Batch experiments, mineralogical studies, and geochemical modeling were conducted to evaluate the effectiveness of sphagnum peat, calcium carbonate, and hydrated lime in removing dissolved concentrations of As, Mo, NO3, and U present in uranium-tailings pore water at Gunnison, Colorado. Amounts of As, Mo, and U removal by sphagnum peat, calcium carbonate, and hydrated lime at 5.0, 2.5, and 2.5 wt.%, respectively, were typically above 97 %. Nitrate removal ranged between 55 and 80 %. Significant contaminant removal was achieved by sphagnum peat alone at pH 3.18. Addition of 2.5 wt.% calcium carbonate to the sphagnum peat-tailings system resulted in formation of soluble uranyl carbonato complexes, which decreased the amount of U(VI) fixed onto sphagnum peat by a factor of 2. Addition of 2.5 wt.% hydrated lime to the acidic tailings increased Mo concentrations by a factor of 2 under moderately alkaline conditions (pH 12). During neutralization of tailings-pore water, precipitation of ferric oxyhydroxides may provide additional removal of As, Mo, and U(VI) from solution through adsorption and coprecipitation processes.