Office of Transportation EPA420-B-04-012
and Air Quality July 2004
Companion Guidance for the
July 1, 2004, Final Transportation
Conformity Rule
Conformity Implementation in
Multi-Jurisdictional
Nonattainment and
Maintenance Areas for
Existing and New Air Quality
Standards
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EPA420-B-04-012
July 2004
July 1,
Conformity
Conformity Implementation in Multi-Jurisdictional
Nonattainment and Maintenance for
Existing and New Air Quality
Transportation and Regional Programs Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
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[signed by Suzanne Rudzinski on July 21, 2004]
MEMORANDUM:
From: Suzanne Rudzinski, Director
Transportation and Regional Programs Division
Office of Transportation and Air Quality
To: EPA Regional Air Directors, Regions I - X
Subject: Companion Guidance for the July 1, 2004, Final Transportation Conformity Rule:
Conformity Implementation in Multi-jurisdictional Nonattainment and Maintenance
Areas for Existing and New Air Quality Standards
Part 1: Introduction
1. Q. What is the purpose of this guidance?
A. The Environmental Protection Agency (EPA) published a final transportation
conformity rule for the new air quality standards on July 1, 2004 (69 FR 40004)1. The
final rule describes in general terms how conformity will apply to new nonattainment and
maintenance areas under the 8-hour ozone and PM2 5 standards, and how nonattainment
areas for the 8-hour ozone standard will use existing adequate or approved motor vehicle
emissions budgets ("budgets") in state implementation plans (SIPs) prepared for the 1-
hour ozone standard. The transportation conformity rule (40 CFR part 93) outlines the
procedures for determining whether federally funded or approved highway and transit
projects are consistent with ("conform" to) state air quality goals.
Both EPA and the U.S. Department of Transportation (DOT) agree it is necessary to
provide additional guidance for conformity implementation to accompany the final rule.
EPA is issuing this guidance to clarify how conformity determinations and the regional
1 This final rule was signed on June 14, 2004, and was available as of that date, before the
effective date of the 8-hour ozone designations. However, EPA uses the Federal Register
publication date when referring to a rule, so that readers know in which Federal Register issue to
find it.
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emissions analyses that support them are completed in existing and new nonattainment and
maintenance areas, particularly those where multiple agencies or states are involved.
This guidance covers questions such as:
> What geographic area is covered by the conformity determination and regional
emissions analysis?
> How can the regional emissions analysis be implemented?
> Who does what to develop the regional emissions analysis?
> What regional emissions test or tests apply for 8-hour ozone nonattainment areas
with 1-hour ozone SIP budgets?
This guidance covers both existing nonattainment and maintenance areas as well as areas
that are designated nonattainment under the new standards, and highlights opportunities
for flexibility wherever possible. It provides examples and interpretations for generic
scenarios that are present in the field and that are expected to occur under the new
standards. It expands on the July 1, 2004, final rule by including additional detail,
examples, and pictorial representations. However, there may be other cases in the field
that this guidance does not address. In the event an area's circumstances are not covered
in this guidance, EPA, together with DOT, will work with implementers on a case-by-case
basis.
This guidance also stresses the importance of the interagency consultation in the
conformity process. Given the fact that no two areas that implement conformity are
exactly alike, the interagency consultation process can be used to make the best choices
for an area's circumstances, where the rule provides flexibility. The interagency
consultation provision of the conformity rule, §93.105, requires that general processes be
established for, and specific decisions be made through, interagency consultation.
DOT, our federal partner in developing and implementing the conformity rule, assisted in
the development of this guidance and concurred on its content.
2. Q. Who can answer questions related to this guidance?
A. For specific questions about circumstances in particular nonattainment or maintenance
areas, the EPA Regional Offices, the FHWA Division Offices, and the FTA Regional
Offices are the first point of contact. A list of EPA Regional conformity staff can be found
on the web at: http://www.epa.gov/otaq/transp/conform/contacts.htm .
General questions about this guidance can be directed to Laura Berry, a member of my
staff at EPA's Office of Transportation and Air Quality, via her email address:
berry.laura@epa.gov or phone number: 734-214-4858.
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3. Q. Does this guidance create new conformity requirements?
A. No. This guidance is based on conformity implementation precedent to date and the
July 1, 2004, final rule. This document provides guidance to EPA Regional Offices,
FHWA Divisional Offices, FTA Regional Offices, state and local agencies, and the general
public on how EPA intends to exercise its discretion in implementing the statutory and
regulatory provisions for determining conformity in multi-jurisdictional areas. The
guidance is designed to clarify and transmit national policy on these issues. The statutory
provisions and EPA regulations described in this document contain legally binding
requirements. This document does not substitute for those provisions or regulations, nor
is it a regulation itself. Thus, it does not impose legally binding requirements on EPA,
states, or the regulated community, and may not apply to a particular situation based upon
the circumstances.
This guidance is based on conformity precedent and interpretations made to date. EPA is
issuing this guidance so that the precedents are gathered in one place as a reference for
conformity implementers. EPA retains the discretion to adopt approaches on a case-by-
case basis that may differ from this guidance, but still comply with the statute and
conformity regulations. Any decisions regarding a particular conformity determination
will be made based on the statute and regulations. This guidance is a living document and
may be revised periodically without public notice.
4. Q. What do we mean by multi-jurisdictional nonattainment and maintenance areas?
A. To answer this question, first it is useful to describe a conformity determination in the
case where there is a single jurisdiction responsible for transportation planning, and a
single jurisdiction responsible for air quality planning. In the simplest case, a
nonattainment or maintenance area is located entirely within one state, and the boundary
of the nonattainment/maintenance area is exactly the same as the metropolitan planning
organization (MPO) boundary, as in Figure 1 below.
Area boundary =
MPO jurisdiction
Figure 1: A Nonattainment or Maintenance Area With One MPO
in a Single State
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The MPO is the agency that is responsible for preparing metropolitan transportation plans
("plans") and transportation improvement programs (TIPs) and demonstrating that plans
and TIPs conform before they are adopted. An MPO is established for each metropolitan
area that has an urbanized population of 50,000 or more according to Section 134 of Title
23, United States Code and Section 5303 of Title 49, United States Code. Section 93.101
of the conformity rule includes the following definition of an MPO:
"that organization designated as being responsible, together with the state,
for conducting the continuing, cooperative, and comprehensive planning
process under 23 U.S.C. 134 and 49 U.S.C. 5303. It is the forum for
cooperative transportation decision-making."
In most cases, a conformity determination for a transportation plan, TIP, or project not
from a plan or TIP includes a regional emissions analysis in which emissions from the
planned transportation system are estimated according to §93.122 of the conformity rule.
In the case where an MPO's boundaries are the same as the nonattainment (or
maintenance) area's boundaries, the MPO is responsible for the regional emission analysis
in the entire area.
However, the boundaries of an MPO do not always correspond to the nonattainment or
maintenance area boundary, nor does a nonattainment or maintenance area always contain
one single MPO. Furthermore, a nonattainment or maintenance area boundary may
encompass portions of more than one state. The conformity rule does not dictate how
MPO planning boundaries are established; MPOs are established according to Titles 23
and 49 of the U.S. Code (as cited above) and DOT's metropolitan planning regulations.
Therefore, there may be more than one MPO responsible for transportation planning, and
thus conformity determinations, in a nonattainment or maintenance area, as in Figure 2
below.
= Area boundary
Figure 2: A Nonattainment or Maintenance Area with Two MPOs,
in a Single State
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Or, there may be some portion of the nonattainment or maintenance area that is not
included in an MPO's jurisdiction, also known as a "donut area" under the conformity
rules. According to §93.101 of the conformity rule:
"Donut areas are geographic areas outside a metropolitan planning area
boundary, but inside the boundary of a nonattainment or maintenance area
that contains any part of a metropolitan area(s). These areas are not
isolated rural nonattainment and maintenance areas."
Though the word "donut" implies that the boundary of the MPO would be entirely within
the nonattainment or maintenance area boundary to form two concentric circles, a
nonattainment or maintenance area's donut area may more typically resemble that in
Figure 3 below.
= Area boundary
Figure 3: A Nonattainment or Maintenance Area With a "Donut" Area
in a Single State
There are also cases where a nonattainment or maintenance area's boundary includes parts
of more than one state, as in Figure 4 below. One MPO may cover the entire multi-state
nonattainment or maintenance area, or MPOs may be established for each state's portion
of the area. In these situations, states may submit SIPs with identical budgets for the
entire nonattainment or maintenance area, or may submit SIPs with budgets that cover
only their state's portion of the area.
= Area boundary
^ = State boundaries
Figure 4: A Multi-State Nonattainment or Maintenance Area
(Area Could Have One or More MPOs)
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Finally, there are some MPOs in the country which are responsible for transportation
planning in more than one nonattainment area. This guidance does in general apply to
such MPOs. The November 24, 1993, conformity rule addresses the case where an MPO
is responsible for more than one nonattainment area, which continues to apply:
"If a metropolitan planning area includes more than one nonattainment
area, a conformity determination must be made for each nonattainment
area. Emissions budgets established in the SIP(s) for the included
nonattainment areas may not be combined or reallocated. Build/no-build
tests must be applied separately in each nonattainment area" (58 FR
62208).
Whether a nonattainment or maintenance area contains more than one MPO, a donut, or is
located within more than one state, the conformity process includes flexibility to
accommodate many differences in state and local agency roles and planning processes
across the country.
5. Q. How is this guidance organized?
A. The remaining parts of this guidance cover how conformity determinations and
regional emissions analyses that support them are done in nonattainment and maintenance
areas ("areas"), in the following circumstances:
• Part 2 covers conformity determinations and regional emissions analyses before an
area has SIP budgets for conformity. Part 2 applies to all nonattainment areas
where transportation conformity is required for existing and new air quality
standards, except 8-hour ozone nonattainment areas with adequate or approved
SIP budgets for the 1-hour ozone standard ("1-hour budgets");
Part 3 covers conformity determinations and regional emissions analyses after SIP
budgets are adequate or approved for the applicable pollutant and standard, and
applies to all existing and newly designated areas where transportation conformity
is required; and
• Part 4 covers conformity determinations and regional emissions analyses in 8-hour
ozone nonattainment areas that have 1-hour budgets, before such areas have
adequate or approved SIP budgets for the 8-hour ozone standard.
