The cause of Sundays brush fire at the base of the Cuesta Grade was a hot piece of metal from the brakes of a car descending the hill, Cal Fire investigator Zach Nichols told The Tribune.
Its extremely common for a brake component or exhaust component to start a fire, he said.
The 10-acre fire was first reported at 11:16 a.m., was contained by 1:43 p.m. and put out by 3:26 p.m. There were no injuries reported, but some of PG&Es power poles were burned in the fire, according to CHP online logs, and traffic was significantly delayed on the Grade.
Nichols said that as drivers descend south on the steep Cuesta Grade, they often brake hard at the base to reduce speed, which heats up the brakes and causes pieces to fly off.
Because of a lack of rain, the heated metal can cause dry grasses to ignite into flame.
Nichols found a piece of metal in a burnt piece of grass on the southbound gutter of the highway, and from there could determine where the fire had spread.