NORTHERN NATURAL GAS CO

Incident Narrative

ON APRIL 29, 2011, AT APPROXIMATELY 14:16, LARRY POTTER AT 38364 200TH ST., SPRINGFIELD, MN 56087, CONTACTED NORTHERN NATURAL GAS COMPANY'S (NORTHERN) OPERATIONS COMMUNICATION CENTER (OCC) TO REPORT THAT A PIPELINE LOCATED ON HIS PROPERTY HAD BEEN HIT BY A CONTRACTOR HE HAD HIRED TO INSTALL DRAINAGE TILE ON HIS PROPERTY. MR. POTTER INDICATED THAT THERE WAS DAMAGE TO THE PIPELINE AND THAT GAS WAS VENTING TO ATMOSPHERE. THE LOCATION OF THE DAMAGED PIPELINE IS THE TRACY BRANCH LINE AT APPROXIMATE MILEPOST 0.20. THE LEGAL DESCRIPTION IS SECTION NW1/2 17, TOWNSHIP 109N, RANGE 34W ALL IN BROWN COUNTY, MINNESOTA APPROXIMATELY 1/2 MILE NORTH OF U.S. HIGHWAY 14 AND 1/8 MILE EAST OF COUNTY ROAD 5. NORTHERN IMMEDIATELY DISPATCHED EMPLOYEES TO THE SITE AND UPON ARRIVAL THEY CONFIRMED THAT IT WAS NORTHERN'S TRACY, MN (MNB65201) 6-INCH BRANCH LINE THAT HAD BEEN HIT. THERE WAS NO FIRE, NO EXPLOSION, NO INJURIES AND NO EVACUATIONS. A GAS DETECTOR WAS UTILIZED TO CHECK THE AREA AND A 20% LEL READING WAS INDICATED APPROXIMATELY 50 YARDS DOWNWIND. A PIR OF 109 FEET WAS ESTABLISH AS A SAFE ZONE RADIUS AROUND THE INCIDENT SITE. THE TRACY BRANCH LINE PROVIDES GAS SERVICE TO THE TOWNS OF SANBORN, WALNUT GROVE, REVERE AND TRACY, MINNESOTA AND THE HIGHWATER ETHANOL PLANT. BOTTLE TRUCKS WERE BROUGHT IN FROM WATERLOO, IA, FARMINGTON, MN, SOUTH SIOUX CITY, IA, OGDEN, IA AND NORTH BRANCH, MN AS BACKUPS TO SUPPLY GAS TO THE TOWNS DURING THE REPAIR PROCESS. A STOPPLE BYPASS HAD TO BE INSTALLED TO MAINTAIN SERVICE TO THE HIGHWATER ETHANOL PLANT DURING THE PIPELINE REPAIRS. APPROXIMATELY 31 FEET OF 6-INCH NOMINAL DIAMETER PIPE WAS REPLACED WITH NEW 6-INCH, 0.280 WALL THICKNESS, ERW, GRADE X42 TESTED PIPE WITH FBE COATING. ROOT CAUSE OF THIS EVENT: THE LANDOWNER HAD MADE A ONE CALL, HOWEVER IT APPEARS THAT THE DESCRIPTION OF THE WORK AREA DID NOT COVER THE AREA OF HIS PROPERTY THAT THE PIPELINE CROSSED, THEREFORE NORTHERN DID NOT RECEIVE NOTIFICATION OF A ONE CALL REQUEST TO LOCATE AND MARK THE PIPELINE ON THE PROPERTY. THERE WAS REQUIRED PERMANENT LINE MARKERS IN THE FENCE LINES INDICATING THE PRESENCE OF A PIPELINE ON THE PROPERTY. THIS IS BEING INVESTIGATED FURTHER BY NORTHERN WITH THE LANDOWNER/CONTRACTOR AND THE ONE CALL CENTER. FILING OF AN INCIDENT REPORT WAS REQUIRED AS THE COST TO COMPLETE REPAIRS EXCEEDED THE $50,000.00 REPORTING THRESHOLD. A SUPPLEMENTAL REPORT WILL BE FILED WHEN ALL FINAL COST OF REPAIRS IS CALCULATED. SUPPLEMENTAL/FINAL REPORT: REVISED COST INCURRED IN PART D, SECTION 7 AS A FINAL ESTIMATED OF ALL COST HAVE BEEN CALCULATED BY NORTHERN. NO FURTHER ACTIONS ARE REQUIRED OR PLANNED OTHER THAN FOLLOW UP BY NORTHERN'S LEGAL DEPARTMENT. THIS FINAL REPORT IS SUBMITTED TO CLOSE OUT THE ORIGINAL REPORT NO. 20110050 -15237 DATED 05/12/2011. SUPPLEMENTAL/FINAL REPORT FILED ON ORIGINAL REPORT # 20110050-15237 DTD 05/12/2011 AND PREVIOUS SUPPLEMENTAL/FINAL REPORT #20110050-15284 TO UPDATE AREAS FROM DISCUSSION WITH MNOPS REPRESENTATIVES REVIEW I.E., UPDATED A7, FILLED IN 19A AND 19B THAT DID NOT CARRY OVER FROM ORIGINAL REPORT, ATTEMPTED TO PUT UNKNOW IN YEAR OF MANUFACTURE BUT FORM WOULD NOT ALLOW, REVISED PIR TO 117 FEET BASED ON 796 MAOP, LENGTH OF 400 FEET OF PIPE ISOLATED WAS DISTANCE BETWEEN STOPPLE VALVES (FORM WOULD NOT ALLOW ADDITIONAL DESCRIPTION). ATTEMPTED TO RESPOND TO G3, LINE 16 REGARDING DID THE DAMAGE CAUSE AN INTERRUPTION IN SERVICE WITH NO, HOWEVER THE FORM SHOWED NUMBERS 15 AND 17 BUT DID NOT LIST ITEM 16. THE EVENT IS CONSIDERED COMPLETE.