The driver of a concrete mixer truck was seriously injured Friday morning after a concrete pump truck tipped, launching him off of a ladder and into nearby equipment. Clark County Fire & Rescue crews were dispatched at 7:47 a.m. to the 7100 block of South 10th Street in Ridgefield for a report of traumatic injuries resulting from an accident at a construction site, Chief John Nohr said. One of the workers suffered multiple broken bones, including his ribs, and was on the ground being tended to by co-workers, Nohr said. It appeared the outriggers, which help stabilize the concrete pump, either failed or sank into the ground, Nohr said, causing the truck to tip to its side and front.