DOMINION ENERGY TRANSMISSION, INC.

Incident Narrative

THIS SUPPLEMENTAL REPORT CONTAINS THE COMPLETE FINDINGS FOR THIS INCIDENT. GAS CONTROL RECEIVED AN INITIAL CALL FROM A LANDOWNER REPORTING THAT A RELEASE OF GAS WAS AUDIBLE ON 10/21/17 AT 3:15 AM. THIS WAS THE INITIAL OPERATOR IDENTIFICATION OF THE INCIDENT. GAS CONTROL RELAYED THE INFORMATION TO THE ON-DUTY OPERATIONS SUPERVISOR. THE ON-DUTY OPERATIONS SUPERVISOR CONTACTED THE LANDOWNER ON 10/21/17 AT 3:20 AM. AT THAT POINT IN TIME, THE LANDOWNER STATED THAT A RELEASE OF GAS WAS INITIALLY AUDIBLE, BUT THE SOUND HAD SINCE SUBSIDED. GAS CONTROL RECEIVED ANOTHER CALL FROM A DIFFERENT LANDOWNER REPORTING THAT A RELEASE OF GAS WAS AUDIBLE ON 10/21/17 AT 8:45 AM. GAS CONTROL RELAYED THE INFORMATION TO THE ON-DUTY OPERATIONS SUPERVISOR. THE ON-DUTY OPERATIONS SUPERVISOR DISPATCHED EMPLOYEE PERSONNEL TO INVESTIGATE. EMPLOYEE PERSONNEL ARRIVED IN THE GENERAL AREA AND INITIATED A SEARCH TO DETERMINE THE EXACT LOCATION OF THE SOURCE OF THE SOUND ON 10/21/17 AT 10:00 AM. ONCE THE EXACT LOCATION OF THE SOURCE OF THE SOUND WAS DETERMINED, THE EMPLOYEE PERSONNEL VISUALLY CONFIRMED ON 10/21/17 AT 12:26 PM THAT GAS WAS BLOWING FROM TWO HOLES IN THE GROUND ON EITHER SIDE OF H-20778. H-20778 CONNECTS LOST CREEK STORAGE WELL CW224 TO TL-414. THIS LEAD TO THE INITIAL BELIEF THAT THERE WAS A MINOR LEAK ON H-20778. THE ESTIMATED PRESSURE ON H-20778 AT THE POINT AND TIME OF THE INCIDENT WAS 995 PSIG. THE EMPLOYEE PERSONNEL ISOLATED THE IMPACTED SEGMENT OF H-20778 BY CLOSING THE UPSTREAM AND DOWNSTREAM MANUAL VALVES ON 10/21/17 AT 1:15 PM. H-20778 WAS EXCAVATED AT THE LOCATION OF THE TWO HOLES IN THE GROUND AND IT WAS DISCOVERED THAT H-20778 HAD A CRACK IN IT ON 10/23/17 AT 1:00 PM. THIS DIFFERED FROM THE INITIAL BELIEF THAT THERE WAS A MINOR LEAK ON H-20778. IT WAS CONFIRMED THAT H-20778 HAD RUPTURED AND THAT THE UNINTENTIONAL ESTIMATED GAS LOSS OF THREE MILLION CUBIC FEET OR MORE THRESHOLD MAY HAVE POSSIBLY BEEN EXCEEDED ON 10/23/17 AT 3:30 PM. INITIAL TELEPHONIC NOTIFICATION WAS MADE TO THE NRC ON 10/23/17 AT 4:07 PM AND NRC REPORT NUMBER 1194074 WAS ISSUED. AN UPDATE NOTIFICATION WAS MADE TO THE NRC ON 10/25/17 AT 8:25 AM, BUT A SUBSEQUENT NRC REPORT NUMBER WAS NOT ISSUED. THE SECTION OF PIPE CONTAINING THE RUPTURE ON H-20778 WAS CUT OUT FOR FURTHER INVESTIGATION. H-20778 WAS NOT IMMEDIATELY RETURNED TO SERVICE AND DID NOT REPRESENT A SAFETY HAZARD. THE INVESTIGATION OF THE SECTION OF PIPE CONTAINING THE RUPTURE ON H-20778 WAS PERFORMED BY KIEFNER AND ASSOCIATES, INC. THE RESULTS OF THE INVESTIGATION INDICATED THAT THE RUPTURE WAS LIKELY THE RESULT OF AXIAL TENSILE OVERLOAD OF THE PIPE WHICH CREATED A CIRCUMFERENTIAL FRACTURE WHICH INITIATED AT THE 12:00 POSITION AND ARRESTED AT THE 3:00 AND 9:00 POSITIONS WITH A MAXIMUM WIDTH OF 0.5 INCHES AND LENGTH OF 9.8 INCHES. THE FRACTURE WAS LOCATED APPROXIMATELY 2.5 INCHES DOWNSTREAM FROM A GIRTH WELD. THE PIPE SURFACE AT AND ADJACENT TO THE GIRTH WELD, WHICH INCLUDED THE LOCATION OF THE FRACTURE, WAS COATED WITH A POLYETHYLENE TAPE / SHRINK SLEEVE WHICH HAD FAILED AT SOME POINT IN TIME AND RESULTED IN CATHODIC PROTECTION SHIELDING. THE PIPE EXHIBITED A BEND AT THE LOCATION OF THE FRACTURE WITH AN APPROXIMATE 3 DEGREE ANGLE OF DEFLECTION. THE PIPE WAS ORIGINALLY INSTALLED WITH NO ANGLE OF DEFLECTION. THIS IMPLIED THAT THE PIPE WAS AFFECTED BY A BENDING LOAD WHICH PLACED THE TOP OF THE PIPE IN TENSION AND THE BOTTOM OF THE PIPE IN COMPRESSION. BENDING OF THE PIPE MAY HAVE OCCURRED DUE TO SOIL MOVEMENT. ADDITIONALLY, THE PIPE SURFACE SURROUNDING THE RUPTURE EXHIBITED METAL LOSS THAT EXCEEDED HALF OF THE PIPE WALL THICKNESS IN SOME LOCATIONS. H-20778 IS LOCATED IN AN OLD STRIP MINE AREA THAT MAY HAVE SUBJECTED H-20778 TO ACID MINE DRAINAGE. BASED ON THE RESULTS OF THE INVESTIGATION AND ADDITIONAL FIELD OBSERVATIONS, A REMEDIATION PLAN WAS DEVELOPED WHICH ENTAILED REPLACING THE ENTIRE LENGTH OF H-20778. THIS WAS COMPLETED AND H-20778 WAS RETURNED TO SERVICE ON 12/5/18 AT APPROXIMATELY 10:30 AM.