This page last reviewed January 27, 2014

2007 Southern California Wildfires and High Winds


Event Description

This widely documented event began with high winds from a surface cold front and the ignition of the Ranch Fire in Los Angeles County on Saturday, October 20, 2007. Numerous additional fires were fueled by strong Santa Ana winds, which helped spread smoke, dust, and ash throughout Southern California. On October 21, the Governor of California declared a State of Emergency for Los Angeles, Orange, Santa Barbara, Ventura, Riverside, San Bernardino, and San Diego Counties. The Federal Emergency Management Agency (FEMA) followed suit on October 24, declaring all seven counties disaster areas. At its peak, the deadly Southern California Fire Siege comprised almost 20 major wildfires, with several smaller fires contributing to the pall of smoke over the region. By the time the last fire had been declared contained on November 13, over a half-million acres had burned, thousands of buildings had been destroyed, and almost a million residents had been displaced.

Although most monitoring sites in the region were affected, ARB is requesting exclusion of data from 14 sites in five Air Districts where smoke, dust and ash caused levels to exceed those historically seen during the fall season.

Regulatory Background

The Code of Federal Regulations (CFR) provides the definition and criteria for determining whether air quality data is impacted by an exceptional event. The 40 CFR 50.1 (j)1 definition states that “exceptional event means an event that affects air quality, is not reasonably controllable or preventable, is an event caused by human activity that is unlikely to recur at a particular location or a natural event, and is determined by the Administrator in accordance with 40 CFR 50.14 to be an exceptional event.” The demonstration to justify data exclusion as outlined in 40 CFR 50.14 specifies that evidence must be provided that:

1. The event meets the definition of an exceptional event;
2. There is a clear causal relationship between the measurement under consideration and the event that is claimed to have affected air quality in the area;
3. The event is associated with a measured concentration in excess of normal historical fluctuations, including background; and,
4. There would have been no exceedance or violation but for the event.


Official Exceptional Events Documentation Submitted to U.S. EPA. - April 20, 2010


Additional Web-based Information regarding the 2007 Southern California Wildfire and High Wind Event (not comprehensive; active as of 1/27/14.)





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