MODEL CLEARINGHOUSE: FY-92 SUMMARY REPORT OCTOBER 1992 Source Receptor Analysis Branch Technical Support Division Office of Air Quality Planning and Standards U.S. Environmental Protection Agency Research Triangle Park, North Carolina 27711 TABLE OF CONTENTS MODEL CLEARINGHOUSE: FY-92 SUMMARY REPORT PAGE 1.0 INTRODUCTION 2.0 FY-92 CLEARINGHOUSE ACTIVITIES . . . . . . . . . . . . 2 2.1 Background and Responsibilities . . . . . . . . . 2 2.2 Summary of Regional Office Requests and Clearinghouse Responses . . . . . . . . . . . . . 4 2.3 Recurring Coordination . . . . . . . . . . . . 10 2.4 Support Center for Regulatory Air Models Bulletin Board System (SCRAM BBS) . . . . . . . . . . . 11 3.0 CLEARINGHOUSE RESPONSES TO RECURRING OR GENERIC ISSUES . . . . . . . . . . . . . . . . . . . . . . . 13 3.1 Review of PM-10 State Implementation Plan . . . 13 3.2 Use of ISC2 Direction-Specific Building Dimensions . . . . . . . . . . . . . . . . . . 14 3.3 Use of an Alternative Screening Technique . . . 16 3.4 Resolution of Attainment Demonstration Procedures for a Large Primary Lead (Pb) Smelter . . . . . 18 Appendix A FY-92 MODEL CLEARINGHOUSE MEMORANDA . . . . . A-1 Appendix B REVIEW OF PM-10 STATE IMPLEMENTATION PLAN ATTAINMENT DEMONSTRATIONS . . . . . . . . . . B-1 Appendix C MODEL CLEARINGHOUSE CONTACTS . . . . . . . . C-1 Appendix D SUMMARY OF THE EPA MODEL CLEARINGHOUSE . . . D-1 1.0 INTRODUCTION This report summarizes major activities of the Model Clearinghouse from August 26, 1991 to August 21, 1992. The report is divided into two parts. First, the FY-92 activities of the Clearinghouse are summarized. The second section summarizes Clearinghouse responses to major categorical modeling problems occurring during FY-92; within each of these there were several issues/questions of a similar nature. Appendix A provides a list of Model Clearinghouse memoranda covering the period October 1, 1991 to September 30, 1992. Appendix B is a memorandum that documents procedures that will be used by the Model Clearinghouse in reviewing PM-10 attainment demonstrations. Appendix C con- tains a list of EPA Model Clearinghouse contact personnel. Appendix D provides a brief summary of the EPA Model Clearing- house responsibility, structure and operational procedures. 2.0 FY-92 CLEARINGHOUSE ACTIVITIES 2.1 Background and Responsibilities The Model Clearinghouse was established on November 20, 1980. The Regional Offices were notified of its general purposes, procedures and limitations on that date. A detailed operational plan describing the functions, structure, procedures, and schedule for implementation was issued on February 25, 1981. Initially the operation of the Model Clearinghouse was limited to the review of proposed deviations from modeling guidance for the regulatory modeling of iron/steel facilities, smelters, and power plants. As such, the reviews were usually limited to sulfur dioxide (SO2), total suspended particulates (TSP), and lead (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. Beginning in 1986, the Clearinghouse began accepting referrals for mobile source problems involving carbon monoxide (CO). During FY-88, the Model Clearinghouse was expanded to cover ozone (O3) and nitrogen dioxide (NO2). A revised Model Clearinghouse operational plan* was issued to reflect that the Model Clearinghouse purview includes all criteria pollutants. During FY-92, the Clearinghouse operation was further expanded to include noncriteria (toxic) pollutants. _______________________ *Model Clearinghouse: Operational Plan, Revised, Source Receptor Analysis Branch, Office of Air Quality Planning and Standards, May 1988 The Model Clearinghouse Operational Plan states that the primary purposes of the Model Clearinghouse are to provide: 1. A mechanism whereby the proposed acceptance by a Regional Office of a nonguideline model or alternative tech- nique 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 performance 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 nonguideline models, data bases or other devia- tions 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. The Clearinghouse is formally located in the Source Receptor Analysis Branch (SRAB) of the Office of Air Quality Planning and Standards (OAQPS). However, the Air Quality Management Division (AQMD) also participates in Clearinghouse matters involving State Implementation Plan (SIP) attainment strategies and other regulatory functions. The primary responsibility for managing the Clearing- house and ensuring that all of its functions are carried out is performed by a person full-time within SRAB. A Clearinghouse support person in SRAB maintains the Clearinghouse's electronic communications interface through the computerized data base and bulletin board systems described below. The responsibility for responding to requests for review of modeling issues is assigned, on a pollutant/program basis to four SRAB individuals. In addi- tion, 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. A current list of OAQPS and Regional Office Model Clearinghouse contacts is provided in Appendix B. The FY-92 activities for the Model Clearinghouse included: 1. Responding to Regional Office requests for review of nonguideline models proposed for use. 2. Reviewing draft and formally submitted Federal Register actions. 