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  1. #1
    Member Rank = Tosai Paul Sabucchi's Avatar
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    Advice needed planning cover for 19'x40' pond

    I am starting to plan how to cover the pond and bog areas. The pond is entirely in ground and in direct sunlight all day. Here on a hill in central Italy temperatures dip below freezing maybe only a dozen nights a year and most days are sunny so I would need to heat only very occasionally. I have some constraints: wind can get really strong, it can dump a fair bit of snow and I usually can rely on no one to help me putting it in place or taking it down.
    Because of the wind I am thinking of making a low A frame, the ridge beam only about 3' above the ground. The strongest winds are usually from the west and I have recently attached a windbreak to the sturdy pond fence on that side to give a bit of shelter, occasionally we get strong gales from the east but the wood chalet should give good cover. South is sheltered by the barn and north is in the lee of the hill.
    Snowfall usually ammounts to 10" or so once or twice a year but maybe once or twice a decade we get a bumper dump of 3' or more, and it can be wet heavy stuff (you would not think that in central Italy on a hill with sea view a snowblower would be an essential bit of kit).
    The wood beams I can most easily get and that I can manage on my own without getting a hernia are 4m 8x8cm (13' 3"x3"), so thinking of building in three 4m long sections with 3 (10') legs each side, span between legs is 1.48m (4.7'). I am thinking of making custom brackets with 90x90mm steel box section 3mm thick so I can easily slip the beams in and hold them in place with a few screws. The whole frame then would be covered by the toughest polyethylene sheet I can get (at least 200micron, hopefully 300micron) and suitably ancored down.
    I would need, on the rare days it snows, to be able to heat the "polytunnel" so the snow would melt as it touches the polyethylene, volume would be approximately 33 cubic meters (1165 cubic feet) so was thinking of ducting hot air from a propane forced air shop heater, I can check with the local nurseries how they keep their polytunnells from buckling.
    Advice much appreciated


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  3. #2
    Member Rank = Tosai Paul Sabucchi's Avatar
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    This is the kind of "above average" snowfall I could have to deal with, the video is from 3 winters ago and the pond is now just by the barn
    https://youtu.be/IeTuGDwkVMQ

  4. #3
    Senior Member Rank = Adult Champion smartin's Avatar
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    Wow that looks very picturesque Paul in the snow..... agree due to potential volume of snow a sloping roof on your cover would be sensible and the heater is a good idea however fumes could well be an issue from the propane as it will build up within the tunnel ..... if you heated the pond via an ASHP however the rising heat from your pond would keep the poly warm enough to melt the snow on contact i would of thought..... Steve
    2200 gallons, infinity window, BD
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  6. #4
    Member Rank = Tosai Paul Sabucchi's Avatar
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    I am not so sure that keeping the pond a few degrees warmer would radiate enough heat to melt the snow falling on the tarp 3 foot above it. Again I am not concerned about the bog standard 10" or so of snow falling, that is only the equivalent of about 1" of water. It is the exceptional snowfalls that have happened here 3 times over the last 16 years, I mean WAIST TO CHEST HIGH in a matter of 48 hours.
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  8. #5
    Member Rank = Tosai Paul Sabucchi's Avatar
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    I think over the next few weeks I will go ahead and build the structure, seriously considering to attach to the underside of each leg (but not on the outermost ones) one of these greenhouse heaters. That would make it 14 X 135w heaters.
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  9. #6
    Extreme Koi Member Rank = Kyusai NickK-UK's Avatar
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    You may also want to look at surface running off during the melt. If the pond is level with the ground, the water will melt off the cover and drop into the ground - it will then find the easiest path.. which is likely to be into the pond.

    Overflowing is one thing, but keeping any ground chemicals from leaching and washing along with the melt is another concern. This was one of the decisions not to make my new pond build at ground level.

    You could use a French drain around the pond and then pass the water out further down the hill side. Careful though over time it will errode a channel as the exit water makes it's way down the hillside (or soaks in).
    1700 litres on 50 watts
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  10. #7
    Member Rank = Tosai Paul Sabucchi's Avatar
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    Quote Originally Posted by NickK-UK View Post
    You may also want to look at surface running off during the melt. If the pond is level with the ground, the water will melt off the cover and drop into the ground - it will then find the easiest path.. which is likely to be into the pond.

    Overflowing is one thing, but keeping any ground chemicals from leaching and washing along with the melt is another concern. This was one of the decisions not to make my new pond build at ground level.

    You could use a French drain around the pond and then pass the water out further down the hill side. Careful though over time it will errode a channel as the exit water makes it's way down the hillside (or soaks in).
    Thank you for the advice, always appreciated. Pond edges are raised 2-3" (on account of the prestressed concrete beams I used all around) and soil around slopes away from the pond to avoid runoff flowing in the pond so no big concerned on that account.
    One issue I may have to deal with is the downhill side to the pond. Soil here sets hard as concrete when dry but if it gets really soaked it can slide (the more so with the pressure from the water pushing from the other side) so I will probably cover it with some kind of semi-permeable membrane to allow for most of the rainwater/snowmelt to pour downhill rather than seep into the soil.
    Am I getting old or is the weather not what it used to be? At least here in Italy it seems to swing between extreme drought/heat (119.84f this summer in Sicily) and bad weather with floods and medicanes (Mediterranean hurricanes) a fortnight ago two men were killed by a tornado in Pantelleria (island south of Sicily) and yesterday another tornado caused a lot of damage in northern Italy.
    As these weather phenomena get more unpredictable and extreme it gets more difficult to prepare for them.
    If the scaremongers are right after all and the Gulf current gets disrupted who knows what will happen to the weather in Britain
    10k gal. 2 BIG BOGS

 

 

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