EPA’s 

failure to find that States failed to 

submit SIPs to address the section 

110(a)(2) requirements. As a part of that 

consent decree, by no later than October 

8, 2008, EPA is required to publish a 

notice in the Federal Register related to 

its determinations of whether each State 

has submitted SIPs for PM2.5 that meet 

the requirements as stated under section 

110(a)(2) of the CAA. 

b. Final Rule 

The final rule maintains the 

regulatory approach described above. 

c. Comments and Responses 

There were no comments on this 

portion of the proposal. 

D. Attainment Dates 

1. Background on Statutory 

Requirements 

Establishing attainment dates. Section 

172(a)(2) states that an area’s attainment 

date ‘‘shall be the date by which 

attainment can be achieved as 

expeditiously as practicable, but no later 

than 5 years from the date such area was 

designated nonattainment * * *, except 

that the Administrator may extend the 

attainment date to the extent the 

Administrator determines appropriate, 

for a period no greater than 10 years 

from the date of designation as 

nonattainment considering the severity 

of nonattainment and the availability 

and feasibility of pollution control 

measures.’’

Since PM2.5 designations have an 

effective date of April 5, 2005, the initial 

5-year attainment date for PM2.5 areas 

would be no later than April 5, 2010. 

For an area with an attainment date of 

April 5, 2010, EPA would determine 

whether it had attained the standard by 

evaluating air quality data from the 

three previous calendar years (i.e. 2007, 

2008, and 2009). 

For any areas that are granted the full 

5 year attainment date extension under 

section 172, the attainment date would 

be no later than April 5, 2015. For such 

areas, EPA would determine whether 

they have attained the standard by 

evaluating air quality data from 2012, 

2013, and 2014. Section 51.1004 of the 

proposed regulations addressed the 

attainment date requirement. Section 

51.1004(b) provided that in their 

attainment demonstrations, States 

would propose an attainment date 

representing attainment as 

expeditiously as practicable based upon 

implementation of existing Federal and 

State measures, and all new reasonable 

local and intrastate measures. The EPA 

would approve a particular attainment 

date based on its review of the 

attainment demonstration. 

Determining Whether an Area Has 

Attained. The EPA has the 

responsibility for determining whether a 

nonattainment area has attained the 

standard by its applicable attainment 

date. Section 179(c)(1) of the Act 

requires EPA to make determinations of 

attainment no later than 6 months 

following the attainment date for the 

area. Under section 179(c)(2), EPA must 

publish a notice in the Federal Register 

identifying those areas which failed to 

attain by the applicable attainment date. 

The statute further provides that EPA 

may revise or supplement its 

determination of attainment for the 

affected areas based upon more 

complete information or analysis 

concerning the air quality for the area as 

of the area’s attainment date. 

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

that the attainment determination for an 

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

quality data as of the attainment date.’’

The EPA will make the determination of 

whether an area’s air quality is meeting 

the PM2.5 NAAQS by the applicable 

attainment date primarily based upon 

data gathered from the air quality 

monitoring sites which have been 

entered into EPA’s Air Quality System 

(AQS) database. No special or additional 

SIP submittal will be required from the 

State for this determination. 

A PM2.5 nonattainment area’s air 

quality status is determined in 

accordance with appendix N of 40 CFR 

part 50. To show attainment of the 24- 

hour and annual standards for PM2.5, the 

most recent three consecutive years of 

data prior to the area’s attainment date 

must show that PM2.5 concentrations 

over a three-year period are at or below 

the levels of the standards. A complete 

year of air quality data, as described in 

part 50, Appendix N, comprises of all 4 

calendar quarters with each quarter 

containing data from at least 75 percent 

of the scheduled sampling days. The 

annual standard for PM2.5 is attained 

when the 3-year average annual mean 

concentration is less than or equal to 

15.05 μg/m3. The 24-hour standard for 

PM2.5 is met when the average of 98th 

percentile values for three consecutive 

calendar years at each monitoring site is 

less than or equal to 65.5 μg/m3. 

The EPA will begin processing and 

analyzing data related to the attainment 

of PM2.5 areas immediately after the 

applicable attainment date for the 

affected areas. Current EPA policy, 

under 40 CFR part 58, sets the deadline 

for submittal of air quality data into the 

AQS database for no later than 90 days 

after the end of the calendar year. 


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While EPA may determine that an 

area’s air quality data indicates that an 

area may be meeting the PM2.5 NAAQS 

for a specified period of time, this does 

not eliminate the State’s responsibility 

under the Act to adopt and implement 

an approvable SIP. If EPA determines 

that an area has attained the standard as 

of its attainment date, the area will 

remain classified as nonattainment until 

the State has requested, and EPA has 

approved, redesignation to attainment 

for the area. 

In order for an area to be redesignated 

as attainment, the State must comply 

with the five requirements listed under 

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

section requires that: 

—EPA has determined that the area has 

met the PM2.5 NAAQS; 

—EPA has fully approved the state’s 

implementation plan; 

—The improvement in air quality is due 

to permanent and enforceable 

reductions in emissions; 

—EPA has fully approved a 

maintenance plan for the area; 

—The State(s) containing the area have 

met all applicable requirements under 

section 110 and part D. 

2. Establishing Attainment Dates 

a. Background 

The EPA proposed rule language on 

attainment dates that closely tracks the 

statutory language. In the preamble, 

EPA noted that the attainment date that 

is as expeditious as practicable should 

reflect the projected impact of existing 

national and State programs (e.g. partial 

implementation of the CAIR rule, final 

Acid Rain Program, motor vehicle tier II 

standards and heavy-duty diesel engine 

standards, NOX SIP call, State 

legislation such as Clean Smokestacks 

bill in North Carolina) as well as 

additional reasonable measures required 

for the PM2.5 nonattainment SIP. 

With respect to its authority to extend 

an area’s date beyond 5 years, EPA 

stated in the preamble that the State can 

submit a SIP demonstrating that it is 

impracticable to attain by the 5-year 

attainment date: ‘‘As stated previously, 

under section 172(a)(2)(A), EPA may 

grant an area an extension of the initial 

attainment date for a period of one to 5 

years. States that request an extension of 

the attainment date under this provision 

of the CAA must submit a SIP by April 

5, 2008 that includes, among other 

things, an attainment demonstration 

showing that attainment within 5 years 

of the designation date is impracticable. 

It must also show that the area will 

attain the standard by an alternative 

date that is as expeditious as 

practicable, but in no case later than 10 

years after the designation date for the 

area (i.e. by April 5, 2015 for an area 

with an effective designation date of 

April 5, 2005). An appropriate extension 

in some cases may be only 1 or 2 

years—a 5-year extension is not 

automatic upon request. 

The attainment demonstration must 

provide sufficient information to show 

that attainment by the initial attainment 

date is impracticable due the severity of 

the nonattainment problem in the area, 

the lack of available control measures, 

and any other pertinent information 

related to these statutory criteria. States 

requesting an extension of the 

attainment date must also demonstrate 

that all local control measures that are 

reasonably available and technically 

feasible for the area are currently being 

implemented to bring about expeditious 

attainment of the standard by the 

alternative attainment date for the area. 

The State’s plan will need to project the 

emissions reductions expected due to 

Federally enforceable national 

standards, State regulations, and local 

measures such as RACT and RACM, and 

then conduct modeling to project the 

level of air quality improvement in 

accordance with EPA’s modeling 

guidance. The EPA will not grant an 

extension of the attainment date beyond 

the initial 5 years required by section 

172(a)(2)(A) for an area if the State has 

not considered the implementation of 

all RACM and RACT local control 

measures for the area (see section III.I 

for a more detailed discussion of RACT 

and RACM). The EPA also will examine 

whether the State has adequately 

considered measures to address 

intrastate transport of pollution from 

sources within its jurisdiction. In 

attainment planning, States have the 

obligation and authority to address the 

transport of pollution from one area of 

the State to another. Any decision made 

by EPA to extend the attainment date for 

an area beyond its original attainment 

date will be based on facts specific to 

the nonattainment area at issue and will 

only be made after providing notice in 

the Federal Register and an opportunity 

for the public to comment.’’

b. Final Rule 

We are adopting the approach 

described above from the proposed rule. 

We also wish to clarify language that 

was in the preamble to the proposed 

rule regarding the criteria for an 

extension. The preamble stated that 

attainment date extensions would be 

based on the two statutory extension 

criteria—‘‘the severity of nonattainment, 

and the availability and feasibility of 

pollution control measures,’’—as well as 

‘‘other pertinent information which 

shows that additional time is required 

for the area to attain the standard.’’ The 

CAA does not include this third clause 

and the regulatory text for the final rule 

does not include this third clause. The 

intent of this language in the preamble 

to the proposal was that States could 

include ‘‘other pertinent information’’

related to the two statutory criteria. 

c. Comments and Responses 

Comment: Some commenters 

expressed concern that EPA’s preamble 

language appeared to assert a new basis 

for granting extensions not provided by 

the statute. They said EPA has authority 

to extend the attainment date under 

Section 7502(a)(2) based solely on 

consideration of two enumerated 

factors: the severity of nonattainment, 

and the availability and feasibility of 

control measures. 

Response: The EPA agrees that 

extensions must be based upon the two 

factors in the statute, which are quite 

broad. A clarification of the preamble 

phrase cited by the commenter is 

provided above. The phrase in 

question—‘‘any other pertinent 

information which shows that 

additional time is required for the area 

to attain the standard’’—refers to 

information that relates to the two 

statutory factors. 

Comment: One commenter stated that 

an area should qualify for an extension 

only if the area will implement stringent 

local controls, yet still cannot 

practicably attain by the five-year 

deadline. The commenter stated that at 

a minimum, EPA must require states to 

adopt RACM for both mobile and 

stationary sources before granting an 

extension. Another commenter said that 

given the difficulty many areas will 

have in meeting the five-year deadline 

for attainment of the PM2.5 NAAQS (and 

especially in light of the fact that the 

deadline occurs only 2 years after states 

are to submit attainment SIPs), EPA 

should provide maximum flexibility in 

allowing extensions to the full 10-year 

period. 

Response: The EPA agrees that 

extensions should be granted only if an 

area cannot practicably attain within 5 

years despite application of all 

reasonable measures, including RACM. 

Although some measures can be 

implemented within a year or two, 

many measures require a longer period 

for installation of controls or full 

program implementation. In light of the 

limited time period between the SIP 

submittal deadline and the 5-year date, 

EPA believes that a significant number 

of areas may warrant extensions ranging 

from one to 5 years, with the length of 


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15See section 51.1005 of the proposed regulation. 

extension depending on the factors 

described above. 

Comment: One commenter advocated 

that EPA include in this final rule a 

determination of those areas for which 

attainment within 5 years is 

impracticable. Another commenter 

advocated that EPA establish guidance 

based on EPA national modeling 

conducted last year to establish 2015 as 

constituting expeditious attainment for 

certain areas. 

Response: The EPA is not determining 

in this rulemaking the areas that should 

receive extensions or should receive the 

maximum 10-year attainment date, for 

several reasons. First, EPA did not 

propose such an approach. Therefore, 

the public has not had the opportunity 

to comment on the approach or on the 

technical information on which EPA 

would make such judgments. 

Second, EPA believes that modeling 

being conducted by the states, with 

updated inventories and finer grids, will 

generally provide a more reliable basis 

for projecting future PM2.5 base case 

levels than national modeling 

conducted by EPA with older 

information. State modeling of future 

year PM2.5 levels that has been 

conducted to date indicates that some 

areas will start closer or farther from the 

standard than EPA had projected. 

Third, the SIP process provides a 

forum for states to identify reasonable 

controls and conduct analyses to 

determine the appropriate attainment 

date for an area. This process provides 

for input from expert stakeholders, the 

general public, other states which may 

share the same multi-State 

nonattainment area, and EPA on 

decisions regarding controls and 

attainment dates. At this time, EPA does 

not have the benefit of this process to 

inform a judgment as to when areas can 

practicably attain. States are responsible 

for developing RACM demonstrations; 

at this time, EPA lacks the information 

to conduct a credible RACM 

demonstration for all PM2.5

nonattainment areas. 

Fourth, no State commenter 

advocated that EPA attempt to make 

these judgments on attainment dates in 

advance of the State SIP process. The 

statute gives the states the lead in 

developing State implementation plans. 

Comment: Another commenter 

recommends that an area should receive 

an attainment date extension when 

collectively the following conditions 

have been met: 

• It is proven through modeling that 

the region is adversely effected by 

transport of PM2.5 emissions from up 

wind sources beyond that State’s 

control; 

• A State has submitted and 

committed to implementing all Federal 

PM2.5 emission reduction requirements 

in a timely manner; and, 

• The extension concept is approved 

through the State air agency or through 

the MPO Interagency Consultation 

Process at the MPO level if applicable. 

Response: This commenter advocates 

for attainment date extensions without 

any consideration of reasonable local 

measures. As stated above, EPA believes 

that extensions should be granted only 

if an area cannot practicably attain 

within 5 years despite application of all 

reasonable measures, including RACM. 

Although some measures can be 

implemented within a year or two, 

many measures may require a longer 

period for installation of controls or full 

program implementation. In light of the 

limited time period between the SIP 

submittal deadline and the 5-year date, 

EPA believes that a significant number 

of areas may warrant extensions ranging 

from one to 5 years, with the length of 

extension depending on the factors 

described above. 

3. Attainment Dates: 1-Year Extensions 

a. Background 

Subpart 1 provides for States to 

request two 1-year extensions of the 

attainment date for a nonattainment area 

under limited circumstances. Section 

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

EPA initially may extend an area’s 

attainment date for 1 year, provided that 

the State has complied with all the 

requirements and commitments 

pertaining to the area in the applicable 

implementation plan, and provided that 

the area has had no more than a 

minimal number of ‘‘exceedances’’ of 

the relevant standard in the preceding 

year. Because the PM2.5 standards do not 

have exceedance-based forms but are 

based on 3-year averaging periods, we 

interpret the air quality test in 40 CFR 

51.1005 to mean that the area would 

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

of the 3 years that are to be evaluated 

to determine attainment.15 By this we 

mean that for the third year, the air 

quality for all monitors in the area as 

analyzed in accordance with Appendix 

N to 40 CFR part 50 each must have an 

annual average of 15.0 μg/m3 or less, 

and a 98th percentile of 24-hour 

monitoring values of 65 μg/m3 or less in 

order to qualify for a 1-year extension. 

(Given the rounding provisions 

specified in 40 CFR part 50, Appendix 

N, these criteria would be satisfied if the 

concentrations before final rounding are 

less than an annual average of 15.05 μg/ 

m3 and a 24-hour value of 65.5 μg/m3.) 

For example, suppose an area in 

violation of the annual standard has an 

attainment date of April 2010, and its 

annual average for 2007 was 15.8 and 

for 2008 was 15.6. If the annual average 

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

year average would be 15.4, and it 

would not have attained the standard. 

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

allowing the area to submit a request to 

EPA for a 1-year extension of its 

attainment date to 2011 (provided the 

State has also complied with its 

requirements and commitments) since 

the 14.9 ambient air quality value in the 

third year (2009) met the test of being 

at or below 15.0. Section 51.1005(a) of 

the proposed regulation addresses the 

initial 1-year attainment date extension. 

The air quality measured in 2010 in 

conjunction with prior data will 

determine if the area attains the 

standard, qualifies for a second 1-year 

extension, or does not attain the 

standard. For example, if the area’s 

annual average for 2010 is 14.3, then its 

3-year average for 2008–2010 would be 

14.9 and it would have met the annual 

standard. 

If the area’s annual average for 2010 

is 14.9, however, then its 3-year average 

for 2008–2010 would be 15.1. In this 

situation the area would not have 

attained the standard, but the area 

would meet the air quality test for the 

second of the 1-year extensions allowed 

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

2010 annual average was at or below 

15.0. Section 51.1005(b) of the proposed 

rule addresses the second 1-year 

attainment date extension. After 

obtaining a second 1-year extension, the 

State would evaluate whether the air 

quality values in 2011, in conjunction 

with 2009 and 2010 data, bring the area 

into attainment. 

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

States must submit additional 

information to EPA to demonstrate that 

they have complied with applicable 

requirements, commitments, and 

milestones in the implementation plan. 

This information is needed in order for 

EPA to make a decision on whether to 

grant a 1-year attainment date extension. 

The EPA will not be inclined to grant 

a 1-year attainment date extension to an 

area unless the State can demonstrate 

that it has met important requirements 

contained in the area’s implementation 

plan. States must demonstrate that: (1) 

Control measures have been submitted 

in the form of a SIP revision and 

substantially implemented to satisfy the 

requirements of RACT and RACM for 

the area, (2) the area has made 

emissions reductions progress that 


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16Memorandum of December 14, 2004, from 

Steve Page, Director, EPA Office of Air Quality 

Planning and Standards to EPA Air Division 

Directors, ‘‘Clean Data Policy for the Fine Particle 

National Ambient Air Quality Standards.’’ This 

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

pmdesignations/guidance.htm. 

represents reasonable further progress 

(RFP) toward attainment of the NAAQS, 

and (3) trends related to recent air 

quality data for the area indicate that the 

area is in fact making progress toward 

attainment of the standard. Any 

decision made by EPA to extend the 

attainment date for an area will be based 

on facts specific to the nonattainment 

area at issue, and will only be made 

after providing notice in the Federal 

Register and an opportunity for the 

public to comment. 

If an area fails to attain the standard 

by the attainment date, EPA would 

publish a finding to this effect in 

accordance with section 179 of the 

CAA. The area then would be required, 

within 1 year of publication of this 

finding, to develop a revised SIP 

containing additional emission 

reduction measures needed to attain the 

standard as expeditiously as practicable. 

b. Final Rule 

The final rule retains the proposed 

criteria for states to receive a 1-year 

attainment date extension for a 

nonattainment area. 

c. Comments and Responses 

Comment: A number of commenters 

supported EPA’s ability to grant a 1-year 

attainment date extension if monitoring 

data indicate that the PM2.5 levels 

during the most recent year were below 

15.05 μg/m3. 

Response: The EPA agrees with these 

comments. 

Comment: Some commenters 

recommended that a 1-year extension be 

provided if the trend line of the area’s 

emissions levels or air quality data 

projects attainment in the extension 

year. 

Response: The EPA believes that 

1-year extensions should be based on air 

quality data, which can be assessed 

quickly after the end of the year. Basing 

such extensions solely on emissions 

trends would be impractical due to the 

longer turnaround time needed to 

evaluate emissions changes affecting a 

monitor. 

Comment: One commenter believes 

the current requirement is overly 

stringent and inconsistent with the 

statute. The commenter believes that 

EPA’s proposed approach incorrectly 

defines the statutory language referring 

to a ‘‘minimal number of exceedances’’

of the standard in the previous year as 

‘‘zero’’ exceedances. Alternatively, the 

commenter suggests EPA could 

withdraw this provision and provide 

more detailed guidance giving the 

Agency and states some flexibility to 

demonstrate that exceedances were 

minimal in a given case since nothing 

in the statute requires the rigid 

definition of minimal that EPA 

proposes. 

Response: The EPA believes the 

policy in the final rule is a reasonable 

application of the statutory language to 

a standard not based on exceedances. 

The EPA does not believe it would be 

appropriate to provide a 1-year 

extension to an area with air quality 

data showing it violating the standard 

over the 3 years prior to the attainment 

year. 

4. Achieving ‘‘Clean Data’’

a. Background 

Section III.D of the preamble to the 

proposed rule describes the incentives 

for attaining the standards prior to April 

2008, when SIP submittals are due, or 

prior to an area’s approved attainment 

date. Areas with design values just over 

the level of the standard may be able to 

achieve reductions in the local area or 

in the State so that, when their effect is 

considered in combination with 

reductions achieved under national 

programs, they may be sufficient to 

attain the standards before SIPs are due 

in 2008. For example, if monitoring in 

a nonattainment area shows that the air 

quality for 2004–2006 meets the 

standards, then the area may be subject 

to reduced regulatory requirements and 

be redesignated as ‘‘attainment.’’

The EPA issued a ‘‘Clean Data’’ policy 

memorandum in December 2004 

describing possible reduced regulatory 

requirements for areas that attain the 

standards, but have not yet been 

redesignated as attainment.16

b. Final Rule 

In the proposed rule, EPA indicated 

that it had issued this ‘‘Clean Data’’

policy to apply for purposes of the PM2.5

standards. In this action EPA is 

finalizing as a rule the statutory 

interpretation that is embodied in the 

policy. Section 51.1004(c). The text of 

the final rule encapsulates the statutory 

interpretation set forth in the policy. 

Determinations as to whether individual 

areas have attained the PM2.5 standard 

and thus qualify for application of the 

new clean data rule will be made in the 

context of rulemakings for those 

individual areas. 

The preamble to the proposed rule 

mistakenly stated that if an area 

achieved ‘‘clean data,’’ it would be 

‘‘relieved of the requirements to 

implement the nonattainment NSR 

program otherwise required for 

nonattainment areas, and instead would 

implement the PSD program.’’ The EPA 

wishes to clarify that the Clean Data 

Policy does not provide for suspension 

of the requirements for NSR nor for 

RACT. The provisions at issue in the 

Clean Data Policy include the 

requirements for an attainment 

demonstration and other related 

requirements, reasonable further 

progress, and contingency measures. 

c. Comments and Responses 

Comment: One commenter stated that 

EPA has absolutely no authority to 

waive NSR or any of the CAA’s other 

requirements for nonattainment areas 

merely because a nonattainment area 

has 3 years of clean data, nor does EPA 

have authority to waive mandatory 

requirements of the CAA such as NSR, 

RACT, and RFP merely because EPA or 

the State claims they are not needed for 

attainment. The commenter believes 

that the only way that a nonattainment 

area can cease implementing controls 

and requirements mandated for such 

areas is to seek and obtain redesignation 

to attainment, and demonstrate in the 

process that the controls and 

requirements are not needed for 

maintenance of standards. The CAA has 

explicit procedures and prerequisites for 

redesignating nonattainment areas to 

attainment (CAA sections 107(d)(3)(E) 

and 175A). The EPA’s ‘‘clean data’’

proposal would illegally circumvent 

those requirements. 

Response: The Clean Data policy does 

not waive requirements for NSR nor for 

RACT. However, EPA believes that 

‘‘clean data’’ policies for the ozone and 

fine particle programs are based on a 

reasonable interpretation of the CAA. 

The Clean Data Policy is the subject of 

two EPA memoranda setting forth our 

interpretation of the provisions of the 

Act as they apply to areas that have 

attained the relevant NAAQS. The EPA 

also finalized the statutory 

interpretation set forth in the policy in 

a final rule, 40 CFR 51.918, as part of 

its Final Rule to Implement the 8-Hour 

Ozone National Ambient Air Quality 

Standard—Phase 2 (Phase 2 Final Rule). 

See discussion in the preamble to the 

rule at 70 FR 71645–71646 (November 

29, 2005). The legal rationale for the 

Clean Data policy is explained in our 

Phase 2 Final Rule, in our December 14, 

2004 memorandum from Stephen D. 

Page entitled ‘‘Clean Data Policy for the 

Fine Particle National Ambient Air 

Quality Standards’’ (Page Memo), and in 

our May 10, 1995 memorandum from 

John S. Seitz, entitled ‘‘Reasonable 

Further Progress, Attainment 


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Demonstration, and Related 

Requirements for Ozone Nonattainment 

Areas Meeting the Ozone National 

Ambient Air Quality Standard’’ (Seitz 

memo). We adopt and reiterate those 

explications here. 

The EPA has also explained its 

rationale for applying the Clean Data 

policy in rulemaking actions associated 

with nonattainment areas for the PM10

and 1-hour ozone standards. For 

rulemaking actions applying the Clean 

Data policy to the PM10 standards, see 

71 FR 27440 (May 11, 2006) (Weirton, 

WVA), 71 FR 13021 (March 14, 2006) 

(Yuma, AZ), 71 FR 6352 (February 8, 

2006) (Ajo, AZ). For a discussion of the 

legal rationale supporting rulemaking 

actions applying the Clean Data policy 

to the 1-hour ozone standards, see, for 

example, 67 FR 49600 (July 31, 2002); 

65 FR 37879 (June 19, 2000) CincinnatiHamilton, Ohio-Kentucky); 61 FR 20458 

(May 7, 1996) (Cleveland Akron-Lorain, 

Ohio); 66 FR 53094 (October 19, 2001) 

(Pittsburgh-Beaver Valley, 

Pennsylvania); 61 FR 31832 (June 21, 

1996 (Grand Rapids, Michigan); 60 FR 

36723 (July 18, 1995) (Salt Lake and 

Davis Counties, Utah); 68 FR 25418 

(May 12, 2003) (St Louis, Missouri); 69 

FR 21717 (April 22, 2004) (San 

Francisco Bay Area). 

The EPA has further elaborated on its 

legal rationale for the Clean Data Policy 

in briefs filed in the 10th, 7th, and 9th 

Circuits, and hereby incorporates those 

briefs insofar as relevant here. See Sierra 

Club v. EPA, No. 95–9541 (10th Cir.), 

Sierra Club v. EPA, No. 03–2839, 03–

3329 (7th Cir.), Our Children’s Earth 

Foundation v. EPA, No. 04–73032 (9th 

Cir.). As stated in the policy, the 

attainment demonstration, RFP 

requirements, and contingency measure 

requirement are designed to bring an 

area into attainment. Once this goal has 

been achieved, it is appropriate to 

suspend the obligation that States 

submit plans to meet these goals, so 

long as the area continues to attain the 

relevant standard. The Tenth, Seventh 

and Ninth Circuits have all upheld EPA 

rulemakings applying the Clean Data 

Policy. See Sierra Club v. EPA, 99 F. 3d 

1551 (10th Cir. 1996); Sierra Club v. 

EPA, 375 F. 3d 537 (7th Cir. 2004); Our 

Children’s Earth Foundation v. EPA, No. 

04–73032 (9th Cir. June 28, 2005 

(Memorandum Opinion). 

The EPA has explained in its 

memoranda on the Clean Data Policy for 

PM2.5 and for ozone that it is reasonable 

to interpret the provisions regarding 

RFP and attainment demonstrations, 

along with certain other related 

provisions, as not requiring further 

submissions to achieve attainment for so 

long as the area is in fact attaining the 

standard. Under the policy, EPA is not 

granting an exemption from any 

applicable requirement under Part D. 

Rather, EPA has interpreted these 

requirements as not applying for so long 

as the area remains in attainment with 

the standard. This is not a waiver of 

requirements that by their terms apply; 

it is a determination that certain 

requirements are written so as to be 

operative only if the area is not attaining 

the standard. 

CAA section 172(c)(2) provides that 

SIP provisions in nonattainment areas 

must require ‘‘reasonable further 

progress.’’ The term ‘‘reasonable further 

progress’’ is defined in section 171(1) as 

‘‘such annual incremental reductions in 

emissions of the relevant air pollutant as 

are required by this part or may 

reasonably be required by the 

Administrator for the purpose of 

ensuring attainment of the applicable 

NAAQS by the applicable date.’’ Thus, 

by definition, the ‘‘reasonable further 

progress’’ provision requires only such 

reductions in emissions as are necessary 

to attain the NAAQS. If an area has 

attained the NAAQS, the purpose of the 

RFP requirement will have been 

fulfilled, and since the area has already 

attained, showing that the State will 

make RFP towards attainment will 

‘‘have no meaning at that point.’’ The 

EPA’s General Preamble for the 

Implementation of Title I of the Clean 

Air Act Amendments of 1990 (General 

Preamble) 57 FR 13498, 13564 (April 16, 

1992). 

CAA section 172(c)(1), the 

requirement for an attainment 

demonstration, provides in relevant part 

that SIPs ‘‘shall provide for attainment 

of the [NAAQS].’’ The EPA has 

interpreted this requirement as not 

applying to areas that have reached 

attainment. If an area has attained the 

standard, there is no need to submit a 

plan demonstrating how the area will 

reach attainment. In the General 

Preamble (57 FR 13564), EPA stated that 

no other measures to provide for 

attainment would be needed by areas 

seeking redesignation to attainment 

since ‘‘attainment will have been 

reached.’’ See also Memorandum from 

John Calcagni, ‘‘Procedures for 

Processing Requests to Redesignate 

Areas to Attainment,’’ September 4, 

1992, at page 6. 

CAA section 172(c)(9) provides that 

SIPs in nonattainment areas ‘‘[S]hall 

provide for the implementation of 

specific measures to be undertaken if 

the area fails to make reasonable further 

progress, or to attain the [NAAQS] by 

the attainment date applicable under 

this part. Such measures shall be 

included in the plan revision as 

contingency measures to take effect in 

any such case without further action by 

the State or [EPA].’’

This contingency measure 

requirement is inextricably tied to the 

reasonable further progress and 

attainment demonstration requirements. 

Contingency measures are implemented 

if reasonable further progress targets are 

not achieved, or if attainment is not 

realized by the attainment date. Where 

an area has already achieved attainment 

by the attainment date, it has no need 

to rely on contingency measures to 

come into attainment or to make further 

progress to attainment. As EPA stated in 

the General Preamble: 

‘‘The section 172(c)(9) requirements for 

contingency measures are directed at 

ensuring RFP and attainment by the 

applicable date.’’ 57 FR 13564. Thus these 

requirements no longer apply when an area 

has attained the standard. 

It is important to note that should an 

area attain the PM2.5 standards based on 

three years of data, its obligation to 

submit an attainment demonstration is 

not waived but is only suspended. If the 

area then has air quality concentrations 

in the following year such that the area 

exceeds the standard for years 2 through 

4, then the area’s obligation to submit an 

attainment demonstration is back in 

effect. 

The determination of attainment 

contemplated by the Clean Data Policy 

does not purport to be a redesignation, 

and thus the requirements for 

redesignation under section 107(d) are 

not applicable. Nor does the Clean Data 

Policy avoid or illegally circumvent the 

redesignation requirements of section 

107 of the CAA. All of the requirements 

for redesignation remain in effect and 

must be satisfied for an area to be 

redesignated. Sierra Club v. EPA, 99 

F.3d at 1557–1558. The Clean Data 

Policy is simply an interpretation of 

certain provisions of the CAA, whose 

express purpose is to achieve attainment 

of the standard, as not requiring SIP 

revisions to be made by the State for so 

long as the area continues to attain the 

standard. The policy does not purport to 

exempt areas from requirements that are 

inapplicable only if an area is 

redesignated to attainment. It interprets 

certain provisions which are written in 

such a way as to impose requirements 

only upon areas that are not attaining 

the NAAQS, regardless of whether they 

have been redesignated to attainment. 

The EPA has not provided for any 

waiver from statutory requirements that 

was not provided by Congress. The area 

at issue remains designated 

nonattainment, and is subject to the risk 

that if a violation occurs it will have to 


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adopt and implement reasonable further 

progress requirements, contingency 

measures, and an attainment 

demonstration, unless it is redesignated 

to attainment. In order to be 

redesignated to attainment, however, 

the area will have to satisfy all of the 

requirements of section 107(d)(3)(E), 

including the requirement for a longterm maintenance plan. 

While a determination of attainment 

is not equivalent to a redesignation to 

attainment, nothing in the Act compels 

EPA to wait until an area meets all the 

requirements for redesignation before 

EPA makes a determination that the area 

is in attainment with the standard, 

thereby suspending the requirements for 

certain provisions related to attainment. 

Indeed, section 179(c) of the Act 

requires EPA to make an attainment 

determination within six months after 

an area’s applicable attainment date 

whether or not the EPA has made a 

finding with respect to redesignation. 

The EPA’s interpretation of the Act’s 

provisions not to require, once 

attainment has been reached, certain 

plan submissions whose purpose is to 

assure attainment, is not at odds with 

the requirements for redesignation. Nor 

does EPA’s construction of the statute 

adversely impact planning for 

maintenance. An area that is monitoring 

attainment, but is still designated as a 

nonattainment area, retains strong 

incentives to seek redesignation to 

attainment, and remains subject to the 

requirement to demonstrate 

maintenance in order to be 

redesignated. For a detailed discussion 

of the relationship of redesignation 

requirements and attainment 

determinations, see the discussions in 

the EPA briefs in Our Children’s Earth 

Foundation v. EPA, supra at pp. 43–60., 

Sierra Club v. EPA No. 95–9541 (10th 

Cir.) at 29–43, and Sierra Club v. EPA 

Nos. 03–2839, 03–3329 (7th Cir.) at 33–

44 which are contained in the docket for 

this rulemaking. 

Comment: A commenter noted that 

EPA’s proposal suggested that areas 

attaining the standard would be subject 

to reduced regulatory requirements. The 

commenter believed that EPA’s 

interpretation should be codified in 

regulatory form, in order to assure that 

areas legally meeting the current PM2.5

standard and those requesting 

redesignation be enabled to be 

redesignated and to benefit from the 

interpretation through regulation, rather 

than by guidance or policy. 

Response: The EPA has adopted the 

commenter’s suggested approach of 

codifying its Clean Data Policy 

interpretation for PM2.5 in regulatory 

form. Section 51.1004(c). As it did for 

ozone in its Phase II Ozone 

Implementation Rule, EPA is including 

in this rulemaking a regulation that 

encapsulates the statutory interpretation 

that is embodied in its Clean Data Policy 

for PM2.5, set forth above. As noted in 

the response to comment above, 

determinations as to whether individual 

areas have attained the PM2.5 standard 

and thus qualify for application of the 

rule will be made in the context of 

rulemakings for those individual areas. 

The EPA believes, however, that 

encapsulating its interpretation in 

regulatory form will lend clarity and 

consistency to the process of applying 

its interpretation. 

E. Modeling and Attainment 

Demonstrations 

1. Background 

[Section III.F.1 of November 1, 2005 

proposed rule (70 FR 66007); sec 

51.1007 in draft and final regulatory 

text] 

As noted in the proposal, Section 

172(c) requires States with 

nonattainment areas to submit an 

attainment demonstration. An 

attainment demonstration consists of: 

(1) Technical analyses that locate, 

identify, and quantify sources of 

emissions that are contributing to 

violations of the PM2.5 NAAQS; (2) 

analyses of future year emissions 

reductions and air quality improvement 

resulting from already-adopted national 

and local programs, and from potential 

new local measures to meet the RACT, 

RACM, and RFP requirements in the 

area; (3) adopted emission reduction 

measures with schedules for 

implementation; and (4) contingency 

measures required under section 

172(c)(9) of the CAA. 

a. Final Rule 

The requirements from the proposal 

are unchanged. Each State with a 

nonattainment area will be required to 

submit a SIP with an attainment 

demonstration that includes analyses 

supporting the State’s proposed 

attainment date. States must show that 

the area will attain the standards as 

expeditiously as practicable and it must 

include an analysis of whether 

implementation of reasonably available 

measures will advance the attainment 

date. 

2. Areas That Need To Conduct 

Modeling 

[Section III.F.2 of November 1, 2005 

proposed rule (70 FR 66007)] 

a. Background 

All nonattainment areas need to 

submit an attainment demonstration, 

but in some cases, States may not need 

new, local-scale modeling analyses. In 

the proposed rule, EPA proposed that 

States may use in a PM2.5 attainment 

demonstration certain local, regional 

and/or national modeling analyses that 

have been developed to support Federal 

or local emission reduction programs, 

provided the modeling meets the 

attainment modeling criteria set forth in 

EPA’s modeling guidance. The proposal 

also stated that nonattainment areas for 

which local, regional, or national scale 

modeling demonstrates the area will not 

attain the standard within 5 years of 

designation would be required to submit 

an attainment demonstration SIP that 

includes new modeling showing 

attainment of the standards as 

expeditiously as practicable. 

b. Final Rule 

In the final rule, EPA is reaffirming 

the potential use of national and/or 

regional modeling as part of an 

attainment demonstration. We are also 

clarifying the types of modeling 

analyses that may be useful as a 

‘‘primary’’ modeling analysis and as a 

‘‘supplemental’’ analysis. The proposal 

suggested that it may be appropriate, in 

certain circumstances, for a State to 

submit regional or national modeling as 

the sole (primary) modeling analysis in 

its attainment demonstration. This 

implies that the State would not need to 

conduct local modeling analyses. We 

wish to further define the differences 

between ‘‘national’’, ‘‘regional’’, and 

‘‘local’’ modeling analyses. In this 

context, national analyses are generally 

those conducted by EPA in support of 

national or regional rules. Regional and 

local modeling analyses are generally 

those conducted by the RPOs and/or 

States for the purpose of developing 

State Implementation Plans (SIPs). EPA 

has conducted national scale modeling 

for a variety of rules and analyses. 

Additionally, the RPOs and many States 

are conducting regional and/or local 

scale modeling of PM2.5 and regional 

haze across the country. The national 

scale of the EPA modeling analyses 

requires basic assumptions concerning 

local model inputs. Compared to 

regional or local modeling done by the 

States and/or RPOs, EPA modeling may, 

in some cases, use coarser grid 

resolution, use inventories that are not 

as refined, and model performance may 

be highly variable from area to area. For 

these reasons, national scale modeling 

may not always be appropriate for local 

area attainment demonstrations. 

Therefore, we believe that regional or 

local modeling conducted by the States 

or RPOs is best suited as the primary 

modeling analysis for a modeled 


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attainment demonstration. The local 

modeling is more likely to meet the 

recommendations contained in EPA’s 

modeling guidance. However, some 

areas having design values close to the 

standard may be projected to come into 

attainment within five years based on 

modeling analyses of national and 

regional emission control measures (e.g. 

CAIR) that are scheduled to occur 

through 2009. Regional scale modeling 

for national rules such as the Tier II 

motor vehicle standards, the Heavy-duty 

Engine standards, the Nonroad Engine 

standards, and CAIR indicate major 

reductions in PM2.5 by 2010. A portion 

of these benefits will occur in the 2006–

2009 PM2.5 attainment timeframe. 

Experience with past ozone 

attainment demonstrations has shown 

that the process of performing detailed 

photochemical grid modeling to develop 

an attainment demonstration can be 

very resource intensive for States. The 

EPA believes that it would be 

appropriate for States to leverage 

resources by collaborating on modeling 

analyses to support SIP submittals, or by 

making use of recent modeling analyses 

that are completed prior to the SIP 

submittal date. For this reason, EPA 

recognizes that States may use in a 

PM2.5 attainment demonstration certain 

local, regional and/or national modeling 

analyses that have been developed to 

support Federal or local emission 

reduction programs, provided the 

modeling meets the attainment 

modeling criteria set forth in EPA’s 

modeling guidance (described below). 

As with all SIPs under subpart 1, the 

State must demonstrate that the area 

will attain the PM2.5 standards as 

expeditiously as practicable. The 

judgment of whether the modeling is 

appropriate for an area should be made 

by the State(s) and their respective EPA 

regional office on a case-by-case basis. 

c. Comments and Responses 

Comment: There were many 

commenters that agreed that States 

should be able to use EPA modeling or 

other national or regional modeling as a 

modeled attainment demonstration. One 

commenter recommended that the final 

rule require States to show that the 

existing modeling incorporates realistic 

assumptions, accurately reflects local 

emissions and trends, and provides 

adequate model performance for the 

local nonattainment area. 

Response: We agree that national and 

regional modeling may be used as part 

of an attainment demonstration as long 

as it is shown to be applicable to the 

local area. This is consistent with the 

proposal where we said that existing 

modeling should ‘‘meet the attainment 

modeling criteria set forth in EPA’s 

modeling guidance.’’ Part of the analysis 

to determine if existing modeling meets 

the criteria in the modeling guidance is 

to assess whether the modeling 

incorporates realistic assumptions, 

accurately reflects local emissions and 

trends, and provides adequate model 

performance for the local nonattainment 

area. 

Comment: Some commenters thought 

States should be able to use EPA 

modeling in the absence of an analysis 

of the applicability of the modeling for 

a local nonattainment area. One 

commenter said that EPA should 

determine that States should not have to 

do any additional modeling analyses if 

the CAIR modeling showed they were 

expected to attain the NAAQS by 2010. 

Response: While we acknowledge 

there may be some circumstances in 

which national or regional modeling 

would be appropriate to use without 

local modeling and allow for such use, 

we disagree that national modeling 

should be used in support of an 

attainment demonstration without 

further analysis of the modeling 

assumptions for a particular area. 

National scale modeling may not always 

be appropriate for local areas. Most 

often, national scale EPA modeling is 

best suited for use as a supplemental 

analysis or as part of a ‘‘weight of 

evidence’’ demonstration. The modeling 

guidance recommends supplemental 

analyses for all attainment 

demonstrations. The guidance 

specifically recommends the 

examination of other modeling studies 

as a supplemental analysis. The EPA 

modeling as well as other ‘‘non-local’’

modeling can be used for this purpose. 

The ‘‘weight’’ of this alternative 

modeling in an attainment 

demonstration should be guided by how 

well the modeling system is suited for 

the local nonattainment area. States 

should consult with their EPA regional 

offices for further guidance and 

recommendations. As such, we do not 

believe it to be appropriate to determine 

a priori that CAIR or any other modeling 

analyses are appropriate to use in a local 

attainment demonstration for any or all 

nonattainment areas. 

Comment: Several commenters 

believe that States should be able to use 

existing EPA modeling (such as CAIR), 

as the basis for an extension of the area’s 

attainment date, if it shows that the 

nonattainment area may not be able to 

attain the NAAQS by 2010. They believe 

that the State should not have to do 

additional modeling to show that they 

need an attainment date extension. 

Response: We disagree with this 

comment. The CAIR modeling included 

national controls that are expected to be 

in place by 2010 (including the CAIR 

rule itself), as well as existing state and 

local controls reflected in the inventory 

used in the CAIR analysis. It did not 

include any additional local controls 

that could be implemented under RACT 

and RACM requirements for the 1997 

standards that may bring the area into 

attainment sooner. Nonattainment areas 

are required to attain the NAAQS as 

expeditiously as practicable. Therefore, 

updated modeling of existing controls as 

well as additional local controls is 

needed before an attainment date 

extension can be granted. Additional 

information on attainment dates and 

extensions is contained in the preamble 

to the final rule, section II.D., and 

additional information on RACT and 

RACM requirements is contained in 

section II.F. 

Comment: Several commenters noted 

an apparent inconsistency in the 

language concerning who would be 

required to perform ‘‘new’’ local-scale 

modeling. First, there are potentially 

conflicting statements in the proposal 

when EPA states that areas with an 

attainment date of 2010 will need to 

conduct local-scale modeling to project 

the estimated level of air quality 

improvement in accordance with EPA’s 

modeling guidance. This conflicts with 

the proposed ability for States to use 

existing national or regional modeling 

as their modeled attainment 

demonstration. Second, a portion of a 

sentence was removed from the Federal 

Register version of the notice which 

differs from the pre-Federal Register 

version. The published version implies 

that all nonattainment areas would be 

required to submit new modeling. 

Response: We agree that there are 

inconsistencies in the proposal 

preamble text. To clarify, new localscale modeling is required for areas that 

are not expected to come into 

attainment by 2010. For other areas, 

there may be national or regional 

modeling which may be applicable to 

the area which shows they are likely to 

come into attainment. As noted earlier, 

national scale modeling is best suited 

for use as a supplemental analysis, but 

in some cases may be acceptable 

evidence that an area will attain by 

2010. 

Additionally, the preamble language 

in the Federal Register contained an 

error. A portion of a sentence was 

mistakenly removed, which led to some 

confusion. The language in the FR 

notice (FR page 66008) stated 

‘‘Nonattainment areas would be 

required to submit an attainment 

demonstration SIP that includes new 

modeling showing attainment of the 


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17The recommendations contained in the 

modeled attainment demonstration guidance are 

separate from the Agency’s future hot-spot 

modeling guidance for transportation conformity 

purposes. 

18 In the March 10, 2006, final transportation 

conformity rule (71 FR 12468), EPA committed to 

develop PM2.5 and PM10 quantitative hot-spot 

modeling guidance for transportation conformity 

determinations for highway and transit projects of 

local air quality concern. 

19Application of the unmonitored area analysis is 

limited to locations which are appropriate to allow 

the comparison of predicted PM2.5 concentrations to 

the NAAQS, based on PM2.5 monitor siting 

requirements and recommendations. 

standards as expeditiously as 

practicable. The new modeling will 

need to include additional emissions 

controls or measures in order to 

demonstrate attainment.’’ The language 

should have read, ‘‘Nonattainment areas 

for which local, regional, or national 

scale modeling demonstrates the area 

will not be in attainment of the NAAQS 

within 5 years of designation would be 

required to submit an attainment 

demonstration SIP that includes new 

modeling showing attainment of the 

standards as expeditiously as 

practicable. The new modeling will 

need to include additional emissions 

controls or measures in order to 

demonstrate attainment.’’ This should 

clarify that States that cannot show 

attainment within 5 years will need to 

develop new modeling analyses which 

contain additional control strategies 

which show how and when they expect 

to attain the PM2.5 NAAQS. 

Comment: One commenter 

maintained that relying on large-scale 

regional modeling alone may allow for 

PM2.5 hot spots (i.e. small unmonitored 

areas projected to exceed the standard) 

to exist past the attainment date. 

Response: We agree that 

nonattainment areas with potential 

hotspot issues (relatively high 

concentrations and/or gradients of 

primary PM2.5) should not rely 

exclusively on regional modeling. The 

EPA’s attainment demonstration 

modeling guidance attempts to address 

several aspects of hotspot issues in both 

monitored and unmonitored areas 17. 

The modeled attainment tests contained 

in EPA’s modeling guidance are 

primarily monitor based tests. Ambient 

data is combined with the model 

predicted relative change in PM 

components to determine if attainment 

of the standards is likely in the future. 

There are several aspects of the 

attainment test. In most cases, States 

will run a photochemical grid model to 

determine the future year predicted 

PM2.5 concentrations at monitors. The 

modeling guidance generally 

recommends that for urban scale PM2.5

modeling, the State performs modeling 

analyses at 12 kilometer grid resolution 

or finer. There is an additional 

component to the attainment test for 

areas that have measured relatively high 

concentrations and/or gradients of 

primary PM2.5 at monitors. In these 

cases, we recommend running a 

Gaussian dispersion model for potential 

primary PM sources, to determine the 

local impact of changes in primary PM 

emissions (from the modeled sources) 

on predicted concentrations at the 

monitor(s). 

In addition, we describe an 

‘‘unmonitored area analysis’’ which 

uses interpolated ambient data 

combined with gridded model outputs 

to examine whether potential violations 

of the NAAQS may occur in 

unmonitored areas. If potential 

violations are indicated, we recommend 

further analysis of the problem through 

additional local modeling. Options for 

State action to address such a situation 

could include imposition of reasonably 

available control technology to reduce 

emissions, or the deployment of an air 

quality monitor to further characterize 

the problem. 

We believe that the combination of 

these model-based tests will adequately 

determine whether attainment of the 

standards is likely by the attainment 

date. We also believe that these tests 

address the issue of hotspots by 

recommending a combination of 

photochemical modeling, dispersion 

modeling of local sources, and 

additional monitoring and/or emissions 

controls. 

3. Modeling Guidance 

[Section III.F.3 of November 1, 2005 

proposed rule (70 FR 66008)] 

a. Background 

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

must contain air quality modeling as 

prescribed by the Administrator for the 

purpose of predicting the effect of 

emissions on ambient air quality. The 

procedures for modeling PM2.5 as part of 

an attainment SIP are contained in 

EPA’s ‘‘Guidance for Demonstrating 

Attainment of Air Quality Goals for 

PM2.5 and Regional Haze.’’ The proposal 

summarized several of the chapters in a 

draft version of the modeling guidance. 

b. Final Rule 

A draft of the PM2.5 attainment 

demonstration and regional haze 

modeling guidance has now been 

revised (September 2006) and is 

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

scram/guidance_sip.htm. The draft 

PM2.5 attainment demonstration and 

regional haze guidance has been 

incorporated into the ozone modeling 

guidance and is now called ‘‘Guidance 

on the Use of Models and Other 

Analyses for Demonstrating Attainment 

of Air Quality Goals for the 8-Hour 

Ozone and PM2.5 NAAQS and Regional 

Haze’’. The final version of the 

modeling guidance will be available at 

the same location in the near future. 

The revised draft PM2.5 modeling 

guidance document is very similar to 

the previous draft version, although 

there were several changes and updates. 

Among them are new methods in 

treating PM2.5 species components as 

part of the PM2.5 attainment test; new 

methods for determining potential 

future year violations in unmonitored 

areas; new procedures for handling 

potential PM2.5 ‘‘hotspots’’; and an 

increased reliance on supplemental 

analyses, including ‘‘weight of 

evidence’’ analyses. The EPA notes that 

the PM2.5 attainment demonstration 

modeling guidance that we have 

released is separate from the Agency’s 

future hot-spot modeling guidance for 

transportation conformity purposes.18

The modeling guidance describes how 

to estimate whether a control strategy to 

reduce emissions of particulate matter 

and its precursors will lead to 

attainment of the annual and 24-hour 

PM2.5 NAAQS. Part I of the guidance 

describes a ‘‘modeled attainment test’’

for the annual and 24-hour PM2.5

NAAQS. Both tests are similar. The 

output of each is an estimated future 

design value consistent with the 

respective forms of the NAAQS. If the 

future design value does not exceed the 

concentration of PM2.5 specified in the 

NAAQS, then the primary modeled test 

is passed. The modeled attainment test 

applies to locations with monitored 

data. 

A separate test is recommended to 

examine projected future year PM2.5

concentrations in unmonitored 

locations.19 Interpolated PM2.5 ambient 

data, combined with modeling data, is 

used to predict PM2.5 concentrations in 

unmonitored areas. The goal of this 

analysis is to identify areas without 

monitors that may be violating the PM2.5

NAAQS, often due to high levels of 

primary PM2.5 (both now and in the 

future). The details of the analysis are 

contained in the final modeling 

guidance. 

The guidance also discusses modeling 

PM2.5 at monitors where high 

concentrations of primary PM2.5 are 

measured. In these cases, it may be 

beneficial to model the primary 

component of the PM2.5 with a Gaussian 

dispersion model. Dispersion models 

are better able to capture the influence 


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of primary PM sources where large 

concentration gradients may exist. Grid 

models spread out the PM emissions to 

the size of the grid (typically 4 or 12 

km). This makes it difficult to judge the 

benefits of control strategies that may 

affect primary PM sources. The final 

modeling guidance recommends 

procedures for applying dispersion 

models in these situations. 

The guidance also recommends the 

submittal of supplemental analyses as 

part of all attainment demonstrations. 

Supplemental analyses are modeling, 

emissions, and/or ambient data analyses 

that are submitted as part of a SIP, in 

addition to the primary modeled 

attainment test. The evaluation of 

supplemental analyses when the 

predicted concentrations in the primary 

attainment test are close to the NAAQS 

(slightly above or slightly below) is 

called a weight-of-evidence (WOE) 

analysis. This is simply a collection of 

evidence that aims to show that 

attainment of the standard is likely. The 

final version of the modeling guidance 

puts more emphasis on the submittal of 

supplemental analyses than in previous 

versions. 

Part II of the guidance describes how 

to apply air quality models to generate 

results needed by the modeled tests for 

attainment. This includes developing a 

conceptual description of the problem 

to be addressed; developing a modeling/ 

analysis protocol; selecting an 

appropriate model to support the 

demonstration; selecting appropriate 

meteorological episodes or time periods 

to model; choosing an appropriate area 

to model with appropriate horizontal/ 

vertical resolution; generating 

meteorological and air quality inputs to 

the air quality model; generating 

emissions inputs to the air quality 

model; evaluating performance of the air 

quality model; and performing 

diagnostic tests. After these steps are 

completed, the model is used to 

simulate the effects of candidate control 

strategies. 

Comment: Several commenters were 

supportive of the weight of evidence 

concept. They said that PM2.5 modeling 

is inherently more uncertain than 

previous ozone modeling and the 

modeling guidance should reflect that. 

One commenter noted that weight of 

evidence demonstrations should be 

‘‘unbiased’’, meaning that States should 

use all relevant analyses and not only 

information that helps their case. 

Response: The EPA agrees with these 

comments. The final modeling guidance 

recommends supplemental analyses 

(including weight of evidence) for all 

attainment demonstrations. All States 

should submit modeling, ambient data, 

and emissions analyses in addition to 

the primary modeling demonstration. A 

weight of evidence analysis is needed if 

the predicted future year PM2.5

concentrations are slightly higher or 

slightly lower than the NAAQS. 

We also agree that a weight of 

evidence demonstration should include 

all relevant information, including 

analyses which support attainment and 

those that do not. The idea of the 

analysis is to ‘‘weigh’’ the evidence, 

both good and bad. That cannot be fairly 

done if some evidence is not presented. 

Comment: Several commenters 

suggested that a modeled attainment 

demonstration should not be 

specifically required. Instead they 

suggest that all demonstrations should 

be weight of evidence demonstrations. 

This would include different analyses of 

ambient data, trends, and modeling. But 

due to the uncertainties in the current 

PM2.5 models and emissions data, 

modeling would be but one part of a 

broader weight of evidence approach. 

