Dirt Moving Big Hole

[Diamondcutter]

I have a Ford 550 backhoe and I am trying to dig my pond down as deep as I can get it...hopefully 30 or 35 foot. I want to keep the walls as steep as I can with one pathway out (perhaps 200 feet or more long). So far I have been using the front end loader to dig. Would it be better to use the back hoe to pull down dirt from the walls before scooping it up? I can usually get a full load with one or two strikes but the ground is heavy clay with large gravel and it is getting harder. I want the pond deep to give me stable temperature water to use for geothermal system in my future house. Any advise would be appreciated.

[Gary Fowler]

If you have clay soils, anything more than 45 degree slope is just going to collapse into the pond when water fills it anyway due to wave action and softening of the clay. Vertical walls are only good in stone or other very stable materials. Taper your walls according to the angle of repose for dry material of the type soil that you have.
I would dig with the FEL rather than the hoe if you can get a full bucket. I dug a small pond using the FEL and a boxblade with scarifiers. Using the scarifiers to loosen up harder soil and rocks then attack it with the FEL. With a little coordinated effort, I could drop the box blade and loosen up while loading up a bucket with the FEL making one pass work for two tasks. The backhoe will dig out harder material than the FEL but try the boxblade and lower the scarifiers as far as they will go, that is assuming that you have one. You will have a huge pond if you get it 35 feet deep assuming a 45 slope, each side will be 70 feet plus what ever you get for the flat bottom. SO if it is like an upside down pyramid that is 140x140 minimum and at least one side would have to be double that to get down to an angle that you can climb your tractor out of. Maybe you should think of terracing it like a strip mine and forming a spiral road up and out.

[Mechanos]

On a related note: I believe that you need 1/4 acre of pond (at depth) for each ton of cooling needed.

[KenKubota]

I wouldn't go near even a ten foot vertical wall of clay and gravel. If I undersand your description correctly, your pond will likely end up contaminated with diesel, oil and human remains.

[MarkV]

The other thing I would be concerned about is digging through the clay layer that will hold the water and getting into a layer that will not. 30 -35 feet would not work in my area. Make sure you know your area. When you say the ground is getting harder...if that means more rock ledge...that is more pores than clay and can drain a pond.

MarkV

[Diamondcutter]

Thanks for the great info. I am totally new at this. Do you think I'm ok at trying to go down that far? I don't want the overall surface area to be too big as the area where I want is is only about 4 acres and I want my house next to it about 200 feet away. I'm not planning on a conventional heat extraction geothermal system. I want to build my own using a series of radiators in the heating & cooling system intake space. I think the water in the bottom of the pond should stay around 60 to 70 degrees year around in my area of Southwest Arkansas.

[Diamondcutter]

Thanks!

[Diamondcutter]

The clay and rock mixture seems about the same as I go down. It is just more compacted. Thanks.

[Diamondcutter]

I don't plan to get steeper than 35 to 45 degrees and I'll stay away from that on my tractor. I want a long slooping channel leading down into it.
Thanks,

[Gary Fowler]

I dont think you will need to go nearly that deep to keep the water at 65 degrees. I remember when a boy that diving into deep water, I didnt have to go very deep to get frigid even on hottest days. I would think 15 feet would be plenty but consult some of the experts in the area that do those ponds for advice. I know you dont need 35 feet for sure. You will likely hit ground water at about 10-12 feet and then you may have to stop anyway.