The Hawaiian star. [volume] (Honolulu [Oahu]) 1893-1912, 1907-04-24
Continued from Page Five,
to leave a vertical bank feet high
DISCUSSION OF POSSIBLE FAII
URE OF NUUANU DAM BY
EITHER OF THE MEANS
SUGGESTED.

/
URE OF NUUANU DAM BY
EITHER OF THE MEANS
SUGGESTED.
The failure of the Nuuanu Dam by
overlapping due to floods exceeding the
capacity of the spillway cannot in my
Judgment be regarded as a possibility
for the reason that the capacity pro-
vided by the plans appears to be rea-
sonably ample and in excess of ali
probable stream flow under extreme
conditions.
In this connection it has seemed to
me that a modification of the plan of
the spillway would be desirable to
avoid the use of ovable flash-boards,
and reduce the height of overflow un-
der extreme conditions. My plans
which meets the approval of the en-
gineres with whom l have discussed it
is to extend the spillway channl auka
of the dam, parallel with the edge of
the reservoirfi forming a long crest OF
overflow, some 300 feet in lngth, pro-
tee ID by lining of reinforced concrete
the channel being ade deepr and wider
and of increased capacity from the up
ner end down to the line of the dam.
In this way it is impossible to secure
the desired capacity with a depth of
overflow not exceeding one foot. Such
an arrangement would admit of per-
manently increasing the height of wa
ter in the reservoir by two feet with
the same height of dam. The avoidance
of any echanical device for regulating
the height of water automatically ap-
pears to me desirable and I recommend
the adoption of this plan for the spill
way.
The second described cans of failure
of earth dams could not occur to the
dam under consideration when built
with the dimensions planned and with
the aterials at hand The corewall
J., will prevent such approximation of
the makai half of the dam, until the
mass had becoe solicited by its own
gravity even if we assume that the
- norton mauka of the corewal were not
copletely compacted before the reser-
voir is filled
FAILURE BY SATURATION OF OUT
FAILURE BY sATURATION OF
OUTER TOE THROUGH
SEEPAGE.
\ IT is unnecessary to discuss this pos
sibility further than to say that tn
rock-fu section of the dam will affor'
such complete drainage of the maka
side of the embankment as to entirel
alter the conditions and produce sta
bility against such action.
In order to preserve the wood diaph
rogn which is to be built of redwood o
the top of the concrete core-wall fror
future decay, 1 should advise movin
the rock-fill makai, a distance of te
feet, filing the space with selecte
clay, rammed in place and puddled mex
4 to the wood with water his will hav
the effect of excluding the air and pro
long the life the wood indefnitel
against the ravages o decay.
1t involves a very slight change ror
the Kellogg plans but one quite as i'm
portant as the change made from Ore
gon pine to California redwood in tn
. material of the core-wall, and in tn
s. same line the prolongation of the dura
biity of the core wall The matera
} for this can be partially obtained b
lessening the thickness of the earth fl
mauka of the core wall by about feet
opposite the rock-fill.
- Regarding the general dimensions o
the dam, I may say that they conform
to the dimensions almost UNIVERSAL.
adopted for earth dams. Thes lopes o
- 8 to 1 inside and on / outside are thos
employed on most of the dams witt
which l am now familiar
RAw
PROPOSED INCREASE OF HEIGHT
= OF NUUANU DAM.
An examination of tht contour ma
of the reservoir reveals the fact tina