Nuclear Testing in Mississippi

After nine years of negotiations, the United States, the Soviet Union, and other countries signed the Limited Nuclear Test Ban Treaty (LTBT) in 1963, which prohibited “any nuclear weapon test explosion, or any other nuclear explosion” “in the atmosphere; beyond its limits, including outer space; or under water, including waters or high seas.”^[i] This treaty, in part, resulted from the Castle Bravo test in 1954, which caused radioactive fallout to spread more than 6,835 miles.^[ii] The eastern winds carried the fallout to the nearby islands of  Rongelap and Utrik, among others, and affected a small Japanese fishing vessel, the Daigo Fukuryu Maru (Lucky Dragon #5).^[iii] These two incidents  incited international backlash against above-ground nuclear testing.

Nine years later, the United States, the USSR, and other countries signed the LTBT. The LTBT prevented further testing above ground but allowed for underground testing. At the time, however, it was hard to detect underground nuclear tests. Therefore, the Department of Defense (DoD) created Project Vela for the purpose of studying seismic waves caused by underground nuclear explosions.^[iv]

Why Mississippi?

As a part of Project Vela Uniform, the DoD and the Atomic Energy Commission (AEC), the predecessor to the Department of Energy, conducted two tests near the rural town of Hattiesburg, Mississippi. The military first tested a 5 kiloton device under codename Project Dribble in 1964 and a second 350 ton device under codename Project Sterling in 1966. In these tests, the departments wanted to see if another country could conduct secret, underground nuclear tests and what those tests might look like. Both of the American tests were not secret. The U.S. government announced when Project Dribble and Sterling would occur and the intentions of conducting these tests.^[v]

The DoD and AEC chose the Tatum Salt Dome, a 2,700 feet deep salt dome near Hattiesburg. Because salt domes are a thick layer of salt that has penetrated a sedimentary basin,^[vi] the government decided they would be a good place to conduct underground testing. First, the domes can be thousands of feet deep,^[vii] which would help hide a test’s seismic waves. The idea was that “in detonation of a nuclear device suspended within a large cavity, the air would cushion and muffle the shock and lessen the chances of detection.”^[viii] Second, a country could use salt domes to hide underground nuclear tests by running water through the dome to dissolve the salt and creating a deep cave. Otherwise, the country in question would have to dig a hole thousands of feet deep, which would let other countries know its intentions to conduct underground testing.^[ix]

Project Dribble and Project Sterling

The DoD and AEC originally wanted to conduct the first test on September 29, 1964 but delayed it by almost a month due to unfavorable weather conditions.^[x] As a part of the preliminary setup for any nuclear test, scientists had to conduct weather forecast analysis and fallout predictions to minimize unintentional radioactive contamination.^[xi]

On October 22, 1964, 400 residents of Hattiesburg evacuated the area. Adults were compensated $10 and children $5.^[xii] A 5 kiloton bomb, about one-third the size of Little Boy, was detonated in the Tatum Salt Dome at 12pm Eastern time.^[xiii] The explosion caused a shockwave that lifted the ground four inches, and the buildings in the area suffered minor damage.^[xiv] (Pictured above: Horace Burge in his kitchen, which was damaged by the test. Image courtesy of the Moncrief Photograph Collection/Mississippi Department of Archives and History).

Seismic stations on the East Coast registered waves four to six times stronger than initially anticipated. Stations in Finland and Sweden recorded some of the shockwaves, but the other stations in Western Europe did not. Scientists concluded that the effects of shockwaves caused by an underground nuclear explosion were stronger in flat areas than in mountains or mountainous regions.^[xv] This test gave hope to the U.S. government that seismographs could detect underground nuclear explosions. As a result, officials felt the United States and the USSR could sign future treaties that prohibit underground testing, since such testing would be verifiable.^[xvi]

Two years later on December 3rd, the DoD and AEC conducted the second test, codename Project Sterling, and used a 350 ton device, which was 7% the size of Project Dribble’s device. The departments wanted to test the theory of “decoupling,” which was first introduced by Dr. Albert Latter from the RAND Corporation in 1958. The idea was that the dampening air barrier in a large cave could cut off the shock waves from a nuclear explosion from the surrounding earth. Thus, this “muffling” would make detection harder. The December 3rd test proved this theory.^[xvii]

The DoD conducted two more tests to determine the feasibility of detecting underground explosions of conventional weapons as a part of Project Miracle Play at Tatum Salt Dome in 1969 and 1970. ^[xviii]

Aftermath

At the time, the U.S. government believed that the risk of radiation contamination and radiation sickness were low since the tests were conducted deep underground. The radioactive nuclides and fission products were supposed to be trapped and safely decay underneath the earth’s surface.

However, follow-up drilling operations that allowed scientists to collect data and to dispose the devices created hazardous, radioactive wastes. ^[xix] According to some of the workers from these projects, the cleanup and disposal procedures were “lax.”^[xx] Nearly thirty years since the first test, the Department of Energy (DoE) could still detect radiation in the ground surface and shallow groundwater aquifers due to insufficient cleanup, although they contested that the levels of radiation posed no threats to residents’ health.^[xxi]

Beginning in the 1990s, Hattiesburg residents and the workers from Projects Dribble and Sterling began to fear that the radiation from these projects caused cancer-related deaths.^[xxii] In 2015, the federal government paid a total of $16.8 million to former DoE workers and contractors who worked on these projects and to “workers who lived in Mississippi but didn’t necessarily work” on these projects.^[xxiii]