Allotment Gardening Advice Help Chat
Chatting => Design and Construction => Topic started by: Balaton Ben on May 22, 2007, 21:37
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I am having a well dug in my garden and the cost is about 25 pounds per metre. The water table is about 6 metres and it has been suggested the dig goes to 10. The well sleeving is about 18 pounds per metre...say 430 pounds complete. Planning permission is not required [I live in Hungary].
Bearing in mind that I have a plot of over 1000 sq metres, the weather is like NY [hot in summer and can be v.cold in winter] and household water is quite expensive and metered, is this a good move?
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Interesting. Can't see why you'd go 4m below water table with the well - and surely not with the liner :?: Wouldn't that defeat the purpose (unless its porous of course)?
Sounds like a nice thing to have though. Do you have low summer rainfall then? How do you get the water out?
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I found this for you : http://www.met.hu/pages/climate/Some_characteristics_of_the_climate_of_Hungary_since_1901.pdf
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Thankyou for the weather link. Just a couple of days rain in the last month or so this end [west] of Lake Balaton. An electric pump will probably do the job and I think you are right about the sleeve. Will find out more hopefully in a few days.
Regards, Ben
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Interesting. Can't see why you'd go 4m below water table with the well - and surely not with the liner :?: Wouldn't that defeat the purpose (unless its porous of course)?
Sounds like a nice thing to have though. Do you have low summer rainfall then? How do you get the water out?
Would the water not rise through the hole at the bottom of the liner? The liner is surely there to stop the walls collapsing.
"When I were a lad" we lived in a house with a cellar, with just a compacted soil floor. Although a fair distance from the river, when it was in flood the cellar also flooded. The water did not come through the walls of the cellar, but rose through the soil floor. I hope you can see the analogy here.
I also cannot see though why you'd go 4m past the water table. As long as there was enough depth to get a pipe in for the pump, I'd have thought that would have been sufficient. But there again, I have no experience in these matters!
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Would the water not rise through the hole at the bottom of the liner?
It would but, unlike your cellar Dorothy, BB wants his well to be full of water so a porous liner would seem desirable. Lifting water by 6m takes quite a pump. I'm sure the experts will have it sussed.
What you might want to consider BB, is using the well as a source of heat too. Water from that depth will be a constant temperature year-round (estimate 11 degs C). This is a useful temperature as it is & with a heat pump it is a very useful temperature. All sorts of possible uses for home and/or horticulture.
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When excavating below ground water level (which will fluctuate depending on season), the water will rise in the excavation to a higher level know as standing water level (which can be considerably higher than GWL if there is an impervious layer over).
Water should find its own level in a waterproof liner unless you do something like excavate through a layer(s) of gravel into an impervious layer(s) of material below.
I would assume that anyone thinking of making a large investment in a well would have a small borehole made with an auger first.
I described my DIY well 3 days ago in the "Small Pond on Plot?" thread a few posts below this one.
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I described my DIY well 3 days ago in the "Small Pond on Plot?" thread a few posts below this one.
http://www.chat.allotment-garden.org/viewtopic.php?p=57247#57247 for those of you who missed it (and threads move a lot quicker than water tables :wink: )
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On my first plot many years ago I had a well, it was about 5-6 yards deep with a metal sleeve made from old oil drums this went all the way down to stop it collapsing in and the water level used to vary by a good 4' foot or so, summer to winter. I used to pull water by hand all summer.
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The water will naturally flow up the tube to the level of the water table, and (unless its an artesian well with the outlet below the water table) will then need pumping. The reason for extending below the level of the water table is a phenomenon called Draw Down. As water is pumped from the well, it is usually pumped at a faster rate that the flow rate through the rock, this leads to a depression of the table at the point of the well, lowering the table level. How fast you can draw of the water, depends on a function called the Hydraulic constant, which is found using an equation called Darcys Law, and takes into account the viscosity of the medium (ie water), the aquifer rocks porosity (how many holes are in it) and its permeability (how many holes are interconnected that water can flow through).
http://en.wikipedia.org/wiki/Darcys_law
Im guessing that the drilling company asked you how much water you intended to draw off and at what rate, and they have calculated the draw down taking that into account, hence they then specify that the well must be sunk to 4m below the table. If the well only went as far as the current level, then very quickly it would become exhausted.
wow! i knew studying S206 environmental science would come in handy one day! just amazed i remembered it.
