NORTHWEST PIPELINE LLC

Incident Narrative

IN APRIL OF 2020 WILLIAMS CONTRACTED WITH AN IN-LINE INSPECTION VENDOR TO COMPLETE TOOL RUNS ON THE WILLIAMS NORTHWEST PIPELINE 1400 POCATELLO TO BURLEY SEGMENT. HIGH-RES MFL TOOL RUNS WERE CONDUCTED, AND A PRELIMINARY REPORT WAS PROVIDED TO WILLIAMS WITH ANOMALIES ON THE WEEK OF 5/25/2020. WILLIAMS INITIATED PROJECTS TO ADDRESS ANOMALIES IN ORDER OF PRIORITY. THIS PARTICULAR DIG DID NOT MEET THE SAME CRITERIA AS OTHER'S IN THE AREA - UNDER CALLED BY THE TOOL. AS A RESULT THIS PIN HOLE WAS NOT DISCOVERED UNTIL REMEDIATION OF OTHER LEAKS IN THE SAME GENERAL AREA HAD BEEN COMPLETED. SIMILAR TO OTHER ANOMALIES IN THE AREA EXCAVATION UNCOVERED A PIN-HOLE LEAK RESULTING FROM CORROSION. LEAK SURVEYS PRIOR TO FEATURE ASSESSMENT DID NOT SHOW ANY SIGNS OF LEAKING. ASSESSMENTS INCLUDED AERIAL LEAK SURVEY 9/22/2020, AND GROUND SURVEY 9/23/2020. THERE WAS NO INDICATION OF FOUL ODORS OR DISCOLORED VEGETATION PRIOR TO DIGGING. THE FIRST INDICATION OF GAS OCCURRED AFTER THE FEATURE WAS UNCOVERED. IT IS ESTIMATED THAT THE FEATURE LEAKED FROM THE FIRST INDICATION OF GAS FOR APPROXIMATELY 3 HOURS BEFORE THE LINE WAS SHUT IN AND BLOWN DOWN FROM AN OPERATING PRESSURE OF ABOUT 600PSIG TO 14PSIG. AFTER ASSESSING REPAIR OPTIONS WILLIAMS PROJECT MANAGEMENT DETERMINED THAT REPAIRS WOULD BE BEST ACCOMPLISHED THROUGH PIPE REPLACEMENT. THE PRELIMINARY COST OF REPAIRS EXCEEDS $50,000, WITH COST OF CONTRACTOR AND INTERNAL LABOR APPROACHING $200,000. IT WAS DETERMINED THAT THIS QUALIFIED AS A DOT REPORT-ABLE INCIDENT BASED ON COST WHEN WILLIAMS MANAGEMENT SETTLED ON PIPE REPLACEMENT AS THE PREFERRED REPAIR OPTION ON 9/24/2020. THE NRC WAS INITIALLY NOTIFIED OF THE INCIDENT ON 9/24/2020. THE LINE WAS RETURNED TO SERVICE ON 10/21/2020