A refinery accused in a March 1995 explosion that killed a motorist and injured several other people has agreed to a $5.5-million settlement, Kern County officials said Tuesday. Kern County Dist. Atty. Edward Jagels said the award settles a civil lawsuit filed against Sunland Refinery for alleged air pollution violations and unfair business practices. Investigators said a mixture of naphtha and crude oil in a tank without vents caused the explosion on March 20, 1995. A toxic cloud blew across a road and was ignited by at least one car, killing Tracy Kildebeck, 22. A vapor recovery system would have made it safe and legal to mix the two chemicals, investigators said. Sunland is a subsidiary of World Oil, Inc., based in South Gate. The suit was filed by Jagel's office and the San Joaquin Valley Unified Air Pollution District.