CONVICT LABOR FOR ROAD WORK. 



73 



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 drUhng 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 

 d'-ep wells should 



ve water-tight 

 ciirbs in addition to 

 * ipervious casings, 

 "! <r the drip from the 

 ^5ump often is the 

 cause of serious pollution. The casing or Hning 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 

 v/ater 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.^ 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 

 prcivent from (jnUiring the wc^U any water which has not been filtered 

 through at least 4 feet of earth. A mcithod of making water-proof 



Fig. 1.— Well protection. 



' Suggi^stfd by K. JJartow In University of Illinois State Water Survey Bull. 7 (1909), No. 2. 



