Evening star., 1932-11-20
BY G. EDWARD pENDRAY.

%r%HE magnitude OF the Hoover
Dam project, where the waters
of the treacherous Colorado
IL River were turned into the first
CT four huge diversion tunnels
this week. staggers human imagination.
Every operation there involves calcula-
ton in millions - millions of cubic
yards of concrete will be poured; mil
lions of tons of sand will have to be
dug. processed and transported; mil
liens of cubic yards of rocks have been
or will be removed The project as a
whole including the dam and asSoci-
atcd power. irrigation and water prof.
ects. will cost hundreds of millions of
dollars
IN the desert Southwest water is
more than money; it means life. Hoo
ve- Dam will back up lake of water
large enough to cover the State of New
York to the depth of one foot-11 times
as much water as that impounded by
the Elephant Butte Dam in New Mex
leo, IL times as much as the great AS
suan Dam on the Nile in Egypt. This
huge rc-ervoir will pour fertility over
2,100, COO ceres of thirsty land. 1t will
put a. snQ to the menace Of floods in
Imperial ':lley. In addition it will
supply water to several populouS cities,
including Los Angeles and its environs.
Moreover, on its way to satisfy all
these thirsts the water impounded by
the dam will be forced to yield up
energy for industries as yet unborn.
The power plant at Hoover Dam will
be eb,e to generate 100000 horse
poWf.', and will be equipped to furnish
q continuous flew Of energy totaling
$4,000 horsepower.
Problems confronting engineers ct
TINNxnr TcV fro If
magnitude They were faced with diff
ficulties due to the isolation of the
site, extremes of weather, the towering
cliffs on either side of the river and
the treacherousness of the river, one
Of the most unpredictable streams on
the American continent. On the aver
age, the Colorado River discharges
about $4,000 cubic feet of water a
second, but in flood time it often en-
larges its flow to 100000 cubic feet
second. 12-fold increase.
Put Through Four Tunnels.
The first step in tanning such a river
Is to dispose of the water during the
to work. The Hoover Dam engineers
undertook this by driving four huge
tunnels-two on each side-through
the solid rock of the canyon. These
tunnels are each more than 5000 feet
long, and 56 feet in diameter, making
q total of 215 miles of tunnel.
The tunnels, one of which is now in
operation, represent the preliminary
step in damming the river Two OF
them will handle the ordinary flow of
the stream, even in high water. All
four will be called into play in time Of
flood. Water is low at present, and
IL IT,. 1y.%1 Il. = l.
has laid bare the bed of the Colorado
River for the first time in its history,
making it possible now to begin exca-
vation for the foundations of the dam
itself. Above the site of the dam there
Is now being erected a temporary cof-
ferdam, to drive the water into the by
pass tunnels. Below, another tempo
rary dam will be erected to keep the
water from backing up. On the site
proper 1t will be necessary to remove
mud and sand to depth of about $50
feet to reach solid rock.
Small as they bulk in relation to |
the entire project, the successful COM |
pletion of the four diversion tunnels |
nearly year ahead of schedule was |
an engineering achievement which Is |
. tribute to modern scientific methods |
and equipment. The length of the tun-
nels, the hardness of the rock, and es-
pecially the huge diameter of the bore,
taxed the ingenuity of the engineers
Most of the equipment had to be spe-
ctally designed for the task
The first step was the driving of pilot
tunnels II feet in diameter, which were
put through the rock by ordinary meth
DDS. The enlargement to the final size
was completed principally with the use
OF novel apparatus developed by en-
gineers at the site. This was the con-
struction of a drilling Jumbo series
Of platforms erected on a flve-ton truck
chassis, equipped with 80 pneumatic
drills. Rock can be removed rapidly
with this contrivance. It Is necessary
only to back up to the wall and set the
30 drills going.
Disposal Was Problem.
So much rock was removed that a
serious problem of disposal arose. The
best place to put it was in the bed of
the river, where it was hauled by trucks
and placed along the sides, making a
road at the base of the cliffs Another
problem raised by the drilling operation
was the volume CT compressed air
needed to operate the drills. More than
10000 cubic feet of air a minute was
required to meet the peak requirements
OF the schedule. To supply it three
compressor plants were constructed, the
air being fed to the points of operation
through 6-inch pipes.
The final step in constructing the