pond - clay or butyl liner???

[Rainy]

Hi
were planning to dig a pond this summer - mainly for our ducks who have a paddling pool at present. Weve identified the spot - its the lowest point on our land and is under a couple of inches of water naturally from September to April. Our dilemma is - do we line the pond with a butyl liner or line it with our own clay. Our soil is about 16" beautiful loam on top of heavy clay. Anyone any advice / experience to share?

[ohareward]

Hi Rainy, You can make the clay more water resistant by mixing lime with it. I am not sure of the ratio, but if you dig out the top soil down to good clay and then sprinkle the lime over and work it in to the top few millimetres it should keep the water in. Try a small sample batch first. Test it with water to see how water proof it will be. You can use a bowl to form the clay so it will hold water.

Robin

[Rainy]

hi
thanks for that. Any suggestions as to how I could get the standing water into the pond as I suppose it wont get in once the pond is formed. If I keep the edge of the pond at the lowest point of the land do you think the water would drain in?

[ohareward]

Hi Rainy. Where is the standing water in relation to the pond site? You could try syphoning it, or channelling it with old guttering.

Robin

[Rainy]

Morning
the pond site is actually within the area that gets standing water. The area covered by the water is about 4m x 10m and I was planning to make the pond about 3m x 5m. Its dry now so I was planning to dig it soon. Our neighbour has a mini digger so at least we wont have to dig it by hand
I'd like it to be quite deep in the middle to avoid winter freezing and also so the ducks can feel safe [ish] on the water. Any tips on how steep I can make the sides without having to reinforce them?

[Paddy's mum]

I'm sure I once read somewhere that if you use a liner in an area where water rises naturally, it will, in the end, cause your liner to drift and bow upwards.

Maybe a call to a large water gardens could get you some good advice.

[Andy Hamilton]

It has to be 2 foot or about 60cm deep in one area to stop all of it freezing.

Clay sounds like a better option, simply because it is more natural. I found this someone how has experienced some problems with a clay lined pond, it might help.

[Rainy]

Thanks that link was useful - and very detailed!
Weve decided to go with clay although I still need to research exactly how to use the lime with it. Weve figured that if we locate the pond in the area that holds water naturally its not going to leek as water is never going to travel upwards . I suppose there could be a wicking effect if the surrounding soil is bone dry but where I live bone dry doesnt happen too often. We can divert rainwater from the roof of our double garage as well - just need to read up on the logistics of dowspouts !!!

[ohareward]

Hi Rainy, I used to do some work with a Geotechnical Engineer. It's to do with soil erosion and the like. The hills to the east of Christchurch and Banks Peninsular are over laid with loess coluvium which is a clay. When it is wet and able to move like in a land slide it goes like porridge. When it is dry it is like concrete. If the rain water gets into the clay and the clay is not held by a retaining wall it can form a tunnel gully and it will keep washing away the clay. To help stop this happening, lime is poured down the start of the tunnel gully and washed down by hose. This is done until the water runs clear. If a concrete path has been washed out underneath, lime is mixed with the clay to form a pug similar to putty. This is rammed into the hole to seal off the water. It is the lime and clay mix that fixes it. I think the ratio is about 1:50. It's a while since I worked on it. I know it was not much. You can either do it by hand or mix it with a concrete mixer.

Robin

[ohareward]

Small correction to above post. I had clay was poured down tunnel gully. It should have read, lime.

Robin

[matty]

You have to try different ratios of lime to clay i believe, as different clay have different properties... try a small patch first. We have a clay out here though that is so awkward the lime thing apparently doesnt really work.