**Manual for Air Quality Considerations in Environmental Documents**

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**Federal Highway Administration**

# Southern Resource Center

**January 2001**

*Disclaimer: Neither regulatory or prescriptive, this manual provides
general information and guidance on appropriate levels of air quality
consideration for individual projects. However, working arrangements
developed between the State DOT and air quality agencies may not exactly
replicate this process, and may even exceed these recommendations. This
manual is intended solely as an informal guideline to be used in the
development of Environmental Documentation. It is in no way intended to
replace or supercede the Transportation Conformity Regulations 40 CFR
Parts 51 and 93, 23 CFR Part 771, or any CEQ, EPA, FHWA, and FTA
regulatory requirements or guidance pertaining to development of
Environmental Documents. The author wishes to thank Larry D. Anderson,
former Air Quality Specialist in Region Four, for his contributory
material. For further information on the correct use of this manual you
may contact:*

*Andrew Edwards, Air Quality Specialist*

*Federal Highway Administration - Southern Resource Center*

*61 Forsyth St., Suite 17T26*

*Atlanta, GA 30303-3104*

*(404) 562-3673*

*Document available on the web at:
[www.fhwa.dot.gov/resourcecenters/southern](http://www.fhwa.dot.gov/resourcecenters/southern)*

*3*

**I. Introduction**

The focus of this effort is centered on suggested methods for
appropriate consideration of project-orientated air quality for the
three types of environmental documentation required by the National
Environmental Policy Act (NEPA): Categorical Exclusion (CE),
Environmental Assessment (EA), and Environmental Impact Statement (EIS).

Project-level air quality considerations may vary significantly in
content and level of detail from one project to another, based on the
following:

-   Previous Federal Highway Administration (FHWA) guidance allows for
    considerable flexibility in performing air quality analyses, in
    which the scope, content, assumptions, and level of technical detail
    are typically coordinated between the State Department of
    Transportation (DOT) and the State and/or local air quality
    agencies.

-   Air quality analyses are performed by different groups with varying
    levels of experience. Although some States rely heavily on
    consultants, some States have centralized operations where analyses
    are performed, while yet others have decentralized operations that
    vary in their technical capabilities to perform project analyses.

-   Local conditions such as project location, topography, and
    meteorology influence the type and level of necessary analysis.
    Large projects located in urbanized areas, as well as controversial
    projects involved in litigation or embroiled in other challenges,
    typically require detailed analyses. Detailed air quality
    examinations may also be necessary for projects located in
    geographical areas with unique topography or adverse meteorology.

-   A few States have environmental laws which require a permit prior to
    the construction of a transportation facility. These laws usually
    have an overriding influence on the scope, content, and level of
    detail of the analyses performed for an environmental document. A
    more elaborate analysis than the one performed for the NEPA document
    may be required to obtain a permit.

-   Finally, more detailed analyses are often necessary in response to
    comments from reviewing agencies.

4

**II. Pollutants**

The following are typical Aon-road@ (i.e, highway and transit-related)
mobile source pollutants that require attention during the
transportation planning and /or project development phases.

A. [Carbon Monoxide (CO)]{.underline}

CO is emitted directly into the atmosphere from automobiles, with the
highest levels occurring at slow speeds, in stop-and-go traffic, and at
colder temperatures. Because it disperses to non-harmful levels fairly
rapidly, CO has been considered a localized, Ahot-spot,@ pollutant, and
is the primary pollutant analyzed at the individual project level. There
are currently two CO National Ambient Air Quality Standards (NAAQSs): a
one-hour standard of 35.0 parts per million (ppm) and an eight-hour
standard of 9.0 ppm.

As a result of the 1990 Clean Air Act (CAA) Amendments, emphasis has
also been focused on regional CO emissions level. Areas with a design
value greater than or equal to 9.1 ppm are now designated as
non-attainment for CO. Like Ozone (see below), CO non-attainment and
maintenance areas must also regard the regional composition of CO
through the systems-level urban transportation planning process.
Appropriate levels of analysis should be performed to assure that
regional or localized violations of the NAAQSs do not occur.

