Geophysical characterization of mine influenced groundwater and surface water in the Mayflower section of the Animas River, Bonita Peak Mining District, Silverton Colorado
This report includes investigations which grew from the 2018 Innovation Project “Monitoring Impacts of Mines on Surface Waters with Robust Sensors”, to investigate groundwater - surface water interactions at mine influenced Superfund Sites in Colorado with an additional focus on the electromagnetic induction (EM or EMI), magnetic, and fiber optic distributed temperature systems (FODTS) investigation of the Mayflower Section of the Animas River in Silverton, Colorado. These geophysical methods measure the bulk earth electrical conductivity, magnetic susceptibility, and temperature of specific surveyed volumes of the earth. These physical parameters are used to understand the groundwater – surface water interactions, which can guide decision makers in their assessment of mine impacted surface water. This report details the results from characterization and monitoring technologies to provide high data density and continuous monitoring of bulk earth electrical conductivity and temperature in the Mayflower section of the Animas River to identify zones of groundwater – surface water interactions and potential metal loading from mine influenced water. The investigation separated right and left bank characterization for each method and suggests more groundwater is entering from the right bank than the left bank and these predominantly right bank discharges potentially contain metal-rich water compared to the left bank. Results also suggest mineral veins facilitate preferential groundwater discharge to the river, Boulder Gulch is likely groundwater dominated and possibly transports large amounts of magnetic material from Mayflower Impoundments #1 and #2, beaver ponds near Blair Gulch may influence groundwater discharge, Mayflower Impoundment #4 is possibly impacting groundwater and surface water and may be connected to the wetlands to the west of the impoundment. These data could be further analyzed for smaller spatial scale analysis within areas of interest. The identification of these locations along sections of the river likely impacted by mine influenced groundwater potentially entering the Animas River and can be used by site investigators, decision makers, and stakeholders in mitigation decisions and strategies.