Atrium Lobby (Hyatt Regency Baltimore on the Inner Harbor)
CDM was contracted by the Montana Department of Environmental Quality to support the preparation of an environmental assessment for the Troy Mine in northwest Montana. One of the most important concerns by the state and the community was the fate of antimony, uranium, and copper within the groundwater downgradient of the tailings facility. The tailings are very low in total sulfides and do not produce acid. However, the tailings and mine waters do contain copper, antimony, and uranium at concentrations slightly above regulatory standards. An evaluation of the chemical data suggested that the tailings water and local groundwater were of very different character, and when mixed would likely result in precipitation. Geochemical modeling using PHREEQC demonstrated that mixing of the waters would result in the precipitation of iron oxyhydroxide. Subsequent jar testing showed that when the waters were mixed, iron oxyhydroxide forms, resulting in removal of antimony (11 to 59%), copper (73 to 97%), and uranium (26 to 84%). The higher metal removals were achieved when higher proportions of the reduced, iron-bearing local groundwater were used, suggesting that more of the attenuation will occur on the outer edges of the plume. The results of the study will provide the agencies with the information necessary to select a remedial alternative for the site. The paper will discuss the methodology and results of both the modeling and bench-scale testing and will provide an analysis of the fate and transport of the metals within the groundwater at the site.
