A six-foot section of a 20-inch diameter Columbia Gas Transmission system that ruptured Dec. 11 in West Virginia had wall thickness measured as low as 0.078 inches, significantly thinner than the nominal wall thickness of 0.281 inches when the pipeline was installed in 1967, according to a preliminary report issued Wednesday by the National Transportation Safety Board (NTSB).

A 20-foot ejected section of the pipeline “was fractured in the base metal along the entire longitudinal direction along the bottom of the pipe,” according to NTSB report. “The longitudinal ERW [electric resistance weld] pipe seam was located near the top of the pipe. The outside surface of the pipe was heavily corroded near the midpoint and along the longitudinal fracture. The thinned area was approximately six feet in the longitudinal direction and two feet in the circumferential direction.”

The report confirmed comments made by NTSB investigators in the first days of their investigation (see Shale Daily, Dec. 17, 2012).

The rupture occurred near Columbia Gas Pipeline’s Lanham Compressor Station in the rural community of Sissonville, WV, which is about 15 miles north of Charleston. The rupture of the gas line, which is owned by NiSource Inc., destroyed at least five homes and closed Interstate 77 for nearly a day (see Shale Daily, Dec. 12, 2012). There were no fatalities and no major injuries reported.

The pipeline’s maximum allowable operating pressure was 1,000 pounds per square inch gauge (psig) and the operating pressure at the time of the rupture was about 929 psig, NTSB said.

The first notification to the Columbia Gas control center was received from a controller from another gas company, who had received a report of a rupture and fire from a field technician near the accident location, NTSB said. Prior to the call from the other company, the Columbia Gas controller received 16 pressure drop alerts.

Columbia Gas said NTSB “has been swift in their response and thorough in its analysis” at Sissonville. The company said it has worked in coordination with the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA), the West Virginia Public Service Commission and other state and local authorities to thoroughly test, inspect and verify the safety and operational integrity of its system in the area.

“We will continue to work in close collaboration with the NTSB as the investigation continues,” the company said Wednesday. “Columbia is committed to a thorough and complete analysis of all factors potentially contributing to the incident.

“Based on that analysis, we will continue to work with the NTSB and PHMSA — as well as state and local officials — to take all steps necessary to ensure the continued safety of our pipeline system. We will also implement appropriate measures based on the recommendations from the NTSB into our infrastructure modernization plan.”

The U.S. Senate Commerce Committee plans to hold a field hearing Jan. 28 on pipeline safety in Charleston, WV, to examine the nation’s pipeline infrastructure. The Senate forum panel also will evaluate the Department of Transportation’s implementation of the Pipeline Safety, Regulatory Certainty and Job Creation Act of 2011, which was signed into law in January 2012 and was based largely on legislation cosponsored by Committee Chairman John D. Rockefeller IV of West Virginia.

Moreover, the committee hearing will review the findings of a Government Accountability Office study, expected to be released on Jan. 23, on the ability of transmission pipeline facility operators to respond to a hazardous liquid or gas release.

In late December, the PHMSA’s Office of Pipeline Safety (OPS) issued a corrective action order against Columbia Gas Transmission. “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 the order. The affected pipeline section was built in 1967, OPS said.

The order found 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.”