Atomic Testing in Mississippi: Project Dribble and the Quest for Nuclear Weapons Treaty Verification in the Cold War Era

1. Humble Origins

11 1. Humble Origins On October 22, 1964, the earth shook near the small town of Baxterville, a hamlet of about 150 people in rural Lamar County in south-central Mississippi. The ground motion, though stronger than expected, was not a surprise. It had been caused by the long-planned and well-publicized detonation of a nuclear-test device. There was no brilliant flash, nor was there a mushroom cloud rising dramatically over the rolling countryside and thick pine groves. The only thing out of the ordinary was the ground motion, which radiated out from the deep underground detonation point and caused dust to rise over the test site, throwing one man’s refrigerator contents onto his kitchen floor, cracking numerous foundations, and rattling windows as far away as Hattiesburg, some thirty miles distant. The atomic detonation in the verdant pine belt of Mississippi was no random act designed to subdue the violent passions of a state embroiled in the civil rights movement, nor was it the result of the seemingly ubiquitous southern male’s tendency to blow something up just for the hell of it. The nuclear test, codenamed Salmon, was precisely planned and metered, conducted under unique surroundings and circumstances. The Salmon device yielded 5.3 kilotons of explosive force, roughly one-third that released by the bomb dropped on Hiroshima near the end of World War II. The test, conducted at a depth of about twenty-seven hundred feet below the surrounding countryside, was fully contained and monitored . Essentially, Salmon was an unusually large outdoor laboratory experiment. Salmon, and a subsequent atomic detonation codenamed Sterling, were the only two nuclear tests to be conducted in the continental United States east of the Mississippi River. Their purpose was to ascertain whether the United States and its allies could enter into subsequent 12 • Atomic Testing in Mississippi treaties placing controls on nuclear tests following the 1963 Limited Test Ban Treaty, which forbade atmospheric, undersea, and space tests with nuclear devices. With the growing desire to limit the size of nuclear weapons, it became clear that restricting test yields would be an important step—but underground testing presented unique limitations to verifying these yields. Seismology, a field rapidly gaining importance in disarmament efforts, would play a major role in test monitoring, yet its incorporation into a system of monitoring and observation raised questions . How did one distinguish an atomic test from an earthquake? What about the explosive eruption of volcanoes or other natural phenomena? How small a test could be detected? Even more to the point, could tests be intentionally hidden in an effort to evade treaty stipulations? These questions were the focus of the Vela Uniform program, a series of seven nuclear detonations spread across several test series. They were conducted in various locations: the Mississippi test site, known as Dribble; the Fallon, Nevada, test site; and Amchitka, Alaska, where the largest of the seven, an eighty-kiloton underground shot, was fired. Vela was also intended to answer the question of the effects of different soil and rock types on seismic signals. The varied locations allowed tests to be conducted in several different environments. Geologically, Mississippi had a unique role in this program. The choice of test site in that state was not accidental. In fact, the location was many millions of years in the making. It was a remarkable geological structure that allowed not only for a fully enclosed and sealed shot location , but also presented an opportunity for assessing theories relating to the concealment of nuclear tests. This geological structure is a mammoth column of solid rock salt, seven to eight miles in height and well over a mile in circumference at its top, poised fifteen hundred feet below the earth’s surface. Because of this enormous salt pillar, Mississippi was chosen as a site for underground nuclear tests. The pillar, or salt dome, that was host to the atomic tests was large but not uniquely so. These enormous salt domes along and under the Gulf Coast, and extending inland for several hundred miles, were extruded upward from a thick subterranean salt formation known as the Louann Salt. Formed during the Jurassic Period, it was up to ten thousand feet thick in some places. The Louann Salt, one of the basal formations within the northern Gulf Humble Origins • 13 Basin, ran (or “trended”) in a large arc, starting in eastern Texas, with its northwestern maximum...