Steve Elwart, P.E., Ph.D., is the executive research analyst with the Koinonia Institute and a subject matter expert for the Department of Homeland Security. He can be contacted at firstname.lastname@example.org.More ↓Less ↑
Southern Louisiana is in danger of experiencing an environmental calamity rivaling the BP Deepwater Horizon disaster, thanks to a massive, expanding sinkhole that is gobbling up the forest and lighting up YouTube with videos of this startling phenomenon.
In southern Louisiana, about 40 miles south of Baton Rouge in Assumption Parish, is the town of Bayou Corne. The town is in the middle of the oil rich area of the coastal United States and is near the nation’s Strategic Oil Reserve.
On May 31 of this year, parish residents began to notice bubbles percolating up from both Bayou Corne and Grand Bayou. This is not unusual for the area known for its “swamp gas,” the product of decaying organic matter. The amount of the gas emanating from the water, however, was unusual. Dennis Landry, who owns guest cabins about half a mile from the hole, said that the number gas bubbles were growing in size, and in some areas they made the bayou look like “a boiling crawfish pot.”
On June 22 state officials began monitoring the gas coming up from the bayou for hydrogen sulfide, carbon dioxide and the explosive levels of natural gasses.
Residents within the community then experienced and reported tremors and the parish enlisted the aid of the United States Geological Service in locating the origin and cause of the seismic activity. Immediately after the USGS began monitoring the area, they detected seismic activity, but no probable cause was able to be detected at that time.
The early in the morning of August 3, reports started to come in of a sinkhole having formed overnight in the swamp in the area. The hole was discovered after a strong diesel smell was experienced in the area.
John Boudreaux, director of the Office of Homeland Security in Assumption Parish stated that initial measurements of the sinkhole found it to be 324 feet in diameter and up to 422 feet at its deepest part. The sinkhole was swallowing trees up to 100 feet tall in its wake. The most current reported estimates suggest it has since grown to over 6 acres in size.
Scientists believe a Texas Brine salt cavern inside the Napoleonville Dome near Bayou Corne failed and initiated a chain of events that created the sinkhole and released methane and crude oil.
Area residents were evacuated from the area, fearing a toxic gas release and possible explosion.
An aerial video of the sinkhole can be seen in the video below, one of several available on the video sharing site YouTube:
Louisiana’s Department of Natural Resources ordered the Texas Brine Company, the company that mines the salt cavern, to drill a well into the cavern to see whether it caused the dark gray slurry-filled hole nearby.
The main concern was that the sinkhole was close to an underground storage facility containing 63 million gallons of liquid butane, a highly volatile liquid that turns into a flammable gas when released into the atmosphere. If the butane was allowed to escape, there could be catastrophic consequences.
Aerial reconnaissance of the area showed that an oil slick had developed on top of the water along with a layer of sludge. Fallen trees and other debris were also floating on the surface. Methane gas is percolating to the surface as well. Louisiana Department of Natural Resources officials, private industry scientists and contractors have been setting up vent wells to burn off the gas in an effort to get evacuees back in their homes and camps. People who live in the area must now decide whether they want gas monitors inside their homes to help reduce the risk of exposure to natural gas at the site.
The salt cavern is part of the Napoleonville salt dome formation that lies under the area. Salt domes are large underground formations of salt in the ground that are used for the commercial mining of petroleum, salt and sulfur, according to the U.S. Army Corps of Engineers.
Texas Brine mines three salt domes to produce brine, a salt-filled water solution used to make raw materials used in products ranging from paper to pharmaceuticals. The Texas Brine cavern has been mined by the company for over 30 years. Salt caverns are what are left from the brine being removed from the salt dome.
DNR scientists said they think an underground Texas Brine Co. salt cavern failed, allowing earth to partially fill the 2,250-foot-long cavern, causing the sinkhole to form about 200 feet northwest of the top of the cavern.
In early September 2010, Texas Brine began renovating the cavern well, increasing the height of the cavern roof, to determine if the salt closer to the surface could be mined. It is this work the DNR suspect caused the sinkhole.
A breech in the salt cavern is the source of the sinkhole. A hole in the cavern ceiling allowed water and soil to migrate into the cavern, depositing soil into the cavern and undermining ground above it. There is a fear that a further collapse could enlarge the sinkhole and endanger a wider area.
There are other fears that have arisen from the sinkhole, namely that natural gas is migrating from other salt domes being used as storage and could cause a massive explosion.
According to the Baton Rouge Advocate, local residents and the sheriff of Ascension Parish say the Louisiana DNR “knew for months” that the Texas Brine well had integrity problems but didn’t tell local authorities.
Landowners near the sinkhole have filed a lawsuit against the DNR and Texas Brine, claiming that the drinking water has now been contaminated by a problem both the department and company allegedly knew about.
“They’re trying to make this something to deal with one well. It’s not just one well, it’s the whole system of Grand Bayou. They just ignored it,” said John Carmouche, a partner with Talbot, Carmouche and Marcello in Baton Rouge who represents the landowners.
Parish officials are concerned that the sinkhole has not stopped growing. Underground tests have shown that the volume of the brine-filled sinkhole is much smaller than the 2.7 million cubic yards of displaced material that was found in the salt cavern, prompting concerns that there are other underground voids in the area that could lead to an ever growing sinkhole.
Texas Brine removed 1,320 barrels of oil from its failed cavern between Tuesday afternoon and Thursday evening and replaced the oil with an equal amount of brine to keep the cavern formation stable.
The company plans to finish a mandated vent well on its property to remove natural gas from the underlying aquifer early this week, while scientists working for DNR are trying to get gas to flow from two finished vent wells north of La.-70.
DNR scientists have presented a worst-case scenario for the sinkhole. Under that model, which was based on a complete collapse of the Texas Brine cavern and a displacement of its entire volume, scientists estimated the existing sinkhole would reach 1,400 feet in diameter.
While the situation seems to have stabilized, the worst may not be over. Hydrocarbons and toxic gasses still lurk beneath the surface and still pose a present danger to the members of the community and the area at large.