1. Reece Parker and Justin Cherry, P.E. Air Permits Division Texas Commission on Environmental Quality Advanced Air Permitting Seminar 2014

2. What Is PM 2.5 ? NO x and SO 2 Stationary Sources PM 2.5 Direct Chemical Formation The chemical composition of PM 2.5 can vary with the local topography, source emissions, time of year, and weather.

3. PM 2.5 Standards NAAQS: 24-hr: 35 µg/m 3 Primary Annual: 12 µg/m 3 Secondary Annual: 15 µg/m 3 Increments: 24-hr: 9 µg/m 3 Annual: 4 µg/m 3 SIL*: 24-hr: 1.2 µg/m 3 Annual: 0.3 µg/m 3 *with sufficient justification

4. Using the SIL Background Value SIL NAAQS

5. 4 Assessment Cases Case 1: Direct PM 2.5 < 10 tpy SER; NO x and/or SO 2 < 40 tpy SER Primary impacts only Case 2: Direct PM 2.5 ≥ 10 tpy SER; NO x and/or SO 2 < 40 tpy SER Primary impacts, still must address secondary formation Case 3: Direct PM 2.5 ≥ 10 tpy SER; NO x and/or SO 2 ≥ 40 tpy SER Primary impacts AND secondary impacts Case 4: Direct PM 2.5 < 10 tpy SER; NO x and/or SO 2 ≥ 40 tpy SER Primary impacts AND secondary impacts

6. Case 1 Direct PM 2.5 emissions < 10 tpy and SO 2 and/or NO x emissions < 40 tpy: Model direct PM 2.5 emissions following guidance for a NAAQS analysis

7. Case 2 Direct PM 2.5 emissions ≥ 10 tpy: Model direct PM 2.5 emissions following guidance for a NAAQS analysis SO 2 and/or NO x emissions < 40 tpy: Discuss in AQA why proposed SO 2 and NO x emissions are not significant to the secondary formation of PM 2.5

8. Case 3 Direct PM 2.5 emissions ≥ 10 tpy: Model direct PM 2.5 emissions following guidance for a NAAQS analysis SO 2 and/or NO x emissions > 40 tpy: Provide a qualitative, hybrid qualitative/quantitative, or quantitative assessment of the secondary formation of PM 2.5

9. Case 3 Qualitative Approach Ideas to consider: Peak impacts from direct emissions and secondarily formed PM 2.5 likely do not overlap Assessment of background data and condition with the NAAQS

10. Case 3 Qualitative Approach (Continued) Ideas to consider: Evaluation of speciated PM 2.5 data: Magnitude of secondary PM 2.5 precursor emissions from existing sources Comparing project precursor emissions to those of existing sources Limitations of chemical species necessary for photochemical reactions to form secondary PM 2.5

11. Case 3 Hybrid Approach Qualitative: Follow the Case 3 qualitative assessments General conclusions from existing photochemical modeling

12. Case 3 Quantitative Approach Quantitative #1: Assume 100% conversion from SO 2 and NO x to PM 2.5 Assess combined impacts of direct and equivalent direct PM 2.5 emissions Quantitative #2: Full quantitative photochemical grid modeling exercise* *No requirement for photochemical modeling - this will be discussed further

13. Case 4 Direct PM 2.5 emissions < 10 tpy: Model direct PM 2.5 emissions following guidance for a NAAQS analysis SO 2 and/or NO x emissions ≥ 40 tpy: Provide a qualitative, hybrid qualitative/quantitative, or quantitative assessment of the secondary formation of PM 2.5

14. Case 3 Example Direct PM 2.5 emissions: 62 tpy NO x emissions: 96 tpy SO 2 emissions: 10 tpy Need to address secondary formation of PM 2.5.

15. Case 3 Qualitative Example Slow transformation and small portions of NO x emissions can convert to PM 2.5 Maximum concentration areas for secondary impacts of NO x are not likely to overlap with direct impacts of PM 2.5

16. Case 3 Example (Cont.) Qualitative (Cont.): Speciated PM 2.5 data shows nitrates make up 2% of total PM 2.5 concentration Regional NO x emissions have a magnitude of 25,000 tons Project emissions of NO x (96 tpy) are small and not likely to contribute to secondary formation of PM 2.5

17. Case 3 Example (Cont.) Quantitative: Assume 100% conversion of NO x to (NH 4 )NO 3 Using NACAA formula: 1 µg/m 3 of NO x could form 1.7391 µg/m 3 of (NH 4 )NO 3 24-hr and annual NO x from the source predicted to be 2.9 µg/m 3 and 0.3 µg/m 3, respectively Using the formula, 24-hr and annual secondary formation from the source would be 5 µg/m 3 and 0.5 µg/m 3, respectively

18. Case 3 Example (Cont.) Quantitative (Cont.): 24-hr and annual predicted concentrations from the direct emissions of PM 2.5 were 2 µg/m 3 and 1 µg/m 3, respectively Add all components together for a total value Pollutant Averaging Time Project GLC max (µg/m 3 ) Secondary Formation from Project (µg/m 3 ) Background (µg/m 3 ) Total Predicted Concentration (µg/m 3 ) NAAQS PM 2.5 24-hr25263335 PM 2.5 Annual10.59.611.112

19. PM 2.5 Increment What to consider: Major source baseline date - October 20, 2010 Trigger date - October 20, 2011 Minor source baseline date - county specific SIL: Additional justification Output metric: Yearly H1H vs. 5-year average

20. PM 2.5 SIL Justification for Increment Evaluate proposed direct PM 2.5 emissions increases: Report the maximum predictions and not a 5-year average Provide justification for using the SILs to compare with the model predictions

21. PM 2.5 SIL Justification for Increment

22. PM 2.5 Monitoring for Increment 5 years of monitoring data (µg/m 3 ): 24-hr Concentrations 20092010201120122013 H1H23.423.222.923.523.3 H2H21.922.121.422.322.9 Increment Consumed 2013-2010 SIL Increment Standard

23. PM 2.5 Increment When predictions are greater than the SIL or if the SIL cannot be justified: Evaluate increment affecting sources together with the project sources Document approach to identify increment affecting sources Receptors - the extent of the receptor grid needs to capture maximum concentrations from the project and show that concentrations are decreasing

24. PM 2.5 Increment (continued) Further detail: PSD major sources were further evaluated: Projects with completion dates 18 months prior to the major source baseline date up to the minor source baseline date were identified Projects were reviewed to determine if PM 2.5 was associated with project The extent of the modeling domain used to limit search for PSD major sources: 24-hr and annual GLC max locations, distance from property line, etc.

25. PM 2.5 Increment (continued)

26. Contact Information Reece Parker Air Dispersion Modeling Team (512) 239-1348 reece.parker@tceq.texas.gov Justin Cherry, P.E. Air Dispersion Modeling Team (512) 239-0955 justin.cherry@tceq.texas.gov Air Permits Division Reece Parker (512) 239-1348 reece.parker@tceq.texas.gov Air Permits Division (512) 239-0955 justin.cherry@tceq.texas.gov Justin Cherry