WHILE EE WAS SERVICING GRD191 GRADER AT DIXON PIT, HE STEPPED OFF THE TANDEM AFTER CHECKING THE ENGINE & TRANSMISSION OIL. HIS FOOT SLIPPED OFF THE STEP & FELL TO THE GROUND. AS HE FELL, HE GR ABBED THE HANDHOLD BUT FELL ONTO THE WIGGINS FUEL NOZZLE PROTECTIVE COVER & BROKE 2 RIBS ON HIS RIGHT SIDE. HE RECEIVED FURTHER MEDICAL ATTN @ MESA OCCUPATIONAL & SPORTS MEDICINE.