Cob: Bentonite

[Darel Henman]

Thanks for the information on ponds and lagoons, dcv..  Someone also
mentioned was the very old traditional use of gley, for pond or dam
usage.

Bentonite, a type of clay, can be used for this purpose as long as it is
wet.   From my understanding gley and clay shrinks when it dries,
leaving cracks.  There would be some kind of time period until any
cracks would become stopped.  For a full time wet pond this would not be
a problem.  

The concern should be about its performance when it would be dry and wet
alternatively.  
This should be a concern and used tested if possible.  In ponds the
cracks from the dried bottom clay let water through.  Usually, buckets
of general clay or special clay such as bentonite, are needed plug up
the cracks suffering from dry crack.   Anybody out there with experience
in this for dry and wet alternating situations.  There should be some
method to make it possible.

Darel

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> Having worked in excavating for several years, on occasion we would work in pond and
> lagoon construction. It was common to "patch" with Bentonite due to the fact that the
> pipe and other water tubing was often laid in place after the excavating was finished.
> Event though we were required to place and tamp adequate clay in place for water
> retention, some leakage would occur around the areas were the piping was installed. 
>  
> Although you should always follow the directions on the product bags, we double dosed the
> area and rototilled it to a depth of 12" in around the area - we never had any problems
> with additional "leaks" afterward. Once this material comes into contact with water it is
>  expands to something like 100 times its dry mass and coagulates or gels with the soil.
>  
> Just some info for your planning efforts.
>  
> dcv