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Part 2: Conformity Determinations and Regional Emissions Analyses Before SIP Budgets
Are Adequate or Approved
1. Q. To what areas does this part of the guidance apply?
Part 2 of this guidance applies to areas designated nonattainment for a pollutant identified
in §93.102(b) of the conformity rule that do not yet have budgets for a standard that can
be used in conformity. Some examples of areas include:
all PM2 5 nonattainment areas before PM2 5 SIP budgets are found adequate or
approved;
• 8-hour ozone areas without adequate or approved 1-hour ozone SIP budgets,
before 8-hour ozone SIP budgets are found adequate or approved;
any 1-hour ozone, carbon monoxide, or PM10 nonattainment area that has no
adequate or approved budgets for that standard.
This part of the guidance does not cover:
• 8-hour ozone nonattainment areas without adequate or approved 8-hour budgets,
but with adequate or approved 1-hour budgets; please refer to Part 4 of this
guidance.
• maintenance areas, as these areas by definition have approved SIPs with budgets.2
2. Q. What tests are used for the regional emissions analysis before a nonattainment area has
motor vehicle emissions budget(s) that are adequate or approved?
A. Conformity applies for an air quality standard one year after the effective date of
EPA's nonattainment designation for that standard. EPA generally believes that
conformity will apply for a standard before an area is able to submit a SIP for that
standard containing budgets and those budgets are found adequate. Section 93.119 of the
conformity rule provides direction for how the regional emissions analysis must be done
before budgets are available. During this time period, these areas must use the interim
emissions test or tests: the build/no-build test, and/or the baseline year test.
2A maintenance area could have a special type of maintenance plan called a limited
maintenance plan. Please see the July 1, 2004, final rule at 69 FR 40063 and the June 30, 2003,
proposed rule at 68 FR 38983-4 for more information about conformity and limited maintenance
plans.
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3. Q. What geographic area must be examined in regional emissions analyses and conformity
determinations before a nonattainment area has adequate or approved budgets?
A. In this case, a conformity determination for a transportation plan, TIP, or project not
from a plan or TIP must be based on a regional emissions analysis that covers the entire
nonattainment area, to satisfy the statute and regulations. Section 93.122(a)(l) of the
conformity rule states:
"the regional emissions analysis required by §§93.118 and 93.119 for the
transportation plan, TIP, or project not from a conforming plan and TIP
must include all regionally significant projects expected in the
nonattainment or maintenance area."
There must be a regional emissions analysis for the entire nonattainment area, whether the
nonattainment area includes one MPO or more than one MPO, a donut area, portions of
more than one state, or any combination of these jurisdictions. Please see the next Q & A
for the options in creating a regional emissions analysis for an entire area.
For all nonattainment areas covered by Part 2 of the guidance, the MPO(s) must
coordinate their plan/TIP conformity determinations together, pursuant to §93.124(d) of
the final conformity rule. In the November 24, 1993, final rule, EPA stated:
"Where a nonattainment area includes multiple MPOs, the control strategy
SIP may either allocate emissions budgets to each metropolitan planning
area, or the MPOs must act together to make a conformity determination
for the nonattainment area."
Once DOT receives all plan/TIP conformity determinations for a given nonattainment
area, DOT will make its conformity determinations at the same time. In order for one
MPO to update or revise its plan and TIP, a DOT conformity determination for each plan
and TIP in that nonattainment area must be made at the same time, according to
§93.124(d)oftherule.
EPA believes that it is necessary for the conformity determinations and regional emissions
analysis to include the entire nonattainment area when there are no SIP budgets to ensure
that the requirements of Clean Air Act section 176(c)(l) are met. That is, before SIP
budgets are available, in order to determine that transportation activities will not cause a
new air quality violation, increase the frequency or severity of a violation, or delay timely
attainment or any other milestone in the nonattainment area, it is necessary to consider
emissions from the entire area in one regional emissions analysis, and for DOT to make all
plan/TIP conformity determinations at the same time.
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4. Q. How can multiple jurisdictions create a regional emissions analysis for the entire
nonattainment area?
A. The agencies involved in the conformity process in a nonattainment area where there is
more than one MPO or a donut area must use the consultation process required by
§93.105 of the conformity rule to decide how best to meet this requirement, regardless of
whether the area is within one state or is a multi-state area. The consultation process
would be used to decide which interim emissions tests apply and what analysis years are
used. MPOs must use the same tests and analysis years for the entire nonattainment area,
as described in the next Q&A.
Nonattainment Areas With More Than One MPO. In One or More States:
In nonattainment areas where there is more than one MPO, the MPOs can develop the
regional emissions analysis for the area in either one of two ways:
1. by separate modeling by each MPO that is combined into one regional analysis; or
2. by one modeling analysis for the entire nonattainment area.
If MPOs in the nonattainment area want to model their emissions separately, each MPO
would do a regional emissions analysis that includes the existing transportation system in
its part of the nonattainment area as well as all new projects in its plan and TIP. Each
MPO would show that the applicable interim emissions test(s) are met for each analysis
year under the regulations. These results would then be compiled in one regional
emissions analysis for the entire nonattainment area that would accompany each plan/TIP
conformity determination. The MPOs in the nonattainment area can work independently
to complete the regional emissions analysis for their own parts of the area, but a single
analysis would be compiled for the entire nonattainment area to satisfy conformity
requirements for an MPO's plan/TIP.
Alternatively, the regional emissions analysis could be completed by showing that the
emissions in each analysis year for the entire nonattainment area meet the applicable
interim emissions test(s). The MPOs in the area would work together to carry out a
regional emissions analysis for the entire nonattainment area that includes all of their plans
and TIPs. Again, these modeling results would be presented in one regional emissions
analysis for the entire nonattainment area that would accompany the conformity
determinations for new or revised plans/TIPs in the nonattainment area.
As an example, suppose there are multiple MPOs within a nonattainment area and they are
demonstrating conformity using the build/no-build test. If each MPO has its own travel
demand model and prefers to run its own analysis, the analysis must show either that each
MPO passes its own build/no-build test; or the "build" scenarios and the "no-build"
scenarios from each MPO must be aggregated, and the total "build" emissions from all
MPOs must be less than the total "no-build" emissions from all MPOs.
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Alternatively, the MPOs could initially create one regional emissions analysis for the entire
nonattainment area that meets the build/no-build test.
In either case, to make the demonstration required by the conformity rule, all MPOs must
use the same test and the same analysis years for the regional emissions analysis. MPOs in
one nonattainment area may want to coordinate their plan and TIP update cycles as well
as the length of their plans, as described in the following bullets.
> New or revised plans and TIPs, as well as significant changes to projects, could
require a new regional emissions analysis (see §§93.104 and 93.122(g) of the
conformity rule). Coordination of plan and TIP update cycles among MPOs in the
same nonattainment area may minimize the number of new regional emissions
analyses and conformity determinations that have to be completed.
> Different transportation plan lengths within one nonattainment area would require
additional analysis years, because according to §93.119(g), an analysis must be
performed for the last year of each plan. For example, if one MPO's plan ends in
2025 and another MPO's plan ends in 2030, both years would have to be analyzed
in the regional analysis for the entire nonattainment area. Coordination of plan
lengths may minimize the number of analysis years that have to be examined in any
one regional emissions analysis.
Nonattainment Areas With a Donut Area:
If there is only one MPO in the nonattainment area conducting conformity determinations,
the conformity rule requires the MPO to include the emissions estimated from the donut
area's existing and proposed transportation system in the regional emissions analysis for
metropolitan transportation plan and TIP conformity determinations. However, either the
MPO or the state transportation agency ("state DOT") could estimate emissions from the
donut area as decided through interagency consultation, as explained in Q&A 7 of this
part.
If there is more than one MPO as well as a donut area in a nonattainment area, the MPOs
must work together and with the state DOT as appropriate to create one regional
emissions analysis for the entire nonattainment area that would accompany each plan/TIP
conformity determination. The emissions estimated from the entire area must meet the
interim emissions test or tests, according to the requirements of §93.119. Again, the
consultation process would be used to coordinate the choice of tests and analysis years
when several agencies are completing emissions analyses, because the same tests and
analysis years must be used as noted above.
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5. Q. What decisions must be made in the interagency consultation process?
A. The agencies responsible for the conformity determination and regional emissions
analysis in a nonattainment area, which are the MPOs and possibly the state DOT(s) for
donut area in a nonattainment area, should use the interagency consultation process to
make certain decisions. Under the conformity rule, there are some aspects of conformity
that must be consistent across the nonattainment area, even when there are more than one
MPO and they each model their own portion separately, as described above. These
include:
timing of plan and TIP conformity determinations, so that DOT can make its
conformity determinations for all plans and TIPs in a nonattainment area at the
same time;
• how the regional emissions analysis is developed, i.e., whether emissions will be
modeled for each MPO's jurisdiction separately and summed together, or modeled
for the nonattainment area as a whole;
the interim emissions test the nonattainment area will meet, in the areas that must
meet only one test as required by §93.119 (e.g., PM25 areas or 8-hour ozone areas
that are classified as marginal or designated under Clean Air Act, part D, subpart 1
that do not have 1-hour budgets).
EPA believes that for consistency and in order to satisfy the conformity rule, the
same test must be used in all portions of the nonattainment area in areas that have
the choice of interim emissions tests. In other words, it would not be acceptable
for one MPO to use the build/no-build test and another MPO within the same
nonattainment area to use the baseline year test, because the rule requires that one
test be met for the entire nonattainment area, according to §§93.119 and
93.124(d);3
• the analysis years for the interim emissions test(s), as required by §93.119(g).
