As part of its continuing investigation into the rupture of a Columbia Gas Transmission pipeline in West Virginia in December, the National Transportation Safety Board (NTSB) has made more than 1,400 pages of documents on the pipeline explosion available to the public.

The documents that have been released are factual in nature and do not provide any analysis. They include interview transcripts, photographs and other documents from the NTSB’s investigation. The documents can be accessed on the agency’s website. Additional material will be added to the docket as it becomes available. Analysis of the accident, along with conclusions and a determination of probable cause, will come at a later date when the final report on the investigation is completed, the NTSB said.

In a preliminary report issued in mid-January, the NTSB reported that a six-foot section of the 20-inch diameter Columbia Gas system that ruptured on Dec. 11 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 (see Daily GPI, Jan. 17).

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 the 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 blast, which occurred near Sissonville, WV, destroyed at least five homes and started several fires that were so intense firefighters were unable to move equipment near burning structures for a short period of time (see Daily GPI, Dec. 12). The explosion also shut down a portion of the interstate.

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