CREWS BATTLE CASTAIC FIRE : ARSON CHARGES FILED AGAINST SUSPECT, 15, IN BLAZE.

Byline: Laurence Darmiento Daily News Staff Writer

Felony arson charges were filed Wednesday against a 15-year-old runaway who is accused of setting a wildfire north of Castaic that has charred more than 18,000 acres.

The teen-ager, who remains unidentified because of his age, was charged in Sylmar Juvenile Court with two counts of arson - setting fire to forest land and setting fire to an inhabited structure, said Deputy District Attorney Richard Taklender.

Held in juvenile hall since his arrest, the youth is scheduled to be arraigned today. He faces up to 10 years in a California Youth Authority prison if convicted, authorities said.

``I don't know if he realized how serious it is,'' said Sgt. Heidi Clark of the Sheriff's Department's arson detail. ``He certainly knows he started a serious brush fire, but he didn't show a lot of emotion.''

The teen-ager was arrested just minutes after the fire started about 12:30 p.m. Monday. He was seen walking south on the northbound lanes of the Golden State Freeway near Lake Hughes Road by a CHP officer, officials said.

The teen said he acted on impulse, using a disposable lighter to set the blaze after his parents' car broke down, Clark said.

His parents, who speak only Spanish, later said the youth, who has no driver's license, took their car on an errand Sunday and never returned. He was reported missing just hours before the fire started.

``He didn't give us any reason for starting it. He didn't extend any apologies. He just said he did it,'' Clark said. ``It's a sad story, but it's really very simple.''

The fire began in Marple Canyon, which separates the northbound and southbound lanes of the Golden State Freeway at the foot of the Grapevine. It quickly consumed thousands of acres of dry, thick brush ferried by erratic winds that have stymied firefighters. By late Wednesday it was just 15 percent contained.

On Wednesday afternoon firefighters once again - as they did on the first day of the fire - ordered the freeway closed from Vista Del Lago to Lake Hughes Road.

This time thick smoke and ash forced the closure of just the northbound lanes at Lake Hughes Road, which allowed firefighters to set backfires next to the freeway in an attempt to better control it, said CHP Officer Larry Albrecht.

The closure of the state's major north-south artery forced northbound travelers to either take mountainous routes through the forest or to backtrack to the Antelope Valley Freeway to get to Highway 138.

Residents of the Paradise Ranch Mobile Home Park east of the freeway also were encouraged to evacuate their homes, as they were Monday.

More than 1,300 firefighters from federal, state and local agencies were attempting to draw a line around the fire with the help of a small fleet of water-dropping helicopter and fixed-wing airplanes.

Although it has burned toward lightly populated wilderness areas of the Angeles National Forest, it has threatened several homes and damaged some, though none has been left uninhabitable, firefighters said.

CAPTION(S):

3 Photos

Photo: (1--color) Firefighters on Wednesday try to preve nt the wildfire in Castaic from crossing the Templin Highway.

(2--color) A firefighter uses a flare to start a backfire as the bulk of the blaze continues to burn toward the Golden State Freeway.

(3--color) A water-dropping aircraft ejects its cargo on the fire. Officials were forced to close the Grapevine and reroute north-south traffic.

Gene Blevins/Special to the Daily News