For an individual project, if the CO hot-spot analysis indicates a
potential violation of a CO standard, the environmental document needs
to commit to appropriate mitigation measures, based on coordination with
EPA and the respective State and local air quality agencies. A possible
exception is an instance in which the proposed project area contains
pre-existing CO violations. Mitigation strategies may not be needed if,
after appropriate coordination with EPA, a demonstration can be made in
the environmental document that the existing localized CO violation
would be ameliorated as a result of project implementation.

B. [Particulate Matter(PM10)]{.underline}

Typical sources of particulate matter emissions include diesel exhaust,
forestry production activities, unpaved roads, and construction
activities. Although normally addressed in regard to the control of dust
from construction activities, project-related particulate matter now
must also be examined in both regional and localized (Ahot-spot@)
analyses in PM10 nonattainment and maintenance areas.

C. [Ozone (O~3~)]{.underline}

Tropospheric ozone (i.e., ground-level photochemical smog) is different
from CO and PM in that it results from a chemical reaction between
volatile organic compounds and oxides of nitrogen in the presence of
sunlight. Also, the concentration and dispersion of ozone are
significantly affected by an area=s meteorology and topography. Because
it is more of an areawide pollutant, and is typically assessed in
systems-level planning as part of the air quality State Implementation
Plan (SIP) development and conformity processes. Therefore, ozone is a
concern at the project level as that project is taken as part of the
whole regional transportation program but not a concern as a Ahot-spot@
pollutant.

5

**III. Considerations**

The NEPA provides broad authority and responsibility for evaluating and
mitigating adverse environmental effects (including air quality) which
result from the implementation of a proposed project receiving Federal
funding and/or approval. Depending upon the scope of the anticipated
impacts, one of three types of environmental documentation must be
prepared to satisfy the NEPA: CE, EA, and EIS.

Regardless of the type of project-orientated NEPA document involved, air
quality considerations must adequately address two requirements:
Transportation Conformity (assuming the area is nonattainment or
attainment in the maintenance period), and the NEPA air quality impact
analysis.

-   Transportation Conformity addresses a project=s influence on the
    overall goals set forth in the Transportation Plan (TP) and
    Transportation Improvement Program (TIP) so that those goals
    contribute to the reduction in the number and severity of violations
    of the NAAQS. [Having the project part of a currently conforming TP
    and TIP demonstrates the requirement of a Aproject-level@ conformity
    analysis (refer to Appendix C)]{.underline}. If the project is not
    in a nonattainment or maintenance area then Aproject-level@
    conformity would not apply.

-   Project-level analysis of CO Ahot-spots@ and the potential impacts
    the project may have in violating the one- and eight-hour CO NAAQS
    usually occurs as part of the project development phase. This
    analysis can be performed to satisfy the requirements of
    transportation conformity for Ahot-spot@ analyses (refer to
    Appendix A) and the air quality portion of the environmental
    document (refer to Appendix B and D). During project development,
    all alternatives under consideration are analyzed to determine the
    relative air quality impacts between them. In addition, Ahot-spot@
    analyses must be performed to satisfy transportation conformity
    requirements in CO and PM10 nonattainment and maintenance areas.
    [Generally, in nonattainment and maintenance areas, the Ahot-spot@
    analysis developed to satisfy transportation conformity is identical
    to the air quality alternative analysis performed in the
    environmental document to satisfy the NEPA]{.underline}.

While Transportation Conformity typically involves a comparison of the
future emissions levels designated in the SIP with those to be expected
from a system-wide perspective (reflected in the TP and TIP), the air
quality analysis performed as part of the NEPA environmental
documentation process is concerned with a project-level examination of
localized circumstances, namely CO emissions dispersion and
concentration in the vicinity of the proposed project.

A. [Transportation Conformity]{.underline}

According to Section 176(c) of the CAA, transportation plans, programs
and projects cannot:

\(1\) Create new NAAQS violations, (2) Increase the frequency or
severity of existing NAAQS violations or (3) Delay attainment of the
NAAQS if located in nonattainment or maintenance areas.

