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Transportation Conformity Reference Guide

Section D: Specific Regional Emissions Analysis Requirements
Chapter 8 8-Hour Ozone Areas with Adequate or Approved 1-Hour Ozone SIP Budgets

NOTE:On October 20, 2006, the DC Circuit U.S. Court of Appeals vacated 40 CFR 93.109(e)(2)(v). 8-hour ozone areas that do not have adequate or approved 8-hour budgets can no longer utilize this provision to use the interim emissions tests instead of their 1-hour budgets to demonstrate conformity. Please see: (Circuit Court Ruling)

Conformity Before Adequate or Approved 8-hour Ozone SIP Budgets
General Requirements for All Scenarios
Scenario 1: 8-Hour Boundary is exactly the same as the 1-Hour Boundary

Scenario 2: 8-Hour Boundary is less than the 1-Hour Boundary

Scenario 3: 8-Hour Boundary is greater than the 1-Hour Boundary

Scenario 4: 8-Hour Boundary Partially Overlaps with the 1-hour Boundary

Consistency with the Budget for the Last Year of the Transportation Plan in Areas with Multiple MPOs and/or Donut Areas
Conformity after 8-hour Ozone SIP Budgets are Adequate or Approved

This chapter covers how regional emissions analyses must be done in 8-hour ozone nonattainment and maintenance areas with existing 1-hour ozone SIPs that covers either part or all of the 8-hour ozone nonattainment area. Once the area has an adequate or approved 8-hour ozone emission budgets, they must be used for all future conformity determinations in accordance with 40 CFR §93.118. For more information on multiple jurisdictions, please see the relevant sections of EPA's 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, July 21, 2004 (http://www.epa.gov/otaq/transp/conform/policy.htm).

