10 



BULLETIN 57, U. S. DEPARTMENT OF AGEICtJLTURE. 



in small seeps in clayey materials, and requires extensive storage space for its conser- 

 vation. Bored wells are wells bored with Aarious types of augers from 2 inches to 3 

 feet in diameter rotated or lifted by hand or horsepower. They are usually Uned with 

 cement or tile sections with cemented Joints and often with iron tubing. They are 

 adapted to localities where the water is at slight or medium depths and to materials 

 similar to those in which open wells are sunk. Punched wells are small holes usually 

 less than 6 inches in diameter sunk by hand or horsepower by dropi^ing a steel cylin- 

 der slit at the side so as to haul and lift material by its spring. They are adapted to 

 clayey material in which water occurs as seeps within 50 feet of the surface, but not at 

 much greater depths. These wells should also be lined with tile, iron tubing, or sheet- 

 iron casing. Driven wells are sunk by driving downward, by hand or horsepower 

 apparatus, small iron tubes, usually 1^ to 4 inches in diameter, and provided with 

 point and screen. They are adapted to soft and fine materials, especially to sand and 

 similar porous materials, carrying considerable water at relatively slight depths, and 



are particularly desirable 

 where the upper soil is 

 likely to be polluted. 



Since most well- 

 water supplies are 

 obtained from, sand 

 and fine gravels, the 

 cheapest and best 

 method of well sink- 

 ing is by dri\TLiig. 

 In a driven well 

 the water can only 

 be polluted at the 

 depth of the strainer. 

 In some materials, 

 such as clay, it is 

 necessary to bore 

 the well, in which 

 case it is absolutely 

 necessary for safety 



that the well be lined with impervious casing to the strainer. Deep 



and shallow dug weUs should also be Imed. 



FOUNP^T/ON 



Fig. 8. — Concrete well lining, showing arrangement of forms. 



PROTECTIVE WELL LININGS. 



For lining shallow dug wells the latest practice has been the use 

 of reenforced concrete. This has also been successfully practiced in 

 lining deep dug wells. Concrete may be made practically unpervi- 

 ous to water, so that a concrete-lined shallow or deep dug weU can 

 only be polluted from the bottom. 



Figure 8^ suggests a method of Immg dug wells -with concrete. 

 Dug wells are usually about 6 feet in diameter. The concrete need 

 be only about 6 inches thick with vertical steel reenforcing of |-inch 

 rods spaced 18 inches apart, and circular reenforcing of ^-inch steel 



1 F. N. Taylor. Small Water Supplies. London [1912], pp. 34-36. 