6

40 CFR Parts 51 and 93 currently require nonattainment and maintenance
areas to determine conformity from two spatial perspectives. First, the
area must demonstrate that regional implementation of projects contained
in the TP and TIP contribute to the overall emissions reductions to be
consistent with the emission reduction goals established in the
applicable SIP. This would satisfy the requirements for Aproject level@
conformity determinations from the individual project perspective (refer
to Appendix C).

The second perspective is at the project development phase. In addition
to the regional emissions analysis requirements, if a project is located
in a CO or PM10 nonattainment or maintenance area, it must satisfy
Ahot-spot@ analysis requirements (refer to Appendix A). Usually
incorporated in the environmental document, this determination must be
based on an analysis of potential local hot-spot effects. While this
additional microscale analysis is not to be confused with the project
related NEPA requirements for CO, the analysis methodologies may in fact
be identical and, therefore, used interchangeably.

In summary, it is possible to have two requirements that must be
satisfied for projects in order to move forward in nonattainment and
maintenance areas: a AProject-level@ conformity analysis (refer to
Appendix C), which must be satisfied in all nonattainment and
maintenance areas, and a Ahot-spot@ analysis for CO or PM10
nonattainment and maintenance areas (refer to Appendix A and D).

B. [NEPA Air Quality Assessment]{.underline}

In addition to the consideration of transportation conformity, a NEPA
air quality assessment, also referred to as project level CO
concentration Ahot-spot@ analysis, is required. For purposes of
environmental documents, the analysis is the general assessment of
potential violations which may occur if the project, with consideration
of alternatives, is implemented. This analysis is compared to the
one-hour and, possibly, the eight-hour CO NAAQS, which again are 35.0
and 9.0 ppm, respectively. The level of analysis depends upon the scope
and location of the proposed project as well as the type of
environmental document involved (CE, EA, or EIS).

In some cases, the level of analysis may not be obvious. The following
discussion provides a summary of the levels of air quality analysis and
the types of NEPA documents for which these methods are most
appropriate. The diagram ALevels of CO AHot-Spot@ Analyses@ summarizes
the ranges of analysis. All analyses methods and assumptions must be
based on best engineering/planning practices. The following is an
explanation of the three types of analyses.

*Simplified Analysis*. This type of analysis is most appropriate for
projects which, by definition, do not involve significant environmental
impacts. In general, such a project will have no affect on areawide air
quality levels, and may even provide some localized air quality
benefits. Therefore, an in-depth examination is not necessary. The main
focus of this approach is to verify that the project will not create a
new violation or exacerbate an existing violation of the various CO
NAAQS.

A simplified analysis is applicable if the project CO contribution, plus
background concentration, can be judged to be well below the one and
eight-hour NAAQS. This judgement may be based on either; (1) previous
analyses from similar projects, or (2) previous general analyses for
various classes of projects. For example, low-volume roads in rural
areas would be an example

7

of one class of project not normally requiring detailed analysis. In
such cases, the environmental document should contain a brief statement
that justifies this determination.

This methodology is appropriate for projects processed with a CE, and
possibly some types of EAs. However, if there is doubt whether a
particular project processed as a CE possesses potential negative air
quality impacts, a sketch analysis methodology may be warranted.

8

**Levels of CO AHot-Spot@ Analyses**

\<\-\-\-\-\-\-\-\-\-\-\-\-\-\--CE\-\-\-\-\-\-\-\-\-\-\-\-\--\>:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::\>

\<\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--EA\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\>:::::::::::::::::::::::::::::::::::::::::::::::\>

\<::::::::::::::::::::::::::::::::::::::::::::::\<\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--EIS\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\>

[Simplified]{.underline}

-   State basis for judgement of no expected CO impacts

[Sketch]{.underline}

-   Look-up tables for CO emission rates

-   Graphic solution for CO concentration

-   Background levels assumed

-   Use worst-case receptor site

-   Computer sketch model

-   

[Modeled]{.underline}

-   Use current AMOBILE model to generate emission factors

-   Choose appropriate CO dispersion model - CALINE, CAL3QHC, other
    approved model

-   Background levels assumed, modeled, or monitored

-   Include all sensitive receptors

-   Include mitigation measures if violations are predicted

-   Include evidence of coordination with EPA and State and local air
    agencies

-   Perform for all Anon-exempt@ projects located in CO nonattainment or
    maintenance areas

