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Transportation Conformity Reference Guide

Section B: SIP Requirements

Overview of State Implementation Plans (SIPs)
General Provisions for SIP Submittals
SIP Development
Specific Provisions of SIPs
Different Types of SIP Submittals That Apply for Transportation Conformity

Relationship of SIPs to Transportation Conformity
Motor Vehicle Emissions Budgets (MVEB) in SIPs

How to Find the Motor Vehicle Emissions Budget in the SIP
Adequacy of Motor Vehicle Emissions Budgets

Which SIP Budget Applies for Transportation Conformity Purposes?

Consequences of Control Strategy Implementation Plan Failures
Questions and Answers

Exhibit B-1: Example of Roles & Responsibilities in SIP Development
Exhibit B-2: Summary of Emissions by Major Source Category
Exhibit B-3: SIP Components From Federal, State & Local/Regional Control Measures
Exhibit B-4: SIP Requirements for Defining Emissions Problem & Due Dates in Nonattainment Areas

Overview of State Implementation Plans (SIPs)

The SIP is a plan prepared by the State that provides for the implementation and enforcement of control measures to attain and maintain the primary and secondary NAAQS. A nonattainment SIP must be adopted by the State and approved by EPA for each pollutant for which the State violates the NAAQS (e.g., carbon monoxide, ozone, PM2.5, and PM10). The Governor designates the responsibility for SIP development and the lead agency is usually the State environmental agency although State DOTs, MPOs and regional air districts (where applicable) must work collaboratively in SIP development, particularly on issues related to transportation strategies to reduce emissions. Roles and responsibilities for SIP planning and development are described in the CAA and included below. Exhibit B-1 provides an example of the roles and responsibilities of agencies in the SIP development process. This is only one example of how responsibilities might be assigned to the various parties in SIP development where State air agencies have a lead role. Exhibit B-1 also illustrates that SIP development must be a truly collaborative process and is to be a key activity of the interagency consultation process as described in Chapter 2.

Exhibit B-1
Example of Roles and Responsibilities in SIP Development
click for text

42 U.S.C. §7504 (a)(b)(c) (Clean Air Act §174) Planning Procedures

  1. In General.--- For any ozone, carbon monoxide, or PM-10 nonattainment area[1], the State containing such area and elected officials of affected local governments shall, before the date required for submittal of the inventory described under 7511(a)(1) and 7512(a)(1) of this title, jointly review and update as necessary the planning procedures adopted pursuant to this subsection as in effect immediately November 15, 1990, or develop new planning procedures pursuant to this subsection, as appropriate. In preparing such procedures the State and local elected officials shall determine which elements of a revised implementation plan will be developed, adopted, and implemented (through means including enforcement) by the State and which by local governments or regional agencies, or any combination of local governments, regional agencies, or the State. The implementation plan required by this part shall be prepared by an organization certified by the State, in consultation with elected officials of local governments and in accordance with the determination under the second sentence of this subsection. Such organization shall include elected officials of local governments in the affected area, and representatives of the State air quality planning agency, the State transportation planning agency, the metropolitan planning organization designated to conduct the continuing, cooperative and comprehensive transportation planning process for the area under section 134 of title 23, the organization responsible for the air quality maintenance planning process under regulations implementing this chapter, and any other organization with responsibilities for developing, submitting, or implementing the plan required by this part. Such organization may be one that carried out these functions before November 15, 1990.
  2. Coordination.--- The preparation of implementation plan provisions and subsequent plan revisions under the continuing transportation air quality planning process described in section 7408(e) of this chapter shall be coordinated with the continuing, cooperative and comprehensive transportation planning process required under section 134 of title 23, and such planning processes shall take into account the requirements of this part.
  3. Joint Planning.--- In the case of a nonattainment area that is included within more than one State, the affected States may jointly, through interstate compact or otherwise, undertake and implement all or part of the planning procedures described in this section.

Contents of each SIP are described as follows:

42 U.S.C. §7410(a)(2)(A) (Clean Air Act §110(a)(2)(A))

Include enforceable emissions limitations and other control measures, means, or techniques (including economic incentives such as fees, marketable permits, and auctions of emissions rights), as well as schedules and timetables for compliance, as may be necessary or appropriate to meet the applicable requirements of this chapter.

Each SIP revision must meet specific criteria and requirements, which are detailed in the CAA[2] and in guidance issued by EPA. Once EPA approves a SIP, it is legally enforceable and a SIP revision is required any time the State cannot meet its commitments to implement the EPA approved SIP strategies or if emissions budget revisions are needed due to updated models. However, an updated model does not necessarily trigger a SIP revision. If a State fails to submit a SIP (or SIP revision) when required, the EPA may develop a Federal Implementation Plan (FIP) for that State. A FIP is a plan developed by the EPA and is enforceable under Federal law. The EPA Administrator shall promulgate a FIP:

42 U.S.C. §7410(c)(1) (Clean Air Act §110(c)(1))

...at any time within 2 years after the Administrator.....A) finds that a State has failed to make a required submission or finds that the plan or plan revision submitted by the State does not satisfy the minimum criteria established under subsection (k)(1)(A) of this section, or B) disapproves a State implementation plan submission in whole or in part, unless the State corrects the deficiency, and the Administrator approves the plan or plan revision, before the Administrator promulgates such Federal implementation plan.

