Optimal Hydraulic Response to a Water Distribution System Contamination Event

The attacks of September 11^th spawned an increased awareness for the potential for intentional contamination of a water distribution network, resulting in reevaluations of emergency response plans by utilities across the country. Recognizing the need to determine appropriate response actions, the authors developed a prototype consequence management tool to address both planning emergency response scenarios and response to an actual emergency. Should a contamination warning system (CWS) detect the presence of a contaminant in a water distribution network, a variety of response actions must be examined in order to implement the most beneficial consequence management strategy, including public notifications and operational changes (e.g., valve closures and flushing). Employment of optimization techniques can be useful in determining the cost/benefit of isolating and/or flushing the system. Assuming an operational CWS and several hypothetical contamination scenarios, this paper will present modeling and simulation results to identify and evaluate potential utility response options to help mitigate the economic and public health impacts of a contamination release. In this work, the authors employ a genetic algorithm to select conventional and unidirectional system flushing programs that minimize a number of objectives, including total network contaminant concentration, total extent of contamination, difference between a maximum contaminant level (MCL) and the concentration of the contaminant in the network, and total mass of the contaminant consumed by nodal demand within the network. In addition, different injection locations will also be explored to examine network sensitivity to source location. Application of this technique to several simple networks demonstrates the usefulness of this optimization method as part of a consequence management strategy.