The acidic reservoir of the mine has long been a source of environmental concerns, primarily due to its potential to contaminate surrounding groundwater and surface water. This study aimed to assess the effectiveness of pollution control and seepage mitigation measures implemented around the reservoir, focusing on water quality, sediment quality, and groundwater contamination. From 2020 to 2024, water quality monitoring downstream of the acidic reservoir showed significant improvements, with heavy metal concentrations decreasing substantially. Specifically, Cu concentration at YB01 decreased by 59.4%, from 1590 mg/kg to 645 mg/kg, and Pb concentration dropped by 84.4%, from 83.2 mg/kg to 13 mg/kg. At YB02, the reductions in heavy metals were smaller, with Cu dropping by 36.9% and Pb by 17.5%, reflecting the influence of external factors like mountain runoff. Sediment analysis indicated that heavy metals primarily existed in stable, non-water-soluble forms, with Hg in the residual form reaching 91%, suggesting minimal bioavailability and low contamination risk. Groundwater monitoring revealed that the well outside the cutoff wall (TK01) exhibited stable water quality, with pH values ranging between 6.5 and 7.5, while the well inside the cutoff wall (YX05) showed fluctuations, including acidic pH values in 2024. Geophysical surveys using Electrical Resistivity Tomography (ERT) and Transient Electromagnetic (TEM) methods identified potential seepage pathways but no significant leakage through the dam body was detected during tracer tests. These findings provide strong evidence that the implemented seepage control measures, particularly the cutoff wall, have successfully reduced the environmental impact of the acidic reservoir, minimizing both groundwater and surface water contamination risks.