General Provisions for SIP Submittals

42 U.S.C. §7502 (c) (Clean Air Act §176(c))

(c) Nonattainment Plan Provisions.-
The plan provisions (including plan items) required to be submitted under this part shall comply with each of the following:

  1. In General.--Such plan provisions shall provide for the implementation of all reasonably available control measures as expeditiously as practicable (including such reductions in emissions from existing sources in the area as may be obtained through the adoption, at a minimum, of reasonably available control technology) and shall provide for attainment of the national primary ambient air quality standards.
  1. RFP.--Such plan provisions shall require reasonable further progress.
  1. Inventory.--Such plan provisions shall include a comprehensive, accurate, current inventory of actual emissions from all sources of the relevant pollutant or pollutants in such area, including such periodic revisions as the Administrator may determine necessary to assure that the requirements of this part are met.
  1. Identification and Quantification.--Such plan provisions shall expressly identify and quantify the emissions, if any, of any such pollutant or pollutants which will be allowed, in accordance with 7503(a)(1)(B) of this title, from the construction and operation of major new or modified stationary sources in each such area. The plan shall demonstrate to the satisfaction of the Administrator that the emissions quantified for this purpose will be consistent with the achievement of reasonable further progress and will not interfere with attainment of the applicable national ambient air quality standard by the applicable attainment date.
  1. Permits for New and Modified Major Stationary Sources.--Such plan provisions shall require permits for the construction and operation of new or modified major stationary sources anywhere in the nonattainment area, in accordance with section 7503 of this title.
  1. Other Measures.--Such plan provisions shall include enforceable emissions limitations, and such other control measures, means or techniques (including economic incentives such as fees, marketable permits, and auctions of emissions rights), as well as schedules and timetables for compliance, as may be necessary or appropriate to provide for attainment of such standards in such areas by the applicable attainment date specified in this part.
  1. Compliance with Section 7410(a)(2).--Such plan provisions shall also meet the applicable provisions of section 7410(a)(2) of this title.
  1. Equivalent Techniques.--Upon application by any State, the Administrator may allow the use of equivalent modeling, emissions inventory, and planning procedures, unless the Administrator determines that the proposed techniques are, in the aggregate, less effective than the methods specified by the Administrator.
  1. Contingency Measures.--Such plan shall provide for the implementation of specific measures to be undertaken if the area fails to make reasonable further progress, or to attain the national primary ambient air quality standard by the attainment date applicable under this part. Such measures shall be included in the plan revision as contingency measures to take effect in any such case without further action by the State or the Administrator.

SIP Development

As discussed earlier, SIPs are collections of regulations and measures used by State to reduce emissions from all sources, and demonstrate attainment and maintenance of air quality standards.

Emissions are generally classified in one of three categories: stationary sources, which are broken down into 1) point sources and 2) area sources, and 3) on-and off-road mobile sources. Point sources are relatively large, fixed sources of emissions such as power plants, chemical process industries, and petroleum refineries. Area sources are small, stationary, and non-transportation sources that may collectively contribute to air pollution (e.g. dry cleaners or bakeries). Mobile sources include on-road sources such as cars, trucks, and buses, and off-road sources such as trains, ships, boats, airplanes, lawnmowers, and construction equipment. There are also natural emissions, called biogenic, which come from the life processes of plants and animals and also contribute to the formation of ozone.

The CAA requires[3] that periodic inventories of emissions be prepared (emissions inventory) which are comprehensive, accurate, and reflect the current level of actual emissions from all sources. All ozone nonattainment areas classified as marginal and above and carbon monoxide areas must conduct these inventories and submit them to EPA every three years until attainment. Emissions reductions needed to achieve the NAAQS are determined based on the emissions inventory. States consider cost-effectiveness and feasibility of control strategies to achieve the overall emissions target and reductions can disproportionately rely on mobile or stationary sources. Emissions budgets are established for individual sources (i.e., mobile, point, and area); emissions reduction targets are established for the region.

It is important that the level of emissions reductions assigned to each of the source categories can be achieved through the implementation of the strategies included in the SIP. In some cases, substantial reductions will be needed from the transportation sector in order to reduce CO, VOC, NOx, PM2.5, and PM10 emissions by the levels needed to achieve the NAAQS. Therefore, it is important that transportation and air quality officials participate in decision-making on the SIP and allocation of reductions to the different sources. Exhibit B-2 shows the major transportation-related pollutants and their contributions to overall emissions levels on a national scale. Source contributions will vary by geographic area.

Exhibit B-2
Summary of Emissions by Major Source Category
2002 Base-year Average Annual Day (tons/day)
National Emissions Trends
Volatile Organic Compound (VOC) Emissions
2002
click for data
National Emissions Trends
Nitrogen Oxide (NOx) Emissions
2002
click for data
National Emissions Trends
Carbon Monoxide (CO) Emissions
2002
click for data
National Emissions Trends
PM10 Emissions
2002
click for data
National Emissions Trends
PM2.5 Emissions
2002
click for data

Source: EPA, National Air Quality and Emissions Trends Report-2003.

Following completion of the emissions inventory, modeling analysis, preparation of forecasts of future emissions, and the calculation of future emissions reduction shortfalls, the State environmental agency allocates emissions reduction budgets to individual pollution sources (i.e. mobile, point, and area). The SIP then assigns specific emissions reduction levels to each source category, based on existing and planned control measures and appropriately accounting for growth. For the on-road mobile source category of emissions, the emissions reduction level is further refined into a regulatory limit on emissions, referred to as a motor vehicle emissions budget for on-road mobile sources and is discussed in detail below. Emissions reduction targets for mobile sources can be achieved in varying degrees through programs that target emissions associated with vehicles and vehicle use or vehicle miles of travel such as:

Government agencies and particularly transportation and air quality agencies, need to cooperatively develop SIPs in order to achieve the needed levels of emissions reductions. The Federal government usually adopts control strategies on automobiles and aircraft, for legal and practical reasons. Other strategies, like controls on fuels, inspection and maintenance programs, or market measures, can be adopted and effectively implemented and enforced at the State level. Finally, control measures such as transit investments or high-occupancy vehicle (HOV) lanes must be implemented at the local or regional level; however, these control measures may require State legislation or approvals. Exhibit B-3 illustrates how the different types of strategies adopted by government agencies at the Federal, State, and regional levels can work together in the SIP to enable a nonattainment area to achieve the NAAQS.

