Davis Pyrite Mine collapsed in 1910 after 28 years of operation. Since that time, acidic drainage has been transporting iron and other trace elements into a local stream and groundwater. Initial observations indicate that the environment has remained stable for decades. New data show a restricted lens of impacted groundwater that moves rapidly through the mine tailings and shallow bedrock fractures, but is contained by ambient groundwater from uncontaminated recharge areas. In these peripheral areas, there is evidence of an active microbial community that reduces the dissolved sulfate, and possibly Fe (III), to remediate the acidic drainage. Present research involves detailed mapping and modeling of the impacted area, and experiments are underway to document the identity and cultivate the sulfate- and iron-reducing bacteria.