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OAR Box 1787 

Prepped by Ollie Stewart 

Document Number: 

15) ll-A-15 

Docket Number: 

A-90-37 

Printed 11/4/2008 10:22:18 AM Sheet 15 of 147 
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GUIDELINE FOR DETERMINING THE APPLICABILITY 

OF NITROGEN OXIDES REQUIREMENTS UNDER SECTION 182(0 

December 1993 

U.S. Environmental Protection Agency 

Office of Air Quality Planning and Standards 

Air Quality Management Division 

Research Triangle Park, NC 27711 
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GUIDELINE FOR DETERMINING THE APPLICABILITY 

OF NITROGEN OXIDES REQUIREMENTS UNDER SECTION 182(f) 

CONTENTS 

CHAPTERS 

INTRODUCTION 

1.1 General 

1.2 Nitrogen Oxides Supplement to the General Preamble for 

Implementation of Title I of the Clean Air Act 

1.3 Section 185B Report 

1.4 Application of Section 182(f) Requirements 

ADMINISTRATIVE PROCEDURES 

2.1 Processing with the State Implementation Plan (SIP) 

Revision 

2.2 Petition 

NET AIR QUALITY BENEFIT 

3.1 Demonstration 

3.2 Factors 

3.3 Geographic Scope 

3.4 Scenarios 

3.5 Sources 

CONTRIBUTE TO ATTAINMENT 

4.1 Demonstration 

4.2 Episodes to Consider 

4.3 Geographic Scope 

4.4 Applicability to Areas Requesting Redesignation to 

Attainment 

NET OZONE AIR QUALITY BENEFIT 

5.1 Demonstration 

5.2 Factors 

5.3 Attainment/Unclassified Portions 

EXCESS EMISSIONS REDUCTIONS 

6.1 General 

6.2 Demonstration 

MODELING TECHNIQUES 

7.1 Photochemical Grid Modeling 

7.2 Urban Airshed Model 

7.3 Regional Scale Modeling 

7.4 Model Results and SIP Interface 

7.5 Other Analytical Techniques 

EMISSIONS ANALYSIS 

8.1 General 

8.2 Biogenic Volatile Organic Compound (VOC) Emissions 
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8.3 Years to Analyze 

8.4 Scenarios to Compare 

8.5 Consistency with the SIP 

8.6 New Source Review 
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CHAPTER 1 

INTRODUCTION 

1.1 General 

The Clean Air Act (CAA), as amended in 1990, includes new 

provisions in section 182(f) to control emissions of nitrogen 

oxides (NOx) in certain ozone nonattainment areas and ozone 

transport regions. Section 182(f) also specifies circumstances 

under which the new NOx requirements would be limited or would 

not apply. This document describes EPA's preliminary views on 

how EPA should interpret section 182(f) and the circumstances 

under which EPA would determine that the new NOx requirements 

would be limited or would not apply. 

Although this document includes various statements that 

States or petitioners must take certain actions, these statements 

are guidance made pursuant to EPA's preliminary interpretations, 

and thus do not bind the States and the public as a matter of 

law. The EPA's interpretation of the section 182(f) provisions 

will provide a basis for subsequent EPA approval or disapproval 

of requests for exemption from the new NOx requirements. While 

this document contains guidance.' on the interpretation of the 

section 182(f) provisions, unique circumstances or as yet 

unrecognized issues are likely to cause case-by-case exceptions 

to arise. The EPA intends to provide the public with an 

opportunity to comment on any exemption requests received by the 

Agency.. 

1.2 Nitrogen Oxides Supplement to the General Preamble for 

Implementation of Title I of the Clean Air Act 

The new NOx requirements, which are summarized below, are 

described in detail in EPA's Nitrogen Oxides Supplement to the 

General Preamble for Implementation of Title I of the Clean Air 

Act. This guidance was published in the Federal Register on 

November 25, 1992 (57 FR 55620). 

Section 182(f) requires States to apply the same 

requirements to major stationary sources of N0X as are applied to 

major stationary sources of volatile organic compounds (VOC). 

The new NOx requirements are reasonably available control 

technology (RACT) and new source review (NSR). These 

requirements apply to major stationary sources in certain areas 

that are designated nonattainment for the ozone national ambient 

air quality standard (NAAQS) and in an ozone transport region. 

The RACT requirements are in section 182(b)(2). This, 

section requires RACT for major NOx stationary sources in ozone 

nonattainment areas classified moderate and above as well—as in 

an ozone transport region. States are required to submit 
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regulations for RACT by November 15, 1992 and sources are 

required to achieve compliance with RACT by May 31, 1995. The 

EPA has defined RACT as the lowest emission limitation that a 

particular source is capable of meeting by the application of 

control technology that is reasonably available considering 

technological and economic feasibility (44 FR 53762; September 

17, 1979). 

The NSR requirements are in section 182(a)(2)(C). This 

section requires States to adopt revised NSR regulations in ozone 

nonattainment areas classified marginal and above as well as 

within an ozone transport region. States are required to submit 

regulations for NSR by November 15, 1992. NSR provisions require 

major new or modified stationary sources to comply with control 

technology that represents the lowest achievable emission rate 

and-requires the sources to obtain emission offsets. 

The RACT and NSR requirements for major sources in 

attainment/unclassified portions of the northeast ozone transport 

region originate in section 184(b)(2). 

1.3 Section 185B Report 

Under section 185B, the Administrator, in conjunction with 

the National Academy of Sciences (NAS), conducted a study on the 

role of ozone precursors in tropospheric ozone formation. The 

section 185B study must examined the role of N0X and VOC 

emissions, the extent to which N0X reductions may contribute or 

be counterproductive to achieving attainment in different 

nonattainment areas, the sensitivity of ozone to the control of 

N0X, the availability and extent of controls for NOx, the role of 

biogenic VOC emissions, and the basic information required for 

air quality models. The EPA announced in the February 26, 1993 

Federal Register a 30-day public comment period on the draft 

section 185B report. The final report was submitted to Congress 

on July 30, 1993. The National Research Council announced the 

completion of the December 1991 NAS report, Rethinking the Ozone 

Problem in Urban and Regional Air Pollution. The final section 

185B report incorporates this NAS report along with a recent EPA 

report addressing the availability and extent of NOx controls. 

In addition, the section 185B report also provides EPA 

perspectives on key ozone control strategy issues addressed by 

the National Research Council, emphasizing the NOx issues as 

directed by section 185B. 

In making a determination under section 182(f) that, the NOx 

requirements do not apply, or may be limited, the EPA must 

consider the section 185B study. This section 182(f) document 

includes consideration of EPA's section 185B report to Congress, 

including the December 1991 NAS report. 
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1.4 Application of Section 182(f) Requirements 

Section 182(f)(1) provides that the new NOx requirements 

shall not apply if the Administrator determines that any one of 

the following tests is met: 

(1) in any area, the net air quality benefits are greater 

in the abs 

concerned; 

in the absence of N0 X reductions from the sources 

(2) in nonattainment areas not within an ozone transport 

region, additional N0 X reductions would not contribute 

to ozone attainment in the area; or 

(3) in nonattainment areas within an ozone transport 

region, additional N0X reductions would not produce net 

ozone air quality benefits in the transport region. 

