The Mankato free press. [volume] (Mankato, Blue Earth County, Minn.) 1879-1924, 1910-04-15
HARVESTING THE POWER IN THE BLUE
EARTH RIVER AT THE RAPLDAN MILLS
From Thursdays Daily.

OF six weeks before the concrete work
on the dam itself is begun. The pre-
urinary work is the slowest part OF
the job, for when everything is i'm readi-
ness for work on the dam itself things
will progress faster. Then a night shift
will be put at work. and the work will
go along day and night and Sundays
without interruption.
A Free Press reporter visited the dam
site yesterday and the officials in
charge very courteously explained the
work already done and its object. and
what is To be done, and gave detailed
description of the dam. The latter
will he entirely different from the pop
ular conception of dam. and embodes
the most modern thought.
Dam to Be Hollow.
The dam is to be hollow one with
thin walls, and the power plant is TO
be located inside of the dam, which
will he spacious room, 100 feet wide
at the bottom and 200 feet long, or
more. In here the huge machines will
be located, that will turn the power of
the river into electricity, to be conveyed
away in cables and put 10 thousand
uses i'm this city and the smaller towns
beyond. 1t is calculated that at least
1900 horse power will be developed.
the walls or shell of the dam are to
he constructed of Portland cement,
heavily reinforced with steel. Although
il will be light, when compared with
solid dams, such dam is said to be
much less likely TO go out in case of
freshets. The face of the dam being at
an .angle of forty five degrees, the
pressure of the water is as much down
ward aS il is pushing out on the DAM
so that il would be practically inn
possible for il to go out. The Ambursen
Hydraulic Construction company. which
has the contract for building the dam
for the Consumers Power company has
bnilt fifty of these dams and there has
been no trouble with any of them. it is
claimed. The dam is known as the Am
bnrsen hollow concrete DAM The ends
will be anchored i'm the rock formation
at the sides of the river with concrete.
and well protected from the river.
The drawing of Il cross section OF
the dam. accompanying this article,
shows what the construction is. At
intervals the shell is braced by solid
walls of concrete, extending entirely
through the dam from the deck TO
the apron. The water will he taken
into the plant inside of the dam
through series of openings, and after
passing through the generators will
flow ont ut the bottom of the dam,
under the apron. Any water that is
not used will flow over the top of the
dam. coming down behind over the
apron and joining that from the power
plant. 4. g.,.
Two doors at the end OF the dam will
give entrance to the floors that will
run through it. As the machinery is
all inside of the dam, there will be
little besides the dam in view after
ii is completed.
Concrete Wagon Bridge.
On top of the dam will extend the
new bridge. as shown i'm the cross sec
tion referred to. This bridge will be
twelve feet above the apex of the
dam, and will be supported on con-
crete piers resting on the buttresses
of the dam. The bridge will be six
teen feet wide. with concrete floor.
and will be $50 to 800 feet long. or
twice the length OF the present bridge
The water line of the river at the top
OF the dam will be 400 feet long, and
the bottom of the dam will be 200
feet long.
If any people think that the water
in the river will he raised as the dam
is built, they are mistaken, for the
basin above the dam is not to be filled
until the dam is completed, or practi-
cally so. The old bridge will be used
until the new one is completed after
The dam has been built. which will not
be until very late in the fall. 1t may
be January before the basin is filled.
The manner OF constructing the
dam will he interesting. Chief En-
oineer +. w. Witherell of Boston, VINO
has charge of the engineering work
assisted By Hugh Harvey and William
Lane, explained the work very fully
to the reporter. The first thing to-
do is to secure the right foundation
for the dam. A large force of men is
engaged in doing this now on the east
side of the river, dumping the eX-
cavated material into the water be-
low Much stone is being taken out,
bes sides earth, but it is not hard
enough to make good concrete ma
terial. Deep in the earth a fair
sandstone foundation has been found.
When the foundation for the two ends
of the dam has been uncovered. work
will begin i'm the harder task of get
ting to the foundation for the bottom
of the dam.
Will Use Golfer Dams.
A Golfer dam will be constructed
half way across the river, to get at
the rock bottom of the river The ont
side work for this dam, or cribbing,
has been constructed and rests on the
west shore When the cribbing has
been placed in the river it will be
planked up and made water tight and
the water pumped out and the exea-
walton sunk to the rock. This part
of the work will be begun in about
two weeks. While on the Golfer dam
is constructed on one half of the river.
tho ,ro ta, will ha Advocated 40 Tho oth pr