CONVICT LABOR FOE ROAD WORK. 
73 
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has been reached, the well is continued through the hardpan or rock 
underlying it until another water-bearing level is reached, the well is 
called an artesian well. 
Such wells are usually made by sinking an iron pipe to the required 
depth if the formation of the ground will permit, or by drilling in stiff 
soils and rocks. The water thus obtained usually has filtered through 
the ground for great distances and generally is free from pollution 
from human and animal sources. Such water may contain mineral 
salts in great abundance, being in some cases so disagreeable to the 
taste that it can not be used for drinking purposes. Questions are 
asked frequently concerning the possible injurious effects of mineral 
salts in water, and the methods of removing them. It is impossible 
to define their ill effects, if any, and, in general, it is not practicable 
to remove the salts. 
To prevent the pollution of artesian wells from the surface it is 
necessary to observe the same precautions to prevent the leaking or 
rusting of the upper 
sections of pipe, as 
were outlined in the 
discussion of driven 
wells. 
Both shallow and 
deep wells should 
have water-tight 
curbs in addition to 
impervious casings, 
for the drip from the 
pump often is the 
cause of serious pollution. The casing or lining should extend 6 or 
8 inches above the ground surface, and a concrete curbing should 
be built over the top with a slope away from the pump opening in the 
center." This cover should extend about 4 feet beyond the edge of 
the well, with the outer edge raised sufficiently to force the waste 
water to run off through a tight drain tile, as shown in figure 1. In 
figure 1 there is also shown a method of protecting a well from direct 
contamination by unfiltered surface water. 1 To construct the cut-off 
shown, the earth should be excavated for 4 feet outside of the regular 
casing to a depth of 4 feet and an extra 4-inch coating of waterproof 
Portland cement mortar should be placed outside of the casing. The 
bottom of the excavation should be covered with from 4 to 6 inches 
of the mortar, and the outer edge of this layer should be raised so as 
to divert the seepage water to the tile drain. This arrangement will 
prevent from entering the well any water which has not been filtered 
through at least 4 feet of earth. A method of making water-proof 
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Fig. 1.— Well protection. 
1 Suggested by E. Bartow in University of Illinois State Water Survey Bull. 7 (1909), No. 2. 
