Air Quality Contacts

For more information, please contact Karen Perritt (202-366-9066).

U.S. Environmental Protection Agency

Subject: Conformity Information to Inform PM2.5 Designations

It has come to my attention that you have been seeking information about the transportation conformity burden associated with designating areas for the PM2.5 air quality standard. My staff has prepared the following Q & A document to explain some aspects of the conformity rule as it relates to this issue. This Q & A document does not create any new policy, it merely summarizes current regulations and practice. As this is a summary document, please refer to the conformity regulations at 40 CFR parts 51 and 93 for the complete legal requirements, as needed.

Please feel free to distribute this information to your states. Questions about the substance of this document can be directed to Laura Berry of my staff at 734 214 4858.

Q1. If a rural area is designated nonattainment because of a stationary source, and it contains a limited number of roads and highways, what flexibility exists for transportation conformity?

A. Two types of flexibility could apply, either because the area is rural, or the transportation sector's contribution to emissions are considered insignificant, or both.

Rural Areas:

In the transportation conformity rule, we distinguish between 1 and 2, below:

1. Donut areas are rural portions of a nonattainment or maintenance area that also contains a metropolitan area. Conformity in donut areas is generally done when the metropolitan area determines conformity. There is no specific flexibility for donut areas; however, in PM2.5 areas the requirements for estimating VMT may be simplified (see §93.122(d), which says "VMT may be estimated using any appropriate methods" and provides some examples), as long as more advanced methods are not the previous practice of the area.

2. Isolated rural areas are completely rural i.e., the nonattainment or maintenance area does not include any part of a metropolitan area. Isolated rural areas only determine conformity when a non exempt Federal project needs approval. Therefore, since 1993 some isolated rural areas never have needed to determine conformity. In addition, these areas have flexibility in the type of test they must meet.

Insignificance:

The conformity rule contains provisions for the regional emissions analysis of a conformity determination to be waived if the motor vehicle portion of the inventory is insignificant. (Only the regional emissions analysis is waived, the other components of a conformity determination are not.)

For EPA to make a finding of insignificance, the SIP must demonstrate that it would be unreasonable to expect that such an area would experience enough motor vehicle emissions growth in that pollutant/precursor for a NAAQS violation to occur.

EPA's finding would be based on a number of factors, including:

• the percentage of motor vehicle emissions in the context of the total SIP inventory,
• the current state of air quality as determined by monitoring data for that NAAQS,
• the absence of SIP motor vehicle control measures, and
• historical trends and future projections of the growth of motor vehicle emissions.

Note: The insignificance provision applies on the basis of an entire nonattainment or maintenance area, rather than a portion of an area. Therefore, an insignificance finding cannot be made on a rural county included in a larger nonattainment area because of a power plant or some other factor, unless the whole nonattainment area meets the criteria for a finding of insignificance.

Q2. If an area is already designated nonattainment for the 8 hour ozone standard, what would be the area's additional transportation conformity burden if it is also designated nonattainment for PM2.5?

A. For the purposes of this question, we assume that the boundaries of the 8 hour ozone area and the PM2.5 area are exactly the same.

When an area is subject to transportation conformity, it must show that its transportation plans, TIPs, and projects conform before they can be adopted or approved.

Conformity of plans and TIPs:

There are several steps for the area to show its plan and TIP conform. Briefly:

Step 1: The area must determine which years are to be analyzed (requirements are specified in the conformity rule) and which assumptions and models are to be used. These decisions are made through interagency consultation.

Step 2: The future VMT from the planned transportation system is estimated in each of the analysis years.

Step 3: Emissions that result from that level VMT are estimated using the latest emission factor model (MOBILE6.2 except in California, where EMFAC2002 is used).

Step 4: Emissions are compared to the relevant test. The budget test is used when areas have a SIP for a pollutant; the interim emissions test(s) are used before areas have SIPs.

Step 5: The MPO makes a conformity determination, including public comment. FHWA/FTA make final conformity determinations to complete the process.

For ozone, the emissions that must be examined in conformity are VOC and NOx.

For PM2.5, the emissions that must be examined in conformity are thus far, direct PM2.5. EPA has yet to finalize which precursors must be examined; EPA proposed that NOx, VOCs, SOx and ammonia could be considered in the conformity process. Please see 69 FR 400031 2 for this discussion.

In some cases, Steps 1 and 2 may be the same for both ozone and PM2.5, that is, no additional work would be required. However, once areas have SIPs for both ozone and PM2.5, analysis years may no longer exactly coincide and areas may have to run an additional analysis year as a result of being designated for both pollutants.

