. 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. A salt dome trap below Lake Peigneur caused upward thrust of the overlying soil, resulting in the formation of Jefferson Island, located near the southeast side of the lake. On November 20, 1980, an
oil rig contracted by
Texaco was drilling on Jefferson Island, when the drilling assembly pierced an inactive third level of the
Diamond Crystal Salt Company salt mine. The drill 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, consisted of several levels up to below the surface. Each tunnel was about .
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. Air displaced by water flowing into the mine caverns erupted through the mineshafts as compressed air and then later as
geysers. 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. The rig's diameter drill assembly had become stuck at two-and-a-half hours before the drilling rig began to tilt. 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. 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 level of the mine. 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. 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. There was concern from local residents in 2009 over the safety of storing the gas under the lake and nearby drilling operations. ==See also==