3. Documenting Clearinghouse decisions and discus- sions. 4. Summarizing Clearinghouse activities at various meetings. 5. Issuing, internally, a summary report for activi- ties of FY-91. 6. Inputting FY-92 Clearinghouse records into a computerized data base. 7. Providing for Regional Office direct access to the computerized data base by modem. 8. Disseminating Clearinghouse memoranda and reports to the public through a bulletin board system. 2.2 Summary of Regional Office Requests and Clearinghouse Responses The number and type of contacts from the Regional Offices to the Clearinghouse during FY-92 are summarized in Table 1. The data in the table under "Recommendations" include those issues where a coordinated clarification of policy was involved or an investigation had to be undertaken by the Clearinghouse. In addition, there were numerous other inquiries to the Clearing- house regarding procedures, technical considerations, and poli- cies which were readily resolved or referred elsewhere. Note from the table that there were a total of 14 regulatory modeling problems referred to the Clearinghouse which required a written response and another 118 referrals in which the issues were resolved orally. In addition, there were another 11 referrals where discussions took place but a Clearinghouse recommendation was not requested. Note also that requests for assistance, either written or by telephone, came from all of the Regional Offices. This suggests that there is an awareness and a desire for Clearinghouse support throughout the Agency. Table 2 contains a summary, by category, of the nature of the referrals and requests for assistance. The table is useful for identifying commonly recurring problems and problem areas. Table 3 tabulates the regulatory/modeling subject area involved in resolution of issues for each referral. More than one subject area was involved in the resolution of issues for most referrals. Also, it should be noted that in Table 3 refer- rals for Interpretation of Modeling Guidance and Interpretation of Regulatory Guidance usually involved broad issues where the applicability of the guidance in general was either called into question or that the issue involved a subject not included in the remainder of the subject area list. TABLE 1. TYPES OF CLEARINGHOUSE RESPONSES DURING FY-92 RECOMMENDATIONS REGION WRITTEN ORAL DISCUSSION/INFORMATION* TOTAL I 4 6 1 11 II 0 9 1 10 III 1 8 3 12 IV 1 10 0 11 V 1 20 0 20 VI 3 12 1 16 VII 0 6 1 7 VIII 2 30 2 34 IX 1 13 0 14 X 1 5 2 8 14 118 11 143 *Did not include a specific Clearinghouse recommendation. TABLE 2. CHARACTERIZATION OF 143 CLEARINGHOUSE REFERRALS DURING FY-92. ONLY REFERRALS CONTAINING SIGNIFICANT MODELING ISSUES ARE INCLUDED. SOME REFERRALS INVOLVED MORE THAN ONE POLLUTANT, SOURCE TYPE, OR REGULATION. Pollutants Involved Number of Referrals SO2 69 TSP 7 CO 13 Pb 10 NOx 9 O3 2 NaC1 1 PM-10 27 White Phosphorus 1 Unspecified 7 Unspecified Non-criteria 6 Generic 4 Source Types Power Plant 12 Power Boiler 2 Smelter 22 Steel Facility 3 Paper Mill 4 Aluminum Plant 3 Refinery 8 Cogeneration Unit 11 Incineration 6 Mine 4 Chemical Plant 1 Roadway 12 Open Burning 1 Lead Processing Plant 1 Gas Compressor 2 Cement Plant 1 Generator (Gas or Oil) 1 Open Dust Fugitive 1 Coating/Painting Operation 1 Rocket 1 Detonation 1 Unspecified Stationary Source 12 Mixed/Multiple Sources 27 Generic to Any Stationary Source 6 Generic to Any Source 2 Urban or Rural Model Involved Urban Only 36 Rural Only 96 Number of Referrals Both Urban and Rural 2 Not Relevant 9 Types of Response Written 14 Oral 118 Not Relevant 11 Applicable Regulations SIP 49 SIP Revision 22 SIP Revision - GEP 9 PSD 37 EIS 4 NSR 2 Redesignation 7 State Regulation 5 Study 1 RCRA 3 Generic 2 Generic - SIP 1 Generic - GEP 3 Not Relevant 2 Terrain Setting High Terrain (above stack height) 5 Low Terrain (below stack height) 48 Both High and Low Terrain 51 Essentially Flat Terrain 19 Not Relevant 20 Guideline or Nonguideline Model Involved Guideline 73 Non-guideline 33 Guideline and Non-guideline 27 Not Relevant 10 Data Bases Used for Model Input On-site 44 Off-site 58 Both Off-site and On-site 13 Not relevant 28 TABLE 3. SUBJECT AREAS INVOLVED IN FY-92 CLEARINGHOUSE REFERRALS Subject Area Number of Occurrences1 Ambient Air 6 Ambient Monitoring 9 Area Wide Analysis 13 Averaging Time for Emission Limits 3 Calibration 1 Calm Winds 4 Clearinghouse Operating Procedures 