Bentonite is a natural clay, which has the ability to swell more than 15 times its normal volume when placed in water. This property is used in the making of a seal in a soil layer. When Bentonite is mixed with soil, and compacted, it swells when water is added filling all the voids between the soil particles. As a result, the opportunity for water to pass through the soil is greatly reduced.

The dam is then excavated and contoured to its final shape with gradual side walls (approximately 20 degrees) the dam needs to be cleared of vegetation, rocks, and foreign material, and the top layer is loosened to 150 mm. Use a sprinkler to wet the loosened soil, do not over wet so that it is muddy. The Bentonite is then spread on top of the surface. Using a rotovator or by hand, mix the Bentonite into the soil. Finally, the area is compacted using a roller, plate compactor or similar equipment until a suitable degree of compaction is obtained. Correct compaction is vitally important to sealing the dam with Bentonite.

Depending on the size of the animals that will roam the dam, the layer of soil/bentonite need to be cover with another layer of soil between 100 – 300mm to prevent the animal from stepping through bentonite layer.

Place rocks, rip rap on the sides of running water or at the inlet so that the bentonite layer will not be washed away.

After compaction the area is then further hydrated by wetting the surface thoroughly. This allows the Bentonite to swell within the soil structure, after a couple of hours the dam can be filled.

As Bentonite takes time to fully hydrate, a certain amount of water loss is experienced initially. After a few days that loss will be reduced and the dam, or pond will successfully retain water.

Due to the simple application methods, Bentonite is ideally suited to both the skilled and unskilled user. Once installed, it forms an integral part of the pond or dam, and being a natural clay it is completely safe for animals or fish. Its function in soils is well understood and with technical advise from the suppliers, a successful result can be assured.

Mixed Blanket Method