DCP MIDSTREAM, LP

Incident Narrative

PIPELINE PRESSURE SNAPSHOT ON 7/19/2023 SHOWED LOWER THAN NORMAL OPERATING PRESSURES ON THE NN LINE, A TYPE C CLASS 1 GATHERING LINE. WE BEGAN PATROLLING THE LINE LOOKING FOR ANY ABNORMALITIES. CONFIRMATION OF A FUTURES RISER FLANGE ASSEMBLY FAILURE OFF OF THE NN LINE WAS DISCOVERED. INCIDENT WAS LATER CONFIRMED REPORTABLE BY GAS LOSS CONFIRMATION. INCIDENT WAS THEN TELEPHONICALLY REPORTED TO THE NMPRC AND NRC AT TIME OF GAS LOSS CALCULATION VERIFICATION. INCIDENT CAUSE UNDER INVESTIGATION. METALLURGICAL EXAMINATION BEING CONDUCTED AND SUPPLEMENTAL REPORT WILL BE FILED INCLUDING COST OF EXAMINATION AND ROOT CAUSE OF FAILURE. DESIGN PRESSURE WAS USED FOR MAOP IN PART E. SUPPLEMENTAL REPORT 10-10-23 ADDRESSING PHMSA COMMENTS. UPDATED COST TO REFLECT METALLURGICAL ANALYSIS. UPDATED CAUSE WITH RESULTS OF METALLURGICAL ANALYSIS. ROOT CAUSE DETERMINED BY METALLURGICAL EXAMINATION REVEAL: THE DEAD LEG OF NN LINE RUPTURED AT THE PUP BETWEEN THE TWO ELBOWS FROM A COMBINATION OF CARBONIC ACID CORROSION AND H2S CORROSION THAT ORIGINATED AT THE INTERNAL DIAMETER OF THE LINE.