Understanding Surface Water and Groundwater Interactions at a Mining District Superfund Site near Silverton, CO

The US Environmental Protection Agency (EPA) has placed the Bonita Peak Mining District (BPMD) on the National Priorities List (NPL) making it eligible for a remedial investigation under the Superfund program. The BPMD consists of 48 historic mines or mining-related sources located in headwaters of the Animas River Watershed near Silverton, CO. The mine sites are located within a volcanic caldera complex with hydrothermally altered fractured bedrock. Surface and sub-surface rock and water interactions across the mining district produce acidic waters which enable the mobilization and transport of metals into the local surface waters.This talk will focus on the methods and techniques used to develop a conceptual model of the hydrologic fluxes within the mining district. Specifically, the talk will highlight the data needs to address complexities of water inputs, flow paths, and discharges in multiple headwater catchments interconnected by both natural (i.e. fracture flow) and anthropogenic (mine workings) hydrologic pathways. Challenges of combining data from physical parameters (i.e. rainfall, discharge, groundwater elevations) with analytical chemistry results, and maps of geologic structures and mine workings will be discussed.