Prevent water seepage from earth dams

Water scarcity is a reality for all South Africans. The agricultural sector in particular is vulnerable to water risks as periods of drought become longer and more frequent.

Farmers need to improve the management of available water and get the most out of this valuable resource. One way of doing this is to reduce water losses by minimizing water seepage from earth dams.

Seepage occurs as the water seeks a path of least resistance through the dam wall and floor. If left unchecked, seepage will erode the embankment or foundation causing dam failure.

Envirobent® is a cost-efficient and durable product that prevents water seepage loss in earth dams. Produced by G&W Mineral Mineral Resources, Envirobent® is a natural clay that swell 11-15 times its original dry volume when coming in contact with water. When mixed with soil and hydrated, the clay particles swell to fill the void spaces in the soil, thus reducing the permeability of the soil.

The product is suitable for use in the initial construction of earth dam floors and walls. It can also be used to fix leaking earth dams by emptying the dam and treating it as recommended.

G&W Mineral Resources recommend that a mixed blanket method be used on site which entails the following:

1. Prepare the area to be sealed, but do not compact.
2. Remove all stones and vegetation. (make sure it is clean)
3. Place 40kg bags of Envirobent® in a grid formation (depending on the application rate).
4. Mix the Envirobent® with the selected soil to a depth of 100-150mm, followed by wetting/damping. However, do not wet too much as the mixture must still be able to be rolled without crumbling.
5. Compact the mixed layer well.
6. Cover the mixed layer with 150-200mm of cover soil.
7. Remove any remaining stones and vegetation.
8. Compact the 150-200mm cover soil.
9. Seal around pipes by placing a puddle flange around the pipe and forming a 100mm bead, consisting of one part Envirobent® and three parts soil, to create a tight fit between the pipe and dam structure.
10. Protect spillways with gravel or rocks.

Application rates of Envirobent® vary from 9 kg/m² for clay soil to 18 kg/m² for sandy soil. G&W Mineral Resources can recommend civil engineers to assist customers to achieve optimal mixtures.
A further consideration is to ensure that the slope of the dam wall does not exceed a 30° angle. If it does, a retaining wall will be required.
Contact G&W Mineral Resources for more information. Tel: 011 878 0354 or email heinrichu@gwminerals.co.za.