The Caldwell tribune. [volume] (Caldwell, Idaho Territory [Idaho]) 1883-1928, 1915-09-17
ARROWROCK DAM IS
A MASTERPIECE

Boise, Idaho, Sept. 16-If the con-
crete in the Arrowrock dam, the high
est in the world located 20 miles
above this city, which will be officially
dedicated October 4 with appropriate
services here, were placed in the aver
age block in most any city in the Unit
ed States, it would stand flush with
the four streets around it, as high as
a 15-story edihce; if it were put into
column 10 feet square, it would stand
20 miles high. No bigger job of con-
4crete mixing for one structure was
ever attempted before in this coun-
try. Today this dam stands complet-
| ed, tribute to the Reclamation Serv-
ice and engineering and constructing
ability of F. E. Weym outh, supervis-
ing engineer of the Idaho district
Charles H. Paul, construction engin-
eer and James Mum, superintendent
of construction.
If this masterpiece in concrete could
be weighed it would tip the beam at
over million tons. Today it is
wedged and anchored in arch shape
with radius of curvation at 662 feet,
| LOO feet long between sheer noun
tains towering a mile high. Its to-
tai height is BASS feet, 81 feet Of
which is below the Boise river bed
across which it has been constructed.
1t rests on base 240 feet wide which
represents its thickness where it is
concerted to granite. AT the top it is
| 10 feet wide, crested with concrete
roadway guarded on either side by a
parapet wall four feet high browning
which are arc light pedestals the en-
| tire sweep of the curve. The sides
are also anchored to granite cliffs.
Inside of it are spacious inspection
| galleries running its full length at
various levels, the lowest 230 feet be-
low normal high water surface In
these galleries is the mechanism that
operates the 20 outlets controlling the
impounded water. Today two of these
four-feet and four inches in diameter
control the total flow of the river.
There are more steps inside the ap-
parently solid dam than are found in
most hostelries. They, too, are made
of croncrete.
One side of this mighty dam con-
tains a concrete deck over which logs
foated down the reservoir can be
snaked across and shot into a concrete
chute through tunnel and dropped
90 feet into the river below. There
are three billion feet Of merchantable
timber valued at thirty-six million
dollars tributary to this reservoir and
it is estimated it will take fifty years
to float and shott it over the dam.
On the opposite side is a concrete
coated spillway cut out of solid gran
lite to take care of water in the flood
season. 1t has capacity of 10000
second feet The crest is 400 feet
long and the water, rushing over it,
drops into a trench 10 to 20 feet deep
and is carried a distance of 900 feet
around the dam cascading down the
mountain side into the river below.
For extreme flood waters the dam is
so built as to allow a flow of four feet
in depth to rush over it without dam
age to the structure.
Turning constantly, mixing and
kneading their two-ten charge of con-
crete, double cone mixers churned
for four years to mix enough concrete
to fill the excavation for the dam and
raise it to its present towering height.
A total of seven hundred thousand
cubic yards of rock and dirt was ex-
cava ID for both dam and spillway and
six hundred cubic yards of concrete
were dumped into the dam Where it
was possible great boulders were used
in the construction. A mountain side
of gravel was moved, screened and
. dumped into gravel trains and carried
Is miles to the mixers. These dumped
with the regularity of clock Elec-
trict cars then rushed the concrete
into tunnel to the distributing tow
er. Galloway buckets sailed through
the air between the tower and hop
> per. 1t was then distributed from the
hopper by chute to various points on
the dam. In less than three mnu>
ties from the time the gravel left its
bin at the mixing plant, it was in its
final resting place in the croncrete of
the dam. Every day saw the dam
1000 cubic yards nearer completion.
A sand-cement plant with a capac-
ity of 1000 barrels per day of "a
hours, or total output of 585, 240 bar
rels, saved the government thousands
of dollars. Crushed granite run
through this plant and ground with
Portland cement, was mixed As per
cent sand from the granite and S.
: per cent Portland cement giving a bet
ter and stronger mixture than pure
cement. The mill was enected below
the dam. Granite from the spillway
excavation was passed to it through
a chute, run through a rock crusher
and sand rolls, dryer and ball mill
and pulverized to pass of 20-mesh
sieve. Mixed later with Portland
cement it passed through 200-mesh
sieve. Afterwards it was stored in
large covered bins and as needed was
blown by air pressure through a tube
across the excavation to the mixers.
All sand cement passed a thorough
5 test before used. The plant is now
: being dismantled.
Before the foundation was laid
holes were drilled 30 to 40 feet into
the granite bed and grouted with pure
cement under air pressure to fill all
nnEc:kln nrn.r.cnr ill., ILL.,. ......