Problem Statement
PSD Baseline and Increment
Tracking Policies
May 2002
Problem Statement
1. Responses to requests from States seeking to establish new PSD baseline
areas, or to redefine existing baseline areas, have been untimely, in part based
on the absence of guidance and criteria to be used by EPA Regional Offices
when evaluating these requests. Guidance is needed to assist States in
preparing such requests, and to ensure that EPA’s responses are consistent and
timely.
2. Tracking increment consumption is resource intensive, especially in States
with large PSD baseline areas. An approach to tracking increment
consumption is needed that balances the need for reasonable estimates of
increment consumed against the resources required to track increment
consumption.
Discussion
The Prevention of Significant Deterioration (PSD) program was designed to keep
the air clean in areas with relatively clean air so that the air quality in these
“cleaner” airsheds does not degrade to the National Ambient Air Quality
Standards (NAAQS). In general, States are required to track the incremental
degradation of air quality with each new or modified emissions source in areas
where major sources have been constructed. Once an area has been “triggered”
for PSD by the submittal of a complete PSD application, States are required to
track emissions from both major and minor sources against the increment for the
specific pollutants that have been triggered. The area within which emissions are
to be tracked is referred to a baseline area. Baseline areas have been established in
a variety of ways. For some states, the entire state is the baseline area. For others,
air quality control regions were defined based on geologic or political boundaries.
The Clean Air Act gives states the authority to re-designate baseline areas (that is
to redefine the boundaries of baseline areas) to provide for more efficient and
effective air quality management. However, attempts by states to re-designate
areas have been slowed by the lack of national guidance to EPA Regions on what
constitutes an approvable request. The most recent policies guiding the
implementation of the PSD program were written in the early 1980’s and have
received new scrutiny over the past few years as the regional affects of air
pollution on Class I areas have become more widely known. While federal land
managers believe that large baseline areas may foster a more comprehensive
evaluation of the regional-scale impact of a proposed new source, it can be a
significant burden on a state to track emissions from all sources over a large area
and can hinder economic development in rural areas of a state.
In a recent Federal Register notice (83 FR 21194), EPA provides some examples
of the types of re-designations that might interfere with effective air quality
management to include “those areas that would have the effect of un-triggering a
minor source baseline date in an area affecting a Class I area or in an area where a
substantial portion of the available increment has been consumed, re-designations
that serve to carve out small “postage stamp” areas encompassing only the
significant impact area around a major PSD source, or large-scale re-designations
creating numerous small baseline areas with little or no basis in effective
management of air quality.” These broad principals need to be discussed with the
states in an open forum, then refined and clarified to provide states with the
guidance necessary to prepare and submit approvable re-designation requests.
Per EPA Guidelines, increment consumption and expansion tracking should be
based on actual emissions. This places the burden upon states to conduct annual
emissions inventories for point and area, major and minor sources of air pollution.
Although many states perform an annual inventory for major sources,
inventorying minor sources and area sources over large areas is not a trivial task
and would involve a great amount of manpower and resources to do so accurately.
EPA guidance allows states to use allowable emission rates (permitted emission
rates) in the absence of actual emission rate data; however, with most sources
requesting permitted levels well above their actual emission rates, this can create
large under and overestimates of increment consumption. Even with the use of
allowable emission rates, area source emission rate determinations are error-prone
and are difficult to calculate and inventory.