Critical Foundations: Protecting America's Infrastructures, the report of the President's Commission on Critical Infrastructure Protection (PCCIP, 1997), concluded that the nation's physical security and economic security depend on our critical energy, communications, and computer infrastructures1. As our dependence on them increases, so too do the vulnerabilities of these infrastructures to a wide range of threats. During the Cold War, the federal government constructed a number of underground facilities (UGFs) to house critical personnel and functions associated with the national defense. Although this threat has warned, the threat of high-casualty terrorist incidents and the diffusion of technologies for weapons of mass destruction have increased. In light of these growing threats, the Defense Special Weapons Agency of the U.S. Department of Defense (DoD) requested the assistance of the National Research Council to investigate how these existing facilities, or new underground sites, may contribute to an emerging national focus on the security of our critical infrastructures.

The PCCIP noted that the potential threats to the nation's critical infrastructures range from natural disasters to criminal and terrorist activities to organized information warfare. Many of these threats are "cyber-threats" and are not readily addressed with traditional physical security techniques. However, some components of advanced information systems are vulnerable to physical damage, whether from terrorist bombings, earthquakes, or apparently ordinary traffic accidents. Other infrastructure systems, such as energy, transportation, and emergency services, also have critical elements that are physically vulnerable. Although the PCCIP did not directly address the role of UGFs for the protection of critical infrastructures, its report recommended a program of joint government and industry cooperation and information sharing to increase the security of our nation's critical infrastructures.

Secure UGFs offer one means of protecting these critical elements and systems. UGFs can be particularly attractive if the perceived threat level or the consequences of loss are high and the vulnerabilities cannot be addressed through system redundancy or other nonstructural means. Although buildings can be hardened (strengthened) against structural failure from earthquakes, explosions, or accidents, beyond a certain threat level or structural loading, providing protection for critical elements in hardened above-ground structures may cost more than building an underground facility. A cost-risk analysis can demonstrate the most cost-effective approach for obtaining the desired level of protection. At the request of the Defense Special Weapons Agency, the Board on Infrastructure and the Constructed Environment of the National Research Council convened a workshop on April 6 and 7, 1998, on the use of underground facilities for the protection of critical infrastructure. The workshop, which was held at the National Academy of Sciences, in Washington, D.C., explored how existing UGFs constructed for defense purposes or new facilities might meet the nation's needs in protecting critical infrastructures. Workshop participants possessed expertise primarily in defense and security matters. Members of the commercial underground and tunneling communities also were in attendance.