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ensure compliance with NEPA, CAAA, and 49 U.S.C. 47106(c)(1)(B). There are recommended and
required time periods associated with many steps (for example, mandatory public comment periods);
consult the appropriate agency document (i.e., FAA Order 1050.1/5050.4, and any subsequent
amendments or USAF Instruction 32-7061) for more information.
2.1 Assessment Process Steps
The process for assessing the air quality impacts of FAA and USAF proposed actions involves
the following key steps*:
· Project definition,
· Inventory of emissions,
· Indirect source review,
· Assessment of transportation and general conformity with SIP, and
· Assessment of NAAQS.
Fortunately for the air quality analyst/environmental specialist, not all of the steps are required for every
action. Many projects at airports and air bases are too small to require detailed air quality analysis and
only a few projects are both broad enough in scope and located in nonattainment or maintenance areas
such that the full complement of analyses described in this handbook would be required. Screening
techniques that streamline the process for many air quality assessment actions are available and discussed
later in this section (Section 2.3). Figure 1 provides a detailed look at the assessment process and
includes some decision points that may allow a particular project to bypass certain steps. As Figure 1
indicates, analysis of projects located in nonattainment and maintenance areas is more complex than for
projects in attainment areas.
1 This handbook only discusses state and local requirements in general terms. Actual requirements must be
considered on an individual project basis.
* These key steps have various “sub-steps” that are performed, including evaluating applicable screening
thresholds and dispersion modeling. The second key step, inventory of emissions, may be a separate
analysis or “sub-step” under another key step (e.g., conformity or NAAQS Assessment).
8
The following sub-sections discuss the key steps of an air quality assessment process. Figures 1
& 2 summarize the types of air quality analyses often required for airport and air base projects
and indicates the different projects that require each type of analysis.
9
Figure 1. Air Quality Assessment Process for Airports and Air Bases - Part 1
10
Figure 2. Air Quality Assessment Process for Airports and Air Bases - Part 2
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2.1.1 Project Definition
The first step of the air quality assessment process, illustrated in Figure 1, is to define the scope
and alternatives of the project or Federal action (if not already accomplished through the EA/EIS
scoping process). This provides the structure and definition to guide subsequent data collection
and analysis activities. Reasonable project options should be identified, including “build” and
“no-build” alternatives.
“Build” alternatives reflect projected airport or air base related operations after a project’s
completion. The “no-build” alternatives reflect projected airport or air base related operations as
they are projected to be in the future without the project’s implementation. The “build” and “nobuild”
alternatives are compared to identify the project’s overall environmental impacts.
2.1.2 Emission Inventory
An emission inventory provides a first indication of the magnitude of a proposed project’s
potential environmental impact. The emission inventory provides the total amount or mass of
pollutants generated by all sources affected by the projects during a specified period of time
(e.g., tons per year). An inventory may include both direct and indirect emissions. See section
three for a detailed discussion. The emission inventory often is used as the basis for further
analysis (e.g., SIP, NAAQS, conformity process). Individual pollutants of concern at airports
and air bases primarily2 include CO, NOx, particulate matter less than 10 micrometers in diameter
(PM-10), HC, and in some cases SOx. Developing an emission inventory involves considerable
data collection reflecting the level of activity at the airport or air base and the specific emission
sources present.
The scenarios for which an emission inventory must be calculated vary depending on the analysis
being performed (e.g. conformity, NAAQS, or SIP process). For a conformity assessment, only
the “build” and “no-build” emissions are analyzed (including construction emissions, which are
the projected temporary emissions resulting from project construction). The difference between
the two emission inventories, in turn, equate to the emissions directly attributable to the project.
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