EMPLOYEE WAS DISMOUNTING THE D-6 BULLDOZER FROM THE TRACK TO THE BLADE WHEN HE SLIPPED. BOTH TRACK AND BLADE ARM HAD WET SILT DEPOSITS ON THEM. HE RETURNED TO WORK THE NEXT DAY AND WORKED UNTI L 6/14/00. CALLED IN ON 6/15/00 AND SAID HE WOULD BE OUT OF WORK BECAUSE HIS BACK HURT. HE HAS NOT RETURNED.