PUBLIC SERVICE CO OF NORTH CAROLINA

Incident Narrative

UPDATE TO FINAL REPORT: REVISED PART A, 5.5F LAT. AND LONG. VALUES TO REFLECT A MORE ACCURATE LOCATION OF INCIDENT. REVISED PART C, 5 TO REFLECT OF HOLE SIZE OF 0.4 INCH INSTEAD OF 375.00 INCHES. THE ACTUAL SIZE WAS 0.375 INCH BUT SYSTEM ONLY ALLOWS ONE DECIMAL PLACE. UPDATED COST INFORMATION IN PART D. REPLACED SYMBOLS IN NARRATIVE THAT CAUSE PRINT ERRORS. ADDITIONAL ACTIONS: PROVIDED HUMAN FACTORS INVESTIGATION REPORT TO NCUC ON 2/22/2019 VIA EMAIL. PROVIDED FOLLOW-UP TRAINING DOCUMENTATION TO NCUC ON 2/22/2019 VIA EMAIL. PROVIDED OPERATOR QUALIFICATION AND PROCEDURE INFORMATION TO NCUC ON 2/22/2019 VIA EMAIL. ORIGINAL PROJECT PLAN ON 1/7/19, A PSNC ENERGY CONTRACTOR WAS RETIRING A 350 PSIG 4 IN. LATERAL (M-320) OFF ON OUR 8 IN. TRANSMISSION LINE (T-04) IN ASHEVILLE. THE SPECIFIC LOCATION OF THE WORK WAS NEAR THE INTERSECTION OF SWANNANOA RIVER AND FAIRVIEW ROADS. THIS WORK WAS THE FINAL STEP TO RETIRING A BRIDGE ATTACHMENT ON FAIRVIEW ROAD. THIS PROJECT INCLUDED REROUTING SOME SECTIONS AND DE-RATING PART OF THE 350 PSIG SYSTEM TO A STANDARD DISTRIBUTION SYSTEM PRESSURE OF 60 PSIG. THIS SECTION OF M-320 USED TO FEED SOME REGULATOR STATIONS THAT ARE NOW RETIRED. THE ORIGINAL PROJECT PLAN WAS TO EXCAVATE AND RETIRE THE 4 IN. LATERAL SECTION USING A 4 IN. TD WILLIAMSON (TDW) STOP-OFF FITTING AND REPAVE THIS AREA BY 11 PM THAT NIGHT. SUMMARY OF WHAT HAPPENED WHEN THE PIPE WAS EXPOSED AT ABOUT 11:00 AM IT WAS DISCOVERED THE PIPE WAS 6 IN. SO 6 IN. FITTINGS OF IDENTICAL PRESSURE SPECIFICATIONS WERE ROUNDED UP. A TDW THREAD-O-RING (TOR WHICH IS BASICALLY A 2IN. FITTING USED IN THE TAPPING OPERATION) AND THE 6 IN. STOP-OFF FITTING WERE WELDED ON THE PIPE. THE TOR WAS TAPPED AT ABOUT 6 PM BY OUR TAPPING CONTRACTOR, WHEN IT WAS DISCOVERED THAT THE 6 IN. PIPE WAS ACTUALLY CASING PIPE OVER THE 4 IN. PIPE. THE PILOT BIT PENETRATED THE 4 IN. LINE CREATING A 3/8 IN. HOLE THAT SENT GAS IN BOTH DIRECTIONS DOWN THE CASING. THE TAPPING CONTRACTOR TECHNICIAN AND THE PIPELINE CONTRACTOR SUPPORT PERSONNEL EVACUATED THE HOLE. PSNC ENERGY HAD AN INSPECTOR ON SITE AND ADDITIONAL PSNC ENERGY PERSONNEL WERE BROUGHT IN TO MONITOR BOTH ENDS OF THE CASINGS FOR GAS MIGRATION. GASEOUS ATMOSPHERE WAS ABOUT 25-30 FT. RADIUS FROM THE BELL HOLE CONTAINING THE TOR. THE PROJECT DESIGN SPECIFIED THE REMAINING LATERAL STUB TO BE AS SHORT AS POSSIBLE SO THERE WAS NO ROOM TO INSTALL ANOTHER STOP-OFF FITTING. THIS MADE THE REPAIR/SHUT-OFF PLAN MORE COMPLEX. THE SECTION OF TRANSMISSION LINE CONTAINING THE LATERAL CONNECTION WAS GOING TO HAVE TO BE ISOLATED TO STOP THE LEAK. THIS IS A SINGLE FEED SYSTEM SO A BYPASS WAS REQUIRED. PSNC ENERGY WAS ABLE TO ROUND UP TWO TDW 3-WAY TEES (WHICH ARE DESIGNED TO FACILITATE BOTH STOP-OFF AND BYPASS) FROM ANOTHER JOB. TRANSMISSION CONTRACT CREWS WERE BROUGHT IN TO WELD ON THE FITTINGS AND TO WELD UP AND INSTALL A 120 FT. 8 IN. BYPASS. TWO REMOTE BELL HOLES WERE DUG TO INSTALL THE FITTINGS ON T-04. THE SHUTDOWN PROCESS OF INSTALLING FITTINGS AND BYPASS, TESTING AND PURGING THE BYPASS, STOPPING OFF THE DAMAGED SECTION, AND TRANSFERRING THE FLOW TO THE BYPASS LASTED FROM APPROXIMATELY 8:00 PM ON 1/7/19 UNTIL 11:10 AM ON 1/8/19. REPLACING THE DAMAGED LATERAL CONTAINING THE SECTION OF T-04 WITH PRE-TESTED PIPE AND PLACING THE PIPELINE BACK IN SERVICE TOOK UNTIL 11:10 AM ON 1/8/19. BACKFILLING AND ROAD REPAIR LASTED THROUGH THE EVENING. OTHER INFORMATION OF NOTE THE EMERGENCY RESPONSE AND REPAIR PROCESSES REQUIRED THE SHUT-DOWN OF SWANNANOA RIVER ROADS. THE ENTIRE STOPPAGE OF THE LEAK AND REPAIR WERE WORKED OUTSIDE OF THE HAZARDOUS GASEOUS ENVIRONMENT. PSNC WORKED WITH LOCAL NEWS TO PUT OUT TRAFFIC ADVISORIES. PSNC ENERGY'S IN HOUSE INSPECTOR WAS DRUG TESTED SINCE HIS ACTIONS CONTRIBUTED TO THE INCIDENT. THE NCUC HAD PIPELINE SAFETY OFFICERS ON THE SCENE. SCANA GAS SERVICES FACILITATED A HUMAN FACTOR INVESTIGATION OF THE INCIDENT. THE HFI REPORT IS INCOMPLETE AS OF 1/29/19.