The one good word I have for the technique called puddling is that it is as good with concrete as it is bad with clay. It works out so well, in fact, that nearly half the ponds being built in the country today are being puddles with concrete.
The one possible disadvantage of-a puddled pond is that it may not have the permanent, indestructible strength of a sunken, straight-sided, reinforced concrete structure which has been poured into wooden forms. Handled correctly, nevertheless, puddled concrete will be strong enough to serve for many years with little or no repair work.
In other comparisons, the puddled pond comes out way ahead. It is cheaper because it takes less concrete. It is less work because it requires only a narrow, extremely simple form for the concrete. Most important of all, it enables a water gardener to dig his pond in exactly the shape he wants it, whether geometrical or in free form.
Puddling a Concrete Pond
You can make a puddled concrete pond (see Drawing 15) in much the same way as a pond poured into forms. There are just fewer steps to the job.
Use the same guides (given in Chapter 1) as to how big to make your pond and where to put it. The shape, particularly if it is irregular, will take a bit of pondering. Outline some trial shapes with the garden hose or a clothesline, as in Drawing 16, and think about them a few days before you start to work.
Once you have decided on the shape, move around the outside of the outline you have formed, driving stout stakes into the ground every 30 inches. Space them a bit closer along the sharper Curves of the outline.
With a string level, determine which stake has been driven into the highest bit of ground, and plan for the rim of the pond to extend an inch or so above ground level at that point. From a mark on the high stake, use the string level to transfer the level point to all the other stakes, and mark them accordingly.(See Drawing 4).
Strips of quarter-inch plywood, cut cross-grain, make the best forms. With shingle nails, fasten the strips lightly to the stakes along the level points. Apply the string level again (and again and again) and when you are sure the form for the pond rim is level, go around and nail the strips securely to the stakes (Drawing 17).
If the site is uneven but the form for the rim is perfectly level, the form will now be touching the ground in some places, standing above
it in other places. When you start excavating, use the dirt to bank in the low spots.
Here, as with other types of ponds, the ideal water depth is 2 feet, and the ideal thickness for the pond shell is 6 inches. However, the pond walls can safely be tapered to a 4-inch thickness at the top if you prefer. The pond shell should set upon a 3- to 4-inch layer of tamped cinders or crushed stone. Therefore, the depth of the excavation will be 2 feet, plus 6 inches for the floor, plus 3 or 4 inches for the foundation layer of cinders or stone.
The end of the pond in which you will locate the outlet-if an outlet is planned-should be dug an inch or two deeper, with the rest of the floor sloping toward it.
While excavating, do not make the slope of the walls any steeper than 40 to 45 degrees. Wet concrete won’t stay in p1ace on a steeper grade.
When the excavation is finished, and when whatever drainage and overflow facilities you desire are in place, spread the cinders or stone and tamp them into a 3- to 4-inch layer, upon both floor and sloping walls.
Reinforcing steel is even more important in a puddled pond than it is in a poured concrete shell. Spread the steel upon the tamped cinders, as shown in Drawing 19. Short lengths of wire can be fashioned into huge hairpins which are quite effective in pinning the steel into place and holding it in position so the concrete will envelop it evenly.
Unless you remember a great deal more solid geometry than I do, you will probably have trouble working out the volume of concrete required for any pond of irregular shape. The easiest thing to do is have a dealer in mixed concrete take a look at your ready-to-pour excavation, and then order according to his specifications.
If you plan to mix your own concrete, estimate your needed volume as best you can, and keep the estimate on the high side.
Pour the floor first, working the concrete in well around the reinforcing steel and lifting the steel back into position from time to time as the concrete pushes it down. Tamp the wet mass in with special care at all corners.
Move around the perimeter of the pond as you build up the walls, depositing 6 to 8 inches of concrete each time around.
Here again, the natural finish of the pond floor will be smooth enough for all practical purposes. If you want a smoother finish for walls and rim, finish them off with a wooden float when the concrete has begun to set.
The concrete should set well enough overnight for you to spread a few planks over it next day. Walk out on the planks, spread burlap, straw, or canvas over all the concrete surface, and keep it wet with the garden hose for ten days.
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