Conformity Before Adequate or Approved 8-hour Ozone SIP Budgets

40 CFR §93.109(e)

  1. 8-hour ozone NAAQS nonattainment and maintenance areas with motor vehicle emissions budgets for the 1-hour ozone NAAQS that cover all or a portion of the 8-hour nonattainment area. This provision applies 1 year after the effective date of EPA's nonattainment designation for the 8-hour ozone NAAQS for an area, according to §93.102(d). In addition to the criteria listed in Table 1 in paragraph (b) of this section that are required to be satisfied at all times, in such 8-hour ozone nonattainment and maintenance areas conformity determinations must include a demonstration that the budget and/or interim emissions tests are satisfied as described in the following:
    1. In such 8-hour ozone nonattainment and maintenance areas the budget test must be satisfied as required by §93.118 for conformity determinations made on or after:
      1. The effective date of EPA's finding that a motor vehicle emissions budget in a submitted control strategy implementation plan revision or maintenance plan for the 8-hour ozone NAAQS is adequate for transportation conformity purposes;
      2. The publication date of EPA's approval of such a budget in the Federal Register; or
      3. The effective date of EPA's approval of such a budget in the Federal Register, if such approval is completed through direct final rulemaking.
    2. Prior to paragraph (e)(1) of this section applying, the following test(s) must be satisfied, subject to the exception in paragraph (e)(2)(v):
      1. If the 8-hour ozone nonattainment area covers the same geographic area as the 1-hour ozone nonattainment or maintenance area(s), the budget test as required by §93.118 using the approved or adequate motor vehicle emissions budgets in the 1-hour ozone applicable implementation plan or implementation plan submission;
      2. If the 8-hour ozone nonattainment area covers a smaller geographic area within the 1-hour ozone nonattainment or maintenance area(s), the budget test as required by §93.118 for either:
        1. The 8-hour nonattainment area using corresponding portion(s) of the approved or adequate motor vehicle emissions budgets in the 1-hour ozone applicable implementation plan or implementation plan submission where such portion(s) can reasonably be identified through the interagency consultation process required by §93.105; or
        2. The 1-hour nonattainment area using the approved or adequate motor vehicle emissions budgets in the 1-hour ozone applicable implementation plan or implementation plan submission. If additional emissions reductions are necessary to meet the budget test for the 8-hour ozone NAAQS in such cases, these emissions reductions must come from within the 8-hour nonattainment area;
      3. If the 8-hour ozone nonattainment area covers a larger geographic area and encompasses the entire 1-hour ozone nonattainment or maintenance area(s):
        1. The budget test as required by §93.118 for the portion of the 8-hour ozone nonattainment area covered by the approved or adequate motor vehicle emissions budgets in the 1-hour ozone applicable implementation plan or implementation plan submission; and
        2. The interim emissions tests as required by §93.119 for either: the portion of the 8-hour ozone nonattainment area not covered by the approved or adequate budgets in the 1-hour ozone implementation plan, the entire 8-hour ozone nonattainment area, or the entire portion of the 8-hour ozone nonattainment area within an individual state, in the case where separate 1-hour SIP budgets are established for each state of a multi-state 1-hour nonattainment or maintenance area;
      4. If the 8-hour ozone nonattainment area partially covers a 1-hour ozone nonattainment or maintenance area(s):
        1. The budget test as required by §93.118 for the portion of the 8-hour ozone nonattainment area covered by the corresponding portion of the approved or adequate motor vehicle emissions budgets in the 1-hour ozone applicable implementation plan or implementation plan submission where they can be reasonably identified through the interagency consultation process required by §93.105; and
        2. The interim emissions tests as required by §93.119, when applicable, for either: the portion of the 8-hour ozone nonattainment area not covered by the approved or adequate budgets in the 1-hour ozone implementation plan, the entire 8-hour ozone nonattainment area, or the entire portion of the 8-hour ozone nonattainment area within an individual state, in the case where separate 1-hour SIP budgets are established for each state in a multi-state 1-hour nonattainment or maintenance area.
      5. Notwithstanding paragraphs (e)(2)(i), (ii), (iii), or (iv) of this section, the interim emissions tests as required by §93.119, where the budget test using the approved or adequate motor vehicle emissions budgets in the 1-hour ozone applicable implementation plan(s) or implementation plan submission(s) for the relevant area or portion thereof is not the appropriate test and the interim emissions tests are more appropriate to ensure that the transportation plan, TIP, or project not from a conforming plan and TIP will not create new violations, worsen existing violations, or delay timely attainment of the 8-hour ozone standard, as determined through the interagency consultation process required by §93.105.
    3. Such an 8-hour ozone nonattainment area must satisfy the interim emissions test for NOX, as required by §93.119, if the only implementation plan or plan submission that is applicable for the purposes of conformity determinations is a 15% plan or other control strategy SIP that addresses reasonable further progress that does not include a motor vehicle emissions budget for NOX. The implementation plan for the 8-hour ozone NAAQS will be considered to establish a motor vehicle emissions budget for NOX if the implementation plan or plan submission contains an explicit NOX motor vehicle emissions budget that is intended to act as a ceiling on future NOX emissions, and the NOX motor vehicle emissions budget is a net reduction from NOX emissions levels in 2002. Prior to an adequate or approved NOX motor vehicle emissions budget in the implementation plan submission for the 8-hour ozone NAAQS, the implementation plan for the 1-hour ozone NAAQS will be considered to establish a motor vehicle emissions budget for NOX if the implementation plan contains an explicit NOX motor vehicle emissions budget that is intended to act as a ceiling on future NOX emissions, and the NOX motor vehicle emissions budget is a net reduction from NOX emissions levels in 1990.
    4. Notwithstanding paragraphs (e)(1) and (e)(2) of this section, ozone nonattainment areas with three years of clean data for the 8-hour ozone NAAQS that have not submitted a maintenance plan and that EPA has determined are not subject to the Clean Air Act reasonable further progress and attainment demonstration requirements for the 8-hour ozone NAAQS must satisfy one of the following requirements:
      1. The budget test and/or interim emissions tests as required by §§93.118 and 93.119 and as described in paragraph (e)(2) of this section;
      2. The budget test as required by §93.118, using the adequate or approved motor vehicle emissions budgets in the submitted or applicable control strategy implementation plan for the 8-hour ozone NAAQS (subject to the timing requirements of paragraph (e)(1) of this section); or
      3. The budget test as required by §93.118, using the motor vehicle emissions of ozone precursors in the most recent year of clean data as motor vehicle emissions budgets, if such budgets are established by the EPA rulemaking that determines that the area has clean data for the 8-hour ozone NAAQS.

