ENBRIDGE PIPELINES (SOUTHERN LIGHTS) L.L.C.

Incident Narrative

"ON DECEMBER 10, 2025, AT 12:25 PM CST A BRIEF FLASH FIRE OCCURRED DURING WELDING ACTIVITIES ON A WHISTLE (A VERTICAL CULVERT USED FOR ACCESSING BELOW GROUND LEVEL PIPELINE SYSTEM COMPONENTRY) AT VIKING STATION AFTER GAS MONITORING INDICATED SAFE CONDITIONS; THE FIRE WAS QUICKLY EXTINGUISHED, AND NO PRODUCT RELEASE WAS OBSERVED AT THE SITE. AFTER THE FLASH FIRE ADDITIONAL GAS MONITORING RESULTED IN NO ELEVATED LEVELS OF HYDROCARBON GASES IN THE VICINITY. AT 2:13 PM CST, ENBRIDGE PERSONNEL OBSERVED A SLIGHT SHEEN AND BUBBLING IN STANDING WATER INSIDE AN ADJACENT WHISTLE (13-PT-1S/2S) LOCATED APPROXIMATELY 50 FEET FROM THE FLASH FIRE. ADDITIONAL GAS MONITORING WAS STARTED IN THIS WHISTLE AND HYDROCARBON GASES WERE SUBSEQUENTLY DETECTED. THE CONTROL CENTER WAS NOTIFIED, AND THE LINE WAS SHUT DOWN AT 2:15 PM CST. AT 3:50 PM CST, IT WAS DETERMINED THAT A ""CONFIRMED DISCOVERY"" OF AN ACCIDENT REQUIRING NOTIFICATION MAY BE POSSIBLE, AS BOTH THE FLASH FIRE COULD BE RELATED TO A RELEASE OF HAZARDOUS LIQUID, AND THE INVESTIGATION AND CLEAN-UP COSTS COULD EXCEED THE NRC REPORTING THRESHOLD. THE NRC WAS NOTIFIED AT 4:44 PM CST (NRC # 1450035), AND THE MINNESOTA DUTY OFFICER WAS NOTIFIED AT 4:53 PM CST. THE INVESTIGATION REVEALED A CRACK ON THE BELOW GROUND AUXILIARY TUBING OF A NEARBY GATE VALVE. SPECIFICALLY, A BELOW-GRADE THREADED CONNECTION ON THE UPSTREAM GATE SEAT INJECTOR LINE, BETWEEN THE VERTICAL PIPING AND 90-DEGREE FITTING. AN INTERNAL EVENT ANALYSIS DETERMINED THAT THE INABILITY TO PERFORM PREVENTATIVE MAINTENANCE ON BELOW GROUND EQUIPMENT, COMBINED WITH REPEATED THERMAL STRESSES FROM SEASONAL TEMPERATURE CYCLES, FURTHER DEGRADED THE PIPE CONNECTION AND CONTRIBUTED TO THE CRACK IN THE AUXILIARY PIPING. BECAUSE THIS SECTION OF PIPING IS LOCATED BELOW GRADE, VISUAL INSPECTIONS ARE NOT PART OF ROUTINE MAINTENANCE. BOTH GATE SEAT INJECTOR AND THE BODY DRAIN PIPING WERE REPLACED. THE EXISTING SCHEDULE 80 RIGID CARBON STEEL TUBING WAS REPLACED WITH SCHEDULE 160 RIGID CARBON STEEL TUBING FOR ADDED STRENGTH AND TO REDUCE THE RISK OF FUTURE FAILURE. THE LINE WAS RESTARTED ON DECEMBER 11, 2025, AND THE 48-HOUR NRC UPDATE WAS MADE ON DECEMBER 12, 2025, AT 2:56 PM CST (NRC # 1450227). DURING THE INITIAL INCIDENT REPORT TO THE NRC, IT WAS ESTIMATED THAT THE RELEASE VOLUME WAS 40 GALLONS OF WATER AND DILUENT MIX. GIVEN THE SIZE OF THE FEATURE, OBSERVED RATE OF DISCHARGE, AND ESTIMATED DURATION, THE VOLUME IS CALCULATED TO BE 10 GALLONS OF DILUENT RELEASED DURING THE EVENT."