Further, section 182(f)(2) states that the application of 

the new NOx requirements may be limited to the extent necessary 

to avoid excess reductions of NOx as determined by applying tests 

similar to tests (l)-(3) above. 

As described in this document, the "net air quality 

benefits" test and the "excess emissions" provision may be 

applied in an ozone transport region or outside the transport 

region; the "contribute to attainment" test may only be applied 

outside of an ozone transport region; and the "net ozone 

benefits" test may only be applied within an ozone transport 

region. Where any one of the tests is met (even if another test 

is failed), the section 182(f) NOx requirements would not apply 

or, under the excess reductions provision, a portion of these 

requirements would not apply. 

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CHAPTER 2 

ADMINISTRATIVE PROCEDURES . 

2.1 Processing with the State Implementation Plan (SIP) Revision 

A State may, at any time, demonstrate to the Administrator 

that the new NOx requirements should not apply. For example, a 

State may submit a demonstration under section 182(f) along with, 

or as a revision to, the SIP at the time the NOx RACT rules are 

due; or a State may choose to submit the section 182(f) 

demonstration at a later date along with or as part of a separate 

SIP revision. The State's demonstration is not required to be a 

SIP revision itself. 

* The EPA will approve or disapprove the State's demonstration 

when the Administrator approves a plan or plan revision. The EPA 

will consider the section 185B report and will base its decision 

on the demonstration and supporting information provided by the 

State. Such demonstration and information should be in 

sufficient detail for/EPA to determine that the exemption request 

is consistent with the guidance-contained in this section 182(f) 

document. The EPA encourages the States to consult with the 

appropriate EPA Regional Office during the development of the 

documentation. This is necessary to ensure that the 

documentation provided by the State is likely to be approved and 

that any required rules can be adopted in a timely manner. NOx 

RACT and/or NSR rules that have been submitted or were previously 

approved by EPA would continue to be processed for approval or 

continue to be enforced while EPA considered the section 182(f) 

demonstration. 

2.2 Petition 

Section 182(f)(3) provides that a person (including a State) 

may petition the Administrator for a N0X exemption at any time 

after the final seqt^ion 185B report is submitted to Congress. 

The petition may be made with respect to any nonattainment area 

or any ozone transport region. The EPA must grant or deny a 

petition within 6 months after its filing. 

Since an individual petition is likely to affect the SIP 

planning process which is primarily a State responsibility, EPA 

believes it is reasonable to require the petitioner to provide a 

copy of the petition and demonstration to the State or States 

which have jurisdiction over the source or sources covered by the 

petition at the same time it is submitted to the Administrator 

(where a petition under section 182(f)(3) is being submitted by a 

person other than the State itself) . Where additional States may 

be affected by the petition, the State receiving the petition 

should coordinate with the other States as necessary. -In-some 

cases there may be multiple petitions for a given area. In other 
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cases a single petition may have multi-State implications. 

Shortly after EPA receives a petition, the Agency will announce 

its receipt and availability for public review in the Federal 

Register. The EPA will provide the State(s) a 3-month period to 

make a recommendation to EPA regarding the petition. This 3-

month period will run concurrently with the 6-month review period 

required under section 182(f)(3). The petitioner should submit 

the petition and demonstration to the Administrator through the 

appropriate EPA Regional Office. 

The EPA encourages any petitioner to consult with the State 

air quality agency and the appropriate EPA Regional Office during 

the development of a section 182(f) demonstration. This is 

necessary to ensure that the documentation provided (1) meets EPA 

guidance, (2) does not conflict with similar analyses by the 

State, and (3) is likely to be accepted by the State and EPA. 

The EPA's decision to grant or deny a petition will include 

consideration of the section 185B report and will be based on the 

demonstration provided by the petitioner, the State's 

recommendation, and the provisions of section 182(f). As noted 

above, this document sets forth EPA's preliminary interpretations 

of the section 182(f) provisions; 

The EPA will provide notice of its final action on a 

petition and the rationale for that action in a letter to the 

petitioner within the 6 month period. In addition, EPA will 

publish a notice describing the petition and EPA's determination 

, in the Federal Register. If EPA denies a petition, the 

petitioner may supplement or revise the original petition at a 

later date. Any revised petition would begin a new 6 month 

period. 

If EPA grants a petition, the section 182(f) NOx 

requirements or portions of those requirements, would no longer 

apply to those sources or areas> as described in EPA's approval 

action. However, States remain free to adopt N0X restrictions 

for other reasons. • For example, a State may determine that NOx 

reductions are needed for purposes of ozone maintenance planning, 

ozone attainment in separate downwind nonattainment areas, 

visibility protection, PM-10 control strategy, acid deposition 

program or other environmental protection. The EPA could approve 

certain NOx restrictions in a SIP revision despite granting a 

petition under section 182(f), so long as the NOx restrictions 

would not interfere with meeting any applicable requirement 

concerning attainment and reasonable further progress or any 

other applicable requirement of the CAA [see section 110(1)]. 

Section 182(f)(3) states that a person may petition the 

Administrator for a determination under section 182(f) at any 

time after the final report under section 185B is submitted to 

Congress. The final section 185B report was sent to Congress by 

the Administrator on July 30, 1993. Section 182(f)(3) also 
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requires the Administrator to grant or deny such a petition 

within .6 months after its filing with EPA. 
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CHAPTER 3 

NET AIR QUALITY BENEFIT 

3.1 Demonstration 

This demonstration applies to specific sources in an ozone 

nonattainment area or in an ozone transport region. It must show 

that N0X reductions from the sources seeking the exemption would 

be counter-productive overall, considering the net air quality 

benefits. Congress specified in this "test" for specific sources 

a higher hurdle than in the other tests for areawide exemptions: 

the demonstration must show a beneficial impact from the 

avoidance of the NOx controls. 

• The procedure for this test is to first project areawide 

baseline conditions that may be expected at the attainment 

deadline (section 8.3). Then, analyses are conducted for 2 

scenarios (section 3.4): with and without NOx reductions at the 

sources concerned. As'described in section 8.2, multi-year 

analyses may also be conducted. 

3.2 Factors 

Unlike the tests described in chapters 4 and 5, the CAA does 

not limit this test to consideration of ozone impacts. Instead, 

this test is based on a broader set of air quality impacts 

\Considered in the CAA. There are many air quality impacts 

explicitly addressed in the CAA, both health and welfare related, 

that may be directly or indirectly related to NOx emissions. 

These impacts include ozone, nitrogen dioxide, and particulate 

matter formation, visibility impairment, acid deposition, air 

toxics formation, and nitrogen deposition in nutrient-sensitive 

areas. 

Due to the number and variety of impacts, it is generally 

impractical or imppssible to compare effects quantitatively from 

one of these factors to those from another factor or among 

several factors. For example, there is no readily available 

scale to use to compare nitrogen dioxide impacts with acid 

deposition impacts and/or visibility impacts. Thus, in order to 

describe a method for determining the "net air quality benefit," 

a distinction must be made regarding which of the many factors 

can and should be analyzed. 

The EPA has concluded that the factors considered for the 

purposes of section 182(f) must be consistent with the 

requirements of the CAA. Thus, although "air quality impacts" 

could potentially be defined in a very broad manner, EPA has 

concluded that the air quality impacts considered under section 

182(f) must related directly to goals, standards, or mandates 

that are explicitly addressed in the CAA. Therefore, the test 
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for net air quality benefits must assure that a decision to grant 

an exemption would not interfere with the achievement of the 

specific programs or goals mandated in the CAA. 

