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Transportation Conformity Guidance for Qualitative Hot-spot Analyses in PM2.5 and PM10 Nonattainment and Maintenance Areas

EPA420-B-06-902; March 2006

United States Environmental Protection Agency
Federal Highway Administration

Table of Contents

Chapter 1: Introduction

Chapter 2: Overview of Transportation Conformity Requirements

Chapter 3: Analytical Requirements

Chapter 4: Developing a Qualitative PM2.5 or PM10 Hot-spot Analysis

Appendix A - Examples of Projects of Air Quality Concern

Appendix B - Examples of Qualitative PM2.5 or PM10 Hot-spot Analyses

Appendix C - Potential Mitigation Measures

Chapter 1: Introduction

1.1. What is the purpose of this guidance?

On March 10, 2006, the Environmental Protection Agency (EPA) published a final rule that establishes the transportation conformity criteria and procedures for determining which transportation projects must be analyzed for local air quality impacts in PM2.5 and PM10 nonattainment and maintenance areas ("areas") (71 FR 12468). The final rule also provides flexibility so that state and local resources are used efficiently. The EPA and the Federal Highway Administration (FHWA) have developed this guidance to help state and local agencies meet the final rule's hot-spot analysis requirements.

Transportation conformity is required under Clean Air Act section 176(c) (42 U.S.C. 7506(c)) to ensure that federally supported highway and transit project activities are consistent with ("conform to") the purpose of the state air quality implementation plan (SIP). Conformity to the purpose of the SIP means that transportation activities will not cause new air quality violations, worsen existing violations, or delay timely attainment of the relevant national ambient air quality standards (NAAQS or "standards"). EPA's transportation conformity rule (40 CFR 51.390 and Part 93) establishes the criteria and procedures for determining whether transportation activities conform to the SIP.

From this date forward, future qualitative PM2.5 and PM10 hot-spot analyses should be based on today's new guidance, which supersedes FHWA's existing September 12, 2001, "Guidance for Qualitative Project-Level 'Hot Spot' Analysis in PM10 Nonattainment and Maintenance Areas." However, any PM10 hot-spot analysis that was started prior to the release of EPA and FHWA's new guidance may be completed with the previous 2001 guidance. Any PM2.5 hot-spot analysis that was started prior to the release of EPA and FHWA's new guidance must meet the March 2006 final rule's requirements, and should meet the new guidance whenever possible.

1.2. What is a hot-spot analysis?

A hot-spot analysis is defined in 40 CFR 93.101 as an estimation of likely future localized PM2.5 or PM10 pollutant concentrations and a comparison of those concentrations to the relevant air quality standards. A hot-spot analysis assesses the air quality impacts on a scale smaller than an entire nonattainment or maintenance area, including for example, congested roadway intersections and highways or transit terminals. Such an analysis is a means of demonstrating that a transportation project meets Clean Air Act conformity requirements to support state and local air quality goals with respect to potential localized air quality impacts. When a hot-spot analysis is required, it is included within the project-level conformity determination that is made by FHWA or the Federal Transit Administration (FTA).

EPA and FHWA are issuing guidance at this time for qualitative hot-spot analyses. Quantitative PM2.5 or PM10 hot-spot analyses will be required when appropriate methods and modeling guidance are available. Qualitative hot-spot analyses involve more streamlined reviews of local factors such as local monitoring data near a proposed project location.

1.3. What projects in PM2.5 and PM10 areas are addressed by this guidance?

This guidance provides information to meet hot-spot analysis requirements for projects in PM2.5 and PM10 areas. See Chapter 2 and Appendix B for more specific information.

For PM2.5 areas

For all PM2.5 areas, this guidance would be used to complete qualitative PM2.5 hot-spot analyses only for "projects of air quality concern" as defined in the final rule by 40 CFR 93.123(b)(1). The final rule specifies that projects of air quality concern are certain highway and transit projects that involve significant levels of diesel traffic, or any other project that is identified by the PM2.5 SIP as a localized air quality concern.

A qualitative PM2.5 hot-spot analysis is not required for projects that are not an air quality concern. For these types of projects, state and local project sponsors should briefly document in their project-level conformity determinations that Clean Air Act and 40 CFR 93.116 requirements were met without a hot-spot analysis, since such projects have been found to not be of air quality concern under 40 CFR 93.123(b)(1).

For PM10 areas without approved conformity SIPs

For these PM10 areas, this guidance would also be used to complete qualitative PM10 hot-spot analyses only for "projects of air quality concern" as defined by 40 CFR 93.123(b)(1).

A qualitative PM10 hot-spot analysis is not required for projects that are not an air quality concern. For these types of projects, state and local project sponsors should briefly document in their project-level conformity determination that Clean Air Act and 40 CFR 93.116 requirements were met without a hot-spot analysis, since such projects have been found to not be of air quality concern under 40 CFR 93.123(b)(1).

