"A large electrical charge was introduced to a fence directly over Chevron's pipeline. The charge jumped from a metal fence post to Chevron's pipeline causing an ~ 1' hole in the fence post and an ~1/2' hole near the 12:00 position on the pipe. The leak occurred near a small creek that runs through a high density populated area. The crude followed the creek to a pond where most of it was captured."
Pipeline and Hazardous Materials Safety Administration: http://phmsa.dot.gov/