TRUNKLINE GAS CO

Incident Narrative

10/17/19 NRC TELEPHONIC NOTIFICATION MADE AT 19:58 NRC#1261451. PHMSA AID NOTIFIED 20:13. 10/18/19 PHMSA AID UPDATED AT 14:00. 10/19/19 48-HOUR UPDATE NRC NOTIFICATION MADE AT 15:19 NRC#1261620. PHMSA AID UPDATED AT 15:39. THE SUPPLEMENTAL/FINAL REPORT DATED 12/11/19, PROVIDES FURTHER CLARIFICATION/CORRECTIONS FOR THE FOLLOWING SECTIONS: PART A, QUESTION 10. THE ESD SYSTEMS OPERATED AS DESIGNED. THERE WAS A STATION YARD BLOCK VALVE OUTSIDE THE ESD SYSTEM THAT WAS INADVERTENTLY OPEN THAT CONTRIBUTED TO THE AMOUNT RELEASED. PART E, QUESTION 7. RECEIVED AN ESD SAFETY STATUS ALARM FOR THE FUEL METER AT EPPS STATION THAT THE CONTROLLER ACKNOWLEDGED IMMEDIATELY. THE COMMUNICATIONS AT EPPS STATION WENT DOWN THE SAME TIME AS THE ESD TRIPPED. GAS CONTROL COULD NOT SEE A PROBLEM UNTIL THERE WAS A PRESSURE DROP AT THE UPSTREAM AND DOWNSTREAM LOCATIONS. COMMUNICATIONS WERE OUT AT THE STATION SO THE CONTROLLERS WERE NOT ABLE TO CONFIRM AN ACTUAL ESD. CONTROLLERS REVIEWED UPSTREAM AND DOWNSTREAM PRESSURES AND THERE WERE NO NEGATIVE RATE OF CHANGE ALARMS PRESENT. UPSTREAM PRESSURE STARTED TO SHOW A SLOW DECLINE IN PRESSURE. LOCAL SHERIFF'S DEPT CALLED IN A FEW MINUTES LATER AND REPORTED THERE WAS GAS BLOWING AT THE STATION. THE CONTROLLERS IMMEDIATELY DISPATCHED FIELD PERSONNEL TO THE SCENE AND STARTED AN EVERBRIDGE CONFERENCE BRIDGE TO ALERT MANAGEMENT AND FIELD PERSONNEL IN THE AREA. PART E, QUESTION 8. UPDATED YES, BASED ON THE INVESTIGATION NO CONTROLLER ISSUES WERE IDENTIFIED. PART H, THE UPS FOR THE ESD SYSTEM AND COMMUNICATION EQUIPMENT IS SIZED TO MAINTAIN POWER FOR A MINIMUM OF 4 HOURS AND WE HAVE A BACK-UP GENERATOR THAT WILL COME ON-LINE WHEN THERE IS A LOSS OF COMMERCIAL POWER ACROSS THE WHOLE STATION. THE BREAKER THAT TRIPPED WAS SUPPLING POWER TO THE CONTROL BUILDING ONLY, WHERE THE ESD CONTROLS AND COMMUNICATION EQUIPMENT IS LOCATED. IF THERE WOULD HAVE BEEN A LOSS OF COMMERCIAL POWER OF THE WHOLE STATION THE GENERATOR WOULD HAVE STARTED AUTOMATICALLY AND GAS CONTROL WOULD HAVE RECEIVED AN ALARM. THE UPS BATTERIES WOULD NOT HAVE RUN DOWN. THE STATION YARD BLOCK VALVE WAS IDENTIFIED AND LOCKED CLOSED. AN ALARM HAS BEEN INSTALLED TO NOTIFY GAS CONTROL IF THERE IS A FUTURE POWER LOSS AT THIS CONTROL BUILDING TO PREVENT RECURRENCE.