Exhibit B-3
Examples of SIP Components from Federal, State, and Local/Regional Control Measures
flowchart: click for text description

Specific Provisions of SIPs

Each SIP must comply with thirteen specific provisions of the CAA.

42 U.S.C. §7410(a)(2) (Clean Air Act §110(a)(2))

  1. Each implementation plan submitted by a State under this Act shall be adopted by the State after reasonable notice and public hearing. Each such plan shall--
    1. include enforceable emissions limitations and other control measures, means, or techniques (including economic incentives such as fees, marketable permits, and auctions of emissions rights), as well as schedules and timetables for compliance, as may be necessary or appropriate to meet the applicable requirements of this Act;
    2. provide for establishment and operation or appropriate devices, methods, systems, and procedures necessary to--
      1. monitor, compile, and analyze data on ambient air quality, and
      2. upon request, make such data available to the Administrator;
    3. include a program to provide for the enforcement of the measures described in subparagraph (A), and regulation of the modification and construction of any stationary source within the areas covered by the plan as necessary to assure that national ambient air quality standards are achieved, including a permit program as required in parts C and D;
    4. contain adequate provisions --
      1. prohibiting, consistent with the provisions of this title, any source or other type of emissions activity within the State from emitting any air pollutant in amounts which will-
        1. contribute significantly to nonattainment in, or interfere with maintenance by, any other State with respect to any such national primary or secondary ambient air quality standard, or
        2. interfere with measures required to be included in the applicable implementation plan for any other State under part C to prevent significant deterioration of air quality or to protect visibility,
      2. insuring compliance with the applicable requirements of sections 7426 and 7415 of this title (relating to interstate and international pollution abatement);
    5. provide
      1. necessary assurances that the State (or, except where the Administrator deems inappropriate, the general purpose local government or governments, or a regional agency designated by the State or general purpose local governments for such purpose) will have adequate personnel, funding, and authority under State(and, as appropriate, local) law to carry out such implementation plan (and is not prohibited by any provisions of Federal or State law from carrying out such implementation plan or portion thereof),
      2. requirements that the State comply with the requirements respecting State boards under section 7428 of this title, and
      3. necessary assurances that, where the State has relied on a local or regional government, agency, or instrumentality for the implementation of any plan provision, the State has responsibility for ensuring adequate implementation of such plan provision;
    6. require, as may be prescribed by the Administrator--
      1. the installation, maintenance, and replacement of equipment, and the implementation of other necessary steps, by owners or operators of stationary sources to monitor emissions from such sources,
      2. periodic reports on the nature and amounts of emissions and emissions-related data from such sources, and
      3. correlation of such reports by the State agency with any emissions limitations or standards established pursuant to this chapter, which reports shall be available at reasonable times for public inspection;
    7. provide for authority comparable to that in section 7603 of this title and adequate contingency plans to implement such authority;
    8. provide for revision of such plan--
      1. from time to time as may be necessary to take account of revisions of such national primary or secondary ambient air quality standard or the availability of improved or more expeditious methods of attaining such standard, and
      2. except as provided in paragraph (3)(C), whenever the Administrator finds, on the basis of information available to the Administrator, that the plan is substantially inadequate to attain the national ambient air quality standard which it implements or to otherwise comply with any additional requirements established under this chapter;
    9. in the case of a plan or plan revision for an area designated as a nonattainment area, meet the applicable requirements of part D (relating to nonattainment area);
    10. meet the applicable requirements of section 7421of this title (relating to consultation), section 7427 of this title (relating to public notification), and part C of this subchapter (relating to prevention of significant deterioration or air quality and visibility protection);
    11. provide for --
      1. the performance of such air quality modeling as the Administrator may prescribe for the purpose of predicting the effect on ambient air quality of any emissions of any air pollutant for which the Administrator has established a national ambient air quality standard, and
      2. the submission, upon request, of data related to such air quality modeling to the Administrator;
    12. require the owner or operator of each major stationary source to pay to the permitting authority, as a condition of any permit required under this chapter, a fee sufficient to cover--
      1. the reasonable costs of reviewing and acting upon any application for such a permit, and
      2. if the owner or operator receives a permit for such source, the reasonable costs of implementing and enforcing the terms and conditions of any such permit (not including any court costs or other costs associated with any enforcement action), until such fee requirement is superseded with respect to such sources by the Administrator's approval of a fee program under chapter V of this chapter; and
    13. provide for consultation and participation by local political subdivisions affected by the plan.

Different Types of SIP Submittals That Apply for Transportation Conformity

The principal types of SIP submittals that are used for transportation conformity are described below. The requirements for nonattainment areas to define the emissions problem and due dates are shown in Exhibit B-4. In addition, the processes specifying how consultation procedures and the enforcement and enforceability of control or mitigation measures will be implemented within a particular State are adopted in the conformity SIP and such procedures are binding and legally-enforceable once approved by EPA.

