Tremors at Bayou Corne salt dome halt work again Friday

The head of Louisiana’s Department of Natural Resources named 13 scientists and other experts Friday to serve on a blue-ribbon commission tasked with determining the long-term stability of the area around northern Assumption Parish’s sinkhole.

The 13-acre sinkhole and consequences of its emergence and continued growth, such as methane trapped under the Bayou Corne area, have forced the evacuation of 350 residents for more than seven months.

The sinkhole, found in swamps between Bayou Corne and Grand Bayou on Aug. 3, is believed to have been caused by a failed Texas Brine Co. LLC cavern mined into the Napoleonville Dome.

Members of the new panel are being asked to set up scientifically based benchmarks in regard to the sinkhole and then determine when they have been met in order to give assurances that the Bayou Corne area is safe for the return of evacuated residents.

“The work of this commission is crucial to the future of public safety in the Bayou Corne area,” DNR Secretary Stephen Chustz said in a prepared statement announcing the 13 appointments.

“We must ensure we have done all that we can to get the right people to provide the right answers in making recommendations for the future of the people who want to return,” Chustz said.

The secretary made the appointments in consultation with Jim Welsh, state Commissioner of Conservation, and Kevin Davis, director of the Governor’s Office of Homeland Security and Emergency Preparedness, the statement says. The Office of Conservation is part of DNR.

Gov. Bobby Jindal called for formation of the commission earlier this month after meeting with Assumption Parish public officials and Texas Brine executives about the sinkhole.

DNR officials said in a statement that the blue-ribbon commission’s first meeting will be held in early April. Patrick Courreges, DNR spokesman, has said some of the group’s meetings would be public, but it was not clear Friday if the panel’s inaugural session would be open to the public or not.

Underscoring the lingering concerns about the growing sinkhole and when it may stabilize, yet another round of seismic activity forced parish officials to halt work around the sinkhole Friday morning for the second time in a little more than a week, officials said.

John Boudreaux, Assumption Parish’s director of Homeland Security and Emergency Preparedness, said the seismic activity was detected about 7 a.m. Friday under the sinkhole and the failed Texas Brine cavern.

Seismic monitors detected an increase Friday in the “very long period” tremors that scientists have said indicate fluid and gas movement below the sinkhole, parish officials said in a blog post.

Parish officials added that Friday’s seismic activity was limited to the sinkhole and the Texas Brine cavern. The activity appears to have had no effect on a second Texas Brine cavern nearby for which structural concerns recently have been raised, parish officials said.

Water movement in the sinkhole and increased bubbling along its western edge were also detected Friday, the post says.

Boudreaux said work was stopped within the 71-acre area surrounded by a berm mandated to encircle the sinkhole. The shutdown area took in the sinkhole’s lake-like surface.

He said crews had been working on oil retardant boom on the sinkhole at the time the work was stopped about 8:30 a.m. Friday.

But he said work related to 3-D seismic surveying of the subsurface — which involves the firing of small, buried explosive charges — continued Friday because it is outside the berm area.

The new blue-ribbon panel members include some of the experts who already have been working on the sinkhole under contract to the state Office of Conservation or on a scientific working group monitoring the sinkhole.

Members Gary Hecox, senior CB&I hydrogeologist, and Will Pettitt, an Itasca Group rock mechanic expert, both have delivered presentations to residents and the state Legislature about the sinkhole.

Working group members include David Borns, Sandia National Laboratories Geotechnology and Engineering Program manager, and Thomas Van Biersel, DNR hydrogeologist and a former Louisiana Geological Survey professor at LSU. Van Biersel is coordinating the sinkhole working group, DNR officials said.

Sandia researches salt domes for the federal Strategic Petroleum Reserve, which stores the nation’s emergency supply of crude oil in Louisiana and Texas salt domes.

Chustz said in the statement Friday that while experts around the world were sought, the panel includes scientists who already have been working on the sinkhole as well as a Bayou Corne-area resident selected, “to ensure that the members share our sense of urgency.”

Before Friday’s work stoppage, a burst of early morning tremors on March 13 caused work to be halted for about a day inside the same berm area.

That halt was followed by one of the sinkhole’s periodic burps on Sunday morning, when oil and debris surfaced, as well as the collapse of 0.95 of an acre of land on the sinkhole’s western edge.

The sinkhole’s surface is believed to be about 13 acres in size with the addition of that last slough-in and with a re-estimation of the sinkhole’s remaining edge, which added a few acres of surface also.