The primary test should be the effect the exemption would 

have on attainment of the primary NAAQS for the criteria 

pollutants. The primary NAAQS are set by the Administrator to 

assure protection of the public health with an "adequate margin 

of safety;" EPA has, thus, concluded that this test should focus 

specifically on the effect of an exemption on the numbers of 

exceedances of the primary NAAQS, A petitioner should model the 

"NOx control" vs. "no NOx control" scenarios to assess the impact 

the NOx controls would have on the numbers of exceedances of the 

primary NAAQS, as described elsewhere in this document. 

* Secondary tests, as needed, can extend to the (qualitative 

or quantitative) consideration of other air quality impacts that 

are explicitly recognized in the CAA. These could include, for 

example, the welfare effects which EPA has considered and deemed 

necessary to protect against in setting secondary NAAQS for the 

criteria pollutants. A petitioner could also consider any other 

air quality effects that are explicitly addressed in the CAA 

through goals, standards or mandates, for example, visibility or 

air toxics emissions. 

The CAA requires the NAAQS to be attained as expeditiously 

as practicable and the CAA includes deadlines for rule adoption, 

submittal of control strategies, and attainment of the primary 

national ambient air quality standards (NAAQS). Thus, the 

impacts on attainment of the primary NAAQS must be a primary 

concern to this net air quality benefit test. In contrast, 

impacts on nutrient-sensitive areas is an important environmental 

issue that is addressed in the CAA, but does not have the same 

detailed set of requirements and deadlines stated in the CAA as 

do the NAAQS; thus, it should generally be a secondary concern to 

this net air quality benefit test. Further, EPA is not aware of 

any conflicts between the section 182(f) exemption and the 

requirements of section 407, concerning acid deposition, that 

might be considered in this analysis; i.e., granting a section 

182(f) exemption would not relieve, conflict with, or otherwise 

affect a source's obligation or ability to achieve NOx reductions 

consistent with the section 407 requirements. In cases where NOx 

reductions from a utility subject to section 407 would be 

counterproductive to the net air quality benefit, EPA encourages 

the State and utility to use the emission averaging provisions of 

section 407 to achieve the required NOx reductions at a location 

where they are not counterproductive to the net air quality 

benefit. If any statutory conflicts are documented, they could 

be considered on a case-by-case basis. 

In all cases, the method for consideration of the- net 

benefits must be related primarily to "air quality" since section 
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182(f) specifically requires a determination of the "air quality" 

benefits. Thus, simpler tests, such as a "net emissions" test, 

should not be relied upon since changes in emissions are not 

necessarily directly related to changes in air quality. In 

general, air quality impacts can be best determined by use of air 

quality dispersion models. However, at the present time, there 

are no EPA-recommended air quality dispersion models for 

simulation of nitrate (particulate) formation or comparison among 

ozone, nitrogen dioxide, and/or PM-10 NAAQS impacts in a single 

nonattainment area. 

In order to use air quality dispersion modeling whenever 

possible and to avoid conflicts with other requirements of the 

CAA, the methods described below should be used to determine the 

net air quality benefit over an appropriate geographic area (see 

section 3.3) which includes the ozone nonattainment areas 

encompassing or nearby the sources concerned. These methods 

include a primary consideration of the primary NAAQS air quality 

benefits and secondary consideration of other air quality 

benefits. 

Ozone Nonattainment Areas ; 

For areas that are nonattainment only for ozone, the effects 

of NOx reductions on ozone concentrations should be quantified 

with currently available air quality modeling techniques (see 

chapter 7). The net air quality benefit should be based on a 

comparison of the geographic area exposed to concentrations above 

the ozone NAAQS with and without NOx reductions from the sources 

concerned. 

Where Urban Airshed Model (UAM) results are available, 

population exposure to concentrations above or near the NAAQS may 

be used instead of the geographic area exposure factor. The 

Regional Oxidant Model (ROM) results for NOx reduction scenarios 

over major emissions/population centers should not be used 

quantitatively for -population exposure analyses. This is because 

ROM results have their largest associated uncertainties in areas 

where there is an inhomogeneous mix of emissions from major 

sources. Since such areas also tend to have greatest 

populations, use of the ROM, by itself, to estimate population 

exposure may have considerable associated uncertainty. 

It is important to note that EPA believes that photochemical 

grid models such as UAM and ROM are not sufficient to assess 

incremental changes to areawide ozone concentrations from 

emissions reductions at a single or group of small sources. 

Emission changes should amount to some significant fraction of 

base emissions before modeling results with ROM or UAM can be 

interpreted with sufficient confidence that the results are not 

lost in the noise of the model and the input data. -•- — 
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The EPA has reservations with respect to modeling NOx 

reductions at a single source or group of sources unless the 

modeling includes at least 10% of the domain-wide emissions. 

Thus, this exemption analysis is appropriate for groups of large 

emitters or for consideration of entire source categories, rather 

than emission reductions at a single or group of small sources. 

However, EPA will consider on a case-by-case basis an analysis 

that considers less than a 10% change in the domain-wide 

emissions. In such cases, the analysis of a small portion of the 

emissions would show only a small difference in ozone 

concentration, if any, between the with NOx and without NOx 

scenarios, and, therefore, consideration of secondary factors 

(described below) is particularly important in order to show a 

net air quality benefit. 

In some cases, the amount of emission reductions assumed in 

the modeling analysis could be very large; thus, there may be 

cases where the analysis does not result in any values above the 

NAAQS for any pollutant and, thus, there would not be a 

comparison of area or population exposed. This could occur even 

though the difference in ozone concentration between the two 

scenarios is large. In such cases, the petitioner should look to 

the factors considered in the secondary test, such as welfare 

effects or other air quality effects addressed by the CAA. 

Areas Nonattainment for Both Ozone and Nitrogen Dioxide 

For areas that are nonattainment for both ozone and nitrogen 

dioxide, NOx reductions clearly are needed to provide for 

attainment of the nitrogen dioxide standard, while either NOx or 

VOC reductions (or both) might best provide for attainment of the 

ozone standard. In such cases EPA would not make a finding of a 

net air quality benefit since the CAA requires the NAAQS for 

nitrogen dioxide to be met as expeditiously as practicable. 

Areas Nonattainment for Both Ozone and PM-10 

For areas that are nonattainment for both ozone and PM-10, a 

determination is first needed if the secondary nitrates formed 

from NOx emissions contribute significantly to the PM-10 NAAQS 

violation(s) in the specific nonattainment area. This 

significance determination is needed since, especially in the 

eastern United States, EPA expects that the nitrate portion of 

measured PM-10 will be found, to be insignificant in many cases. 

Where sufficient and reliable data exist to determine the nitrate 

contribution to ambient PM-10 concentrations, this determination 

may be limited to those NOx emissions sources subject to the 

section 182(f) requirements. Where the contribution is 

insignificant (see below) , then the net air quality determination 

should be based primarily .on the ozone impacts. Where the 

contribution is significant, EPA would not make a finding of a 

net air quality benefit since the CAA requires the NAAQS for PM-
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10 to be met as expeditiously as practicable. For this purpose, 

EPA intends to use its definition of a significant contribution 

to a PM-10 nonattainment area which is 1.0 microgram per cubic 

meter (nitrate and associated materials) for the annual standard 

and 5 micrograms per cubic meter for the 24-hour standard (40 CFR 

51.165). 

