Tetra Tech specializes in the development of advanced fate and transport models to predict chemical migration in the environment, which is a key component of conducting a defensible exposure/health risk assessment and allows for the most efficient allocation of resources in regard to sampling efforts that may be required. For example, modeling results can indicate which environmental media and exposure pathways are likely to be the primary contributors to potential exposures. Once primary media/exposure pathways are identified, financial resources can be allocated in the most efficient manner to maximize the amount of data collected for the primary exposure media of interest, while also helping to determine an appropriate amount of data for media associated with other less significant exposure pathways to validate the modeling results and verify that these secondary pathways would not be associated with significant levels of exposure. Tetra Tech has developed over 10 fate and transport models for clients such as the U.S. Air Force, Electric Power Research Institute, U.S. Environmental Protection Agency, and U.S. Geological Service.