TRANSCONTINENTAL GAS PIPE LINE COMPANY

Incident Narrative

ON WEDNESDAY, 08/23/2023 AT APPROXIMATELY 3:07 PM EST (15:07), OPERATIONS WAS NOTIFIED BY THE CHIEF INSPECTOR FOR THE TRYON LATERAL ANOMALY DIGS AND INSPECTIONS THAT THEY HAD EXCAVATED, SAND BLASTED, AND WERE INSPECTING ANOMALY 24520 WHEN THEY STARTED SMELLING GAS. THE CREW STOOD DOWN AND AWAITED OPERATIONS ARRIVAL. TRYON LATERAL PIPELINE HAD ALREADY BEEN ISOLATED AT STATION 140 AND DRAWN DOWN TO 557 PSI ON 8/22/2023 IN PREPARATION FOR THE ANOMALY DIGS PLANNED TO BE STARTED ON 8/23/2023. OPERATIONS ARRIVED AT SITE WITH ADDITIONAL LEAK DETECTION EQUIPMENT AT APPROXIMATELY 3:50 PM ET (15:50) AND BEGAN SURVEYING FOR GAS USING AN INFRARED OPTICAL GAS DETECTOR WITH A PUMP NEAR THE ANOMALY INSPECTION AREAS, DETECTING A LEAK AT APPROXIMATELY 3:58 PM ET (15:58). THE LEAK WAS VERY SMALL BUT REGISTERED GAS WITH INFRARED LEAK DETECTOR CUP IMMEDIATELY OVER REGION OF CRACK AREA AND CAUSED READILY VISIBLE BUBBLING OF THE SNOOP THE OPS TECHS NOTIFIED OPS MANAGER AT 4:10 PM ET (16:10). IT WAS DECIDED THAT THE ISOLATED PIPELINE PRESSURE WOULD BE FURTHER REDUCED TO LESS THAN 400 PSI WHICH WOULD RESULT IN CALCULATED STRESS LEVEL OF 24.6% SMYS. AND IN ADDITION TO THE ADDITIONAL REDUCTION IN PRESSURE, TEMPORARY REPAIR CLAMPS WOULD BE INSTALLED, AND ONCE INSTALLED, IT WOULD BE SAFE TO COMPLETE THE REMAINING ANOMALY DIGS BEFORE COMING BACK TO CUT OUT THE LEAKING FEATURE. DUE TO THE PROXIMITY TO A NEARBY HOME, IT WAS DECIDED TO INFORM THE RESIDENT OF THE SITUATION AND OFFER FOR THEM TO GO TO A LOCAL HOTEL FOR THE NIGHT. THE RESIDENT ACCEPTED AND VACATED THEIR HOME FOR APPROXIMATELY 24 HOURS UNTIL THE TEMPORARY REPAIR CLAMPS WERE INSTALLED. ONCE IT WAS DECIDED THAT REPAIR CLAMPS WOULD BE UTILIZED AND THAT THE LOCAL RESIDENT WAS LEAVING THEIR HOME, THE NRC WAS NOTIFIED OF THE EVENT. STATION 140 WAS UTILIZED TO COMPLETE DRAWING DOWN THE TRYON LATERAL PRESSURES TO 387 PSI AT 8:33 PM ET (20:33). THE LATERAL REMAINED ISOLATED OVERNIGHT. THE FOLLOWING MORNING, THURSDAY, 8/24/2023, THE TEMPORARY CLAMPS ARRIVED AT STATION 140 AT AROUND 8:30 AM ET AND WERE TRANSPORTED TO THE DIG SITE TO BE INSTALLED. AT 11:30 AM ET, CLAMP 1 INSTALLATION WAS COMPLETED, LEAK CHECKED, AND NO LEAKS PRESENT AFTER INSTALLATION. AT 1:00 PM ET (13:00), CLAMP 2 INSTALLATION WAS COMPLETED, LEAK CHECKED, AND NO LEAKS PRESENT AFTER INSTALLATION. DIG #14 (ANOMALY 24520) IS BEING VISITED BY OPERATIONS / CONSTRUCTION DAILY UNTIL THE CUTOUT AND REPLACEMENT TO VERIFY DIG SITE IS SECURE, FENCING IS IN GOOD SHAPE, AND TO PERFORM LEAK SURVEYS TO VERIFY NO LEAKS.