Abandoned mines are potential and underutilized reservoirs for low-temperature geothermal heat pump systems. We are exploring the potential for a ground-source heat exchange system in the abandoned and flooded Steward Mine in Butte, Montana. This mine is located within the Butte Mining District, within 1000 m of the Berkeley Pit (a large feature within the Butte Area Superfund site). There is a steep groundwater flow gradient from the Steward mineshaft to the Berkeley Pit, creating the potential for vertical flows in the mineshaft as water flows between horizontal drifts and to the pit. Proper design of heat exchangers in the mine shaft and predictions on the possible energy return and sustainability require measurements of the shaft temperatures, water levels, water chemistry, water movement vertically in the shaft and horizontally across the shaft. Using tools typically applied to borehole geophysics, we collected vertically distributed water temperature, conductivity, and pH. In addition, we measured vertical flows in the shaft using a spinner flow meter. We also collected shaft dimensions using SONAR in the flooded sections of the mine. We then attempted to correlate those flows with mine construction records. We found that flow is variable from near zero m/s to around 0.030 m/s and moving downward in the mineshaft starting from near the surface of the water at 150 m below land surface to 396 m below land surface. Variations in flow are likely due to horizontal workings (drifts) that intercept the shaft, creating areas available for flow in the mineshaft.

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