Concerns raised about 2nd salt dome cavern

Second Salt Dome Cavern Map Show caption
Second Salt Dome Cavern Map

New seismic surveys suggest a second Texas Brine Co. LLC cavern is closer to the Napoleonville Dome’s outer face than previously thought, leading the Assumption Parish sheriff to call Friday for the need to plan for emergence of a second sinkhole in the Bayou Corne area, however unlikely the possibility may be.

Also on Friday, officials announced that Gov. Bobby Jindal will meet with parish officials in Baton Rouge about the sinkhole that formed last year.

That sinkhole was discovered in early August in a swampland area between Bayou Corne and Grand Bayou after the failure of another Texas Brine cavern carved from the same part of the salt dome containing the latest cavern that is starting to raise concerns.

Scientists think the cavern that failed, known as Oxy Geismar No. 3, was mined too close to the outer face of the giant salt deposit and eventually underwent a sidewall collapse. admitting a great amount of rock strata abutting the dome. This led to the sinkhole’s formation, the release of crude oil and methane gas and the evacuation of 350 people from the Bayou Corne area for more than seven months.

Jindal is meeting with parish officials Monday amid building criticism for his decision to decline requests for a sit-down with the evacuated residents.

“The Governor is meeting with local officials from Assumption Parish and state agency directors on Monday to determine what more can be done for citizens affected by this event,” the governor’s press secretary, Sean Lansing, said by email Friday.

Assumption Parish Police Jury President Martin “Marty” Triche said he got a call from the governor’s staff on Thursday, a day after Jindal sidestepped news reporters’ questions about when he planned to meet with residents affected by the sinkhole.

“I’m anxious to meet with (the governor) on Monday whether it’s in Baton Rouge or in Bayou Corne,” Triche said.

He said he wants to talk to the governor about continued support for oversight and technical analysis as well as leaning on Texas Brine about residents’ requests for buyouts.

The new seismic testing, which the Louisiana Office of Conservation ordered Texas Brine to conduct after the failure of Oxy 3, found that the latest cavern is within 200 feet of the Napoleonville Dome’s outer wall, conservation officials said.

At that distance, the cavern, known as Oxy Geismar No. 1, would be closer to the vertical outer face of the dome than would be allowed under new minimum safety standards that the Office of Conservation is proposing in light of the earlier Texas Brine cavern failure. The proposed standard would set a minimum distance of 300 feet horizontally.

The failure of Oxy 3 is suspected of having at least a months-long build up, preceded by bubbling in area bayous and sharp earth tremors that residents reported feeling at the time.

Patrick Courreges, Office of Conservation spokesman, said the agency has been monitoring the second cavern. Measurements of its internal pressure and of nearby seismic activity do not suggest any sort of failure may be under way, he said.

“We’ve got no indication of that happening right now,” Courreges said.

The state Office of Conservation is under the state Department of Natural Resources.

Office of Conservation officials said in a statement Friday that previously ordered three-dimensional seismic tests are needed to confirm the distance between Oxy 1’s wall and the outer face of the salt dome. The other testing has a built-in margin of error.

The 3-D data must be submitted to the Office of Conservation on April 21. Monitoring will continue in the meantime, officials said.

Texas Brine and other salt dome operators use fresh water to dissolve hollow cavities from salt domes deep underground and sell the brine to industrial users. Other companies later use the cavities created by the salt brine mining process for storage of oil, gas and other hydrocarbons.

Oxy 1, which was mined for brine from 1976 to late 2011, is on the same 40-acre site as Oxy 3 and the sinkhole. Texas Brine leases the property south of La. 70 South from Occidental Petroleum Corp.

Assumption Parish Sheriff Mike Waguespack, who plans to attend Monday’s meeting with Jindal, said he wants government officials and area companies to meet to develop contingency plans for a possible “sinkhole No. 2,” however remote.

One of the sheriff’s leading concerns is possible danger posed by a second sinkhole to La. 70 South, a key thoroughfare that is about 950 feet from the Oxy 1 cavern’s outer wall.

“We’ve got to have plans in place where we can move fast,” Waguespack said. “We hope that there’s enough (monitoring in place) to have warning, but you just never know.”

The first sinkhole opened up overnight between Aug. 2 and 3 and was detected by parish officials after residents reported a strong hydrocarbon odor early on Aug. 3 as people awoke. La. 70 was shut for about 24 hours due until area pipelines could be closed.

State Rep. Karen St. Germain, D-Pierre Part, said the governor’s staff has been “very involved” in the sinkhole response. But the governor could illustrate his involvement by making a trip to Assumption Parish at some point, she said.

“It’s a great idea for him to go. He can dispel the fear that he really has not been on top of it,” St. Germain said.

Sinkhole activist John Achee Jr., who owns a camp in the area, said Jindal needs to give residents 15 to 20 minutes of his time.

“While we are pleased that after seven months he has chosen to grace our officials with his presence, we look forward to seeing him March 19 at our next community meeting on the Bayou Corne sinkhole in person,” he said.

Lansing said the governor tasked the Governor’s Office of Homeland Security and Emergency Preparedness, Louisiana State Police, the state Department of Natural Resources, the state Department of Environmental Quality and the state Department of Transportation and Development with responding to the sinkhole emergency.

“The DNR has said several times that Texas Brine should consider buyouts for residents in the evacuation area who want to leave,” Lansing said.

The Oxy 1 cavern has a cylindrical shape except at the top, where it is much wider across. This creates the overall appearance of a Roman column with an exaggerated capital at the top, a 2011 sonar survey shows.

These kinds of wider areas are called “wings” and usually result from areas where salt dissolves more easily than the rest of the cavern.

Courreges said Oxy 1’s wings are the parts of the cavern closer to the salt dome outer face than expected.

Oxy 1 is about 900 feet northeast of Oxy 3 and extends from 2,492 feet to 3,228 feet underground, shallower than Oxy 3, officials said.

Oxy 1 was the subject of a 1995 Sandia National Laboratories study that suggested the cavern might have breached the salt dome face near the cavern’s bottom. Texas Brine officials said later testing by Texas Brine argued against that conclusion.

Texas Brine spokesman Sonny Cranch said the company agrees with DNR’s assessment of the situation.