June 7, 1988
MEMORANDUM
SUBJECT Revised Model Clearinghouse Operational Plan
FROM: Joseph A. Tikvart, Chief
Source Receptor Analysis
TO:
Chief,	Air Branch, Region VII
Chief,	Technical Support Branch, Region	I
Chief,	Air and Radiation Branch, Region	V
Chief,	Air Programs Branch, Regions II,	III, IV, VI, VIII, IX, X
On February 9, 1988 I notified you of the expansion of the Model
Clearinghouse to include all criteria pollutants. That memorandum
explained briefly how the expanded Clearinghouse would operate and
identified individuals in the Technical Support Division and in the Air
Quality Management Division who would be involved in resolving Agency
regulatory modeling issues. The memorandum also promised that we would
be revising the 1981 Operational Plan for the Model Clearinghouse to reflect
the current operation. Attached is a copy of that revised plan.
To highlight major functions of the operational plan which you should
become most familiar with, please note the structure of the Clearinghouse
contained in Section 3, particularly Figure 1. Also you should become
familiar with the procedures for referring modeling issues to the
Clearinghouse, described in Section 4. Appendix B identifies the contacts
in the Regions for various types of modeling problems. Please check over
these lists for accuracy and keep us informed of any changes of these
personnel in your Region.
It should be remembered that the Model Clearinghouse is a service
we provide to the Regional Offices. We do not normally deal directly with
the State/local agencies or with industry since this would compromise our
function as second level reviewers and would interfere with your function.
However we have discussed access by States to Clearinghouse expertise
through the Regional Offices. Where a State wishes such a contact, we
urge your staff to work closely with their State counterparts to establish
a mutally agreed-upon position on the issue.
Finally, for purposes of responding to questions from States and local
agencies about the Clearinghouse and its operation, we have no problem if
you wish to furnish them with a copy of this plan. For questions from the
public we would prefer that you instead provide them with a copy of Appendix C,
a separate copy of which is attached. This Appendix is a revised version
of a flyer we have distributed for a number of years at the EPA booth at
the annual APCA meeting.

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EPA Model Clearinghouse
Summary
The Model Clearinghouse is the single EPA focal point for reviewing the use of
modeling techniques for criteria pollutants in specific regulatory applications.
The Clearinghouse also serves to compile and periodically report for Regional
Office benefit Agency decisions concerning deviations from the requirements of the
"Guideline on Air Quality Models (Revised)."
Need for the Model Clearinghouse
The Guideline states that when a recommended model or data base is not used,
the Regional Administrator may approve the use of other techniques that are demon-
strated to be more appropriate. However, there is also a need to provide for a
mechanism that promotes fairness and consistency in modeling decisions among the
various Regional Offices and the States. The Model Clearinghouse promotes this
fairness and uniformity and also serves as a focal point for technical review of
"nonguideline" techniques proposed for use/approval by a Regional Administrator.
deviations from strict interpre-
the guidance, e.g., Regional
bases. This is handled in two
Regional Office, will review the
of a nonguideline model for tech-
the Clearinghouse will screen
Functions of the Model Clearinghouse
The major function of the Clearinghouse is tcj review specific proposed actions
which involve interpretation of modeling guidance
tation of such guidance and the use of options in
Office acceptance of nonguideline models and data
ways: (1) the Clearinghouse, on request from the
Region's position on proposed (specific case) use
nical soundness and national consistency, and (2)
Federal Register regulatory packages for adherence! to modeling policy and make
recommendations for resolution of any issues identified.
A secondary function of the Model Clearinghoi
latory model users in EPA significant decisions irvolving the interpretation of
modeling guidance. This is accomplished through an annual "Clearinghouse Report"
which itemizes the significant decisions that have been made and the circumstances
involved. This report serves to improve consistency in future decisions and as
a source of technical information for the Regional Offices. In addition to the
annual report the Clearinghouse informs users on a contemporary basis of signi-
ficant decisions through copies of written decisions and briefings at various
meetings and workshops.
Structure of the Clearinghouse
The Clearinghouse is formally located in the Source Receptor Analysis Branch
(SRAB) of OAQPS. However, the Air Quality Management Division (AQMD) also parti-
cipates in Clearinghouse matters involving SIP attainment strategies and other
regulatory functions.
The primary responsibility for managing the Clearinghouse and ensuring that
all of its functions are carried out is performed by a person full-time within
SRAB. The responsibility for responding to requests for review of modeling
issues is assigned, on a pollutant/program basis to three SRAB individuals. In
addition, AQMD supports the Clearinghouse with staff who are also knowledgeable in
modeling policy. These individuals are responsible for screening SIP submittals
and related documents, referring modeling issues to SRAB through the Clearinghouse
and documenting the final (and any significant interim) decision on disposition of
the issues.
Communication Chain
The Model Clearinghouse functions within the organizational structure of EPA.
As such the Clearinghouse serves the EPA Regional Offices. It coordinates with
and communicates decisions to the Regional Offices. Any coordination with State
and local agencies and individual sources on Clearinghouse activities is a function
of the EPA Regional Offices.

