The daily Gate City. [volume] (Keokuk, Iowa) 1855-1916, 1911-12-20
Are Made of steel Frames and Plate.
and Fitted so True That There
viii be No Leakage
Through Them.
RESIST
IRRESISTIBLE
Will Keep the Water Level Above the
Dam at One Exact and Con.
slant Height Regardless of
River Changes.

One hundred nineteen gates each
made like bridge truss thirty-two
feet long, eleven feet high and nearly
two feet thick sliding up and down in
grooves as easily as the door of a
chicken coop, although weighing, a
good many tons-this is one of the
details Of the greatest dam on earth
here at Keokuk.
The necessity of keeping the water
above the turbines at one certain
height all the time made necessary
some method of causing more or less
water to run over the big dam, ac-
cording to river conditions. The
method chosen was the use Of gigan-
tic gates with the function of what
have previously been called stop-logs
although here at Keokuk the thing
seems to have become too big for
the word.
These gates are to be placed in the
bridge spans above the spillways, fill
ing the space under the arches to the
top of the spans.
As Big as the Side Of a House.
Each gate is built up of structural
steel criss-crossed and riveted and
braced something like the frame of a
titanic harrow. Then the frame
work is covered with plates of steel
over half an inch thick, making a
steel wall eleven by thirty-two feet in
size and water tight The steel frame
work covered by the steel plate fac
ing is one Of the gates.
An important part of the whole
thing is the point of pressure. The
hitherto irresistible Mississippi will
press against a closed gate with a
steady, great force. This force will
be resisted by the downstream face
of the grooves in which the plate is
placed.
There is a groove in the concrete
dam pier on each side of the arched
opening. Each groove is a little less
than two feet wide and about foot
deep and extends vertically from the
top of the bridge structure down II
the top of the spillway.
How Pressure Prevents Leakage.
1 The total thickness of a gate is
| twenty-five inches, and there is about
a half inch of clearance space, between
/ its end and the walls of the groove
all this clearance being on the up
stream side, because the tremendous
weight of water is pressing the gate
/ tightly downstream.
| Each end of a gate, pressing with
| many tons force downstream, is fac
ed with smooth plate on that side
which plate presses against an ,iror
| facing of the groove in the concrete
pier 1t is these two plates, one or
| the gate and one on the concrete
which is the point of contact anc
counter forces as the gate is in place
with head of water against it; ant
| it is at that point of contact that the
friction occurs when gate is raised
or lowered.
The great pressure against the
gates makes that joint water tight
The bottom of the gate, true as t.
line and smooth as to surface. rests
with all the weight of the entire gate
upon an iron sill of the same Width
set down into the concrete of tn,
crown of the spillway and permanent
] ly anchored there. The trueness o
| this contact and the great weight
sustains makes water-tight join
there at the bottom of the gate. N,
packing is used, and indeed would b,
impractical with such great forces II
use, but there will be no leakag
when the gate is closed.
Everything Prepared for.
The dimensions and quality of tn
plates of contact are sufficient to en-
able them to last for many years.
But provision is made for any re
pairs needed at any time to the gate
or to the grooves in which they NOV
up and down.
The crane which will be built upol
the completed dam is designed i
such fashion that 1t will not only rails
and lower each gate as much as nee6
ed in the operation of the WATERPROOF
er, but may lift any gate entirely on
of it's place and lay it on top of tn
dam structure where every part of
may be reached. Since almost an
time at least one gate may be opene
completely, any gate may be taken GU