While puddled ponds are the most economical to construct they probably require most in the way of repairs. Besides, they are possible only where the necessary material – a heavy clay – is ready at hand. The first steps of their construction are the same as for all other ponds, at least as far as locating and excavating are concerned; but from there onward the methods of procedure differ. For while both in natural ponds and in ponds built of concrete there is no trouble about their ability to hold water, an artificial pond, where no concrete has been used, must be made water-tight by special means. For such a purpose hydraulic engineering knows of no better material than puddled clay, clay which by a mechanical process has been made homogeneous and very plastic.
Unless you absolutely feel the need of exercising your muscles it is better to get some unskilled labor to do this preparation. For, to reduce even a wheelbarrow load of clay to an absolutely homogeneous mass by working it over and over is no sinecure.
This is the process: Clamp together several boards so as to make a platform, say 6 x 10 ft. Spread the clay, a wheelbarrow load at a time, on the boards, and with a spade, chop it up thoroughly. No lumps larger than a walnut should remain. Remove all sticks, stones etc; then, adding a little water, begin to pound, using a wooden maul and do not stop pounding until a perfectly homogeneous mass, of the consistency of putty, has been obtained. When this is accomplished start on the second load.
Happily it is not necessary to use a layer more than four inches thick, so that for a pond twenty feet in length, and with an average width of ten feet, seven to eight wheelbarrow loads of puddled clay will be ample. The cost of this material is generally about 100 dollars, including hauling, puddling, etc.
Having reduced the clay to the proper consistency, spread it evenly over the bottom of the pond, thoroughly beating it down as laid.
The clay is fairly impervious to water and is not injured by freezing. The margins, from mean water level to a depth of twelve inches, may be lined with stones pounded into the clay. This prevents washing away by ripples or by moving ice. It is also advisable to cover the clay bottom with a few inches of sand so that the puddling may be protected and the mud not so easily stirred up. If this process is carried out consistently, an absolutely water-tight pond will result. The puddling is carried up to within three inches of the rim. Overflow pipes (preferably one pipe with two openings), and a water faucet are to be arranged for beforehand.
When an existing pond is to be converted for the growing of water-lilies, it must be our aim to provide for two things, the outline, and a proper depth of water at all times. The outline depends largely on surrounding conditions and no hard and fast rules can be laid down. The water level should be two feet above the bottom of the pond. Ordinarily this will necessitate the construction of a small dam which is easily constructed of grass sods. First empty the pond and then excavate to a depth of four feet where the dam is to be. Then put in the sod. Make the dam four feet wide at the base and at least two and one-half feet wide at the top, and thoroughly cover the sides with puddled clay.