For PM10 areas with approved conformity SIPs

In areas where EPA has already approved conformity SIPs that include PM10 hot-spot provisions from previous conformity rulemakings, the revised PM10 hot-spot requirements in the March 10, 2006 final rule will only be effective when a state either:

For more information on revising approved conformity SIPs, please see the February 14, 2006 EPA and DOT guidance entitled, "Interim Guidance for Implementing the Transportation Conformity Provisions in the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU)." [1]

Therefore, for all non-exempt federally funded or approved projects, PM10 areas with approved conformity SIPs must continue to follow the PM10 hot-spot procedures in their existing conformity SIPs until the SIP is updated and subsequently approved by EPA. PM10 areas with approved conformity SIPs most likely are required to complete a qualitative PM10 hot-spot analysis for every project-level conformity determination, since these were the federal conformity requirements prior to the March 10, 2006 final rule.

1.4. How is this guidance structured?

This guidance is in the form of questions and answers for basic components of PM2.5 and PM10 hot-spot analyses. The guidance addresses many issues such as:

Following the question and answer section are three appendices that provide examples of:

These examples demonstrate different levels of inquiry that may be used to qualitatively consider the local air quality impacts of projects in a given PM2.5 or PM10 nonattainment or maintenance area. This guidance is not definitive for any specific project but rather is general guidance for all relevant projects.

Additional assistance is available from:

See Question 1.6 for specific contact information.

1.5. Which parts of this guidance apply to PM2.5 hot-spot analyses and which parts of this guidance apply to PM10 hot-spot analyses?

The criteria and procedures for hot-spot analyses will be generally the same for both PM2.5 and PM10 areas, except for PM10 areas with approved conformity SIPs as noted elsewhere in this guidance. Questions and answers in this guidance address PM2.5 and PM10 together where the requirements or analytical methods and data are the same. Separate answers are provided where the answers differ.

1.6. Who can I contact for more information?

For specific questions concerning a particular nonattainment or maintenance area, please contact the transportation conformity staff person responsible for your state at the appropriate EPA regional office, FHWA division office, or FTA regional office.

General questions about this guidance can be directed to:

1.7. Does this guidance create new requirements?

No, this guidance explains how to implement the hot-spot analysis requirements of the March 10, 2006 final rule, and does not create any new requirements.

The regulations described in this document contain legally binding requirements. This document is not a substitute for those provisions or regulations, nor is it a regulation itself. Thus, it does not impose legally binding requirements on EPA, FHWA, FTA, states, or the regulated community, and may not apply to a particular situation based upon the circumstances. EPA, FHWA, and FTA retain the discretion to adopt approaches on a case-by-case basis that may differ from this guidance, but still comply with the Clean Air Act and the transportation conformity regulations. Any decisions regarding a particular conformity determination or hot-spot analysis will be made based on the statute and regulations, after appropriate public input. This guidance may be revised periodically without public notice.

Chapter 2: Overview of Transportation Conformity Requirements

2.1. What are the primary requirements for assessing the impacts of projects in PM2.5 and PM10 nonattainment and maintenance areas?

Clean Air Act section 176(c)(1)(B) is the statutory criterion that must be met by all projects in nonattainment and maintenance areas that are subject to transportation conformity. Section 176(c)(1)(B) states that federally-supported transportation projects must not "cause or contribute to any new violation of any standard in any area; increase the frequency or severity of any existing violation of any standard in any area; or delay timely attainment of any standard or any required interim emission reductions or other milestones in any area."

To meet statutory requirements, the March 10, 2006 final rule requires PM2.5 and PM10 hot-spot analyses to be performed for projects of air quality concern. Qualitative hot-spot analyses would be done for these projects before appropriate methods and modeling guidance are available and quantitative PM2.5 and PM10 hot-spot analyses are required under 40 CFR 93.123(b)(4). In addition, through the final rule, EPA determined that projects not identified in 40 CFR 93.123(b)(1) as projects of air quality concern have also met statutory requirements without any further hot-spot analyses (40 CFR 93.116(a)). Please see Questions 1.3 and 2.3 for information on when the new PM10 hot-spot analysis requirements can be used in PM10 areas with and without approved conformity SIPs.

2.2. What is a project of air quality concern?

EPA specified in 40 CFR 93.123(b)(1) of the final rule that projects of air quality concern are certain highway and transit projects that involve significant levels of diesel vehicle traffic, or any other project that is identified in the PM2.5 or PM10 SIP as a localized air quality concern. See the preamble of the March 10, 2006 final rule for further information regarding how and why EPA defined projects of air quality concern (71 FR 12491-12493).

