NORTHERN NATURAL GAS CO — Gas transmission and gathering — incident on 2011-09-23

Gas transmission and gathering incident in CYRUS, STEVENS County, MN. Reported cause: EXCAVATION DAMAGE. Reported consequences: 0 fatalities, 0 injuries, 1700 NATURAL GAS released, $10,172 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: 20110387.

Operator ID: 13750.

Reported incident date: 9/23/2011 13:50.

Location detail: M.P. 37.03

Cause detail: EXCAVATION DAMAGE BY THIRD PARTY

Cause detail: NOTIFICATION ISSUE

Cause detail: NO NOTIFICATION MADE TO THE ONE-CALL CENTER/811

Cause detail: ON SEPTEMBER 23, 2011, AT APPROXIMATELY 1:50 P.M., MECHANIZED FARM TILING EQUIPMENT, OWNED AND OPERATED BY LEROY EDLUND, STRUCK THE MORRIS, MINNESOTA SIX-INCH DIAMETER BRANCH LINE (MNB65101) NEAR MILEPOST 37.03 LOCATED IN THE NORTHWEST 1/4 OF THE NORTHEAST 1/4 OF SECTION 26, T125N, R41W IN STEVENS COUNTY, MINNESOTA. LEROY EDLUND OWNS THE TILING OPERATION AND OPERATES IT UNDER THE NAME LEROY EDLUND CONSTRUCTION. EDLUND WAS INSTALLING FARM DRAINAGE TILE UTILIZING A FARM TILING IMPLEMENT ATTACHED TO A 9380 CASE IH TRACTOR. THE BLADE PLOWED A DEPTH OF APPROXIMATELY THREE FEET DEEP. EDLUND WAS ASSISTED BY DAN THOMPSON, WHO WAS OPERATING A FARM TRACTOR STRINGING TILE IN FRONT OF THE 9380 CASE IH TRACTOR OPERATED BY EDLUND. THE PIPELINE PRESSURE AT THE TIME OF THE INCIDENT WAS 528 PSIG. THE FARM TILING IMPLEMENT STRUCK AND SEVERED THE PIPELINE AT A DEPTH OF THREE-FEET. THE ESCAPING GAS DID NOT IGNITE. EDLUND AND THOMPSON VACATED THE EQUIPMENT AND RAN OUT OF THE FIELD. EDLUND CONTRACTED NORTHERN'S OPERATION COMMUNICATION CENTER (OCC) AT 1:56 P.M. INDICATING THAT HE HAD STRUCK A PIPELINE WHILE WORKING IN THE FARM FIELD. THE MORRIS BRANCH LINE CONSISTS OF 42.23 MILES OF PIPELINE CONSISTING OF 16.45 MILES OF EIGHT-INCH X 0.188 WALL THICKNESS PIPE AND 25.78 MILES OF SIX-INCH X 0.156 WALL THICKNESS PIPE. THE PIPE THAT WAS HIT WAS SIX-INCH X 0.156 WALL THICKNESS, GRADE X-42. THE PIPE WAS COATED WITH X-TRUCOAT COATING. THE PIPELINE WAS INSTALLED IN 1967 AND HAS AN MAOP OF 975 PSIG. THERE WAS A LOSS OF SERVICE TO THE THREE COMMUNITIES OF MORRIS, BENSON AND HANCOCK, MINNESOTA. RESIDENTS AND BUSINESSES IN THESE COMMUNITIES WERE TEMPORARILY OUT OF NATURAL GAS SERVICE FROM APPROXIMATELY 3:30 P.M. ON SEPTEMBER 23, 2011, TO APPROXIMATELY 12:00 P.M. ON SEPTEMBER 24, 2011. CENTER POINT ENERGY, THE LOCAL DISTRIBUTION COMPANY, UTILIZED THEIR ODORIZED NATURAL GAS TRUCK AT THE HOSPITAL IN MORRIS, MINNESOTA TO MAINTAIN SERVICE TO THEIR SANITIZING SYSTEM. CENTER POINT ENERGY HAD TO RE-LIGHT APPROXIMATELY 3,600 CUSTOMERS THAT LOST GAS SERVICE TO THE INCIDENT. REPAIRS WERE MADE BY REPLACING THE DAMAGE PIPE WITH 13-FEET AND SIX-INCHES OF SIX-INCH DIAMETER, 0.280-INCH WALL THICKNESS, X-42 PIPE COATED PIPE. THE JOINT OF PIPE WAS BACK BEVELED TO 0.219-INCH FOR TRANSITION. MIDWEST X-RAY CHECK THE PIPE FOR UT AND MAG PARTICLE FOR CRACKING AND IT CHECKED OUT OK WITH A WALL THICKNESS OF 0.155 TO 0.156 RECORDED ON THE PIPE. THE PIPE WELDS WERE X-RAY INSPECTED AND THE PIPE WAS BACKFILLED WITH SOIL PRIOR TO COMMENCING PURGING AND RE-PRESSURIZATION FOR RETURNING TO SERVICE. THERE WERE NO INJURIES, NO EXPLOSION, NO FIRE AND NO EVACUATION OF PERSONNEL. WHEN ASKED ABOUT WHETHER HE HAD MADE A ONE-CALL PRIOR TO EXCAVATION, MR. EDLUND ACKNOWLEDGED THAT HE HAD NOT MADE A ONE-CALL AND ADMITTED THAT HE KNEW A ONE-CALL WAS REQUIRED PRIOR TO INITIATING EXCAVATION ACTIVITIES. THE SECTION OF DAMAGED PIPE IS BEING EXAMINED BY AN OUTSIDE SERVICES METALLURGICAL COMPANY. FILING OF AN INCIDENT REPORT WAS REQUIRED AS IT IS EXPECTED THAT THE TOTAL COST OF THE INCIDENT WILL EXCEED THE $50,000 REPORTING THRESHOLD. IN ADDITION, THE LOSS OF SERVICE TO COMMUNITIES IS CONSIDERED AS A SIGNIFICANT EVENT BY NORTHERN. A SUPPLEMENTAL REPORT WILL BE FILED WHEN ALL FINAL COST OF REPAIRS AND THE METALLURGICAL REPORT FINDINGS ARE AVAILABLE. SUPPLEMENT/FINAL REPORT - TOTAL COST OF REPAIRS HAS BEEN UPDATED TO THE FINAL CALCULATED COSTS

PHMSA trend classification: not significant, not serious.

PHMSA standardized cause: EXCAVATION DAMAGE — THIRD PARTY EXCAVATION DAMAGE.

PHMSA indexed costs: $79,735 reported total cost, $43,847.244 in 1984 dollars, $102,314.508 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.