Status of EPA’s Guideline on Air Quality Models

2013 R/S/L Modelers Workshop

April 23, 2013

Tyler Fox Office of Air Quality Planning and Standards

Overview

• Challenges to Our Current Guideline

• Recent Guidance Helps But Not Solution

• Revising EPA’s Guideline on Air Quality Models

• Addressing Compliance Demonstration Issues & Clarification Memos

• Engaging with Modeling Community 3

EPA’s Guideline on Air Quality Models • Provides recommendations on the use of air quality

models to determine compliance with National Ambient Air Quality Standards (NAAQS), and other regulatory requirements such as New Source Review (NSR) and Prevention of Significant Deterioration (PSD) regulations.

• Published as Appendix W of 40 CFR Part 51, which was originally published in April 1978 to provide consistency and equity in the use of modeling within the U.S. air quality management system.

• These guidelines are periodically revised to ensure that new model developments or expanded regulatory requirements are incorporated.

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Challenges to our current guideline • Demonstrating compliance with new 1-hour NO2 and SO2

NAAQS • Challenges with 2006 and 2012 PM2.5 NAAQS • Sierra Club Petition Grant – Ozone and PM2.5

• Two Recent NSR/PSD Court Decisions for PM2.5 – SMC/SILS - In Jan 2013, the U.S. Court of Appeals for the D.C.

Circuit vacated the SMC for PM2.5,and vacated and remanded the provision for PM2.5 SILs in EPA’s two PSD regulations.

– Subpart 4 - Also in January, the D.C. Circuit held that the EPA should have issued its 2008 NSR/PSD rule for the 1997 PM2.5 NAAQS according to Subpart 4, not Subpart 1. No vacatur.

• Overall renewed tension between environmental protection and economic growth

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Recent PSD Modeling Guidance Helps But Is Not a Full Solution

• Applicability of Appendix W Modeling Guidance for the 1-hour NO2 National Ambient Air Quality Standard, June 28, 2010

– http://www.epa.gov/ttn/scram/ClarificationMemo_AppendixW_Hourly-NO2-NAAQS_FINAL_06-28-2010.pdf

• Applicability of Appendix W Modeling Guidance for the 1-hour SO2 National Ambient Air Quality Standard, August 23, 2010

– http://www.epa.gov/ttn/scram/ClarificationMemo_AppendixW_Hourly-SO2-NAAQS_FINAL_08-23-2010.pdf

• Additional Clarification Regarding Application of Appendix W Modeling Guidance for the 1-hour NO2 National Ambient Air Quality Standard, March 1, 2011

– http://www.epa.gov/ttn/scram/Additional_Clarifications_AppendixW_Hourly-NO2-NAAQS_FINAL_03-01-2011.pdf

• Draft Guidance for PM2.5 Permit Modeling, March 2013 – http://www.epa.gov/ttn/scram/guidance/guide/Draft_Guidance_for_PM25_Permit_Mod

eling.pdf 6

Updates to Designations & SIP Modeling Guidance

• Area Designations for 2010 Primary Revised Sulfur Dioxide National Ambient Air Quality Standard, March 24, 2011

– http://www.epa.gov/air/sulfurdioxide/pdfs/20110411so2designationsguidance.pdf – Consistent with ‘SO2 White Paper’, EPA expects to provide draft technical assistance

document in Spring 2013 to address use of modeling for future designations

• Guidance for 1-hour SO2 SIP Submissions, September 22, 2011 – http://www.epa.gov/airquality/sulfurdioxide/pdfs/DraftSO2Guidance_9-22-11.pdf – Update in June/July 2013

• Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for O3, PM2.5 and Regional Haze, April, 2007

– http://www.epa.gov/ttn/scram/guidance/guide/final-03-pm-rh-guidance.pdf – Update in Summer/Fall 2013 7

Revisions to EPA’s Guideline on Air Quality Models

• Notice and Comment Rulemaking to Update Appendix W to 40 CFR Part 51 – In response to Sierra Club petition grant for ozone & PM2.5 ,and

necessary technical updates to address challenges with new 1-hour NAAQS.

