Corrosion, Alarm Issues Cited in Blast
Deteriorated coatings, ineffective cathodic protection, and a 24-year gap in inspections led to the rupture of a severely corroded pipeline and subsequent massive fire in West Virginia, federal regulators have concluded.
The National Transportation Safety Board released its Accident Report on Monday (March 10) detailing the missteps that caused a natural-gas transmission pipeline to explode in Sissonville, WV, on Dec. 11, 2012.
The pipeline, owned and operated by Columbia Gas Transmission Corporation, exploded with such force that a buried 20-foot segment of pipe was launched more than 40 feet and set off a blaze that shot flames 50 to 75 feet in the air.
Literally adding fuel to the fire, NTSB said, was the pipeline operator's "inadequate" alert system. The system prevented the controller from realizing a rupture had occurred until 10 minutes later, and a lack of automatic shutoff or remote-control valves allowed natural gas to continue flowing for more than hour before it was turned off.
By then, the report said, more than over 76 million cubic feet of natural gas had been released and burned.
The fire torched three houses, damaged several others, and engulfed part of Interstate 77 in flames. The highway was closed for 18 hours, and surfaces sustained thermal damage. No one was killed or seriously injured.
According to the NTSB, the rupture was caused by external corrosion that the pipeline operator could have discovered.
Line SM-80 was constructed in 1967 and had not been inspected or tested since 1988. The ruptured pipe, 20 inches in diameter, had suffered severe external corrosion that reduced the thickness of its wall by 70 percent in some areas, the report said.
Not only were the pipe joint's polymer and coal tar enamel coatings deteriorating, but large rock backfill around the pipeline blocked cathodic protection from exposed areas.
'Potential for Tragedy'
"Remarkably, no lives were lost in this accident, but the potential for tragedy was clearly there," NTSB Chairman Deborah A.P. Hersman said in a statement. "Inspection and testing improve the chances of locating defects early, and reduce the probability of a catastrophic failure which can have devastating results."
Columbia Gas also operates two pipelines that run parallel to the SM-80 pipeline.
The company issued a statement Monday, responding to the report and thanking NTSB for "conducting a thorough investigation."
"While Columbia was in full compliance with all Federal and State pipeline safety regulatory requirements for the pipeline, the report identifies areas for continuous improvements [sic] opportunities, many of which are already underway," the statement said.
"This was a difficult situation for all of us, but we recognize and embrace the critical importance of learning from the Sissonville event and applying what we learn to our pipeline system and operational procedures."
A control-room worker first learned about the incident in a phone call from a Cabot Oil and Gas controller who had been contacted from someone on the outside, NTSB said.
No one was killed or seriously injured in the explosion, but three houses were torched and part of Interstate 77 suffered thermal damage.
Despite receiving a series of alerts that the pipeline's pressure was dropping, it took the controller more than 10 minutes to recognize that a rupture had occurred, officials said. More than an hour passed before field personnel were able to shut down the supply of natural gas to the broken pipe.
Columbia Gas relies on the controller to recognize an abnormal condition from the system's alarms, and this accident "demonstrates the need to configure alerts to provide actionable information about the state of the pipeline system and the need for a timely and appropriate response," the report states.
"Without such information, the controller might not recognize that a safety-significant situation is developing or has occurred," NTSB said.
SM-80 was not in a "high-consequence area" at the rupture location, so in-line inspection or other integrity assessment methods were not required.
Integrity management regulations administered by the Pipeline and Hazardous Materials Safety Administration identify high-consequence areas based on potential impact radius and number of buildings within that circle that are intended for human occupancy.
NTSB issued a safety recommendation to PHMSA, asking the agency to add principal arterial roadways to the list of "identified sites" that establish a high-consequence area.
NTSB also issued three safety recommendations to Columbia Gas Transmission:
"While Columbia was in full compliance with all Federal and State pipeline safety regulatory requirements for the pipeline, the report identifies areas for continuous improvements opportunities, many of which are already underway," the company said.
Columbia Gas reported the cost of pipeline repair at $2.9 million; the cost of system upgrades to accommodate in-line inspection at $5.5 million; and the cost of gas loss at $285,000, according to NTSB.
Previous Action Order
Less than two weeks after the blast, PHMSA issued a Corrective Action Order to Columbia Gas, calling a section of the SM-80 pipeline "hazardous to life, property and the environment."
The order called for immediate actions, including assessing coating integrity; verifying cathodic protection equipment and test stations on all three pipelines, three miles upstream and downstream of the incident location; and inspecting all critical valves.
In response to PHMSA's order, Columbia Gas replaced and then pressure-tested several pipe segments in SM-80.
Columbia Gas, a subsidiary of NiSource Inc., owns and operates about 11,453 miles of pipeline in Delaware, Kentucky, Maryland, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Virginia, and West Virginia.
NiSource, headquartered in Houston, TX, serves customers in at least 16 states with approximately 1.3 trillion cubic feet of natural gas flowing through its pipeline each year, according to the company.