After two years of waiting for the canal cratering experimental program to begin, the Anderson Commission received the wonderful news in January 1968 that President Johnson had finally permitted the 2.3- kiloton Cabriolet shot to proceed at the Nevada Test Site. Because radioactive fallout might escape into the atmosphere and contaminate the local milk supply or cross the border to cause an international incident, the timing had to be precise—after the State of the Union address, but before the Nevada grazing season. In a stroke of good
luck for the advocates of Plowshare, the winds on the day of the test blew away from Mexico, and a snowstorm prevented debris from reaching Canada in de-tectable amounts.8
Although the Cabriolet test created a crater of only 360 feet wide and 120 feet deep, a follow- up experiment in March generated exciting results for propo-nents of the nuclear waterway. Project Buggy, a simultaneous detonation of five nuclear explosives (spaced 150 feet apart at a depth of 150 feet), produced what Representative Chet Holifield of the Joint Committee on Atomic Energy called a “miniature- size canal in the Nevada desert” (300 feet wide by 80 feet deep by 900 feet long). His assessment of the situation as “very hopeful, very promising”
renewed calls to amend the Limited Nuclear Test Ban Treaty “to reconcile it with common sense.”9 More favorable publicity appeared in news reports that fallout from both shots occurred only a few hundred yards from the craters, and that no radiation could be detected three days afterward, unlike earlier tests.
An unnamed AEC source attributed the smaller amount of radiation to the
“really tiny fission device” used to trigger the thermonuclear explosive. For the
“friends of Plowshare,” the 97 percent fallout- free device—dubbed the Ivory Soap Bomb—offered great reassurance: “We’ve been talking about doing it for years, but now we could really get down and dig a second Panama Canal with atomic explosives.”10 The long political delays had served their purpose of giving the science and technology of PNEs time to catch up with expectations.
Or so it seemed. Such rhetoric discounted the continuing opposition by Latin Americans to the use of nuclear explosives on their lands. Panamanian ambassa-dor Jorge T. Velasquez, who called instead for expanding the existing waterway, announced, “We know that experiments have not shown there is control over the dangers of atmospheric and underground radioactivity, nor the practical possibility of this technique in the construction of a sea- level canal.”11 Not only were the AEC’s assurances about clean PNEs wearing thin, so was the techno- economic rationale for building a second waterway. The U.S. Navy’s largest ships needed to be able to cross the isthmus as quickly as possible, but that was not the case for an emerging class of commercial vessels. In 1966, massive new tankers, some capable of carrying 2.2 million barrels of crude oil from the Middle East to Europe, had already begun bypassing the Suez Canal to save on tolls; voyaging around the Cape of Good Hope took longer, but the size of their cargoes made up for the loss of time.12 That same year, the burgeoning Japanese shipbuilding industry completed a 215,000- ton tanker capable of drawing fifty- six feet, which exceeded the Panama Canal’s maximum channel depth of forty feet, and ana-lysts predicted that tankers of 500,000 and even 1 million tons would soon be
feasible.13 The global shipping industry was changing in ways that demonstrated the need for the Panama Canal to adapt or else become a mere monument to a bygone era—but that also undercut the long- standing arguments for a sea- level channel.
As the Anderson Commission’s economic advisors tried to predict future shipping trends, the Route 17 geological consultants delivered unwelcome news.
Drilling samples verified that about half of the route, a twenty- mile stretch in the Chucunaque valley, crossed land whose bedrock consisted of clay shales (rather than basalt, the much harder material underlying most of the Continental Di-vide, the assumption of which had underpinned the 1964 selection of routes).
Nuclear explosives would likely not form stable slopes in such an unstable me-dium, meaning that achieving the shallow slopes needed to prevent the crater from collapsing over time would require conventional excavation techniques.14
Clay shale happened to be the same type of sedimentary rock that had caused destructive landslides during the construction of the original Panama Canal, and thus the problem was not a surprise to engineers familiar with the physics of the isthmus. As one of the leaders of the Army Corps of Engineers’ Nuclear Cratering Group explained at the March 1968 commission meeting, “The orig-inal thinking was that if we ran into a bad actor like clay shale along the routes, we could approach it from a conventional excavation standpoint.”15 However, the prospect of bulldozing such a large area undermined the financial advantage PNEs had offered in the first place.
While engineers consulted with leading soil mechanics specialists to deter-mine whether the geological discovery really did rule out PNEs, the Livermore physicists conducted chemical explosive experiments to try to model the effects of burying thermonuclear devices in wet clay shale. John Kelly of the AEC’s Division of Peaceful Nuclear Explosives later even discussed the matter with his Soviet counterparts, who insisted it was not a problem.16 A few days after the March 1968 CSC meeting at which the issue was first unveiled, commission member Milton Eisenhower vented his frustration in a private letter to Execu-tive Secretary Sheffey that the group’s most vociferous member, Raymond Hill, already appeared ready to abandon Route 17: “When we began our deliberations, we were enthusiastic about atomic construction. Now we are on the verge of deciding that, largely because of possible conditions of soil instability, atomic excavation is not practical . . . I don’t want to be drawn inexorably to route 10 and a sea- level canal by traditional construction methods . . . merely because his expert opinion points in that direction.”17 Route 10 referred to a new potential seaway site about ten miles west of the existing canal, to which the commission
had begun devoting attention in the fall of 1967 as an alternative to the nonnu-clear option of converting the existing canal.18
If nuclear excavation of Route 17 was no longer possible, then that had major implications for future U.S.- Panama treaty negotiations. The 1967 draft treaties had established the U.S. commitment to building the sea- level canal in Panama and had granted Panama the right to veto nuclear methods. However, as outsider analysts explained, if the existing waterway continued its descent into obsoles-cence, and if PNEs constituted the only financially feasible means of construct-ing a new passage, then Panama would pretty much have to agree to a U.S.- built nuclear canal.19 To preserve the U.S. upper hand in future negotiations, how much should the commission reveal about the clay shale problem?
The deadline for the fourth annual report, covering the period from July 1, 1967 to June 30, 1968, was approaching, and it would be the last one prepared for President Johnson, who had decided not to run for reelection. The previous three reports had already erred on the side of vagueness, and thus to mollify the commission’s critics while preserving as much U.S. leverage as possible, Sheffey recommended a selective, semitransparent approach: it should “start surfacing some of the problems we foresee and not catch the Congress by surprise when the final report comes in. The problem is that we don’t want to disclose things that will handicap treaty negotiations in the future by our action.”20 But recon-ciling such opposing goals proved impossible. In conveying the ensuing report to Congress, President Johnson omitted the clay shales matter from his public statement, and sent mixed messages by emphasizing both the benefits of the conventional Route 10 and the favorable results of the two 1968 Nevada Test Site shots.21 He also overlooked another unwelcome issue consuming more and more of the commission’s attention: regardless of the method used to cut the channel, what would happen once the flora and fauna of the two oceans reunited after a few million years of evolutionary separation and speciation?