The final rule defines the projects of air quality concern that require a PM2.5 or PM10 hot-spot analysis in 40 CFR 93.123(b)(1) as:

  1. "New or expanded highway projects that have a significant number of or significant increase in diesel vehicles;
  2. Projects affecting intersections that are at Level-of-Service D, E, or F with a significant number of diesel vehicles, or those that will change to Level-of-Service D, E, or F because of increased traffic volumes from a significant number of diesel vehicles related to the project;
  3. New bus and rail terminals and transfer points that have a significant number of diesel vehicles congregating at a single location;
  4. Expanded bus and rail terminals and transfer points that significantly increase the number of diesel vehicles congregating at a single location; and
  5. Projects in or affecting locations, areas, or categories of sites which are identified in the PM2.5 or PM10 applicable implementation plan or implementation plan submission, as appropriate, as sites of violation or possible violation.

Appendix A of this guidance includes the final rule's examples of projects that are most likely to be an air quality concern, as well as examples of projects that are not considered an air quality concern (and therefore do not require a PM2.5 or PM10 hot-spot analysis). However, as described in Questions 1.3 and 2.3, a PM10 hot-spot analysis is required for any project-level conformity determination in PM10 areas with approved conformity SIPs, until such SIPs are revised and approved by EPA.

2.3. When is a PM2.5or PM10 hot-spot analysis required?

In general, a hot-spot analysis would be done for required projects when a project-level conformity determination is completed. This is typically done during the environmental review process for the National Environmental Policy Act (NEPA). There can be limited cases, as described below, when transportation conformity requirements initially apply in a nonattainment area after the NEPA process has been completed for a project, but a project-level conformity determination is required for a subsequent federal approval.

The following paragraphs provide more specific information for PM2.5 and PM10 areas.

PM2.5areas

The March 10, 2006 final rule requires a qualitative PM2.5 hot-spot analysis to be completed for project-level conformity determinations for projects of air quality concern completed on or after April 5, 2006, when PM2.5 conformity requirements apply and the final rule is effective. [2]

Prior to April 5, 2006, FHWA or FTA could voluntarily make a project-level conformity determination that includes a PM2.5 hot-spot analysis that meets the final rule's requirements.

If a project still requires a FHWA or FTA approval or authorization, a project-level conformity determination will be required prior to the first such action on or after April 5, 2006, even if the project has already completed the NEPA process. After project-level conformity is determined for a project, a new conformity determination is only required under the scenarios discussed in 40 CFR 93.104(d). [3]

A project-level conformity determination and hot-spot analysis will not be required for projects that have already completed the NEPA process and require no further FHWA or FTA approval or authorization on or after April 5, 2006. A project-level conformity determination would only be required for such projects under the scenarios discussed in 40 CFR 93.104(d).

PM10 areas without approved conformity SIPs

The revised PM10 hot-spot requirements in the final rule are not effective until April 5, 2006. A qualitative PM10 hot-spot analysis that meets the final rule's requirements must be completed for project-level determinations for projects of air quality concern completed on or after April 5, 2006.

Prior to April 5, 2006, any project-level conformity determination made by FHWA or FTA in these PM10 nonattainment and maintenance areas must meet the previous conformity rule's requirements for PM10 hot-spot analyses.

PM10 areas with approved conformity SIPs

As described above, PM10 areas that have approved conformity SIPs that include PM10 hot-spot provisions from previous rulemakings cannot take advantage of the March 10, 2006 final rule until the conformity SIP is revised and approved by EPA.

Prior to that time, all project-level conformity determinations in these PM10 areas must include a PM10 hot-spot analysis that meets the requirements in the approved conformity SIP.

2.4. What air quality standards are evaluated in PM2.5or PM10 hot-spot analyses?

The Clean Air Act and transportation conformity regulation require that conformity be met for all national ambient air quality standards (NAAQS or "standards") for a given pollutant. Therefore, a conformity determination must address all relevant standards for a given pollutant, unless meeting conformity for the controlling standard would ensure that Clean Air Act requirements are met for all standards. This conformity approach is consistent with how SIPs are developed for pollutants with multiple standards.

The following paragraphs provide more specific information on the current 24-hour and annual standards that must be addressed in respective PM2.5 and PM10 hot-spot analyses.[4]

PM2.5areas

PM2.5 nonattainment and maintenance areas are required to attain and maintain two standards:

The current 24-hour standard is based on a 3-year average of the 98th percentile of 24-hour PM2.5 concentrations; the current annual standard is based on a 3-year average of annual mean PM2.5 concentrations.

A PM2.5 hot-spot analysis must consider both standards, unless it is determined for a given area that meeting the controlling standard would ensure that Clean Air Act requirements are met for both standards. The interagency consultation process should be used to discuss how the qualitative PM2.5 hot-spot analysis meets statutory and regulatory requirements for both PM2.5 standards, depending on the factors that are evaluated for a given project.

PM10 areas

PM10 nonattainment and maintenance areas are required to attain and maintain two standards as well:

The 24-hour PM10 standard is attained when the average number of exceedances in the past three calendar years is less than or equal to 1.0. An exceedance occurs when a 24-hour concentration of 155 µg/m3 or greater is measured at a site. The annual PM10 standard is attained if the average of the annual arithmetic means for the past three calendar years is less than or equal to 50 µg/m3.

