WHILE MOVING RAIL CARS TO DERAIL AT 2130, MATERIAL HANDLER TWISTED HIS RIGHT ANKLE AS HE WENT TO SET THE RAILWHEEL CHOCK ON THE RAIL. MATERIAL HANDLER SAID THAT THE GROUND WAS SOFT AND GAVE WAY AS HE STEPPED FORWARD. MATERIAL HANDLER REPORTED THAT HIS ANKLE WAS SORE. HE WAS TAKEN TO THE CLINIC FOR EVALUATION. MATERIAL HANDLER WAS SEEN BY PHYSICIAN AND PRESCRIBED 550MG NAPROXEN.