Obsolescing Shibboleths

Even as popular writers extolled the almost-completed Panama Canal as a wonder of the modern world, serious challenges remained to be solved. As one author conceded in 1913, “Of course, a vast amount remains to be done, and capricious nature may devolve extra labor upon us if she persists in trying to close the cut we have so laboriously excavated at Culebra.”3 In fact, landslides at the Culebra Cut continued to cause dangerous obstructions in the decades following the canal’s opening in 1914, necessitating frequent, expensive rounds of dredging (fig. 2.1).4

Another threat posed by capricious nature involved disruptive variations of rainfall entering the Chagres River watershed. Despite the immensity of the canal’s water source, the 163.5-square-mile Gatun Lake, it could not store enough water during droughts for the increasing traffic. Nor could the Gatun Dam control all upstream deluges, forcing occasional canal closures. U.S. officials responded by invoking the clause of the Hay–Bunau-Varilla Treaty that allowed them to expropriate land from Panama for canal maintenance and protection, and built the Madden Dam on the mountainous upper Chagres from 1931 to 1935. The resulting 22-square-mile Alajuela lake provided an additional freshwater supply for operating the locks and generating hydroelectricity. It also flooded out more forests and people and expanded the dominion of Canal Zone officials.5

A third major problem was not as amenable to a quick technological fix: naval and cargo vessels were growing in size, just as sea-level canal proponents had predicted. In 1929, Congress authorized feasibility studies to determine the cost of expanding the existing waterway and of building a second one in Nicaragua, with which the United States had signed a canal treaty in 1914.6 The colossal expenses for both endeavors led officials to concentrate instead on the Madden Dam project, but pressure coalesced in the late 1930s in favor of expanding the existing waterway. Congress allocated $277 million for a third lane of locks, each measuring 1,200 feet long, 140 feet wide, and 45 feet deep. As a PCC publication announced in June 1941, shortly after excavation began on the New Gatun Locks, “The original builders were aware that the Canal’s capacity would eventually require enlargement,” but not so soon.7

Construction stopped in 1942, however, and officials focused instead on preparing for a Pearl Harbor–style attack by stocking extra lock gates and building new defensive infrastructure within and outside the Zone.8 After the war, the atom bomb cast doubt on the viability of lock canals. The attacks against Hiroshima and Nagasaki, and the experimental detonations in the South Pacific, showed the staggering effect of exploding the equivalent of thousands of pounds of TNT: “One has only to recall the movies of the Bikini atomic bomb tests,” wrote one engineer in 1947, “where a column of water that looked to be half a mile across was thrown several thousand feet in the air, to visualize what would happen to a lock.”9

Such sobering thoughts resurrected the “sea-level canal ghost.”10 At the 1946 annual meeting of the American Society of Civil Engineers, one of the Panama Canal’s longest-serving employees invoked the 1906 consulting board’s majority decision about the invulnerability of sea-level waterways. He called for converting the famous bridge of water to a sea-level channel, as did others seeking a “bomb-proof canal.”11

Congress authorized the president of the PCC (who also served as governor of the Canal Zone) to initiate a new modernization study in December 1945. PCC personnel worked closely with the Army Corps of Engineers, the venerable federal agency that had played a key role in building the Panama Canal, to complete the report, titled Isthmian Canal Studies—1947. The investigation included a meta-analysis of historical surveys of thirty possible routes spanning Central America, eight of which now appeared suited to sea-level excavation. The report also drew on new geological mapping and exploratory drilling work, and even featured the construction of a half-mile-long hydraulic model that engineers used to measure the effects of currents and tidal-regulating structures. Finally, the authors consulted with experts in soil mechanics, dynamics, and seismology to determine the effects of nuclear bombing on canal structures.12

In place of the triumphant portrait that had prevailed since the start of the century, the 1947 engineering report painted a grim picture of the Panama Canal. A “determined and resourceful enemy” could shut it down at any moment. Once breached, the Gatun Dam would empty into the Caribbean, rendering the waterway unusable for one to two years and leaving operators at the mercy of the rains for refilling. If hit with a nuclear weapon, another two years at least would be needed for the radioactivity to dissipate. A generation after it had opened for business, the world wonder now inspired fear rather than confidence: “No lock canal can meet fully the future needs of national defense.”13

