Geochemical and geophysical investigations were performed in the area of the Komsomolsk tailings impoundment. Gold ore tailings produced with cyanidation have been generated by the Komsomolsk Gold Extraction Plant. The relatively low sulfide content in the Komsomolsk tailings and the presence of carbonates result in a low acid production potential (AP) for these tailings. The tailings pond is characterized by neutral to slightly alkaline conditions and metal concentrations, except for those of As and Sb, below the maximum permissible concentration (MPC). The situation is complicated by the fact that the displaced Berikul tailings are stored in the southern part of the Komsomolsk tailings impoundment. Sulfide concentrate cyanidation tailings were produced by the former Berikul Gold Extraction Plant. In the Berikul tailings, the sulfide content is approximately 25%. This high content has resulted in a high AP and the formation of acidic and ultra-acidic surface ponds (pH ∼2) with extremely high concentrations of metals and metalloids (As up to 4.1 g L−1). The estimated duration of acid drainage generated by the Berikul tailings is approximately 2400 years. Surface drainage from the tailings enters the Voskresenka River; as a result, the concentrations of As and Sb in the river water approach the MPCs established by the Russian Ministry of Health. Based on electrical resistivity tomography (ERT), the uncontrolled leakage of acidic and highly mineralized solutions through a natural geological fault into groundwater horizons was revealed. Groundwater contamination was confirmed via an analysis of drinking water from a well located near the fault.