ANR PIPELINE CO — Gas transmission and gathering — incident on 2011-05-11

Gas transmission and gathering incident in HAMILTON, ALLEGAN County, MI. Reported cause: INCORRECT OPERATION. Reported consequences: 0 fatalities, 0 injuries, 4500 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: 20110170.

Operator ID: 405.

Reported incident date: 5/11/2011 16:15.

Cause detail: PIPELINE OR EQUIPMENT OVERPRESSURED

Cause detail: THE HAMILTON STATION, OPERATING AT 809 PSI, TRIPPED ON MAIN LINE OVER PRESSURE DUE TO A HIGH PRESSURE CONDITION IN THE TRIP CIRCUITRY PIPING. IT IS BELIEVED THAT HIGH TEMPERATURES IN THE BUILDING CAUSED THE PRESSURE TO INCREASE ABOVE THE 876 PSI SET POINT. WHEN THE STATION PRESSURE EQUALIZED, THE STATION BLOCK GATE (BYPASS VALVE) OPENED WHICH ALLOWED GAS TO FLOW THROUGH THE OPEN VENTS ON THE 30 INCH PIG LAUNCHER. THE PIG LAUNCHER HAD BEEN LEFT IN AN ABNORMAL LINE-UP, WITH THE ILI PIG IN THE DEPRESSURIZED TRAP, FOR AN EARLY MORNING LAUNCH.

PHMSA trend classification: not significant, not serious.

PHMSA standardized cause: INCORRECT OPERATION — PIPELINE/EQUIPMENT OVERPRESSURED.

PHMSA indexed costs: $60,250 reported total cost, $35,661.546 in 1984 dollars, $70,279.524 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.