EE WAS PERFORMING HIS USUAL JOB AS THE SUPERVISOR OF THE GRAVEL EXTRACTION BARGE ON THE UMPQUA RIVER. AS HE WAS WALKING ON THE STEEL DECK OF THE BARGE HE STEPPED ON A SMALL, ROUND STONE. THIS CAUSED HIS FOOT & LEG TO SLIDE FORWARD. HE ARRESTED HIS FALL BUT FELT HIS KNEE OVEREXTEND. THE EE DID NOT THINK HE WAS HURT, BUT HE DID NOTE THESLIP IN HIS CAPTAIN'S LOG. HE ALSO NOTED THE SLI