Response: We disagree with this 

comment. Model results should be the 

primary analysis of an attainment 

demonstration. Regardless of current 

uncertainties in the PM2.5 models and 

emissions, models are the only tool that 

can predict future concentrations of 

PM2.5. The uncertainties in the model 

inputs and formulation should be taken 

into account when evaluating the 

results. We agree that a broad analysis 

of modeling, ambient data and 

emissions trends should be part of the 

attainment demonstration. This is 

reflected in the final modeling guidance. 

4. Modeled Attainment Test 

[Section III.F.4 of November 1, 2005 

proposed rule (70 FR 66008)] 

a. Background 

The proposal described the nature of 

the attainment tests for the annual 

average and 24-hour average PM2.5

NAAQS contained within the modeling 

guidance. Both tests use monitored data 

to estimate current air quality. The 

attainment test for a given standard is 

applied at each monitor location within 

or near a designated nonattainment area 

for that standard. There is also an 

additional attainment test to be 

performed in unmonitored areas. 

Models are used in a relative sense to 

estimate the response of measured air 

quality to future changes in emissions. 

Future air quality is estimated by 

multiplying current monitored values 

times modeled responses to changes in 

emissions. Because PM2.5 is a mixture of 

chemical components, the guidance 

recommends using current observations 

and modeled responses of major 

components of PM2.5 to estimate future 

concentrations of each component. The 

predicted future concentration of PM2.5

is the sum of the predicted component 

concentrations. 

b. Final Rule 

The nature of the PM2.5 attainment 

tests is unchanged. The final modeling 

guidance recommends refinements to 

the test and discusses the treatment of 

individual PM2.5 species. The speciated 

modeled attainment test (SMAT) that 

was used to estimate future PM2.5

concentrations for CAIR has been 

(mostly) implemented in the final 

guidance. Among the new 

recommendations is to better account 

for the known differences between the 

PM2.5 Federal Reference Method (FRM) 

measurements and the PM2.5 speciation 

measurements. For example, it is 

recommended to account for the 

volatilization of nitrate from the FRM 

filters and to account for uncertainties 

in organic carbon measurements by 

employing an ‘‘organic carbon by mass 

balance’’ technique. This assumes that 

all remaining mass not accounted for by 

other species is organic carbon mass. 

Additional details are contained in the 

modeling guidance. 

The guidance also recommends, 

where necessary, to spatially interpolate 

PM2.5 species data to estimate the 

species concentrations at FRM sites. It is 

necessary to estimate species 

concentrations when there are no 

species measurements at FRM sites. 

Several techniques can be used to 

estimate species concentrations. Spatial 

interpolation techniques may be useful 

in many areas. In other cases, it may be 

adequate to assume that data from a 

speciation monitor may be 

representative of multiple FRM 

monitors. It is particularly important to 

develop credible techniques to estimate 

species concentrations at the locations 

of the highest FRM monitors. 

The guidance lists several techniques 

that can be used. The EPA will provide 

software which will apply the modeled 

attainment test, using ambient data and 

model outputs. Additionally, the 

software will interpolate the PM2.5

species data to allow application of 

SMAT for all FRM monitors. The 

software will be available at the same 

location as the final modeling guidance 

(http://www.epa.gov/scram001/ 

guidance_sip.htm). 

Ultimately, it is up to the States to 

determine the best method to represent 

the PM2.5 species concentrations, subject 

to EPA’s review and approval. These 

estimates are needed to perform the 

modeled attainment test. 


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c. Comments and Responses 

Comment: Several commenters were 

concerned that interpolation of PM2.5

species concentrations may not be 

appropriate in certain areas or 

situations. The concentrations can vary 

significantly between urban and rural 

areas and even between nearby urban 

areas. One commenter suggested that it 

might be useful to use older field study 

measurements to derive current species 

concentrations. Another commenter 

suggested that it might be reasonable to 

assume that speciation measurements 

were representative of nearby FRM sites. 

Response: We agree that 

interpolations of species data may not 

always be the best way to estimate 

species concentrations at FRM sites. The 

modeling guidance lists several different 

possible techniques. States should 

review their data and situation and 

choose the most reasonable 

methodology to estimate species 

concentrations. Nonattainment areas 

that don’t have speciation 

measurements at the highest FRM site(s) 

need to be especially careful. The result 

of the speciated attainment test can be 

heavily influenced by the assumed 

species concentrations at the highest 

FRM sites. The attainment test will be 

more straightforward in areas with 

speciation monitors at the highest FRM 

sites. States are also encouraged to place 

speciation monitors at the highest FRM 

sites. This will aid in future assessments 

of attainment and ambient trends. 

5. Multi-Pollutant Assessments 

[Section III.F.5 of November 1, 2005 

proposed rule (70 FR 66009)] 

a. Background 

The formation and transport of PM2.5

is in many cases closely related to the 

formation of both regional haze and 

ozone. There is often a positive 

correlation between measured ozone 

and secondary particulate matter. Many 

of the same factors affecting 

concentrations of ozone also affect 

concentrations of secondary particulate 

matter. For example, similarities exist in 

sources of precursors for ozone and 

secondary particulate matter. Emissions 

of NOX may lead to formation of nitrates 

as well as ozone. Sources of VOC may 

be sources or precursors for both ozone 

and organic particles. Presence of ozone 

itself may be an important factor 

affecting secondary particulate 

formation. The proposal recommended 

multi-pollutant assessments for PM2.5

attainment demonstrations. A multipollutant assessment, or oneatmosphere modeling, is conducted 

with a single air quality model that is 

capable of simulating transport and 

formation of multiple pollutants 

simultaneously. This type of model 

simulates the formation and deposition 

of PM2.5, ozone, and regional haze 

components, and it includes algorithms 

simulating gas phase chemistry, 

aqueous phase chemistry, aerosol 

formation, and acid deposition. 

b. Final Rule 

The recommendation to conduct 

multi-pollutant assessments remains 

unchanged. It is recommended to model 

the impacts of future year control 

strategies on PM2.5, ozone, and regional 

haze. It may not always be possible or 

convenient to do so, but it can be 

beneficial to the strategy development 

process. 

PM2.5 control strategies will have an 

impact on regional haze, and will 

possibly impact ozone. Even if high 

ozone and high PM2.5 concentrations 

don’t typically occur during the same 

time of the year, controls that affect 

precursors to PM2.5 may also affect 

ozone (e.g. NOX). The SIP submittal 

dates for PM2.5, ozone, and regional haze 

do not currently line up. The PM2.5 SIPs 

are due almost 1 year later than ozone. 

But States can still do modeling 

analyses that can provide information 

for multiple pollutants. States can use 

one-atmosphere models that are capable 

of simulating both ozone and PM2.5. 

They can also try to use consistent 

meteorological fields and emissions 

inventories so that the same control 

strategies are relatively easy to evaluate 

for both ozone and PM2.5. Modeling the 

same future year(s) for PM2.5 and ozone 

can also make it easier to evaluate the 

impacts of controls on both pollutants. 

It should be noted that there are no 

specific modeling requirements other 

than the recommendation to try to 

harmonize the ozone, PM2.5, and 

regional haze analyses whenever 

possible. 

c. Comments and Responses 

Comment: One commenter suggests 

that multi-pollutant assessments may 

not be beneficial because their area 

experiences winter PM2.5 exceedances 

and summer ozone exceedances. 

Response: We disagree with the 

comment. Even in situations where high 

PM2.5 and ozone don’t occur during the 

same time of year, multi-pollutant 

assessments may be helpful. NOX

controls that may be needed to reduce 

nitrates in the winter are likely to have 

an impact on ozone in the summer. As 

well, changes in VOCs may have an 

impact on both PM2.5 and ozone. 

Running potential control strategies 

through the same modeling platform for 

ozone, PM2.5, and regional haze may 

allow the development of optimized 

strategies. 

6. Which Future Year(s) Should Be 

Modeled? 

[Section III.F.6 of November 1, 2005 

proposed rule (70 FR 66009)] 

a. Background 

Modeling analyses consist of base 

year modeling and future year 

modeling. The attainment test examines 

the change in air quality between the 

base and future years. The proposal 

recommended, where possible, future 

modeling years should be coordinated 

so that a single year can be used for both 

PM2.5 and ozone modeling. This 

coordination will help to reduce 

resources expended for individual 

modeling applications for PM2.5 and 

ozone and will facilitate simultaneous 

evaluation of ozone and PM impacts. 

Although there is some flexibility in 

choosing the future year modeling time 

periods, unless the State believes it 

cannot attain the standards within 5 

years of the date of designation and 

must request an attainment date 

extension, the choice of modeling years 

for PM2.5 cannot go beyond the initial 5 

attainment period. Attainment date 

extensions will only be granted under 

certain circumstances. Among other 

things, the State must submit an 

attainment demonstration showing that 

attainment within 5 years of the 

designation date is impracticable. 

b. Final Rule 

Further information is now known 

concerning the modeling years for 

ozone. Moderate nonattainment areas 

are presumed to be modeling 2009. This 

is consistent with the last year of the 5 

year period allowed under Subpart I for 

PM2.5. Therefore, it is logical to presume 

that areas that are able to attain the 

PM2.5 NAAQS within 5 years will model 

a future year of 2009. Areas that won’t 

be able to attain the standard in 5 years 

will need to request an attainment date 

extension (of up to 5 additional years). 

The NAAQS must be attained as 

expeditiously as practicable. Therefore, 

attainment date extensions must contain 

modeling analyses to justify the 

extension. Details of the required 

analyses are contained in the RACT and 

RACM sections of the final rule. See 

section F for more details. 

F. Reasonably Available Control 

Technology and Reasonably Available 

Control Measures 

This section of the preamble discusses 

the final rule requirements for RACT 

and RACM. In order to explain EPA’s 


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20Under the Tribal Air Rule (TAR), requirements 

for RACT and RACM may be considered to be 

severable elements of implementation plan 

requirements for Tribes. 

21See, 44 FR 53782, September 17, 1979, and 

1976 memorandum from Roger Strelow, Assistant 

Administrator for Air and Waste Management to 

Regional Administrators, ‘‘Guidance for 

Determining Acceptability of SIP Regulations in 

Non-attainment Areas’’ (Dec. 9, 1976). 

22See e.g. Workshop on Requirements for Nonattainment Area Plans—Compilation of 

Presentations (OAQPS No. 1.2–103, revised edition 

April 1978). 

approach in the final rule more clearly, 

we first discuss the statutory and 

regulatory background for the RACT and 

RACM requirements, and we then 

explain the key options and 

interpretations upon which we took 

comment in the proposal. Thereafter, we 

discuss significant comments we 

received on the proposal and provide 

brief responses to those comments. 

[Additional comments and responses 

appear in the RTC for this final rule 

located in the docket.] Most of the 

comments received on this topic 

addressed the three options EPA 

proposed for the RACT requirement, the 

relationship between the RACT 

requirement and EPA’s Clean Air 

Interstate Rule (CAIR), and the control 

measures to be required or considered 

for RACT and RACM. 

1. Background on Statutory 

Requirements for RACT and RACM 

Subpart 1 of Part D of the CAA 

(sections 171–179B) applies to all 

designated nonattainment areas. Section 

172 of this subpart includes general 

requirements for all attainment plans. 

Notably, Congress provided EPA and 

States a great deal of deference for 

determining what measures to include 

in an attainment plan. Specifically, 

Section 172(c)(1) requires that each 

attainment plan ‘‘provide for the 

implementation of all reasonably 

available control measures as 

expeditiously as practicable (including 

such reductions in emissions from 

existing sources in the area as may be 

obtained through the adoption, at a 

minimum, of reasonably available 

control technology), and shall provide 

for attainment of the national primary 

ambient air quality standards.’’ By 

including language in Section 172(c)(1) 

that only ‘‘reasonably available’’

measures be considered for RACT/ 

RACM, and that implementation of 

these measures need be applied only ‘‘as 

expeditiously as practicable,’’ Congress 

clearly intended that the RACT/RACM 

requirement be driven by an overall 

requirement that the measure be 

‘‘reasonable.’’ Thus, the rule of ‘‘reason’’

drives the decisions on what controls to 

apply, what should be controlled, by 

when emissions must be reduced, and 

finally, the rigor required in a State’s 

RACT/RACM analysis. For example, we 

previously stated that the Act ‘‘does not 

require measures that are absurd, 

unenforceable, or impractical’’ or result 

in ‘‘severely disruptive socioeconomic 

impacts’’ 55 FR 38327. Moreover, we 

interpret the term ‘‘reasonably 

available’’ to allow States to consider 

both the costs and benefits of applying 

the measure, and whether the measure 

can be readily and effectively 

implemented without undue 

administrative burden. 66 FR 26969. 

We also interpret the ‘‘reasonably 

available control measures’’ in these 

provisions as referring to measures of 

any type that may be applicable to a 

wide range of sources, whereas the 

parenthetical reference to ‘‘reasonably 

available control technology’’ refers to 

measures applicable to stationary 

sources. RACM can apply to mobile 

sources, areas sources and stationary 

sources not already subject to PM2.5

RACT requirements. Thus, RACT is a 

type of RACM specifically designed for 

stationary sources. As noted above, 

States are required to implement RACM 

and RACT ‘‘as expeditiously as 

practicable’’ as part of attainment plans 

designed to attain the standards.20

Section 172 does not include any 

specific applicability thresholds to 

identify the size of sources that States 

and EPA must consider in the RACT 

and RACM analysis. Nor, does Section 

172 specifically indicate which 

pollutant(s) or precursor(s) must be 

subject to RACM or RACT measures to 

attain the NAAQS. Other pollutantspecific provisions of the CAA do 

include applicability thresholds 

pertaining to attainment plan 

requirements for NAAQS and precursor 

pollutants. For example, subpart 2 of 

part D, which establishes additional 

requirements for ozone nonattainment 

areas, establishes thresholds ranging 

from 100 to 10 tons per year for 

requirements applicable to ‘‘major 

sources’’ or ‘‘major stationary sources,’’

depending on the area’s classification or 

level of nonattainment. Subpart 4 of part 

D, which provides additional plan 

requirements for PM10 nonattainment 

areas, establishes thresholds of 100 and 

70 tons per year for requirements 

applicable to a ‘‘major source’’ or ‘‘major 

stationary source.’’

Moreover, subpart 1, unlike subparts 

2 and 4, does not identify specific 

source categories for which EPA must 

issue control technology documents or 

guidelines, or identify specific source 

categories for State and EPA evaluation 

during attainment plan development. 

For ozone, subpart 2 contains a list of 

specific requirements for control 

techniques guidelines (CTGs) and 

alternative control techniques (ACT) 

documents. For PM10, section 190 of the 

CAA (in subpart 4) places particular 

emphasis on specific sources of area 

emissions, but does not identify specific 

stationary source categories for which 

RACT guidance must be issued. Section 

190 requires EPA to develop RACM 

guidance documents for residential 

wood combustion, silvacultural and 

agricultural burning, and for urban 

fugitive dust control. 

2. What Is the Overall Approach To 

Implementing RACT and RACM in the 

Final Rule? 

a. Background for RACT 

Since the 1970s, EPA has interpreted 

RACT to mean ‘‘the lowest emissions 

limitation that a particular source is 

capable of meeting by the application of 

control technology that is reasonably 

available considering technological and 

economic feasibility’’ as well as other 

considerations.21 Presumptive RACT 

has been described as the norm 

achievable by the source category.22

Section 110 of the 1970 Clean Air Act 

required States to develop SIPs 

providing for attainment of the NAAQS 

by 1975 or 1977. A number of areas 

were having difficulty with developing 

attainment plans, particularly for the 

ozone standard. In response to the 

implementation needs of this time 

period, EPA introduced the term 

‘‘RACT’’ in a 1976 memorandum from 

Roger Strelow, Assistant Administrator 

for Air and Waste Management to 

Regional Administrators, ‘‘Guidance for 

Determining Acceptability of SIP 

Regulations in Non-attainment Areas’’

(Dec. 9, 1976). In this early guidance 

relating to the acceptability of SIP 

regulations, we indicated that our 

overriding concern in approving SIPs 

was attaining the particular NAAQS as 

expeditiously as practicable through 

reasonably available control technology 

and other reasonably available control 

measures. ‘‘The basis for fully approving 

state-submitted SIP regulations 

continues to be demonstrated 

attainment and maintenance of all 

national ambient air quality standards 

as expeditiously as practicable,’’ the 

memo stated. 

The 1977 Clean Air Act amendments 

added Part D to Title I of the Act, and 

for the first time the Act specifically 

called for EPA to designate 

nonattainment areas and for SIPs to 

require RACT and RACM in those 

nonattainment areas. In a 1979 Federal 


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23Under the Tribal Air Rule (TAR), requirements 

for RACT and RACM may be considered to be 

severable elements of implementation plan 

requirements for Tribes. 

24 In Sierra Club v. EPA, 294 F.3d 155 (D.C. Cir. 

2002), the court stated in upholding EPA’s statutory 

interpretation of RACM that the Act does not 

compel a state to consider a measure without regard 

to whether it would expedite attainment. 

25 In this notice, where we use the shorthand 

phrase ‘‘advance the attainment date,’’ it means 

‘‘advance the attainment date by one year or more.’’

Register notice, EPA noted its view that 

Congress adopted EPA’s pre-existing 

conception of RACT in the 1977 

amendments. (44 FR 53782, September 

17, 1979). Also during the late 1970s, 

EPA developed a number of new control 

techniques guideline (CTG) documents 

as directed in the 1977 amendments. 

These CTGs provided States with 

information on controls for a number of 

categories of sources emitting VOCs, 

and recommended a ‘‘presumptive 

norm’’ for State RACT determinations 

based on the control levels achievable 

by sources in a given industry. CTGs 

reduced the burden on States by 

eliminating the need for each State to 

develop its own technical support for 

implementing the RACT requirement. 

Since the CTG-recommended controls 

were based on general capabilities of an 

industry, EPA in the 1979 guidance (44 

FR 53782) urged States in setting RACT 

to judge the feasibility of the 

recommended controls on particular 

sources, and to adjust accordingly. 

As noted above, EPA’s early guidance 

related to the RACT requirement 

indicated that our overriding concern in 

approving State RACT requirements was 

attaining the particular NAAQS. We 

initially required States to apply RACT 

to qualify for attainment extensions, and 

in some cases, for plans that could not 

demonstrate attainment. 

During the 1980s, EPA implemented 

the RACT requirements with a number 

of CTGs and guidance documents. 

These materials were aimed at 

addressing the attainment deadlines of 

1982 and 1987 under the 1977 Clean Air 

Act amendments. During this time, EPA, 

for pollutants other than ozone, 

considered RACT to be dependent upon 

reductions needed for attainment as 

expeditiously as practicable. For ozone, 

where the State performed 

photochemical grid modeling, the 

approach was the same, but where the 

State used less sophisticated tools, we 

considered RACT to be independent of 

whether the controls were needed to 

reach attainment as expeditiously as 

practicable. We took this alternate 

approach because of concerns related to 

the precision of modeling techniques. In 

other words, in those cases, we required 

that a stationary source of the requisite 

type and size be subject to RACT, 

whether or not such controls were 

actually demonstrated to be necessary 

for the area to attain by its specified 

date. (44 FR 20375–20376, April 4, 

1979) 

Congress followed a similar approach 

in the 1990 amendments to the CAA for 

purposes of the ozone NAAQS in the 

subpart 2 provisions added at that time. 

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

the imposition of RACT controls for all 

VOC source categories covered by a CTG 

and for all other major stationary 

sources of VOC located within certain 

nonattainment areas. Thus, Congress 

required these controls without 

allowing for an area-specific 

demonstration by the State that the area 

needed the controls for attainment as 

expeditiously as practicable. Extensive 

discussion of this requirement appeared 

in the 1992 general preamble (57 FR 

13541), in which EPA provided 

guidance for implementation of the 

ozone NAAQS. 

Notably, Congress did not 

significantly amend the generally 

applicable provisions for nonattainment 

areas that appear in subpart 1 of Part D 

in 1990. This indicates that Congress 

intended that the Agency retain the 

authority to interpret the generally 

applicable nonattainment area plan 

requirements of section 172(c), 

including the RACT and RACM 

requirements, in the way that is most 

appropriate for new NAAQS that are 

subject to subpart 1. As discussed 

below, EPA has determined that an 

approach to the RACT requirement in 

which RACT varies in different 

nonattainment areas based on the 

reductions needed for attainment as 

expeditiously as practicable, is 

appropriate for implementation of the 

PM2.5 NAAQS. We believe that the 

improved ability to model air quality 

impacts of emissions controls allows for 

this approach. 

b. Proposed Options for RACT 

The EPA proposed and requested 

comment on three alternative 

approaches for interpretation of the 

RACT requirement of section 172(c)(1) 

for implementation of the PM2.5

NAAQS. The EPA proposed these 

approaches in order to evaluate which 

method would best ensure that States 

consider and adopt RACT measures for 

stationary sources in a way that is 

consistent with the overarching 

requirement to attain the standards as 

expeditiously as practicable, while 

providing flexibility for States to focus 

regulatory resources on those sources of 

emissions that contribute most to local 

PM2.5 nonattainment. 

Under the first proposed alternative, 

EPA would require States to conduct a 

RACT analysis and to identify and 

require reasonably available controls for 

all affected stationary sources in the 

nonattainment area, comparable to the 

implementation of RACT provided in 

subpart 2 governing implementation of 

the 1-hour ozone NAAQS. Under this 

option, covered sources would be 

required to apply reasonable available 

controls considering technical and 

economic feasibility, and there would 

be no opportunity for States to excuse 

stationary sources from control on the 

basis that the emissions reductions from 

those controls would not be necessary to 

meet RFP requirements or to reach 

attainment. Under this alternative, EPA 

proposed to limit the universe of 

sources for which States must conduct 

a RACT analysis and impose RACT 

controls, by providing an applicability 

threshold based upon the amount of 

emissions potentially emitted by the 

sources. Under this first option, EPA 

requested comment on a number of 

alternative emissions applicability 

thresholds. 

Under the second proposed 

alternative, EPA would require States to 

conduct a RACT analysis and to identify 

reasonably available controls for all 

affected stationary sources. Under this 

option, however, States could thereafter 

determine that RACT does not include 

controls that would not otherwise be 

necessary to meet RFP requirements or 

to attain the PM2.5 NAAQS as 

expeditiously as practicable.23 Under 

this approach, RACT would be 

determined as part of the broader RACM 

analysis and identification of all 

measures—for stationary, mobile, and 

area sources—that are technically and 

economically feasible, and that would 

collectively contribute to advancing the 

attainment date.24 Because RACT and 

RACM are considered together under 

this alternative, we did not propose 

emissions threshold options for 

evaluation of stationary source RACT. In 

addition, consistent with existing 

policies, States would be required to 

evaluate the combined effect of 

reasonably available measures to 

determine whether application of such 

measures could advance the attainment 

date by at least one year.25

The third proposed alternative, EPA’s 

preferred option in the proposal, 

combined the first two options and is 

similar to the RACT approach adopted 

in the final implementation rule for the 

8-hour ozone program. Under the third 

option, EPA would require States to 

conduct a RACT analysis and to require 

reasonably available controls for all 

affected stationary sources in 


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26 In the context of the PM10 NAAQS, EPA has 

concluded that ‘‘advancement of the attainment 

date’’ should mean an advancement of at least one 

calendar year. See State Implementation Plans; 

General Preamble for the Implementation of Title I 

of the CAA Amendments of 1990, 57 FR 12498 

(April 16, 1992). See also Sierra Club v. EPA, 294 

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

nonattainment areas with attainment 

dates more than 5 years from the date 

of designation. For areas with an 

attainment date within 5 years of 

designation (e.g. by April 5, 2010 for 

areas with an effective date for 

designation of April 5, 2005), EPA 

would require RACT as under the 

second proposed alternative, in which 

RACT would be determined as part of 

the broader RACM analysis. For these 

areas, States could determine that RACT 

does not include controls that would 

not otherwise be necessary to meet RFP 

requirements or to attain the PM2.5

NAAQS as expeditiously as practicable. 

The same proposed suboptions with 

respect to the size of sources for 

consideration under the first alternative 

were also included under this 

alternative. 

c. Proposed Approach for RACM 

The EPA proposed and asked for 

comment on one approach for 

interpreting the RACM requirement for 

PM2.5. The EPA based the proposal on 

the approach that we adopted for other 

NAAQS implementation programs. 

Under this approach, a State provides a 

demonstration in its SIP that it adopted 

all reasonably available measures 

needed to meet RFP requirements and to 

attain the standard as expeditiously as 

practicable and that no reasonably 

available additional measures would 

advance the advance the attainment 

date by at least 1 year or would be 

necessary to meet the RFP requirement 

for the area.26

Under section 172(a)(2), the state 

implementation plan must provide for a 

nonattainment area to attain as 

expeditiously as practicable, but no later 

than 5 years after the effective date of 

designation of the area (e.g., no later 

than April 2010 for the final 

designations effective April 2005). The 

statute thus creates a presumption for 

attainment within 5 years of designation 

unless certain statutory criteria are met 

for an extension of the attainment date. 

Under the proposed approach to RACM 

for PM2.5, each State would evaluate 

available measures for sources of PM2.5

or its regulatory precursors in the area 

to determine if reasonable measures 

were needed to meet the RFP 

requirement or to achieve attainment as 

expeditiously as practicable. If modeling 

of all RACM and other state, regional 

and federal measures indicates that the 

State will not be able to demonstrate 

attainment within 5 years after 

designation based upon the severity of 

nonattainment in that area or the 

availability or feasibility of 

implementing controls in that area, then 

the State may request an attainment date 

extension. We proposed that under 

these circumstances, the EPA could 

extend the attainment date for a period 

of 1 to 5 years, when the State shows 

that it will implement all RACT and 

RACM as expeditiously as practicable, 

has met its obligation to address 

intrastate pollution transport from 

sources within its jurisdiction, and still 

needs additional time to attain. 

In the proposed rule, the EPA also 

took comment on the following overall 

steps for implementing the statutory 

requirement for RACM. 

(1) Identification of measures. The 

State would begin the process of 

determining RACM by identifying all 

available control measures for all 

sources of PM2.5 and its precursors in 

the nonattainment area. The RACM can 

apply to mobile sources, area sources, 

and stationary sources. 

(2) Evaluation of measures. After the 

State identifies the universe of available 

measures for the sources in the area, the 

State would evaluate them to determine 

whether implementation of such 

measures is technically and 

economically feasible, and whether the 

measure will contribute to advancing 

the attainment date. 

(3) Adoption of measures. The State 

would adopt all reasonably available 

measures for the area consistent with 

meeting the applicable RFP 

requirements and attaining the NAAQS 

as expeditiously as practicable, in 

accordance with applicable policy and 

guidance for attainment demonstrations. 

We would then approve or disapprove 

the State’s plan through notice and 

comment rulemaking. We also noted 

that in reviewing the State’s selection of 

measures for RACM, or determining that 

certain measures are not RACM, EPA 

may independently supplement the 

rationale of the State or provide an 

alternative reason for reaching the same 

conclusion as the State. 

c. Final Rule 

The EPA carefully considered our 

interpretation of section 172(c)(1) for the 

PM2.5 NAAQS. Because of the variable 

nature of the PM2.5 problem in different 

nonattainment areas, which may require 

States to develop attainment plans that 

address widely disparate circumstances 

(e.g., different source types and mixes, 

different precursors and mixes of 

precursors, and different meteorological 

conditions), we determined that the 

regulations implementing the PM2.5

NAAQS should provide for a great 

degree of flexibility with respect to the 

RACT and RACM controls. 

Selected approach to RACT and 

RACM. The final rule reflects EPA’s 

decision to select option 2 for RACT and 

to require a combined approach to 

RACT and RACM. Under this approach, 

RACT and RACM are those measures 

that a State finds are both reasonably 

available and contribute to attainment 

as expeditiously as practical in the 

specific nonattainment area. 

By definition, measures that are not 

necessary either to meet the RFP 

requirement, or to help the area attain 

the NAAQS as expeditiously as 

practicable, are not required RACT or 

RACM for such area. The EPA believes 

that this approach provides the greatest 

flexibility to a State to tailor its SIP 

control strategy to the needs of a 

particular PM2.5 nonattainment area, but 

it may require the State to conduct a 

more detailed analysis to identify the 

most effective RACT/RACM strategy to 

attain the NAAQS. 

During the comment period, 

commenters raised concerns that this 

approach may be overly burdensome on 

States because of the number of 

potential control measures a State 

would need to consider. Today, we 

clarify that although the State must 

conduct a thorough analysis of 

reasonably available measures, States 

need not analyze every conceivable 

measure, as explained in the guidance 

below. Instead, ‘‘reason’’ should drive 

States identification of potential 

measures, but States should remain 

mindful of the public health risks of 

PM2.5. As long as a State’s analysis is 

sufficiently robust in considering 

potential measures to ensure selection 

of all appropriate RACT and RACM, and 

the State provides a reasoned 

justification for its analytical approach, 

we will consider approving that State’s 

RACT/RACM strategy. 

Guidance on State analysis to identify 

RACT, RACM and appropriate 

attainment date. A State must consider 

RACT and RACM for all of its 

nonattainment areas. However, EPA 

believes that if the State projects that an 

area will attain the standard within 5 

years of designation as a result of 

existing national measures (i.e. 

projected to have a design value of 14.5 

or lower), then the State may conduct a 

limited RACT and RACM analysis that 

does not involve additional air quality 

modeling. A limited analysis of this 

type would involve the review of 

reasonably available measures, the 

estimation of potential emissions 


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27The EPA believes that it is not necessary to 

identify every possible variation of every type of 

control measure, or all possible combinations of 

technologies and measures that would apply to a 

given source or activity if the State has properly 

characterized the potentially available emissions 

reductions and their costs. For example, EPA 

believes that the State can conduct a thorough 

analysis of VMT reduction measures without 

including every possible level or stringency of 

implementation of certain possible measures or 

combinations of measures for reducing VMT, so 

long as those measures would not affect the overall 

assessment of VMT reduction capabilities and the 

associated costs. 

reductions, and the evaluation of the 

time needed to implement these 

measures. If the State could not achieve 

significant emissions reductions during 

2008 due to time needed to implement 

the potential measures or other relevant 

factors, then the State and EPA could 

conclude that there are no further 

reasonably available control measures 

for that area that would advance the 

attainment date by one year or more 

relative to the presumptive outer limit 

for attainment dates, i.e., 5 years from 

designation. In lieu of conducting air 

quality modeling to assess the impact of 

potential RACT and RACM measures, 

States may consider existing modeling 

information to determine the magnitude 

of emissions reductions that could 

significantly affect air quality and 

potentially result in attaining prior to 

2010 (e.g. in 2009 based on 2006–8 air 

quality data). If the State, in 

consultation with EPA, determines from 

this initial, limited RACT and RACM 

analysis that the area may be able to 

advance its attainment date through 

implementation of reasonable measures, 

then the State would conduct a more 

detailed RACT and RACM analysis, 

including appropriate air quality 

modeling analyses, to assess whether it 

can advance the attainment date. 

In general, the combined approach to 

RACT and RACM in the final rule 

includes the following steps: (1) 

Identification of potential measures that 

are reasonable; (2) modeling to identify 

the attainment date that is as 

expeditious as practicable; and (3) 

selection of RACT and RACM. 

Identification of potential measures. 

The State’s review of potential measures 

must be sufficient to identify all 

appropriate RACT and RACM. As stated 

previously, inherent to RACT/RACM is 

the basic requirement that the measure 

be ‘‘reasonable.’’ A State need not 

evaluate measures in its RACM/RACT 

analysis that it determines are 

unreasonable such as measures that are 

‘‘absurd, unenforceable, or impractical’’

or that would cause ‘‘severely disruptive 

socioeconomic impacts, (e.g. gas 

rationing and mandatory source 

shutdowns); such measures are not 

required by the Act. 55 FR 38327. 

As we also stated earlier, a State’s 

RACT/RACM analysis not only involves 

an assessment about what emissions 

sources to control and to what level, but 

also a judgment as to when it is 

reasonable to require a sector to comply 

with a given measure. Accordingly, if 

the State or Federal rules already 

heavily regulate a given sector, it is 

reasonable for the State to first look to 

unregulated parts of the sector for 

RACT/RACM measures, especially, in 

light of costs already realized by the 

regulated sector. A State may conclude 

that it is unreasonable to further 

regulate the industry, or that it is only 

reasonable to impose measures in the 

latter years of the attainment plan. 

Finally, the State should use reason in 

the extent of its efforts to identify 

potential control measures. For 

example, if a review of monitoring data 

and modeling studies indicates that 

reductions in SO2 are much more 

effective in reducing ambient PM2.5 than 

reductions in other pollutants, we 

expect that the State will more 

vigorously identify RACT/RACM 

measures for SO2 than for other 

pollutants. Conversely, if reductions in 

a given pollutant, even in large 

quantities, would have trivial impacts 

on PM2.5, less rigor is needed in the 

State’s assessment of controls for that 

pollutant, because such controls could 

not contribute to advancing the 

attainment date. Likewise, where 

reducing emissions of a pollutant is 

effective in reducing ambient PM2.5, if 

the emissions inventory for that 

pollutant is dominated by a given type 

of emissions source, then it would be 

appropriate to focus the analysis on 

measures for that segment of the 

inventory. No RACT/RACM analysis is 

needed for pollutants that are not 

attainment plan precursors for a 

particular PM2.5 nonattainment area. 

As supporting information for 

identification of RACT and RACM, the 

State ordinarily provides data on 

technologically feasible control 

measures: 

—A list of all emissions source 

categories, sources and activities in 

the nonattainment area (for multiState nonattainment areas, this would 

include source categories, sources and 

activities from all states which make 

up the area) 

—For each source category, source, or 

activity, an inventory of direct PM2.5

and precursor emissions; 

—For each source category, source, or 

activity, a list of technologically 

feasible emission control technologies 

and/or measures 27

—For each technologically feasible 

emission control technology or 

measure, the State should provide the 

following information: (1) The control 

efficiency by pollutant; (2) the 

possible emission reductions by 

pollutant; (3) the estimated cost per 

ton of pollutant reduced; and (4) the 

date by which the technology or 

measure could be reasonably 

implemented. 

Based on this and other relevant 

information, the State will identify the 

reasonable measures (potential RACT 

and RACM) to be included in air quality 

modeling. (At its option, the State may 

prefer not to make a judgment on 

whether certain measures are 

technically and economically feasible, if 

it believes they will not contribute to 

earlier attainment. In that case, the State 

could include those measures in the 

modeling, and later exclude them from 

RACT and RACM by showing that all 

the excluded measures together would 

not advance the attainment date by at 

least 1 year.) As previously mentioned, 

in determining the attainment date that 

is as expeditious as practicable, the 

State should consider impacts on the 

nonattainment area of intrastate 

transport of pollution from sources 

within its jurisdiction, and potential 

reasonable measures to reduce 

emissions from those sources. 

Modeling to determine the attainment 

date that is as expeditious as 

practicable. Second, for purposes of 

determining the attainment date that is 

as expeditious as practicable, the State 

will need to conduct modeling to show 

the combined air quality impact of all of 

the potential measures identified in the 

first step with a modeling analysis for 

the year 2009. A base case scenario for 

the year 2009 would project future air 

quality given implementation of existing 

measures (Federal, State and local). If 

this base case scenario demonstrates 

attainment by 2010, then the State must 

demonstrate why attainment could not 

be achieved in an earlier year. (As noted 

above, given the April 2008 due date for 

SIP submissions, it may be difficult to 

achieve earlier attainment in many 

cases). 

If the base case scenario does not 

demonstrate attainment, then a control 

case scenario (described below) is 

needed to examine whether the 

reasonable, technically and 

economically feasible measures 

identified by the State would result in 

attainment in 2009. The control case 

scenario would add potential SIP 

measures—e.g. potential RACT/RACM, 

plus any candidate intrastate transport 

measures that the State has identified 


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20614 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

and would be feasible to implement by 

that year. States in multi-State 

nonattainment areas are strongly 

encouraged to collaborate on their 

modeling analyses. This modeling, 

along with other information known as 

weight of evidence considerations, 

would inform a judgment as to whether 

reasonable measures could lead to 

attainment of the standards within 5 

years after designation. If the analysis 

does not demonstrate attainment by 

April 2010 (2009 analysis year), then the 

analysis would serve as the technical 

basis for the State to seek an extension 

of the attainment date for that area. 

Further analysis would then be 

necessary and is required to identify the 

specific attainment date. 

The choice of future years to model 

beyond 2010 may vary from area to area. 

Often, modeling potential controls in 

two different future years may be 

necessary to support a judgment that a 

projected attainment year is as 

expeditious as practicable. If the area is 

projected to remain over the standard in 

the early projection year (e.g., 2009) 

despite the emission reductions from 

the modeled control measures, but is 

projected to be well below the standard 

in the later projection year (e.g., 2012), 

interpolation and emission inventory 

analysis could identify an intermediate 

year as the appropriate attainment date. 

There may be cases in which modeling 

a single year is sufficient because 

modeling of all technically and 

economically feasible controls results in 

attainment by a narrow margin in that 

year. 

For many areas, EPA modeling 

analysis for CAIR and other modeling 

analyses that have been performed 

suggest a number of nonattainment 

areas will have a modest amount (in 

some cases only a few tenths of a 

microgram) of needed reductions in 

ambient levels after 2010 to reach 

attainment. For any such area, and for 

areas otherwise expected to attain 

relatively soon after 2010 (for example, 

due to substantial reductions in a 

dominant local source), EPA believes 

that this analysis should be for a year no 

later than 2012. A later date (e.g., 2014) 

may be appropriate for areas with very 

high PM2.5 levels that face difficulty 

attaining within 10 years. 

The EPA believes that it is not 

reasonable to require States to model 

each and every year between 2009 and 

2014 to determine the appropriate 

attainment date. Modeling future year 

inventories is a time consuming and 

resource intensive process. Multiple 

models and pre-processors are needed 

in order to generate year specific 

emissions for the various emissions 

sectors (e.g. mobile, non-road, non-EGU 

point, EGU point, etc.). Because it is not 

reasonable to model every year, a logical 

choice often may be to model a year in 

the middle of the period. As such, we 

recommend modeling an emissions year 

no later than 2012 as the initial 

extension date (which translates to a 

2013 attainment date). If this modeling 

indicates that the area can reach 

attainment by 2012, then the State can 

further analyze emissions and strategies 

to determine if the attainment date can 

be advanced to an earlier year. If the 

modeling indicates that the area cannot 

reach attainment by 2012, then the 

modeling will serve as further 

justification for granting a longer 

attainment date extension (e.g., 

attainment date of 2015 with modeling 

for 2014). In that case, additional 

modeling of 2014 with further emissions 

controls would be required in order to 

show attainment. Again, the State 

should then further analyze emissions 

and strategies to determine if the 

attainment date can be advanced to an 

earlier year between 2012 and 2015. 

Additionally, in the discussion of air 

quality modeling issues in section II.E 

above, we discuss the benefits of 

addressing control strategies for 

multiple pollutants. Part of the 

challenge of multi-pollutant modeling is 

coordinating the future modeling years 

for different pollutants in order to 

minimize the number of required future 

year model runs. As part of the 

requirements of the 8-hour ozone 

implementation rule, States are 

currently working on modeling analyses 

for 2009 and in some cases for 2012 

(serious nonattainment areas). For an 

area that cannot attain the PM2.5

NAAQS by 2010, this may be reason to 

select 2012 as the year to model, so that 

the State could conduct the modeling 

for both ozone and PM2.5 in tandem. 

This would, in some cases, allow the 

pooling of resources (e.g., inventories, 

model runs, etc.) and provide for faster 

development of a PM2.5 attainment 

demonstration. 

It may also be possible for the State 

to look at 2009 and 2014 only. In this 

instance, the State may find sufficient 

data to interpolate results for the years 

in between based on estimated changes 

in emissions. 

We emphasize that when a State 

models later years, that this analysis 

must take into account potential 

controls that the State may have 

determined would not be RACT or 

RACM for an earlier year. For example, 

some measures that are impractical to 

implement by 2009 could be reasonable 

if implemented by 2010, 2011 or 2012. 

Thus, when the State models later years, 

the list of potential controls should be 

expanded to include technically and 

economically feasible measures that can 

be implemented by the analysis year. 

Selection of RACT & RACM. Based on 

this analysis, the State should make 

decisions on RACT, RACM, intrastate 

measures, and the attainment date that 

is as expeditious as practicable. Because 

EPA is defining RACT and RACM as 

only those reasonable, technically and 

economically feasible measures that are 

necessary for attainment as 

expeditiously as practicable, the State 

need not adopt all feasible, reasonable 

measures. The State may exclude those 

reasonable measures that, considered 

collectively, would not advance the 

attainment date. 

Comments and Responses 

Comment: A number of commenters 

generally supported EPA’s second 

proposed alternative to RACT (option 

2). Most of these commenters expressed 

concern that the other options would 

require the imposition of controls 

whether or not they were needed to 

attain the PM2.5 standards as 

expeditiously as practicable. Some State 

and local commenters also urged EPA to 

select option 2 as the best interpretation 

of the RACT requirement for PM2.5

because they believe that it will be the 

most appropriate approach for designing 

attainment strategies for their particular 

nonattainment area or areas. 

Response: The EPA agrees that these 

two points are important considerations. 

After carefully considering the options, 

we concluded that Option 2 was the 

most suitable approach for the PM2.5

NAAQS. Options 1 and 3 do not reduce 

the States’ burden to analyze potential 

control measures as the States would 

still be required to look beyond the 

mandated RACT for reasonably 

available control measures (RACM). 

Moreover, Options 1 and 3 could 

require imposition of controls on some 

sources that would not strictly be 

necessary to attain the NAAQS as 

expeditiously as practicable. Given the 

nature of the PM2.5 nonattainment 

problem, EPA concluded that an 

interpretation that provides the 

maximum flexibility is a better 

approach. 

Comment: Some commenters 

recommended that EPA modify 

proposed option 2 to include a tons-peryear threshold. Under such an 

approach, the States and EPA would 

only require RACT for sources whose 

emissions were above the threshold. 

Most of these comments recommended 

a RACT threshold of 100 tons per year. 

These commenters expressed concern 

that if option 2 were implemented 


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without such a threshold, States would 

be burdened with conducting RACT 

analyses for very small sources or 

source categories with low emissions. 

Response: The EPA believes that 

under the approach chosen for the final 

rule in which RACT is considered to be 

a part of the overall RACM process, it 

would be difficult to define a threshold 

that would apply for all types of sources 

and for all types of control measures in 

all nonattainment areas. It has not been 

common practice under past EPA policy 

to establish or use an emissions 

threshold when considering sources for 

possible emission reductions as part of 

a RACM analysis to show attainment as 

expeditiously as practicable. Indeed, 

many of the control technique 

guidelines for VOC RACT do not 

recommend an emissions threshold. A 

state needing significant emission 

reductions to attain the standards in a 

given area even by 2015 would likely 

conclude that controls should be 

considered on smaller sources. In 

contrast, a State with an area that 

exceeds the standard by only a few 

tenths of a microgram per cubic meter 

may not need to consider controls on 

smaller source to reach attainment as 

expeditiously as practicable. The EPA 

has selected option 2 for interpretation 

of the RACT requirement for PM2.5, in 

part, specifically because that approach 

contemplates that States will conduct an 

appropriate analysis of the spectrum of 

source categories and potential controls 

available. To cut off such analysis at a 

set emissions-based cut point for all 

sources and all areas would undermine 

one of the key benefits of the approach. 

Accordingly, EPA disagrees with 

comments that option 2 should include 

a nationally-defined threshold for the 

size of sources or source categories that 

require RACT analyses. 

Comment: A number of commenters 

supported EPA’s first and third 

proposed alternative approaches to 

RACT (option 1 and option 3). 

Commenters supporting these two 

options used similar reasoning. 

Commenters cited the statutory 

language in section 172(c)(1) requiring 

that the attainment plan provide for ‘‘at 

a minimum’’ the adoption of RACT. 

Accordingly, these commenters argued 

that RACT is an independent, minimum 

requirement of attainment plans 

irrespective of the attainment 

demonstration and that option 2, which 

would not require the adoption of RACT 

for all sources, has no policy or legal 

justification. Other commenters noted 

that option 1 would be much easier to 

implement, because RACT would be 

defined according to technical 

reasonableness and would not hinge on 

complicated determinations involving 

attainment demonstrations. Some 

commenters argued that option 1 

provides for greater equity, because 

similar measures would be required for 

similar sources for all nonattainment 

areas. Finally, some commenters 

believed that it is inherently 

inconsistent to assert that plans have 

met the requirement for attainment ‘‘as 

expeditiously as practicable’’ without 

applying RACT to all major sources. 

Response: The EPA disagrees with 

these comments. The EPA believes that 

option 2 is fully consistent with section 

172(c)(1). Section 172(c)(1) requires that 

attainment plans must provide for the 

implementation of RACM as 

expeditiously as practicable (including 

such reductions in emissions from 

existing sources in the area as may be 

obtained through the adoption, at a 

minimum, of RACT). Contrary to the 

commenters’ assertions, this language 

does not demonstrate that RACT is 

required for all sources, independent of 

RACM and attainment demonstrations. 

Moreover, this provision does not 

require RACT whether or not imposition 

of technology would advance the 

attainment date. Instead, section 

172(c)(1) explicitly provides that RACT 

is included within the definition of 

RACM, and EPA has previously 

determined that the CAA only requires 

such RACM as will provide for 

attainment as expeditiously as 

practicable. (See 57 FR 13498, 13560). 

The courts have deferred to this 

interpretation and concluded that EPA 

interprets RACM as a collection of 

reasonable measures that would 

advance the attainment date. See Sierra 

Club v. EPA, 294 F.3d 155, 162 (D.C. 

Cir. 2002); see also Sierra Club v. EPA, 

314 F.3d 735, 744 (5th Cir. 2002). The 

CAA does not ‘‘compel [ ] a State to 

consider whether any measure is 

‘reasonably available’ without regard to 

whether it would expedite attainment in 

the relevant area.’’ Sierra Club v. EPA, 

294 F.3d at 162. The EPA concludes that 

because section 172(c)(1) establishes 

that RACT is a part of RACM, EPA is 

reasonably applying the same 

interpretation to the RACT requirement 

for PM2.5. The RACT is a part of the 

collection of measures that are 

necessary to reach attainment as 

expeditiously as practicable. It is thus 

directly related to what a specific area 

needs to attain the NAAQS, and States 

need not implement reasonably 

available measures that would not 

advance the attainment date as part of 

the PM2.5 RACT requirement. 

The EPA also finds that option 2 is 

consistent with the statutory language 

providing that a State must apply RACT 

to existing sources, ‘‘at a minimum,’’ to 

meet its requirement to apply RACM. 

We interpret the ‘‘at a minimum’’ clause 

to mean that when a State determines 

that control of a specified existing 

stationary source(s) is necessary to 

attain, the State must apply RACT to 

that source. Further, EPA believes this 

requirement for RACT applies to 

stationary sources as a group, and not to 

each stationary source. 

The EPA finds sound policy reasons 

for choosing option 2. While an 

approach that provided for application 

of the same controls in all areas would 

provide for more equity across areas, 

EPA emphasizes that equity is only one 

of many factors considered by EPA 

when deciding between options 1, 2 and 

3. The EPA believes that it is also 

important to ensure that control 

strategies focus on the most effective 

measures with the greatest possibility 

for significant air quality improvements. 

In addition, while EPA agrees that 

options 1 and 3 could provide for 

greater ease of implementation, this is 

also only one of the factors EPA 

considered when deciding between the 

proposed options. Under option 2, 

States have a greater burden and 

responsibility to identify the local 

strategy that is tailored to their 

particular air quality problem. At the 

same time, the States have the ability to 

identify the sources with the greatest 

impact on nonattainment and to identify 

a sound strategy that achieves 

attainment in the most sensible manner. 

The EPA believes that approaching 

RACT and RACM in this manner is 

consistent with the overall philosophy 

imbedded in the SIP program since its 

inception in the late 1960s and early 

1970s. 

Comment: Some commenters believed 

that the proposed RACM requirement 

was too broad. These commenters 

believed that the requirement to analyze 

the entire ‘‘universe’’ of possible 

measures was too burdensome for 

States. Commenters felt this was 

especially true in light of the lack of 

federally issued CTG and ACT 

documents for PM2.5 and its precursors 

for all potential source categories. 

Response: As explained earlier, States 

should apply ‘‘reason’’ in identifying 

measures to evaluate as potential 

RACM/RACT. We recognize that States 

are implementing the PM2.5 standard for 

the first time, and do not have the long 

history and experience in implementing 

PM2.5 as they have in implementing the 

PM10 and ozone standards. Accordingly, 

we expect that both the States and EPA 

will expend extra effort in developing 

and evaluating attainment plans that 

contain appropriate controls. A number 


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of resources exist to provide States with 

information on potential control 

measure costs and emissions reductions. 

We intend to facilitate the sharing of 

information through a control measure 

website and other efforts, and expect 

that States will develop screening 

methods to reduce the burden of 

analysis. 

Comment: One commenter asserted 

that EPA should not require the analysis 

for, or implementation of, RACT and 

RACM for sources throughout the entire 

nonattainment area, and should permit 

States to focus only on sources located 

in smaller specific ‘‘problem areas’’

within the nonattainment area. 

Response: The EPA designated areas 

nonattainment based upon analysis of 

the geographic area with sources that 

‘‘contribute’’ to the violation of the 

NAAQS in the area, in accordance with 

section 107(d). These designations are 

based upon, among other things, a 

network of monitors that the State and 

EPA previously agreed represented the 

ambient air concentrations throughout 

the area. Additional analysis of 

information during the designation 

process indicated those areas that 

contributed to the violations at the 

violating monitor because of, among 

other things, the amount of emissions in 

such adjoining areas. Accordingly, the 

State in which a nonattainment area is 

located must evaluate the full range of 

sources of PM2.5 and its precursors 

throughout the designated 

nonattainment area during the 

development of the SIP. The EPA agrees 

that there are some nonattainment areas 

where one or a few large emissions 

sources may be causing localized 

concentrations at a monitor that are 

much higher than those within the 

remainder of the nonattainment area. 

For such areas, the nonattainment 

strategy will likely not succeed without 

addressing those sources. The EPA does 

not, however, believe it is acceptable 

that the nonattainment strategy focus 

only on those sources, because 

additional reductions within the 

nonattainment area would still have the 

potential to advance the attainment 

date. Exempting portions of the 

nonattainment area could expose a 

portion of the public residing 

downwind in the area to exposure to 

levels of PM2.5 that exceed the NAAQS 

for longer than necessary, and the health 

detriments from such exposure, merely 

to minimize the impact of having to 

impose control strategies on sources 

upwind. Moreover, to the extent that 

monitoring in one portion of a 

nonattainment area indicates violations 

in multiple portions of the area, a 

strategy that solely focused upon the 

sources in the immediate vicinity of the 

monitor might fail to assure that the 

NAAQS is achieved throughout the 

area. Because NAAQS violations 

generally reflect a combination of 

regional scale, metropolitan scale, and 

local scale impacts, and all three scales 

must be addressed, EPA requires RACT/ 

RACM submittals to address sources 

throughout the nonattainment area. 

Comment: Some commenters agreed 

with EPA’s view that State’s RACM 

analysis must address those measures 

that a State declines to adopt and must 

show whether the combined measures 

would cumulatively advance the 

attainment date by at least 1 year. One 

commenter questioned the legal basis 

for EPA’s determination that the only 

controls necessary to attain the PM2.5

NAAQS as expeditiously as practicable 

are those that would cumulatively 

advance an area’s projected attainment 

date by at least one calendar year. The 

commenter suggested that control 

measures that would advance 

attainment by a smaller increment 

‘‘would meet the criteria endorsed in 

Sierra Club [Sierra Club v. EPA, 294 

F.3d 155 (D.C. Cir 2002)] by 

‘expedit[ing] attainment in the relevant 

area.’ ’’

Response: The EPA has consistently 

interpreted RACM as a collection of 

measures that would advance the 

attainment date by at least 1 year, and 

the courts have determined that the 

statutory RACM requirement is 

ambiguous and deferred to EPA’s 

interpretation of the requirement. See 

Sierra Club v. EPA, 314 F.3d 735, 744 

(5th Cir. 2002); see also Sierra Club v. 

EPA, 294 F.3d, 155 162 (D.C. Cir. 2002). 

Contrary to the commenter’s suggestion, 

the court in Sierra Club v. EPA, did not 

endorse specific criteria for identifying 

control measures that expedite 

attainment, but instead deferred to 

EPA’s interpretation of an ambiguous 

statutory term. The courts deferred to 

EPA’s interpretation after reviewing 

EPA’s approval of State SIP 

submissions. The EPA conducts such 

reviews consistent with its 

determination that the CAA only 

requires such RACM as will provide for 

attainment as expeditiously as 

practicable, and its belief that it would 

be unreasonable to require 

implementation of measures that would 

not in fact advance attainment. See 57 

FR 13498, 13560 (April 15, 1992); see 

also 44 FR 20372, 20374 (April 4, 1979). 

