Controlled Burns

Controlled burning of wild-land brush is often misunderstood by present-day Southern Californians, who might not see past the smoke it creates and the land it blackens. Even in centuries past, Native Americans burned land to improve hunting, create travel routes and rejuvenate succulent vegetation.

Firefighters today closely monitor prescribed burns to renew plant growth, enhance wildlife and prevent huge fires. Prescribed burns also are used to train firefighters and study fire behavior.

The Los Angeles County Fire Department currently has 12 sites that are under study for controlled burns. But because of weather restrictions, only seven burns have been conducted this year-- six in the Santa Clarita Valley and one in San Dimas--totaling just 240 acres. More than a dozen controlled-burn days have been cancelled because of high temperatures and/or low humidity, a dangerous combination for keeping a fire under control. County fire officials doubt that any burns will be conducted the rest of this year because of extremely dry vegetation.

Controlled-burn specialist Don Pierpont, a county fire battalion chief, calls the burns complex, “choreographed” events. They require months of detailed planning. Each controlled-burn project has its own prescription listing ideal conditions for burning and a plan detailing how the burn will be conducted.

From Proposal to Action

Recommendations for a controlled burning site come from area fire stations, as well as residents. Then the site must get approval.

* Area homeowners are sent a map drawn by Fire Department vegetation management officials.

* Environmental impact studies are done to ensure the safety of endangered or threatened species, and archaeological research determines the existence of any important areas such as ancient burial grounds.

* Fire officials then write a “burn plan” detailing how the burn will be done--including the number of acres to be burned and personnel needed. Final approval comes from the California Department of Forestry.

* The burn contract is good for three years--a controlled burn can occur there within that time, dependent on the right conditions.

Ideal Conditions

Once a burn plan is OKd, fire officials must wait for a window of opportunity when weather and vegetation conditions are optimal for burning. High temperature and wind, coupled with low humidity, can cause a fire to get out of control. The best times of the year for controlled burns are in the spring and immediately after winter rains.

* Temperature: 70-75 degrees

* Wind: 7-10 m.p.h.

* Humidity: 35%

* Fuel moisture: 90%

Preparing A Burn Site

Containment lines are cut by hand crews or bulldozed

Samples of vegetation are taken and analyzed for moisture content

The Day of A Burn

Pre-planning: The fire department obtains the following day’s weather and air quality forecasts. If acceptable, all divisions involved are notified, as well as area residents.

7 a.m.: Supervisors meet to review plan, go over topographical maps. Spot forecast is obtained from weather service. Weather balloon is launched and tracked to determine wind speed. Small corner of area is ignited to test how it will burn.

9 a.m.-noon: Various sections of burn area are lighted in sequence, shown below.

Noon-5 p.m.: Fire is allowed to burn within limits--usually 30-foot flame height. Smolders are doused by engines or helicopters to prevent spot fires.

Overnight: Several firefighters keep watch to make sure embers don’t start spot fires.

Next day: Two crews put out any remaining smolders.

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Before and during burn, weather balloons are released and tracked to determine wind speed and direction of smoke.

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Setting Headfires: Once backfire has burned about 150 feet, smaller headfires are set, which are pushed by wind to meet main backfire.

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Controlling the Direction: Firefighters armed with hand tools are stationed at fire’s perimeter to keep fire from jumping prescribed line.

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Engines are nearby in case fire jumps containment line.

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Fires are usually started with drip torches, a canister from which a gasoline/diesel mixture is squirted. Other methods include terra torches, which shoot flaming gel up to as far as 100 feet; helitorches, aerial tanks attached to helicopters that pump jelled gas from the air; or small plastic balls filled with a flammable substance dropped from helicopters.

Setting A Backfire: A backfire is set downwind from a firebreak such as a road or creek. It is intended to burn vegetation slowly and creates a “blackline” at which headfires will stop.

Sources: Los Angeles County Fire Department; National Park Service; Nature Conservancy; “Fire: A Force of Nature’; Researched by JULIE SHEER / Los Angeles Times