If a fire is 75 percent contained, what does that actually mean?
When the Lilac Fire exploded across San Diego's inland North County Thursday images of uncontrollable flames matched a description of zero containment.
But one day later, as the flames and thick, black smoke had nearly disappeared, the fire was still at zero percent containment.
People wondered how the fire could still be zero percent contained. It turns out that the containment measure alone does not give a wholly accurate picture of firefighters’ progress.
Cal Fire Captain Jon Heggie says airdrops alone can't contain a fire. That requires bulldozers and hand crews, often made up of inmates, to get in along the outer edges of a fire in what's often described as the grunt work.
"If there's hot material, there's the opportunity for fire growth. So until we get all that hot material extinguished, that's when we feel comfortable calling it contained," he explained. “So we're going in there with hose lines and squirting water to ensure all those hotspots, 100 to 300 feet, are completely extinguished. Not only that — we've removed all the vegetation from the fire's edge all the way down to bare minimum soil, all the way down to four to five feet.”
Only when hot spots near the fire's perimeter are out and fire lines are dug all the way around it, can a fire be 100 percent contained.
Cal Fire often uses lakes, rivers, and roads as part of their containment lines. In the case of the Lilac Fire Interstate 15 became one of their first containment lines.