A PM10 hot-spot analysis must consider both standards, unless it is determined for a given area that meeting the controlling standard would ensure that Clean Air Act requirements are met for both standards. The interagency consultation process should be used to discuss how the qualitative PM10 hot-spot analysis meets statutory and regulatory requirements for both PM10 standards, depending on the factors that are evaluated for a given project.

2.5. What is the definition of causing a new violation or increasing the frequency or severity of an existing air quality violation?

A PM2.5 or PM10 hot-spot analysis assesses potential new or worsened future violations due to the project in combination with changes in background air quality concentrations. The interagency consultation process would be used to determine if new violations or increases in the frequency or severity of existing violations are anticipated based on the hot-spot analysis.

40 CFR 93.101 already defines when a new or worsened air quality violation is determined to occur:

"Cause or contribute to a new violation for a project means:

  1. To cause or contribute to a new violation of a standard in the area substantially affected by the project or over a region which would otherwise not be in violation of the standard during the future period in question, if the project were not implemented; or
  2. To contribute to a new violation in a manner that would increase the frequency or severity of a new violation of a standard in such area."

"Increase the frequency of severity means to cause a location or region to exceed a standard more often or to cause a violation at a greater concentration than previously existed and/or would otherwise exist during the future period in question, if the project were not implemented."

These definitions apply whether air quality information at the project location is used or when a monitor not in the geographic area of the project is used because it is located near a different project with similar characteristics (i.e., a "surrogate").

In addition, as discussed in the preamble to the November 24, 1993, transportation conformity rule, EPA believes that "a seemingly new violation may be considered to be a relocation and reduction of an existing violation only if it were in the area substantially affected by the project and if the predicted [future] design value for the "new" site would be less than the design value at the "old" site without the project - that is, if there would be a net air quality benefit" (58 FR 62213).

2.6. What are the interagency consultation requirements for PM2.5 and PM10 hot-spot analyses?

The interagency consultation process is an important tool to completing project-level conformity determinations and hot-spot analyses. [5] Interagency consultation must also be used to evaluate and choose associated methods and assumptions to be used in PM2.5 and PM10 hot-spot analyses (40 CFR 93.105(c)(1)(i)).

The different agencies that can be involved in the interagency consultation process include the project sponsor, other state and local transportation and air quality agencies, EPA, FHWA, and FTA.

2.7. What are the roles and responsibilities of different agencies in project-level conformity determinations?

Roles and responsibilities of different agencies for meeting the transportation conformity requirements are addressed in 40 CFR 93.105 or in the approved conformity SIP. The following paragraphs provide more information on the potential roles and responsibilities in implementing the PM2.5 and PM10 hot-spot analysis requirements.

Project Sponsor

The project sponsor is the agency responsible for implementing the project. Typically, the project sponsor is a local government, transit operator, or state department of transportation. The project sponsor is responsible for providing the PM2.5 and/or PM10 qualitative hot-spot analysis addressed in this guidance and meeting consultation requirements described in 40 CFR 93.105 or the approved conformity SIP. The interagency consultation process is critical to completing project-level conformity determinations and qualitative PM2.5 and PM10 hot-spot analyses. The project sponsor, in cooperation with federal agencies, is also responsible for conducting the environmental analysis and review to comply with NEPA as required by the Council on Environmental Quality regulations (40 CFR 1500-1508) and the FHWA/FTA Environmental Impact and Related Procedures (23 CFR Part 771).

FHWA and FTA

FHWA and FTA are responsible for determining that the requirements of the transportation conformity rule are met. PM2.5 or PM10 hot-spot analyses would generally be included in documents prepared to meet NEPA requirements. Such documents may include:

It is the responsibility of either FHWA or FTA to review and approve these NEPA documents for their certain actions.

EPA

EPA is responsible for promulgating transportation conformity regulations and related guidance, and as such, provides general and specific policy and technical assistance to federal, state, and local conformity implementers. EPA is also an active member of the interagency consultation process regarding conformity determinations. Additionally, EPA reviews submitted SIPs and makes adequacy or other findings as appropriate for conformity purposes, and provides policy and technical support with air quality modeling and monitoring issues.

State and local air agencies

State and local air quality agencies are part of the interagency consultation process and aid in air quality and transportation modeling. These agencies may provide much of the data required to perform a qualitative PM2.5 or PM10 hot-spot analysis, as described in Questions 4.4 and 4.5). The state air quality agency also operates the air quality monitoring network and is responsible for developing SIPs for PM2.5 and PM10 nonattainment and maintenance areas.

2.8. What are the public participation requirements for PM2.5 and PM10 hot-spot analyses?

Affected agencies developing project-level conformity determinations (and any associated PM2.5 or PM10 hot-spot analysis) need to establish a proactive public involvement process that provides opportunity for public review and comment. The NEPA public involvement process can be used to satisfy these public participation requirements, since project-level conformity determinations are usually conducted as part of the NEPA process. If a project-level conformity determination that includes an associated hot-spot analysis is done after NEPA is completed, as described in Question 2.3, a public comment period is also to be provided.

