SOUTHWEST GAS CORP

Incident Narrative

EXCAVATOR CREWS WERE DRILLING TO INJECT A SOIL STABILIZATION POLYMER WHEN THEY HIT A 6-INCH STEEL HIGH PRESSURE DISTRIBUTION GAS PIPE. STATE LAW REQUIRES THE EXCAVATOR TO USE SPECIAL CARE WITHIN A TOLERANCE ZONE OF 24 INCHES ON EITHER SIDE OF A MARKED PIPE. THE EXCAVATOR WAS DRILLING OUTSIDE THE TOLERANCE ZONE AND SO WAS NOT REQUIRED TO USE SPECIAL CARE. THE ELECTRONIC LINE LOCATE EQUIPMENT SIGNAL CORRESPONDED WITH AN ABANDONED 6-INCH STEEL PIPE, WHICH WAS LOCATED AND MARKED INSTEAD OF THE ACTIVE PIPE. THE DIMENSIONS SHOWN ON THE COMPANY'S AS-BUILT DOCUMENTATION AND MAPPING RECORDS CONTAINED THE SAME INACCURATE, AND INTERNALLY CONTRADICTORY, DEPICTIONS OF THE LOCATION OF THE ACTIVE 6-INCH STEEL PIPE. THE ELECTRONIC LINE LOCATE EQUIPMENT SIGNAL CORRESPONDED WITH PORTIONS OF THOSE RECORDS AND CONFLICTED WITH OTHER PORTIONS OF THOSE RECORDS. THE COMPANY'S LINE LOCATE PERSONNEL FAILED TO FOLLOW ESTABLISHED PROCEDURES TO POTHOLE WHEN ENCOUNTERING SUCH DISCREPANCIES. CORRECTION TO PART G3, 14: A NEARBY ABANDONED FACILITY WAS LOCATED INSTEAD OF THE ACTIVE FACILITY.