The Idaho Republican. [volume] (Blackfoot, Idaho) 1904-1932, 1915-10-15

mtllion 0OliarS tributary 10 tnlS res
ervoir and it is estimated It will take
SO years to float and shoot it over
the dam. On the opposite side is a
concrete coated spillway cut out of
solid granite to take care of waters
in food season. 1t has capacity of
10000 second feet. The crest is 400
feet long and the water, rushing over
it, drops into trench 10 to TO feet
deep and is carried a distance of 900
feet around the dam cascading down
the mountain side into the river be-
low. For extreme flood waters the
dam Is so built as to allow flow of
four feet in depth to rush over 1t
without damage 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 con-
crete to fill the excavation for the
dam and raise it to it's present tower
ling height. A total of seven hundred
thousand cubic yards of rock and dirt
was excavated for both dam and spill
way 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 regu-
larity of a clock. Electric cars then
rushed the concrete into tunnel to
the distributing tower. Galloway
buckets sailed through the air be-
tween the tower and hopper. 1t was
then distributed from the hopper by
chute to various points on the dam.
In less than three minutes from the
time gravel left its bin at the mixing
plant, it was in its final resting place
in the concrete of the dam. Every
day saw the dam 1000 cubic yards
nearer completion.
A sand cement plant with capa-
city of 1000 barrels per day of "a
hours or a total output of 585,24O
barrels saved the government thou
sands Of dollars. Crushed granite
run through this plant and ground
with Portland cement, was mixed As
per cent said fro mthe granite and
SIS per cent Portland cement giving
better and stronger mixture than
pure cement. The mill was erected
below the dam. Granite from the
spillway excavation was passed to it
through a chute, run through rock
crusher and sand rolls, dryer and ball
mill and pulverized to pass 20-mesh
sieve. Mixed later with Portland
cement it passed through a 2O0-mesh.
Afterwards it was stored in large
covered bins and as needed was
blown by air pressure through tube
across the excavation to the mixers.
All sand cement passed thorough
tet before used. The plant is now
being dismantled.
Before the foundation was laid,
holes were drilled 80 to 40 feet into
the granite bed and grouted with
pure cement under air pressure to fill
all possible crevices. These holes
were carried up into the dam to-
gether with seepage test holes into
the inspection galleries where grout-
ing machines can be set up and
grouting resumed If water is found
to seep through. If seepage de-
velopes the water will be carried on
Through the galleries.
The dam was started four years
ago and completed over year ahead
of time at a saving under the esti-
mates of $2,5OO,OO0. The total cost
was five million dolalrs. Behind 1t
is impounded enough water to flood
the city of Boston with eight Ieet
of water, or 244,3OO acre feet. II
spread over $50 square miles it would
cover that area foot deep. The
reservoir so created is IS miles lang
bounded by mountains; the water 10
200 feet deep. This water together
with that in the Deer Flat reservoir
below will irrigate 100000 acres of
land in the Boise project, located in
western Idaho tributary to Boise.
When used for irrigation purposes
the water is allowed to pass from the
outlets in the dam back into the river
below which carries it Is miles down
stream where a diversion dam d.
verts it into the New York canal, q
cement lined artificial river, which
in turn takes it on IS miles to he
valley below for storage in Deer Flat
reservoir from which it is passed
through the distributing canal system
to the lands.
|