Chapter 3: Analytical Requirements

3.1. What are the general analytical requirements for PM2.5 and PM10 hot-spot analyses?

In the March 2006 final rule, EPA retained for PM10 areas and extended for PM2.5 areas the general requirements in 40 CFR 93.123(c) for all hot-spot analyses (71 FR 12496-12497). These requirements are as follows:

For a project-level conformity determination, the design concept and scope of the project must be consistent with that included in the conforming transportation plan and transportation improvement program (TIP). Any significant change in a project's design concept or scope will require a reevaluation of regional emissions (i.e., a new plan/TIP conformity determination) and a new project-level conformity determination and hot-spot analysis.

PM2.5 and PM10 hot-spot analyses must also be based on the latest planning assumptions. In addition, FHWA or FTA, as applicable, must obtain from the project sponsor and/or operator enforceable written commitments to implement any required project-level control or mitigation measures, prior to making a project-level conformity determination (40 CFR 93.125(c)).

3.2. What emissions are considered in PM2.5and PM10 hot-spot analyses?

Hot-spot analyses under this guidance must be based only on directly emitted PM2.5 or PM10 emissions. Tailpipe, break wear, and tire wear PM2.5 or PM10 would always be considered in a project's hot-spot analysis. See Questions 3.3 and 3.4 for further information regarding when re-entrained road dust and construction emissions would be considered in a PM2.5 or PM10 hot-spot analysis.

PM2.5 and PM10 precursors are not considered in respective hot-spot analyses. Secondary particles formed through PM2.5 and PM10 precursor emissions from a transportation project take several hours to form in the atmosphere giving emissions time to disperse beyond the immediate project area of concern for localized analyses.

3.3. When is re-entrained road dust considered in PM2.5or PM10 hot-spot analyses?

For PM2.5nonattainment and maintenance areas

Re-entrained road dust must only be considered in PM2.5 hot-spot analyses if EPA or the state air agency has made a finding that such emissions are a significant contributor to the PM2.5 air quality problem in a given area (40 CFR 93.102(b)(3)). See the July 1, 2004 final conformity rule for further information (69 FR 40004). Please refer to the EPA regional office for information on whether a finding of significance for re-entrained road dust was made for a given PM2.5 nonattainment or maintenance area.

For PM10 nonattainment and maintenance areas

Re-entrained road dust must be included in all PM10 hot-spot analyses. EPA has historically required road dust emissions to be included in all conformity analyses of direct PM10 emissions -- including hot-spot analyses. See the March 2006 final conformity rule for further background (71 FR 12496).

3.4. When are construction emissions considered in PM2.5or PM10 hot-spot analyses?

Construction-related PM2.5 or PM10 emissions due to a particular project are not required to be included in hot-spot analyses, if such emissions are considered temporary as defined in 40 CFR 93.123(c)(5) (i.e., emissions which occur only during the construction phase and last five years or less at any individual site).

While, for most projects, it is anticipated that construction emissions would not be included in PM2.5 or PM10 hot-spot analyses, there may be limited cases where a large project is constructed over a longer time period where it may be appropriate to include construction emissions, when an analysis year is chosen during project construction. For example, PM2.5 or PM10 emissions, as applicable, would be considered for projects that take more than five years to build at any individual site. See Question 3.5 for further information on analysis years for PM2.5 or PM10 hot-spot analyses.

3.5. What time frame and analysis years should be used in hot-spot analyses?

The March 2006 final rule does not change the time frame and analysis years required when PM2.5 or PM10 hot-spot analyses are conducted. As discussed in the July 1, 2004, final conformity rule (69 FR 40056-40058), hot-spot analyses in metropolitan nonattainment and maintenance areas must consider the full time frame of an area's transportation plan at the time the analysis is conducted. Hot-spot analyses for projects in isolated rural nonattainment and maintenance areas must consider the full time frame of the area's 20-year regional emissions analysis since these areas are not required to develop a transportation plan under DOT's statewide transportation planning regulations. Although SAFETEA-LU and Clean Air Act section 176(c)(7) now allow the election of changes to the time horizons for transportation plan and TIP conformity determinations, these changes to do not affect the time frame and analysis requirements for hot-spot analyses.

To ensure that conformity requirements are being satisfied, areas should examine the year(s) within the transportation plan or regional emissions analysis, as appropriate, during which:

EPA believes that conformity requirements are met if areas demonstrate that no new or worsened violations occur in the year(s) of highest expected emissions - which includes the project's emissions in addition to background regional emissions. If such a demonstration occurs, then no adverse impacts would be expected to occur in any other years within the time frame of the transportation plan or regional emissions analysis. See the July 2004 final rule for further information on this topic.

Chapter 4: Developing a Qualitative PM2.5 or PM10 Hot-spot Analysis

This chapter provides general information on the methods and data that can be used to meet qualitative PM2.5 and PM10 hot-spot requirements. The interagency consultation process would be used to determine what is needed for a particular project.