\<\-\-\-\-\-\-\-\-\-\-\-\--\> Normal Range

\<::::::::::::::::\> Possible Range

*9*

*Sketch Analysis*. A sketch analysis technique normally consists of
using Alook-up tables@ based on the most recent version of MOBILE to
estimate emission factors, combined with nomographs to yield simplified
dispersions of CO concentrations. When utilizing the sketch analysis
methodology, project-specific total CO concentrations (project plus
background concentrations) are calculated for the preferred alternative
at a reasonable worst-case receptor site (refer to Section C). The
results should then be reported and compared with the NAAQS and any
applicable state standards. Reliance on the use of sketch-type graphical
evaluations should be documented with a brief discussion of the basis
for such judgement.

Upon completion of the sketch analyses, several types of results are
possible. The following summarizes these situations, and provides
discussion for conducting additional analyses.

1.  If the sketch methodology predicts site-specific impacts which are
    judged to be well below the one and eight-hour NAAQS, additional or
    more tensive microscale CO analyses (utilizing a dispersion model)
    are not necessary. The threshold for such a determination is
    dependent on the meteorological persistence factor (PF) used to
    convert the one-hour CO concentration to an eight-hour estimate. For
    example, an estimated one-hour CO concentration of less than 15.0
    ppm (assuming a PF of 0.6) would not necessitate a microscale
    analysis.

2.  Additionally, if a project is located in an area where high traffic
    volumes of meteorological stagnation conditions are expected over an
    eight-hour period of time, a modeled emission analysis should be
    performed.

Generally, sketch analysis procedure is adequate for most projects
processed with an EA. In addition, some CE-type projects may need to be
analyzed with this technique. Regardless, if the predicted CO
concentrations exceed the criteria noted above, a more detailed analysis
using computer modeling techniques should be conducted. A modeled
microscale analysis is also necessary if it is uncertain whether a
potential air quality impact exists from implementation of the project.

*Modeled Analysis*. A modeled microscale CO analysis involves generation
of area-specific mobile source CO emission factors, based on the most
current version of the MOBILE model. Depending on the type of project
analyzed, these emission factors are then utilized in an appropriate
pollutant dispersion model. The current stock of such models assumes a
normal (Gaussian) dispersion of pollutants, adjusted by factors such as;
wind speed, wind direction, atmospheric stability, temperature, surface
roughness, and elevation. The dispersion models primarily recognized by
EPA, at this time, are CALINE (California Line Source Dispersion Model)
and CAL3QHC (California Intersection/Line Source Dispersion Model). A
modeled CO microscale analysis is appropriate for most projects
processed with an EIS, as well as some EA projects.

A modeled CO analysis considers each alternative - including the
no-build - rather than only the preferred alternative, for the estimated
time of completion and design year. Although a brief summary of analysis
methodologies and assumptions should be included in the environmental
document, lengthy discussions should be provided in a separate technical
report and referenced in the project document.

10

Total CO concentrations (project contributions plus background) at
reasonable receptor sites for each alternative should be reported and
compared with applicable State and national standards. In most
circumstances, the "build" alternatives will show an improvement in air
quality over the "no-build" scenario, with these results to be
appropriately reflected in the environmental document. Use of a table is
recommended for purposes of comparison in showing concentrations, with
associated location, by alternative.

Upon completion of the modeled one-hour CO analyses, three types of
results are possible. The following summarizes these situations, and
provides guidance for conducting additional analyses and/or reporting
results.

1.  If the modeled one-hour CO concentration is equal to or greater than
    the eight-hour NAAQS (9.0 ppm), a simplified calculation of an
    eight-hour concentration should be performed by multiplying the
    eight-hour average traffic by a PF, dividing by the one-hour
    traffic, then multiplying by the one-hour CO analysis concentration:

8-hour CO = \[(PF) x (8-hour average hourly traffic) / (peak hour
traffic)\] x 1-hour CO

> If no exceedence of the eight-hour standard is predicted with this
> procedure, further analysis is generally not necessary.

2.  If use of the above eight-hour modification of the modeled one-hour
    analyses continues to predict an exceedence, then eight separate
    modeled one-hour analyses should be performed and the results
    averaged.