In considering whether a collection of 

measures would advance the attainment 

date of an area, EPA has previously 

interpreted the phrase ‘‘advance the 

attainment date’’ as meaning that the 

attainment date would be advanced by 

at least 1 year. See e.g., 66 FR 57160, 

57182 (Nov. 14, 2001) (approval of 

Houston SIP); 66 FR 586 (Jan 3. 2001) 

(approval of DC area SIP). Further, 

EPA’s use of a one-year increment in 

determining whether a collection of 

measures would advance the attainment 

date is reasonable and consistent with 

the fact that all areas will be designing 

attainment demonstrations for the 

annual PM2.5 standard. Section 

172(a)(2)(C) statute uses 1 year as the 

increment by which attainment date 

extensions can be granted. Thus, 

requiring evaluation of whether control 

measures would advance attainment by 

an increment of 1 year is a reasonable 

approach for the PM2.5 NAAQS. 

Comment: Some commenters 

recommended that EPA consider not 

requiring a RACM analysis for areas 

projected to attain the standards within 

5 years of designation, i.e., by April 

2010 for the areas currently designated 

nonattainment. One commenter 

suggested that practical considerations 

would make it impossible for any State 

projected to attain by 2010 to advance 

the attainment date by a year. This 

commenter noted that because measures 

to provide for attainment by 2010 must 

be implemented by the beginning of 

2009, and SIPs are not submitted until 

April 2008, it would impossible to 

advance the implementation of 

measures by 1 year (that is, the 

beginning of 2008). 

Response: The EPA generally agrees 

that given the time constraints it will be 

difficult for States with areas currently 

designated nonattainment to devise, 

adopt, and implement RACM measures 

to advance the attainment date before 

2010. At the same time, however, we 

note that nothing precludes States from 

taking early action and we encourage 

States to take actions to reduce PM2.5

concentrations where feasible even 

before the SIPs are submitted. RACM is 

required by the CAA and thus EPA 

cannot waive the requirement for the 

analysis. At the same time, EPA 

recognizes that a streamlined analysis 

may be appropriate given the short time 

periods involved. 

3. Observations and Considerations in 

Determining RACT and RACM 

a. Background 

The preamble to the proposed rule 

included a discussion of general 

considerations for RACT (70 FR 66020 

and 66021, latter part of section III.I.6) 

and RACM (70 FR 66028, section 

III.1.15). The preamble to the final rule 

retains this discussion with some 

modifications and restructuring to 


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28For example, see past EPA guidance on PM2.5

control technologies: Stationary Source Control 

Techniques Document for Fine Particulate Matter 

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

Planning and Standards, October 1998. 

reflect the combined approach to RACT 

and RACM 

b. Final Rule 

General considerations. Once the 

State has identified measures and 

technologies that are available for 

implementation in the nonattainment 

area, then it must evaluate those 

measures to determine whether 

implementation of such measures are 

reasonable, and would collectively 

advance attainment. Many of the factors 

that the State should take into 

consideration in determining whether a 

measure is ‘‘reasonable’’ are related to 

the measure’s technical and economic 

feasibility. Since RACM applies to area 

and mobile sources as well as stationary 

sources, the State should consider other 

factors as well in conducting its RACM 

analysis. For example, in many cases 

obtaining emissions reductions from 

area and mobile sources is achieved not 

by adding control technology to a 

specific emissions source, but by 

reducing the level of activity of a fleet 

of vehicles or by modifying a type of 

commercial process. In these situations, 

the State should also consider local 

circumstances such as infrastructure, 

population, or workforce and the time 

needed to implement the measure in 

light of the attainment date. 

The EPA believes that while areas 

projected to attain within 5 years of 

designation as a result of existing 

national measures should still be 

required to conduct a RACT and RACM 

analysis, such areas may be able to 

conduct a limited RACT and RACM 

analysis that does not involve additional 

air quality modeling. A limited analysis 

of this type could involve the review of 

available reasonable measures, the 

estimation of potential emissions 

reductions, and the evaluation of the 

time needed to implement these 

measures. If the State could not achieve 

significant emissions reductions by the 

beginning of 2008 due to time needed to 

implement reasonable measures or other 

factors, then it could be concluded that 

reasonably available local measures 

would not advance the attainment date. 

In lieu of conducting air quality 

modeling to assess the impact of 

potential RACT and RACM measures, 

existing modeling information could be 

considered in determining the 

magnitude of emissions reductions that 

could significantly affect air quality and 

potentially result in earlier attainment. 

If the State, in consultation with EPA, 

determines from this initial, more 

limited RACT and RACM analysis that 

the area may be able to advance its 

attainment date through implementation 

of reasonable measures, then the State 

would conduct a more detailed RACT 

and RACM analysis. 

Observations on control 

opportunities. The implementation of 

the PM2.5 NAAQS is in its initial stages, 

and many of the designated PM2.5

nonattainment areas are not current or 

former PM10 nonattainment areas. Thus, 

some existing stationary sources in 

these areas may currently be 

uncontrolled or undercontrolled for 

PM2.5 or PM2.5 precursors. Further, to 

this point in time, emissions controls for 

existing sources in these areas may have 

focused primarily on particulate matter 

that is filterable at stack temperatures 

and thus may not adequately control 

condensable emissions. In addition, 

States should bear in mind that the 

controlled sources may have installed 

emission controls 15 years ago or more, 

and there may now be cost-effective 

opportunities available to reduce 

emissions further through more 

comprehensive and improved emissions 

control technologies, or through 

production process changes that are 

inherently lower in emissions. 

Moreover, improved monitoring 

methods may enhance the ability of 

sources to maintain the effectiveness of 

installed emissions controls and to 

reduce emissions by detecting 

equipment failures more quickly. For 

example, State imposition of 

requirements for more frequent 

monitoring (e.g., continuous opacity 

monitors, PM continuous emissions 

monitors, etc.) may provide greater 

assurance of source compliance and 

quicker correction of inadvertent upset 

emissions conditions than existing 

approaches. 

Even in former or current PM10

nonattainment areas, existing 

requirements for controlling direct PM 

emissions (e.g., with a baghouse or 

electrostatic precipitator) may not have 

been revised significantly since the 

1970’s. When EPA established the PM10

standards in 1987, we stated in the 

preamble that it was reasonable to 

assume that control technology that 

represented RACT and RACM for total 

suspended particulates (TSP) should 

satisfy the requirement for RACT and 

RACM for PM10. 52 FR 24672 (July 1, 

1987). The basis for EPA’s belief was 

that controls for PM10 and TSP would 

both focus on reducing coarse 

particulate matter, and specifically that 

fraction of particulate matter that is 

solid (rather than gaseous or 

condensable) at typical stack 

temperatures. However, emission 

controls to capture coarse particles in 

some cases may be less effective in 

controlling PM2.5. For this reason, there 

may be significant opportunities for 

sources to upgrade existing control 

technologies 28 and compliance 

monitoring methods to address direct 

PM emissions contributing to fine 

particulate matter levels with 

technologies that have advanced 

significantly over the past 15 years. 

Precursor Controls. It will be 

important for States to conduct RACT 

and RACM determinations for stationary 

sources of PM2.5 precursors as well as 

direct PM2.5 emissions although, as 

noted above, the known atmospheric 

chemistry of the area may dictate the 

necessary rigor of this analysis. A 

significant fraction of PM2.5 mass in 

most areas violating the standards is 

attributed to secondarily-formed 

components such as sulfate, nitrate, and 

some organic PM, and EPA believes that 

certain stationary sources of precursors 

of these components in nonattainment 

areas currently may be poorly 

controlled. Accordingly, to address 

these precursors, States should review 

existing sources for emission controls or 

process changes that could be 

reasonably implemented to reduce 

emissions from activities such as fuel 

combustion, industrial processes, and 

solvent usage. 

Multi-State Nonattainment Areas. 

States in multi-State nonattainment 

areas will need to consult with each 

other on appropriate level of RACT and 

RACM for that area. We anticipate that 

States may decide upon RACT and 

RACM controls that differ from State to 

State, based upon the State’s 

determination of the most effective 

strategies given the relevant mixture of 

sources and potential controls in the 

relevant nonattainment areas. So long as 

each State can adequately demonstrate 

that its chosen RACT and RACM 

approach will provide for meeting RFP 

requirements and for attainment of the 

NAAQS as expeditiously as practicable 

for the nonattainment area at issue, we 

anticipate approving plans that may 

elect to control a somewhat different 

mix of sources or to implement 

somewhat different controls as RACT 

and RACM. Nevertheless, States should 

consider RACT and RACM measures 

developed for other areas or other 

States. EPA may consider such 

measures in assessing the approvability 

of a State’s SIP. 

c. Comments and Responses 

Comment: In the proposed rule, EPA 

indicated that States could consider the 

‘‘social acceptability’’ of measures as a 


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29Stationary Source Control Techniques 

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

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

Standards, October 1998. See also: Controlling SO2

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

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

November 2000. 

factor in the determination of what 

constitutes RACM in a given area. A 

number of commenters recommended 

that EPA eliminate use of this factor. 

Some commenters questioned whether 

States or EPA had the legal authority to 

exclude measures from consideration 

based on social acceptability or 

popularity, if the measures are 

technically and economically available, 

and are needed to attain the NAAQS for 

protection of public health. Others 

expressed concerns that inclusion of 

such a factor would inevitably result in 

the elimination of controls for area and 

mobile sources and for this reason 

would unfairly focus emissions 

reduction strategies on industrial 

sources of PM2.5 and precursors. 

Response: The EPA believes that in 

developing RACM measures, it is 

important that States not rely unduly on 

measures that would be very difficult to 

enforce in practice. We discourage 

States from relying on measures that on 

paper may seem reasonably available 

but in practice might fail to achieve 

benefits due to the problems and costs 

of effectively enforcing these measures. 

However, we recognize that the CAA 

does not identify ‘‘social acceptability’’

as a factor in the definition of what may 

constitute RACT or RACM, and more 

generally the CAA does not establish a 

preference for measures that affect 

industrial sources instead of the general 

public and are therefore more likely to 

be ‘‘socially acceptable.’’ Therefore, 

given the concerns raised by 

commenters that establishment of 

‘‘social acceptability’’ as a factor in the 

RACM analysis is without basis in the 

CAA and might result in inappropriate 

skewing of control strategies, we have 

removed this term from the final rule. 

We reiterate, however, that capability of 

effective implementation and 

enforcement are relevant considerations 

in the RACM analysis, even though 

public ‘‘unpopularity’’ is not. Moreover, 

in assessing the efficacy of measures 

and the credit they should be given in 

the context of attainment 

demonstrations or RFP calculations, 

EPA believes that such considerations 

are important. 

4. What Factors Should States Consider 

in Determining Whether an Available 

Control Technology or Measure Is 

Technically Feasible? 

a. Background 

The following provides guidance for 

States to consider in determining 

whether an available control technology 

is technologically feasible. 

b. Final Rule 

The technological feasibility of 

applying an emission reduction method 

to a particular source should consider 

factors such as the source’s process and 

operating procedures, raw materials, 

physical plant layout, and any other 

environmental impacts such as water 

pollution, waste disposal, and energy 

requirements. For example, the process, 

operating procedures, and raw materials 

used by a source can affect the 

feasibility of implementing process 

changes that reduce emissions and the 

selection of add-on emission control 

equipment. The operation and longevity 

of control equipment can be 

significantly influenced by the raw 

materials used and the process to which 

it is applied. The feasibility of 

modifying processes or applying control 

equipment also can be influenced by the 

physical layout of the particular plant. 

The space available in which to 

implement such changes may limit the 

choices and will also affect the costs of 

control. 

Reducing air emissions may not 

justify adversely affecting other 

resources by increasing pollution in 

bodies of water, creating additional 

solid waste disposal problems or 

creating excessive energy demands. An 

otherwise available control technology 

may not be reasonable if these other 

environmental impacts cannot 

reasonably be mitigated. For analytic 

purposes, a State may consider a PM2.5

control measure technologically 

infeasible if, considering the availability 

(and cost) of mitigating adverse impacts 

of that control on other pollution media, 

the control would not, in the State’s 

reasoned judgment, provide a net 

benefit to public health and the 

environment. However, in many past 

situations, States and owners of existing 

sources have adopted PM2.5 control 

technologies with known energy 

penalties and some adverse effects on 

other media, based on the reasoned 

judgment that installation of such 

technology would result in a net benefit 

to public health and the environment. 

States should consider this in 

determining technical feasibility. The 

costs of preventing adverse water, solid 

waste and energy impacts should be 

included in assessing the economic 

feasibility of the PM2.5 control 

technology. 

One particular cross-media issue 

relates to concentrated animal feeding 

operations (CAFOs). Should a State 

determine that reductions of direct 

PM2.5 or PM2.5 precursors from CAFOs 

are necessary for attainment in a 

nonattainment area, EPA strongly 

suggests that the State address these 

reductions from a cross-media 

perspective. Since 2003, EPA and many 

stakeholders have been interested in 

developing a framework to enable 

CAFOs to pursue superior 

environmental performance across all 

media. We are aware that today some 

CAFOs voluntarily conduct whole-farm 

audits to evaluate releases of pollutants 

to all media through Environmental 

Management Systems, self-assessment 

tools, performance track, ISO 14001 

certification, and State-approved trade 

offs in meeting regulatory thresholds 

between air and water that accomplish 

the best overall level of environmental 

protection given State and local 

conditions. The EPA continues to 

believe the development of new and 

emerging technologies offers the 

potential to achieve equivalent or 

greater pollutant reductions than 

achieved solely by effluent guidelines 

and standards. Many of these are 

superior from a multimedia perspective, 

and EPA would like to encourage 

superior multimedia solutions. SIPs 

which need to address ammonia may 

provide a unique opportunity to 

encourage multimedia approaches at 

CAFOs. For example, the addition of 

animal by-products provides a valuable 

source of nutrients for crops, improves 

soil structure which enhances soil 

permeability, and adds valuable organic 

matter that improves soil health. 

However, inappropriate application can 

lead to air and water quality concerns or 

the improvement of one media at the 

cost of another. Optimal application 

technologies and rates reduce potential 

air and water quality standards 

violations. The EPA does not want to 

discourage approaches that are superior 

from a cross media perspective. 

The EPA recommends that States 

evaluate alternative approaches to 

reducing emissions of particulate matter 

by reviewing existing EPA guidance 29

and other sources of control technology 

information. The EPA’s 1998 guidance 

presents information on topics such as 

the design, operation and maintenance 

of general particulate matter control 

systems such as electrostatic 

precipitators, fabric filters, and wet 

scrubbers. The filterable particulate 

matter collection efficiency of each 

system is discussed as a function of 

particle size. The guidance document 

also provides information concerning 


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30See EPA’s Web site for more information: 

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

31EPA Air Pollution Control Cost Manual—Sixth 

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

Quality Planning and Standards, Research Triangle 

Park, NC, Jan 2002. 

32See: U.S. EPA 2006. Regulatory Impact 

Analysis for the Particulate Matter National 

Ambient Air Quality Standards. Air Benefits and 

Cost Group, Office of Air Quality Planning and 

Standards, Research Triangle Park, NC, October 6, 

2006. Appendix A provides an analysis of estimated 

benefits and costs of attaining the 1997 PM NAAQS 

standards in 2015. 

other relevant considerations such as 

energy and environmental 

considerations, procedures for 

estimating costs of particulate matter 

control equipment, and evaluation of 

secondary environmental impacts. 

Because control technologies and 

monitoring approaches are constantly 

being improved, the State should also 

consider more updated or advanced 

technologies not referenced in this 1998 

guidance when conducting a RACT 

determination. Emissions reductions 

may also be achieved through the 

application of monitoring and 

maintenance programs that use critical 

process and control parameters to verify 

that emission controls are operated and 

maintained so that they more 

continuously achieve the level of 

control that they were designed to 

achieve.30

c. Comments and Responses 

Comment: One commenter noted that 

the guidance for ‘‘technical feasibility’’

implies that States look at individual 

sources with a BACT-like case-by-case 

analysis. The commenter recommended 

that source owners conduct such a sitespecific analysis and submit the 

analysis to the State through the 

permitting process. 

Response: While the analytical 

analysis to identify RACT is similar to 

BACT, as noted above, EPA in the past 

has issued CTGs that describe the 

presumptive norm for RACT controls for 

a given industry, but that allow for caseby-case considerations for a given 

source. Where States wished to require 

source owners to conduct such a sitespecific analysis as part of the control 

technology review, EPA supports this 

type of process. On the other hand, EPA 

does not believe it would be appropriate 

to require all RACT-eligible sources to 

conduct such an analysis, given that 

States have the primary responsibility 

for identifying and analyzing measures 

for such sources. 

5. What Factors Should States Consider 

in Determining Whether an Available 

Control Technology or Measure Is 

Economically Feasible? 

a. Background 

The follow provides guidance for 

States to consider in determining 

whether an available control technology 

is economically feasible for purposes of 

identifying reasonably available control 

measures. This guidance is slightly 

modified from our proposal. 

b. Final Rule 

Economic feasibility encompasses 

considerations such as whether the cost 

of a potential measure is reasonable 

considering attainment needs of the area 

and the costs of other measures, and 

whether the cost of a measure is 

reasonable for the regulated entity to 

bear, in light of benefits. 

While many States generally establish 

RACT requirements for a category of 

sources, the Act does not require the 

same level of control on all sources in 

a category, nor does the Act require that 

each source be controlled individually. 

Similar sources may have different 

marginal costs, profit margins and 

abilities to pass costs through to the 

consumer. These factors are appropriate 

to consider in determining whether a 

given level of control is appropriate for 

an individual source or category of 

sources. Accordingly, there is no 

presumption that a given source must 

bear a cost similar to any other source. 

States should consider the capital 

costs, annualized costs, cost 

effectiveness of an emissions reduction 

technology, and effects on the local 

economy in determining whether a 

potential control measure is reasonable 

for an area or State. One available 

reference for calculating costs is the 

EPA Air Pollution Control Cost 

Manual,31 which describes the 

procedures EPA uses for determining 

these costs for stationary sources. The 

above costs should be determined for all 

technologically feasible emission 

reduction options if such measure is 

inherently ‘‘reasonably available’’ (e.g., 

not absurd or clearly impractical). States 

may give substantial weight to cost 

effectiveness in evaluating the economic 

feasibility of an emission reduction 

technology. The cost effectiveness of a 

technology is its annualized cost ($/ 

year) divided by the emissions reduced 

(i.e., tons/year) which yields a cost per 

amount of emission reduction ($/ton). 

Cost effectiveness provides a value for 

each emission reduction option that is 

comparable with other options and 

other facilities. Where multiple control 

options exist for a given source or 

source category, States should consider 

both the cost effectiveness (dollars per 

ton) of each option, and the incremental 

cost effectiveness per ton between the 

options (incremental increase in cost 

between options divided by the 

incremental tons reduced). 

In determining whether a given 

measure is reasonable, States may 

consider costs per ton of other measures 

previously employed to reduce that 

pollutant, but similar costs are not 

conclusive. As discussed above, States 

may evaluate equity considerations in 

weighing the economic feasibility of 

imposing a measure on a given source 

or source category. 

We anticipate that States may decide 

upon RACT and RACM controls that 

differ from State to State, based on the 

State’s determination of the most 

effective strategies given the relevant 

mixture of sources and potential 

controls in the relevant nonattainment 

areas, and differences in the difficulty of 

reaching attainment. 

In considering what level of control is 

reasonable, EPA is not proposing a fixed 

dollar per ton cost threshold for RACT, 

consistent with the views of multiple 

commenters. Areas with more serious 

air quality problems typically will need 

to obtain greater levels of emissions 

reductions from local sources than areas 

with less serious problems. Where 

essential reductions are more difficult to 

achieve (e.g., because many sources are 

already controlled), the cost per ton of 

control may necessarily be higher. 

It is not appropriate to assume that 

the same cost per ton range is 

reasonable for direct PM2.5 and different 

precursors, because an equal amount of 

emission reduction in different 

pollutants has a different impact on 

PM2.5 ambient levels. For example, in a 

given nonattainment area, reductions of 

direct PM2.5 emissions may prove more 

expensive than reductions of NOX

emissions, but the resulting benefits of 

reductions of direct PM2.5 might warrant 

the higher costs. A State should 

consider this differential impact on 

ambient PM2.5 in considering RACT for 

controlling different pollutants. During 

the SIP process, States and regional 

planning organizations typically 

conduct sensitivity modeling that can 

provide this information. Also, the PM 

NAAQS RIA provides information on 

the differential impact of PM2.5 and PM 

precursor reductions on ambient PM2.5

levels in various areas.32

One of the factors that could affect 

estimated compliance costs of an 

emission reduction measure is the 

timing of its implementation. 

Hypothetically, if a short compliance 

period were contemplated for a set of 

sources, and if the short compliance 


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33There are a number of sources of information 

on technologies for reducing emissions of PM2.5 and 

its precursors. Links are provided to a number of 

national, state and local air quality agency sites 

from EPA’s PM2.5 Web site: http://www.epa.gov/ 

pm/measures.html. 

period resulted in high demand for a 

limited supply of labor or other 

resources, compliance costs could be 

higher than if the same measure were 

implemented by a later compliance 

date. In such a case it may be reasonable 

for the State to find that the measure is 

reasonable only if implemented by the 

later date. 

If a source contends that a sourcespecific RACT level should be 

established because it cannot afford the 

technology that appears to be RACT for 

other sources in its source category, the 

source can support its claim with such 

information as: 

—Fixed and variable production costs 

($/unit) 

—Product supply and demand 

elasticity, 

—Product prices (cost absorption vs. 

cost pass-through), 

—Expected costs incurred by 

competitors, 

—Company profits once the technology 

or measure is in operation 

(considering the annualized costs and 

the marginal costs of alternative 

technologies and measures), 

—Employment costs, and 

—Any other unique factor(s) particular 

to the individual source. 

Finally, the EPA clarifies that if the 

State demonstrates through economic 

analysis that the imposition of the 

measure would cause unacceptable 

economic disruption for the local 

economy, that is, a plant shutdown or 

a severe curtailment in plant 

employment or output, a State may 

reject the measure as not reasonable to 

reach attainment as expeditiously as 

practicable. 

c. Comments and Responses 

Comment: Some commenters agreed 

with EPA’s proposal not to establish 

presumptive cost-effectiveness 

thresholds. 

Response: The EPA agrees with the 

commenters. 

Comment: A number of commenters 

expressed concerns over the references 

to health benefits as a consideration in 

whether measures are technically or 

economically available. Some 

commenters believed this is a 

consideration not authorized by the 

CAA. Others believed that consideration 

of benefits, in combination with EPA’s 

estimates of benefits per ton, would 

have the effect of converting RACT to 

more stringent LAER levels. Some 

commenters expressed concerns 

whether States had the resources or 

expertise to conduct cost-benefit 

analyses for this purpose. 

Response: The EPA wishes to clarify 

that the reference to health benefits does 

not mean that a cost-benefit, or a 

detailed health benefits assessment, is a 

necessary part of a control strategy 

demonstration. We also wish to clarify 

that EPA is not requiring that the costs 

of all technologies and measures for 

PM2.5 and precursors be deemed 

acceptable at any dollar/ton levels at or 

below the calculated monetized benefits 

per ton of reduction. We do, however, 

continue to believe that the significant 

benefits associated with PM2.5 ambient 

reductions is a relevant consideration in 

control strategy development. The EPA 

disagrees that this limited consideration 

of benefits would convert the RACT 

process to the equivalent of LAER. 

Comment: One commenter objected to 

EPA’s proposed requirement that States 

consider competitive factors such as 

production costs, demand elasticity, 

product prices, and cost incurred by 

competitors in the determination of 

RACT. The commenter believed that 

this information is generally not 

accessible to States or industrial facility 

owners, and is not necessary for a RACT 

determination. 

Response: The EPA generally 

disagrees that this type of information is 

unavailable. For example, EPA 

calculates or reviews this type of data 

on a regular basis as part of our work on 

MACT, NSPS, and other emissions 

standards. A document that describes 

these types of analyses and the data 

used to prepare them is the OAQPS 

Economic Resource Manual found at 

http://www.epa.gov/ttn/ecas/ 

analguid.html. EPA believes that this 

issue is most relevant to category-wide 

RACT rules where a source seeks a caseby-case exemption. Further, EPA 

believes most RACT determinations will 

be developed through case-by-case 

analyses rather than rules affecting 

entire source categories. Accordingly, 

this analysis likely will be relevant in 

few cases. 

6. What Specific Source Categories and 

Control Measures Should a State 

Evaluate When Determining RACT and 

RACM for a Nonattainment Area? 

a. Background 

Section 172 does not provide a 

specific list of source categories and 

control measures that must be evaluated 

for RACT and RACM for PM2.5. 

However, section 172(c)(3) indicates 

that the attainment plan must include a 

‘‘comprehensive, accurate, current, 

inventory of actual emissions from all 

sources of the relevant pollutant.’’ This 

indicates that States should look 

broadly at the different types of sources 

in the nonattainment area. We recognize 

that PM2.5 is a new NAAQS without a 

long history of implementation as with 

ozone. Therefore, we included a list of 

potential RACM measures in the 

preamble to the proposed rule, based 

upon a review of information about the 

contribution of various sources to 

emissions inventories and a review of 

potential control measures for such 

sources. We requested comment on the 

specific sources and potential control 

measures recommended for RACM 

analysis on this list. Based on comments 

received and additional information 

available to EPA since the proposal, we 

have made some changes to the list. We 

also refer to this list of potential ‘‘RACT 

and RACM’’ measures for the combined 

approach to RACT and RACM in the 

final rule. 

In the preamble to the proposed rule, 

EPA indicated that due to the short time 

available, it does not plan to develop 

new control techniques guidance (CTG) 

or ACT documents specifically for 

purposes of PM2.5 implementation. The 

EPA indicated that other information 

was available on control technologies, 

and EPA also indicated its intention to 

maintain an updated list of references 

for new PM2.5 control technology 

information. 

b. Final Rule 

Emission reduction measures 

constituting RACM should be 

determined on an area-by-area basis. We 

believe that a State should consider 

each of the measures listed in this 

section to determine if each measure is 

reasonably available in the applicable 

nonattainment area. However, we do not 

presume that each of these measures is 

reasonably available in each 

nonattainment area. 

We recommend that each State use 

the list of source categories in this 

section as a starting point for identifying 

potentially available control strategies 

(regulatory and voluntary) for a 

nonattainment area. States are 

encouraged and expected to add other 

potentially available measures to the list 

based on its knowledge of the particular 

universe of emissions sources in the 

area and comments from the general 

public. We expect that, depending on 

the potential measure being analyzed, 

the State’s degree of evaluation will vary 

as appropriate. Detailed information on 

emission control technologies is 

available from a number of sources.33

The EPA intends to maintain a website 

with links to sources of information for 


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34See Clean School Bus USA program at http:// 

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

Should Know About Diesel Exhaust and School Bus 

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

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

35See EPA’s voluntary diesel retrofit program 

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

overfleetowner.htm. 

36See EPA’s voluntary diesel retrofit program 

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

idling.htm. 

37See EPA’s Web site on transportation control 

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

traqtcms.htm. 

38See EPA’s Web site on nonroad engines, 

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

otaq/nonroad.htm. 

39Fuels adopted in SIPs must be consistent with 

the Energy Policy Act of 2005 and EPA guidance 

on SIP-approved boutique fuels at 71 FR 78192 

(December 28, 2006). 

controlling emissions of direct 

particulate matter and PM precursors. 

As discussed in section II.J.5. above, 

EPA recognizes that control technology 

guidance for certain source categories 

has not been updated for many years. 

Section 183(c) of the CAA, which 

addresses control technologies to 

address ozone nonattainment problems, 

requires EPA to ‘‘revise and update such 

documents as the Administrator 

determines necessary.’’ As new or 

updated information becomes available 

States should consider the new 

information in their RACT 

determinations. A State should consider 

the new information in any RACT 

determinations or certifications that 

have not been issued by the State as of 

the time such updated information 

becomes available. 

Stationary Source Measures 

—Stationary diesel engine retrofit, 

rebuild or replacement, with 

catalyzed particle filter 

—New or upgraded emission control 

requirements for direct PM2.5

emissions at stationary sources (e.g., 

installation or improved performance 

of control devices such as a baghouse 

or electrostatic precipitator; revised 

opacity standard; improved 

compliance monitoring methods) 

—Improved capture of particulate 

emissions to increase the amount of 

PM2.5 ducted to control devices, and 

to minimize the amount of PM2.5

emitted to the atmosphere, for 

example, through roof monitors 

—New or upgraded emission controls 

for PM2.5 precursors at stationary 

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

or dry scrubbers, or reduced sulfur 

content in fuel; desulfurization of 

coke oven gas at coke ovens; 

improved sulfur recovery at refineries; 

increasing the recovery efficiency at 

sulfuric acid plants) 

—Energy efficiency measures to reduce 

fuel consumption and associated 

pollutant emissions (either from local 

sources or distant power providers) 

—Measures to reduce fugitive dust from 

industrial sites 

Mobile Source Measures 

—Onroad diesel engine retrofits for 

school buses,34 trucks and transit 

buses using EPA-verified technologies 

—Nonroad diesel engine retrofit, rebuild 

or replacement, with catalyzed 

particle filter 35

—Diesel idling programs for trucks, 

locomotive, and other mobile 

sources 36

—Transportation control measures 

(including those listed in section 

108(f) of the CAA as well as other 

TCMs), as well as other transportation 

demand management and 

transportation systems management 

strategies 37

—Programs to reduce emissions or 

accelerate retirement of high emitting 

vehicles, boats, and lawn and garden 

equipment 

—Emissions testing and repair/ 

maintenance programs for onroad 

vehicles 

—Emissions testing and repair/ 

maintenance programs for nonroad 

heavy-duty vehicles and equipment 38

—Programs to expand use of clean 

burning fuels 39

—Low emissions specifications for 

equipment or fuel used for large 

construction contracts, industrial 

facilities, ship yards, airports, and 

public or private vehicle fleets 

—Opacity or other emissions standards 

for ‘‘gross-emitting’’ diesel equipment 

or vessels 

Area Source Measures 

—New open burning regulations and/or 

measures to improve program 

effectiveness such as programs to 

reduce or eliminate burning of land 

clearing vegetation 

—Programs to reduce emissions from 

woodstoves and fireplaces including 

outreach programs, curtailments 

during days with expected high 

ambient levels of PM2.5, and programs 

to encourage replacement of 

woodstoves when houses are sold 

—Controls on emissions from 

charbroiling or other commercial 

cooking operations 

—Reduced solvent usage or solvent 

substitution (particularly for organic 

compounds with 7 carbon atoms or 

more, such as toluene, xylene, and 

trimethyl benzene) 

Category-Specific Guidelines on 

innovative approaches. The EPA has 

issued a number of category specific 

guidelines on approaches to taking into 

account innovative approaches to 

emissions reductions for purposes of 

SIPs. Categories currently covered by 

these guidelines include: (1) Electricsector Energy Efficiency and Renewable 

Energy Measures; (2) Long Duration 

Switch Yard Locomotive Idling; (3) 

Long Duration Truck Idling; (4) Clean 

Diesel Combustion Technology; and (5) 

Commuter Choice Programs. See http:// 

www.epa.gov/ttn/airinnovations/ 

measure_specific.html. 

c. Comments and Responses 

Comment: Some commenters 

recommended that EPA provide new 

CTGs or other control technology review 

documents for purposes of assisting 

States to address PM2.5 and its 

precursors, because the information in 

some current documents is out-dated. 

Response: The EPA recognizes that 

issuance of new or updated CTGs 

specifically tailored for PM2.5 would be 

useful. Unfortunately, limitations on 

time and resources preclude EPA from 

developing such CTGs in advance of the 

SIP submission date. The EPA cannot 

delay the statutorily specified outer date 

for SIP submission. However, EPA 

believes that there are already many 

sources of information and guidance on 

key source categories. To the extent that 

States need to examine potential control 

measures for sources never addressed 

before in any area or other context for 

a previous NAAQS, EPA anticipates that 

it will work closely with States during 

the process of plan development and 

approval to ensure an appropriate 

approach. 

Comment: A number of commenters 

expressed concerns with references to 

the STAPPA and ALAPCO Menu of 

Options document. Some commenters 

believed that this document must be 

subject to formal review and comment 

to ensure appropriate stakeholder input. 

Response: The language in the final 

preamble has been changed to refer to 

a Web site EPA maintains that provides 

access to a variety of information 

sources regarding control technologies 

that may be useful to States to consider 

in developing their PM2.5 SIPs. These 

links include evaluations developed by 

government and nongovernment 

organizations. One such source with 

potentially useful information is the 

STAPPA and ALAPCO Menu of 

Options. However, EPA is not 

specifically endorsing any of the 

specific evaluations as being 

appropriate in any specific situation. 

Rather, we think documents such as the 


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20622 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

Menu of Options provide potentially 

useful ideas. Specifically, States would 

need to assess which items on the menu 

are applicable in their areas, and will 

have to assess the costs of applying 

controls locally. Accordingly, there 

would be ample opportunity for public 

review of the State’s analysis of the local 

cost and air quality impacts of any 

measure listed in the document which 

is included in a State’s SIP. The EPA is 

not requiring that States adhere to the 

list of measures in the Menu of Options. 

The EPA does not in any way mean to 

imply that the measures in the Menu of 

Options are presumed to be RACM, 

merely that they are potential controls 

for areas to consider. The Menu of 

Options has no regulatory significance 

and thus need not be issued through 

notice-and-comment rulemaking. The 

EPA notes, however, that the Menu of 

Options does provide a broad list of 

potential sources and measures that can 

help inform States in the development 

of their plans. Similarly, our own list of 

potential measures is not intended to be 

a categorical list of measures which 

States must adopt, rather it is intended 

to provide guidance about the types of 

sources and measures that States can 

consider in constructing their 

attainment plans. The EPA emphasizes 

that whether a source category or 

potential measure is or is not on this list 

is simply not conclusive as to whether 

a given measure is appropriate to 

consider in the RACT and RACM 

analysis. That can be determined only 

through the State’s development of the 

attainment plan, and EPA’s evaluation 

of such plan. 

Comment: A commenter representing 

the paper industry interpreted the 

proposed rule as requiring electrostatic 

precipitator and tighter sulfur-in-fuel 

requirements for the forest products 

industry. The commenter believed that 

EPA was creating limits for such sources 

without adequate rulemaking process. 

Response: The EPA disagrees that the 

listing of control technologies in the 

table in the rule creates a ‘‘rebuttable 

presumption.’’ Rather, the table 

identifies potential opportunities for 

emissions reductions which should be 

reviewed in light of technical and 

economic feasibility, and which a State 

should consider in a list of possible 

RACT and RACM measures for purposes 

of attaining the standards as 

expeditiously as practicable. The EPA is 

currently conducting a sector-based 

approach to the paper industry. One of 

the goals of the sector initiative on pulp 

and paper is to work with the industry 

to identify reductions in SO2 and PM2.5

that will assist us in meeting the 

NAAQS, considering facility locations, 

magnitude of emissions, emission 

stream characteristics, and cost 

effectiveness of controls. 

Comment: A number of commenters 

believed that EPA should develop not 

only a list of measures to consider for 

RACM, but should develop a list of 

mandatory measures that States should 

include, particularly for areas with 

attainment dates more than 5 years after 

designation. 

Response: See discussion in section 

II.D.3 regarding rule requirements for 

attainment date extensions and the issue 

of whether certain measures should be 

mandatory in order for an area to 

receive an extension. 

Comment: Some commenters believed 

that the list of possible measures was 

deficient in not including sources of 

PM2.5 and PM2.5 precursors from 

agricultural sources. One commenter 

believed the list is incomplete without 

identifying the contribution of ammonia 

emissions associated with livestock, 

poultry, and crop fertilizers. 

Response: As we indicated in the 

proposal, we included a list of potential 

RACM measures in the preamble to the 

proposed rule, based upon a review of 

information about the contribution of 

various sources to the emissions 

inventories and a review of potential 

control measures for such sources. We 

did not identify emissions from 

agricultural sources in this review. 

Because ammonia is not presumed to be 

a PM2.5 precursor unless identified for a 

specific area by the State or EPA, 

regulation of ammonia emissions from 

agricultural sources may not be 

necessary. 

We also note that the agricultural 

industry presents unique challenges to 

regulators given the nature of relevant 

emissions sources. Moreover, we 

currently lack good methods to quantify 

agricultural emissions, and we do not 

fully understand their contribution to 

nonattainment problems. We have 

entered into an agreement with several 

animal producer sectors to monitor 

animal feeding operations to develop 

better tools to assess emissions from this 

industry. Hopefully, these tools will 

enhance our knowledge of agricultural 

emissions and their contribution to 

nonattainment problems. Until 

emissions from these sources are better 

understood, States should be judicious 

in determining whether any specific 

measure is RACT/RACM for this 

industry. 

The EPA recognizes that the United 

States Department of Agriculture 

(USDA) has been working with the 

agricultural community to develop 

conservation systems and activities to 

control coarse particle emissions. Based 

on current ambient monitoring 

information, these USDA-approved 

conservation systems and activities have 

proven to be effective in controlling 

these emissions in areas where coarse 

particles emitted from agricultural 

activities have been identified as a 

contributor to a violation of the PM10

NAAQS. The EPA has found that where 

USDA-approved conservation systems 

and activities have been implemented, 

these systems and activities have 

satisfied the Agency’s reasonably 

available control measure and best 

available control measure requirements 

for areas needing to attain the PM10

standards. 

The EPA believes that in the future, 

certain USDA-approved conservation 

systems and activities that reduce 

agricultural emissions of fine particles 

may be able to satisfy the requirements 

of applicable sources to implement 

reasonably available control measures 

for purposes of attaining the PM2.5

NAAQS. The EPA will work with States 

to identify appropriate measures to meet 

their RACM requirements, including 

site-specific conservation systems and 

activities. The EPA will continue to 

work with USDA to prioritize the 

development of new conservation 

systems and activities; demonstrate and 

improve, where necessary, the control 

efficiencies of existing conservation 

systems and activities; and ensure that 

appropriate criteria are used for 

identifying the most effective 

application of conservation systems and 

activities. 

Comment: Some commenters raised 

concerns about a statement in the 

proposal that ‘‘[i]n addressing a 

nonattainment area having military 

training, testing and operational 

activities occurring within it, the State 

should not need to target these activities 

for emission reductions.’’ Some 

commenters interpreted this statement 

as an exemption from any emission 

reduction requirements for military 

sources. 

Response: The statement in the 

proposal was not intended as an 

exemption for all military activities. 

Emissions potentially contributing to 

PM2.5 concentrations at military 

installations originate from a variety of 

sources: basic operational activities 

(such as power generation, other fuel 

combustion, and transportation to and 

from residences, offices, and schools); 

and from field training and testing 

activities (such as personnel training, 

obscurants used in training, operation of 

nonroad vehicles and equipment, and 

related prescribed burning operations). 

The EPA believes that in evaluating 

emissions for a specific nonattainment 


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40Windblown dust from agricultural tilling 

activities also can be a periodic source of inorganic 

PM in some areas. In some cases such dust would 

be expected to be predominantly composed of 

coarse PM rather than fine PM. Depending on the 

available information and specific circumstances 

for a particular area, it is possible that a State could 

find in its SIP development analyses that direct 

PM2.5 emissions from agricultural tilling activities 

do not significantly contribute to annual average 

PM2.5 concentrations in the nonattainment area, and 

therefore would not need to require emission 

reductions from agricultural tilling activities in the 

plan for attaining the annual standard. However, 

States should be mindful of the contribution of 

these sources to 24-hour fine particle 

concentrations. 

area having military activities occurring 

within it, the State should consult with 

DOD for information on the nature of 

these activities and their associated 

emissions. 

With regard to military training 

activities specifically, such activities are 

periodic in nature, and when they do 

occur, the principal type of emissions 

generated by these activities is dust (i.e. 

inorganic direct PM emissions) from 

field operations. Other pollutants may 

be emitted to a lesser degree from 

certain onroad and nonroad motor 

vehicles. While military training 

activities may contribute some degree of 

primary PM2.5 emissions to certain 

nonattainment area inventories, the 

fugitive dust generated from military 

training activities is predominantly 

composed of coarse PM rather than fine 

PM. 

Based on data from the PM2.5

speciation monitoring network operated 

by EPA and the States, the contribution 

of inorganic dust to total PM2.5 mass on 

an annual average basis is relatively low 

in most nonattainment areas, on the 

order of 0.5 to 1.5 micrograms per cubic 

meter (generally 10% or less of total 

PM2.5 mass). Dust from military training 

activities would be a subset of these 

levels. Depending on the available 

information and specific circumstances 

for a particular area, a State could find 

in its SIP development analyses that 

direct PM2.5 emissions from military 

training activities do not significantly 

contribute to PM2.5 concentrations in the 

nonattainment area, and therefore 

would not need to target military 

training activities for emission 

reductions in its attainment plan.40

7. How Should States Consider EGU 

Reductions for CAIR in Meeting RACT/ 

RACM Requirements? 

a. Background 

In section III.I.11 of the preamble to 

the proposed rule, we discussed the 

nature of the SO2 and NOX RACT 

obligations of electric generating unit 

(EGU) sources in states subject to the 

CAIR emission reduction requirements. 

The CAIR rulemaking was finalized in 

March 2005 and published at 70 FR 

25221 (May 12, 2005). CAIR requires 28 

states and the District of Columbia to 

significantly reduce emissions of SO2

and/or NOX. The 26 jurisdictions in the 

CAIR PM2.5 region are required to 

reduce annual emissions of SO2 and 

NOX, and the 26 jurisdictions in the 

CAIR ozone region are required to 

reduce seasonal emissions of NOX. 

These jurisdictions also have the option 

of participating in EPA-administered 

annual SO2, annual NOX, and seasonal 

NOX cap-and-trade programs (the CAIR 

trading programs) to meet these 

emission reduction requirements. In 

addition, in March 2006, EPA 

promulgated a Federal implementation 

plan (FIP) to implement CAIR in these 

jurisdictions until they have EPA 

approved CAIR SIPs in place (71 FR 

25328, April 28, 2006). The FIP adopts, 

as the control measure, the CAIR trading 

programs slightly modified to allow for 

Federal instead of State implementation. 

When fully implemented, CAIR will 

reduce SO2 emissions in these 

jurisdictions by over 70 percent and 

NOX emissions by over 60 percent from 

2003 levels. This will result in $85 to 

$100 billion in health benefits and 

nearly $2 billion in visibility benefits 

per year by 2015 and will substantially 

reduce premature mortality in the 

eastern United States. The benefits will 

continue to grow over time as the 

program is fully implemented (i.e., the 

SO2 emission bank is depleted and the 

final cap is met), and as growth in 

populations and the aging of the 

population continues (which increases 

the susceptible population). 

Sources subject to cap-and-trade 

programs such as the CAIR trading 

programs generally have the option of 

installing emissions control technology, 

adopting some other strategy to reduce 

emissions, or purchasing emissions 

allowances and thereby effectively 

paying other sources covered by the cap 

to reduce emissions. In the proposal, we 

noted that a number of EGUs expected 

to be covered by the CAIR trading 

programs are located in nonattainment 

areas. Based on emissions projections 

for 2010 and 2015 using the Integrated 

Planning Model (IPM), some of these 

EGUs are expected to comply with CAIR 

by purchasing allowances under the 

trading program and some are expected 

to comply by installing emission 

controls. 

The proposal also described our past 

experience with the implementation of 

the NOX SIP Call and our belief that 

many power companies will develop 

their strategies for complying with CAIR 

based, in part, on consultations with 

State and local air quality officials in 

order to address local PM2.5 and ozone 

attainment planning needs. The EPA 

suggested that consultations on location 

of CAIR controls would be timely 

during State development of the CAIR 

SIP, which is due in 2006, prior to the 

April 2008 deadline for submitting 

PM2.5 nonattainment area SIPs. 

The EPA proposed a determination 

that in States that fulfill their CAIR SO2

emission reductions entirely through 

EGU emission reductions (i.e. without 

reductions from non-EGU sources or 

allowing non-EGU sources to opt-in to 

the CAIR SO2 trading program), 

participation in the CAIR SO2 trading 

program would satisfy the SO2 RACT 

requirement for the EGU sources. The 

EPA also proposed that in states that 

fulfill their CAIR NOX emission 

reductions entirely through EGU 

emission reductions, CAIR would 

satisfy NOX RACT for the EGU sources, 

provided that those sources with 

existing selective catalytic reduction 

(SCR) emission control technology 

installed on their boilers operate that 

technology on a year-round basis 

beginning in 2009. Note that direct 

PM2.5 emissions are not addressed by 

the CAIR program, and EPA did not 

propose any determination that 

compliance with CAIR would satisfy 

RACT for direct PM2.5 emissions. The 

proposal included a discussion of the 

rationale for these proposed 

determinations for SO2 and NOX, and 

requested comments on the issue. 

b. Final Rule 

As discussed in section II.F.2 on our 

overall policy for RACT and RACM, we 

consider an area’s obligation to 

implement RACT to be part of the area’s 

overall RACM obligation—to adopt 

those reasonably available measures 

needed to reach PM2.5 attainment as 

expeditiously as practicable. The final 

rule also reflects this combined RACT/ 

RACM approach regarding EGU control 

obligations under CAIR and the extent 

to which meeting CAIR also satisfies a 

source’s RACT and RACM requirements 

for attainment. 

Specifically, the final rule includes a 

presumption that in States that fulfill 

their CAIR SO2 emission reduction 

requirements entirely through EGU 

emission reductions (i.e. without 

reductions from non-EGU sources or 

allowing non-EGU sources to opt in to 

the CAIR SO2 trading program), 

compliance by EGU sources with an 

EPA-approved CAIR SIP or a CAIR FIP 

would satisfy their SO2 RACT/RACM 

requirements for attaining the fine 

particle NAAQS. This section also 

includes a presumption that in States 


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that are subject to CAIR annual NOX

emission reduction requirements and 

fulfill these requirements entirely 

through EGU emission reductions (i.e. 

without reductions from non-EGU 

sources or allowing non-EGU sources to 

opt in to the CAIR annual NOX trading 

program), compliance by EGU sources 

with an EPA-approved CAIR SIP or a 

CAIR FIP would satisfy the NOX RACT/ 

RACM requirement for the PM2.5

NAAQS, provided that the sources with 

existing selective catalytic reduction 

(SCR) emission control technology 

installed on their boilers operate that 

technology on a year-round basis 

beginning in 2009. This final position is 

based on a number of factors identified 

in the proposal and discussed below. 

Many PM2.5 nonattainment areas are 

projected to achieve significant SO2 and 

NOX reductions under the CAIR 

program. We do not believe that 

requiring source-specific RACT/RACM 

controls on specified EGUs in 

nonattainment areas would reduce total 

SO2 and NOX emissions from sources 

covered by CAIR below the regionwide 

levels that will be achieved under CAIR 

alone. Nor do we believe that ‘‘beyond 

CAIR’’ EGU controls for SO2 and NOX

are ‘‘reasonably available’’ control 

measures for most areas within the 

CAIR Region. Accordingly, most States 

need not evaluate additional control 

measures on EGUs to satisfy RACT/ 

RACM requirements as explained above. 

As discussed previously, we are not 

requiring that States impose RACT on 

any specific size or type of source. 

Instead, States must conduct a RACT/ 

RACM analysis considering measures 

that are ‘‘reasonably available’’ to meet 

the overarching requirement to attain 

the standards as expeditiously as 

practicable. Thus, the final rule imposes 

no specific requirement on States to 

impose RACT/RACM on EGUs. 

Nonetheless, in evaluating RACT/ 

RACM for EGUs, EPA believes it is 

appropriate for States (states that 

achieve all reductions from EGUs) to 

consider the special attributes of that 

group of facilities including the unique 

interrelated nature of the power supply 

network, and their participation in the 

CAIR program. For EGUs in the CAIR 

region, based upon the presumption 

explained here, States may define 

RACT/RACM as the CAIR level of 

control on the collective group of 

sources in the region rather than impose 

a specific level of control on an 

individual source. This approach is 

similar to the Agency’s past ‘‘bubble’’

policy, as discussed in section (c) 

addressing comments on the proposal. 

As discussed more fully in the CAIR 

final rulemaking notice, EPA has set the 

2009 and 2010 CAIR caps for SO2 and 

NOX at a level that will require EGUs to 

install emission controls on the 

maximum total capacity on which it is 

feasible to install emission controls by 

those dates. The EPA concluded that the 

CAIR compliance dates represent an 

aggressive schedule that reflects the 

limitations of the labor pool, and 

equipment/vendor availability, and 

need for electrical generation reliability 

for installation of emission controls. 

Although the actual SO2 cap does not 

become effective until 2010, we 

designed banking provisions in CAIR so 

that covered EGUs will begin to reduce 

their SO2 emissions almost immediately 

after CAIR is finalized, and will 

continue steadily to reduce their 

emissions in anticipation of the 2010 

cap and the more stringent cap that 

becomes effective in 2015. The 2015 

SO2 and NOX caps are specifically 

designed to eliminate all SO2 and NOX

emissions from EGUs that are highly 

cost effective to control (the first caps 

represent an interim step toward that 

end). 

Moreover, we predicted that the 

majority of large coal-fired utilities will 

install advanced control technologies 

under CAIR because the larger and 

higher emitting source offer an 

opportunity to obtain more costeffective emissions reductions. We 

expect that the largest-emitting sources 

will be the first to install SO2 and NOX

control technology and that such control 

technology will gradually be installed 

on progressively smaller-emitting 

sources until the ultimate cap is 

reached. As a result, few, if any coalfired units with greater than 600 MW of 

operating capacity should operate in 

PM2.5 nonattainment areas without 

advanced control after full 

implementation of CAIR. Of the 

remaining units operating without 

advanced pollution controls, a great 

many of these units will have operating 

capacities below 300 MW. We predict 

that these units ‘‘will be utilized less 

often,’’ and ‘‘typically have baghouses 

and electrostatic precipitators for 

particulate control, have combustion 

controls for NOX control, and burn lowsulfur coal.’’ See ‘‘Contributions of 

CAIR/CAMR/CAVR to NAAQS 

Attainment: Focus on Control 

Technologies and Emission Reductions 

in the Electric Power Sector,’’ Office of 

Air and Radiation, U.S. Environmental 

Protection Agency, April 18, 2006 

(available at http://www.epa.gov/ 

airmarkets/cair/analyses/ 

naaqsattainment.pdf). In light of these 

expected results, we generally believe 

that the cost to install additional 

controls on these smaller units would be 

unreasonable. 

We are also concerned that if States 

require specific EGUs to install 

advanced pollution control measures, it 

could interfere with the market-based 

incentives inherent in the cap and trade 

program. This could increase the cost of 

compliance and shift the location of the 

units that would otherwise opt to install 

advanced emissions controls. Such a 

result may be counterproductive to that 

State’s attainment efforts, as the State 

may forego a larger quantity of more 

beneficial reductions in transported 

pollutants, in exchange for a smaller 

quantity and less beneficial reduction in 

local emissions. Moreover, it may 

reduce the benefits expected in other 

nonattainment areas as well. 

Accordingly, even if a State found the 

cost to control an individual unit 

acceptable on a cost per ton basis, the 

potential overall disbenefit of control 

may nonetheless make imposition of the 

control not ‘‘reasonably available.’’

The EPA finds that the control 

installations projected to result from 

CAIR NOX and SO2 caps in 2009 and 

2010 are as much as feasible from EGUS 

across the CAIR Region by those dates. 

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

to meet source-specific RACT 

requirements by 2009, they would likely 

use labor and other resources that 

would otherwise be used for emission 

controls on larger sources. Because of 

economies of scale, more boiler-makers 

may be required per megawatt of power 

generation for smaller units than larger 

units. In this case, the imposition of 

source-specific RACT/RACM on smaller 

emitting sources by 2009 could actually 

reduce the amount of banking that 

would otherwise occur and result in 

higher SO2 emissions in 2009 as 

compared to the level that would result 

from implementation of CAIR alone. 

In any event, the imposition of 

source-specific control requirements on 

a limited number of sources also 

covered by a cap-and-trade program 

would not reduce the total regionwide 

emissions from sources subject to the 

program. Under a cap-and-trade 

program such as CAIR, a given number 

of allowances are issued in order to 

achieve a given emission level. Sourcespecific control requirements within the 

CAIR program may affect the temporal 

distribution of emissions (by reducing 

banking and thus delaying early 

reductions) or the spatial distribution of 

emissions (by moving them around from 

one place to another), but they would 

not affect total regional emissions under 

the program. If source-specific 

requirements were targeted at the units 


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that could be controlled most costeffectively, then the imposition of 

source-specific controls would likely 

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

imposition of source-specific 

requirements would make any given 

level of emission reduction more costly 

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

imposition of source-specific RACT on 

EGUs covered by CAIR would not 

reduce total regionwide emissions, but 

would likely achieve emission 

reductions under the program in a more 

costly way. 

Given the considerations described 

above, we think that in many areas 

additional controls on EGUs generally 

would not be ‘‘reasonably available.’’

