EMPLOYEE CLIMBED A 10' LADDER TO FUEL TANK UP; WHILE HE WAS LEANING ON THE 300 GAL. TANK, THE STAND IT WAS ON GAVE WAY; HE FELL WITH HIS FEET UNDER LADDER, TWISTING LEFT ANKLE. HE RADIOED FROM FUEL TRUCK TO GET SUPERVISOR TO AREA; THEN HE WORKED FROM THAT TIME UNTIL AROUND NOON. SEEATTACHED SHEET.