NORTHERN NATURAL GAS CO

Incident Narrative

ON APRIL 27, 2014, A FARMER NEAR MECHANICSVILLE, IOWA, OBSERVED A LIGHTNING STRIKE AT APPROXIMATELY 8 P.M., THEN NOTICED A BURNING FLAME APPROXIMATELY 5-6 FEET HIGH IN A NEARBY FIELD. THE WITNESS CALLED AREA EMERGENCY RESPONDERS TO REPORT THE FIRE AND EMERGENCY RESPONDERS REPORTED TO THE SITE TO INVESTIGATE. NORTHERN NATURAL GAS' GAS CONTROL DEPARTMENT DID NOT REGISTER A PRESSURE DROP; ONCE NOTIFIED OF THE FIRE, LOCAL PERSONNEL WERE DISPATCHED TO THE SITE. ONCE LOCAL EMPLOYEES CONFIRMED THE GAS WAS COMING FROM NORTHERN NATURAL GAS' LINE, NORTHERN NATURAL GAS NOTIFIED THE NRC WAS NOTIFIED AND LOWERED PRESSURE IN THE LINE TO 80% OF THE PRESSURE AT THE TIME OF INCIDENT. UPON CONFIRMATION OF THE LOAD REQUIRED TO MAINTAIN SERVICE TO FIVE NEARBY TOWNS, PRESSURE WAS LOWERED TO 400 POUNDS. BOTTLE TRUCKS WERE BROUGHT IN AS A CONTINGENCY AND WERE USED DURING REPAIRS TO MAINTAIN SERVICE TO THE TOWNS. ONCE THE TOWNS WERE SUPPLIED BY THE BOTTLE TRUCKS, THE PRESSURE IN THE LINE WAS REDUCED TO EXTINGUISH THE FIRE AND THE SEGEMENT WAS EXCAVATED. THE SUBSEQUENT INVESTIGATION IDENTIFIED A PINHOLE-SIZED LEAK ATTRIBUTED TO AN APPARENT LIGHTNING STRIKE. THE DAMAGED PIPE WAS REPARIED BY A PRESSURIZED SLEEVE. THE PRESSURE IN THE LINE WAS RETURNED TO 80% OF THE OPERATING PRESSURE AT THE TIME OF INCIDENT, MONITORED FOR APPROXIMATELY 4 HOURS, THEN RESTORED TO NORMAL PRESSURE.