Areas Nonattainment for Ozone and Carbon Monoxide. Lead or 

Sulfur Dioxide 

For carbon monoxide, lead, and sulfur dioxide, EPA is not 

aware of any significant impacts from NOx reductions. Therefore, 

the net air quality benefits determination should be primarily 

based on the ozone modeling analysis described above for areas 

nonattainment for only ozone. 

As noted above, equal consideration of all NOx impacts is 

generally impractical in this net air quality benefit test 

because of the lack of scales to compare the impacts among the 

various factors. Nevertheless, additional factors explicitly 

addressed in the CAA such as those listed below must be 

considered at least on a qualitative basis in addition to any 

information developed from the NAAQS analyses. Consideration of 

the factors below is especially important in cases where the 

analyses on the NAAQS pollutants cannot clearly determine the net 

air quality benefit. In any case, EPA believes the amended CAA 

places a substantial burden on the applicant to provide a clear 

\Showing that NOx reductions would be counterproductive overall, 

considering the net air quality benefits. Additional factors to 

determine net air quality benefit may include but are not limited 

to: 

1. Effects associated with long-term exposures to plants, 

animals, and materials. 

2. Visibility impairment, long-term and episodic acid 

deposition, air toxics, and deposition of nitrogen in 

nutrient-sensitive watersheds. 

3.3 Geographic Scope 

In contrast to the other section 182(f) tests, the net air 

quality benefit test is not specifically limited to an ozone 

nonattainment area or ozone transport region and may be directed 

at a specific set of sources. Thus, a very broad geographic area 

should be considered. The area may, in some cases, extend beyond 

an ozone nonattainment area or ozone transport region. In 

addition, the area must not be so small that downwind impacts 

from NOx emissions are not fully considered. Sufficient area is 

needed to allow for completion and consideration of the various 

chemical transformations of NOx and interaction with other 

pollutants. At a minimum, the geographic area should include the 
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ozone nonattainment area(s) encompassing or nearby the sources 

concerned. For example, petitioning sources located in 

attainment portions of the ozone transport region should analyze 

their impact on nearby nonattainment areas and should consider 

other factors, such as visibility impacts throughout the 

surrounding area 

3.4 Scenarios 

Section 182(f) states, for this test, that EPA must 

determine that the net air quality benefits are greater in "the 

absence of reductions of oxides of nitrogen from the sources 

concerned." The procedure for this test is to first project 

areawide baseline emissions that may be expected at the 

attainment deadline (see sections 3.3 and 8.3). (As described in 

section 8.3, multi-year analyses may also be conducted.) Second, 

the projected baseline emissions are held constant, except for 

the subject individual sources. Then, the air quality analyses 

are conducted for these two scenarios: 

1. the projected baseline emissions of VOC and NOx 

(without NOx reductions from the sources concerned) and 

2. the projected baseline emissions of VOC and NOx 

emissions including NOx reductions at all emission 

sources subject to the NOx NSR and RACT provisions of 

section 182(f). 

With respect to new major sources, the two scenarios should 

take into account application of the section 182(f) NSR 

requirements as described in section 8.5. 

3.5 Sources 

For this net air quality benefit test, the CAA refers to 

"reductions of oxides of nitrogen from the sources concerned." 

For purposes of this analysis, "the sources concerned" are 

defined as the sources that would be exempted from the section 

182(f) NOx requirements by the petition or State request. The 

sources concerned may be identified in any of the following ways: 

(1) specific individual sources, (2) one or more source 

categories, or (3) a geographic area containing a group of 

sources. As described in section 3.4, the sources concerned must 

be analyzed together with other NOx and VOC sources in the area; 

these other NOx sources should take into account application of 

the section 182(f) RACT and NSR requirements (as part of the 

areawide baseline conditions expected at the attainment deadline 

year) since those NOx reductions are not the subject of the 

exemption request. 
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CHAPTER 4 

CONTRIBUTE TO ATTAINMENT 

4.1 Demonstration 

This demonstration applies only to ozone nonattainment areas 

that are not within an ozone transport region. The demonstration 

must show that additional NOx reductions would not contribute to 

ozone attainment in the area. 

The procedure for this test is to utilize a photochemical 

grid model (see chapter 7) to simulate several episode cases over 

the nonattainment area under conditions that may be expected at 

the attainment deadline (see section 8.2) considering three 

emission reduction scenarios (see section 8.3): (1) substantial 

VOC reductions; (2) substantial NOx reductions; and (3) both the 

VOC and NOx reductions. If the areawide predicted maximum 1-hour 

ozone concentration for each day modeled under scenario (1) is 

less than or equal to that from scenarios (2) and (3) for the 

same day, then the test is passed and the section 182(f) 

requirements would not apply. 

4.2 Episodes to Consider 

In most ozone nonattainment areas it is likely that portions 

of the area would benefit from NOx reductions and other portions 

would not for each modeled day. The EPA believes it is 

appropriate to focus this analysis on the areawide maximum 1-hour 

predicted ozone concentration since this value is critical to the 

attainment demonstration. In contrast, it should not be 

necessary to examine the maximum 1-hour ozone concentrations at 

each point modeled in the area since these points are not 

necessarily important to development of the attainment 

demonstration and since this is the only one of the section 

182(f) tests which is not keyed to net benefits. 

i i 

In certain ozone nonattainment areas it is possible 

that NOx emission reductions may help to reduce the areawide 

maximum predicted ozone concentration under some meteorological 

conditions but not under others. The phrase "would not 

contribute to attainment" could be interpreted to mean that NOx 

emission reductions would not help reduce (1) any areawide 

maximum 1-hour predicted ozone concentration, (2) the majority of 

areawide maximum 1-hour predicted ozone concentrations, or 

(3) the most severe areawide maximum 1-hour predicted ozone 

concentration. 

The EPA believes that the "majority" option is not 

appropriate since this is the only one of the section 182(f) 

tests which is not keyed to net benefits. Furthermore,- (1) an 

area may need to demonstrate attainment under multiple 
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meteorological conditions, (2) generally a small number of 

episodes will be modeled and (3) the NAAQS is based on multiple 

exceedances rather than a single, most severe value. For the 

above reasons, EPA believes this determination should be based on 

each areawide maximum 1-hour predicted ozone concentration 

modeled in accordance with this guidance (chapter 7). Thus, all 

of the areawide maximum 1-hour predicted ozone concentrations 

modeled must be greater with NOx reductions at the sources 

concerned than without the reductions, or no exemption would be 

granted. An area is not required to model all past exceedances; 

only those episodes selected for modeling in accordance with EPA 

guidance (chapter 7) need to be considered. 

4.3 Geographic Scope 

This demonstration focuses on attainment of the ozone NAAQS 

"in the area." The EPA interprets this to mean, at a minimum, in 

the nonattainment area. In contrast to the provision for 

transport regions, which is likely to consider several attainment 

and nonattainment areas in the section 182(f) analysis, this 

demonstration is limited to consideration of the effects in a 

single nonattainment area due to N0X emissions reductions from 

sources in the same nonattainment area. However, since the 

effects of an attainment strategy may extend beyond the 

designated nonattainment area and since photochemical grid 

modeling is necessary for this demonstration and is likely to use 

a modeling domain larger than the nonattainment area, EPA 

encourages States/petitioners to include consideration of the 

entire modeling domain. 

