NORTHERN NATURAL GAS CO — Gas transmission and gathering — incident on 2009-06-23

Gas transmission and gathering incident in BESSEMER, GOGEBIC County, MI. Reported cause: 1. Reported consequences: 0 fatalities, 0 injuries, $692,449 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: 20090071.

Operator ID: 13750.

Reported incident date: 6/23/2009.

Cause detail: CORROSION, EXTERNAL

Cause detail: ON JUNE 23, 2009, AT APPROXIMATELY 11:54 A.M. CDT, NORTHERN'S OPERATION COMMUNICATION CENTER, IN OMAHA, NE RECEIVED AN EMERGENCY CALL REPORTING THAT THERE WAS GAS BLOWING TO ATMOSPHERE AND A POSSIBLE RUPTURE OF THE PIPELINE APPROXIMATELY 1 1/4 MILES NORTH OF THE TOWN OF BESSMER, MICHIGAN. PERSONNEL WERE IMMEDIATELY DISPATCHED TO THE AREA AND IT WAS DETERMINED THAT A PIPE RUPTURE HAD OCCURRED ON THE M432B (MIM10101) 16-INCH CARLTON-WAKEFIELD B LINE @ APPROXIMATE MILEPOST 121.26. LOCAL LAW ENFORCEMENT EVACUATED APPROXIMATELY 15 HOME SITES AND ESTABLISHED A 1/2 MILE SAFE ZONE. THE INCIDENT OCCURRED IN THE SE1/4 OF SECTION 3, T47N, R46W IN GOGEBIC COUNTY, MICHIGAN. LINE PRESSURE AT THE TIME OF THE INCIDENT WAS APPROXIMATELY 923 PSIG. THE EVENT WAS IMMEDIATELY REPORTED TO THE NRC (TICKET # 909472), PHMSA, MICHIGAN PUBLIC SAFETY, EPA AND LOCAL AND STATE AGENCIES. INITIAL INVESTIGATION INDICATED THAT APPROXIMATELY 66 FEET OF PIPE HAD BLOWN OUT OF THE GROUND. IMMEDIATE ACTIONS WERE TAKEN TO ISOLATE THE SEGMENT OF LINE AND ATTEMPT TO MAINTAIN AS MUCH SERVICE TO CUSTOMERS AS POSSIBLE. NORTHERN'S BOTTLE TRUCKS WERE BROUGHT IN AND PLACED IN SERVICE FOR THE TOWN OF BESSEMER AND RAMSAY. GAS SERVICE TO APPROXIMATELY 380 HOMES IN RAMSAY WAS LOST AND HAD TO BE RESTORED BY XCEL ENERGY. SERVICE TO INTERRUPTIBLE BUSINESSES IN BESSEMER WAS INTERRUPTED. THE PIPE IN THE FAILED SEGMENT WAS MANUFACTURED BY YOUNGSTOWN AND INSTALLED IN 1965. IT IS 16-INCH X 0.203 AND 0.250 INCH WALL THICKNESS, GRADE X-60 ELECTRIC RESISTANCE WELDED (ERW) PIPE. REPAIRS WERE MADE BY INSTALLING APPROPRIATE STOPPLE FITTINGS TO ENABLE REPLACEMENT OF APPROXIMATELY 219 FEET OF NEW 16-INCH TESTED, X-60, 0.312 WALL THICKNESS PIPE. THE NEW PIPE WAS PRESSURE TESTED TO A MINIMUM TEST PRESSURE OF 1620 PSIG. A RETURN TO SERVICE PLAN WAS DEVELOPED AND SUBMITTED TO THE CENTRAL REGION OFFICE OF PHMSA FOR REVIEW. PHMSA DID NOT IDENTIFY ANY CONCERNS WITH THE PLAN THEREFORE NORTHERN WAS AUTHORIZED TO RE-START THE CARLTON TO MARQUETTE LINE AT A REDUCED PRESSURE AS REQUIRED BY A CORRECTIVE ACTION ORDER ISSUED BY THE ASSOCIATE ADMINISTRATOR FOR PIPELINE SAFETY. THE CORRECTIVE ACTION ORDER REQUIRES THAT THE PRESSURE AT THE FAILURE SITE AND DOWNSTREAM OF THE FAILURE SITE IS NOT TO EXCEED 80% OF THE OPERATING PRESSURE IMMEDIATELY PRIOR TO THE FAILURE. SPECIFICALLY, THE PRESSURE AT THE FAILURE SITE IS NOT TO EXCEED 739 PSIG. THIS PRESSURE RESTRICTION WILL REMAIN IN EFFECT UNTIL WRITTEN APPROVAL TO INCREASE THE PRESSURE OR RETURN THE PIPELINE TO ITS PRE-FAILURE OPERATING PRESSURE IS OBTAINED FROM THE REGIONAL DIRECTOR, PHMSA. PIECES OF THE FAILED PIPE HAVE BEEN SENT TO BRYAN LAB IN HOUSTON, TX FOR FAILURE ANALYSIS. AN ADDITIONAL SECTION OF PIPE WERE SENT TO KEIFNER & ASSOCIATES LABORATORY IN OHIO. KEIFNER AND BRYAN LABS WILL ASSIST NORTHERN WITH IDENTIFYING THE CAUSE OF THE FAILURE AND THE INSPECTION TECHNIQUES NORTHERN WILL USE TO IDENTIFY OTHER RISKS TO THE PIPELINE SYSTEM. ADDITIONAL SUPPLEMENTAL REPORTS WILL BE FILED AS THE ROOT CAUSE AND FINAL, ACCURATE COST OF GAS LOSS/REPAIRS ARE DETERMINED. SUPPLEMENTAL/FINAL REPORT: THIS REPORT IS BEING SUBMITTED TO UPDATE THE COTS INCURRED IN THE REPAIR PROCESS OF THIS INCIDENT. IN ADDITION, THE ROOT CAUSE HAS BEEN IDENTIFIED AS STRESS CORROSION CRACKING (SCC). A CORRECTIVE ACTION ORDER (CAO) WAS ISSUED BY PHMSA, RE; CPF NO.3-2009-1010H. ADDITIONAL ACTIONS AND COST ARE BEING INCURRED TO COMPLY WITH THE CAO, AND MUST BE COMPLETED PRIOR TO RESTORATION OF THE LINE PRESSURE BACK TO IT'S CAPABILITY PRIOR TO THE RUPTURE. THESE ACTIONS AND COST ARE BEING ADDRESSED VIA QUARTERLY REPORTS TO THE DIRECTOR, CENTRAL REGION OF OPS. AS FAR AS COST AND REPAIR ACTIONS TAKEN TO ADDRESS THE RUPTURE EVENT, PER THIS 7100 REPORT, THERE ARE CONSIDERED COMPLETE. SUPPLEMENTAL/FINAL REPORT: DO TO THE IDENTIFICATION OF ADDITONAL COST, FROM EMPLOYEE EXPENSE AND OUTSIDE SERVICES, THIS SUPPLEMENTAL REPORT IS BEING SUBMITTED TO CORRECT THE PREVIOUS TOTAL COST OF $674,379 TO $692, 449. 09/18/2012 ADDED INCIDENT COORDINATES AS PER REQUEST OF JIM BUNN, PHMSA.

PHMSA trend classification: significant incident, not serious.

PHMSA standardized cause: MATERIAL FAILURE OF PIPE OR WELD — ENVIRONMENTAL CRACKING-RELATED.

PHMSA indexed costs: $692,449 reported total cost, $400,048.401 in 1984 dollars, $751,852.474 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.