Methodology for Evaluating Dredged Material Alternatives Using Risk-Cost Analysis Under Uncertainty

by J. Stansbury, Univ of Nebraska--Lincoln, Lincoln, United States,
I. Bogardi, Univ of Nebraska--Lincoln, Lincoln, United States,
W. E. Kelly, Univ of Nebraska--Lincoln, Lincoln, United States,

Abstract: A methodology and a case example was presented at the 1989 Conference on Risk-Based Decision Making in Water Resources, Santa Barbara, to perform risk-cost analysis for dredged material alternatives. This methodology is extended to account for uncertainties using a fuzzy set approach. Disposal of contaminated dredged material may pose risks to ecological and human populations through direct contact or indirect contact, such as through the food chain. These risks may be reduced by incorporating measures to confine the contaminated dredged material; however, these confinement measures may increase disposal costs significantly. Risk-cost trade-off analysis can be used to evaluate potential disposal alternatives and select those alternatives that are both environmentally sound and cost effective. However, risk and cost assessments for dredged material management alternatives are often associated with very large uncertainties. If risk-cost analysis is conducted without considering these uncertainties, inappropriate management policies may result. On the other hand, considering these uncertainties may cause difficulties in decision making if they make management alternatives effectively indistinguishable. Therefore, a risk-cost analysis methodology that uses fuzzy set methods to incorporate uncertainty directly into the risk-cost trade-off decision framework is developed. Carcinogenic and noncarcinogenic risks to humans and physical (e.g., burial and habitat disruption) and toxicological risks to ecological species are estimated for each of several disposal alternatives. Composite programming, a multicriteria decision-making (MCDM) method, is used to trade off the risks and costs for these disposal alternatives. Uncertainties are encoded into the composite programming algorithm by means of fuzzy set membership functions. The final risk-cost trade-off distance for each management option is computed as a fuzzy number allowing the disposal alternatives with their associated uncertainties to be compared and ranked.

Subject Headings: Risk management | Dredged materials | Uncertainty principles | Fuzzy sets | Environmental issues | Decision making | Health hazards | Hazardous materials

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