4.1. What methods can be used for performing qualitative PM2.5and PM10 hot-spot analyses?

This guidance highlights two methods for completing qualitative PM2.5 and PM10 hot-spot analyses. These methods are provided as examples only, and there may be other methods. Elements of both methods may also be combined for a given hot-spot analysis. The method chosen will be affected by the characteristics of a particular project, the project location, and available information.

The data and method used, whether one of those below or an alternate method, must be selected and documented through the interagency consultation process (40 CFR 93.105(c)(1)(i)).

  1. Comparison to another location with similar characteristics

This method is a simple approach for demonstrating that a new project will meet statutory conformity requirements. It involves reviewing existing highway or transit facilities that were constructed in the past and built in locations similar to the proposed project and, whenever possible, near an air quality monitor (a "surrogate") to allow a comparison of PM2.5 or PM10 air quality concentrations. See Examples A, C, and D in Appendix B for suggestions of when this method can be used.

The interagency consultation process would be used to determine what project(s) and air quality monitor(s) are appropriate to be used as a surrogate for the air quality impacts of the proposed project. The project sponsor would document in the project-level conformity determination the reasons for picking a surrogate project and air quality monitor, including similarities to and differences between the surrogate and proposed project and location. See Question 4.3 for more information on what other documentation should be included for a hot-spot analysis.

  1. Air quality studies for the proposed project location

Air quality information from many sources may be available for the proposed project's location. See Examples B, C, and D in Appendix B for suggestions of when this method can be used.

The SIP can be an important tool to be referenced when conducting qualitative hot-spot analyses, especially for PM10 nonattainment and maintenance areas that already have SIPs in place. PM2.5 nonattainment areas may use, as appropriate, any preliminary data or modeling from a PM2.5 SIP under development. The SIP contains specific information on the air quality conditions of a given nonattainment or maintenance area. Such information may include monitoring data and modeling data for past or future years at or near a project's location. Even if a state has not yet begun work on its PM2.5 SIP, the air agency would be able to supply data from air quality monitors that may be useful in a given hot-spot analysis.

In some cases, the state or local air agency or a university may also have performed an air quality study near the location of a proposed project. In addition, other scientific studies may be appropriate to understand the potential air quality impact from certain projects. [6]

The interagency consultation process would be used to determine what air quality information from a SIP or other air quality study is appropriate for assessing the air quality impacts of the proposed project. The project sponsor would document within the project-level conformity determination the air quality information used and why it is appropriate. See Question 4.3 for more information on what other documentation should be included for a hot-spot analysis.

4.2. What should be documented for a qualitative PM2.5or PM10 hot-spot analysis?

The hot-spot analysis should include sufficient documentation to justify the conclusion that a proposed project meets conformity hot-spot analysis requirements in 40 CFR 93.116 and 93.123. The amount of documentationneeded and method of analysis chosen will vary depending on individual circumstances (e.g., local background PM2.5 or PM10 concentrations, the size and nature of the project, etc.).

The hot-spot analysis should include a summary of the method and data that were used, such as:

4.3. What are some of the factors that may be considered in describing existing conditions absent the proposed project?

An accurate description of existing conditions and factors that may influence PM2.5 or PM10 concentrations in the proposed project area should be provided. Analysis of those conditions and how they are projected to change over time with the addition of the proposed project is the basis of the hot-spot analysis.

While the following list is not intended to be exhaustive or prescriptive, factors that are relevant to PM2.5 or PM10 levels may include:

  1. Air Quality

Existing and future air quality information should be considered to assess the probability of the project causing or contributing to an air quality violation. Analysts and reviewers should be aware of the existing air quality conditions so that they can understand the relative impact that the proposed project is likely to have. The description of existing air quality information may include the following:

Sources: State/local air quality agencies or public health departments would have monitoring data and modeling results included in a nonattainment or maintenance area's SIP or recent monitoring, modeling, or other data. Universities or other sources may have completed independent air quality studies for the project or similar location. Air quality information may also be useful from other nonattainment and maintenance areas with similar types of projects and locations.

  1. Transportation and traffic conditions

Available traffic information such as current volumes and expected volumes should be included, including any information regarding the types of percentages of diesel and other vehicles on the affected roadway(s). Planned or expected development that will affect traffic volume growth rates should be taken into consideration.

Understanding whether vehicle miles traveled (VMT) are increasing or decreasing, or how a project would change the mix of vehicles on the road will assist in judging the project=s air quality impacts. For example, it would be important to consider the PM2.5 or PM10 air quality impacts of any increase in diesel truck or bus traffic due to the proposed project or other activities at the project location. Also, increased VMT and how re-entrained road dust emissions are impacted would be considered in PM10 areas and PM2.5 areas where re-entrained road dust is found to be significant (40 CFR 93.102(b)(3)).

