The National Exposure Research Laboratorys Ecosystems Research Division (ERD) in Athens, Georgia, conducts research on organic and inorganic chemicals, greenhouse gas biogeochemical cycles, and land use perturbations that create direct and indirect, chemical and non-chemical stresses, exposures, and potential risks to humans and ecosystems. ERD develops, tests, applies and provides technical support for exposure and ecosystem response models used for assessing and managing risks to humans and ecosystems, within a watershed / regional context. The Regulatory Support Branch (RSB) conducts problem-driven and applied research, develops technology tools, and provides technical support to customer Program and Regional Offices, States, Municipalities, and Tribes. Models are distributed and supported via the EPA Center for Exposure Assessment Modeling (CEAM). The Internet tools described in this report provide methods and models for evaluation of contaminated sites. Two problems are addressed by models. The first is the placement of wells for correct delineation of contaminant plumes. Because aquifer recharge can displace plumes downward, the vertical placement of well screens is critical to obtain proper characterization data. The second is the use of models where data are limited. In this case some form of uncertainty analysis is necessary to evaluate transport behavior. The remainder of the report describes a series of tools for estimating various model input parameters.