States should consider imposition of the NOx requirements if 

needed to avoid adverse impacts in downwind areas, either intraor inter-State. States need to consider such impacts since they 

are ultimately responsible for achieving attainment in all 

portions of their State (see generally section 110) and for 

ensuring that emissions originating in their State do not 

contribute significantly to nonattainment in, or interfere with 

maintenance by, any other State [see section 110(a)(2)(D)(i) (I) ] . 

4.4 Applicability to Areas Requesting Redesignation to 

Attainment 

In some cases, an ozone nonattainment area might attain the 

ozone standard, as demonstrated by 3 years of adequate monitoring 

data, without having implemented the section 182(f) NOx 

provisions over that 3-year period. Where the State submits a 

request for redesignation to attainment along with necessary 

supporting documentation and where NOx RACT and NSR requirements 

were not implemented over that 3-year period, it is clear that 

the section 182(f) language is met since."additional reductions 

of oxides of nitrogen would not contribute to attainment." That 

is, since attainment has already occurred, additional NOx 
P.19 

15 

reductions could not improve the area's attainment status and, 

therefore, the section 182(f) demonstration could be approved. 

Additional guidance on this subject is contained in a September 

17, 1993 memorandum from Michael Shapiro to the EPA Regional 

Offices regarding requests for redesignation to attainment. 

The section 182(f) demonstration would not be approved if 

there is evidence, such as photochemical grid modeling, showing 

that the NOx exemption would interfere with attainment or 

maintenance in downwind areas. As noted above, section 110 

prohibits such impacts. 
P.20 

16 

CHAPTER 5 

NET OZONE AIR QUALITY BENEFIT 

5.1 Demonstration 

This demonstration applies in an ozone transport region. It 

must show that additional N0X reductions would not produce net 

ozone benefits in the transport region. In this test the net 

benefit must be demonstrated on a regionwide basis. Regionwide 

includes all portions of the ozone transport region in which 

impacts from NOx emissions from the area seeking the exemption 

can be determined by the photochemical grid model. 

The procedure for this test is to utilize a photochemical 

grid model (see chapter 7) to simulate conditions that may be 

expected at the attainment deadline (see section 8.3) considering 

three emission reduction scenarios (section 8.4): (1) 

substantial (se section 8.4) VOC reductions; (2) substantial NOx 

reductions; and (3) both the VOC and NOx reductions. The net 

ozone benefit may be determined by comparing the ozone 

concentrations modeled in scenario (1) with results modeled from 

scenarios (2) and (3). If the exposure to ozone concentrations 

from scenario (1) is less than or equal to the exposure to ozone 

concentrations from scenarios (2) and (3), then the section 

182(f) net ozone benefits demonstration could be approved. As 

described in section 8.3, multi-year analyses may also be 

conducted. 

5.2 Factors 

The ozone NAAQS is set at 0.12 parts per million (ppm). In 

defining "net ozone benefit,'.1 however, EPA recognized that 

various forms of expression could be considered with respect to 

ozone impacts. These forms include the 1-hour 0.12 ppm NAAQS, a 

1-hour value less than 0.12 ppm, an 8-hour value set lower than 

0.12 ppm, and a seasonal value set lower than the 0.12 ppm value. 

However, ozone concentrations with different averaging periods 

and values cannot readily be compared to each other. For 

example, it is difficult to compare a set of 1-hour ozone peak 

concentrations above 0.12 ppm against a set of 8-hour ozone peak 

concentrations above 0.06 and determine which results are more 

beneficial. 

The EPA believes it is reasonable to focus the net ozone 

benefits test on the 1-hour 0.12 ppm ozone NAAQS, where possible 

for the following reasons: (1) the 0.12 ppm ozone NAAQS has been 

set by the Administrator as the level necessary to protect the 

most sensitive individuals from adverse health effects with an 

"adequate margin of safety;" (2) ozone concentrations with 

different averaging periods and values cannot readily be compared 

to each other, (3) the purpose of the various section 182 
P.21 

17 

provisions is primarily to attain the ozone NAAQS, and (4) it is 

important for this guidance document to avoid any conflicts (as 

noted in chapter 3) with the section 182 requirements. 

Therefore, the averaging time to be used should be the one-hour 

daily maximum ozone concentration and the analysis should focus 

on values above the 0.12 ppm NAAQS level. Specifically, the net 

ozone benefits test focuses on the total geographic area exposed 

to ozone concentrations above the 0.12 ppm NAAOS level. 

Where Urban Airshed Model (UAM) results are available, 

population exposure to concentrations above or near the ozone 

NAAQS may be used, instead of the geographic area exposure 

factor. The Regional Oxidant Model (ROM) results for NOx 

reduction scenarios over major emissions/population centers 

should not be used quantitatively for population exposure 

analyses. This is because ROM results have their largest 

associated uncertainties in areas where there is an inhomogeneous 

mix of emissions from major sources. Since such areas also tend 

to have greatest populations, use of the ROM, by itself, to 

estimate population expdsure may have considerable associated 

uncertainty. 

Depending on the amount of NOx and VOC reductions selected 

for each scenario, the model results in some cases might show all 

scenarios to be below the 0.12 ppm ozone NAAQS level. In such 

cases some might argue that there is no ozone benefit and, thus, 

the NOx requirements should not apply. The EPA does not agree 

with such an interpretation because the CAA specifies "net ozone" 

rather than "ozone attainment" for this test. In fact, a "net" 

ozone test is necessary to integrate the benefits and disbenefits 

of NOx reductions that are likely to vary from grid to grid in a 

given analysis area. That is, NOx reductions may reduce hourly 

ozone concentrations in some locations and increase hourly ozone 

concentrations in other locations within the same modeling 

domain. Therefore, a broader factor is needed than the areawide 

0.12 ppm where the modeled scenarios show all values below the 

ozone NAAQS. i * 

- ' 

Consideration of ozone air quality impacts other than the 

primary NAAQS values is appropriate as a secondary factor. Thus, 

values such as the following are appropriate for consideration 

where no conclusion can be drawn through the above analysis based 

on the ozone NAAQS values: effects associated with long-term 

exposures to ecosystems, crops, animals, and materials. 

5.3 Attainment/Unclassified Portions 

The section 182(f)(1)(B) demonstration explicitly refers to 

nonattainment areas within an ozone transport region. The CAA 

does not clearly state whether or not portions of ozone transport 

regions that are attainment/unclassified can make the net ozone 

benefit demonstration. The section 182(f)(1) net air quality 

J 
P.22 

18 

benefit test is available to any area; however, as noted 

previously it is a higher hurdle. Thus, while a severely 

polluted area might be able to demonstrate that NOx reductions do 

not apply because the "net ozone benefits" test is satisfied, the 

CAA could be interpreted to require NOx reductions in the 

surrounding attainment area because that area cannot meet the 

same test. It is unlikely that Congress intended such a result. 

