TRANSCONTINENTAL GAS PIPE LINE COMPANY

Incident Narrative

ON FRIDAY, FEBRUARY 9TH, 2024, WILLIAMS CALLED THE NRC TO REPORT AN INCIDENT NORTH OF STATION 190 NEAR MILEPOST 1655 ON TRANSCO MAINLINE A, ORIGINAL NRC# 1391164. A GAS SMELL WAS REPORTED THURSDAY, FEBRUARY 8TH, 2024. WILLIAMS EMPLOYEES HEADED TO THE SCENE TO INVESTIGATE THE SAME DAY BUT WERE UNABLE TO LOCATE THE LEAK. OPERATIONS CONTINUED TO LOOK FOR THE LEAK AND LOCATED IT THE FOLLOWING MORNING ON FRIDAY, FEBRUARY 9TH, 2024. THE AFFECTED SECTION OF THE LINE WAS SUBSEQUENTLY ISOLATED WITHIN 3 HOURS AFTER THE LEAK WAS IDENTIFIED. RELEASE RATE IS CURRENTLY ESTIMATED AT 2342 SCF PER DAY. EQUIPMENT WAS MOBILIZED TO SITE TO DRAWDOWN AND EXCAVATE. DRAWDOWN BEGAN SUNDAY, FEBRUARY 11TH, 2024 AND WAS COMPLETED ON THE 13TH. EXCAVATION WAS SUBSEQUENTLY STARTED THE SAME DAY. EXCAVATION AND DRAW DOWN WAS COMPLETED ON THE 14TH. BLOWDOWN OCCURRED ON THE 14TH AND CUT-OUT/TIE-IN WAS DONE ON THE 15TH. ON FEBRUARY 16TH, 2024 THE COATING PROCESS WAS COMPLETED AND THE LINE WAS PLACED BACK IN SERVICE. AN INVESTIGATION AND ROOT CAUSE WAS CONDUCTED TO IDENTIFY THE CAUSE OF THE FAILURE. AFTER THE INVESTIGATION AND RESULTING METALLURGICAL ANALYSIS, THE LEAK ORIGINATED WITHIN AN ORIGINAL MANUFACTURING MILL WELD REPAIR OR ""SQUIRT WELD"" PASS APPLIED TO THE DSAW SEAM WELD IMMEDIATELY UPSTREAM OF THE GIRTH WELD PROVIDED. THE LEAK WAS THE RESULT OF SOLIDIFICATION CRACKS PRESENT WITHIN THE EXTERNAL AND INTERNAL SEAM WELD PASS THAT WERE POSITIONED IMMEDIATELY ADJACENT TO ONE ANOTHER.