Exhibit B-4
SIP Requirements for Defining Emissions Problem & Due Dates in Nonattainment Areas
Pollutant and Requirements SIP Submittal Due Date

*8-Hour Ozone Pending Phase 2 of the 8-hour Implementation Rule

 June 15, 2007
Carbon Monoxide (CO) Moderate <12.7 ppm: Carbon Monoxide Emissions Inventory - These areas must submit a 1990 emissions inventory and control plan by November 15, 1992, of all CO emissions, including mobile, stationary, and area sources, and revise every three years thereafter until attainment. These inventories do not create motor vehicle emissions budgets for conformity[4]. There is no obligation to revisit motor vehicle emissions budgets when inventories are updated. November 15, 1992 and every three years there-after until attainment
Carbon Monoxide (CO) Moderate > 12.7 ppm: Attainment Demonstration - Demonstrate that attainment will be reached by the December 31, 1995 deadline. Also, provide provisions in the SIP for annual emissions reductions necessary for reaching attainment November 15, 1992
Carbon Monoxide (CO) Serious: Attainment Demonstration - Demonstrate that attainment will be reached by the December 31, 2000 deadline. Also provide provisions in the SIP for annual emissions reductions necessary for reaching attainment November 15, 1992
Particulate Matter (PM10) Moderate: Attainment Demonstration - Submit a SIP by November 15, 1991, demonstrating attainment of the NAAQS by December 31, 1994. Milestones- Meet quantitative milestones in the SIP which are to be achieved every 3 years November 15, 1991
Particulate Matter (PM10) Serious: Attainment Demonstration - Submit a SIP no later than 4 years after reclassification of the area to serious. The SIP must demonstrate attainment of the NAAQS by no later than the 10th calendar year after the area's classification 4 years after reclassification to serious with attainment demonstrated no later than 10 calendar years after reclassification
*PM2.5 Pending PM2.5 Implementation Rule April 5, 2008

Source: A Summary of Transportation Programs and Provisions of the Clean Air Act Amendments of 1990, Federal Highway Administration, FHWA-PD-92-023.
* SIP requirements for 8-hour ozone are detailed in the Phase 2 Implementation Rule, and requirements for PM2.5 will be detailed in the final PM2.5 Implementation Rule.

Attainment SIPs

States must make an air quality attainment demonstration using emissions modeling or any other approved analytical method. An attainment demonstration provides specific annual reductions in emissions needed to attain the NAAQS by the CAA mandated attainment dates for 1-hour ozone (Exhibit l-3), 8-hour ozone (Exhibit l-4), CO (Exhibit l-5), PM10 (Exhibit l-6), and PM2.5 (Exhibit l-7). Attainment SIPs contain motor vehicle emissions budgets for the attainment year.

Maintenance Plans

Maintenance plans provide assurance that an area maintains the ozone, CO, PM10, PM2.5, or NO2 standard over time. Maintenance plans also contain motor vehicle emissions budgets that must address the level of motor vehicle emissions in the last year of the maintenance plan period. Please refer to Section D for detailed information on maintenance area requirements including timeframes for maintenance plans.

Conformity SIPs

SAFETEA-LU section 6011(f)(4)(E) Inclusion of Criteria and Procedures in SIP

This provision streamlines the requirements for state conformity SIPs. It amends section 176(c)(4)(E) of the Clean Air Act (42 U.S.C. 7506(c)(4)(E) to read:

Not later than 2 years after the date of enactment of the SAFETEA-LU the procedures under subparagraph (A) shall include a requirement that each State include in the State implementation plan criteria and procedures for consultation required by subparagraph (D)(i), and enforcement and enforceability (pursuant to section 93.125(c) and 93.122(a)(4)(ii) of title 40, Code of Federal Regulations) in accordance with the Administrator's criteria and procedures for consultation, enforcement and enforceability.

A conformity SIP (also called the conformity SIP revision) must be submitted to EPA within 1 year of either nonattainment designations or the publication of EPA's conformity rule amendments that affect applicable provisions. The conformity SIP must address three specific provisions of the transportation conformity rule: 1) interagency consultation, 2) enforcement and enforceability of control measure commitments relied on in a plan/TIP conformity determination (93.122(a)(4), and (3)) enforcement and enforceability of mitigation measures committed to in a project-level conformity determination (93.125).

Conformity SIPs do not contain motor vehicle emissions budgets. The conformity SIP must be submitted within 12 months of an area's designation from attainment to nonattainment and, for existing nonattainment and maintenance areas, within 12 months of the date of publication of amendments to the conformity rule affecting the three sections described above. The conformity SIP must include tailored interagency consultation procedures. A State can establish more stringent criteria and procedures than Federal rule provisions as long as the State's procedures apply equally to non-federal and Federal entities. The conformity SIP is legally enforceable through either a Memorandum of Understanding or legislation and therefore the State must implement the SIP provisions. Please refer to Chapter 2 for additional information.

On November 18, 2004, EPA released guidance (see Appendix P) to assist areas with approved conformity SIPs to know which provisions of the July 1, 2004, conformity rule amendments apply immediately in their areas, and which provisions cannot apply until their conformity SIPs are revised. In addition, the guidance document includes questions and answers on other aspects of conformity SIPs. See the interim guidance on SAFETEA-LU released by DOT and EPA for how areas with approved conformity SIPs should handle the changes in the conformity SIP provisions.

Relationship of SIPs to Transportation Conformity

Regardless of which type of SIP is required, motor vehicle emissions budgets included in SIPs become the ceiling on transportation related emissions for each year that a budget is established and until attainment of the respective NAAQS. Adherence to the motor vehicle emissions budget becomes the key measure of conformity between transportation plans, programs and projects and the submitted or approved SIP.

Once approved by EPA, a SIP is a legally binding commitment to implement the control strategies on the schedules included in the SIP. For transportation conformity purposes, the control strategies related to transportation activities represent commitments to their implementation on the SIP schedules, in the respective nonattainment or maintenance area.

