AWWA JAW60919

The objective of the study discussed in this article is to utilize commercial distribution system modeling software to understand how a drinking water system could be affected by the intentional introduction of chemical contaminants. The hydraulic model results are used to estimate the risk involved in several feed scenarios and chemical contaminants. The model results are then combined with concentration-response sensitivity data from routine monitoring instruments to determine the ability of each chemical contaminant to be detected. Because the four chemicals studied -- parathion, VX, sodium monofluoroacetate (1080) and cyanide -- are modeled as highly persistent, their comparative effects are determined by the toxicity of the highest practical dosage. The results of the modeling scenarios show that large-scale contamination of a drinking water system may be accomplished through backflow into major network water supply lines. Strategically located points of attack outside of the major supply lines can also produce large-scale contamination at lesser concentrations. Points chosen at random for a covert contamination attack within the distribution system will optimally affect an area of a few neighboring streets of up to 1 sq mi, depending on the pipe velocities and flow patterns within the distribution system as well as other factors. The Expanded Summary in this issue offers a condensed review of study findings; a full discussion of the study results can be found online at www.awwa.org/communications/e-journal/index-past issues/2005/January. Includes 12 references.