– Comprehensive rulemaking to: • Updates for conducting individual source and cumulative impact analysis for

new 1-hour NAAQS • Incorporate new analytical techniques to address ozone and secondary

PM2.5 • Update, as appropriate, current EPA preferred models to address input and

science issues. – Expected timeline (implied by the Sierra Club petition grant)

• NPRM: Spring 2015 (in connection with 11th Modeling Conference)

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Coordinate Update with NSR/PSD Rulemakings

• PM2.5 SIL Reconsideration Rule – In response to court decision on the SMC and SILs. – Comprehensive rulemaking to:

• Re-establish PM2.5 SILs on a firmer technical and legal foundation. • Establish SERs for PM2.5 precursors (NOx and SO2) for PSD

applicability and triggering need for air quality analysis, logically linked to the SILs.

• EPA Ozone PSD and NNSR Requirements Rule – EPA will need to establish ozone SIL and SERs for VOC and

NOx as precursors to ozone, logically linked to the SIL. • Leverage outcomes from PM2.5 SIL rulemaking to inform approach

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Major Updates to Appendix W • Model improvements to existing regulatory models

– AERMOD Modeling System – CALPUFF Modeling System – Near road modeling

• Use of Prognostic Meteorological Inputs – MMIF

• Tiered Approach for NO2 – ARM2 and pursue Tier 3 techniques as refined methods

• New models/techniques for long-range transport and single-source modeling for O3 and PM2.5

• Addressing Compliance Demonstration Issues 10

• December 2012 update: – Addition of a minimum wind speed threshold option for 1-min ASOS

wind data in AERMET (addressed in recent Clarification Memo)

– New “Beta” option in AERMET addressing "low wind speed" issue based on review of 10th Modeling Conference comments, input from AERMIC committee and other published literature

– Two new “Beta” options included in AERMOD related to “low wind speed” issue to facilitate further evaluations by EPA and others

AERMOD Modeling System Updates

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• Longer-term (FY13+): – Consider updates incorporating EPA ORD’s development of

enhanced line-source characterization and algorithm focused on near-road environment.

– Reviewing issues with building characterization and downwash algorithms based on ORD research

– Reviewing issues and options for NO2 chemistry in AERMOD

– Potential enhancement to include buoyant line source option in AERMOD, as alternative to current BLP model

– Further evaluation of AERMOD-COARE and potential platform downwash option in AERMOD to address offshore sources, as an alternative to current OCD model, in coordination with Region 10

AERMOD Modeling System Updates

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Future Plans for AERMOD Updates • Given the recent inclusion of Beta options in AERMOD and

AERMET, and recognizing the range of issues being raised in relation to application of AERMOD, we are developing plans and procedures to more effectively and efficiently manage the maintenance and development of the AERMOD modeling system. This plan will address: – Standard Protocol for updating the AERMOD modeling system; – Tracking, reporting, and timely assessment and correction of bugs; – Conducting and documenting evaluations of model performance.

• These efforts are also in recognition of EPA plans for developing proposed revisions to Appendix W and possible revisions to regulatory options in AERMOD for the 11th Conference on Air Quality Models in Spring 2015 (tentative).

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CALPUFF Modeling System Updates • August 2012 update:

– CALPUFF version 5.8 updated to include newer version of the post processing program (CALPOST)

• Spring 2013 update (under EPA/FLM review at present): – CALPUFF version 5.8 updated to address known bug fixes

• Next steps (FY13+) are to evaluate state of science modeling tools as potential replacement for CALPUFF modeling system for long range transport – See IWAQM Phase 3 effort

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Roadway Modeling Updates • PM Hot Spot Conformity requirements took effect in December,

requiring project level modeling for many new roadway projects: – OAQPS updated CAL3QHCR to meet conformity requirements and is now

consistent with EPA-FHWA PM hot-spot training. – In parallel, reviewed CAL3QHCR model updates submitted by FHWA but

significant concerns were noted with their submittal.

