v>EPA
United States
Environmental Protection
Agency
Transportation Conformity
Guidance for Qualitative
Hot-spot Analyses in
PM25 and PM10
Nonattainment and
Maintenance Areas
EPA420-B-06-902 March 2006
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EPA420-B-06-902 March 2006
Transportation Conformity Guidance for Qualitative
Hot-spot Analyses in PM25 and PM10
Nonattainment and Maintenance Areas
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
Office of Natural and Human Environment
Federal Highway Administration
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Table of Contents
Chapter 1: Introduction
1.1. What is the purpose of this guidance?
1.2. What is a hot-spot analysis?
1.3. What projects in PM2.5 and PMio areas are addressed by this guidance?
1.4. How is this guidance structured?
1.5. Which parts of this guidance apply to PM2.5 hot-spot analyses and which parts of this
guidance apply to PMio hot-spot analyses?
1.6. Who can I contact for more information?
1.7. Does this guidance create new requirements?
Chapter 2: Overview of Transportation Conformity Requirements
2.1. What are the primary requirements for assessing the impacts of projects in PM2.5 and
nonattainment and maintenance areas?
2.2. What is a project of air quality concern?
2.3. When is a PM2.5 or PMio hot-spot analysis required?
2.4. What air quality standards are evaluated in PM2.5 or PMio hot-spot analyses?
2.5. What is the definition of causing a new violation or increasing the frequency or severity of
an existing air quality violation?
2.6. What are the interagency consultation requirements for PM2.5 and PMio hot-spot analyses?
2.7. What are the roles and responsibilities of different agencies in project-level conformity
determinations?
2.8. What are the public participation requirements for PM2.5 and PMio hot-spot analyses?
Chapter 3: Analytical Requirements
3.1. What are the general analytical requirements for PM25 and PMio hot-spot analyses?
3.2. What emissions are considered in PM2.5 and PMio hot-spot analyses?
3.3. When is re-entrained road dust considered in PM2.5 or PMio hot-spot analyses?
3.4. When are construction emissions considered in PM2 5 or PMio hot-spot analyses?
3.5. What time frame and analysis years should be used in hot-spot analyses?
Chapter 4: Developing a Qualitative PM^or PM_m Hot-spot Analysis
4.1. What methods can be used for performing qualitative PM2 5 and PMio hot-spot analyses?
4.2. What should be documented for a qualitative PM2 5 or PMio hot-spot analysis?
4.3. What are some of the factors that may be considered in describing existing conditions absent
the proposed project?
4.4. How would changes in existing conditions be evaluated for future scenarios with the
proposed project?
4.5. What are the potential measures to mitigate PM2 5 or PMio air quality concerns?
Appendix A - Examples of Projects of Air Quality Concern
Appendix B - Examples of Qualitative PM2 5 or PMio Hot-spot Analyses
Appendix C - Potential Mitigation Measures
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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 PMio
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 PMio 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 PMio Nonattainment and Maintenance Areas."
However, any PMio 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 PMio 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 PMio hot-spot analyses will be required when appropriate methods and modeling
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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 PMi.sand PMin areas are addressed by this guidance?
This guidance provides information to meet hot-spot analysis requirements for projects in PM2.5
and PMio areas. See Chapter 2 and Appendix B for more specific information.
For PMg_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)(l).
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)(l).
For PMui areas without approved conformity SIPs
For these PMio areas, this guidance would also be used to complete qualitative PMio hot-spot
analyses only for "projects of air quality concern" as defined by 40 CFR 93.123(b)(l).
A qualitative PMio 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)(l).
For PM_m areas with approved conformity SIPs
In areas where EPA has already approved conformity SIPs that include PMio hot-spot provisions
from previous conformity rulemakings, the revised PMio hot-spot requirements in the March 10,
2006 final rule will only be effective when a state either:
• withdraws the existing provisions from its approved conformity SIP and EPA approves
the withdrawal, or
• includes the revised PMio hot-spot requirements in a SIP revision and EPA approves that
SIP revision.
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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, PMi0 areas with approved
conformity SIPs must continue to follow the PMio hot-spot procedures in their existing
conformity SIPs until the SIP is updated and subsequently approved by EPA. PMio areas with
approved conformity SIPs most likely are required to complete a qualitative PMio 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
hot-spot analyses. The guidance addresses many issues such as:
• What requirements must be met under the March 10, 2006 final rule?
