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Exceptional Event Case Studies Clark County, Nevada

Exceptional Event Case Studies Clark County, Nevada

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Exceptional Event Case Studies Clark County, Nevada

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  1. Exceptional Event Case Studies Clark County, Nevada WESTAR-EPA Meeting San Francisco, CA February 25, 2009 1

  2. Outline • Wildfire Event on June 29th and 30th, 2005 • Event Demonstration Overview • Event Demonstration Elements • DAQEM Conclusion • Region IX Response • Past and Future Studies • Questions and Discussion 2

  3. Wildfire EventWILDFIRE EFFECTS: Blazes! It's a stew out there • June 29th and 30th, 2005 Clark County was surrounded by wildfires. • NE Clark County, NV • SE Washington County, UT • Northwestern and Central AZ • Southern CA • Highest O3 concentrations in Clark County in 25 years • Typical summertime O3 season of May 1 to September 30 3

  4. Event Demonstration Overview • Analysis based on 4 main criteria: • Evidence that wildfire smoke intruded into the Las Vegas Valley (LVV) • O3 concentrations elevated • PM2.5 and CO correlate to O3 • O3 concentrations were in the 95th percentile of all readings for the previous five-year period • Demonstration included local meteorological, ambient air, and wildfire event data • Demonstration also included National Oceanic and Atmospheric Agency (NOAA) data 4

  5. Event Demonstration Elements Clark County Monitoring Network 5

  6. Event Demonstration Elements Clark County Monitoring Network 6

  7. Event Demonstration Elements Smoke Intrudes Las Vegas Valley June 29, 2005 June 30, 2005 The Las Vegas Valley was surrounded by wildfires, the smoke impact was almost simultaneous, there was a huge volume of smoke 7

  8. Event Demonstration Elements Smoke Intrudes Las Vegas Valley June 30, 2005 June 29, 2005 The 36 hr back trajectory on June 30 shows that the smoke was hanging and swirling in the valley 8

  9. Event Demonstration Elements O3 concentrations at all stations O3 concentrations on the fire days was 9 to 20 ppb higher than on non-fire days 9

  10. Event Demonstration Elements O3 concentrations at all stations 10

  11. Event Demonstration Elements Fire Days are within the 95th Percentile Not only are the concentrations within the 95th percentile, they are within the 99th percentile of all data in a 5 year period 11

  12. Event Demonstration Elements AQI and Weather Data 12

  13. Event Demonstration Elements Correlation between O3, CO and PM2.5 13

  14. DAQEM Conclusions • DAQEM was convinced all the requirements described in the EER were met: • Evidence that smoke intruded the LVV • Tables and charts show the relationship between PM2.5, CO and O3 • Weather had little influence on the concentrations • AQI for O3, PM2.5 and CO track uniformly and were elevated proportionately • Clark County took steps to protect public health • Concentrations were in the 99th percentile of all readings for the previous five-year period 14

  15. Region IX Response to Demonstration • Documentation failed to show that Clark County was impacted by smoke at the surface level • The measured O3 values were not outside of the normal magnitude seen in the county • Documentation failed to show unusually high levels of PM2.5 and CO • No data was provided which characterizes the fire events relative to specific stations • Failed to prove that high concentrations of O3 were found in forest fire plumes that were transported long distances 15

  16. Region IX Response to Demonstration Region IX did not concur with our findings and flagging of the measurements as exceptional because DAQEM failed to provide weight of evidence to support the “but for” argument Region IX made several suggestions regarding weight of evidence elements: measure VOC concentrations; measure levoglucosan concentrations; measure formaldehyde concentrations; develop a regression model… 16

  17. What is next? Ozone Characterization Study- Analyzed weather, transport and local ozone production trends for 1999 – 2003 Clark County Regional Ozone & Precursor Study(CCROPS) –Conducted saturation sampling during 2005 summer season to better characterize the role of local versus transported ozone and ozone precursors Southwest Desert/ Las Vegas Ozone Transport Study(SLOTS)- Assessed the role of pollutant transport into southern Nevada Characterization of Wildfire Smoke Impacts on Ozone Concentrations- Study the impacts and relationships of wildfire smoke on O3 concentrations in Clark County Develop Regression Model–Prediction of daily O3 concentrations Summer 2009–Addition enhanced monitoring for O3, PM2.5 and levoglucosan during wildfire events during the 2009 ozone season 17