By contrast, a sea-level channel of sixty feet deep and six hundred feet wide would more than justify the $2.483 billion price tag. Granted, it would require special devices to regulate the tidal currents caused by the differences between the tides in the Pacific and Atlantic. Flood-control dams and spillways would also be needed to control river inflows. Nevertheless, the loss of such auxiliary structures would not close the canal for too long. Even an atomic attack would shut it down for a matter of weeks rather than years.14

Converting the existing canal to sea level would take ten years and the removal of one billion cubic yards of soil and rock using conventional construction equipment. Also, although ten thousand acres downstream of Madden Dam would be inundated, some of the lands submerged beneath Gatun Lake would resurface, thereby permitting their “return to Panamanian jurisdiction.” For all these reasons, the PCC report concluded that conversion constituted “the best means of increasing the capacity and security of the Panama Canal to meet the future needs of interoceanic commerce and national defense.”15

But the PCC’s $2.5 billion solution gained little traction. President Harry Truman submitted the report without comment to Congress, and the ensuing hearings privileged the testimony of atomic warfare specialists that no canal could be rendered bombproof.16 Looking back several years later, one of the most ardent guardians of the Panama Canal Zone, Representative Daniel Flood of Pennsylvania, denounced the report as “heedless of the diplomatic consequences and costs involved” and praised his colleagues for having “exposed the fallacies upon which it was founded.”17

Yet the technological status quo could not persist indefinitely, as the Panama Canal’s strategic and commercial value slipped throughout the 1950s. The development of air power and a two-ocean fleet had undermined the Mahanian rationale for an Atlantic-Pacific link, and the navy had begun building aircraft carriers that exceeded the dimensions of the locks and the narrow Culebra Cut. Jet planes, the interstate highway, and dieselized railroads could now transport goods and people across the continental United States more quickly than ever. And the voracious industrial expansion of California precluded the need to continue exporting its petroleum and other natural resources eastward.18

Had U.S. control of the Panama Canal become “an obsolete shibboleth?” That was how two Stanford political scientists titled a provocative article in a 1959 issue of Foreign Affairs magazine that called for internationalizing the waterway under the United Nations. Not only were military and civilian transportation alternatives undermining U.S. interests in the canal, but so was the increasing “toll in terms of Latin American resentment” exacted by the Canal Zone.19

The Zone’s fans celebrated it as a beautifully landscaped enclave of tropical suburbs, whose U.S. residents enjoyed subsidized housing, health care, and other perks provided by Uncle Sam.20 But for Panamanians, the Zone featured segregated towns, U.S. government–run businesses that undercut local entrepreneurship, American flags and military checkpoints, and other daily reminders of Panama’s subservient status (fig. 2.2). U.S. officials made some concessions via supplemental treaties in 1936 and 1955. The latter Eisenhower-Remón Treaty increased the annuity to Panama to $1.93 million, transferred some zone lands, provided for a high bridge to be built across the canal, and guaranteed equal pay for Panamanian and U.S. employees in the Zone. Congress delayed implementing the changes, however, and the Hay–Bunau-Varilla Treaty provisions granting U.S. control over the Zone remained in place.21

A momentous event in July 1956 drew unexpected attention to the Zone’s quasi-colonial status. The Egyptian seizure and nationalization of the Suez Canal intensified U.S. concerns about maintaining control in Panama, leading the Eisenhower administration to revisit the seaway proposal as a technopolitical lever. As the U.S. ambassador in Panama wrote to a State Department official in August 1956, “I can think of nothing that would have a more sobering effect than a revival of talk in Washington about the possibility of a sea level canal across Nicaragua,” which would force the Panamanians “to accept gracefully the many benefits they are now reaping.”22 While such a strategy might backfire, the official responded, the United States could quietly invoke the 1914 canal treaty with Nicaragua by sending in a surveying team: “If word of this action is picked up in Nicaragua by the Panamanians through their own intelligence channels the desired effect may be obtained.”23

