ENBRIDGE PIPELINES (OZARK) L.L.C.

Incident Narrative

ON MAY 23, 2017 A MARATHON EMPLOYEE PERFORMING AN INSPECTION OF REMOTE VALVES SITES ON LINE 51 MADE ENBRIDGE AWARE THAT THE 20"" AUXILIARY VALVES (CG-51-5.80L) THAT CONNECTS TO THE 22"" TRANSMISSION PIPELINE AT MP 5.80 SHOWED EVIDENCE OF CRUDE OIL SEEPAGE FROM THE CLAMP RING. ENBRIDGE REGULARLY MONITORED THESE VALVES FOR LEAKAGE, HOWEVER AFTER NOTIFICATION THAT NEW SEEPAGE HAD BEEN OBSERVED BEGAN VISITING THE VALVES DAILY TO MITIGATE POTENTIAL ENVIRONMENTAL IMPACTS. ENBRIDGE (THE OPERATOR OF THE LINE 51 PIPELINE), IN COLLABORATION WITH MARATHON (THE OWNER OF THE LINE 51 PIPELINE), DECIDED TO STOP THE SEEPAGE BY INJECTING A SEALANT INTO THE ANNULAR SPACE BETWEEN THE BONNET OF THE VALVE AND THE CLAMP RING. A THIRD PARTY CONTRACTOR WAS ENGAGED AND THE REPAIR STRATEGY WAS PLANNED AND THE INJECTION OF SEALANT TOOK PLACE IN JULY. THE AUXILIARY VALVES WERE MONITORED DAILY FOR TWO WEEKS TO DETERMINE IF THE REPAIR STRATEGY WAS SUCCESSFUL. AS OF AUGUST 8, THE VALVES STILL SHOWED EVIDENCE OF SEEPAGE SO ANOTHER REPAIR STRATEGY THAT WILL BE EXECUTED BY MARATHON WAS DETERMINED TO BE NECESSARY. THE AUXILIARY 20"" VALVES WILL BE REMOVED FROM THE PIPELINE SYSTEM AND BLIND FLANGES WILL BE INSTALLED IN THEIR PLACE. NEW STOPPLES WILL BE INSTALLED AT MP 5.80 TO PROVIDE ISOLATION. THE NRC WAS NOTIFIED AT 17:26 CDT ON AUGUST 8, 2017 (NRC#1186651) WHEN IT WAS DETERMINED THAT COSTS WOULD EXCEED THE $50,000 THRESHOLD FOR THE NEW REPAIR STRATEGY. APPROXIMATELY 1 GALLON OR LESS OF CRUDE OIL HAD RELEASED INTO THE VALVE CONTAINMENT AREA. THE CAUSE OF THE RELEASE HAS BEEN DETERMINED TO BE DUE TO THERMAL EXPANSION. SHUTDOWN AND ISOLATION WAS NOT REQUIRED DUE TO THE NATURE AND MINIMAL VOLUME OF THE LEAK; HOWEVER, THE PHMSA PORTAL SYSTEM REQUIRED ANSWERS TO PART E, QUESTIONS 5.A - 5.C. WHICH DO NOT APPLY TO THIS RELEASE. .