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New Guideline on Air Quality Models and the Electric Utility Industry

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The revision of the Guideline on AQ Models (Appendix W) will prompt many changes in the way dispersion modeling is conducted for regulatory purposes. Some of the changes to the Guideline include enhancements and bug fixes to the AERMOD modeling system, new screening techniques to address ozone and secondary PM2.5, delisting CALPUFF as the preferred long-range transport model, and updates on the use of meteorological input data. These changes will have a significant impact on the regulated community. This presentation will cover the main highlights from this guidance and how the electric utility industry will be impacted. In addition, the latest information provided by EPA during the 2016 Regional, State, and Local Modelers' Workshop will also be presented.

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New Guideline on Air Quality Models and the Electric Utility Industry

  1. 1. www.cppwind.comwww.cppwind.com New Guideline on Air Quality Models and the Electric Utility Industry EUEC 2017, San Diego, CA Sergio A. Guerra, PhD February 9, 2017
  2. 2. Outline 1. Background 2. Highlights of Revisions to Modeling Guideline 3. Main Changes 2 New Guideline on Air Quality Models and the Electric Utility Industry
  3. 3. Regulatory Modeling History Appendix W from 40 CFR Part 51: Guideline on Air Quality Modeling – Purpose is to promote consistency – Periodically revised to ensure that new model developments or expanded regulatory requirements are incorporated – Defines the accepted regulatory models • 1978 Original Guideline • 1986 Revised Guideline • 1987 Supplement A- Preferred Models • 1993 Supplement B- Alternative Models • 1995 Supplement C – Updates and revisions • 2003 Revised Guideline • Nov 2005 Revised Guideline • Jan 2017 Revised Guideline* 3 New Guideline on Air Quality Models and the Electric Utility Industry
  4. 4. Appendix W Revisions • Proposed on July 2015 • 11th Conference on Air Quality Modeling: August 12 & 13 https://www3.epa.gov/scram001/11thmodconf.htm • 90 day public comment period • Finalized on December 20, 2016 – Included AERMOD version 16216 • January 17, 2017: Published in the FR – Including a revised AERMOD version 16216r – Effective day February 16, 2017 • Jan 26, 2017 effective day delay until March 21, 2017 4 New Guideline on Air Quality Models and the Electric Utility Industry
  5. 5. Related EPA Actions • 8-hour Ozone NAAQS strengthened from 75 to 70 ppb • Draft SIL values – 1-ppb for 8-hour Ozone and – 1.2 mg/m3 for 24-hr PM2.5 – 0.2 mg/m3 for annual PM2.5 New Guideline on Air Quality Models and the Electric Utility Industry5
  6. 6. AERMOD Changes • AERMOD v16216r – New Default Options • Adjusted u-star • Tier 2 and Tier 3 Options for NOx to NO2 conversion • Horizontal and capped stacks – New Adjusted u-star • “Bug” change between v15181 vs v16216r – Tall stacks near small urban areas 6 New Guideline on Air Quality Models and the Electric Utility Industry
  7. 7. AERMOD Changes NOx to NO2 Conversion: • Tier 2: ARM2 replaces ARM – NO2/NOx Minimum Ambient Ratio (MAR) of 0.5 – Alternative lower MARs need justification/approval New Guideline on Air Quality Models and the Electric Utility Industry7 Porez, M. (2015), An update to the ambient ratio method for 1-h NO2 air quality standards dispersion modeling, Atmos. Env. http://dx.doi.org/10.1016/j.atmosenv.2014.12.021
  8. 8. AERMOD Changes NOx to NO2 Conversion: • Tier 3: OLM and PVMRM now regulatory default options • PVMRM2 replaces PVMRM New Guideline on Air Quality Models and the Electric Utility Industry8
  9. 9. Adjusted u-star “Bug” Fix • Adjusted u-star is an option in AERMET to adjust the surface friction velocity (u*) to address issues with AERMOD model overprediction under stable, low wind speed conditions • AERMET v 16216r reduced ADJ_U* for wind speeds approaching zero by a factor of 2 • This action diminishes the effectiveness of the low wind correction and can lead to increases in concentrations 9 New Guideline on Air Quality Models and the Electric Utility Industry
  10. 10. Backburner • Probabilistic methods • Lowwind 3 option • 3rd party review of updates to AERMOD New Guideline on Air Quality Models and the Electric Utility Industry10
  11. 11. Guideline Changes Revisions include: – O3 and Secondary PM2.5 modeling – Delisting of CALPUFF for LRT – Prognostic Meteorological Data 11 New Guideline on Air Quality Models and the Electric Utility Industry
  12. 12. O3 and Secondary Formation of PM2.5 • July 29, 2010 Sierra Club submitted petition to address secondary PM2.5 and ozone • January 4, 2012 EPA granted Sierra Club’s petition 12 New Guideline on Air Quality Models and the Electric Utility Industry
  13. 13. O3 and Secondary Formation of PM2.5 App W establishes a two tiered approach through: "Guidance on the Development of Modeled Emission Rates for Precursors (MERPs) as a Tier I Demonstration Tool for Ozone and PM2.s under the PSD Permitting Program” https://www3.epa.gov/ttn/scram/guidance/guide/EPA-454_R-16-006.pdf Comment period extended to March 31, 2017 Tier 1 – Use existing empirical relationships between precursors and secondary formation • Tier 2 – Use a chemical transport model 13 New Guideline on Air Quality Models and the Electric Utility Industry
