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Bayou Corne sinkhole

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From Wikipedia, the free encyclopedia
Bayou Corne sinkhole
Pic from the canoe on Bayou Corne.jpg

Image of Bayou Corne taken from canoe
Location Assumption Parish, Louisiana
Coordinates 30°0′38.24″N 91°8′35.44″WCoordinates: 30°0′38.24″N 91°8′35.44″W
First flooded August 3, 2012
Surface area 25 acres (10 ha)
Max. depth at least 750 ft (230 m)

The Bayou Corne sinkhole was created from a collapsed underground salt dome cavern operated by Texas Brine Company and owned by Occidental Petroleum. The sinkhole, located in northern Assumption Parish, Louisiana, was discovered on August 3, 2012, and 350 nearby residents were advised to evacuate.[1] Scientists have stated that the evacuation order could last for years.[2] The sinkhole continues to expand as of June 3, 2014.[3]

 

 

Background

Bayous such as Bayou Corne were largely settled by the Acadians in the late 1700s, who were attracted to the locations for its economic potential as an alligator and crayfish nesting site.[4] Beneath much of the state of Louisiana, including these bayous, are salt domes, gigantic deposits left during the formation of the North American continent. These domes vary wildly in scale and depth, some as much as 35,000 feet below the surface and as large as Mount Everest.[5] With such depths and dimensions, these domes are naturally under thousands of pounds per square inch of pressure.[6]

The economic value of salt domes has been exploited for centuries.[7] Salt mining has been going on in Louisiana since the Antebellum period, and in the 20th century, the government began using these underground salt caverns as storage reservoirs for liquefied natural gas.[8] Where there is a juncture of mining, petroleum engineering, and an already-fragile geologic situation, care must be taken to maintain stability, so as to prevent a disaster as happened at Lake Peigneur.[9]

Louisiana with Assumption Parish highlighted.

Bayou Corne is located in Assumption Parish, the highlighted region of southern Louisiana

The Napoleonville Dome lies beneath Assumption Parish, and was characterized by 53 distinct caverns, six of which were operated by Texas Brine.[10] One of these, Oxy3, owned by Occidental Petroleum, was more than a mile below the surface, making an accurate picture of the mine difficult to come by. Oxy3 was less than 100 feet from the nearest oil and gas storage-sheath, a distance that, while unsafe, was not illegal.[11] In 2010, Texas Brine applied for a permit to expand Oxy3. Its subsequent pressure tests were unsatisfactory, yet the company felt that the cavern would be able to withstand the pressure regardless.[12]

The incident

In June 2012, residents of Bayou Corne began to notice unusual phenomena; the ground was prone to shaking and bubbles began to arise from the water.[12] The US Geological Survey noted an increase in seismic activity,[13] but could not point to an exact source or cause. The local government sent in experts, who suspected a natural gas pipeline leak, but that assumption proved false.[12] As the symptoms worsened towards the end of July, Texas Brine officially denied the likelihood of a sinkhole. Oxy3 had begun to cave-in.[12]

On August 3, as residents reported the smell of sweet crude oil wafting through the town, Louisiana Governor Bobby Jindal issued an evacuation order.[14] Texas Brine drilled a relief well to investigate, only to discover that the outer wall of the salt dome had, indeed, collapsed. Sediment was pouring into the cavern, allowing oil and gases to escape to the surface—hence the bubbles.[15]

Expansion

When first the sinkhole appeared, it spanned a hectare.[16] As of late February 2014, the sinkhole is 26-acres and growing.[3] Texas Brine is still responsible for managing the sinkhole and has burned off 25 million cubic feet of gas in an attempt to deplete the escaping reserves.[17] Areas in the vicinity of Bayou Corne have demonstrated a similar, bubbling-up phenomenon, though as of yet no definite connection has been made between these and the original sinkhole.[18] Scientists have no conclusive answer to when the evacuation orders—largely dependent on the escaping methane gas—will be removed, yet 3D seismic surveys completed at the beginning of January 2014 show that the sinkhole’s expansion is slowing as it begins to stabilize.[19] Aside from the methane escaping via bubbles to the surface, the sinkhole has a tendency to “burp” up debris.[20] This is how its expansion is patterned. Seismic activity will occur, causing it to eject some debris—both solid matter and oil—which makes room for more to slough into the hole, including dirt and trees.[12]

Impact

The residents of Bayou Corne, who as of March 2014 have been evacuated for 19 months, have involved themselves in a protracted legal battle with Texas Brine.[21] From the start of the evacuation, each resident received weekly checks from Texas Brine for $875 per week.[22] Some residents receive these checks without having even left the town, in defiance of the evacuation order.[12] One such resident, Mike Schaff, said of Texas Brine’s financial settlement option “They think we’re just a bunch of ignorant coonasses.” [12]Nine months after the evacuation, Governor Jindal threatened to sue Texas Brine unless they offered a buyout option to residents.[23] Accordingly, Texas Brine offered to deal with the 350 affected residents. As of March 2014, 65 people had accepted some form of buyout.[24] Others have opted to join a class-action lawsuit against Texas Brine which is set to take trial in 2014.[25] The ecological effects of these developments on local flora and fauna are yet unstudied, but the sinkhole continues to destroy nearby cypress trees, swallowing them during expansion.[26] The Atlantic’s Tim Murphy has summarized the incident thusly: “Bayou Corne is the biggest ongoing industrial disaster in the United States you haven’t heard of.” [12]