An alternative reading of the CAA can be found through 

section 184(b)(2). This provision states that the attainment/ 

unclassified portions of the transport region must meet "the 

requirements which would be applicable to major stationary 

sources if the area were classified as a moderate nonattainment 

area." Thus, the CAA could be interpreted to provide the same 

section 182(f)(1)(B) demonstration process for these attainment/ 

unclassified areas, since they should be treated as moderate 

nonattainment areas for the purpose of applying the section 

182(f) requirements and moderate nonattainment areas in the 

transport region are eligible to meet the "net ozone benefits" 

test. -'';' 

Even without that language,'EPA would be inclined to allow 

an attainment/unclassified area in a transport region to satisfy 

the "net ozone benefits" test. It would be absurd, and therefore 

it is unlikely that Congress intended to apply more stringent 

requirements in the attainment/unclassified portions of the 

transport region than would apply to the more severely polluted 

portions. Congress apparently did not intend any lesser 

requirements to apply in the attainment/unclassified portions of 

the transport region. The EPA believes that it is appropriate to 

extend the section 182(f) provision beyond the boundaries of a 

nonattainment area into adjacent attainment/unclassified areas 

which are part of the same section 182(f) demonstration. Thus, 

where a State/petitioner demonstrates that NOx reductions would 

not produce net ozone benefits in the transport region, then the 

section 182(f) NOx requirements would not apply to those sources 

or areas as described in EPA's approval action. Such a 

demonstration must 'include all portions of the ozone transport 

region in which impacts from NOx emissions from the area seeking 

the exemption can be determined by the photochemical grid model. 
P.23 

19 

CHAPTER 6 

EXCESS EMISSIONS REDUCTIONS 

6.1 General 

Section 182(f)(2) provides the flexibility to limit the 

scope of the NOx NSR and RACT requirements. Application of the 

NOx NSR and/or RACT requirements can be. limited to the extent 

that any portion of those reductions are demonstrated to result 

in "excess reductions." The tests for demonstrating excess 

reductions are generally the same as in section 182(f)(1): net 

air quality benefit, contribute to attainment and net ozone 

benefit. However, in this case, the demonstration must show that 

a portion of the otherwise required NOx reductions are either 

counterproductive to the net air quality, do not contribute to 

attainment, or do not provide a net ozone benefit [depending on 

the section 182(f) test applied]. 

As described below> for the contribute to attainment or net 

ozone tests, the excess reductions test must show that certain 

NOx reductions are in excess of;the reductions specified in 

either the attainment demonstration required by section 182 and 

contained in the approved SIP or an attainment demonstration 

adopted by the State to meet the section 182 attainment 

demonstration requirement and submitted to EPA for approval. The 

excess emission reductions may be described, for example, as (1) 

an areawide across-the-board tonnage reduction; (2) emissions 

attributed to specific sources; or (3) emissions from a 

geographic portion of the nonattainment or transport area. 

6.2 Demonstration 

The "contribute to attainment" and "net ozone benefit" tests 

described in chapters 4 and 5 both require an areawide or 

regional analysis. In such areawide/regional analyses, NOx 

emission reductions tat a large number of sources are considered. 

These analyses are appropriate to determine in a directional 

manner whether or not NOx reductions are expected to be 

beneficial with respect to the air quality in the area/region. 

The analyses described in chapters 4 and 5 may be less precise 

than an attainment demonstration required under section 182(c). 

The EPA believes that the excess reductions provision 

requires a more precise analysis; specifically an analysis which 

is based on the attainment demonstration. That is, the excess 

reductions provision must be more than a directional finding on 

an areawide basis. Under the excess reductions provision, an 

analysis is needed to show that a specific portion of the total 

areawide NOx emissions is not beneficial under one of the three 

tests. Thus, individual or groups of sources may petition to 

show that, while NOx reductions may be beneficial directionally 
P.24 

20 

in the area, NOx reductions from their specific sources are not 

beneficial and, thus, should be exempt from the NOx requirements. 

Without providing some constraints in this guidance 

document, the excess reductions provisions could undermine the 

section 182(f) requirements, since each individual emission 

source could theoretically petition for an exemption with the 

argument that their small contribution to the overall ozone 

problem is inconsequential. Such a petition might be considered 

consistent with the analyses required in chapters 4 and 5, since 

an exemption may be granted where the modeled NOx reductions show 

no impact on ozone concentrations. Certainly, if EPA allowed 

very small amounts of NOx reductions to be modeled individually, 

this interpretation would create a significant loophole. 

Congress would not have intended, and therefore EPA does not 

accept the argument, that the owner/-opera tor of one car or one 

small boiler can be excused from the CAA requirements because 

their emissions, - viewed alone, are small. Considered together 

with other small contributions, the emissions may be important to 

attainment. That is, emissions from one car or one commercial 

boiler would not change--the areawide ozone concentration, yet 

together with other cars or boilers, they may be critical to the 

area's attainment strategy. Furthermore, as previously 

described in this document, ozone, air quality models should not 

be applied solely to determine the incremental effect of small 

sources as such emissions could be lost in the noise of the air 

quality model and emissions inventory uncertainties when 

considered alone. 

For the above reasons, EPA has determined that the excess 

reductions demonstration for the "contribute to attainment" or 

"net ozone benefits" tests must be tied to the area's SIP 

attainment demonstration. Thus, this test must show that the 

excess reductions are reductions in excess of those specified in 

the attainment demonstration required by section 182 and either 

contained in the approved SIP or as adopted by the State to meet 

the section 182 attainment demonstration requirement and 

submitted to EPA for approval. This tie to the attainment 

demonstration assures that an excess reductions petition would 

not arbitrarily be based on small emissions and would not 

undermine the State's control strategy. 

In contrast, the "net air quality benefit" test discussed in 

chapter 3 is intended to address an individual or small number of 

sources and already has an adequate constraint. The net air 

quality benefit test requires a showing that NOx reductions 

specifically from the sources concerned are counterproductive. 

The net air quality benefit test imposes a higher hurdle than the 

other two tests and EPA believes this higher hurdle is adequate 

for purposes of the excess emissions test as well. 
P.25 

21 

CHAPTER 7 

MODELING TECHNIQUES 

7.1 Photochemical Grid Modeling 

As described in chapters 3-6, photochemical grid modeling is 

generally needed to document cases where NOx reductions are 

counterproductive to net air quality (chapter 3), do not 

contribute to attainment (chapter 4), do not show a net ozone 

benefit (chapter 5), or include excess reductions (Chapter 6) . 

As described below, the Urban Airshed Model (UAM) or, in an ozone 

transport region, the Regional Oxidant Model (ROM) are acceptable 

models for these purposes. 

The EPA investigated the feasibility and acceptability of 

applying relatively inexpensive screening techniques to evaluate 

if NOx control measures are likely to be beneficial with respect 

to attainment of the ozone NAAQS (Langstaff and Scheffe, 1991). 

However, EPA determined that, as a technical matter, 

photochemical grid modeling is the only reliable tool to justify 

an areawide exemption from the NOx requirements. 

The EPA's reliance on photochemical grid models is supported 

by the recently published findings of the NAS on tropospheric 

ozone (December 1991). The NAS report concluded that threedimensional or grid-based ozone air quality models are currently 

the best available models for representing the chemical and 

physical processes of ozone formation. The report provides a 

list of such models (Table 10-1), including UAM and ROM. The NAS 

report also states that "ROM is the only regional model available 

for assessment of control strategies for urban and rural ozone in 

the eastern United States" (page 365). 

