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ILLINOIS ACADEMY OF SCIENCE 



all shallow dug wells but the ideal cannot be obtained in this 

 as in many other matters. 



As indicated in the discussion of the sources of 

 municipal water supplies in the state, it is impos- 

 sible in some parts of the state to obtain a satisfactory 

 water from deep wells so that the shallow well is a necessity. 

 Whenever the water bearing stratum is porous enough to 

 allow free flow, a driven or bored well less than 50 feet deep 

 should furnish satisfactory water. In many cases however 

 the flow through the water bearing stratum is so small that 

 it is necessary to make a reservoir into which the water may 

 slowly percolate and from which i't can be drawn as needed. 

 Hence the shallow dug well is a necessity. Granting that it 

 is a necessity, great care must be taken to protect the water. 

 The character of the strata which it penetrates must be taken 

 into consideration. Strata of sand may serve as a filter and 

 purify the water. Strata of clay or other material through 

 which water may flow in crevices or cracks may allow pollu- 

 tion to be carried a considerable distance. Wells should be 

 located on a higher level than cesspools, privies or barnyards 

 and these must be built at a distance from the well. The 

 immediate surroundings of the well must be carefully protect- 

 ed. A surface water should not be allowed to pass through 

 the casing within at least four feet from the top. The cover 

 should be tight so that water from the pump may not flow 



