IMPERIAL COUNTY AIR POLLUTION CONTROL DISTRICT. September 25, 2013 Exceptional Event Documentation For the Imperial County PM 10 Nonattainment Area

Transcription

1 IMPERIAL COUNTY AIR POLLUTION CONTROL DISTRICT September 25, 2013 Exceptional Event Documentation For the Imperial County PM 10 Nonattainment Area DRAFT FINAL REPORT November 9, 2015

2 Table of Contents TABLE OF CONTENTS SECTION PAGE I Introduction...1 I.1 Demonstration Contents...2 I.2 Requirements of the Exceptional Event Rule...2 I.2.a Public Notification that a potential event was occurring...2 I.2.b Notification to USEPA of the intent to exclude a measured violation (40 CFR (c)(2)(i))...3 I.2.c Documentation that the public comment process was followed for the event demonstration that was flagged for exclusion (40 CFR (c)(3)(v))...3 I.2.d Documentation submittal supporting an Exceptional Event Flag (40 CFR (a)(1-2))...3 I.2.e Necessary demonstration to justify an exclusion of data under (40 CFR (c)(3)(iv))...4 II September 25, 2013 Conceptual Model...5 II.1 Geographic Setting and Monitor Locations...5 II.2 Climate...9 II.3 Event Day Summary...12 III Historical Norm...20 III.1 Analysis...20 III.2 Summary...27 IV Not Reasonably Controllable or Preventable...28 IV.1 Background...28 IV.1.a Control Measures...28 IV.1.b Additional Measures...29 IV.1.c Review of Source-Permitted Inspections and Public Complaints...30 IV.2 Forecasts and Warnings...31 IV.3 Wind Observations...31 IV.4 Summary...31 V Clear Causal Relationship...33 V.1 Discussion...33 V.2 Summary...41 VI But-For-Analysis...42 VI.1 Discussion...42 VI.2 Summary...43 i

3 Table of Contents VII Conclusions...45 VII.1 Affects Air Quality...45 VII.2 Not Reasonably Controllable or Preventable...45 VII.3 Natural Event...46 VII.4 Clear Causal Relationship...46 VII.5 Historical Norm...46 VII.6 But For...46 Appendix A: Public Notification that a potential event was occurring (40 CFR 50.14(c)(1)(i))...47 Appendix B: Meteorological Data...54 Appendix C: Correlated PM 10 Concentrations and Winds...65 Appendix D: Regulation VIII Fugitive Dust Rules...70 ii

4 Table of Contents LIST OF FIGURES FIGURE PAGE Figure 2-1: Colorado Desert Area Imperial County...5 Figure 2-2: Surrounding Areas of the Salton Sea...6 Figure 2-3: Location and Topography of Imperial County...7 Figure 2-4: Deserts in California, Yuma and Mexico...7 Figure 2-5: Monitoring Sites in Imperial County...8 Figure 2-6: Sonoran Desert Region...10 Figure 2-7: Imperial County Historical Weather...11 Figure 2-8: Weather System Movement US Outlook...12 Figure 2-9: Weather System Movement California Outlook...13 Figure 2-10: Prevailing and Dominant Wind Direction...13 Figure 2-11: NEXRAD Wind Velocity on September 25, Figure 2-12: NEXRAD Weather System Intensity on September 25, Figure 2-13: Time Sequence Analysis September 25, Figure 2-14: NOAA HYSPLIT Model...18 Figure 2-15: HYSPLIT Sectional View from Figure Figure 2-16: 72 Hour PM 10 Concentrations at Various Stations on September 25, Figure 3-1 Figure 3-2 Figure 3-3 Westmorland Historic FRM 24-Hr Concentrations September 1, 2009 to December 31, Brawley Historic Comparison 24-Hr Avg & Daily September 01, 2009 to December 31, Niland Historic Comparison 24-HR Avg & Daily iii

5 Table of Contents September 01, 2009 to December 31, Figure 3-4 Figure 3-5 Figure 3-6 Figure 3-7 Figure 3-8 Figure 3-9 Figure 3-10 Figure 3-11 Figure 3-12 Figure 4-1 Figure 5-1 Brawley, Niland and Westmorland Historic Comparison 24-Hr Avg & Daily September 01, 2009 to December 31, Westmorland Seasonal Comparison 24-Hr Avg Sept 2009 to Nov Brawley Seasonal Comparison 24-Hr Avg & Daily Sept 2009 to Nov Niland Seasonal Comparison 24-Hr Avg & Daily Sept 2009 to Nov Westmorland, Brawley and Niland Seasonal Comparison 24-Hr Avg & Daily Sept 2009 to Nov Westmorland Percentile Ranking 24-Hr Avg Sept 01, 2009 to Dec 31, Brawley Percentile Ranking 24-Hr Avg & Daily Sept 01, 2009 to Dec 31, Niland Percentile Ranking 24-Hr Avg & Daily Sept 01, 2009 to Dec 31, Combined Percentile Westmorland, Brawley and Niland Sept 01, 2009 to Dec 31, Regulation VIII Graphic Timeline Development...32 Low Pressure System Moving Across California and into Imperial County...33 Figure 5-2 Deviation of Normal West to East Wind Patterns...34 Figure 5-3 Figure 5-4 Wind Speeds at Sites Through Out the Salton Sea Air Basin September 24 thru September 26, Wind Speeds at Sites Located to the South and East September 24 thru September 26, Figure 5-5 Brawley Correlation of PM 10 Concentrations & Wind Speed...37 iv

6 Table of Contents Figure 5-6 Niland Correlation of PM 10 Concentrations & Wind Speed...37 Figure 5-7 Figure 5-8 Figure 5-9 Figure Hour Time Series PM10 Concentrations & Wind Speeds Blythe Airport (KBLH) Hour Time Series PM 10 Concentrations & Wind Speeds Jacqueline Cochran Regional Airport (KTRM) Hour Time Series PM10 Concentrations & Wind Speeds Imperial County Airport (KIPL)...40 Brawley-Niland 3-Day 24-Hr PM 10 Concentrations September 24 thru September 26, Figure 6-2 Imperial County Comparison to Normals...44 v

7 Table of Contents LIST OF TABLES TABLE Table 1-1 Table 2-1 PAGE Westmorland, Brawley and Niland Concentrations of PM 10 on September 25, Monitoring Sites in Imperial County, Riverside County and Arizona September 25, Table 2-2 Wind Speeds on September 25, Table 7-1 Technical Elements Checklist...45 vi

