Prologue Magazine

Safeguarding Hoover Dam during World War II, Part 2

Summer 2003, Vol. 35, No. 2

By Christine Pfaff


Hoover Dam The top of Hoover Dam, with transmission wires on the left, by Ansel Adams. (NWDNS-79-AA-B14)

Upon instructions from the President, in February 1941, the Federal Power Commission prepared a secret memorandum outlining measures to be taken to protect the U.S. power supply against hostile acts. The memo also recognized that because of the unlimited number of methods that could be used to sabotage equipment, and the varying circumstances at different power plants, it would be impossible to cover the problems of sabotage and air-raid protection in an exhaustive manner.

Following this broad evaluation of security concerns, the Federal Power Commission conducted intensive surveys at major power facilities. In May 1941 the agency completed its assessment of protective measures at Hoover Dam power plant. While the inspecting engineer found the plant "reasonably well protected" by lighting, fencing, a guard force of sixty men, and the natural topography of the deep canyon, he made nineteen recommendations for improving security. The first two were to prohibit visitors from entering the plant and automobiles from parking on the dam or roadway above the power plant. Other suggestions addressed increased lighting, fencing, alarm systems, and other barriers. The final recommendation was to install fog nozzles at various places around the dam, a measure that would later receive substantial scrutiny by Reclamation. Over the next three years, the Federal Power Commission conducted six supplemental reviews of security at Hoover Dam.

On September 17, 1941, the secretary of the interior approved "Regulations Governing the Protection of Structures" on Reclamation projects in operation or under construction. Different levels of protection were specified depending on the national, state, or local significance of the facility. Hoover Dam fell under the definition of a Class I structure "of paramount importance to and irreplaceable in operations of national defense by reason of major power supply." The highest level of protection was reserved for these facilities and consisted of "adequate and complete protection of all vulnerable features at all times by a sufficient number of armed guards."

Despite the escalating war and the ever-increasing possibility of direct U.S. involvement, visitors continued to be allowed to tour Hoover dam and power plant, although under tighter restrictions.

The bombing of Pearl Harbor changed that immediately. On December 7, 1941, E. A. Moritz, director of power at Hoover Dam, sent a telegram to Page stating that "Effective 5 pm today Boulder power plant has been closed to visitors and flood lights extinguished. All persons and cars will be checked in at boundary gates in Nevada and Arizona and cars convoyed across the dam. Request all unauthorized flying over this area be prohibited." The next day, Page closed the dam to all visitors except those on official business. In a press release, he said, "I regret exceedingly that it has been necessary to close this great public work to the public, but the step obviously now is necessary."

Also on December 8, Ickes sent a letter to Stimson requesting army assistance in guarding major facilities of the Department of the Interior, in particular Boulder, Grand Coulee, and Shasta dams. He wrote, "I assume that the present conditions constitute circumstances justifying such action by the Army." The army cooperated and established additional posts in Boulder City, at the switchyards, and at a few other key places in the vicinity of the dam. Reclamation officials felt that the dam was still not safe against air attacks, however, and that antiaircraft guns and fighter planes were essential to protect the facility. Although the army did not share Reclamation's concern about the threat of an aerial bomb attack, Stimson wrote to Ickes on March 14, 1942, that he intended to designate Boulder Dam a prohibited zone that would deny right of entry to within one mile of the dam to enemy aliens and "other classes of persons so designated" by the commanding general of the Western Defense Command and Fourth Army. Stimson did not elaborate on whether he intended the military to enforce this prohibition.

Just four months later, Moritz registered a complaint that none other than the military was violating safety precautions. On July 6, 1942, Maj. Gen. George S. Patton, Jr., flew dangerously low over the dam at about five hundred feet. Moritz wrote to Chief Engineer S. O. Harper, "It appears that if the Army feels any responsibility for the safety of the project and for continuity of power service, it should be the first to frown upon such hazardous acts." Moritz noted that the local army officers had always cooperated with Reclamation and also did not condone Patton's behavior. Harper forwarded Moritz's letter to the army, adding his own objection to the incident. The lack of adequate control of air traffic over Hoover Dam continued to be an issue between Reclamation and the military over the next year.

As in the past, private citizens wrote letters to Reclamation expressing deep concern for the safety of the dam. Chester Versteeg with Pacific Mutual Life Insurance Company provided the following recommendation just days after the attack on Pearl Harbor: "Because of the real danger of one or more enemy suicide planes loaded with powerful explosives following up the gorge of the Colorado River and striking horizontally against and destroying the Power Plants at Boulder Dam, I urge the immediate construction of a strong chain net or group of wire cables approximately 200 yards below the dam and from the river surface to the height of the dam." The sheriff of Nevada City, California, contacted the FBI to express his opinion that Hoover Dam was not properly guarded. His concerns made it to Ickes. Ickes also received notification from FBI Director Hoover that an informant had reported to him a number of safety breaches at the dam. In response, Ickes sent a team to investigate the alleged conditions.

