A text-book on hygiene and pediatrics from a chiropractic standpoint

by J. H. Craven

Ground or Subsoil Water

In the consideration of the three sources of water supply it is difficult to draw definite lines of demarcation since the rain and snow water soon becomes surface water and the surface water may percolate through the ground and become subsoil water.

Well water and spring water are classed as ground or subsoil water. From a hygienic standpoint water obtained from wells or springs forms a very reliable and satisfactory source of supply.

Especially is well or spring water desirable for private domestic use, since it is usually in a reasonable degree of purity and does not, therefore, require any artificial process for purification. The sources of water supply used for public purposes, made necessary because of the volume of water required, are not so satisfactory for a private or domestic supply because its purification would entail too great an expense to warrant the practicability on such a small scale. Therefore, the most desirable source when only a limited amount of water is required is the wells.

Wells may be used for public water supply and are in some of the smaller towns, but they are not so practicable as their supply is likely to be inconstant. In other words, there is danger of the wells going dry, and since they are put down at a great expense, this would be too great a risk to take even though the water thus obtained is satisfactory from a hygienic standpoint.

The above illustration shows the fluctuation of ground water. When the ground water is at the low mark the shallow well becomes dry; as the water rises it flows into the well. When the water has reached the high mark the intermittent spring becomes a flowing spring. The pressure of the ground water is great enough to produce flowing wells down on the level.

Not all wells, by any means, will furnish a pure water supply. There are many factors to consider from the viewpoint of the pollution of well water and these will be considered in due time. When water reaches an impervious strata it remains at that level and moves in a horizontal plane. Water may form in beds or be found in underground streams. It is only in the limestone regions that water forms in streams under the ground.

Poorly constructed well, polluted by seepage thru limestone.

The depth at which water is found beneath the surface varies. The water directly beneath the surface, or that which is derived from surface drainage and the rainfall, is, by some, styled the ground water. This is the shallow water. That which is found at a lower level is called the lower subsoil water or underground water.

The ground water does not provide a very desirable source of well water because there is danger of pollution from the surface. The degree of this impurity will depend largely upon the character of the soil. If it is sandy and thus provides a good filter medium there is little danger from pollution; but if the soil is of a limestone formation it makes a very poor filter and the shallow water is likely to be polluted from the surface drainage.

The subsoil water moves in the direction of the nearest body of water. That is, if it is near a river or lake its movement will be in the direction of this river or lake. For this reason a well near the seashore will contain fresh water.

In wells less than fifty feet deep the temperature of the water will be influenced by that of the atmosphere. It will be warmer in summer and cooler in winter. Some authors put this depth at much less than fifty feet, maintaining that the atmospheric temperature will have no influence whatsoever at such a depth. It is true, however, and the fact is undisputed, that in wells 50 feet deep or more the water is cool and the temperature remains constant. It is not influenced by the change in atmospheric temperature.

Sand and gravel deposits form the best source through which to obtain subsoil water. To supply any very great amount there must be a number of wells and these must be far enough apart so as not to draw from the same territory. Seventy-eight million gallons of subsoil water per day is provided at Brooklyn from twenty-four separate pumping stations. Memphis, Tennessee, is the largest city in the United States which gets its entire water supply from sand and gravel deposits.

Poorly constructed well, polluted by surface drainage.

Sandstone rock furnishes an excellent source for subsoil water since it makes an excellent filter. Because of the limited amount of water obtained in a sandstone formation this source is practicable only for a very limited supply.

Limestone formation is the most undesirable source of subsoil water supply from a hygienic standpoint. Limestone is not porous and therefore has no filtering qualities. If water does pass through this sort of a formation it must travel through its crevices and fissures.

It is very difficult to know where the pollution of water passing through limestone originates. As these fissures are usually very long, and as the water is in no way filtered as it passes through them, the contamination might enter the water at a point far distant from where the well is sunk. The water supply from limestone is likely to be inconstant because the water is not contained in the limestone, but flows through the cracks and crevices. In this way it may soon flow away unless the source is replenished by rain or snow.

Water from the subsoil is obtained, as has been stated, from wells. Wells are classified as shallow and deep. By a shallow well is commonly meant one that is dug and not more than thirty feet deep. This type is usually walled up with brick or stone and is from five to six feet in diameter. Shallow wells may also be driven. That is, a gaspipe with a sand point is driven into the ground until the water-table is reached, the water being pumped out with an ordinary suction pump.

Shallow wells must never be considered a satisfactory source of water supply where there are conditions existing which would result in such pollution of the ground that the water percolating through can not be more or less filtered. Sewage polluted soil never is satisfactory for shallow wells.

Showing a properly constructed well in unsanitary locations.

Deep wells are drilled and are from six to eight inches in diameter. The water from deep wells may be free from contamination but may contain a great deal of mineral in solution and different salts which render it permanently or temporarily hard. This decreases its value from a sanitary viewpoint and more particularly from an economic standpoint.

Special attention should be given the construction of the well. The casing or walls should be as tight as possible. Special care should be exercised against the possibility of surface water percolating through the casing as this drainage will bring impurities.

The casing should project far enough above the surface of the ground to insure against water running from the surface. It should extend at least eighteen inches above the ground. The well should have a tight covering.

The ground possesses great filtering qualities and therefore great quantities of impurities will be taken from the water as it filters through. The danger is when the ground becomes so filled with impurities that its filtering qualities have been destroyed or when there is not sufficient distance between the source of pollution and the water level; also when the soil is of a limestone formation and the water, instead of percolating through it, passes through cracks and crevices, in which event it will in no sense be filtered.

It was at one time considered that wells should be ventilated and a great deal of stress was laid upon it. When it is taken into consideration that the water under ground is in no way ventilated except through the natural means, it will readily be understood that it is not necessary to provide ventilation merely because the water has been tapped by a well.

If the origin of pollution, such as cesspools, is too near the well or the well is too shallow, not allowing enough distance for purification, there will be great danger from such sources. The greatest danger is in the shallow wells. However, these are entirely satisfactory as a source of domestic supply, providing the soil is of a sandy or gravel formation and there are no barnyard or cesspools, for example, too near the wells. A shallow well in a limestone region is not satisfactory and should be discarded when at all possible. If it is necessary to use such, every precaution possible should be taken to eliminate the possibility of contamination.