ENBRIDGE ENERGY, LIMITED PARTNERSHIP

Incident Narrative

ON NOVEMBER 5, 2022 STORMS AND HIGH WINDS OCCURRED IN THE AREA AROUND FLANAGAN TERMINAL. LINE 61 SHUT DOWN AT 10:41 AM CDT DUE TO A 5-7 SECOND POWER DISRUPTION AT THE TERMINAL WHICH SENT A LOW VOLTAGE ALARM TO THE LINE 61 PLC RESULTING IN AN EMERGENCY SHUT DOWN TO OCCUR ON THE SYSTEM COOLER. LINE 61 MAINLINE DELIVERY PCV CLOSED IN APPROXIMATELY 10 SECONDS WHICH ACTIVATED THE LINE 61 DELIVERY RELIEF VALVES TO OPEN AND DIRECT VOLUME TO THE DEDICATED RELIEF TANK. THE EDMONTON CONTROL CENTER CONTACTED FIELD PERSONNEL TO INVESTIGATE THE EVENT. FIELD PERSONNEL DISCOVERED CRUDE OIL ON THE GROUND AROUND THE RELIEF SYSTEM AT 10:58 AM CDT. APPROXIMATELY 50 BARRELS OF CRUDE OIL WAS RELEASED WITH THE MAJORITY OF PRODUCT REMAINING ON COMPANY PROPERTY. AN IMMEASURABLE AMOUNT REACHED THE ROADSIDE FROM PRODUCT MIST OVER DUE TO STRONG WINDS. ICS WAS STOOD UP AND OSRO CONTRACTORS WERE MOBILIZED TO THE SITE TO COMMENCE THE CLEANUP. THE NRC WAS NOTIFIED AT 12:00 PM CDT (NRC #1351798). THE 48-HOUR UPDATE TO THE NRC WAS MADE ON NOVEMBER 7, 2022 AT 9:44 AM CST (NRC #1351920). THE SOURCES OF THE RELEASE HAVE BEEN IDENTIFIED AS MECHANICAL FAILURE OF CERTAIN SMALL-BORE COMPONENTS ON THE LINE 61 MAINLINE RELIEF SYSTEM, SPECIFICALLY A NEEDLE VALVE ASSEMBLY, PT FLUSH RING AND ASSOCIATED TUBING ON A 2"" VENT VALVE BODY RELIEF. REPAIRS WERE MADE AND LINE 61 WAS RETURNED TO SERVICE ON NOVEMBER 7, 2022 AT 1:38 AM CST. APPROXIMATELY 501 TONS OF CONTAMINATED SOIL WAS REMOVED FROM THE RELEASE SITE. THROUGH THIRD-PARTY DESTRUCTIVE TESTING OF THE FAILED COMPONENTS, THE INVESTIGATION TEAM FOUND THAT THE APPROXIMATELY 10-SECOND CLOSURE OF THE LINE 61 MAINLINE DELIVERY PCV CAUSED AN OVERLOAD EVENT. ANALYSIS OF THE DAMAGED AND FAILED COMPONENTS ALSO REVEALED EVIDENCE OF HIGH-CYCLE, INTERMITTENT FATIGUE FROM INDUCED HARMONICS ON THE SMALL-BORE EQUIPMENT, INDICATING A WEAKENED STATE PRIOR TO THE EVENT. THE OVERLOAD EVENT COMBINED WITH THE FATIGUE LED TO THE SUBSEQUENT CRUDE OIL RELEASE.