Opportunities to improve water quality during abandoned mine-tunnel reclamation

In the western United States, bulkheads are constructed to limit drainage from abandoned, draining mine adits and to protect downstream resources from uncontrolled releases of degraded adit water. Although bulkheads improve safety and water-quality conditions at the mouth of the adit, elevated hydraulic pressure behind the bulkhead often causes continuing water-quality problems in new locations. Solutions to improve water-quality outcomes from bulkheads might include in situ or ex situ passive or active treatment of mine-pool water or continuing tunnel drainage, in situ treatment of groundwater plumes resulting from bulkhead emplacement, direct extraction of metals from mine water, or bactericide application.