Abstract: In the report, wetland technology is described in which the main reactive layer is limestone gravel (rather than organic material) which is overlain by a fine gravel filter and soil. The three-year project included laboratory and field studies. Vertical aerated wetlands, simulated by columns, constructed in the field and in the laboratory, were operated during the project. The report presents a summary of results given in previous reports and summaries of results obtained using water from Butte, MT, and field studies at the Rockford Tunnel, near Idaho Springs, CO.

Abstract: An experimental diversion of acid mine drainage was set up near an abandoned mine in Saint Kevin Gulch, Colorado. A mass-balance approach using natural tracers was used to estimate flows into Saint Kevin Gulch. The diversion system collected about 85 percent of the mine water during its first year of operation (1994). In the first 2 months after the diversion, benthic algae in an experimental reach (stream reach around which mine drainage was diverted) became more abundant as water quality improved (increase in pH, decrease in zinc concentrations) and substrate quality changed (decrease in rate of metal hydroxide deposition). Further increases in pH to levels above 4.6, however, led to lower algal biomass in subsequent years (1995-97). An increase in deposition of aluminum precipitates at pH greater than 4.6 may account for the suppression of algal biomass. The pH in the experimental reach was lower in 1998 and algal biomass increased. Mine drainage presents a complex, interactive set of stresses on stream ecosystems. These interactions need to be considered in remediation goals and plans.

Abstract: Many industries produce a waste-water stream high in heavy metals. Disposal of sludge from these wastewater treatment plants has become increasingly difficult and expensive in the US due to passage of the Resource Conservation and Recovery Act's 'land disposal ban' for hazardous wastes. Innovative methods can be found for dealing with such wastes. For example, in performing a mandated clean-up under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), Asarco's California Gulch water-treatment plant in Colorado meets CERCLA clean-up goals while using a waste water treatment sludge as a smelter feedstock, recovering incidental saleable metals, and producing non-hazardous products. In this plant, Asarco treats acidic mine-drainage water having high metal concentrations and uses the waste sludge generated as a lime replacement in lead smelting operations. -Author