The Natural Transportation Safety Board (NTSB) Wednesday began sifting through pieces of the Columbia Gas Transmission system that ruptured near the pipeline's Lanham Compressor Station sear Sissonville, WV, a rural community of 4,000 about 15 miles north of the state capital, Charleston.

The 20-inch diameter Columbia Gas pipeline, which is owned by NiSource Inc., ruptured at 12:41 p.m. EST Tuesday under Interstate 77, with the gas igniting and subsequently causing significant damage to several residences and all four lanes of Interstate 77, said NTSB investigator Robert Sumwalt. The flow of gas was stemmed at approximately 1:45 p.m. All persons were accounted for and no significant injuries were reported, he noted. Columbia Gas reported that the pipeline pressure at the time of the rupture was 929 psi, below its maximum allowable operating pressure of 1,000 psi.

The blast destroyed at least five homes and created several fires that were so intense firefighters were unable to move equipment near burning structures for a short period of time (see Shale Daily, Dec. 12). The explosion also shut down a portion of the interstate, which straddles Sissonville. Repairs were made overnight and the interstate was reopened Wednesday, the Associated Press reported.

The NTSB investigators began arriving in Charleston Tuesday night, and are expected to remain in Sissonville over the next five to seven days. The 10-member investigation team will be led by Ravi Chhatre, an expert on pipeline operations, fire and explosions and emergency-response efforts. "Our mission is to determine not only what happened but to determine why it happened to prevent future accidents," Sumwalt said during a briefing.

"We're going to be particularly interested [in] the the rupture site," he noted. The board will "probably cut out a section of the pipe and take it back to Washington" to be carefully examined under a microscope, he said. "We have not spoken in detail to Columbia Gas at this point, but certainly that is something that we will be doing and we will have their representatives here working with us for the next several days."

Columbia Gas said it has isolated the damaged portion of pipeline, secured the site and begun assessing damages. It noted that the transmission line is part of a network of lines that deliver natural gas primarily to local utility companies, and that service to those customers was not affected by the rupture.

As part of its investigation, Sumwalt noted that the NTSB would look at pipeline operations, specifically talking to people in the gas control center; bring in a fire explosion expert; and bring aboard emergency-response people to review the "thoroughness and immediacy" of the response efforts following the rupture. "Did the people in the control center act appropriately once this pipeline ruptured?"

"We are very fortunate for the time of the explosion," said West Virginia Gov. Earl Ray Tomblin, as reported by Jeff Morris of WCHS TV in Charleston. No one was at home at the residences that were destroyed, the governor said, and "there were no vehicles on the interstate."

It was the second explosion on a NiSource pipeline in less than a month. In late November, an explosion on the Columbia Gas Co. of Massachusetts distribution system rocked Springfield, MA, damaging 42 homes and businesses and sending 18 people to area hospitals. Preliminary findings said a Columbia Gas employee "accidentally punctured" a pipe. The blast is being investigated by the Massachusetts' Department of Utilities, not the NTSB, because it occurred on a gas distribution system, which is under state jurisdiction.