The wet closure of exposed tailings is a remediation technology that has been used to reduce or eliminate the toxicity and mobility of.heavy metal contaminants. For constructed wet closure cells, the application of this technology is easily accomplished and chemical amendments can be readily added, as needed, to control pH and dissolved metal concentrations. As part of the Warm Springs Ponds site remediation, exposed shoreline tailings located on the southern perimeter of Pond 2 in the Active Area of the Warm Springs Ponds Operable Unit of the Silver Bow Creek/Butte Area NPL Site (Anaconda, MT), were to be wet closed. During the flooding of these tailings, Pond 2 discharge was required to meet Interim Water Quality Standards and the impact of this remediation action on aquatic life was to be minimized. To address this problem, a series of soil column studies were undertaken to evaluate the suitability of direct surficial lime additions to exposed tailings. Results of these studies indicated that lime slurry application rate of 8.96 Mg ha·• (4.0 ton/acre) would be optimal in· reducing metal release into the overlying water column. Monitoring of dissolved metal concentration in Pond 2 discharge during the Pond raise showed slightly higher dissolved Cu concentrations (0.055 -0.105 mg/L) than predicted from column studies (0.050 mg/L). Complexation of dissolved Cu with organic exudates originating from a corresponding algal bloom in Pond 2 was believed responsible for the difference. Surficial lime application to exposed tailings prior to wet closure was effective in reducing metals release from tailings into the overlying water.Additional