Bombing the Boulders

Caltrans workers intentionally blew it Tuesday.

The result was a rocky midmorning commute for motorists on the Antelope Valley Freeway in Santa Clarita.

Traffic was briefly halted in both directions so Caltrans could blow up two auto-size boulders perched precariously on a rain-soaked slope above the west side of the freeway near San Fernando Road.

One rock was roughly the size of a Volkswagen bug and the other the size of a station wagon, said Jim Bullard, a Caltrans superintendent and explosives expert. He estimated the boulders weighed 7 and 10 tons.

They were found on a 250-foot slope by a Caltrans worker clearing rubble from the shoulder of the highway, Bullard said.

“He looked up and said, ‘Whoa, what’s that,” Bullard said. “Then he got out of there.”

To prevent the unstable rocks from rolling down onto passing motorists, Caltrans workers drilled holes four- to six-feet deep in the boulders with a jackhammer, said John Yslas, another Caltrans superintendent. Then they mixed the powder and liquid components of a binary explosive called Kinepak and embedded sticks of it in the holes, he said.

California Highway Patrol officers shut down the freeway in both directions for two five-minute periods while Caltrans detonated the explosives with electric blasting caps.

A bulldozer quickly cleared the debris, and the freeway was reopened.

Bullard said he “shoots” boulders about once a month in rocky areas of Malibu and the San Fernando, Santa Clarita and Antelope valleys, particularly in the rainy season.

“Otherwise,” Yslas said, “they could have killed somebody, our geologist said.”