IMPERIAL COUNTY AIR POLLUTION CONTROL DISTRICT https://www.hikespeak.com/trails/wind-caves-trail-anza-borrego-desert/ April 11, 2018 and April 12, 2018 Exceptional Event Documentation For the Imperial County PM10 Nonattainment Area An exceedance of the National Ambient Air Quality Standard (NAAQS) for PM10 at the Brawley, Calexico, El Centro and Niland monitors in Imperial County, California on April 11, 2018 and April 12, 2018 April 11 and April 12, 2018 Exceptional Event, Imperial County Table of Contents TABLE OF CONTENTS SECTION PAGE I Introduction .................................................................................................................................. 1 I.1 Public Notification [40 CFR §50.14(c)(1)] .............................................................. 3 I.2 Initial Notification of Potential Exceptional Event (INPEE) (40 CFR §50.14 (c)(2)) ................................................................................................... 3 I.3 Public Comment Process [40 CFR §50.14(c)(3)(v)(A-C)] .................................. 4 I.4 Mitigation of Exceptional Events [40 CFR §51.930] .......................................... 4 II Conceptual Model – A narrative that describes the event causing the exceedance and a discussion of how emissions from the event led to the exceedance at the affected monitor .................................................................................... 9 II.1 Description of the event causing the exceedance ............................................ 9 II.2 How emissions from the event led to an exceedance .................................... 10 III Clear Causal Relationship – A demonstration that the event affected air quality illustrating the relationship between the event and the monitored exceedance .................................................................................................................................. 22 III.1 Summary of Forecasts and Warnings ................................................................... 32 III.2 Summary of Wind Observations ............................................................................ 32 IV Concentration to Concentration Analysis – An analyses comparing the event- influenced concentrations to concentrations at the same monitoring site at other times .............................................................................................................................. 33 V Both Not Reasonably Controllable and Not Reasonably Preventable – A demonstration that the event was both not reasonably controllable and not reasonably preventable ........................................................................................................... 42 V.1 Other PM10 Control Measures ................................................................................. 43 V.2 Wind Observations ...................................................................................................... 45 V.3 Review of Source Permitted Inspections and Public Complaints ............... 46 VI A Natural Event – A demonstration that the event was a human activity that is unlikely to recur at a particular location or was a natural event .............................. 49 VI.1 Affects Air Quality ........................................................................................................ 50 VI.2 Not Reasonably Controllable or Preventable .................................................... 50 VI.3 Natural Event ................................................................................................................. 50 i April 11 and April 12, 2018 Exceptional Event, Imperial County Table of Contents VI.4 Clear Causal Relationship .......................................................................................... 51 VI.5 Concentration to Concentration Analysis ........................................................... 51 VI.6 Conclusion ...................................................................................................................... 51 Appendix A: National Weather Service Notices ......................................................................... 52 Appendix B: Wind Data ...................................................................................................................... 314 Appendix C: Public Information and other Notices ................................................................. 343 ii April 11 and April 12, 2018 Exceptional Event, Imperial County Table of Contents LIST OF FIGURES FIGURE PAGE Figure 1-1 Imperial County ............................................................................................................. 6 Figure 1-2 Monitoring Sites in and Around Imperial County ............................................. 8 Figure 2-1 Monitoring and Meteorological Sites .................................................................. 10 Figure 2-2 Concentrations for All Sites Listed in Table 2-1 ................................................ 12 Figure 2-3 Local and Vicinity Airport Wind Speeds and Gust ........................................... 13 Figure 2-4 Wind Speeds and Gust Upstream Sites ............................................................... 14 Figure 2-5 HYSPLIT Model All Sites April 11, 2018 0700 PST ............................................ 16 Figure 2-6 HYSPLIT Model All Sites April 11, 2018 1500 PST ............................................ 17 Figure 2-7 HYSPLIT Model All Sites April 11, 2018 1900 PST ............................................ 18 Figure 2-8 HYSPLIT Model All Sites April 12, 2018 0000 PST ............................................ 19 Figure 2-9 HYSPLIT Model All Sites April 12, 2018 0700 PST ............................................ 20 Figure 3-1 Dust Over Southeastern California April 12, 2018 ........................................... 23 Figure 3-2 Visual Ramp-Up Analysis as Discussed for April 11, 2018 ............................ 24 Figure 3-3 Visual Ramp-Up Analysis as Discussed for April 12, 2018 ............................ 25 Figure 3-4 72-Hour Time Series PM10 Concentrations and Visibility .............................. 27 Figure 3-5 Imperial Valley Air Quality Index for Niland April 11, 2018 .......................... 30 Figure 3-6 Imperial Valley Air Quality Index for Brawley April 12, 2018 ........................ 31 Figure 3-7 Imperial Valley Air Quality Index for Calexico April 12, 2018 ...................... 31 iii April 11 and April 12, 2018 Exceptional Event, Imperial County Table of Contents Figure 3-8 Imperial Valley Air Quality Index for El Centro April 12, 2018 ..................... 32 Figure 4-1 Brawley Historical Comparison FRM and FEM PM10 24-Hr Avg Concentrations January 1, 2010 To April 12, 2018 .......................................... 34 Figure 4-2 Calexico Historical Comparison FRM and FEM PM10 24-Hr Avg Concentrations January 1, 2010 To April 12, 2018 .......................................... 35 Figure 4-3 El Centro Historical Comparison FRM and FEM PM10 24-Hr Avg Concentrations January 1, 2010 To April 12, 2018 .......................................... 36 Figure 4-4 Niland Historical Comparison FRM and FEM PM10 24-Hr Avg Concentrations January 1, 2010 To April 11, 2018 .......................................... 37 Figure 4-5 Brawley Seasonal Comparison FRM and FEM PM10 24-Hr Avg Concentrations April 1, 2010 To April 12, 2018 ................................................ 38 Figure 4-6 Calexico Seasonal Comparison FRM and FEM PM10 24-Hr Avg Concentrations April 1, 2010 To April 12, 2018 ................................................ 39 Figure 4-7 El Centro Seasonal Comparison FRM and FEM PM10 24-Hr Avg Concentrations April 1, 2010 To April 12, 2018 ................................................ 40 Figure 4-8 Niland Seasonal Comparison FRM and FEM PM10 24-Hr Avg Concentrations April 1, 2010 To April 11, 2018 ................................................ 41 Figure 5-1 Regulation VIII Graphic Timeline Development ................................................ 43 Figure 5-2 Permitted Sources ....................................................................................................... 47 Figure 5-3 Non-Permitted Sources ............................................................................................. 48 iv April 11 and April 12, 2018 Exceptional Event, Imperial County Table of Contents LIST OF TABLES TABLE PAGE Table 1-1 Title 40 CFR §50.14(c)(3)(iv) Checklist .................................................................... 1 Table 1-2 Procedural Checklist .................................................................................................... 2 Table 2-1 Hourly Concentrations of Particulate Matter ..................................................... 11 Table 3-1 Wind Speeds and PM10 Concentrations April 11, 2018 ................................. 28 Table 3-2 Wind Speeds and PM10 Concentrations April 12, 2018 ................................. 29 Table 5-1 San Diego Air Pollution Control District Rules .................................................. 44 Table 5-2 Mojave Desert Air Quality Management District Rules ................................. 44 Table 5-3 South Coast Air Quality Management District Rules ...................................... 45 v April 11 and April 12, 2018 Exceptional Event, Imperial County Table of Contents ACRONYM DESCRIPTIONS AOD Aerosol Optical Depth AQI Air Quality Index AQS Air Quality System BACM Best Available Control Measures BAM 1020 Beta Attenuation