Herblady, Have done earth casting but nothing this size, too much excavation. I've used wood for large troughs. If you do the excavation, I'd love to see pictures. Billie

These will weigh over 600 pounds, even using light weight tufa but probably closer to 800.
They will need serious rebar reenforcement and how you get something that heavy out of the ground is beyond me.

Herblady, Although I have not made any troughs this large I have contemplated it. There are two ways that I have for lifting the troughs: 1.) A cable hoist or come-along and 2.) the tractor hydraulic lift with a boom pole. If you do not have a tractor then you can purchase a 1-ton come-along for less than $100. You will have to build a strong frame to place above the troughs to which you will attach the hoist. As Tufaenough says, you will need a substantial armature of steel bar and from this you will need to weld two lifting eyes that will stick up from the bottom of the trough and near the ends.

The other consideration is breaking the trough loose from the earth. This depends on shape and whether or not you line the "mold" with plastic or something. I am supposing that you want an "earthy" look, i.e., rugged, rocky, not uniform. In that case, with or without a lining, you will probably have to dig the earth away from the sides before you attemp to lift the trough.

Once you have the trough hoisted then you must have some way of transporting it.

This will be a major project but when you succeed (not "if you succeed") it will be a great raised herb bed. I saw a Martha Stewart magazine in which an article told about setting a large stone trough in place for her small herbs. It looked great and the top of the trough was about as high as one's hips... no bending!! Ever since then I have been looking for a place to do the same for my DW.

We would love to see pictures of your progress.

David

I think this might be easier if the 4 sides were cast flat with a bit of exposed steel at each end that would allow welding or drawbolting the four sides together.
I don't think a bottom is needed but if you want to keep out the crtters the troughs could be placed on a sheet steel mesh.

Tufaenough raises another question. Will the troughs rest on the ground or will they be elevated?

Again, you can tell the voice of experience. Tufaenough's idea of casting flat slabs and assembling them later is a good idea if the troughs will rest on the ground and be bottomless. You can always come back and patch the bolt holes later or else provide for the hardware to be inside the trough (as my lifting eyes would be). This does not really fit the concept of a trough but rather a raised bed with tufa borders.

A tufa bottom could be cast in place then the walls cemented in place on top of that.

I once read an article about large troughs being made in place with forms. This would alleviate your having to try and hoist and move them -- which sounds like it would be savage amusement on a good day -- with or without a tractor -- and this would also eliminate excavating that big trench. Forms could be made of wood; or perhaps 2" styrofoam insulation would be strong enough to hold. It comes in big sheets and wouldn't be too costly to make the form with this. Maybe someone has an idea of how they would tolerate the winter if they were semi-buried in the ground -- would the frost heave them?

Maybe this will help. Post some pictures -- this sounds like a great project!!

Wow! So much help! Thank you for all the insightful advice. I had NO idea that the troughs would weigh so much. As I said, I am new to this. I would love to have the primative, earthy look, but I believe that I need to abandon the idea of attempting to lift them out of the earth. I do have a tractor with a hoist, but I don't think I want to risk breaking them in the transport. I think the styrafoam forms constructed at the site of the herb bed will be the most logical way to proceed. Frost/freezing is not an issue in my area as in 18 years we have had only one winter of freezing temps low enough to bother my potted plants. I will keep you apprised of my progress. The rainy season seems to be trying to come early this week in the northwest, but I am hopeful that we will still have some dry weeks left...

Oh to live in a place where it hasn't frosted/frozen in 18 years...