State looking into piping problem in cavern near Bayou Corne sinkhole

An internal piping problem inside a Dow Hydrocarbons underground storage cavern in Assumption Parish prompted automatic emergency systems to burn off propylene and shut the cavity, but the situation presents no immediate public safety risk.

Dow officials are working on plans to check the cavern — located south of La. 70 South about two miles away from the 24-acre Assumption Parish sinkhole.

John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness, said he visited Dow’s Grand Bayou facility on the Napoleonville Dome on Thursday after a report from a concerned resident.

Boudreaux said he visited the control room and saw that the cavern and its surface access well do not appear to be compromised.

“They showed me everything I needed to see. From what I saw, yes, there is a problem, but I don’t think there is a public risk,” he said.

The problem involves metal piping, that hangs freely inside the cavern and is not relied upon to seal the flammable propylene underground, officials said. Part of the pipe is missing for reasons unknown.

The Dow 3A cavern is about one-third of a mile underground in the salt dome and stores 600,000 barrels of propylene under pressure as a liquid, officials said.

Boudreaux said safety systems burned off propylene in lines tied to the cavern as a precaution a few days ago.

Patrick Courreges, spokesman for the Louisiana Department of Natural Resources, said Dow officials first noticed a problem the night of July 11 and requested a work permit from the agency the next day to investigate.

Courreges said Dow plans to examine the damaged piping and test the integrity of the cavern and its access well. He said Dow will remove propylene for those tests.

The Dow cavern is on the opposite side of the 1-by-3-mile salt dome from the Bayou Corne-area sinkhole and the failed Texas Brine Co. cavern suspected of causing it.

Dow Hydrocarbons is part of Dow Chemical.

Dow’s more than 880-acre salt dome facility supplies brine for chlorine manufacturing and stores hydrocarbon feedstocks, like propylene, for its instate plants, the company’s website says.

A message left with a Dow spokeswoman was not immediately returned Thursday.