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Hand building a clay pond

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GemmaJF View Drop Down
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    Posted: 19 Sep 2011 at 2:15pm
Hi all,

Has anyone any experience of forming a small clay pond by hand along the lines of the old dew ponds?

I'm up to speed with doing this on a large scale these days, it involves a JCB, a supply of suitable clay delivered and and some form of mechanical compactor, geofabrics etc.

This is fine for building a GCN pond during a mitigation, but my needs are a little less demanding.

We have what was an established wildlife pond. It's not large but not that small either. Interestingly it never did dry up completely long after the PVC liner perished. I remember well only digging so far originally, well because I hit very heavy clay. 

The idea now is to remove all the plant shelves I originally put in, make it a gentle gradient and line with the naturally occurring clay at the bottom of the pond. The species to benefit are our smooth newt population.

Any tips or thoughts etc appreciated. I'm particularly concerned regarding capillary leaching of water as there will be a reasonably deep top soil layer surrounding the pond. I'm also prepared to the line with an artificial liner if it doesn't all workout, it would though be very nice indeed to form a pond without the need of an artificial liner.
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Caleb View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Caleb Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 2011 at 9:47am
I don't have any hands-on experience, but I did look into it a while ago for volunteer project with a derelict school pond, about 10m x 5m. In the end, it was decided against, mainly because of the amount of labour needed, and difficulty in finding a clay supplier.

If I remember right, it was recommended (probably by BTCV) to use a very gentle gradient, apply clay about a foot deep, take one man-hour per square foot to puddle it, and not to let it dry out under any circumstances.

This worked out to about 15 tonnes of clay, and 550 man-hours of puddling- that's when a liner started looking more appealing. We didn't get as far as thinking about capillary barriers.

The shallow gradient needed means that it would have to be a pretty big pond to get any reasonable depth- but then you'd have to dig a pretty big hole to get enough clay anyway.

Sounds like a fantastic project, but not the sort of thing that could be done in a weekend...


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GemmaJF View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GemmaJF Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 2011 at 10:31am
Cheers Caleb very helpful info. I'm mostly considering the project to battle the winter blues, the more time I spend outside the happier I am, but mostly in the winters I hibernate and stay indoors, then get depressed. Puddling a pond on freezing cold days actually has some appeal compared to depression lol.

I think my main problem will be to get a gentle gradient and reasonable depth. here is the pond as it appears at the moment:



The water in the sump has sat there all summer which sparked the idea that  a natural pond was possible. Max dimensions are 5.4m x 4.6m current max depth is 60cm. Standing water is about 20cm at deepest point. I'm pretty much constrained to the max dimensions as the pond already takes up as much available space as possible.

I think the issue is going to be that to dig out the clay from the bottom, the pond is going to get deeper and thus the sides steeper, making it very difficult to produce the gentle gradient required. 

I guess one option would be to go for a sunken pond, thus avoiding capillary action of the top soil  and making it easier to form a gentle gradient. Not entirely sure if that is what I would want though, as seeing water in the garden is part of the appeal of a pond for me.
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Hawley View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hawley Quote  Post ReplyReply Direct Link To This Post Posted: 21 Sep 2011 at 1:40pm
You could try asking Chris Rumming, he knows a lot about ponds. His website is http://www.rummingfishpond.net/contact.html 
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Caleb View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Caleb Quote  Post ReplyReply Direct Link To This Post Posted: 22 Sep 2011 at 9:11am
Originally posted by GemmaJF GemmaJF wrote:

I think the issue is going to be that to dig out the clay from the bottom, the pond is going to get deeper and thus the sides steeper, making it very difficult to produce the gentle gradient required. 


In theory, you could dig out the whole pond to depth, and put the topsoil back under the clay. Sounds like a lot of work, though.

I've just a found a section on puddling in 'The Pond Book' by Valerie Porter, which makes it sound a bit easier than I'd been led to believe:


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GemmaJF View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GemmaJF Quote  Post ReplyReply Direct Link To This Post Posted: 22 Sep 2011 at 9:45pm
Cheers Caleb. The thought of digging out the top soil, then digging out the clay, filling with top soil and lining with the clay might just be the answer. I was pondering this myself yesterday.

I like Valerie's method, sounds much more doable than other stuff I've read and I think is exactly what I was looking for, a scaled-down method for a garden pond. Does she mention anywhere the gradient? I don't know why but for some reason I think it might not need to be so shallow on a smaller scale. Not sure why I think this, perhaps something I read a long time ago.

I'll go for it I think and see what I end up with. Not sure where I would find soot these days though, perhaps I can find a local chimney sweep.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Caleb Quote  Post ReplyReply Direct Link To This Post Posted: 26 Sep 2011 at 3:32pm
Originally posted by GemmaJF GemmaJF wrote:

Does she mention anywhere the gradient?


She says that clay is suitable for 'any shape or gradient'. Presumably the more vertical it gets, the more difficult it will be to compress it properly...

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GemmaJF View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GemmaJF Quote  Post ReplyReply Direct Link To This Post Posted: 26 Sep 2011 at 5:59pm
Excellent, I'll be getting on a bit with it tomorrow, shall post up some progress as I go along.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote herpetologic2 Quote  Post ReplyReply Direct Link To This Post Posted: 26 Sep 2011 at 6:07pm
Do you need the depth? would it be possible to make it shallower? reprofile the shape of the pond perhaps and re puddle?


Report your sightings to the Record Pool http://arguk.org/recording
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Suzy Quote  Post ReplyReply Direct Link To This Post Posted: 26 Sep 2011 at 7:01pm
I think traditionally these ponds were like massive saucers - i.e. round and shallow. They must have overflowed with rain at times but often there was water in the centre but not right to the edges where the grass grew. The edges were kept plastic by the sheep's feet trampling as they walked to get to the water. At night the water vapour/mist condensed on this cold shiny surface and trickled down into the pond. It does seem like some sort of magic but these ponds used to hold water even in the driest summers when spring fed ponds had dried up.
The ponds are supposedly good for newts as fish can't get along in them as they are not very permanent. How this quite squares up with always holding water I'm not sure!
My brother remembers a GCN dewpond in Dorset being ruined by the National Trust who dug it all out to improve it and after that it never held water and all the GCNs disappeared!
Lime was often put under the pond to stop burrowing earthworms destroying the clay liner.
Suz
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