Sodium bentonite is a natural clay mineral that swells dramatically when it contacts water, creating an impermeable barrier that stops water seepage through dams and ponds. How Sodium Bentonite Seals Dams When applied to a dam or pond, sodium bentonite absorbs water and expands up to 15 times its dry volume. This expansion fills cracks, fissures and porous areas in the soil, creating a flexible waterproof liner. Application Method 1: Blanket Application The blanket method involves spreading dry bentonite granules evenly across the dam floor and walls at a rate of 8kg per m² (7–10kg/m² depending on soil type), then covering with 100-150mm of compacted soil. This method is ideal for new dam construction. Application Method 2: Reservoir (Pond in Pond) Method For existing dams, bentonite can be added directly to the water as a slurry or mixed into the top soil layer. The bentonite migrates to problem areas and seals leaks from within. Quantity Calculator Estimate your bentonite requirements by multiplying your dam’s total surface area (floor + walls, in m²) by 8kg: – 200m² surface area: approximately 1,600kg (1.6 tonnes) – 500m² surface area: approximately 4,000kg (4 tonnes) – 1,000m² surface area: approximately 8,000kg (8 tonnes) Contact us for a detailed site assessment and custom recommendation.