ENBRIDGE STORAGE (CUSHING) L.L.C.

Incident Narrative

ON OCTOBER 5, 2023, AFTER MANIFOLDS M107 AND M207 WERE DRAINED SUCCESSFULLY, TWO FOAM PIG'S WERE LOADED INTO THE LAUNCHING TRAP TO PURGE THE 8"" ALLIED LATERAL. NITROGEN WAS INTRODUCED TO THE SYSTEM. TEN ABOVE GROUND MONITORING (AGM) STATIONS WERE LOCATED ALONG THE PIPE SEGMENT AT APPROXIMATELY 1-MILE INTERVALS TO IDENTIFY THE PIG'S AS THEY TRAVELED FROM THE LAUNCHING TRAP TO THE RECEIVING TRAP. PIG TRACKERS WERE UNABLE TO IDENTIFY PIG'S AT AGM 9 AND 10 AFTER RESUMPTION OF NITROGEN INJECTION. AT APPROXIMATELY 2:10 PM CDT A RELEASE OCCURRED WHEN THE NITROGEN THAT WAS PUSHING THE PIG BYPASSED IT AND BURPED THE SEAL ON TANK 2514. THE INITIAL VOLUME ON THE TANK ROOF WAS APPROXIMATELY 3 BARRELS OF CRUDE OIL INTERMIXED WITH WATER. OPERATIONS PERSONNEL REQUESTED 3 VACUUM TRUCKS TO BEGIN DRAINING VOLUME FROM TANK 2514 ROOF DRAIN. ADDITIONAL CRUDE OIL WAS OBSERVED RELEASING FROM THE TANK LEGS THROUGHOUT THE NIGHT NECESSITATING THE REQUEST OF 3 FRAC TANKS. ALL CRUDE OIL AND WATER MIXTURE WAS DRAINED INTO THE FRAC TANKS OF WHICH APPROXIMATELY 1220 BARRELS WAS ESTIMATED TO BE CRUDE OIL AND RETURNED TO THE SYSTEM. THE NRC WAS NOTIFIED ON OCTOBER 6, 2023, AT 9:08 AM CDT (NRC# 1381026) WHEN THE CLEANUP COSTS WERE EXPECTED TO EXCEED THE NRC REPORTING THRESHOLD. A 48-HOUR UPDATE TO THE NRC WAS MADE ON OCTOBER 8, 2023, AT 12:02 PM CDT. NO CRUDE OIL REACHED THE GROUND AND WAS FULLY CONTAINED ON THE TANK ROOF. CLEANUP WAS COMPLETED ON THE ROOF OF TANK 2514 ON OCTOBER 11, 2023. THE CAUSE OF THE RELEASE IS ATTRIBUTED TO INADEQUATE MONITORING OF THE LOCATION OF THE PIG'S WHILE INJECTION OF NITROGEN CONTINUED TO FLOW. THE PRESSURE OF NITROGEN INTRODUCED INTO TANK 2514 CAUSED CRUDE OIL TO RELEASE FROM THE TANK'S PRIMARY/SECONDARY SEALS AND ROOF LEGS AS THE GAS ESCAPED THE TANK.