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If you have any questions please call me at FTS 629-5562.
Attachments
cc: J. Calcagni
R. Campbell
U. Laxton
D. Wilson
Regional Modeling Contact, Regions I-X
Regional EKMA Contact, Regions I-X
/Regional CO Contact, Regions I-X
Regional Receptor Modeling Contact, Regions I-X

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MODEL CLEARINGHOUSE: OPERATIONAL fLAN
Revi sed
May 1988
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Technical Support Division
Source Receptor Analysis Branch
Research Triangle Park, North Carolina 27711

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Preface
Since 1981 the Office of Air Quality Planning and Standards (OAQPS)
and the Regional Offices have successfully coordinated EPA's regulatory
air modeling activities through the Model Clearinghouse. With the recent
reorganization of OAQPS, all air quality modeling activities are now
focused in the Source Receptor Analysis Branch (SRAB). This has allowed
SRAB to devote greater attention to a broad scope of modeling needs and
provided the basis for a logical expansion of the Clearinghouse to cover
all criteria pollutants. This report describes the expanded Clearinghouse,
its functions, organization and operating procedures.

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TABLE OF CONTENTS
Page
Preface		i
1.0 Introduction	*		1
1.1	Need for a Model Clearinghouse		1
1.2	Purposes of the Clearinghouse		4
1.3	Scope of This Plan		4
2.0 Functions of the Clearinghouse		6
2.1	Review of Proposed Regulatory Actions		6
2.2	Maintaining Awareness of Current Modeling
Guidance and Historical Precedents		7
2.3	Communication of Decisions		9
2.4	Identifying Needs for Additional Modeling
Guidance		10
3.0 Structure of the Clearinghouse		12
4.0 Clearinghouse Procedures		16
4.1	Advance Review of Proposed Modeling Techniques		16
4.2	Review of Regulatory Packages and Policy Issues		18
4.3	Documentation and Communication of Results		20
5.0 References				22-
Appendix A. History of the Model Clearinghouse		A1
Appendix B. Model Clearinghouse Personnel		B1
Appendix C. Summary of EPA Model Clearinghouse		CI
i i

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MODEL CLEARINGHOUSE: OPERATIONAL PLAN
1.0	Introduction
The Model Clearinghouse is the single EPA focal point for review of
air quality simulation models proposed for use in specific regulatory
applications. The Clearinghouse also serves to compile and periodically
publish Agency decisions concerning deviations from the requirements of
the "Guideline on Air Quality Models (Revised)."!
This plan describes the functions, structure and operating procedures
of the Model Clearinghouse. It is directed to those EPA staff involved
in the submittal and review of modeling techniques for either new source
review or SIP revisions. The goal is to ensure that modeling techniques
are technically sound and are consistent with current policy. The Clear-
inghouse promotes the use of the most appropriate models, the use of cor-
rect input to models and adherence to policy directives on how to use
models.
1.1	Need for a Model Clearinghouse
Section 165 of the Federal Clean Air Act^ states that with regard to
PSD analyses, "The Administrator...shal1 specify with reasonable particu-
larity each air quality model or models to be used under specified sets
of conditions for the purposes of this part. Any models or models desig-
nated under such regulations may be adjusted upon a determination after
notice and opportunity for public hearing, by the Administrator that such
adjustment is necessary to take into account unique terrain or meteorolog-
ical characteristics of an area potentially affected by emissions from a
source applying for a permit required under this part."

