rorist attacks on power systems might be coupled with other types of terrorist attacks, particularly in large cities. Finally, vulnerabilities of control systems to cyber- and physical attacks need special attention.
The Board on Energy and Environmental Systems of the Division on Engineering and Physical Sciences of the National Research Council also provided briefings on relevant activities and studies. Three overriding concerns regarding terrorist attacks on energy-related systems are (1) electrical systems, especially transmission network substations; (2) petroleum refineries, which if attacked could threaten nearby residents although the overall impact would be less than an attack on an electrical system; and (3) gas pipelines, which if attacked could also threaten nearby residents, but again would have less impact than disrupted electrical systems. Among the approaches to protect electrical systems are physical barriers around critical components, modular extra-high-voltage transformers, improved surveillance technologies, and adaptive electrical grids that limit cascading failures. Relevant studies currently under way address the safety and security of commercial spent nuclear fuel storage and enhanced resilience of electric transmission networks. A study of safety at liquefied natural gas facilities may soon be launched.
The discussion with the American Petroleum Institute centered on security vulnerability assessment methodology for the petroleum and petrochemical industries. The assets of concern include 4,200 offshore oil platforms, 100 U.S. ports, 148 refineries, 160,000 miles of liquid pipelines, 35,000 gasoline tanker trucks, 7,500 bulk storage plants, and 170,000 service stations. Important concepts include definition and prioritization of risks, types of direct and indirect consequences of an attack, attractiveness to terrorists of different assets, threat scenarios involving groups with different motivations, and vulnerabilities in protection of different types of assets. The methodology should give considerable attention to countermeasures that can be employed, including consideration of cost and vulnerability tradeoffs. Various sources of data were discussed, and the relevance of previous experiences in countering all types of threats was emphasized. Finally, the types of personnel injuries, economic losses, and environmental damage that must be anticipated were highlighted. The importance of individual companies working with local law enforcement officials is obviously of utmost importance given the wide variation in facility types and locations.
The emphasis during the discussion with the Edison Electric Institute was on the working relationships between the private sector and the government (both federal government organizations and local agencies). Industry includes federal utilities, investor-owned utilities, municipal and state utilities, and rural electric cooperatives. The North American Electric Reliability Council provides an important umbrella organization for addressing standards and methodologies for countering threats of terrorism. At the same time, the U.S. Congress is concerned about insurance coverage, regulations and mandatory standards, and frequency allocations. The U.S. Department