EPA Issues Transportation Conformity
Guidance for Quantitative Hot-spot
Analyses in PM25 and PM10 Nonattain-
ment and Maintenance Areas
Overview
The U.S. Environmental Protection Agency (EPA) released final guidance for quan-
tifying the local air quality impacts of certain transportation projects and comparing
them to the PM25 and PM10 (PM) national ambient air quality standards (NAAQS).
This guidance is to be used by state and local agencies to conduct quantitative
"hot-spot analyses" for new or expanded highway or transit projects with significant
increases in diesel traffic,
EPA originally released this guidance in December 2010,1 and released revised guid-
ance in November 2013 (EPA-420-B-13-053) to reflect California's latest approved
emissions model, EMFAC2011, and EPA's 2012 PM NAAQS final rule. See EPA's
"PM Hot-spot Guidance Change Bulletin: November 2013" (EPA-420-B-13-056) for
a complete list of changes made in this revised guidance; all other parts of the guid-
ance are unchanged. EPA developed the November 2013 guidance in coordination
with the Department of Transportation and, for the EMFAC2011 parts of the guid-
ance, the California Air Resources Board,
Note that this guidance is limited to quantitative PM hot-spot analyses. EPA has
developed separate guidance for using MOVES to estimate carbon monoxide emis-
sions for transportation projects, including roadway intersections, highways, transit
projects, parking lots and intermodal terminals.
The quantitative PM hot-spot guidance, Federal Register notice, CO project-level
MOVES guidance, and related documents can be found on EPA's Office of Trans-
portation and Air Quality website at: www.epa.gov/otaq/stateresources/transconf/
proj ectlevel-hotspot.htm.
1 In developing the original 2010 guidance, EPA released a draft version of this guidance for public
comment on May 26, 2010 with a closing date of July 19, 2010 (75 FR 29537-29538). EPA received
15 sets of comments on the draft guidance and considered these comments when developing the
guidance.
SEPA
United States
Environmental Protection
Agency
Office of Transportation and Air Quality
EPA-420-F-13-049
November 2013
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Purpose of the Guidance
This guidance describes how to complete quantitative PM hot-spot analyses. A hot-spot analysis
is an analysis of a transportation project's impact on future localized pollutant concentrations
and a comparison of those concentrations to the relevant N AAQS. These analyses are required
only for new or expanded highway or transit projects with significant increases in diesel traffic.
While this guidance addresses quantitative PM hot-spot analyses for transportation conformity
purposes, certain sections of this guidance may be applicable when completing air quality analyses
for transportation projects for other purposes.
This guidance describes how to estimate project emissions using EPA's MOVES model, California's
EMFAC model, and other methods. It also outlines how to apply air quality models (AERMOD
and CAL3QHCR) for PM hot-spot analyses. Finally, the guidance includes additional resources
that may assist state and local agencies in conducting quantitative PM hot-spot analyses,
Background
Transportation conformity is a Clean Air Act requirement that ensures that federally supported
highway and transit projects are consistent with state air quality implementation plans. Confor-
mity helps protect public health through early consideration of the air quality impacts of trans-
portation decisions in places where air quality does not currently meet the NAAQS or has not
met them in the past,
Steps for Completing a Quantitative PM Hot-spot Analysis
The flowchart below illustrates the basic steps for completing a quantitative PM hot-spot analysis
as described in the guidance. In general, a hot-spot analysis compares the air quality concentra-
tions with the proposed project (the "build" scenario) to air quality concentrations without the
project (the "no-build" scenario). For each scenario, it is necessary to consider emissions from
the project and any nearby sources, as well as determine background concentrations. From this
information, design values can be calculated to determine if a project conforms. If the build
design values are less than or equal to the relevant NAAQS, the project is considered to
conform. A project will also conform if the build scenario design values are greater than the
NAAQS but less than or equal to the design values for the no-build scenario.
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Overview of a Quantitative PM Hot-spot Analysis
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/ Do emissions, from \ No
construction \ . /
dust need to f
be estimated? /
Yes
other sources (e.g..
locomotives) need
to be considered?
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Step 5: Select Air
Juality Model, Data
iputs, and Receptors
Obtain and input
required site data (e.g..
meteorological)
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Input MOVES/
EMFAC, dust, and
nearby source outputs
^
Run air quality model
and obtain results
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Step 6:
Determine Background
Concentrations
Step 7: Calculate Design
Values and Determine
Conformity
Add Step 5 results to
background concentrations
to obtain design values for
build'no-build scenarios
Do the design
values allow the
project to
conform?
Yes
Step 8:
Consider Mitigation or
Control Measures
Consider measures to
reduce emissions and redo
analysis
Do the design
values allow the
project to
conform?
