The document discusses proposed refinements to the New Source Review (NSR) program's Prevention of Significant Deterioration (PSD) increment modeling procedures. Specifically, it proposes clarifying how emissions increases are calculated to determine compliance with PSD increment thresholds and addressing issues related to modeling actual emissions and meteorological data usage. The proposal seeks to provide more consistency in increment analysis methods while allowing permitting authorities flexibility in selecting appropriate modeling approaches.

1. www.epa.gov/nsr
New Source Review (NSR) Prevention
of Significant Deterioration (PSD):
Refinement of Increment Modeling
Procedures Proposal
Jessica Montañez
Office of Air Quality Planning and Standards
New Source Review Group
1

2. Agenda
• What is New Source Review?
• What are the Requirements of the PSD
Program?
• PSD Increments
• Purpose of this Proposal
• Refinements of Increment Modeling
Procedures Proposal
• Topics Addressed in this Proposal
2

3. What is New Source Review?
• Thresholds used to identify whether a source is major or minor. Major sources for:
• PSD are those with potential to emit (i.e. capability at maximum design capacity to emit a
pollutant) 100 or 250 tons/year or more depending on the source category
• NA NSR are those with potential to emit 100 tons/year or more. Sources might be subject
to NA NSR because lower thresholds apply depending on the nonattainment severity.
• Regulated NSR pollutants. For:
• PSD include National Ambient Air Quality Standards (NAAQS) and other pollutants such
as sulfuric acid mist and hydrogen sulfide
• NA NSR include only the NAAQS
Major NSR
in attainment
areas (PSD)
Minor NSR
in both attainment and
nonattainment areas
Major NSR
in nonattainment
areas (NA NSR)
New Source Review
pre-construction permitting
program for new or modified
stationary sources
NSR is divided into three parts:
3

4. What Are the Requirements of the PSD
Program?
• Once it is determined that a source is subject
to the PSD program, the program requires:
• Installation of Best Available Control Technology
(BACT)
• Performing Air Quality Analysis to preserve
existing clean air (including National Parks and
Wilderness Areas where applicable)
• NAAQS Analysis (monitoring and modeling)
• Increment Analysis (modeling)
• Performing an Additional Impacts Analysis
• Public Involvement
4

5. PSD Increments
• One of the significant components of the PSD
program is the requirement to evaluate increment
consumption
• Baseline Concentration - the ambient concentration
that existed in the area before a PSD source submits
the first PSD application in the area
• Increment - maximum allowed increase in
concentration of a pollutant above the baseline
concentration in an area
• Increment standards exist for 3 pollutants for a
variety of averaging periods and area
classifications
• Particulate Matter (PM10)
• Sulfur Dioxide (SO2)
• Nitrogen Dioxide (NO2)
• Increment standards for Class I areas are the
smallest ones followed by Class II and Class III
• Class I - national parks and other natural areas of
concern
• Class II - nearly all other areas in the United States
• Class III – areas targeted for industrial development
Increment per Area
Classification
(µg/m3
)
Averaging
Period
Pollutant I II III
Annual PM-10 4 17 34
SO2 2 20 40
NO2 2.5 25 50
24-hr PM-10 8 30 60
SO2 5 91 182
3-hr SO2 25 512 700
5

6. Purpose of this Proposal
• Purpose:
• Refine the method for analyzing increment
consumption through rulemaking
• Why?
• Over time, EPA has developed recommended
approaches for increment analyses through
guidelines and guidance documents because PSD
regulations contained only a few basic requirements
• Guidance on Air Quality Models, 40CFR Part 51
Appendix W
• Draft NSR Workshop Manual
• However, different interpretations and approaches
have resulted over how binding the guidelines and
guidance documents are and who has the ultimate
discretion to determine which approaches are
reasonable for a specific increment analysis
“EPA and
states have
generally used
an emissions
inventory and
modeling
approach to
calculate
increment
consumption.”
6

