QUESTAR PIPELINE COMPANY — Gas transmission and gathering — incident on 2011-12-04

Gas transmission and gathering incident in NEAR EVANSTON, WY, UINTA County, WY. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 2000 NATURAL GAS released, $134,000 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: 20120003.

Operator ID: 12874.

Reported incident date: 12/4/2011 8:40.

Cause detail: OTHER EQUIPMENT FAILURE

Cause detail: THIS SUPPLEMENTAL REPORT IS BEING FILED TO DOCUMENT THE OPERATOR'S ESTIMATED COST OF PROPERTY LOSS AND REPAIR AND TO SUBMIT THE FINAL VERSION OF THIS REPORT AND COMPLETE PART E5F. THE LEROY STORAGE FIELD WAS ON STAND-BY FOR WITHDRAWAL. SEVERAL DEHY UNITS, INCLUDING THE UNIT ON WELL 11 WERE IDLING. THE WELL WAS OPEN, THE GLYCOL REBOILER WAS OPERATING AT 375 DEGREES, AND ONE OF THE TWO GLYCOL PUMPS WAS CIRCULATING GLYCOL THROUGH THE UNIT. STORAGE FIELD OPERATING PRESSURE WAS 1485 PSIG. SOMETIME PRIOR TO THE FIRE, A 1/4 INCH DIAMETER TUBING LINE ON THE BOTTOM OF A GLYCOL PUMP BROKE RELEASING A GLYCOL AND GAS MIXTURE INSIDE THE DEHY UNIT BUILDING. AT SOME POINT, THE GLYCOL AND GAS WERE IGNITED AND THE RESULTING FIRE DAMAGED THE DEHY UNIT. THE UINTA COUNTY (WYOMING) FIRE DEPARTMENT MONITORED THE FIRE, QUESTAR PIPELINE COMPANY OPERATING PERSONNEL ARRIVED ON SCENE AT 09:10 AM. AT 09:30 AM THE FIRE DEPARTMENT PERSONNEL ASSISTED COMPANY OPERATORS IN CLOSING THE WELLHEAD WING VALVE, MASTER VALVE, AND TWO VALVES NEAR THE DEHY, THE INJECTION BLOCK VALVE AND WITHDRAWAL BLOCK VALVE. THE VALVE ON THE PLANT END OF THE LEROY #11 STORAGE LATERAL WAS ALREADY CLOSED (NO VOLUME SET POINT). CLOSING THESE VALVES ISOLATED PRESSURE IN THE DEHY UNIT AND PRODUCTION LINE. THE BROKEN TUBING LINE INSIDE THE DEHY UNIT CONTINUED TO VENT GAS, AND THE FIRE CONTINUED TO BURN. A 1/2 INCH VENT VALVE ON THE PRODUCTION LINE, NEAR THE WELLHEAD ESD VALVE WAS USED TO VENT PRESSURE TO ATMOSPHERE, AND HELP LOWER THE PRESSURE ON THE DEHY PIPING. THE CONTROL VALVE ON THE WELL #11 LATERAL AT THE LEROY PLANT WAS LOCKED OUT AND TAGGED OUT, AND THE LATERAL WAS DEPRESSURED TO 140 PSIG USING A BLOWDOWN VENT IN THE PLANT. AT APPROXIMATELY 10:00 AM, AS THE PRESSURE ON THE ISOLATED DEHY UNIT NEARED ZERO, THE FIRE SUBSIDED AND THE FIRE DEPARTMENT SPRAYED WATER AND FOAM ON AND IN THE DEHY UNIT, TO EXTINGUISH THE FIRE AND COOL THE PIPING AND VESSELS. THE VALVES WERE CONFIRMED CLOSED, THE UNIT TOTALLY DEPRESSURED AND MOSTLY COOLED, THE FIRE DEPARTMENT DEMOBILIZED AT 11:15 AM. THE DEHY FACILITY WAS REPAIRED AND PLACED INTO SERVICE ON MAY 31, 2012.

PHMSA trend classification: significant incident, not serious.

PHMSA standardized cause: EQUIPMENT FAILURE — OTHER EQUIPMENT FAILURE.

PHMSA indexed costs: $142,240 reported total cost, $77,322.171 in 1984 dollars, $185,014.592 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.