Biopolymers have several properties that make them attractive for use in geo-environmental engineering including their high affinity for heavy metals, non-toxicity, and sustainability. This study investigates the potential of using biopolymer-treated pond ash as a landfill liner by improving its strength, water permeability, pH reduction, and heavy metal attenuation capacity. Two biopolymers xanthan and gaur gum were used in percentages of 0.5, 1, 2, and 3 by dry weight of pond ash. The unconfined compressive strength at various curing periods of pond ash biopolymer compacted samples fulfils the landfill liner strength criteria. Biopolymer-treated pond ash showed a significant reduction in the hydraulic conductivity. The 28-day cured samples exhibit hydraulic conductivity of less than 10–9 m/s. Scanning electron microscopy images demonstrate how the addition of biopolymer caused beneficial changes in the geotechnical characteristics of the stabilized pond ash by causing gel plug development and bio-clogging in the pond ash matrix. The concentration of heavy metals in the leachate of stabilized pond ash decreased substantially due to encapsulation of metal ions in the matrix. The study demonstrates the use of biopolymer as an ideal landfill liner material over non-renewable material like bentonite.