Other relevant information may include transportation modes, volumes, speed, congestion, trends, etc. When the project analysis is incorporated in a NEPA document, this description should largely reference other sections of the NEPA document that address traffic and transportation issues in greater depth.

Sources: Project sponsor, state department of transportation, local planning agency or metropolitan planning organization.

  1. Built and natural environment

This description would include whether the character of the project area is urban, suburban or rural, and whether adjacent buildings or topography create barriers to dispersal of PM2.5 or PM10. Relevant development trends and land use patterns should be addressed if they have a bearing on potential PM2.5 or PM10 emissions and concentrations in the vicinity of the project (e.g., a new area or stationary emissions source, increased rail traffic resulting from a rail terminal, increased truck traffic due to a port or intermodal freight terminal, or due to industrial or agricultural purposes).

Sources: State department of transportation, the project sponsor, local planning agency or metropolitan planning organization.

  1. Meteorology, climate and seasonal data

This description could address atmospheric inversions, prevailing wind direction and speed, as they impact PM2.5 or PM10 concentrations in the project area, if appropriate.

Sources: State/local air quality agencies, review of the applicable PM2.5 or PM10 SIP, and the National Weather Service.

  1. Retrofit, anti-idling or other adopted emission control measures

Emission control measures, such as retrofit or anti-idling measures, may mitigate any potential increase in PM2.5 or PM10 emissions at the proposed project's location. The impact of phase-in of national rules and regulations that EPA has promulgated, such as heavy-duty diesel rules, that are currently being implemented should also be considered.

Source: State/local air agency, EPA, review of the applicable PM10 or PM2.5 SIP.

4.4. How would changes in existing conditions be evaluated for future scenarios with the proposed project?

Many factors may change air quality in the future and whether increases or decreases in PM2.5 or PM10 levels are expected should be documented in the project-level conformity determination. Examples of changes in factors that may lead to changes in PM2.5 or PM10 concentrations in the project are listed below. Potential sources for this type of information are similar to those in Question 4.4.

PM2.5and PM10

PM10 (unless fugitive dust is included in a PM2.5area - see Questions 3.3 and 3.4)

As described in Question 3.5, the future (build) scenario should consider whether the proposed project would be expected to increase or decrease PM2.5 or PM10 concentrations at the project location over the time frame of the area's transportation plan or, in the case of an isolated rural area, over the 20-year period covered by the area's regional emissions analysis. The hot-spot analysis should address the expected air quality changes resulting from the proposed project, and address whether the build scenario(s) would be expected to result in new or worsened air quality violations of the PM2.5 or PM10 standards.

4.5. What are the potential measures to mitigate PM2.5 or PM10 air quality concerns?

Where the proposed project may lead to a potential new PM2.5 or PM10 violation or increase the severity or frequency of an existing PM2.5 or PM10 violation, mitigation measures would be considered to reduce project emissions and any local air quality impact. In these cases, written commitments for project-level mitigation or control measures must be obtained from the project sponsor and/or operator prior to making a project-level conformity determination (40 CFR 93.125(a)). A table including a menu of available options is included in Appendix C; however, many others may be possible.

Appendix A: Examples of Projects of Air Quality Concern

Examples of Projects of Air Quality Concern

Note: EPA noted in the March 2006 final rule that the examples below are considered to be the most likely projects that would be covered by 40 CFR 93.123(b)(1) and require a PM2.5 or PM10 hot-spot analysis (71 FR 12491).

Some examples of projects of air quality concern that would be covered by 40 CFR 93.123(b)(1)(i) and (ii) are:

Some examples of projects of air quality concern that would be covered by 40 CFR 93.123(b)(1)(iii) and (iv) are:

Examples of Projects of That Are Not an Air Quality Concern

Note: The March 2006 final rule also provided examples of projects that would not be covered by 40 CFR 93.123(b)(1) and would not require a PM2.5 or PM10 hot-spot analysis (71 FR 12491). However, as noted elsewhere in this guidance, PM10 nonattainment and maintenance areas with approved conformity SIPs that include PM10 hot-spot provisions from previous rulemakings must continue to follow those approved conformity SIP provisions until the SIP is revised.

The following are examples of projects that are not an air quality concern under 40 CFR 93.123(b)(1)(i) and (ii):

Examples of projects that are not an air quality concern under 40 CFR 93.123(b)(1)(iii) and (iv) would be:

Appendix B: Examples of Qualitative PM2.5 or PM10 Hot-spot Analyses

Note: The information in Appendix B is intended to briefly summarize the types of methods and data that can be considered in qualitative PM2.5 or PM10 hot-spot analyses. An actual qualitative PM2.5 or PM10 hot-spot analysis would include more documentation regarding the proposed project, the analysis method and data considered, and the analysis' final conclusion.