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In response to this requirement and other regulatory needs, the
Office of Air Quality Planning and Standards (OAQPS) issued the "Guideline
on Air Quality Models (Revised)*". The Guideline recommends air quality
modeling techniques that may be applied to air pollution control strategy
evaluations and new source reviews, including prevention of significant
deterioration. It is intended for use by EPA Regional Offices in judging
the adequacy of modeling analyses performed by EPA, by State and local
agencies, and by industry and its consultants. It also identifies modeling
techniques and data bases for model input that EPA considers acceptable.
The Guideline makes specific recommendations concerning air quality models,
data bases, and general requirements for concentration estimates.
However, the Guideline also recognizes that (1) there are situations
where the adjustment of the "preferred" air quality models is necessary to
take into account unique terrain or meteorological characteristics of an
area; (2) the developing state of modeling science may provide the oppor-
tunity for application of a new or revised model which is more appropriate
than the recommended model; (3) for some classes of modeling problems the
state of the modeling science does not provide a basis for identifying
appropriate refined models; and (4) data base availability in particular
situations may warrant deviations from the Guideline. To allow for these
situations the Guideline states that when a preferred model or data base
is not used, the Regional Administrator may approve the use of other
techniques that are demonstrated to be more appropriate. The Guideline
provides general criteria for determining the technical acceptability of
alternative techniques. To assist Regional Office staffs in making such
technical judgments, a mechanism is needed by which in-depth review of
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alternate models can be performed. Access to Agency personnel who have
specialized knowledge about specific types of modeling techniques is
highly desirable.
Section 301a of the Clean Air Act^ authorizes-the Administrator to
delegate authority for carrying out regulations and policies to the Re-
gional Offices. However, this Section also requires the Administrator to
"	promulgate regulations establishing general applicable procedures
and policies for regional officers and employees (including the Regional
Administrator) to follow in carrying out a delegation... Such regulations
shall be designed-
(A)	to assure fairness and uniformity in the criteria, procedures,
and policies applied by the various regions in implementing and enforcing
the Act;
(B)	to assure at least an adequate quality audit of each State's
performance and adherence to the requirements of this Act in implementing
and enforcing the Act, particularly in the review of new sources and in
enforcement of the act; and
(C)	to provide a mechanism for identifying and standardizing
inconsistent or varying criteria, procedures, and policies being employed
by such officers and employees in implementing and enforcing the Act."
Thus, although the Regional Administrator has the authority to
specify models that are appropriate for use in & given situation, there
is a need to provide for a mechanism that promotes fairness and consis-
tency in modeling decisions among the various Regional Offices and the
States.
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1.2	Purposes of the Clearinghouse
To fulfill the needs described in Section 1.1, a Model Clearinghouse
has been established in OAQPS. The primary purposes of the Model Clear-
inghouse are to provide:
1.	A mechanism whereby the proposed acceptance by a Regional Office
of a nonguideline model or alternative technique can be reviewed for national
consistency before final approval by the Regional Administrator. Such
reviews promote the use of equivalent acceptance criteria by all Regions.
2.	A mechanism whereby the in-depth technical evaluation and/or per-
formance evaluation of a proposed technique can be reviewed by those EPA
personnel who are most familiar with the types of techniques to be employed.
3.	A communication outlet for EPA's experience with the use of non-
guideline models, data bases or other deviations from current guidance.
The Clearinghouse maintains a high level of expertise on the applicability
of various models and classes of models and allowed deviations from accepted
procedures in specified circumstances. This information is communicated on
a periodic basis to EPA personnel involved in regulatory model applications.
1.3	Scope of This Plan
The remainder of this plan describes the Clearinghouse and how it
operates. Section 2 presents the functions of the Clearinghouse. Section
3 presents the structure of the Clearinghouse including personnel from both
the Technical Support Division and the Air Quality Management Division of
OAQPS who are involved. Section 4 provides the procedures to be followed
in submitting material to the Clearinghouse and how the review of material,
development of comments and the communication of relevant inportant infor-
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mation to all parties is accomplished. Appendix A provides background
information and a brief review of the Model Clearinghouse operations from
its creation in 1980 to 1988. Appendix B lists OAQPS and Regional Office
personnel assigned to Clearinghouse contact positions. Appendix C provides
a summary of the CI earinghouse in a format suitable for release to individuals
seeking information on this activity.
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2.0	Functions of the Clearinyhouse
The three main functions of the Model Clearinghouse are to: (1) review
proposed regulatory actions that contain modeling issues; (2) develop and
maintain a historical record of modeling decisions'; and, (3) communicate
decisions on regulatory modeling issues to all users. These functions are
more fully described in Sections 2.1-2.3. As a byproduct of its operation
the Clearinghouse is also in a position to identify needs for changes/clari-
fications of modeling guidance. This aspect of the Clearinghouse operation
is described in Section 2.4.
2.1	Review of Proposed Regulatory Actions
The major function of the Clearinghouse is to review specific
proposed actions which involve interpretation of modeling guidance, devi-
ations from strict interpretation of such guidance and the use of options
in the guidance, e.g., Regional Office acceptance of nonguideline models
and data bases. This is handled in two ways:
1.	The Clearinghouse, on request from the Regional Office, reviews
the Region's position on proposed (specific case) use of a nonguideline
model or other deviation from modeling guidance for technical soundness
and national consistency.
2.	The Clearinghouse screens regulatory actions, either in advance
(upon request) or when officially submitted, for adherence to modeling
policy and makes recommendations for resolution of any issues identified.
In the review of guide1ine models, the Clearinghouse first attempts
to conduct the review irithin its c*s«i resources. The basis for tt>e revie
is the available guidance aod historical record discussed in Section
-mortise 0f the Clearinghouse personnel, and thr
• - -"nnpsted "

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the Clearinghouse calls upon other EPA personnel with specific expertise
to assist in the review of all or parts of the proposed nonguideline
model as the need arises. In all cases the final outcome of the review
takes the form of a single recommendation, with supporting rationale, to
the Regional Office.
In the review of regulatory actions the Clearinghouse similarly
attempts to first resolve any inconsistencies before requesting outside
assistance. Again the basis for the review is the position submitted by
the Regional Office, the available guidance, the record for analogous
cases and the technical expertise of Clearinghouse personnel. In some
cases it may be necessary to contact the Regional Offices to obtain
additional information to resolve the issue.
2.2 Maintaining Awareness of Current Modeling Guidance and Historical
Precedents
In order for the Clearinghouse to properly judge consistency in the
interpretation of modeling guidance, it is necessary to maintain awareness
of current modeling guidance and to be cognizant of past decisions involv-
ing the interpretation of this guidance in specific cases. The location
of the Clearinghouse in OAQPS (See Section 3) allows for easy access and
awareness of current modeling guidance. The primary basis for modeling
policy considered by the Clearinghouse is the "Guideline on Air Quality
Models (Revised)". Other written material including workshop reports,
guidelines, Federal Register rules and regulations and reports/ records
of past Clearinghouse recommendations also constitute part of the modeling
guidance.
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One very important aspect of this function is the development and
maintenance of a historical record of regulatory decisions that involved
interpretation of modeling guidance. Although most regulations, e.g.,
SIPs, are relatable to a strict interpretation of the "Guideline on Air
Quality Models (Revised)" and related documents, there are still many
situations that involve a deviation from a strict reading for either
technical or broad policy reasons. For example, it might be expeditious
to approve the emission rate from a small source which would result in an
insignificant effect on air quality even though the recommended data
bases or perhaps the recommended model were not used in the analysis.
However, it is essential to document the circumstances involved with the
approval so as not to set a precedent for all sources of this size; the
environmental setting or other criteria may be different in future cases.
In order for the Clearinghouse to maintain technical and policy
consistency in its recommendations, it is necessary that a current file
of decisions involving interpretation of or deviation from modeling
guidance be maintained. As noted in Appendix A, for referrals involving
point sources of SO2, TSP(PMiu), and Pb, records of Clearinghouse recom-
mendations have been maintained since FY81. Also specific efforts were
made to identify Regional Office practices with respect to modeling these
pollutants through Clearinghouse staff visits to the Regional Offices.
Records of referrals involving mobile sources of CO also exist back to
FY81 but are more sparse since the Clearinghouse did not begin accepting
such referrals on a routine basis until FY86. Beginning in December 1987
the Clearinghouse began maintaining files for referrals involving O3 and

