REPORT OF INVESTIGATIONS No. 40


confining bed or possibly from numerous lenses of confining material. The
flowing wells are for the most part old, and accurate drilling records and
drill cuttings are not available to define definitely the geologic feature.
However, the gradient defined by the well depth tends to follow south-
ward dip of the formations. Figure 42 shows that mineralization of the


) s SAN T A
 4.
C) 30
 20 ROSA
 ^71I


D NK
 MNo


 1.8e0 I
 IAO-
 1.20- -
 I B OI ll.


 080-

 060- 60
 0.40- =/40
 0.20- 20
 000- -0
 2 3 4 5
WELL NUMBER o04-71B.T o04.i -I 0o4-e20-I 0o0-719-I1 o51-7t-I
Figure 42. Graphs showing chemical composition of water from
 sand-and-gravel aquifer from Molino to McDavid.


L CI,F, NO3

s o04


Mg CO%, HCO3



102, in ppm



















wells in the


water increases to the south, indicating longer contact between the water
and the minerals in the ground. This limited evidence suggests the pos-
sible existence of a single confining layer extending over several miles.
The increased mineralization in this area is no real problem because
even the most mineralized water in the aquifer is within the limits of
most municipal and industrial criteria. The only exception is that the
silica content of water from all flowing wells' samples exceeds the maxi-
mum allowable limits for boiler feed water.
 Generally, the sand-and-gravel aquifer is a source of water of excep-
 tionally low mineral content.


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