A natural gas pipeline explosion that occurred last month in Marshall County was likely caused by land subsidence, or movement, according to federal regulators.
In a notice of proposed safety order, issued to TransCanada Corp. this week, the Pipeline and Hazardous Materials Safety Administration (PHMSA) said shifting land likely triggered the explosion of the Leach Xpress pipeline.
"The preliminary investigation suggests that the failure was the result of land subsidence causing stress on a girth weld," PHMSA said.
The explosion occurred during the early hours of June 7 near Moundsville, West Virginia. No injuries or damage to private property were reported, but a fireball burned for several hours after an 83-foot section of the pipeline burst into flames, releasing more than $430,000 worth of natural gas.
TransCanada’s own incident report released this week states the pipeline failed due to a landslide, but not one caused by heavy rainfall.
The full federal investigation is still ongoing, but PHMSA’s proposed safety order states TransCanada should conduct extra surveillance and analysis on a 50-mile section of the pipeline that is buried in terrain geologically similar to where the explosion took place.
TransCanada is the parent company of Columbia Gas Transmission LLC, which operates the 130-mile pipeline that runs from Majorsville, West Virginia to Crawford, Ohio. The pipeline went into operation in January and was not running at full capacity when the explosion occurred.
In the order, the federal safety agency also said it identified six other locations where similar geography could cause the pipeline to fail. It outlines a series of additional corrective actions the company should undertake.
TransCanada has 30 days to review the order and request consultation with PHMSA regarding the proposed suggestions.
Lindsey Fought, a spokeswoman for the company said an email TransCanada had reviewed the notice.
"The investigation into our pipeline incident in Marshall County, West Virginia, on June 7, 2018 remains ongoing and we are fully cooperating with PHMSA to determine the root cause," she stated. "Initial findings noted in the PHMSA Proposed Safety Order, as well as our internal findings, point to land subsidence as the cause of the rupture."
This story was updated on 07/13/18 to include comment from TransCanada.