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Thus, while a long record of modeling practices exists for SO2 and
particulate matter, some effort may be necessary to establish the Regions'
historical practice/precedents for regulatory modeling for CO, NO2 and
ozone. Also it may be desirable to examine Regional practices with respect
to NSR/PSD issues where these issues are modeling related. To the extent
that such data acquisition is necessary, one or more of the following
mechanisms can be used.
1.	Significant historical decisions made by OAQPS: Examination of
Clearinghouse annual reports; reports and memoranda related to OAQPS
assistance on ozone modeling, including EKMA modeling meetings and personal
interviews with those personnel most often involved with interpretation of
modeling guidance.
2.	Significant Regional Office practices and precedents: Visits to
Regional Offices; participation in the annual Regional/State modelers work-
shop; telephone interviews.
3.	Other Headquarters elements that have been involved in past modeling
decisions, e.g. ORD, OMS, SCSD^ Telephone interviews.
In addition to gathering historical data the Clearinghouse documents
all modeling issues which come to its attention. This includes the cir-
cumstances involved and the Clearinghouse recommendations. This documentation
forms the basis for the periodic reporting described in Section 2.3.
2.3 Communication of Decisions
It is important that all model users be made aware of significant
decisions involving the interpretations of modeling guidance. To
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fulfill this function an annual report is issued to Clearinghouse users;
significant decisions that have been made and the circumstances involved
are itemized. The basis for this report is the case file records maintained
in the Clearinghouse. The report can be used to irtiprove consistency in
future decisions and as a source of technical information.
The Clearinghouse also informs users on a timely basis of signifi-
cant decisions that may affect their modeling procedures. Copies of
written decisions and briefings at the annual Regional/State Modelers
Workshop have worked well in the past in this regard and are expected to
conti nue.
2.4 Identifying Needs for Additional Modeling Guidance
By the very nature of its business, the Clearinghouse is in a unique
position to identify areas where gaps exist and clarification is needed in
EPA's modeling guidance and also in regulatory policy related to modeling.
The Clearinghouse is also a valuable resource for making recommendations
and developing guidance to cover such situations because it is familiar with
the circumstances involved. The Clearinghouse will continue to serve this
functi on.
A historical example of a gap identified by the Clearinghouse was
the need to provide additional guidance to the Regional Offices on how to
make technically sound and consistent decisions on the use of nonguideline
models. As a result, Clearinghouse personnel participated in developing
the "Interim Procedures for Evaluating Air Quality Models."3
There are also several examples from the past where the Clearinghouse
identified generic issues that were frequently referred to the Clearinghouse.
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When such issues became apparent, the Clearinghouse participated in the
development of guidance memoranda to cover the subject.
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3.0 Structure of the Clearinghouse
This section describes the location of the Model Clearinghouse within
EPA and the personnel involved, including support staff.
The Clearinghouse is formally located in the Source Receptor Analysis
Branch (SRAB), Technical Support Division (TSD), of OAQPS. As such, the
Clearinghouse exists within the normal chain of command of a Branch whose
primary function is to deal with regulatory and technical issues related
to air quality simulation modeling. This provides ready access to model-
ing policy and technical expertise on modeling. It also allows for effi-
cient hierarchy clearance concerning Clearinghouse determinations on sensi-
tive issues. The Air Quality Management Division (AQMD) also participates
in matters involving SIP attainment strategies, NSR/PSD referrals and issues
and other regulatory functions.
In order to ensure that modeling issues contained in SIP submittals
and related documents are reviewed for consistency in policy and for tech-
nical credibility, there are two main modes of access to the Clearinghouse.
Regional Office requests for review of nonguideline model applications
and other proposed deviations from modeling guidance are handled directly
by Clearinghouse personnel in SRAB. SIP submittals and related documents,
as well as requests from the Regions for assistance on NSR/PSD issues,
are screened by Clearinghouse personnel in AQMD for adherence to modeling
policy. Deviations from modeling policy are flagged for examination
by Clearinghouse personnel in SRAB.
The location of Clearinghouse personnel in SRAB and in AQMD is shown
in Figure 1. This organization is intended to take advantage of the cur-
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FIGURE 1 Location of Personnel in the Model Clearinghouse
NEW
SOURCE
REVIEW
SECTION
POLICY
DEVELOPMENT
SECTION
MODELING
CONTACT
FOR
SO2 /PW/PB/N02
NON-CRITERIA
POLLUTANT
PROGRAMS
BRANCH
REGULATORY
CONTACT
FQp
03 /CO/NO2
so2/pm
PROGRAMS
BRANCH
O3/CO
PROGRAMS
BRANCH
SOURCE
RECEPTOR
ANALYSIS
BRANCH
MOOEUNC
CONTACT
FOR
MOOEUNC
CONTACT
FOR
CO
OFFICE OF
AIR QUALITY
PLANNING AND
STANDARDS
AIR
QUALITY
MANAGEMENT
DIVISION
TECHNICAL
SUPPORT
DIVISION

