12 
BULLETIX 1456, U. S. DEPARTMENT OF AGRICULTURE 
Other information regarding pumping plants and wells in this area 
is given in Tables 1 and -1. 
A closed gravity drain built between October, 1920, and September, 
1921, was designed for relief of area F, but three drainage pumping 
plants have since been installed at the locations shown in Figure 1. 
The present gravity drain consists of 18,205 feet of 10, 12, 15, and 
18 inch concrete and vitrified clay tile laid through the length of 
the area and at an average depth of 10 feet. From the boundary of 
the Salt River project the drainage water is carried through Salt 
River Indian Reservation in an open ditch. The capacity of the 
closed drain varies from 1 to 3 second- feet according to the size of 
pipe, but the actual discharge varies from in winter to a maximum 
of 1.5 second- feet in summer. Its location with respect to the lands 
requiring 
drainage 
is shown in 
Figure 
1. 
/?./£ 
P. 2 £. 
Salt River Project Boundory 
lOFt. Ground-water Contour 
Area F, Ocfober,l9J8 
urns So// 
^ C/ay and Cemented Mate/'ial 
KCT Ca/iche 
rss) Gravel and Bowlders 
EZ3 Sand 
• Test Wells 
The drainage plants 
which were recently 
placed in this area 
are of the new type 
installed in area D. 
(P1.2.B.) 
Power for operat- 
ing all the drainage 
pumps is supplied by 
hydroelectric plants 
owned and operated 
by the Salt River 
Valley "Water Users' 
Association. Be- 
cause of the use of 
off-peak power for 
operating drainage 
pumps, only about 
one-fourth cent per 
k i 1 o w a t t-hour is 
charged against the 
drainage system. 
This charge repre- 
sents the average 
cost of maintaining and operating the power system during those 
periods when power is used by the drainage pumps. To a very large 
extent power that would otherwise be wasted is utilized for operating 
the drainage system, which accounts for the low power rate charged, 
In some cases pumping plants have been located close to existing 
irrigation canals and pumped water is discharged directly into 
them, but in many instances it has been necessary, to make ditches 
of some length to dispose of it and this work has been carried as part 
of the regular drainage construction. 
EFFECTIVENESS OF DRAINAGE BY PUMPING FROM WELLS 
The efficiency of the drainage system has been ascertained by re- 
cording accurately the quantity of water removed from the ground 
and by noting the effect of this removal on water levels in the neigh- 
borhood of individual pumping plants and throughout the valley. 
The running time of pumping plants has been kept to the nearest 
15 minutes of their starting and stopping and the capacity of pumps 
Fig. 
202' 
10. — Map with vertical cross sections showing forma- 
tions penetrated by wells in area F 
