COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

ON DECEMBER 19, 2017, FLAT TOP COMPRESSOR STATION (CS) WAS SUBJECT TO AN UNINTENTIONAL RELEASE OF NATURAL GAS (MATERIAL) RESULTING IN GAS LOSS OF MORE THAN 3,000 MCF. FLAT TOP IS A TRANSMISSION CS THAT IS MAINTAINED BY COLUMBIA GAS TRANSMISSION, LLC (TRANSCANADA). FLAT TOP CS IS LOCATED IN SUMMERS COUNTY, NEAR THE TOWN OF FLAT TOP, WEST VIRGINIA. AFTER THE REMOTE SHUTDOWN OF CS UNIT# 3, MATERIAL PASSED THROUGH A SMALL OPENING OF A 20 INCH BALL VALVE. SUBSEQUENTLY, MATERIAL EXITED A 3 INCH BLOWDOWN STACK TO ATMOSPHERE BEGINNING ON DECEMBER 19, 2017 AT APPROXIMATELY 21:19 EST FOR ABOUT 164 MINUTES. THE PRESSURE IN THE CS UNIT'S PIPING SLOWLY DECREASED FROM APPROXIMATELY 813 PSIG TO 740-760 PSIG. THE 20 INCH BALL VALVE WAS CLOSED AT 00:35 EST ON DECEMBER 20, 2017. OPERATION PERSONNEL NOTICED UNIT# 3 WAS DOWN WHILE INVESTIGATING A NOTIFICATION OF A STATION MODE CHANGE. GAS CONTROL WAS CONTACTED TO SEE IF A CALLOUT WAS MADE. PERSONNEL WAS NOT DISPATCHED TO MONITOR THE VALVE OPERATION. LOCAL PERSONNEL REPORTED TO THE LOCATION TO CLOSE THE VALVE AND STOP THE RELEASE OF NATURAL GAS. SCADA UPGRADES PLACED INTO SERVICE ON 8/22/2017, SET WARNING TAG TO ALERT THE GAS CONTROLLER TO REQUEST A CALLOUT FOR LOCAL OPERATING PERSONNEL TO MONITOR THE 20 INCH BALL VALVE OPERATION ON UNIT# 3. THIS WAS SET UP AS AN INTERIM PROCESS UNTIL A NEW VALVE ACTUATOR WAS INSTALLED IN 2018. DURING THE SCADA UPGRADE THE WARNING TAG WAS INADVERTENTLY REMOVED FROM THE DISPLAY. IN ORDER TO PREVENT A REOCCURRENCE, PROCEDURE CHANGES HAVE BEEN IMPLEMENTED TO PREVENT A WARNING TAG FROM BEING REMOVED. ADDITIONALLY, A NOTIFICATION EMAIL HAS BEEN ESTABLISHED IF UNIT#3 GOES OUT OF RUN STATUS FOR ANY REASON, SEVERAL KEY OPERATORS ARE NOTIFIED OF THE STATUS CHANGE.