Motor Vehicle Emissions Budgets (MVEB) in SIPs

Motor vehicle emissions budgets are developed based upon the emissions inventory and reflect effects of control measures included in the SIP. The budget is developed as part of the SIP process and is subject to the interagency consultation process as discussed in Chapter 2. Motor vehicle emissions are estimated based upon the number of vehicles in the region, their age, the rate of fleet turnover to newer and cleaner vehicles, seasonal temperatures in the region, vehicle miles traveled (VMT), population growth, and other factors. A motor vehicle emissions budget is:

"...that portion of the total allowable emissions defined in the submitted or approved control strategy SIP revision or maintenance plan for a certain date for the purpose of meeting reasonable further progress milestones or demonstrating attainment or maintenance of the NAAQS, for any criteria pollutant or its precursors, allocated to highway and transit vehicle use and emissions."[5]

Once the motor vehicle emissions budget is established and submitted to EPA and EPA's positive adequacy determination is made or the budget is approved, it must be used for conformity purposes. Emissions expected from implementation of transportation plans and programs must be consistent with estimates of emissions from motor vehicles and necessary emissions reductions contained in the SIP. The motor vehicle emissions budget is the mechanism EPA has identified for carrying out the demonstration of consistency, and transportation conformity determinations are an affirmation that this test has been met. A detailed discussion of regional emissions requirements and conformity tests is included in Chapters 5 through 11.

Some Common MVEB Issues

NOx Budgets

A NOx budget would not be established in the SIP if the attainment demonstration or maintenance SIP demonstrates that NOx increases are not a problem based upon modeling that demonstrates that NOx growth would not increase ozone concentrations or preclude attainment by the statutory deadline. Some areas have historically applied for a NOx waiver to eliminate the requirement for the NOx emission reduction tests. A NOx waiver is a finding by the EPA Administrator under Clean Air Act sections 182(b) or 182(f) that additional reductions of NOx would not contribute to attainment of the ozone standard by the statutory deadline. The granting of a NOx waiver by EPA however does not mean the area will not be required to have a NOx budget. It should be noted that a NOx waiver under the 1-hour standard is not applicable to the 8-hour standard; however, 8-hour ozone nonattainment areas may request a NOx waiver from EPA.

Subarea Budget Option

If a nonattainment or maintenance area includes more than one MPO, then the SIP may establish motor vehicle emissions budgets for each MPO (subarea budgets) or the MPOs must collectively analyze emissions for the entire nonattainment area[6]. The SIP must explicitly indicate intent to create such subarea budgets for the purposes of conformity[7]. If the SIP establishes subarea budgets for conformity purposes, then the MPO and DOT must consider the estimates of future emissions by geographic subarea within the nonattainment area for subsequent conformity determinations.

The SIP may specify emissions budgets for subareas of the region, provided that the SIP includes a demonstration that the subregional emissions budgets, 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 subarea emissions budget in the SIP.

Safety Margins in Emissions Budgets

A SIP submittal could show that emissions from all sources will be less than the total emissions that would enable an area to meet applicable requirements to demonstrate reasonable further progress, maintenance or attainment and have quantified that difference in emissions. In these cases, a safety margin[8] exists that equals the difference between expected emissions and emissions, which could occur and still enable the area to reach attainment. A State may submit a SIP revision to the EPA, which assigns some or all of the safety margin to highway and transit sources for the purposes of conformity. Such a SIP revision must explicitly assign the safety margin in order for it to be used in conformity. See the questions and answers at the end of this chapter for further information on safety margins.

Trading Emissions Among Budgets

A conformity determination cannot be based upon the trading of emissions among budgets from various sources of pollution unless the SIP establishes appropriate mechanisms for such trades[9]. For example, emissions from motor vehicles are allocated a certain amount of the total emissions budget from all sources and changing that allocation in order to make a conformity determination is not allowed unless provided for in the SIP. If the SIP does not establish such a mechanism, then a SIP revision would be required to change the budgets.

Insignificant Motor Vehicle Emissions

A SIP may show that the motor vehicle emissions for a pollutant or precursor for a given standard are an insignificant contributor to an area's regional air quality problem or that the area only has a hot spot problem. In these areas, the regional emissions analysis requirements in §§ 93.118 and 93.119 are waived for the insignificant pollutant or precursor upon the effective date of EPA's adequacy finding or approval of such a SIP. In addition, the hot-spot requirements in §§ 93.116 and 93.123 in CO and PM10 areas may be waived if EPA also determines that the SIP demonstrates that potential localized hot-spot emissions are not a concern. Under these provisions, areas are still required to make a conformity determination that satisfies all other relevant requirements.

How to Find the Motor Vehicle Emissions Budget in the SIP

All control strategy SIPs and maintenance plans submitted after the November 24, 1993 transportation conformity rule should have explicitly identified budgets. Motor vehicle emissions budgets may not have been explicitly labeled in SIPs, which existed prior to that date. In these cases, the future highway and transit-related emissions used in the milestone or attainment demonstration is, in effect, the motor vehicle emissions budget. The interagency consultation process (see Chapter 2) will also have an established procedure for ensuring that copies of documents, including SIP submittals, are circulated among the participants and this documentation will provide the explicit motor vehicle emissions budget information.

Adequacy of Motor Vehicle Emissions Budgets

The transportation conformity rule defines minimum criteria for determining the adequacy of a motor vehicle emissions budget in a submitted control strategy SIP or maintenance plan. The six minimum criteria for adequacy are listed below:

40 CFR §93.118 (e)(4)

  1. The submitted control strategy implementation plan revision or maintenance plan was endorsed by the Governor (or his or her designee) and was subject to a State public hearing;
  2. Before the control strategy implementation plan or maintenance plan was submitted to EPA, consultation among Federal, State, and local agencies occurred; full implementation plan documentation was provided to EPA; and EPA's stated concerns, if any, were addressed;
  3. The motor vehicle emissions budget(s) is clearly identified and precisely quantified;
  4. The motor vehicle emissions budget(s), when considered together with all other emissions sources, is consistent with applicable requirements for reasonable further progress, attainment, or maintenance (whichever is relevant to the given implementation plan submission);
  5. The motor vehicle emissions budget(s) is consistent with and clearly related to the emissions inventory and the control measures in the submitted control strategy implementation plan revision or maintenance plan; and
  6. Revisions to previously submitted control strategy implementation plans or maintenance plans explain and document any changes to previously submitted budgets and control measures; impacts on point and area source emissions; any changes to established safety margins (see §93.101 for definition); and reasons for the changes (including the basis for any changes related to emissions factors or estimates of vehicle miles traveled).

