Abstract
Certain industrial processes, including generation and storage of Coal Combustion Residuals (CCR), can lead to release of cobalt into the environment due to leaching of CCR. At a former coal power plant site in the southeastern United States, cobalt concentrations in groundwater downstream from a CCR unit were above background concentrations and groundwater protection standards, yet cobalt concentrations were low within pore water of the CCR unit. This paper will present a weight-of-evidence approach to identify the most likely provenance of cobalt in the groundwater downstream of a CCR unit. A chemical equilibrium modeling software was used to predict the observed cobalt concentration in downstream groundwater based on the conceptual site model for existing conditions. The equilibrium mode was then used to evaluate the success of a proposed mitigation measure option. Topics covered will include cobalt sources and geochemical conditions that affect the mobility of cobalt, and implications for mitigation measures at a confidential site in the USA.