• Central coordination w/ ORD and OTAQ on research efforts – Reviewing formulation and documentation of their new line source model, R-

LINE (formerly AERLINE). – Evaluation of the line source algorithm/model for potential implementation

into AERMOD.

• Ultimately make determination of what Appendix W updates are necessary to appropriately address dispersion modeling of mobile & related sources.

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Research Efforts on Model Science • EPA’s Office of Research and Development is

supporting model improvements:

– Conducting wind tunnel research on downwash issue – Working with OAQPS and OTAQ on line source algorithm

development (AERMOD) and evaluation of air quality models for near-road assessments

– Working with OAQPS (and EPRI) on review of fine-scale model development and evaluation (e.g., SCICHEM and CMAQ-APT)

– Working with OAQPS on model development for instrumented techniques in photochemical models to develop credible screening tools for O3 and PM2.5

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Mesoscale Model Interface Program (MMIF) • The MMIF beta program that converts MM5 or WRF

meteorological output to formats appropriate for CALPUFF, SCICHEM, and AERMOD

– Prototype by USEPA, continued development by ENVIRON – MMIF Version 2.2 User’s Guide dated August 30, 2012

• MMIF Version 2.2 beta features: – Linux/Unix or Windows environment – Options to re-diagnose or pass-through PBL depth – Can process subset of MM5/WRF domain – An option to perform layer aggregation – Retains original MM5/WRF map projection and horizontal grid resolution – Support for Polar Stereographic and Mercator projections

• Ultimately issue guidance on appropriate use of prognostic met inputs for regulatory modeling and then make determination of what Appendix W updates are necessary to codify such use.

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Modeling for 1-hr NO2 NAAQS • NO2 NAAQS revised February 2010 • Standard is 100 ppb based on 3-year average of the

98th percentile of daily maximum 1-hour concentrations • AERMOD is the preferred model for estimating NO2

impacts in near-field applications (out to 50 km) • Three-tiered screening approach in Section 5.2.4 is

generally applicable for 1-hour NO2 modeling, with additional/different considerations:

– Tier 1 assumes full conversion of NO to NO2; – Tier 2 applies ambient ratio to Tier 1 result (annual default ratio = 0.75); – Tier 3 “detailed screening methods” on a case-by-case basis, including OLM (ozone

limiting method) and PVMRM (plume volume molar ratio method) options implemented in AERMOD

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Updates for NO2 Modeling • Industry-stated issues with demonstrating compliance

using existing tiered approach in Appendix W. • For demonstrating compliance with new 1-hour NAAQS

– Currently reviewing API sponsored updates to the Tier 2 “Ambient Ratio Method” (ARM) known as ARM2

– Consider updates to Tier 3 approaches with evaluation in hopes of establishing as refined approach(es)

• OLM, PVMRM, • SCICHEM w/ limited reactions (See EPRI presentation at AWMA)

• Spring /Summer 2013: Provide clarification memo that establishes the appropriate use of the revised ARM2

• Later in 2013 or 2014: Address updates to Tier 3 approaches, if deemed appropriate, via AERMOD model updates.

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Permit Modeling for PM2.5 NAAQS

• On January 4, 2012, the EPA granted a petition submitted on behalf of the Sierra Club on July 29, 2010.

– In the petition grant, the EPA committed to engage in rulemaking to evaluate updates to the Guideline on Air Quality Models as published as Appendix W to 40 CFR 51, and, as appropriate, incorporate new analytical techniques or models for ozone and secondary PM2.5.

– As part of this commitment with the Sierra Club and in compliance with Section 320 of the Clean Air Act, the EPA conducted the 10th Conference on Air Quality Modeling (10th Modeling Conference) was held in March 2012.

