The silver state. [volume] (Winnemucca, Nev.) 1909-1925, 1923-01-04

parts at the surface were engulfed
in the moving mass and the shole
cooled before complete crystalliza-
ton. From the standpoint of con-
struction this type of rock has suffi-
cient strength for all purposes but
it has such an irregular fracture
that dimension stone cannot be OBJ
tanned. 1t is, however, suitable
for a rockfill and will make excel
lent crushed rock and "plums" for
concrete work.
| The most important Characters
tic of the rock is the type of wealth
ering and the existence of joints
The dense almost CLASSY texture of
the ground mass produces, under
the expansion and contraction con-
sequent on changes in temperature,
numerous and very irregular cracks
The existence in this ground mass
of irregular shaped masses or rock
of similar composition but different
texture increases this tendency.
Consequently the surface is broken
by innumerable irregular cracks that
give the rock the appearance of
being poorly consolidated rubble
Below this surface however the rock
is firm as is proved by the persist
ence of thin pillars such as the
ones in the center of the view in
Fig. 2. Also, where the crack runs
on the rock and all loose material
has been removed it may be seen
that the rock is hard and free from
cracks. This condition is we'll shown
1t the east end of the old mill dam
A characteristic feature of this
lava bed are vertical joints. They
are spaced at intervals of 2 to
30 feet. Along these joints wealth
ering proceeds with relative ease
and the joints become open crevices
that in many places separate pillars
of rock from the wall of the canyon
Much of the picturesqueness of the
gorge is due to this type of weather
ing. The presence of open crevices
along joints will cause some con-
Germ as to leakage at the ends of
the dam. However, a careful in
spection shows that the joints are
sealed in their lower parts. The
open crevices exist only in the
immediate walls of the gorge and
in the upper exposed parts of the
ava sheet. In the construction of
the dam a careful stripping of the
site and removal of loose rock, nee
essary on account of the weather
cracks mentioned above, will reveal
the open joints. Further excava-
ton or grouting of the joints can
then be relied on to prevent leak
age at the points of contact of the
dam and the wall of the gorge.
Two places in the gorge were
considered in detail as dam sites
the mill dam site, and point near
the upper end of the gorge. So far as
character of rock is concerned there
is little choice. The decision must
rest on engineerings considerations
At the upper site, however, the
lava sheet is cut by dixie of similar
rock % feet wide and strikes across
the gorge N. 40 degrees w. and
dips rs degree SW. This dixie is
sheeted in fakes 2 to IL inches
thick. Along these sheets are open
cracks. 1t is improbable that these
cracks continue for any great dis
lance into the rock, so as to form
channels for the loss of water out
of the reservoir. 1t will, however,
be more expensives to clear the
site of this dixie. The dixie should
be avoided, and the dam built at the
narrow place just down the stream
from it
The depth to bed rock in a gravel
filled gorge is difficult to predict.
However, the bottom of this gorge
is only 80 feet wide in places. Even
in these narrow places rock out
crops are numerous. The old mill is
a masonry structure about feet
thick. 1t is broken on the east
side where bedrock is exposed. In
flood the water goes through this gap,
turns, and plunges into a pool at
the foot of the dam. 1t, therefore,
seems likely that the wall rests on
rock or it would have been under
mined long ago. At the upper dam
site one or two pits will probably be
sufficient to show the depth of
gravel and sand.
In conclusion: There are no diff
fcult problems of dam construction
due to the rocks of the site and
there is no probability of leakage
through the rocks of the reservoir.
Little Humboldt River Damsites
The Little Humboldt River rises
on the east flank of the Santa Roosa
range north of Martin Creek and
for about % miles pursues a course
parallel with it. In T. 43. NJ, R. 43
E., it swings to the south southeast
IS miles to a junction with the
east fork Of Little Humboldt river,
half mile above damsite No. 1.
From the junction the river flows
west IL miles to Paradise Valley
where, Joined by other streams, it
forms the principal drain of the
valley. The east fork of the Little
Humboldt river is about IL miles