The 1990 CAA requires the use of gridded models in many 

ozone nonattainment areas. In 1990, EPA released an updated 

version of the UAM> (reflecting numerous advances in 

photochemistry and ^numerical solution techniques which emerged 

during the 1980s. An extensive multi-volume UAM User's Manual 

was prepared to facilitate operation of the UAM. Guidance on 

regulatory application of the UAM was completed in July 1991. 

Several efforts are underway to improve pre- and post-processing 

UAM capabilities and train the States in applying the model. 

The EPA encourages applications of advanced modeling methods 

where they are found to be more appropriate. Such methods may be 

acceptable on a case-by-case basis after (1) preparation of a 

modeling protocol, (2) proper testing and evaluation, and (3) 

approval by the appropriate EPA Regional Office. 

Less sophisticated models, such as EKMA, lack the detailed 

treatment/consideration of physical orientation of NOx sources 
P.26 

22 

and dispersion of their plumes. Further, since trajectory models 

only address a limited number of trajectories, they cannot assess 

whether NOx control contributes to attainment at all locations in 

an ozone nonattainment area.' Therefore, such models are 

insufficient and not acceptable for the section 182(f) 

demonstration. 

7.2 Urban Airshed Model 

UAM results are acceptable for the purpose of the section 

182(f) demonstrations. Application of UAM should be consistent 

with techniques specified in the EPA "Guideline on Air Quality 

Models (Revised).'1 Further, application of UAM should also be 

consistent with procedures contained in the EPA "Guideline for 

Regulatory Application of the Urban Airshed Model" (July 1991). 

Thus, episode selection for the section 182(f) demonstration 

should be consistent with the UAM guidance for SIP attainment 

demonstrations. An assessment of the model's performance and a 

copy of the modeling protocol should be included in the analysis 

for informational purposes. 

7.3 Regional Scale Modeling 

In an ozone transport region, the net ozone benefits test 

should be met by use of regional scale modeling. Regional scale 

modeling is needed since the section 182(f) language explicitly 

refers to net ozone benefits "in such region." Regionwide or 

regional scale modeling includes all portions of the ozone 

transport region in which impacts from NOx emissions from the 

area seeking the exemption can be determined by the photochemical 

grid model. Prior to the availability of ROM and/or UAM results 

supporting the section 182(c) attainment demonstrations, the 

EPA's "Regional Ozone Modeling for Northeast Transport" study 

(June 1991) is an acceptable basis for this demonstration. When 

more recent ROM and/or UAM regionwide studies for the Northeast 

Ozone Transport Region have been completed and are available, 

they must be used for any section 182(f) demonstration. 

Where UAM studies have been completed and are available, ROM 

results are acceptable for evaluating effects outside of the UAM 

modeling domains established pursuant to attainment demonstration 

requirements for section 182. Thus, ROM results are acceptable 

for evaluating effects in portions of a transport region outside 

of the UAM modeling domain for the purpose of a section 182(f) 

demonstration. It is not appropriate, however, to use ROM to 

assess the effects in an individual city outside of any UAM 

domain. ROM is most suitable for assessing composite impacts 

over large areas (which may include individual cities) where UAM 

results are unavailable. Results of available ROM applications 

are archived on the EPA's Gridded Model Information Support 

System (GMISS). 
P.27 

23 

7.4 Model Results and SIP Interface 

Where a petition for an exemption [section 182(f)(1)] or 

excess reductions determination [section 182(f)(2)] is granted by 

EPA prior to adoption and submittal" of the State's rules, the 

State may simply choose not to submit the NOx rules. If a 

petition is granted after submittal of the NOx rules, but prior 

to EPA approval, the State may choose to withdraw the rules and 

preclude further EPA action. In a case where a petition is 

granted ("exempted area") after EPA approves of the N0X rules, 

the SIP would need to be modified through a SIP revision to . 

rescind the N0X rules provided such rescission would not 

interfere with attainment or reasonable further progress 

[section 110(1)]. 

Following application of a photochemical grid model that is 

required for serious and above areas to support the attainment 

demonstrations due by November 1994, a State must select and 

adopt a control strategy that provides for attainment as 

expeditiously as practicable, but no later than the date 

prescribed in section 181. This decision must be addressed by a 

State whether or not an area was exempted from the November 1992 

submittal of NOx RACT and/or NSR rules and may result in revision 

of the previously adopted rules. In some instances the NOx RACT 

and NSR requirements already adopted may need to be supplemented 

with additional or more advanced N0X controls in order for the 

area to attain the NAAQS. 

In other cases, an area initially exempted may choose, based 

on the new photochemical grid modeling results, to adopt certain 

N0X reduction rules in order to attain and/or meet reasonable 

further progress requirements through N0X substitution. The area 

would be removed from "exempt" status since NOx reductions were 

subsequently found to be beneficial in their ozone attainment 

plan. Consequently, the area would have to adopt the NOx RACT 

and NSR rules except to the extent modeling shows that the 

controls beyond those chosen are "excess reductions" (chapter 6) 

or are counterproductive to the net air quality (chapter 3) . 

Credit for NOx substitution would be granted only if in 

accordance with the EPA guidance. In any event, these changes 

must be submitted as a SIP revision and must provide for 

attainment as expeditiously as practicable and meet reasonable 

further progress requirements. 

Alternatively, for an area that adopted the NOx RACT and NSR 

rules as required by section 182 (i.e., not exempt), a State may 

choose to revise some or all of those rules to require less NOx 

stationary source controls. This action would be based on the 

application of a photochemical grid model showing that the 

subject NOx controls result in excess emission reductions, as 

determined using the section 182(f) tests set forth at the 

beginning of this section. The revisions must be submitted as a 
P.28 

24 

SIP revision and the SIP must demonstrate attainment as 

expeditiously as practicable. 

7.5 Other Analytical Techniques 

Guidelines on analytical techniques for assessing other air 

quality impact factors, such as acid deposition, population 

exposure or visibility, are not readily available. Therefore, 

EPA encourages petitioners to consult with the State and EPA 

Regional Office to agree on an acceptable methodology on a caseby-case basis. 
P.29 

25 

. CHAPTER 8 

EMISSIONS ANALYSIS 

8.1 General 

As described in chapters 3-6, photochemical grid modeling is 

needed to document cases where NOx reductions are 

counterproductive to net air quality (chapter 3), do not 

contribute to attainment (chapter 4), do not show a net ozone 

benefit (chapter 5), or include excess reductions.(chapter 6). 

Application of these models requires the use of a representative 

emissions inventory. This chapter describes the emission 

inventory requirements for the various section 182(f) 

demonstrations. 

8.2 Biogenic Volatile Organic Compound (VOC) Emissions 

The NAS report states that, in some cases, "without control 

of NOx emissions, this-VOC background should be able to generate 

ozone concentrations that exceed the NAAQS concentration of 120 

ppb" (page 244) . Biogenic emissions can influence both the 

nature (i.e., VOC or NOx) and extent of required emissions 

controls. Therefore, inclusion of biogenic emissions are 

necessary inputs to model applications which assess the roles of 

VOC and NOx in ozone formation for purposes of section 182(f). 

In estimating biogenic emissions, the most recent version of the 

Biogenic Emissions Inventory System (BEIS) (available through the 

EPA Regional Offices) should be used. 