Eisenhower authorized his secretary of state to initiate talks with Nicaragua, “pointing out that already ships were being built too big to go through the Panama Canal and that a sea level canal through Nicaragua would be much more practical.”24 Such views indicated the technological and political appeal of a streamlined seaway, but also ignorance of isthmian geography. Engineers had long since deemed locks necessary for the route through the high-level Lake Nicaragua. While not impossible, a sea-level channel would require the draining of the lake, one of Nicaragua’s most important natural resources.25

A follow-up assessment in November 1957 revealed little enthusiasm among the Joint Chiefs of Staff and the State Department for assuming the enormous cost of either a second canal or converting the existing one.26 Even so, during the late 1950s, the PCC, the House of Representatives Committee on Merchant Marine and Fisheries (which oversaw appropriations for the canal), and other interested parties continued to investigate the question of canal modernization. Despite its decline as a strategic asset, the waterway remained a useful conduit. Equally if not more important, the Canal Zone’s military complex had become a major instrument of hemispheric security by housing telecommunications and other means of monitoring Central America.27

“A storm is building up in Panama,” warned the perceptive authors of the April 1959 Foreign Affairs article.28 On May 1, university students surprised U.S. officials by planting several dozen Panamanian flags in civilian spaces of the Canal Zone. “Operation Sovereignty,” as the students called it, broadcast their demand to end U.S. control over the Zone. White Zonians dismissed the demonstration as a joke, but later in the month, riots broke out, marking the second year in a row of lethal anti-U.S. protests in Panama.29

As gestures of goodwill, the outgoing Eisenhower administration issued an economic aid package and an executive order that the Panamanian flag be raised beside the Stars and Stripes at a conspicuous site in the Zone bordering Panama City. But again, change proceeded slowly due to court challenges and congressional resistance to reforms that might dilute U.S. dominance over the Canal Zone.30 Representative Flood spoke for many of his colleagues by denouncing the 1936 and 1955 modifications of the 1903 treaty as “a piecemeal liquidation of our sovereign rights, power, and authority on the isthmus.” Concessions served only to encourage more acts of “irresponsible political extortion” by Panamanian radicals and Communist agitators. The recent victory of Fidel Castro’s Soviet-supported revolution in Cuba compounded conservative U.S. fears of “a rising Red tide” converging against the Hay–Bunau-Varilla Treaty, the Monroe Doctrine, and the United States of America itself.31

It was in this context of increasing tensions between the United States and Panama, between U.S. advocates and opponents of making concessions to Panama, and between the U.S. and Soviet systems—which competed for influence and allies in the developing world—that the “Panama Canal II” proposal reemerged with a technological twist.32

Plowsharing Alaska and Panama

The Suez Crisis had manifested the threat to Europe’s empires posed by the postwar decolonization movements, and the temporary closure of the canal divulged the dependence of European and Israeli consumers on petroleum, tea, and other strategic commodities transported via the Red Sea–Mediterranean shortcut.33 For an elite group of scientists at the Lawrence Radiation Laboratory in Livermore, California, the Suez closure sparked a different realization. What if atomic energy could be harnessed to cut an alternative route through “friendly territory”?34

The idea of using nuclear power for nonmilitary purposes, such as generating electricity and treating cancer, had already taken root via Eisenhower’s “Atoms for Peace” program.35 Applying the atom’s explosive power to megaproject planning became the central goal of Project Plowshare, which the Atomic Energy Commission, the federal agency responsible for developing and promoting nuclear power, initiated in July 1957. PNEs would provide not only an economic boon to the construction industry and a diplomatic option for decision makers facing transportation crises like the Suez closure but also job security to nuclear scientists and engineers if the superpowers succeeded in negotiating treaties mandating disarmament, an important geopolitical development of the late 1950s. Indeed, Project Plowshare provided a rationale for the Livermore facility to continue operating while the United States observed a voluntary moratorium on nuclear testing from November 1958 to September 1961.36

