The leachate produced by waste disposal sites contains a large amount of contaminants which are likely to pollute ground water. The impact of such sites upon ground water can be judged by monitoring the concentration of potential contaminants at a number of specific monitoring points. In this study, the quality of ground water around a municipal solid waste dumping site was investigated. Groundwater samples were collected from locations near the Ramchak–Bairiya landfill site in Patna, Bihar, to assess the influence of landfill leachate on groundwater quality. The samples were analyzed for major physicochemical parameters, including temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), total alkalinity, total hardness, chloride (Cl⁻), nitrate (NO₃⁻), calcium (Ca²⁺), magnesium (Mg²⁺), sodium (Na⁺), potassium (K⁺), and selected heavy metals (Pb, Cd, Cr, As, Ni and Co). Elevated EC, TDS, hardness, and nitrate concentrations were observed near the landfill boundary, demonstrating clear evidence of leachate infiltration and subsequent groundwater contamination. As landfill leachate typically contains complex mixtures of organic and inorganic pollutants, along with toxic heavy metals, its subsurface migration can significantly alter groundwater chemistry and frequently exceed BIS drinking water standards. The results indicate progressive groundwater degradation driven by uncontrolled leachate percolation and highlight the need for continuous monitoring, engineered leachate containment systems, and sustainable solid waste management practices to protect groundwater resources in landfill-affected regions.