Step 9:
Document Analysis
No
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Summary of Contents of Guidance
The following is a section-by-section description of the guidance:
Section 1: Introduction
This section provides general information about quantitative PM hot-spot analyses, including
what they are and when they are required, and introduces the organization of the guidance. This
section also includes contact information of EPA staff for questions regarding the guidance,
Section 2: Transportation Conformity Requirements
This section outlines the transportation conformity requirements for quantitative PM hot-spot
analyses. This section also describes general statutory and regulatory requirements, specific
analytical requirements, and the different types of agencies that are involved in developing hot-
spot analyses,
Section 3: Overview of a Quantitative PM Hot'Spot Analysis
This section provides an overview of the process for conducting a quantitative PM hot-spot
analysis. This section may be particularly helpful to those who are looking for a general under-
standing of this process. All individual elements or steps presented in this section are covered in
more depth throughout the remainder of the guidance,
Section 4: Estimating Project-Level PM Emissions Using MOVES
This section describes how to use EPA's MOVES emissions model to estimate a project's exhaust,
brake wear, and tire wear emissions for PM hot-spot analyses outside of California. This section
focuses on determining appropriate project-level inputs and how MOVES should be run to provide
the necessary information to complete air quality modeling,
Section 5: Estimating Project-Level PM Emissions Using EMFAC (in California)
This section describes how to use the EMFAC model to estimate a project's exhaust, brake wear,
and tire wear emissions for PM hot-spot analyses in California. The California Air Resources
Board (GARB) maintains EMFAC, which is approved by EPA for developing on-road motor
vehicle emission inventories and conformity analyses in California,
Section 6: Estimating Emissions from Road Dust, Construction, and Additional Sources
This section describes how to estimate re-entrained road dust and transportation-related con-
struction dust emissions, if dust is required to be included in the PM hot-spot analysis. This section
also includes information on quantifying emissions from construction vehicles and equipment,
locomotives, and additional sources of emissions in the area, when applicable,
Section 7: Selecting an Air Quality Model, Data Inputs, and Receptors
This section describes the recommended air quality models (AERMOD and CAL3QHCR), data
inputs, and receptor considerations for PM hot-spot analyses. This guidance is consistent with
the conformity rule and recommendations for air quality modeling in EPA's "Guideline on Air
Quality Models" (Appendix W to 40 CFR Part 51).
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Section 8: Determining Background Concentrations from Nearby and Other Emission
Sources
This section describes how to determine background concentrations for PM hot-spot analyses,
which can include nearby sources (sources other than the project that contribute to ambient
concentrations in the project area) and other sources (background concentrations in the project
area that are not from the project or any other nearby sources that are modeled),
Section 9: Calculating PM Design Values and Determining Conformity
This section describes how to combine all steps of a PM hot-spot analysis, as discussed in previous
sections, into a design value so that a project sponsor can determine if conformity requirements
are met. For conformity purposes, a design value is a statistic that describes a future air quality
concentration in the project area that can be compared to a particular NAAQS,
Section 10: Mitigation and Control Measures
This section describes mitigation and control measures that could be considered by project
sponsors to reduce emissions in the project area,
Appendices
The guidance also contains the following appendices to supplement the above sections and assist
state and local agencies when conducting PM hot-spot analyses:
• Appendix A is a clearinghouse of information and resources external to this guidance
that may be useful when completing PM hot-spot analyses,
• Appendix B gives examples of projects of local air quality concern,
• Appendix C discusses what projects in PM10 areas need a hot-spot analysis if a state has
a pre-2006 approved conformity SIP,
• Appendix D demonstrates how to characterize links in an intersection when running
MOVES.
• Appendices E and F are abbreviated PM hot-spot analysis examples (using MOVES) for
a highway and transit project, respectively,
• Appendices G and H are examples of how to configure and run EMFAC for a highway
and transit project, respectively,
• Appendix I includes guidance for estimating locomotive emissions in the project area,
• Appendix J includes details on how to input air quality modeling data and run AERMOD
and CAL3QHCR for a PM hot-spot analysis and prepare outputs for design value
calculations,
• Appendix K has examples of how to calculate design values and determine transportation
conformity.
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For More Information
For specific questions concerning using this guidance for a project in a particular nonattainment
or maintenance area, please contact the transportation conformity staff person responsible for
your state at the appropriate EPA Regional Office. Contact information for EPA Regional
Offices can be found at:
www.epa.gov/otaq/stateresources/transconf/contacts.htm.
General questions about this guidance can be directed to Meg Patulski at:
U.S. Environmental Protection Agency
Office of Transportation and Air Quality
Transportation and Regional Programs Division
(734) 214-4842
E-mail: patulski.meg@epa.gov
Technical questions about completing emissions and air quality modeling for CO and PM hot-
spot analyses can also be sent to:
conformity-hotspot@epa.gov
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