DRAINAGE OF IRRIGATED SHALE LAND. 23 
With labor at $0.25 per hour, actual unit costs for excavating, lay- 
ing tile and back-filling trenches in shale ranging from 6 to 7 feet 
in depth averaged $0.12 per linear foot on four small projects agegre- 
gating a total of 4,480 feet of trench. A contract job of 2,768 feet 
of 7-foot trench was let for $0.20 per linear foot, while another job 
of 5,600 feet, running 6 feet in depth, was let so as to average about 
$0.114 per linear foot. These figures do not include the cost of 
boring relief wells in the bottoms of the trenches. However, taking 
the work as a whole, this need not increase the cost by more than 
an average of $0.02 per foot, as there are nearly always some por- 
tions of trench on any job in which the relief wells are not essential. 
The cost of boring the relief wells probably averages about $0.05 
per linear foot of well where the depth below the bottom of the 
trench runs from 8 to 16 feet. Where the depths vary from 16 to 
25 feet the cost per foot of well may run as high as $0.10, especially 
if much sand rock, lime rock, or other hard material be encountered 
that renders necessary the use of a drill. 
The acreage costs of drainage of the affected portions of those 
projects referred to in this bulletin have been high. This is due in 
part to the relatively high cost of trenching, but the chief reason 
is the frequency of drains required, as will be noted by referring to 
the maps of the several tracts. Based on the actual affected areas, 
the costs have ranged from $13 to $100 per acre. Almost invariably, 
however, at the time of drainage the trouble was spreading rapidly, 
so that the cost in most instances should in all fairness be dis- 
tributed over the area afforded protection as well as over that directly 
benefited. As a matter of fact much of the real value of the drain- 
age of shale lands is the benefit that accrues from arresting the de- 
velopment of the trouble. This is especially true because of the very 
serious alkali problem that results when the lands are allowed to re- 
main in a water-logged condition for any considerable length of 
time. Once the alkali salts have accumulated in the soil to an 
extent that renders the land wholly unproductive, it becomes very 
difficult to bring the land under satisfactory cultivation again. Es- 
sentially, then, the most practical way to make this type of drainage 
both economical and satisfactory is to install the drains at the very 
first indication of trouble. 
EXAMPLES OF METHODS. 
EXAMPLE I. 
The area of very wet land as indicated on the map in figure 2 
aggregates about 224 acres. Much of this was actually covered with 
water, and in but few places was it more than two feet from the 
ground surface to water. These 224 acres by no means represent 