Notwithstanding these conclusions, we 

recognize that States are in the best 

position to determine how best to 

achieve attainment with the PM2.5

NAAQS in light of local needs and 

conditions. As we acknowledged in our 

proposed rule, power plant operators 

typically have ongoing relationships 

with the State and local officials 

involved in air quality planning. We 

expect that power plants will continue 

to collaborate with State officials to 

determine how best to address multiple 

air quality goals, and which plant 

locations to control under CAIR, 

considering local PM2.5 and ozone 

attainment needs. 

The EPA expects States and local air 

agencies to identify reasonably available 

control measures that are necessary and 

reasonable to attain the standards as 

expeditiously as practicable; and that 

after consulting with power companies, 

the State may conclude that establishing 

additional ‘‘beyond CAIR’’ emission 

control requirements on specific sources 

in nonattainment areas is warranted to 

provide for attainment as expeditiously 

as practicable. Nevertheless, in 

preparing the overall attainment 

demonstration, States should be aware 

of the expected benefits of the marketbased incentives of the CAIR program, 

the cost effectiveness of control, 

feasibility of implementation, and any 

disbenefits that would result from 

requiring ‘‘beyond CAIR’’ controls on 

any specific EGU before concluding that 

additional controls on EGUs are 

‘‘reasonably available’’ and necessary to 

satisfy RACT/RACM requirements. 

Year-round NOX controls. In the CAIR 

final rulemaking notice, EPA found that 

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

only during the ozone season, could 

achieve NOX reductions at low cost 

relative to other available NOX controls. 

The EPA projected that power 

generators would employ this control 

measure to comply with CAIR SIPs. 

Based on this control opportunity, EPA 

estimated the average cost of non-ozoneseason NOX control at $500/ton. These 

considerations support a finding that 

RACT should include year-round 

operation of existing SCRs that are 

located in PM2.5 nonattainment areas. 

Because all PM2.5 nonattainment areas 

violate the annual form of the PM2.5

standard and public health can be 

affected by high PM2.5 levels in the 

winter as well as the summer, we 

believe that year-round operation of 

existing SCR that are located in 

nonattainment areas where NOX is an 

attainment plan precursor will provide 

additional health benefits for relatively 

low dollar cost per ton of pollutant 

reduced. 

In the proposal notice, EPA proposed 

to define ‘‘existing’’ SCRs as those units 

that were in place by the date of the 

proposed rule (November 1, 2005). We 

selected this date rather than the final 

date to avoid creating an incentive to 

delay installation of new SCR. Today, 

we finalize our proposed approach with 

one clarification. To avoid confusion 

over the proper interpretation of the 

phrase ‘‘in place,’’ we are clarifying that 

an existing SCR is one which is fully 

installed and capable of operation by 

November 1, 2005. 

We also proposed that these existing 

SCR begin year-round operations no 

later than January 1, 2009 to qualify as 

RACT/RACM under our presumptive 

approach. We noted that year round 

operation of existing SCR involves little 

to no alteration of existing equipment, 

and that EGUs could conduct any 

required work during normal outages. 

Today, after taking these factors into 

account, we finalize our proposed rule. 

The year-round operation requirement, 

however, will not be federally 

enforceable to individual EGUs until 

EPA approves a State’s SIP including 

the requirement. 

c. Comments and Responses 

Comment: Some commenters 

supported the proposed determination 

described in section (a) that in States 

that fulfill their CAIR SO2 emission 

reduction requirements entirely through 

EGU emission reductions (i.e. without 

reductions from non-EGU sources or 

allowing non-EGU sources to opt in to 

the CAIR SO2 trading program), 

compliance by EGU sources with an 

EPA-approved CAIR SIP or a CAIR FIP 

would satisfy the SO2 RACT 

requirement for the sources; and in 

States that are subject to CAIR annual 

NOX emission reduction requirements 

and fulfill these requirements entirely 

through EGU emission reductions (i.e. 

without reductions from non-EGU 

sources or allowing non-EGU sources to 

opt in to the CAIR annual NOX trading 

program), compliance by EGU sources 

with an EPA-approved CAIR SIP or a 

CAIR FIP would satisfy the NOX RACT 

requirement for the sources, provided 

that the sources with existing selective 

catalytic reduction (SCR) emission 

control technology installed on their 

boilers operate that technology on a 

year-round basis beginning in 2009. One 

commenter supported EPA’s approach 

so long as States may pursue additional 

reductions from EGUs if needed for 

attainment as expeditiously as 

practicable. A number of other 

commenters opposed the proposed 

determination regarding RACT for EGUs 

based on a number of issues. 

Response: Based on the rationale 

described in the sections above, the 

final rule includes a presumption that 

compliance with CAIR satisfies SO2 and 

NOX RACT/RACM requirements for 

EGUs in many areas. Nonetheless, States 

can require ‘‘beyond CAIR’’ EGU 

controls if a State determines that it is 

a necessary and reasonable means to 

attain the PM2.5 standards. Comments 

opposing this approach are addressed in 

more detail below. 

Comment: A number of commenters 

objected to the proposed determination, 

arguing that it would result in greater 

control requirements and economic 

burden on non-EGU sources located in 

nonattainment areas. These commenters 

urged EPA to adopt a final rule that 

provides for implementing the most 

cost-effective controls necessary to 

attain the standard. They assert that 

with the proposed finding that 

compliance with CAIR satisfies RACT 

for EGUs, the proposed rule would not 

provide for the most cost-effective 

approach to attainment. They argue EPA 

and States should develop costeffectiveness guidance that includes all 

stationary source control measures and 

they should develop SIPs based on the 

most economic means to attain the 

standard. They make several arguments 

to support this position. The 

commenters asserted that if an EGU 

control is more cost-effective than a 

non-EGU control, the EGU should be 

subject to ‘‘beyond-CAIR’’ controls. 

They also asserted that if EPA chooses 

to consider the CAIR rule as satisfying 

SO2 and NOX RACT for EGUs, then 

other sources should not be subjected to 

control costs greater than those found 

reasonable under CAIR (i.e., $800/ton). 

They believe it would be inequitable to 

require smaller sources to pay a higher 

cost for emissions reductions than larger 

sources, which are a more significant 


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contributor to the problem and which 

may be able to make more cost-effective 

emission reductions. One commenter 

also suggested that EPA should 

authorize a presumption that emissions 

reductions required on electric utilities 

under the CAIR will be equivalent to 

RACT only if a particular source in a 

CAIR State has installed controls that 

achieve the average level of control that 

EPA has projected will occur for the 

particular pollutant under the CAIR 

requirements. 

Response: The EPA has determined 

that implementation of the CAIR trading 

program represents highly cost-effective 

controls that will achieve widespread 

regional SO2 and NOX emissions 

reductions from EGUs and will provide 

significant air quality benefits for ozone 

and PM2.5 nonattainment areas. In 

developing attainment SIPs and 

identifying RACM, States will need to 

consider additional cost-effective and 

reasonable controls to reach attainment 

as expeditiously as practicable. The EPA 

does not agree with the commenter’s 

argument that controls on non-EGUs 

should be no more than the projected 

cost of EGU controls under CAIR. The 

EPA expects that in order to achieve 

attainment as expeditiously as 

practicable, some States may need to 

adopt control measures for some sources 

which cost more per ton but which still 

are considered to be reasonable and 

cost-effective. 

In addition, States must consider the 

economic feasibility of implementing a 

given control measure. Because of 

facility-specific factors, EPA believes it 

would be inappropriate to establish a 

threshold of control effectiveness (e.g. 

dollars per ton) based on control of 

EGUs and apply this threshold to all 

source categories. The ability of a source 

to cost-effectively reduce emissions is 

dependent on case-specific factors, 

including the ability of the given source 

to sustain the cost of control, and 

prevailing costs in the specific 

geographical location. A direct 

correlation between the size of an 

emissions source and the economic 

feasibility of controls for that source and 

location does not necessarily exist. 

We also disagree with the commenter 

who suggests that RACT requirements 

should only be satisfied if a source 

achieves an average level of control that 

EPA projects to occur under CAIR. The 

EPA maintains that the presumption 

that CAIR satisfies SO2 and NOX RACT/ 

RACM for EGUs in most areas is an 

appropriate policy. As discussed further 

below, we have always recognized that 

States could determine RACT for a 

single source or group of sources. 

Comment: A number of commenters 

opposed the proposed determination 

that CAIR would satisfy the SO2 and 

NOX RACT requirement for EGUs. The 

commenters argued that this 

determination is unlawful, that it does 

not comply with section 172(c)(1) of the 

CAA which requires RACT (i.e. controls 

that are technologically and 

economically feasible) ‘‘at a minimum’’

for all existing sources in the 

nonattainment area, that it would allow 

very large stationary sources to escape 

cost-effective controls entirely, and that 

it is largely based on the legallyirrelevant contention that CAIR will 

reduce emissions more cost-effectively 

than RACT. They claim that EPA has no 

authority to displace the 

Congressionally-mandated RACT 

requirement, that CAIR was designed to 

address regional pollution transport (not 

to be an attainment strategy), and that 

EPA should remove these proposed 

provisions in the final rule. Commenters 

claim that the EPA’s proposed approach 

to allow EGU emissions to be addressed 

solely through CAIR would undermine 

states’ efforts to meet the Federal PM2.5

health standard, particularly when EGU 

sources are among the most costeffective to control. Another commenter 

claimed that EPA’s proposal allowing 

States that choose to fulfill their CAIR 

requirements entirely through emission 

reductions from EGUs to also use CAIR 

to satisfy their SO2 and NOX PM2.5

RACT requirements, thereby equating 

these two requirements for the EGU 

sector, is flawed. This commenter 

argued that allowing a cap-and-trade 

program, such as the CAIR, to substitute 

for the RACT requirement undermines 

the effectiveness of the controls by 

allowing facilities to use allowances to 

offset emissions, rather than control 

them at the source. The purchase of 

allowances, they assert, does not satisfy 

RACT requirements. 

Response: The EPA disagrees with 

these comments. The final rule does not 

displace the RACT requirement for any 

sources. Instead, EPA is exercising its 

authority to interpret the section 172 

RACT and RACM requirements for the 

purposes of implementing the 1997 

PM2.5 standards. For the reasons 

described in section (b) above, we 

believe that States can rely on EPA’s 

presumption that compliance with a 

CAIR SIP or FIP, meeting certain 

requirements, will satisfy the RACT/ 

RACM requirement for certain EGU 

sources. The EPA historically issued 

control technology guidelines setting 

forth presumptive levels of emissions 

control that satisfy the RACT 

requirement for a given industry. The 

final rule is similar to this practice in 

establishing a presumption that SO2 and 

NOX reductions under the CAIR 

program satisfy the RACT/RACM 

requirement for EGUs in CAIR States. In 

identifying reasonably available control 

measures to ensure attainment as 

expeditiously as practicable, States will 

need to take CAIR reductions into 

account as well as any additional costeffective reductions that are 

technologically and reasonably 

available. 

We further find that the attempt by 

many commenters to characterize CAIR 

as a strategy to address only regional 

pollution transport and not an 

attainment strategy as overly simplistic. 

The EPA analyses for CAIR show that 

there are significant air quality benefits 

projected for individual nonattainment 

areas as a result of SO2 and NOX

reductions across the multistate CAIR 

region. The Act does not prevent States 

from properly crediting measures that 

achieve multiple objectives (e.g. 

regional transport or local 

nonattainment). Moreover, Section 

110(a)(2)(D) requires SIPs to contain 

adequate provisions to assure that 

sources in the State do not contribute 

significantly to nonattainment in any 

other State. The CAIR rule is an integral 

element in meeting the States’ Section 

110 attainment obligations. 

Accordingly, it is reasonable to 

incorporate this consideration in 

determining what measures qualify as 

RACT/RACM. 

Finally, EPA does not interpret the 

provisions of Section 172(c)(1) related to 

the RACT requirement as precluding 

States’ use of a cap and trade approach 

as a means of regulating existing sources 

and achieving RACT/RACM reductions, 

especially in light of Congresses’

expressed authorization to auction 

emission rights in Section 172(c)(6). 

The EPA has long recognized that 

RACT need not apply to individual 

sources. As stated earlier, our early 

guidance on RACT requirements stated 

that States could establish RACT for an 

‘‘individual sources or a group of 

sources.’’ (emphasis added) See Memo. 

Strelow (Dec. 1976) and 44 FR 71779. 

Importantly, Congress ratified the early 

interpretations of RACT and RACM 

when it enacted the 1990 Amendments. 

See 42 U.S.C. Section 7515 (Clean Air 

Act section 193). Our 1986 emissions 

trading policy also recognized a number 

of advantages offered through 

application of a ‘‘bubble’’ approach 

including faster compliance with RACT 

limits and earlier reductions. Moreover, 

Courts have upheld EPA’s approval of 

States’ use of ‘‘bubbling’’ multiple units 

to meet RACT requirements. See e.g. 


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41See the regulatory impact analysis chapter on 

air quality for the 2006 PM NAAQS review at 

http://www.epa.gov/ttn/ecas/regdata/RIAs/ 

Chapter%204-Air%20Quality.pdf. 

Natural Resources Defense Council v. 

EPA, 941 F.2d 1207 (finding that EPA 

need not adhere to a source specific 

RACT determination to satisfy RACT 

requirements and acknowledging EPA’s 

special knowledge and expertise in the 

area.) 

Comment: The EPA’s proposal to 

allow EGU emissions to be addressed 

solely through CAIR undermines 

prospectively States’ efforts to meet the 

Federal PM2.5 health standard. EGU 

sources are among the most costeffective to control. 

Response: For the reasons described 

in section (b) above, EPA believes that 

States can rely on EPA’s presumption 

that compliance with a CAIR SIP or FIP, 

meeting certain requirements, satisfies 

the SO2 and NOX RACT/RACM 

requirement for certain EGU sources. 

Areas can require ‘‘beyond CAIR’’ EGU 

controls if a State determines that it is 

a necessary and reasonable means to 

attain as expeditiously as practicable. 

Nonetheless, as discussed above, EPA 

believes that implementation of the 

CAIR requirements will provide for 

substantial progress in attaining the 

PM2.5 standards and that States may 

presume that RACT/RACM 

requirements are equal to the CAIR level 

of control. 

Comment: CAIR fails to address the 

need for short-term reductions in PM2.5

and precursor emissions on high 

pollution days. While RACT restricts 

emissions over a 1-hour to 24-hour 

period, CAIR only provides for an 

annual or seasonal cap. Reliance on 

CAIR therefore fails to recognize the 

importance of reducing short-term 

emissions, which was recently 

highlighted by the EPA’s own proposal 

to tighten the 24-hour PM2.5 health 

standard. Local and short-term adverse 

air quality effects of PM2.5, must be 

addressed in the final rule by requiring 

RACT for all major facilities in addition 

to CAIR. 

Response: The CAIR program is 

oriented toward reducing SO2 and NOX

emissions in order to reduce air quality 

concentrations on an annual and 

seasonal basis. Because all PM2.5

nonattainment areas were designated 

due to violations of the annual standard 

(and the two designated areas in 

California also violated the 24-hour 

standard), the focus of this 

implementation rule is attainment of the 

annual standard. CAIR is projected to 

provide significant air quality benefits 

in 2010 and 2015 for eastern PM2.5

nonattainment areas on both an annual 

basis and on a 98th percentile 24-hour 

basis.41

Comment: The proposal is silent on 

the issue of whether EGUs are subject to 

direct PM2.5 emissions RACT 

requirements. It is critical that RACT be 

required for all facilities with respect 

direct PM2.5 emissions, regardless of a 

facility’s participation in CAIR. 

Response: In the final rule and 

preamble, EPA has clarified that all 

EGUs in nonattainment areas are subject 

to RACT/RACM for direct PM2.5

emissions. The presumption described 

above applies only to SO2 and NOX

RACT/RACM, not RACT/RACM for 

direct PM2.5 emissions from EGUs. 

Comment: The EPA fails to consider 

the geographical distributional impacts 

of the emission reductions. Equating 

CAIR with RACT fails to take into 

account the substantial contribution that 

emissions from EGUs within a 

nonattainment area may make toward 

that area’s PM2.5 nonattainment 

problem. The EPA does not attempt to 

explain how such a generalized 

determination satisfies RACT for PM2.5. 

Response: The establishment of 

recommended levels for RACT/RACM is 

an area Congress delegated to the 

specific expertise of the Agency. Based 

on our analysis, we conclude that the 

CAIR emissions caps presumptively 

represent the level of emissions control 

achievable through application of 

‘‘reasonably available’’ control 

technologies. Nonetheless, in 

developing attainment plans, each State 

will evaluate the impact of stationary 

sources located within the 

nonattainment area in developing its 

attainment strategies for the local area. 

Comment: A few commenters stated 

that EPA should explain how this 

proposal would be implemented for 

States that request an extension of an 

attainment date because attaining in 5 

years or less is impracticable; i.e., 

whether EPA would still hold to its 

interpretation that CAIR equals RACT 

for EGUs and not require additional 

reductions from EGUs even if an area 

cannot attain in 5 years and controls on 

EGUs could lead it to attain more 

expeditiously. These commenters argue 

that, in considering if additional RACT 

is needed in states that obtain 

extensions of the attainment deadline 

after 2010, EPA cannot ignore potential 

RACT for electric generating units any 

more than they would be allowed 

legally to avoid consideration of any 

other RACT candidates. One commenter 

is particularly concerned that States 

would not include EGUs in their RACT 

determinations and instead require 

smaller industrial boilers or process 

heaters to control emissions. 

Response: The EPA’s determination 

regarding CAIR and RACT is not limited 

to areas attaining within five years. The 

Agency’s rationale is presented in the 

‘‘final rule’’ section above. We disagree 

that the CAIR–RACT presumptions 

necessarily shift emission control 

burdens from EGUs to smaller industry 

boilers and process heaters because, in 

implementing the RACM requirement, 

the State may include an evaluation of 

control options on those sources as part 

of their RACT/RACM analyses. As 

stated above, EPA concluded that the 

CAIR compliance dates represent an 

aggressive schedule that reflects the 

limitations of the labor pool, and 

equipment/vendor availability, and 

need for electrical generation reliability 

for installation of emission controls. 

Accordingly, additional controls on 

EGUs may not be a reasonably available 

control measure that can be effectively 

implemented in a manner that advances 

an area’s attainment date. 

Comment: The EPA designated many 

partial counties nonattainment for PM2.5

solely because the areas contained EGU 

emission sources thought to cause or 

contribute to violations of the NAAQS. 

In implementing attainment plans, it 

makes sense to consider further control 

of these sources, and because they are 

located in nonattainment areas, the 

ability to do so is provided for and legal 

under the CAA. 

Response: The EPA designated PM2.5

nonattainment counties because they 

either had a violating monitor or they 

contributed to a nearby air quality 

problem. Importantly, EPA designated 

these areas without considering the air 

quality benefits expected in the future 

from CAIR. Accordingly, the fact that an 

EGU is located in a partial county and 

we included the partial county in the 

nonattainment area because we believe 

that the EGU was causing or 

contributing to the nonattainment 

violations, does not equate with a 

finding that more than CAIR is required 

to remedy the nonattainment problem. 

Nonetheless, EPA believes that States 

should evaluate the impact of stationary 

sources in all designated counties, 

including those partial counties noted 

by the commenter, in its assessment of 

reasonably available control strategies to 

ensure attainment as expeditiously as 

practicable. 

Comment: The EPA should adopt the 

Ozone Transport Commission’s (OTC’s) 

approach to cap-and-trade programs. 

When the OTC developed its NOX


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42EPA’s CAIR–RACT presumption also would 

not apply if a State required sources other than 

EGUs to achieve a portion of the reductions 

required by CAIR (e.g., the State’s CAIR SIP 

achieved some reductions from EGUs but took 

credit for non-EGU reductions achieved under new, 

more stringent requirements implemented to meet 

NOX SIP call caps). Under the CAIR rule such a 

State would not be eligible to participate in the 

EPA-administered CAIR trading system. 

Budget Program (which was the basis 

for EPA’s NOX SIP call and 

subsequently CAIR), it assumed that 

RACT was applied first. Thus the capand-trade program operated in an 

environment that assumed RACT was in 

force, not in lieu of RACT. 

Response: Under the ozone national 

ambient air quality standards, NOX and 

VOC RACT have been implemented 

progressively for the past 30 years or 

more, prior to development of the NOX

SIP call regional control program. In 

contrast, the PM2.5 implementation 

program is the first instance in which 

we have required RACT/RACM 

specifically for fine particle pollution. 

For this reason, the CAIR program is not 

operating with SO2 and NOX RACT 

limits already in place for attainment of 

the PM2.5 standards. Nonetheless, as 

discussed above, EPA believes that 

implementation of the CAIR 

requirements will provide for 

substantial progress in attaining the 

PM2.5 standards and that States may 

presume that RACT/RACM 

requirements are equal to the CAIR level 

of control. 

Comment: A few commenters stated 

that EPA should clarify and modify the 

part of its proposal that explains why a 

State cannot rely on EPA’s 

determination that CAIR can satisfy the 

NOX RACT requirement for PM2.5 if the 

State ‘‘elect[s] to allow non-EGU sources 

to voluntarily enter the EPAadministered CAIR trading program 

through an opt-in provision in the CAIR 

model rule.’’ (70 FR 66025 col. 3). These 

commenters believe that this part of the 

proposal might be construed to preclude 

States subject to both the NOX SIP Call 

and included in the CAIR region for 

ozone from relying on the NOX RACT 

determination for PM2.5 if the States 

choose ‘‘to bring their non-CAIR 

[including non-EGU] NOX SIP Call 

trading sources into the CAIR ozone 

season NOX cap and trade program.’’ (70 

FR 49708, 49728 col. 3) (August 24, 

2005). The commenters assert that EPA 

gave States the option of bringing nonEGU NOX SIP Call sources into the 

CAIR seasonal NOX trading program to 

ensure that non-CAIR sources, including 

non-EGUs, that are subject to the NOX

SIP Call rule would not be ‘‘stranded,’’

starting in 2009, by being left in an 

ozone season NOX control program with 

no EGU trading partners. The 

commenters argued that ‘‘EGUs should 

not be penalized, in the form of denial 

of CAIR–RACT treatment, as a result of 

States exercising their option to avoid 

financial and compliance difficulties for 

non-EGUs that otherwise would be left 

without allowance trading partners in 

the EGU sector after the NOX SIP Call 

trading program ends in 2008.’’ These 

commenters point to EPA’s 

determination in the final Phase 2 ozone 

implementation rule, that participation 

in the CAIR trading programs can satisfy 

NOX RACT for ozone even if a State 

brings non-EGUs in the NOX SIP Call 

trading program into the trading 

program after 2008, see 70 FR 71657 col. 

2, provided the State retains an ‘‘EGU 

[emission] budget under CAIR that is at 

least as restrictive as the EGU budget 

that was set in the State’s NOX SIP call 

SIP,’’ id. At 71658 col. 1. These 

commenters argue that EPA should 

make a similar determination here 

regarding NOX RACT for purposes of 

PM2.5 NAAQS implementation. 

Response: All states with EPA 

approved CAIR SIPs or subject to a 

CAIR FIP implementing the annual NOX

emission reduction requirements, and 

obtaining those reductions solely from 

EGUs may rely on EPA’s determination 

that CAIR presumptively satisfies NOX

RACT/RACM for PM2.5 for these 

sources. This determination is 

unaffected by whether or not a State 

permits NOX SIP Call non-EGUs to 

participate in the CAIR ozone season 

trading program. In the final rule, we 

have included the presumption that 

NOX RACT/RACM for PM2.5 is satisfied 

for EGUs complying with a CAIR SIP or 

CAIR FIP implementing the annual 

CAIR NOX emission reduction 

requirements (provided the State 

implementation of the CAIR NOX

annual trading program includes EGUs 

only).42

In the final ozone implementation 

rule, EPA addressed numerous issues 

relating to the transition from the NOX

SIP Call to the CAIR ozone season 

trading program, including the impact 

of bringing NOX SIP Call non-EGUs into 

the CAIR ozone season trading program. 

Commenters’ suggestion that these 

determinations are relevant to this PM2.5

implementation rule ignores the fact 

that both the NOX SIP Call and the CAIR 

ozone season trading program are 

seasonal, not annual, trading programs. 

The NOX SIP Call EGU and non-EGU 

budgets are seasonal NOX budgets and 

do not address annual NOX emissions. 

As discussed above, PM2.5 levels yearround contribute to an area’s annual 

average concentration, and NOX

emissions during non-summer months 

contribute to nitrate concentrations, 

which are typically highest in cooler 

temperatures. For these reasons, EPA 

believes it would be inappropriate to 

accept commenters’ suggestion. 

8. What Are the Required Dates for 

Submission and Implementation of 

RACT? 

a. Background 

The EPA requested comment on a 

general approach for the dates for 

submission and implementation of 

RACT rules. The final rule retains the 

proposed approach, as described in the 

following section. 

b. Final Rule 

The final rule requires the following: 

(1) Date of submission. States must 

submit adopted RACT rules to EPA 

within 3 years of designation, at the 

same time as the attainment 

demonstration due in April 2008. 

(2) Dates for implementation of 

control measures. States should also 

implement any measures determined to 

be RACT expeditiously, as required by 

section 172. Implementation of RACT 

measures should in no case start later 

than the beginning of the year before the 

nominal attainment date. For example, 

if an area has an attainment date of 

April 2010, then any required RACT 

measures should be in place and 

operating no later than the beginning of 

2009. This is intended to help provide 

for clean air in calendar year 2009. As 

discussed in section II.D, if other criteria 

are also met, EPA could then grant the 

area a 1-year attainment date extension 

if the air quality level in the 3rd of the 

3 years was below the level of the 

standard. If the area observes a second 

year of clean air, EPA could grant a 

second 1-year attainment date 

extension. In this case, the 2009 to 2011 

period would then be reviewed to assess 

whether the area attains the standards. 

(3) Provisions for a demonstration that 

additional time is needed. While EPA 

expects that States will implement 

required RACT controls by January 2009 

in most situations, there may be cases 

where additional time is needed to 

implement an innovative control 

measure or to achieve a greater level of 

reduction through a phased approach. If 

a State has provided an adequate 

demonstration showing that an 

attainment date extension would be 

appropriate for an area, then the State 

may consider phasing-in certain RACT 

controls after January 2009. The EPA 

would allow the implementation of 

selected RACT controls after January 

2009 if the State can show why 

additional time is needed for 


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implementation, and such delayed 

implementation still would need to be 

on a schedule that provides for 

expeditious attainment. In no event 

could the State wait to implement RACT 

controls until the last few years prior to 

the attainment date without an adequate 

rationale for why earlier 

implementation was not feasible. 

c. Comments and Responses 

Comment: One commenter supported 

EPA’s position that implementation of 

RACT and RACM by January 1, 2009 is 

necessary to achieve the effect on air 

quality for calendar year 2009. 

Response: The EPA agrees with this 

comment. 

Comment: Some commenters 

supported allowing for an 

implementation schedule that allowed 

for implementation of RACT and RACM 

for a time frame extending beyond 2009. 

These commenters favored such an 

approach if States provided an adequate 

demonstration of why the measures 

cannot be implemented earlier. 

Commenters noted that a phased 

approach to emissions reductions in 

some cases could lead to additional 

reductions that could not occur by 2009. 

Response: The EPA agrees with these 

comments. 

Comment: One commenter believed 

that so long as a State demonstrates 

attainment by 2015, EPA should not 

require implementation of any RACT 

measures. The commenter further 

asserted that it would be bad policy to 

require costly emissions reductions 

through imposition of RACT on areas 

expected to attain the standards through 

other means by 2015. 

Response: The EPA disagrees with 

this comment. The CAA requires States 

to demonstrate that the attainment plan 

will attain the standards as 

expeditiously as practicable and must 

include RACT and RACM. The 

requirement for ‘‘reasonable’’ measures 

does not require that any theoretical 

measure be implemented, but does 

require implementation of those 

reasonable measures which could 

advance the attainment date by at least 

1 year. Given the health effects 

associated with PM2.5, EPA believes this 

approach is sound public policy. 

9. Which Pollutants Must Be Addressed 

by States in Establishing RACT and 

RACM Limits in Their PM2.5 Attainment 

Plans? 

a. Background 

In the proposed rule, and in the final 

rule as discussed in detail in section 

II.A above, EPA discusses the pollutants 

which States must address in the 

attainment plans, in particular with 

respect to RACT, RACM and NSR. 

These pollutants include not only direct 

PM2.5, but also gaseous precursors to the 

formation of PM2.5. In general, the 

decisions that States and EPA make 

with respect to which precursors are 

significant contributors to an area’s 

PM2.5 nonattainment problem define the 

pollutants and sources to be addressed 

by States in developing RACT and 

RACM. 

b. Final Rule 

In the final rule, in establishing RACT 

and RACM limits, those RACT and 

RACM limits must address: 

—Direct emissions of PM2.5

—SO2, a precursor to PM2.5 formation, 

and 

—NOX, unless a State makes a finding 

that NOX emissions from sources in 

the State do not significantly 

contribute to the PM2.5 problem in a 

given nonattainment area. 

The EPA generally presumes that 

RACT and RACM limits are not needed 

for ammonia or VOC unless that State or 

EPA determines otherwise for a given 

nonattainment area. RACT and RACM 

limits are needed for ammonia if a State 

or EPA makes a finding that ammonia 

emissions significantly contribute to the 

PM2.5 problem in a given nonattainment 

area, and thus finds that control of 

ammonia would help address the PM2.5

problem. RACT and RACM limits are 

needed for VOC only if a State or EPA 

makes a finding that VOC emissions 

significantly contribute to the PM2.5

problem in a given nonattainment area. 

(As a point of clarification, ‘‘VOCs,’’

which are gaseous organic precursors to 

the chemical formation of secondary 

organic aerosol, are treated differently 

from semivolatile or nonvolatile organic 

compounds which are addressed as 

directly emitted PM2.5). Issues related to 

the finding of ‘‘significant contribution’’

for these pollutants are discussed in 

Section II.A above. 

10. Under the PM2.5 Implementation 

Program, When Does a State Need To 

Conduct a RACT Determination for an 

Applicable Source That Already Has a 

RACT, BACT, LAER, or MACT 

Determination in Effect? 

a. Background 

For PM2.5 nonattainment areas, States 

are required to implement the RACT 

requirement to reduce emissions of 

direct PM2.5 and PM2.5 precursors from 

applicable sources. The EPA anticipates 

that for some sources located in PM2.5

nonattainment areas, the State would 

have previously conducted RACT 

determinations for VOC or NOX under 

the 1-hour ozone standard, or for direct 

PM10 emissions under the PM10

standards. Some of the RACT 

determinations established under these 

other programs would be relatively 

recent while other determinations may 

be more than 10 years old. In some 

cases, a new RACT determination might 

reach the conclusion that the 

preexisting determination is still valid 

and would require the installation of 

similar control technology because the 

relevant pollutant was addressed, the 

same emission points were reviewed, 

and the same fundamental control 

techniques would still have similar 

costs. In other cases, however, a new 

RACT analysis could determine, for 

example, that better technology has 

become available, and that cost-effective 

emission reductions are achievable. 

In the proposed rule, the EPA 

requested comments on a general 

approach to taking prior RACT 

determinations into account, and within 

the general approach, invited comments 

on two specific questions: (1) Should 

new RACT determinations be required 

for all existing determinations that are 

older than a specified amount of time 

(such as 10 years old)?; and (2) what 

supporting information should a State 

be required to submit as part of its 

certification to demonstrate that a 

previous RACT analysis meets the 

RACT requirement currently for 

purposes of the PM2.5 program? 

In the proposed rule, EPA also noted 

that sources subject to RACT may also 

have been subject to other prior 

technology determinations such as 

BACT, LAER or MACT determinations. 

The proposed rule requested comment 

on approaches to taking these prior 

technology determinations into account. 

b. Final Rule 

The EPA has determined that it is 

appropriate to follow the approach in 

the proposed rule, which is described 

below. State RACT SIPs for PM2.5 must 

assure that RACT is met, either through 

a new RACT determination or a 

certification that previously required 

RACT controls represent RACT for 

PM2.5. 

Where a State adopted and EPA 

approved a control measure as RACT for 

a pollutant emitted from a specific 

stationary source or source category 

under another NAAQS program, the 

State may submit as part of its SIP 

revision a certification, with appropriate 

supporting information, that the 

previous determination represents a 

current RACT level of control for those 

emissions for purposes of the PM2.5

program. Otherwise, the State should 

revise the SIP to reflect a modified 


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43There are some MACT categories for which it 

may not be possible to determine the degree of VOC 

reductions from the MACT standard without 

additional analysis; for example, the miscellaneous 

metal parts and products (40 CFR part 60, subpart 

MMMM) due to the uncertainty of the compliance 

method that will be selected. 

RACT requirement for specific sources 

or source categories. 

In cases where the State’s prior RACT 

analysis under another NAAQS program 

concluded that no additional controls 

were necessary, a new RACT 

determination is required for that 

source. In cases where the previous 

RACT determination did not require any 

controls on the source, it is more likely 

that a new review might find that 

emission controls are now economically 

and technically feasible. This is because 

emissions reductions from a potential 

control measure are likely to be greater, 

and the cost per ton of emission 

reduction is likely to be lower, than in 

the case of a source that previously 

installed controls to meet RACT under 

another program. 

A RACT determination for a source or 

source category subject to a prior RACT 

determination is also required for any 

pollutants that were not the subject of 

the prior RACT determination, but 

which the State has determined should 

be regulated for purposes of PM2.5. The 

EPA advises that the State should 

closely review any existing RACT 

determinations established under 

another NAAQS program. For RACT 

certifications and determinations, States 

are to consider new information that has 

become available since the earlier RACT 

determination. For example, where 

updated information on control 

technologies is presented as part of 

notice-and-comment rulemaking, 

including a RACT SIP submittal for 

sources previously controlled, States 

(and EPA) must consider the additional 

information as part of that rulemaking. 

Existing EPA guidance on control 

technologies can be used to help inform 

RACT decisions. However, EPA believes 

it may not be sufficient for a State to 

rely on technology guidance that is 

several years old and issued to provide 

recommendations on control measures 

and levels for a different NAAQS in 

evaluating RACT for PM2.5. 

With respect to prior technology 

determinations other than RACT, the 

final rule provides that: 

(1) Prior BACT and LAER 

Determinations. In many cases, but not 

all, best available retrofit technology 

(BACT) or lowest achievable emission 

rate (LAER) provisions for new sources 

would assure at least RACT level 

controls on such sources. The BACT/ 

LAER analyses do not automatically 

ensure compliance with RACT since the 

regulated pollutant or source 

applicability may differ and the 

analyses may be conducted many years 

apart. States may, however, rely on 

information gathered from prior BACT 

or LAER analyses for the purposes of 

showing that a source has met RACT to 

the extent the information remains 

valid. We believe that the same logic 

holds true for emissions standards for 

municipal waste incinerators under 

CAA section 111(d) and NSR/PSD 

settlement agreements. Where the State 

is relying on these standards to 

represent a RACT level of control, the 

State should present its analysis with its 

determination during the SIP adoption 

process. 

(2) Compliance With MACT 

Standards Affecting VOC. In situations 

where the State has determined VOC to 

be a significant contributor to PM2.5

formation in an area, compliance with 

MACT standards may be considered in 

VOC RACT determinations. For VOC 

sources subject to MACT standards, 

States may streamline their RACT 

analysis by including a discussion of the 

MACT controls and relevant factors 

such as whether VOCs are well 

controlled under the relevant MACT air 

toxics standard, which units at the 

facility have MACT controls, and 

whether any major new developments 

in technologies or costs have occurred 

subsequent to establishment of the 

MACT standards. We believe that there 

are many VOC sources that are well 

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

or through substitution of non-VOC 

non-HAP materials for VOC HAP 

materials) because they are regulated by 

the MACT standards, which EPA 

developed under CAA section 112. Any 

source subject to MACT standards must 

meet a level that is as stringent as the 

best-controlled 12 percent of sources in 

the industry. Examples of these HAP 

sources that may effectively control 

VOC emissions include organic 

chemical plants subject to the hazardous 

organic NESHAP (HON), 

pharmaceutical production facilities, 

and petroleum refineries.43 We believe 

that, in many cases, it will be unlikely 

that States will identify VOC emission 

controls more stringent than the MACT 

standards that are not prohibitively 

expensive and are thus unreasonable. 

We noted our view that this will allow 

States, in many cases, to conclude that 

the control measures implemented to 

meet MACT standards satisfy any 

requirement for VOC RACT. 

(3) Compliance With MACT 

Standards Affecting PM2.5 Emissions. 

Compliance with MACT standards may 

be considered in direct PM2.5 RACT 

determinations. For direct PM2.5 sources 

subject to MACT standards, States may 

streamline their RACT analysis by 

including a discussion of the MACT 

controls and relevant factors such as 

whether PM2.5 emissions are well 

controlled under the relevant MACT air 

toxics standard, which units at the 

facility have MACT controls, and 

whether any major new developments 

in technologies or costs have occurred 

subsequent to the MACT standards. We 

believe that there are many direct PM2.5

sources that are well controlled (e.g., 

through add-on controls that represent 

state-of-the-art measures for PM2.5

reduction) because they are regulated by 

the MACT standards which EPA 

developed under CAA section 112. For 

some MACT standards, PM2.5 is used as 

a surrogate for achieving MACT for 

HAPs such as heavy metals. Any source 

subject to MACT standards must meet a 

level that is as stringent as the bestcontrolled 12 percent of sources in the 

industry. We believe that there will be 

sources for which it will be unlikely 

that States will identify emission 

controls more stringent than the MACT 

standards that are not prohibitively 

expensive and are thus unreasonable. In 

addressing whether a MACT standard 

represents best controls for PM2.5, it is 

important that the State consider all 

PM2.5 sources at a given facility and the 

nature of the PM limit (i.e., whether the 

limit ensures control of the fine fraction 

of particulate matter). Also, the State 

should evaluate the degree of capture of 

PM2.5—that is, the amount of PM2.5 that 

is collected and sent to a pollution 

control device in addition to the 

efficiency of the device itself. This 

evaluation should consider the PM2.5

emissions reductions that could be 

achieved by improving the degree of 

capture. 

(4) Year-Round Controls for NOX. In 

some cases, sources subject to NOX

RACT for PM will also be subject to 

controls under the NOX SIP Call. In the 

8-hour ozone implementation rule, EPA 

concluded that certain sources which 

have installed emission controls to 

comply with the NOX SIP call would be 

deemed to meet NOX RACT for the 

purposes of the 8-hour ozone 

implementation program. Some of these 

sources subject to the NOX SIP call may 

choose to control NOX emissions only or 

primarily during the ozone season. For 

purposes of PM2.5, however, EPA 

concludes that the operation of emission 

controls only or primarily during the 

ozone season would not constitute 

RACT for PM2.5 purposes. Indeed PM2.5

control programs must address annual 

average concentrations, and in many 


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areas nitrate concentrations are 

generally highest in the winter. 

Therefore, RACT for PM2.5 is year-round 

operation of controls. For sources 

subject to both the NOX SIP call and 

NOX RACT for PM, we believe that, in 

most cases, the additional costs of 

running the NOX SIP call controls yearround would impose only modest, 

reasonable additional costs and the cost 

effectiveness would be better than the 

average cost effectiveness for many 

other sources subject to PM RACT. (See 

further discussion in section F.7 above 

related to EGU sources subject to CAIR 

requirements for NOX). 

c. Comments and Responses 

Comments: A number of commenters 

agreed with the requirement for the 

State to conduct a new RACT 

determination for any source for which 

the State’s prior RACT analysis under 

another NAAQS program concluded 

that RACT was defined as no additional 

controls. One commenter noted that for 

a source having a previous RACT 

determination for ozone or PM10 to 

show that its level of control currently 

meets RACT for PM2.5 purposes, the 

source must provide supporting 

documentation showing that the 

previous RACT determination was 

based on the same universe of controls 

that are ‘‘reasonably available’’ for the 

source in the present day. 

Response: The EPA agrees with these 

comments. 

Comments: A few commenters 

recommended that EPA clarify that 

RACT determinations resulting only in 

‘‘operational changes’’ should be treated 

in an equivalent manner as those 

resulting in no controls. The 

commenters suggested that, unlike 

‘‘physical modification,’’ such 

operational changes should always be 

revisited with a new RACT 

determination. 

Response: The EPA does not agree 

with the implicit recommendation to 

impose different RACT review 

requirements based on the types of 

control previously implemented. The 

EPA believes that a reassessment of 

RACT is warranted, irrespective of the 

type of control previously implemented, 

to consider the reasonableness of 

modifying or adding controls in the 

particular circumstances. Furthermore, 

we are concerned that making such a 

distinction based upon the fairly broad 

term ‘‘operational change’’ would be 

difficult to interpret and implement, 

and would invite unnecessary disputes 

concerning the application of the term. 

Comment: Commenters differed on 

whether new RACT determinations 

should be required for all existing 

determinations made before a specific 

date, and on what that date should be. 

Some commenters recommended that 

EPA allow States to rely on any 

previous RACT determinations made 

after 1990, and one commenter 

recommended that EPA require States to 

review only those older than 10–15 

years, another recommended 10 years. 

One commenter believed that a 15-year 

period would be reasonable where 

previous controls were installed, to 

allow for a 15-year amortization of the 

cost of those controls. Other 

commenters recommended that new 

RACT determinations be made for any 

RACT determinations older than 5 

years. Another commenter 

recommended that all RACT 

determinations should be reviewed. 

Response: The EPA has not included 

any specific time frame in the final rule. 

The EPA agrees that the more recent the 

RACT determination, the greater the 

probability that technology advances or 

decreases in control cost will not have 

occurred. At the same time, technology 

advances and decreases in control cost 

can and have occurred frequently. 

Accordingly, we believe it is necessary 

for States to review whether such 

technology advances or decreases in 

control cost have occurred before 

relying on previous RACT 

determinations. We do not believe there 

is any specific date or age that could be 

identified after which States could 

ensure that no technology advances or 

decreases in control cost will have 

occurred. 

Comment: A number of commenters 

expressed concerns with the resources 

required to conduct the certifications 

required by the proposed approach, and 

argued that expending the resources 

required to review and to certify 

previous RACT determinations would 

not be productive. One commenter 

recommended that EPA provide 

guidance on the previous RACT 

categories for which old RACT 

determinations are believed to be out of 

date. Another commenter asserted that 

the only possible exception to the 

acceptability of previous RACT 

measures for purposes of the ozone 

standards would be when the new 

RACT is year-round for an existing 

ozone-season RACT measure. 

Response: The EPA believes that the 

proposed certification approach strikes 

an appropriate balance in requiring 

States to verify whether previous RACT 

determinations currently represent an 

appropriate RACT level of control for 

PM2.5 purposes, while stopping short of 

requiring an exhaustive re-analysis for 

all RACT sources. The EPA believes that 

much of the resource concerns 

expressed in comments were based 

upon concerns that VOC sources are 

very numerous, and that this approach 

would require detailed review for these 

sources. As noted previously, a RACT 

analysis for VOC sources is required 

only if a State makes a finding that VOC 

sources significantly contribute to 

nonattainment in the State. We believe 

the commenters likely overestimate the 

resource implications of the certification 

process for prior RACT determinations. 

Another mitigating factor is that many 

of these same sources would be 

reviewed for purposes of implementing 

the eight-hour ozone standard. On the 

other hand, where a State or EPA 

determines that it is appropriate to 

regulate VOC sources for PM2.5, EPA 

believes that it likely would be 

productive to review the previous 

determination for such sources, some of 

which have not been reviewed for many 

years. 

Comment: One commenter believed 

that EPA should acknowledge detailed 

RACT and RACM analyses for the South 

Coast and San Joaquin Valley in 

California prepared during the 1990s for 

purposes of implementing the ozone 

and PM10 standards. The commenter 

believes that EPA acceptance of these 

determinations as RACT for PM2.5

would enable States to focus resources 

on developing new measures needed for 

attainment. 

Response: The EPA agrees that States 

should focus resources on new 

technologies and new developments. At 

the same time, EPA recognizes that for 

most source categories, new technology 

continues to be developed, and new 

information continues to be generated. 

Thus, even recent RACT determinations 

for a given source category may be 

outdated. Hence, the certification 

approach in the rule for the relevant 

sources or source categories is a 

reasonable approach which is designed 

to provide for the type of focused efforts 

suggested by the commenter. 

Comment: One commenter believed 

that a State certification should only 

have to identify the existing RACT 

levels in a SIP and pollutants affected, 

but the State should not be required to 

provide any additional information. 

Response: The EPA disagrees with 

this comment. The EPA believes that 

prior technology determinations should 

be taken into account in the RACT 

determination process. In reviewing 

existing RACT determinations, the State 

should provide supporting information 

to show that the existing technology in 

use should still be considered RACT, or 

it should show that there have been 

technology advances or cost reductions 

that have occurred since the previous 


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44The consolidated emissions reporting rule was 

published in the Federal Register on June 10, 2002, 

pages 39602–39616. 

RACT limits were developed that make 

lower emissions technically and 

economically feasible in the context of 

RACT and would contribute to 

advancing the attainment date by at 

least one year. 

Comment: Some commenters 

supported EPA’s requirement for yearround operation of NOX pollution 

control devices as RACT, given that 

PM2.5 is an annual standard, while 

ozone is a summertime problem. 

Response: The EPA agrees with these 

comments. 

Comment: One commenter concluded 

that BACT and LAER determinations 

should be considered to satisfy RACT, 

regardless of the date they were made, 

because BACT and LAER by definition 

are more stringent than RACT. 

Response: The EPA disagrees with 

this comment. The EPA believes that in 

many cases, but not all, BACT and 

LAER would assure RACT level of 

controls. Reasons that BACT and LAER 

might not satisfy RACT include: The 

pollutant of concern could have been 

different, the applicability threshold for 

BACT and LAER may have excluded 

smaller sources potentially subject to 

RACT controls, and technology 

advances or reductions in control costs 

may have occurred since the old 

determination was conducted. 

Comment: One commenter 

recommended that EPA allow States to 

use information gathered from prior 

BACT or LAER analyses to complete the 

RACT determination, as was allowed in 

the 8-hour ozone NAAQS 

implementation rule. 

Response: The final rule allows for 

use of such information, to the extent it 

remains valid, to inform a certification 

by the State that BACT or LAER 

technology continues to exceed what 

would currently be considered RACT. 

Comment: Some commenters argued 

that any MACT determination that 

controls the pollutants of concern 

should be more than sufficient to satisfy 

RACT. Some commenters made similar 

recommendations regarding specific 

standards where PM limits were 

developed as a surrogate for HAPs, such 

as the MACT standard for integrated 

iron and steel mills, the MACT standard 

for iron and steel foundries, and the 

section 129 standards for waste to 

energy facilities. 

Response: While agreeing that MACT 

controls are relevant, the EPA disagrees 

that all MACT determinations should be 

automatically considered to satisfy 

RACT. Reasons include: A MACT 

standard aimed at toxics might not 

ensure that the relevant PM2.5

pollutant(s) are well controlled, MACT 

applicability provisions might have 

excluded units potentially subject to 

RACT, and technology advances or 

reductions in control costs might have 

occurred since EPA conducted the 

MACT analysis. The EPA believes that 

the State should review whether 

technology advances have occurred 

including available ‘‘beyond the MACT 

floor’’ technologies that may be 

reasonable in the context of RACT for 

PM2.5 nonattainment, but which were 

not selected as MACT for purposes of 

implementing section 112. The EPA 

believes that RACT analyses should 

evaluate whether increased capture of 

PM2.5 could be achieved, and whether 

an increased efficiency in controlling 

the fine fraction of particulate matter is 

reasonably available. The EPA has, 

however, added a specific recognition 

that MACT standards can reduce PM2.5

as well as VOC, and that PM2.5

information gathered for MACT 

standards development may inform a 

State’s conclusions on available 

technologies for direct PM2.5 emissions. 

Comment: One commenter expressed 

a concern that EPA should not presume 

that MACT represents RACT where the 

MACT rule allows for a risk-based 

exemption from the control technology 

requirement. 

Response: The EPA agrees with this 

comment. 

11. How Should Condensable Emissions 

Be Treated in RACT Determinations? 

a. Background 

Certain commercial or industrial 

activities involving high temperature 

processes (fuel combustion, metal 

processing, cooking operations, etc.) 

emit gaseous pollutants into the ambient 

air which rapidly condense into particle 

form. The constituents of these 

condensed particles include, but are not 

limited to, organic material, sulfuric 

acid, and metals. In general, 

condensable emissions are taken into 

account wherever possible in emission 

factors used to develop national 

emission inventories, and States are 

required under the consolidated 

emissions reporting rule (CERR) 44 to 

report condensable emissions in each 

inventory revision. Currently, some 

States have regulations requiring 

sources to quantify condensable 

emissions and to implement control 

measures for them, and others do not. In 

1990, EPA promulgated Method 202 in 

Appendix M of 40 CFR Part 51 to 

quantify condensable particulate matter 

emissions. In the proposed rule, EPA 

discussed and requested comment on 

issues related to condensable emissions 

in RACT determinations. 

In the proposed rule, we noted that 

EPA is in the process of developing 

detailed guidance on a new test method 

which quantifies and can be used to 

characterize the constituents of the 

PM2.5 emissions including both the 

filterable and condensable portion of the 

emissions stream. We also noted that 

when a source implements either of 

these test methods addressing 

condensable emissions, the State will 

likely need to revise the source’s 

emissions limit to account for those 

emissions that were previously 

unregulated. For the purposes of 

determining RACT applicability and 

establishing RACT emission limits, EPA 

indicated in the proposal that it intends 

to require the State to adopt the new test 

method once EPA issues its detailed 

guidance. This guidance would be for 

use by all sources within a PM2.5

nonattainment area that are required to 

reduce emissions as part of the area’s 

attainment strategy. 

b. Final Rule 

Issues and comments related to test 

method and emissions limit issues for 

direct PM2.5 for RACT, including 

discussion of test methods for 

condensable PM2.5, are discussed in 

section II.L.3 of this preamble. The EPA 

recognizes that in some cases 

condensable emissions are more 

difficult to control than filterable 

emissions. However, condensable 

emissions may be assumed to be almost 

entirely in the 2.5 micrometer range and 

smaller, so these emissions are 

inherently more significant for PM2.5

than for prior particulate matter 

standards addressing larger particles. 

Therefore, EPA encourages States to 

consider the potential for reducing 

condensable emissions when evaluating 

potential measures for RACT. 

12. What Criteria Should Be Met To 

Ensure Effective Regulations To 

Implement RACT and RACM? 

a. Final Rule 

After the State has identified a RACT 

or RACM measure for a particular 

nonattainment area, it must then 

implement that measure through a 

legally enforceable mechanism (e.g., a 

State rule approved into the SIP). The 

legally enforceable mechanism must 

meet four important criteria. 

First, the baseline emissions from the 

source or group of sources and the 

future year projected emissions must be 

quantifiable so that the projected 

emissions reductions from the sources 

can be attributed to the specific 


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45The RFP test uses inventories for the full year, 

e.g. the year of 2009 or the year of 2012. EPA does 

not specifically require that the relevant measures 

be implemented by the beginning of the year, but 

RFP inventories must reflect the fact that measures 

that are implemented later in the year have 

correspondingly less impact on the year’s annual 

total emissions. 

measures being implemented. It is 

important that the emissions from the 

source category in question are 

accurately represented in the baseline 

inventory so that emissions reductions 

are properly calculated. In particular, it 

is especially important to ensure that 

both the filterable and condensable 

components of PM2.5 are accurately 

represented in the baseline since 

traditional Federal and State test 

methods have not included the 

condensable component of particulate 

matter emissions and have not required 

particle sizing of the filterable 

component. 

Second, the control measures must be 

enforceable. This means that they must 

specify clear, unambiguous, and 

measurable requirements. When 

feasible, the measurable requirements 

for larger emitting facilities should 

include periodic source testing to 

establish the capability of such facilities 

to achieve the required emission level. 

Additionally, to verify the continued 

performance of the control measure, 

specific monitoring programs 

appropriate for the type of control 

measure employed and the level of 

emissions must be included to verify the 

continued performance of the control 

measure. The control measures and 

monitoring program must also have 

been adopted according to proper legal 

procedures. 

Third, the measures must be 

replicable. This means that where a rule 

contains procedures for interpreting, 

changing, or determining compliance 

with the rule, the procedures are 

sufficiently specific and nonsubjective 

so that two independent entities 

applying the procedures would obtain 

the same result. 

Fourth, the control measures must be 

accountable. This means, for example, 

that source-specific emission limits 

must be permanent and must reflect the 

assumptions used in the SIP 

demonstration. It also means that the 

SIP must establish requirements to track 

emission changes at sources and 

provide for corrective action if 

emissions reductions are not achieved 

according to the plan. 

b. Comments and Responses 

There were no comments on this 

section. The language above is very 

similar to the language in the proposal. 