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rent OAQPS organization and responsibilities. Each of the CIearinyhouse
contacts has, as part of his/her normal assignment outside of the Clear-
inghouse, responsibility for a specific modeling or regulatory program,
e.g. NSR/PSD, SO2, etc. Thus it is appropriate for these individuals to
also include the Clearinghouse function as part of their responsibilities.
Although these personnel comprise the formal operation of the
Clearinghouse and most of the work of the Clearinghouse can be done by
them, it may be necessary on occasion to draw upon modeling and policy
expertise throughout the Agency to assist in resolving difficult and
complex issues. Thus, modeling experts in SRAB, the Office of Research
and Development (ORD) and the Regional Offices may be called on from time
to time to review material that is related to their particular area of
expertise. However, the Clearinghouse is responsible for resolving and
condensing all comments received into a single recommendation on the
issue. Recommendations are concurred on by both TSD and AQMD.
The primary responsibility for managing the Clearinghouse and ensuring
that all of the functions described in Section 2 are carried out is per-
formed by a person full-time from SRAB (the Clearinghouse Coordinator).
This individual is responsible for ensuring that proper communications
are maintained on individual referrals, for maintaining files on the
referrals and for the periodic summary reports communicating the results
to al1 users.
Appendix B provides a list of the individuals assigned to the Clearing-
house contact positions identified in Figure 1 as well as the current
Clearinghouse Coordinator. Appendix B also identifies the Regional Office
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contact personnel most often involved in Clearinghouse communications. Peri-
odically (as needed) the Regional Offices will be notified of changes in the
personnel listed in Appendix B.
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4.0	Clearinghouse Procedures
This section describes the procedures that the Clearinghouse follows
to: (1) review modeling techniques proposed for specific applications,
(2) screen regulatory packages/issues for adherence to modeling policy,
and (3) document decisions and communicate results.
4.1	Advance Review of Proposed Modeling Techniques
Requests for review of modeling techniques should be sent by Regional
Offices di rectly to:
Model Clearinghouse
Source Receptor Analysis Branch (MD-14)
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711.
The Regional Office should develop a position on the application of the
technique and substantiate that position with its own thorough analysis
before submission to the Clearinghouse. Also, all pertinent information
relative to the technique and its application should be forwarded to the
CIeari nghouse.
Upon receipt of a request for review from a Regional Office, the Clear-
inghouse normally assigns the primary responsibility for conducting the
review and preparing the response to one of the three SRAB Clearinghouse
contacts shown in Figure 1, depending on the pollutant involved. If regulatory
issues are involved the primary reviewer coordinates these issues with the
appropriate Clearinghouse contact(s) in AQMD. The Clearinghouse Coordinator
is responsible for tracking the review to ensure a timely response. If
expertise outside of the Clearinghouse is needed to assist in review, the
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Clearinghouse Coordinator normally arranges for such assistance.
Copies of the response to the Region, along with the incoming request,
are provided to the appropriate Clearinghouse contacts in all of the Regional
Offices and to the Clearinghouse Coordinator. If the issue(s) involved are
of broad national significance, it may be necessary to obtain a consensus
of all the Regional Offices before finalizing a response. The "Guideline
on Air Quality Models (Revised)" provides the criteria for deciding when
it is appropriate to refer a modeling technique to the Clearinghouse for
review. This Guideline allows the Regional Administrator to approve the
use of models or techniques not specifically recommended in the Guideline
when he or she determines that the recommended approach is inappropriate,
that another approach would be better, or that the Guideline does not
recommend a specific technique. Thus, when the Regional Administrator
determines that the techniques specified in the Guideline are appropriate,
there is no purpose served by having the Clearinghouse review the proposed
approach. Only in those cases where there is a clear deviation from
modeling techniques recommended in the Guideline is it useful to obtain a
technical and a consistency review from the Clearinghouse.
While the formal requests for review of proposed modeling techniques
are necessary for complex and important problems, the predominant mechanism
for obtaining Clearinghouse opinions on current and upcoming issues con-
sists of direct telephone discussions to the Clearinghouse modeling con-
tacts in SRAB. As is the case with the written requests, the Regional
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Office should have thoroughly discussed the issues internally and have a
tentative position before contacting the Clearinghouse. In this way the
Clearinghouse maintains its defined function of providing a second-level
technical review and second-level opinion with regard to national consis-
tency; it is not merely an extension of the Regional Office staff. Clear-
inghouse coordination on telephone inquiries follows the scheme illustrated
in Figure 2.
For written requests the Clearinghouse makes every effort to
provide a written response to the Regional Office within four weeks of
receipt of the request. The primary exceptions to the four-week limit
are those cases where a consensus opinion of all the Regional Offices
is needed or where additional information from the Regional Office or
from other EPA Offices, e.g. OGC, ORD, etc., is required to resolve the
issue(s). For telephone calls the Clearinghouse normally responds
within two working days if the issues can be resolved within the
Clearinghouse, or five working days if Branch level review is required.
Again, issues that require coordination at higher levels of management
of OAQPS or review outside of OAQPS normally take longer.
4.2 Review of Regulatory Packages and Policy Issues
All Federal Register action packages (advanced opinion, proposal or
final) or NSR/PSD questions on specific applications submitted to OAQPS
are screened by Clearinghouse contacts in AQMD (See Figure 1) for consistency
with current modeling guidance. If significant deviations from guidance
are identified, these issues are then discussed within the Clearinghouse
via the coordination mechanism in Figure 2. (Where there are significant
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FIGURE 2 Coordination Procedure for Model Clearinghouse Referrals
CLEARINGHOUSE
COORDINATOR





