COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

ON AUGUST 12TH, 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 AUGUST 12TH, 2017 AT APPROXIMATELY 11:00 ET. THE PRESSURE IN THE CS UNIT'S PIPING SLOWLY DECREASED FROM 770 PSIG UNTIL APPROXIMATELY 22:00 EST ON AUGUST 12TH, 2017. AT THIS TIME, THE PRESSURE STABILIZED AT 560 PSIG UNTIL THE LEAK WAS ISOLATED. AT APPROXIMATELY 09:00 EST ON AUGUST 13TH, 2017, A PASSERBY REPORTED TO TRANSCANADA THAT IT APPEARED THAT MATERIAL WAS VENTING THROUGH A BLOW-OFF VALVE AT FLAT TOP CS. IMMEDIATELY AFTER THIS WAS REPORTED, OPERATIONS PERSONNEL WERE DISPATCHED TO INVESTIGATE THE SITUATION. ON AUGUST 13TH, 2017, OPERATIONS PERSONNEL ARRIVED ON-SITE AT APPROXIMATELY 09:40 EST, THE UNINTENDED RELEASE OF MATERIAL WAS IDENTIFIED AND ISOLATED AT APPROXIMATELY 10:15 EST. ONCE OPERATIONS PERSONNEL HAD ISOLATED THE LEAK AND MADE THE AREA SAFE, GAS CONTROL WAS NOTIFIED AND IMMEDIATELY CONTACTED TRANSCANADA'S ON-CALL SPECIALIST AT 11:05 AM ON AUGUST 13TH. AFTER TRANSCANADA'S ON-CALL SPECIALIST HAD BEEN NOTIFIED, AND GAS LOSS CALCULATIONS WERE DETERMINED TO BE GREATER THAN 3,000 MCF, THE EVENT WAS REPORTED TO THE NATIONAL RESPONSE CENTER. BEFORE RETURNING THE UNIT BACK TO SERVICE, THE FAULTY VALVE WAS MANUALLY CYCLED FROM THE STATION PANEL AND FULL CLOSURE WAS ACHIEVED. THE OPERATOR THEN CYCLED THE VALVE ONCE MORE TO ENSURE PROPER FUNCTIONALITY. NO ISSUES WERE DISCOVERED ON THE FOLLOW UP INVESTIGATION. A RCA DISCOVERED A REPLACED VALVE ACTUATOR DID NOT HAVE THE REQUIRED TORQUE TO CLOSE A A 20"" BALL VALVE. A NEW ACTUATOR WILL BE INSTALLED IN 2018. UNTIL A NEW ACTUATOR IS INSTALLED, SCADA WARNING TAGS WILL BE USED TO ALERT GAS CONTROL AN EMPLOYEE WILL NEED TO BE PRESENT TO OBSERVE THE VALVE CLOSURE WHEN UNIT 3 IS SHUTDOWN.