The Pipeline and Hazardous Materials Safety Administration's (PHMSA) Office of Pipeline Safety (OPS) agrees with the National Transportation Safety Board (NTSB) that pipeline wall thinning may have significantly contributed to the rupture on the Columbia Gas Transmission in West Virginia last month.
"OPS observed general wall thinning on the underside of the affected pipeline at the failure location. OPS has preliminarily concluded that general wall thinning is a major factor in the cause of the failure," wrote Jeffrey D. Wiese, associate administrator for pipeline safety, in a corrective action order. The affected pipeline section was built in 1967, OPS noted.
The order finds that operation of the pipeline without corrective action would be "hazardous to life, property or the environment and requires [Columbia Gas] to take immediate action to ensure the safe operation of the pipeline." The pipeline can request a hearing on the corrective action order.
The 20-inch diameter Columbia Gas line, which is owned by NiSource Inc., ruptured on Dec. 11, destroying at least five homes and closing down Interstate 77 for nearly a day. The wall thickness of the section of pipe on the system that ruptured was significantly deteriorated, the NTSB concluded (see NGI, Dec. 17).
"In parts of [the] area, pipe wall thickness was measured to be less than a 10th of an inch thick," said NTSB board member Robert Sumwalt just days after the rupture near the pipeline's Lanham Compressor Station in the rural community of Sissonville, WV. He said the pipe wall was only 0.078 inch thick in certain areas, which amounts to about a 70% loss in wall thickness. The agency estimated that the wall was thinner along the bottom of the pipeline for about six feet.
The NTSB has taken parts of the ruptured pipe to its offices in Washington, DC, to be studied more closely.
After evaluating the preliminary findings and "considering the age of the pipe, circumstances surrounding this failure, the proximity of the pipeline to populated areas and public roadways, the hazardous nature of the product [that] the pipeline transports, I find that a failure to issue this order expeditiously to require immediate corrective action would result in likely serious harm to life, property and the environment," Wiese said in the order.
To return the ruptured line to restricted operation, the order directs Columbia Gas Transmission to make the necessary repairs on its system; verify that all cathodic protection equipment and test stations are operating properly on the affected pipeline and two adjacent lines; and inspect and partially operate all critical valves that might be required during any emergency to ensure that they can be can be completely closed.
The order also requires the company to analyze and validate the discharge pressure at the Lanham Compressor Station at the time of the rupture; and temporarily operate at a lower maximum allowable operating pressure (use the lower of 741 MAOP or 80% of the validated Lanham Compressor Station pressure).
In addition, the order also requires Columbia Gas Transmission to conduct an in-line inspection for high-resolution deformation and metal loss within 30 days of returning to service, and to submit the results to the director of the OPS eastern regional office. It further calls on the pipeline to submit monthly and quarterly reports to the OPS eastern regional office on its progress in complying with the order.
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