Preliminary NTSB Report: No External Corrosion, Damage From Excavation Found in Line 132

The pipeline that erupted in a deadly explosion on Sept. 9 in the Crestmoor neighborhood didn't show any evidence of external corrosion or damage from excavation, according to a preliminary report released today by the National Safety Transportation Board following the fire.

The report also said there wasn't a pre-existing leak in before the explosion, which confirms that the complaints from residents that they smelled gas in the neighborhood before Sept. 9 weren't related to the explosion.

The findings in the report are the second set of revelations to be revealed about the  into the gas pipeline explosion, which killed eight people and left 38 homes destroyed.

Investigators have yet to determine a cause of the explosion. That evidence is still expected to take more than a year. However, officials and experts agree this latest report shows the NTSB is getting closer to determining a possible reason why the pipeline might have failed.

At a news conference this morning, Congresswoman Jackie Speier said she was pleased with those findings. However, Speier said, she was troubled by findings in the report that PG&E didn't know that section of pipeline had a number of seams in it—contrary to what the utility had previously reported.

"One of the things that was focused on was the fact that PG&E always identified the pipe as being seamless," Speier said this morning at the news conference in San Mateo. "The evaluation showed this was not a seamless pipe. It was seamed and welded at a number of junctions."

According to the report, a metallurgical examination of the pipeline showed that the longitudinal seams on a number of the pipe segments had been welded from both inside and outside of the pipe. However, some segments were only welded from outside of the pipe, which has raised some concerns among investigators about the welding practices and standards that were used on the gas transmission line when it was originally installed in 1956.

, a pipeline safety expert, said the findings about the pipeline's welds are key.

"It looks like they had incomplete welds here," said Kuprewicz, who is a pipeline safety engineer in Redmond, Wash. "That means it could have been a manufacturing issue, but more likely it was a construction issue."

If NTSB investigators later find that the welding issues did, in fact, lead to the explosion, Kuprewicz added, that would confirm what many experts have been saying all along: that direct assessments, the method by which Pacific Gas & Electric Co. has been inspecting many of its pipelines, aren't the best way to detect problems.

Kuprewicz said the best inspection method would either be a method called hydrotesting, which requires pumping water through the pipeline at a high pressure and checking for blow-outs, or using a "very highly specialized" smart pig, a robotic device used to detect the physical condition of a pipeline. 

In a response through its Twitter page, PG&E said it couldn't comment on the report in detail because the NTSB investigation is still ongoing but that it welcomed the additional clarity the report provided.

In the meantime, PG&E said, the utility is conducting "an exhaustive check" of records to ensure accuracy.

"Customers have our pledge that we will continue 2 work aggressively 2 ensure system safety," the utility said. "Safety is the foundation for everything we do." 

Speier said she hopes the she is introducing will address many of the issues that have been raised since the explosion by requiring more oversight for the many natural gas pipelines that run underneath cities throughout the country. She said that she would also be calling on the Pipeline and Hazardous Materials Safety Administration to get more involved with the California Public Utilities Commission and the agency's pipeline inspections.

She described PHMSA's involvement with the CPUC so far as nothing more than "desk audits."

Investigators are now expected to be looking into several other areas as part of the ongoing NTSB investigation:

• PG&E's computerized system that monitored and maintained the pressure in the pipeline, known as SCADA (Supervisory Control and Data Acquisition system);
• whether any of the pipeline's operators were fatigued before the explosion;
• PG&E's pipeline maintenance practices and records; and
• the regulation and oversight of PG&E's pipelines.