Project Plowshare’s most visible advocate was Livermore’s cofounder, Hungarian-American physicist Edward Teller. Teller had achieved fame for his foundational scientific and controversial political roles in the development of nuclear weapons during and after World War II. He rejected the qualms of fellow physicists regarding the development and stockpiling of nuclear weapons and considered the dangers of radioactive fallout from nuclear weapons testing to have been “greatly exaggerated.”37

Teller’s vision for nuclear civil engineering included many applications, including fracturing underground rock formations to harness natural gas, heating tar sands to recover oil, and creating isotopes for medical purposes. The most dramatic uses of PNEs pertained to earthmoving endeavors. Canals, harbors, reservoirs, mountainous roads, and other such products of “geographical engineering” could be quarried at a fraction of the cost and risk of conventional explosives. Geographical engineering was in essence the Atomic Age version of the utilitarian conservationist “gospel of efficiency”—the philosophy of subjecting natural resources to technocratic oversight and development in order to reduce waste and provide the greatest good for the greatest number.38

The concept of PNE-facilitated public works was “very simple,” as Teller’s colleague Gerald Johnson explained to the chair of the congressional committee responsible for nuclear energy policy-making: “A ditch is constructed by detonating a sequence of buried nuclear explosives so spaced as to provide a smooth channel. The explosion is used not only to shatter the material, but also to eject it from the cut. In this way the desired excavation is accomplished in a single step.”39 Although everyone within a ten-thousand-square-mile fallout area might have to be evacuated for a year, excavating a six-hundred-foot-wide waterway by nuclear means might reduce costs by 84 percent. Even if the preliminary calculations were off by as much as 50 percent, “the savings would still be substantial.”40

The desire to demonstrate the feasibility of large-scale nuclear excavation on U.S. soil led Teller to promote Project Chariot, an initiative to use five buried nuclear bombs equaling five hundred thousand tons of TNT to create an “instant” harbor in northwestern Alaska.41 As discussed by several scholars, Chariot involved a great deal of hubris and miscalculation on the part of the AEC from the project’s start in 1958 until its demise four years later.42

Teller and Johnson, Plowshare’s first director, underestimated resistance to Chariot by Alaskans, who distrusted the claim that “all but a very small percentage of the radioactivity will be safely contained underground.”43 To allay such concerns, the AEC offered grants to University of Alaska biologists for baseline studies of the coastal Arctic tundra’s ecological and human communities. Ecological and anthropological insights would help determine the optimal time of year to detonate the explosives so as to limit exposure to radiation. Ideally, the lucrative grants would also provide authoritative endorsements for the nuclear harbor by local scientists.44

For John Wolfe, the founding director of the AEC’s new Environmental Sciences Division, the Alaskan research program represented a priceless opportunity to conduct a predetonation biological survey. At Plowshare’s second symposium in 1959, the former professor of botany emphasized the uniqueness of the Arctic ecosystem, a time when most outsiders considered it a wasteland. He also urged his colleagues to heed the advice of the conservationist Aldo Leopold to recognize “the complexity of the land organism.”45 In the 1930s and 1940s, Leopold had challenged the utilitarian approach to conservation by arguing that humans must appreciate nature as a life-giving system of interdependent ecological relationships, not merely as a set of commodities to be managed.46 Wolfe even argued for applying Leopold’s ethical framework to the sea, long before most biologists expressed concern about oceanic health.

Wolfe concluded his Plowshare symposium presentation on an unexpected historical note. The idea of preliminary biological surveys was nothing new, he argued; it underpinned the famous Lewis and Clark Expedition of the early 1800s. After acquiring a vast landscape extending westward from the Mississippi River, President Thomas Jefferson had instructed Captain Meriwether Lewis to collect data on the natural history and Indigenous peoples of the Missouri and Columbia River basins. While conceding that the expedition achieved few of Jefferson’s scientific objectives, Wolfe deemed the inspiring intellectual quest applicable to the Alaska project.47

As the Chariot researchers quantified food webs and other aspects of coastal Arctic ecology, the Livermore physicists three thousand miles to the south worked with engineers of the PCC and a special subdivision of the Army Corps of Engineers, the Nuclear Cratering Group, to investigate the feasibility of building a nuclear seaway even farther south.