2 Deposition 1 Downwash 17 Emissions Characterization 11 Emission Rates for Model Input 17 Equivalency 4 Fluid Modeling 8 Grandfathering of Guidance 3 Interpretation of Guideline Language 1 Interpretation of Modeling Guidance 21 Interpretation of Regulatory Guidance 17 Length of Record - Meteorological Data 4 Long-Range Transport 7 Meteorological Monitoring 14 Mixed Terrain Modeling 15 Model Development Projects 2 Modeled Background 17 Monitored Background 4 Monitoring in Lieu of Modeling 7 Open Dust Fugitives 2 Performance Evaluations 23 Plume Rise 2 PSD Increment Calculation 13 Reactive Pollutant Modeling/Chemical Transformations 5 Receptor Modeling 14 Receptor Networks 9 Representativeness of Meteorological Data 14 Screening Procedures 3 Shoreline/Offshore Modeling 2 Significant Air Quality Impacts 7 Stability Classes 3 State Modeling Guidelines 2 Technical Credibility of Nonguideline Techniques 18 Terrain Correction Factors 2 Time Scaling 3 Urban/Rural 2 Worst Case Meteorology 1 Stagnation 6 Visibility 3 ____________________ 1 More than one subject was involved in the resolution of most referrals. 2.3 Recurring Coordination During FY-92 the Clearinghouse conducted or participated in a number of activities that can be categorized as coordination and information exchanges with the Regional Offices. One of the first activities was to prepare and distribute to the Regional Offices in October 1991, a Clearinghouse report; this report served to inform Clearinghouse users about the issues and responses which occurred in FY-91. The report included summaries of generic issues which occurred during the fiscal year. During FY-92 the Clearinghouse continued its policy of sending 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, in order for the Regions to be assured that their records are complete, the Clear- inghouse attaches to each response, an updated list of all Clearinghouse memoranda issued during the fiscal year. The list is provided as Appendix A. During FY-92, the Clearinghouse continued inputting records of Regional Office referrals to the Model Clearinghouse Information Storage and Retrieval System (MCHISRS). During FY-92 the Clearinghouse added approximately 143 entries to the approximately 925 FY-81 to FY-91 referrals into MCHISRS. The Regional Offices can access by modem the MCHISRS in a search and retrieve mode for any national precedents that might affect their position on a current specific modeling issue. The Model Clearinghouse has a policy whereby an advance opinion of the Regions is sought on particularly sensi- tive issues with national implications. During FY-92 one such case arose involving the use of Huber-Snyder directional downwash in the Industrial Source Complex model (ISC2). In this case an advance draft response agreeing with the Region VI position on the issue was circulated to all the Regional Offices for comment. After a series of discussions with Regional Offices having con- cerns, the response was revised and finalized. This issue is summarized in Section 3.2 of this report. Also, the August 21, 1992 response is contained in the "Current Year" memoranda on the Support Center for Regulatory Air Models Bulletin Board System (SCRAM BBS). 2.4 Support Center for Regulatory Air Models Bulletin Board System (SCRAM BBS) During FY-91 EPA began disseminating Agency memoranda and reports generated by the Clearinghouse to the public through the SCRAM BBS. Three types of information are included: 1) selectedhistorical memoranda on generic/recurring issues that have been generated by the Clearinghouse in the FY-81 through FY-92 timeframe; 2) the most recent, i.e. FY-89 through FY-92 Clearinghouse memoranda; and 3) the FY-89 through FY-91 Model Clearinghouse annual reports. Information on the SCRAM BBS is not intended to be a complete set of information relative to any subject. Rather, it serves as a means to communicate to regulatory model users significant decisions involving the interpretation of current modeling guidance and experience with the use of nonguideline models, data bases and other deviations from the current guidance. The SCRAM BBS cautions users to consult the Guideline on Air Quality Models and contact the appropriate State or Regional Office before using the information for indivi- dual/regulatory applications. As new Clearinghouse information becomes available it is placed on the bulletin board in one of the three categories mentioned above. However, in regard to the current year Model Clearinghouse memoranda, a one to two month delay occurs before the information is placed on the bulletin board. 3.0 CLEARINGHOUSE RESPONSES TO RECURRING OR GENERIC ISSUES During FY-92 the Clearinghouse responded to a number of queries/referrals which had common themes or common consistency/technical issues. The more significant issues, and their resolution, are described below. 