REGULATORY

MODELING

CONTACT

CONTACT
I ¦ ¦ ¦ P '
REGIONAL
OFFICE
CONTACT

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deviations from guidance, the Regional Office should have presented a
position, with appropriate justification, in the Federal Register package
supporting either approval or disapproval.) In all cases final resolution
of the regulatory action rests with AQMD, with input from SRAB. The
Clearinghouse then, if at all possible, reaches a decision on the acceptability
of the approach being utilized in the regulatory action within the normal
review period for SIP processing. If particularly complex issues are
involved which require coordination with personnel outside the Clearinghouse,
an extension to the regular review period may be requested as provided
for in the "Guidance on Processing SIP Revisions (and 11Id plans)"^. All
significant decisions involving modeling in regulatory packages are
included in the Modeling Clearinghouse files and in the annual reports.
4.3 Documentation and Communication of Results
All communications on modeling issues brought to the attention of
the Clearinghouse are documented and kept on file by the Clearinghouse
Coordinator. Meetings and telephone conversations are summarized on a
"Record of Communication" form and filed according to the specific SIP
action or model proposal. Official memoranda, technical information a-nd
other pertinent material are included in the file.
The files are reviewed at least twice per year for information
that would be of benefit to all users. At the annual Regional/State
Modelers Workshop, held in the Spring of the year, the Clearinghouse
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presents an oral summary of significant Clearinghouse referrals that have
occurred since the beginning of the fiscal year. At the end of each
fiscal year, the Clearinghouse writes a summary report to users
covering all referrals that have occurred during the year. Similar to
the summary reports that were written for FY81 through FY87, these reports
will: (1) summarize in a statistical fashion the nature of the year's
referrals; (2) summarize in "text" form the several most significant
and involved referrals; (3) summarize generic issues that occurred or
reoccurred during the year; and (4) provide, in capsule form, a list of
all significant referrals to the Clearinghouse during the year.
In addition to the summary reports the Clearinghouse, as mentioned
earlier, sends copies of its written responses (along with incoming
requests) to all the Regional Offices. In this way the Regional Offices
are made aware, in a timely fashion, of decisions that may affect their
modeling activities. Also, as mentioned earlier, the Model Clearinghouse
seeks an advance opinion of the Regions on particularly sensitive issues
with national implications.
Finally, as needed, the Clearinghouse continues to provide other
communications/services that have been useful in the past. These include:
(1) periodic visits to Regional Offices to exchange information and maintain
the rapport of the Clearinghouse; (2) periodic reports and information
sheets on the Clearinghouse and its activities for the public; and
(3) identification of areas where modeling guidance is lacking or ambiguous
and make recommendations for correcting these problems.
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.5.0 References
1.	Environmental Protection Agency, "Guideline on Air Quality Models
(Revised)," EPA-450/2-78-U27R, Office of Air Quality Planning and
Standards, Environmental Protection Agency, Research Triangle
Park., N.C., July 1986.
2.	U.S. Congress. "Clean Air Act Amendments of 1977." Public Law
95-95, Government Printing Office, Washington, D.C., August 1977.
3.	EPA, "Interim Procedures for Evaluating Air Quality Models
(Revised)", EPA-45U/4-84-023, Office of Air Quality Planning and
Standards, Environmental Protection Agency, Research Triangle
Park, N.C., September 1984.
4.	EPA, "Guidance on Processing SIP Revisions (and 11Id plans),"
Office of Air Quality Planning and Standards, Environmental
Protection Agency, Research Triangle Park, N.C., September 1987.
22

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Appendix A
History of the Model Clearinghouse
This Appendix provides a brief review of the operations of the EPA
Model Clearinghouse from 1980-1988.
Original Organization and Operating Plan
The Model Clearinghouse was established on November 20, 1980.1 jhe
Regional Offices were notified of its general purposes, procedures and
limitations on that date. A detailed operational plan2 describing the
functions, structure, procedures and schedule for implementation was
issued on February 25, 1981.
The Clearinghouse formally operated in the Source Receptor Analysis
Branch (SRAB) of the OAQPS. Regional Office requests for review of non-
guideline models were sent directly to SRAB. However, prior to December
1987 the Control Programs Operations Branch (CPOB) also maintained respon-
sibility for review/approval of Federal Register packages submitted from
the Regions. These packages often contained modeling issues; as such,
these issues were considered by the Clearinghouse. For each Branch an
individual was assigned to the Model Clearinghouse. Close coordination
was maintained between the two Branches on all Regional Office modeling
issues that came to their attention.
Initially the operation of the Model Clearinghouse was limited to
the review of proposed deviations from modeling guidance for the regula-
tory modeling of iron/steel facilities, smelters and power plants. As
such the reviews were usually limited to SO2, TSP and Pb. On a gradual
basis the limitation to these facilities was relaxed to the point where
the Clearinghouse, by the mid 1980's, was accepting referrals for all point
sources of stable pollutants.