8 Table of Contents ACRONYM DESCRIPTIONS AQI Air Quality Index AQS Air Quality System BACM Best Available Control Measures BAM 1020 Beta Attenuation Monitor Model 1020 BLM United States Bureau of Land Management BP United States Border Patrol CAA Clean Air Act CARB California Air Resources Board CMP Conservation Management Practice DCP Dust Control Plan DPR California Department of Parks and Recreation EER Exceptional Events Rule FEM Federal Equivalent Method FRM Federal Reference Method HF Historical Fluctuations HYSPLIT Hybrid Single Particle Lagrangian Integrated Trajectory Model ICAPCD Imperial County Air Pollution Control District ITCZ Inter Tropical Convergence Zone KIPL Imperial County Airport MPH Miles Per Hour MST Mountain Standard Time MXL Mexicali Airport NAAQS National Ambient Air Quality Standard NCAR National Center for Atmospheric Research NEAP Natural Events Action Plan NEXRAD Next-Generation Radar NOAA National Oceanic and Atmospheric Administration nrcp Not Reasonably Controllable or Preventable NWS National Weather Service PM 10 Particulate Matter less than 10 microns PM 2.5 Particulate Matter less than 2.5 microns PSP Palm Springs Airport PST Pacific Standard Time QA/QC Quality Assured and Quality Controlled RACM Reasonable Available Control Measure SIP State Implementation Plan SLAMS State Local Ambient Air Monitoring Station SMP Smoke Management Plan SSI Size-Selective Inlet USEPA United States Environmental Protection Agency USGS United States Geological Survey UTC Coordinated Universal Time ( WRCC Western Regional Climate Center vii

9 Introduction I Introduction On September 25, 2013, three State and Local Ambient Air Monitoring Stations (SLAMS) (AQS Site Codes , and ) located in Westmorland, Brawley, and Niland, California recorded a violation of the National Ambient Air Quality Standard (NAAQS). The Westmorland s Federal Referenced Method (FRM) Size-Selective Inlet (SSI) high volume sampler measured a (midnight to midnight) 24-hour (hr) average Particulate Matter less than 10 microns (PM 10 ) concentration of 194 µg/m 3. In addition, the Federal Equivalent Method (FEM), Beta Attenuation Monitors Model 1020 (BAM 1020) located in Brawley and Niland, California, measured a (midnight to midnight) 24-hr average concentration of µg/m 3 and µg/m 3, respectively. PM hr measurements recorded above the 150 µg/m 3 are violations of the NAAQS. The SLAMS in Westmorland, Brawley and Niland were the only stations, in Imperial County to record violations of the PM 10 NAAQS on September 25, DATE TABLE 1-1 WESTMORLAND, BRAWLEY AND NILAND CONCENTRATIONS OF PM 10 ON SEPTEMBER, 25, 2013 MONITORING SITE AQS ID POC(s) HOURS 24-HOUR CONCENTRATION ug/m 3 PM 10 NAAQS ug/m 3 09/25/2013 Westmorland /25/2013 Brawley /25/2013 Niland The Imperial County Air Pollution Control District (ICAPCD) has been submitting PM 10 data from FRM SSI instruments since 1986 into the United States Environmental Protection Agency's (USEPA) Air Quality System (AQS). Most recently, since 2013 ICAPCD has been submitting continuous PM 10 data from BAM 1020's. On September 25, 2013 the Westmorland, Brawley and Niland monitors were impacted by elevated particulate matter caused by the entrainment of fugitive windblown dust from high winds generated by a low pressure system entering Imperial County. This report demonstrates that the violations observed on September 25, 2013 were caused by a naturally occurring event which elevated particulate matter affecting air quality, was not reasonably controllable or preventable (nrcp), was in excess of normal historical fluctuations (HF) and would not have occurred "but for" the entrainment of fugitive windblown dust from outlaying deserts and mountains from the Sonoran Desert. The document further substantiates the request by the ICAPCD to flag the PM hour NAAQS violations of 194.0, and µg/m 3 as an exceptional event. This demonstration substantiates that this event meets the definition of the USEPA Regulation for the Treatment of Data Influenced by Exceptional Events (EER) 1. 1 "Treatment of Data Influenced by Exceptional Events; Final Rule", 72 FR 13560, March 22,

10 Introduction I.1 Demonstration Contents Section II - Describes the September 25, 2013 event as it occurred in California and into Imperial County, providing background information of the exceptional event and explaining how the event affected air quality. Overall, this section provides the evidence that the event was a natural event. Section III - Describes the normal historical fluctuations using data charts, summaries, and timeseries graphs which demonstrate that the elevated concentrations of PM 10 on September 25, 2013 were in excess of normal historical fluctuations. Section IV - Provides evidence that the event of September 25, 2013 was not reasonably controllable or preventable despite the full enforcement and implementation of Best Available Control Measures (BACM) Section V - Discusses and establishes the clear causal relationship between the violations at the Westmorland, Brawley and Niland stations and the natural event which occurred on September 25, This section provides evidence that the event affected air quality as a result of a natural event. Section VI - Brings together the evidence presented within this report and shows a clear causal relationship between the natural event, the violations and how BACM is overwhelmed making it nrcp concluding that the violations which occurred on September 25, 2013 would not have occurred "but for" the natural event. I.2 Requirement of the Exceptional Event Rule The above sections combined comprise the technical requirements described under the Exceptional Events Rule (EER) under 40 CFR 50.14(c)(3)(iv). However, there are additional non-technical requirements that must be met in order for the USEPA to concur with flagged air quality monitoring data. I.2.a Public Notification that a potential event was occurring The ICAPCD provided notification via the ICAPCD s webpage that winds could potentially gust in excess of 30 miles per hour (mph) potentially elevating particulate matter for several days beginning with September 23, The Desert Review, an Imperial Valley Publication serving Brawley California, similarly reported a High Wind Warning For Mountains, Deserts Wednesday Afternoon Thru Thursday Morning on September 25, Because of the potential for suspended particles and poor air quality, the ICAPCD issued a "No Burn" day in Imperial County. In addition, the ICAPCD posted the notices issued by the National Weather Service (NWS) Phoenix office warning of potential blowing dust and sand. Appendix A contains copies of notices as they were issued during the morning of September 25,

11 Introduction I.2.b Notification to USEPA of the intent to exclude a measured violation (40 CFR 50.14(c)(2)(I)) States are required under federal regulation to submit measured ambient air quality data into the AQS. AQS is the federal repository of Quality Assured and Quality Controlled (QA/QC) air ambient data used for regulatory purposes. Ambient data that is potentially influenced by an exceptional event must be appropriately flagged and initially described and submitted to USEPA according to 40 CFR 50.14(c)(2)(iii) no later than July 1 st of the calendar year following the year in which the flagged measurement occurred. The ICAPCD made two separate written requests to the California Air Resources Board (CARB) to place preliminary flags on SLAMS measured concentrations in Westmorland, Brawley and Niland. The first request dated March 17, 2014 requested an initial flag for the measurement from the PM 10 SSI Hi Volume Gravimetric sampler in Westmorland of µg/m 3. The second request, dated May 14, 2014, requested an initial flag for the measurements from the BAM 1020 monitors in Brawley and Niland of µg/m 3 and µg/m 3, respectively. A brief description was included with the initial flag of the meteorological data which indicated a potential natural event had occurred on September 25, I.2.c Documentation that the public comment process was followed for the event demonstration that was flagged for exclusion (40 CFR 50.14(c)(3)(v)) The ICAPCD posted, for a 30 day public review, a draft version of this demonstration on the ICAPCD webpage and published a notice of availability in the Imperial Valley Press on XX XX, The notice advised the general public that comments were being solicited regarding this demonstration which supports the request, by the ICAPCD, to exclude the measured concentrations of 194.0, and µg/m 3 which occurred on September 25, 2013 in Westmorland, Brawley and Niland, respectively. The final closing date for comments was XX XX, Appendix A contains a copy of the public notice affidavit along with any comments received by the ICAPCD for submittal as part of the demonstration (40 CFR 50.14(c)(3)(i)). I.2.d Documentation submittal supporting an Exceptional Event Flag (40 CFR 50.14(a)(1-2)) States that have flagged data as a result of an exceptional event and who have requested an exclusion of said flagged data are required to submit a demonstration that justifies the data exclusion to the USEPA no later than 3 years following the end of the calendar quarter in which the flagged concentration was measured or 12 months prior to the date that a regulatory decision must be made by USEPA. The ICAPCD, after the close of the comment period and after consideration of the comments will submit this demonstration along with all required elements, including received comments and responses to USEPA Region 9 in San Francisco, California. The deadline for the submittal of this demonstration is December 31,

