EE WAS WORKING IN OUR 'OLD TUNNEL' PICKING UP ROCKS THAT HAD FALLEN OFF THE TUNNEL CONVEYOR. AS HE PICKED UP A LARGE ROCK OFF OF THE FLOOR TO PLACE IT BACK ONTO THE IDOL BELT HE STRAINED HIS L OWER BACK. HE HAD HAD A PREEXISTING BACK PROBLEM THAT ORIGINATED FROM A TRAFFIC ACCIDENT IN OCT 2001. LIFTING OF THE ROCK FURTHER AGGRAVATED HIS CONDITION. LOST TIME DID NOT OCCUR TILL 12/17