All 8-hour ozone nonattainment or maintenance areas with adequate or approved 1-hour budgets must use these budgets for 8-hour conformity before adequate or approved 8-hour budgets are available, unless it is determined through interagency consultation process that using the interim emissions test is more appropriate for meeting Clean Air Act requirements. The budget test using the existing 1-hour ozone SIP budgets fulfills the regional emissions analysis requirement for the 8-hour ozone standard, rather than the 1-hour standard. (69 FR 40022, July 1, 2004)

There are circumstances under which an 8-hour ozone area with 1-hour ozone budgets would not use those budgets. According to the July 1, 2004 preamble (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 another 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 adequate or approved 1-hour SIP budgets cannot be considered inappropriate simply because it is difficult to pass for 8-hour conformity purposes. In addition, 1-hour SIP budgets cannot be discarded simply because they are based on older planning assumptions or emission 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 and reductions are achieved in certain areas.

There are four potential scenarios into which areas covered by this section can be categorized:

The following questions and scenarios are taken from EPA's 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, July 21, 2004.

General Requirements for All Scenarios

Do 8-hour areas with 1-hour budgets have to use the 1-hour budgets for conformity determinations under the 8-hour standard?

Yes, in most cases. As required in §93.109(e)(2), 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 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.

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 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. (69 FR 40025, July 1, 2004)

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. (69 FR 40025, July 1, 2004)

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?

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. 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.

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?

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 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. 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 be subject to the lapse provisions.

How are subsequent 8-hour conformity determinations made in an 8-hour area where the 1-hour SIP establishes subarea budgets?

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. (See Scenario 3 and Scenario 4 below for more information)

What precursors must be examined in 8-hour areas with 1-hour budgets?

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). 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) for further information.

How is the budget test generally implemented in 8-hour areas with 1-hour budgets?

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). Also, SAFETEA-LU section 6011(c) provides an option to reduce the time period covered by the conformity determination (see Section D). Under this section, a modeling analysis must be completed for:

The attainment year analysis is to be for an area's attainment year for the 8-hour standard (See EPA's Guidance for Determining the "Attainment Years" for Transportation Conformity in New 8-Hour Ozone and PM2.5 Nonattainment Areas, March 8, 2005, for more information), which probably will be different than the attainment year under the 1-hour standard. The 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), consistency with 1-hour budgets must be shown for:

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 for which the MPO has not elected to shorten its horizon under SAFETEA-LU is designated nonattainment for the 8-hour ozone standard with an 8-hour attainment date of 2010 and has the following 1-hour budgets:

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:

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 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.

Where 8-hour areas have to use both the budget test and the interim emissions test(s), what analysis years would be chosen?

As described in the July 2004 final rule, there will be cases in scenario 3 or scenario 4 areas below 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:

In the interim emissions tests, the years that must be analyzed (§93.119(g)) are:

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 for which the MPO has not elected to shorten its horizon under SAFETEA-LU and 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:

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:

As described in §93.109(e)(2)(iii), 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. 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. [4]

Scenario 1: 8-Hour Boundary is exactly the same as the 1-Hour Boundary

In this case, the 8-hour and 1-hour ozone nonattainment area boundaries cover exactly the same geographic area. Such an area could be formed from a single 1-hour area, or more than one 1-hour area, as long as the entire 8-hour area boundary is exactly the same as the previous 1-hour area or areas.

In these areas, conformity must be generally demonstrated using the budget test according to §93.118 with the 1-hour SIP budgets. The interagency consultation process should be used to clarify the 1-hour budget(s) for the 8-hour area. The interim emissions test(s) would only be used if it is determined through interagency consultation process that an adequate or approved 1-hour budget is not appropriate for a give year(s) in a regional emissions analysis. (69 FR 40022, July 1, 2004) See Section D for details about the budget and interim emissions tests.

How is conformity demonstrated in Scenario 1 areas when the 1-hour SIP budgets apply to the entire 1-hour area?

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.

How is conformity demonstrated in Scenario 1 areas when the 1-hour SIP includes subarea budgets?

Conformity determination 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.