12 Introduction I.2.e Necessary demonstration to justify an exclusion of data under (40 CFR 50.14(c)(3)(iv)) A This demonstration provides evidence that the event, as it occurred on September 25, 2013, satisfies the definition in 40 CFR 50.1(j) and (k) for an exceptional event. a The event affects air quality b The event is not reasonably controllable or preventable. c The event is caused by human activity that is unlikely to recur at a particular location or [is] a natural event. d The event is a natural event where human activity played little or no direct casual role. B C D This demonstration provides evidence that air quality was affected by the exceptional event in Imperial County. There is a clear causal relationship between the event and the measured concentrations in Westmorland, Brawley and Niland supporting that the event affected the air quality in Imperial County. This demonstration provides evidence that the measured concentration, caused by the event, is in excess of normal historical fluctuations. This demonstration provides evidence that but-for the event there would have been no exceedance (violation). [Intentionally left blank] 4

13 Conceptual Model II September 25, 2013 Conceptual Model This section provides a summary description of the meteorological and air quality conditions under which the September 25, 2013 event unfolded in Imperial County. The subsection elements include» A description and map of the geographic setting of the air quality and meteorological monitors» A description of Imperial County s climate» An overall description of meteorological and air quality conditions on the event day. II.1 Geographic Setting and Monitor Locations According to the United States Census Bureau, Imperial County has a total area of 4,482 square miles of which 4,177 square miles is land and 305 square miles is water. Much of Imperial County is below sea level and is part of the Colorado Desert an extension of the larger Sonoran Desert (Figure 2-1). FIGURE 2-1 COLORADO DESERT AREA IMPERIAL COUNTY Fig 2-1: 1997 California Environmental Resources Evaluation System. According to the United States Geological Survey (USGS) Western Ecological Research Center the Colorado Desert bioregion is part of the bigger Sonoran Desert Bioregion which includes the Colorado Desert and Upper Sonoran Desert sections of California and Arizona, and a portion of the Chihuahuan Basin and Range Section in Arizona and New Mexico (Forest Service 1994). A notable feature in Imperial County is the Salton Sea which is at 235 feet below sea level. The Chocolate Mountains are located east of the Salton Sea and extend in a northwest-southeast direction for approximately 60 miles (Figure 2-2). In this region, the geology is dominated by 5

14 Conceptual Model the transition of the tectonic plate boundary from rift to fault. The southernmost strands of the San Andreas Fault connect the northern-most extensions of the East Pacific rise. Consequently, the region is subject to earthquakes and the crust is being stretched, resulting in a sinking of the terrain over time. FIGURE 2-2 SURROUNDING AREAS OF THE SALTON SEA Fig 2-2: Image courtesy of the Image Science and Analysis Laboratory NASA Johnson Space Center, Houston Texas All of the seven incorporated cities are surrounded by agricultural fields to the north, east, west and south (Figure 2-3). Together, the incorporated cities and agricultural fields make what is known as the Imperial Valley. Surrounding the Imperial Valley are desert areas found on the eastern and western portions of Imperial County. [Intentionally left blank] 6

15 Conceptual Model FIGURE 2-3 LOCATION AND TOPOGRAPHY OF IMPERIAL COUNTY Fig 2-3: Depicts the eight incorporated cities within Imperial Valley and the City of Mexicali, Mexico Furthermore, the deserts located to the east and west of Imperial County expand to the southeast, and southwest into Mexico (Sonoran Desert) (Figure 2-4). Combined, these deserts are sources of dust emissions which impact the Imperial County during high wind events. FIGURE 2-4 DESERTS IN CALIFORNIA, YUMA AND MEXICO Fig 2-4: Depicts the Sonoran Desert as it extends from Mexico into Imperial County. The air quality and meteorological monitoring stations used in this demonstration are shown in Figure 2-5. SLAMS in Imperial County are located in Calexico, El Centro, Westmorland, and Niland. Each station measures air quality and meteorological data; the station located in 7

16 Conceptual Model Brawley only measures air quality and no meteorological data. Other air monitoring stations with air quality and meteorological data used for this demonstration include stations in Riverside County and Arizona (Figure 2-5 and Table 2-1). As mentioned above, the PM 10 violation on September 25, 2013, occurred at the Westmorland, Brawley and Niland stations. The Westmorland, Brawley and Niland stations are regarded as the northern monitoring sites within the Imperial County air monitoring network. In order to properly analyze the contributions of meteorological conditions occurring on September 25, 2013, other meteorological sites used in this demonstration include the Palm Springs Airport (PSP), the Naval Air Facility (NJK), Imperial County Airport (KIPL), and when available the Mexicali Airport (MXL) (Figure 2-5). FIGURE 2-5 MONITORING SITES IN IMPERIAL COUNTY Fig 2-5: Depicts a select group of meteorological and PM 10 monitoring sites in Imperial County, eastern Riverside County and Mexicali. The image exemplifies the regional area impacted by the exceptional event which occurred on September 25,

17 Conceptual Model Monitor Site Name Operator* TABLE 2-1 MONITORING SITES IN IMPERIAL COUNTY, RIVERSIDE COUNTY AND ARIZONA SEPTEMBER 25, 2013 Monitor Type AQS ID AQS PARAMETER CODE ARB Site Number Elevation (meters) 24-hr PM10 (ug/m 3 ) Avg 1-hr PM10 (ug/m 3 ) Max Time of Max Reading (PDT) Max Wind Gust (mph) Time of Max Wind Gust IMPERIAL COUNTY Bombay Beach Brawley- Main Street #2 Hi-Vol Gravimetric :00 (81102) BAM : :00 Calexico- Ethel Street El Centro-9th Street Naval Test Base Niland- English Road IID TEOM N/A PM10_LHR : ICAPCD CARB ICAPCD Hi-Vol Gravimetric Hi-Vol Gravimetric (81102) :00 (81102) :00 IID TEOM N/A PM10_LHR , : :00 ICAPCD Salton City IID TEOM N/A PM10_LHR :00 Sonny Bono IID TEOM N/A PM10_LHR : :00 Westmorland IID Hi-Vol Gravimetric Hi-Vol Gravimetric :00 (81102) BAM : : (81102) :00 RIVERSIDE COUNTY Palm Springs Fire Station SCAQMD Indio (Jackson St.) SCAQMD TEOM TEOM (81102) : :00 (81102) : :00 RIVERSIDE COUNTY - INDIAN TRIBAL LAND Torres - TM TEOM Martinez CARB = California Air Resources Board IID = Imperial Irrigation District APCD = Air Pollution Control District, Imperial County SCAQMD = South Coast Air Management Quality District TM = Torres-Martinez Tribal Environmental Department ADEQ =Arizona Department of Environmental Quality LHR=Local Hourly (81102) : II.2 Climate As mentioned above, Imperial County is part of the Colorado Desert, which is a subdivision of the larger Sonoran Desert (Figure 2-6) encompassing approximately 7 million acres (28,000 km 2 ). The desert area encompasses Imperial County and includes parts of San Diego County, Riverside County, and a small part of San Bernardino County. 9

