The potential for intentional contamination of the nation's drinking water infrastructure has heightened utility awareness regarding distribution system security. Corrective actions implemented by a water utility following a contamination incident have the potential to significantly mitigate public health and infrastructure impacts. Many mitigation and response options are available (e.g., flushing at hydrants to remove contaminants from pipes, injecting disinfectant or decontamination agents at booster stations to treat the water or remove the contaminant from pipe walls, sampling at locations throughout the network to determine the extent of contamination, or instituting "Do Not Drink" or "Do Not Use" public advisories). For any given utility, some options might be more effective than others, and the effectiveness might depend on timing and other factors. Modeling and simulation studies can help utility decision-makers evaluate the effectiveness and feasibility of various response actions. However, utilities need to use realistic input parameters to ensure that modeling results are meaningful. This paper summarizes the input parameters needed to realistically model utility response options as well as lessons learned from discussions with two water utilities on the practicality of initiating specific response actions. The purpose of the utility discussions was to ground-truth modeling assumptions and eliminate impractical and inefficient response options, while also placing realistic bounds on input parameters. With more accurate information, the results from simulation and optimization models will be more acceptable to water utilities and policy makers. Generating plausible approaches to dealing with a contamination incident will support the utilities' decision making process and facilitate selection of the most effective operational response. The value of this type of response planning is discussed for a wide audience of water utilities.
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