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Beginning in 1986 the Clearinghouse began accepting referrals for
mobile source problems involving CO. Individuals in SRAB and CPOB were
identified to facilitate the review of referrals for this class of
problems. Finally, at the end of 1987 the Clearinghouse expanded to
cover -03 and NO2.
Review of Proposed Regulatory Actions
The primary purpose of the Model Clearinghouse was to review the
proposed applications of air quality simulation models to specific regu-
latory situations. Such applications were "referred" to the Model Clear-
inghouse in one of two ways. In the first way a Regional Office may have
believed that it was appropriate to approve a regulatory action involving
a deviation from modeling guidance. However, before doing so the Regional
Office wanted to obtain a second opinion on whether the proposed modeling
technique was technically sound and consistent with similar applications
in other Regions. The issue was then referred to the Model Clearinghouse,
usually to SRAB, for this second opinion.
The other mode of operation of the Clearinghouse involved the review
of Federal Register packages being forwarded for concurrence prior to
publication. These packages were reviewed by the Clearinghouse contact
person in CPOB for adherence to modeling guidance. When deviations from
guidance were identified, they were discussed with the SRAB Clearinghouse
contact person and a determination of technical adequacy and consistency
were made. Oftentimes the Regions would forward drafts of Federal Register
packages to CPOB for a preliminary review; as such the identification/
review of modeling issues was similar to the "advanced opinion" referral
described above.
A2

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Development and Maintenance of Records
In order for the Clearinghouse to make reasoned decisions on
consistency, it was necessary to build and maintain a set of records on
past decisions involving deviations from modeling guidance. It was
determined that the best way to build an "initial" set of records was to
visit each of the Regional Offices and discuss with them deviations
from guidance that had occurred prior to formation of the Clearinghouse.
The stated purposes of these visits, conducted by both CPOB and SRAB
Clearinghouse personnel, were: (1) to gather information on the historical
usage of models by Regional Offices; (2) to identify current/upcoming modeling
problems which may come to the attention of the Clearinghouse; and 3) to
communicate information to the Regions on the current and future operation
of the Clearinghouse. A first set of visits which took place in 1981-82
accomplished these purposes. A second set of visits in 1986-87 updated
information on these purposes and also served to orient new personnel in
the Clearinghouse and in the Regional Offices to the Clearinghouse
ope rati on.
In order to document recommendations and decisions by the Model
Clearinghouse, records on each referral were created. Each record
contained telecons (for oral discussions) and/or memoranda containing
Clearinghouse recommendations and/or pertinent written background material
(technical reports, Federal Register notices, etc). A set of files of
these records were maintained in SRAB.
Communication of Information
Several activities took place to serve the purpose of communicating
the Clearinghouse experience with use of nonguideline models and other
deviations from modeling guidance. First, to serve the "newsletter"
A3

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function identified in the original operations plan, at the end of each
fiscal year a Clearinghouse Summary Report was prepared and distributed
to all users. This report served to inform the users about the issues
and responses in which the Clearinghouse was involved during the year.
In a more informal communication, significant issues/responses were
usually discussed at the Regional/State modelers Workshop held in the
Spring of each year.
While these activities served to inform users of pertinent issues on
a periodic basis, it was pointed out to the Clearinghouse in 1982, that
there was a need to more promptly inform Regional Offices of important
contemporary decisions. Thus in FY83 the Clearinghouse initiated a policy
of sending copies of its written responses, along with the incoming
requests, to all the Regional Offices. In this way the Regional Offices
were made aware, in a timely fashion, of decisions that may affect their
modeling activities.
While the above communications served to inform Agency users of the
activities of the Clearinghouse, there was no mechanism to inform the
general public. To serve this identified need, a five-year summary report,
primarily summarizing the number and general nature of Clearinghouse
referrals, was prepared in Hay 1986.3
Table 1 summarizes the number and nature of contacts from the Regional
Offices to the Clearinghouse from FY81 to FY87. Note from the table that
during the seven-year period there were a total of 103 modeling issues
referred to the Clearinghouse which required a written response and 394
issues which were resolved orally. In addition, CPOB directly reviewed
A4

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more than 724 regulatory action packages which contained modeling analyses
that followed guidance and required no further technical review by SRAB.
Although there is some variation from year to year, on average the Model
Clearinghouse handled 100 cases per year.
Table 1. Clearinghouse Responses by Year
FY81 FY82 FY83 FY84 FY85	FY86	FY87 Total
Written ResponsesU) 12 12 19 11 11	19	19 103
Telephone/Oral ResponsesU) 18 24 46 82 71	73	80 394
Federal Register Actions^?) 65 43 71 26 12	7	*(3) 224(3)
Total	95 79 136 119 94 99 99 721
(1)	Cases containing modeling issues requiring a technical review and
coordination between CPOB and SRAB.
(2)	Cases that followed current guidance; reviewed directly by CPOB.
(3)	Beginning in FY87 Federal Register reviews were included in Telephone/
Oral Responses.
A5

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References
1.	EPA, "Model Clearinghouse: Operational Plan," Office of Air Quality
Planning and Standards, Environmental Protection Agency, Research
Triangle Park, N.C., February 1981.
2.	EPA, "Model Clearinghouse," Memorandum to Regions I-X and to Division
of Stationary Enforcement, Office of Air Quality Planning and
Standards, Environmental Protection Agency, Research Triangle Park,
N.C., November 2U, 1980.
3.	EPA, "Activities of the EPA Model Clearinghouse, A Summary
Report: FY81-FY85," EPA-450/4-86-006, Office of Air Quality
Planning and Standards, Environmental Protection Agency, Research
Triangle Park, N.C., May 1986.
A6