• When must the analysis be performed?
• What are the different agencies involved in PM2.5 and PMio hot-spot analyses and
project-level conformity determinations?
• What information should be included in a qualitative hot-spot analysis?
Following the question and answer section are three appendices that provide examples of:
• Projects that are or are not an air quality concern,
• Approaches for qualitative PM2.5 and PMio hot-spot analyses, and
• Potential project-level mitigation measures.
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 PMio 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:
• EPA regional and headquarters offices,
• FHWA division and headquarters offices, and
• FTA regional and headquarters offices.
See Question 1.6 for specific contact information.
1 SAFETEA-LU is Public Law 109-59. EPA and DOT's interim conformity guidance is available at either
http://www.epa.gov/otaq/stateresources/transconf/420b06901.pdf. or
http://www.fhwa.dot.gov/environment/conformitv/sec6011guidmemo.htm.
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1.5. Which parts of this guidance apply to PMi.g hot-spot analyses and which parts of this
guidance apply to PMin hot-spot analyses?
The criteria and procedures for hot-spot analyses will be generally the same for both PM2.s and
PMio areas, except for PMio areas with approved conformity SIPs as noted elsewhere in this
guidance. Questions and answers in this guidance address PM2.5 and PMio 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.
• Contact information for EPA regional offices can be found at:
http://www.epa.gov/otaq/stateresources/transconf/contacts.htm.
• Contact information for FHWA division offices can be found at:
http://www.fhwa.dot.gov/field.html.
• Contact information for FTA regional offices can be found at:
http://www.fta.dot.gov/about/offices/4978 ENG HTML.htm.
General questions about this guidance can be directed to:
• Meg Patulski at EPA's Office of Transportation and Air Quality, patulski.meg@epa.gov,
(734)214-4842;
• Joe Pedelty at EPA's Office of Transportation and Air Quality, pedelty.joe@epa.gov,
(734)214-4410;
• Cecilia Ho at FHWA's Office of Natural and Human Environment,
cecilia.ho@fhwa.dot.gov, (202) 366-9862; or
• Abbe Marner at FTA's Office of Planning and Environment, abbe.marner@fta.dot.gov,
(202)366-4317.
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.
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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.
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Chapter 2: Overview of Transportation Conformity Requirements
2.1. What are the primary requirements for assessing the impacts of projects in PMi.sand
nonattainment and maintenance areas?
Clean Air Act section 176(c)(l)(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)(l)(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 PMio 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 PMio 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)(l) as projects of air quality concern have also met statutory requirements without any
further hot-spot analyses (40 CFR 93.1 16(a)). Please see Questions 1.3 and 2.3 for information
on when the new PMio hot-spot analysis requirements can be used in PMio 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)(l) 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 PMio 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 PMio hot-spot
analysis in 40 CFR 93.123(b)(l) as:
"(i) New or expanded highway projects that have a significant number of or
significant increase in diesel vehicles;
(ii) 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;
(iii) New bus and rail terminals and transfer points that have a significant number
of diesel vehicles congregating at a single location;
(iv) Expanded bus and rail terminals and transfer points that significantly increase
the number of diesel vehicles congregating at a single location; and
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(v) Projects in or affecting locations, areas, or categories of sites which are
identified in the PM2 5 or PMi0 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 PMio hot-spot analysis). However, as described
in Questions 1.3 and 2.3, a PMio hot-spot analysis is required for any project-level conformity
determination in PMio areas with approved conformity SIPs, until such SIPs are revised and
approved by EPA.
2.3. When is a PM^or PMin 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 PMio areas.
areas
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
40CFR93.104(d).3
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)."
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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).
PMui areas without approved conformity SIPs
The revised PMio hot-spot requirements in the final rule are not effective until April 5, 2006. A
qualitative PMio 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 PMio nonattainment and maintenance areas must meet the previous conformity rule's
requirements for PMio hot-spot analyses.
PMui areas with approved conformity SIPs
As described above, PMio areas that have approved conformity SIPs that include PMio 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 PMio areas must include a
hot-spot analysis that meets the requirements in the approved conformity SIP.
