External corrosion was the cause of September's natural gas pipeline rupture that caused an explosion on Route 26, north of the Town of Appomattox.

John Batchelder, Williams Transco Gas Pipeline integrity expert, explained during a public meeting on Monday that there was an error in the inspection testing results taken earlier this year.

"The initial results that we got back did not identify the corrosion as deep as it was," he said explaining that the inspection tools did not discover the severity of the corrosion.

Batchelder explained the geography affected the coating of the pipe.

He said that the area in which the pipe is laid is very rocky and has an affect on how water moves.

"So at some point in the life of this pipeline the coating became compromised. The rocks in this ditch make it very difficult to protect this area," said Batchelder. "This area has an unique signature of corrosion. It stretched the limits of technology."

He noted that Williams would take what they have learned and apply it to the whole piping industry.

During inspections, a tool called a pig is used to determine any defects in the pipe.

Batchelder explained that there is a new generation of "smart pig," which predicts where there are areas of metal loss.

He said that they are using the smart pig now for all of their pipelines to determine metal loss.

In the midst of the investigation, a part of the ruptured pipeline metal was sent to a metallurgical lab in Houston for analysis and soil analysis was performed, that later determined the cause of the explosion.

Batchelder said that based on the failure analysis there was no internal corrosion or stress corrosion, which he said was a good thing.

The pipeline has been out of service since the explosion occurred on September 14 that destroyed two homes and injured five people.

Williams officials have completed repairs to the line and are hoping to obtain written approval this month from the Pipeline and Hazardous Materials Safety Administration (PHMSA), which is the federal agency that oversees the safety element of the pipeline.

A week after the rupture, PHMSA issued a corrective action order outlining steps for Williams to take before the line is restored.

Williams has since completed all the steps and has done additional work as well.

Williams has met with PHMSA this week.

Rob Shoaf, pipeline integrity team leader said that Williams is awaiting PHMSA confirmation to restore 80 percent of the pressure to the pipeline.

At normal pressure, the gas is funneled through at 800 pounds per square inch.

Shoaf said line C, the adjacent line will remain at 600 pounds per square inch of pressure through the winter.

Gas has been funneled at low pressure in line C since the explosion.

The other adjacent line, line A was restored to full service last month after being at low pressure for two months.

Williams has taken several measures to ensure the safety of the pipeline before service is restored.

Approximately, 65 miles of pipe was inspected and 49 areas were excavated.

Shoaf said that of the 49 sites only eight sites needed to be looked at.

There were sections cut out and replaced with a total of 2,500 feet of new piping.

Six segments comprised of 15 miles yielded no leaks when pressured with water at 1100 pounds per square inch.

Shoaf said that they are doing additional leak surveys.

"We are looking at this with a fine tooth comb," said Shoaf.

Williams Vice President Larry Hjalmarson said that they want to restore citizens' confidence in the safety of the pipeline.

"This has been a very difficult time for us," he said. "We work our careers to prevent this from happening."

He said that all the extensive work of repairs have been successful except for one incident where a valve was leaking - it has since been corrected.

Additional work that Williams has done includes hydrostatic testing, in which the pipe is filled with water and held at a pressure of 1100 pounds per square inch for eight hours and is monitored for leaks.

Hjalmarson said that the explosion affected 100 homes, some of which had cracked foundations.

He said all but 20 houses so far have been fixed.

During Monday's meeting, Beverly Gaydas of the American Red Cross praised Williams for their work.

"Williams has done a wonderful job testing and getting things done," she said. "You should be proud of Williams."

The failed pipeline, line B is a 30-inch diameter pipe crossing Virginia, was installed in 1955.

The pipeline totals 10,500 miles running from Gulf of Mexico to New York. The gas funnels through the pipe on a three to four day journey to get from one end to the other.

The line is used to heat and generate electricity to homes.

Williams has a storage facility in Pennsylvania.

Williams produces enough natural gas for more than four million homes per day and is the 13th largest natural gas producer in the nation.