How is conformity demonstrated in multi-state Scenario 1 areas, where each state has its own separate 1-hour SIP budgets?

Conformity determination 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 same 8-hour area, or conformity had not yet been determined for the 8-hour ozone standard in another state in the same area. This independence in a multi-state 8-hour area applies as long as all states are using 1-hour budgets to determine conformity.

Scenario 2: 8-Hour Boundary is less than the 1-Hour Boundary

In this case, the 8-hour nonattainment area is smaller than and completely encompassed by the 1-hour nonattainment boundary. In these areas, conformity must generally be shown using of the following:

The first budget test option listed above is available to an area if it is possible to determine what portion of the 1-hour budget applies to the 8-hour area. In that case, that portion can be used as the budget for the 8-hour ozone area. For example, if the budget corresponds directly with an on-road mobile inventory for the 1-hour ozone SIP that was calculated by county and the portion to be subtracted is a specific county that is not part of the 8-hour ozone area. However, this method may not be available where the 1-hour SIP does not clearly specify the amount of emissions in the portion of the 1-hour ozone area not covered by the 8-hour ozone. The consultation process would be used to determine whether using a portion of a 1-hour ozone SIP budget is appropriate and feasible, and if so, how deriving such a portion would be accomplished. A SIP revision is not necessary.

In the second budget test option, a conformity determination based on the entire 1-hour ozone budget would include a comparison between the on-road regional emissions produced in the entire 1-hour ozone area and the existing 1-hour ozone budgets. However, if additional emissions reductions are required to meet conformity beyond those produced by control measures in the 1-hour SIP budgets, only reductions within the 8-hour ozone nonattainment area can be included in the regional emissions analysis.

Once an area selects either of these budget options, it must be used consistently for each analysis year of a given conformity determination. The interim emissions test(s) would only be used if it is determined through the consultation process that an adequate or approved 1-hour budget is not appropriate for a given year(s) in the regional emissions analysis. (69 FR 40022-23)

How is conformity demonstrated in Scenario 2 areas, when the 1-hour SIP establishes budgets that apply to the entire 1-hour area?

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.

These areas can choose either of two versions of the budget test, as required by§93.109(e)(2)(ii):

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.

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 as required by the conformity rule.

Note that a Scenario 2 8-hour area could be formed from one 1-hour area, or more than one 1-hour area with adequate or approved 1-hour budgets for the 8-hour area. In these cases, consultation should be used to determine how the 1-hour budgets will apply.

How is conformity demonstrated in multi-state Scenario 2 areas, where each state has its own separate 1-hour SIP budgets?

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-hourarea 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:

Scenario 3: 8-Hour Boundary is Greater than the 1-Hour Boundary

These scenarios will result when an entire 1-hour ozone nonattainment or maintenance area is contained with in a larger 8-hour ozone area. For example, a Scenario 3 area would result when an 8-hour area is formed from an existing 1-hour area plus an additional county or counties that were not covered by the 1-hour standard. In these areas the budgets from the previous 1-hour ozone area will not cover the entire 8-hour area. However, conformity must consider regional emissions for the entire 8-hour ozone nonattainment area.

In these areas, conformity must generally be demonstrated using the budget test based on the 1-hour ozone SIP budgets for the 1-hour ozone area, plus the interim emission test(s) for one of the following:

The budget test would be completed according to the requirements of §93.118. The interim emissions tests would only be used instead of the 1-hour budget if it is determined through interagency consultation process that an adequate or approved 1-hour budget is not appropriate for a given year in the regional emissions analysis.

The options for interim emissions tests are intended to give areas the flexibility to continue to implement conformity as they have under the 1-hour standard. EPA acknowledges that there may be cases where it is difficult to model the remaining portion of the 8-hour ozone area separately e.g., in an area where the remaining 8-hour ozone area is a ring of counties around the 1-hour ozone area. In this case, an area may choose to complete the interim emissions test(s) for the entire 8-hour ozone area, rather than just the portion not covered by the 1-hour ozone budgets. Once an area selects a particular interim emissions test(s) and geographic coverage for such test(s), these choices must be applied consistently for all regional analysis years in a given conformity determination.