  18. What is next? EPA Headquarters needs to define the requirements for event demonstrations Region IX needs to define a set of tools to use to evaluate packages Region IX needs to work with state/local agencies to develop what they want included in the packages and not make determinations ad hoc EPA needs to be reasonable in their requests 18

  19. Questions and Discussion 19

  20. Clark County High Wind Exceptional Events Program • Program developed as part of the Natural Events Action Plan • Program has been very successful for Clark County • Proactive approach to protecting public health • Proactive approach to minimizing high wind impacts on air quality

  21. High Wind Exceptional Event Demonstrations • Exceptional event wind speed thresholds • Meteorological forecasting program • Proactive public notification program • BACM implemented for all sources • Proactive enforcement prior to and during the event • Resources are available to stabilize sources • Compliance and enforcement activity documentation

  22. Empirically Derived Criteria for High Winds • Wind tunnel testing established: • Wind threshold velocities, sustained winds of 25 miles per hour or more, and/or wind gusts of 40 miles per hour or more are the thresholds • Velocities necessary to entrain PM10 from undisturbed native soil • Velocities necessary to entrain PM10 from disturbed soils controlled with BACM • Winds at or above thresholds overwhelm native conditions and BACM controlled activities • Selection ofwind thresholds will depend on local conditions and soils

  23. Example High Wind EventPM10 Concentration and Max Wind Gust

  24. High-Wind Event Activities Public Notification and Advisory Procedures • Notifications based on forecasted conditions • Notifications typically occur 24-36 hours in advance of predicted high winds • All permit holders receive a fax advisory • News media, schools, agencies, and interested persons receive email via list server • This year, DAQEM started using EnviroFlash notifications

  25. High-Wind Event Activities Implementation of BACM • BACM required for all significant sources of PM10: • Open areas and vacant land stabilization • Unpaved road stabilization and paving requirements • Unpaved parking lot and staging area stabilization • Construction activities best management practices • Activity specific, site specific, and soil specific • Construction activities must cease when dust cannot be effectively controlled • Regulatory program is well enforced year round • Clark County’s program has proven very effective • Winds exceeding Clark County’s high-wind thresholds do not always result in a violation day

  26. High-Wind Event Activities Enforcement Procedures • All permitted sources and vacant lands are inspected by enforcement staff on the day prior to the event • Site/facility manager warned of forecasted high winds • Enforcement action occurs where site/facility/vacant land not stabilized for high winds • During event all field enforcement staff patrol assigned areas • In extreme cases, enforcement staff may employ county contractor to stabilize problem areas

  27. High-Wind Event Activities Demonstration Package Contents • When NAAQS violation occurs and high wind criteria met: • Data flagged in AQS • Clark County justification document included: • - Description of event • - Hourly concentration and hourly sustained wind speeds • - Other meteorological data (forecast, satellite imagery, and QA NWS data) • - Summary of enforcement inspections documenting implementation of BACM and enforcement activities • - Photo documentation of local conditions • - Public notices and news media documentation • EPA concurred with 8 out of 8 DAQEM demonstration packages

  28. Non-exceptional Event Violation Days • Violation days are not considered exceptional events and justification documentation is not submitted when: • Wind speeds do not meet Clark County high wind criteria • Application of BACM cannot be documented

  29. Summary of Key Program Elements • High-wind thresholds are based on local empirical measurements that demonstrate: • Wind speeds overwhelm undisturbed native soils • Wind speeds overwhelm BACM • BACM must be applied to all significant dust sources • High wind forecasting • Proactive public notification program • Proactive source notification program • Proactive enforcement and stabilization

  30. Where Do We Go From Here? • Clark County has an effective program that is protective of public health and minimizes high-wind impacts on air quality • Clark County has two justification packages pendingsubmittal • Are additional elements required beyond our current program for approval by EPA under the Exceptional Events Rule? • Consistent guidance is needed to allow states to effectively utilize resources

  31. Discussion Where Do We Go From Here?