(Bloomberg) -- A federal agency has ordered the owner of the controversial Mountain Valley Pipeline to undertake a series of safety inspections on the 300-mile project, arguing that segments of pipe left exposed or buried underground for years amid project delays could pose a safety risk. 

The review, issued by the Pipeline and Hazardous Materials Safety Administration, has the potential to result in cumbersome and expensive fixes for Equitrans Midstream Corp., which has already seen its project held up by legal challenges by environmental groups for years.  

“The commissioning and operation of the MVP pipeline without appropriate inspection and corresponding corrective measures first being undertaken would pose a pipeline integrity risk to public safety, property, and the environment,” the agency said in a Notice of Proposed Safety Order.

Read More: Supreme Court Lets Work Resume on Manchin-Backed Gas Pipe

The $6.6 billion pipeline project, which aims to provide drillers in the gas-rich Appalachian Basin with much-needed transport capacity, is backed by Senator Joe Manchin. The West Virginia Democrat succeeded in having language approving the beleaguered project woven into the legislation that was needed to lift the national debt limit. 

The must-pass debt ceiling legislation signed into law June 3 by President Joe Biden included a measure expediting the 300-mile line, which will cut through the Appalachian Mountains, a national forest and hundreds of stream crossings as it carries natural gas from Manchin’s home state of West Virginia to southern Virginia.

The US Supreme Court last month granted a company request and let work resume on its construction. 

A Manchin spokeswoman didn’t immediately respond to a request for comment on PHMSA’s order. 

Environmental Concerns

The PHMSA order was issued Friday, the same day a US Appeals Court rejected a challenge by environmentalists to the project, and comes as the condition of the pipeline becomes a new battleground for the project.

Natalie Cox, an Equitrans spokeswoman, said the company has requested an informal consultation with PHMSA and the project remains targeted for completion by the end of the year. 

“While the proposed preliminary findings do not present an accurate view of the extraordinary efforts we have taken to ensure the safety and integrity of the pipeline, which has faced unprecedented delays due to circumstances beyond our control, Mountain Valley remains committed to working with PHMSA and other regulators as the project enters the final phase of construction,” Cox said in an email. 

Earlier this summer, environmental groups urged federal agencies, including PHMSA, to impose additional safety measures for the pipeline’s construction, including requiring any needed fixes to be done at a plant indoors, which in some cases could mean uninstalling pipeline segments so it could be hauled away. 

“We appreciate the concerns community members have been raising for years are in focus,” said Jessica Sims, Virginia field coordinator for the environmental group Appalachian Voices. “The materials for the Mountain Valley Pipeline have in some cases been sitting in the sun for six years.”

PHMSA, in its safety order, noted that segments of the pipe have been buried with out certain corrosion protections installed or exposed to the elements and ultraviolet radiation “for long periods of time.” In addition, the safety agency said it observed pipe placed “within a rock-laden trench without adequate support” to protect the pipeline’s coating  to damage.

The agency ordered Equitrans to do third-party testing on the pipeline coating for nearly the entire length of the pipeline and conduct analysis on all pipe stored in outdoor locations by an independent, among other testing as well as submit a work plan to make any needed fixes. 

--With assistance from Ruth Liao.

(Updates with additional background starting in fourth paragraph.)

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