Again, EPA believes that analysis years must be consistent in all portions of the
nonattainment area, even if emissions are modeled for each MPO's jurisdiction
separately, otherwise they cannot be summed together to produce a complete
analysis to satisfy the test. Regional emissions analyses for all MPOs must cover
3In 8-hour and 1-hour ozone areas classified moderate or higher, serious CO, and
moderate CO areas with a design value greater than 12.7 ppm, both interim emissions tests must
be met under §93.119. Please read Section IV.D. of the preamble of the July 1, 2004, final rule
for further explanation.
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the same time period and thus need to include the last year of each transportation
plan.
As described in the above example, in a nonattainment area with two MPOs where
one MPO's transportation plan covers a 25-year period from 2005 to 2030, and
the other MPO's plan covers only a 20-year period from 2005 to 2025, the
regional emissions analysis for both MPOs must examine emissions in the years
2025 and 2030; and
• the emissions model used for the interim emissions test(s), in the case where there
is more than one emissions model version that could be used, per §93.111 of the
rule.
In addition, the MPO jurisdictions involved in the conformity determination(s) for the
nonattainment area should discuss the planning assumptions they will use in the regional
emissions analysis and the sources of that information. Section 93.105(c)(l)(i) of the rule
specifically requires that planning assumptions be discussed in the interagency consultation
process. Where feasible and appropriate, MPOs and where applicable, state DOTs should
use consistent planning assumptions for the regional emissions analysis in their
jurisdictions.
6. Q. In a nonattainment area that does not have SIP budgets for conformity, if one MPO in
the area can meet the requirements of §93.119 of the rule, but another MPO or a donut
area cannot, can the MPO that meets the requirements show that its plan and TIP conform
and proceed?
A. No. EPA believes that before budgets are adequate or approved, the whole
nonattainment area must conform to meet the Clean Air Act 176(c)(l) requirements.
These requirements are that transportation activities will not:
> cause a new air quality violation,
> increase the frequency or severity of a violation, or
> delay timely attainment or any other milestone in the area for an air quality
standard.
It is necessary to estimate emissions from the entire nonattainment area in all plan/TIP
conformity determinations and the supporting regional analysis because separate SIP
budgets are not yet available. For example, in Figure 2 repeated below, there are two
MPOs. If they choose to model their emissions separately and West MPO appears to pass
the applicable test(s) of §93.119 but East MPO does not, West MPO cannot proceed to
determine conformity alone. It cannot be known for sure that West MPO's transportation
plan and TIP would not cause a new violation, increase the frequency or severity of a
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violation, or delay timely attainment (or other milestone) in the area, because East MPO
cannot also pass the test. Thus, the nonattainment area in this example as a whole cannot
demonstrate that it will not cause or contribute to violations. To resolve this situation,
( (East MPO\ CZ) = Area boundary
I West MPO V ) ^^
Figure 2: A Nonattainment Area With Two MPOs
East and West MPOs would consult on what options are available for demonstrating
conformity, including the option of adding or modeling their emissions together to see if
they pass the applicable regional emissions test(s).
7. Q. Who is responsible for estimating emissions in a donut area of a nonattainment or
maintenance area?
A. In a nonattainment or maintenance area with a donut area, the lead agency for
developing the regional emissions analysis that applies to the donut area can be:
the MPO within the nonattainment area. In some cases, an adjacent MPO is better
suited to conduct such an analysis. An MPO could run an analysis for the donut
area's projects, or include the donut area's projects in the regional emissions
analysis supporting its plan and TIP. An MPO could also include the donut area's
projects in its plan and TIP, but this practice is not common;
the state DOT. In some cases, the state DOT may take the lead in conducting
regional emissions analysis for the donut area; or
• another local planning agency. In limited cases, another local planning agency in
the donut area (e.g., a county planning commission) may also be the lead agency
for the donut area.
Section 93.105(c)(3) of the conformity rule relies on the interagency consultation process
(including the MPO and state DOT) to determine how best to consider projects that are
planned for donut areas located outside the metropolitan area and within the
nonattainment or maintenance area in the conformity process. Section 93.105 also
requires that such procedures for demonstrating conformity of donut area projects be
included in an area's conformity SIP that is approved by EPA according to §51.390 of the
rule.
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Part 3: Conformity Determinations and Regional Emissions Analysis Once SIP Budgets
Are Adequate/Approved
General
1. Q. To what areas does this part of the guidance apply?
A. Part 3 applies to areas designated nonattainment for any pollutant identified in
§93.102(b) of the rule, once the area has adequate or approved budgets from a SIP
addressing a particular standard for a pollutant. This part of the guidance applies to:
• an 8-hour ozone nonattainment area once it has adequate or approved budgets for
the 8-hour standard, regardless of whether or not the area had 1-hour budgets;
a PM2 5 nonattainment area once it has adequate or approved PM2 5 SIP budgets;
any 1-hour ozone, carbon monoxide, or PM10 nonattainment area that has
adequate or approved budgets from a SIP addressing that standard; and
• maintenance areas, as these areas by definition have approved SIPs with budgets.4
2. Q. How do nonattainment and maintenance areas determine conformity for a given
standard once adequate or approved SIP budgets are available for that standard?
A. Clean Air Act section 176(c)(l) states that federal activities must conform to the SIP.
Once a SIP with budgets has been submitted and EPA finds the budgets adequate or
approves the SIP, the "budget test" using the new budgets must be used for conformity
determinations according to §§93.109 and 93.118 of the conformity rule. EPA's
adequacy finding or approval means that the SIP's budgets are an appropriate measure for
whether transportation activities conform due to many factors, including:
the budgets are identified and precisely quantified;
the budgets are consistent with the SIP's purpose of reasonable further progress,
attainment, or maintenance of an air quality standard; and
4A maintenance area could have a special type of maintenance plan called a limited
maintenance plan. Please see the July 1, 2004, final rule at 69 FR 40063 and the June 30, 2003,
proposed rule at 68 FR 38983-4 for more information about conformity and limited maintenance
plans.
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the budgets are consistent with and clearly related to the emissions inventory and
the control measures in the SIP.5
3. Q. What geographic areas might budgets from a SIP address, and how is
conformity generally determined in multi-jurisdictional areas with SIP budgets?
A. In a nonattainment or maintenance area located entirely within one state, the state air
agency may develop a SIP that establishes either:
a budget (or budgets) that applies to the entire nonattainment or maintenance area,
or
• a subarea budget (or budgets) for each MPO within the nonattainment or
maintenance area.
In a multi-state nonattainment or maintenance area, the state air agencies may decide to
establish SIPs in each state that contain either:
• identical budgets that apply to the entire nonattainment or maintenance area, or
• unique budgets that apply only to one state's portion of the nonattainment or
maintenance area.
State and local agencies can develop SIPs in many different ways. Section 93.124(d) of
the conformity rule acknowledges this fact and covers SIPs developed in areas where
there is more than one MPO:
"If a nonattainment area includes more than one MPO, the implementation
plan may establish motor vehicle emissions budgets for each MPO, or else
the MPOs must collectively make a conformity determination for the entire
area."
Once budgets have been found adequate or approved, the conformity determination(s) and
regional emissions analysis is done for the geographic area that is addressed by the
budgets in the SIP. This general principle applies in all situations, although there is
flexibility in how the regional emissions analysis is developed, and in coordinating
conformity determinations, when several MPOs are involved. The table on the next page
summarizes the general situations. The questions and answers that follow provide further
detail on the different circumstances that can occur.
5 There are other criteria that SIP budgets must meet for EPA to find them adequate; for
the full list of adequacy criteria, see §93.118(e) of the conformity rule.
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Summary Table: How SIPs Affect Geographic Areas Considered in Conformity
For a nonattainment
or maintenance area
located:
within one state
within one state
in multiple states
in multiple states
where SIP budgets
are established for:
the entire area
subareas
the entire area
each state
the geographic area
considered in
regional analysis is:
the entire area*
each subarea
the entire area*
each state
the geographic area
considered in final
conformity
determination(s) is:
the entire area**
each subarea
the entire area**
each state
* There is flexibility in how the regional emissions analysis is done when there is more
than one MPO. See below for more details.
** There may be more than one plan/TIP conformity determination in a nonattainment or
maintenance area because there may be more than one MPO making determinations for
separate plans and TIPs. There is flexibility in how these conformity determinations are
coordinated. See below for more details.
Nonattainment or Maintenance Areas Located in One State. Where Budgets Are Established for
the Entire Area
4. Q. How is conformity done when budgets are established for an entire nonattainment or
maintenance area that is within one state?
One MPO. In the simplest case, an area is located entirely within one state and the MPO
boundary is the same as the nonattainment/maintenance area boundary (Figure 1). In
Figure 1, the nonattainment or maintenance area boundary, the MPO, and the SIP budgets
all address the same geographic area. In this case, because the SIP establishes budgets for
the entire area, the MPO will use those budgets in the regional emissions analysis done for
the MPO's plan/TIP conformity determination for the entire nonattainment or maintenance
area.
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Area boundary =
MPO jurisdiction
Figure 1: A Nonattainment or Maintenance Area With One MPO
in a Single State
More than One MPO. When budgets are established for the nonattainment or
maintenance area as a whole, and there is more than one MPO, the MPOs would complete
their respective plan/IIP conformity determinations and submit them to DOT, as
explained in Part 2, Q & A 3. Once all determinations for a given area are received, DOT
would make its conformity determinations at the same time. The MPOs must collectively
develop a regional emissions analysis for the entire area that meets the requirements of
§93.118 of the rule that would accompany all plan/TIP conformity determinations. For
example, all MPOs would have to use the same analysis years for the regional emissions
analysis. Each MPO would show conformity of its plan and TIP using the regional
emissions analysis done for the entire area. See Part 2, Q & A 4 for more information.
The MPOs can develop the regional analysis for the area in either one of two ways:
1. Each MPO can model emissions for its geographic part of the nonattainment or
maintenance area separately. For each analysis year, the emissions estimated by
each MPO would be summed together and compared to the area's applicable
budgets. EPA believes that the MPOs must all use the same analysis years when
completing the budget test in accordance with §93.118.