18 Conceptual Model FIGURE 2-6 SONORAN DESERT REGION Fig 2-6: Depicts the magnitude of the region known as the Sonoran Desert The majority of the Colorado Desert lies at a relatively low elevation, below 1,000 feet (300 m), with the lowest point of the desert floor at 275 feet (84 m) below sea level at the Salton Sea. Although the highest peaks of the Peninsular Range reach elevations of nearly 10,000 feet (3,000 m), most of the region's mountains do not exceed 3,000 feet (910 m). In the Colorado Desert (Imperial County), the geology is dominated by the transition of the tectonic plate boundary from rift to fault. The southernmost strands of the San Andreas Fault connect to the northern-most extensions of the East Pacific Rise. Consequently, the region is subject to earthquakes, and the crust is being stretched, resulting in a sinking of the terrain over time. The Colorado Desert's climate distinguishes it from other deserts. The region experiences greater summer daytime temperatures than higher-elevation deserts and almost never experiences frost. In addition, the Colorado Desert experiences two rainy seasons per year (in the winter and late summer), especially toward the southern portion of the region; the more northerly Mojave Desert usually has only winter rains. The west coast Peninsular Ranges, or other west ranges, of Southern California northern Baja California, block most eastern Pacific coastal air and rains, producing an arid climate. Other short or longer-term weather events can move in from the Gulf of California to the south, and 10

19 Conceptual Model are often active in the summer monsoons. These include remnants of Pacific hurricanes, storms from the southern tropical jet stream, and the northern Inter Tropical Convergence Zone (ITCZ). The arid nature of the region is demonstrated when historic annual average precipitation levels in Imperial County average 3.11 (Figure 2-7). During the 12 month period prior to September 25, 2013, Imperial County recorded total average precipitation levels at 1.98 inches, well below the historical average. Six months prior to September 25, 2013 precipitation was 0.19 inches average. FIGURE 2-7 IMPERIAL COUNTY HISTORICAL WEATHER Temperature (degrees F) Precipitation (inches) Precipitation Max Temp Min Temp Fig 2-7: Historic Brawley weather. In the 12 months prior to September 25, 2013, the region received 1.98 inches of precipitation (dotted line), well below the historical annual average of MET data courtesy of Weather Underground, California Observed Climate Normals, and Western Regional Climate Center (WRCC). While windblown dust events in Imperial County during the summer monsoon season are often due to outflow winds from thunderstorms, windblown dust events in the fall, winter, and spring are usually due to strong winds associated with low-pressure systems and cold fronts moving southeast across California. These winds are the result of strong surface pressure gradients between the approaching low-pressure system, accompanying cold front, and higher pressure ahead of it. As the low-pressure system and cold front approaches and passes, gusty southwesterly winds typically shift to northwesterly. The strong winds can loft dust into the air and transport it over long distances, especially if soils in the region are dry. [Intentionally left blank] 11

20 Conceptual Model II.3 Event Day Summary The exceptional event for September 25, 2013, occurred over a span of several hours throughout the day due to a meteorological event that was not preventable. A strong low pressure system, driven by a weather system that was predominantly west, produced excessive winds which lasted several hours in the Imperial Valley region during the late-morning through evening hours of September 25, 2013 (Figure 2-8, 2-9 and 2-10). FIGURE 2-8 WEATHER SYSTEM MOVEMENT US OUTLOOK Fig 2-8: The Northern Hemisphere graphical depiction of the issued weather forecast for Wednesday September 25, 2013 by the National Weather Service. The low pressure systems with accompanying wind directions are clearly depicted. Courtesy of the NWS Weather Prediction Center [Intentionally left blank] 12

21 Conceptual Model FIGURE 2-9 WEATHER SYSTEM MOVEMENT CALIFORNIA OUTLOOK Fig 2-9: The Satellite surface composite map (14:30 PST) on Wednesday September 25, 2013 showing the frontal system that impacted Imperial County. The large system extended over the entire Southwest, bringing steep pressure gradients and strong winds. Image courtesy of Unisys and the National Center for Atmospheric Research (NCAR). FIGURE 2-10 PREVAILING AND DOMINANT WIND DIRECTION Fig 2-10: Prevailing and dominant wind direction as it occurred on September 25, Strong west winds prevailed with west-southwest mixing occurring late afternoon into the evening hours on September 25,

22 Conceptual Model Surface weather maps, for September 25, 2013 revealed a strong low pressure system traveling west (onshore flow) resulting in sustained winds outside the normal historic average for the Westmorland, Brawley and Niland monitors. The weather system prompted the The Desert Review to publish a High Wind Warning For Mountains, Deserts Wednesday Afternoon Thru Thursday Morning, on September 25, 2013, found in Appendix A. The article quotes the NWS, advising of increased afternoon gusts up to 30 mph with the strongest winds expected within the southwestern area of Imperial County where sustained winds were expected to create blowing dust. As the weather system moved into Imperial County, strong mixing winds did in fact occur. Figure 2-11 and 2-12 illustrates the wind velocity and the mixing nature of the winds created by the intensity of the weather system, reaching over 50 mph, as it moved to and from Imperial County. FIGURE 2-11 NEXRAD WIND VELOCITY ON SEPTEMBER 25, 2013 Fig 2-11: NEXRAD base velocity derived from KYUX Yuma, Arizona on September 25, 2013 which confirms the mixing direction of the weather system as it passed through Imperial County. The base velocity depiction confirms the elevated wind speeds and mixing direction found on Table [Intentionally left blank] 2 NEXRAD or Nexrad (Next-Generation Radar) is a network of 160 high-resolution S-band Doppler weather radars operated by the National Weather Service (NWS), an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United States Department of Commerce, the Federal Aviation Administration (FAA) within the Department of Transportation, and the U.S. Air Force within the Department of Defense. Its technical name is WSR-88D, which stands for Weather Surveillance Radar, 1988, Doppler. NEXRAD detects precipitation and atmospheric movement or wind. It returns data which when processed can be displayed in a mosaic map which shows patterns of precipitation and its movement. The radar system operates in two basic modes, selectable by the operator a slow-scanning clear-air mode for analyzing air movements when there is little or no activity in the area, and a precipitation mode, with a faster scan for tracking active weather. 14