Process to Determine Budget Adequacy

The July 1, 2004 rulemaking modified several provisions under §§93.109 and 93.118 of the conformity regulation to specify that EPA must affirmatively find submitted budgets adequate before they can be used in a conformity determination. The rule now addresses only the procedures for making adequacy findings for submitted SIPs in accordance with the March 1999 court decision. The rule is now consistent with the adequacy procedures already in place as a result of EPA's May 14, 1999 guidance issued to implement the court decision (69 FR 40038, July 1, 2004).

40 CFR §93.118(f) Adequate review process for implementation plan submissions.

EPA will use the procedures listed in paragraph (f)(1) or (f)(2) of this section to review the adequacy of an implementation plan submission:

  1. When EPA reviews the adequacy of an implementation plan submission prior to EPA's final action on the implementation plan,
    1. EPA will notify the public through EPA's website when EPA receives an implementation plan submission that will be reviewed for adequacy.
    2. The public will have a minimum of 30 days to comment on the adequacy of the implementation plan submission. If the complete implementation plan is not accessible electronically through the internet and a copy is requested within 15 days of the date of the website notice, the comment period will be extended for 30 days from the date that a copy of the implementation plan is mailed.
    3. After the public comment period closes, EPA will inform the State in writing whether EPA has found the submission adequate or inadequate for use in transportation conformity, including response to any comments submitted directly and review of comments submitted through the State process, or EPA will include the determination of adequacy or inadequacy in a proposed or final action approving or disapproving the implementation plan under paragraph (f)(2)(iii) of this section.
    4. EPA will publish a Federal Register notice to inform the public of EPA's finding. If EPA finds the submission adequate, the effective date of this finding will be 15 days from the date the notice is published as established in the Federal Register notice, unless EPA is taking a final approval action on the SIP as described in paragraph (f)(2)(iii) of this section.
    5. EPA will announce whether the implementation plan submission is adequate or inadequate for use in transportation conformity on EPA's website. The website will also include EPA's response to comments if any comments were received during the public comment period.
    6. If after EPA has found a submission adequate, EPA has cause to reconsider this finding, EPA will repeat actions described in paragraphs (f)(1)(i) through (v) or (f)(2) of this section unless EPA determines that there is no need for additional public comment given the deficiencies of the implementation plan submission. In all cases where EPA reverses its previous finding to a finding of inadequacy under paragraph (f)(1) of this section, such a finding will become effective immediately upon the date of EPA's letter to the State.
    7. If after EPA has found a submission inadequate, EPA has cause to reconsider the adequacy of that budget, EPA will repeat actions described in paragraphs (f)(1)(i) through (v) or (f)(2) of this section.
  2. When EPA reviews the adequacy of an implementation plan submission simultaneously with EPA's approval or disapproval of the implementation plan,
    1. EPA's Federal Register notice of proposed or direct final rulemaking will serve to notify the public that EPA will be reviewing the implementation plan submission for adequacy.
    2. The publication of the notice of proposed rulemaking will start a public comment period of at least 30 days.
    3. EPA will indicate whether the implementation plan submission is adequate and thus can be used for conformity either in EPA's final rulemaking or through the process described in paragraphs (f)(1)(iii) through (v) of this section. If EPA makes an adequacy finding through a final rulemaking that approves the implementation plan submission, such a finding will become effective upon the publication date of EPA's approval in the Federal Register, or upon the effective date of EPA's approval if such action is conducted through direct final rulemaking. EPA will respond to comments received directly and review comments submitted through the State process and include the response to comments in the applicable docket.

Criteria for EPA Adequacy Determination of a SIP With a Motor Vehicle Emissions Budget

In general, the same criteria apply for EPA approval of a SIP with a motor vehicle emissions budget as apply for the entire SIP. The following key requirements should be noted by transportation practitioners (see the earlier sections of this chapter for more detailed information on general and specific provisions of SIPs):

  1. The SIP must identify specific control strategies that will result in emissions reductions from highway and transit sources consistent with the motor vehicle emissions budget;
  2. The SIP must identify how the State expects to achieve the reductions on the schedule that will achieve the purpose of the SIP (e.g., attainment or reasonable further progress); and,
  3. Implementation of all transportation-related actions, including TCMs must be committed to by the entity with legal authority to carry out the measures (i.e. State, MPO, transit agency, local government).

Which SIP Budget Applies for Transportation Conformity Purposes?

Approved SIPs Versus Submitted SIPs

EPA believes that Clean Air Act section 176(c) clearly requires transportation plans, TIPs and projects to conform to a nonattainment or maintenance area's approved SIP before such activities can be funded or approved. Therefore, EPA believes it has no statutory authority to allow submitted budgets that are established for the same year and Clean Air Act requirement to supercede budgets that have already been approved into the SIP. In general, a submitted budget replaces a previously approved budget established for the same year and Clean Air Act requirement only after EPA has approved the submitted budget. EPA notes, however that submitted budgets that are established for a different year or Clean Air Act requirement than a previously approved budget must be used in conformity upon EPA's adequacy finding, along with all other applicable adequate and approved budgets. (69 FR 40043, July 1, 2004)

Multiple SIP Submissions

When multiple SIPs have been submitted to satisfy the same CAA requirement, the budgets from the most recent SIP submissions would replace the budgets from other prior SIP submissions that have not yet been approved, once they have been found adequate, or are approved.

