ENABLE GAS TRANSMISSION, LLC — Gas transmission and gathering — incident on 2018-05-28

Gas transmission and gathering incident in SUBIACO, LOGAN County, AR. Reported cause: EXCAVATION DAMAGE. Reported consequences: 0 fatalities, 0 injuries, 21700 NATURAL GAS released, $59,000 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: 20180064.

Operator ID: 602.

Reported incident date: 5/28/2018 12:57.

Location detail: BT-14

Cause detail: PREVIOUS DAMAGE DUE TO EXCAVATION ACTIVITY

Cause detail: MISCELLANEOUS ROOT CAUSES

Cause detail: ROOT CAUSE NOT LISTED (COMMENT REQUIRED)

Cause detail: ON 5/28/18 AT 13:03 ENABLE GAS TRANSMISSION NOTICED HIGH DIFFERENTIAL READINGS AT LINE J TO BT-14 TAKE OFF AND FLOW INCREASE TO APPROXIMATELY 80 MILLION. FALLING UPSTREAM AND DOWNSTREAM PRESSURE READINGS INDICATED A POTENTIAL GAS RELEASE. AT 13:12 A O&M TECHNICIAN WAS DISPATCHED TO INVESTIGATE. ENABLE GAS TRANSMISSION SYSTEM CONTROL RECEIVED A CALL FROM THE LOGAN COUNTY SHERIFF'S OFFICE AT 13:20 WITH A REPORT OF GAS BLOWING. AROUND 13:51 IT WAS CONFIRMED THAT BT-14 HAD FAILED AND THE UPSTREAM VALVE WAS CLOSED. THE DOWNSTREAM VALVE WAS CLOSED AT 14:09 AND THE SEGMENT WAS ISOLATED. ONE HOUSE WAS EVACUATED AS A PRECAUTION BY THE LOGAN COUNTY SHERIFF'S OFFICE AND 11 DOMESTIC METERS LOST SERVICE. UPON ARRIVAL TO THE INCIDENT SITE, FIRST RESPONDERS OBSERVED TREES PUSHED OVER IN THE RIGHT-OF-WAY AND THE DIRT BEHIND THE INCIDENT SITE, AND IN THE GENERAL AREA, LOOKED LIKE IT HAD BEEN REMOVED BY MECHANICAL EQUIPMENT. IN REVIEWING LOCATE TICKETS BACK TO 2015, A ONE CALL LOCATE REQUEST HAS NOT BEEN SUBMITTED IN THE INCIDENT AREA. THE NRC WAS NOTIFIED AT 14:38 (NRC#1213484) AND A 48 HOUR FOLLOW UP CALL WAS PROVIDED ON 5/30/2018 AT 07:13 (NRC#1213629). AN ILI RUN WAS PERFORMED ON BT-14 IN APRIL 2018. THE ILI REPORT DID CALL OUT DENTS AND GEOMETRIC MAGNETIC ANOMALIES (GMA) IN THE AREA OF THE INCIDENT, BUT THE INCIDENT OCCURRED BEFORE THE PRELIMINARY ILI RESULTS WERE RECEIVED FROM THE VENDOR. ANALYSIS OF THE FINAL ILI REPORT SHOWED NO OTHER SECTIONS IN THE AREA OF THE INCIDENT SITE CONTAINING GMA'S. THE LINE WAS REPAIRED AND PLACED BACK INTO SERVICE ON 5/30/2018. INITIAL INSPECTION OF THE FAILED SECTION INDICATE MECHANICAL DAMAGE AND EXCAVATION ACTIVITIES HAVE OCCURRED NEAR THE PIPELINE. CURRENTLY, THE INCIDENT IS UNDER INVESTIGATION AND THE FAILED SECTION OF PIPE HAS BEEN SENT FOR METALLURGICAL ANALYSIS. WHEN THE INVESTIGATION TEAM RECEIVES THE RESULTS OF THE METALLURGICAL ANALYSIS, AND DETERMINE FINAL COSTS, A SUPPLEMENTAL REPORT WILL BE SUBMITTED. SUPPLEMENTAL REPORT ??/??/???? PART A 15B CHANGED RESTART TIME FROM 0800 TO 1630 PART C 3A. NOMINAL PIPE CHANGED FROM 12.75 TO 12.00 6. TYPE OF INCIDENT LONGITUDINAL CHANGED TO CIRCUMFERENTIAL .5 INCHES WIDE AND 28 INCHES LONG INSERTED. PART E 8. "INCIDENT WAS INITIATED BY A RUPTURE" TO "THE INCIDENT WAS CAUSED BY A RUPTURE DUE TO MECHANICAL DAMAGE.." PART G 3. CHANGED FROM "EXCAVATION DAMAGE BY THIRD PARTY" TO "PREVIOUS DAMAGE DUE TO EXCAVATION ACTIVITY. 16A. CHANGED OUTAGE HOURS FROM 30 TO 51. PART H UPDATED FINAL REPORT RECEIVED FROM METALLURGIST STATING THE FOLLOWING: THE RESULTS OF THE METALLURGICAL FAILURE EXAMINATION INDICATED THAT THE STEEL PIPELINE FAILED DUE TO THE PRESENCE OF MECHANICAL DAMAGE ON THE OD SURFACE OF THE PIPE. THE MECHANICAL DAMAGE WAS IN THE FORM OF A SERIES OF DENTS AND A GOUGE THAT WAS APPROXIMATELY 28 INCHES LONG AND 0.5 INCHES WIDE LOCATED IN THE 12:00 POSITION. THE EDGE OF THE GOUGE EXHIBITED SCORE MARKS THAT CAUSED CRACK INITIATION. AFTER THE CRACK INITIATED, THE CRACK BEGAN TO PROPAGATE BY FATIGUE FROM THE OD TO THE ID UNTIL THE CRACK REACHED SUFFICIENT DEPTH TO PROPAGATE THE LENGTH OF THE PIPE IN A FAST BRITTLE FRACTURE MODE. FROM A METALLURGICAL AND CORROSION VIEWPOINT, THE PIPE WAS IN GOOD CONDITION AND WOULD NOT HAVE FAILED HAD IT NOT BEEN MECHANICALLY DAMAGED.

PHMSA trend classification: significant incident, not serious.

PHMSA standardized cause: EXCAVATION DAMAGE — PREVIOUS DAMAGE DUE TO EXCAVATION.

PHMSA indexed costs: $138,861 reported total cost, $95,004.36 in 1984 dollars, $161,481.163 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.