Oddly, i was contemplating Darcys Law yesterday, for no apparent reason at all... :?
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have a plot of over 1000 sq metres
I have finally calculated the area of my (& my wifes) plots:
73 poles/1,845 m2/0.46 acre
We have no mains water supply or deep well.
We also assist my elderly, disabled father in law on his 20 poles, who also has no water other than what he can carry there.
So the above costs seem rather expensive for watering what is essentially only 40 poles.
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I understood that a pole was 16.5 feet, i.e. a linear measurement rather than an areal measurement. How are you relating 73 poles to 1845 sq m please?
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Sorry if I've got it wrong, but everyone at my allotment, at the Parish Council, District Council and Church Allotment management surveyors refer to a pole as a square pole when describing allotments.
So 20,049 sq ft = 73.64 pole (SQUARE)
Built up as follows (five plots: 4,5,8,9 &11)
Plots L W Sq Ft
4 49x 170.5ft = 8354.5
5 24.5x 149ft= 3650.5
8 24x 106ft= 2544
9 24x 110ft= 2640
11 26x 110ft= 2860
Total 20049 sq feet
20,049sq feet X 0.092 (approx 10sq ft/m2) = 1,844.51 m2
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Got you now. Many thanks for the explanation.
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:shock: wow zak the rabbit im inpressed nice one
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Having had wells in every house I've lived in, I think yours is a wise move, B.Ben. Concrete liners are the best as they'll last a long time, far more preferable than metal which can eventually give a 'tinny' taste to the water. And you always need the surplus below the water level, or as someone else put it, you'll run out too quickly. Once the well is finished, you'll need to keep an eye on the levels for a month or 2 to see just how much you use and how fast the well replenishes. If we did several loads of laundry in one day, then we could have a few short showers but no garden watering. That had to wait until next day when the level topped itself. If your well guy doesn't suggest it, then after they finish and the mud settles, pour 1 cup of household bleach into the well to kill existing pathogens. Don't use this on the garden until the faint bleachy taste goes away, often by the 2nd day. Repeat once a year to keep the well fresh.
Your's isn't a particularly deep well but should serve you well considering your situation. My current well is a drilled one, 270 ft (67.5M)with the level at 240ft (60 M) and cost about 37 quid per M plus all the extras. The bill for that one really hurt but dug wells are now forbidden by law where I live.
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The Well digging team of 4 turned up at 7am this morning and had a beer before digging out a slightly bigger round of 1 metre by 1 meter down [topsoil]. Rigged up a tripod gantry with steel hawser windlass, had another beer and then continued down through extremely sandy soil to the water table which was about 6 metres. Had another beer and then started lowering the 1 metre concrete interlocking sleeves. Had another beer and then continued excavating by hand sending up buckets of sandy sludge and lowering more sleeves down using 9 metres. Had another beer each. Put the final sleeve level with the ground to give a 1 metre platform. [The lagged the joints between the sleeves with strips of some material soaked in a cement solution] Dismantled and cleared their equipment and were gone before 2pm....job done!
I've just got to decide what to raise the water with and what to do with the hugh pile of sandy soil on my lawn!.....any suggestions?
Regards, Ben
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the obvious is a bucket and rope!
i would first consider an electric submersible pump, and some suitable waterproof cable and switchgear. But why not look into some form of wind pump?
I was expecting your well to have been a boretube, say 6inch diameter, for which a pump would have been easy. whatever pump you use will need to be self contained and have a pipe system of its own.
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Zak's right - lots of buckets and sweat, unless you know someone with a tractor and bucket to level it out or move it.
In the early 1900's in Ontario, farms everywhere watered cattle with small wells like yours using a small windmill unit, about 20 ft tall with an attached pump. The troughs self-filled as the cattle drank so they were located out in the fields where they were needed. Short of a hurricane, almost nothing went wrong with them, other than eventually going out of fashion (can you believe!). What a shame we don't use more today. Try Google for info.
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Forgot to post that I decided on a submersible elec pump in the end and it works very well [no pun intended] which is just as well [oh dear!!] as whereas UK has had rather a lot of rain, we have had very hot weather for months and our first real rain today.
Once again many thanks to members for your advice.