A contractor hired to replace an old pipeline damaged it with a backhoe and created a leak. There was a trench about 3 feet deep and 18 inches wide. The injured employee was on scene to evaluate the leak. He moved from one side of the trench to the other. The soil on the opposite side gave way and exposed a tree root; he hit his chin on that root. The employee broke two bones in his left leg about 2 inches from his ankle.