Their joint report, completed in 1960, updated the 1947 PCC study by focusing on five routes that appeared most amenable to nuclear geographical engineering: in Mexico, along the Nicaragua–Costa Rica border, in eastern Panama along two separate routes, and in northwestern Colombia. Although none of the report’s economic analyses included estimates for acquiring land or securing treaty rights, the construction costs of nuclear excavation appeared very favorable. The cheapest conventional option, of converting the existing canal to a six-hundred-foot-wide seaway, was $2.3 billion—three times as much as the least expensive nuclear sea-level canal, a thousand-foot-wide channel to be blasted out along the Sasardi-Morti route in the Panamanian portion of the Darién, 110 miles east of the existing waterway. While requiring precise meteorological conditions and the temporary evacuation of thousands of residents, the $770 million project appeared feasible and safe. Accordingly, the report urged the AEC to continue developing cleaner nuclear explosives with an eye toward using them for a seaway outside the Canal Zone.48

Around the same time, the House Committee on Merchant Marine and Fisheries released its own update on the canal modernization issue. The 1960 report, authored by a group of engineers that included General Leslie Groves, the former director of the Manhattan Project, investigated many aspects of the Panama Canal’s long-term viability. The engineering consultants called for more research into isthmian sea-level canal routes and new conventional and nuclear methods of canal construction. However, they warned, “As of now, the only hope for an economically justifiable sea-level canal appears to be by excavation through as yet unproven nuclear means.” Until safe, cheap PNEs could be developed, they recommended making interim improvements to the existing, aging canal as soon as possible.49

Only the last recommendation satisfied Representative Flood, who considered the seaway idea an artifact of postwar hysteria over atomic attacks. Now that the even more powerful hydrogen bomb had exposed “the underlying fallacies in the ‘security’ thesis for planning navigational projects,” as he asserted in numerous speeches, he argued that policy makers should resume the World War II–era expansion project.50

Despite the opposition of Flood and other congressmen, in January 1961 the National Security Council issued a policy guidance report identifying the sea-level canal as an important project. To complete it by 1980, its location and means of construction “must be made soon.” Comprehensive feasibility studies should thus proceed, including of the “physical, biological and psychological effects of nuclear explosives under conditions to be encountered at the canal site.”51

For the new president, however, the seaway proposal provided a way to postpone hard decisions about U.S.-Panama relations. John F. Kennedy’s administration tried to dissuade President Roberto Chiari of Panama from broaching the subject of treaty reform, but Chiari insisted the time had come for abrogating the 1903 pact. As he wrote in a September 1961 letter that soon became public, “There is no place in the mentality of man in this second half of the 20th century for the proposition that a state, no matter how strong, can exert sovereign rights over any part of the territory of another state, no matter how small or weak.”52

Kennedy stalled in penning a comprehensive response to Chiari for seven months while another National Security Council working group reexamined the Panama Canal’s current and future needs.53 The resulting report recommended deferring any decision on a sea-level canal for five years, while conducting feasibility studies and delaying formal treaty negotiations affecting the existing waterway during that period. As for containing Panamanian pressure, the working group advised redirecting attention to the sea-level canal studies, reinterpreting the 1903 treaty “to satisfy Panamanian aspirations which are reasonable and consistent with the basic interests of the United States,” and providing more economic aid to reduce dependence on canal revenues.54

