The Louisiana Office of Conservation on Thursday night placed the blame for a 4.2-acre sinkhole, gas trapped in an underground aquifer and other events in northern Assumption Parish on the owner of a failed salt cavern inside the Napoleonville Dome.
Commissioner James Welsh ordered Texas Brine Co. of Houston to assess and abate threats to public safety and the environment caused by the failure of the cavern on the dome’s west side, including gas in the aquifer.
The sinkhole emerged in wooded swamps Aug. 3 between Grand Bayou and Bayou Corne south of La. 70 South. The slurry hole sparked a mandatory evacuation of 150 homes in the area that remains in place.
Welsh said in his Thursday evening statement that the order is based on an analysis by the office and its contracted agent, Shaw Environmental and Infrastructure. The analysis relied, in part, on molecular analysis of gas and crude oil found in the Texas Brine cavern, on the surface of the sinkhole and in area waterways.
Welsh said the “preponderance of the scientific evidence” indicates the failure of a cavern sidewall provided a path into the aquifer and to the surface for oil and gas normally confined in natural formations thousands of feet underground along the side of the dome.
“We have been driven by scientific data in all of our efforts to determine the cause of the natural gas found in the aquifer, the formation of the sinkhole and the presence of crude oil found on the surface of the sinkhole,” Welsh said.
Officials with Shaw Environmental said Tuesday that new scientific data suggests the gas, sinkhole and a failed Texas Brine cavern are related. Shaw Environmental officials also said they were investigating whether crude could get into the aquifer, where gas has already been found.
They noted, for instance, that crude oil samples found in the sinkhole and also in the cavern are virtually identical while the gas samples from the cavern and waterways have “a lot of similarities.”
DNR hired Shaw Environmental to manage removal of gas in the aquifer and determine the root cause of the events around Bayou Corne area. A contract drilling company managed by Shaw and DNR recently finished three vent wells to remove the gas.
A Texas Brine spokesman was not immediately available for comment Thursday night but said Wednesday that while the events might be related, it is still not clear how they are all connected.
The Office of Conservation news release followed several events made public Thursday.
Butane burned off early Thursday morning at Crosstex Energy LP’s cavern facility east of the sinkhole, shutting La. 70 South for about 10 minutes, parish officials said.
Crosstex of Dallas has two caverns inside the Napoleonville Dome just east of the sinkhole.
Officials with the parish and the company, Crosstex Energy LP, said Thursday that the flare was not related to the sinkhole but part of normal operations by equipment designed to burn off the gas.
“It did what it was supposed to do,” said John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness.
However, the company planned by early Thursday evening to resume flaring through the night to remove butane from lines connected to the caverns and do repairs, Boudreaux said. La. 70 will remain open.
Also, Friday plans to start burning gas believed trapped in the aquifer area have been delayed, Boudreaux said.
He said not enough pressure was found in the two vent wells located north of La. 70 South and east of the Bayou Corne community. The third well west of Bayou Corne did not find gas.
Reported to parish officials about 6 a.m., the Thursday morning flare reached a reported 40 feet for about 10 minutes and gradually lowered before going out, Boudreaux said.
Jill McMillan, spokeswoman for Crosstex, said the flaring was an emergency response mechanism related to Crosstex’s Cavern No. 2, which is closer to the sinkhole of the company’s two caverns.
She said company officials are working on why flaring happened.
After the sinkhole’s emergence, Crosstex agreed to move butane from Cavern No. 2 to Cavern No. 1, as a precaution, so the gas is farther from the sinkhole. That process remains under way, she said.
“It’s going as expected,” McMillan said.
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