3.1 Review of PM-10 State Implementation Plans (SIP's) During FY-92, the Model Clearinghouse began reviewing PM-10 SIP's forwarded from the Regional Offices for Headquarters concurrence on the approval or disapproval recommendation. The Model Clearinghouse role was the review of the attainment demonstrations. Because of the potential for confusion regarding applicable guidance for PM-10 attainment demonstrations as well as the level of documentation needed in the Federal Register package, the Model Clearinghouse wrote an internal memorandum documenting the guidance and documentation requirements. A copy of that June 10, 1992 memorandum is provided as Appendix B to this Clearinghouse report. Note from the attachment to the memorandum that there are indeed many pieces of guidance that may need to be considered in regard to the demonstration. Of partic- ular note is that the Regional Offices need to identify whether the SIP qualifies for a "modified" demonstration because it meets procedural and regulatory timeframe criteria outlined in a March 4, 1991 memorandum from OAQPS to the EPA Regional Offices (see Item 8 of the attachment to the June 10, 1992 memorandum). Many of the first round of SIP submittals are expected to meet that requirement. During FY-92 several PM-10 SIP's or draft SIP's were reviewed, using the criteria in the June 10 memorandum, as a guide. As expected, the quality of the SIP's and the Regional documentation in their Technical Support Documents were a "mixed bag." Several of the SIP's clearly followed the applicable guidance or only had minor documentation deficiencies. For a few, the documentation was too scanty to be able to tell whether the demonstration was supportable, or there appeared to be some problems with the demonstration. Communications with the Air Quality Management Division and the Regional Offices are ongoing for these SIP's. The bulk of the SIP demonstrations are expected to be received during FY-93. Also, work will likely begin on any necessary Federal Implementation Plans during FY-93. 3.2 Use of ISC2 Direction-Specific Building Dimensions On March 1, 1992, the testing and evaluation of the ISC2 model was completed and ISC2 became the preferred version for use in regulatory assessment modeling analyses. This new version of the ISC provides the capability of computing the hour-by-hour characterization of dispersion using direction-spe- cific building dimensions for all building downwash situations. Prior to thisrelease of ISC, use of hour-by-hour direction-speci- fic building dimensions was limited to only situations with relatively low-level releases. With the advent of the new version of the model, the question has arisen whether receptor-specific building dimensions should be used in all cases, or should the use of receptor-speci- fic dimensions continue to be limited as before? This issue was resolved in August 1992 in response to a request from Region VI. The Region recommended that the direction specific downwash be used for all downwash situations for modeling of an aluminum plant in Texas. The Clearinghouse agreed that the Region's recommendation is correct. The following rationale was used in arriving at that conclusion. In the December 1979 and December 1987 versions of the ISC User's Guide, the Huber-Snyder downwash characterization was implemented using a single effective building width þ for all wind directions. The simplification of using only one building width for all wind directions was described in the user's guide as a necessary constraint imposed on the program in order to not sacrifice other desired ISC model features. The user's guide outlined a recommended procedure for refining the design concentration estimate if it was believed the estimate was a consequence of building downwash and the Huber-Snyder characterization was operative. It was recommended in these cases that the ISC model calculations be repeated for receptors near the source with the highest calculated concentration (or deposition) values using receptor-specific values of the building dimensions. When the ISC model was revised to include the Schulman-Scire characterization, it provided for the use of direction-specific building dimensions and procedures were given on the manner in which the building dimensions were to be speci- fied. No alterations were made at that time to the Huber-Snyder characterization, thus necessitating the continued practice of using a single effective building width for all wind directions. However, the recommended procedure for refining the design concentration estimates for receptors near the source with the highest calculated concentration (or deposition) values using direction-specific values of the building dimensions was continued. Thus it is evident that at no time in history has there been any intention to preclude the use of direction-speci- fic building dimensions with the Huber-Snyder characterization of building effects on dispersion on the grounds that it was technically insupportable. To the contrary, the early versions of the ISC user's guide specifically mentioned that the Huber-Snyder characterization was implemented in a simplified form because of computer memory limitations. By extending ISC2 to provide for the use of hour-by-hour receptor-specific building dimensions for both the Huber-Snyder and the Schulman-Scire characterizations of building downwash, ISC2 obviates the use of the work-around solution previously in place for refining impacts resulting when Huber-Snyder downwash calculations were operative. 