23 Conceptual Model FIGURE 2-12 NEXRAD WEATHER SYSTEM INTENSITY ON SEPTEMBER 25, 2013 Fig 2-12: NEXRAD base reflectivity derived from KYUX Yuma, Arizona on September 25, 2013 which confirms the intensity of the weather system as it passed through Imperial County. The base reflectivity depiction substantiates the elevated wind speeds and mixing of the wind direction. The chain of events, as it occurred on September 25, 2013 is visually demonstrated in Figure Meteorological data reveals that during the early morning hours of September 25, variable wind directions existed in Imperial County with Niland demonstrating greater variability. A dominant westerly direction was reported by the Imperial County Airport (KIPL) for much of the day while the Niland station reported a general southerly direction during the early hours of September 25, However, by the afternoon and evening hours all meteorological stations in Imperial County were reporting consistent westerly winds. As the strong low pressure weather system moves into Imperial County, the accompanying dominant west wind begins increasing in speed by 10 AM with gusts above 15 mph. By 5 PM the westerly winds dominate with wind speed in excess of 20 mph and wind gusts near 32 mph. Wind speeds subside nominally after 11 PM but continue onto September 26, [Intentionally left blank] 15

24 Conceptual Model FIGURE 2-13 TIME SEQUENCE ANALYSIS SEPTEMBER 25, 2013 Fig 2-13: Time sequence analysis for the Westmorland, Brawley and Niland stations identifying the wind direction with associated increase in wind speed as the weather system moved into the region on September 25, Several stations, including the Palm Springs Airport (PSP), the Jacqueline Cochran Regional Airport (KRTM) in Riverside County and the Naval Air Facility (NJK) in Imperial County all recorded wind gusts over 30 mph for a number of hours. For a more detailed analysis of wind direction and wind speed as it impacted specific sites see Appendix B. [Intentionally left blank] 16

25 Conceptual Model Station Monitor Airport Met Data TABLE 2-2 WIND SPEEDS ON SEPTEMBER 25, 2013 Maximum Wind Speed (WS) (mph) Wind Direction during Max WS (degrees) Time of Max Wind Speed (PDT) 24 hr Maximum Wind Gust (WG) (mph) Time of Max WG (PDT) PM 10 correlated to time of Max Wind Speed Hourly Maximum Observed PM 10 Blythe (KBLH) : : Palm Springs Fire Station/(PSP)* : : Calexico (Ethel St) : El Centro : :51 - Niland : El Centro Naval Air Facility (KNJK) : : Westmorland**** : :53-194** Imperial/(KIPL) : : Indio (Jackson St)/(PSP)* : : Jacqueline Cochran Regional Airport (KRTM) : : * PS Fire Station, Indio-Jackson use Palm Springs International Airport (PSP) MET Data ** Calexico no hourly data (FRM) concentration ***El Centro no hourly data (FRM) concentration ****Westmorland Station was not collecting MET Data, use Imperial Airport MET Data. No hourly data (FRM) concentration The back trajectory National Oceanic and Atmospheric Administration (NOAA) Air Resources Laboratory HYSPLIT model, 3 Figure 2-14, indicates an impact to the Westmorland, Brawley and Niland monitors by as early as 8:00 AM when dust particles from largely barren desert soils to the west southwest were entrained during these strong winds, impacting PM 10 monitors throughout Imperial County (Tables 2-1 and 2-2). Figure 2-16 illustrates the elevated levels of PM 10 concentrations measured in Riverside, Imperial and Yuma Counties. The elevated concentrations were significantly higher in Imperial County which supports the mixing nature of the winds created by the weather system that impact Imperial County. The unique nature of this meteorological event resulted in steep but short-lived increases in PM 10 concentrations in Imperial County, heavily impacting the Brawley, Niland and Westmorland monitoring sites (Figure 2-16). The entrained dust particles resulted in a 24-hr FRM PM 10 concentration (midnight to midnight) of 194 µg/m 3 in Westmorland. In addition, the FEM PM 10 Monitors located in Brawley and Niland measured a (midnight to midnight) 24-hr average concentration of µg/m 3 and 180 µg/m 3, respectively. Best Available Control Measures (BACM) was overwhelmed by the suddenness and intensity of the meteorological event. Although the (ug/m3) 3 The Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) is a computer model that is a complete system for computing simple air parcel trajectories to complex dispersion and deposition simulations. It is currently used to compute air parcel trajectories and dispersion or deposition of atmospheric pollutants. One popular use of HYSPLIT is to establish whether high levels of air pollution at one location are caused by transport of air contaminants from another location. HYSPLIT's back trajectories, combined with satellite images (for example, from NASA's MODIS satellites), can provide insight into whether high air pollution levels are caused by local air pollution sources or whether an air pollution problem was blown in on the wind The initial development was a result of a joint effort between NOAA and Australia's Bureau of Meteorology. 17

26 Conceptual Model Westmorland, Brawley and Niland sites saw dramatic increases in PM 10 concentrations, the violations were concurrent to a sharp spike in winds during the exceptional event. Although the winds nominally decline the following day concentrations, although elevated, above normals it is not enough to cause a violation. FIGURE 2-14 NOAA HYSPLIT MODEL Fig 2-14: Twenty four hour back trajectory displaying the wind direction at the 50, 100, and 1000 meter height during September 25, 2013 ending 0700 Coordinated Universal Time (UTC) 4 (00:00 PDT). As the weather system moved over the Sonoran Desert it entrained particulate matter which impacted the Westmorland, Brawley and Niland monitors. Dynamically generated through the National Oceanic and Atmospheric Administration (NOAA) Air Resources Laboratory HYSPLIT model. [Intentionally left blank] 4 The official abbreviation for Coordinated Universal Time is UTC. It came about as a compromise between English and French speakers. Coordinated Universal Time in English would normally be abbreviated CUT. Temps Universel Coordonné in French would normally be abbreviated TUC. 18

27 Conceptual Model FIGURE 2-15 HYSPLIT SECTIONAL VIEW FROM FIGURE 2-14 Fig 2-15: Sectional view of the 24-hour back trajectory supporting the wind direction at the 50, 100, and 1000 meter height during September 25, 2015 ending 19:00 Coordinated Universal Time (12:00 PDT) (Figure 2-14) FIGURE HOUR PM 10 CONCENTRATIONS AT VARIOUS STATIONS ON SEPTEMBER 25, PM 10 Concentration µg/m :00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 09/24/ /25/ /26/2013 Brawley Niland Westmorland (Daily) Indio (Jackson St) Palm Springs Fire Station Torres-Martinez Reservation Yuma Supersite Calexico-Ethel St (Daily) El Centro-9th St (Daily) Fig 2-16: is the graphical representation of the 72 hour relative PM 10 concentrations at various monitoring locations throughout Imperial County, Riverside and Yuma counties. The graph clearly illustrates the elevation of PM 10 concentrations on September 25, 2013 at Imperial County sites that were impacted by the weather system and accompanying winds. In addition, note that concentrations for those sites in Imperial County remain slightly elevated on September 26,

