NORTHERN NATURAL GAS CO — Gas transmission and gathering — incident on 2018-09-22

Gas transmission and gathering incident in Not Within a Municipality, GREEN County, WI. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 3489 NATURAL GAS released, $100 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: 20180102.

Operator ID: 13750.

Reported incident date: 9/22/2018 1:30.

Location detail: WI-001

Cause detail: MALFUNCTION OF CONTROL/RELIEF EQUIPMENT

Cause detail: ON 9/22/2018, AT APPROXIMATELY 1:30AM, A PLC FAILED ON UNIT #4 AT THE BELLEVILLE COMPRESSOR STATION RESULTING IN A GAS RELEASE. THE FACILITY WAS SECURED AT ~4:30AM. THE ESTIMATED GAS LOSS WAS 3,489 MCF. THE INITIAL CALCULATION HAD AN ERROR AND IT WAS THOUGHT TO BE UNDER THE REPORTING LIMIT. UPON FURTHER REVIEW WHEN IT WAS REALIZED THAT THE REPORTING THRESHOLD WAS EXCEEDED, AN URGENT OCC CALL WAS INITIATED AT 10:55AM WITH MEMBERS FROM THE PLATTEVILLE TEAM, FACILITY PLANNING, AND PIPELINE SAFETY DEPARTMENTS. UPDATE: ON 12/07/2018 THE NRC REPORT NUMBER WAS CORRECTED TO SHOW THE ORIGINAL IN PLACE OF THE 48-HOUR UPDATE.

PHMSA trend classification: not significant, not serious.

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

PHMSA indexed costs: $9,497 reported total cost, $8,594.687 in 1984 dollars, $10,906.893 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.