Rural Hygiene

by Henry N. Ogden

The roof of the spring-chamber may be of plank, but this is temporary and undesirable. It is far better, for all spans up to ten feet, to make the roof a flat slab of concrete six inches thick, imbedding in the concrete in the bottom of the mass some one-half-inch iron rods, spaced about a foot apart each way and extending well into the side walls. The size of these rods should increase with the size of the chamber, making them three-quarter-inch rods up to a nine-foot span, and one-inch rods up to a twelve-foot span. There should be some way of getting into the spring, preferably by an opening in one corner so arranged as to carry the side walls of the opening or manhole up above the ground, where it may be protected with an iron cover locked fast (see Fig. 38, after Imbeaux). Besides the outlet pipe from the spring, which will naturally pass through the side walls about halfway between top and bottom in order to get the best water, there should be a drainpipe from the lowest part of the inclosure, the valve of which can be reached through a valve box coming to the surface. In the figure the drainpipe is shown by the dotted line, and the twofold chamber is for the purpose of allowing an examination of the spring to be made at any time.

The concrete used in this work should be of good quality, one part of cement to five parts of gravel or to four parts of stone and two parts of sand. A concrete bottom, although sometimes used, is not necessary. The position of the drain, of the house pipe, and of the several collection pipes must not be overlooked when the wall is being built, since it is much easier to leave a hole than to dig through the concrete afterwards.

Stream supplies.

If the volume of a stream is more than enough for the maximum consumption, nothing is needed but to carry the intake pipe from the shore out under water and protect the end with a strainer. In this case, however, the stream may freeze down to the level of the strainer and even around the strainer, so that the supply of water in winter would be cut off. To avoid this possibility the intake pipe ought to be in a pool of water so deep that it never freezes, and this means sometimes creating a pool for this very purpose. If storage is to be provided, a reservoir must be built, and this intake pipe would naturally be placed at least two feet below the surface of the water.

Dams.

If the stream is not deep, or if there is not a pool of satisfactory depth, or if the minimum flow of the stream is not adequate for the maximum needs of the consumers, a dam across the stream becomes a necessity. There are two or three types of dams suitable for a reservoir on a small stream, and they may be described briefly.

A dirt dam is not generally desirable, since in most cases the dam must also be used as a waste weir; that is, the freshets must run over the dam. This means that unless the crest of the dam is protected with timber or masonry the dam will be washed out; as happened, indeed, in the terrible flood at Johnstown, Pennsylvania, several years ago. If it is possible to carry the overflow water of the stream away in some other channel than over the dam, then a dirt dam is not objectionable, although always a dirt dam is best with a masonry core. A very good dam can be made by driving three-inch tongue-and-grooved planking tight together across a gulley and then filling in on each side so that the slope on each face is at least two feet horizontal for every foot in height. This last requirement means that if the dam is ten feet high, the width of the dam at the base shall be at least forty-five feet, the other five feet being required to give the proper thickness to the dam at the top.

Fig. 39.—Concrete core in a dam.

In the second type of dam this central timber core is replaced with a thin wall of concrete as shown in Fig. 39, from six to twelve inches thick, sufficing to prevent small animals burrowing through the dam and at the same time to make the dam more nearly water-tight. Sometimes stone masonry is used, building a light wall to serve as the true dam, and then holding up this light wall with earth-filling on each side. If neither plank, stone, nor concrete can be used, the central core is made of the best earth available, a mixture of clay and sand preferably, and special pains are taken in the building to have this mixture well rammed and compacted.