In conveying the report to Kennedy, the State Department’s second-highest official, George Ball, issued two warnings. The United States must take care not to oversell PNEs for canal construction, since such an approach could “provide a golden opportunity for Soviet propaganda throughout Latin America.” Delay tactics might also backfire given the growing pressure in Panama for change and the concomitant resistance in the U.S. Congress against any dilution of U.S. sovereignty in the Canal Zone.55 Ball’s admonitions informed an ensuing National Security Action Memorandum. The confidential document directed the AEC to determine the feasibility of nuclear excavation within five years and to participate in a joint sea-level canal research program with the Army Corps of Engineers that would include prompt on-site surveys in Panama and Colombia.56

On the same day of the National Security Action Memorandum’s internal release, April 30, 1962, Kennedy finally responded to Chiari. The timing was critical because Panama’s academic year commenced in May, and Chiari’s government feared that the new school year would reignite leftist student activism.57 Kennedy invited the Panamanian president to Washington for a state visit in June, but asserted that treaty negotiations must await the completion of seaway-oriented studies over an unspecified “period of years.”58 After the visit, the two nations formed a task force to examine Panamanian grievances, but the committee kept the focus on symbolic matters, such as the postage stamps and flags used in the Canal Zone.59

Nineteen sixty-two did not constitute the turning point Panamanian treaty reformers had hoped for, but it did result in major changes for Project Plowshare. On the one hand, the Chariot initiative ground to a halt. The AEC had acquired the scientific data it sought, but not the concomitant political support. Rather than keeping quiet after providing the contracted information, the University of Alaska biologists worked with grassroots organizers to publicize their concerns about how the project’s radioactive fallout might affect Arctic food chains. Organizers in Alaska and the continental United States generated so much negative publicity that the AEC called off Chariot after four frustrating years.60

It was a heavy blow for officials who viewed the harbor project as an ideal demonstration project for the nuclear seaway in Central America. And yet during the same year, the United States lifted the ban against testing nuclear weapons. Plowshare administrators wasted no time in conducting thermonuclear cratering experiments at the Nevada Test Site. The first one, Project Sedan, took place in July 1962. Sedan, a hundred-kiloton device buried 635 feet underground in alluvium, emitted a mushroom cloud that could be seen 65 miles away in Las Vegas. Its massive crater—1,280 feet in diameter and 320 feet deep—is now listed on the National Register of Historic Places. Within two hours of the shot, the AEC announced that 95 percent of the radioactivity had been contained.61 Yet elevated levels of iodine-131 soon appeared in milk supplies in Salt Lake City, Utah. AEC officials assured worried public health officials that everything would be okay once dairy farmers shifted their cows from fallout-contaminated pasture to dry feed.62

Over the next year, high-profile publicity reiterated the agency’s confidence in its ability to develop so-called clean explosives for nuclear excavation.63 Meanwhile, bills to fund detailed technical site surveys along the proposed Central American routes languished in Congress throughout 1963, as members debated who should oversee the feasibility study—the agencies with a vested interest in new construction, top administration officials such as the secretary of state and secretary of defense, private citizens, or various combinations thereof.64

Representative Herbert Bonner, the chair of the Committee on Merchant Marine and Fisheries who had commissioned the 1960 House canal report, introduced a bill to authorize the PCC to investigate methods of improving the canal’s security and capacity or of building a new channel to address future commercial and defense requirements. By contrast, Representative Flood demanded an investigative commission independent of the PCC and Army Corps of Engineers, and advocated for an adapted version of the suspended third-locks expansion of 1939–42 so as to maintain U.S. territorial rights in the Canal Zone. He blamed the failure to modernize the present canal on procrastinating officials and the few stakeholders who stood to benefit from a sea-level canal—earthmoving machinery manufacturers and military and civilian engineers hoping to gain long-term contracts.65

Despite his nationalist biases and blind spots, Flood made valid points about the seaway proposal’s limited nongovernmental support. A key potential user, the shipping industry, sought to keep tolls as low as possible and distrusted claims that a new sea-level waterway would remain as cheap to transit as the Panama Canal, an issue that would be explored in much more detail by the succeeding administration. Furthermore, the Livermore laboratory and AEC had a strong stake in finding new projects as public support increased for nuclear arms control. In a similar vein, the Army Corps of Engineers had a well-deserved reputation as a powerful Washington lobby that leveraged congressional relationships to ensure an endless pipeline of projects.66

