Failure to hold water is the most common problem with earth dams. The earth dams that do leak were not planned and build properly and sometimes it is hard to pinpoint the exact cause of the problem.
Common causes of dam leakage are the work of a contractor unfamiliar with earth dam construction, failure to remove topsoil and vegetation at the embankment site, use of an unsuitable soil type in the dam wall, failure to construct a cutoff trench, poor soil compaction, failure to back fill exposed rock, gravel or sand in the storage basin and poor maintenance of the dam.
The method used to repair the dam is often determined by the cost of the repairs in relation to the short or long term benefits.
The methods that we use to seal earth dams include:
Clay lining with available local material.
If suitable clay can be found on or near your property then clay lining may be a cost-effective way of sealing your dam. There are several ways to use clay lining to seal a dam depending on the nature of the seepage problem. The cost of clay lining depends on many factors including the transport cost of the clay, the amount of clay to be moved, the cost of emptying the dam and access to the site.
Bentonite is a naturally occurring clay which is commercially mined. In dam building it is useful because, when it is wet, it swells to many times its dry volume. We use bentonite in several ways depending on the soil type on site and whether it is practical to empty the dam. The area to be treated is first cleared of loose rocks and vegetation, and then it is rotavated. After the bentonite is spread over the area it is mixed with the existing soil by rotavating and then compacting with a roller. The bentonite is then covered by a layer of site soil to prevent cracks developing in the bentonite blanked as it dries out. The product that we use is locally manufactured and is environmental friendly. After a dam is treated with bentonite the water is save for animals to drink.
There are a few types of commercial liners available to seal leaking dams. They are all flexible membranes but offer different levels of strength, durability and resistance to UV breakdown. The soil on which the liner rests must be well compacted, offer an even grade, have no vegetation and be free from protrusions like stone and branches which would damage the liner.