The Department of Transportation (DOT) has issued a correction action order against Tennessee Gas Pipeline in the wake of a July 22 rupture and fire on a segment of its Line 100-1 natural gas pipeline system in Kentucky.

The rupture occurred on Tennessee’s 24-inch diameter Line 100-1 pipeline near Clay City, which is located in the eastern central part of Kentucky. This resulted in the release and ignition of natural gas and a subsequent fire. No injuries or fatalities were reported. The cause of the failure still is under investigation, but preliminary reports indicate that external pitting corrosion of the 60-year-old pipe was to blame, according to the DOT’s Pipeline and Hazardous Materials Safety Administration (PHMSA).

The PHMSA, the Office of Pipeline Safety and the Kentucky Public Service Commission have initiated an investigation of the failure on the Tennessee pipeline segment.

The corrective action order, which was issued by the PHMSA in late July, directed the El Paso pipeline subsidiary to limit the operating pressure on Line 100-1 to 80% of the operating pressure that was in effect prior to the July 22 mishap. The pressure restriction was to remain in effect until Tennessee received written approval from the PHMSA to return the pipeline to its pre-failure operating pressure.

A Tennessee Pipeline spokesman said Monday that Line 100-1 still is operating under restricted pressure.

The PHMSA also ordered Tennessee to conduct a detailed metallurgical analysis of the pipe that ruptured on July 22 to determine the cause and contributing factors. The failed pipe segment and adjacent pieces were transported to El Paso’s metallurgical laboratory in Dearborn, MI, for further analysis, according to the PHMSA.

In addition, Tennessee was ordered to submit a written plan, with a schedule, to verify the integrity of the pipe segment between its Campbellsville Compressor Station 96 and Clay City Compressor Station 105.

The PHMSA corrective order said the last time Tennessee internally inspected the ruptured line was in 1986, and that it last pressure tested the line in 1986 at a minimum pressure of 940 pounds per square inch for eight hours with no leaks. Tennessee reported that the failed line was scheduled to be internally inspected the week of July 24 — two days after the mishap.

The order noted that a major pipeline failure occurred on Tennessee’s 26-inch diameter Line 100-3 in July 1980, approximately three miles from the latest accident. A subsequent investigation revealed that several operational and hydrostatic test pipeline failures had occurred on Tennessee’s 100 pipelines in shale terrain near Clay City, and were attributable to external bacterial corrosion, according to PHMSA.

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