A slurry-filled sinkhole in the Bayou Corne area of Louisiana’s Assumption Parish that first developed earlier this month now reaches 476 feet (NE to SW) by 640 feet (NW to SE), stretching 300 feet at its deepest as of August 15.

Photo courtesy of the Louisiana Department of Natural Resources
An aerial view of the slurry-filled Bayou Corne sinkhole in Assumption Parish, Louisiana, from August 3.

While the sinkhole continues to expand, its exact cause remains unknown, a representative from the Department of Environmental Quality tells ENR. However, speculation has pointed to a nearby brine mining cavern that was capped and abandoned by Texas Brine Co. in 2011 after nearly two decades of operation.

Sonny Cranch, a spokesman with Texas Brine Co. told the New Orleans Times-Picayune that the sinkhole is along one edge of the salt dome, not on top of it. Cranch further added that the top of the salt dome is 700 feet underground, while the cavern is additional 2,800 feet beyond that.

Texas Brine is drilling an observation well near the sinkhole to help root out its cause. The company was ordered to complete a permit to drill this new well as part of an Emergency Declaration on August 3 in order to determine the structural status of the brine cavern and its contents, according to the Louisiana Department of Natural Resources. Texas Brine would have faced $5,000 a day in fines each day until the permit was complete under the declaration.

Numerous reports peg the timeline for the well to reach the cavern at around 40 days. The DNR is monitoring the activity to help ensure regulatory compliance as drilling continues.

Another concern is related to large deposits of butane located in another cavern below the sinkhole. The gas is more than half a mile underground and located within the stable salt dome, the Louisiana DEQ noted. However, both the DEQ and DNR reviewed cavern owner Crosstex Energy’s calculations and agreed that it poses little-to-no threat to the growing sinkhole.

Assumption Parish reported today that a boom was placed along the perimeter of the sinkhole and containment is now in place. Texas Brine also noted the well has reached 600 feet, still 100 feet from the top of the salt dome. The company added that characteristics of the sinkhole remain unchanged, but that surface monitoring equipment is now being installed.

The sinkhole first formed around August 2 after numerous reports of “unexplained bubbling and tremors in the area” during several weeks before, according to the Governor’s Emergency Preparedness Office.

Assumption Parish already ordered a mandatory evacuation of the area, as the nearest residence is about half a mile from the sinkhole. And despite several reports of the contrary, a representative with the DEQ told ENR that all air quality and radiation samples from the sinkhole have come back at levels below health concerns.