NORTHWEST PIPELINE LLC — Gas transmission and gathering — incident on 2017-03-29

Gas transmission and gathering incident in SUMNER, PIERCE County, WA. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 21000 NATURAL GAS released, $0 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.

Report number: 20170038.

Operator ID: 13845.

Reported incident date: 3/29/2017 10:01.

Location detail: 0.84

Cause detail: MALFUNCTION OF CONTROL/RELIEF EQUIPMENT

Cause detail: 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.

PHMSA trend classification: significant incident, not serious.

PHMSA standardized cause: EQUIPMENT FAILURE — MALFUNCTION OF CONTROL/RELIEF EQUIPMENT.

PHMSA indexed costs: $68,250 reported total cost, $64,804.688 in 1984 dollars, $79,570.313 in current-year dollars.

PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.