28 Historical Norm III III.1 Historical Norm Analysis While naturally occurring high wind events may occur seasonally and at times frequently and qualify for exclusion under the EER, historical fluctuations of the particulate concentrations and associated winds provide insight into the frequency of events within an identified area. The following time series plots illustrate that PM 10 concentrations measured at the Westmorland, Brawley and Niland monitors on September 25, 2013, were unusual and in excess of normal historical fluctuations. The analysis, also, provides convincing evidence that the event affected air quality. Figures 3-1 through 3-4 show the time series of available FRM and BAM 24-hr PM 10 concentrations at the Westmorland, Brawley and Niland monitors for the five year period of 2009 through 2013, for a total of 3,930 credible sample run days. Note that prior to 2013, the BAM data was not considered FEM and was not submitted to AQS. In order to properly establish the intensity of the event, as it occurred on September 25, 2013, 24 hour averaged PM 10 concentrations were compiled and plotted as a time series, September 1, 2009 to December 21, 2013, to provide a historical perspective of PM 10 concentrations. FIGURE 3-1 WESTMORLAND HISTORIC FRM 24-HR AVG CONCENTRATIONS SEPT 01, 2009 TO DEC 31, 2013 PM 10 Concentration µg/m /25/ Fig 3-1: A historic comparison of PM 10 concentrations demonstrates the September 25, 2013 measured concentration of 194 µg/m 3 from the Westmorland FRM SSI high volume sampler was outside the recorded normal. [Intentionally left blank] 20

29 Historical Norm FIGURE 3-2 BRAWLEY HISTORIC COMPARISON 24-HR AVG & DAILY SEPT 01, 2009 TO DEC 31, 2013 PM 10 Concentration µg/m /25/ FEM 24 Hr Daily FRM 24 Hr (1-6) Fig 3-2: A historic comparison of PM 10 concentrations demonstrates the September 25, 2013 measured concentration of µg/m 3 from the Brawley FEM BAM 1020 monitor was outside the recorded normal FIGURE 3-3 NILAND HISTORIC COMPARISON 24-HR AVG & DAILY SEPT 01, 2009 TO DEC 31, /25/ PM 10 Concentration µµg/m FEM 24 Hr Daily FRM 24 Hr (1-6) Fig 3-3: A historic comparison of PM 10 concentrations demonstrates the September 25, 2013 measured concentration of 180 µg/m 3 from the Niland FEM BAM 1020 monitor was outside the recorded normal 21

30 Historical Norm FIGURE 3-4 BRAWLEY, NILAND AND WESTMORLAND HISTORIC COMPARISON 24-HR AVG & DAILY SEPT 01, 2009 TO DEC 31, PM 10 Concentration µg/m Brawley (24hr Avg) Niland (24hr Avg) Westmorland (Daily) Fig 3-4: The historic combined comparison of PM 10 concentrations for Brawley, Niland and Westmorland demonstrates the September 25, 2013 measured concentrations of µg/m 3, 180 µg/m 3, and 194 µg/m 3, respectively, were outside the recorded normal The time series, Figures 3-1 thru Figure 3-4 for Westmorland, Brawley and Niland, includes 3,930 credible samples, measured by either FRM or FEM monitors, between September 1, 2009 and December 31, Overall, the time series illustrates there were six violations measured by FRM samplers, 20 FEM violations and 3 measured violations by both FRM and FEM samplers not including September 25, Of the 30 total violations only two were recorded during the 1 st quarter (Jan thru Mar). Seven violations were measured during the 2 nd quarter (Apr thru Jun). Eleven (11) violations were measured during the 3 rd quarter (Jul thru Sep) and finally ten (10) violations were measured during the 4 th quarter (Oct thru Dec). As mentioned above FEM BAM data was not considered regulatory from 2010 to [Intentionally left blank] 22

31 Historical Norm FIGURE 3-5 WESTMORLAND SEASONAL COMPARISON 24-HR AVG SEPT 2009 TO NOV /25/ PM 10 Concentration µg/m Fig 3-5: The seasonal historic comparison of PM 10 concentrations for Westmorland for the 3 rd quarter months, September thru November, for the years 2009 through 2013 supports the conclusion that the September 25, 2013 measured violation as measured at the Westmorland station was outside the normal historical norm FIGURE 3-6 BRAWLEY SEASONAL COMPARISON 24-HR AVG & DAILY SEPT 2009 TO NOV 2013 PM 10 Concentration µg/m /25/ Fig 3-6: The seasonal historic comparison of PM 10 concentrations for Brawley for the 3 rd 23

32 Historical Norm quarter months, September thru November, for the years 2009 through 2013 supports the conclusion that the September 25, 2013 measured violation as measured at the Brawley station was outside the normal historical norm. 24

33 Historical Norm FIGURE 3-7 NILAND SEASONAL COMPARISON 24-HR AVG & DAILY SEPT 2009 TO NOV PM 10 Concentration ug/m /25/ Fig 3-7: The seasonal historic comparison of PM 10 concentrations for Niland for the 3 rd quarter months, September thru November, for the years 2009 through 2013 supports the conclusion that the September 25, 2013 measured violation as measured at the Niland station was outside the normal historical norm FIGURE 3-8 WESTMORLAND, BRAWLEY AND NILAND SEASONAL COMPARISON 24-HR AVG & DAILY SEPT 2009 TO NOV Brw BAM Nil BAM Brw FRM Nil FRM West FRM Fig 3-8: The seasonal historic comparison of PM 10 concentrations for Westmorland, Brawley and Niland for the 3 rd quarter months, September thru November, for the years 2009 through 2013 supports the conclusion that the September 25, 2013 measured violation as measured at the Niland station was outside the normal historical norm. 25

34 Historical Norm FIGURE 3-9 WESTMORLAND PERCENTILE RANKING 24-HR AVG SEPT 01, 2009 TO DEC 31, 2013 Number of Days Percentile 194 µ/m 3 PM 10 Concentration µ/m 3 Fig 3-9: FRM 24-hr PM 10 concentrations at the Westmorland monitoring site demonstrates the September 25, 2013 event was in excess of the 99 th percentile FIGURE 3-10 BRAWLEY PERCENTILE RANKING 24-HR AVG & DAILY SEPT 01, 2009 TO DEC 31, 2013 Number of Days Percentile µ/m 3 PM 10 Concentration µ/m3 Fig 3-10: Like the Westmorland monitoring site the 24-hr average PM 10 concentrations at the Brawley monitoring site demonstrates the September 25, 2013 event was in excess of the 99 th percentile [Intentionally left blank] 26

35 Historical Norm FIGURE 3-11 NILAND PERCENTILE RANKING 24-HR AVG & DAILY SEPT 01, 2009 TO DEC 31, 2013 Number of days µ/m 3 PM 10 Concentration µ/m 3 Fig 3-11: The 24-hr average PM 10 concentrations at the Niland monitoring site, similarly, demonstrates the September 25, 2013 event was in excess of the 99 th percentile FIGURE 3-12 COMBINED PERCENTILE WESTMORLAND, BRAWLEY AND NILAND SEPT 01, 2009 TO DEC 31, 2013 Number of Days Brw µ/m 3 Nil Wes 180 µ/m µ/m 3 PM 10 Concentrations µ/m 3 Fig 3-12: The combined Daily and 24-hr average PM 10 concentrations at the Westmorland, Brawley and Niland similarly, demonstrates that the September 25, 2013 event was in excess of the 99 th percentile [Intentionally left blank] 27