For example, a marginal 8-hour ozone area that is larger than the 1-hour ozone area with an applicable 1-hour SIP can complete the regional emissions analysis by meeting the budget test for the 1-hour ozone nonattainment area and the no-greater-than-2002 test for the remaining portion of the 8-hour area for all analysis years. (69 FR 40023, July 1, 2004)

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?

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:

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?

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:

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.

How is conformity demonstrated in multi-state Scenario 3 areas, where all of the states have their own separate 1-hour SIP budgets?

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 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.

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?

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:

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).

What are the special issues that the interagency consultation process should consider in Scenario 3 areas?

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:

Scenario 4: 8-Hour Boundary Partially Overlaps with the 1-hour Boundary

This scenario results when 1-hour and 8-hour boundaries partially overlap. For example, a Scenario 4 area could be an 8-hour area formed from a portion of one or more 1-hour areas plus new counties that were not covered by the 1-hour standard. As in the other scenarios, these areas must generally use existing 1-hour budgets whenever feasible to determine conformity, plus the interim emissions test(s) when a portion of the 8-hour nonattainment area is not covered by existing 1-hour budgets.

In Scenario 4 areas, conformity must generally be demonstrated using the budget test based on the portion of the 1-hour ozone SIP budget(s) that covers both the 1-hour and 8-hour areas, plus the interim emissions test(s) for one of the following:

The interim emissions test would be used instead of a 1-hour budget only if it is determined through the consultation process that an adequate or approved 1-hour budget is not appropriate for a given year in the regional emissions analysis, or if it is not possible to determine what portion of the 1-hour budgets apply to the 8-hour area. This outcome could occur if 1-hour SIP does not include an emissions inventory by county.

The options for interim emissions tests are intended to give areas the flexibility to continue to implement conformity as they have under the 1-hour standard. EPA acknowledges that there may be cases where it is difficult to model the remaining portion of the 8-hour ozone area. Once an area selects a particular interim emissions test(s) and geographic coverage for such test(s), these choices must be applied consistently for all regional analysis years in a given conformity determination.

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?

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:

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. [6]

How does a multi-state Scenario 4 area determine conformity when the 1-hour SIPs have separate budgets that apply to each state?

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 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:

The consultation process would be used to determine which test option is selected in Scenario 4 areas.

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?

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.

What are special issues that the interagency consultation process should consider in Scenario 4 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:

Consistency with the Budget for the Last Year of the Transportation Plan in Areas with Multiple MPOs and/or Donut Areas

These requirements are found in conformity rule sections 93.118(b) (consistency) and 93.118(d) and 93.119(g) (analysis years). These examples specifically address situations where subarea 1-hour ozone emissions budgets exist for the MPOs and each MPO's long range plan covers a different forecast period.

Please see the SAFETEA-LU Transportation Conformity Interim Guidance www.fhwa.dot.gov/environment/conformity/sec6011guidmemo.htm to address analysis years in multi-jurisdictional areas whose MPO(s) elect to shorten their conformity horizons.

While the following examples use 8-hour ozone areas to illustrate how areas with subarea budgets would meet the requirements of conformity rule sections 93.118(b) and (d) and 93.119(g), they would apply to other pollutants.

Example 1: An 8-hour ozone nonattainment area in a single state contains multiple MPOs; each MPO's long-range plan covers a different forecast period and the area's 1-hour ozone SIP establishes a subarea budget for each MPO.

How should each MPO address the requirements of section 93.118(b) and (d) to determine conformity (i.e., demonstrate consistency and analyze) for the last year of the transportation plan's forecast period?

As described in Questions 7 and 8 of Part 4 of the July 21, 2004 multi-jurisdictional guidance, each MPO would show that its plan conforms to its 1-hour subarea budgets independently. Since each MPO has its own subarea emissions budgets each MPO would determine conformity for the last year of its respective transportation plan. For the initial 8-hour determinations, DOT will not make conformity determinations until every MPO in the nonattainment area has made conformity determinations on their plans and TIPs. For subsequent 8-hour determinations, each MPO can determine conformity independently, as long as all the other MPOs are in conformity.