G. Reasonable Further Progress (RFP) 

1. Background 

Clean Air Act Section 172(c)(2) 

requires that plans for nonattainment 

areas ‘‘shall require reasonable further 

progress,’’ which as defined in Section 

171(1) ‘‘means such annual incremental 

reductions in emissions of the relevant 

air pollutant as are required by this part 

or may reasonably be required by the 

Administrator for the purpose of 

ensuring attainment of the applicable 

national ambient air quality standard by 

the applicable date.’’ This section 

describes the requirements the 

Administrator is establishing for states 

to achieve reasonable further progress. 

In general terms, the goal of these RFP 

requirements is for areas to achieve 

generally linear progress toward 

attainment. The RFP requirements were 

included in the Clean Air Act to assure 

steady progress toward attaining air 

quality standards, as opposed to 

deferring implementation of all 

measures until the end date by which 

the standard is to be attained. 

2. Requirements for Areas With 

Attainment Dates of 2010 or Earlier 

a. Background 

In 40 CFR 51.1009(b)(1) of the 

proposed rule, EPA proposed that a 

State which submits an implementation 

plan that demonstrates that an area will 

achieve attainment by 2010 (i.e., 

achieves attainment level emissions 

during 2009) would not be required to 

submit a separate reasonable further 

progress plan for that area. In such 

cases, EPA proposed that the attainment 

demonstration would also be considered 

to demonstrate that the area is achieving 

RFP. 

b. Final Rule 

In the final rule, EPA is maintaining 

the approach described in the proposed 

rule. An area that demonstrates 

attainment by 2010 will be considered 

to have satisfied the RFP requirement 

and need not submit any additional 

material to satisfy the RFP requirement. 

The EPA will view the attainment 

demonstration as also demonstrating 

that the area is making reasonable 

further progress toward attainment. 

c. Comments and Responses 

Comment: A number of commenters 

supported EPA’s view that a 

demonstration of attainment by 2010 

would also demonstrate that the area is 

making reasonable further progress 

toward attainment. 

Response: The EPA appreciates the 

support and is adopting the supported 

approach. 

Comment: A set of commenters 

objects to EPA’s proposal, arguing that 

EPA cannot waive RFP requirements for 

areas where the state purports to 

demonstrate attainment. These 

commenters believe that Subpart 4 of 

Part D requires milestones prior to 2009, 

and these commenters believe that even 

Subpart 1 requires a demonstration of 

interim progress that EPA cannot waive. 

Response: In brief, EPA is not waiving 

the RFP requirements for any area. 

Instead, EPA is concluding that a 

demonstration of attainment by 2010 

also serves to demonstrate achievement 

of RFP. If the state submittal purports to 

demonstrate attainment but does not 

adequately make this demonstration, 

then the submittal also would not 

demonstrate achievement of RFP. The 

nature of the RFP requirement would 

then depend on whether the remedied 

attainment demonstration provides for 

attainment by 2010. Finally, as 

discussed above, EPA believes that 

Subpart 4 requirements do not apply to 

PM2.5 plans. More detailed discussion of 

this comment and EPA’s response are 

provided in the response to comments 

document. 

3. Requirements for Areas With 

Attainment Dates Beyond 2010 

a. Background 

The proposed rule required a State to 

submit an RFP plan along with its 

attainment demonstration and SIP due 

in April 2008 for any area for which the 

State demonstrates that 2011 or later is 

the most expeditious attainment date. 

EPA proposed that the 2008 RFP plan 

must provide adequate emission 

reductions by 2009 45 and, in some 

cases, by 2012. The plan must 

demonstrate that emissions will decline 

in a manner that represents generally 

linear progress from the 2002 baseline 

year to the attainment year. 

b. Final Rule 

The final rule requires a State to 

submit an RFP plan along with its 

attainment demonstration and SIP due 

in April 2008 for any area for which the 

State justifies an extension of the 

attainment date beyond 2010. The RFP 

plan must provide emission reductions 

such that emissions in 2009 represent 

generally linear progress from the 2002 

baseline year to the attainment year. 

Where the State justifies an extension of 

the attainment deadline to 2014 or 2015, 

the state must additionally provide 

emission reductions such that emissions 

in 2012 represent generally linear 

progress from the 2002 baseline year to 

the attainment year. 


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If the State demonstrates that 

attainment will occur by 2010 or earlier, 

EPA will consider the attainment 

demonstration to demonstrate 

achievement of reasonable further 

progress, and the State will not be 

required to submit an additional RFP 

plan for the area. 

c. Comments and Responses 

Comment: For areas that demonstrate 

attainment by 2015 without adopting 

additional measures, a commenter 

recommended that the attainment 

demonstration be viewed as also 

demonstrating that the area is achieving 

RFP. The commenter therefore 

recommended that the state not be 

required to submit an RFP plan for such 

an area. 

Response: A submittal that 

demonstrates attainment at the latest 

allowable date and does not address 

interim air quality fails to show that the 

path to attainment will yield interim 

incremental air quality improvements. 

States have ample opportunity to adopt 

measures that would provide interim air 

quality improvement long before 2015. 

Indeed, as discussed elsewhere as part 

of the discussion of attainment dates, a 

submittal that only addresses 2015 

would also fail the attainment 

demonstration requirement, insofar as it 

would not be addressing whether 

attainment is as expeditious as 

practicable, because the submittal 

would fail to assess whether attainment 

could be achieved earlier. Therefore, 

irrespective of whether additional 

measures are needed to attain by 2015, 

the Clean Air Act mandates assessing 

progress at reasonable interim dates as 

well as mandating attainment. 

4. Generally Linear Progress and 

Associated Timeline 

a. Background 

The EPA proposed that states with 

areas needing an extension of the 

attainment deadline beyond 2010 would 

be required to submit a plan 

demonstrating that emissions would be 

sufficiently reduced by 2009 to achieve 

a generally linear incremental 

improvement in air quality. The notice 

of proposed rulemaking provided an 

example calculation for an area with a 

2013 attainment date, i.e. an area that 

achieves attainment level emissions in 

2012. (See section III.G.4.b.iv of the 

proposal, 70 FR 66013.) In this example, 

the 2009 emissions year represents 7/10 

of the period extending from the 

baseline year of 2002 to the 2012 year 

of attainment level emissions. 

Therefore, for this example, EPA’s 

proposed requirement would be for this 

area to achieve emission reductions by 

2009 representing approximately 7/10 of 

the emission reductions needed to attain 

the standards. For states with areas 

needing the attainment deadline 

extended to 2014 or 2015, EPA 

proposed to require achievement of 

generally linear emission reductions at 

two RFP milestone years—the 2009 and 

2012 emission years. 

The EPA received several comments 

on various elements of its proposed 

approach. Several commenters objected 

to EPA’s proposed requirement to 

achieve linear progress toward 

attainment, asserting that EPA cannot 

reasonably expect states to achieve a 

significant amount of progress within a 

short time after plan submittals are due. 

Some commenters recommended 

requiring a specific emission reduction 

percentage, similar to the rate of 

progress requirement for ozone. These 

comments are addressed below. 

b. Final Rule 

The EPA is requiring States with areas 

needing an extension of the attainment 

deadline to submit RFP plans. These 

plans must demonstrate that generally 

linear reductions in emissions will 

occur by 2009, i.e. that emissions in 

2009 will be reduced to the extent 

represented by a generally linear 

progression from 2002 base year 

emissions to attainment-level emissions. 

For any area that needs an extension of 

the attainment deadline to 2014 or 2015, 

the State’s RFP plan would also need to 

demonstrate that generally linear 

reductions will be achieved in the 2012 

emissions year as well. 

c. Comments and Responses 

Comment: Several commenters 

objected to EPA’s proposed requirement 

that states demonstrate linear progress 

toward attainment. For example, a 

commenter stated that a ‘‘generally 

linear reduction process may not be 

practicable.’’ A commenter stated that it 

‘‘agrees that areas should be able to take 

credit for reductions from 2002 forward, 

[but] EPA should allow for fewer 

reductions (as opposed to linear 

reductions) prior to 2008.’’

A commenter noted that EPA’s 

‘‘proposed approach ignores several 

important realities about PM NAAQS 

implementation. First, * * * [n]ot until 

SIP submittal in April 2008, some 6 

years after the RFP baseline date, will 

any local measures be finally adopted 

and approved. Under [the example EPA 

provided in its proposed rulemaking], 

states will be required to play ‘catch-up’

by achieving 70 percent of the required 

reductions in 2009. * * * Second, the 

‘generally linear’ approach ignores that 

EPA intends for states to rely in large 

part on mobile source reductions and 

reductions in NOX and SO2 from CAIR 

implementation to achieve attainment 

in many areas. These measures fail a 

‘generally linear’ test since most of the 

reductions they provide will not be 

realized until after 2009.’’ This 

commenter continues that the 

incremental reductions in emissions 

required in the Clean Air Act need not 

be equal increments, that the absence of 

a specific statutorily mandated 

increment (such as the 3 percent per 

year requirement for ozone) allows EPA 

to be more flexible and to rely more 

heavily on later reductions. The 

commenter also argues that EPA’s 

proposal is more stringent than the 

ozone RFP requirement, insofar as the 

ozone RFP requirement provides for 

averaging over 3 years. Similar 

comments were submitted by other 

commenters. 

Another commenter supported EPA’s 

proposal. This commenter supported 

requiring demonstrations that areas 

achieve emission reductions that will 

yield incremental improvement in air 

quality on a path toward expeditious 

attainment. 

Response: The EPA believes that the 

requirement for generally linear 

reductions is reasonable because it 

allows States to take credit for early 

reductions achieved due to federal, 

State, and local programs. We find that 

it appropriately implements the RFP 

requirement in the Clean Air Act. For 

these reasons, EPA is finalizing the 

requirement that RFP plans for areas 

needing an attainment deadline 

extension show generally linear 

progress in reducing emissions from the 

base year through the 2009 emissions 

year. EPA is also requiring that areas 

needing an attainment deadline 

extension to 2014 or 2015 (i.e. 

attainment level emissions projected to 

start in 2013 or 2014) show generally 

linear progress in reducing emissions 

through the 2012 emissions year. 

The commenters objecting to the 

requirement for generally linear 

progress appear to be assuming that 

only minimal emission reductions can 

be expected before 2008, so that a 

requirement for generally linear 

progress would require plans submitted 

in 2008 to compensate by achieving 

unrealistically high levels of emission 

reductions. The EPA disagrees with this 

assumption. 

In fact, substantial emission 

reductions have occurred in the past 

few years and can be expected to occur 

through the 2009 emissions year. The 

EPA has promulgated significant mobile 

source rules recently that will yield 


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substantial benefits in the coming years, 

and these benefits follow a series of 

prior rules that provide a steady 

progression of emission reductions as 

newer, cleaner vehicles replace older, 

dirtier vehicles. For utilities, significant 

NOX reductions occurred in 2004 under 

the NOX SIP call, and substantial SO2

reductions are expected to occur under 

the CAIR trading program prior to 2010 

due to incentives for early reductions 

and the banking of allowances. 

The EPA has also promulgated many 

other regulations that will reduce 

particulate matter and particulate matter 

precursor emissions before as well as 

after 2009. States have also been 

implementing a variety of measures. 

With use of a 2002 baseline, the 

assessment of RFP allows credit for 

these measures. The following is a 

partial list of the measures that have 

been adopted and will contribute to 

achieving generally linear reductions: 

• NOX SIP Call. 

• Tightened emission limits for new 

gasoline and diesel vehicles. 

• Numerous regulations requiring 

Maximum Achievable Control 

Technology, including regulations for: 

—Iron and steel plants, including coke 

plants 

—Industrial boilers 

—Cement plants 

—Lime plants 

—Primary aluminum plants 

• Numerous consent decrees for 

refineries. 

• Numerous consent decrees for 

power plants. 

• The Clean Air Interstate Rule for 

utilities. 

• Retrofitted controls on diesel 

vehicles, and related programs for 

reducing diesel vehicle emissions. 

• Closures of coke plants and other 

facilities (and, from a national 

perspective, replacement with cleaner 

new facilities). 

While different control measures 

require various timelines for 

implementation, EPA believes that 

many of the additional measures that 

states might adopt for attainment 

planning purposes can be implemented 

in a timely fashion for addressing RFP 

requirements. Thus, EPA believes that 

states can reasonably be expected to 

assure that the combination of existing 

measures and additional measures as 

necessary will provide for generally 

linear progress in reducing emissions. 

Furthermore, particularly with respect 

to the 2009 RFP milestone year, when 

EPA evaluates whether the emission 

levels in a state plan represent generally 

linear progress, EPA will consider the 

availability of measures that can be 

implemented by 2009. 

It is difficult to compare the 

stringency of this RFP requirement to 

the RFP requirement for ozone. The RFP 

requirement for ozone measures one 

form of progress that occurs after 3 

years, and the requirement for PM2.5

measures a different form of progress 

that occurs after 7 years (and for some 

areas also after 10 years). That is, the 

ozone RFP requirement applies a fixed, 

universally applicable emission 

reduction percentage for one pollutant 

(VOC), whereas EPA is defining the 

PM2.5 RFP requirement as an areaspecific combination of emission 

reductions for multiple pollutants, 

defined on the basis of each area’s 

attainment demonstration. 

The EPA believes that the Clean Air 

Act mandates not merely eventual 

attainment by 2015 but also that states 

demonstrate that emissions are being 

incrementally reduced in earlier years. 

(As discussed elsewhere, states must 

also demonstrate attainment by earlier 

than 2015 if feasible.) The requirement 

for RFP reflects Congressional intent 

that areas make steady progress toward 

attainment in the years before 

attainment occurs, and states have 

ample opportunity to assure that 

reductions occur well before 2015. 

Comment: A commenter observes that 

the PM2.5 nonattainment areas in its 

state also violate the ozone standard. 

The commenter observes, ‘‘[i]n setting 

plan requirements, U.S. EPA should 

choose options that best facilitate 

harmonization of fine particulate and 

ozone control programs. This includes 

using a fixed percentage of emission 

reductions per year for reasonable 

further progress (RFP). We recommend 

the ozone RFP metric of three percent 

annual emission reductions averaged 

over three years.’’ Another commenter 

also supports a more prescriptive RFP 

requirement, and comments that ‘‘As 

suggested by EPA, nonattainment areas 

must be required to achieve ‘a fixed 

percentage reduction of the emissions of 

direct PM2.5 and regulated PM2.5

precursors and in specific milestone 

years’ between the base year and the 

attainment year proposed in the 

attainment demonstration.’’ A third 

commenter supported establishing a 

requirement for a fixed emission 

reduction percentage, set at ‘‘no less 

than the 3 percent rate’’ in Section 182, 

with the possibility of higher rates in 

areas with more severe air quality 

problems. 

Other commenters prefer the 

approach that EPA proposed. For 

example one commenter states that it 

agrees with EPA’s approach of using the 

attainment demonstration to define the 

parameters for determining what 

constitutes RFP, and the commenter 

supports the flexibility of EPA’s 

proposed approach ‘‘rather than 

requiring fixed linear percentage 

reductions.’’ Regarding the proposed 

option to require 3 percent per year 

emission reductions for areas classified 

as serious, some commenters 

recommended against establishing 

classifications and a fixed emission 

reduction percentage for any area. 

Response: Requiring a fixed annual 

emission reduction percentage would 

impose a ‘‘one-size-fits-all’’ approach to 

address a range of circumstances. 

Requiring a fixed annual emission 

reduction percentage would overstate 

the reductions needed to achieve timely 

attainment in some areas and would 

understate the reductions needed to 

achieve timely attainment in other 

areas. The EPA believes that defining 

the RFP requirement in terms of 

achieving generally linear progress 

toward the emission reductions needed 

for timely attainment assures that each 

area will achieve a steady rate of 

progress most appropriate for the area to 

achieve timely attainment. 

The EPA recognizes that many areas 

are nonattainment for both PM2.5 and 

ozone and that the control programs for 

the two pollutants are sufficiently 

intertwined that harmonization of 

planning for meeting requirements 

applicable to the two pollutants is 

important. However, because the 

statutory requirements set forth in 

section 182 do not apply to PM2.5 RFP 

plans, EPA believes it is neither 

necessary nor appropriate to impose 

these requirements for PM2.5. Indeed, 

given the multiple pollutants that 

contribute to PM2.5 and the variations 

that exist in the nature and composition 

of PM2.5 across the country, EPA 

believes that the PM2.5 RFP 

requirements for generally linear 

reductions are better defined to reflect 

these variations and thus better targeted 

toward the emission reductions that in 

each area can be expected to lead 

toward timely attainment. Further, EPA 

believes that application of a different 

form of the RFP requirement does not 

cause conflicts in implementation 

planning for the two standards. For 

example, reductions of NOX emissions 

will generally reduce concentrations of 

both ozone and PM2.5, and NOX

emission reductions are creditable for 

meeting both the ozone and the PM2.5

RFP requirements. 

An important distinction between 

PM2.5 and ozone is that fine particle 

formation is in general a more complex 

process, affected by both direct 

emissions and numerous precursor 

pollutants. The EPA does not believe 


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that RFP targets for PM2.5 should be the 

same as those used for the ozone 

implementation program, nor should 

the same percentage reduction be used 

for all PM2.5 related pollutants. Instead, 

EPA believes that RFP plans should 

reflect an appropriate combination of 

pollutant reductions that most 

effectively provides for attainment. 

Therefore, EPA has defined an RFP 

requirement in which target emission 

reductions are established in 

conjunction with the area’s attainment 

plan. 

5. Geographic Coverage of Emissions 

Sources 

a. Background 

PM2.5 concentrations reflect a 

combination of impacts over a wide 

range of geographic scales. For some 

components of PM2.5, observed 

concentrations typically arise 

predominantly from sources within the 

nonattainment area. For other 

components, PM2.5 concentrations may 

be influenced by sources across a broad 

area extending outside the 

nonattainment area. The EPA’s intent is 

to define the RFP requirement in terms 

of emissions reductions that can be 

expected to provide generally linear 

improvements in air quality in the 

nonattainment area. For this purpose, 

EPA continues to believe that RFP 

requirements for PM2.5 are best defined 

such that states evaluate emissions of 

each pollutant throughout the area in 

which the emissions substantially 

influence PM2.5 concentrations in the 

nonattainment area. 

As described in the proposed 

rulemaking, EPA expects each area’s 

attainment demonstration to identify 

many of the parameters used to define 

the emission reductions that would 

represent RFP. First, the attainment plan 

will identify the pollutants that are 

being reduced to achieve attainment. 

Second, the attainment plan will 

identify the amount of reduction of each 

pollutant and the date by which 

attainment can be achieved. This 

information suffices to calculate a 

baseline set of reductions to be achieved 

by 2009 to provide for RFP. Third, 

where a state chooses to achieve RFP by 

reducing some pollutants earlier than 

others, the attainment plan will provide 

the information needed to assess 

whether the intended set of reductions 

can be expected to provide a 

comparable level of air quality 

improvement. Fourth, if the State 

intends to include emissions sources 

located outside the nonattainment area 

in its RFP plan, the information 

necessary to justify inclusion of such 

sources will likely be found in the 

attainment plan. 

The EPA’s proposed rulemaking 

identified several expectations regarding 

regional versus local impacts. For 

directly emitted PM2.5 (including 

organic and other carbonaceous 

particles as well as miscellaneous 

inorganic particles and including 

condensable particulate matter), EPA 

recognized that impacts are commonly 

localized, and that direct emissions of 

PM2.5 outside the nonattainment area 

should not be included in the RFP plan. 

Conversely, EPA recognized the regional 

nature of secondarily-formed sulfate and 

nitrate, and proposed that states could 

justify inclusion in the RFP plan of SO2

and NOX emissions sources located 

within 200 kilometers of the 

nonattainment area. 

The EPA recognizes that fine particles 

travel over long distances, and that 

distant emissions of SO2 and NOX

emissions can influence a 

nonattainment area’s air quality. At the 

same time, distant sources can be 

expected to have less impact than 

sources closer to the nonattainment 

area. EPA’s procedures for assessing 

RFP rely on a general assumption that 

all the sources included in the 

assessment have a comparable impact 

per ton of emissions. For this reason, it 

would be inappropriate to include 

distant emission sources in the 

assessment. Indeed, limiting the 

consideration of SO2 and NOX

emissions to a 200 kilometer range is 

intended to assure that only sources 

with comparable impacts are included 

in the assessment. 

b. Final Policy 

The policy for addressing direct PM2.5

emissions in RFP plans remains 

unchanged from the proposal: only 

emissions from within the 

nonattainment area may be included. 

Conversely, for SO2 and NOX, EPA 

believes that states could be able to 

justify considering not only all 

emissions in the nonattainment area but 

also emissions within a distance that 

may be up to 200 kilometers from the 

nonattainment area. States may also be 

able to justify consideration of VOC and 

ammonia emissions outside the 

nonattainment area on a case-by-case 

basis. As we explain more fully below 

in responding to comments, in 

situations where the state demonstrates 

that VOCs are a significant contributor 

to PM2.5 concentrations in the area, it 

may be appropriate to include VOC 

emission sources within a distance of 

up to 100 kilometers of the 

nonattainment area. Given the 

uncertainties regarding ammonia 

emission inventories and the effects of 

reducing ammonia, EPA is not 

establishing a policy on this issue with 

respect to ammonia. States that expect 

to regulate ammonia should consult 

with their regional offices to determine 

appropriate approaches for those areas. 

The justification for considering 

emissions outside the nonattainment 

area shall include justification of the 

state’s recommended definition of the 

area used in the RFP plan for each 

pollutant. 

The EPA received comments objecting 

to the possibility that RFP inventories 

for areas outside the nonattainment area 

could include selected sources 

expecting substantial emission 

reductions while excluding other nearby 

sources expecting emission increases. 

Based on its review of these comments, 

EPA is revising its approach for 

considering regional emissions. If the 

state justifies consideration of precursor 

emissions for an area outside the 

nonattainment area, EPA will expect 

state RFP assessments to reflect 

emissions changes from all sources in 

this area. The State cannot include only 

selected sources providing emission 

reductions in the analysis. The 

inventories for 2002, 2009, 2012 (where 

applicable) and the attainment year 

would all reflect the same source 

domain (i.e. the same set of sources 

except for the addition of any known 

new sources or removal of known, 

creditably and permanently shut down 

sources). 

In cases where the state justifies 

consideration of emissions of specified 

precursors from outside the 

nonattainment area, the state must 

provide separate information regarding 

on-road mobile source emissions within 

the nonattainment area for 

transportation conformity purposes. The 

EPA’s transportation conformity 

regulations (40 CFR Part 93.102(b)) only 

require conformity determinations in 

nonattainment and maintenance areas, 

and these regulations rely on SIP onroad motor vehicle emission budgets 

that address the designated boundary of 

the nonattainment area. For this reason, 

if the state addresses emissions outside 

the nonattainment area for a pertinent 

precursor (i.e. a precursor for which 

mobile sources are significant, as 

discussed in the May 6, 2005 

transportation conformity rule on PM2.5

precursors at 72 FR 24280), the on-road 

mobile source component of the RFP 

inventory will not satisfy the 

requirements for establishing a SIP 

budget for transportation conformity 

purposes. 

In such a case, the state must 

supplement the RFP inventory with an 


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inventory of onroad mobile source 

emissions to be used to establish a 

motor vehicle emissions budget for 

transportation conformity purposes. 

This inventory must address on-road 

motor vehicle emissions that occur 

within the designated nonattainment 

area, must be provided for the same 

milestone year or years as the RFP 

demonstration (i.e. 2009 and 2012 as 

applicable), and must satisfy other 

applicable requirements of the 

transportation conformity regulations. 

So long as the state provides this 

separate emissions budget EPA believes 

that this approach will optimally 

address both the RFP and the 

transportation conformity provisions of 

the Act. 

The EPA is restricting the geographic 

area for RFP assessments to include 

only areas within the state or states 

represented in the nonattainment area. 

For a single state nonattainment area, 

only emissions within that state would 

be considered, even if other states may 

be within 200 kilometers of the 

nonattainment area. For multi-state 

nonattainment areas, only regions 

within states represented in the 

nonattainment area shall be included in 

the RFP assessment. This restriction is 

intended to address commenters’

concerns about the enforceability of 

emission reductions included in the 

RFP assessment and helps assure 

accountability for these reductions. This 

topic is discussed further in the 

discussion below about multi-state 

nonattainment areas. 

The EPA is retaining the approach 

that RFP assessments may not include 

direct PM2.5 emissions from sources 

outside the nonattainment area. If a 

State regulates VOC or ammonia 

emissions as part of its attainment 

strategy, the RFP plan must include 

emissions of these pollutants. In the 

event that a State technical 

demonstration indicates that emissions 

of VOC or ammonia from sources 

outside the nonattainment area 

contribute significantly to PM2.5

concentrations in the nonattainment 

area, EPA will consider on a case-bycase basis whether it would be 

appropriate to include emissions from 

such sources in the RFP plan. 

c. Comments and Responses 

The EPA received numerous 

comments on its proposal regarding 

how regional versus local impacts 

would be addressed. Multiple 

commenters objected to EPA’s proposal 

that states could consider sources 

reducing emissions but ignore 

neighboring sources increasing 

emissions. Other commenters 

recommended that EPA support 

granting credit for reductions of direct 

PM2.5 emissions that occur outside 

nonattainment areas. A few commenters 

also recommended different treatment 

of selected pollutants. 

Comment: Several commenters object 

to the methods by which EPA proposed 

to account for reductions outside the 

nonattainment area. According to a set 

of commenters, if indeed sources 

outside the nonattainment area 

contribute to nonattainment, ‘‘then EPA 

cannot lawfully or rationally allow the 

state to claim RFP credit from a single 

source’s reductions without including 

in the baseline emissions from all 

sources (mobile, area and stationary) 

within the same distance from the 

nonattainment area, and without 

calculating the impacts of increases and 

decreases in such emissions on RFP. 

Viewing reductions from a single 

‘outside the area’ source in isolation 

will invariably provide an incomplete 

and inaccurate picture of the actual 

increase or decrease in emissions 

contribution to the nonattainment area 

from all ‘outside the area’ sources. 

Moreover, EPA’s proposal creates 

numerous opportunities to game and 

undermine the system. By allowing 

nonattainment areas to rely on RFP 

reductions made outside the 

nonattainment area, the proposed rule 

strays from the Act’s focus on achieving 

emissions reductions from sources 

within the nonattainment area.’’

Another commenter insisted that states 

should not be allowed to consider 

emissions from sources outside the area 

unless they can demonstrate the impacts 

of these sources on nonattainment area 

concentrations. 

In addition, a commenter objects to 

consideration only of sources that are 

reducing emissions and recommends 

that EPA allow credit for upwind source 

reductions only ‘‘on the condition that 

all other major sources in the 200 

kilometer boundary are also not allowed 

to increase emissions.’’ Another 

commenter supports an option which 

states would only consider emissions 

within the nonattainment area, 

observing that to consider emissions 

outside the nonattainment area would 

be difficult to administer and might 

inappropriately ‘‘dilute the reductions 

needed in the nonattainment area.’’ This 

commenter also observes that a 200 

kilometer limit does not include much 

of the emissions that yield long range 

transport. Another commenter supports 

crediting reductions outside the 

nonattainment area but requests that 

EPA define the area to be considered. 

Response: The EPA agrees that 

examining emissions reductions of only 

selected sources outside the 

nonattainment area gives an inaccurate 

assessment of the progress that an area 

is making. For example, if a state took 

credit for emission reductions at Source 

A but ignored equal emission increases 

at neighboring Source B, the state would 

claim emission reductions in its RFP 

plan when in fact no net emission 

reductions had occurred. 

The commenters suggest various 

remedies for this problem. One 

suggestion is to include all sources 

within the area that is used. Another 

suggestion is to allow no consideration 

of emissions outside the nonattainment 

area. Yet another suggestion is to allow 

consideration of selected sources so 

long as other sources do not increase 

emissions. 

The EPA is adopting the first of these 

suggestions: for the pertinent area 

outside the nonattainment area, the RFP 

assessment must include emissions (for 

all years evaluated) for all sources. The 

EPA believes that inclusion of all 

sources is needed to ensure that the RFP 

plan reflects the actual net emissions 

changes that are occurring in the 

relevant area. 

In cases where the state justifies 

consideration of emissions of specified 

precursors from outside the 

nonattainment area, EPA is accepting 

the recommendation of various 

commenters that the inventories of these 

precursors used for RFP purposes shall 

include mobile source emissions as well 

as stationary and area source emissions. 

However, in cases where onroad mobile 

source emissions are significant and are 

therefore included, the state would need 

to submit additional information for 

transportation conformity purposes. As 

discussed above, in accordance with 

existing transportation conformity 

regulations (40 CFR Part 93), the SIP’s 

motor vehicle emissions budget(s) must 

reflect an emissions inventory of onroad mobile source emissions for the 

nonattainment area. Consequently, in 

these cases, the state would need to 

supplement its RFP inventory with 

information identifying the inventory of 

on-road mobile source emissions within 

the nonattainment area for the pertinent 

precursor(s) for the applicable year or 

years (i.e. 2009 and potentially 2012) to 

be used to establish a motor vehicle 

emissions budget for transportation 

conformity purposes. 

The relevant comments in general did 

not address the dimensions of spatial 

domain of the sources outside the 

nonattainment area that would be used 

in assessing RFP. EPA agrees with a 

commenter urging, as a prerequisite to 

including sources of the pertinent 

pollutants outside the nonattainment 


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area in the assessment, that states must 

justify the inclusion of sources outside 

the nonattainment area. This 

justification would need to demonstrate 

that these emissions have a substantial 

impact on nonattainment concentrations 

that warrants including these emissions 

along with nonattainment area 

emissions in assessing RFP. Another 

commenter recommends that EPA 

define the area to be included. Since the 

demonstrations of impact are best done 

by states, in conjunction with their 

attainment planning, EPA intends to 

allow States to justify the area to be 

included, within distance limits 

discussed above. 

Comment: Numerous commenters 

recommend that EPA allow credit for 

reductions of direct PM2.5 emissions 

outside the nonattainment area. Some of 

these commenters also recommend that 

EPA allow credit for mobile source 

emission reductions outside the 

nonattainment area. Other commenters 

support EPA’s proposed approach, in 

which states may justify considering 

precursor emissions outside the 

nonattainment area but must evaluate 

direct PM2.5 emissions based solely on 

emissions within the nonattainment 

area. 

Response: Under Section 107 of the 

Clean Air Act, EPA is to designate 

nonattainment areas that include areas 

nearby to the violations that contribute 

to the violations. Given the spatial scale 

of the impacts of direct PM2.5 emissions, 

EPA believes that any direct PM2.5

emission source that demonstrably 

influences nonattainment area 

violations (and thus would contribute to 

these violations) would also be 

considered to be nearby to the violations 

for designation purposes. The EPA 

believes that it has properly defined the 

nonattainment areas to include all 

nearby contributing sources. 

Nevertheless, EPA asks anyone with 

evidence that an additional source or 

source area contributes to violations in 

a nonattainment area to submit that 

information to EPA and to recommend 

incorporation of that source or source 

area into the nonattainment area. 

The EPA has commented on 

consideration of mobile source 

emissions above. For direct PM2.5

emissions, EPA believes that the 

nonattainment area properly defines the 

area of consideration, and emissions 

from mobile sources outside the 

nonattainment area, like emissions from 

stationary sources outside the 

nonattainment area, should not be 

considered. For precursors for which 

consideration of emissions outside the 

nonattainment area is justified, the 

applicable inventories would include 

emissions from all sources including 

mobile sources as well as stationary 

sources. 

Comment: A commenter states that 

‘‘RFP credits for VOC should be granted 

for reductions achieved within the 

nonattainment area as well as [within] 

geographical limits outside of the 

nonattainment area.’’ This commenter 

supports consistency with the ozone 

policy, which allows credit for NOX

reductions within 200 kilometers and 

VOC reductions within 100 kilometers 

of the nonattainment area. Another 

commenter makes similar comments 

regarding VOC and comments that ‘‘[a]s 

the science and understanding of PM2.5

formation increases, EPA must revisit 

the 200 kilometer parameter and 

develop a possible proposal for 

ammonia.’’

Response: Conceptually, EPA agrees 

that in areas where anthropogenic VOC 

emissions outside the nonattainment 

area are shown to be a significant 

contributor to nonattainment area PM2.5

concentrations, presumably by 

formation of organic particles that 

influence nonattainment area 

concentrations, reduction of these VOC 

emissions could help improve air 

quality in the nonattainment area. 

Therefore, EPA is revising its policy to 

accommodate consideration of these 

potential impacts. The EPA believes that 

as the impacts of anthropogenic VOC on 

PM2.5 concentrations are better 

understood, it may in some cases be 

appropriate to consider sources outside 

the nonattainment area in RFP plans if 

the impacts from such sources can be 

properly quantified and justified. 

Nevertheless, EPA must highlight the 

technical challenges involved in 

assessing the impacts of VOC emission 

reductions. First, it is essential that the 

impacts of secondary organic particle 

formation from anthropogenic VOC 

emissions be differentiated from the 

impacts caused by biogenic VOC 

emissions and from the impacts of 

direct organic particle emissions. 

Second, the process of organic particle 

formation is highly complex, and 

currently available atmospheric models 

typically perform poorly in assessing 

the mass of particles thus formed. Third, 

the distance range of impacts, and to be 

more precise the distance range over 

which source impacts are comparable, is 

especially uncertain. While the distance 

range for organic particle formation is 

not necessarily the same as for the 

influence of VOC on ozone formation, it 

may be appropriate to include sources 

within 100 kilometers of the 

nonattainment area for both purposes, 

as the commenter recommended. 

However, any state wishing to include 

such sources outside the nonattainment 

area must justify the distance range that 

is appropriate for the area. 

The EPA is not prepared at this time 

to establish generally applicable 

guidance with respect to how RFP plans 

should address ammonia in cases where 

that precursor is found to be significant. 

States that expect to regulate ammonia 

emissions should consult their regional 

office regarding appropriate approaches 

for their particular areas. 

Finally, EPA agrees with the 

commenter that EPA should revisit the 

range of issues regarding geographic 

distances of impacts as more 

information and understanding become 

available. 

6. Pollutants To Be Addressed in the 

RFP Plan 

a. Background 

A number of commenters appeared to 

be confused by the discussion in the 

notice of proposed rulemaking regarding 

the pollutants to be included in the RFP 

assessment. The EPA proposed that the 

attainment demonstration would 

provide the key parameters of the RFP 

demonstration, and that the list of 

pollutants to be addressed in the RFP 

demonstration would match the list of 

pollutants regulated as part of the 

attainment demonstration. However, the 

notice of proposed rulemaking also 

suggested that the presumptions 

regarding whether different pollutants 

are to be regulated under NSR and 

RACM (including RACT) would also 

apply to RFP. This led some 

commenters to recommend different 

treatment of specific pollutants. 

In fact, the presumptions of 

applicability that EPA is promulgating 

for RACM are not germane to RFP. The 

pollutant coverage of RFP assessments 

is determined on an area-specific basis 

according to each area’s attainment 

demonstration, and EPA need not 

establish presumptions as to what 

pollutants are included in the RFP 

assessment. For example, if a state 

includes no NOX emission reductions in 

its attainment plan, then the RFP plan 

would not include NOX, irrespective of 

whether the (uncontrolled) NOX

emissions contribute significantly to the 

areas PM2.5 concentrations. 

The contrast between establishment of 

presumptions for RACM and having no 

such presumptions for RFP (or for 

attainment demonstrations) reflects 

differences in regulatory context. For 

RACM, at issue is whether the impact of 

the pollutant is sufficient to warrant full 

implementation of the RACM 

requirements. In contrast, for RFP (as for 

attainment plans), EPA is establishing 


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an overall progress requirement that 

may be met by applying various control 

levels to various pollutants, so long as 

overall emission reductions are 

adequate. Indeed, if the state chooses 

not to control a particular pollutant in 

its attainment plan, then the 

presumption is that that pollutant 

would not be reduced in the RFP plan 

either. Furthermore, states have the 

flexibility to meet the overall progress 

with any adequate combination of 

control of relevant pollutants, regardless 

of the significance or insignificance of 

these pollutants’ impacts. For these 

reasons, EPA is making no 

presumptions as to what pollutants will 

be included in RFP plans. 

b. Final Policy 

As proposed, the pollutants to be 

addressed in the RFP plan are those 

pollutants that are subject to control 

measures in the attainment plan. 

c. Comments and Responses 

Comment: A commenter states that 

‘‘VOC should be considered a 

presumptive PM2.5 precursor.’’ Another 

commenter recommends presuming that 

VOC and ammonia are included in the 

RFP plan. 

Response: The EPA’s approach to RFP 

does not rely on presumptions as to 

whether a pollutant does or does not 

warrant regulation as a precursor. 

Instead, pollutants are to be included or 

excluded according to whether the 

attainment demonstration includes 

emission controls for the pollutant that 

yield quantitative air quality benefits. 

Thus, irrespective of the presumptions 

applicable to RACM, the RFP plan 

would not include VOC unless the 

attainment plan reflects air quality 

improvements from VOC emission 

controls. The challenges of addressing 

VOC as part of an RFP plan were 

discussed earlier in this section. 

Similarly, ammonia would not be 

included in the RFP plan if the 

attainment plan does not regulate 

ammonia emissions. 

7. Equivalent Air Quality Improvement 

a. Background 

The EPA proposed that states could 

use alternative combinations of various 

types of emission control programs to 

meet RFP requirements if the alternative 

would be expected provide air quality 

improvements that are approximately 

equivalent to those of the benchmark 

emission reductions. Some control 

programs for some pollutants can be 

implemented more quickly than other 

control programs. EPA believes that it is 

unnecessary to require that all 

pollutants be reduced at the same rate 

or by the same fraction of the ultimate 

attainment plan reductions. The EPA 

believes instead that the states should 

have flexibility to ‘‘mix and match’’

control strategies, so long as they 

provide a demonstration that the 

adopted approach can be expected to 

yield approximately the same air quality 

progress as an approach in which the 

state achieves an identical fraction of 

the attainment strategy for all pollutants 

by the RFP milestone date. 

The notice of proposed rulemaking 

presented examples of the assessment of 

RFP, illustrating EPA’s recommended 

approach for establishing a benchmark 

set of emission reductions and 

illustrating EPA’s recommended 

procedures for whether modified 

approaches that control some pollutants 

earlier than other pollutants may be 

considered equivalent. While not 

repeated here, the examples remain 

appropriate for describing the approach 

included in the final rule. (See 70 FR 

66012–66013). 

Most commenters supported EPA’s 

proposal to allow alternative 

combinations of control that can be 

shown by simple means to be 

equivalent. A set of commenters 

objected to this approach, given the 

uncertainties involved in the 

equivalency assessment. Nevertheless, 

for this aspect of RFP policy, EPA’s final 

policy reflects the policy that it 

proposed. 

b. Final Policy 

The EPA is adopting an approach that 

establishes a benchmark level of 

controls but allows states the flexibility 

to adopt any combination of controls of 

the various pollutants that can be shown 

to provide equivalent benefits using 

procedures that EPA is recommending 

(or at the State’s option, air quality 

modeling). The first step is to determine 

the ratio of the number of years from the 

baseline year to the RFP review year 

(e.g., the 7 years from 2002 to 2009) 

divided by the number of years from the 

baseline year to the year in which 

attainment level emissions are achieved 

(e.g. the 10 years from 2002 to 2012, for 

an area with a 2013 attainment 

deadline). The benchmark level of 

controls is then determined by 

multiplying this ratio times the level of 

control being achieved for each 

pollutant. For example, for an area with 

an attainment deadline extended to 

2013, the benchmark level of controls 

would reflect 7⁄10 of the emission 

reductions of each pollutant that is 

controlled in the attainment plan. 

The equivalency process involves 

consideration of the air quality benefits 

for the emission reductions in the 

alternative plan for each regulated 

pollutant. In effect, the air quality 

benefits for each pollutant are used as 

weighting factors, such that pollutants 

for which controls yield larger benefits 

are weighted more heavily in 

determining the adequacy of the 

resulting plan. For each pollutant, the 

first step is to find the ratio of the 

emission reductions achieved by the 

RFP milestone date (e.g. the emission 

reductions achieved between 2002 and 

2009) divided by the emission 

reductions achieved by the attainment 

date. The second step is to multiply this 

ratio times the air quality improvement 

attributable to full implementation in 

the attainment year of the attainment 

strategy relevant to that pollutant. The 

third step is to add these pollutantspecific results to obtain a total 

estimated air quality benefit of the 

alternative plan. 

The air quality benefits of the 

benchmark reductions are easier to 

determine. The first step, inherent to 

defining the benchmark reductions, is to 

determine the ratio of the number of 

years to the RFP review divided by the 

number of years to attainment level 

emissions (in the example above, 7⁄10). 

The second step is simply to multiply 

this ratio times the quantity of air 

quality improvement achieved by the 

attainment plan. (Conceptually, the 

calculations are the same as are done for 

the alternative plan, but the 

mathematics are simpler because one is 

applying the same assumed fraction of 

the attainment plan emission reductions 

(e.g. 7⁄10) for all pollutants, so that there 

is no need to subdivide by pollutant.) 

For each milestone date, any alternative 

that provides estimated air quality 

benefits by the RFP milestone date that 

at a minimum are generally equivalent 

to the estimated benefits of the 

benchmark level of emission reductions 

will be considered to satisfy RFP 

requirements. 

c. Comments and Responses 

Comment: A set of commenters argues 

that the equivalency process is too 

uncertain, and recommends instead that 

states be required to achieve at least a 

fixed percentage reduction for all 

pollutants. The commenters cite the 

uncertainties acknowledged by EPA, 

including potential nonlinearity (i.e. 

that a given percentage of an emission 

reduction may yield a different 

percentage of the related air quality 

benefit). The commenters contrast EPA’s 

willingness to accommodate these 

uncertainties, for purposes of giving 

states flexibility for alternate RFP plan 

designs, with EPA’s unwillingness to 

accommodate the uncertainties inherent 


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in regulating ammonia emissions. The 

commenters state that ‘‘Rather than 

propose a standardized process for 

coherently determining ‘equivalency,’

EPA embraces the possibility that States 

will invent multiple and disparate 

methodologies.’’ The commenters argue 

that the need for certainty in achieving 

emission reductions trumps the benefits 

of state flexibility, not the other way 

around. The commenters state that if 

‘‘EPA decides nonetheless to accept 

equivalency demonstrations, it should 

at least * * * require States to conduct 

dispersion modeling’’ to confirm 

equivalency. The commenters further 

find unlawful the fact that EPA would 

allow ‘‘rough equivalency’’ rather than 

full equivalency to the benchmark 

approach. The commenters would 

prefer that EPA required a fixed 

percentage reduction of the emissions of 

direct PM2.5 emissions and of each 

precursor. 

Response: The EPA believes that its 

proposed approach satisfies the intent of 

the RFP requirement, which is to make 

ongoing, steady progress toward 

attainment rather than backloading 

control strategies. A requirement to 

obtain at least a given percentage of 

each of the pollutants that contribute to 

PM2.5 concentrations would impose an 

inflexibility that EPA concludes is 

unnecessary where not required by the 

statute. The EPA proposed to require 

that areas achieve emission reductions 

that are generally linear, and a plan that 

provides for rough equivalency to the 

benchmark approach would indeed 

provide generally linear reductions. In 

response to commenters’ requests for a 

standardized process for assessing 

equivalency, EPA believes the process 

outlined in the final rule is responsive 

to this request. It is not clear whether 

the fixed reduction percentage that 

certain commenters recommended 

would be an area-specific percentage 

(such as EPA uses to define the 

benchmark approach) or a universally 

applicable percentage (such as 3 percent 

per year). If the former, then EPA would 

repeat the response above regarding 

flexibility being consistent with the 

Act’s requirements; if the latter, then 

responses in III.6.4 regarding a fixed 

reduction percentage apply. The EPA 

believes that the procedures it is 

establishing to assess equivalency are 

adequate for assessing RFP and that 

dispersion modeling need not be 

required for this purpose. 

8. Other RFP Issues 

a. Multi-State Nonattainment Areas 

As stated in the proposed rulemaking, 

EPA seeks to ensure that nonattainment 

areas that include more than one State 

meet RFP requirements as a whole. 

Some commenters expressed concern 

about how one state’s submittal should 

address emissions in other states, 

including how the state might address 

questions about the enforceability of 

another state’s requirements. 

The issues here resemble the issues 

for attainment demonstrations. In that 

context as well, EPA seeks plans that 

reflect active consultation by the 

affected states and provide a 

combination of reductions that are 

enforceable by the respective states that 

collectively provide for attainment. The 

active involvement of regional planning 

organizations helps assure a collective 

design of a plan with specific 

requirements to be adopted by specific 

states. Likewise for RFP, EPA would 

expect states with multi-state 

nonattainment areas to consult with 

other involved states, to formulate a list 

of the measures that they will adopt and 

the measures that the other state(s) will 

adopt, and then to adopt their list of 

measures under the assumption that the 

other state(s) will adopt their listed 

measures. That is, each state would be 

responsible for adopting and thereby 

providing for enforcement of its list of 

measures, and then that state and 

ultimately EPA (at such time as the plan 

is approved) would be responsible for 

assuring compliance with the SIP 

requirements. 

In accordance with this view of RFP, 

as is the case for attainment plans, EPA 

expects states sharing a multi-state 

nonattainment area to submit a common 

assessment of whether RFP will occur. 

As a default, if the assessment only 

includes emissions within the 

nonattainment area, then each state 

would submit an assessment based on 

emissions from the full nonattainment 

area including portions of the area in 

other states. If the assessment includes 

precursor emissions from additional 

area outside the nonattainment area, 

then the states should have a common 

rationale for the area included, and all 

affected states would use the same 

inventory of the same multi-state area 

thus defined in assessing whether RFP 

will occur. The EPA would judge such 

submittals based on (1) whether the 

overall projected emission reductions 

will achieve RFP and (2) whether the 

submitting state has adopted the 

necessary enforceable measures to 

assure that the reductions projected 

within its boundaries will in fact occur. 

As a point of clarification, even if a 

state justifies consideration of emissions 

outside the nonattainment area in its 

RFP assessment, EPA intends that these 

assessments not use emissions from 

outside the state or states represented in 

the nonattainment area. For single state 

nonattainment areas, only emissions 

within that state would be considered. 

This will help assure accountability for 

the emission reductions included in the 

plan. 

b. Tribal Areas 

The EPA received no comments on its 

proposed policy regarding RFP for tribal 

areas, and EPA is finalizing the 

proposed policy. Under its Tribal 

Authority Rule (40 CFR 49.4), EPA 

found that it was not appropriate to 

apply SIP schedule requirements to 

tribes. For similar reasons, EPA is not 

requiring tribes to submit RFP plans. 

Generally this exemption will have 

limited if any impact on the 

achievement of RFP by an area. 

Nevertheless, consistent with its general 

role in implementing programs for tribes 

where ‘‘necessary and appropriate,’’

EPA will work with the affected tribes 

and states to ensure that emissions on 

tribal lands are addressed appropriately. 

The EPA intends to ensure that areas 

that include both state and tribal lands 

will satisfy RFP on a collective basis, 

similar to the policy applicable to multistate nonattainment areas. 

9. Mid-Course Review 

a. Background 

The EPA proposed requiring midcourse reviews on a case-by-case basis. 

The proposal described a mid-course 

review as a combination of reviews 

aimed at assessing whether a 

nonattainment area is or is not making 

sufficient progress toward attainment of 

the PM2.5 standards. The proposal 

described the mid-course review as 

involving ‘‘three basic steps: (1) 

Demonstrate whether the appropriate 

emission limits and emission reduction 

programs that were approved as part of 

the original attainment demonstration 

and SIP submittal were adopted and 

implemented; (2) analyze available air 

quality, meteorology, emissions and 

modeling data and document relevant 

findings; and (3) document conclusions 

regarding whether progress toward 

attainment is being made using a weight 

of evidence determination.’’ (Cf. 70 FR 

66010) 

The EPA views mid-course review 

requirements as part of a set of 

requirements for implementing the 

Clean Air Act requirements for 

reasonable further progress. For areas 

that demonstrate attainment by April 5, 

2010, EPA believes that this attainment 

demonstration also demonstrates that 

reasonable further progress is being 

achieved. For areas that demonstrate 


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attainment after April 5, 2010, EPA is 

requiring states to submit an RFP plan, 

due on April 5, 2008, showing that 

emissions in 2009 and, in some cases, 

in 2012, will be sufficiently reduced to 

provide generally linear progress toward 

levels that are expected to yield 

attainment. At issue here is how then to 

conduct ongoing tracking of whether the 

planned progress toward attainment is 

in fact occurring. Subparts 2 (for ozone) 

and 4 (for PM10) include explicit 

requirements for ongoing milestone 

tracking. Since Subpart 1 (applicable for 

PM2.5) allows EPA flexibility in 

determining how ongoing progress is to 

be tracked, EPA may adopt other 

approaches for achieving the necessary 

assurances that ongoing progress toward 

attainment is occurring. 

Milestone reviews can be confounded 

by changes in inventory methods (a 

concern expressed by a commenter 

particularly with respect to condensable 

emissions) and involve lengthy delays 

while inventories are compiled before 

planning can begin. Other approaches 

involving only air quality data reviews 

also do not provide for timely planning, 

insofar as such approaches involve 

waiting for three years of air quality data 

after implementation of controls before 

planning can begin. The EPA believes 

that a mid-course review provides the 

most productive approach, in lieu of 

establishing milestone tracking or other 

requirements, to assure that reasonable 

further progress in reducing emissions 

is being achieved. For this reason EPA 

proposed a requirement for mid-course 

reviews. 

The EPA proposed a process for 

establishing and implementing midcourse review. After the state submits an 

attainment plan (due in April 2008), 

EPA would evaluate whether a midcourse review is warranted after 

considering various factors including 

factors identified in the proposal. The 

EPA did not propose to conduct further 

rulemaking on establishing this 

requirement, but EPA proposed that 

‘‘[w]here EPA finds that a MCR would 

be required, the approval of the 

[attainment] demonstration would be 

contingent on a commitment from the 

State to conduct the MCR.’’ The midcourse review would then be due April 

2010. The EPA’s proposal also stated 

that ‘‘EPA would determine [based on 

review of the mid-course review] 

whether additional emissions 

reductions are necessary,’’ so that states 

would need to complete the mid-course 

review ‘‘three or more years before the 

applicable attainment date to ensure 

that any additional controls that may be 

needed can be adopted [in timely 

fashion].’’ Finally, EPA stated ‘‘[i]f a 

mid-course review will be required for 

certain PM2.5 nonattainment areas, 

separate PM2.5 mid-course review 

guidance will be written to address the 

specific requirements of PM2.5

nonattainment areas.’’

The EPA received numerous 

comments objecting to EPA’s proposed 

approach. Several commenters noted 

the inconsistency between requiring a 

mid-course review in April 2010 versus 

requiring a mid-course review due 3 or 

more years before an attainment date of 

2012 or earlier. Multiple commenters 

objected to EPA requiring a mid-course 

review only 2 years after the initial 

attainment plan is due. A commenter 

requested ‘‘nationally applicable 

guidance on when an MCR would be 

required and what it would need to 

include.’’ No commenters supported 

EPA’s timeline for mid-course reviews. 

Based on the comments that EPA 

received, EPA has reevaluated the 

process for mid-course reviews. Upon 

reevaluation, EPA shares many of the 

concerns expressed by commenters 

about the proposal. The proposal indeed 

presents conflicting dates for submittal. 

The EPA agrees that a deadline just 2 

years after the initial SIP submittal is 

too soon for states to conduct 

meaningful analyses of whether areas 

are making progress towards attainment. 

This problem would be exacerbated by 

the proposed process, in particular the 

fact that states would not know to begin 

work on a mid-course review until after 

they had submitted their initial SIP and 

after EPA had sufficiently reviewed the 

submittal to determine the need for a 

mid-course review. An early mid-course 

review also would defeat one of the 

purposes of the mid-course review, 

which is to take advantage of advances 

in the science and understanding of the 

nature of condensables and other 

components of PM2.5, to adjust plans to 

be better targeted at solving problems. 

For these reasons, EPA is significantly 

revising its approach to mid-course 

reviews as recommended by the 

commenters. The EPA is establishing a 

rule which provides more certainty to 

the states as to applicability and content 

of mid-course review requirements, 

thereby avoiding the need for future 

EPA rulemakings on the subject. The 

EPA’s rule clearly does not require 

states with early attainment dates to 

conduct a mid-course review and would 

clearly mandate a mid-course review 

only for areas with later attainment 

dates. The EPA’s final rule clarifies the 

content of mid-course reviews and 

provides for states to make decisions on 

whether further controls are needed 

rather than having EPA make this 

determination. The mid-course review 

shall include an updated modeled 

attainment demonstration as well as a 

review of the implementation of 

measures in the April 2008 SIP and a 

review of recent air quality data. The 

EPA believes that all of these elements 

are necessary and should be sufficient 

for the state to identify whether 

additional measures are needed to 

achieve attainment by the attainment 

date in the approved plan. The EPA 

believes that states, not EPA, should 

make the initial determination as to 

whether additional measures are 

needed, and EPA has designed its midcourse review requirements to provide 

for the states to make this 

determination. 

