Lake Peigneur

Lake Peigneur<ref>Template:IPAc-en Template:Respell; Template:IPA</ref> is a brackish lake in the U.S. state of Louisiana, Template:Convert north of Delcambre and Template:Convert west of New Iberia, near the northernmost tip of Vermilion Bay. With a maximum depth of Template:Convert, it is the deepest lake in Louisiana. Its name comes from the French word "peigneur", meaning "one who combs."

Previously, it had been a Template:Convert freshwater lake, popular for recreation, until human activity caused an unusual disaster on November 20, 1980, that changed its structure and the surrounding land.<ref name="epa">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="v">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Drilling disaster

File:Salt dome trap.svg

Geology of a generic salt dome trap. At Lake Peigneur, the upward thrust of a salt dome, which became the Diamond Crystal salt mine, formed Jefferson Island.

In petroleum geology, the formation of a salt dome often pushes terrain upward from the surrounding land, while also creating a subterranean salt dome trap, holding petroleum deposits. On Thursday, November 20, 1980, the drill assembly of a Texaco contracted oil rig, just offshore of the salt dome-caused Jefferson Island (itself in the east southeast section of Lake Peigneur), pierced an inactive third level of the Diamond Crystal Salt Company salt mine. The hole produced a vortex that drained the lake into the mine, filling the enormous caverns that had been left by the removal of salt.

The mine, in operation since 1919, was made up of several levels up to Template:Convert below the surface. Each tunnel was about Template:Convert. Pillars of salt had been left in place to support the ceiling at each level. The pillars were dissolved by the encroaching fresh water and caused the mine tunnels to collapse.<ref name="v"/>

File:Lake Peigneur Waterfall.png

The backwards flow of the normally outflowing Delcambre Canal temporarily created the biggest waterfall in Louisiana

The resultant sinkhole swallowed the drilling platform, eleven barges holding supplies for the drilling operation, a tugboat, many trees, and Template:Convert of the surrounding terrain, including much of Jefferson Island. So much water drained into the caverns that the flow of the Delcambre Canal that usually empties the lake into Vermilion Bay was reversed, causing salt water from the Gulf of Mexico to flow into what was now a dry lakebed. This backflow created for a few days the tallest waterfall ever in the state of Louisiana, at Template:Convert, as the lake refilled with salty water from the Delcambre Canal and Vermilion Bay.<ref name=ModernMarvels>Template:Cite episodeTemplate:Cbignore</ref> Air displaced by water flowing into the mine caverns erupted through the mineshafts as compressed air and then later as Template:Convert geysers.<ref name=ModernMarvels />

Although there were no human deaths, three dogs were reported killed. All 55 employees in the mine at the time of the accident escaped, with six employees later given awards by Diamond Crystal for heroism. Their successful evacuation was thanks to the mine's electrician who noticed a torrent of water and sounded the alarm, as well as the employees' discipline and training making their escape via the only elevator in an orderly fashion.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite report</ref> The crew of seven on the drilling rig fled the platform shortly before it collapsed into the new depths of the lake. A fisherman who was on the lake at the time piloted his small boat to shore and escaped. Days after the disaster, once the water pressure equalized, nine of the eleven sunken barges popped out of the whirlpool and refloated on the lake's surface.<ref name=ModernMarvels />

Cause

On the date of the disaster, the oil rig was conducting exploratory drilling in the lake alongside the edge of the salt dome.<ref>Template:Cite news</ref>

The rig's Template:Convert drill assembly had become stuck at Template:Convert two-and-a-half hours before the drilling rig began to tilt.<ref name="MHSAReport">Template:Cite report</ref>

The drill assembly punctured the salt mine beneath the lake, and the water entered the mine. Over the course of several hours, the fresh lake water dissolved the salt and enlarged the hole, causing the lake to drain into the mine.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite book</ref>

The Mine Safety and Health Administration was unable to determine blame because they could not determine whether Texaco was drilling in the wrong place or if the mine's maps were inaccurate.<ref name="v"/>

Evidence that could have confirmed the cause was washed away in the maelstrom. Engineers from Texaco and Diamond Crystal worked together after the fact and pinpointed the likely location of the hole within a mined out portion of the Template:Convert level of the mine.<ref>Template:Cite report</ref>

Aftermath

In 1983, Texaco and the drilling contractor Wilson Brothers paid Template:US$Template:Nbspmillion (equivalent to $Template:Inflation million in Template:Inflation/year) to Diamond Crystal, while Texaco, Wilson Brothers, and Diamond Crystal also paid a total of $12.8Template:Nbspmillion (equivalent to $Template:Inflation million in Template:Inflation/year) to the Live Oak Gardens botanical garden and plant nursery, in out-of-court settlements to compensate for the damage caused.<ref>Template:Cite news</ref> The Mine Safety and Health Administration released a report on the disaster in August 1981 which exhaustively documented the event but stopped short of identifying an official reason for the disaster.<ref name=MHSAReport /> The mine was finally closed in December 1986.

Since 1994, AGL Resources has used Lake Peigneur's underlying salt dome as a storage and hub facility for pressurized natural gas.<ref name="ag">{{#invoke:citation/CS1|citation |CitationClass=web }} AGL resources, 2007, (map of lake showing current and planned gas caverns)</ref><ref name="a">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> There was concern from local residents in 2009 over the safety of storing the gas under the lake and nearby drilling operations.<ref>Template:Cite news</ref>

See also

• Bayou Corne sinkhole
• Döda fallet
• Lake Beloye (Nizhny Novgorod Oblast)
• List of sinkholes of the United States
• Rylands v Fletcher

External links

• Lake Peigneur: The biggest sinkhole ever created (archived)
• Template:YouTube
• Endangered Earth - Sinkholes Assorted
• Template:Cite book Contains a description of the event, with a focus on the geology of the region.
• Mine-mouth geyser problem, Chemical Engineering Education, an in-depth discussion of how the inrush of water could have created a powerful geyser
• Template:Cite magazine
• The podcast Eclipsed has a two-part episode about Lake Peigneur. Part 1 Part 2