Additional work for Step 3 may be required if an area is nonattainment for both ozone and PM2.5, compared to an area that is designated only for ozone. For example, the emissions factor model will need to be run once using summertime conditions for ozone, and may need to be run separately for PM2.5 using a different season's conditions. Note that in a case where an area has a travel model that is able to capture seasonal differences in VMT generated, Step 2 may need to be run twice as well once for summertime for ozone, and possibly for a different season for PM2.5.

Effort that does not need to be duplicated, though, is the interagency consultation process needed (Step 1) and public consultation in Step 5.

Related issues to be considered:

1. In cases where the boundaries of the 8 hour ozone area and PM2.5 area are different, additional effort would be needed in Steps 2 and 3 for plan and TIP conformity determinations.

2. 8 hour ozone areas that have already demonstrated conformity for the 8 hour ozone standard that are subsequently designated nonattainment for PM2.5 will need to demonstrate conformity of their plan and TIP for PM2.5 standard as well; these areas may need to work through all steps of the conformity determination a second time.

3. For 8 hour areas with 1 hour ozone budgets that are designated nonattainment for PM2.5, the test used in Step 4 will differ for each pollutant, which may require additional work.

Conformity of projects:

In an ozone area, the project level conformity determination consists simply of checking to see that there is a conforming plan and TIP in place, and the project comes from that plan and TIP.

In a PM2.5 area, those two checks must be made but there are additional steps that may have to be taken. First, after a PM2.5 SIP is approved, the project must comply with any PM2.5 control measures in the PM2.5 SIP. Second, EPA has decided to request further public comment on options for hot spot analyses in PM2.5 areas. A hot spot analysis is an estimation of a likely future localized pollutant concentrations and a comparison of those concentrations to the air quality standards. The amount of additional burden hot spot analyses will impose on new PM2.5 areas will depend on the option EPA finalizes in its future conformity rulemaking. See 69 FR 40037 for more information on this issue.

The remainder of this paper expands on the information in these Q & As and is included for reference.

Additional Information for Reference

Rural Areas

In transportation conformity rule, we distinguish between metropolitan and rural areas because metropolitan areas have metropolitan planning organizations (MPOs) which are specifically charged with determining conformity under the Clean Air Act. The MPO is responsible for transportation planning including the development of federally required metropolitan transportation plans and transportation improvement programs (TIPs) and determining conformity of such plans and TIPs.

Transportation projects in rural areas are not included in MPO plans and TIPs. However, there are two types of rural areas for the purposes of the transportation conformity program, and the conformity requirements in these two types of rural areas are different. These two types of rural areas are defined in §93.101 of the conformity rule:

Conformity Requirements in Isolated Rural Areas

Isolated rural areas do not have to determine conformity with regular frequency like metropolitan or donut areas do, which is a significant flexibility. Instead, these areas determine conformity only when a non exempt federal transportation project needs approval, which may mean the area does not need to determine conformity for years. For example, from an FHWA survey, of 11 isolated rural areas for PM10, only 3 have done conformity the other 8 never have needed to make a conformity determination, because they have not had to build a non exempt federal transportation project since conformity applied.

In the Information Collection Requirement (ICR) for the new standards conformity rule, we estimated that isolated rural areas do conformity on average every 5 years. We believe this is a conservative estimate, that is, likely to overestimate the frequency.

In general, the state DOT takes responsibility for the regional emissions analysis for an isolated rural area, if and when a conformity determination is needed.

In addition, isolated rural areas have flexibility in the type of conformity test they must meet for years after those considered by the SIP, described in §93.109(l) of the conformity rule.

There are no specific modeling requirements in PM2.5 areas, unless the area already has been using a network model for estimating emissions in transportation conformity in which case they must continue to use it. However, most likely an isolated rural area would not have a network model. Therefore, in most cases, an isolated rural area's VMT can be estimated using "appropriate methods," such as extrapolating historical VMT growth, or projecting future VMT by considering growth in population (see 93.122(d)).

Conformity Requirements in Donut Areas

Because donut areas are located in nonattainment or maintenance areas that also contain an MPO, emissions in these areas must be considered when conformity of the MPO's plan and TIP are determined (unless the area has a SIP that establishes subarea budgets). Either the state DOT or the associated MPO take responsibility for estimating emissions from a donut area for a conformity determination, as decided through consultation.

In most cases, the regional emission analysis done for the metropolitan plan and TIP includes the donut area's transportation projects, if there are any. (See the preamble of the November 1993 conformity rule at 58 FR 62207 for the complete discussion. If the regional emissions analysis does not include the donut area's projects, it has to be repeated before a project in the donut area can proceed.)