2. The MPOs could also work together to model the entire nonattainment or
maintenance area as a whole at the same time. In this case, §93.118 of the
conformity rule would be met if estimated emissions in each analysis year are less
than or equal to the area's applicable budgets.
MPOs in one nonattainment or maintenance area may want to coordinate their plan and
TIP update cycles as well as the length of their plans.
> New or revised plans and TIPs, as well as significant changes to projects, could
require a new regional emissions analysis (see §§93.104 and 93.122(g) of the
conformity rule). Coordination of plan and TIP update cycles among MPOs in the
same nonattainment or maintenance area may minimize the number of new regional
emissions analyses and conformity determinations that have to be completed.
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> Different transportation plan lengths within one nonattainment or maintenance area
would require additional analysis years, because according to §93.118(d), an
analysis must be performed for the last year of each plan. For example, if one
MPO's plan ends in 2025 and another MPO's plan ends in 2030, both years would
have to be analyzed in the regional analysis for the entire nonattainment area.
Coordination of plan lengths may minimize the number of analysis years that have
to be examined in any one regional emissions analysis.
One or More MPOs and a Donut Area: If there is only one MPO in the nonattainment
or maintenance area conducting conformity determinations, the regulations require the
MPO to include the emissions estimated from the donut area's existing and proposed
transportation system in the regional emissions analysis for the metropolitan transportation
plan and TIP conformity determinations. However, either the MPO or the state
transportation agency ("state DOT") could estimate emissions from the donut area as
decided through interagency consultation, as explained in Part 2, Q&A 7.
If there is more than one MPO as well as a donut area in a nonattainment or maintenance
area, the MPOs must work together and with the state DOT or other donut area agency as
appropriate to create one regional emissions analysis for the entire area that would
accompany all plan/TIP conformity determinations. The emissions estimated from the
entire area must be less than or equal to the budget(s) established for the entire area,
according to the requirements of §93.118. The consultation process would be used to
coordinate the analysis years when several agencies are completing emissions analyses,
because the same analysis years must be used.
Nonattainment or Maintenance Areas Within One State. Where the SIP Establishes Subarea
Budgets
5. Q. How do nonattainment or maintenance areas with more than one MPO in a single state
determine conformity once SIP budgets are adequate or approved, and the SIP establishes
subarea budgets for each MPO?
A. When subarea budgets are created for each MPO, the sum of the subarea budgets
equals the total amount of emissions the area can have from the transportation sector and
still make progress toward, attain, or maintain the standard. Therefore, if each MPO
meets its subarea budgets for a pollutant and standard in accordance with the requirements
of §93.118, then the entire area meets the total SIP's purpose for that pollutant and
standard. As EPA noted in the January 11, 1993, conformity proposal,
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"subarea budgets provide additional assurance that through future
conformity determinations transportation plans and TIPs will produce
emission patterns that will achieve attainment" (58 FR 3780).
When the SIP for an area establishes subarea budgets for conformity purposes, these
subarea budgets must be met for plans and TIPs in the area to conform, as required in
§93.124(c) and (d) of the conformity rule. Section 93.124(c) states:
"If the applicable implementation plan (or implementation plan submission)
estimates future emissions by geographic subarea of the nonattainment
area, the MPO and DOT are not required to consider this to establish
subarea budgets, unless the applicable implementation plan (or
implementation plan submission) explicitly indicates an intent to create such
subarea budgets for the purposes of conformity."
The MPOs can make independent conformity determinations for their plans and TIPs as
long as all of the other subareas in the nonattainment or maintenance area have
conforming transportation plans and TIPs in place at the time of each MPO's and DOT's
plan/TIP determination. In other words, under the conformity rule in order for an MPO or
DOT to determine conformity for its subarea, the rest of the area must also be in
conformity. The preamble to the November 24, 1993, conformity rule explains this as
follows:
"The SIP may specify emissions budgets for subareas of the region,
provided that the SIP includes a demonstration that the subregional
emissions budget, when combined with all other portions of the emissions
inventory, will result in attainment and/or maintenance of the standard.
The conformity determination must demonstrate consistency with each
subregional emissions budget in the SIP" (58 FR 62196).
Thus, when any subarea demonstrates conformity, it must be demonstrated that all
subareas have conforming plans and TIPs. For example, suppose the subarea budgets in a
SIP have just been found adequate, and one of the MPOs in the area needs to update its
TIP. That MPO can make a conformity determination using its subarea budgets for the
first time without waiting for the other MPOs in the area, as long as the other MPOs have
conforming plans and TIPs in place, even if these plans and TIPs were previously found to
conform using the interim emissions test(s).
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Once an area has adequate or approved subarea budgets, if conformity lapses6 for one
subarea, the other subarea(s) can continue to implement projects in their currently
conforming plans and TIPs, but they cannot make new plan and TIP conformity
determinations until the lapse is resolved and conformity is determined in the lapsed
subarea. In other words, if the conformity status of one subarea lapses, the existing plans
and TIPs in other subareas continue to be valid and consequences would not apply to any
other subareas unless the lapse is not resolved by the time other subareas need to make
new conformity determinations.
6. Q. Why can't an MPO that has its own subarea budgets determine conformity of its
transportation plan and TIP when another MPO in the same area is in a lapse?
A. Section 176(c) of the Clean Air Act clearly states that conformity applies in
nonattainment and maintenance areas, rather than individual metropolitan planning areas.
Section 176(c) also states that the federal government and MPOs cannot approve
transportation activities unless they conform to the SIP and its budgets. Therefore, in a
nonattainment or maintenance area with more than one MPO, all MPOs must conform
even if the SIP has established subarea budgets.
If an individual MPO lapses, it has not demonstrated that it can conform to its subarea
budgets. Therefore, there is no way for the other MPOs in the same area to know
whether their transportation plans and TIPs are consistent with the SIP as a whole. Using
Figure 2 again as an example (found in Part 2, Q & A 6), if East MPO is in a conformity
lapse, it cannot be assured that West MPO's transportation activities still meet the purpose
of the SIP even if West MPO meets its subarea budgets. That is, it is unknown whether
the total amount of emissions in the area from the planned transportation sector would still
meet the SIP's purpose of progress toward, attainment of, or maintenance of the standard,
because East MPO cannot meet its subarea budgets. When one subarea lapses, there is no
way for the other MPO to show that their planned transportation activities would conform
to the SIP for the whole area until the lapse is resolved.
6A lapse is defined in §93.101 of the rule: "Lapse means that the conformity determination
for a transportation plan or TIP has expired, and thus there is no currently conforming
transportation plan or TIP." A lapse occurs when conformity of a plan or TIP is not determined
according to the frequency requirements of §93.104 of the conformity rule.
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7. Q. How do I know whether the SIP establishes subarea budgets? Are county-by-county
emissions projections subarea budgets?
A. The SIP must specifically state that it creates subarea budgets. County-by-county
emissions projections in a SIP inventory are not subarea budgets unless they are
specifically labeled as such. Section 93.124(c) of the conformity rule states,
"If the applicable implementation plan (or implementation plan submission)
estimates future emissions by geographic subarea of the nonattainment area, the
MPO and DOT are not required to consider this to establish subarea budgets,
unless the applicable implementation plan (or implementation plan submission)
explicitly indicates an intent to create such subarea budgets for the purposes of
conformity."
If county level emissions projections are included in a SIP but not explicitly defined as
subarea budgets for the purposes of conformity, the SIP is considered to have budgets for
the entire area and MPOs must work together to have plan/TIP conformity determinations
for the entire nonattainment or maintenance area approved by DOT at the same time, as
described above in Q & A 4 of this part and Part 2, Q & A 4. According to §93.124(d),
"If a nonattainment area includes more than one MPO, the implementation plan
may establish motor vehicle emissions budgets for each MPO, or else the MPOs
must collectively make a conformity determination for the entire nonattainment
area."
If MPOs within one nonattainment or maintenance area would prefer to have subarea
budgets, they should communicate their preference to the state and local air agencies
within the interagency consultation process during the development of the SIP. Section
93.105(c) of the conformity rule requires interagency consultation on the development of
SIPs, as well as transportation plans, TIPs, and conformity determinations.
Multi-State Nonattainment/Maintenance Areas:
8. Q. How do multi-state nonattainment and maintenance areas determine conformity if each
state submits a SIP that contains the same budgets for the entire multi-state area?
A. If these multi-state areas have SIPs that contain budgets for the multi-state area as a
whole, one regional emissions analysis would be completed for the entire area using the
budget test, according to the requirements in §93.118 of the conformity rule. This
regional analysis would accompany all plan/TIP conformity determinations in the area that
would be submitted to DOT. Once all determinations for a given area are received, DOT
would make its conformity determinations at the same time. The MPOs must collectively
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develop a regional emissions analysis for the entire area that meets the requirements of
§93.118 that would accompany all plan/TIP conformity determinations. For example, all
MPOs would have to use the same analysis years for the regional emissions analysis. Each
MPO would show conformity of its plan and TIP using the regional emissions analysis
done for the entire area.
For example, in Figure 4, repeated below, suppose there is one budget for the multi-state
area, but each state has its own MPO. In this case, one regional emissions analysis would
be made for the entire oval and the conformity determinations for each MPO's plans and
TIPs within the area would be based on this regional emissions analysis. DOT would wait
to make its conformity determinations for the plans and TIPs in the area until it receives all
of them. This answer is similar to single state areas with SIP budgets that cover the entire
nonattainment or maintenance area. See Q & A 4 of the part, and Part 2, Q & A 4, for
further information.
= Area boundary
= State boundaries
J
Figure 4: A Multi- State Nonattainment or Maintenance Area
9. Q. When would it be likely for state air agencies in a multi-state nonattainment or
maintenace area to submit SIPs with budgets that apply to the entire area?
A. This option would most likely be chosen in areas where there is one MPO responsible
for the transportation planning of the entire multi-state nonattainment or maintenance
area. However, the option is available to any multi-state nonattainment or maintenance
area. In areas with more than one MPO, additional coordination would be necessary for
plan/TIP conformity determinations and the regional emissions analysis because they
would need to cover the entire nonattainment or maintenance area pursuant to
§§93.124(d)and93.118.