• http://www.epa.gov/ttn/scram/10thmodconf.htm – The recent release of the Draft Guidance for PM2.5 Permit Modeling is

consistent with the EPA’s commitments in the January 4, 2012, administrative grant of the Sierra Club petition.

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Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 3

• Interagency collaborative effort to provide additional guidance for modeling single source impacts on secondarily formed pollutants in the near-field and for long range transport.

• Inform Agency’s commitment to update Appendix W, as appropriate, to address chemically reactive pollutants.

• Steering committee to more broadly coordinate across Federal partners and stakeholders

• 2 technical working groups: – Long-range transport of primary and secondary pollutants – Near-field single source impacts of secondary pollutants

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• EPA’s Approach – Establish SERs for precursor pollutants for PSD applicability and

triggering need for air quality analysis, logically linked to SILs – Development of technically sound screening approach to

efficiently evaluate impacts of new or modifying sources • See Sydney, Australia example using instrumented techniques in CAMx • EPA case study to be presented at CMAS Conference in October 2013

– Establish when full chemistry modeling is necessary and how to evaluate new source impacts

• Guidance on appropriate use of existing photochemical models and instrumented techniques

• Consider SCICHEM and CMAQ-APT model development by EPRI

Single Source Impacts of O3 and PM2.5

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Addressing Compliance Demonstration Issues

• Permit Modeling Guidance for PM2.5 – Draft guidance released on 3/4/13 for public review and extended public

comment period until May 31st. – Focused on form of standard, precursor impacts and cumulative impact

analysis for PM2.5 NAAQS and increments. – Issue revised guidance on Fall 2013.

• NO2 – Released NO2 In-Stack Ratio (ISR) database on EPA’s SCRAM website on

August 30, 2012 – Working with stakeholders on improving Tier 2 and Tier 3 approaches – Advocating new field studies to allow more full evaluation so these Tier 3

approaches can be considered as refined techniques

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Addressing Compliance Demonstration Issues (cont.)

• SO2 – Engaging with states and stakeholders on model performance issues

(e.g., Indiana power plant and Tennessee industrial facility)

– Reviewing EPRI-funded variable emissions tools (EMVAP) and related programs for consideration as part of future state attainment demonstrations in determining enforceable emissions limits

– Preparing guidance for SO2 attainment demonstrations (nonattainment areas), and modeling and monitoring guidance for future SO2 designation purposes

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Clarification Memos

• Meteorological data and use of AERMINUTE – March 8, 2013

• Monitoring in lieu of modeling under Section 10 of Appendix W – Spring 2013

• Further clarifications on Appendix W guidance regarding inventory of modeled sources and extent of modeling domain – Spring 2013

• GEP stack height changes in AERMOD (legal bug fix) – Fall 2013

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Engaging with Modeling Community

• Technical modeling workgroup

• Specific model improvements and evaluations

• EPA Modeling Conference (mandated by Clean Air Act)

• 2013 AWMA Specialty Dispersion Modeling Conference

• Annual Regional, State, Local Modelers Workshop

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Appendix

Air Quality Modeling Group Staff

• George Bridgers Model Clearinghouse Director PM2.5 Permit Modeling Point of Contact

• Roger Brode AERMOD Model Development Lead NO2 Permit Modeling Point of Contact

• Chris Owen Mobile Source Modeling Point of Contact Modeling Lead on SER/SIIL Development

• James Thurman SO2 Permit & SIP Modeling Point of Contact

MATS Final Rule & NATA

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Air Quality Modeling Group Staff

• Chris Misenis Mesoscale Model Interface (MMIF) Program Development Lead

• Kirk Baker Instrumented Modeling Techniques Lead

Fine-scale Modeling Team Lead

• Jim Kelly PM2.5 Photochemical Modeling Lead Fine-scale Team, Model Evaluation Lead for SCICHEM

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