36 Historical Norm For the combined FRM and FEM annual 2009 thru 2013 Westmorland, Brawley and Niland dataset, the FRM concentration of 194 µg/m 3 and the FEM concentrations of µg/m 3 and 180 µg/m 3 are all above the 99 th percentile ranking individually and combined. Looking at the annual time series concentrations, the seasonal time series concentrations and the percentile ranking the September 25, 2013 measured violations of 194 µg/m 3, µg/m 3 and 180 µg/m 3 are clearly in excess of normal historical fluctuations with seasonal violations of the NAAQS not occurring frequently. III.2 Summary The information provided, above, by the time series plot, seasonal time series plot and the percentile ranking illustrate that the PM 10 concentrations and excess wind speeds observed on September 25, 2013 occur infrequently. When comparing the measured PM 10 levels on September 25, 2013 and following USEPA EER guidance, this demonstration provides supporting evidence that the measured violations measured at the Westmorland, Brawley and Niland sites were outside the normal historical fluctuations. This historical concentration data and the demonstration found under the clear casual relationship supports that the measured violations on September 25, 2013 were an exceptional event and that it affected air quality. [Intentionally left blank] 28

37 Not Reasonably Controllable or Preventable IV IV.1 Not Reasonably Controllable or Preventable Background Inhalable particulate matter (PM 10 ) contributes to effects that are harmful to human health and the environment, including premature mortality, aggravation of respiratory and cardiovascular disease, decreased lung function, visibility impairment, and damage to vegetation and ecosystems. Upon enactment of the 1990 Clean Air Act (CAA) amendments, Imperial County was classified as moderate nonattainment for the PM 10 NAAQS under CAA sections 107(d)(4)(B) and 188(a). By November 15, 1991, such areas were required to develop and submit State Implementation Plan (SIP) revisions providing for, among other things, implementation of reasonably available control measures (RACM). Partly to address the RACM requirement, ICAPCD adopted local Regulation VIII rules to control PM 10 from sources of fugitive dust on October 10, 1994, and revised them on November 25, USEPA did not act on these versions of the rules with respect to the federally enforceable SIP. On August 11, 2004, USEPA reclassified Imperial County as a serious nonattainment area for PM 10. As a result, CAA section 189(b)(1)(B) required all BACM to be implemented in the area within four years of the effective date of the reclassification, i.e., by September 10, On November 8, 2005, partly to address the BACM requirement, ICAPCD revised the Regulation VIII rules to strengthen fugitive dust requirements. On July 8, 2010, USEPA finalized a limited approval of the 2005 version of Regulation VIII, finding that the seven Regulation VIII rules largely fulfilled the relevant CAA requirements. Simultaneously, USEPA also finalized a limited disapproval of several of the rules, identifying specific deficiencies that needed to be addressed to fully demonstrate compliance with CAA requirements regarding BACM and enforceability. In September 2010, ICAPCD and the California Department of Parks and Recreation (DPR) filed petitions with the Ninth Circuit Federal Court of Appeals for review of USEPA s limited disapproval of the rules. After hearing oral argument on February 15, 2012, the Ninth Circuit directed the parties to consider mediation before rendering a decision on the litigation. On July 27, 2012, ICAPCD, DPR and USEPA reached agreement on a resolution to the dispute which included a set of specific revisions to Regulation VIII. These revisions are reflected in the version of Regulation VIII adopted by ICAPCD on October 16, 2012 and approved by USEPA April 22, Since 2006 ICAPCD had implemented regulatory measures to control emissions from fugitive dust sources and open burning in Imperial County IV.1.a Control Measures A brief summary of Regulation VIII which is comprised of seven fugitive dust rules is found below. The complete set of rules can be found in Attachment D. 29

38 Not Reasonably Controllable or Preventable ICAPCD s Regulation VIII consists of seven interrelated rules designed to limit emissions of PM 10 from anthropogenic fugitive dust sources in Imperial County. Rule 800, General Requirements for Control of Fine Particulate Matter, provides definitions, a compliance schedule, exemptions and other requirements generally applicable to all seven rules. It requires the United States Bureau of Land Management (BLM), United States Border Patrol (BP) and DPR to submit dust control plans (DCP) to mitigate fugitive dust from areas and/or activities under their control. Appendices A and B describe methods for determining compliance with opacity and surface stabilization requirements in Rules 801 through 806. Rule 801, Construction and Earthmoving Activities, establishes a 20% opacity limit and control requirements for construction and earthmoving activities. Affected sources must submit a DCP and comply with other portions of Regulation VIII regarding bulk materials, carry-out and trackout, and paved and unpaved roads. The rule exempts single family homes and waives the 20% opacity limit in winds over 25 mph under certain conditions. Rule 802, Bulk Materials, establishes a 20% opacity limit and other requirements to control dust from bulk material handling, storage, transport and hauling. Rule 803, Carry-Out and Track-Out, establishes requirements to prevent and clean-up mud and dirt transported onto paved roads from unpaved roads and areas. Rule 804, Open Areas, establishes a 20% opacity limit and requires land owners to prevent vehicular trespass and stabilize disturbed soil on open areas larger than 0.5 acres in urban areas, and larger than three acres in rural areas. Agricultural operations are exempted. Rule 805, Paved and Unpaved Roads, establishes a 20% opacity limit and control requirements for unpaved haul and access roads, canal roads and traffic areas that meet certain size or traffic thresholds. It also prohibits construction of new unpaved roads in certain circumstances. Singlefamily residences and agricultural operations are exempted. Rule 806, Conservation Management Practices, requires agricultural operation sites greater than 40 acres to implement at least one conservation management practice (CMP) for each of several activities that often generate dust at agricultural operations. In addition, agricultural operation sites must prepare a CMP plan describing how they comply with Rule 806, and must make the CMP plan available to the ICAPCD upon request. IV.1.b Additional Measures Imperial County Natural Events Action Plan (NEAP) On August 2005, the ICAPCD adopted a NEAP for the Imperial County, as was required under the former USEPA Natural Events Policy, to address PM 10 events by: 30

39 Not Reasonably Controllable or Preventable Protecting public health; Educating the public about high wind events; Mitigating health impacts on the community during future events; and Identifying and implementing BACM measures for anthropogenic sources of windblown dust. Smoke Management Plan (SMP) Summary There are 35 Air Pollution Control Districts or Air Quality Management Districts in California which are required to implement a district-wide smoke management program. The regulatory basis for California s Smoke Management Program, codified under Title 17 of the California Code of Regulations is the Smoke Management Guidelines for Agricultural and Prescribed Burning (Guidelines). California s 1987 Guidelines were revised to improve interagency coordination, avoid smoke episodes, and provide continued public safety while providing adequate opportunity for necessary open burning. The revisions to the 1987 Guidelines were approved March 14, All air districts, with the exception of the San Joaquin Valley Air Pollution Control District (SJAPCD) were required to update their existing rules and Smoke Management Plans to conform to the most recent update to the Guidelines. Section of Title 17 specifies the special requirements for open burning in agricultural operations, the growing of crops and the raising of fowl or animals. This section specifically requires the ICAPCD to have rules and regulations that require permits that contain requirements that minimize smoke impacts from agricultural burning. On a daily basis, the ICAPCD reviews hourly surface meteorological reports from various airport agencies, the NWS, State fire agencies and CARB to help determine whether the day is a burn day. Using a four quadrant map of Imperial County allowed burns are allocated in such a manner as to assure minimal to no smoke impacts safeguarding the public health. Finally, all permit holders are required to notice and advise members of the public of a potential burn. This noticing requirement is known as the Good Neighbor Policy. On September 25, 2013 the ICAPCD declared a no burn day due to high winds. No complaints were filed for agricultural burning on September 25, IV.1.c Review of Source-Permitted Inspections and Public Complaints A query of the ICAPCD permit database was compiled and reviewed for active permitted sources throughout Imperial County and specifically around Westmorland, Brawley and Niland during the time of the September 25, 2013 PM 10 violation. An evaluation of all inspection reports, air quality complaints, compliance reports, and other documentation indicate no evidence of unusual anthropogenic-based PM 10 emissions. September 25, 2013 was officially designated as a No burn day. No complaints were filed on September 25, 2013 related to agricultural or waste burning or fugitive dust complaints. 31