2.4. What air quality standards are evaluated in PMi.gor PMin 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 PMio hot-spot analyses. 4
areas
PM2.5 nonattainment and maintenance areas are required to attain and maintain two standards:
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).
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24-hour standard - 65 |ig/m3 , and
annual standard - 15.0 |ig/m3
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.
PM_m areas
nonattainment and maintenance areas are required to attain and maintain two standards as
24-hour standard - 150 |ig/m3, and
Annual standard - 50 |ig/m3
well:
The 24-hour PMio 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 |ig/m3 or greater is measured at a site. The annual PMio standard is attained if the average
of the annual arithmetic means for the past three calendar years is less than or equal to 50 |ig/m3.
A PMio 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 PMio hot-spot analysis meets statutory and regulatory requirements for both
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.s or PMio 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:
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(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 PMi.g and PMm 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 PMio hot-spot analyses
(40CFR93.105(c)(l)(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
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.
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paragraphs provide more information on the potential roles and responsibilities in implementing
the PM2 5 and PMi0 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 PMio 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 PMio 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 FFIWA/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 PMio hot-spot analyses would generally be included in
documents prepared to meet NEPA requirements. Such documents may include:
• an Environmental Impact Statement (EIS) with a Record of Decision (ROD);
• an Environmental Assessment (EA) with a Finding of No Significant Impact (FONSI); or
• a Categorical Exclusion (CE) determination.
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.
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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 PMi0 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 PMio nonattainment and maintenance areas.
2.8. What are the public participation requirements for PMi.g and PMin hot-spot
analyses?
Affected agencies developing project-level conformity determinations (and any associated PM2.5
or PMio 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.
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Chapter 3: Analytical Requirements
3.1. What are the general analytical requirements for PM2 s and PMin hot-spot analyses?
In the March 2006 final rule, EPA retained for PMi0 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:
• Analyzing the total emissions burden of direct PM2 5 or PMi0 emissions which may result
from the implementation of the projects (including re-entrained road dust and
construction emissions as appropriate, as described below), summed together with future
background concentrations;
• Analyzing the entire transportation project, after the identification of major design
features which will significantly impact local concentrations;
• Using consistent assumptions with those used in regional emissions analyses for inputs
that are required for both analyses (e.g., temperature, humidity);
• Assuming the implementation of mitigation or control measures only where written
commitments for such measures have been obtained (40 CFR 93.125(c)); and
• Not considering temporary emissions increases from construction-related activities which
occur only during the construction phase and last five years or less at any individual site.
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 PMio hot-spot analyses must also be based on the latest planning assumptions. In
addition, FHWA or FT A, 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 PM2sand PMin hot-spot analyses?
Hot-spot analyses under this guidance must be based only on directly emitted PM2 5 or
emissions. Tailpipe, break wear, and tire wear PM2.5 or PMio 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 PMio hot-spot
analysis.
PM2.s and PMio precursors are not considered in respective hot-spot analyses. Secondary
particles formed through PM2 5 and PMio 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.
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3.3. When is re-entrained road dust considered in PMi.sor PMin hot-spot analyses?
For PM nonattainment 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 . 1 02(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 PMu) nonattainment and maintenance areas
Re-entrained road dust must be included in all PMio hot-spot analyses. EPA has historically
required road dust emissions to be included in all conformity analyses of direct PMio 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.sor PMm hot-spot analyses?
Construction-related PM2.5 or PMio 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 PMio 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 PMio 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 PMio 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 PMio 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
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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:
• peak emissions from the project are expected, and
• a new violation or worsening of an existing violation would most likely occur due to the
cumulative impacts of the project and background concentrations in the project area.
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.
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Chapter 4: Developing a Qualitative PM2.s or PMin Hot-spot Analysis
This chapter provides general information on the methods and data that can be used to meet
qualitative PM2.5 and PMio 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.sand PMm hot-spot
analyses?
This guidance highlights two methods for completing qualitative PM2.5 and PMio 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)(l)(i)).
