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

from evaporation of 2,00o aere-iee''
An earth dam with a clay core
and necessary gates and waste way
structures will require $4,000 cubic
wards of fill and 400 cubic yards
of concrete. 1t will cost S60,00o.
The reservoir site is a broad al
luvium floored valley at the juno
ton of the two streams, Little Hum
boldt river and its east fork. This
valley has been eroded from rela-
lively soft tufts that overlie thick
bed of lava. The beds dip 10 de-
grees southeast and trend about
35 degrees northwest. The bed
of lava has a thickness of more
than 100 feet and forms most of the
south and west sides of the reser-
voir. In the narrow gorge cut IN
this bed is the proposed dam site.
The spillway will be built on the
broad bench south of the gorge.
This bench was cut by Little Hum
boldt river when it flowed in a
broad valley about so to 70 feet
above the present level. The bench
therefore is cut across the lava bed
and, below thin layer of gravel,
the lava outcrops.
The lava bed is firm hard rhyo-
lite with small crystals of field
spar and quartz in find grained
ground mass. The rock was poured
nut molten and there is well de-
fined plating due to molten flow
The flow structure consists of lines
Of finely porous rock that repre-
sent the frothy part of the flow. The
porosity of the rock due to this
structure is low and will be of
10 moment in the construction of
the dam and spillway. There are,
however, well defined cracks or
joints at right angles to the plated
structure at intervals of 4 to 10
feet. Where the ends of the dam
join the rock the loose rock should
be blasted out and these joints well
grouted.
The tufts underlying the bed of
rhyolite are concealed and their
characteristics undetermined. The
dip upstream insures that the find
grained member of the series will
present general leakage from the
'eservoir. Any tendency of the bed
If rhyolite to slip on the underly-
ing material will be defeated by
the upstream dip.
The depth of alluvium above rock
at the damsite is at least 10 feet,
rs shown in the present stream
channel. How much more alluvium
cannot be predicted. Pits should
be dug.
In conclusion, the site is well
suited to a low earth dam, and
there is no probability of serious
leakage through the sides of the
reservoir, or at the ends of the
dam; the rock of the spillway site
will resist erosion.
Site No. 2
No survey has yet been made of
site on tn east fork of little
Humboldt river about half mile
northeast of the Site No. l. This
site, here called No. 2, consists of
narrow gorge in lava bed with
broad valley above called Farrel
Flat. If the dam were built at this
point Little Humboldt river would
be led to the reservoir through a
canal over low divide. The rela.
tive cost of this design is not
known.
The gorge is narrower than al
the other site and higher dam car
be built. The bench on the south i,
narrower and the cost of spillway
construction will doubtless be higher
The rocks of the reservoir anc
dam site are similar to those al
Site Nc. /. The reservoir is ar
open valley in tufts that dip gently
eastward. On the evidence OF
vegetation and aldalina soil thi.
fiat has a shallow water table in
the alluvial floor. The existenc,
of this shallow water indicates
that the bottom of the reservoir i.
tight.
The gorge in which dam would
be built is cut in thick bed OF
rhyolite lava that dips about II
degrees east. 1t resembles the rocl
at Site No. / very closely and may
be part of the same bed redupli
Gated by faulting. A satisfactor,
tie for an earth dam can be mad,
in the same manner as at SITE
No. I.