DRIVER OF UNIT 2199 A 1999 MACK RD 888 SX TANDOMN COAL TRUCK WAS LOADED WITH COAL, ENROUTE TO THE OMAR BY PASS BIN. HE WAS ENTERING THE BLIND CURVE SECTION OF HAUL ROAD NEAR MANTANCE YARD. HE MEET A 777 WATER TANKER IN CURVE HAD TO GET OVERTHE LOAD SHIFTED CAUSING TRUCK TO OVERTURN.