Assumption Parish, Louisiana sinkhole growing larger, evacuations and Parish state of emergency declared

Two days ago I posted a news excerpt about a large and sudden sinkhole mysteriously appearing in Louisiana--
"A nearly 400-foot deep sinkhole in Louisiana has swallowed all of the trees in its area and enacted a mandatory evacuation order for about 150 residences for fear of potential radiation and explosions. The 400-square-foot gaping hole is in Assumption Parish, La., about 50 miles south of Baton Rouge. The sinkhole sits in the middle of a heavily wooded space where it has consumed all of the soaring cypress trees that had been there. Flyover photos show some of the treetops still visible through the mud."'

"While officials are not certain what caused the massive sinkhole, they believe it may have been caused by a nearby salt cavern owned by the Texas Brine Company. After being used for nearly 30 years, the cavern was plugged in 2011 and officials believe the integrity of the cavern may have somehow been compromised, leading to the sinkhole. '

Now, a serious concern has emerged. Serious. Actually, the officials are saying potentially catastrophic. The sinkhole may be happening because a salt cavern that had been used to store butane and then plugged might have structural integrity problems. First, look at what a salt cavern is:

Salt Caverns

"Underground salt formations offer another option for natural gas storage. These formations are well suited to natural gas storage in that salt caverns, once formed, allow little injected natural gas to escape from the formation unless specifically extracted. The walls of a salt cavern also have the structural strength of steel, which makes it very resilient against reservoir degradation over the life of the storage facility."

"Once a suitable salt dome or salt bed deposit is discovered, and deemed suitable for natural gas storage, it is necessary to develop a 'salt cavern' within the formation. Essentially, this consists of using water to dissolve and extract a certain amount of salt from the deposit, leaving a large empty space in the formation. This is done by drilling a well down into the formation, and cycling large amounts of water through the completed well. This water will dissolve some of the salt in the deposit, and be cycled back up the well, leaving a large empty space that the salt used to occupy. This process is known as 'salt cavern leaching'."

It is all perfectly normal and legitimate. However, it is a disaster if something happens to the cavern, as has potentially happened to one in Assumption Parish in Louisiana--

Fox News reports,
"The situation is made all the worrisome because the sinkhole is believed to be close to a well containing 1.5 million barrels of liquid butane, a highly volatile liquid that turns into a highly flammable vapor upon release. A breach of that well, Assumption Parish Sheriff Mike Waguespack has said, could be catastrophic."

"The sinkhole appeared August 3, more than two months after local residents started noticing bubbles in the water. The bubbles grew in number and frequency, and in some spots they made the bayou look like a boiling crawfish pot, said Dennis Landry, who owns guest cabins about half a mile from the hole."

A Declaration of Emergency for that Parish has been issued. If ignited, "the butane well would release as much explosive energy as 100 Hiroshima bombs, Deborah Dupré's scientist sources told her Sunday."

Just an hour ago, the State approved a permit for a relief well. All this is depressingly familiar. It was just  two years ago, in April 2010, that the Deepwater Horizon well exploded and the relief well for the Macondo blowout happened. In that disaster, oil gushed into the Gulf Of Mexico unabated for three months before it was capped.

In the Sinkhole-butane-salt cavern problem, the natural gas officials are saying it will be at least 40 days until they get a relief well going and some answers surface. Meanwhile, residents are watching the hole grow larger and crumble inexorably toward their homes. Residents who have already been evacuated are told it will be at least a month before they can return...