SOUTH LAKE TAHOE, Calif. - A much-anticipated federal report on the Angora fire found that many of the 254 homes lost were ignited by other homes and not flaming trees.
Released Friday, the analysis of the 3,072-acre blaze found several reasons for the blaze and not one single factor that was responsible for the fire's spread into the North Upper Truckee and Tahoe Mountain residential areas.
The largest recorded fire in Lake Tahoe Basin history was sparked on June 24 near Seneca Pond by an illegal camp fire. It was contained on July 2.
The report concludes that forest treatment that was done before the fire prevented much of the potential for "crowning" - a term used where a fire spreads itself from the tops of trees rather than at the surface.
"About 405 acres of USFS area fuel treatment burned with surface-fire intensity. More than 80 percent of the urban lots burned as surface fire. Almost all of the nontreatment and other vegetation management areas burned with crown fire intensity," the report states.
The report suggests conditions that day - including clocked wind speeds of 20 to 30 mph - as well as homes that weren't in tandem with defensible space practices, stacks of firewood piled adjacent to homes, dry decking, dead trees and limb debris around properties were among factors contributing to the fire's rapid spread.
Still, the USFS report examined the effect of thinning projects conducted within and next to the burn area to reduce fire risk and concluded that they had worked.
Efforts to reduce fuels were "very effective in most cases," said Kathy Murphy, regional fuels operations manager for the Forest Service and one of the report's authors. "They're not designed to stop a fire. They're designed to lower the intensity."
The report includes several photographs of houses engulfed in flames but surrounded by trees that did not burn. The authors concluded that a number of homes were set ablaze by embers blown from other buildings rather than by the burning forest in almost a domino-like effect. Once the embers were airborne they would land on firewood piles propped against homes and along dry, wooden decks.
In some cases it appears the houses caught fire from low-growing vegetation that had not been cleared. In other instances, embers ignited decks or shake roofs or piles of firewood stacked near the homes.
On some lots, char marks showed that the houses set the trees on fire.
New building codes effective Jan. 1, 2008, will address these flammable materials and include a set of regulations for property owners.
California's Wildland-Urban Interface Building Codes were created to make homes near wild areas less susceptible to the potentially devastating effects of direct heat and flames, as well as burning embers.
The codes will be required for all homes, whether standing or up for rebuilding inside the Angora fire burn area. The codes will require changes to windows, siding and decks.
Chris Sauer, fire chief for Fallen Leaf Lake Fire Department, near where the blaze began, said in June that firefighters had about 30 engines mobilized during the initial two hours, all trying to protect about 300 homes.
"You do the math. I was amazed about how fast some of these structures burned to the ground," he said.
The wildfire raced through acreage that had been commercially thinned in the mid-1990s to remove insect-killed trees. The Forest Service had allowed the loggers to leave logging debris scattered on the ground and the long-dead material provided fuel for the flames.
The report concluded that the fire burned just as intensely in those areas as on forest acreage that had not been thinned.