Example A: Comparison of a New Bus Terminal to Another Site Based on Monitoring Data

Proposed project

Analysis method

Data considered

Conclusion

Example B: Consideration of a Highway Project and Nearby Monitoring Data

Proposed project

Analysis method

Data considered

Conclusion

Example C: Comparison of New Highway Project to Similar Project Location in the SIP

Proposed project

Analysis method

Data considered

Conclusion

Example D: Determination of Screening Threshold for Multiple Projects

Proposed projects to be considered

Analysis method

Data considered

Conclusion

Appendix C: Potential Mitigation Measures

Potential PM2.5 or PM10 Project-level Mitigation Measures: Diesel Emissions
Suspected Source of PM2.5 or PM10 Problem Type of PM primarily controlled Options to Reduce PM Pollution
Mitigation Measure Comments
Diesel emissions in general from a highway or transit facility PM2.5 or PM10 Provide a "retrofit" program for older, higher emitting vehicles Retrofits could be used on truck or bus fleets to install newer engines or technologies known to have lower emissions
Anti-idling requirements or policies (e.g., restrictions on idling, truck stop electrification) Anti-idling polices are relevant where significant numbers of diesel vehicles congregate for extended periods of time
Routing existing traffic away from populated areas (e.g., truck restricted zone) Routing traffic away from populated areas may change an area's VMT
Replace a significant number of older buses with cleaner busses (e.g., those meeting 2007 heavy-duty diesel standards, as practical, hybrid-electric vehicles, etc.) Cleaner buses will reduce localized PM2.5 and PM10 emissions for these types of transit projects

 

Potential PM2.5 or PM10 Project-level Mitigation Measures: Fugitive Dust Emissions
Suspected Source of PM2.5 or PM10 Problem Type of PM primarily controlled Options to Reduce PM Pollution
Mitigation Measure Comments
Fugitive Dust PM10 Truck cover laws May require greater enforcement effort in some areas
PM10 Street cleaning program Includes vacuuming and flushing
PM10 Site watering program Regular program will reduce dust
PM10 Street and shoulder paving; Runoff and erosion control Should reduce significant quantities of dust material
PM10 Changes in highway weight and length restrictions for trucks May change an area's fugitive dust emissions or change the number of trucks on the road
Snow and Ice Control PM10 Reduce the quantity of sand Use harder material that is not prone to grinding into finer particles or additional chemical treatments

Note: The above table focuses on measures for mitigating PM10 fugitive dust emissions because all PM10 areas must include these emissions in their PM10 hot-spot analyses. However, as described in Questions 3.3. and 3.4., there may be PM2.5 areas that also could take advantage of the above measures if re-entrained road dust or construction dust is required for a PM2.5 hot-spot analysis.


[1] SAFETEA-LU is Public Law 109-59. EPA and DOT's interim conformity guidance is available at http://www.fhwa.dot.gov/environment/air_quality/conformity/policy_and_guidance/sec6011guidmemo.cfm.

[2] On January 5, 2005 (70 FR 943), EPA designated areas as attainment and nonattainment for the PM2.5 standards. These designations became effective on April 5, 2005. As a result, conformity for the PM2.5 standards will apply to newly designated nonattainment areas on April 5, 2006.

[3] 40 CFR 93.104(d) states, "FHWA/FTA projects must be found to conform before they are adopted, accepted, approved, or funded. Conformity must be redetermined for any FHWA/FTA project if one of the following occurs: a significant change in the project's design concept and scope; three years elapse since the most recent major step to advance the project; or initiation of a supplemental environmental document for air quality purposes. Major steps include NEPA process completion; start of final design; acquisition of a significant portion of the right-of-way; and, construction (including Federal approval of plans, specifications and estimates)."

[4] This guidance document implements conformity under the current PM2.5 and PM10 air quality standards. EPA proposed revisions to the current PM2.5 and PM10 air quality standards on January 17, 2006 (71 FR 2620).

[5] Throughout this document, the term "interagency consultation process" is intended to mean that process required by 40 CFR 93.105 for transportation conformity determinations.

[6] EPA will be providing a summary of scientific studies that have been completed on the potential impacts of transportation projects. See EPA's website for further information: http://www.epa.gov/otaq/transp/traqconf.htm.

[7] The appropriate section of the NEPA document can also be referenced when relevant.

[8] This percentage is the national average of truck vehicle miles traveled (VMT) to total VMT, based on FHWA's Highway Statistics publication which can be found at: www.fhwa.dot.gov/policy/ohim/hs04/index.htm. EPA's MOBILE6.2 motor vehicle emissions model also uses 8% truck VMT as a national default.

[9] 40 CFR 93.101 defines a "regionally significant project" as "a transportation project (other than an exempt project) that is on a facility which serves regional transportation needs (such as access to and from the area outside of the region, major activity centers in the region, major planned developments such as new retail malls, sports complexes, etc., or transportation terminals as well as most terminals themselves) and would normally be included in the modeling of a metropolitan area's transportation network, including at a minimum all principal arterial highways and all fixed guideway transit facilities that offer an alternative to regional highway travel."

Updated: 07/18/2013
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