The EPA is promulgating a fixed date 

of April 2011 as a date for submittal of 

mid-course reviews for areas with 

attainment dates in 2014 or 2015. This 

fixed date will facilitate joint planning 

for multiple areas to apply common 

assumptions regarding regional 

transport. This date also gives states 

adequate notice for preparing these 

reviews and adequate time after the 

April 2008 submittal to incorporate new 

information and understanding of PM2.5

nonattainment problems to adjust 

attainment strategies as appropriate. 

The EPA is not requiring areas 

demonstrating attainment by 2013 or 

before to conduct a mid-course review. 

Such areas plan to have attainment level 

emissions by 2012, and EPA believes 

that an April 2011 mid-course review 

would not provide a timely 

reassessment of such areas’ attainment 

plans. Instead, EPA is clarifying that 

mid-course reviews are only required 

for areas that demonstrate a need for an 

attainment date extension at least to 

April 2014. 

b. Final Rule 

For each area with an approved 

attainment date in 2014 or 2015, EPA is 

requiring the state to submit a midcourse review by April 2011. The midcourse review shall include an updated 

attainment demonstration as well as a 

review of the implementation status of 

measures included in the April 2008 

submittal and a review of recent air 

quality data. The state shall determine 

whether additional measures are needed 

for timely attainment, just as the state is 

responsible for determining whether 

additional measures are needed in the 

April 2008 attainment demonstration, 

subject to formal EPA SIP review. The 

EPA is not requiring RFP milestone 

reviews, and EPA is requiring midcourse reviews for areas with 

sufficiently extended attainment dates 

in lieu of any other form of tracking 

reasonable progress. 


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c. Comments and Responses 

Comment: A number of commenters 

objected to EPA’s proposed timeframe 

that would have areas submit a midcourse review only 2 years after the 

initial SIP is due. They recommended, 

instead, that areas with attainment dates 

2 years or more beyond the first 5-year 

period submit mid-course reviews 3 

years after the SIPs are due (April 2011) 

and every 3 years thereafter, if 

necessary. Their reason for this 

suggestion is that the timing of midcourse review requirements needs to be 

clearer and should allow adequate time 

between plans and mid-course reviews 

if they are to serve as meaningful 

reviews. 

Several commenters also noted an 

inconsistency in the timing of midcourse review requirements under 

EPA’s proposal. The EPA proposed that 

mid-course review submittals would be 

due 5 years after the initial designation, 

which for all the original designations 

means 5 years after April 2005, i.e. April 

2010. However, EPA also proposed that 

mid-course reviews would be due 3 

years before the attainment date, which 

for areas with an April 2012 attainment 

date means April 2009. The commenters 

considered April 2009 for a mid-course 

review submittal to be too soon after the 

initial SIP submittal in April 2008, 

arguing that EPA would not have had 

time to review the 2008 SIP submittal, 

and the states would not have time to 

prepare a mid-course review by 2009. 

Some of these commenters expressed a 

view that EPA should not require midcourse reviews earlier than 3 years after 

the SIP submittal date. 

Response: The EPA agrees with these 

comments. The EPA is remedying the 

inconsistency in submittal dates by 

establishing the single submittal due 

date of April 2011 that was 

recommended by the commenters. As 

requested by commenters, EPA is also 

clarifying the applicability of the midcourse review requirement. The 

requirement shall apply to areas with 

attainment dates of 2014 or 2015; midcourse reviews shall not be required for 

areas that are expected to attain the 

standards by 2013. 

Comment: A commenter supports 

mid-course reviews as a means of 

assuring that areas with longer-term 

compliance dates are on track to attain 

the NAAQS as expeditiously as 

practicable. 

Response: The EPA agrees that midcourse reviews can be a critical step in 

assuring expeditious attainment for 

areas with extended attainment dates. 

Indeed, EPA is relying on mid-course 

reviews rather than milestone reviews 

or other forms of RFP tracking to serve 

this purpose. 

Comment: A commenter 

recommended eliminating mid-course 

review requirements for any area with 

less than seven years between SIP 

submittal and attainment. The 

commenter urged that EPA carefully 

reconsider its overall timelines for PM2.5

while considering the feasibility and 

practical usefulness of the steps 

required of States and emission sources. 

Response: The EPA agrees that the 

proposed timeline potentially required 

mid-course reviews in areas where such 

reviews would not be warranted, and 

the timeline did not provide the clarity 

as to the applicability of the 

requirement that states need to fulfill 

their planning responsibilities. In 

response, EPA is not requiring midcourse reviews for areas demonstrating 

attainment prior to 2014. For those areas 

that cannot demonstrate that attainment 

will occur prior to 2014, EPA has 

streamlined the mid-course review 

process so that the state bears 

responsibility for making the initial 

determination as to whether additional 

measures are needed to achieve timely 

attainment, rather than requiring 

additional steps of EPA rulemaking and 

initial findings by EPA as to the level of 

controls needed in the state’s SIP. With 

the revised timetable, states can be 

assured of a meaningful mid-course 

review effort that focuses on the areas 

that particularly warrant such a review 

and for which time is available for a 

productive assessment of the need for 

additional measures. 

Comment: One commenter stated that 

the proposal that allows the Agency to 

determine whether or not a State needs 

to submit a mid-course review with 

their attainment demonstration on a 

case-by-case basis lacks sufficient 

information. Since these attainment 

demonstrations must meet rigorous 

criteria, and require substantial work by 

the States, the commenter is concerned 

that the proposal neglects to outline the 

criteria EPA will use to make the caseby-case mid-course review 

determinations. The commenter asks 

that EPA provide the States with 

nationally applicable guidance on when 

an MCR would be required and what it 

would need to include. 

Response: The EPA agrees with this 

comment. In particular, EPA agrees that 

establishing clear criteria for 

applicability and content of a midcourse review requirement will provide 

states the opportunity to plan for these 

reviews and conduct appropriate 

reviews in a timely fashion. Therefore, 

this final rule is establishing specific 

criteria for the applicability of the midcourse review requirement, namely that 

a mid-course review shall be conducted 

for any area that cannot demonstrate 

attainment before 2014. This final rule 

is also identifying the necessary 

elements of this mid-course review, i.e. 

a review of the implementation of 

measures in the 2008 SIP, and review of 

recent air quality data, and an updated 

modeled attainment demonstration. 

H. Contingency Measures 

a. Background 

Under subpart 1 of the CAA, all PM2.5

nonattainment areas must include in 

their SIPs contingency measures 

consistent with section 172(c)(9). 

Contingency measures are additional 

control measures to be implemented in 

the event that an area fails to meet RFP 

or fails to attain the standards by its 

attainment date. These contingency 

measures must be fully adopted rules or 

control measures that are ready to be 

implemented quickly upon failure to 

meet RFP or failure of the area to meet 

the standard by its attainment date. The 

preamble to the proposal stated that the 

SIP should contain trigger mechanisms 

for the contingency measures, specify a 

schedule for implementation, and 

indicate that the measures will be 

implemented without significant further 

action by the State or by EPA. The 

contingency measures should consist of 

other control measures for the area that 

are not included in the control strategy 

for the SIP. 

The April 16, 1992 General Preamble 

provided the following guidance: 

‘‘States must show that their 

contingency measures can be 

implemented without further action on 

their part and with no additional 

rulemaking actions such as public 

hearings or legislative review. In 

general, EPA will expect all actions 

needed to affect full implementation of 

the measures to occur within 60 days 

after EPA notifies the State of its 

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

include Federal measures and local 

measures already scheduled for 

implementation, as explained below. 

The EPA has approved numerous SIPs 

under this interpretation—i.e., that use 

as contingency measures one or more 

Federal or local measures that are in 

place and provide reductions that are in 

excess of the reductions required by the 

attainment demonstration or RFP plan. 

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

66279, December 18, 1997; 66 FR 30811, 

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

January 3, 2001.) The key is that the 

statute requires that contingency 

measures provide for additional 

emission reductions that are not relied 


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on for RFP or attainment and that are 

not included in the demonstration. The 

purpose is to provide a cushion while 

the plan is being revised to meet the 

missed milestone. In other words, 

contingency measures are intended to 

achieve reductions over and beyond 

those relied on in the attainment and 

RFP demonstrations. Nothing in the 

statute precludes a State from 

implementing such measures before 

they are triggered. In fact, a recent court 

ruling upheld contingency measures 

that were previously required and 

implemented where they were in excess 

of the attainment demonstration and 

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

575, 5th Circuit., 2004. 

One basis EPA recommends for 

determining the level of reductions 

associated with contingency measures is 

the amount of actual PM2.5 emissions 

reductions required by the control 

strategy for the SIP to attain the 

standards. The contingency measures 

are to be implemented in the event that 

the area does not meet RFP, or attain the 

standards by the attainment date, and 

should represent a portion of the actual 

emissions reductions necessary to bring 

about attainment in area. Therefore, the 

emissions reductions anticipated by the 

contingency measures should be equal 

to approximately 1 year’s worth of 

emissions reductions necessary to 

achieve RFP for the area. 

As stated previously, EPA believes 

that contingency measures should 

consist of other available control 

measures beyond those required to 

attain the standards, and may go beyond 

those measures considered to be RACM 

for the area. It is important, however, 

that States make decisions concerning 

contingency measures in conjunction 

with their determination of RACM for 

the area, and that all available measures 

needed in order to demonstrate 

attainment of the standards must be 

considered first; all remaining measures 

should then be considered as candidates 

for contingency measures. It is 

important not to allow contingency 

measures to counteract the development 

of an adequate control strategy 

demonstration. 

The preamble to the proposal stated 

that contingency measures must be 

implemented without ‘‘significant 

further action’’ after EPA determines 

that the area has either failed to meet 

RFP, or has failed to attain the standard 

by its attainment date. The purpose of 

the contingency measure provision is to 

ensure that corrective measures are put 

in place automatically at the time that 

EPA makes its determination that an 

area has either failed to meet RFP or 

failed to meet the standard by its 

attainment date. The EPA is required to 

determine within 90 days after receiving 

a State’s RFP demonstration, and within 

6 months after the attainment date for 

an area, whether these requirements 

have been met. The consequences for 

states which fail to attain or to meet RFP 

are described in section 179 of the CAA. 

2. Final Rule 

The final rule includes regulatory text 

for contingency measures and maintains 

the overall policy approach as described 

in the preamble to the proposal. The key 

requirements associated with 

contingency measures are: 

—Contingency measures must be fully 

adopted rules or control measures that 

are ready to be implemented quickly 

upon failure to meet RFP or failure of 

the area to meet the standard by its 

attainment date. 

—The SIP should contain trigger 

mechanisms for the contingency 

measures, specify a schedule for 

implementation, and indicate that the 

measures will be implemented 

without further action by the State or 

by EPA. 

—The contingency measures should 

consist of other control measures for 

the area that are not included in the 

control strategy for the SIP. 

—The measures should provide for 

emission reductions equivalent to 

about 1 year of reductions needed for 

RFP, based on the overall level of 

reductions needed to demonstrate 

attainment divided by the number of 

years from the 2002 base year to the 

attainment year. Contingency 

measures are those measures that 

would not be included in the 

attainment strategy for various 

reasons; for example, they may not be 

as economically feasible as other 

measures that are considered to be 

RACM, or it may not be possible to 

implement the measures soon enough 

to advance the attainment date (e.g. 

federal mobile source measures based 

on the incremental turnover of the 

motor vehicle fleet each year). 

3. Comments and Responses 

Comment: Several comments were 

received concerning the requirement for 

contingency measures under section 

172(c)(9). The proposal indicated that 

contingency measures adopted as part of 

the State plan are to be equal to 

approximately 1 year’s worth of 

emissions reductions necessary to 

achieve RFP, as determined by the 

attainment demonstration for the area. 

One commenter indicates that this 

amount of reductions for contingency 

measures may be excessive in some 

cases. The commenter stated that States 

should be allowed to demonstrate 

appropriate amount of reductions for 

contingency measures in each area 

based on the degree of the PM2.5

nonattainment area problem and the 

progression of emission reductions 

planned for the area as a part of the SIP. 

Response: The EPA agrees that the 

CAA does not include the specific level 

of emission reductions that must be 

adopted to meet the contingency 

measures requirement under section 

172(c)(9). One possible interpretation of 

the CAA would assume that 

contingency measures should be in 

place in the event that all of the State’s 

measures fail to produce their expected 

emission reductions. Under this 

scenario, the State theoretically would 

be required to adopt sufficient 

contingency measures to make up for 

the entire short fall. In other words, the 

State would have to adopt ‘‘double’’ the 

measures required to satisfy the 

applicable emissions reduction 

requirements. 

The EPA believes that this scenario 

would be highly unlikely and that this 

interpretation would be an unreasonable 

requirement. The adoption of double the 

measures needed for attainment would 

be difficult for States. Therefore, the 

EPA believes that it is reasonable that 

contingency measures should, at a 

minimum, ensure that an appropriate 

level of emissions reduction progress 

continues to be made if attainment or 

RFP is not achieved, or if an area fails 

to attain the standard by its statutory 

attainment date and additional planning 

is needed by the State. The EPA believes 

that the contingency measures adopted 

by the State for the affected area should 

represent a portion of the actual 

emissions reductions necessary to bring 

about attainment in the area. Therefore, 

EPA believes that it is reasonable to 

require states to adopt contingency 

measures equal to approximately 1 

year’s worth of emissions reductions 

necessary to achieve RFP for the area. 

Comment: One commenter claimed 

that EPA incorrectly quoted the CAA as 

requiring SIPs to provide for 

implementation of contingency 

measures upon an attainment or RFP 

failure, without ‘‘significant’’ further 

action by the State or EPA. The 

commenter stated that section 172(c)(9) 

does not contain the word ‘‘significant.’’

The CAA requires that contingency 

measures take effect ‘‘without further 

action’’ by the State or EPA. 

Response: The EPA agrees with the 

commenter that the general 

requirements for attainment plans 

specified under section 172(c)(9) State 

that each plan must contain additional 

measures that will take effect without 


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‘further action’ by the State or EPA if an 

area either fails to make RFP or fails to 

attain the standard by the applicable 

attainment date. Section 51.1012 of the 

final rule describes the contingency 

measures requirement and does not 

include the word ‘‘significant.’’

However, as a matter of practicality 

states need to take minimal steps to 

make contingency measures effective 

and alert the affected public that the 

measures are in force. Thus, EPA has 

indicated based on conclusions first 

made in the 1992 General Preamble that 

states should complete all of these 

administrative steps within 60 days and 

that all regulatory steps be completed 

before SIP submission. 

Comment: The commenter further 

states that EPA is wrong in asserting 

that contingency measures can include 

Federal measures and local measures 

already scheduled for implementation, 

or previously implemented measures 

that provide ‘excess’ reductions. The 

CAA requires contingency measures to 

consist of controls ‘to be undertaken if ’

the area fails to meet attainment or RFP. 

The commenter states that this language 

clearly states that such measures are to 

be new measures that will be 

undertaken upon the triggering event 

specifically to address RFP or failure to 

attain, not measures already in place, or 

measures required for other reasons. 

Further, the commenter claims that 

EPA can not rationally refer to any 

reductions prior to an attainment or RFP 

failure as ‘excess’ when total reductions 

in the area in fact prove insufficient to 

meet attainment RFP. The commenter 

states that EPA cites a 5th Circuit case 

as support, but the commenter 

respectfully submits that the case was 

incorrectly decided on this issue for the 

aforementioned reasons. 

Response: In response to comments 

claiming that EPA is wrong in asserting 

that contingency measures can include 

Federal measures and local measures 

already scheduled for implementation, 

or previously implemented measures 

that provide ‘excess’ reductions, as 

stated previously, the EPA has approved 

numerous SIPs under this 

interpretation. The statute requires that 

contingency measures provide for 

additional emission reductions that are 

not relied on for RFP or attainment and 

that are included in the attainment 

demonstration for the area. These 

measures are intended to provide a 

‘‘cushion’’ in terms of emissions 

reductions for the area while the State 

is revising the SIP for the area due to the 

failure to show RFP or attain. In other 

words, contingency measures are 

intended to achieve reductions over and 

beyond those relied on in the attainment 

and RFP demonstrations. Nothing in the 

statute precludes a State from 

implementing such measures before 

they are triggered. 

As noted above, EPA’s General 

Preamble interpreted the control 

measure requirements of sections 

172(c)(9) and 182(c)(9) to allow 

nonattainment areas to implement their 

contingency measures early. 57 FR 

13498, 13511 (April 16, 1992). The EPA 

has applied this interpretation in 

rulemakings. See, for example, 67 FR 

6,590, 6,591–92 (September 26, 2002). 

See also rulemakings cited in the 

Background section, above. As set forth 

above, the Fifth Circuit has upheld 

EPA’s interpretation. Louisiana 

Environmental Action Network v. EPA, 

382 F.3d 575 (Fifth Cir. 2004). (‘‘LEAN’’) 

Commenters have not provided a basis 

for concluding that the Fifth Circuit in 

the LEAN case wrongly interpreted the 

CAA. 

Commenters contend that the 

language in the CAA regarding 

contingency measure controls ‘‘to be 

undertaken’’ requires measures not 

already in place or required for other 

reasons. The Fifth Circuit disagreed, 

finding that the terms in section 

172(c)(9)—‘‘to be undertaken’’ and ‘‘to 

take effect’’—were ambiguous, and 

finding persuasive EPA’s interpretation 

that this language allows measures 

already in place or otherwise required. 

The Court held: 

‘‘Here, the EPA’s allowance of early 

reductions to be used as contingency 

measures comports with a primary purpose 

of the CAA—the aim of ensuring that 

nonattainment areas reach NAAQS 

compliance in an efficient manner—and 

necessary requirements of the CAA.’’ 382 

F.3d at 583. 

The Court further found that ‘‘By 

utilizing contingency measures early, 

the contingency measures ensured that 

‘an appropriate level of emissions 

reduction progress’ would be 

implemented while the State ‘adopt[ed] 

newly required measures resulting from 

the bump-up to a higher classification.’’

[citing the General Preamble]. Id. 

In addition, the Court agreed with 

EPA that ‘‘early reductions are 

necessary in order to create an incentive 

for nonattainment areas to implement 

‘all reasonably available control 

measures as expeditiously as 

practicable’ ’’ in accordance with section 

172(c)(1) of the CAA. Thus the Court 

concluded that it would be ‘‘illogical to 

penalize nonattainment areas that are 

taking extra steps, such as implementing 

contingency measures prior to a 

deadline, to comport with the CAA’s 

mandate that such states achieve 

NAAQS compliance as ‘expeditiously as 

practicable.’ ’’ Id. at 583–584. 

The Fifth Circuit also endorsed the 

concept of ‘‘excess’’ reductions, noting 

that the reductions credits at issue in 

that case, ‘‘although already 

implemented, are in effect set aside, ‘to 

be applied in the event that attainment 

is [not] achieved’ and such reduction 

credits ‘are not available for any other 

use.’ [citations omitted]. The setting 

aside of a continuing, surplus emissions 

reduction fits neatly within the CAA’s 

requirement that a necessary element of 

a contingency measure is that it must 

‘take effect without further action by the 

State or [EPA]’.’’ The Court concluded 

that ‘‘the early activation of continuing 

contingency measures is consistent with 

the purpose and requirements of the 

CAA statute.’’ Id. at 584. 

Thus, EPA’s approval of early 

implemented contingency measures is 

consistent with the CAA, as well as with 

EPA guidance. For example, EPA has 

consistently taken the position that 

ozone nonattainment areas classified 

moderate and above must include 

sufficient contingency measures so that 

‘‘upon implementation of such 

measures, additional emissions 

reductions of up to 3 percent of the 

emissions in the adjusted base year 

inventory (or such lesser percentage that 

will cure the identified failure) would 

be achieved in the year following the 

year in which the failure has been 

identified.’’ 57 FR at 13511 (EPA’s 

General Preamble). Thus the 

contingency measures are supposed to 

ensure that progress towards attainment 

will occur while the relevant State 

adopts whatever additional controls 

may be necessary to correct a shortfall 

in emissions reductions. Id. The EPA 

has historically allowed early 

reductions—that is, reductions achieved 

before the contingency measure is 

‘‘triggered’’—to be used as contingency 

measures. See also August 13, 1993 

Memorandum from G.T. Helms: Early 

Implementation of Contingency 

Measures for Ozone and Carbon 

Monoxide (CO) Nonattainment Areas). 

The commenter’s argument that 

emission reductions cannot be valid 

contingency measures if they are 

otherwise required is also misplaced. A 

State must have the legal authority to 

require whatever reductions it may 

require as a contingency measure. As 

EPA has previously stated, ‘‘all 

contingency measures must be fully 

adopted rules or measures.’’ 62 FR 

15844, 15846 (April 3, 1997). The fact 

that the State or Federal government has 

already exercised that authority is 

irrelevant because, as noted above, 

contingency measures must ‘‘take effect 


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without further action by the State or 

[EPA].’’ Section 172(c)(9). Thus, by 

definition, the State necessarily will 

have already exercised its legal 

authority to require reductions as a 

contingency measure before the measure 

is triggered. It does not matter whether 

or not a specific contingency measure is 

already required by law, as long as the 

emissions reductions that will result 

from that contingency measure have not 

been accounted for in the attainment 

and reasonable further progress 

demonstrations. If the reductions from 

the contingency measure are not 

available for any other use, then they are 

surplus that is set aside in the event 

reasonable further progress or 

attainment is not achieved. 

A key element of a valid contingency 

measure reduction is that the State may 

not use the reduction in its attainment 

or reasonable further progress 

demonstrations if it is already using the 

reduction as a contingency measure. 

Those demonstrations must account for 

the actual emissions reductions that will 

make reasonable further progress 

towards, and achieve attainment of the 

NAAQS in the absence of contingency 

measures. 

I. Transportation Conformity 

Transportation conformity is required 

under CAA section 176(c) (42 U.S.C. 

7506(c)) to ensure that Federally 

supported highway and transit project 

activities are consistent with (‘‘conform 

to’’) the purpose of the SIP. Conformity 

currently applies to areas that are 

designated nonattainment, and those 

redesignated to attainment after 1990 

(‘‘maintenance areas’’ with plans 

developed under CAA section 175A) for 

the following transportation-related 

criteria pollutants: ozone, particulate 

matter (PM2.5 and PM10), carbon 

monoxide (CO), and nitrogen dioxide 

(NO2). Conformity to the purpose of the 

SIP means that transportation activities 

will not cause new air quality 

violations, worsen existing violations, or 

delay timely attainment of the relevant 

NAAQS (or ‘‘standards’’). 

The final PM2.5 implementation rule 

does not contain any revisions to the 

transportation conformity regulation. 

The EPA addressed the transportation 

conformity requirements that apply in 

PM2.5 nonattainment and maintenance 

areas in three separate rulemakings as 

described below. 

First, on July 1, 2004, EPA published 

a final rule (69 FR 40004) that addressed 

the majority of requirements that apply 

in PM2.5 areas including: 

• Regional conformity tests to be used 

in conformity determinations both 

before and after SIPs are submitted and 

motor vehicle emissions budgets are 

found adequate or are approved; 

• Consideration of direct PM2.5

emissions in regional emissions 

analyses; 

• Consideration of re-entrained road 

dust in PM2.5 regional emissions 

analyses; 

• Consideration of transportation 

construction-related fugitive dust in 

PM2.5 regional emissions analyses; and 

• Compliance with PM2.5 SIP control 

measures. 

Then on May 6, 2005, EPA 

promulgated a final rule (70 FR 24280) 

that specified the transportation-related 

PM2.5 precursors and when they apply 

in transportation conformity 

determinations in PM2.5 nonattainment 

and maintenance areas. 

Finally, on March 10, 2006, EPA 

promulgated a final rule (71 FR 12468) 

that establishes the criteria for 

determining which transportation 

projects must be analyzed for local 

particle emissions impacts in PM2.5 and 

PM10 nonattainment and maintenance 

areas. If required, an analysis of local 

particle emissions impacts is done as 

part of a transportation project’s 

conformity determination. 

Transportation conformity for the 

PM2.5 standards began applying in PM2.5

nonattainment areas on April 5, 2006, 

one year after the effective date of EPA’s 

PM2.5 nonattainment designations (i.e., 

April 5, 2005). CAA section 176(c)(6) 

and 40 CFR 93.102(d) provide a oneyear grace period before conformity 

applies in areas newly designated 

nonattainment for a new standard. PM2.5

SIP submissions such as RFP and 

attainment demonstrations would 

identify motor vehicle emissions 

budgets (‘‘budgets’’) for direct PM2.5 or 

PM2.5 precursors, as described below. 

These budgets would be used for 

satisfying transportation conformity 

requirements, once the budgets are 

found adequate or the SIP containing 

the budgets is approved by EPA. For 

example, state and local agencies would 

consider during the development of the 

PM2.5 SIP whether reductions of on-road 

mobile source S02 emissions are a 

significant contributor to an area’s PM2.5

air quality problem, and if so, establish 

a S02 motor vehicle emissions budget 

for transportation conformity purposes. 

The EPA has previously addressed its 

intentions regarding when budgets must 

be established in PM2.5 SIPs for 

transportation conformity purposes. 

RFP plans, attainment demonstrations, 

and maintenance plans must include a 

budget for direct PM2.5 emissions, 

except for certain cases as described 

below. All PM2.5 SIP budgets would 

include directly emitted PM2.5 motor 

vehicle emissions from tailpipe, brake 

wear, and tire wear. States should also 

consider whether re-entrained road dust 

or highway and transit construction 

dust are significant contributors and 

should be included in the PM2.5 budget. 

For further information, see 40 CFR 

93.102(b) and 93.122(f) of the 

transportation conformity regulation, as 

well as Sections VIII–X of the July 1, 

2004 conformity rule preamble at 69 FR 

40031–40036. 

Under certain circumstances, directly 

emitted PM2.5 from on-road mobile 

sources may be found an insignificant 

contributor to the air quality problem 

and NAAQS. Section 93.109(k) of the 

conformity rule states that ‘‘[s]uch a 

finding would be based on a number of 

factors, including the percentage of 

motor vehicle emissions in the context 

of the total SIP inventory, the current 

state of air quality as determined by 

monitoring data for that NAAQS, the 

absence of SIP motor vehicle control 

measures, and historical trends and 

future projections of the growth of 

motor vehicle emissions.’’ The EPA 

discussed its intentions for applying the 

insignificance provision in the July 2004 

final rule (69 FR 40061–40063). 

In the May 6, 2005 final rule, EPA 

provided details regarding when states 

must establish SIP budgets for any PM2.5

precursor (i.e., NOX, VOCs, S02 and 

ammonia). If through the SIP process a 

state concludes that on-road mobile 

source emissions of one or more 

precursors are significant (i.e. need to be 

addressed in order to attain the PM2.5

standards as expeditiously as 

practicable), then EPA expects that the 

state will include a budget in the SIP for 

each of the relevant precursors. (70 FR 

24287) The EPA also noted in the May 

2005 conformity rule that, if inventory 

and modeling analyses demonstrating 

RFP, attainment or maintenance 

indicate a level of emissions of a 

precursor that must be maintained to 

demonstrate compliance with the 

applicable requirement, then that level 

of emissions should be clearly identified 

in the SIP as a budget for transportation 

conformity purposes, even if the SIP 

does not establish particular controls for 

the given precursor. If the state fails to 

identify such a level of emissions as a 

budget, EPA will find the submitted SIP 

budgets inadequate because the SIP fails 

to clearly identify the motor vehicle 

emissions budget as required by the 

conformity rule (40 CFR 

93.118(e)(4)(iii)). (70 FR 24287) In 

determining whether the on-road mobile 

source emissions of a PM2.5 precursor 

are significant, state and local agencies 

would use the criteria for insignificance 

findings provided in 40 CFR 93.109(k) 


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of the transportation conformity 

regulation. A further discussion of the 

criteria to be considered in establishing 

PM2.5 precursor budgets is contained in 

the May 2005 final transportation 

conformity rule (70 FR 24282–24288). If 

state and local agencies conclude that 

on-road sources of a precursor are not a 

significant contributor to the area’s 

PM2.5 air quality problem, as described 

above, motor vehicle emissions budgets 

would not be established even though 

emissions may be addressed in the 

area’s RFP plan, attainment 

demonstration and/or maintenance 

plan. 

J. General Conformity 

a. Background 

The General Conformity regulations 

promulgated in 1993 establish an 

implementation process where Federal 

agencies are responsible for making 

their own determination of conformity 

with State implementation plans (SIPs), 

and EPA plays an advisory role. 

Recognizing that it was impracticable to 

evaluate all Federal actions for 

conformity, EPA created a number of 

exemptions in those regulations for 

actions with insignificant or not 

reasonably foreseeable emission 

increases, including exemptions for 

Federal actions with emissions below 

specified de minimis levels. When a 

Federal agency must demonstrate 

conformity for an action, the regulations 

provide several methods for making that 

demonstration. With the designations of 

PM2.5 nonattainment areas on April 5, 

2005, requirements for demonstrating 

conformity become effective in those 

areas on April 5, 2006. 

On July 17, 2006 EPA issued a final 

rule (71 FR 40420) to amend the General 

Conformity Regulations to establish de 

minimis levels for PM2.5 for the General 

Conformity program. The final rule 

established 100 tons/year of direct PM2.5

emissions and its precursors as the de 

minimis level where the General 

Conformity regulations would apply in 

PM2.5 nonattainment areas. In the 

process of finalizing the de minimis 

level for PM2.5 three comments were 

received. One commenter was 

concerned about emissions from 

burning by Federal agencies. Another 

commenter proposed that the de 

minimis level for emissions of direct 

PM2.5 should be set significantly lower 

than 100 tons—in the range of 25–50 

tons per year (TPY) in areas that are 

likely to attain the PM2.5 national 

ambient air quality standard within 5 

years, and a level of 10–25 TPY in areas 

that are likely to take more than 5 years 

to achieve the national ambient air 

quality standard. A third commenter 

supported the proposed de minimis 

level. 

The final rule revises the tables in 

sub-paragraphs (b)(1) and (b)(2) of the 

General Conformity Regulations by 

adding a de minimis emission level for 

PM2.5 and its precursors. This action 

maintained our past policy of 

consistency between the conformity de 

minimis emission levels and the size of 

a major stationary source under the New 

Source Review program (70 FR 65984). 

These levels are also consistent with the 

levels promulgated for Reasonably 

Available Control Technology 

applicability levels for volatile organic 

compound and nitrogen oxide 

emissions in subpart 1 areas under the 

8-hour ozone implementation strategy 

(68 FR 32843). Since EPA is not 

finalizing any classifications for the 

PM2.5 nonattainment areas, we did not 

establish differing PM2.5 de minimis 

emission levels for higher classified 

nonattainment areas. 

b. Comments and Responses 

Comment: One commenter requests 

that EPA communicate to all Federal 

agencies the value of the agencies 

advising the States as soon as possible 

of any planned future projects in 

nonattainment areas that may be above 

the General Conformity de minimis 

values or that will have to be evaluated 

to show that they are below de minimis. 

This is for projects that are very likely 

to proceed. The aim is to consider these 

future emissions in any growth 

projections during SIP development 

since such growth may not be 

anticipated well by the available growth 

model (E–GAS). States can 

communicate with existing Federal 

facilities now concerning this issue. 

Response: The EPA sees the value in 

Federal agencies working with States to 

anticipate growth in emissions and 

include those anticipated emissions in 

the applicable SIP. The EPA is in the 

process of proposing regulatory 

amendments to the General Conformity 

regulations that provide a framework for 

Federal facilities to work with States to 

account for facility-wide emissions in 

SIPs and to include Federal facility 

emissions in future SIPs. The EPA 

anticipates that these rule amendments 

should be proposed before the end of 

summer 2006. 

Comment: Some commenters stated 

that the de minimis level for PM2.5 for 

conformity applicability should be less 

than 100 tons per year. A level of 50 

tons per year was suggested for direct 

PM2.5 emissions. 

Response: Similar comments were 

received when the PM2.5 de minimis 

level was proposed on April 5, 2006. 

The response to those comments can be 

found in the preamble to the final rule 

setting the de minimis level for PM2.5 at 

71 FR 40420. 

Comment: Are the precursors for 

general conformity consistent with this 

rulemaking or with the transportation 

conformity rulemaking? 

Response: The precursors for general 

conformity are generally consistent both 

with this rule and the transportation 

conformity rule. The only difference 

between the transportation rule and this 

rule is that SO2 is not considered a 

precursor for transportation conformity 

determinations that occur prior to a 

PM2.5 SIP unless EPA or the State air 

agency finds on-road mobile source 

emissions significant. For more 

information, see the May 6, 2005 

transportation conformity rule on PM2.5

precursors at 70 FR 24283. Since general 

conformity includes analysis of 

stationary sources the general 

conformity rule requires SO2 as a 

precursor both before and after a PM2.5

SIP is submitted. 

Comment: When will rulemaking 

containing the de minimis levels for 

PM2.5 and for the precursors be issued? 

There is some confusion, since the 

proposed rule says that states should 

assume 100 tpy for all PM2.5 pollutants, 

as this would make it consistent with 

the levels for NOX and VOC for the 

subpart 1 areas under 8-hour ozone. 

However, since New Jersey’s 

classification is moderate under the 8- 

hour ozone standard and we are in an 

Ozone Transport Region, the de minimis 

level for VOC is 50 tons per year. 

Response: On July 17, 2006 EPA 

issued a final rule (71 FR 40420) to 

amend the General Conformity 

Regulations to establish de minimis 

levels for PM2.5 for the General 

Conformity program. The final rule 

established 100 tons/year of direct PM2.5

emissions and its precursors as the de 

minimis level where the General 

Conformity regulations would apply in 

PM2.5 nonattainment areas. Since EPA is 

not finalizing any classifications for the 

PM2.5 nonattainment areas, we did not 

establish differing PM2.5 de minimis 

emission levels for based on a 

classification scheme. 

Comment: If a Statement of 

Conformity has been issued on a project 

and if the project has not been 

completed to date, are they required to 

address PM2.5 prior to completion of the 

project or will they be grandfathered in? 

Response: If a Federal action has 

completed a conformity determination 

and the action has started (regardless of 

whether the project is complete or not) 

then no new determination is needed. If 


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46Emissions Inventory Guidance for 

Implementation of Ozone and Particulate Matter 

National Ambient Air Quality Standards (NAAQS) 

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

001, November 2005. 

the conformity determination was 

completed, but the action did not start 

in 5 years a new determination is 

needed under the general conformity 

rules. 

Comment: What guidance should 

states use to establish budgets for large 

facilities or military bases? 

Response: The EPA has not issued 

any guidance for States and Federal 

facilities to establish facility-wide 

budgets in the applicable SIP. There is 

nothing in the General Conformity 

regulations preventing this approach 

which would allow Federal actions that 

do not increase total facility emissions 

over the budget in the SIP from 

determining the action conforms on the 

basis of its compliance with the budget 

limit. The EPA sees this practice as a 

positive step to encourage States and 

Federal agencies to work together to 

account for emissions in a SIP so they 

conform with the purposes and goals of 

the SIP. The EPA intends to address the 

approach and provide guidance in 

planned revisions to the General 

Conformity regulations which are 

expected to be proposed in 2006. 

K. Emission Inventory Requirements 

a. Background 

Emission inventories are critical for 

the efforts of State, local, tribal and 

federal agencies to attain and maintain 

the NAAQS that EPA has established for 

criteria pollutants including PM2.5. 

Pursuant to its authority under section 

110 of Title I of the CAA, EPA has long 

required States to submit emission 

inventories containing information 

regarding the emissions of criteria 

pollutants and their precursors. The 

EPA codified these requirements in 40 

CFR part 51, subpart Q in 1979 and 

amended them in 1987. 

The 1990 CAAA revised many of the 

provisions of the CAA related to 

attainment of the NAAQS and the 

protection of visibility in mandatory 

Class I Federal areas (certain national 

parks and wilderness areas). These 

revisions established new emission 

inventory requirements applicable to 

certain areas that were designated 

nonattainment for certain pollutants. In 

the case of particulate matter, the 

emission inventory provisions are in the 

general provisions under Section 

172(c)(3). 

In June 2002, EPA promulgated the 

Consolidated Emissions Reporting Rule 

(CERR) (67 FR 39602; June 10, 2002), 40 

CFR part 51 subpart A. The CERR 

consolidated the various emissions 

reporting requirements that already 

existed into one place in the CFR, 

established new reporting requirements 

for PM2.5 and ammonia, and established 

new requirements for the statewide 

reporting of area source and mobile 

source emissions. 

The CERR established two types of 

required emission inventories: annual 

inventories, and 3-year cycle 

inventories. The annual inventory 

requirement is limited to reporting 

statewide emissions data from the larger 

point sources. For the 3-year cycle 

inventory, States need to report data 

from all of their point sources plus all 

of the area and mobile sources on a 

statewide basis. A special case existed 

for the first 3-year cycle inventory for 

the year 2002 which was due on June 1, 

2004. 

The EPA issued guidance suggesting 

that 2002 be used as the Base Year for 

8-hour ozone, PM2.5 and regional haze 

planning efforts (November 18, 2002 

EPA memorandum ‘‘2002 Base Year 

Emission Inventory SIP Planning: 8-hr 

Ozone, PM2.5 and Regional Haze 

Programs’’ http://www.epa.gov/ttn/ 

chief/eidocs/2002

baseinven_102502new.pdf). 

States should estimate mobile source 

emissions by using the latest emissions 

models and planning assumptions 

available at the time the SIP is 

developed. Information and guidance on 

the latest emissions models is available 

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

stateresources/transconf/ 

policy.htm#models and at http:// 

www.epa.gov/otaq/models.htm. 

By merging the information on point 

sources, area sources and mobile 

sources into a comprehensive emission 

inventory, State, local and tribal 

agencies may do the following: 

• Set a baseline for SIP development. 

• Measure their progress in reducing 

emissions. 

• Have a tool to support future 

trading programs. 

• Answer the public’s request for 

information. 

The EPA uses the data submitted by 

the States to develop the National 

Emission Inventory (NEI). The NEI is 

used by EPA to show national emission 

trends, as modeling input for analysis of 

potential regulations, and other 

purposes. 

Most importantly, States need these 

inventories to help in the development 

of control strategies and demonstrations 

to attain the annual and 24-hour PM2.5

NAAQS. In April 1999, EPA published 

the ‘‘Emissions Inventory Guidance for 

Implementation of Ozone and 

Particulate Matter National Ambient Air 

Quality Standards (NAAQS) and 

Regional Haze Regulations,’’ EPA–454/ 

R–99–006. The EPA updated this 

guidance in November 2005.46 The 

current version of this guidance is 

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

chief/eidocs/eiguid/index.html. The 

EPA developed this guidance document 

to complement the CERR and to provide 

specific guidance to State and local 

agencies and Tribes on how to develop 

emissions inventories for 8-hour ozone, 

PM2.5, and regional haze SIPs. While the 

CERR sets forth requirements for data 

elements, EPA guidance complements 

these requirements and indicates how 

the data should be prepared for SIP 

submissions. 

The SIP inventory must be approved 

by EPA as a SIP element and is subject 

to public hearing requirements, whereas 

the CERR is not. Because of the 

regulatory significance of the SIP 

inventory, EPA will need more 

documentation on how the SIP 

inventory was developed by the State as 

opposed to the documentation required 

for the CERR inventory. In addition, the 

geographic area encompassed by some 

aspects of the SIP submission inventory 

will be different from the statewide area 

covered by the CERR emissions 

inventory. The CERR inventory was due 

June 1, 2004, while the SIP inventory 

due date is later. Because of this time 

lapse, the State may choose to revise 

some of the data from the CERR when 

it prepares its SIP inventory to account 

for improvements in emissions 

estimates. If a State’s 2005 emission 

inventory (or a later one) becomes 

available in time to use for timely 

development of a nonattainment area 

SIP, then that inventory can be used. We 

also encourage the cooperation of the 

Tribes and the State and local agencies 

in preparing their emissions inventories. 

b. Final Rule 

In the proposed rulemaking, in 

§ 51.1008(a), to meet the emission 

inventory requirements of section 

172(c)(3), EPA proposed to require 

submission of the CERR inventories as 

well as ‘‘any additional emission 

inventory information needed to 

support an attainment demonstration 

and RFP plan ensuring expeditious 

attainment of the annual and 24-hour 

PM2.5 standards.’’ Section 51.1008(b) set 

forth specifications for baseline 

emissions inventories for attainment 

demonstrations and RFP requirements. 

Section 51.1008 of the final rule reflects 

our proposed rule but is different from 

the draft regulatory text. The proposal 

did not specify a deadline for 


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submission of the emission inventory. 

To ensure clarity, the final rule contains 

language addressing the deadline for 

submission of emissions inventories for 

nonattainment areas under section 

172(c)(3) and section 172(b), and reflects 

the statutory requirement of no later 

than 3 years after designation of the 

area. See § 51.1008(a). In addition, 

§ 51.1008(a)(1) of the proposed rule has 

been changed for purposes of 

clarification. The proposal referred to 

the requirement to submit statewide 

emission inventories under the (CERR), 

contained in 40 CFR part 51, subpart A. 

The final regulatory text clarifies this to 

refer to the requirements for data 

elements under 40 CFR part 51, subpart 

A. The EPA did not intend that the 

emissions inventories developed under 

the CERR, which are statewide, would 

be appropriate for and satisfy all aspects 

of SIP inventories developed for SIP 

submissions. Section 51.1008(b) has a 

minor change to clarify that this 

subsection refers to the inventories 

required for submission under 

paragraph (a) of section 51.1008, and 

also clarifies the reference to 40 CFR 

Part 51 subpart A, which currently 

contains the CERR. In addition, section 

51.1008(b) as finalized provides that 

‘‘The baseline emission inventory for 

calendar year 2002 or other suitable year 

shall be used for attainment planning 

and RFP plans for areas initially 

designated nonattainment for the PM2.5

NAAQS in 2004.’’ The EPA added this 

flexibility to be consistent with EPA’s 

ozone implementation rule, and to 

enable a State to use a more recent and 

improved base year inventory if it is 

completed in time to allow for timely 

development of the attainment plan. As 

noted above, we expect that States will 

consult the guidance document titled 

Emission Inventory Guidance for 

Implementation of Ozone and 

Particulate Matter National Ambient Air 

Quality Standards (‘‘NAAQS’’) and 

Regional Haze Regulations, November 

2005,and submit inventories that are 

appropriate for the geographic area at 

issue and consistent with regulations 

and this guidance. We expect the States 

to include in their SIP submission 

documentation explaining how the 

emissions data were calculated. 

In the proposed rulemaking, EPA 

asked ‘‘What emission inventory 

requirements should apply under the 

PM2.5 NAAQS.’’ Several specific 

questions followed this general question 

to assess whether or not additional 

emission inventory requirements or 

guidance are needed to implement the 

proposed standard. It was noted in the 

proposal that the basis for EPA’s 

emission inventory program is specified 

in the Consolidated Emissions 

Reporting Rule (CERR) and the related 

guidance document titled Emissions 

Inventory Guidance for Implementation 

of Ozone and Particulate Matter 

National Ambient Air Quality 

Standards (NAAQS) and Regional Haze 

Regulations. 

Subsequent to the proposed 

rulemaking, EPA proposed the Air 

Emissions Reporting Rule (AERR) at 71 

FR 69 (Jan. 3, 2006). The AERR would 

update CERR reporting requirements by 

consolidating and harmonizing new 

emissions reporting requirements with 

pre-existing sets of reporting 

requirements under the Clean Air 

Interstate Rule (CAIR) and the NOX SIP 

Call. At this time, EPA is reviewing 

comments submitted on the AERR 

proposal and expects to finalize this 

rulemaking during calendar year 2007. 

The AERR is expected to be a means by 

which the Agency will implement 

additional data reporting requirements 

for PM2.5 SIP emission inventories. 

Since the AERR rulemaking is in 

progress, EPA believes it is appropriate 

to defer responding to certain comments 

on the proposed PM2.5 Implementation 

Rule related to data reporting and 

emission inventory requirements that 

were discussed in the AERR proposal. 

Those comments will be addressed in 

the final AERR rulemaking. Significant 

comments that are separable from the 

AERR rulemaking and relate to data 

reporting and emission inventory 

requirements for the PM2.5 NAAQS are 

addressed below and in EPA’s 

Responses to Comments document. 

With respect to SIP emission 

inventory requirements under this 

rulemaking, EPA recognizes NOX, SO2, 

VOCs, and ammonia as potential 

precursors of PM2.5 because these 

pollutants can contribute to the 

formation of PM2.5 in the ambient air. To 

provide a technical foundation for 

understanding contributions to PM2.5

nonattainment problems and for 

identifying potential future measures to 

reduce PM2.5 concentrations, EPA is 

requiring under 40 CFR part 51 subpart 

A and 40 CFR 51.1008 of this rule that 

States develop and submit inventories 

for direct PM2.5 and all precursors of 

PM2.5. This requirement stands apart 

from the policies in this rule regarding 

the required treatment of various 

precursor emissions in the development 

of control strategies for attaining the 

PM2.5 standards. With respect to the 

latter requirements, EPA has not made 

a finding that all precursors should be 

evaluated for potential control measures 

in each specific nonattainment area. The 

policy approach in the rule instead 

requires evaluation of control measures 

for direct PM2.5 and sulfur dioxide in all 

areas, and describes general 

presumptive policies that NOX sources 

need to be evaluated for control 

measures in all areas unless findings of 

insignificance are made, but that control 

measure evaluations are not required for 

sources of ammonia and VOC unless 

findings of significance are made. The 

rule also provides a mechanism by 

which the State and/or EPA can make 

an area-specific demonstration to 

reverse the general presumption for 

these three precursors. (See section 

II.A.8 for additional discussion on these 

issues.) 

c. Comments and Responses 

1. Should EPA Specify an Inventory 

Approval Process? 

Comment: Several commenters 

indicated that the current process of 

approving SIP inventories by EPA 

regional offices is appropriate and did 

not believe that additional approval 

requirements were necessary. Some 

commenters noted that flexibility is 

needed to address regional concerns. 

Several commenters noted that SIP 

emission inventories may include 

requirements or information in addition 

to data required by the Consolidated 

Emissions Reporting Rule (CERR). One 

commenter observed that States 

routinely develop information outside 

the CERR for purposes of their SIP 

development and that additional 

requirements should not be defined by 

EPA. Another commenter recommended 

that requirements for nonattainment 

area emission inventories be 

incorporated in the CERR or AERR. A 

few commenters felt that additional 

guidance was needed on the SIP 

emission inventory approval process. 

Response: The SIP emissions 

inventory is a plan provision that must 

be approved by EPA under section 

110(k) of the CAA and is subject to 

public hearing requirements pursuant to 

section 110(a)(2). The EPA believes that 

it need not further specify a SIP 

approval process for emissions 

inventories beyond that set forth in the 

statute, regulation (51.1008), other 

related sections of this rulemaking and 

EPA’s current guidance. The EPA agrees 

with many of the commenters that the 

approval process for SIP emission 

inventories need not be further defined 

and that approval should be conducted 

at the regional level to provide 

flexibility to address regional concerns. 

The EPA also agrees that use of Quality 

Assurance Project Plans developed for 

each state will be helpful in establishing 

the proper approval process. The EPA 


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addresses the issue of what data 

elements are needed for SIP approval in 

the responses to comments below, 

including the responses to comments 

under Issue 2, below. 

As noted by two commenters EPA 

describes procedures for approval of SIP 

inventories in a document titled 

Emissions Inventory Guidance for 

Implementation of Ozone and 

Particulate Matter National Ambient Air 

Quality Standards (NAAQS) and 

Regional Haze Regulations, November 

2005. Section 2.5, Inventory Approval, 

references a memorandum titled Public 

Hearing Requirements for 1990 BaseYear Emissions Inventories for Ozone 

and CO Nonattainment Areas, 

September 29, 1992. The EPA intends to 

use the procedures discussed in the 

guidance and memorandum to the 

extent that they are applicable to 

approval of PM2.5 emission inventories 

submitted as part of the SIP. 40 CFR 

51.1008 sets forth the requirements for 

emissions inventories under section 

172(c)(3), which will be reviewed in the 

context of the SIP approval process. See 

also 40 CFR 51.1007 and 51.1009 

regarding attainment demonstrations 

and RFP plans. Thus, EPA believes that 

its existing SIP approval process is 

adequately described in statute, 

regulation and guidance, and that it 

provides flexibility to deal with issues 

that arise in individual nonattainment 

areas. 

2. Are the Data Elements Specified 

Within the CERR Sufficient To Develop 

Adequate SIPs? For Example, in the 

Determination of RACT, Should More 

Information on Existing Control Devices 

Be Required? 

Comment: Several commenters 

recommended that any additional 

reporting requirements should be 

addressed through the CERR/AERR and 

associated guidance and that no 

additional reporting requirements 

should be specified in the Rule. Another 

commenter stated that more detail 

concerning control equipment would be 

helpful but was concerned about the 

additional burden on industry 

compared to the benefit to State and 

local agencies, and suggested that this 

would be further addressed in the 

context of comments on the AERR. One 

commenter believed that the reporting 

requirements within the CERR are 

sufficient to develop a PM2.5 SIP for 

most areas but noted that nonattainment 

areas may require additional inventory 

information which will need evaluation 

on a case-by-case basis. The commenter 

further stated that any additional 

inventory requirements should be 

identified during the SIP development 

process, in cooperation with the EPA 

regional office, and should not be part 

of this rule. 

Response: In section 40 CFR 

51.1008(a)(1) of the final rule, EPA 

incorporates the requirements for data 

elements required under 40 CFR part 51, 

subpart A, which contains the CERR, for 

inventories submitted under this 

section. The EPA notes, however, that 

the issue of whether to require 

additional reporting requirements 

beyond those required in the CERR is 

currently being addressed in the Air 

Emissions Reporting Rule (AERR) 71 FR 

69 (January 3, 2006). At this time EPA 

believes that the requirements for data 

elements under the CERR, in 

conjunction with the other provisions of 

40 CFR 51.1008, as well as 40 CFR 

51.1007 and 51.1009, are generally 

adequate to meet the needs for PM2.5

nonattainment emission inventory SIP 

development. The AERR as proposed 

includes additional provisions which 

may be helpful for PM2.5 SIP emission 

inventory development. The EPA will 

address this aspect of the AERR, 

including comments received in this 

rulemaking on the issues raised and the 

additional elements proposed in the 

AERR, in the final AERR rulemaking. 

This final rule indicates that States shall 

include data elements for PM2.5

inventories as required under 40 CFR 

part 51, subpart A. In addition, 40 CFR 

51.1008(a)(2) requires that States submit 

‘‘any additional emission inventory 

information needed to support an 

attainment demonstration and RFP plan 

ensuring expeditious attainment of the 

annual and 24-hour PM2.5 standards.’’

See also 40 CFR 51.1007 and 51.1009. 

Thus States should be aware that data 

elements in addition to those required 

under the CERR may be needed to 

support attainment demonstrations and 

RFP inventories. Additional data 

elements needed for other SIP emission 

inventory purposes should be handled 

on a case-by-case basis. Because of the 

nature of SIP development, which varies 

depending on the nature and needs of 

individual areas, it may not be possible 

to require a level of detail in regulations 

that will enable a ‘‘one-stop-shop’’

information request as suggested by one 

of the commenters. 

As recommended by one commenter, 

guidance on reporting requirements is 

contained in Emissions Inventory 

Guidance for Implementation of Ozone 

and Particulate Matter National 

Ambient Air Quality Standards 

(NAAQS) and Regional Haze 

Regulations (EPA–454/R–05–001, 

November 2005). For example, Section 

3.2.1 for Pollutant and Pollutant 

Precursors to be Inventoried presents 

guidance to states on PM2.5 pollutants 

and their components that should be 

reported for PM2.5 SIP development. See 

also section 5, Emission Inventory 

Development, and other related sections 

of the guidance. 

With respect to the comment on 

additional detail on control 

requirements, see also EPA’s Response 

to Comment Document. 

3. Is the Current Approach for Reporting 

Specific Pollutants Sufficient, or Should 

EPA Require More Specific Emission 

Component Reporting Such as Groups 

of Compounds or Reporting of 

Elemental Carbon and Organic Carbon? 

Comment: Currently the CERR 

requires the reporting of SO2, VOC, 

NOX, CO, Pb, PM10, PM2.5, and NH3. 

VOC and PM are speciated by the 

emissions processing models based on 

speciation profiles for specific source 

categories. Most commenters supported 

retaining the existing reporting 

requirements under the CERR. Others 

encouraged expansion of the 

requirements to include reporting of 

specific organic compounds and organic 

fractions although some thought this 

should be a requirement while others 

thought it should be optional. One 

commenter thought that EPA should 

work with industry trade groups to 

develop and improve the speciation 

profiles of the most important source 

categories rather than asking the state 

and local agencies to characterize VOC 

and PM species. Several commenters 

thought that EPA should encourage the 

reporting of PM components (filterable, 

condensable and total) for development 

of control strategies and attainment 

demonstrations. Another commenter 

noted that including condensable 

emissions raises ‘‘uncertainty’’ issues 

and urged EPA to devote resources to 

developing better test methods. One 

commenter believed that in addition to 

reporting PM2.5 and its components, 

states should report all precursors to 

PM2.5 (SO2, NOX, ammonia and VOC). 