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10. Q. How is conformity determined for multi-state nonattainment or maintenance areas
when each state submits a SIP that contains budgets only for its state's portion of the
area?
A. States in a multi-state area have the option of submitting SIPs with budgets for just
their own portion of the area that, when taken together, meet the applicable Clean Air Act
requirement. Where states have done so and EPA has found such budgets adequate, the
MPO or MPOs in each state with such budgets can determine conformity completely
independently of the other states. EPA concluded that these states can operate
independently for conformity because the Clean Air Act refers to conformity to a SIP.
Each state's SIP in these cases includes inventories, control measures and programs, and
budgets that apply to only that state's portion of the nonattainment or maintenance area.
States that have SIPs with adequate or approved budgets for only their own portions of a
multi-state area are distinct from MPOs in a nonattainment or maintenance area that have
subarea budgets within the same SIP, and also distinct from states that have SIP budgets
that apply to an entire multi-state nonattainment or maintenance area. Where states have
their own SIP budgets, if a conformity lapse is occurring in one state's portion of an area,
the MPO(s) in the other state(s) in the nonattainment or maintenance area can continue to
make conformity determinations for new or revised transportation plans and TIPs because
they continue to show conformity to their SIP's budgets.
Using Figure 4 above as an example, suppose States A, B, and C each have SIPs with
adequate or approved budgets that apply only to their own state's portion of the area. If
State A lapses, States B and C can continue to make new conformity determinations. In
contrast, as described previously:
• MPOs that have subarea budgets within one SIP are determining conformity to the
same SIP, therefore when one makes a conformity determination, all other
subareas must be in conformity as well in order to show conformity to the SIP; and
• multi-state areas that have budgets for the entire nonattainment or maintenance
area are also determining conformity to the same SIP, therefore, there must be one
regional emissions analysis for this area and conformity determinations for plans
and TIPs in the area must be made at the same time as described in Q & A 8 of this
part.
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Part 4: Conformity Determinations and Regional Emissions Analyses in 8-Hour Ozone
Nonattainment Areas With Adequate or Approved 1-Hour SIP Budgets
Background
1. Q. To what areas does this part of the guidance apply?
A. This part of the guidance clarifies the implementation of conformity in nonattainment
areas for the 8-hour ozone standard that were nonattainment or maintenance areas for the
1-hour ozone standard and have adequate or approved SIP budgets that address the 1-
hour ozone standard. However, this part of the guidance applies only until these areas
have 8-hour budgets that they can use for conformity. Once an area submits an 8-hour
SIP with budgets and EPA finds the budgets adequate or approves the 8-hour SIP that
contains budgets, that area must use the 8-hour budgets for conformity according to
§93.109(e)(l) of the conformity rule. At that point, Part 3 of this guidance would apply,
and Part 4 would no longer be relevant to that area. In Part 4 of the guidance, the terms:
• 8-hour area means a nonattainment area for the 8-hour ozone standard, and
1-hour area means a nonattainment or maintenance area for the 1-hour standard.
The July 2004 final rule allows 8-hour areas with 1-hour SIPs to implement conformity in
the same way as they have been under the 1-hour standard, to the extent possible. In
other words, the 8-hour areas with 1-hour budgets will continue to use them wherever
possible. This part of the guidance is intended to assist in understanding how that general
principle applies in various circumstances.
2. Q. How is Part 4 organized?
A. Part 4 is organized under headings for background, boundary scenario, and general
implementation topics, as follows:
Background (questions 1 - 8);
Scenario 1 (questions 9-11);
Scenario 2 (questions 12 - 13);
Scenario 3 (questions 14 - 18);
Scenario 4 (questions 19 - 22); and
General Implementation of the Final Rule (questions 23 - 25).
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3. Q. What are the ways an 8-hour area could be related to a 1-hour area that has adequate
or approved 1-hour budgets?
A. As described in the July 1, 2004, conformity rule, there are four generic scenarios for
how 8-hour area boundaries relate to 1-hour area boundaries, and the conformity rule is
written with these four scenarios in mind.
To determine which scenario appropriately describes an area, it is necessary to consider
the boundary of the entire 8-hour area. For example, in a multi-state 8-hour area, the 8-
hour boundary refers to the entire multi-state area, rather than each state's individual
portion. Figure 5 illustrates the four generic boundary scenarios.
Scenario 1 Scenario 2 Scenario 3 Scenario 4
= 1-hour area boundary
^"^ = 8-hour area boundary
Figure 5: The Four Boundary Scenarios
Scenario 1: the 8-hour area boundary and the 1-hour area boundary are identical.
Scenario 2: the 8-hour area boundary is smaller than the 1-hour area boundary.
Scenario 3: the 8-hour area boundary is larger than the 1-hour area boundary.
Scenario 4: the 8-hour area boundary partially overlaps the 1-hour area boundary.
4. Q. Do 8-hour areas with 1-hour budgets have to use the 1-hour budgets for conformity
determinations under the 8-hour standard?
A. Yes, in most cases. As required in §93.109(e)(2) of the July 2004 final rule, the 1-
hour budgets must be used for 8-hour conformity determinations, unless the interim
emissions test(s) is more appropriate as decided through the interagency consultation
process (see §93.109(e)(2)(v)). Section 176(c) of the Clean Air Act states that
transportation activities must not cause new violations, increase the frequency or severity
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of existing violations, or delay timely attainment. Using 1-hour budgets where available
and appropriate ensures that air quality progress to date is maintained, air quality will not
be worsened and attainment of the 8-hour standard will not be delayed because of
emissions increases prior to the development of SIPs with 8-hour budgets. Once EPA
finds a budget adequate or approves the SIP that includes it, the budget test provides the
best means to determine whether transportation plans and TIPs meet Clean Air Act
conformity requirements. EPA believes this principle applies with respect to the 1-hour
budgets in 8-hour nonattainment areas as well: in most cases, the 1-hour budgets are the
best test for determining conformity to the 8-hour standard before 8-hour budgets are
available because the 1-hour budgets have led to current air quality improvements.
5. Q. Are there circumstances under which an 8-hour area with 1-hour budgets would not
use them?
As described in the preamble to the July 2004 final rule (69 FR 40025), though EPA
anticipates that exceptions to the use of the 1-hour budgets will be infrequent, there are
some cases where using the interim emissions test(s) may be more appropriate to meet
Clean Air Act requirements. EPA expects such limited cases to be supported and
documented in the 8-hour conformity determination for a given area. EPA notes that an
adequate or approved 1-hour SIP budget cannot be considered inappropriate simply
because it is difficult to pass for 8-hour conformity purposes. In addition, as noted below
and consistent with past conformity precedent, 1-hour budgets cannot be discarded simply
because they are based on older planning assumptions or emissions models, unless through
interagency consultation it is determined that a different emissions test(s) is more
appropriate to ensure that air quality is not worsened for all 8-hour areas and that
reductions are achieved in certain ozone areas.
The most likely example of when the 1-hour budgets may not be the most appropriate test
is where a 1-hour budget is not currently used in conformity determinations for the 1-hour
standard, and thus is currently not relied upon to measure whether transportation activities
are consistent with Clean Air Act requirements. Such a case would happen when the 1-
hour budget year is no longer in the timeframe of the transportation plan and there is no
requirement to meet the budget test prior to the year in which the next 1-hour budget is
established, (e.g., the SIP established a budget for the 1-hour attainment year, but that
attainment year has passed and budgets for future years are available). For example,
suppose a 1-hour maintenance area attained in 1999 and has a maintenance plan with
budgets for 2009. If the area has an 8-hour attainment date of 2007, for an 8-hour
conformity determination it would have to compare emissions in 2007 to the budgets from
the most recent prior year, which would be the 1-hour attainment budgets for the year
1999. In this case, the budgets are not currently in use for the 1-hour standard, and it may
be more appropriate for an area to use the 2002 baseline year test for the 2007 analysis
year in the 8-hour conformity determination, since the 2002 baseline could be lower and
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therefore more protective than the 1999 budgets. However, the maintenance area would
use its 2009 budgets in the 1-hour maintenance plan to show 8-hour conformity for 2009
and all future analysis years.
However, if the budget year has passed but the budgets have continued to be used for
conformity for the 1-hour standard, they would likely continue to apply for 8-hour
conformity. For example, suppose a severe 1-hour nonattainment area has budgets only
for its 2005 attainment year. Once the 8-hour standard applies and before the area has
adequate or approved 8-hour budgets, the area would likely continue to use its 1-hour
attainment budgets for all analysis years for 8-hour conformity determinations, even after
the year 2005 is no longer in the timeframe of the transportation plan. Note, although the
2005 budgets would be used after 2005 is no longer in the timeframe of the plan, 2005
would no longer be a required analysis year.
Another example of when the interim emissions test(s) would be more appropriate than
existing adequate or approved 1-hour budgets would be in certain Scenario 4 areas where
it is impossible to determine which portion of a 1-hour budget covers an 8-hour
nonattainment area. In this case, applying the budget test with 1-hour budgets is not
feasible, and consequently, only the interim emissions test(s) are available for such unique
areas.
As described in Section V. of the July 1, 2004, preamble (69 FR 40019 - 21), when a SIP
budget is not established a moderate or above ozone area would need to pass both interim
emissions tests. Areas classified as marginal or designated under Clean Air Act, Part D,
subpart 1 can choose between the two tests when no budgets apply. However, in these
cases where a 1-hour budget is available but the area demonstrates it is not the most
appropriate test, EPA believes that the no-greater-than-2002 baseline year test would
most likely be used. EPA believes it is extremely unlikely that the build/no-build test alone
would ever be a more appropriate test than the budget test with existing 1-hour budgets
that are currently used for conformity purposes. Please refer to the July 1, 2004, rule
preamble on this point (69 FR 40025).
