NORTHWEST PIPELINE LLC

Incident Narrative

AT 10:01 AM MARCH 29 2017 GAS CONTROL RECEIVED A HIGH PRESSURE ALARM AT THE NORTH TACOMA METER STATION. THIS WAS DUE TO AN 8 INCH SINGER AXIAL FLOW REGULATOR SLEEVE THAT FAILED BY RUPTURING. AT 11:15 AM THE FAILED REGULATOR RUN 1 WAS ISOLATED ALLOWING THE STATION TO FLOW ONLY THROUGH REGULATOR RUN 2 AT WHICH POINT THE RELIEF VALVE CLOSED. AT 12:14 PM NORTH TACOMA METER STATION WAS RETURNED TO NORMAL OPERATIONS. GAS LOSS WAS CALCULATED AS 21 MMSCF. ALTHOUGH THE RELEASE EXCEED 3 MMSCF, THE INITIAL NRC NOTIFICATION WAS NOT MADE BECAUSE THE RELIEF SYSTEM OPERATED AS DESIGNED. THIS ACTION MATCHED WILLIAMS' PHILOSOPHY AND PROCEDURES AND WAS SUPPORTED BY AN INTERNAL WHITE PAPER. PHMSA AGREED TO REVIEW THE INTERNAL WHITE PAPER AND CONSIDER THE MERITS OF WILLIAMS' POSITION WHILE DELAYING A DECISION ON THE NEED FOR AN NRC REPORT. THREE WEEKS LATER AND AFTER ADDITIONAL DISCUSSION WITH PHMSA AND WUTC, PHMSA DETERMINED AN NRC NOTIFICATION AND INCIDENT REPORT WOULD BE REQUIRED FOR THIS EVENT. INITIAL NRC REPORT (#1177100) AND FOLLOW UP REPORT (#1177126) WERE MADE ON MAY 1, 2017.