Sodium bentonite clay has been successfully used as a sealant for earth dams where the soil is of a permeable nature and where less than optimum compaction can be achieved. It is extremely important that the bentonite clay is incorporated and compacted correctly as less than satisfactory results may be obtained if attention is not given to applying the process correctly.
Bentonite clay is perfectly safe, environment-friendly and can be used in most earth dams, irrigation dams and channels, wildlife and domestic farm animal watering holes, without negatively impacting the environment.
Our expertise includes the construction and sealing of clear and polluted water storage dams, evaporation ponds, leach pads, wetlands, decorative ponds, and streams.
For the reader’s edification, we provide a very simplistic overview of the standard specification for using sodium bentonite in earth dam sealing which generally entails the following.
Sodium bentonite can be thought of as a concentrated clay such that relatively small amounts blended with sandy soils drastically reduces permeability.
Sodium bentonite is most effective, when used as a mixed blanket, in the construction stage of a dam or when an existing dam has been completely drained, as only under these conditions can the necessary compaction be achieved.
Mixed Blanket Method
- Pump out existing water.
- Loosen the soil in the area to be sealed to a depth of 200-300mm.
- All slopes should ideally be prepared to a maximum of 1:3
- Remove all plants, organic or foreign matter (stones, rocks, rubble, roots etc) from below the final water level.
- Wet the area to be sealed to * Wet Of Optimum
- Lay the bags of bentonite in a grid formation at centers to be advised.
- Open the bags and spread the bentonite evenly using a rake or similar implement.
- Mix the sodium bentonite into the soil by hand, disc plow, rotary tiller or rotavator, to achieve as accurate a mixture as possible.
- Compact the area using a smooth drum vibratory roller or similar compactor to provide a final sealed thickness of approximately 100-150mm.
- The last step would be to check the water levels and form an adequate spillway.
We advise on typical bentonite usage rates based on the dam specifications and on the quality and structure of the soil.
*The water content of a compacted soil is expressed with reference to the OMC (optimum moisture content). Thus, soils are said to be compacted dry of optimum or wet of optimum (i.e. on the dry side or wet side of OMC).
Sealing Leaking Dams Using The Sprinkle Method
When leaking occurs below the water level and the leakage area can be identified with reasonable accuracy, bentonite may be broadcast onto the surface of the water in that vicinity, several applications may be necessary to effectively seal the dams leak. Although some success may be obtained by using this method, it will not be as successful or reliable as the soil blanket method mentioned above as the very important aspect of soil compaction cannot be applied. One must also be aware of the fact that dam sealing using the sprinkle method requires a much coarser grade of sodium bentonite as the clay is sprinkled over the surface of the water and it must sink quickly to be drawn into the leaking area by the escaping water. Contact us for typical bentonite usage rates in this type of application.
If you would like to discuss any of the above or need advice on designing or sealing your earth dam, waterhole or similar please feel free to contact Barry from Bentonite SA today on +27 72 341 2428 or email your requirements to barry@bentonitesa.co.za