Areas must use the consultation process to decide whether the applicable interim
emissions tests are more appropriate to meet Clean Air Act requirements than the budgets
in each 1-hour SIP. As described in the first example above, there may be cases where an
area has multiple 1-hour SIPs, some of which have appropriate budgets while others do
not. In areas where only one interim emissions test may be selected, the rule requires that
areas must also justify selection of the specific test chosen as being more appropriate for
meeting Clean Air Act requirements than the available 1-hour budgets. This decision
should be discussed with all interagency consultation parties and documented in the
conformity determination for the 8-hour standard. (Please refer to the preamble of the
July 2004 final conformity rule at 69 FR 40025 for more information.)
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6. Q. In 8-hour areas with 1-hour subarea budgets, do all subareas have to use the 1-hour
budgets for 8-hour conformity determinations? Likewise, in multi-state 8-hour areas
where each state has separate 1-hour budgets, do all states have to use their 1-hour
budgets for 8-hour conformity?
A. In general, each subarea or state can determine conformity independently as long as
everyone is using 1-hour budgets to determine conformity. However, in the unlikely
event that one subarea or state determines that its 1-hour budgets are inappropriate, other
subareas or state budgets may also be inappropriate. See Part 3 of this guidance for
further rationale for conformity determinations using subarea and multi-state SIP budgets.
When any subarea or state believes that is inappropriate to use its budgets, all subareas or
states would consult to determine the impact on future conformity determinations. EPA
believes that where one subarea or state determines its budgets are inappropriate, it is
likely that the other budgets are also inappropriate because they are collectively intended
to address the same Clean Air Act purpose.
EPA notes, however, that in a Scenario 4 area, the circumstances are different and more
complex. In these areas, the 8-hour area partially overlaps the 1-hour area. In a multiple
MPO or multi-state Scenario 4 area, it may be the case that one or more other MPOs or
states cannot use their 1-hour budgets because it is not possible to determine what portion
of the budgets apply. However, other MPOs or states may still be able to use their 1-
hour budgets for their portions of the 8-hour area. See below for further information on
the various scenarios.
7. Q. In an 8-hour area with a 1-hour SIP that establishes subarea budgets, how should
MPOs demonstrate conformity for the first time under the 8-hour standard?
A. As described in Part 3 of this guidance, when an area has subarea budgets, conformity
for an MPO's plan and TIP can only be determined if all other subareas have conforming
transportation plans and TIPs in place for a given pollutant and standard.
To the extent possible, EPA believes that the subarea budgets must be used in the 8-hour
conformity determination, unless it is determined through consultation that they are not
appropriate for meeting Clean Air Act conformity requirements. Subarea budgets in 1-
hour SIPs must continue to be used under the conformity rule for the 8-hour standard,
because they ensure that air quality progress to date is maintained.
In general, where an 8-hour area has multiple MPOs with subarea budgets for the 1-hour
standard, EPA and DOT believe it is necessary for the first conformity determination
under the 8-hour standard to be done as follows: each MPO would show its plan and TIP
conform to its 1-hour subarea budgets independently. All of the MPOs' plan/TIP
conformity determinations would then be submitted to DOT for its determinations. DOT
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will not make its conformity determination on any of the plans or TIPs from the 8-hour
area until every MPO in the area has made a conformity determination for its plan and
TIP. Please note that this answer may differ for Scenario 3 and 4 areas where an
additional portion of the 8-hour area is not covered by the 1-hour budgets (these
Scenarios are discussed later in this part, beginning with Q & 14). All MPOs in the 8-hour
area must have an initial valid conformity determination for the 8-hour standard by the end
of the one-year grace period. If any do not, DOT will be unable to make any 8-hour
conformity determinations for the 8-hour area, and all of the MPOs' plans and TIPs will
lapse.
Q. How are subsequent 8-hour conformity determinations made in an 8-hour area where
the 1-hour SIP establishes subarea budgets?
A. In general, once DOT has made its initial 8-hour conformity determination for the area,
the MPOs will operate as usual: before any MPO in the area determines conformity using
subarea budgets, all other MPOs in the area must have a conforming plan and TIP in
place. If one subarea is in a conformity lapse, conformity determinations for new or
revised plans and TIPs cannot be made in other subareas until the lapse ends. This answer
may differ for Scenario 3 and 4 areas where an additional portion of the 8-hour area is not
covered by the 1-hour budgets (discussed later in this part, beginning with Q & A 14).
Scenario 1 Areas
9. Q. How is conformity demonstrated in Scenario 1 areas when the 1-hour SIP budgets
apply to the entire 1-hour area?
A. Using 1-hour budgets for 8-hour conformity determinations is straightforward in
Scenario 1 areas, because the boundaries of the 8-hour area and 1-hour area(s) are exactly
the same. The MPO or MPOs must coordinate their plan/TIP conformity determinations
and submit them to DOT. Once DOT receives all plan/TIP conformity determinations for
the 8-hour area, DOT will make its conformity determinations at the same time. If there is
more than one MPO, the planning agencies will have to work together to develop one
regional emissions analysis for the entire 8-hour area under §93.109(e)(2)(i), just as they
would have been doing for the 1-hour standard. Please see Part 3 of this guidance for
further information regarding how a regional emissions analysis could be completed for
these areas.
Note that a Scenario 1 8-hour area could be formed from one or more 1-hour areas with
adequate or approved 1-hour budgets for the entire 8-hour area.
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10. Q. How is conformity demonstrated in Scenario 1 areas when the 1-hour SIP includes
subarea budgets?
A. As discussed in Part 3, Q & A 1, conformity follows the SIP. Therefore, conformity
and the supporting regional emissions analysis is done for the geographic area that is
covered by the SIP's budgets, i.e., each subarea's portion of the nonattainment area. See
Part 3, Qs & As 5 - 7, and Qs & As 7 and 8 of this part for additional information.
11. Q. How is conformity demonstrated in multi-state Scenario 1 areas, where each state has
its own separate 1-hour SIP budgets?
A. As discussed in Part 3, Q & A 1, conformity follows the SIP. Therefore, conformity
and the supporting regional emissions analysis is done for the geographic area that is
covered by the SIP's budgets, i.e., each state's portion of the nonattainment area.
Before 8-hour ozone budgets are found adequate or approved, EPA concludes that where
each state has its own 1-hour budgets, each state can continue to demonstrate conformity
to its SIP independently for the 8-hour ozone standard. Therefore, conformity
determinations for the 8-hour standard can be made in one state of a multi-state 8-hour
area even if a lapse is occurring in another state in the 8-hour area, or conformity had not
yet been determined for the 8-hour ozone standard in another state in the area. This
independence in a multi-state 8-hour area applies as long as all states are using 1-hour
budgets to determine conformity. Please see Part 3 of this guidance for further
information regarding how a regional emissions analysis could be completed for these
areas.
Scenario 2
12. Q. How is conformity demonstrated in Scenario 2 areas, when the 1-hour SIP establishes
budgets that apply to the entire 1-hour area?
A. Regardless of whether the area is located entirely within one state, or is a multi-state
area, the MPO or MPOs must coordinate plan/TIP conformity determinations and submit
them to DOT to satisfy the conformity rules. Once DOT receives all plan/TIP conformity
determinations for the 8-hour or 1-hour area (as applicable), DOT will make its
conformity determinations at the same time. Please see Part 3 of this guidance for further
information regarding how a regional emissions analysis could be completed for these
areas.
[answer continues next page]
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These areas can choose either of two versions of the budget test, as required by
§93.109(e)(2)(ii):
• the budget test using the subset or portion of existing adequate or approved 1-hour
budgets that cover the 8-hour area, where such portion can be appropriately
identified (§93.109(e)(2)(ii)(A)); or
• the budget test using the existing adequate or approved 1-hour budgets for the
entire 1-hour area, however in this case any additional emissions reductions needed
to pass the budget test must come from within the 8-hour area
(§93.109(e)(2)(ii)(B)).
The interagency consultation process should be used to determine whether budgets for the
8-hour area can reasonably be derived from the 1-hour budgets. It may be possible to
create budgets for only the 8-hour area, for example if the 1-hour SIP contains estimates
of emissions by county in the years for which budgets are established, and emissions from
the county or counties not included in the 8-hour area can be subtracted from the 1-hour
budgets.
In Figure 6 below:
Budget for 8-hour area = 1-hour budget - county or counties not in the
8-hour area
(Area in the bold line) =
(emissions in the -
gray circle)
(emissions from
the crescent shape)
Crescent shape = 1-hour county or counties
not included in the 8-hour area
= 1-hour area and budget
= 8-hour area
Figure 6: A Scenario 2 Area (the 8-Hour Area is Smaller Than the 1-Hour Area)
If is not possible to create budgets that apply to only the 8-hour area, the MPO or MPOs
will have to determine conformity to the 1-hour budgets for 8-hour conformity as they
have for the 1-hour standard, and if reductions are needed to meet the budgets, they must
come from within the 8-hour area (inside the bold line in Figure 6) as required by the
conformity rule.
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Note that a Scenario 2 8-hour area could be formed from one 1-hour area as in Figure 6
above, or more than one 1-hour area with adequate or approved 1-hour budgets for the 8-
hour area, as depicted in Figure 7, below. In these cases, consultation should be used to
determine how the 1-hour budgets will apply.
ii|||: = 1-hour areas with budgets
= 8-hour area
Figure 7: A Scenario 2 Area Composed of Several 1-Hour Areas
13. Q. How is conformity demonstrated in multi-state Scenario 2 areas, where each state has
its own separate 1-hour SIP budgets?
A. As discussed in Part 3, Q & A 1, conformity follows the SIP. Therefore, conformity is
determined for the geographic area that is covered by the SIP's budgets, i.e., each state's
portion of the nonattainment area.
Before 8-hour ozone budgets are found adequate or approved, EPA concludes that where
each state has its own 1-hour budgets, each state can continue to demonstrate conformity
to its SIP independently for the 8-hour ozone standard. Therefore, conformity
determinations for the 8-hour standard can be made in one state of a multi-state 8-hour
area even if a lapse is occurring in another state of the area. This independence in a multi-
state area applies as long as all states are using 1-hour budgets to determine conformity.
