While the magnitude of emissions from a facility is an important metric, it is often necessary to evaluate these emissions in terms of their impact on air quality or in the cases of toxics, on the health of the local community. Dispersion models are used in both types of assessment. When assessing air quality impacts, the criteria pollutant emissions from a proposed or operational facility are calculated, modeled, and the impacts compared to specified standards. When performing a risk assessment, toxic pollutant emissions are modeled and the resulting estimated concentrations are used along with specified algorithms to assess risk to public health. Verdant personnel have performed hundreds of dispersion modeling studies and health risk assessments to support a wide variety of projects. They are adept at running a significant number of models, including ISC, AERMOD, CALPUFF, CALINE, Fugitive Dust Model (FDM), and DEGADIS, the dense gas dispersion model.