TENNESSEE GAS PIPELINE COMPANY

Incident Narrative

ON MARCH 29TH, 2021, AT 12:35AM, TENNESSEE GAS PIPELINE COMPANY, LLC (TGP) RECEIVED AN ESD ALARM AT ITS COMPRESSOR STATION 542 IN KEMPER COUNTY, MISSISSIPPI. UPON RECEIPT OF THE ALARM, GAS CONTROL DISPATCHED A TECHNICIAN TO THE SITE TO INVESTIGATE. AFTER ARRIVING ON SITE AT APPROXIMATELY 12:55AM THE TECHNICIAN FOUND VALVE 542AS-2R, AN EMERGENCY VALVE WHICH IS USED TO ISOLATE THE STATION IN THE EVENT OF THE ESD, OPEN AND THE VALVE SELECTOR IN THE MANUAL POSITION. AFTER CHANGING THE VALVE SELECTOR TO THE AUTOMATIC POSITION THE VALVE CLOSED AT 1:05AM, ENDING THE GAS RELEASE. INITIAL GAS RELEASE ESTIMATES PUT THE RELEASE BELOW THE 3,000 MCF THRESHOLD FOR REPORTING. LATER THAT MORNING AT 9:40AM TGP HAD CONFIRMED DISCOVERY OF THE INCIDENT WHEN IT WAS DISCOVERED THAT THE INITIAL GAS RELEASE CALCULATIONS WERE INCORRECT AND THE GAS LOSS WOULD EXCEED THE REPORTABLE THRESHOLD. TGP BEGAN TESTING THE ESD SYSTEM AT STATION 542 ON OCTOBER 26, 2020. DURING THIS TEST, TGP SWITCHED THE VALVE 542AS-2R SELECTOR INTO THE MANUAL POSITION AND INSTALLED PLUGS WITHOUT WEEP HOLES INTO THE ESD SYSTEM. TGP STATION 542 HAS A PRESSURE TO ACTIVATE ESD SYSTEM. THE PLUGS WITH WEEP HOLES DO NOT ALLOW A SMALL VALVE LEAK ON THE ESD SYSTEM TO PRESSURIZE THE ESD SYSTEM AND TRIGGER AN ESD. AFTER COMPLETION OF THE ESD TEST, TGP DID NOT REINSTALL THE PLUGS WITH WEEP HOLES INTO THE SYSTEM. THE ESD SYSTEM WAS ACTIVATED AS A RESULT OF THE SYSTEM SLOWLY BECOMING PRESSURIZED DUE TO NOT REINSTALLING THE PLUGS WITH WEEP HOLES INTO THE ESD SYSTEM AFTER COMPLETION OF THE ESD TEST. BECAUSE THE VALVE 542AS-2R SELECTOR WAS IN THE MANUAL POSITION, THE VALVE DID NOT CLOSE WHEN THE ESD SYSTEM WAS ACTIVATED. RESULTANTLY, AFTER THE ESD, GAS CONTINUED TO VENT UNTIL THE VALVE 542AS-2R SELECTOR WAS PLACED INTO THE AUTOMATIC POSITION. TGP HAS REVOKED THE OPERATOR QUALIFICATION ASSOCIATED WITH ESD TESTING FOR THE INDIVIDUALS INVOLVED IN THE OCTOBER 2020 ESD TEST. TGP WILL INSTALL SIGNAGE TO REMIND EMPLOYEES TO LEAVE THE ESD REMOTE VALVE SELECTORS IN THE AUTOMATIC POSITION. TGP WILL REVISE ITS STATION 542 ESD TESTING PROCEDURES TO PROVIDE INSTRUCTIONS FOR LEAVING THE WEEP-HOLE PLUGS IN THE ESD SYSTEM DURING THE TEST AND LEAVING ESD VALVE SELECTORS IN THE CORRECT POSITION UPON COMPLETION OF THE TEST. IN PART E 1.A, THE ESTIMATED GAS FLOW IN PIPE SEGMENT AT THE POINT AND TIME OF THE INCIDENT (MSCF/D) IS 1,322,000 MSCF/D.