Shepherdstown register. [volume] (Shepherdstown, Va. [W. Va.]) 1849-1955, 1912-07-25
Damming the "Father of. Waters. -

The Mississippi River is to be curbed
and harnessed at last. The greatest dam
that has ever been built in this country
now bridges half the nearly mile-wide
gap between Hamilton, Illinois, and Ke-
okuk, Iowa, at the foot ofthe Des Moines
rapids. Only one other similar structure
in the whole world is larger, the colossal
Assuan Dam across the Upper Nile,
which provides uniform water-supply
for the rice-fields of Egypt. The Miss
issippi River project is not to serve an
agricultural purpose. 1t will develop
from two hundred thousand to three hun
dred thousand horsepower for the lar
gest single power-plant in existence, and
will also greatly improve navigation in
the most difficult stretch Of the river be-
tween St. Paul and St. Louis.
Although the Mississippi River is over
two thousand five hundred miles long,
almost three times as long as the Rhine,
and with its fifty-four navigable tributar-
les drains two-fifths of the entire United
States, region nearly as large as the
whole of Eastern Europe, its descent is
very gradual, and there are but few falls
and rapids in the entire watershed. The
cities of st. Paul and Minneapolis, al
though two thousand miles from the
mouth of the river, are but eight hundred
feet above sea-level.
The Des Moines rapids, however, al
ford opportunity to develop enormous
power. They extend from Montrose,
Iowa, to the mouth of the Des Moines
River, within the site of the three States
of Illinois, Iowa and Missouri. In dis
tance of twelve miles the river falls about
twenty -four feet, and the minimum daily
flow OF water is twenty thousand cubic
feet second. The velocity of the stream
is about two and one-half miles an hour,
but the bottom of the river is so smooth
and free from boulders or projecting rocks
that foam and eddies seldom disturb the
surface of the water. The rapids are not
navigable, except at high water; at 9th
er times vessels have been obliged to
pass round them through a government
canal eleven and half miles long, which
contains three small locks. When the
great dam is completed, there will be a
single lock one hundred and ten feet
long and four hundred feet wide, large
enough to accommodate vessels OF greater
size than any now afloat on the lMissis-
sippi. The water-level Of the dam will
be about thirty-five feet higher than at
present, and in place of the rapids there
will be great lake, sixty-five miles long
and mile and half wide.
The Des Moines rapids flow over a
continuous level bed OF smooth blue lime
stone, many miles in extent; high bluffs
of the same hard rock line both banks OF
the river. Limestone is formed by the
sediment deposited by water, and affords
an ideal foundation for the colossal dam.
Engineers declare that on such founda-
tion a well-constructed concrete dam,
power house, dry dock and lock should
last longer than the famous concrete
structures of the Romans, many OF which
have existed for more than twenty CEN
turies. 1t is interesting to notice how
rigidly the modern engineer tests even
such ideal foundations as these. Every
twelve yards throughout the whole length
of the dam holes are drilled in the lime
stone rock to depth of thirty-six feet.
Air at one hundred pounds to the square
inch is applied to each bore-hole, and
cages in the adjoining holes show it there
is any leakage Of air from the hole at
which pressure is applied. If leakage IS
perceptible, the excavation is carried
down until solid, impervious rock bot
tom is found.
The immense barrier that is to control
the flow of the "Father of Waters" viii
consist of three great divisions: first, a
dam four thousand four hundred feet
long and fifty-three feet high, extending
from the Illinois side in a straight line
across the river; second, power-house
one thousand seven hundred feet long,
nearly parallel to the shore and at right
angles to the main dam; third, a lock
and dry dock-thatw will connect the south
ern end of the power-house with the
Iowa shore. The entire concrete wall
will be nearly mile and quarter long.
and more than half million barrels OF
cement and seven thousand tons OF steel
will be used in its construction.
The dam itself consists OF one hundred
and nineteen massive concrete arches.
These form a bridge, the level OF which
is fifty-three feet above the bed OF the
river. Each of the spans OF the bridge
will be walled up TO a point thirty-two
feet from the river-bottom. These In
terspan walls will form the great spill
way of the dam, and the level OF the wa
ter may be maintained at a still higher
level by the use of steel lash-boards con-
trolled from the top of the dam.
The great steel and concrete power
house will be; large enough to contain
thirty turbine wheels, capable OF
generating ten thousand horsepower
each. The present plans, however, pro-
vide for the use of but half that number
of turbines. The discharge from each