For example, one MPO in such an area has a transportation plan that covers 2005 to 2025 and the other MPO has a plan that covers 2005 to 2030. The first MPO would fulfill the 93.118(b) and (d) requirements for the last year of the transportation plan's forecast period by analyzing and showing consistency for the year 2025. The second MPO would fulfill the 93.118(b) and (d) requirements for the last year of the transportation plan's forecast period by analyzing and showing consistency for the year 2030 in its conformity determination. Conversely, if only one budget was established for the entire area (i.e., the area's 1-hour ozone SIP did not establish subarea budgets), both MPOs would be required to analyze and show consistency for both 2025 and 2030 in the conformity determination for the area in order to fulfill the 93.118(b) and (d) requirements for the last year of the transportation plan's forecast period.

Example 2: A Scenario 3 or 4 8-hour ozone nonattainment area contains multiple MPOs; each MPO's long-range plan has a different forecast period and the area's 1-hour ozone SIP establishes a subarea budget for each MPO. The 8-hour area also includes a donut area that does not have 1-hour ozone budgets.

How should each MPO address the section 93.118(b) and (d) requirements for the last year of the transportation plan's forecast period?

In general, Question 15 of Part 4 of the July 21, 2004, multi-jurisdictional guidance is applicable in this type of situation. However, this example clarifies how the area would proceed when the MPOs' transportation plans have different forecast periods.

The MPOs would proceed as described in the answer to Example 1 above. Since the 1-hour ozone SIP established subarea budgets, each MPO would be required to analyze the last year of its own transportation plan in its conformity determination.

How should the section 93.119(g) requirement that the last year of the transportation plan's forecast period also be an analysis year be addressed in the donut area?

The donut area does not have an MPO and therefore does not have a metropolitan transportation plan.

The preamble to the 1993 final rule (58 FR 62207) describes how conformity is demonstrated for a nonattainment area that includes a donut area. Specifically, the preamble states that in order to demonstrate conformity the MPO and State DOT may choose to include projects in the donut area in the MPO's plan and TIP. In such a case no further regional emissions analysis would be necessary for projects in the donut area, but project-level determinations for projects in the donut area would have to document that they were from a conforming plan and TIP. Alternatively, projects in the donut area could be included in the regional emissions analysis that is done by the MPO for the nonattainment area. In this case no further regional emissions analysis would be needed for projects in the donut area; however, project-level determinations for projects in the donut area would have to document that they had been included in the regional emissions analysis done by the MPO for its current plan and TIP. One additional alternative is to perform a new regional emissions analysis that reflects the donut area's projects and the MPO's plan and TIP. The new analysis would have to satisfy all of the conformity requirements for plan and TIP conformity determinations and make use of latest planning assumptions and the latest emissions model. The project level determination for projects in the donut area would have to document this new regional emissions analysis.

The situation described in this example is different from the one described in the preamble to the 1993 final rule. In this example the MPOs are using subarea 1-hour ozone emissions budgets to demonstrate conformity to the 8-hour ozone standard and the donut area is using an interim emissions test(s) to demonstrate conformity to the 8-hour ozone standard. Therefore, the MPOs will be conducting separate regional emissions analyses to demonstrate that they meet their subarea budgets.

The donut area has three options for demonstrating conformity using the interim emissions test(s):

  1. Apply the interim emissions test(s) to the donut area
  2. Apply the interim emissions test(s) to the entire nonattainment area
  3. If the nonattainment area is multi-state, apply the interim emissions test(s) to the portion of the nonattainment area within an individual state, in the case where separate 1-hour budgets are established for each state.

Option 1

If the first option is selected through the area's interagency consultation process, then consistent with the discussion of how conformity is demonstrated in donut areas in the preamble to the 1993 rule (58 FR 62207) the nonattainment area's interagency consultation process should be used to determine which MPO or MPOs the donut area is most closely associated with. In general, this determination should be based on factors such as the geography of the nonattainment area (e.g., which MPO or MPOs does the donut area border), the road and transit networks in the area, commuting patterns from and to the donut area and other similar factors. Once this decision is made the conformity determination for the donut area would include the last year(s) of that MPO's or MPOs' transportation plan or plans in order to fulfill the requirement of section 93.119(g) of the conformity rule that the last year of the transportation plan's forecast period also be an analysis year. EPA believes that to avoid confusion once a decision is made concerning whether the donut area is associated with one MPO or whether specific portions of the donut area are associated with different MPOs, the decision should not be revised prior to the time that a SIP is submitted and motor vehicle emissions budgets are found adequate or approved except under extenuating circumstances identified through the interagency consultation process.