A. 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 PMio 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.
B. 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 PMio 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
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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.sor PMm 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 documentation needed and method of analysis chosen will vary depending on
individual circumstances (e.g., local background PM2.5 or PMio 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:
• A description of the proposed project,7 including where the project is located, the project's
scope (adding an interchange, widening a highway, expanding a major bus terminal, etc.),
when the project is expected to be open to traffic, and what part of 40 CFR 93.123(b)(l) is
applicable.
• A description of the method chosen to conduct the hot-spot analysis (see Question 4.1);
• A description of the type of PM2.5 or PMio emissions from the proposed project that are
considered in the qualitative hot-spot analysis (see Questions 3.2, 3.3, and 3.4).
• A description of existing conditions pertaining to the project and project location (see list of
factors that may be considered in Question 4.3).
• A description of the changes in these factors that will result from the project for future
scenarios, including changes in the surrounding environment that will affect PM2.5 or PMio
air quality, changes in traffic and emissions trends (see Question 4.4);
• A description of the analysis year(s) that is examined (see Question 3.5).
• A discussion of any mitigation measures that will be implemented and their expected effects;
and
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/stateresources/transconf/policv.htm.
7 The appropriate section of the NEPA document can also be referenced when relevant.
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A conclusion for how the proposed project meets 40 CFR 93.116 and 93.123 conformity
requirements for the PM2.5 and/or PMio air quality standards.
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
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 PMio levels may include:
A. 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:
• Summarize PM2.5 or PMio design values from nearby monitors in the nonattainment or
maintenance area. Determine if a monitoring station is near the project that will provide data
on local air quality conditions, including PM2.s and PMio concentrations. Monitors closer to
the project location, but still within the nonattainment or maintenance area are preferable to
those further away. In the absence of a nearby monitor, other appropriate monitors in the
nonattainment or maintenance area can also be used. Interagency consultation would be used
to select appropriate monitors for a given project, when monitoring information is necessary
for a hot-spot analysis.
• Consider reviewing data from monitoring stations located in other PM2.s or PMio
nonattainment or maintenance areas that may have similar traffic and environmental
conditions to the proposed project and location.
• Describe future estimated air quality for the attainment year, years beyond the attainment
year, and any changes in PM2.s or PMio concentrations needed to meet attainment and
maintenance schedules. Expected changes in air quality at the project location may result in
changes in the background concentration and the likelihood that a given project may create
or worsen an air quality problem.
• Consider PM2.5 or PMio source apportionment studies when available.
• Consider future emissions trends that could affect air quality concentrations at the project's
location, such as a stationary source, port, or other new source of PM2.s or PMio emissions.
• It is appropriate to also cite published scientific studies or other information regarding
regional or local trend data on PM2.s or PMio concentrations, when such data is available and
applicable to a given project and location.
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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.
B. 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 PMio 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 PMio 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.
C. 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 PMio.
Relevant development trends and land use patterns should be addressed if they have a bearing
on potential PM2.5 or PMio 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.
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IX Meteorology, climate and seasonal data
This description could address atmospheric inversions, prevailing wind direction and speed, as
they impact PM2.5 or PMio concentrations in the project area, if appropriate.
Sources: State/local air quality agencies, review of the applicable PM2.5 or PMio SIP, and the
National Weather Service.
E. 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 PMio 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 PMio 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
PMio 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 PMio concentrations in the
project are listed below. Potential sources for this type of information are similar to those in
Question 4.4.
PM^andPMio
• Changes in traffic volumes and VMT, broken out by estimated diesel fraction and diesel
vehicle class;
• Changes in traffic congestion and traffic flow;
• Changes in diesel truck or bus routes;
• Changes in truck weight limits;
• Retrofit projects, idling policies, truck hoteling electrification infrastructure, or other
emission reduction policies;
• Date the project is expected to open;
• Effect on phase-in of heavy-duty diesel emission; and
• Changes in the built and natural environment that may change existing PM2.5 or
dispersion patterns.
(unless fugitive dust is included in a PMg^area - see Questions 3.3 and 3.4)
street sanding/sweeping practices.
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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 PMi0 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 PMio standards.
4.5. What are the potential measures to mitigate PMij or PMin air quality concerns?
Where the proposed project may lead to a potential new PM2.5 or PMio violation or increase the
severity or frequency of an existing PM2.5 or PMio 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.