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Appendix B
MODEL CLEARINGHOUSE PERSONNEL
5/1/88
OAQPS CONTACTS
Di vision
Branch
Name
FTS Number
TSD
SRAB
Dean Wilson
629-5683
TSD
SRAB
SRAB
SRAB
Dean Wilson
Keith Baugues
Tom Braverman
629-5683
629-5366
629-5383
AQMD
SDPMPB
OCPB
NCPB
Sharon Reinders
Ray Vogel
Dan deRoeck
629-5255
629-5284
629-5593
Responsibility
Clearinghouse Coordinator
SO2, PM, Pb, NO2 Modeling
O3 Modeling
CO Modeling
S02, PM, Pb SIPs
CO, O3, N02 SIPs
PSD/NSR for all criteria
pollutants
REGIONAL MODELING CONTACTS
Region
I
II
III
IV
V
VI
VII
VIII
IX
X
Regional Contact
Susan Kulstad
Ray Werner
A1 Cimorelli
Lew Nagler
Mike Koerber
Jim Yarbrough
Richard Daye
John Notar
John Vimont
Rob Uilson
FTS Telephone No.
835-3226
264-2517
597-6563
257-2864
886-6061
255-7214
757-2896
564-1755
454-7640
399-1531
B1

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CO CONTACTS
Region	Regional Contact	FTS Telephone No.
I
Tom Wholley
835-3233
II
Steve Sambol
264-2517
III
Alan Cimorelli
597-6563
IV
Tom Hansen
257-2864
V
Ed Doty
886-6057
VI
Jim Yarbrough
255-7214
VII
Larry Hacker
757-2893
VIII
John Notar
564-1755
IX
John Vimont
454-8223
X
Rob Wilson
399-1531
EKMA CONTACTS
Region	Regional Contact	FTS Telephone No.
I	Richard Burkhart	835-3223
II	Rudy Kapichak	264-2517
III	Larry Budney	597-0545
IV	Tom Lyttle	257-2864
V	Ed Doty	886-6057
VI	Jim Yarbrough	255-7214
VII	Larry Hacker	757-2893
VIII	John Notar	564-1755
IX	John Vimont	454-7640
X	Rob Wilson/Dave Bray	399-1531
RECEPTOR MODEL CONTACTS
Region	Regional Contact	FTS Telephone No.
I
Susan Kulstad
835-3226
11
Rudy Kapichak
264-1446
III
Denis Lohman
597-8375
IV
Lew Nagler
257-2864
V
Mike Koerber
886-6061
VI
Jim Yarbrough
225-7214
VII
Richard Daye
757-2893
VIII
John Notar
564-1755
IX
Alison Bird
454-7659
X
Dave Bray
399-4253
B2

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APPENDIX C
EPA Model Clearinghouse
Summary
The Model Clearinghouse is the single EPA focal point for reviewing the use of *
modeling techniques for criteria pollutants in specific regulatory applications.
The Clearinghouse also serves to compile and periodically report for Regional
Office benefit Agency decisions concerning deviations from the requirements of the
"Guideline on Air Quality Models (Revised)."
Need for the Model Clearinghouse
The Guideline states that when a recommended model or data base is not used,
the Regional Administrator may approve the use of other techniques that are demon-
strated to be more appropriate. However, there is also a need to provide for a
mechanism that promotes fairness and consistency in modeling decisions among the
various Regional Offices and the States. The Model Clearinghouse promotes this
fairness and uniformity and also serves as a focal point for technical review of
"nonguideline" techniques proposed for use/approval by a Regional Administrator.
Functions of the Model Clearinghouse
The major function of the Clearinghouse is to review specific proposed actions
which involve interpretation of modeling guidance, deviations from strict interpre-
tation of such guidance and the use of options in the guidance, e.g., Regional
Office acceptance of nonguideline models and data bases. This is handled in two
ways: (1) the Clearinghouse, on request from the Regional Office, will review the
Region's position on proposed (specific case) use of a nonguideline model for tech-
nical soundness and national consistency, and (2) the Clearinghouse will screen
Federal Register regulatory packages for adherence to modeling policy and make
recommendations for resolution of any issues identified.
A secondary function of the Model Clearinghouse is to communicate to regu-
latory model users in EPA significant decisions involving the interpretation of
modeling guidance. This is accomplished through an annual "Clearinghouse Report"
which itemizes the significant decisions that have been made and the circumstances
involved. This report serves to improve consistency in future decisions and as
a source of technical information for the Regional Offices. In addition to the
annual report the Clearinghouse informs users on a contemporary basis of signi-
ficant decisions through copies of written decisions and briefings at various
meetings and workshops.
Structure of the Clearinghouse
The Clearinghouse is formally located in the Source Receptor Analysis Branch
(SRAB) of OAQPS. However, the Air Quality Management Division (AQMD) also parti-
cipates in Clearinghouse matters involving SIP attainment strategies and other
regulatory functions.
The primary responsibility for managing the Clearinghouse and ensuring that
all of its functions are carried out is performed by a person full-time within
SRAB. The responsibility for responding to requests for review of modeling
issues is assigned, on a pollutant/program basis to three SRAB individuals. In
addition, AQMD supports the Clearinghouse with staff who are also knowledgeable in
modeling policy. These individuals are responsible for screening SIP submittals
and related documents, referring modeling issues to SRAB through the Clearinghouse
and documenting the final (and any significant interim) decision on disposition of
the issues.
Communication Chain
The Model Clearinghouse functions within the organizational structure of EPA.
As such the Clearinghouse serves the EPA Regional Offices. It coordinates with
and communicates decisions to the Regional Offices. Any coordination with State
and local agencies and individual sources on Clearinghouse activities is a function
of the EPA Regional Offices.
CI

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