Another action-forcing event in 1963 publicized the nuclear canal proposal: the congressional hearings regarding an international agreement to ban nuclear weapons tests in the atmosphere, in outer space, and under water. By that time, U.S. and Soviet physicists had long since developed bombs that dwarfed the explosive power of the ones deployed against Japan. In 1954, the AEC tested a thermonuclear bomb at Bikini Atoll with an astounding yield of fifteen megatons of TNT. The experiment unleashed radioactive fallout over a much wider swath of the Pacific Ocean than expected and sickened the members of a Japanese fishing boat, generating worldwide outrage. No matter how remote test sites appeared to be, the dozens of experimental detonations conducted each year by the three nuclear powers—the United States, United Kingdom, and Soviet Union—released radioactive isotopes that made their way into human bodies. Campaigns to expose the public health effects of radioactive fallout helped drive the diplomatic efforts to decelerate the nuclear arms race during the late 1950s and early 1960s.67

While allowing underground tests to continue, the proposed test ban treaty posed an existential threat to PNE projects in smaller nations by banning cross-border releases of radionuclides. Because buried nuclear charges might vent enough radiation to cross hundreds of miles into adjacent nations, how could an interoceanic canal be built in any of the countries spanning the Central American isthmus?

When asked at one of the hearings whether the United States had “any immediate plans to begin exploding atomic energy to build canals or to build harbors or to blow up mountains,” Atomic Energy commissioner Glenn Seaborg admitted, “We are not ready.” Nevertheless, he asserted, excavation technology experiments could proceed under the proposed treaty, and future nuclear construction projects could take place as long as the parties to the treaty agreed to amend it.68

In October 1963, the U.S. Senate ratified the Limited Nuclear Test Ban Treaty, a milestone for international arms control, Cold War diplomacy, and environmental health protection. But it upset advocates of geoengineering because the final document, unlike earlier versions, included no exceptions for PNEs, not even on an experimental basis.69

Cautious optimism prevailed nevertheless that agreements could be worked out with the Soviets, who were pursuing their own PNE projects, to allow cratering shots to continue.70 Moreover, as Plowshare director Gerald Johnson assured the chair of the congressional Joint Committee on Atomic Energy, in the three years since the completion of the 1960 report, researchers had reduced both the cost estimates of PNEs and projected levels of radioactivity in fallout. The technical, economic, and military rationales for the sea-level canal appeared ripe for reanalysis.71

Conclusion

Midcentury technological and economic innovations reduced U.S. reliance on the Panama Canal as a commercial and military conduit, but by then the Panama Canal Zone had become a critical locale for Latin American–focused surveillance, security, and defense infrastructure. Accordingly, except for a few modifications, postwar U.S. officials resisted making fundamental changes to the Hay–Bunau-Varilla Treaty.

Yet maintaining hemispheric security interests while managing the more obvious issues of canal ownership and operation was becoming more and more difficult. The unequal living standards and employment privileges enjoyed by U.S. civilian canal employees and their families, and many other instances of injustice, bred bitterness and violent demands to revise the 1903 U.S.-Panama treaty.

The proposal for a sea-level canal, especially one constructed with the new technology of PNEs, appeared to address the technopolitical outdatedness of the Panama Canal and its zone. For Presidents Eisenhower and Kennedy, the seaway idea, in concert with symbolic concessions, offered a background kind of diplomatic leverage to placate Panamanian dissent indefinitely. Because it was such a technically complex undertaking, the proposal bought time for Plowshare scientists and engineers to develop safer explosives and build greater public trust, and for U.S. officials to improve diplomatic relations with Panama without provoking the many Americans who considered the Canal Zone their own.

In hindsight, each of these endeavors was as riddled with unsustainable, contradictory premises as the Canal Zone system itself. Nevertheless, they reinforced the exciting conditions of possibility embodied by the nuclear seaway of the future, a project designed to imbue the Panamanian landscape with multiple forms of modernity.