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APPENDIX A
EXAMPLES OF PROJECTS OF AIR QUALITY CONCERN
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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)(l) and require a PM2.s or PMi0
hot-spot analysis (71 FR 12491).
Some examples of projects of air quality concern that would be covered by 40 CFR
93.123(b)(l)(i)and(ii)are:
• A project on a new highway or expressway that serves a significant volume of diesel
truck traffic, such as facilities with greater than 125,000 annual average daily traffic
(AADT) and 8% or more8 of such AADT is diesel truck traffic;
• New exit ramps and other highway facility improvements to connect a highway or
expressway to a major freight, bus, or intermodal terminal;
• Expansion of an existing highway or other facility that affects a congested intersection
(operated at Level-of-Service D, E, or F) that has a significant increase in the number of
diesel trucks; and,
• Similar highway projects that involve a significant increase in the number of diesel
transit busses and/or diesel trucks.
Some examples of projects of air quality concern that would be covered by 40 CFR
93.123(b)(l)(iii) and (iv) are:
• A major new bus or intermodal terminal that is considered to be a "regionally significant
project" under 40 CFR 93.1019; and,
• An existing bus or intermodal terminal that has a large vehicle fleet where the number of
diesel buses increases by 50% or more, as measured by bus arrivals.
Q
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:
http://www.fhwa.dot.gov/policv/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."
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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)(l) and would not require a PM2.5 or PMio hot-spot analysis (71 FR 12491).
However, as noted elsewhere in this guidance, PMio nonattainment and maintenance areas with
approved conformity SIPs that include PMio 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)(l)(i)and(ii):
• Any new or expanded highway project that primarily services gasoline vehicle traffic
(i.e., does not involve a significant number or increase in the number of diesel vehicles),
including such projects involving congested intersections operating at Level-of-Service
D,E, orF;
• An intersection channelization project or interchange configuration project that involves
either turn lanes or slots, or lanes or movements that are physically separated. These
kinds of projects improve freeway operations by smoothing traffic flow and vehicle
speeds by improving weave and merge operations, which would not be expected to create
or worsen PM2.5 or PMio violations; and,
• Intersection channelization projects, traffic circles or roundabouts, intersection
signalization projects at individual intersections, and interchange reconfiguration projects
that are designed to improve traffic flow and vehicle speeds, and do not involve any
increases in idling. Thus, they would be expected to have a neutral or positive influence
on PM2 5 or PMio emissions.
Examples of projects that are not an air quality concern under 40 CFR 93.123(b)(l)(iii) and (iv)
would be:
• A new or expanded bus terminal that is serviced by non-diesel vehicles (e.g., compressed
natural gas) or hybrid-electric vehicles; and,
• A 50% increase in daily arrivals at a small terminal (e.g., a facility with 10 buses in the
peak hour).
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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 PMi0 hot-spot analyses. An actual qualitative
PM2.5 or PMio hot-spot analysis would include more documentation regarding the proposed
project, the analysis method and data considered, and the analysis' final conclusion.
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Example A: Comparison of a New Bus Terminal to
Another Site Based on Monitoring Data
Proposed project
• A new major bus terminal is proposed to be built along a public transit route in a rapidly
growing suburban area. The proposed project would significantly increase diesel bus
traffic at the project's location.
• The project would be located in a PM2.5 nonattainment area.
• A PM2 5 hot-spot analysis is required for this project since it is covered by 40 CFR
Analysis method
• The interagency consultation process is used to decide that the hot-spot analysis would
rely on a comparison to an existing project with similar characteristics as the proposed
project, as discussed in Question 4.2.
Data considered
• The hot-spot analysis would not consider PM2.5 road dust emissions, since a finding of
significance has not been made by EPA or the state air agency.
• A nearby air quality monitor indicates that the proposed project's location is significantly
below the 24-hour PM2.5 standard (50 |ig/m3) and close to the annual PM2.5 standard (14.5
|ig/m3).
• A monitor in the vicinity of an existing bus terminal in another part of the PM2 5
nonattainment area has recorded data near the 24-hour PM2.5 standard (60 |ig/m3) and a
violation of the annual PM2.5 standard (15.1 |ig/m3).
• The existing bus terminal also has significant levels of diesel bus traffic and other similar
traffic characteristics as the proposed project.