  14. 14. O3 and Secondary Formation of PM2.5 Tier 1 • Use existing empirical relationships between precursors and secondary formation • Based on existing AQ Modeling e.g., modeling performed for SIP, permit actions, similar policy assessment, AQ modeling of hypothetical industrial sources • Also screening approaches based on full science chemical transport modeling systems (e.g., reduced form models) 14 New Guideline on Air Quality Models and the Electric Utility Industry
  15. 15. Step 1: Compare with Most Conservative MERPs • Table 7.1 Most Conservative (Lowest) Illustrative MERP Values (tons per year) by Precursor, Pollutant and Region. 15 New Guideline on Air Quality Models and the Electric Utility Industry https://www3.epa.gov/ttn/scram/appendix_w/2016/MERPs_WebinarPresentation_01192017.pdf
  16. 16. Step 2: Develop Case Specific MERP MERP = Cthr x ModE-rate / ModImpact MERP= in tpy Cthr = Critical AQ Threshold in (e.g., SIL) in µg/m3 or ppb ModE-rate = Modeled Emission Rate from hypothetical source in g/s ModImpact = Modeled air quality impact in µg/m3 or ppb New Guideline on Air Quality Models and the Electric Utility Industry16
  17. 17. MERP Development Scenario B Example Ozone Analysis for Source in Southeast region: • 0 tpy PM2.5 (primary) • 0 tpy VOC • 310 tpy of NOx • 75 tpy of SO2 New Guideline on Air Quality Models and the Electric Utility Industry17
  18. 18. MERP Development Scenario B Example Ozone Analysis for Source in Southeast region: • 0 tpy PM2.5 (primary) • 0 tpy VOC • 310 tpy of NOx > 126 tpy from table 7-1 • 75 tpy of SO2 < not an ozone precursor MERP = Cthr x ModE-rate / ModImpact = 1.0 ppb x 500 tpy / 1.53 ppb (Source 19 , H in Table A-1) MERP = 327 tpy > 310 tpy of NOx = no Tier 2 needed New Guideline on Air Quality Models and the Electric Utility Industry18
  19. 19. MERP Development Scenario B’ Example Ozone Analysis for Source in Southeast region: • 0 tpy PM2.5 (primary) • 0 tpy VOC • 500 tpy of NOx > 126 tpy from table 7-1 • 75 tpy of SO2 < not an ozone precursor MERP = Cthr x ModE-rate / ModImpact = 1.0 ppb x 500 tpy / 1.53 ppb (Source 19 , H in Table A-1) MERP = 327 tpy < 500 tpy of NOx = MERP exceeded! New Guideline on Air Quality Models and the Electric Utility Industry19
  20. 20. O3 and Secondary Formation of PM2.5 Tier 2 • If above MERPs, chemical transport models (CTMs) to be used for ozone and secondary PM2.5 impacts • Photochemical grid models seem to be preferred (i.e., CMAQ and CAMx) • Lagrangian puff models (e.g., SCICHEM) may be appropriate also 20 New Guideline on Air Quality Models and the Electric Utility Industry
  21. 21. O3 and Secondary Formation of PM2.5 MERPs: Tier 1 • Information from a different region may be used based on comparisons of: – Avg. and peak temperatures – Humidity – Terrain – Rural or urban location – Nearby regional sources (e.g., biogenics or anthropogenic sources) – Ambient concentrations of relevant pollutants 21 New Guideline on Air Quality Models and the Electric Utility Industry
  22. 22. Long Range Transport Modeling • CALPUFF no longer the preferred model for LRT (> 50 km) • Still allowed for screening purposes • In near field (< 50 km) still alternative model for complex terrain and complex winds • CALPUFF still the Federal Land Managers (FLM) preferred model for Class I Air Quality Related Value (AQRV) New Guideline on Air Quality Models and the Electric Utility Industry22
  23. 23. Meteorological Data Prognostic meteorological data • Allowed when no representative NWS station and infeasible to collect site-specific data • No fewer than 3-years of data • Mesoscale Model Interface Program (MMIF) developed to read prognostic data (i.e., WRF) to create data for input into AERMET and AERMOD New Guideline on Air Quality Models and the Electric Utility Industry23
  24. 24. Model Clearinghouse • Applicant sends request to regulatory agency • Regulatory agency reviews and submits recommendation to EPA Regional Office • EPA RO reviews and sends to Model Clearinghouse • MCH engages and consults on solutions • MCH issues formal concurrence • MCH decisions are archived in Searchable database (MCHISRS): http://cfpub.epa.gov/oarweb/MCHISRS/ New Guideline on Air Quality Models and the Electric Utility Industry24
  25. 25. Summary The good: • Default options will help achieve compliance – NOx-NO2 conversion – Adjusted u-star • Prognostic meteorological data potential of savings in cost and time for new projects New Guideline on Air Quality Models and the Electric Utility Industry25
  26. 26. Summary The challenges: • Changes to the adjusted u-star option • Tier 2 requirements for Ozone and Secondary PM2.5 • Long Range Transport • Too much flexibility may lead to legal challenges and potential delays New Guideline on Air Quality Models and the Electric Utility Industry26
  27. 27. Take Away • Case-by-case basis will be the norm • Modeling protocols will be very important • Communication and coordination with regulatory agency, EPA Regional Office and Model Clearinghouse is paramount New Guideline on Air Quality Models and the Electric Utility Industry27
  28. 28. Sergio A. Guerra, PhD sguerra@cppwind.com Mobile: + 612 584 9595 CPP, Inc. 2400 Midpoint Drive, Suite 190 Fort Collins, CO 80525 + 970 221 3371 www.cppwind.com @CPPWindExperts Questions? 28 New Guideline on Air Quality Models and the Electric Utility Industry

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