SOUTHERN NATURAL GAS CO — Gas transmission and gathering — incident on 2009-12-31

Gas transmission and gathering incident in HEFLIN, CLEBURNE County, AL. Reported cause: 14. Reported consequences: 0 fatalities, 0 injuries, $265,000 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: 20090139.

Operator ID: 18516.

Reported incident date: 12/31/2009.

Cause detail: BODY OF PIPE

Cause detail: CLEBURNE COUNTY (ALABAMA) EMA REPORTED A SUSPECTED NATURAL GAS RELEASE IN THE VICINITY OF SOUTHERN NATURAL GAS (SNG) COMPANY'S 24" NORTH MAIN LOOP PIPELINE ON DECEMBER 31, 2009. DISPATCHED SNG PERSONNEL CONFIRMED THE EXISTENCE OF THE GAS RELEASE AT APPROXIMATE PIPELINE MILEPOST 399.631, ABOUT 835 FEET EAST OF CLEBURNE COUNTY ROAD 488. THE 24-INCH NORTH MAIN LOOP LINE LEAKED DUE THE CUMULATIVE EFFECTS OF STRESSES (TENSILE AND TORSIONAL) ACTING ON A WRINKLE BEND CONTAINING A LONGITUDINAL WELD SEAM. THE FAILURE CONSISTED OF A 2�- 7.5� LONG CIRCUMFERENTIAL CLEAVAGE FRACTURE ALONG THE APEX OF THE CONVOLUTION OF AN UNDER BEND. STRUCTURAL CAPACITY WAS EXCEEDED DUE TO THE FOLLOWING FACTORS: (A) NATURAL SOIL MOVEMENT DUE TO THE GEOLOGICAL CHARACTERISTICS COMBINED WITH THE PRESENCE OF WATER (B) GEOMETRICAL STRESSES INHERENT IN THE BENDING OF THE PIPE MATERIAL AND PROPERTIES OF THE LONGITUDINAL WELD METAL (C) NORMAL INTERNAL PRESSURES ASSOCIATED WITH THE OPERATION OF THE NATURAL GAS PIPELINE (D) EXCAVATIONS AND SOIL DISTURBANCES NEARBY THE PIPELINE�S RIGHT-OF-WAY. THE WRINKLE BEND WAS INSTALLED DURING THE PIPELINE'S ORIGINAL CONSTRUCTION AND WAS USED IN A SAG BEND WITH THE PIPE'S LONGITUDINAL SEAM HAVING BEEN PLACED IN THE INSIDE PORTION OF THE BEND. THE FAILURE SITE WAS REPAIRED BY REPLACEMENT WITH A NEW PIPELINE SEGMENT.

PHMSA trend classification: significant incident, not serious.

PHMSA standardized cause: MATERIAL FAILURE OF PIPE OR WELD — BODY OF PIPE.

PHMSA indexed costs: $265,000 reported total cost, $148,565.363 in 1984 dollars, $335,761.912 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.