For example, if it is determined that the donut area is most closely associated with the MPO that has a transportation plan that extends to 2030, the donut area's projects would be included in an analysis for 2030 in order to demonstrate conformity.

Other situations could occur. For example it may be determined through interagency consultation that different portions of the donut area are associated with different MPOs. This situation is discussed in more detail below.

Also, for the initial 8-hour determinations, DOT will not make conformity determinations until every MPO in the nonattainment area has made conformity determinations on their plans and TIPs, reflecting any associated donut area. Additionally, the regional emissions analysis for the initial determination must reflect the entire nonattainment area, including the entire portion of the nonattainment area not covered by adequate or approved 1-hour budgets.

For subsequent 8-hour determinations made before 8-hour ozone motor vehicle emissions budgets are established for the nonattainment area, each MPO can determine conformity independently, as long as all the other MPOs are in conformity, and the MPO making the conformity determination includes any associated donut area in its analysis. It should be noted, in this example (i.e., a donut area associated with one MPO), that the regional emissions analysis must include the entire portion of the nonattainment area not covered by adequate or approved 1-hour budgets (i.e., the entire donut area). However, if parts of a donut area are associated with different MPOs, conformity could be determined independently by each MPO as long as all other MPOs and their associated portions of the donut area are in conformity. EPA has determined that they can allow areas with subarea budgets to proceed in this way because it is consistent with their previous guidance for areas with subarea budgets. When the regional emissions analysis is performed it would include only the emissions from the relevant MPO and its associated portion of the donut area. The regional emissions analysis would not have to include emissions from the entire donut area.

Options 2 and 3

However, if it is decided that the donut area will demonstrate conformity under option 2 or option 3 by applying the interim emissions test(s) to the entire nonattainment area or the entire portion of the nonattainment area within a single state, then in order to meet the requirements of section 93.119(g) a regional emissions analysis would have to be performed for the last year of each MPO's transportation plan forecast period, either within the entire nonattainment area, or within the individual State, respectively.

For example, if one MPO in such an area has a transportation plan that covers 2005 to 2025 and the other MPO has a plan that covers 2005 to 2030, regional emissions analyses would have to be done for both 2025 and 2030 in order to fulfill the requirements of section 93.119(g) that a regional emissions analysis be performed for the last year of each MPO's transportation plan forecast period.

Conformity after 8-hour Ozone SIP Budgets are Adequate or Approved

40 CFR §93.109(d)(1)

In such 8-hour ozone nonattainment and maintenance areas the budget test must be satisfied as required by §93.118 for conformity determinations made on or after:

  1. The effective date of EPA's finding that a motor vehicle emissions budget in a submitted control strategy implementation plan revision or maintenance plan for the 8-hour ozone NAAQS is adequate for transportation conformity purposes;
  2. The publication date of EPA's approval of such budget in the Federal Register; or
  3. The effective date of EPA's approval or such a budget in the Federal Register, if such approval is completed through direct final rulemaking.

Once a SIP for the 8-hour ozone standard is submitted with a budget(s) that EPA has found adequate or approved, the budget test must be used in accordance with §93.118 to complete all future applicable regional emissions analyses for 8-hour conformity determinations. The 1-hour ozone SIP budgets and or interim emissions test will no longer apply for that precursor. (69 FR 40022, July 1, 2004)

For more information on the budget test please see Section D.

[1] EPA has previously interpreted that only attainment budgets apply beyond the attainment year, in cases where ozone areas also have budgets for ROP SIPs.
[2] The year 2020 is chosen for this example, but any year from 2015 through 2019 would also be acceptable for the interim year analysis.
[3] The year 2015 is chosen for this example, but any year between 2016 and 2020 would also be acceptable for the interim year analysis.
[4] The 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.
[5] Though 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.
[6] 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 wherever it is appropriate and possible.

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