3.  If the modeled one-hour analysis predicts a CO concentration which
    is less than 9.0 ppm, separate eight-hour analyses are not
    necessary. In this case, the environmental document should indicate
    that no violations of the eight hour CO standard are expected since
    the worst one-hour CO concentration is less than the eight-hour CO
    NAAQS.

If the analysis of the preferred alternative indicates a potential
violation of a CO NAAQS, the environmental document needs to commit to
the implementation of appropriate mitigation strategies, based on
coordination with EPA and the respective State and local air quality
agencies. Although somewhat limited, air quality mitigation strategies
for CO generally include any activity which reduces congestion and
increases facility speeds. For urban intersections, this may involve
measures such as parking restrictions or changes in signal timing.

A possible exception to the need to develop air quality mitigation
strategies occurs when the proposed project area contains pre-existing
CO violations. Mitigation strategies may not be needed if, after
coordination with EPA, a demonstration can be made in the environmental
document that the existing localized CO violations will be either
eliminated or reduced in severity and number as a result of the project.
Therefore, any "new" or relocated violations must be confined to the
immediate project area.

11

C. [Modeling Considerations]{.underline}

*Receptors*. A receptor location is the point at which concentrations
are estimated. The general rule is to locate or analyze receptors at a
reasonable sample of sites where the general public is likely to have
access and the maximum total project concentrations are likely to occur.
A rule of thumb is to model any locations within 250 feet of the
right-of-way which meet the following criteria. The general criteria can
be restated as having three main parts: (1) places of expected one-hour
and eight-hour maximum concentrations, (2) places where the general
public has access over the time periods specified by the NAAQS, and (3)
reasonableness. Receptors should not be located within 3 meters of the
traveled roadway because vehicle turbulence does not allow current
models to make valid concentrations estimates. If there is a structure
within the 3 meter zone, then the EPA Regional Office should be
contacted for a determination of proper receptor siting. Examples of
reasonable receptor sites include, but are not limited to: residences,
hospitals, rest homes, schools, playgrounds, and building entrances.
When selecting receptor locations, particular attention should also be
given to areas where pollution is likely to accumulate. For more
detailed guidance reference the EPA publication "Guidelines for Air
Quality Maintenance Planning and Analysis - Volume 9: Evaluating
Indirect Sources," EPA-450/4-78-001.

*Persistence Factor (PF)*. As discussed in the previous section, a
persistence factor may be used to convert modeled one-hour CO
concentration to an eight-hour concentration. The following details on
the derivation and application of PF is extracted from EPA's "Guidelines
for Modeling CO from Roadway Intersections," EPA-454/R-92-005.

> Utilized since the mid-1970s, the concept of a PF represents a
> combination of the variability in both traffic and meteorological
> conditions, focusing on one-hour and eight-hour durations. Therefore,
> the ideal method for deriving a locally based PF is to use measured
> monitored CO concentration data.
>
> A calculated PF is typically based on values obtained using the ratio
> of the eight-hour to the maximum one-hour measured CO concentration
> within the eight-hour period. This PF should be calculated for each of
> the ten highest non-overlapping eight-hour concentrations obtained
> from the latest three CO seasons of monitoring data and averaged. A CO
> season is generally defined as the period from October through April,
> but may vary in different areas of the country. If less than three CO
> seasons are not available, then the use of one or two seasons of data
> is acceptable.
>
> However, if monitoring data are not available at all or there are less
> than three months of one CO season of data available, EPA recommends
> the use of a default factor of 0.7 to convert from a peak one-hour
> concentration to a peak eight-hour concentration. The 0.7 factor is a
> reasonably conservative PF based on studies of monitoring data
> throughout many regions of the country. If a PF other than 0.7 is
> obtained through the use of monitored data in a local area, it should
> be used instead of the default factor.

