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Modeling and Impact Assessment in Air Permits Review Process

Learn about the process of evaluating impacts of emissions for air permits. Understand modeling techniques, permit reviewer duties, impacts evaluation, criteria for modeling, and options to reduce impacts.

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Modeling and Impact Assessment in Air Permits Review Process

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  1. Modeling, Impacts, and Effects Review Dom Ruggeri, P.E., Manager Technical Program Support Section TCEQ, Air Permits Division Austin, Texas September 27, 2006

  2. Introduction • Discuss general approach to modeling, impacts, and effects review • Prepare to evaluate impacts of MSS emissions

  3. Applicant Submits Application • Identifies all emissions from production and planned MSS • Provides scenarios, emission factors, control technologies, representations  • Provides all supporting documentation  • Addresses known concerns  

  4. Table 1 (a) • Includes all normal operation scenarios • Provides separate scenarios for short-term, long-term operations • Includes all facilities and related activities and frequency • Includes hours of production and MSS and the number of startups and shutdowns

  5. Permit Reviewer Duties • Agrees to BACT or BMP • Agrees with proposed emission rates and stack parameters • Conducts preliminary impacts evaluation • Requests modeling as needed

  6. Impacts Evaluation • Look at all contaminants, project emissions • Include MSS not previously evaluated • Include PBRs and standard permits • Compare to de minimis, SIL, 10% ESL • Conduct applicable modeling • Modeling sitewide? Include everything!

  7. Basic Questions • Do I have to evaluate all emissions from normal operations? • Yes • Can I evaluate planned MSS separately from production? • Maybe • Is there a de minimis for MSS? • Yes and no

  8. If Modeling is Requested • Which Model? • Staff prefer SCREEN3 and AERMOD • When do we switch from ISCST3? • Federally required December 2006 • Could we use ISCST3 instead of AERMOD? • Maybe

  9. Modeling ProcessTry Conservative, Worst-Case Approach First • Continuous emissions; max hourly rate • Simultaneous PMSS • Set model for overall max and individual source concentrations • Pass: site meets standards and/or ESLs

  10. Modeling ProcessFailed? Are Impacts “Possible” or “Probable”? • Identify likely worst-case scenario (s) • Emissions at max hourly rate for short-term, average hourly rate for long-term • Use emission rate scaling factors • Set model for overall max and individual source concentrations • Pass: site meets standards and/or ESLs

  11. Modeling ProcessStill failed? Are Impacts Possible? • Apply appropriate post-modeling techniques • For example: • Consider buildings, obstructions • Particle size • Stability class and wind speed

  12. Modeling ProcessImpacts Possible But Not Probable • Are the emissions continuous? • Rate based on spikes or steady state? • If steady state, then meteorology not an adjustment factor for single source • If noncontinuous, probability approach may be appropriate

  13. Modeling ProcessImpacts Possible, Analyze Operations • Identify the issues • What are the culpable sources? • How are the culpable sources authorized? • What are the applicable scenarios, hours of operation, emission rates? • Are the emissions from production or MSS?

  14. Modeling ProcessOptions to Reduce Impacts • Modify stack parameters • Reduce emissions with proposed BACT • Propose new BACT • Limit normal operations • Limit use of standard permits and PBRs

  15. Show Air Quality BenefitStill Can’t Demonstrate Compliance? Can we show an air quality benefit? Assumes: • Standards met; issue related to ESLs • All refined modeling, control, emission and scenario options fully explored • No backsliding • No significant air quality impact

  16. Air Benefit AnalysisBasic Questions • What is the ESL issue? • Acute or chronic health • Nuisance • APWL or mobile monitoring • What are the BACT issues? • Technical reasonableness • Economic feasibility • Timing

  17. Air Benefit AnalysisMore Basic Questions • Does the source of emissions exist? • What are the operational issues? • Production or MSS? • Existing PBRs and/or standard permits? • Should we limit future PBRs, standard permits?

  18. Air Benefit AnalysisStill More Basic Questions • What is the compliance history? • What is the region’s input? • What is toxicology’s input? • What is the public’s input? • Is there a net air quality improvement from the project?

  19. Summary • Applicants provide technical information • Permit reviewers evaluate • BACT • Compliance with rules/regulations • Protectiveness • Models are tools • Engineering judgment can be used to weigh air quality benefits

  20. Questions

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