MARATHON PIPE LINE LLC

Incident Narrative

ON AUGUST 1, A MARATHON PIPE LINE CONTRACTED PILOT OBSERVED BUBBLING IN THE LOWER SAN JACINTO BAY. THE RESPONSIBLE PARTY WAS UNKNOWN, THE RELEASE WAS IMPACTING WATER, AND MPL MADE A COURTESY REPORT TO THE NRC (REPORT #1155009) AND TO THE TEXAS RAILROAD COMMISSION. MPL CONTINUED TO WORK WITH OTHER OPERATORS AND REGULATORY AGENCIES IN THE AREA UNTIL AUGUST 3, WHEN DIVERS CONFIRMED THE RELEASE TO BE COMING FROM MPL'S PIPELINE. A SECOND NRC REPORT (#1155262) WAS MADE IN ORDER TO CLAIM RESPONSIBILITY FOR THE RELEASE, HOWEVER A VOLUME ESTIMATE WAS NOT AVAILABLE AT THE TIME. A TEMPORARY REPAIR CLAMP WAS SUCCESSFULLY INSTALLED ON AUGUST 5 AND THE RELEASE WAS STOPPED. A THIRD NRC REPORT (#1155462) WAS MADE IN ORDER TO PROVIDE A VOLUME. MPL COMPLETED ITS INVESTIGATION AND DETERMINED THAT THE FAILURE OF THE PIPELINE WAS THE RESULT OF AC INDUCED CORROSION ON THE PIPE. AT THE TIME THE PIPELINE WAS FIRST LAID, IT WAS LAID CONCURRENTLY WITH AN ADJACENT THIRD-PARTY 6"" PIPELINE AND WAS COLLOCATED WITH MULTIPLE HVAC OVERHEAD POWER LINES. THE MPL PIPELINE AND THE THIRD-PARTY PIPELINE WERE TIED TOGETHER WITH BOLTED BRACKETS WHICH REMAINED ON THE PIPES AS PERMANENT APPURTENANCES. THE PRESENCE OF BRACKETS ON THE LINE APPEARED TO HAVE DAMAGED THE PIPE COATING AND PROVIDED A LOW-RESISTANCE PATH FOR AC CURRENT DISCHARGE, RESULTING IN LOCALIZED CORROSION CONCENTRATED IN THE BRACKETED AREA. THE SEGMENT OF THE PIPE CONTAINING THE LEAK WAS CUT OUT AND PERMANENTLY REPAIRED BY INSTALLING NEW PIPE. ANODE SLEDS WERE INSTALLED TO MITIGATE FUTURE AC INDUCED CORROSION. 2/21/17: PART D.6. WAS UPDATED WITH FINAL COSTS. THE TIME OF SHUTDOWN IN PART A.14.A WAS REVISED SLIGHTLY. 6/16/17 UPDATE: PART A, QUESTIONS 4 AND 7: TIMES WERE REVISED. PART C, QUESTION 3A: THE NOMINAL DIAMETER OF PIPE WAS CHANGED TO 8 INCHES. PART G, QUESTION 2: THE TYPE OF CORROSION WAS UPDATED FROM ""OTHER"" TO ""STRAY CURRENT"". TO CLARIFY, THE STRAY CURRENT WAS ALTERNATING CURRENT (AC) INDUCED AND NOT RELATING TO CATHODIC PROTECTION.