7. Refinements of Increment Modeling
Procedures Proposal
• Proposed rule:
• Clarifies how PSD emissions increases are calculated to
determine compliance with the PSD increment
• Incorporates some of Western States Air Resources
Council (WESTAR) recommendations
• Addresses issues related to the 2004 State of North
Dakota and the U.S. EPA Memorandum of
Understanding (MOU)
• Proposal:
• Published in Federal Register on June 6, 2007
• Comment period closed on August 6, 2007
• Comment period reopened on August 29, 2007
• New comment period closes on September 28, 2007
7

8. Refinements of Increment Modeling
Procedures Proposal (Continued)
• Topics addressed in the proposal:
• What is the effect of the 1990 Draft NSR Workshop
Manual?
• How should actual emissions from applicable sources
that consume the PSD increment be estimated?
• How is a source with a Class I Area Federal Land
Manager (FLM) variance treated in subsequent
increment consumption modeling?
• What alternative time periods can be used to model
pollutant concentrations?
• How should actual emissions be calculated for
modeling short-term increments?
• What are appropriate types of meteorological data and
processing that should be used for certain dispersion
model applications?
• How many years of meteorological data are appropriate
for modeling increment consumption?
• What are the requirements for modeling
documentation, data and software availability?
8

9. What is the Effect of the 1990
Draft NSR Workshop Manual?
• We are only proposing to clarify that
the 1990 Draft NSR Workshop
Manual does not by itself establish
final policies or interpretations
• Policies or interpretations from the
NSR Workshop Manual that where
issued in final form (such as
rulemakings, guidance memorandum,
or adjudications by the Administrator
or the Environmental Appeals Board)
are the ones that will be followed by
EPA
9

10. How Should Actual Emissions from Applicable Sources
that Consume the PSD Increment be Estimated?
• Increment consumption analysis include:
• Actual emissions:
• From any major stationary source on which construction
commenced after the major source baseline date
• Increases and decreases at any stationary source
occurring after the minor source baseline date
• Secondary emissions
• Mobile sources emissions:
• States that have neglected to account for these emissions
in prior increment analysis should simply include them in
their next permit review or periodic review of increment
consumption
• We are proposing to amend the reference to ”any
stationary source” in 40 CFR 51.166(b)(13)(ii)(b) and 52.21
(b)(13)(ii)(b) of our regulations to make clear that actual
increment consuming emissions are not limited solely to
stationary source emissions
• Increment consumption analysis exclude:
• Categories mentioned in Clean Air Act Section 163(c)
• Concentrations attributable to temporary increases in
emissions from sources affected by SIP revisions
approved by EPA, 40 CFR 51.166(f)(1)(v)
Secondary emissions:
emissions which occur as
a result of the
construction or operation
of a major source or
modification, but do not
come from the major
source itself. They
include emissions from
any offsite support facility.
Must be specific, well-
defined, quantifiable,
and impact the same
general area as the
major source or
modification under
review.
10

11. How Should Actual Emissions from Applicable Sources
that Consume the PSD Increment be Estimated?
(Continued)
• Proposing to:
• Give each reviewing authority the discretion to use
its best professional judgment when determining
sources’ actual emissions
• Adopt a revised definition of “actual emissions” for
increment calculation purposes in 40CFR51.166(f)
and 52.21(f) rather than revising 40CFR 51.166(b)
(21) and 40CFR 52.21(b)(21)
• Requesting comment on WESTAR’s
recommended two-step approach:
• EPA should develop a menu of acceptable
emissions calculation approaches for both short-
term and annual PSD analyses
• Allow the reviewing authority to select what they
believe to be the most appropriate option from the
menu based on a set of guiding principles
11

12. How Should Actual Emissions from Applicable Sources
that Consume the PSD Increment be Estimated?
(Continued)
• WESTAR’s suggested guiding principles:
• Maximize the accuracy of the method(s) used in
reflecting the actual status of air quality during each time
period associated with applicable standards
• Conform to the Act, Federal PSD rules, and other
applicable laws and rules
• Ensure consistency between emissions calculation
methods used for sources in the baseline emissions
inventory and the current emissions inventory
• Ensure that selected methods are practical given the
availability of reviewing authority access to the emissions
data
• Support fairness and consistency on how emissions are
calculated for various source types across and within
States
• Support key air quality management objectives that
States and EPA are seeking to achieve, such as
encouraging sources’ use of continuous emissions
monitoring systems (CEMS) and discouraging sources
from seeking more permitted air quality than they need
12

