Pond restoration - advice needed

[Cotham Marble]

a few thoughts:
(1) this looks agricultural/domestic rather than simply 'ornamental'. It would be worth looking at some old maps to see how old it may be. Some Councils have put the first edition OS maps for their respective County online - date is around 1885. Otherwise it probably means a trip to the local Records Office.

(2) if more than fifty years old the structure has probably been achieved by daming a spring head, it may be this dam that can be seen as the 'lining'. This probably exists on one side only.

(3) prolonged build up of leaf deposit in a pond can be very problematic. The material is subject only to very slow breakdown - primarily by anaerobic decay which can result in quantities of some very unpleasant gases being trapped within material. There may be a toxicity issue (hydrogen sulphide) which may be a concern both for any human invoved in clearing the pond, and for any resident wildlife.

(4) willow toxicity. I'm unsure how big a problem this can be - certainly there are cases where fish have been killed by willow leaf fall into still ponds.

CM

[Tursiops2]

Originally Posted by Cotham Marble

a few thoughts:
(1) this looks agricultural/domestic rather than simply 'ornamental'. It would be worth looking at some old maps to see how old it may be. Some Councils have put the first edition OS maps for their respective County online - date is around 1885. Otherwise it probably means a trip to the local Records Office.

(2) if more than fifty years old the structure has probably been achieved by daming a spring head, it may be this dam that can be seen as the 'lining'. This probably exists on one side only.

(3) prolonged build up of leaf deposit in a pond can be very problematic. The material is subject only to very slow breakdown - primarily by anaerobic decay which can result in quantities of some very unpleasant gases being trapped within material. There may be a toxicity issue (hydrogen sulphide) which may be a concern both for any human invoved in clearing the pond, and for any resident wildlife.

(4) willow toxicity. I'm unsure how big a problem this can be - certainly there are cases where fish have been killed by willow leaf fall into still ponds.

CM

Thank you Cotham Marble, that's just the sort of feedback I was hoping for:

1) Spot on. I followed your advice, did some online searching and found this excellent site Old-Maps - the online repository of historic maps - home page
They have maps of this area between 1888 and 1938 that clearly show the pond in a field outside the property boundary - obviously agricultural in origin, as you say. They also show a building to the SE of the pond which no longer exists. The garden area was obviously annexed to the pub, and trees planted, post-WW2.

2) Damming of spring head - distinctly possible. There are some subtle changes in ground level around the pond which could be related, and the stone/brickwork I noted could easily be the original spring head rather than just the mouth of a field drain.

3/4) Leaf build up + toxicity - this is what worries me. I wasn't aware that willow leaves were toxic, but I'll take your word for it. Presumably, the future management solution is daily removal of leaf-fall in the autumn, but what about the material that's already there? Can the situation be redeemed without draining the pond and removing all that sediment? (Actually, the archaeologist in me quite likes that idea, but it would be a difficult and messy job to do it by hand, and I don't think The Boss will share my enthusiasm ).

Btw, I've encountered H2S before. I expect you know that in small, non-lethal, quantities, Hydrogen Sulphide both anaesthetises the olfactory nerves, and acts as a laxative. I can vouch for this personally . Seriously though, I wouldn't have thought it would be a major hazard to anybody working the site, given that it's outdoors and the quantities will be fairly small. Don't know about the effects on wildlife though - does it affect the chemistry of water?

It's not a healthy pond. Friday's visit was not our first. We first went there on August Bank Holiday Sunday - the first really warm, sunny day of the summer. On a day like that, a pond like that should have been buzzing with life, but there was nothing. No pond skaters, no water boatmen, no damselflies, no gnats - nothing. It clearly has potential, but the question is, how much work is needed to develop it?

Where can I get more advice on this?

Much obliged
T2

[Tursiops2]

Originally Posted by Tursiops2

3/4) Leaf build up + toxicity - this is what worries me. I wasn't aware that willow leaves were toxic, but I'll take your word for it. Presumably, the future management solution is daily removal of leaf-fall in the autumn, but what about the material that's already there? Can the situation be redeemed without draining the pond and removing all that sediment? (Actually, the archaeologist in me quite likes that idea, but it would be a difficult and messy job to do it by hand, and I don't think The Boss will share my enthusiasm ).

Just had a chat with The Boss - draining and removal of leaf build up may be possible. Would this material then be suitable for use as a soil improver?
T2

[Gill Catton]

I han't heard about the willow leaf toxicity issue either - I would have thought most non garden ponds in the country have an attendant willow tree of some kind! - plus keeping fish numbers down is god for everything else!! I would imagine stirring any kind of leaf litter up has the potential to release toxic gases into the water and that might have an effect too......

[paulchandler6]

Originally Posted by Cotham Marble

(4) willow toxicity. I'm unsure how big a problem this can be - certainly there are cases where fish have been killed by willow leaf fall into still ponds.

CM

Not heard of this either. Is it the Tanin and/or salicylates or something else responsible?
Thanks

Paul

[Cotham Marble]

Originally Posted by Tursiops2

(Actually, the archaeologist in me quite likes that idea, but it would be a difficult and messy job to do it by hand, and I don't think The Boss will share my enthusiasm ). T2

This made me laugh - it was exactly my thinking when looking at your photos. I've recently done a bit of cursory research on a putative 'moat', now filled in and built over, the old maps were very useful - but so also was the most recent 1:1250 series which included culverts etc. In addition to paper format you can buy the 1:1250 series in data set form though it is expensive, also local authorities sell 1:500 block plans for planning purposes though I'm not sure what useful details these would have in a rural context.