*Background Concentration*. The one-hour CO concentration includes both
the background and project-related CO concentration levels. Appropriate
background concentrations can be estimated by looking at monitored
values from previous analyses, taking monitoring data from State and
local air quality agency monitors, or modeling efforts. However,
monitoring data

12

should be used with caution, since most existing CO monitors are
purposely located where violations occur or are expected, and thus do
not provide realistic background levels. Project monitoring, for either
background or current project levels, should only be performed when
other data are not available and the effort is warranted by expected
controversy or air quality impacts. Consultation with State air quality
agencies to assist in determining appropriate background levels may be
beneficial. Except in areas with unusual meteorological conditions,
typical background CO concentrations are 1.0 ppm for rural areas, or
between 2.0 and 3.0 ppm for urban locations.

13

**IV. Summary**

Environmental documents must address air quality from two perspectives;
Transportation Conformity (Including "Hot-Spot" requirements) and NEPA
Air Quality Assessment. The level of work needed to adequately fulfill
both the CAA and NEPA requirements is dependent on several factors: (1)
the various NAAQS designations of the project area, (2) the type of
project(s) under consideration, (3) the type of environmental
documentation being prepared (CE, EA, or EIS), (4) the existence of any
overriding State laws, policies, or procedures, (5) location specific
features, such as weather conditions and topography, and (6) the level
of anticipated controversy associated with the project.

**Appendix A**

## Specific Citing from 40 CFR Part 93

**Transportation Conformity "Hot-Spot" Requirements**

**\' 93.116 Criteria and procedures: Localized CO and PM** 10
**violations (hot spots).**

\(a\) This paragraph applies at all times. The FHWA/FTA project must not
cause or contribute to any new localized CO or PM10 violations or
increase the frequency or severity of any existing CO or PM10 violations
in CO and PM10 nonattainment and maintenance areas. This criterion is
satisfied if it is demonstrated that no new local violations will be
created and the severity or number of existing violations will not be
increased as a result of the project. The demonstration must be
performed according to the consultation requirements of \'
93.105(c)(1)(i) and the methodology requirements of \' 93.123.

\(b\) This paragraph applies for CO nonattainment areas as described in
\' 93.109(d)(1). Each FHWA/FTA project must eliminate or reduce the
severity and number of localized CO violations in the area substantially
affected by the project (in CO nonattainment areas). This criterion is
satisfied with respect to existing localized CO violations if it is
demonstrated that existing localized CO violations will be eliminated or
reduced in severity and number as a result of the project. The
demonstration must be performed according to the consultation
requirements of \' 93.105(c)(1)(i) and the methodology requirements of
\' 93.123.

**\' 93.123 Procedures for determining localized CO and PM** 10
**concentrations (hot-spot analysis).**

\(a\) CO hot-spot analysis. (1) The demonstrations required by \' 93.116
(\>\>Localized CO and PM10 violations==) must be based on quantitative
analysis using the applicable air quality models, data bases, and other
requirements specified in 40 CFR part 51, Appendix W (Guideline on Air
Quality Models). These procedures shall be used in the following cases,
unless different procedures developed through the interagency
consultation process required in \' 93.105 and approved by the EPA
Regional Administrator are used: (i) For projects in or affecting
locations, areas, or categories of sites which are identified in the
applicable implementation plan as sites of violation or possible
violation; (ii) For projects affecting intersections that are at
Level-of-Service D, E, or F, or those that will change to
Level-of-Service D, E, or F because of increased traffic volumes related
to the project; (iii) For any project affecting one or more of the top
three intersections in the nonattainment or maintenance area with
highest traffic volumes, as identified in the applicable implementation
plan; and (iv) For any project affecting one or more of the top three
intersections in the nonattainment or maintenance area with the worst
level of service, as identified in the applicable implementation plan.
(2) In cases other than those described in paragraph (a)(1) of this
section, the demonstrations required by \' 93.116 may be based on
either: (i) Quantitative methods that represent reasonable and common
professional practice; or (ii) A qualitative consideration of local
factors, if this can provide a clear demonstration that the requirements
of \' 93.116 are met.

