10 
BULLETIN 51, U. S. DEPARTMENT OF AGRICULTURE. 
in small seeps in clayey materials, and requires extensive storage space for its conser- 
vation. Bored wells are wells bored with various types of augers from 2 inches to 3 
feet in diameter rotated or lifted by hand or horsepower. They are usually lined 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 dropping 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 driving. 
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 
Fig. 8. — Concrete well lining, showing arrangement of forms. „ u 
necessary lor safety 
that the well be lined with impervious casing to the strainer. Deep 
and shallow dug wells should also be lined. 
FOUNPATtON 
STRATUM 
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 impervi- 
ous to water, so that a concrete-lined shallow or deep dug well can 
only be polluted from the bottom. 
Figure 8 1 suggests a method of lining 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 f-inch 
rods spaced 18 inches apart, and circular reenforcing of |-inch steel 
i F. N. Taylor. Small Water Supplies. London [1912], pp. 34-36. 