13. How is a Source with a Class I Area Federal Land
Manager (FLM) Variance Treated in Subsequent
Increment Consumption Modeling?
• When a proposed source subject to permitting has the
potential to adversely impact a Class I area, an
additional review is required to assess whether the
source has the potential to adversely impact the area’s
AQRVs
• AQRVs – resource that might be affected by a change in
air quality as defined by the FLM, State or Indian
Governing Body
• Sections 165(d)(2)(C)(ii) and 165(d)(2)(C)(iii) of the
CAA state that AQRVs control whether a permit is
issued or not
• The FLM, State or Indian Governing Body has the
burden of demonstrating an adverse impact on
AQRVs, if any, when the Class I increment is not
exceeded.
• The permit applicant has the burden of convincing the
FLM, State or Indian Governing Body that the proposed
source will not have an adverse impact on AQRVs
when the source causes or contributes to a violation of
the Class I increment13

14. How is a Source with a Class I Area Federal Land
Manager (FLM) Variance Treated in Subsequent
Increment Consumption Modeling? (Continued)
• Section 165(d)(C) of the Act is ambiguous as to
whether the Class I increment should continue to apply
in the Class I area for which a variance has been
issued
• For that reason, we are proposing to:
• Retain the Class I increment for the purpose of
establishing the burden of proof in the AQRV analysis
• Not require a SIP to be amended to offset the contribution
of sources that have received a variance because they do
not adversely affect AQRVs
• Allow States to exclude the emissions from sources
receiving an FLM variance from the Class I increment
calculation
• Require States to include the emissions from the variance
source for purposes of determining compliance with the
Class II increment assessment
14

15. What Alternative Time Periods Can be Used to
Model Pollutant Concentrations?
• When modeling air quality, we have called for the
change in concentration to be based on the actual
emissions rates from increment consuming sources
over the 2 years immediately preceding a particular
date.
• Exception: a different time period of time may be used
when it is more representative of normal source
operations (40CFR 51.166(b0(21)(ii) and 52.21 (b)(21)
(ii))
• Usually applied to catastrophic occurrences only
• In the 2002 new definition of “baseline actual emissions” for
modifications. The definition allows for any consecutive:
– 2-year period in the last 10 years for non-utilities
– 2-year period in the last 5 years for utilities
• This proposal intends to clarify those circumstances
when it is permissible to use another time period to
represent actual emissions as of a particular date
15

16. What Alternative Time Periods Can be Used to
Model Pollutant Concentrations?
• We are proposing to:
• Establish a new definition of “actual emissions” in
40 CFR 51.166(f)(1)(iv) and 52.21(f)(1)(iv) to clarify
this issue
• A different time period than the 24 months preceding
a particular date may be used as long as it is more
representative of normal source operations and
there is credible information that the unit’s operations
in the 24 months preceding the date where not
typical operations as of that date
• A period after the particular date may be used, but
only if such period is more representative of normal
source operations as of the particular date
• Operations occurring prior to a particular date are
not representative of normal source operations for a
particular date if they permanently ceased more than
24 months prior to that date
• The time period most be one consecutive 24 month
period or two non-consecutive 12 month periods16

17. How Should Actual Emissions be Calculated
for Modeling Short-Term Increments?
• Short-term increments are available for SO2
(24-hr and 3-hr) and PM
• In the past we have recommended using the
maximum actual emission rate (i.e., the
highest occurrence for that averaging period
during the previous two years of operation) to
calculate short term increments
• We have recognized in practice that there is often
not sufficient data available to determine the
maximum short-term emissions rate over a 2-year
period
17

