TENNESSEE GAS PIPELINE COMPANY

Incident Narrative

ON AUGUST 2, 2021 AT 15:55 LOCAL TIME, TGP STATION 546 UNDERWENT AN EMERGENCY SHUTDOWN (ESD) THAT OCCURRED WHILE THE STATION WAS OFFLINE RESULTING IN THE RELEASE OF NATURAL GAS EXCEEDING THE PHMSA REPORTING THRESHOLD DUE TO NEARBY PIPELINE MAINTENANCE. TGP STATION PERSONNEL ON SITE DURING THE EVENT CONFIRMED THE GAS RELEASE AT 15:55 LOCAL TIME AND AT 16:30, TGP CONFIRMED THE RELEASE EXCEEDED THREE (3) MMSCF AFTER THE STATION ESD SIDE GATE FAILED TO CLOSE DURING THE EVENT. ALL NATURAL GAS SAFELY DISCHARGED TO THE ATMOSPHERE THROUGH THE STATION VENT STACK AT THE STATION. TGP NOTIFIED THE NRC OF THE RELEASE AT 16:40 LOCAL TIME. THE INVESTIGATION REVEALED THAT THE ESD SOLENOID CONTAINED AN INTERNAL SHORT THAT CAUSED THE STATION TO ESD. TGP IDENTIFIED THE ROOT CAUSE OF THE SHORT TO BE AN ELECTRICAL SURGE SUSPECTED TO HAVE ORIGINATED DUE TO A RECENT ELECTRICAL STORM THAT CAUSED THE ESD. TGP ALSO IDENTIFIED THAT THE STATION SIDE-GATE VALVE REMAINED SLIGHTLY OPEN AFTER THE ESD RESULTING IN EXCEEDING THE PHMSA REPORTING THRESHOLD FOR AN UNINTENDED GAS RELEASE. TGP'S INVESTIGATION FOUND THAT PIPELINE DEBRIS WAS PRESENT IN THE SIDE-GATE VALVE ACTUATOR. TGP REPLACED THE DAMAGED SOLENOID AND CLEANED ALL DEBRIS FROM THE SIDE-GATE VALVE INLET FILTERS. THE STATION BECAME AVAILABLE FOR SERVICE ON AUGUST 6, 2021.