NEW ORLEANS (AP) — A collapsed wall of an abandoned underground salt cavern where a Texas company had operated is being blamed with causing a sinkhole and contaminating an aquifer in a sparsely populated area of swampland west of New Orleans.
The Louisiana Office of Conservation said new data shows that a series of problems — natural gas bubbling up in local bayous and a growing sinkhole that's swallowed about 4 acres of swamp forest — are linked to the collapse of a side wall of an underground salt cavern that Houston-based Texas Brine Co. LLC operated. The company extracted brine and piped it to nearby petrochemical facilities.
Late Thursday, Conservation Commissioner James H. Welsh ordered Texas Brine to make sure the collapsed cavern does not worsen and to do more testing, monitoring and analysis to understand what is happening underground.
"We have a sense of what happened, now we're trying to figure out what is still happening," said Patrick Courreges, a spokesman for the Louisiana Department of Natural Resources.
In August, the sinkhole opened up near a community along Bayou Corne in Assumption Parish, about 60 miles west of New Orleans. Residents in the area had reported strange bubbling in their waterways and tremors before the sinkhole opened up. Officials then issued a voluntary evacuation order to about 350 people living near the sinkhole.
Extracting brine from salt domes is a common practice in Louisiana, where there are 75 active brine wells. Brine is used to make chlorine, an important building block for petrochemical and plastics manufacturers.
Sonny Cranch, a Texas Brine spokesman, said the company has not finished its own analysis of what happened but that it would comply with the Office of Conservation's order.
The company has acknowledged a relationship between the sinkhole, the breached cavern and gas and oil found in both. But the company has suggested geologic tremors in the area may have caused the cavern breach.
State officials say probes of the cavern and surrounding area reveal that a side wall of the cavern collapsed. When that happened, natural gas and crude oil that had been trapped underground began seeping to the surface, the state said.
Natural gas and crude oil has seeped into a nearby aquifer too, state officials said. The aquifer is not used for drinking water but some businesses rely on it.
Texas Brine stopped using the cavern in June 2011 after pressure readings indicated possible problems with the cavern, which the company had planned to expand, Courreges said.
Texas Brine has not been fined. The company, however, may face fines for groundwater and surface water contamination.
The company is paying residents in the evacuation zone near the sinkhole $875 a week in compensation.
Wilma Subra, a chemist working with the Louisiana Environmental Action Network on monitoring the Bayou Corne sinkhole, said it appeared that the cavern was mined too close to the edge of the salt dome. She said more should have been done to figure out if the cavern was prone to collapsing when problems were discovered in 2010.
Wells are being installed to vent natural gas in the aquifer. Texas Brine has proposed injecting more brine into the cavern to force out whatever oil and gas is in there, but the state has not approved that plan yet. Courreges said the state needs more data to figure out what future steps need to be taken to get the sinkhole and gas and oil releases under control.
Residents are worried and some are asking to be relocated.
"My wife no longer feels safe here. She wants to get bought out," said Nick Romero, a 64-year-old retired postal worker. He said he lives just under a mile from the sinkhole.
"The gas is our biggest concern, when the gas started bubbling around us in the bayous," he said. "We've got bubbling in the water five houses down from where I live."
He said the company and officials so far have told the community not to worry. "They say it's not harmful to the fish, to the water, to humans. But I'm skeptical."