Sinkhole update: Methane threat diminishing, Assumption officials partially lift evacuation order _lowres


In another sign that the risk is lessening from the methane gas bubbling up in the Bayou Corne-area sinkhole, Assumption Parish officials on Wednesday lifted the voluntary evacuation order in a sparsely populated area east of the big, lake-like hole in the swamp.

Though the main populated area in Bayou Corne continues to be under the mandatory evacuation order in place since August 2012, this section east of Grand Bayou in a largely unpopulated community also known as Grand Bayou is now free of any kind of evacuation order, parish officials said.

“The area has been investigated and through the preponderance of evidence, the area has been deemed no longer at risk due to the sinkhole and gas associated with its creation,” Assumption Parish Office of Homeland Security and Emergency Preparedness said in a statement issued Wednesday morning.

The sinkhole opened up in the swamp south of La. 70 in early August 2012 after months of unexplained rumblings and bubbling gas in area bayous.

Though what caused the sinkhole is the focus of intense litigation in state and federal court, scientists working for the state contend the it was caused by the structural failure of an underground salt dome cavern operated by Texas Brine Co. That failure opened up a hole in the large, hollow cavern and allowed millions of tons of rock and mud to flow inside the cavern, shifting the strata surrounding the cavern hundreds to thousands of feet underground.

While all that geological scrambling caused the sinkhole to grow eventually to 31 acres, natural pockets of methane gas also cracked open, state scientists say. The methane filtered up to bayous and shallow layers of earth directly under the Bayou Corne community, posing an invisible, explosive risk to homeowners.

Though Texas Brine contends in a court case tangled with insurers and others that the salt dome cavern failure was sparked by oil drilling years earlier, the company has taken responsibility for the incident and has been burning off the gas for several years.

As that process has continued, Texas Brine has had to make the case to the parish and state regulators that the risk from the Bayou Corne sinkhole and its associated gas has been eliminated. Parish officials gradually have been notching back the evacuation status of some parts of the area around the sinkhole, though not the primary area where most residents lived at the time the sinkhole appeared, and a few still remain.

John Boudreaux, director of the parish Office of Homeland Security, said Wednesday one person still lives in the area where the evacuation order was lifted and another owns an unoccupied home and business in the area.

Though the sinkhole prompted buyouts of most families living or owning camps in Bayou Corne, about a dozen remain in the area where the mandatory evacuation order is still in effect.

The mandatory order means staying in Bayou Corne poses a risk, parish officials say. While residents aren’t forced to evacuate, parish officials cannot guarantee their safety if something goes wrong with the sinkhole.

Parish officials said in their statement that other areas still under evacuation orders will remain that way until the gas is depleted and it is shown all risks from the sinkhole and the methane gas are eliminated.

The area where the evacuation order was lifted Wednesday was shifted from mandatory order to a voluntary request in December 2014.