Leaking Pond

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geoff88

Forager
Jul 14, 2006
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SW England
Hi all,
hope you may be able to help. Some friends are having problems with their pond leaking.
The pond is about 20m across and something arround 1.5m deep when full. The leak has been coming from the area where the pond overflows into a stream. It seems that the leak has been going on for some time and has washed out some of the interior of the bank where it meets the stream. To compound matters the bank has some smallish trees on it that I think may be adding to the problems.
The pond has been partly drained and the water level is now below where the leaks are.
We have seen sonething called Bentonite which is a clay and is used to repair leaks anybody have any experience of anything this?

Geoff
 

swyn

Full Member
Nov 24, 2004
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I see that you are in the SW of the country so it is worth looking at this site for HYDRAULIC LIME products in particular NHL 5 graded. See www.theoldhousestore.co.uk. We use lime mortar as a matter on course nowdays as it blends in with the older cottages here. The NHL 5 rated is good for works where there is water and is reccommended for sea works too. This may help your friends repair the leak. This method would be aimed at masonary such as stones or bigger rocks.
We are lucky to be on a clay cap here in the Chilterns, there are many ponds locally. When they have been dredged it is best to ensure that those that are NOT spring fed have their bottoms puddled. This used to be done with cattle, but nowdays this is done with a digger bucket. I would imagine that the clay that you call Bentonite may be of a similar consistancy to our local clay(which if it is flint free makes very good bricks...see The Mersey tunnell) This would be used in several ways from slurry to solid.
An other idea is to make up sand bags with lime mortar mix and build a small wall infilling behind with your clay. The size of the wall is dictated by the size of the sandbags+ what is safe to lift! This method may be the easiest as I do not know if you are skilled at construction work and it is very disheartening to do a load of masonary work only to see it collapse when you turn your back. I would advise go up a little, along a bit more and leave for a day and repeat untill required height is reached and remember to lean in towards the bank.
There are also sites that specialise in using Willow woven into riverbanks to stop erosion but as we do not have running water I know nothing on this apart from what I have read and that is very little!
I hope even a small bit of this is useful from Swyn
 
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geoff88

Forager
Jul 14, 2006
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SW England
Thanks Swyn,
had been thinking about using willow hurdles or gabions then backfilling as you suggest. Just need to try to make it look natural but hessian sandbags could work too.
Bentonite comes as a dried powder and can be mixed with soil, when it becomes wet it expands and turns into a waterproof jelly.
Not too sure about the use of lime as the retaining bank is mostly rocks and soil.
Any thoughts about the trees on the bank? Are the roots holding the bank together or helping to destroy it? If it is windy will the tree rocking back and forth loosen the soil. The bank isn't very wide perhaps less tham 1m in places at tue top.

Geoff
 

swyn

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Nov 24, 2004
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Depending on the species or not as it probably makes no difference! If you pollard or crown the trees the root system will more than likely be beneficial in binding the bank. Also consider coppicing as this will allow bushy growth with no height at all.
Swyn.
 

Roving Rich

Full Member
Oct 13, 2003
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Nr Reading
I'm not sure about the use of Lime ? I believe it is poisonous to fish ?
But wattle and plug it with clay would seem to be the way to go to me. Trying to silt up the water as little as possible.

Cheers
Rich
 

sandsnakes

Full Member
May 22, 2006
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London
depends on the pH of your pond. also the lime if is in sacks will be captured and solid, so you wont have a massive run off into the pond as it will set hard in the sack. you could use portland cement in the same way. If you double sack and make sure the outer is hessian plants will grow on it very quickly.

sandsnakes
 

swyn

Full Member
Nov 24, 2004
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I hope that you do not think that I meant neat lime.... There is a mix ratio of: 2 soft sand 1 sharp sand and 1 hydraulic lime. With sandbags you could probably replace the sharp sand with 1 ballast to get the mix a little coarser. This is set with water so immersion is not a problem.
As Sandsnakes has said as this is in bags unless you have a disaster there should be little leakage. It is certainly worth doing a little experiment with mixes and given time you will be pleasantly surprised! Time is all important with this medium. This is why it was replaced by cement in the construction world as cement went 'off' overnight and with proper lime mix it takes about three days.
My reasons for suggesting this method was to use as natural a material as possible in an environment that needs treating with the greatest of care. Please remember that this is HYDRAULIC NOT HYDRATED lime. Hydrated you can get at virtually any builders merchant. Hydraulic is the real natural thing and consequently a little harder to obtain, although not horribly expensive for this.
Swyn
 

sandsnakes

Full Member
May 22, 2006
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London
Have you considered using clay in sacks?

Brunnel had the same problem and he used sacks filled with clay and with hazel rods driven through them. You could build your 'wall' drive long stakes through the sacks and then back fill with soil in hessian sacks. Job done. I know it lasts and works because you can still use the tunnel under the Thames.

:)

Sandsnakes

As Swyn said, natural and enviromentally friendly.