A 5.3 kiloton nuclear device codenamed "Salmon" explodes inside the Tatum Salt Dome near Baxterville in Lamar County.
In the middle of the Cold War, the United States, Great Britain and the Soviet Union were the first signers of the Partial Nuclear Test Ban Treaty. The Ban called for total elimination of all atmospheric nuclear testing, allowing only underground tests up to specified sizes. At that time, the primary method of detecting and researching nuclear explosions came from tracing post-shot fallout. Detecting underground nuclear detonations was much more difficult. Some feared that the Soviet Union would "cheat" the ban by exploding much larger that prescribed test weapons underground inside caverns or salt domes and "muffle" these tests' seismic waves, making a massive test appear as a much smaller one.
The Atomic Energy Commission sought a suitable salt dome in the United States with which to test the concept of decoupling, where a nuclear explosion occurs inside a medium such as salt deep underground, modifying the explosion's seismic signature. The Commission settled on the Tatum Salt Dome near Baxterville. The AEC chose the Tatum Salt Dome because of its massive size, its deep depth and the suitable nature of its chemical composition.
Project Dribble involved boring a primary shaft 2,760 feet into the salt. In 1964, they lowered a nuclear device one-third the explosive power of the bomb dropped on Hiroshima in 1944 into the salt. When it exploded it created a cavity about 110 feet in diameter. This cavern was used several times as a focus of seismic testing with the 1966 "Sterling" nuclear test, which was much smaller than Salmon, along with some conventional explosions. These tests proved that it was indeed possible to modify the seismic signatures of nuclear weapons when detonated inside caverns and salt domes. Salmon and Sterling are the only two nuclear explosions east of the Mississippi River.
The lessons learned in the experiments at the Tatum Salt Dome proved valuable through the Cold War and can be considered precursors to modern nuclear detection technology.
When the Salmon Site was decommissioned, the shafts and boreholes were plugged and filled in. All radioactive waste in the form of contaminated soil, water, and drilling excesses was disposed of. Some of the waste was poured into the Salmon cavity. The cavity contains the vast majority of the radioactive material generated by the explosions in the form of tritium. That radioactivity is safely stored inside the salt. It has no means of escape. The Mississippi Department of Health regularly tests hundreds of test wells around the Salmon Site to make sure there is no radiation leaking.
The Salmon Site surface now belongs to the State of Mississippi and is maintained by the Mississippi Forestry Commission. The Forestry Commission uses the Salmon Site as a demonstration forest and as a source of income from timber.
The Department of Energy's Office of Legacy Management owns the subsurface rights and the contamination inside the Salmon cavity. DOE conducts regular maintenance and testing alongside the Mississippi Department of Health.