PROTECTION OF DRINKING; WATER.

The next subject to claim our attention is the protection of the sources of drinking water. In the country water is, as a rule, obtained from wells and springs. The important bearing upon well water of soil purity demands a few explanatory remarks concerning the origin of well water. Wells are excavations made into the ground to a variable depth until water is reached. This water is denominated ground or subsoil water. Its origin may be better understood if, for the moment, we conceive the surface of the earth as more or less irregular and entirely impervious to water. The rain would collect on this surface and form lakes, ponds, and streams, according to the configuration of the surface. If, now, we conceive this surface covered with sand or other porous earth to a greater or lesser height, and the top of this be considered the earth's actual surface, the water will remain in the same position, but it will be buried within and fill the pores of the overlying soil as subterranean lakes, ponds, and streams. In digging a well we remove this porous layer of earth until we reach these subterranean streams or reservoirs of ground-water. If the above description be thoroughly understood, the condition under which well water may be obtained at different depths will become intelligible, and it will also appear plain why ground-water may flow as any surface stream and pick up on its way various substances which have percolated into the ground.

When the bed of porous soil overlying the impervious layers is very deep, wells will have to be dug down to a considerable depth to reach the surface of the ground-water. Where this layer of pervious earth is of slight thickness wells will be shallow, and the ground-water may appear on the bottom of gullies, trenches, and wherever the porous layer has been dug or washed away.

The movement of the ground-water depends on the inclination or slope of the impervious strata, and has been observed to be quite rapid in some instances. By adding common salt to the water in a well its detection in other wells at a short distance has been found a guide in the determination of the rapidity and direction of the underground current.

When the ground-water resting on the uppermost impervious layers is near the surface, and therefore not safe or fit to use as drinking water, it may be possible by digging below this layer to find another porous bed containing water. This source will, in general, be much purer since it is less exposed to pollution from above, and since the water has to travel longer distances underground. Such a deep supply must, however, be protected from the superficial supply by a water-tight wall extending to the surface of the deep supply, otherwise the water from the upper layers will simply drain into the well.

WAYS OF CONTAMINATION.

Wells are exposed to contamination in two ways. The surface water from rain, house slops, and barnyard drainage may find its way into the well at or near the surface of the ground. Or the ground-water stream supplying the well with water may in its subterranean movements encounter cesspools or seepings from cesspools, and carry with it soluble and suspended particles, some of which may enter the well. There can be no doubt that a large percentage of the wells are exposed to contamination with refuse matter in the manner described; and it now remains to gauge the danger to health and life which may be carried in the contaminating substance. The danger of typhoid-fever bacteria entering the water has already been mentioned. These may be washed in from the surface or they may pass from cesspools near by through fissures in the ground, passages dug by rats, etc. Whether such bacteria can pass through the pores of a compact, unbroken soil from a cesspool to a well near it is a matter not fully settled. Since, however, the actual condition of the deeper layers of the soil between cesspool and well can not be known, it becomes imperative to prevent all pollution of the ground-water current supplying wells by either abolishing the cesspools or else placing them at a considerable distance from all sources of water.

Beside typhoid-fever bacteria, those organisms which cause digestive disturbances, and severer troubles, such as diarrhea, dysentery, and possibly other unknown diseases, may be carried into well water. During cholera epidemics, polluted wells might form centers of infection. Eggs of animal parasites may be washed in from the surface. Again, the barnyard manure, representing the mixed excrement of various animals, may under certain conditions be bearers of disease germs, and such excrement should, under no conditions, be looked upon as entirely harmless to human beings.[2]

Besides the protection of the ground-water near the well from pollution emanating from cesspools, etc., the surface of the ground about the well should be kept free from manure, slops, and other waste water; hence the well should not be dug under or close by the house,[3] nor should it be located in the barnyard, where the ground is usually saturated with manure. It should be surrounded by turf, and not by richly manured, cultivated, or irrigated soil. The ground immediately around it should slope gently away from it and be paved if possible. The waste water from the well should not be allowed to soak into the ground, but should be collected in water-tight receptacles or else conducted at least 25 feet away in open or closed channels which are water-tight.

CONSTRUCTION OF WELLS.

The well itself must be so constructed that impurities can not get into it from above or from the sides. If water can soak into it after passing through a few feet of soil only, it can not be regarded as secure from pollution. To prevent this, the well may be provided with a water-tight wall built of hard-burned brick and cement down to the water level. The outside surface of this wall should be covered with a thin layer of cement, and clay pounded and puddled in around it. Or, tile may be used to line the well and the joints made water-tight with cement down to the water level. Driven wells, i. e., wells constructed of iron tubing driven into the ground, are, perhaps, the safest where the quantity of water needed is not large and where other conditions are favorable.

These different devices are all designed to keep water near the surface of the soil from percolating into the well. To keep impurities from entering the well directly from the top considerable care is necessary. Such impurities are likely to prove the most dangerous because there is no earth niter to hold them back and destroy them before they can reach the water. Adequate protection above may be provided in several ways. The sides of the tiled wells should project above the surface and be securely covered with a water-tight lid. The ordinary well should also have its sides project above the surface and a water-tight cover of heavy planks provided, which should not be disturbed excepting for repairing or cleansing the well. Under no circumstances should objects be let down into the well to cool. A still better method of protecting the water from above is to have the lining wall of the well end 3 feet below the surface of the ground and to be topped there with a vaulted roof, closed in the center with a removable iron or stone plate. The top should be covered with 12 inches of clay or loam; above this there should be a layer of sand, and lastly a pavement sloping away in all directions.

Too much care can not be bestowed upon the household well. It should be guarded jealously and all means applied to put the water above any suspicion of being impure. This is especially true in dairies where well water is used in cleaning the milk cans, and where steam and boiling water have not yet found their way for this end. Polluted wells in such houses not only endanger the health of the inmates but that of a more or less numerous body of city customers.

In those regions where rain water is the only safe drinking water, the same care is necessary to protect the stored supply from contamination, and no suggestions beyond those already given are necessary here.