WHILE ASCENDING THE STAIRS TO CHECK ON A BLOCKAGE IN THE RIP RAP CHUTE (AT THE SCREEN TOWER) THE EMPLOYEE WAS STRUCK ON THE HARD HAT BY A ROCK. THE ROCK GLANCED OFF THE HARD HAT AND HIT HIS LE FT HAND WHICH WAS GRIPPING THE HANDRAIL. DOCTOR IMMOBILIZED HAND WITH A CAST AND ISSUED WORK RESTRICTIONS.