During the summer of 1942, Reclamation continued its own exploration of measures to protect the dam from possible air raids. The previous year it had begun to evaluate, with assistance from the Corps of Engineers, the strength of the powerhouse roof against bomb attacks. In 1942, models of the structure were built at the Aberdeen, Maryland, Proving Ground and then fired at to test the vulnerability of the roof. Other Reclamation investigations focused on the possibilities of protection by camouflage and chemical smoke screens.

Learning that the army was conducting its own similar studies at Bonneville Dam in Washington State, Reclamation drafted a letter for Ickes to send to Stimson requesting that the army install and maintain "camouflage, smokescreens, and other protective measures at Boulder, Grand Coulee [Washington] and Parker Dams [straddling Arizona and California]." Reclamation officials were becoming increasingly frustrated by the army's unwillingness to clearly state where the protection of Hoover Dam fit into its plans to defend the West Coast in the event of aerial bombardment. The response from the army at the end of October 1942 helped to clarify its position, although it was disappointing to Reclamation: its three major dams of concern were outside a two-hundred-mile radius of the West Coast and therefore would not receive smoke protection. The army did agree to conduct surveys at the three dams to determine requirements for future possible installations. Months would pass before this was completed.

In the meantime, as the war raged on, Reclamation's concern for the vulnerability of its facilities continued to mount, prompting the agency to investigate on its own the use of smoke screens and camouflage. In February 1943, a Reclamation engineer, E. H. Heinemann, attended a demonstration of smoke-generating apparatus at the Norfolk, Virginia, Naval Air Station. Circling above the test area in a small plane, Heinemann observed the artificial fog completely envelop and obscure miles of ground. He concluded that the screen was very effective and could be useful in protecting the power installations at Hoover, Grand Coulee, and Parker. That same month, a fascinating report on the usefulness of camouflage to protect Reclamation structures was submitted by "color consultant" Allen T. True. For a second time, one of the artists engaged in the original design of Hoover Dam became involved in safeguarding it. True, a Colorado painter who specialized in depicting Western and Native American themes, had executed the imaginative Indian designs for the terrazzo floors of the powerhouse and lobby of the elevator towers at the top of the dam.

During the summer of 1942, True had attended a camouflage training course conducted by the Corps of Engineers in Virginia. From his experiments at Reclamation's Denver laboratories, True concluded that various degrees of camouflage would be effective but only in combination with a smoke screen. To help conceal the dam from planes overhead, True recommended various treatments including "toning down" the dam and spillways by painting them with bold, simple masses of colors in larger areas and darker tones than would seem acceptable. To create the illusion of water above and below the dam being connected, True suggested installing a thin sheet of water on the horizontal planes such as the roofs of the power plant and on the dam roadway.

Probably the most intriguing element was the proposal to build a "dummy" dam downstream from the real one as a decoy. The decoy, three-fourths the size of the real one and made of "garnished wire," would be painted various colors and different textures to simulate the concrete and the rocks of the cliffs. True's decoy study never went beyond a fascinating proposal tucked away in a forgotten file. Finally, in the spring of 1943, the War Department's Office of Chemical Warfare Service conducted its study on the feasibility of employing large-area smoke screens to protect Hoover, Grand Coulee, and Parker dams. Allen True was designated to represent Reclamation in carrying out the investigations. After accompanying a representative of the Chemical Warfare Service to the three dams, True wrote a memo to Chief Engineer Harper saying that he felt the trio of structures were the most attractive in the West to bomb because they supplied more than half of all the electric power used by war industries on the West Coast. Planes were still flying over these plants day and night with little or no controls in place. True recommended that Ickes take the matter of adequate protection directly to Stimson.

True's suggestion was taken seriously, and matters came to a head when Ickes sent a letter to Stimson on April 26, 1943. He began with, "what we would still like to obtain, is a statement of policy on the part of the War Department as to what assistance we can expect from the Army in the event of enemy air raids." Ickes' concluding paragraph was blunt: "Because the loss of Boulder, Parker, and Grand Coulee power plants would be a fatal blow to war production on the West Coast, because the Department of the Interior does not have the facilities for their protection from air assault, and because there is a need for the coordination of measures for passive defense, I request that the Army assume the entire responsibility for their protection."

It took Stimson more than a month to reply. "The importance of these dams as power installations has been fully recognized by the War Department," he wrote. "The threat at this time is considered to be limited to nuisance or sporadic air raids by light airplanes released from submarines, or at most, medium bombers launched from carriers. . . . To make such attacks an impossibility would require a much greater air force on this continent than can properly be spared from offensive action against the enemy." Stimson wrote that the chances of intercepting Japanese bombers en route from the coast to the dam were excellent. His concluding paragraph was equally as straightforward as that of Ickes, "Under the circumstances I believe that the acceptance of the risk involved is justified and that assumption by the Army of responsibility for passive protection of the dams in question is not necessary."