3.3 Use of an Alternative Screening Technique The Guideline on Air Quality Models (Revised) refer- ences a number of screening techniques that may be applied to show the source(s), at its proposed emissions limit(s), would not pose a threat to the National Ambient Air Quality Standards (NAAQS) or the Prevention of Significant Deterioration (PSD) Increments. These techniques are known to produce conservative estimates of ambient concentrations because they contain a number of "worst case" inputs, primarily meteorological inputs. The Guideline goes on to say that if the estimates from the screening technique exceed the applicable ambient criteria, e.g., the NAAQS or PSD Increments, then a refined technique should be selected and the situation remodeled. The refined technique is designed to produce an unbiased estimate of the expected potential design concentration. The refined technique may be the preferred tech- nique for that situation identified in the Guideline or may be chosen from other nonguideline techniques and substantiated using the criteria contained in Section 3.2.2 of the Guideline. The Guideline contains no provisions for selecting alternative screening techniques for situations where estimates using the technique referenced in the Guideline are unacceptably high, or for some other reason. However, over the course of years there have been a number of such proposals that have come to the Model Clearinghouse for resolution. Past recommendations from the Clearinghouse on these techniques have been quite consistent, that is, if the alternative screening technique does not yield estimates that are at least as conservative as the technique referenced in the Guideline, then it should not be used. In FY-92 there was another such case. Although this case contained somewhat convincing reasons, the Clearinghouse recom- mendation was still the same. Since it had not been shown that the technique produced more conservative results than the tech- nique referenced in the Guideline, it should not be applied. Briefly, the situation in the FY-92 case is as fol- lows. The source of nitrogen oxides made estimates with Tier 1 and Tier 2 of the 3-tiered screening approach recommended in the Guideline. Concentrations of nitrogen dioxide (NO2) above the NAAQS were found. Apparently the source was unable to use the third level screen application of the ozone limiting method on an hourly basis, due to a lack of representative ambient NO2 and ozone data in the area. Instead they proposed to apply an expo- nential decay mechanism to describe the conversion of nitrogen oxide (NO)to NO2, with a five minute half life for the NO. The Clearinghouse noted that the proposed technique is arguably conservative in most cases. However, the proposed technique is clearly not a refined model but another screening technique. It is not as conservative as the Tier 1 and Tier 2 Guideline screen- ing techniques, and has not been shown to be conservative for the given application. Thus the Clearinghouse recommended against acceptance of the technique at this time but suggested that the collection of additional ambient data in the area of application might allow a demonstration that the technique is conservative for that case. More detail is provided by the Clearinghouse response contained on the SCRAM BBS. 3.4 Resolution of Attainment Demonstration Procedures for a Large Primary Lead (Pb) Smelter The negotiation of an acceptable modeling protocol, the resolution of data bases issues associated with the modeling and the subsequent application of the models for the ASARCO Pb Smelter in East Helena, Montana is a process that has taken several years. During FY-92 most of the remaining issues were resolved in this complex modeling application. There were a number of important principles and precedents established in this successful process and it is useful to briefly summarize the most significant of these determinations. In the summary that follows no attempt has been made to document all events or accurately reflect dates; the purpose is to focus on the major technical issues, in their approximately chronological order of occurrence. In circa 1981, a