8.3 Years to Analyze 

In general, the purpose of the section 182(f) requirements 

for NOx is related to attainment of the ozone standard. This 

suggests an analysis that is focussed on the time that attainment 

of that standard is required. In addition, other sections of the 

CAA require moderate and above ozone nonattainment areas to 

develop modeling analyses which demonstrate attainment by the 

appropriate statutory deadline; to the extent that such modeling 

analyses are already underway, they could be useful for the 

section 182(f) demonstration also. 

Considering these points, EPA believes that the 182(f) 

demonstrations should, at a minimum, reflect conditions expected 

at the time the subject area is required to attain the ozone 

standard. For example, in a serious ozone nonattainment area, 

the year would be 1999. As described in section 8.5, the 

conditions should also be consistent with assumptions contained 

in the SIP. Thus, base year emissions would be projected to the 

year reflecting the attainment deadline and would include growth 

in VOC and NOx emissions as well as CAA-mandated VOC emission 

reductions. Specific emission scenarios with and without NOx 
P.30 

26 

reductions would be built upon this projected emissions baseline 

as described elsewhere in this document. In addition, as 

described later in this section, multi-year analyses may also be 

conducted. 

In an ozone transport region, a section 182(f) demonstration 

would likely cover an area which includes ozone nonattainment 

areas of more than one classification, and thus more than one 

attainment deadline. For example, a. metropolitan area may have a 

higher classification than a nearby rural nonattainment area. 

For these areas, it is possible that NOx reductions may be 

beneficial to attainment in the near term with respect to the 

rural nonattainment area (and lesser classification deadline) 

but, at the same time or in a longer timeframe, NOx reductions 

might be shown to be not beneficial when considering the area as 

a whole (since NOx reductions are generally expected to be more 

beneficial in rural areas). In order to determine whether the 

NOx reduction requirements should apply, EPA believes that, at a 

minimum, the section 182(f) demonstration should reflect 

conditions expected at the latest attainment deadline for the 

area as a whole. In addition, States should consider imposition 

of the NOx requirements if needed to avoid adverse impacts in 

downwind areas, either intra- or.inter-State. States need to 

consider such impacts since they are ultimately responsible to 

provide for attainment in all portions of their State and must 

not contribute significantly to nonattainment in, or interfere 

with maintenance by, any other State. 

Alternatively, the State/petitioner may include a multi-year 

analysis in its section 182(f) demonstration. This is 

appropriate for areas demonstrating either a net air quality 

benefit or a net ozone benefit. In these demonstrations, the 

analysis may include periodic assessments of the effects of NOx 

reductions and integrate those effects to arrive at a finding on 

whether or not NOx reductions are beneficial. For example, an 

area may develop geographic area exposure analyses for each year 

or for every third -year up to the attainment year and assess the 

overall impact of NOx reductions from that information. 

8.4 Scenarios to Compare 

For the contribute to attainment and net ozone benefit 

tests, the projected emissions should, at a minimum, consider 

three scenarios which vary emission reductions from anthropogenic 

sources: (1) substantial VOC reductions; (2) similar NOx 

reductions; and (3) both the VOC and NOx reductions. Total 

emissions to model include both anthropogenic and biogenic 

emissions. 

In contrast to the net air quality demonstration (chapter 3) 

which focuses on the scenario "in the absence of reductions of 

oxides of nitrogen from the sources concerned," the contribute to 
P.31 

27 

attainment and net ozone benefit demonstrations concern an 

unspecified "additional reductions" of NOx. Thus, while the net 

air quality benefit test must focus on NOx reductions due to NSR 

and RACT, the other demonstrations may more broadly consider NOx 

reductions, including reductions that employ advanced control 

technology (i.e., beyond RACT). The application of the VOC and 

NOx reductions should be as source category specific as possible, 

rather than across-the-board, in order for the results to be most 

useful. 

In the first scenario the demonstration should use the VOC 

reductions needed to attain (demonstrated by EKMA or UAM 

analyses). Alternatively, if the attainment demonstration has 

not been completed, the demonstration may use some other 

substantial VOC reduction. Reductions associated with attainment 

are appropriate for the reasons described above. In any case, 

the VOC reductions should be substantial and documented as 

reasonable to expect for the area due to the CAA requirements. 

For example, a minimum of a 40% anthropogenic VOC reduction 

areawide from the 1990-emission inventory may be reasonable to 

expect for serious areas, considering motor vehicle emission 

controls, inspection/maintenance, reasonable further progress and 

other CAA requirements. 

In the second scenario, NOx reductions should be modeled 

without any VOC reductions above the attainment year baseline. 

The level of NOx reductions should reflect the same percent 

reduction of anthropogenic VOC emissions in scenario (1) above. 

It is important to model this case since NOx reductions, instead 

of additional VOC reductions, may show a clearer benefit. 

In the third scenario, a similar level of NOx reductions 

would be modeled along with the level of VOC reductions chosen. 

That is, if a 40% VOC reduction is chosen in scenario (1) , then 

the model for scenario (3) would simulate a 40% VOC reduction and 

approximately a 40% NOx reduction. It would be inappropriate to 

select a high level,of VOC reductions and a low level of NOx 

reductions since this couid artificially favor a finding that NOx 

reductions are not beneficial; the two levels should be similar. 

8.5 Consistency with the SIP 

Any section 182(f) demonstration must include a showing that 

the exemption request uses assumptions that are consistent with 

requirements of the SIP and the CAA. It is possible that a 

petition could demonstrate that, under some circumstances, NOx 

reductions are not needed to attain the ozone standard. However, 

unless the State actually adopts those particular circumstances 

into its SIP, there is no assurance that the petition's analysis 

is valid. That is, if the assumptions contained in the 

petitioner's demonstration are not valid, the conclusions are 

similarly not valid and EPA would not approve the petition. The 

section 182(f) petition process should not undermine the State's 
P.32. 

28 

implementation plan. The petition should reflect measures 

consistent with mandatory CAA requirements, federally-approved 

SIP requirements, and recent SIP revisions adopted by the state 

and submitted to EPA for approval. The EPA encourages 

petitioners to coordinate•these analyses with the appropriate 

State(s) as they are being developed. 

8.6 New Source Review 

The section 182(f) exemption provisions center on the effect 

on ozone concentrations due to NOx emission reductions. With 

respect to RACT, which involves emissions reductions from 

existing sources, this is a perfect fit. In the case of new or 

modified sources, however, other factors should be considered. 

Even after the application of on-site controls appropriate for a 

major new or modified source, the source will, considered alone, 

result in major increases in NOx emissions. However, the NSR 

offset provisions would require the new source to obtain emission 

reductions from other sources so as offset any emissions increase 

associated with the new source. 

To take into account the full impact of the NSR program, the 

term "NOx reductions" must be carefully interpreted. When 

considering the air quality impacts in chapters 3-6 of this 

document "with NOx reductions" or with "substantial NOx 

reductions," the analysis should reflect a zero emissions 

increase from stationary sources after November 15, 1992 due to 

the NSR offset requirement; when considering the "without" NOx 

reductions scenarios, the analysis should include NOx emission 

increases after November 15, 1992 due to new or modified 

stationary sources of NOx, many of which would be subject to the 

best available control technology requirement through the 

prevention of significant deterioration program, but not to 

offsets.