18. How Should Actual Emissions be Calculated for
Modeling Short-Term Increments? (Continued)
• We propose:
• Add a provision that allows permitting authorities to use
their discretion to use data that promotes consistency in
the analysis and does not bias the analysis in favor of
one group of sources over another
• That maximum short term-rates may continue to be used
where sufficient data are available, but need not be used
in all circumstances
• Not to preclude reviewing authorities from mixing data of
different types when they consider it appropriate
• To preserve the option of using allowable emissions at
the discretion of the source or reviewing authority
• To adopt revised language for purposes of increment
consumption assessment that requires the use of
projected actual emissions for a modified source
• To continue to require the increment assessment be
based on the potential to emit for a new source
18

19. What Are Appropriate Types of Meteorological Data
and Processing that Should be Used for Increment
Consumption Modeling?
• Dispersion model applications have utilized:
• meteorological data inputs derived from the direct
processing of National Weather Service (NWS)
observation data or
• meteorological data collected as part of a site-specific
measurement program
• Prognostic meteorological models and other tools are
available to project meteorological conditions in order
to fill gaps in site-specific observational data
• 40 CFR Part 51 Appendix W indicates criteria for
judging the adequacy and appropriateness of
meteorological input data
• Spatial, temporal representativeness of the data
• Meteorological parameters selected to properly
characterize the transport and diffusion conditions for a
specific dispersion model
Dispersion
models
estimate the
concentration
of pollutants at
specified
ground-level
receptors
surrounding an
emissions
source.
19

20. What Are Appropriate Types of Meteorological Data
and Processing that Should be Used for Increment
Consumption Modeling? (Continued)
• We propose:
• A determination of appropriateness would involve
a process equal in rigor to that already used to
review prognostic meteorological model output
data for use in photochemical grid modeling
applications at the regional scale
• We believe that our existing guidance for ozone,
PM2.5, and regional haze SIP1
modeling provides a
useful basis for the process by which the State may
allow use of certain data sets created by prognostic
meteorological models as input into dispersion model
applications provided these data sets, by using the
process, are appropriate
1
http://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf
Photochemical grid
models simulate the
impacts from all
sources by
estimating pollutant
concentrations and
deposition of both
inert and chemically
reactive pollutants
over large spatial
scales.
20

21. How many years of meteorological data are
appropriate for modeling increment consumption?
• When meteorological observation data is used for
dispersion modeling, Appendix W states that:
• Five years of representative NWS meteorological
observation data are required – the most recent, readily
available 5-year period is preferred
• At least 1 year of site-specific meteorological data is
required – as many as 5 years are preferred
• When prognostic meteorological data is used,
Appendix W states that:
• Less than 5, but at least 3 years of data are required –
the years need not be consecutive
• We propose:
• To allow the State to consider any data years that is has
determined to be appropriate using the process
described above even if those data years were not
produced by the same exact meteorological model
configuration and simulation
• That the State must further determine that a particular
set of data years can be modeled to produce an
appropriate depiction of the air quality issue at hand21

22. What are the requirements for modeling
documentation, data and software availability?
• Appendix W:
• Documentation and software availability for preferred
modeling techniques include that the “model and its code
cannot be proprietary.”
• Does not address the application of the non-proprietary
requirement to data developed for input into or use by a
preferred model, or to other software used to process
input data for a preferred model
• A strict requirement to be non-proprietary is currently
not applied to alternative models that may be selected
for use on a case-by-case basis, subject to the
approval of the appropriate reviewing authority
22

23. What are the requirements for modeling
documentation, data and software availability?
(Continued)
• What we propose in case of proprietary data:
• It is currently within the discretion of the State to require
some independent review of the proprietary data by an
oversight agency, if such a review is deemed critical to
the overall assessment of the appropriateness of data for
a particular modeling application
• It is also within the discretion of the State to conduct the
review, provided that proprietary information and trade
secrets are protected under a system that is equivalent
to EPA’s rules for requesting non-disclosure of
Confidential Business Information (CBI) submitted to the
Agency
• What we propose in case of proprietary software:
• Document:
• The reproducibility of the data or model simulation and the
applicant should facilitate such a demonstration when
required
• The quality assurance procedures used in the development
of the proprietary software to support the integrity and
accuracy of the results
23

24. Questions?
24