Rural Hygiene

by Henry N. Ogden

Deep wells.

Deep wells are of the same general character as shallow wells. Usually, the ground on which the rainfall occurs is more distant, so that the source of the water is often unknown, and usually, also, the stratum from which the water comes is overlaid by an impervious one.

Fig. 30.—A properly protected well.

It often happens that there are several layers of water or of water-bearing strata alternating with more or less impervious strata, and that wells might be so dug as to take water from any one of them. Indeed, not infrequently in driving down a pipe to reach water, a fairly satisfactory quantity is obtained at a certain level, and then, in order to increase the supply, the pipe is driven further, shutting off the first supply and reaching some other, less abundant.

Deep wells are reached usually by wrought-iron pipe driven into the ground. Sometimes this is done by taking a one-and-one-quarter inch pipe, with its lower end closed and pointed, and driving it with wooden mauls into the ground. When it has gone six or eight feet, it is pulled up, cleared from the earth, and replaced, to be driven six feet again.

Fig. 31.—Well-drilling apparatus.

With ordinary soil, the pipe is easily withdrawn with a chain wrench, and two men will drive one hundred feet in a couple of days. When water is reached, a well point is put on through which water may percolate without carrying too much soil. This type of well is suitable for use in soft ground or sand, up to depths of about one hundred feet, and in places where the water is not abundant. It is most useful for testing the ground to see where water may be found and by pumping from such a well to see what quantity of water may be expected. This type is often used as a shallow well, and the author has seen such wells driven only a dozen feet. Such a well has no protection against pollution, and an ordinary dug well is better for shallow depths. A driven well always has a disadvantage also from the ever present danger that the iron pipe will rust through at the top of the ground water and so admit to the well the most polluted part of the drainage.

For larger supplies and for greater depths, a machine like a pile-driver has to be used for forcing down the pipe. This is not usually removed, but driven down as far as possible, and when the limit of the machine has been reached, a smaller size is slipped down inside the driven pipe, to be in turn driven to refusal. In rock, that is, if the well has to penetrate a layer of rock, a drill is used that will work inside of the pipe last driven, and by alternately lifting and dropping the drill, and at the same time twisting it back and forth, a hole through rock may be made many hundred feet below the surface of the ground. Figure 31 shows a cut of a common type of well-drilling machine.