WELLS OF MCLEAN COUNTY, ILLINOIS. 6!) 3 



a depth of but a few feet. The greater part of the county is, however, 

 sufficiently drained to need but little artificial ditching. 



This is one of the most elevated counties in central Illinois, much of 

 its surface being more than 800 feet above tide and occasional points 900 

 feet. The northern border and also the southwest corner fall below 750 feet. 

 A very small area in the southwest corner falls below 700 feet. 



The Bloomington morainic system traverses the county nearly centrally 

 in an east-west direction and occupies a belt G to 10 miles in width. The 

 Mackinaw River. drains its north border and the Sangamon and tributaries 

 its south border. A small moraine, Cropsey Ridge, follows the north border 

 of the Mackinaw River across the northeast part of the county, separating 

 this drainage system from the Vermilion drainage system. 



The drift is of great depth, averaging probably over 200 feet. Records 

 of ten deep borings were obtained which reach rock at an average of 155 

 feet, but twenty-one others have an average depth of 174 feet without 

 entering rock. The drift is apparently thinnest in the northern part of the 

 county, where rock is struck at about 100 feet. The drift in the central 

 and southern portions has a depth of 200 to 250 feet. Buried soils are 

 found at two or more horizons at depths usually of 100 feet or more, but 

 on the plain outside the morainic system a soil occurs at 40 feet or less. 

 The drift above the first buried soil is usually a soft blue till. At greater 

 depths the till is frequently found to be very hard, as in the neighboring 

 counties to the north and northeast, already discussed. In some of the deep 

 borings a large amount of sand and gravel is found in the lower part of the 

 drift. Many wells have been sunk to a depth of 150 to 200 feet in order to 

 reach the water-bearing beds beneath the blue till, there being onlj- a, small 

 amount of water-bearing gravel interbedded with the blue till. 



INDIVIDUAL WELLS. 



At Chenoa, on the north border of the county, several strong wells 

 have been obtained from depths of 100 to 150 feet near the surface of the 

 Coal Measures sandstone. The public supply is from two wells 135 and 

 214 feet in depth. 1 Rock is entered at this village at about 80 feet. Wells 

 from the drift are usually weak compared with those from the rock. 



1 Manual of American Waterworks, 1897. 



