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Cause Of Pipeline Explosion Still Unknown, But Experts Say Corrosion Could Be Factor

Erica Peterson

Federal investigators have taken over the site of Thursday’s natural gas pipeline explosion that killed one person and left five injured south of Danville.

The blast ejected 30 feet of pipeline into the air, scorched railroad tracks and burned mobile homes, forcing the evacuation of about 75 people after midnight on Thursday morning. Firefighters battled the 300-foot blaze for hours before extinguishing it.

Investigators with the National Transportation Safety Board took over the scene Thursday and will begin looking for a cause.

“Our mission is to understand not just what happened, but why it happened and to recommend changes to prevent it from reoccurring again,” said Mike Hiller, NTSB senior accident investigator on Friday.

The Lincoln County Coroner has identified the deceased woman as Lisa Denise Derringer, 58, of Stanford. Hiller said residents will likely be able to return to the site to gather their belongings on Saturday.

Possible Causes

Thursday’s explosion in Lincoln County came from a rupture in the 30-inch wide natural Texas Eastern Transmission pipeline, which is owned and operated by Calgary-based Enbridge.

The affected section of Texas Eastern Transmission pipeline was installed in 1957 and runs from Ohio to Mississippi, Hiller said.

Since 2011, the Pipeline and Hazardous Materials Safety Administration has received 38 reports of “serious” and “significant” incidents along the entire length of the roughly 9,000 mile long Texas Eastern Transmission pipeline, nearly half of which were caused by corrosion.

Hiller declined to speculate on what may have caused Thursday’s explosion, but said the investigation would include looking into a variety of possibilities including corrosion.

While the cause of the explosion remains unclear, WFPL News spoke with two experts who said it’s possible a rock formation may have heaved or accelerated corrosion of the pipeline. And it could happen again.

“I did see a good picture of it and it looks like it’s definitely within the black shale,” said Warren Anderson, a retired geochemist who has studied black shale for a decade. “This is not the last one. There will be others and I can’t say they are going to occur in more frequency, but this is definitely not the last one.”

An outcrop of New Albany black shale runs in a horseshoe shape around central Kentucky, including through the area of the explosion. The organic sedimentary rock often contains pyrite (also known as fool’s gold for its metallic luster), which can cause problems.

When the pyrite begins to oxidize, two things can happen: It can expand from 10 to 100 times its original size and it can create a mild sulfuric acid that can accelerate corrosion on a steel pipeline.

The crystal growth can heave foundations, damage sidewalks, utility lines and walls while “the sulfuric acid really accelerates that weathering,” Anderson said.  He has recorded 15 or 20 incidents of pipelines and homes that have been condemned because they’ve been built in the black shale, he said.

Anderson said black shale was most likely what caused a 1985 explosion that killed five people and injured three others on the same pipeline in Beaumont, Kentucky. An accident report from the incident notes “… in the presence of water, the sulfate ions would have the corrosive effect of dilute sulfuric acid.”

But not everyone agrees with Anderson’s take on the 1985 explosion.

David Harris, head of the energy and mineral section at the Kentucky Geological Survey, said it’s possible that black shale could damage a pipeline, but also said the accident report doesn’t “directly link the corrosion with black shale bedrock or pyrite.”

A 2006 investigation into a failure in Clay City, Kentucky, found a similar outcome, though attributed it to bacterial corrosion.

“The pipeline failed in the bottom of a valley in an area of wet shale. Shale terrain in this part of Kentucky is known to cause corrosive environments on buried pipelines,” it read.

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