For these Scenario 2 8-hour areas, each state can choose either of two versions of the
budget test:
the budget test using the subset or portion of existing adequate or approved 1-hour
budgets that cover the 8-hour area within its state, where applicable and when such
portion can be appropriately identified (§93.109(e)(2)(ii)(A)); or
the budget test using the existing adequate or approved 1-hour budgets for the
portion of the 1-hour area within its state, however in this case any additional
emissions reductions needed to pass the budget test must come from within that
state's portion of the 8-hour area (§93.109(e)(2)(ii)(B)).
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Scenario 3 Areas Within One State
14. Q. How is conformity demonstrated in a Scenario 3 area located entirely within one state,
when the 1-hour SIP establishes budgets that apply to the entire 1-hour area?
A. In this case, the conformity rule requires that the MPO or MPOs must work together
to apply the 1-hour budgets to the portion of the 8-hour area covered by them. An 8-hour
area whose boundary is larger than the 1-hour area boundary includes one or more new
counties that were not covered by the 1-hour standard. According to §93.109(e)(2)(iii),
conformity can be determined for the 1-hour area by using the 1-hour budgets for that
portion of the 8-hour area covered by them, plus the interim emissions test(s) for either:
the remaining portion of the 8-hour area (the new county or counties), or
• the entire 8-hour area.
In Figure 8 below, the budget test must be used for the gray portion of the area, and the
interim emissions test either for the white portion of the 8-hour area, or the entire 8-hour
area.
Portion of 8-hour area not covered by 1-
hour budgets
= 1-hour area
el = 8-hour area
X'
Scenario 3
Figure 8: A Scenario 3 Area
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15. Q. How is conformity demonstrated in a Scenario 3 area located entirely within one state,
when the 1-hour SIP establishes subarea budgets that apply for each MPO?
A. As described in Part 3, Q& As 5 - 7, and in Q & As 6 - 8 of this part, each MPO can
develop its own regional emissions analysis and conformity determination for its plan and
TIP, as long as all of the other MPOs in the area have a conforming plan and TIP in place
The twist for a Scenario 3 area is that there is a portion of the 8-hour area that is not
covered by 1-hour budgets. For this portion of the 8-hour area, a regional emissions
analysis using the interim emissions test(s) must be done for either:
> the part of the 8-hour area not covered by 1-hour budgets, or
> the entire 8-hour area.
As addressed in Q & A 7 of this part, for the initial conformity determinations under the 8-
hour standard, each MPO can determine conformity for its own plan and TIP and DOT
will wait to receive a conformity determination for each MPO before making its
conformity determination for the plans and TIPs in the area.
= 1-hour area
= 8-hour area
A, B, C, D =MPOs with 1-hour
subarea budgets
E = new county in
8-hour area
Figure 9: A Scenario 3 Area Within One State
With 1-Hour Subarea Budgets
In Figure 9, above, MPOs A, B, C, and D can develop conformity determinations for just
their own plans and TIPs using their 1-hour subarea budgets. The regional emissions
analysis for Part E must be done using the interim emissions test(s), according to
§93.109(e)(2)(iii)(B) of the conformity rule. Part E may be a donut area or may have its
own MPO. If Part E is a donut area, per §93.105(c)(3) of the rule, the parties involved in
interagency consultation must discuss which agency will be responsible for Part E's
regional emissions analysis, and for what geographic area it will be done. DOT would
wait until it had conformity determinations for all MPO plans/TIPs and the donut area
before making its initial conformity determinations for the 8-hour standard.
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Scenario 3 Multi-State Areas
16. Q. How is conformity demonstrated in multi-state Scenario 3 areas, where all of the states
have their own separate 1-hour SIP budgets?
A. As described above, conformity determinations can continue to be made independently
in each state that has separate 1-hour budgets, as long as all states in the area use their
respective 1-hour budgets for their 8-hour conformity determinations. In addition, if the
8-hour boundary in a state is larger than the 1-hour boundary in that state, the interim
emissions test(s) must be met for either:
• the portion outside the 1-hour boundary and inside the 8-hour boundary in that
state,
• that state's entire portion of the 8-hour nonattainment area, or
the entire multi-state 8-hour area.7
The provision of the rule that requires the interim emissions test(s) in Scenario 3 areas,
§93.109(e)(2)(iii)(B), could apply to any of these three geographic choices.
For example, in Figure 10 below, an 8-hour nonattainment area includes parts of three
states. The 8-hour boundary in States A and B is unchanged from the 1-hour boundary,
but the 8-hour boundary in State C is larger. States A, B, and C can continue to
determine conformity independently from one another for the 8-hour standard as follows:
States A and B would determine conformity by meeting their 1-hour budgets.
State C would determine conformity by meeting its 1-hour budgets, plus the
interim emissions test(s) either for:
> the portion in State C not covered by the 1-hour budgets (in Figure 10, the
white portion inside the bold line),
> the entire portion of the 8-hour area in State C, or
> the entire multi-state area (see footnote 7).
7Though the interim emissions test(s) could be done for the entire 8-hour nonattainment
area under the final rule, as explained in the preamble (69 FR 40023), "doing so may not allow
each MPO in this example to develop transportation plans and TIPs and conformity
determinations independently." Please consult with EPA and DOT to discuss the implications for
all states before choosing this option.
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Portion of the 8-hr area not covered by 1-hr budgets
= 1-hour nonattainment areas
= 8-hour nonattainment area
\ = state boundaries/ 1-hour SIP
boundaries
Figure 10: A Multi-State Scenario 3 Area
17. Q. How is the regional emissions analysis done in multi-state Scenario 3 areas, where only
one of the states has its own 1-hour SIP budgets?
A. Consistent with Clean Air Act section 176(c), EPA interprets §93.109(e)(2)(iii) of the
conformity rule to mean that a state can determine conformity completely independently,
even if it is the only state in the 8-hour area that has 1-hour budgets. If one state has 1-
hour budgets and the 8-hour area is a two-state area, then both states can determine
conformity on their own:
• the state with the 1-hour budgets would continue to use them for 8-hour
conformity;
• the state without budgets would use the interim emissions test(s).
In Figure 11 below, each state can determine conformity for its own portion of the 8-hour
area, even though State B does not have 1-hour budgets.
= 1-hour area
= 8-hour area
*X = state boundary
*»
Figure 11: A Two-State Area
However, if the 8-hour area was a three-state area and only one state had 1-hour budgets,
only the state with the budgets could determine conformity on its own. The other two
states would determine conformity for the 8-hour standard together using the interim
emissions test(s).
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Scenario 3 - General
18. Q. What are the special issues that the interagency consultation process should consider
in Scenario 3 areas?
A. The interagency consultation process is of key importance in these areas. Because the
8-hour area is larger than the 1-hour area, one or more planning agencies previously not
involved in conformity may become part of the interagency process. These planning
agencies need to be included in the decision-making process for the area.
Through the interagency consultation process as required by §93.105 of the conformity
rule, the involved parties must decide:
• whether to apply the interim emissions test(s) to the entire 8-hour area (or in a
multi-state area where one or more of the states have 1-hour budgets, to one
state's entire portion of the area) or just the portion not covered by the 1-hour
budgets;
• whether it is more appropriate for the state DOT or an MPO to prepare the
regional emissions analysis for a donut area, if there is one;
• which interim emissions test will be used, in areas permitted to select only one test;
and
• analysis years for the budget test and interim emissions test(s). It may be possible
to choose analysis years that satisfy both the budget and interim emissions test
requirements in §§93.118(d)(2) and 93.119(g), as described below.
Scenario 4 Areas Within One State
19. Q. How is conformity done in a Scenario 4 area, when 1-hour budgets apply to the entire
1-hour area, that is, the SIP does not establish subarea budgets?
A. It may be possible to use the budgets from the 1-hour SIP, if the SIP includes
emissions by county and it is possible to determine which portions of the 1-hour budgets
apply to the 8-hour area. In this case, the 8-hour area would show conformity in a manner
similar to a Scenario 3 area. It would use:
the relevant portion of the 1-hour budgets for the portion of the 8-hour area where
it has them, plus
the interim emissions test(s), either for:
> the remaining portion of the 8-hour area, or
> the entire 8-hour area.
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For example, in Figure 12 below, if it is possible to determine what portion of the 1-hour
budgets apply for the portion of the 1-hour area that is now inside the 8-hour area
boundary, the area would use:
• the budget test, for that portion of the 8-hour area that has them (as indicated by
the arrow in Figure 12), and
• the interim emissions test(s) must be met for either:
> the part of the 8-hour area not covered by budgets - in Figure 12, the
portion shaded with the pattern, or
> the entire 8-hour area.
= 8-hour area
= 1-hour area - no budgets
= 1-hour area w/budgets
Figure 12: A Scenario 4 Area Within One State
However, it may not be possible for the 8-hour area to use the 1-hour budgets at all. This
outcome would occur, for example, if 1-hour SIP does not include an emissions inventory
by county. It could also occur if the 8-hour boundary includes and excludes portions of
counties instead of entire counties. The interagency consultation process would be used
to discuss use of 1-hour budgets in Scenario 4 areas. When such cases occur, a Scenario
4 area would determine conformity using the applicable interim emissions test(s) for the
entire area.8
Scenario 4 Multi-State Areas
20. Q. How does a multi-state Scenario 4 area determine conformity when the 1-hour SIPs
have separate budgets that apply to each state?
A. As described above, multi-state Scenario 4 areas are a unique case. Where each state
has separate 1-hour budgets that apply only to its portion of the nonattainment or
maintenance area, each state in a multi-state Scenario 4 area can operate entirely
independently. Where a state's portion can use its 1-hour budgets, it must use them
8 This statement does not preclude agencies from developing a reasonable way to utilize
the 1-hour budgets, via the interagency consultation process where possible. The final conformity
rule requires the use 1-hour budgets where ever it is appropriate and possible.
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according to §93.109(e)(2)(iv) of the rule. Any portion of a state's area not covered by
the budgets would have to be included in an interim emissions test(s), for:
• that part not covered by 1-hour budgets,
the state's entire portion of the 8-hour area, or
• the entire 8-hour area.
