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The unsaturated zone at two sites in fluvial tailings deposits, one of which was remediated by the incorporation of lime and biosolids (municipal sewage sludge) into the soil, were monitored for water movement and water chemistry. Preliminary results indicate that the differences observed are generally attributable to the heterogeneity between the two sites rather than remediation. Remediation increased alkalinity in the tilled zone but this has not penetrated greater than 30 cm. Continued monitoring will indicate whether it has been effective in alleviating the spring flush of zinc to the aquifer., The unsaturated zone at two sites in fluvial tailings deposits, one of which was remediated by the incorporation of lime and biosolids (municipal sewage sludge) into the soil, were monitored for water movement and water chemistry. Preliminary results indicate that the differences observed are generally attributable to the heterogeneity between the two sites rather than remediation. Remediation increased alkalinity in the tilled zone but this has not penetrated greater than 30 cm. Continued monitoring will indicate whether it has been effective in alleviating the spring flush of zinc to the aquifer.

Instream zinc concentrations were depicted by OTIS (One-dimensional-Transport with Inflow and Storage) and it was also used to simulate the effect of two remediation scenarios on zinc concentrations at the mouth of Cement Creek. The Creek is dominated by inflows of natural and mining-related low-pH water. Preliminary simulations using the reactive solute-transport model OTEQ (OTis with EQuilibrium calculations) to account for instream pH changes were unsuccessful due to the partial nature of the mixing processes and lack of information on the thermodynamic properties of precipitates forming in mixing zones., Instream zinc concentrations were depicted by OTIS (One-dimensional-Transport with Inflow and Storage) and it was also used to simulate the effect of two remediation scenarios on zinc concentrations at the mouth of Cement Creek. The Creek is dominated by inflows of natural and mining-related low-pH water. Preliminary simulations using the reactive solute-transport model OTEQ (OTis with EQuilibrium calculations) to account for instream pH changes were unsuccessful due to the partial nature of the mixing processes and lack of information on the thermodynamic properties of precipitates forming in mixing zones.

Tailings deposits transported downstream from historical mining operations in the Leadville area are a possible source of acid and metal contamination to surface and groundwater. Four different approaches and observational scales were used by the US Geological Survey to study and evaluate the effects of these fluvial tailings on water quality: batch water-leaching tests of surficial material; excavation and leaching of an intact eight-inch diameter core; evaluation of water quality of shallow groundwater beneath the deposit; and water quality monitoring of an adjacent 5 km reach of the Arkansas River. The leaching of surficial samples indicates a ready source of water-soluble metals and high acidity but there are minimal measurable water quality effects in the river. The integration of the four scales of observation indicates that hydrogeochemical processes may attenuate metals as they migrate through the fluvial tailings deposit. The influence of storm events on water quality was not evaluated., Tailings deposits transported downstream from historical mining operations in the Leadville area are a possible source of acid and metal contamination to surface and groundwater. Four different approaches and observational scales were used by the US Geological Survey to study and evaluate the effects of these fluvial tailings on water quality: batch water-leaching tests of surficial material; excavation and leaching of an intact eight-inch diameter core; evaluation of water quality of shallow groundwater beneath the deposit; and water quality monitoring of an adjacent 5 km reach of the Arkansas River. The leaching of surficial samples indicates a ready source of water-soluble metals and high acidity but there are minimal measurable water quality effects in the river. The integration of the four scales of observation indicates that hydrogeochemical processes may attenuate metals as they migrate through the fluvial tailings deposit. The influence of storm events on water quality was not evaluated.

Column leaching experiments were carried out to simulate leaching of metals from the fluvial tailings deposit to shallow ground water. Unsaturated, partially saturated and fully saturated conditions were simulated. Leachates were analysed for pH, metal concentrations and specific conductance. For about the first 100 hours of unsaturated flow through the core, conductivity and metal concentrations rose steadily and pH fell below 3. Metal concentrations peaked at about 170 mg/l Zn, 110 mg/l Al, 35 mg/l Fe, 8,7 mg/l Mn, 4.0 mg/l Cd, 1.9 mg/l Cu and 0.1 mg/l Pb. The results show that large amounts of acidity and metals can be readily leached from these tailings deposits. The pH remained fairly stable under partially and fully saturated conditions, and Zn, Al, Mn, Cd and Cu concentrations declined. Pb exhibited unique behaviour throughout the leaching experiment indicating that there is a readily available reservoir of Pb throughout the tailings sample., Column leaching experiments were carried out to simulate leaching of metals from the fluvial tailings deposit to shallow ground water. Unsaturated, partially saturated and fully saturated conditions were simulated. Leachates were analysed for pH, metal concentrations and specific conductance. For about the first 100 hours of unsaturated flow through the core, conductivity and metal concentrations rose steadily and pH fell below 3. Metal concentrations peaked at about 170 mg/l Zn, 110 mg/l Al, 35 mg/l Fe, 8,7 mg/l Mn, 4.0 mg/l Cd, 1.9 mg/l Cu and 0.1 mg/l Pb. The results show that large amounts of acidity and metals can be readily leached from these tailings deposits. The pH remained fairly stable under partially and fully saturated conditions, and Zn, Al, Mn, Cd and Cu concentrations declined. Pb exhibited unique behaviour throughout the leaching experiment indicating that there is a readily available reservoir of Pb throughout the tailings sample.

The fluvial deposits are composed of mine wastes washed downstream from the Leadville Mining District, which contain gold, silver, lead and zinc ores mined over the last 100 years. Continuous cores were collected from a small fluvial tailings deposit, barren of living vegetation. Bulk chemical composition, mineralogy, and water-leachable chemical constituents were investigated for visually distinct sections of the cored material. A large reservoir of water-leachable lead was found; bulk lead concentrations were not a good indicator of water-leachable lead concentrations., The fluvial deposits are composed of mine wastes washed downstream from the Leadville Mining District, which contain gold, silver, lead and zinc ores mined over the last 100 years. Continuous cores were collected from a small fluvial tailings deposit, barren of living vegetation. Bulk chemical composition, mineralogy, and water-leachable chemical constituents were investigated for visually distinct sections of the cored material. A large reservoir of water-leachable lead was found; bulk lead concentrations were not a good indicator of water-leachable lead concentrations.

Vallombrosa, 1-4 septembre 1996, Technical Report NE-236, info:eu-repo/semantics/published