When a series of control strategy SIPs have been submitted to fulfill different Clean Air Act requirements for a particular pollutant, the budget test would be demonstrated using each relevant submitted SIP that is adequate for conformity purposes. SIP budget(s) that address the latest future year would apply for all subsequent years in the timeframe of the regional emissions analysis on the transportation plan and program. (61 FR 36117-8, July 9, 1996)

Consequences of Control Strategy Implementation Plan Failures

It is important to note the consequences on the transportation plan, TIP, and projects in the event of a control strategy SIP failure (control strategy SIPs are 15% SIPs, post-1996 SIPs, and attainment demonstrations[10]). The consequences of SIP disapproval only apply when control strategy SIPs are disapproved. The rule provisions and definition of a protective finding are included below and a complete discussion of these issues is provided in Chapter 4.

40 CFR §93.120 Consequences of Control Strategy Implementation Plan Failures

  1. Disapprovals.
    1. If EPA disapproves any submitted control strategy implementation plan revision (with or without a protective finding), the conformity status of the transportation plan and TIP shall lapse on the date that highway sanctions as a result of the disapproval are imposed on the nonattainment area under section 179(b)(1) of the CAA. No new transportation plan, TIP, or project may be found to conform until another control strategy implementation plan revision fulfilling the same CAA requirements is submitted and conformity to this submission is determined.
    2. If EPA disapproves a submitted control strategy implementation plan revision without making a protective finding, only projects in the first three years of the currently conforming transportation plan and TIP may be found to conform. This means that beginning on the effective date of a disapproval without a protective finding, no transportation plan, TIP, or project not in the first three years of the currently conforming transportation plan and TIP may be found to conform until another control strategy implementation plan revision fulfilling the same CAA requirements is submitted, EPA finds its motor vehicle emissions budget(s) adequate pursuant to §93.118 or approves the submission, and conformity to the implementation plan revision is determined.
    3. In disapproving a control strategy implementation plan revision, EPA would give a protective finding where a submitted plan contains adopted control measures or written commitments to adopt enforceable control measures that fully satisfy the emissions reductions requirements relevant to the statutory provision for which the implementation plan revision was submitted, such as reasonable further progress or attainment.
  2. Failure to submit and incompleteness. In areas where EPA notifies the State, MPO, and DOT of the State's failure to submit a control strategy implementation plan or submission of an incomplete control strategy implementation plan revision (either of which initiates the sanction process under CAA sections 179 or 110(m)), the conformity status of the transportation plan and TIP shall lapse on the date that highway sanctions are imposed on the nonattainment areas for such failure under section 179(b)(1) of the CAA, unless the failure has been remedied and acknowledged by a letter from the EPA Regional Administrator.
  3. Federal implementation plans. If EPA promulgates a Federal implementation plan that contains motor vehicle emissions budget(s) as a result of a State failure, the conformity lapse imposed by this section because of that State failure is removed.

Please refer to Chapter 4 for further information on consequences of SIP disapproval.

40 CFR §93.101, Definitions

Protective finding means a determination by EPA that a submitted control strategy implementation plan revision contains adopted control measures or written commitments to adopt enforceable control measures that fully satisfy the emissions reductions requirements relevant to the statutory provision for which the implementation plan revision was submitted, such as reasonable further progress or attainment.

Questions and Answers

Can I use a submitted SIP budget for conformity determinations?

Yes, once EPA affirmatively finds the submitted SIP motor vehicle emissions budget adequate for conformity purposes, through the processes described below.

What if I have a submitted budget now or will soon submit a new budget, and this budget was never used in a previous conformity determination? Can I use it in future conformity determinations?

Yes, once EPA affirmatively finds the budget adequate for conformity purposes, it must be used in subsequent determinations. (Submitted budgets cannot be used if there is an approved SIP covering the same timeframe and Clean Air Act requirements as the newly submitted SIP. This aspect of the 1997 rule was unchanged by the court.)

Even if EPA finds the SIP budget adequate for conformity purposes, this does not necessarily mean the SIP will be found complete or be approved. If EPA finds the SIP budgets adequate, it still can disapprove the SIP. However, conformity determinations made before a SIP is disapproved still stand. See the questions and answers at the end of this chapter for more information. Additional information about conformity tests and regional emissions analysis requirements are included in Chapters 5-8.

Is EPA willing to expedite adequate findings?

EPA can expedite adequacy findings through parallel processing procedures. As stated in the June 2003 proposal, EPA will parallel process a SIP if requested to do so by the state. However, the parallel processing can expedite the adequacy review of a submitted SIP only if no changes to that SIP and its budgets are made before the state officially submits the SIP to EPA for approval. In the event that the SIP significantly changes between the time EPA begins its initial adequacy review and the state's formal submission of the SIP, EPA would have to re-start the adequacy process once the new SIP is formally submitted.

What conformity test do I use before EPA has found the submitted budget adequate?

Use whatever conformity test applied before the new budget was submitted. For example, if your area has not submitted and received approval for budgets for the given criteria pollutant, you would use the interim emissions tests that are required by 40 CFR 93.119 of the conformity rule. If you had previously approved budget(s) for a given pollutant or previously submitted budget(s) that EPA had found adequate, you would need to meet the approved or adequate budget(s) for all analysis years. The submitted budget is not used until EPA finds it adequate. Contact your EPA Regional Office if you have questions about what conformity tests apply in your area.

What criteria will EPA use to determine the adequacy of a submitted budget?

The adequacy criteria are contained in 40 CFR 93.118(e)(4) of the conformity rule. EPA encourages air quality and transportation agencies to work closely with EPA Regional Offices to ensure that the SIP includes clearly defined, adequate motor vehicle emissions budgets. Close consultation during the SIP's development will assist EPA in making adequacy determination on submitted budgets quickly.

