QUESTAR PIPELINE COMPANY — Gas transmission and gathering — incident on 2011-07-21

Gas transmission and gathering incident in ROCK SPRINGS, SWEETWATER County, WY. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 22000 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: 20110297.

Operator ID: 12874.

Reported incident date: 7/21/2011 2:45.

Cause detail: MALFUNCTION OF CONTROL/RELIEF EQUIPMENT

Cause detail: USING SCADA INFORMATION, CONTROL ROOM PERSONNEL FOUND A DROP IN PRESSURE. THEY DISPATCHED OPERATIONAL PERSONNEL TO INVESTIGATE THE ISSUE. THE OPERATIONAL PERSONNEL FOUND A RELIEF VALVE RELEASING GAS EVEN THOUGH THE PRESSURE WAS BELOW THE RELIEF SET POINT. OPERATIONAL PERSONNEL FOUND AN OBSTRUCTION IN THE RELIEF VALVE 3/8" TUBE SENSING LINE CAUSING THE RELIEF VALVE TO OPEN PREMATURELY. OPERATIONAL PERSONNEL REPAIRED THE ISSUE AND RETURNED THE RELIEF VALVE TO PROPER OPERATIONS.

PHMSA trend classification: significant incident, not serious.

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

PHMSA indexed costs: $91,450 reported total cost, $64,144.666 in 1984 dollars, $78,826.137 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.