Friday, October 18 – 3:30 pm – POST 723

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Alan Mair

USGS Pacific Islands Water Science Center

An Objective Approach for Assessing Drinking Water Source Vulnerability to Contamination in Hawaii
Capture zone analysis combined with a subjective susceptibility index is currently used in Hawaii to assess vulnerability to contamination of drinking water sources derived from groundwater. In this study, we developed an alternative objective approach that combines well capture zones with multiple-variable logistic regression (LR) modeling and applied it to the highly-utilized Pearl Harbor and Honolulu aquifers on the island of Oahu, Hawaii. The LR models utilized explanatory variables based on hydrogeology, land use, and well geometry/location. A suite of 11 target contaminants detected in the region, including elevated nitrate (> 1 mg/L), four chlorinated solvents, four agricultural fumigants, and two pesticides, was used to develop the models. We then tested the ability of the new approach to accurately separate groups of wells with low and high vulnerability, and the suitability of nitrate as an indicator of other types of contamination. Our results show that the objective LR modeling approach is flexible enough to address a wide range of contaminants and represents a suitable addition to the current subjective approach.

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