• Two measures were added to the project to mitigate potential local air quality impacts.
These measures were an anti-idling policy for diesel buses and retrofitting older buses
that were committed to be implemented at the project location.
Conclusion
• The interagency consultation process concluded that additional mitigation measures for
the new bus terminal would be beneficial and should allow concentrations to be lower
than the standards compared to the air quality monitoring data found by the existing
terminal that did not have the mitigation measures that were near or slightly over the 24-
hour and annual PM2 5 standards.
• These measures allowed the project to meet the conformity hot-spot requirements in 40
CFR 93. 116 and 93. 123.
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Example B: Consideration of a Highway Project and Nearby Monitoring Data
Proposed project
• The project entails a major modification to a highway interchange connecting a primary
route to an interstate. A significant number of diesel vehicles are expected to use the
interchange.
• The project would be located in a suburban portion of a larger metropolitan city. The
project is located in a nonattainment area for PM2.5 and PMio standards.
• PM2.5 and PMio hot-spot analyses are required pursuant to 40 CFR 93.123(b)(l)(i).
Analysis method
• The interagency consultation process was used to decide that the hot-spot analysis would
rely on air quality data at the proposed project location, as discussed in Question 4.2.
Data considered
• Air quality information supplied by the state air quality agency found the project's
location did not have any current violations and was significantly below the annual and
24-hour PM2.5 and PMio standards. This information also showed that PM2.5 and PMio
emissions from existing sources were decreasing in the project area into the future.
• The hot-spot analysis would not consider PM2.5 road dust emissions, since a finding of
significance has not been made by EPA or the state air agency. Road dust emissions
would be considered for the PMio hot-spot analysis.
• The traffic change resulting from the project was estimated. It was found to be consistent
with VMT increases in the metropolitan area generally where no increase in PM2 5 and
PMio emissions or concentrations has been noted.
• The meteorology at the project location can generally be categorized as variable, since
the wind varies during the day. There is often some wind that acts to disperse PM2.5 and
PMio emissions at the site. Temperature, humidity, and rainfall do not seem to influence
the level of PM2 5 and PMio pollution at this site.
• A nearby monitor has not registered any violations, and through the consultation process,
it was determined that emissions from the project would not result in a new violation as
any increased emissions that might affect concentrations would be offset by the
decreasing PM2 5 and PMio emissions and concentrations at the project location. In other
words, any increase in the emissions due to traffic changes associated with the project,
would be offset by decreases in the emissions from the transportation facility due to
decreasing on-road vehicle emissions trends, as well as decreasing background
concentrations. This conclusion was supported by scientific journal articles about the air
quality impact of similar projects, which were discussed through the consultation process
and cited in the final hot-spot analysis.
Conclusion
• For the reasons described above, future new or worsened PM2.5 and PMio violations of
any standards are not anticipated, and therefore, the project meets the conformity hot-spot
requirements in 40 CFR 93.116 and 93.123 for both PM2.5 and
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Example C: Comparison of New Highway Project to Similar Project Location in the SIP
Proposed project
• A new 6-lane freeway interchange is proposed to be built at the edge of an urban area.
This interchange would lead to a significant increase in diesel vehicle traffic from both
additional travel on the new connecting road, and from commercial and industrial
development planned for the vicinity of the interchange.
• The project would be located in a PMio maintenance area.
• A PMio hot-spot analysis is required for this project since it is covered by 40 CFR
Analysis method
• The interagency consultation process is used to decide that the hot-spot analysis would
rely on a hybrid of the two methods discussed in Question 4.2, which include a
comparison to another location with similar characteristics and air quality studies.
Data considered
• Through the interagency consultation process, it was determined that the approved
maintenance plan included a modeled demonstration of maintenance for the 24-hour
PMio standard extending out to the year 2015. The SIP also included a modeled
demonstration that the annual PMio standard would be met as long as the 24-hour
standard was met. Therefore, consistent with the SIP's demonstration, conformity
requirements can also be achieved by evaluating only the 24-hour PMio standard in this
particular area.
