developed, and increasingly detailed cost estimates can be prepared. When the drawings and specifications are ready and the final cost estimate has been approved, bidding or another procurement method can begin. Typically, public work is subject to competitive bidding, but increasingly some agencies have used design-build as a procurement method. The design-build method usually involves preparation of preliminary drawings and specifications (the design development documents). These documents are used to solicit competitive bids for the completion of the design and construction as a package with a fixed lump sum or a guaranteed maximum price.


The Concepts

Many fundamental concepts of human health risk assessment from chemical and biological hazards have been described in Risk Assessment in the Federal Government: Managing the Process (NRC, 1983). The basic paradigm developed in that report is shown in Figure 6-1, and it captures the two key components—risk assessment and risk management—that apply equally well to building protection situations.

Generally, human health risk assessments for biological and chemical threat agents include a risk assessment component that addresses the identification and characterization of agents involved (hazard or threat assessment), exposure potential for scenarios of interest (exposure or vulnerability assessment), and important uncertainties to fully characterize the resulting risk estimates (risk characterization or consequence assessment). The output of the risk assessment is used in the risk management process to identify and prioritize risk reduction strategies. Thus, risk management is the process of weighing alternatives and selecting the most appropriate actions that often integrates the results of risk assessment on human health risk with social, economic, and political concerns to reach a decision (NRC, 1983).

Implementation of a systematic approach for decision making for building protection requires input of various experts, including experts in medicine, health sciences, security and infrastructure protection, and building use and design. In addition to building protection, risk assessment and risk management have been applied to many other areas. Each area of application has fairly well-developed approaches that are optimized to its unique needs. Consequently, the areas of application might use somewhat different terminology and methodology. The following summary of risk assessment and risk management presents the highlights of what is judged to be common across different disciplines with potential applications to building protection.

Risk assessment provides an objective, often science-based, approach to compare risks. Risk assessments are inputs used by decision makers to deter-

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