\(b\) PM*10* hot-spot analysis. (1) The hot-spot demonstration required
by \' 93.116 must be based on quantitative analysis methods for the
following types of projects: (i) Projects which are located at sites at
which violations have been verified by monitoring; (ii) Projects which
are located at sites which have vehicle and roadway emission and
dispersion characteristics that are essentially identical to those of
sites with verified violations (including sites near one at which a
violation has been monitored); and (iii) New or expanded bus and rail
terminals and transfer points which increase the number of diesel
vehicles congregating at a single location. (2) Where quantitative
analysis methods are not required, the demonstration required by \'
93.116 may be based on a qualitative consideration of local factors. (3)
The identification of the sites described in paragraph (b)(1)(i) and
(ii) of this section, and other cases where quantitative methods are
appropriate, shall be determined through the interagency consultation
process required in \' 93.105. DOT may choose to make a categorical
conformity determination on bus and rail terminals or transfer points
based on appropriate modeling of various terminal sizes, configurations,
and activity levels. (4) The requirements for quantitative analysis
contained in this paragraph (b) will not take effect until EPA releases
modeling guidance on this subject and announces in the Federal Register
that these requirements are in effect.

\(c\) General requirements. (1) Estimated pollutant concentrations must
be based on the total emissions burden which may result from the
implementation of the project, summed together with future background
concentrations. The total concentration must be estimated and analyzed
at appropriate receptor locations in the area substantially affected by
the project. (2) Hot-spot analyses must include the entire project, and
may be performed only after the major design features which will
significantly impact concentrations have been identified. The future
background concentration should be estimated by multiplying current
background by the ratio of future to current traffic and the ratio of
future to current emission factors. (3) Hot-spot analysis assumptions
must be consistent with those in the regional emissions analysis for
those inputs which are required for both analyses. (4) PM10 or CO
mitigation or control measures shall be assumed in the hot-spot analysis
only where there are written commitments from the project sponsor and/or
operator to implement such measures, as required by \' 93.125(a). (5) CO
and PM10 hot-spot analyses are not required to consider
construction-related activities which cause temporary increases in
emissions. Each site which is affected by construction-related
activities shall be considered separately, using established
\>\>Guideline== methods. Temporary increases are defined as those which
occur only during the construction phase and last five years or less at
any individual site.

**Appendix B**

## Excerpt from FHWA Technical Advisory 6640.8A

**Guidance for Preparing and Processing Environmental**

**and Section 4(f) Documents**

**8. Air Quality Impacts**

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## Appendix C

**AProject-Level@ Conformity Determination Documentation**

The first discussion needs to center on the area=s current designation
under the NAAQS. This should be accompanied by dates of
designation/redesignation for the NAAQS and, where appropriate, the most
current mobile source emission budgets with date of publication in the
Federal Register. Providing a copy of the actual Federal Register notice
would be most beneficial, but is not necessary.

Example:

> Fakeville County was designated nonattainment for the ozone NAAQS on
> (month/day/year). Upon submission of the attainment demonstration and
> maintenance plan the area was redesignated to attainment on
> (month/day/year). The area is currently in the (number) year of its
> maintenance period. The current mobile source emission budgets were
> effective on (month/day/year) and are found in the (month/day/year)
> Federal register.

The discussion of conformity needs to identify that the project comes
from the currently conforming plan and TIP. Dates need to be identified
for when the conformity determination was made for both documents. This
also should include which plan and TIP the project comes from. Providing
a copy of the conformity determination would be most beneficial but is
not necessary.

Example:

> Project Fake comes from the currently conforming Fakeville 2025
> Transportation Plan and 2000-2005 Fakeville TIP found to jointly
> conform via the federal conformity determination on (month/day/year).

##  

## Appendix D

**Documentation of AHot-Spot@ and NEPA Analysis**

Again, the Ahot-spot@ analysis is used interchangeably to satisfy the
NEPA and transportation conformity (for CO and PM10 nonattainment and
maintenance areas) Ahot-spot@ requirements.

In addition to the previous discussion, it is recommended that analysis
documentation should contain the following information, however, these
are not all encompassing and would vary from project to project. Further
specifications can be sought through State DOT and FHWA Division office
representatives.

-   The analysis should document receptor locations with the highest 1
    hour and 8 hour values taken into account the criteria outlined in
    III.C.

-   The reported values should include the wind angle at which the
    highest values occurred.

-   A map showing the project and receptor location should be included.

-   All pertinent assumptions and data should be documented which led to
    the reported receptor values.

-   Finally, a statement that violations occurred or not should be
    reported.