For the remainder of the war, Reclamation was on its own in protecting Hoover Dam.

More bad news from the military followed. In early September 1943, Reclamation was notified that the small number of army guards stationed at Hoover Dam and the convoy service that the army provided would be discontinued as the soldiers were being shipped elsewhere. Assistance from the FBI was also not forthcoming. In November 1943, J. Edgar Hoover turned down a request from recently appointed Commissioner Bashore that the FBI conduct another survey of the protective measures at Hoover Dam. Bashore had made the appeal following repeated charges by one of the rangers that security at the dam was inadequate due to a number of reasons, including laxness on the part of the ranger staff. By then, it was indeed becoming difficult to recruit competent men; morale was low, and turnover was high due to the shortage of housing, the high cost of living in Boulder City, and the attraction of higher paying jobs in the defense industry.

Dismissed by the FBI, Reclamation turned to U.S. Army Intelligence, which conducted a security survey. The report, prepared in January 1944 by Major Owen of the Continuous Security Branch, Ninth Service Command, concluded that many of the ranger's charges, which he made to an array of politicians, including the President and other top officials, were without merit or exaggerated, while others were justified, either wholly or in part. In a letter to Ickes defending Reclamation's continuous efforts to ensure adequate security at Hoover Dam, Bashore wrote, "While I realize the constant danger of sabotage to a project of the importance and vulnerability of Boulder Dam, it is significant that there has been no incident there."

Just when it appeared that security matters had calmed down at Hoover Dam, another alleged sabotage plot surfaced. This time the ostensible conspirators were Japanese and Chinese, operating through two Mexican agents. The news reached the press and on April 17, 1944, headlines in the Boulder City Evening Journal announced "Scheme to Dynamite Boulder Dam Nipped by San Diego Federals Today." The FBI had arrested Andres Sanchez, a Mexican laborer, on charges of attempting to wreck a railroad train in southern California. The newspaper recounted that Sanchez admitted to being involved in a plot to dynamite Hoover Dam. Just days later, the FBI Director Hoover wrote to Ickes to notify him that the sabotage plot had been investigated further and found to be entirely fabricated. The FBI informant confessed that there was no truth at all to the rumor of a plan to blow up Hoover Dam.

As the war turned in favor of the Allies, the intense security concerns at Hoover Dam lessened. The fear of sabotage abated, and the investigations into the "loyalty and trustworthiness" of project employees were discontinued. Bashore felt strongly that Reclamation facilities should allow visitors, subject to rules based on "facts, reasonable precautions, logic, equity, and practicability." To Bashore, offering the public a firsthand opportunity to view Reclamation projects was of utmost importance to acquaint them with the agency's purposes and accomplishments.

As conditions started to return to normal in 1946, the matter of law enforcement was dealt with in a few paragraphs in the project's annual report. Reclamation's ranger force continued to maintain law and order in Boulder City and the vicinity of the dam. A monthly average of twenty-nine rangers and seven watchmen were on duty, patrolling the city, checking traffic, watching for suspicious characters, and maintaining the peace on Bureau of Reclamation lands.

The events of September 11, 2001, rekindled fears of attack on Hoover Dam. Newspaper articles reminiscent of those published during World War II raised the specter of possible sabotage and the need for increased security. Once again, safeguarding one of the country's most well-known and recognized landmarks became a matter of national security.

Safeguarding Hoover Dam, Part 1

Christine Pfaff is a historian with the U.S. Bureau of Reclamation in Denver. She researches and writes about water development and irrigation projects throughout the West.


Note on the Sources


Information for this article was almost entirely drawn from records housed at the National Archives and Records Administration - Rocky Mountain Region, Denver, Colorado. See Record Group 115 (Bureau of Reclamation), Entry 7, general correspondence and project (Colorado River Project) correspondence files for the years 1930 - 1945. Reclamation's monthly journal Reclamation Era also provided material on the sequence of events relating to the establishment of law enforcement provisions at Hoover Dam. Information on the artistic achievements of Oskar Hansen and Allen True at Hoover Dam can be found in Reclamation Era (see January and February 1936 volumes for articles on Allen True) and a brochure entitled "Sculptures at Hoover Dam" published by the Bureau of Reclamation in 1978. Learn more about the history of Hoover Dam and the Bureau of Reclamation at

The author wishes to thank the NARA staff in Denver; Roy Wingate, records manager in Reclamation's Denver office; and Emme Woodward, museum specialist, and Karen Cowan, both with the Bureau of Reclamation in Boulder City, Nevada, for all their assistance.

Articles published in Prologue do not necessarily represent the views of NARA or of any other agency of the United States Government.