TALLGRASS INTERSTATE GAS TRANSMISSION, LLC

Incident Narrative

ON AUGUST 16, 2023, AT 8:07 MT, TALLGRASS OCC RECEIVED A CALL FROM KEITH COUNTY 911 INDICATING A RELEASE OF GAS ON A PIPELINE LOCATED NEAR A MILE MARKER ON HIGHWAY 30. TALLGRASS OCC PERSONNEL LOCATED THE GENERAL AREA OF THE RELEASE AND NOTIFIED TALLGRASS FIELD OPERATIONS PERSONNEL OF THE RELEASE WHO MOBILIZED TO THE SITE. TALLGRASS OCC INITIATED EMERGENCY RESPONSE PROCEDURES AND BEGAN SHUT DOWN OF COMPRESSOR STATIONS TO LIMIT THE RELEASE OF NATURAL GAS. TALLGRASS FIELD OPERATIONS ARRIVED ONSITE AND CONFIRMED LOCATION OF RELEASE AND THE LOCAL FIRE DEPARTMENT HAD ALREADY BLOCKED AND ISOLATED HIGHWAY 30. TALLGRASS FIELD OPERATIONS PERSONNEL THEN CLOSED VALVES TO FURTHER ISOLATE THE RELEASE. ONCE THE RELEASE WAS STOPPED, HIGHWAY 30 WAS REOPENED. THE IMPACTED PIPELINE WAS EXPOSED FOR EVALUATION AND REPAIR. PIPE ON EITHER SIDE OF RELEASE LOCATION ALONG WITH PIECES OF THE PIPE IN THE EXCAVATION WERE COLLECTED AND HAVE BEEN SENT FOR METALLURGICAL EVALUATION. REPLACEMENT PIPE, THAT WAS ALREADY PRESSURE TESTED, WAS WELDED INTO PLACE AND UNDERWENT A UT SURVEY, BLAST AND RECOAT, AND COATING INSPECTION WITH NO HOLIDAYS FOUND. THE PIPELINE WAS PLACED BACK INTO SERVICE ON AUGUST 17, 2023 AT 19:25 MT. 04/17/2024 UPDATE UPDATED E.11 WITH RESULTS FROM CONTROL ROOM INVESTIGATION UPDATED EQUIPMENT IN G3.5 UPDATED WORK PERFORMED IN G3.6 INVESTIGATION RESULTS CONCLUDED THAT THE THIRD-PARTY EXCAVATOR FAILED TO USE ONE CALL SYSTEM PRIOR TO EXCAVATION AND STRUCK THE PIPELINE, RESULTING IN A PIPELINE RUPTURE. THIRD PARTY METALLURGICAL REPORT CONFIRMED THE PIPELINE FAILED DUE TO MECHANICAL DAMAGE AND DID NOT HAVE PREEXISTING DEFECTS AND DID NOT FAIL DUE TO OVERPRESSURE.