Mixed Blanket Method

  • Empty the dam or pond by pumping out all existing water.
  • Loosen the soil in the area to be sealed to a depth of 200-300mm.
  • Adjust all slopes to a maximum slope of 1:3 (approximately 18 degrees)
  • Prepare the entire area below the final water level by removing all plants, organic or foreign matter (stones, rocks, rubble, roots etc)
  • Wet the entire area to be sealed to  *Wet Of Optimum
  • Lay the bags of bentonite in a grid formation across the area to be sealed. (grid centers to be advised based on the type of soil being sealed.
  • 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, the water quality and the quality and structure of the soil.

* Wet Of Optimum

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).