EMPLOYEE STATED WHILE WORKING IN THE WEST VALLEY FILL AREA. HE WAS ABOUT 10 TO 15 FT UP ON THE SPOIL BANK. HE ATTEMPTED TO COME DOWN THE BANK, HIS FOOT SLIPPED. HE FELL ON HIS HIPS AND BACK AN D SLID DOWN THE BANK ABOUT 12 FT. AFTER HE STOPPED SLIDING A ROCK ROLLED OVER HIS RIGHT SIDE, CAUSING HIS TO HAVE PAIN WHILE BREATHING. (REDNESSIN THE AREA OF PAIN).