Abstract: Remediation of the Eagle Mine Superfund Site began in 1988. Remedial action included: bulk-heading adits, flooding mine workings; constructing diversion ditches around waste rock; consolidating mine wastes in an on-site tailings pile; capping the tailings pile with a multi-layer, engineered cap; and revegetating disturbed areas with native plants. Flooding the mine workings resulted in unacceptable seepage into the Eagle River in late 1989. A water treatment plant was constructed to collect mine seepage and groundwater at the main tailings pile. In October 2001, construction of the remedy was declared “complete” and the site is now in the operation, maintenance and monitoring phase. A strong downward trend in zinc and cadmium concentrations in the Eagle River has occurred and, trout and macroinvertebrate populations have increased. Biological data are being used to establish water quality standards for the Eagle River.

Abstract: The aim was to assess over 2 years the treatment efficiencies of vertical-flow wetland filters containing macrophytes and granular media of different. adsorption capacities. Different concentrations of lead and copper sulfate (constant for 1 year each) were added to urban beck inflow water in order to simulate pretreated (pH adjustment assumed) mine wastewater. After 1 year of operation, the inflow concentrations for lead and copper were increased from 1.30 to 2.98 and from 0.98 to 1.93 mg/L, respectively. However, the metal mass load rates (mg/m(2)/d) were increased by a factor of approximately 4.9 for lead and 4.3 for copper. No breakthrough of metals was recorded. Lead and copper accumulated in the biomass of the litter zone and rhizomes of the macrophytes. Furthermore, microbiological activity decreased during the second year of operation. Bioindicators such as ciliated protozoa and zooplankton decreased sharply in numbers but diatoms increased. In conclusion, the use of macrophytes and, adsorption media did not significantly enhance the filtration of lead and copper. Particulate lead is removed by filtration processes including straining. Furthermore, some expensive and time-consuming water quality variables can be predicted with less expensive ones such as temperature in order to reduce sampling costs.

Abstract: The Gilt Edge gold mine is an acid drainage site that has been put on an accelerated closure schedule. The mine ceased activities in 1999 when Dakota Mining Corporation declared bankruptcy forcing the State of South Dakota to immediatly assume water treatment operations. Evaluation of conceptual closure plan options and cost estimates led the State of South Dakota to a decision to seek Federal assistance. The site has quickly moved into reclamation mode for the principal contamination source, the Ruby waste-rock dump. Designs and specifications for capping the Ruby waste-rock dump were prepared while Superfund listing was pursued. In October of 2000, mobilization of the first reclamation contractor began and by December the site was added to the National Priorities List. Capping the waste-rock dump will address a major acid drainage source. Water treatment requirements are expected to decline as conventional methods such as diverting clean water, backfilling, grading, capping, limestone neutralization, and revegetation are implemented. Acid seepage from underground workings, steep highwalls, and some pit backfills will remain. Major field trials of emerging technologies are nearing completion and some are showing promising results. Carbon reduction in a pit lake, and pyrite microencapsulation on simulated waste dumps, are showing initial success. Their application may minimize or eliminate the need for long-term active water treatment which has been a long sought goal for major acid rock drainage sites.