OKLAHOMA NATURAL GAS CO

Incident Narrative

AT APPROXIMATELY 05:05 ON NOVEMBER 12, 2012, OKLAHOMA NATURAL GAS DISPATCH IN OKLAHOMA CITY RECEIVED NOTIFICATION FROM THE TULSA FIRE DEPARTMENT OF A LOUD NOISE AND ODOR OF GAS IN THE VICINITY OF OUR TRANSMISSION PIPELINE STATION NEAR 91ST & MEMORIAL ROAD IN TULSA, OK. ONG DISPATCH NOTIFIED THE OPERATING AREA, WHICH CONTACTED EMPLOYEES TO INVESTIGATE. THE FIRST ONG PERSONNEL ARRIVED ON SITE AT APPROXIMATELY 06:00 AND BEGAN EVALUATION OF THE CONDITIONS. IT WAS DETERMINED THAT THE GAS RELEASE WAS A RELIEF VALVE THAT WAS VENTING. COMPANY PERSONNEL FURTHER EVALUATED CONDITIONS ON ALL CONNECTING LINES WITHIN THE STATION TO DETERMINE IF ANY OVERPRESSURE SITUATIONS HAD EXISTED DUE TO REGULATOR FAILURE. THERE WAS NO REGULATOR FAILURE OR OVERPRESSURE CONDITION. PERSONNEL ALSO VERIFIED THEIR GAUGE READINGS WITH THE GAS CONTROL SCADA SYSTEM, CONFIRMING NO OVERPRESSURE INDICATIONS HAD OCCURED ON ANY OF THE LINES. THE ONG PERSONNEL DETERMINED IT WOULD BE SAFE TO CLOSE THE ISOLATION VALVE BELOW THE RELIEF VALVE WHICH IMMEDIATELY STOPPED THE VENTING AT 06:40. REDUNDANT PRESSURE REDUCTION AND OVERPRESSURE MONITORING EQUIPMENT WAS IN PLACE, SO THE SETTING IN QUESTION WAS ISOLATED FROM THE SYSTEM INSURING THERE WAS NO POSSIBILITY OF AN OVERPRESSURE DUE TO THE RELIEF VALVE BEING ISOLATED. THE VALVE ASSEMBLY WAS REMOVED AND TESTED AT THE VENDOR'S FACILITY UNDER DIRECTION OF ONG PERSONNEL. TESTING AND DISSASEMBLY PROVIDED NO INDICATION OF THE CAUSE. ANY SUBSEQUENT DETERMINATIONS OF CAUSE WILL BE REPORTED VIA A SUPPLEMENTAL FILING. NOTE REGARDING PART A, QUESTION 18: THE NUMBER OF PERSONS EVACUATED WAS ESTIMATED WITH INFORMATIONAL ASSISTANCE FROM THE TULSA FIRE DEPARTMENT. PART E, 5.F ADDED ""FUNCTION OF PIPELINE"" INFORMATION AS REQUESTED BY MR. BLAINE KEENER FOR REPORTS SUBMITTED ON OR AFTER 1-1-2010.