NORTHERN NATURAL GAS CO

Incident Narrative

ON APRIL 25, 2012, NORTHERN NATURAL GAS' 24-INCH-DIAMETER SOUTH SIOUX CITY-TO-PAULINA M560C MAINLINE (C-LINE) WAS DAMAGED DURING THE INSTALLATION OF FARM DRAINAGE TILE IN A FIELD IN PLYMOUTH COUNTY NEAR HINTON, IOWA. THE TILING WORK WAS BEING PERFORMED BY DEROCHER CONSTRUCTION HEADQUARTERED IN LE MARS, IOWA, ON BEHALF OF RANDY RIEDIGER OF HINTON, IOWA, THE FARM TENANT. THE DAMAGED C-LINE RUPTURED AND THE ESCAPING GAS IGNITED. TWO TILING WORKERS WERE TREATED FOR INJURIES AT A SIOUX CITY HOSPITAL BUT THEIR INJURIES ARE NOT BELIEVED TO BE LIFE THREATENING. NO ONE CALL REQUEST WAS PLACED FOR THE TILING OPERATION. REPAIRS TO THE C-LINE AND INSPECTION OF THE NEARBY 16-INCH-DIAMETER SOUTH SIOUX CITY-TO-PAULINA B-LINE WERE COMPLETED APRIL 27, 2012. NO CUSTOMERS LOST SERVICE DUE TO THE LINE HIT OR THE SUBSEQUENT INVESTIGATION AND REPAIRS. FACILITY PLANNING ESTIMATES THE TOTAL GAS LOST AS A RESULT OF THIS INCIDENT TO BE 57.576 MMCF. THE IOWA ATTORNEY GENERAL OFFICE CONTACTED NORTHERN NATURAL GAS IMMEDIATELY FOLLOWING THE INCIDENT AND HAS OPENED AN INVESTIGATION INTO THE ONE CALL VIOLATION. SUPPLEMENTAL/FINAL REPORT FOR REPORT NO. 20120049-15515 DATED 05/14/2012. UPDATED INFORMATION IN PART A, SECTION 11, PART D, SECTION 7 WITH ESTIMATED FINAL TOTAL COST. APPROXIMATELY 102 FEET OF NEW 24-INCH-DIAMETER TESTED PIPE WAS REPLACED. THE LEGAL DEPARTMENT OF NORTHERN NATURAL GAS COMPANY IS FOLLOWING UP WITH SEEKING REIMBURSEMENT FOR COST INCURRED FROM THE INCIDENT. SUPPLEMENTAL/FINAL UPDATE TO REPORT # 20120049-15648 - IN SECTION C, ITEM 6 WHERE A MECHANICAL PUNTURE WAS INDICATED, ALTHOUGH THERE EXTENSIVE DAMAGE TO THE PIPE, THE SIZE OF THE PUNTURE IS ESTIMATED AS 10 INCHES AXIAL BY A CIRCUMFERENTIAL SIZE OF 18-INCHES. SUPPLEMENTAL/FINAL: REPORT # 20120049, DATED 5/14/2012 - UPDATED PART D ITEM 7A, PART G3 ITEM 10 TO TRENCHER AND ITEM 16. THE TWO TILING WORKERS INJURIES: ONE INCURRED 1ST DEGREE BURNS ON HIS BACK AND THE OTHER INCURRED 1ST AND 2ND DEGREE BURNS ON HIS BACK.