How does EPA's adequacy process relate to completeness review or approvability of the SIP?

EPA's completeness review of a submitted SIP is separate from the conformity adequacy process, and it uses different criteria. Likewise, EPA's approval process requires a more detailed examination of the SIP's control measures and technical analyses than the conformity adequacy process. Although the minimum criteria for adequacy allow EPA to make a cursory review of the submitted control strategies, demonstrations, and motor vehicle emissions budgets for conformity purposes, EPA recognizes that other elements must also be in the SIP for it to ultimately be approved.

EPA's adequacy review should not be used to prejudge EPA's ultimate approval or disapproval of the SIP, since additional information may be submitted and more extensive review may change some of the conclusions. However, if EPA judges the budget inadequate, the State and local agencies should work closely with EPA to address the problems identified. A control strategy SIP or maintenance plan must contain an adequate motor vehicle emissions budget(s) in order for EPA to approve the SIP.

EPA's adequacy process will only be completed on SIPs that create motor vehicle emissions budgets used in conformity determinations (i.e., 15% SIPs, 9% SIPs[11], attainment demonstrations, and maintenance plans), SIPs that claim regional motor vehicle emissions are insignificant, and limited maintenance plans.

If EPA finds a submitted budget inadequate, can it reevaluate the decision later and call it adequate based on further analysis or if new information on the adequacy of the budget is submitted? Can the opposite occur?

EPA can change an adequacy finding from adequate to inadequate or from inadequate to adequate for a specific reason such as receiving new information or conducting further review and analyses that affect its previous finding. For example, EPA might change a finding of inadequacy if a state submits additional information that clarifies or supports the adequacy of the submitted SIP and budget. In this case, EPA will treat the additional information as a supplement to the previous SIP submission, and would post a notice on the adequacy Web site and begin a new 30-day public comment period on the entire SIP including this new information. After reviewing any comments, EPA would make a new finding, as appropriate, in accordance with those procedures in Sec. 93.118(f) of this final rule.

EPA could change its finding to inadequate in the case where it finds the budgets in a submitted SIP adequate but later discover, based on additional information or further review, that they do not meet the criteria for adequacy. EPA requested comment in the June 30, 2003 proposal on whether the public should be provided an opportunity to comment on any new information before a subsequent finding of inadequacy becomes effective in cases where EPA reconsiders its initial finding of adequacy.

Based on comments received, the final rule does provide for a subsequent public comment period of at least 30 days in cases where EPA believes the public could provide helpful insight and analysis for determining whether an initial finding of adequacy should be changed because of new information. In such cases, EPA would re-post the SIP on the adequacy Web site and start another minimum 30-day public comment period. EPA would also provide an explanation of how the new information has caused it to reconsider its initial adequacy finding. After evaluating any comments received during the public comment period, EPA will determine whether the submitted SIP is inadequate using the adequacy procedures described in either Sec. 93.118(f)(1) or (f)(2) of the rule. In cases where EPA reverses its previous finding to a finding of inadequacy using procedures in Sec. 93.118(f)(1), such findings would become effective immediately upon the date of EPA's letter to the state. EPA believes this is necessary to prevent further use of inadequate budgets. Under Sec. 93.118(f)(1), EPA would also publish a notice of its inadequacy finding in the Federal Register and announce its finding on EPA's adequacy Web site.

However, the final rule does not provide for a subsequent comment period under certain circumstances where it is obvious that a budget has become inadequate. For instance, if a state has submitted a new SIP indicating that the prior SIP submission no longer provides for attainment, it would be clear that the prior submission is inadequate. The final rule allows EPA to proceed on a case-by-case basis using the adequacy procedures described in §93.118(f)(1) to make a finding of inadequacy effective immediately by explaining these facts in a letter to the state. In this case, EPA would also publish a Federal Register notice of that finding and post it on the adequacy Web site. EPA believes that in such situations public comment would not be necessary or in the public interest. Rather, it would be more important for EPA to complete the adequacy process quickly and limit further use of such clearly inadequate budgets in the conformity process. (69 FR 40044, July 1, 2004)

Can safety margins still be allocated to motor vehicle emissions budgets for use in conformity determinations?

Yes. In general, areas that do not have approved SIPs can use submitted safety margins in conformity determinations once EPA finds them adequate. Areas that have approved SIPs and wish to reallocate their safety margin could use such a budget revision for conformity purposes once EPA has approved it.

Many attainment demonstrations model multiple episodes with varying meteorology. Which episode establishes the motor vehicle emissions budget?

Even if these are multiple episodes modeled in the SIP, there will be only one motor vehicle emissions budget for the purposes of transportation conformity. The motor vehicle emissions budget should be explicitly identified in the SIP, and would normally be based on conditions for a typical day in the season when violations of the applicable NAAQS most commonly occur.

[1] This provision also applies to PM2.5 areas.
[2] 42 U.S.C. §7410
[3] 42 U.S.C. §7511(a)
[4] Readers should note: inventories are a significant input to the development of motor vehicle emissions budgets
[5] 40 CFR §93.101
[6] 40 CFR §93.124 (d)-(e)
[7] 40 CFR §93.124 (a)
[8] 40 CFR §93.101 "A safety margin means the amount by which the total projected emissions from all sources of a given pollutant are less than the total emissions that would satisfy the applicable requirement for reasonable further progress, attainment, or maintenance."
[9] 40 CFR §93.124(c)
[10] Control strategy SIP requirements for 8-hour ozone are detailed in the Phase 2 Implementation Rule, and requirements for PM2.5 will be detailed in the final PM2.5 Implementation Rule.
[11] SIP requirements for 8-hour ozone are detailed in the Phase 2 Implementation Rule, and requirements for PM2.5 will be detailed in the final PM2.5 Implementation Rule.

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