I am getting 20,000 pounds of Bentonite delivered on Friday and was curious if anyone had a preferred method for adding the bentonite to the pond. I have seen a lot of mention of the mixed blanket and pure blanket methods. Does anyone have any experiences they would like to share on the benifits/drawback of each methods and which they prefer?
Mixed Blanket method is tilling the soil to 4 - 6", broadcasting the Bentonite, mixing the bentonite in, and then compacting.
Pure blanket is broadcasting the bentonite over the pond bottom, covering with 2 - 4" of local material, and compacting.
I am currently leaning towards the mixed blanket approach and covering it with 2- 4" of local material, compacting with a sheepsfoot after the mixed blanket and after adding local material.
I have a pic of Otto using his suggested method. Mixed Blanket method is tilling the soil to 4 - 6", broadcasting the Bentonite, mixing the bentonite in, and then compacting. I will post the pic later.
Maybe this will help, I too am thinking of using Bentonite. The local (Houston) Baroid rep wrote this paper on bentonite.
POND SEALING WITH BENTONITE 2010
Historically, clays have been used to provide earthen seals. Modern technology recognizes that sodium bentonite, a clay having superior qualities, will provide a better barrier to the movement of fresh water through soils.
Sodium bentonite is a unique material. In the presence of fresh water bentonite will swell. Depending on the quality of the bentonite and of the water, the bentonite will increase several dimensions in volume. When exposed to large volumes of fresh water, bentonite will continue to expand forming a “gel” slurry and eventually going into a state of free swell; breaking down into its smallest dimensions, resulting in muddy water. To prevent this from occurring in a “sealing” application the dry bentonite is protected by mixing it with the soil and then compacting into a sealing blanket.
It should be noted that the presence of salt or salt water can have a negative effect on the ability of the bentonite to fully hydrate and develop a satisfactory seal.
SITE PREPARATION:
Remove boulders, tree stumps, roots and foreign objects. Grade and level as necessary & cover exposed sand and gravel or any other area that obviously would leak with a “preliminary base” of the local clay. Sides or banks should have a slope in the range of 3:1.
BENTONITE:
The amount of bentonite required depends on the type of soil to be sealed. A soil engineering report would be helpful however a simple and cost-free analysis is described here.
In the bottom of a 5 gallon pail, drill 20 to 25 holes about an eighth to quarter inch diameter. Gather enough soil from the area to be sealed to fill about 3 inches of the pail. You can either select the most porous soil which is sand, or a mixture of soil taken from several areas of concern in order to present an average soil.
In this soil, mix 1 to 2 pounds of the selected bentonite and tamp down in the bottom of the pail. Into this, pour a gallon or two of water; wait and see if the bentonite as it swells, provides the necessary seal. This should only take a minute or two.
If not, repeat the process and increase the amount of bentonite by half a pound until the water is contained within the pail.
The bottom of the pail represents about one square foot. When you know how many pounds of bentonite it takes to seal the pail, then you know how many pounds per square foot to distribute and roto-till into the pond, dam, or other earthen structure.
BENTONITE SELECTION:
Sodium bentonite is available in various grind sizes, from a fine powder like drilling mud to 30-Mesh up to ¼ in chips. The two best particle sizes are Benseal an 8 mesh or Casing Seal which is a mixture of particle sizes. Any of these products are available from authorized Baroid IDP retailers.
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APPLICATION:
The required amount of bentonite is uniformly applied over the area of concern. Mix dry bentonite into the top 4 inches of the soil to be sealed. Moisten the working area with a spray of fresh water and compact, taking care not to puncture the sealing layer. In some instances the decision has been made to apply a second layer, consisting of compacted local clay approximately 2 inches thick. This is done to protect the bentonite-sealed area.
The sealed area never becomes hard but remains soft and plastic. Effort should be made to prevent punctures by hoofed animals, people or vehicles.
Experience indicates that in a bentonite-sealing project, the majority of success is dependent upon proper installation. The use of high quality sodium bentonite, adequate coverage and uniform placement are important for successful sealing. Bentonite is not a miracle or a magic material, it is just a tool to help you achieve a desired result and like any tool it must be properly used.
Often the customer wants to “short-cut” the process by dropping the bentonite through standing water. There is no possible way to determine exactly where the bentonite will settle making this a true hit & miss proposition. In addition as mentioned before a situation of free swell will occur that does not contribute to a long term seal.
If the customer insists on this method, it should be noted that while sodium bentonite is not toxic, the powder residues from the package can settle on gill plates of fish and suffocate them.
Phil Polak
Baroid IDP
817-832-5260
OK additional question, what type of roller to get to do the compaction smooth or sheepsfoot? Since this is the final compaction wouldn't a smooth roller be better?
With only 2-4" of cover, I would think a smooth roller would be better to avoid exposing the 'blanket'.
I am planning on using about a foot of cover to protect the blanket in case one of the horses finds his way through the fence and into the pond. If I'm all wet, someone please let me know.
Greg
Here are a couple of pics that might help.
Call Mike Otto and ask him.
Thanks for the pictures. That roller looks like the one I plan on renting. I will call otto in the AM.
This link will show an application chart depending on your soil type.
http://www.pondsealer.net/application.html