permaculture

[Nick Ritar <nick@milkwood.net>]

Hey all,

We've built quite a few dams on our place that have leaked over the years
due to dispersive clays and shale. We've tried quite a few methods to seal
them with variable success.

*Method 1 - Bentonite*
Bentonite does not seem to be effective at all when used with our
dispersive clays and shale. We have added up to 500kg of bentonite by
raking into the wall in a 1 megalitre dam with no appreciable improvement.

*Method 2 - Artifical gley & plastic liner*
We laid a thick layer over the entire dam wall of nitrogen rich lucerne
(alfalfa) hay (20cm compacted) , added additional urea in order to create a
manure like material then covered with a layer of thin, cheap, black
builders plastic film. Then buried it in a 30cm thick layer of rock and
clay. We tried this in 4 dams with varied success. In one dam it's worked
perfectly, in two it's worked ok and in one it had no benefit at all. It
was difficult, expensive and I didn't like using the plastic or urea for
obvious reasons.

*Method 3 - Polyacrylamide**
*
This is sold in Australia as "Water$ave Plug"
http://www.polymerinnovations.com.au/ It does seem to help and is very easy
to apply, but it is expensive stuff and i am very dubious of it's impact on
the environment and human health. We have only used it on one dam and that
dam does still leak, although much less than previously.

*Method 4 - Gypsum*
It seemed counterintuitive, given that gypsum is used to improve
infiltration in heavy clays, but when you add gypsum to dispersive clays,
it binds the particles together to make them large enough to to "plug"
leaks. We added about 1000kg raked into the wall of a 1.8Ml dam wall....
 it worked a treat and had the added benefit of clarifying the water in the
dam.

I'd really like to use more natural methods in the future, such as animal
manure and green leafy gleys and the general addition of organic matter to
build algae, but when we were faced with these issues in a remote location
in startup phase we have been short of animals and green leafy material,
hence the above experimentation

Anyhow, you can read more about our dam building sagas if your interested
here http://milkwood.net/tag/dams/ ... keep in mind that our experience
must be kept in context with the particular material type we have to work
with here in central west NSW.

Happy new year!

Cheers
Nick Ritar
http://www.milkwoodpermaculture.com.au
http://www.regenag.com


On Sat, Jan 7, 2012 at 9:12 AM, Toby Hemenway <toby@patternliteracy.com>wrote:

> > On Jan 5, 2012, at 3:08 PM, Cory Brennan wrote:
> >
> > Gley the pond with pig or cow manure, it will be watertight. At Pine
> Ridge, the rancher there puts salt licks in his dams and the cows stay
> there and poop. It takes a couple of years, but it's watertight.  You can
> do it in a couple of days with a bobcat.
>
> I'm curious about gleying ponds. We have a big old pond here in Sonoma
> that had a cheap liner that failed due to deer hooves and age, and
> replacing the liner would be expensive and a lot of oil. I've not
> personally been involved in gleying, and would love to hear details from
> people who have actually done it successfully. Many people mention it, but
> few seem to have actually done it.
>
> The hole for the pond is about 1400 square feet, 10 feet deep, and in a
> soil with silty clay, and shale just below a soil layer. The old liner is
> still in it, with many punctures.
>
> I've done some pond work with bentonite, too, and would appreciate hearing
> of experience with that, as that is another option.
>
> Toby
> http://patternliteracy.com
>
>
>
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