Response: The EPA agrees with the 

commenters who argued that the need 

for additional speciation should be 

determined based on specific SIP needs. 

40 CFR part 51, subpart A which 

contains the CERR, does not require 

reporting of specific compounds or 

compound groups nor does it require 

reporting of organic and elemental 

carbon fractions. As discussed in the 

response to comment above, EPA 

believes that the requirements for data 

elements contained in 40 CFR part 51 

subpart A, in conjunction with the 

provisions of 40 CFR 51.1008, are 

generally adequate to meet the needs for 

PM2.5 nonattainment emissions 


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20650 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

inventory SIP development. Section 

51.1008(a)(1) applies the data element 

requirements contained in 40 CFR part 

51 subpart A. Section 51.1008(a)(2) 

requires States to submit ‘‘any 

additional emission inventory 

information needed to support an 

attainment demonstration and RFP plan 

ensuring expeditious attainment of the 

annual and 24-hour PM2.5 standards.’’

Thus data elements in addition to those 

required under the CERR may be needed 

to support attainment demonstrations 

and RFP inventories under 40 CFR 

51.1008(a)(2). Additional data elements 

needed for other SIP emission inventory 

purposes should be handled on a caseby-case basis. Where States need to 

develop speciated emissions for PM2.5

SIP emission inventories, EPA provides 

guidance in the document titled 

Emissions Inventory Guidance for 

Implementation of Ozone and 

Particulate Matter National Ambient Air 

Quality Standards (NAAQS) and 

Regional Haze Ozone Regulations, 

November 2005. Section 3.2.1, 

Pollutants and Pollutant Precursors to 

be Inventoried identifies pollutants and 

their components to be reported for 

PM2.5 SIPs. Section 3.3.5, Speciation 

Procedures, discusses the preferred 

approach for speciating PM2.5 emission 

inventories for use in ambient air 

quality simulations. The approach 

discussed in the guidance is application 

of emission models which use 

speciation profiles to estimate the mass 

of specific compounds and compound 

groups for VOC and elemental and 

organic carbon fractions for PM. The 

EPA encourages further research and 

development of technical tools to better 

characterize emissions inventories for 

specific VOC compounds and to 

determine the extent of specific VOC 

compounds and organic PM mass. The 

EPA also encourages States to continue 

efforts to refine their ammonia 

inventories. See sections II.A.3 and 

II.A.4 of the Preamble. 

As discussed in the guidance 

document, EPA encourages reporting of 

organic and elemental fractions of PM2.5

by state agencies (see Section 3.2.1, 

Pollutants and Pollutant Precursors to 

be Inventoried). While elemental or 

black carbon (EC/BC) and organic 

carbon (OC) will be identified in default 

speciation profiles, more locally-specific 

data should be collected where available 

as an input to model preprocessing. 

Where such data are available, they 

should be provided to EPA to help in 

improving EPA’s speciation profiles. 

Certain organic gases have been 

identified as precursors to secondary 

organic aerosols (SOA). Toluene, xylene 

and ethyl benzene are known to be 

important SOA precursors. Additional 

organic gases may be identified by 

ongoing research. While these gases will 

be identified in default speciation 

profiles, more locally-specific data 

should be collected, where available, as 

an input to model preprocessing. State, 

local and Tribal agencies can contact 

EPA’s EIAG for more information. 

EPA agrees with the comment that it 

should take the lead in updating VOC 

and PM profiles for most important 

source categories. The Agency is close 

to completing a multi-year effort to 

update the SPECIATE database. 

SPECIATE is EPA’s repository of Total 

Organic Compound (TOC) and PM 

speciated profiles for a wide variety of 

sources. The profiles in this system are 

provided for air quality dispersion 

modeling and as a library for sourcereceptor and source apportionment type 

models. This recent initiative to update 

SPECIATE was needed because 

speciated emissions profiles continue to 

be developed and the data in the 

existing EPA database (SPECIATE 3.2) 

was becoming outdated. 

This work was coordinated with 

interested parties including industry 

through an Agency sponsored 

workgroup. It has depended largely on 

the collection and review of existing 

profile data to accomplish, as the 

commenter suggests, delivering the best 

results for the least amount of resources 

spent. Previously, these data were not 

widely available to emission inventory 

developers and lacked the quality 

assurance review and evaluation needed 

to develop profiles used by emissions 

models to generate speciated emissions. 

As suggested by the commenter, the 

workgroup was used to help prioritize 

source categories for investigation to 

ensure that updates to existing profiles 

and development of new profiles 

focused on areas of greatest need. 

SPECIATE v4.0 contains more than 

2500 source profiles and is currently 

undergoing peer review. The EPA 

expects the final work product to be 

available for use by emission inventory 

preparers during early calendar year 

2007 and it will be distributed through 

EPA’s CHIEF Web site. 

The EPA agrees with a commenter 

who noted that in order to meet the 

requirements under section 172(c) of the 

CAA for ‘‘a comprehensive, accurate, 

current inventory * * *,’’ condensable 

emissions of PM2.5 and PM2.5 precursors 

are important to support development of 

local control strategies and attainment 

demonstrations. The EPA believes that 

the final rule provides for the 

submission of PM2.5 nonattainment area 

inventories meeting the requirements of 

section 172(c)(3). 

Section 51.1008(a)(1) requires that 

States submit emission inventories for 

PM2.5 that satisfy the data elements 

reporting requirements under 40 CFR 

part 51 subpart A, which contains the 

CERR. The CERR requires reporting of 

‘‘Primary PM2.5’’ which is defined as the 

sum of the filterable and condensable 

portions of PM2.5. Therefore, SIP base 

year inventories will include the 

condensable fraction of PM which was 

of concern to several commenters. The 

CERR also requires reporting of SOx, 

NOX, ammonia and VOC which are 

potential precursors to PM2.5. EPA notes 

that the AERR as proposed would 

require reporting of the same precursors 

and would also require reporting of 

Primary PM2.5. However, the proposed 

AERR requires the reporting of the 

filterable and condensable fractions of 

PM2.5 (optional under the CERR) in 

addition to the primary PM2.5 total mass. 

The EPA will address this requirement 

in its final rulemaking on the AERR. 

As noted above, in addition to the 

data element requirements under 

section 51.1008(a)(1), under section 

51.1008(a)(2) States must submit ‘‘any 

additional emission inventory 

information needed to support’’ an 

attainment demonstration and RFP plan. 

Thus States should be aware that data 

elements in addition to those required 

under the CERR may be needed to 

support attainment demonstrations and 

RFP inventories under 40 CFR Part 

51.1008(a)(2). Additional data elements 

needed for other SIP emission inventory 

purposes should be handled on a caseby-case basis. 

The EPA is aware of the issues raised 

by one commenter regarding 

measurement uncertainty for 

condensable PM. This issue is 

addressed in detail under Section II.L of 

the preamble (‘‘Condensable particulate 

matter test methods and related data 

issues,’’). We believe that for purposes 

of emissions inventories and attainment 

demonstrations, States should continue 

to describe the impacts of baseline 

emissions and develop future air quality 

strategies using information available on 

primary PM2.5 emissions, including 

condensable PM2.5. However, with 

respect to developing enforceable 

emissions limits for condensable PM2.5

emissions, the final rule reflects EPA’s 

adoption of a transition period during 

which we will allow time for 

development of emissions limits for 

condensable PM2.5. See 40 CFR 

51.1002(c). 

For additional comments and 

responses related to speciation issues, 


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see the Response to Comments 

Document. 

4. Should EPA Require That States 

Develop Their Own Estimates for Area 

and Mobile Source Emissions? 

Comment: The CERR allows states to 

adopt EPA developed emission 

estimates from area and mobile sources 

in lieu of making those estimates 

themselves if they accept these 

estimates for their emission inventory. 

One commenter thought that EPA 

should require States to develop their 

own estimates for area and mobile 

sources based on the specified 2002 

base year. Three commenters thought 

that the existing process (under the 

CERR) was adequate. One of the 

commenters expressed concerns about 

the reporting burden for States if they 

were required to compile their own 

mobile and area source inventories. 

Another commenter did not believe that 

States should be required to submit data 

on area and mobile sources but noted 

that many States would continue to run 

the MOBILE model for onroad mobile 

sources and calculate area source data 

for SIP emission inventories. Two of the 

commenters thought that the existing 

process provided flexibility needed by 

States to focus on source categories of 

most concern and address problematic 

areas with special inventory needs. One 

commenter recommended that EPA 

continue developing models for area 

and mobile sources. 

Response: The EPA strongly 

encourages states to submit their own 

estimates for area (nonpoint) and mobile 

sources unless they can establish that it 

is impracticable to do so, given time and 

resources. We will continue, in 

appropriate circumstances, to allow a 

State to use EPA-developed emission 

estimates for mobile and nonpoint 

sources in lieu of making those 

estimates itself if the State accepts the 

estimates for its emission inventory. 

While this has been the case with 

respect to reporting under the CERR for 

the 3-year cycle inventories, for 

development of emission inventories to 

support PM2.5 SIPs, the ability to rely on 

EPA-developed emission estimates for 

development of emission inventories to 

support PM2.5 SIPS is more complex and 

problematic. For mobile sources, the 

practical use of these EPA-developed 

mobile source inventories in a SIP may 

be very limited. While EPA has 

developed inventories for 2002, states 

will still have to develop attainment 

year inventories, including projections 

of future activity and the effects of 

control measures. For mobile sources, 

future year inventories are not 

developed by simply growing a base 

year inventory, but instead are 

developed by running an emissions 

model with appropriate inputs for the 

future year. In order to develop an 

attainment demonstration that 

accurately accounts for the change in 

emissions from the base year to the 

attainment year, inventories for both of 

those years will need to be developed 

using consistent methods and modeling 

assumptions. For mobile sources 

especially, it may be very difficult for 

states to replicate the methods used by 

EPA for the base year when creating the 

attainment year inventory. 

In addition, states cannot use the EPA 

developed inventories for the base year 

if newer models or planning 

assumptions are available at the time 

they begin working on the SIP. For 

example, if new or better information 

about the composition of the local fleet 

of highway vehicles in the base year 

becomes available to the state after the 

EPA developed inventories were 

created, that information should be used 

by the state to create a new base year 

inventory. 

Given the need for emissions 

modeling for mobile sources in the 

projection year, the need for consistency 

in tools and methods between the base 

year and attainment year, and the need 

to use latest available models and 

planning assumptions, EPA believes 

that most if not all states will choose to 

develop their own base year inventories 

for mobile sources. 

With respect to nonpoint (area) source 

emissions, States must make every 

effort, consistent with available timing 

and resources to ensure that their area 

source emission inventories are as 

accurate as possible. While EPA 

prepares a national area source emission 

inventory that covers all counties, it is 

designed for national analyses. EPA 

does not have access to the more 

detailed information available to States 

that is used to develop an area source 

inventory. Therefore, states should 

develop as much of their area source 

inventory as possible using local and 

State information, and in particular 

should develop the inventory for the 

most significant area source categories 

which are critical to ensuring overall 

accuracy. Where time and resources 

preclude a State from developing the 

estimates for less-critical area source 

categories, the State may rely on EPAdeveloped area source emissions 

information for those categories. 

The EPA points out that although 

guidance has recommended that 2002 

be used as the base year for emissions 

inventories for states initially 

designated nonattainment in 2004–5, 

states remain free to use an alternate 

base year, as appropriate. Section 

51.1008(b) provides in relevant part that 

‘‘The baseline emission inventory for 

calendar year 2002 or other suitable year 

shall be used for attainment planning 

and RFP plans for areas initially 

designated nonattainment for the PM2.5

NAAQS in 2004.’’

EPA agrees with the comment that it 

should continue to develop models and 

other emission estimation tools. As an 

example, EPA’s Office of Transportation 

and Air Quality (OTAQ) is developing 

a modeling system termed the Motor 

Vehicle Emission Simulator (MOVES). 

This new system will estimate 

emissions for on-road and nonroad 

sources, cover a broad range of 

pollutants, and allow multiple scale 

analysis, from fine-scale analysis to 

national inventory estimation. When 

fully implemented MOVES will serve as 

the replacement for MOBILE6.2 and 

NONROAD. In addition, as the NEI is 

reengineered, OAQPS will examine the 

need for updating emissions estimation 

guidance materials and developing tools 

which will assist State agencies in 

estimating emissions from area source 

categories. See also EPA’s ‘‘Emissions 

Inventory Guidance for Implementation 

of Ozone and Particulate Matter 

National Ambient Air Quality Standards 

(NAAQS) and Regional Haze 

Regulations,’’ November 2005. 

5. Other Inventory Issues 

The EPA’s responses to additional 

comments concerning emission 

inventory issues can be found in EPA’s 

Response to Comments Document. 

L. Condensable Particulate Matter Test 

Methods and Related Data Issues 

a. Background 

As noted in the preamble to the 

November 1, 2005 proposed rule, 

certain commercial or industrial 

activities involving high temperature 

processes (fuel combustion, metal 

processing, cooking operations, etc.) 

emit gaseous pollutants into the ambient 

air which rapidly condense into particle 

form. The constituents of these 

condensed particles include, but are not 

limited to, organic material, sulfuric 

acid, and metals. Because condensable 

emissions exist almost entirely in the 

2.5 micrometer range and smaller, these 

emissions are inherently more 

significant for PM2.5 than for prior 

particulate matter standards addressing 

larger particles. Therefore, we believe 

that it is important that the air quality 

management of particulate matter 

promote a comprehensive approach to 

condensable particulate matter. 


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20652 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

We proposed to require a 

comprehensive inclusion of 

condensable PM for all aspects of SIP 

development for PM2.5. Under the 

proposal, EPA would require 

condensable PM to be considered in the 

emissions inventories and analyses used 

in attainment demonstrations. Also 

under the proposal, any stationary 

source emissions limits developed to 

implement RACT or RACM would 

reflect control and measurement of 

condensable PM. 

We received numerous comments on 

whether these requirements were 

unreasonable in light of the current state 

of knowledge of and uncertainties 

around the measurement of direct PM2.5. 

Most commenters supported the overall 

view that condensable PM should be 

addressed in order to provide a 

complete air quality management 

program for PM2.5. On the other hand, 

many commenters raised concerns 

about the availability and 

implementation of test methods and 

related issues about the uncertainties in 

existing data for condensable PM2.5. As 

a result of the concerns, these 

commenters believed EPA would be 

premature in requiring a comprehensive 

evaluation of condensable PM2.5, 

especially as it related to developing 

any new emissions limits for stationary 

sources. In recognition of these 

concerns, the final rule reflects EPA’s 

adoption of a transition period during 

which we will assess possible revisions 

to available test methods and we will 

allow time for States to update 

emissions inventories as needed to 

address direct PM2.5 emissions. In this 

section of the preamble, we outline the 

elements of the final rule addressing 

inventories reflecting control of direct 

PM2.5. We also discuss the specific 

comments raised regarding methods for 

measuring direct PM2.5, both filterable 

and condensable PM, in implementing 

the rule. The particular comment areas 

include defining test methods, 

quantifying direct PM2.5 for inventories, 

and a transition period for developing 

effective regulations. Below are also our 

responses to those comments. 

b. Final Rule 

For the final rule, EPA addresses two 

broad issues related to inclusion of 

condensable PM. The first issue is 

whether emissions inventories and 

attainment demonstrations should 

include the condensable portion of 

direct PM2.5 emissions. The second 

issue is whether direct PM2.5 emissions 

limitations established by States for 

purposes of RACT and RACM must 

include limits on condensable PM 

emissions or limits on total direct PM2.5

that includes the condensable PM 

fraction. 

For purposes of developing emissions 

inventories and attainment 

demonstrations, the final rule reflects a 

requirement to account for significant 

contributors of direct PM2.5 emissions, 

both filterable and condensable PM2.5. 

We recognize that some States have 

established inventories consistent with 

requirements of the consolidated 

emissions reporting rule (CERR) to 

report direct PM2.5 emissions, including 

condensable PM, in each inventory 

revision. While uncertainties remain 

with significant issues to address related 

to our current knowledge base on 

condensable PM emissions, we believe 

that for purposes of emissions 

inventories and attainment 

demonstrations, States should continue 

to describe the impacts of baseline 

emissions develop future air quality 

strategies using information available on 

direct PM2.5 emissions including 

condensable PM. 

With respect to developing 

enforceable emissions limits for 

condensable PM emissions, we note that 

some States have established emissions 

limits or otherwise require PM 

emissions testing that includes 

measurement of condensable PM. We 

recognize that in some States there 

remain questions about the viability of 

available test methods, the availability 

of representative direct PM2.5 emissions 

data, the uncertainty of the methods 

used to establish inventories, and the 

short time frame within which States 

must develop SIPs. In response we have 

decided to provide a transition period 

for developing emissions limits and 

regulations for condensable PM2.5. 

During this transition period, we will 

provide technical support to States as 

requested in establishing effective PM2.5

emissions limits and corresponding 

emissions testing requirements. 

As described further below, we will 

devote resources early during this 

transition period to assessing and 

improving the available test methods for 

condensable PM. During this transition 

period, we will also solicit the 

involvement of stakeholders with an 

interest in conducting emissions testing 

to collect updated direct PM2.5

emissions data. The purpose of these 

stakeholder projects will be to collect 

new direct filterable and condensable 

PM emissions data using methodologies 

that provide data more representative of 

source direct PM2.5 emissions. The EPA, 

States, and others will use these data to 

improve emissions factors and to help 

define or revise source emissions limits 

in permits and State implementation 

plans. 

The time required for our 

stakeholders and EPA to complete the 

test method assessment will limit the 

degree to which State and local agencies 

can address effectively the necessary 

direct PM2.5 regulations in inventories 

and in the 2008 SIP submittals. In 

recognition of this, we will not require 

that the emissions limits included in the 

2008 submittals account for the 

condensable fraction of direct PM2.5 or 

to establish limits for total direct PM2.5, 

including condensable PM. 

We will expect States to continue 

developing more complete inventories 

with regard to direct PM2.5 emissions, 

particularly for condensable PM, during 

this transition period. We expect no 

such allowance period for method 

assessment or data collection to be 

necessary for implementing regulations 

addressing precursor PM2.5 emissions. 

The period of transition for 

establishing emissions limits for 

condensable direct PM2.5 will end 

January 1, 2011. We expect States to 

address the control of direct PM2.5

emissions, including condensable PM, 

with any new actions taken after 

January 1, 2011. For example, States 

must address condensable PM 

emissions in any direct PM2.5 emissions 

limits resulting from midcourse reviews. 

Additionally, EPA expects that any 

direct PM2.5 regulations or limits 

developed under any new NAAQS for 

particulate matter would also address 

condensable PM emissions. 

Notwithstanding the issues and 

uncertainties related to condensable 

PM, EPA encourages States to identify 

measures for reducing condensable PM 

emissions, particularly where those 

emissions are deemed significant 

contributors to the control strategy 

needed for expeditious attainment. We 

wish to clarify that in order to take 

credit in the SIP for reduction of any 

such condensable PM emissions, there 

must be enforceable limitations that 

ensure that reduction in condensable 

PM emissions. These enforceable limits 

could take the form of a limitation on 

the condensable PM emissions or total 

direct PM2.5 emissions (or a 

commitment to develop such limitations 

after the end of the transition period 

described above). Alternatively, these 

enforceable limitations could provide 

for enforceable conditions that ensure 

that the effect on condensable PM 

emissions is assured (for example, 

enforceable limitations on operating 

temperature, or limits on FGD scrubber 

operations which have the effect of 

reducing condensable PM emissions). 


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Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 20653 

47 ‘‘Optimized Method 202 Sampling Train to 

Minimize the Biases Associated with Method 202 

Measurement of Condensable Particulate Matter 

Emissions,’’ John Richards, Tom Holder, and David 

Goshaw, Air Control Techniques, P.C.; Air & Waste 

Management Association, Hazardous Waste 

Combustion Specialty Conference AWM, November 

2–3, 2005, St. Louis, MO. 

c. Comments and Responses 

We received many comments on 

quantification of direct PM2.5 emissions 

particularly about the need to conduct 

further validations for the available test 

methods, the availability of direct 

filterable or condensable PM2.5 data or 

lack thereof for representative baselines, 

and the procedures for applying 

baseline data for developing effective 

regulations. 

1. Method 202 

Comment: A majority of commenters 

characterized the performance of 

Method 202 as lacking in reliability. 

Some commenters characterized the 

formation of artifacts in Method 202 as 

significant and the primary reason for 

their recommendation to defer the 

inclusion of condensable particulate 

matter in the baseline assessments and 

regulatory development for the initial 

SIPs. The commenters stated that the 

principal artifact formed when using 

Method 202 was the result of SO2

dissolving in the impinger water and 

converting to sulfuric acid. 

Response: We agree that SO2 in 

particular, and perhaps other gaseous 

compounds, can react with the 

collecting liquids used in the method to 

form materials (artifacts) that would not 

otherwise be solid or liquid or would 

not condense upon exiting the stack. We 

believe that when Method 202 is 

applied appropriately (i.e., with the N2

purge as prescribed), the SO2 artifact 

formation is reduced by as much as or 

more than 90 percent; however, we 

agree that further verification and 

refinement would be appropriate to 

verify the potential for artifact 

formation. 

In response, we are undertaking 

laboratory studies in collaboration with 

several stakeholders to characterize the 

artifact formation and other 

uncertainties associated with 

conducting Method 202, and to identify 

procedures to be used in applying 

methods to minimize uncertainties. We 

are involving stakeholders representing 

industry and State and local agencies in 

the project design and results review. 

Stakeholders who have expressed 

interest in participating in these studies 

include the Electric Power Research 

Institute, companies associated with the 

National Environmental Development 

Association’s Clean Air Project (NEDA/ 

CAP), the Portland Cement Association, 

the Lime Manufacturing Association, 

the American Foundry Association, the 

National Aluminum Association, and 

several governmental organizations 

represented by National Association of 

Clean Air Agencies. Other parties may 

participate in the study as well. 

By the end of 2007, we intend to have 

conducted a comprehensive laboratory 

study that examines the relationship 

between several critical condensable PM 

sampling and analysis parameters (e.g., 

SO2 concentration, moisture 

concentration, sample duration, and 

water acidity) and the artifact formation 

associated with the measurements. One 

intended result of the project will be 

identifying possible modifications to 

Method 202 to minimize and quantify 

the uncertainties. We will publish the 

results of the laboratory study along 

with an assessment of other input and 

data from stakeholders on the EPA 

website and, to the extent possible, in a 

widely circulated peer review journal. 

Also, to the extent necessary, we intend 

to propose revisions to the method to 

incorporate improvements and to clarify 

application. 

2. Conditional Test Methods 039 

and 040 

Comment: Several commenters cited 

as a deficiency that neither conditional 

test method 040 (CTM–040) for 

measuring filterable PM2.5 nor the 

dilution sampling method (CTM–039) 

has been thoroughly validated through 

EPA Method 301. There were also 

comments that neither of the CTMs was 

published in the Federal Register. 

Response: We agree with the 

comments that neither method has been 

subjected to adequate public notice and 

comment rulemaking. Taking that step 

will facilitate application of the 

appropriate methods for implementing 

the SIPs. On the other hand, there are 

a number of levels of validation already 

achieved for one or more of these 

methods that will determine what, if 

any, additional validation work will be 

necessary. For example, while we could 

seek resources to evaluate dilution 

sampling technology, including CTM–

039, and to request public involvement 

in the project planning, conduct, and 

review with the possibility of a Federal 

Register proposal, our preference would 

be to incorporate by reference an 

approved voluntary consensus test 

method (e.g., ASTM standard). 

We believe that a dilution sampling 

method for measuring direct PM2.5

eliminates essentially all artifact 

formation and provides the most 

accurate emissions quantification. To 

the extent that we need to and can 

secure resources and stakeholder 

interest, we plan to perform additional 

validation testing of CTM–039 or other 

dilution sampling technologies to 

characterize the precision of this 

approach. In conjunction with our 

validation efforts, we intend to continue 

participation in the ASTM D22 

committee to develop and publish a 

dilution sampling method and 

encourage other volunteers on that 

committee to approve the consensus 

based dilution sampling method. We 

believe that this work is nearly 

complete. As outlined above, we are 

already undertaking laboratory studies 

to assess the method and to identify 

possible modifications to reduce 

formation of these artifacts. Preliminary 

laboratory evaluations conducted by 

EPA and by Environment Canada47

indicate that additional artifact 

reductions of 60 to 90 percent may be 

achieved with other minor 

modifications to Method 202. These 

preliminary findings indicate that 

Method 202 is essentially a viable 

method that these proposed laboratory 

studies will serve to enhance. Within 18 

months we intend to propose, if 

necessary, modifications to Method 202 

or similar methodologies suitable for 

measuring condensable PM2.5. 

As for CTM–040, we believe that 

further validation of this method is 

unwarranted since the technology and 

procedures are based upon the same as 

evaluated for promulgated Method 

201A. Method 201A has undergone 

public review and comment (55 FR 

14246, April 17, 1990). Also, as noted 

earlier, we have already begun 

laboratory and data evaluation work the 

possible result of which would be a 

revised Method 202 to be proposed in 

the Federal Register to include 

improvements indicated by the 

evaluation. At that same time, we may 

propose CTM–040 to be used in 

combination with Method 202 for 

measuring direct PM2.5 with additional 

guidance on appropriate approaches to 

testing for direct PM2.5 emissions from 

various types of control measures (e.g., 

electrostatic precipitator and flue gas 

desulphurization combinations). 

3. Role of Condensable PM Emissions in 

Defining RACT 

Comment: Commenters indicated that 

States must reassess and revise 

emissions limits if the States adopt 

methods for measuring direct PM2.5

including condensable PM where not 

required previously. Commenters noted 

that most existing PM emissions limits 

are not reflective of data collected with 


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48U.S. Environmental Protection Agency. PM–10 

SIP Development Guideline. Office of Air Quality 

Planning and Standards, Research Triangle Park, 

NC. EPA Publication No. EPA–450/2–86–001. June 

1987. 

49The General Preamble is available online at 

http://www.epa.gov/ttn/oarpg/t1pfpr.html. 

50Clean Air Act Advisory Committee, 

Recommendations to the Clean Air Act Advisory 

Committee—Phase I and Next Steps, Air Quality 

Management Work Group, Environmental 

Protection Agency, http://www.epa.gov/air/caaac/ 

pdfs/report1-17-05.pdf, January 2005. 

51Option Paper 4—Providing Guidance 

Regarding The Use Of Emissions Factors For 

Purposes Other Than Emissions Inventories, 

September 2005, http://www.epa.gov/ttn/chief/ 

efpac/projects.html. 

methods that measure condensable or 

filterable PM2.5 and, therefore, not 

enforceable using a new or different test 

method. 

Response: We agree that coordinating 

the test method with the pollutant 

defined by the emissions limit is critical 

to an effective regulation. In the case of 

direct PM2.5 regulations, the methods for 

measuring filterable and condensable 

PM provide data that are significantly 

different than do methods often used in 

implementing many current regulations 

(i.e., filterable plus condensable PM2.5

versus filterable PM only). The existing 

PM emissions regulations implementing 

many current SIPs have focused almost 

exclusively on filterable PM at stack 

conditions or other elevated 

temperatures (e.g., 250 °F) with little or 

no measurement of condensable PM, let 

alone filterable PM2.5. These 

deficiencies exist in spite of the 

Agency’s policies and guidance 

presented in documents such as the 

1987 PM10 SIP Development 

Guideline 48 and the General Preamble 

for the Implementation of Title 1 of the 

Clean Air Act Amendments of 1990 49

issued in 1992. These documents set 

forth Agency policy stating that direct 

PM10 and direct PM2.5 emissions include 

both filterable and condensable 

particulate matter. The policies are 

reinforced by a 2005 directive from the 

CAA Advisory Committee.50

More to the point, the use of test 

methods that quantify only filterable PM 

would limit the capability of any 

assessment of control measures 

available for developing cost effective 

strategies to achieve attainment of the 

PM2.5 NAAQS. Examples include an 

attainment demonstration that includes 

control methodologies for PM 

precursors which are likely to result in 

a significant decrease in the emissions 

of direct PM2.5 (for example, alkaline 

scrubbers to reduce SO2 emissions) and 

incorporate these direct PM2.5 emissions 

reductions in their attainment 

demonstration or allow for the use of 

these reductions as credits for other 

programs. 

Some States may decide to measure 

and control condensable PM emissions 

prior to the end of the transition period. 

To the extent that a State has the 

supporting technical information and 

test methods, the State may also assess 

the capabilities of current control 

technologies, possible modifications to 

such technologies, or new technologies 

as appropriate relative to control of 

condensable PM2.5 emissions in 

developing effective control strategies 

and regulations. As an example, a 

specific approach for controlling 

condensable PM could be a change in 

control device operating temperature to 

achieve necessary emissions reductions. 

We also note that it is important that 

implementation of any new or revised 

rules and test methods should be 

prospective and clearly differentiated 

from existing regulations to avoid 

confusion over status of compliance 

relative to existing PM emissions limits. 

4. Sufficiency of Current Baselines 

Relative to Direct PM2.5 for Regulatory 

Development 

Comment: Many commenters 

indicated that the currently available 

baselines for direct PM2.5 emissions are 

not sufficient for States to develop 

effective emissions control regulations. 

One commenter claimed that States will 

need additional information regarding 

how to arrive at enforceable PM2.5

emissions limitations through 

application of correlations to existing 

PM10 emissions limitations. 

Response: We agree that State 

inventories accounting for direct PM2.5

emissions are important to the NAAQS 

implementation decision-making 

process. For example, the current 

national emissions inventories have 

characterized the contribution of the 

condensable PM emissions to range 

from 40 to 80 percent of the direct PM2.5

emissions particularly from combustion 

source categories. We also agree in 

many cases, the emissions baselines are 

not sufficiently representative of 

significant direct PM2.5 contributors to 

allow States to develop effective and 

enforceable emissions limitations for 

sources that may require control of 

direct filterable or condensable PM2.5

emissions in order for States to come 

into attainment with the PM2.5 NAAQS. 

We note that States are already 

required under the consolidated 

emissions reporting rule (CERR) to 

report direct PM2.5 emissions, including 

condensable PM, in each inventory 

revision. That means that inventories 

and associated baselines must address 

sources and contributions of direct 

PM2.5 emissions, both filterable and 

condensable PM, from individual 

sources and groups of sources as well as 

for future year projected emissions. 

These data are important for the 

purposes of calculating emissions 

reductions and demonstrating that such 

reductions are attributable to the control 

measures being implemented. 

In taking the process to the next step, 

we contend that many current baselines 

established using the available direct 

filterable and condensable PM2.5

national industry average emissions 

factors (e.g., those found in AP–42 and 

WebFIRE, http://www.epa.gov/ttn/chief/ 

efpac/index.html) often are of quality 

insufficient to establish effective sourcespecific emissions limits. First, national 

industry average emissions factors are 

subject to significant uncertainties as 

they usually represent data from a very 

limited number of example facilities in 

a category and for a very limited number 

of operating conditions. Second, the 

available emissions factors databases 

may not include direct PM2.5 emissions 

data for specific source types that 

appear in some State and local 

inventories. 

In short, we believe that States should 

rely on directly measured emissions 

data in developing source category or 

pollutant-specific emissions limits for 

regulations. This approach is preferable 

to the use of these national industry 

average emissions factors such as those 

found in AP–42. If there are no directly 

measured emissions data available from 

the subject sources, national average 

emissions factors should be used only 

with appropriate and significant 

adjustments for uncertainty. Based on 

our initial study 51 of the uncertainties 

associated with national average 

emissions factors when applied to sitespecific or rule-development activities, 

we would expect multipliers of 0.1 to 

3.3 for an A-rated national average 

filterable and condensable direct PM2.5

emissions factors. The level of a 

particular multiplier would depend on 

how representative of the source 

category the applicable emissions factor 

is, the quantity of data supporting that 

emissions factor, and the specific 

application. Determining what 

adjustment may apply for a particular 

application requires detailed knowledge 

of the emissions control variability, the 

expected range of operational and 

process variability, and the statistical 

uncertainty in the measured emissions 

data. While more general adjustments to 

emissions factors are possible for these 

purposes, we believe that the better 

approach is to improve and update the 

emissions factors used in the database 

for a particular area with measured 


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direct PM2.5 emissions data. For these 

reasons and to allow time for data 

collection and analysis, we have 

determined the need for a period of 

transition for States in developing direct 

PM2.5 emissions reduction strategies. 

5. Transition Period 

Comment: Some commenters 

suggested that EPA should allow States 

to base their initial 2008 SIPs on NOX, 

SO2, and filterable PM or PM10 (as a 

surrogate for filterable PM2.5) rather than 

require State and local agencies to 

develop direct PM2.5 emissions 

regulations immediately. Commenters 

suggested that EPA provide a transition 

period for sources to adopt SIPs that 

address direct PM2.5 and to apply the 

appropriate test methods. The 

commenters proposed that during this 

transition period, a source should be 

able to continue to use Method 5, 

Method 17, or whatever method was 

used to set the underlying limit 

contained in the source’s title V 

operating permit. Commenters believe 

that such a transition plan must provide 

additional time to collect data related to 

condensable PM emissions. 

Commenters believe that this additional 

time is necessary because it is 

unrealistic to develop SIP revisions 

addressing condensable emissions by 

April 2008. Other commenters 

suggested that source emissions 

inventories used for regulatory decisionmaking and identifying regulatory 

control measures must be based on 

accurate measurements. 

Response: As outlined above, we 

agree that a transition period should be 

allowed to allow time to resolve and 

adopt appropriate testing procedures for 

condensable PM emissions, to collect 

total (filterable and condensable) PM2.5

emissions data that are more 

representative of the sources in their 

areas, and develop effective regulations 

for control of direct PM2.5, including 

condensable PM. 

6. Data Collection for Regulatory 

Development 

Comment: Several commenters 

recommended that EPA should be 

responsible for developing data of 

emissions from common sources of 

direct PM2.5. 

Response: We disagree with the 

commenters’ recommendation that EPA 

should be primarily or solely 

responsible for developing baseline data 

on common sources of direct PM2.5

emissions. Commenters are suggesting 

that we should collect data 

representative of direct PM2.5 emissions 

from source categories potentially 

subject to regulation of direct PM2.5

emissions. Furthermore, they suggest 

that we expand or improve the current 

compilation of national industry average 

emissions factors such as found in AP–

42 and WebFIRE (http://www.epa.gov/ 

ttn/chief/efpac/index.html). Given the 

limited extent to which national 

industry average emissions factors are 

suitable for developing State or local 

regulations that set limits on direct 

PM2.5 emissions, we believe that it is 

inherent that States instead have 

primary responsibility for reviewing and 

applying measured emissions data 

collected from their sources in 

enhancing their current baselines. In 

some cases, this will mean that States 

and other stakeholders will need to 

conduct more focused direct PM2.5

emissions data collection and improve 

relevant emissions factors. 

This approach is appropriate for 

several reasons. First, we believe that 

stakeholders other than EPA are better 

equipped to identify specific data needs 

and that they have the means to collect 

the data. Second, we believe we are 

better positioned to provide guidance on 

test planning, data collection, and 

emissions factors calculations with a 

less direct role in data collection and 

evaluation. Third, we believe that States 

in need of additional information can 

also benefit from experience of other 

States with similar source types and 

who are developing regulations to 

implement the NAAQS including the 

control of condensable PM. See also the 

discussion in section II.L.2.c.1 above on 

the currently active collaborative study 

to assess direct PM2.5 emissions 

measurement technologies and to 

collect updated direct PM2.5 emissions 

data. 

7. Developing Effective Regulations for 

Direct PM2.5, Including Condensable 

PM, Emissions 

Most current PM regulations focus on 

the control and measurement of 

filterable PM emissions and do not 

account for condensable PM emissions. 

At issue are assessing and accounting 

for the differences in methodology and 

applicable limits when changing to a 

program designed to achieve reductions 

in PM2.5 emissions, including 

condensable PM. 

Comment: A number of respondents 

commented that EPA needs to 

promulgate a PM2.5 test method and 

adopt regulatory language that 

determines the PM2.5 limits based on 

that promulgated PM2.5 test method as 

soon as possible. Other commenters 

suggested that EPA and States have no 

choice but to revise the underlying 

standard by adopting new monitoring 

requirements through a notice and 

comment rulemaking. Further, these 

commenters indicate that it is essential 

that EPA require that no change in a test 

method or in methods of monitoring for 

determining compliance until such time 

as EPA or the permitting agency have 

undertaken a notice and comment 

process to determine how the emissions 

limitations must be revised. A number 

of commenters cited specific 

components necessary for effective 

regulations. 

Response: We agree that notice and 

comment rulemaking is appropriate for 

establishing effective regulations. As 

noted above, we are already undertaking 

a study of the available test methods to 

determine the need for regulatory 

revisions. We also agree that new 

regulations limiting direct PM2.5

emissions must include effective 

emissions limitations to the extent that 

a State must reduce sources of direct 

PM2.5. How a State determines to take 

such regulatory action depends on the 

State’s implementation plan. Regarding 

the specific components necessary for 

effective regulations, see section O 

below on enforcement and compliance 

issues. 

M. Improving Source Monitoring 

a. Background 

In the November 1, 2005 proposal, we 

discussed a number of actions the EPA 

would undertake to improve the 

effectiveness of existing and new 

regulations with improved source 

monitoring provisions. Specifically, we 

repeated a plan outlined on January 22, 

2004 (69 FR 3202; a Federal Register 

notice describing requirements for 

monitoring in operating permits), that 

includes a four-part strategy for 

improving monitoring of emissions at 

the source where necessary through 

rulemaking. One element of that plan is 

for EPA to develop guidance on how 

States can reduce PM2.5 emissions by 

improving source monitoring related to 

PM2.5 emissions limits. We noted that 

we expect to describe in such guidance 

methods of improving monitoring 

frequency or adopting more appropriate 

monitoring for States to consider in 

developing their PM2.5 SIPs and to 

illustrate the amount of credit that 

States could receive in PM2.5 SIPs for 

adopting such improved monitoring. We 

suggested that States with areas where 

additional reductions are needed to help 

the area achieve compliance with the 

NAAQS could implement improved 

monitoring measures to obtain 

additional emissions reductions. We put 

forward that State agencies could 

receive SIP credits as a result of 

enforceable improved monitoring or 


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voluntary emissions monitoring 

programs meeting EPA voluntary 

program policies. 

Specific examples of improved 

monitoring we outlined included: (1) 

Conducting the currently required 

monitoring more frequently (i.e., 

increased monitoring frequency), (2) 

changing the monitoring technique to a 

parameter more closely related to 

control of direct or precursor PM2.5

emissions (i.e., a correlated parametric 

monitoring technique), (3) changing the 

technique to more measurement of 

direct PM2.5 emissions and PM2.5

precursors, or (4) a combination of these 

improvements. These types of 

monitoring improvements could be 

conducted for both controlled and 

uncontrolled emissions units. The 

improved monitoring control measure 

would require facilities to pay more 

attention to the operation of add-on air 

pollution control devices, work 

practices, and other control measure 

activities. The additional attention will 

reduce periods during which control 

devices and other control measures do 

not operate as intended or required. The 

result would be increased emissions 

reductions from implementing existing 

and new rules. 

We discussed a range of currently 

applied and new monitoring 

technologies. We addressed concerns 

we have about the limitations of the 

widespread use of visual emissions (VE) 

monitoring techniques, such as visible 

emissions checks, to show compliance 

with PM emissions limits. We noted 

particular concerns about VE 

approaches, even with frequent 

application, having the ability to verify 

compliance when the margin of 

compliance is small or the ability to 

detect relatively significant changes in 

emissions control performance. The 

other concern we noted about the use of 

VE tools is the limited frequency at 

which they are conducted. We cited 

studies on the availability of continuous 

instrumental methods for monitoring 

opacity and operational parameters 

closely related to PM control levels 

including the development of repeatable 

correlations between parameter levels 

and PM emissions. We noted that PM 

continuous emissions monitoring 

systems (PM CEMS) technology 

provides the opportunity to quantify PM 

emissions levels (concentration or 

emissions rates). These additional data 

provide the source owner/operator with 

a level of information that can be useful 

for understanding and operating the 

process and the control measures in 

ways to minimize emissions, improve 

operating efficiencies, and reduce 

enforcement liabilities. Furthermore, we 

noted that this technology will provide 

the State with quantitative information 

on PM emissions which will help 

improve the inventories and to 

implement effective control strategies to 

meet the NAAQS. 

We also discussed at some length 

what we believe constitutes improved 

monitoring and the potential for 

monitoring-related emissions 

reductions. We discussed a study of 

how these emissions reductions would 

be achieved by increasing the 

monitoring frequency or improving the 

monitoring of an add-on air pollution 

control device or other process activity 

above the level currently required in 

existing rules. The increased frequency 

or improved technique would allow 

owners or operators to achieve greater 

emissions reductions by identifying and 

responding more quickly to periods of 

ineffective control measure operation. 

States could use an improved 

monitoring control measure in 

regulations or through other means to 

reduce emissions levels and receive 

credits towards attainment. Specifically, 

we cited materials that indicate that 

source owners and operators who 

increase monitoring frequency could 

achieve emissions reductions up to 13 

percent and those who improve the 

monitoring technique could achieve 

emissions reductions up to 15 percent. 

States with nonattainment areas in need 

of additional reductions to achieve 

compliance with the NAAQS could 

implement an improved monitoring 

measure and develop additional 

emissions reductions credits. We 

outlined several specific examples. 

In order to inform our improved 

monitoring guidance development 

efforts, we used the 2005 proposal to 

solicit specific comments on (1) how 

potentially inadequate source 

monitoring in certain SIPs could be 

improved; (2) how improved PM2.5

monitoring relates to title V monitoring; 

(3) whether instrumental techniques are 

more appropriate than visual emissions 

(VE) techniques for monitoring 

compliance with PM emissions limits; 

and (4) a basis for determining whether 

improved monitoring would be effective 

and under what conditions should be 

required. We also requested comment 

on the feasibility of monitoring of copollutant control measures and 

requested examples of improved 

monitoring for any applications. 

b. Final Rule 

We maintain that improved 

monitoring is critical to implementing 

the PM2.5 direct and precursor emissions 

reductions programs. We also believe 

that improving monitoring both in terms 

of increasing data collection and 

analysis frequency and in measuring the 

pollutant of interest more directly will 

accomplish several important and 

advantageous outcomes. First, improved 

monitoring will improve verification of 

compliance and assurance of the 

intended emissions reductions. Second, 

improved monitoring can provide 

additional emissions reductions through 

quicker detection and correction of 

control measure problems. Third, 

improved monitoring can improve 

operating efficiencies that often result in 

cost savings to the facility exceeding the 

cost of the monitoring. We will continue 

to evaluate the effects of improved 

monitoring on emissions reductions and 

ways to quantify the benefits associated 

with improved monitoring. 

We intend to move forward with 

developing and providing additional 

technical and informational materials 

regarding technologies constituting 

improved monitoring and for 

developing regulations with improved 

monitoring. These materials may also 

include guidance and tools for 

establishing emissions reductions 

credits and the economic benefits 

associated with improved monitoring. 

As noted in section L above, we also 

reaffirm our policy that effective 

regulations must include certain 

elements that define applicable 

emissions limitations, the testing and 

monitoring requirements, and 

compliance, reporting, and corrective 

action obligations. 

c. Comments and Responses 

We expected to receive practical 

advice concerning improved PM2.5

source emissions monitoring methods 

and field-tested examples. Instead, 

commenters focused on (1) critiquing 

PM CEMS technology (2) insisting that 

improving monitoring changes 

stringency of existing rules and requires 

rulemaking, and (3) critiquing the 

theoretical study linking emissions 

reductions with improved monitoring. 

1. Currently Available PM CEMS for 

Monitoring Direct PM2.5 Emissions 

Comment: Commenters noted that 

because currently available PM CEMS 

measure filterable PM at stack 

conditions or at other elevated 

temperatures, the instruments do not 

measure the condensable portion of 

PM2.5. 

Response: We agree with this 

comment relative to PM CEMS in use to 

date and the ability to detect 

condensable PM. PM CEMS as applied 

today can be calibrated to measure 

filterable PM2.5 emissions with very 

good sensitivity and repeatability. Note 


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that we are aware of a number of PM 

CEMS vendors developing devices 

relying on much the same technology 

but modified to measure condensable 

PM. Further, we are aware of at least 

one manufacturer offering a PM CEMS 

applicable to stationary sources that also 

complies with ASTM requirements for 

mobile source emissions monitoring. 

We also believe that monitoring for 

filterable PM2.5 will be as important in 

some cases as monitoring for 

condensable PM and that PM CEMS in 

use today are markedly better at 

monitoring PM emissions than other 

frequently used monitoring approaches. 

We realize that PM CEMS represent 

just one of a range of monitoring options 

that constitute improvements over the 

current monitoring. For instance, we 

believe that improved monitoring would 

include replacing current periodic VE 

measurements or daily recording of 

pressure drop of fabric filters with 

continuous bag leak detectors. We know 

of projects (e.g., ASTM committee work) 

for continuing the development of 

optical, as well as electromagnetic, 

monitoring tools to increase sensitivity 

and cost-effectiveness. Such monitoring 

would increase monitoring frequency 

and would yield data much more 

closely related to and more sensitive to 

control device operation than most 

currently applied monitoring. To the 

extent that condensable PM control is 

critical in implementing a regulation, 

we believe that monitoring must address 

that need. We will continue to collect 

and also provide information on source 

monitoring approaches that are 

improvements over current methods in 

both frequency and representativeness 

relative to implementing PM2.5

emissions control strategies. 

2. Status of Guidance Relative to 

Regulations 

Comment: A significant majority of 

commenters suggested that improving 

monitoring in an existing regulation 

increases its stringency and requires 

notice and comment rulemaking, not 

guidance. Just one commenter suggested 

guidance could be developed and used. 

Response: There are two aspects to 

the comments on this issue. One is 

whether improved monitoring would 

change source operations. We agree 

with the commenters that increasing the 

frequency of data collection or 

providing data more directly related to 

the pollutant of concern with improved 

monitoring could result in changes in 

how a facility is operated relative to 

compliance. We disagree with 

commenters that such changes in 

process operation resulting from 

improved monitoring constitute an 

increase in a regulation’s stringency 

with respect to compliance. First, as 

mentioned in the preamble to the 

Credible Evidence rule (62 FR 8326, 

February 24, 1997), an emissions 

standard’s required stringency is 

unaffected by the frequency of 

monitoring given no decrease in 

averaging time or emissions limitation. 

Secondly, data from improved 

monitoring will provide a facility 

operator better information on control 

measure performance more quickly and 

allow for reducing the duration and the 

number of periods that may lead to 

compliance problems. Reducing the 

duration of excess emissions periods, 

for example, with improved monitoring 

is not an increase in regulatory 

stringency but a decrease in 

enforcement liability. 

The second aspect to the comment is 

questioning whether we can issue 

technical information about improved 

monitoring as guidance without 

applying it to a Federal Register notice 

and comment process. We disagree with 

commenters who believe that our 

developing and disseminating technical 

resource information is limited to notice 

and comment rulemaking. We note that 

making technical and other information 

materials available to the public, states, 

and industry is an important Agency 

function. There are many examples of 

the Agency dispensing such information 

including the Monitoring Knowledge 

Base (http://cfpub.epa.gov/mkb/) that 

provides just such information on 

improved monitoring. On the other 

hand, we agree with commenters that 

any significant change to an existing 

regulation, including the addition of 

new monitoring requirements, would be 

subject to notice and comment 

rulemaking. To the extent that States 

determine the need for changing 

existing or developing new regulations, 

public notice and comment rulemaking 

is appropriate. Our role in developing 

technical resources and information 

informing the states in developing those 

revised or new regulations does not 

require, nor should be subject to the 

rulemaking process. In that light, we 

recognize the value in obtaining and 

responding to public comments and 

suggestions on informative technical 

materials. Further, we believe 

rulemaking is not necessarily required 

for source owners or operators who 

volunteer to participate in an optional 

improved monitoring program, such as 

the one mentioned in the proposal. That 

program seeks to provide SIP credits to 

States where source owners or operators 

agree to improve their PM monitoring 

approaches. We plan on continuing to 

prepare and offer non-regulatory 

incentives for source owners and 

operators who volunteer to improve 

existing monitoring. 

3. Study of Improved MonitoringInduced Emissions Reductions 

Comment: Commenters recommended 

that the proposal’s theoretical study 

showing PM emissions reductions from 

the use of improved monitoring needs to 

be validated with field data. 

Response: We agree with commenters 

that one should base any costs and 

benefits findings as well as validating 

the approach on available data. To the 

extent that this applies to assessing the 

benefits of emissions reductions 

achieved through improved monitoring, 

we requested that commenters provide 

data or leads to other information or to 

other alternatives that show how 

improved monitoring yields emissions 

reductions and ways to quantify 

possible PM credits for SIPs. In fact, we 

are disappointed that commenters failed 

to provide these data or examples of 

other approaches. As resources allow, 

we will investigate opportunities for 

field validation of the theoretical study, 

as well as other means to offer 

incentives for use of improved 

monitoring. 

N. Guidance Specific to Tribes 

a. Background 

The proposal set forth guidance for 

Tribes regarding various aspects of air 

quality management, and this guidance 

remains largely the same as described in 

the section below. 

b. Final Rule 

The 1998 Tribal Authority Rule (TAR) 

(40 CFR part 49), which implements 

section 301(d) of the CAA, gives Tribes 

the option of developing tribal 

implementation plans (TIPs). 

Specifically, the TAR provides for the 

Tribes to be treated in the same manner 

as a State in implementing sections of 

the CAA. However, Tribes are not 

required to develop implementation 

plans. The EPA determined in the TAR 

that it was inappropriate to treat Tribes 

in a manner similar to a State with 

regard to specific plan submittal and 

implementation deadlines for NAAQSrelated requirements, including, but not 

limited to, such deadlines in CAA 

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

and 191. (Add footnote) See 40 CFR 

49.4(a). In addition, EPA determined it 

was not appropriate to treat tribes 

similarly to states with respect to 

provisions of the CAA requiring as a 

condition of program approval the 

demonstration of criminal enforcement 


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authority or providing for the delegation 

of such criminal enforcement authority. 

See 40 CFR 49.4(g). To the extent a tribe 

is precluded from asserting criminal 

enforcement authority, the Federal 

government will exercise primary 

criminal enforcement responsibility. See 

40 CFR 49.8. In such circumstances, 

tribes seeking approval for CAA 

programs provide potential investigative 

leads to an appropriate federal 

enforcement agency. (end footnote) 

If a Tribe elects to do a TIP, we will 

work with the Tribe to develop an 

appropriate schedule which meets the 

needs of the Tribe, and which does not 

interfere with the attainment of the 

NAAQS in other jurisdictions. The 

Tribe developing a TIP can work with 

the EPA Regional Office on the 

appropriateness of addressing RFP and 

other substantive SIP requirements that 

may or may not be appropriate for the 

Tribe’s situation. 

The TAR indicates that EPA is 

ultimately responsible for implementing 

CAA programs in Indian country, as 

necessary and appropriate, if Tribes 

choose not to implement those 

provisions. For example, an unhealthy 

air quality situation in Indian country 

may require EPA to develop a FIP to 

reduce emissions from sources on the 

reservation. In such a situation, EPA, in 

consultation with the Tribe and in 

consideration of their needs, would 

work to ensure that the NAAQS are met 

as expeditiously as practicable. 

Likewise, if we determine that sources 

in Indian country could interfere with a 

larger nonattainment area meeting the 

NAAQS by its attainment date, we 

would develop a FIP for those sources 

in consultation with the Tribe, as 

necessary or appropriate. 

The TAR also provides flexibility for 

the Tribe in the preparation of a TIP to 

address the NAAQS. If a Tribe elects to 

develop a TIP, the TAR offers flexibility 

to Tribes to identify and implement on 

a Tribe-by-Tribe, case-by-case basis only 

those CAA programs or program 

elements needed to address their 

specific air quality problems. In the 

proposed Tribal rule, we described this 

flexible implementation approach as a 

modular approach. Each Tribe may 

evaluate the particular activities, 

including potential sources of air 

pollution within the exterior boundaries 

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

demonstrated jurisdiction), which cause 

or contribute to its air pollution 

problem. A Tribe may adopt measures 

for controlling those sources of PM2.5- 

related emissions, as long as the 

elements of the TIP are reasonably 

severable from the package of elements 

that can be included in a whole TIP. A 

TIP must include regulations designed 

to solve specific air quality problems for 

which the Tribe is seeking EPA 

approval, as well as a demonstration 

that the Tribal air agency has the 

authority from the Tribal government to 

develop and run their program, the 

capability to enforce their rules, and the 

resources to implement the program 

they adopt. In addition, the Tribe must 

receive an eligibility determination from 

EPA to be treated in the same manner 

as a State and to receive authorization 

from EPA to run a CAA program. 

