Threat Assessment of Water Supply Systems Using Markov Latent Effects Modeling

Recent amendments to the Safe Drinking Water Act emphasize efforts toward safeguarding our nationʹs water supplies against attack and contamination. Specifically, the Public Health Security and Bioterrorism Preparedness and Response Act of 2002 established requirements for each community water system serving more than 3,300 people to conduct an assessment of the vulnerability of its system to a terrorist attack or other intentional acts. Integral to evaluating system vulnerability is the threat assessment, which is the process by which the credibility of a threat is quantified. Unfortunately, full probabilistic assessment is generally not feasible, since there is insufficient experience and/or data to quantify the associated probabilities. For this reason, an alternative approach is proposed predicated on Markov latent effects (MLE) modeling, which provides a framework for quantifying imprecise subjective metrics through possibilistic or fuzzy mathematics. Here, the MLE approach is introduced and demonstrated within the context of water supply system threat assessment.