Pb SIP was developed for the Smelter. This SIP was based on receptor modeling; for whatever reasons, dispersion modeling was determined at that point in time not to be appropriate. After the Smelter achieved the emissions limita- tions provided for in that SIP it was found that there were still monitored violations of the ambient Pb levels in the vicinity of the Smelter. Because of these observed violations, in 1988 EPA officially notified the State of Montana that their SIP was deficient and needed to be revised. It was at this point in time that the Model Clearinghouse began to get significantly involved in the process of resolution of modeling issues. The following capsular summary of issues and their resolution are in approximate chronological order, beginning in late 1988 and carrying up to the end of FY-92. Issue Resolution 1. Base the new SIP on receptor The SIP will be based on modeling again. dispersion modeling recon- ciled with receptor modeling unless reconciliation fails. 2. Use ISCLT and Valley with off- On-site data adequate to run site meteorological data or some old ISCST and RTDM to be on-site data of marginal quality and collected. representativeness. 3. Collection of on-site data from To mitigate the influence of booms erected on an existing non- the stack, a short tower was operating stack. erected on top of the stack, and double booms, 180 degrees apart, were installed at the lower levels. 4. Use of a minimum mixing depth in Look at low mixing depths on ISCST modeling. a case-by-case basis when they are germane to determining the design concentration. 5. Use of non-recommended options Use regulatory default in ISCST. options. 6. Adjustments of both Only adjust the emissions meteorological and emissions inputs inputs. to ISCST as part of the reconciliation process. 7. Period of ambient data 6 months of data are collection to be used in the acceptable in this case reconciliation. 8. Performance testing of the 6 months of independent reconciled ISCST model before data should be set aside application. for model testing. 9. Use of a modified ISCST. Can be done but that Agency guidance on performance evaluations need to be followed and the SIP sched- ule needs to be maintained. 10. What to do if reconciliation is Guidance is to use the not successful? dispersion model. Agreed that all parties would meet to discuss reasonable options in the event that they do not reconcile. (The issue was moot since recon- ciliation was successful.) 11. Use of ISCST in intermediate Agreed that the ISCST was terrain. demonstrated to always be conservative in this case; thus its use is acceptable in lieu of following the Agency's intermediate terrain policy. 12. Acceptability of the receptor All studies were carried out modeling and reconciliation. according to Agency guidance and the agreed-upon proto- col. Reconciliation was successful. 13. Verification on the independent Agreed that the independent data set. data adequately demonstrated that the reconciled disper- sion model was working acceptably. 14. Determination of design value Design value was done with reconciled dispersion model. correctly. All receptors outside of fenced Company property are to be considered. In summary, the development of successful modeling study for the ASARCO Pb smelter, while complicated and time consuming, has demonstrated that reconciliation between receptor modeling and dispersion modeling can be made successful. Lessons learned and precedents set by this application may be useful for other similar studies. It is also clear that the details of the reconciliation process is indeed complicated and, while the resolution of the issues summarize above provide some guidance, the details for other applications need to be worked out on a case-by-case basis. APPENDIX A FY-92 MODEL CLEARINGHOUSE MEMORANDA FY-92 MODEL CLEARINGHOUSE MEMORANDA Date Region Subject 10/16/91 IV Dade County, Florida, Stack Height Increase 11/7/91 VI Phelps Dodge--Hidalgo Modeling Protocol 11/15/91 VIII ASARCO E. Helena Lead State Implementation Plan (SIP) 12/04/91 I Proposal to Use a Non-Guide- line Model to Satisfy Interme diate Terrain Policy in New Source Permitting (Pine State Power; Jay, Maine) 12/23/91 VIII East Helena Lead SIP - Protocols for Design Value Determination, and Model "Verification" 12/26/91 VI Information Copy of El Paso- Juarez PM-10 Modeling 01/13/92 I NHARD Modeling Guideline 01/27/92 VIII East Helena Lead SIP - Protocols for Design Value Determination and Model "Verification"; Clarification of Model Clearinghouse Memo randum of December 23, 1991 03/06/92 I Modeling Credits for Stack Height Increases and Merging Flue Gases at Taunton Munici- pal Light Plant 04/06/92 V Proposal for Resolving the SO2 State Implementation Plan Revision for Rhinelander, Wisconsin 06/23/92 I Ozone Modeling Requirements for the Lewiston-Auburn and