News & Columns > Michael P. Neufeld > Impact of Fuel Reduction Efforts in the Grass Valley Fire

Impact of Fuel Reduction Efforts in the Grass Valley Fire

US Forest Service Releases Reports

By Michael P. Neufeld
Wednesday, July 23, 2008

San Bernardino, CA – The US Forest Service has issued reports on last October's Grass Valley Fire near Lake Arrowhead. The two-part report covers fire behavior, suppression effectiveness, and structure ignition. Researchers assessed the effectiveness of fuels treatments in the fire area and how home vulnerability and ignition exposure contributed to home destruction.

The reports, titled Fuel Treatment Effects on Fire Behavior, Suppression Effectiveness, and Structure Ignition, Grass Valley Fire and Home Destruction Examination, Grass Valley Fire, can be found on-line at http://www.fs.fed.us/r5/sanbernardino/news/index.shtml.

(Photo by B Spencer.)

Key findings as listed in the reports, include:

• Fire behavior in fuel treatment areas was less rapid and less intense than in adjacent untreated wildland fuel and urban-structural fuel. The reduced spread rate and intensity allowed suppression forces to concentrate on protecting structures and on preventing additional fire spread to the south.

• Fuel treatments improved visibility-enabling firefighters to engage the fire directly in places and to protect homes without jeopardizing their safety.

• The Mountain Area Safety Task Force (MAST) coordinates hazard reduction efforts of all the organizations and agencies managing land, infrastructure, and emergency response in the Lake Arrowhead area. Their efforts greatly enhanced the safe evacuation of thousands of people due to previous dead tree removal. Removal of these dead trees reduced the amount of tree fall in roadways along main routes and also reduced ember production and associated spot fires.

• The Grass Valley Fire burned more intensely within the residential area than in adjacent wildland fuels. Mass ember production from structures ignited adjacent and downwind structures in many cases.

• Although torching and crowning occurred during the Grass Valley Fire, the wildfire did not spread as a continuously crowning, high intensity fire.

• With minor exception (six homes), high intensity wildfire was not a direct factor in igniting homes.

• Of the 199 destroyed and damaged homes, 193 ignited in two principal ways: (1) From fire largely spreading through surface fuels within the residential area that contacted homes and/or from firebrands generated by burning vegetation and/or 2. From thermal exposures directly related to burning residences (from structure flames and firebrands).

• Firefighters were overwhelmed in their attempt to prevent the residential fire spread due to multiple homes burning simultaneously. However, more homes would have burned without their intervention.

• The Grass Valley residential fire disaster was principally the result of high home ignition potential. The wildfire initiated the residential burning, but burning homes predominantly continued the fire spread to other homes without the wildfire as a significant factor.

Slash burning information available. (Photo by Michael P. Neufeld.)

The Grass Valley Fire started at approximately 5:08 a.m. on October 22, near Lake Arrowhead. The fire spread to the south through wildland fuels and then transitioned to urban structural fuels where it destroyed or damaged approximately 199 structures. The fire was contained on October 26.

For additional information about the San Bernardino National Forest, please visit: http://www.fs.fed.us/r5/sanbernardino/.