There are no specific modeling requirements in PM2.5 areas, unless the area already has been using a network model for estimating emissions in transportation conformity in which case they must continue to use it. Therefore, in most cases, a donut area's VMT can be estimated using "appropriate methods," such as extrapolating historical VMT growth, or projecting future VMT by considering growth in population (see 93.122(d)). This requirement is relatively easy to meet, particularly if the donut area is a small area without many roads. The donut area would just be included in overall VMT estimates.

Areas with Insignificant Motor Vehicle Emissions

Since 1993, EPA has allowed the regional emissions analysis of a conformity determination to be waived in areas where motor vehicle emissions are insignificant. We recently codified this policy into the regulation itself. We added two new provisions, §93.109(k) and §93.121(c), which apply to nonattainment and maintenance areas where EPA finds that the SIP's motor vehicle emissions for a pollutant or precursor for a given standard are an insignificant contributor to an area's regional air quality problem. These insignificance provisions could apply to any standard for which conformity is determined, including PM2.5.

These provisions waive the regional emissions analysis requirements for an insignificant pollutant or precursor in these areas upon the effective date of EPA's adequacy finding or approval of such a SIP. Under this final rule and the existing policy, areas with insignificant regional motor vehicle emissions for a pollutant or precursor are still required to make a conformity determination that satisfies other relevant requirements including: timely implementation of TCMs in an approved SIP, interagency and public consultation, hot spot requirements including the use of latest planning assumptions and emissions models in CO and PM10 areas (if EPA has not made a finding that such emissions are also not a concern), and compliance with SIP control measures in PM10 and PM2.5 areas. Areas are also required to satisfy the regional emissions analysis requirements in §§93.118 and/or 93.119 for pollutants or precursors for which EPA has not made a finding of insignificance.

The insignificance provision provides flexibility for areas where motor vehicle emissions have little to no impact on an area's air quality problem. EPA believes that requiring these areas to perform a regional emissions analysis is not necessary to meet Clean Air Act section 176(c) requirements that transportation actions not worsen air quality, since the overall contribution of motor vehicle emissions in these areas is small and thus any significant change in such emissions over time would be unlikely.

How would an area qualify for insignificance?

Rather than a "one size fits all" definition, EPA's existing policy as articulated in the July 2004 conformity rule and previous conformity rulemakings and the new §93.109(k) gives EPA and the states the ability to examine whether motor vehicles are a significant contributor to regional and hot spot air quality on a case by case basis, while still providing a framework for EPA's action. In §93.109(k), the rule states:

One comment we received indicated concern that motor vehicle emissions could go from insignificant to significant simply because a reduction of emissions from other source sectors results in motor vehicle emissions comprising a greater percentage of the area's total inventory. EPA recognizes that this may occur. Initial inventories and strategies to attain or maintain air quality standards may change over time. Any changes to the significance of motor vehicle emissions must be discussed through interagency consultation in SIP development.

This example also illustrates the reason EPA believes it is important to have flexibility in implementing this provision. Although the commenter specifically mentions 10% as the threshold for finding motor vehicle emissions insignificant, this figure is a general guideline only. Depending on the circumstances, we may find that motor vehicle emissions that make up less than 10% of an area's total inventory are still significant. Conversely, we may also find that motor vehicle emissions in excess of 10% are still insignificant, under certain circumstances relating to the overall composition of the air quality situation. In general, the percentage of motor vehicle emissions in the area's total inventory is an important criterion for determining whether motor vehicles are a significant or insignificant contributor to an area's air quality problem, yet there are other criteria that EPA will examine when making this finding, as described in the regulatory text for §93.109(k).

If it is determined that regional and/or hot spot motor vehicle emissions are insignificant, such a finding should be clearly stated and well supported in a SIP that is subsequently submitted to EPA for adequacy review and/or approval. We anticipate that interagency consultation regarding insignificance will occur as a result of the requirement for consultation on the development of the SIP in §93.105(b) of the conformity rule. Further, the public will have appropriate opportunities to comment on proposed findings of insignificance in the process of both state adoption, EPA SIP approval and adequacy finding of submitted SIPs.

Where has the insignificance provision been used?

To date, approximately a dozen PM10 areas have taken advantage of the insignificance policy, mainly areas with air quality problems caused primarily by stationary or area sources. The following table includes examples of areas that have used the insignificance policy:

The insignificance provision of the rule applies on the basis of an entire nonattainment or maintenance area, rather than a portion of an area. Therefore, an insignificance finding cannot be made on a rural county included in a larger nonattainment area because of a power plant or some other factor, unless the whole nonattainment area meets the criteria for a finding of insignificance.