Construction of dug wells.
The construction of shallow wells requires little comment. Ordinarily, they are dug down to the water, or to such a depth below the level of the water as is convenient, by the use of an ordinary boat pump to keep down the water, and then are stoned up with a dry wall. Such a well for a single house requires an excavation of about eight feet diameter, with an inside dimension of about five feet.
Fig. 27.—Mode of sinking a well.
If the soil at the bottom of the well is sandy, it is possible to take a barrel or a large sewer pipe and sink it into the bottom of the well in the water by taking out material from the inside and loading the outside to keep it pressed down into the sand. This same plan may be used to sink the whole body of the well wall, first supporting the lower course of masonry on a curb, so called (see Fig. 27). This curb is usually made of several thicknesses of two-inch plank well nailed together, the plank breaking joints in the three or four layers used. It is a good plan to have this shoe or curb extend outwardly beyond the walls of the well so that some clearance may be had, otherwise the dirt may press against the walls so hard as to hold it up and prevent its sinking. While this arrangement may be put down in water, it requires some sort of bucket which will dig automatically under water and has not been therefore a customary method except for large excavations where machinery can be installed. There is no reason, however, why the method might not be used for a single house.
Fig. 28.—A well that will catch surface waste.
In whatever way the well is dug, one point in the construction that needs to be emphasized is that the wall should be well cemented together, beginning about six feet below the surface and reaching up to a point at least one foot above the surface. This is to prevent pollution from the surface gaining direct access to the well, and if this cementing is well done for the distance named, it is not likely that any surface pollution in the vicinity of the well could ever damage the water. Figure 28 shows the section of a well where no such precautions have been taken, and it is evident that not only surface wash, but subsurface pollution may readily contaminate the water. Figure 29 (after Imbeaux), on the other hand, shows a shallow well properly protected by a good wall and water-tight cover. Figure 30 shows a photograph also of this latter type of well. Even if a cesspool or privy is located dangerously near the well, in the second case the fact that the contaminating influence must pass downward through at least six feet of soil before it can enter the well is a guarantee that the danger is reduced to the smallest possible terms.
Fig. 29.—A well properly protected.