QUESTAR PIPELINE COMPANY — Gas transmission and gathering — incident on 2013-01-14

Gas transmission and gathering incident in MYTON, DUCHESNE County, UT. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 54400 NATURAL GAS released, $1,300 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: 20130014.

Operator ID: 12874.

Reported incident date: 1/14/2013 5:00.

Cause detail: MALFUNCTION OF CONTROL/RELIEF EQUIPMENT

Cause detail: FREEZE IN SENSING LINE TUBING TO PILOT-OPERATED RELIEF VALVE CAUSED THE 6"X8" RELIEF VALVE TO OPEN AND VENT GAS AT APPROXIMATELY 726 PSIG, WHICH IS WELL-BELOW ITS SET-POINT OF 827 PSIG. DURING THE VENTING PROCESS THE TUBING TO THE SENSING LINE FAILED, WHICH PREVENTED THE RELIEF VALVE FROM RE-SEATING AND RESULTED IN VENTING GAS FOR APPROXIMATELY 4 HOURS AND 55 MINUTES. FIELD OPERATIONS ARRIVED ON-SITE AND ISOLATED THE RELIEF VALVE BY CLOSING THE 6" ISOLATION VALVE INSTALLED IMMEDIATELY UPSTREAM OF THE RELIEF VALVE. THE PILOT VALVE AND SENSING LINE TUBING WERE REPAIRED AND THE RELIEF VALVE WAS PLACED BACK INTO SERVICE.

PHMSA trend classification: significant incident, not serious.

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

PHMSA indexed costs: $177,330 reported total cost, $143,068.047 in 1984 dollars, $176,687.756 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.