MARATHON PIPE LINE LLC

Incident Narrative

ON OCTOBER 27, A STATION OPERATOR DISCOVERED STAINING ON SOIL ADJACENT TO TANK 5 AT MPL'S HARTFORD TERMINAL DURING A ROUTINE FACILITY INSPECTION. TANK 5 IS AN EL SEGUNDO-STYLE DOUBLE-BOTTOM TANK (CONCRETE INTERSTITIAL FILL) WITH LEAK DETECTION GROOVES AND PORTS. THE LEAK DETECTION PORTS WERE DRY AND CONTAINED 0% LEL. INITIAL SAMPLING AND LABORATORY TESTING OF THE PRODUCT (DIESEL FUEL) IDENTIFIED IT TO BE HISTORICAL IN NATURE. THERE WAS A KNOWN HISTORICAL SPILL IN 2013 (PRIOR TO INSTALLATION OF THE DOUBLE-BOTTOM). A MONITORING PLAN WAS IMPLEMENTED. ON NOVEMBER 8, A NEW SAMPLE WAS ANALYZED AND DETERMINED TO MATCH THE PRODUCT CURRENTLY IN THE TANK. WITH THIS NEW INFORMATION, IT WAS DETERMINED THAT THE TANK WOULD BE REQUIRED TO BE TAKEN OUT OF SERVICE, DE-GASSED, CLEANED, AND INSPECTED. AT THIS POINT, MPL HAD SUFFICIENT INFORMATION TO BELIEVE THAT TOTAL COSTS WERE LIKELY TO EXCEED $50K; THEREFORE, NOTIFICATION TO THE NRC WAS MADE ON NOV. 8 AT 16:28. THE TANK FLOOR LINING AND SUCTION/FILL LINE EXTENSION WELDS WERE INSPECTED AND NO INDICATIONS OF A LEAK POINT WERE DISCOVERED. IT IS SUSPECTED THAT THE LIKELY LEAK POINT IS THE DEDICATED SUCTION/FILL LINE WHICH RUNS UNDERNEATH THE TANK; HOWEVER, THE LINE CANNOT BE ACCESSED FOR INSPECTION AT THIS TIME. MPL HAS TAKEN THE TANK OUT OF SERVICE WITH NO PLANS TO RECOMMISSION IT. IMPACTED SOIL AND GRAVEL WAS CLEANED UP. A 48-HOUR NRC REPORT WAS COMPLETED ON 11-10-21 AT 12:00 CST. #1321654