El Paso herald. (El Paso, Tex.) 1901-1931, 1913-07-31
Hats


! the world, the Keokuk dam, is the dam
/; itself, the colossal barrier of concrete
I that halts the Mississippi on its course
to the Gulf and diverts its waters
4 through a power house where their
! power.
No such dam ever was built before.
! no such river ever was halted before,
4 there were no precedents and no guides
I TO follow. It was an engineering
! problem as difficult in its way as that
at Panama, and one the solution Of
| which can stand only second to that
| of the great canal
Nature Helps in Work
At Keokuk is the foot of the Des
Moines rapids, place where nature
work In the II miles above Keokuk
! the water falls % feet and it is these
rapids that have always INSTRUCTED
navigation in the upper Mississippi.
The power house was to be on the
Iowa side. The dam was started from
the Illinois side. keyed into the lime
stone bluff and built out into the river
under the protection Of an advance
cofferdam. Another cofferdam IN
Watered the bed Of the river on the
power house site. Including the abut-
ments, the dam is a mile long, but the
dam itself, the 119 concrete spans,
measure 427S feet. or over four
fifths of a mile. Each pier is six feet
thick, the distance between the pier
the inside measurement of the spans
is so feet The viaduct that tops
the dam structure is 29 feet wide and
the dam at the bottom of the river is
AZ feet wide.
Work Is Done Gradually.
When these piers Were finished the
dam had the appearance of a many
spanned bridge, for there was nothing
comparatively little obstruction to the
river flow. The spillways between the
piers were built in later. On the up
per side they have a vertical face, but
On the down stream side they are so
curved down and out that their sur
face is just the shape of the under
side of the water as it falls over the
top of the spillway. These spillways
were built gradually so as to offer the
minimum resistance to the flow of the
river. The work was done by building
slowly from one side of the river to
the other, and also by building slowly
from the bottom up Five feet of con-
crete was laid at first between two
piers, the only obstruction then being
one 80 foot Golfer dam in the whole
stream. Span at a time was filled in
this way, until the bottom layer was
finished Then another five foot LAYER
was built all across, span at time,
and so on until the last layer brought
the top of the spillWay sections to 81
feet above the river bed.
On the up river side Of each span
the top Of the spillWay. in which slots
slide 11S steel gates. These can be let
down so as to form a complete obstruc-
ton TO the river These gates are Il
by 30 feet in dimensions and will be
raised and lowered by electric power,
each being operated singly from an
electric power, each being operated
slngly from an electric travelling crane
On top Of the viaduct These gates
VIII keep the water above the dam at
a constant level, never varying. In
nigh water they will all be open and the
surplus will flow through In low wa
ter a sufficient number of them VII
De closed to maintain the desired level.
Calculations Carefully Made.
On account Of the great range OF
temperature at this point, nice calcu-
Iatlons had to be made of the probable
erect on the cement structure Ex-
pansion joints were set in the TOP of
the dam, sheets Of tar paper being sus-
pended vertically across the structure
inside the steel molds when the con-
crete was poured in When this paper
which viii pull apart in hot weather
and close up in cold Careful expert
ments showed that these expansion
joints were necessary only for the sur
lace work, as the concrete under wa
ter would be but little affected by the
change in temperature
The actual work of construction was
most difficult. The Golfer dam built !
dAAEcu VI the Jam sections was OF cTlDS /
of logs, filled in with rock and faced I
with a seal of puddled clay. The log
work was done by timber jacks from
canada, men who were trained in the
handling of heavy logs IN swift water.
A ra1t the size of the crib would be /
made and floated out to the place
where the crib was to be sunk Then
eareIuI measurements were made OF !
the bottom of the river at that place /
and the bottom set of logs cut to fit I
Then the logs were built up criss cross, I
ike log house, and filled in These
usedams leaked but little and made the /
use OF the concrete comparatively easy. /
First Span From Illinois side
The first span was built from the Il /
Anols shore and then each succeeding /
span worked out from that end. AS |
The last few were always too soft to !
work on huge travelling crane of the (
canuleVer type was employed, a l
monster with an arm $50 feet long, 1
from which it poured the concrete n 4
the forms When built it was the 4
largest travelling crane in the world, /
ana OF itself was one Of the chief items /
In the more than a million dollars /
worth of tools used in the work on the /
power plant.
The dam was built, of course to Gre
ate power, but as the Mississippi is a
river it must be kept so
Therefore the power company agreed /
In consideration of permission to
build the dam to keep open navigation
ana TO SUBSTITUTE Tor the old govern
ment canal that skirted the rapids on
the Iowa side new canal, lock and
dry dock This part of the work alone
cost over two million dollars.
Lock Larger Than Panama.
The lock here is larger even than
those at Panama, being of equal
width, ITO feet, and of greater height
The lock chamber is much shorter, be-
ing only 400 feet inside measure
nent, since the steam boats on the
river do require such a length of wa
ter space The gates at Keokuk,
built exactly as are those at Panama,
are higher, the lift here being 40 feet /
as against 80 feet and % feet in the I
Panama locks The total lift is great
er at Panama, but there the locks re
built in stairs of three flights. The
lower gate of this lock is just like !
those at Panama, except that it Is
higher. The upper gate at Keokuk is
IF an entirely new type of lock gate,
being raised and lowered in a vertical
runway by hydraulic power. Over the
-op of this gate when lowered runs
he railroad track that will convey
supplies to the power house in the
liver.
Boats may pass through this new
ock in from 10 to Is minutes. as COM
Jared with two or three hours through
he three locks Of the old canal. to say
lothine of the two hours slow going