NORTHERN NATURAL GAS CO — Gas transmission and gathering — incident on 2014-03-14

Gas transmission and gathering incident in NICKERSON, DODGE County, NE. Reported cause: MATERIAL FAILURE OF PIPE OR WELD. Reported consequences: 0 fatalities, 0 injuries, 37500 NATURAL GAS released, $3,000,000 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: 20140042.

Operator ID: 13750.

Reported incident date: 3/14/2014 8:29.

Location detail: 58.04

Cause detail: DESIGN-, CONSTRUCTION-, INSTALLATION-, OR FABRICATION-RELATED

Cause detail: AT 8:30 AM ON MARCH 14, 2014 THE PALMYRA TO HOOPER B-LINE, ALSO KNOWN AS NEM50102-M581B, RUPTURED AND CAUGHT FIRE. THE RUPTURE INITIATED NEAR A 12-INCH TIE-OVER LINE BETWEEN THE 1ST LINE (A-LINE) AND THE SECOND LINE (B-LINE). THE RUPTURE AND FIRE DAMAGED TWO MAINLINE VALVE SETTINGS AND A BRANCH LINE TAKE-OFF. THREE HOMES WERE EVACUATED BY THE THE LOCAL EMERGENCY RESPONDERS BUT HOMEOWNERS WERE ALLOWED TO RETURN LATER IN THE DAY. AT THIS TIME, THE CAUSE HAS NOT BEEN DETERMINED. THE PIPE FAILURE PIECE WAS SENT TO STRESS ENGINEERING IN HOUSTON FOR TESTING. METALLURGICAL ANALYSIS COULD NOT PRECISELY DETERMINE THE ROOT CAUSE OF THE RUPTURE. IT IS BELIEVED THAT INTERACTING DEFECTS FROM ORIGINAL CONSTRUCTION WITH SOME GROUND MOVEMENT MAY HAVE CAUSED A CRACK IN THE FILLET WELD OF A REINFORCING SADDLE TO FAIL. COST UPDATE INFORMATION: NORTHERN'S EMERGENCY RESPONSE WAS ACTUALLY ON THE ORDER OF ABOUT $200,000. HOWEVER, WHEN WE BEGAN TO REMOVE 2 MAINLINE BLOCK VALVE SETTINGS AND PIPE, 4 CROSSOVERS AND THEIR VALVES, REBUILT THE BLAIR LOOP (CARGILL) BRANCHLINE TAKE-OFF, REROUTED ABOUT 600 FEET OF 6-INCH PIPE ALL WHILE MAINTAINING SERVICE TO BLACK HILLS ENERGY. OUR CONTRACTOR WAS ON THIS PROJECT FOR NEARLY ONE MONTH.

PHMSA trend classification: significant incident, not serious.

PHMSA standardized cause: MATERIAL FAILURE OF PIPE OR WELD — CONSTRUCTION, INSTALLATION OR FABRICATION-RELATED.

PHMSA indexed costs: $3,404,215 reported total cost, $1,764,119.88 in 1984 dollars, $4,174,151.53 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.