The consultation process would be used to determine which test option is selected in
Scenario 4 areas.
21. Q. How is the regional emissions analysis done in a multi-state Scenario 4 area, where
only one of the states has its own 1-hour SIP budgets?
A. EPA interprets §93.109(e)(2)(iv) to mean that if any state in the 8-hour area has 1-
hour budgets, that state can determine conformity completely independently from the
other states in the 8-hour area. The state or states that have 1-hour budgets would
continue to use them or portions of them as appropriate, to the extent possible, for their 8-
hour regional emissions analysis and conformity determination. The state or states
without 1-hour SIP budgets would use the interim emissions test(s) for 8-hour conformity;
if there is more than one state in the area without 1-hour budgets, these states would
determine conformity together.
22. Q. What are special issues that the interagency consultation process should consider in
Scenario 4 areas?
A. As in Scenario 3 areas, the interagency consultation process is of key importance in
Scenario 4 areas. Where an 8-hour area partially overlaps a 1-hour area, one or more
MPOs may no longer have to determine conformity, and one or more new MPOs may
become part of the interagency process. All MPOs in the 8-hour area as well as the other
parties involved in interagency consultation need to be involved in the decision-making
process for the area.
Through the interagency consultation process as required by §93.105 of the conformity
rule, the involved parties must decide:
whether to apply the interim emissions test(s) to the entire area (or in a multi-state
area, to one state's portion of the area) or just the portion not covered by the 1-
hour budgets;
• whether it is more appropriate for the state DOT or an MPO to prepare the
regional emissions analysis for a donut area, if there is one;
• which interim emissions test will be used, in areas permitted to select only one test;
and
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analysis years for the budget test and interim emissions test(s). It may be possible
to choose analysis years that satisfy both the budget and interim emissions test
requirements in §§93.118(d) and 93.119(e) of the rule, as described below.
General Implementation of Final Rule
23. Q. What precursors must be examined in 8-hour areas with 1-hour budgets?
A. As described in the preamble to the July 1, 2004, final transportation conformity rule
the regional emissions analyses for ozone areas must address the ozone precursors
nitrogen oxides (NOx) and volatile organic compounds (VOC) (§93.102(b)(2)(i)). In
cases where budgets are used, conformity is demonstrated with the budget test for
adequate and approved NOx and VOC budgets (§93.118). In all cases where areas use
the interim emissions test(s), both precursors must be analyzed unless EPA issues a NOx
waiver for the 8-hour standard for an area under Clean Air Action section 182(f). These
requirements are consistent with the conformity rule to date, although the July 2004 final
rule moves these provisions to §93.119(f) due to reorganization of §93.119. Areas must
also complete the interim emissions test(s) for NOx if the only SIP available is a
reasonable further progress SIP for either the 1-hour or 8-hour standard that contains a
budget for VOCs only (e.g., a 15% SIP). See §93.109(e)(3) of the final rule for further
information.
24. Q. How is the budget test generally implemented in 8-hour areas with 1-hour budgets?
A. The budget test requirements in §93.118 for 8-hour areas will be generally
implemented in the same manner as in 1-hour areas, with a few exceptions. First, as
described above, the geographic area covered by the 8-hour standard may be different
than that covered by the 1-hour standard and SIP budgets in some cases. Second, the
years for which regional modeling is required (i.e., analysis years) may differ.
Areas that use 1-hour budgets for their 8-hour conformity determinations will need to
determine the modeling analysis years that apply for the 8-hour standard per §93.118(d).
Under this section, a modeling analysis must be completed for:
the last year of the transportation plan,
• the attainment year for the relevant pollutant and standard, and
an intermediate year(s) such that analysis years are not more than 10 years apart.
The attainment year analysis is to be for an area's attainment year for the 8-hour standard,
which probably will be different than the attainment year under the 1-hour standard. The
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area must then calculate emissions in the analysis years from the planned transportation
system.
Once modeling is completed per §93.118(d)(2), 8-hour areas using 1-hour SIPs will also
demonstrate consistency with the 1-hour budgets according to §93.118(b), except for
cases where it is determined that 1-hour budgets are not appropriate through the
consultation process as described above and in §93.109(e)(2)(v) of the conformity rule.
According to §93.118(b) the July 1, 2004, final rule, consistency with 1-hour budgets
must be shown for:
all 1-hour budget years that are within the timeframe of the transportation plan,
• the 8-hour attainment year,
the last year of the plan, and
• an intermediate year(s) so that all years are not more than 10 years apart.
Emissions projected for each analysis year must be within the budgets in the 1-hour SIP
from the most recent prior year. Interpolation can be used between analysis years for
demonstrating consistency with budgets, just as has been done under the 1-hour standard.
For example, suppose an area designated nonattainment for the 8-hour ozone standard
with an 8-hour attainment date of 2010 has the following 1-hour budgets:
2005 rate-of-progress (ROP) budgets for NOx and VOCs,
2007 ROP budgets for NOx and VOCs, and
2007 attainment budgets for NOx and VOCs.
By 2005, this area would determine conformity for its 2005-2025 transportation plan and
its TIP, and the conformity determination would be accomplished as follows:
2005 budget test, using the 2005 ROP budgets;
2007 budget test, using both 2007 ROP and attainment budgets;
• 2010 budget test, using the 2007 attainment budgets9;
2020 budget test,10 using the 2007 attainment budgets; and
• 2025 budget test, using the 2007 attainment budgets.
As described in §93.118(d)(2), emissions for the year 2005 could be generated with a
regional emissions analysis, or could be interpolated if the area has run a regional
9EPA has previously interpreted that only attainment budgets apply beyond the attainment
year, in cases where ozone areas also have budgets for ROP SIPs.
10The year 2020 is chosen for this example, but any year from 2015 through 2019 would
also be acceptable for the interim year analysis.
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emissions analysis for an earlier year. Emissions for the year 2007 could also be
interpolated or the area could choose to model emissions for this year. A regional
modeling analysis must be done for the year 2010 (the 8-hour attainment year), any year
between 2015 and 2020 for the intermediate year (in this example, 2020 is the
intermediate year), and the year 2025 (the last year of the transportation plan) as required
by §93.118(d)(2).
As stated above, once adequate or approved 8-hour budgets are established for a given
precursor, the budget test would be completed with only the 8-hour budgets for that
precursor, rather than the 1-hour budgets.
25. Q. Where 8-hour areas have to use both the budget test and the interim emissions test(s),
what analysis years would be chosen?
A. As described in the July 2004 final rule, there will be cases in Scenario 3 or 4 areas
where both the budget and interim emissions tests are used. Sections 93.118 and 93.119
of the conformity rule cover the criteria and procedures for the budget test and the interim
emissions tests, respectively. Each of these sections define the analysis years that must be
examined in the particular test.
In the budget test, the years that must be analyzed (§93.118(d)(2)) are:
the 8-hour attainment year,
• the last year of the transportation plan, and
an intermediate year or years as necessary, so that analysis years are no more than
ten years apart.
In the interim emissions tests, the years that must be analyzed (§93.119(g)) are:
• a year no more than five years in the future (from the year in which the conformity
determination is made)
the last year of the transportation plan, and
• an intermediate year or years as necessary, so that analysis years are no more than
ten years apart.
The interagency consultation process can be used to choose analysis years that meet the
requirements of both §§93.118 and 93.119 so that the number of analysis years is
minimized. For example, consider a Scenario 3 area in one state that is classified as
moderate for the 8-hour standard that has 1-hour budgets for the years 2005 and 2007.
This area needs to use both the budget and interim emissions tests to determine conformity
for the 8-hour standard, because there is a portion of the area that is not covered by the 1-
hour budgets. The plan covers the years 2005 through 2025 and the conformity
determination will be made in the year 2005. This area could examine the following
analysis years in its 8-hour conformity determination:
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• 2010. which fulfills the §93.118 requirement to analyze the 8-hour attainment year,
and the §93.119 requirement to analyze a year no more than five years in the
future;
• 2015. which fulfills the requirement in both rule sections to analyze an intermediate
year so that analysis years are no more than 10 years apart; and
• 2025. which fulfills the requirement in both rule sections to analyze the last year of
the plan.
In addition, the rule requires that the portion of the area covered by the 1-hour budgets
must also demonstrate consistency with the budgets for the years 2005 and 2007.
Consistency can be demonstrated using interpolation for a year between two analysis years
as described in §93.118(d)(2) of the conformity rule. In this example, the area could do a
regional emissions analysis for 2005 and interpolate emissions for 2007 using the 2005 and
2010 analyses. Alternatively, the area could interpolate 2005 and 2007 emissions by using
an analysis for a year before 2005 done for model validation purposes, if such a year is not
more than 10 years earlier than 2010 (so that analysis years are no more than 10 years
apart).
In this example, the budget test and interim emissions test requirements would then be
satisfied as follows:
2005: budget test, using the 2005 budgets
2007: budget test, using the 2007 budgets
2010: budget test, using the 2007 budgets
and interim emissions test(s) for 2010
2015: budget test, using the 2007 budgets
and interim emissions test(s) for 2015n
2025: budget test, using the 2007 budgets
and interim emissions test(s) for 2025
As described in §93.109(e)(2)(iii) of the July 1, 2004, final rule, the regional emissions
analysis for the budget test in Scenario 3 would cover the 1-hour area portion of the 8-
hour area (i.e., the portion covered by the 1-hour budgets). The regional analyses for the
interim emissions tests in an area located within a single state would cover either the
portion of the 8-hour area not covered by the 1-hour budgets, or the entire 8-hour area.
[answer continues on the next page]
nThe year 2015 is chosen for this example, but any year between 2016 and 2020 would
also be acceptable for the interim year analysis.
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The regional analyses for the interim emissions tests in a multi-state area would cover
either the portion of a state's 8-hour area not covered by its 1-hour budgets, or a state's
entire 8-hour area.12
12The July 1, 2004, final rule also provides a third interim emissions test option for certain
Scenario 3 multi-state areas: the regional emissions analysis could cover the entire multi-state
area. Please consult EPA before choosing this option to discuss its implications.
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