Knox-Lincoln Counties' Moderate Ozone Nonattainment Areas in Maine FY-92 MODEL CLEARINGHOUSE MEMORANDA (Cont'd) 08/03/92 X Healy Clean Coal Visibility Analysis 08/18/92 III Transcontinental Gas Pipe Line Corporation's Use of a Nonguideline Approach for Estimating the Amount of NO that is Converted to NO2 08/20/92 VI Use of ISC2 Direction-Specific Building Dimensions in Modeling for Alcoa APPENDIX B REVIEW OF PM-10 STATE IMPLEMENTATION PLAN ATTAINMENT DEMONSTRATIONS June 10, 1992 MEMORANDUM SUBJECT: Review of PM-10 State Implementation Plan (SIP) Attainment Demonstrations FROM: Edwin L. Meyer, Acting Chief Source Receptor Analysis Branch (MD-14) TO: Joseph W. Paisie, Acting Chief SO2/Particulate Matter Programs Branch (MD-15) I have read your May 8, 1992 note to Joe Tikvart providing some insight into the number and nature of upcoming PM-10 SIP attainment demonstration reviews that my Branch will be undertaking in the near future. We appreciate your "heads up" on this. I am also aware that Dean Wilson of my staff has reviewed one such attainment demonstration (Kent, Washington) and has provided comments to your staff. The comments on this SIP essentially say that the Region needs to provide more documentation and justification of the modeling used in the demonstration. The purpose of this memorandum is to document the procedures we intend to follow in the review of the PM-10 SIP demonstrations and the guidance documents that we intend to refer to in our reviews. There is really nothing new here. The procedures are essentially the same as we have been following for SO2 SIP attainment demonstration reviews for many years. The guidance materials we will be using for review of the SIP demonstrations are not new; your staff has been party to their development. However, since these procedures and guidance may be unfamiliar to some, it is important that everyone understand what we will be looking for in the demonstrations. First, we will be looking for a Technical Support Document (TSD) for each SIP. This may sound kind of obvious but in the early years of reviewing SO2 SIP's, it was sometimes difficult to get the Regional Offices to write such a document. This TSD should contain enough information on the attainment demonstration that the reader can understand what modeling or other techniques and what input data were used, as well as the concentration estimates for the design year and the attainment year(s). Attached is a list which contains, to the best of our knowledge, most of the guidance documents that the demonstration will need to be reconciled against. (Not all of these documents are applicable in every case.) We have also very briefly noted the focus of each document. The TSD should clearly indicate whether the demonstration falls within the purview of Item 8 in the attached list, and should then go on to reconcile the modeling with applicable guidance. In general, if the Regional Offices can, in their TSD's, reconcile the attainment demonstrations against the guidance, our review of most SIP's can proceed quickly and we can easily identify and thus focus our attention on those SIP's where there are indeed problems with the attainment demonstration. Of course, judgment should be used in assessing the amount of information to be included in the TSD. If a nonguideline technique is employed, then it is important to provide supporting information regarding the technical basis for the decisions and choices made. Whereas, if a Guideline technique is employed, it can be assumed that the technique is known. Then it is important to explain the technical basis for any deviations that have been made in implementing the technique. If you have any questions please contact Dean Wilson at extension 5683 or me at 5562. Attachment cc: J. Calcagni E. Ginsburg W. Laxton J. Tikvart D. Wilson bcc: G. Blais T. Coulter J. Irwin Attachment In reviewing the attainment demonstration for PM-10 SIP's, the following pieces of historical guidance will be considered. The TSD should reconcile the attainment demonstration with these materials. 1) The Guideline on Air Quality Models (Revised). This document provides basic guidance for use in regulatory air modeling, including PM-10. 2) The PM-10 SIP Development Guideline. This document provides the link between the Guideline on Air Quality Models and PM-10 SIP's and provides some clarifications on the applicability of various modeling techniques to PM-10. Most importantly, the document provides the hierarchy of guidance between dispersion modeling and receptor modeling. 3) Response to questions regarding PM-10 SIP Development (1988). This document provides answers to a number of questions, including questions related to modeling, that have been raised to EPA (prior to 1988). 4) Receptor Model Technical Series, Volumes I-VI, and related EPA documents dealing with receptor modeling. These documents provide technical details on how to conduct receptor modeling. 