TENNESSEE GAS PIPELINE COMPANY

Incident Narrative

DAY OF DISCOVERY: ON 11/18/19, A KM MEASUREMENT TECH ARRIVED AT THE UNMANNED TGP STATION 856 FOR THE PURPOSE OF READING FUEL METER INDEXES. HE NOTICED A GAS RELEASE SOUND UPON EXITING HIS VEHICLE NEAR THE COMPRESSOR BUILDING. THE TECH REPORTED THE ISSUE TO THE OPERATIONS SUPERVISOR AND WAS INSTRUCTED TO TRY TO IDENTIFY THE LEAK. HE IDENTIFIED IT WAS COMING FROM THE BLOWDOWN SILENCER AS THE TECH COULD VISUALLY SEE THE GAS VENTING AND ALSO OBSERVED FROSTING ON THE SILENCER. THE TECH THEN PROCEEDED TO THE CONTROL ROOM AND ULTIMATELY IDENTIFIED THAT THE NORMALLY CLOSED REMOTED OPERATED 4IN COMPRESSOR LOADING VALVE WAS OPEN ON THE UNIT #2 LOAD LINE ALLOWING GAS TO VENT THROUGH THE NORMALLY OPEN COMPRESSOR VENT VALVE. THE TECH PROCEEDED TO CLOSE THE MANUAL BLOCK VALVE ON THE LOAD LINE ASSEMBLY AT 1:36PM TO STOP THE LEAK. THE LEAK STOPPAGE WAS REPORTED TO KM MANAGEMENT AT 1:40PM. AT THE TIME OF THE INCIDENT, IT WAS UNKNOWN THE QUANTITY OF GAS RELEASED BUT ON THE 2:35PM ERL CALL IT WAS DETERMINED TO REPORT TO THE NRC AS A PRECAUTION. IT WAS REPORTED TO THE NRC AT 2:46PM LOCAL TIME WITH THE UNKNOWN AMOUNT. THE REPORT NUMBER WAS 1264245. 48 HOUR UPDATE: DURING INVESTIGATION, IT WAS DETERMINED THAT THE GAS HAD BEEN VENTING THROUGH THE BLOWDOWN SILENCER FOR ABOUT 6 DAYS. THIS WAS REPORTED TO THE NRC (#1264366) ON THE 48 HR UPDATE AT 4:54PM LOCAL TIME ON 11/19/19. INVESTIGATION: DURING INVESTIGATION, IT WAS IDENTIFIED THAT THE UNIT #2 LOAD LINE VALVE OPENED ON 11/12/19 AT 11:43PM. THE LOAD LINE VALVE OPENED AS A RESULT OF FREEZING UP OF MOISTURE IN THE SOLENOID CONTROL BOX. AT STA 856, THE TEMPERATURE ON 11/12/19 WENT BELOW FREEZING AT 4PM AND WAS APPROXIMATELY 22