The EPA would review and approve, 

where appropriate, these partial TIPs as 

one step of an overall air quality plan to 

attain the NAAQS. A Tribe may step in 

later to add other elements to the plan, 

or EPA may step in to fill gaps in the 

air quality plan as necessary or 

appropriate. In approving a TIP, we 

would evaluate whether the plan 

interferes with the overall air quality 

plan for an area when Tribal lands are 

part of a multi-jurisdictional area. 

Because many of the nonattainment 

areas will include multiple 

jurisdictions, and in some cases both 

Tribal and State jurisdictions, it is 

important for the Tribes and the States 

to work together to coordinate their 

planning efforts. States need to 

incorporate Tribal emissions in their 

base emission inventories if Indian 

country is part of an attainment or 

nonattainment area. Tribes and States 

need to coordinate their planning 

activities as appropriate to ensure that 

neither is adversely affecting attainment 

of the NAAQS in the area as a whole. 

c. Comments and Responses 

No public comments were received on 

this section. 

O. Enforcement and Compliance 

a. Background 

The proposed rule included a 

discussion of the specific requirements 

that must be addressed in order for SIP 

regulations to be enforceable. 

b. Final Rule 

The final rule includes similar 

guidance on enforceable SIP regulations, 

with some additional discussion about 

specific elements that must be 

addressed regarding compliance testing 

and compliance monitoring. (Note that 

enforceable SIP regulations may address 

these key elements in different ways 

depending on the type of source 

category being regulated.) 

In general, for a SIP regulation to be 

enforceable, it must clearly spell out 

which sources or source types are 

subject to its requirements and what its 

requirements (e.g., emission limits, 

work practices, etc.) are. The regulation 

also needs to specify the time frames 

within which these requirements must 

be met, and must definitively state 

recordkeeping and monitoring 

requirements appropriate to the type of 

sources being regulated. The 

recordkeeping and monitoring 

requirements must be sufficient to 

enable the State or EPA to determine 

whether the source is complying with 

the emission limit on a continuous 

basis. An enforceable regulation must 

also contain test procedures in order to 

determine whether sources are in 

compliance. 

Complete and effective regulations 

that ensure compliance with an 

applicable emissions limit must include 

requirements for both performance 

testing of emissions and ongoing 

monitoring of the compliance 

performance of control measures. SIP 

regulations must include the following 

critical elements of regulatory 

compliance testing: 

• Indicator(s) of compliance—the 

pollutant or pollutants of interest (e.g., 

filterable PM2.5 plus condensable PM2.5) 

and the applicable measurable units for 

expressing compliance (e.g., ng/J of heat 

input, lb/hr); 

• Test method—reference to a 

specific EPA or other published set of 

sample collection and analytical 

procedures, equipment design and 

performance criteria, and the 

calculations providing data in units of 

the indicator of compliance (see section 

II.L. below for descriptions of available 

and potential improved test methods); 

• Averaging time—the minimum 

length of each required test run and the 

requirement to average the results of the 

test runs (e.g., three runs) representing 

a specified period of time (e.g., 8 hours); 

and 

• Frequency—the maximum time 

between conduct of emissions or 

performance tests (e.g., within 30 days 

of facility start-up and once each 

successive quarter, every 6-month 

period, yearly). 

In order to be complete with regard to 

compliance monitoring provisions, SIP 

regulations must include the following 

critical elements: 

• Indicator(s) of performance—the 

parameter or parameters measured or 

observed for demonstrating proper 

operation of the pollution control 

measures or compliance with the 

applicable emissions limitation or 

standard. Indicators of performance may 

include direct or predicted emissions 

measurements, process or control device 

(and capture system) operational 


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52See 40 CFR 70.5(c)(3)(i), 70.5(b), and 

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

71.7(a)(1)(i). 

parametric values that correspond to 

compliance with efficiency or emissions 

limits, and recorded findings of 

verification of work practice activities, 

raw material or fuels pollutant content, 

or design characteristics. Indicators may 

be expressed as a single maximum or 

minimum value, a function of process 

variables (e.g., within a range of 

pressure drops), a particular operational 

or work practice status (e.g., a damper 

position, completion of a waste recovery 

task), raw material or fuel pollutant 

content, or an interdependency between 

two or more variables; 

• Measurement technique—the 

means used to gather and record 

information of or about the indicators of 

performance. The components of the 

measurement technique include the 

detector type or analytical method, 

location and installation specifications, 

inspection procedures, and quality 

assurance and quality control measures. 

Examples of measurement approaches 

include continuous emissions 

monitoring systems, continuous opacity 

monitoring systems, continuous 

parametric monitoring systems, 

performance testing, vendor or 

laboratory analytical data, and manual 

inspections and data collection that 

include making records of process 

conditions, raw materials or fuel 

specifications, or work practices; 

• Monitoring frequency—the number 

of times to obtain and record monitoring 

data over a specified time interval. 

Examples of monitoring frequencies 

include at least one data value every 15 

minutes for continuous emissions or 

parametric monitoring systems, at least 

every 10 seconds for continuous opacity 

monitoring systems, upon receipt or 

application of raw materials or fuel to 

the process, and at least once per 

operating day (or week, month, etc.) for 

performance testing, work practice 

verification, or equipment design 

inspections; and 

• Averaging time—the period over 

which to average and use data to verify 

compliance with the emissions 

limitation or standard or proper 

operation of the pollution control 

measure. Examples of averaging time 

include a 3-hour average in units of the 

emissions limitation, a 30-day rolling 

average emissions value, a daily average 

of a control device operational 

parametric range, periodic (e.g., 

monthly, annual) average of raw 

materials or fuel pollutant content, and 

an instantaneous alarm. 

These regulatory elements are 

essential for effective implementation of 

the rules and clear and enforceable 

applicable requirements. We believe 

that approval of regulations 

implementing the SIPs must ensure that 

these critical elements are present and 

clearly defined to be approvable. We 

reiterate that the compliance 

obligations, including emissions limits 

and other applicable requirements, must 

be representative of and accountable to 

the assumptions used in the SIP 

demonstration. This accountability 

includes the ability to transfer the 

applicable regulatory requirements to an 

operating permit subject to EPA and 

public review. 

Under the Title V regulations, sources 

have an obligation to include in their 

Title V permit applications all 

emissions for which the source is major 

and all emissions of regulated air 

pollutants. The definition of regulated 

air pollutant in 40 CFR 70.2 includes 

any pollutant for which a NAAQS has 

been promulgated, which would 

include both PM10 and PM2.5. To date, 

some permitted entities have been using 

PM10 emissions as a surrogate for PM2.5

emissions. Upon promulgation of this 

rule, EPA will no longer accept the use 

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

sources will be required to include their 

PM2.5 emissions in their Title V permit 

applications, in any corrections or 

supplements to these applications, and 

in applications submitted upon 

modification and renewal.52 The degree 

of quantification of PM2.5 emissions 

required will depend on the types of 

determinations that a permitting 

authority needs to address for a 

particular source, the requirements of 

title V, and the informational needs and 

requirements of the particular State in 

question. Sources must continue to 

describe their PM10 emissions in their 

applications as indicated above because 

the original PM10 NAAQS remains in 

effect. 

c. Comments and Responses 

Comment: One commenter disagreed 

with language in the preamble to the 

proposal regarding Title V permitting 

requirements and the requirement to 

include various emissions information 

in title V permit applications. As 

described in 40 CFR 70.5(c)(3)(i) and 

71.5(c)(3)(i), sources are required to 

include in their permit applications all 

emissions for which the source is major 

and all emissions of regulated air 

pollutants. In the preamble to the 

proposal, the EPA stated that in the past 

some permitted entities have been using 

PM10 emissions as a surrogate for PM2.5

emissions in permit applications, or in 

corrections or supplements to 

applications. The EPA stated that upon 

promulgation of this rule, the EPA will 

no longer accept the use of PM10 as a 

surrogate for PM2.5. 

The commenter disagreed with 

language in the proposal stating that 

sources would be required to detail or 

quantify PM2.5 emissions in permit 

applications, or in corrections or 

supplements to applications. The 

commenter asserts that the inclusion of 

PM2.5 emissions information is required 

in a Title V permit application only if 

there is an applicable requirement in 

existence for which the source’s 

applicability is in question and cited to 

various examples from the 

memorandum entitled ‘‘White Paper for 

Streamlined Development of Part 70 

Permit Applications,’’ from Lydia N. 

Wegman, Deputy Director, Office of Air 

Quality Planning and Standards, to Air 

Division Directors, Regions I–X, dated 

July 10, 1995. 

Response: The commenter is 

concerned that as a result of this rule all 

applications (including initial, 

modification, and renewal applications) 

will need to include a quantification of 

PM2.5 emissions, and that a State will 

request that every source supplement or 

correct any existing title V application 

in order to provide an estimation of 

PM2.5 emissions at the source. 

The EPA is not implying that this is 

the case. The degree of quantification of 

PM2.5 emissions required in an 

application (including an initial, 

modification, or renewal application), or 

in a correction or supplement to an 

existing application, depends on the 

types of determinations that a 

permitting authority needs to address 

for a particular source, the requirements 

of title V, and the informational needs 

and requirements of the particular State 

in question. For example, if a source 

which emits PM2.5 emissions has 

submitted a title V application, but a 

draft permit has not yet been issued, 

then the source is required to submit 

information relative to the 

quantification of its PM2.5 emissions if 

such information is needed or requested 

and it has not previously submitted 

such information. See 40 CFR 70.5(b) 

and 71.5(b). 

Circumstances necessitating the 

quantification of PM2.5 emissions and 

the submittal of this information 

include: (1) Determining all of the 

pollutants for which a source is major; 

(2) determining whether an applicable 

requirement or program applies, e.g., 

determining the applicability of a SIP 

requirement or a PSD or nonattainment 

NSR program, etc.; or (3) determining 

what fees a source owes a permitting 


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53For background information on issues 

surrounding implementation of the PM2.5 NAAQS, 

see the EPA memo entitled ‘‘Implementation of 

New Source Review Requirements in PM2.5

Nonattainment Areas,’’ from Stephen D. Page, 

Director, Office of Air Quality Planning and 

Standards, to Regional Air Directors, Regions I–X, 

dated April 5, 2005. 

54For background information on regulated air 

pollutants, see the EPA memo entitled ‘‘Definition 

of Regulated Air Pollutant for Purposes of Title V,’’

from Lydia N. Wegman, Deputy Director, Office of 

Air Quality Planning and Standards, to Air Division 

Directors, Regions I–X, dated April 26, 1993. 

55The PM2.5 monitoring regulations are located at 

40 CFR part 58. 

authority as a result of considering 

PM2.5 emissions. 

In all circumstances, however, a State 

may require that a source quantify its 

PM2.5 emissions information in an 

application, supplement, or correction, 

even if it is not needed for the particular 

determination at issue. The State, for 

example, may choose to obtain this 

information for air quality planning 

purposes, developing emission 

inventories, or for other purposes 

related to its air quality management 

goals. Requesting such emissions 

information is an option for any title V 

permitting authority. 

The ‘‘White Paper for Streamlined 

Development of Part 70 Permit 

Applications,’’ referenced by the 

commenter, was a confirmation of EPA 

policy with respect to the fact that the 

specificity of emissions quantification 

can vary significantly, depending on the 

circumstances of a particular source. It 

is also important to note that this 

guidance document is a statement 

regarding the range of discretion 

available to permitting authorities in 

implementing the emissions 

quantification requirement, not a 

restriction of that discretion to 

minimum practices. Thus, States can 

implement this guidance document at 

their option, either in part or in its 

entirety. 

In summary, the purpose of the 

statements made in the preamble to the 

proposal was to notify sources that as of 

the promulgation of this final rule, the 

EPA will no longer accept the use of 

PM10 emissions information as a 

surrogate for PM2.5 emissions 

information 53 given that both pollutants 

are regulated by a National Ambient Air 

Quality Standard and therefore are 

considered regulated air pollutants. See 

the definition of regulated air pollutant 

in 40 CFR 70.2 and 71.2.54 The degree 

of quantification of PM2.5 emissions now 

required in an application (including an 

initial, modification, or renewal 

application), or provided in a correction 

or supplement to an existing 

application, will depend on the types of 

determinations that a permitting 

authority needs to address for a 

particular source, the requirements of 

title V, and the informational needs and 

requirements of the particular State in 

question. 

P. Emergency Episodes 

a. Background 

In the proposal, we noted that subpart 

H of 40 CFR part 51 specifies 

requirements for SIPs to address 

emergency air pollution episodes and 

for preventing air pollutant levels from 

reaching levels determined to cause 

significant harm to the health of 

persons. We noted that we anticipate 

proposing a separate rulemaking in the 

future to update portions of that rule. 

The preamble to the proposal 

b. Final Rule 

We have not yet proposed any rule 

revision related to emergency episodes. 

c. Comments and Responses 

We received no comments on this 

section of the proposal. 

Q. Ambient Monitoring 

a. Background 

Ambient air quality monitoring for 

PM2.5 plays an important role in 

identifying areas violating the NAAQS, 

control strategy development, and 

tracking progress to attainment. We 

indicated in the proposal that States are 

required to monitor PM2.5 mass 

concentrations using Federal Reference 

Method devices to determine 

compliance with the NAAQS.55 We did 

not propose any revisions to current 

ambient monitoring requirements listed 

in 40 CFR part 58. Currently, there are 

more than 1200 FRM monitors located 

across the country. States will need to 

maintain monitors in designated 

nonattainment areas in order to track 

progress toward attainment and 

ultimately determine whether the area 

has attained the PM2.5 standards. 

In addition to the FRM network, EPA 

and the States have also deployed more 

than 250 speciation monitoring sites 

around the country to sample for 

chemical composition of PM2.5. The data 

provided from these speciation monitors 

are invaluable in identifying 

contributing source categories and 

developing control strategies to reach 

attainment. Source apportionment and 

other receptor modeling techniques rely 

on the detailed data on species, ions, 

and other compounds obtained from 

chemical analysis. Analyses of rural 

versus urban sites to identify which 

PM2.5 components comprise the ‘‘urban 

excess’’ (urban minus rural levels) 

portion of PM2.5 mass also rely on data 

from speciation monitors. The EPA 

encourages states to expand their data 

analysis efforts using the wealth of 

information provided from the 

speciation monitoring network. 

b. Final Rule 

There is no change from the proposal. 

We are not promulgating any additional 

monitoring requirements as part of this 

rulemaking. Revised monitoring 

regulations were issued in 2006 along 

with the revised PM NAAQS. 

c. Comments and Responses 

There were no comments on this 

section. 

III. Statutory and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

Under section 3(f)(1) of Executive 

Order (EO) 12866 (58 FR 51735, October 

4, 1993), this action is an ‘‘economically 

significant regulatory action.’’

Implementation of the PM2.5 NAAQS is 

likely to have an annual effect on the 

economy of $100 million or more. 

Accordingly, EPA submitted this action 

to the Office of Management and Budget 

(OMB) for review under EO 12866 and 

any changes made in response to OMB 

recommendations have been 

documented in the docket for this 

action. For clarity, we note that the 

estimated costs and benefits of 

implementing the 1997 PM2.5 NAAQS 

are not created by this rule, because the 

Clean Air Act requires state 

implementation of the 1997 PM2.5

standards (through state development of 

plans with enforceable requirements for 

sources) on a statutory timetable 

regardless of whether EPA issues this 

rule interpreting the statutory 

requirements. The rule reflects the 

statutory requirements. 

As part of the ‘‘Regulatory Impact 

Analysis for Particulate Matter National 

Ambient Air Quality Standards 

(September 2006),’’ EPA prepared an 

assessment of the estimated costs and 

benefits associated with attaining the 

1997 PM2.5 NAAQS in 2015, 

incremental to currently promulgated 

federal and state programs including for 

example the Clean Air Interstate Rule, 

the Nonroad Diesel Rule, and other 

programs. This analysis is included as 

Appendix A of the report and is 

available in the docket for this action 

and on EPA’s Web site at: http:// 

www.epa.gov/ttn/ecas/regdata/RIAs/ 

Appendix%20A—

2015%20Analysis.pdf. This illustrative 


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analysis finds that the estimated 

monetized benefits of attaining the 1997 

standards in 2015 are between $43 

billion and $97 billion annually, and the 

estimated monetized costs are $6.7 

billion annually. The RIA states: ‘‘Note 

that because this analysis was intended 

to compare costs and benefits of 

attaining alternative standards by fixed 

dates, it did not attempt to identify for 

each designated PM2.5 area measures 

that may be needed to meet subpart 1 

Clean Air Act requirements, such as 

reasonably available measures and 

attainment as expeditiously as 

practicable. It is expected that 

additional costs and benefits will begin 

to accrue in earlier years as states 

comply with these requirements.’’ (RIA, 

p. 1–4) 

B. Paperwork Reduction Act 

The information collection 

requirements in this rule have been 

submitted for approval to the Office of 

Management and Budget (OMB) under 

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

3501 et seq. In a separate Federal 

Register notice published today, EPA is 

requesting comment on the information 

collection requirements of this rule. The 

information collection requirements are 

not enforceable until OMB approves 

them. 

The data collected from the State or 

local air agency respondents will 

include the required SIP elements 

prescribed in CAA sections 110 and part 

D, subpart 1 of title I for Implementation 

plans and the requirements in this 

Implementation Rule (40 CFR 51.1000–

51.1012). The PM2.5 SIP will contain 

rules and other requirements designed 

to achieve the NAAQS by the deadlines 

established under the CAA, and it also 

contains a demonstration that the State’s 

requirements will in fact result in 

attainment. The SIP must meet the 

requirements in subpart 1 to adopt 

RACM, RACT, and provide for RFP 

toward attainment for the period prior 

to the area’s attainment date. 

The Agency anticipates additional 

administrative burden during the 3 year 

period of the ICR for State governments 

and the Agency of 630,000 hours and 

69,300 hours, respectively. Fifty percent 

of the hours are expended in the first 

year with the remainder evenly divided 

between the second and third years of 

the ICR period. Tribes are not required 

to conduct attainment demonstrations 

or submit the RFP, RACT, or RACM 

requirements. 

The present value of the total 

additional costs for State government 

respondents is estimated at $33.4 

million for the 3 year period. On an 

equivalent annual basis that is $12.7 

million per year during the 3 year 

period of the ICR. The present value of 

the Agency administrative cost burden 

is estimated at $3.7 million dollars for 

the 3 year period. This is equivalent to 

an equal annual stream of costs of $1.4 

million per year during the three year 

period. Burden means the total time, 

effort, or financial resources expended 

by persons to generate, maintain, retain, 

or disclose or provide information to or 

for a Federal agency. This includes the 

time needed to review instructions; 

develop, acquire, install, and utilize 

technology and systems for the purposes 

of collecting, validating, and verifying 

information, processing and 

maintaining information, and disclosing 

and providing information; adjust the 

existing ways to comply with any 

previously applicable instructions and 

requirements; train personnel to be able 

to respond to a collection of 

information; search data sources; 

complete and review the collection of 

information; and transmit or otherwise 

disclose the information. 

An agency may not conduct or 

sponsor, and a person is not required to 

respond to a collection of information 

unless it displays a currently valid OMB 

control number. The OMB control 

numbers for EPA’s regulations in 40 

CFR are listed in 40 CFR part 9. 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 final action on small entities, 

small entity is defined as: (1) A small 

business as defined by the Small 

Business Administration’s (SBA) 

regulations at 13 CFR 121.201; (2) a 

small governmental jurisdiction that is a 

government of a city, county, town, 

school district, or special district with a 

population of less than 50,000; or (3) a 

small organization that is any not-forprofit enterprise that 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 

and it is not necessary to prepare a 

regulatory flexibility analysis in 

conjunction with this final rule. The 

final rule governing SIPs will not 

directly impose any requirements on 

small entities. Rather, this rule 

interprets the obligations established in 

the CAA for States to submit 

implementation plans in order to attain 

the PM2.5 NAAQS. 

D. Unfunded Mandates Reform Act 

Title II of the Unfunded Mandates 

Reform Act of 1995 (UMRA), Public 

Law 104–4, establishes requirements for 

Federal agencies to assess the effects of 

their regulatory actions on State, local, 

and Tribal governments and the private 

sector. Under section 202 of the UMRA, 

EPA generally must prepare a written 

statement, including a cost-benefit 

analysis, for proposed and final rules 

with ‘‘Federal mandates’’ that may 

result in expenditures to State, local, 

and tribal governments, in the aggregate, 

or to the private sector, of $100 million 

or more in any 1 year. Before 

promulgating an EPA rule for which a 

written statement is needed, EPA is 

required by section 205 of the UMRA to 

identify and consider a reasonable 

number of regulatory alternatives, and 

adopt the least costly, most costeffective or least burdensome alternative 

that achieves the objectives of the rule. 

The provisions of section 205 do not 

apply when they are inconsistent with 

applicable law. Moreover, section 205 

allows EPA to adopt an alternative other 

than the least costly, most cost-effective 

or least burdensome alternative if the 

Administrator publishes with the final 

rule an explanation why that alternative 

was not adopted. Before EPA establishes 

any regulatory requirements that may 

significantly or uniquely affect small 

governments, including Tribal 

governments, it must have developed 

under section 203 of the UMRA a small 

government agency plan. The plan must 

provide for notifying potentially 

affected small governments, enabling 

officials of affected small governments 

to have meaningful and timely input in 

the development of EPA regulatory 

proposals with significant Federal 

intergovernmental mandates, and 

informing, educating, and advising 

small governments on compliance with 

the regulatory requirements. 

This rule contains no Federal 

mandate that may result in expenditures 


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20662 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

of $100 million or more for State, local, 

and Tribal governments, in the 

aggregate, or the private sector in any 1 

year. The estimated administrative 

burden hours and costs associated with 

implementing the PM2.5 NAAQS are 

estimated in the ICR for this rule. The 

estimated costs presented there for 

States totals $33.4 million for a threeyear period. Thus, this rule is not 

subject to the requirements of section 

202 and 205 of the UMRA. The EPA 

consulted with governmental entities 

affected by this rule and has determined 

that this rule contains no regulatory 

requirements that may significantly or 

uniquely affect small governments, 

including Tribal governments. 

The CAA imposes the obligation for 

States to submit SIPs to implement the 

PM2.5 NAAQS. In this rule, EPA is 

merely providing an interpretation of 

those requirements. However, even if 

this rule did establish an independent 

requirement for States to submit SIPs, it 

is questionable whether a requirement 

to submit a SIP revision would 

constitute a Federal mandate in any 

case. The obligation for a State to submit 

a SIP that arises out of section 110 and 

section 172 (part D) of the CAA is not 

legally enforceable by a court of law, 

and at most is a condition for continued 

receipt of highway funds. Therefore, it 

is possible to view an action requiring 

such a submittal as not creating any 

enforceable duty within the meaning of 

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

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

be viewed as falling within the 

exception for a condition of Federal 

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

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

E. Executive Order 13132: Federalism 

Executive Order 13132, entitled 

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

1999), requires EPA to develop an 

accountable process to ensure 

‘‘meaningful and timely input by State 

and local officials in the development of 

regulatory policies that have Federalism 

implications.’’ ‘‘Policies that have 

Federalism implications’’ is defined in 

the Executive Order to include 

regulations that have ‘‘substantial direct 

effects on the States, on the relationship 

between the national government and 

the States, or on the distribution of 

power and responsibilities among the 

various levels of government.’’

At the time of proposal, EPA 

concluded that the proposed rule would 

not have any federalism implications. 

The EPA stated that the proposed rule 

would 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 

CAA establishes the scheme whereby 

States take the lead in developing plans 

to meet the NAAQS. This rule clarifies 

the statutory obligations of States in 

implementing the PM2.5 NAAQS. 

However, EPA recognized that States 

would have a substantial interest in this 

rule and any corresponding revisions to 

associated SIP requirements. 

Therefore, in the spirit of Executive 

Order 13132, and consistent with EPA 

policy to promote communications 

between EPA and State and local 

governments, EPA held a number of 

calls with representatives of State and 

local air pollution control agencies and 

hosted a public hearing in Washington, 

DC in November 2005. The EPA 

considered the comments from State 

and local governments in developing 

the final rule. 

EPA concludes that this final rule 

does not have federalism implications, 

for the reasons proposed. The final rule 

will not modify the relationship of the 

States and EPA for purposes of 

developing programs to implement the 

NAAQS. As noted above in section D on 

UMRA, this rule does not impose 

significant costs on State and local 

governments. (EPA estimates the costs 

to States to implement the PM2.5

NAAQS to be $33.4 million.) Thus, 

Executive Order 13132 does not apply 

to this rule. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

Executive Order 13175, entitled 

‘‘Consultation and Coordination with 

Indian Tribal Governments’’ (65 FR 

67249, November 9, 2000), requires EPA 

to develop an accountable process to 

ensure ‘‘meaningful and timely input by 

Tribal officials in the development of 

regulatory policies that have Tribal 

implications.’’ This final rule does not 

have ‘‘Tribal implications’’ as defined in 

Executive Order 13175. This rule 

concerns the requirements for State and 

tribal implementation plans for 

attaining the PM2.5 air quality standards. 

The CAA provides for States to develop 

plans to regulate emissions of air 

pollutants within their jurisdictions. 

The Tribal Air Rule (TAR) under the 

CAA gives Tribes the opportunity to 

develop and implement CAA programs 

such as programs to attain and maintain 

the PM2.5 NAAQS, but it leaves to the 

discretion of the Tribe the decision of 

whether to develop these programs and 

which programs, or appropriate 

elements of a program, they will adopt. 

Although Executive Order 13175 does 

not apply to this rule, EPA did reach out 

to Tribal leaders and environmental 

staff in developing this rule. From 

2001–2004, the EPA supported a 

National Designations Workgroup to 

provide a forum for tribal professionals 

to give input to the designations 

process. In 2006, EPA supported a 

national ‘‘Tribal Air call’’ which 

provides an open forum for all Tribes to 

voice concerns to EPA about the 

NAAQS implementation process, 

including the PM2.5 NAAQS. In these 

meetings, EPA briefed call participants 

and Tribal environmental professionals 

gave input as the rule was under 

development. Furthermore, in December 

2005, EPA sent individualized letters to 

all federally recognized Tribes about the 

proposal to give Tribal leaders the 

opportunity for consultation. 

This final rule does not have Tribal 

implications as defined by Executive 

Order 13175. It does not have a 

substantial direct effect on one or more 

Indian Tribes, since no Tribe has 

implemented a CAA program to attain 

the PM2.5 NAAQS at this time. The EPA 

notes that even if a Tribe were 

implementing such a plan at this time, 

while the rule might have Tribal 

implications with respect to that Tribe, 

it would not impose substantial direct 

costs upon it, nor would it preempt 

Tribal law. 

Furthermore, this rule does not affect 

the relationship or distribution of power 

and responsibilities between the Federal 

government and Indian Tribes. The 

CAA and the TAR establish the 

relationship of the Federal government 

and Tribes in developing plans to attain 

the NAAQS, and this rule does nothing 

to modify that relationship. As this rule 

does not have Tribal implications, 

Executive Order 13175 does not apply. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

EO 13045, ‘‘Protection of Children 

from Environmental Health and Safety 

Risks,’’ (62 FR 19885, April 23, 1997) 

applies to any rule that (1) Is 

determined to be ‘‘economically 

significant’’ as defined under Executive 

Order 12866, and (2) concerns an 

environmental health or safety risk that 

EPA has reason to believe may have 

disproportionate effect on children. If 

the regulatory action meets both criteria, 

the Agency must evaluate the 

environmental health or safety effects of 

the planned rule on children, and 

explain why the planned regulation is 

preferable to other potentially effective 

and reasonably feasible alternatives 

considered by the Agency. This final 


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Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 20663 

56See 62 FR 38652–38760, National Ambient Air 

Quality Standards for Particulate Matter, Final Rule; 

also 40 CFR part 50. 

rule is subject to EO 13045 because it is 

economically significant as defined in 

EO 12866, and we believe that the 

environmental health risk addressed by 

this action may have a disproportionate 

effect on children. This rule implements 

a previously promulgated health-based 

Federal standard—the PM2.5 NAAQS 56. 

The NAAQS constitute uniform, 

national standards for PM pollution; 

these standards are designed to protect 

public health with an adequate margin 

of safety, as required by CAA section 

109. However, the protection offered by 

these standards may be especially 

important for children because children, 

along with other sensitive population 

subgroups such as the elderly and 

people with existing heart or lung 

disease, are potentially susceptible to 

health effects resulting from PM 

exposure. Because children are 

considered a potentially susceptible 

population, we have carefully evaluated 

the environmental health effects of 

exposure to PM pollution among 

children. These effects and the size of 

the population affected are summarized 

in section 9.2.4 of the Criteria Document 

and section 3.5 of the Staff Paper. 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This final rule is not a ‘‘significant 

energy action’’ as defined in Executive 

Order 13211, ‘‘Actions That 

Significantly Affect Energy Supply, 

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

May 22, 2001) because it is not likely to 

have a significant adverse effect on the 

supply, distribution, or use of energy. 

This rule is not a ‘‘significant energy 

action,’’ because it does not establish 

requirements that directly affect the 

general public and the public and 

private sectors, but, rather, interprets 

the statutory requirements that apply to 

States in preparing their SIPs. The SIPs 

themselves will likely establish 

requirements that directly affect the 

general public, and the public and 

private sectors. 

I. National Technology Transfer 

Advancement Act 

Section 12(d) of the National 

Technology Transfer Advancement Act 

of 1995 (‘‘NTTAA’’), Public Law No. 

104–113, section 12(d) (15 U.S.C. 272 

note) directs EPA to use voluntary 

consensus standards (VCS) in its 

regulatory activities unless to do so 

would be inconsistent with applicable 

law or otherwise impractical. Voluntary 

consensus standards are technical 

standards (e.g., materials specifications, 

test methods, sampling procedures, and 

business practices) that are developed or 

adopted by VCS bodies. The NTTAA 

directs EPA to provide Congress, 

through OMB, explanations when the 

Agency decides not to use available and 

applicable VCS. 

This final rulemaking does not 

involve technical standards. Therefore, 

EPA is not considering the use of any 

VCS. The EPA will encourage the States 

and Tribes to consider the use of such 

standards, where appropriate, in the 

development of their implementation 

plans. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

EO 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, 

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 the final 

rule should not have disproportionately 

high and adverse human health or 

environmental effects on minority or 

low-income populations because it 

increases the level of environmental 

protection for all affected populations 

without having any disproportionately 

high and adverse human health or 

environmental effects on any 

population, including any minority or 

low-income population. The health and 

environmental risks associated with fine 

particles were considered in the 

establishment of the PM2.5 NAAQS. The 

level is designed to be protective with 

an adequate margin of safety. This final 

rule provides a framework for 

improving environmental quality and 

reducing health risks for areas that may 

be designated nonattainment. 

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 the 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 a ‘‘major 

rule’’ as defined by 5 U.S.C. 804(2). This 

rule will be effective June 25, 2007. 

L. Petitions for 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 June 25, 2007. 

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. This action may not 

be challenged later in proceedings to 

enforce its requirements. See Act 

section 307(b)(2). 

M. Judicial Review 

Under sections 307(d)(1)(E) and 

307(d)(1)(V) of the CAA, the 

Administrator determines that this 

action is subject to the provisions of 

section 307(d). Section 307(d)(1)(V) 

provides that the provisions of section 

307(d) apply to ‘‘such other actions as 

the Administrator may determine.’’

While the Administrator did not make 

this determination earlier, the 

Administrator believes that all of the 

procedural requirements, e.g., 

docketing, hearing and comment 

periods, of section 307(d) have been 

complied with during the course of this 

rulemaking. 

IV. Statutory Authority 

The statutory authority for this action 

is provided by 42 U.S.C. 7401, 7408, 

7410, 7501–7509a, and 7601(a)(1). This 

notice is also subject to 307(d) of the 

CAA (42 U.S.C. 7407(d)). 

List of Subjects in 40 CFR Part 51 

Administrative practice and 

procedure, Air pollution control, 

Intergovernmental relations, Nitrogen 

dioxide, Ozone, Particulate matter, 

Sulfur oxides, Transportation, Volatile 

organic compound. 

Dated: March 29, 2007. 

Stephen L. Johnson, 

Administrator. 

■ For the reasons set out in the 

preamble, title 40, chapter I of the Code 


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20664 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

of Federal Regulations is amended as 

follows: 

■ 1. The authority citation for part 51 

continues to read as follows: 

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

7671q. 

■ 2. A new Subpart Z is added to read 

as follows: 

Subpart Z—Provisions for 

Implementation of PM2.5 National 

Ambient Air Quality Standards 

Sec. 

51.1000 Definitions. 

51.1001 Applicability of part 51. 

51.1002 Submittal of State implementation 

plan. 

51.1003 [Reserved] 

51.1004 Attainment dates. 

51.1005 One-year extensions of the 

attainment date. 

51.1006 Redesignation to nonattainment 

following initial designations for the 

PM2.5 NAAQS. 

51.1007 Attainment demonstration and 

modeling requirements. 

51.1008 Emission inventory requirements 

for the PM2.5 NAAQS. 

51.1009 Reasonable further progress (RFP) 

requirements. 

51.1010 Requirements for reasonably 

available control technology (RACT) and 

reasonably available control measures 

(RACM). 

51.1011 Requirements for mid-course 

review. 

51.1012. Requirements for contingency 

measures. 

§ 51.1000 Definitions. 

The following definitions apply for 

purposes of this subpart. Any term not 

defined herein shall have the meaning 

as defined in 40 CFR 51.100. 

Act means the Clean Air Act as 

codified at 42 U.S.C. 7401–7671q. 

(2003). 

Attainment date means the date by 

which an area, under an approved State 

implementation plan, is required to 

attain the PM2.5 NAAQS (based on the 

average of three consecutive years of 

ambient air quality data). 

Baseline year inventory for the RFP 

plan is the emissions inventory for the 

year also used as the base year for the 

attainment demonstration. 

Benchmark RFP plan means the 

reasonable further progress plan that 

requires generally linear emission 

reductions in pollutants from the 

baseline emissions year through the 

milestone inventory year. 

Date of designation means the 

effective date of the PM2.5 area 

designation as promulgated by the 

Administrator. 

Direct PM2.5 emissions means solid 

particles emitted directly from an air 

emissions source or activity, or gaseous 

emissions or liquid droplets from an air 

emissions source or activity which 

condense to form particulate matter at 

ambient temperatures. Direct PM2.5

emissions include elemental carbon, 

directly emitted organic carbon, directly 

emitted sulfate, directly emitted nitrate, 

and other inorganic particles (including 

but not limited to crustal material, 

metals, and sea salt). 

Existing control measure means any 

Federally enforceable national, State, or 

local control measure that has been 

approved in the SIP and that results in 

reductions in emissions of PM2.5 or 

PM2.5 precursors in a nonattainment 

area. 

Full implementation inventory is the 

projected RFP emission inventory for 

the year preceding the attainment date, 

representing a level of emissions that 

demonstrates attainment. 

Milestone year inventory is the 

projected RFP emission inventory for 

the applicable RFP milestone year (i.e. 

2009 and, where applicable, 2012). 

PM2.5 NAAQS means the particulate 

matter national ambient air quality 

standards (annual and 24-hour) codified 

at 40 CFR 50.7. 

PM2.5 design value for a 

nonattainment area is the highest of the 

three-year average concentrations 

calculated for the monitors in the area, 

in accordance with 40 CFR part 50, 

appendix N. 

PM2.5 attainment plan precursor 

means S02 and those other PM2.5

precursors emitted by sources in the 

State which the State must evaluate for 

emission reduction measures to be 

included in its PM2.5 nonattainment area 

or maintenance area plan. 

PM2.5 precursor means those air 

pollutants other than PM2.5 direct 

emissions that contribute to the 

formation of PM2.5. PM2.5 precursors 

include S02, NOX, volatile organic 

compounds, and ammonia. 

Reasonable further progress (RFP) 

means the incremental emissions 

reductions toward attainment required 

under sections 172(c)(2) and 171(1). 

Subpart 1 means the general 

attainment plan requirements found in 

subpart 1 of part D of title I of the Act. 

§ 51.1001 Applicability of part 51. 

The provisions in subparts A through 

X of this part apply to areas for purposes 

of the PM2.5 NAAQS to the extent they 

are not inconsistent with the provisions 

of this subpart. 

§ 51.1002 Submittal of State 

implementation plan. 

(a) For any area designated by EPA as 

nonattainment for the PM2.5 NAAQS, 

the State must submit a State 

implementation plan satisfying the 

requirements of section 172 of the Act 

and this subpart to EPA by the date 

prescribed by EPA which will be no 

later than 3 years from the date of 

designation. 

(b) The State must submit a plan 

consistent with the requirements of 

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

State already has fulfilled this obligation 

for the purposes of implementing the 

PM2.5 NAAQS. 

(c) Pollutants contributing to fine 

particle concentrations. The State 

implementation plan must identify and 

evaluate sources of PM2.5 direct 

emissions and PM2.5 attainment plan 

precursors in accordance with 

§§ 51.1009 and 51.1010. After January 1, 

2011, for purposes of establishing 

emissions limits under 51.1009 and 

51.1010, States must establish such 

limits taking into consideration the 

condensable fraction of direct PM2.5

emissions. Prior to this date, States are 

not prohibited from establishing source 

emission limits that include the 

condensable fraction of direct PM2.5. 

(1) The State must address sulfur 

dioxide as a PM2.5 attainment plan 

precursor and evaluate sources of SO2

emissions in the State for control 

measures. 

(2) The State must address NOX as a 

PM2.5 attainment plan precursor and 

evaluate sources of NOX emissions in 

the State for control measures, unless 

the State and EPA provide an 

appropriate technical demonstration for 

a specific area showing that NOX

emissions from sources in the State do 

not significantly contribute to PM2.5

concentrations in the nonattainment 

area. 

(3) The State is not required to 

address VOC as a PM2.5 attainment plan 

precursor and evaluate sources of VOC 

emissions in the State for control 

measures, unless: 

(i) the State provides an appropriate 

technical demonstration for a specific 

area showing that VOC emissions from 

sources in the State significantly 

contribute to PM2.5 concentrations in the 

nonattainment area, and such 

demonstration is approved by EPA; or 

(ii) The EPA provides such a technical 

demonstration. 

(4) The State is not required to 

address ammonia as a PM2.5 attainment 

plan precursor and evaluate sources of 

ammonia emissions from sources in the 

State for control measures, unless: 

(i) The State provides an appropriate 

technical demonstration for a specific 

area showing that ammonia emissions 

from sources in the State significantly 

contribute to PM2.5 concentrations in the 


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Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 20665 

nonattainment area, and such 

demonstration is approved by EPA; or 

(ii) The EPA provides such a technical 

demonstration. 

(5) The State must submit a 

demonstration to reverse any 

presumption in this rule for a PM2.5

precursor with respect to a particular 

nonattainment area, if the 

administrative record related to 

development of its SIP shows that the 

presumption is not technically justified 

for that area. 

§ 51.1003 [Reserved] 

§ 51.1004 Attainment dates. 

(a) Consistent with section 

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

date for an area designated 

nonattainment for the PM2.5 NAAQS 

will be the date by which attainment 

can be achieved as expeditiously as 

practicable, but no more than five years 

from the date of designation. The 

Administrator may extend the 

attainment date to the extent the 

Administrator determines appropriate, 

for a period no greater than 10 years 

from the date of designation, 

considering the severity of 

nonattainment and the availability and 

feasibility of pollution control measures. 

(b) In the SIP submittal for each of its 

nonattainment areas, the State must 

submit an attainment demonstration 

justifying its proposed attainment date. 

For each nonattainment area, the 

Administrator will approve an 

attainment date at the same time the 

Administrator approves the attainment 

demonstration for the area, consistent 

with the attainment date timing 

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

paragraph (a) of this section. 

(c) Upon a determination by EPA that 

an area designated nonattainment for 

the PM2.5 NAAQS has attained the 

standard, the requirements for such area 

to submit attainment demonstrations 

and associated reasonably available 

control measures, reasonable further 

progress plans, contingency measures, 

and other planning SIPs related to 

attainment of the PM2.5 NAAQS shall be 

suspended until such time as: the area 

is redesignated to attainment, at which 

time the requirements no longer apply; 

or EPA determines that the area has 

violated the PM2.5 NAAQS, at which 

time the area is again required to submit 

such plans. 

§ 51.1005 One-year extensions of the 

attainment date. 

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

of the Act, a State with an area that fails 

to attain the PM2.5 NAAQS by its 

attainment date may apply for an initial 

1-year attainment date extension if the 

State has complied with all 

requirements and commitments 

pertaining to the area in the applicable 

implementation plan, and: 

(1) For an area that violates the annual 

PM2.5 NAAQS as of its attainment date, 

the annual average concentration for the 

most recent year at each monitor is 15.0 

μg/m3 or less (calculated according to 

the data analysis requirements in 40 

CFR part 50, appendix N). 

(2) For an area that violates the 24- 

hour PM2.5 NAAQS as of its attainment 

date, the 98th percentile concentration 

for the most recent year at each monitor 

is 65 μg/m3 or less (calculated according 

to the data analysis requirements in 40 

CFR part 50, appendix N). 

(b) An area that fails to attain the 

PM2.5 NAAQS after receiving a 1-year 

attainment date extension may apply for 

a second 1-year attainment date 

extension pursuant to section 

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

with all requirements and commitments 

pertaining to the area in the applicable 

implementation plan, and: 

(1) For an area that violates the annual 

PM2.5 NAAQS as of its attainment date, 

the two-year average of annual average 

concentrations at each monitor, based 

on the first extension year and the 

previous year, is 15.0 μg/m3 or less 

(calculated according to the data 

analysis requirements in 40 CFR part 50, 

appendix N). 

(2) For an area that violates the 24- 

hour PM2.5 NAAQS as of its attainment 

date, the two-year average of annual 

98th percentile concentrations at each 

monitor, based on the first extension 

year and the previous year, is 65 μg/m3

or less (calculated according to the data 

analysis requirements in 40 CFR part 50, 

appendix N). 

§ 51.1006 Redesignation to nonattainment 

following initial designations for the PM2.5

NAAQS. 

Any area that is initially designated 

‘‘attainment/unclassifiable’’ for the 

PM2.5 NAAQS may be subsequently 

redesignated to nonattainment if 

ambient air quality data in future years 

indicate that such a redesignation is 

appropriate. For any such area that is 

redesignated to nonattainment for the 

PM2.5 NAAQS, any absolute, fixed date 

that is applicable in connection with the 

requirements of this part is extended by 

a period of time equal to the length of 

time between the effective date of the 

initial designation for the PM2.5 NAAQS 

and the effective date of redesignation, 

except as otherwise provided in this 

subpart. 

§ 51.1007 Attainment demonstration and 

modeling requirements. 

(a) For any area designated as 

nonattainment for the PM2.5 NAAQS, 

the State must submit an attainment 

demonstration showing that the area 

will attain the annual and 24-hour 

standards as expeditiously as 

practicable. The demonstration must 

meet the requirements of § 51.112 and 

Appendix W of this part and must 

include inventory data, modeling 

results, and emission reduction analyses 

on which the State has based its 

projected attainment date. The 

attainment date justified by the 

demonstration must be consistent with 

the requirements of § 51.1004(a). The 

modeled strategies must be consistent 

with requirements in § 51.1009 for RFP 

and in § 51.1010 for RACT and RACM. 

The attainment demonstration and 

supporting air quality modeling should 

be consistent with EPA’s PM2.5

modeling guidance. 

(b) Required time frame for obtaining 

emissions reductions. For each 

nonattainment area, the State 

implementation plan must provide for 

implementation of all control measures 

needed for attainment as expeditiously 

as practicable, but no later than the 

beginning of the year prior to the 

attainment date. Consistent with section 

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

provide for implementation of all RACM 

and RACT as expeditiously as 

practicable. The plan also must include 

RFP milestones in accordance with 

§ 51.1009, and control measures needed 

to meet these milestones, as necessary. 

§ 51.1008 Emission inventory 

requirements for the PM2.5 NAAQS. 

(a) For purposes of meeting the 

emission inventory requirements of 

section 172(c)(3) of the Act for 

nonattainment areas, the State shall, no 

later than three years after designation: 

(1) Submit to EPA Statewide emission 

inventories for direct PM2.5 emissions 

and emissions of PM2.5 precursors. For 

purposes of defining the data elements 

for these inventories, the PM2.5 and 

PM2.5 precursor-relevant data element 

requirements under subpart A of this 

part shall apply. 

(2) Submit any additional emission 

inventory information needed to 

support an attainment demonstration 

and RFP plan ensuring expeditious 

attainment of the annual and 24-hour 

PM2.5 standards. 

(b) For inventories required for 

submission under paragraph (a) of this 

section, a baseline emission inventory is 

required for the attainment 

demonstration required under § 51.1007 

and for meeting RFP requirements 


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20666 Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 

under § 51.1009. As determined on the 

date of designation, the base year for 

this inventory shall be the most recent 

calendar year for which a complete 

inventory was required to be submitted 

to EPA pursuant to subpart A of this 

part. The baseline emission inventory 

for calendar year 2002 or other suitable 

year shall be used for attainment 

planning and RFP plans for areas 

initially designated nonattainment for 

the PM2.5 NAAQS in 2004–2005. 

§ 51.1009 Reasonable further progress 

(RFP) requirements. 

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

of the Act, State implementation plans 

for areas designated nonattainment for 

the PM2.5 NAAQS must demonstrate 

reasonable further progress as provided 

in § 51.1009(b) through (h). 

(b) If the State submits to EPA an 

attainment demonstration and State 

implementation plan for an area which 

demonstrates that it will attain the PM 

NAAQS within five years of the date of 

designation, the State is not required to 

submit a separate RFP plan. Compliance 

with the emission reduction measures 

in the attainment demonstration and 

State implementation plan will meet the 

requirements for achieving reasonable 

further progress for the area. 

(c) For any area for which the State 

submits to EPA an approvable 

attainment demonstration and State 

implementation plan that demonstrates 

the area needs an attainment date of 

more than five years from the date of 

designation, the State also must submit 

an RFP plan. The RFP plan must 

describe the control measures that 

provide for meeting the reasonable 

further progress milestones for the area, 

the timing of implementation of those 

measures, and the expected reductions 

in emissions of direct PM2.5 and PM2.5

attainment plan precursors. The RFP 

plan is due to EPA within three years of 

the date of designation. 

(1) For any State that submits to EPA 

an approvable attainment demonstration 

and State implementation plan 

justifying an attainment date of more 

than five and less than nine years from 

the date of designation, the RFP plan 

must include 2009 emissions milestones 

for direct PM2.5 and PM2.5 attainment 

plan precursors demonstrating that 

reasonable further progress will be 

achieved for the 2009 emissions year. 

(2) For any area that submits to EPA 

an approvable attainment demonstration 

and State implementation plan 

justifying an attainment date of nine or 

ten years from the date of designation, 

the RFP plan must include 2009 and 

2012 emissions milestones for direct 

PM2.5 and PM2.5 attainment plan 

precursors demonstrating that 

reasonable further progress will be 

achieved for the 2009 and 2012 

emissions years. 

(d) The RFP plan must demonstrate 

that in each applicable milestone year, 

emissions will be at a level consistent 

with generally linear progress in 

reducing emissions between the base 

year and the attainment year. 

(e) For a multi-State nonattainment 

area, the RFP plans for each State 

represented in the nonattainment area 

must demonstrate RFP on the basis of 

common multi-State inventories. The 

States within which the area is located 

must provide a coordinated RFP plan. 

Each State in a multi-State 

nonattainment area must ensure that the 

sources within its boundaries comply 

with enforceable emission levels and 

other requirements that in combination 

with the reductions planned in other 

state(s) will provide for attainment as 

expeditiously as practicable and 

demonstrate reasonable further progress. 

(f) In the benchmark RFP plan, the 

State must identify direct PM2.5

emissions and PM2.5 attainment plan 

precursors regulated under the PM2.5

attainment plan and specify target 

emission reduction levels to be achieved 

during the milestone years. In 

developing the benchmark RFP plan, 

the State must develop emission 

inventory information for the 

geographic area included in the plan 

and conduct the following calculations: 

(1) For direct PM2.5 emissions and 

each PM2.5 attainment plan precursor 

addressed in the attainment strategy, the 

full implementation reduction is 

calculated by subtracting the full 

implementation inventory from the 

baseline year inventory. 

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

the ratio of the number of years from the 

baseline year to the milestone inventory 

year divided by the number of years 

from the baseline year to the full 

implementation year. 

(3) For direct PM2.5 emissions and 

each PM2.5 attainment plan precursor 

addressed in the attainment strategy, a 

benchmark emission reduction is 

calculated by multiplying the full 

implementation reduction by the 

milestone date fraction. 

(4) The benchmark emission level in 

the milestone year is calculated for 

direct PM2.5 emissions and each PM2.5

attainment plan precursor by 

subtracting the benchmark emission 

reduction from the baseline year 

emission level. The benchmark RFP 

plan is defined as a plan that achieves 

benchmark emission levels for direct 

PM2.5 emissions and each PM2.5

attainment plan precursor addressed in 

the attainment strategy for the area. 

(5) In comparing inventories between 

baseline and future years for direct 

PM2.5 emissions and each PM2.5

attainment plan precursor, the 

inventories must be derived from the 

same geographic area. The plan must 

include emissions estimates for all types 

of emitting sources and activities in the 

geographic area from which the 

emission inventories for direct PM2.5

emissions and each PM2.5 attainment 

plan precursor addressed in the plan are 

derived. 

(6) For purposes of establishing motor 

vehicle emissions budgets for 

transportation conformity purposes (as 

required in 40 CFR part 93) for a PM2.5

nonattainment area, the State shall 

include in its RFP submittal an 

inventory of on-road mobile source 

emissions in the nonattainment area. 

(g) The RFP plan due three years after 

designation must demonstrate that 

emissions for the milestone year are 

either: 

(1) At levels that are roughly 

equivalent to the benchmark emission 

levels for direct PM2.5 emissions and 

each PM2.5 attainment plan precursor to 

be addressed in the plan; or 

(2) At levels included in an 

alternative scenario that is projected to 

result in a generally equivalent 

improvement in air quality by the 

milestone year as would be achieved 

under the benchmark RFP plan. 

(h) The equivalence of an alternative 

scenario to the corresponding 

benchmark plan must be determined by 

comparing the expected air quality 

changes of the two scenarios at the 

design value monitor location. This 

comparison must use the information 

developed for the attainment plan to 

assess the relationship between 

emissions reductions of the direct PM2.5

emissions and each PM2.5 attainment 

plan precursor addressed in the 

attainment strategy and the ambient air 

quality improvement for the associated 

ambient species. 

§ 51.1010 Requirements for reasonably 

available control technology (RACT) and 

reasonably available control measures 

(RACM). 

(a) For each PM2.5 nonattainment area, 

the State shall submit with the 

attainment demonstration a SIP revision 

demonstrating that it has adopted all 

reasonably available control measures 

(including RACT for stationary sources) 

necessary to demonstrate attainment as 

expeditiously as practicable and to meet 

any RFP requirements. The SIP revision 

shall contain the list of the potential 

measures considered by the State, and 


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Federal Register / Vol. 72, No. 79 / Wednesday, April 25, 2007 / Rules and Regulations 20667 

information and analysis sufficient to 

support the State’s judgment that it has 

adopted all RACM, including RACT. 

(b) In determining whether a 

particular emission reduction measure 

or set of measures must be adopted as 

RACM under section 172(c)(1) of the 

Act, the State must consider the 

cumulative impact of implementing the 

available measures. Potential measures 

that are reasonably available 

considering technical and economic 

feasibility must be adopted as RACM if, 

considered collectively, they would 

advance the attainment date by one year 

or more. 

§ 51.1011 Requirements for mid-course 

review. 

(a) Any State that submits to EPA an 

approvable attainment plan for a PM2.5

nonattainment area justifying an 

attainment date of nine or ten years 

from the date of designation also must 

submit to EPA a mid-course review six 

years from the date of designation. 

(b) The mid-course review for an area 

must include: 

(1) A review of emissions reductions 

and progress made in implementing 

control measures to reduce emissions of 

direct PM2.5 and PM2.5 attainment plan 

precursors contributing to PM2.5

concentrations in the area; 

(2) An analysis of changes in ambient 

air quality data for the area; 

(3) Revised air quality modeling 

analysis to demonstrate attainment; 

(4) Any new or revised control 

measures adopted by the State, as 

necessary to ensure attainment by the 

attainment date in the approved SIP of 

the nonattainment area. 

§ 51.1012 Requirement for contingency 

measures. 

Consistent with section 172(c)(9) of 

the Act, the State must submit in each 

attainment plan specific contingency 

measures to be undertaken if the area 

fails to make reasonable further 

progress, or fails to attain the PM2.5

NAAQS by its attainment date. The 

contingency measures must take effect 

without significant further action by the 

State or EPA. 

[FR Doc. E7–6347 Filed 4–24–07; 8:45 am] 

BILLING CODE 6560–50–P 


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