Abandoned mines are found throughout western United States. Acid-mine drainage and trace metals contamination associated with these sites can create significant water quality problems in nearby and downstream surface waters. One such abandoned mine site is the Alice Mine in the Front Range of the Rocky Mountains west of Denver, Colorado.
Because of the health hazards and aquatic impacts caused by the mine drainage and tailings, the Colorado Mined Land Reclamation Division initiated a reclamation project at the Alice Mine site to reduce acid drainage and to stabilize and revegetate tailings. The objectives of the present study were to monitor the success of the reclamation efforts and to determine whether whole effluent toxicity testing was applicable to monitoring effort.
Water samples were collected at six stations upstream from the mine discharge and tailings and within the affected area. Samples were collected in August 1988 prior to beginning reclamation and in October 1989 and 1990 after these activities had been completed. Brook trout (1988), fathead minnows (1989 and 1990), and Ceriodaphnia dubia (1988–1990) were exposed in acute toxicity tests. Water samples were also analyzed for trace metals concentrations. Duplicate benthic samples were collected at each station for macroinvertebrate analysis.
Good correlation was found between the toxicity and benthic data. The data showed a highly impacted area in 1988 prior to reclamation. The 1989 benthic and toxicity data indicated that the system appeared to be recovering although residual toxicity remained at two of the stations. High levels of trace metals were present at downstream stations in 1988 but concentrations were markedly reduced in 1989. Toxicity seemed to correlate with low pH's and high metals concentrations in 1988, but the relationship was less obvious in 1989 and 1990. Renewed acidmine drainage during spring 1990 had a marked effect on water quality which was mirrored in increased toxicity to Ceriodaphnia in toxicity tests. Benthic communities measured in October 1990 also appeared to be depressed compared to the previous year. Overall, toxicity testing seemed to be a good predictor of impacts in this system. Benthic sampling seemed to be a better indicator of the degree of recovery.