Luck, Along With Weed Control, Cuts Chatsworth Fire Loss : Arson: Though four firefighters were burned, a combination of factors is credited with saving homes and lives in the Santa Susana Pass blaze.

The arsonist who set the Chatsworth-Santa Susana fire failed to spark a major conflagration only because the fire was hindered by a lucky combination of natural and man-made obstacles, fire officials said Thursday.

Although four firefighters were severely burned when a wall of flame 50 feet high roared out of a ravine, officials said no lives were lost, or homes damaged or destroyed in the 1,500-acre blaze Wednesday because:

* Large sandstone boulders that dot the area formed a natural firebreak.

* Several major brush fires in the past 15 years had thinned out the brush.

* Zoning codes limit density in some areas to a maximum of one house per half-acre.

* The blaze began so early--before the other 12 fires in Southern California broke out--that enough firefighters and equipment were on hand to put it out promptly.

* Weed abatement programs that required brush to be cleared within a 100-foot radius of homes had been aggressively enforced in the area by local fire departments.

“I always gripe about having to spend $400 or $500 a year on clearing out weeds, but I can see the benefit of it now,” said Steve Lamarche, pointing to a charred area just 50 feet from his two-story house on Trigger Street in Chatsworth.

Human bones were found in a shallow grave in a Chatsworth field in the fire area, but authorities did not know how long they had been in the vacant lot, a Los Angeles County coroner’s investigator said.

The bones were found about 5 p.m. in a field on Jeffrey Mark Court, which runs for a block just south of Chatsworth Park, said Michael Joseph of the coroner’s office.

Los Angeles police did not say who found the bones or how they were discovered. The bones will be analyzed by an anthropologist later this week, Joseph said.

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Arson investigators from the Los Angeles Fire Department said Thursday that the blaze was intentionally set shortly before 1:30 a.m. in a one-acre gully off Santa Susana Pass Road in Chatsworth, half a mile south of the Simi Valley Freeway. They pinpointed that area by tracing the physical evidence of the fire back to its point of origin and reconstructing its early development by listening to tape-recordings of residents who reported the blaze to the 911 emergency phone number.

“There’s no other way it could have been started--no electrical power lines, mechanical devices down there or anything,” said one investigator, adding that illegal campfires had been ruled out.

Wearing leather gloves, investigators combed the blackened earth for an incendiary device. One possibility, they said, is that a road flare was tossed out of a passing car and it immediately set fire to the dry brush.

To test the theory, they ignited a flare to examine the remaining residue and compare it to debris found in the gully. They said that a man detained for questioning Wednesday because he fit the description of a man residents said had been camping in the area, could not be linked to the fire and had been, or would soon be, released.

Even if they can determine the cause of the fire, investigators said the chances of convicting the arsonist are extremely slim.

“We’d almost have to have an eyewitness or other direct evidence like a fingerprint,” one investigator said.

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But any information they can glean from the scene will be fed into a computer and could be used to bring additional charges in the future if the arsonist is ever caught in the act of setting a fire, they said.

While investigators hunted for arson evidence, relieved residents put their homes back in order. Many who grabbed valuables and fled during the blaze returned to soot-coated carpets, windows and swimming pools.

“It’s a mess, but it could have been worse,” said Betty Butler, whose house on Dale Court narrowly escaped the flames. “If I hadn’t been so busy, I just would have sat and cried for those people in Altadena and Laguna who lost everything.”

In Box Canyon, where the number of horses nearly equals the 700 human inhabitants, residents gratefully carted home their livestock from corrals in the San Fernando and Simi valleys where they had taken them Wednesday.

“It was like being in a chimney--my horse was so scared he was sweating and shaking,” said Robin Seward, 20, a waitress who lives in the canyon. “It’s beautiful up here and I wouldn’t trade it for the world, but it’s scary.”

Her neighbor, Chris Schmitt, 35, credited the weed abatement program for keeping the fire at bay while he transported 22 horses out of the canyon on back roads.

“We all gripe about it, but it worked,” Schmitt said.

If residents fail to clear the brush within a 100-foot radius of their houses, authorities in Los Angeles and Ventura counties hire contractors to perform the work. In addition to the cost of the contractor, residents are billed $200-$225 in administrative fees. If they don’t pay the bill, a tax lien is placed on the property.

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In comparison to high losses in other Southland areas, across Ventura County where fires had blackened more than 33,111 acres, only 33 dwellings had been destroyed as of Thursday evening, said Ventura County spokesman Alice Allen, who credited the abatement program.

“All over the county, it has been a little easier to save buildings because property owners have been vigilant in removing brush,” she said.

Some Box Canyon residents have been reluctant to comply with the program in the past, but Ventura County Fire Capt. Tom Kruschke expects to see a change in attitude now.

“Over the next few years I think we’ll probably get a whole lot of cooperation,” he said.