5) Protocol for Reconciling Differences Among Receptor and Dispersion Models. As the title implies, this document is used as the basis for determining justified adjustments to receptor and dispersion model inputs in order to reconcile the differences in the estimates, for a given application. 6) A March 15, 1989 Region X memorandum to the Model Clearinghouse outlining procedures that the Region encourages for States to follow in establishing the applicability of a stagnation model, primarily the WYNDValley model. 7) A July 5, 1990 memorandum from the Office of Air Quality Planning and Standards (OAQPS) to the Regional Offices providing guidance for the use of receptor modeling alone when an area does not have significant point source contributions to the PM-10 problem. 8) A March 4, 1991 OAQPS memorandum to the Regional Offices outlining requirements for "modified" attainment demonstrations for SIP's due on November 15, 1991. (The March 4, 1991 memorandum was actually an attachment to an April 2, 1991 memorandum from OAQPS to the Regional Offices.) 9) A September 17, 1987 letter from Region X to the State of Washington regarding the use of WYNDValley for PM-10 SIP's involving stagnation. This letter may effectively be limited to SIP's in the State of Washington. 10) Various Model Clearinghouse communiques that either document recommendations provided to Regional Offices on specific SIP modeling issues or, because of their widespread applicability, effectively set national precedents. APPENDIX C MODEL CLEARINGHOUSE CONTACTS MODEL CLEARINGHOUSE PERSONNEL 9/17/92 OAQPS CONTACTS Division Branch Name Number Responsibility TSD SRAB Dean Wilson 919-541-5683 Clearinghouse Coordinator SRAB Dean Wilson 919-541-5683 SO2, PM, Pb, NO2 Modeling SRAB Rich Scheffe 919-541-4650 O3 Modeling SRAB Tom Braverman 919-541-5383 CO Modeling SRAB Tom Coulter 919-541-0832 Receptor Modeling SRAB Joe Touma 919-541-5381 Toxics Modeling AQMD SDPMPB Gary Blais 919-541-3223 SO2, PM-10, Pb SIPs OCPB Doug Grano 919-541-3292 CO, O3, NO2 SIPs PPB Dan deRoeck 919-541-5593 PSD/NSR for all criteria pollutants REGIONAL MODELING CONTACTS Region Regional Contact Telephone No. I Brian Hennessey 617-565-3223 II Robert Kelly 212-264-2551 III Al Cimorelli 215-597-6563 IV Lew Nagler 404-347-5014 V Rebecca Calby 312-886-6065 VI Quang Nguyen 214-655-7238 VII Richard Daye 913-551-7619 VIII Kevin Golden 303-293-0955 IX Carol Bohnenkamp 415-744-1298 X Rob Wilson 206-553-1531 CO CONTACTS Region Regional Contact Telephone No. I Donald Cooke 617-565-3227 II Robert Kelly 212-264-2551 III Larry Budney 215-597-0545 IV Yasmin Yorker 404-257-2864 V Rebecca Calby 312-886-6065 VI Quang Nguyen 214-655-7238 VII Royan Teter 913-551-7609 VIII Kevin Golden 303-293-0955 IX Carol Bohnenkamp 415-744-1298 X Rob Wilson 206-553-1531 OZONE MODELING CONTACTS Region Regional Contact Telephone No. I Ian Cohen 617-565-3229 II Robert Kelly 212-264-2551 III Todd Ellsworth 215-597-2906 IV Brenda Johnson 404-347-2864 V Rebecca Calby 312-886-6065 VI Quang Nguyen 214-655-7238 VII Royan Teter 913-551-7609 VIII Kevin Golden 303-293-0955 IX Carol Bohnenkamp 415-744-1298 X Rob Wilson/Dave Bray 206-553-1531 RECEPTOR MODEL CONTACTS Region Regional Contact Telephone No. I Brian Hennessey 617-565-3223 II Marlon Gonzales 212-264-2517 III Tom Casey 215-597-2746 IV Lew Nagler 404-347-5014 V John Summerhays 312-886-6067 VI Quang Nguyen 214-655-7238 VII Richard Daye 913-551-7619 VIII Dale Wells 303-293-0957 IX Barbara Bates 415-744-1201 X George Lauderdale 206-553-6511 APPENDIX D SUMMARY OF THE EPA MODEL CLEARINGHOUSE EPA Model Clearinghouse Summary The Model Clearinghouse is the single EPA focal point for reviewing the use of modeling techniques 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) (Guideline). 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 demonstrated 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 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, will review the Region's position on proposed (specific case) use of a nonguideline model for technical 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 regulatory 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 significant decisions through copies of written decisions and briefings at various meetings and workshops; the public has access to Agency memoranda and reports through an EPA electronic bulletin board system. Structure of the Clearinghouse The Clearinghouse is formally located in the Source Receptor Analysis Branch (SRAB) of the Office of Air Quality Planning and Standards. However, the Air Quality Management Division (AQMD) also participates in Clearinghouse matters involving State implementation plan 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 four 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.