WELLHEAD TREATMENT COSTS FOR GROUNDWATER CONTAMINATED WITH PESTICIDES- A PRELIMINARY-ANALYSIS FOR PINEAPPLE IN HAWAII

In Hawaii, trace concentrations of pesticides used in the production o f pineapple were found in the groundwater supplies of Mililani Town in the Pearl Harbor Basin on the island of Oahu. Groundwater serves as t he major source of drinking water and residents pay for wellhead treat ment of the contaminated water, via their monthly water bill. The agri cultural chemical users within the Pearl Harbor Basin do not include t hese wellhead treatment costs in their production costs. The agricultu ral industry benefits from using pesticides but does not pay the entir e societal cost of using these chemicals. In this study we evaluate th e specific financial cost of wellhead treatment, and not the economic value of groundwater. While wellhead treatment costs could conceivably be shared by several parties, this study focuses on the financial imp act of the pineapple industry alone. This study factors annual wellhea d treatment costs into annual pineapple production costs to measure th e effect on annual financial return from pineapple production. Wellhea d treatment costs are calculated from the existing granulated activate d carbon (GAC) water treatment facility for Mililani Wells I and II. P ineapple production costs are estimated from previous cost of producti on studies. The inclusion of wellhead treatment costs produces differe nt production-cost results, depending on the scale of analysis. At the local scale, the Mililani wellhead treatment costs can be factored in to the production costs of the pineapple fields, which were probably r esponsible for contamination of the Mililani Wells, without causing a deficit in economic return. At the larger regional scale. however, the return from all of the pineapple grown in the Pearl Harbor Basin can not sustain the cost of wellhead treatment for the entire water supply of the basin. Recommendations point to the prevention of groundwater contamination as more cost-effective measure than wellhead treatment.