NORTHWEST PIPELINE LLC

Incident Narrative

ON JULY 28TH, 2022 THERE WAS AN IMPROPER SEALING OF A UNIT VALVE AT NORTHWEST PIPELINE WILLARD COMPRESSOR STATION. WILLIAMS OPERATIONS RECEIVED A CALL FROM SKAMANIA COUNTY 911 DISPATCH AT 22:10 LOCAL TIME REPORTING A STRONG SMELL OF GAS FROM A NEIGHBOR NEAR THE COMPRESSOR STATION. WILLIAMS OPERATIONS PERSONNEL IMMEDIATELY RESPONDED TO THE CALL AND ARRIVED ON-SITE AT 23:50 LOCAL TIME TO ASSESS THE SITUATION. WHILE ON-SITE IT WAS DISCOVERED THAT THE VENT VALVE ON UNIT ONE AT THE COMPRESSOR STATION WAS SHOWING CLOSED ON THE HMI BUT WAS STILL VENTING GAS. IN AN EFFORT TO STOP THE GAS FROM VENTING AS QUICKLY AS POSSIBLE OPERATIONS TECHNICIANS AT THE SITE CONSULTED WITH PIPELINE CONTROL AND THE OPERATIONS SUPERVISOR AND AGREED TO ISSUE A START COMMAND TO UNIT ONE. ISSUING THIS START COMMAND WAS FOUND TO CAUSE ALL VALVES TO POSITION THEMSELVES CORRECTLY, THUS STOPPING THE GAS FROM VENTING TO THE ATMOSPHERE. SHORTLY AFTER, A STOP COMMAND WAS SUBSEQUENTLY ISSUED TO THE SAME UNIT, WITH OPERATIONS NOTING THAT ALL VALVES ALSO CORRECTLY POSITIONED THEMSELVES AGAIN. IT WAS NOTED BY PIPELINE CONTROL THAT THIS UNIT WOULD NOT BE NEEDED FOR THE REST OF THE NIGHT, SO UNIT ONE WAS LEFT OFF AND UNAVAILABLE UNTIL THE NEXT DAY. ONCE THE UNIT HAD BEEN SHUT DOWN AND NO ADDITIONAL VENTING WAS CONFIRMED, OPERATIONS CONTACTED THE SECURITY OPERATIONS CENTER (SOC) AT 01:40 LOCAL TIME. AT THIS TIME, THE SOC RAN GAS LOSS ESTIMATION CALCULATIONS AND WAS ABLE TO CONFIRM DISCOVERY THAT THE 3MMSCF RELEASE THRESHOLD WAS REACHED. SHORTLY AFTER, AT 01:52, AFTER A CONVERSATION BETWEEN THE SOC AND PIPELINE SAFETY, IT WAS DETERMINED TO REPORT THE INCIDENT TO THE NRC. OPERATIONS PERSONNEL THAT RESPONDED TO THE INCIDENT WENT HOME TO REST BEFORE ARRIVING ON-SITE THE NEXT MORNING TO CONTINUE THE TROUBLESHOOTING PROCESS. THE FOLLOWING MORNING OPERATIONS AND TECH SERVICES EMPLOYEES WORKED TO TROUBLESHOOT THE VALVE POSITION INDICATORS AND WERE NOT ABLE TO RECREATE THE PROBLEM THAT CAUSED UNIT ONE SUCTION VALVE TO REMAIN CRACKED DURING A REMOTE STOP. TO BETTER ALERT OPERATION PERSONNEL OF A SIMILAR INCIDENT OCCURRING, PIPELINE CONTROL PLACED A TEMPORARY PRESSURE ALARM TO MONITOR CASE PRESSURE. OVER THE COURSE OF THE FOLLOWING WEEKS, OPERATIONS PERSONNEL ATTEMPTED TO RECREATE THE ISSUE TO BETTER UNDERSTAND WHAT CAUSED THE INITIAL INCIDENT. MULTIPLE EFFORTS TO RECREATE THE ISSUE WERE UNSUCCESSFUL AND A FULL ROOT-CAUSE INVESTIGATION HAS SINCE TAKEN PLACE. THE FINDINGS OF THE INVESTIGATION REVEALED THAT THE UNIT 1 BLOWDOWN VALVE HAD BEEN LEAKING 12 HOURS PRIOR TO PIPELINE CONTROL RECEIVING NOTIFICATION FROM THE EMERGENCY DISPATCH. THE INVESTIGATION INTO WHY THE BLOWDOWN VALVE FAILED TO SEAL FOUND THAT THERE WAS LIKELY SOME DEBRIS IN THE SEAT OF THE UNIT VALVE THAT CAUSED IT TO NOT SEAL PROPERLY. IT'S BELIEVED THAT THESE DEBRIS MAY HAVE ORIGINATED FROM PIPELINE CLEANING / PIGGING EFFORTS AS PART OF A SERIES OF HYDROTEST PROJECTS THAT HAD RECENTLY OCCURRED IN THE AREA. IT WAS ALSO FOUND THAT POWER TURBINE PERCENT SPEED AND SUCTION/DISCHARGE PRESSURES WERE NOT UTILIZED TO SHOW INDICATION OF A POTENTIAL ISSUE WITH THE COMPRESSOR. THESE ITEMS WEREN'T SPECIFICALLY REVIEWED AT THE TIME AS THERE WERE NO ALARMS GIVEN TO PIPELINE CONTROL. TO PREVENT THIS FROM HAPPENING IN THE FUTURE, WILLIAMS IS IMPLEMENTING A CONTINUOUS VENTING UNIT ALARM WITHIN SCADA, STATION, AND UNIT CONTROL SYSTEMS.