The Washington herald., 1911-11-19

the gigantic dam is being accomplished
A timber crib cofferdam 400 feet long is
built around a section Of the dam and is
made watertight by means of clay pud-
| die Then the water is pumped out of It,
| and in the space thus pumped dry is ex-
! cavated trench in the solid rock on
which the dam is founded. The piers and
I arches forming the bridge and the bottom
/ part Of the dam between these piers are
] then built.
After this the cofTerdam is removed: an
other section OF 400 feet IS cofferdamrhed,
and the process of construction is con-
tinued in the same way. This will go
on until the bridge is extended all the
way from the Illinois shore to the juno
ton with the power house on the Iowa
side. incidentally there are left 116 or
more large openings bet Heen the bridge
piers, through which the water passes
unobstructed. These openings will finally
he closed. a few at time, by steel gates,
and the balance of the concrete part Of
the dam will be placed behind these steel
gates, gradually raising the crest OF the
dam until II has reached its full height.
The rover house Gtself a marveD will
be l23 feet wide and a quarter OF a mile
long. Its substruCture is being built of
massive concrete. in which are nodded
the water passages and water-wheeI
chambers. For this purpose the method
adopted Is to construct a cofferdam
around the entire area to be occupied by
the power house, ncIosing about thirty
seven acres, to pump the water out OF
the Enclosure, and then to proceed with
the concrete work Tho latter is a kind
of work presenting extraordinary difficult
ties, inasmuch as the molds or forms for
the water passages and wheel chambers
are complicated.
Huge Power House.
placed 4 superstructure of brick and steel
which will contain the electric genera
tors, transformers, and switchboards. The
height of the power house from founda-
ton to roof will be 133 feet. From 1t
will run a wall of concrete, built I'M
stream, and curving to a junction with
the shore. This wall, over half a mile
long, will be designed as an ice fender,
for protection against logs and floating
ice. Below the surface of the river it
will have arched openings, through which
the water will find its way to the power
house
The United States government built in
1877, and has since maintained as an aid
to navigation, a drydock, a canal. and
a series of three locks. extending along
the Iowa shore from Keokuk to a point
below Fort Madison-a distance Of eleven
and half miles. These made feasible the
points above and below the rapids. But
the artificial lake created by the new
dam will suomerge the old canal and
locks, and so the company engaged in
making the hydro-electric improvements
at Keokuk has been required by the
government to construct a lock and dry
dock which will conveniently and safely
accommodate the present and prospec-
tive commerce of the Mississippi River.
while affOrding ample facilities for the
repair of vessels. Incidentally II Is de-
manded that suitable fishways shall be
provided, by which fishes may pass up
and down the stream.
The project now being carried out,
while utilizing for power purposes the
entire energy Of the Des Moines Rapids,
will transform navigation perhaps as
difficult as anywhere along the Missis-
sippi into comparatively safe and con-
venient travelling. It is estimated by
the engineers in charge OF the work that
the minimum amount of water passing
Keokuk at the season when the river is
lowest is. certainly not less than 10000 |
cubic feet per second. Probably 1t is |
quite a bit more than that. There is to |
be only single lock under the new |
arrangement, and, in addition to build |
ing this lock and the drydock, the COM !
pany has agreed to carry out certain |
Improvements in channel facilities i'm |
mediately below the dam. The lock will |
be of concrete and steel. 400 feet longI
from, gate to gate, 110, feet wide. and |
capable OF lowering vessels about thirty |
five feet. Between 1t and the bank OF
the river will be the concrete drydock, /
+SS feet long. and 40 feet wide.s
The New Turbines.
To start with, 1t Is planned to install |
fifteen main pressure turbines, each with
a capacity OF 1850 horsepower. There |
Will be step-up transformers OF suffi- |
Client capacity to deliver In st. Louis the
50, 900 electrical horsepower already con-
tracted for In that city. Later on, how
ever, there will be thirty turbines and |
and four or more EXETER tur-
hines for the generation Of at least S0o.-
300 delivered horsepower, making the out
ut one OF the greatest hydro-electric |
plants in the world. REM BA0HE I