By Melissa Gray, CNN
(CNN) — Louisiana officials are investigating whether an underground salt cavern may be responsible for a large sinkhole that has swallowed 100-foot-tall cypress trees and prompted evacuations in a southern Louisiana bayou.
The state’s Department of Natural Resources ordered Texas Brine Company, which mines the cavern, to drill a well into the cavern to see whether it caused the dark gray slurry-filled hole nearby.
Measurements taken Monday showed the sinkhole measures 324 feet in diameter and is 50 feet deep, but in one corner it goes down 422 feet, said John Boudreaux, director of the Office of Homeland Security in Assumption Parish, about 30 miles south of Baton Rouge.
Assumption Parish police said Thursday the sinkhole has since grown another 10 to 20 feet.
The sinkhole appeared August 3, more than two months after local residents started noticing bubbles in the water. The bubbles grew in number and frequency, and in some spots they made the bayou look like a boiling crawfish pot, said Dennis Landry, who owns guest cabins about half a mile from the hole.
Assumption Parish police ordered the evacuation of all residents in the area, though Landry said it’s not a forced evacuation so he and his wife have decided to stay.
“When you have a beautiful home like I have on the bayou and have a little business that I run in the home, it would be very difficult to leave this behind,” he told CNN. “We kind of feel that if something drastic were to happen, we could jump in a car and get out of here.”
Assumption Parish Sheriff Mike Waguespack said Thursday he is now concerned the sinkhole is close to a well containing 1.5 million barrels of liquid butane, a highly volatile liquid that turns into a highly flammable vapor upon release. A breach of that well, he said, could be catastrophic.
The salt cavern is part of the Napoleonville salt dome that sits under the area. Salt domes are large, ancient formations of salt in the ground that are used for the commercial mining of petroleum, salt and sulphur, according to the U.S. Army Corps of Engineers.
Texas Brine says it mines salt domes to produce brine, a salt-filled water used for the manufacture of chlorine and caustic soda, which in turn are used in products ranging from paper and plastics to pharmaceuticals.
Salt domes can be as deep as 10,000 feet and are mostly found along the northern coast of the Gulf of Mexico and in Texas and Louisiana, according to the National Oceanic and Atmospheric Administration.
Louisiana has more than 100 identified salt domes, according to the state’s Department of Natural Resources.
Texas Brine is investigating whether a breach in its salt cavern might have caused the sinkhole 100 yards away, company spokesman Sonny Cranch said from the site.
The company conducted ground imaging of the dome and well Thursday and plans to do satellite imaging soon, Cranch said.
Landry said his business, Cajun Cabins of Bayou Corne, has stalled ever since people found out about the sinkhole.
“Our beautiful little paradise is in jeopardy,” he said.
He said he suspects a cavern collapse is to blame, and he said there’s a fear in the community that a further collapse could enlarge the sinkhole and endanger a wider area.
Local emergency planning officials are keeping residents updated through online blog posts and community meetings, he said. They’ve had three so far.
Local residents and the sheriff say the Department of Natural Resources “knew for months” that the Texas Brine well had integrity problems but didn’t tell local authorities.
“DNR failed to report to anybody that this cavern could be the source of the bubbles,” Landry said.
“I’m very upset about it. A lot of local residents are upset about it,” he said. “I feel like I’ve been betrayed by the Louisiana Department of Natural Resources.”
One resident told CNN affiliate WAFB, “Somebody at DNR should have woke up and realized, hey, remember this salt dome, this salt cavern that had a problem, maybe we should be looking at that. That’s a little bit upsetting.”
Said the sheriff, “DNR has lost all credibility with me.”
Landowners near the sinkhole filed a lawsuit this week against the DNR and Texas Brine, claiming the drinking water has now been contaminated by a problem both the department and company allegedly knew about.
“They’re trying to make this something to deal with one well. It’s not just one well, it’s the whole system of Grand Bayou. They just ignored it,” said John Carmouche, a partner with Talbot, Carmouche, and Marcello in Baton Rouge who represents the landowners.
A representative for DNR could not be reached for comment Thursday evening.
Landry flew over the sinkhole the other day and said diesel and other chemicals are floating on top of the sludge. Some of the tall cypress trees that fell in are now floating on top of the hole because of the buoyancy of the salty water, he said.
Landry said he and his wife were taking a boat ride on the bayou when they first noticed the bubbles May 30. He knew there are three natural gas pipelines in the area, including one directly beneath the bubbles, so he reported the bubbles to the owners, Crosstex and Enterprise Products, both based in Texas.
Both companies checked their lines for weeks, bringing in divers and crews to swim down and look for leaks, but every time they reported finding no problems, Landry said. Crosstex even brought in a tugboat and a barge, launching them from his boat landing, he said.
Once officials eliminated gas pipelines as the source of the bubbles, Landry said, they began checking gas storage domes and abandoned wells in the area. They were still looking for the source when the sinkhole popped up last Friday, he said.
While Landry said he feels somewhat safe for now, he laments what is happening to his “sportsman’s paradise” on the bayou.
“I believe in the good book, and they say in there that all things shall pass, and this too shall pass, but it remains to be seen in what form it will pass,” Landry said.
— CNN’s Carma Hassan and Nigel Walwyn contributed to this report.