EMPLOYEE SAID HE WAS OPERATING A COAL HAULER IN THE INTERIOR PIT WHEN HE HIT A ROUGH SPOT IN THE ROAD; HE WAS IN 4TH GEAR GOING 20 MPH. THIS CAUSED PAIN AND NUMBNESS IN HIS LEFT LEG; HE WAS U NABLE TO WORK HIS NEXT 3 SCHEDULED SHIFTS. HE SAW HIS DOCTOR AND IS GOING TO HAVE SURGERY ON HIS BACK.