Grand Forks herald. [volume] (Grand Forks, N.D.) 1916-1955, 1922-04-26
M!||aryels OF


YNHE dam that is to span the Colorado
= Canyon will be. a titanic structure
nearly three quarters Of q mile thick at its
bottom and $50 feet or 731 feet high, ac-
cording to different engineering plans. 1t
will close a Cup $50 feet wide 1.-THE breadth
of ths-canyon at the place c%hosen), and its
thickness al. the top will be thirty feet.
!. This will allow for a roadway across the
canyon, along the top Of. the dam, If de-
sired. The great cut is half a mile deep at
that point, but most Of the descent from
the level of the high plateau is by a series
Of huge steps, and it would be practicable to
make a road down to the dam apd up
again OF the other side Of the canyon.
In starting the erection OF, the dam the
first thing requisite will be to lay bare the
bed of the Colorado River, and this will be
accomplished by boring two large tunnels
through the cliffs, one on each side Of the
dam site, and turning the stream into them.
The tunnels, just above the river level, will
Of necessity be equipped with controlling
works.
The next thing to do will be to build a
concrete wall Of great thickness-the des-
tined face Of the dam-across the gap. Be-.
hAuN ~ " uu CilOI uldlcS III SldlALC1
slanting downward and upstream to a dis
tancc Of 5000 feet, and covered with a
pavement Of concrete re-enforced with
steel. u
Where is all this granite to come from?
That is. easily explained. The canyon cliffs
are GRANTEE and all that is necessary is to
bore many small tunnels through them par
allel to the river, fill the tunnels, with black
gunpowder and blow them up. Broken
rock will thereby be thrown In great guam
titles into the river bed below, contributing
to the building Of the dam. Gunpowder
will be used in preference to dynamite or
TINT, because It is not desired to SKATER
the rock too much. Big chunks ara best.
When q certain amount of this kind or
work has been done, the river will be turned
back into its bed and allowed to scour out
the rock dust and small stuff, the large
blocks thus undermined being thereby per-
mitted to settle deep and solidly. The tun-
neling and blowing up process will be re-
peated again and again, with incidental,
securing" until the structure has been
brought to the desired height and shape.
Masses of granite can be obtained in this
way much larger than could be moved by
available machinery. AS for the big "di-
version ; tunnels, which carry the river
when. turned out 81 its-bssfs they must of
necessity have a capacity Sufficient to pre-
vent overflow Of the dam at high water.
when Tin the food season. the turbulent
Colorado flaws iat a rate of 100000 cup,c
feet per second. (
Brought thus far toward completion, the
upstream slope Of the dam will be levclcd
to- an even incline with small rock, until the
surface is smooth enough. to be paved with
re-enforced concrete. This paving will cover
the entire slope from the river bed to the
top, and will be securely sealed to the cliffs
on both sides to prevent percolation Of
water. \
An alternative plan, now being discussed,
is that Of making the dam wholly of con-
crete. This is believed to be feasible but
the idea as yet is no more than Gin the air.