Obviously this particular pond may be fed by a culvert from a water source that rises some distance away rather than an adjacent spring. This may have implications for the health of the pond as it increases the potential for contamination - slurry, pesticide/herbicide residue, road runoff, domestic oil heating oil spillage, sewerage leakage etc. It may be worth contacting the local Water comany to ask what records they have about the head water for the pond.

Willow leaf toxicity - I fear I may be guilty of promoting a modern myth as I can't find any hard evidence. This was something I heard about over twenty years ago and was specific to fish. However willow leaves do contain high levels of complex chemicals and in a closed system like a pond there must be some likelihood of a build up of toxicity where there is heavy leaf fall. In most UK watercourses where willow is prevalent, leaf fall is accompanied by seasonal increases in waterflow so there is a natural 'flushing' process.

The issue of toxic gasses trapped in sediments is an issue for a pond where the upper water 'strata supports resident fauna because by 'cleaning' one can do more harm than good - basically releasing gases that cause a mass kill, when the gases would otherwise disperse gradually without ill effect.

The H&S issue is just something to bear in mind - basically it's not a good idea to have someone working alone where they could get a blast of a gas that may cause them to pass out and fall into a body of water ! A circumstance in which I was put when a young and naieve gardener; not that I fell in but I was stumbling around in a pretty unco-ordinated fashion for a while. Luckily I didn't suffer any laxative effect

As you say the pond is not 'healthy' I think that increases the options for how you can proceed, however there are peole who offer 'consultancies' on pond management and given that this particular pond is not just a (potential) wildlife feature but also an established and possibly ancient landscape feature, it might be wise to seek expert advice, even if that were to cost.

All other things being equal - I'd make two suggestions. Firstly I would consider removing some of the encroaching trees. The Willow canopy is dense and makes a tough competitor for other plants you may want to introduce. Secondly, if there is no resident fauna I would consider 'cleaning' by using a Trash Pump. Obviously there's an issue of where tens of thousands of litres of grotty water are going to drain, but if that is feasible to sort out, then the bulk of the silting can simply be pumped out at relatively little cost without any fear of digging into the pond bed. Obvioulsly branches and larger debris will require removal by hand but Trash pumps deal with particles up 2cm. An alternative maybe to hire a slurry bowser.

I would treat any extracted sludge with caution, it would probably be safe to use as a soil conditioner though I'd suggest giving it a couple of months weathering before applying to beds.

Good luck

CM

[Tursiops2]

Originally Posted by Cotham Marble

I would consider removing some of the encroaching trees. The Willow canopy is dense and makes a tough competitor for other plants you may want to introduce.
CM

Oh yes, the trees . If it was just down to me, I'd take them out, and good riddance. Unfortunately it's not that simple. The only mature trees on the site, they are a major feature of the garden, providing a backdrop to, and view from, the pub and creating structure and character in an otherwise fairly nondescript garden. Taking them out would irrevocably alter that character, and that's something I want to avoid. If and when this becomes a live project, they'll just have to be worked around. I might take the Horse Chestnut out though.

Trash pump. I've heard of these, never used one, not sure if it would actually be appropriate. My guess (I emphasise "guess") is that the bank of sediment, once drained, will prove to be pretty solid, and removable by spade. Messy and smelly, but I've done worse jobs, and the rest of the pond seems fairly free of sediment. I'd also like the chance to retrieve any small items, e.g. coins etc, that might have ended up in there.

I take your point about historical/landscape value. The pub itself is Grade 2 listed, so there's obviously a lot of history there. I'll certainly look into that in more depth, as and when, and also the matter of water quality.

This is all speculation at the moment anyway. My friend is definitely interested in the place, and he's putting in his application, but he's not the only person applying. In the end, the brewery will decide who gets it. Fingers crossed .

Many thanks for your input, CM, it's much appreciated. And now... I have a report to write by Friday. I'd better get on with it .

All the best
T2

[Nick T]

Originally Posted by paulchandler6

Not heard of this either. Is it the Tanin and/or salicylates or something else responsible?
Thanks

Paul

Isn't it willow where Asprin was derived from ? If so then I guess that wildlife could OD on it.

It's been soooo long since I did chemestry but I'm sure Hydrogen sulphide & water gives you some acid or other - it wont help. If you remove the leaf litter I'd still leave it on the bank for a few days just in case ther are anything in there - if it's clear water it means it's not stagnant.

The willow may look nice but it's roots will be in the water somewhere and will be sucking it out but if you can't remove it ( and it will encourage some insects - you could always pollard it see the somerset levels - there are loads of pollarded willows there.

THe fact that is has some shade is a bonus. If you read most fishpond books they say that you need to have half to 1/3 of the surface covered to help keep the water clear so if it's in full sun your blanket weed problem will be worse.

I'm sot sure that Ferns would like to be planted on the beachy bit it may be too damp for them there but it sounds like a good place for iris and the like Candelabra pimula's as well ( take a trip to the northern RHS garden at Harlow Carr & look at there plantings. ALso you might want to import some cobbles for the Beach bit as well give you some areas for wildlife to bathe in. and finally I'd put in some nice water lillies or the like to give you some shade and somewhere for insects to get near the water and a few fish ( carp, tench that type of thing they will help contain the mozzies )