EMPLOYEE WAS OUT OF THE GOB TRUCK PREPARING TO FUEL IT. HE WAS STANDING ON A HOME MADE LADDER LEANING AGAINST THE WEST SIDE OF THE 1000 GALLON FUEL TANK. WHILE STANDING THE SECOND WRUNG OF T HE LADDER GAVE WAY CAUSING HIM TO FALL HITTING HIS HEAD ON THE FUEL TANK AND TWISTING HIS BACK.