Initial Chemicals of Interest were determined from EPA testing in 1997 and formed the basis of the listing of the Portland Harbor as a Superfund Site in 2000. Since then samples have been analyzed for nearly 400 chemicals. Four chemical groups - total PCBs, total dioxins and furans, total DDTs, and total PAHs are considered "bounding" indicator chemicals because their distribution is believed to encompass the spatial extent of chemicals posing potentially unacceptable risk identified in the baseline risk assessments. Other chemicals have been investigated and will be evaluated in the feasibility study.