40 Not Reasonably Controllable or Preventable IV.2 Forecasts and Warnings Wind and dust advisories, were issued by ICAPCD and the NWS. The web based advisory by the ICAPCD identified potential elevated wind for September 25, 2013 on September 23, Be Advised: High wind levels have the potential to suspend particulate matter into the air. High levels of PM10 may pose an impact to public health. It is recommended that active children and adults, and people with respiratory disease, such as asthma, limit their outdoor activities". The NWS issued a Zone Forecast for Imperial County, CA on Wednesday, September 25, 2013, identifying the potential for wind speeds between 15 and 25 mph, wind gusts of up to 35 mph. In addition, as mentioned above, the The Desert Review published a High Wind Warning For Mountains, Deserts Wednesday Afternoon Thru Thursday Morning, on September 25, 2013, found in Appendix A. The article quotes the NWS, as advising of increased afternoon gusts up to 30 mph with the strongest winds expected within in the gap passes within the far southwestern area of Imperial County where sustained winds were expected to create blowing dust. IV.3 Wind Observations Wind data during the event were available from the Palm Springs Airport (PSP) and the Jacqueline Cochran Regional Airport (KRTM) in Riverside County, the Naval Air Facility (NJK), and the Imperial County Airport (KIPL), which recorded wind gusts over 30 mph. As mentioned above, from 13:00 to 23:00 PDT, the Imperial Airport (KIPL) measured sustained wind gusts exceeding 25 mph as well as measuring sustained wind speeds of up to 25 mph Table 2-2. In addition, according to the Quality Controlled Local Climatological Data (QCLCD) reports for the Naval Air Facility (NJK) and the Blythe Airport (KBLH) wind speed measurements over 20 mph begin as early as 12:00 PDT with sustained wind speeds over 20 mph by 14:00 PDT and wind gusts consistently over 25 mph by 13:00 PDT. Sustained wind speeds of over 25 mph are normally sufficient to overcome most PM 10 control measures. During the September 25, 2013 event wind speeds were sustained above the 25 mph threshold overcoming the BACM in place. IV.4 Summary The weather and air quality forecasts and warnings outlined in this section demonstrate that a strong low pressure system, driven by a weather system that was predominantly west, produced excessive winds that caused uncontrollable PM 10 emissions. The BACM list as part of the control measures in Imperial County for fugitive dust emissions were in place at the time of the event. These control measures are required for areas designated as "serious" nonattainment for PM 10, such as Imperial County. Thus, the BACM in place at the time of the event were beyond reasonable. In addition, surface wind measurements in Westmorland, Brawley and Niland and surrounding areas to the west and north of Brawley during the event were high enough (at or above 25 mph, with wind gusts over 25 mph) that BACM PM 10 control measures would have been overwhelmed. 32

41 Not Reasonably Controllable or Preventable Finally, a high wind dust event can be considered as a natural event, even when portions of the wind-driven emissions are anthropogenic, as long as those emissions have a clear causal relationship to the event and were determined to be not reasonably controllable or preventable. This demonstration has shown that the event that occurred on September 25, 2013 was not reasonably controllable or preventable despite the strong and in force BACM within the affected areas in Imperial County. This demonstration has similarly established a clear causal relationship between the violation and the high wind event timeline and geographic location. The September 25, 2013 event can be considered an exceptional event under the requirements of the exceptional event rule. FIGURE 4-1 REGULATION VIII GRAPHIC TIMELINE DEVELOPMENT Fig. 4-1: Regulation VIII Graphic Timeline [Intentionally left blank] 33

42 Clear Causal Relationship V Clear Causal Relationship V.1 Discussion Meteorological observations for September 25, 2013 identified a strong low pressure system traveling in a westerly direction producing strong sustained winds impacting the Westmorland, Brawley and Niland monitors. Steep pressure gradients at the 500mb level (04:00 PST) brought high winds exceeding 25 mph to Imperial County. The NWS weather maps for September 25, 2013 demonstrate an impact to California, particularly the southern portion of California. Entrained windblown dust from natural areas, particularly from the desert area located within the western portion of Imperial County, and anthropogenic sources which are controlled with BACM, is verified by the meteorological and air quality observations on September 25, Weather observations indicate that a strong low pressure system accompanied by gusty winds, approaching the southern section of California was directly responsible for the high PM 10 concentrations observed in Imperial County on September 25, During the afternoon hours of September 25, a low pressure system, moving westerly across California, impacted Imperial County Figure 5-1. In addition, weather observations indicate that the low pressure system encountered a secondary system coming from the northeast which created a mixing and variable wind effect that lasted into the following day. FIGURE 5-1 LOW PRESSURE SYSTEM MOVING ACROSS CALIFORNIA AND INTO IMPERIAL COUNTY Fig 5-1: GOES W visible image of weather system that brought high winds into Imperial County. 11:00 PDT. Courtesy of San Francisco State University California Regional Weather Server 34

43 Clear Causal Relationship The analysis of the meteorological setting, including weather reports, NWS satellite imagery, indicates that a steep pressure gradient associated with a strong low pressure system lead to the development of a period of gusty predominantly west winds across Southern California and into Imperial County. Appendix B contains wind rose information. The exceptional event of September 25, 2013 was notable for the unusual wind patterns that occurred during and after the violation of September 25, Meteorological patterns during early too late fall include west winds resulting from low pressure systems that take a west to east path. Normally, these weather patterns include winds that pass through Imperial County impacting the Chocolate Mountains on the County s eastern side. These southeast trending mountains generally deflect the winds to the southeast, into Yuma Arizona. However, on September 25, 2013 this pattern appeared to deviate. Based on GOES-W visible and infrared surface composite maps imaged at various times throughout the day, Figure 5-2, it is probable that a large scale weather pattern over the western United States promoted variable wind directions and speeds. A low pressure system over southern Nevada and Utah moved southwest toward southern California. It encountered high pressure off the West Coast. The differing pressure gradients and the positions of the two systems appear to have promoted variable wind directions at the microscale level in the Imperial County. Although winds remained robust into September 26, the varying wind directions created by the mixing of the two weather systems apparently caused wind patterns to remain in the valley and mix in a circular manner, and did not move out of the valley in the normal manner. Therefore, elevated wind speeds remained in the valley into the following day, but were not strong enough to trigger elevated readings at other monitoring sites. FIGURE 5-2 DEVIATION OF NORMAL WEST TO EAST WIND PATTERNS Fig 5-2: GOES-W visible and infrared (upper right) surface composite maps courtesy of San Francisco State University Meteorological Department. 35