Air Pollution Control District


High winds have the potential to suspend particulate matter into the air potentially causing significant changes in ambient concentrations that may pose a health concern. When high winds cause an exceedance of the National Ambient Air Quality Standard for particulate matter of less than 10 microns and certain meteorological conditions exist that allow for the classification of a meteorological event, seasonal or otherwise, evidence may demonstrate that the exceedance was caused by an Exceptional Event.

Changes in ambient concentrations are displayed by the Air Quality Index as moderate or unhealthy.


August 7, 2019

The Imperial County Air Pollution Control District (Air District) has prepared four Draft Exceptional Event (EE) Demonstrations which support the requested exclusion of the measured 24-hour concentrations at the Air District air monitoring sites. Listed below by date, site and concentration as measured by a continuous Federal Equivalent Method monitor (FEM) are the four Draft EE's prepared by the Air District.

February 17, 2017; Niland - 247 ug/m3

March 30, 2017; Brawley - 180 ug/m3; Calexico-167 ug/m3; El Centro-196 ug/m3; Niland-227 ug/m3; Westmorland-214 ug/m3

May 6, 2017; Brawley-449 ug/m3; Calexico-409 ug/m3; El Centro-268 ug/m3; Niland-345 ug/m3; Westmorland-297 ug/m3

May 15, 2017; Brawley-190 ug/m3; Westmorland-246 ug/m3

May 25, 2017; Brawley-164 ug/m3

The public and all interested parties are encouraged to review and comment on the four Draft EE's for listed above. These demonstrations provide the supporting evidence that on the days indicated for 2017 Air District air monitors were affected by transported elevated levels of particulate matter of an aerodynamic size less than 10 microns (PM10). Winds, associated with a weather event suspended and transported PM10 into the region affecting areas within San Diego, Riverside, Yuma and Imperial counties. The four Draft EE's provide the scientific justification for the requested exclusion. The Air District is soliciting and accepting comments for 30 days commencing the date of the publication of this notice. The final closing date for submitting comments is September 6, 2019 by close of business.

To view hard copies of the Draft EE demonstrations, please visit the Air Pollution Control District office at 150 S. 9th Street, El Centro. Should you have any questions or concerns please feel free to call our office between 8am and 5pm at (442) 265-1800 and ask for Monica N. Soucier

Date of Notice


Closing Date