• The interagency consultation group decided to evaluate the new interchange by
comparing it to an existing interchange that is within the PMio maintenance plan's
modeling domain. The interagency consultation group located an existing interchange
that was located near another edge of the urban area that was similar in terms of
meteorological conditions, and had higher diesel traffic volumes and more intensive
surrounding development than that expected at the new interchange location.
• This existing interchange was within the PMio maintenance plan's modeling grid that
was predicted to experience concentrations of approximately 110 |ig/m3. The current 24-
hour PMio standard is 150 |ig/m3.
Conclusion
• Since this existing interchange was not predicted to experience new or worsened
violations of the 24-hour and annual PMio standards, and the new interchange would see
lower traffic volumes and less development, the interagency consultation group
concluded that the new interchange met the conformity hot-spot requirements in 40 CFR
93. 116 and 93. 123.
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Example D: Determination of Screening Threshold for Multiple Projects
Proposed projects to be considered
• The state department of transportation (DOT) for a PMi0 nonattainment area anticipates a
large number of new highway interchange projects involving significant levels of diesel
traffic that would require a qualitative PMio hot-spot analysis in the next few years.
• These projects would be considered of air quality concern by 40 CFR 93.123(b)(l)(i).
Analysis method
• The interagency consultation process is used to decide that a screening method that
would support future qualitative PMio hot-spot analyses for such projects. The screening
method is based on a hybrid of the two methods discussed in Question 4.2, which include
a comparison to another location with similar characteristics and air quality studies.
Data considered
• The interagency consultation group agreed that it would be the most efficient use of their
resources to develop an analysis for a hypothetical project to which individual projects
could be compared.
• The state DOT retained a consultant to conduct an air quality analysis of some
hypothetical interchange projects that were representative of those the State may wish to
construct in the future. This PMio nonattainment area's on-road mobile source inventory
is dominated by re-entrained road dust.
• The consultant conducted an air quality modeling exercise, using typical project
configurations and the highest background values typically experienced in the
metropolitan area, and concluded that a project would have to generate 500,000 daily
VMT within a one-square-mile area in order to cause a potential violation of the PMio
standard.
• After discussing the situation with the interagency consultation group, it was decided that
certain projects, depending on their characteristics, could be constructed without
triggering a violation of the PMio standard.
Conclusion
• Any applicable future project would meet the conformity hot-spot requirements in 40
CFR 93.116 and 93.123 by referencing the study and providing project-specific
information for comparison.
• Under this example, if a future project has less than 500,000 VMT/day, no further hot-
spot analysis and no mitigation is required.
• If a future project has more than 500,000 VMT/day, further hot-spot analysis is required,
and possibly mitigation measures.
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APPENDIX C
POTENTIAL MITIGATION MEASURES
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Potential PMi.s or PMm Project-level Mitigation Measures: Diesel Emissions
Suspected Source
ofPM25 orPM10
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
Provide a "retrofit" program
for older, higher emitting
vehicles
Anti-idling requirements or
policies (e.g., restrictions on
idling, truck stop
electrification)
Routing existing traffic
away from populated areas
(e.g., truck restricted zone)
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.)
Retrofits could be used on truck or
bus fleets to install newer engines
or technologies known to have
lower emissions
Anti-idling polices are relevant
where significant numbers of
diesel vehicles congregate for
extended periods of time
Routing traffic away from
populated areas may change an
area'sVMT
Cleaner buses will reduce
localized PM2.5 and PMio
emissions for these types of transit
projects
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Potential PMi.s or PMm Project-level Mitigation Measures: Fugitive Dust Emissions
Suspected Source
of PM2 5 or PMio
Problem
Fugitive Dust
Snow and Ice
Control
Type of PM
primarily
controlled
PMio
PMio
PMio
PMio
PMio
PMio
Options to Reduce PM Pollution
Mitigation Measure
Truck cover laws
Street cleaning program
Site watering program
Street and shoulder paving;
Runoff and erosion control
Changes in highway weight
and length restrictions for
trucks
Reduce the quantity of sand
Comments
May require greater enforcement
effort in some areas
Includes vacuuming and flushing
Regular program will reduce dust
Should reduce significant quantities
of dust material
May change an area's fugitive dust
emissions or change the number of
trucks on the road
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 PMio fugitive dust emissions because
all PMio areas must include these emissions in their PMio 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.s hot-spot
analysis.
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