Rock Island Argus. (Rock Island, Ill.) 1893-1920, 1901-12-05
DAM is MOVABLE
Novel Piece of Mechanism in
Connection With Henne-
pin Canal.
RESEMBLES AN IMMENSE BRIDGE
To Begin Construction Next Sum.
mer-Descrip-
ton.

y big surprise VIII be caused by
the announcemtnt that the Hennepin
canal dam across Rock river at Ster-
ling is TO be a movable dam. largely
of a mechanical nature, instead of a
solid wall of masonry, as il has been
pictured for the past few years i'm the
public imagination. 1t will resemble
an immense steel trussed bridge
about forty feet high rather than
dam. the latter feature being only n
part of the structure that will span
the river.
Large movable dams of any kind
are not common, but those heretofore
built, including one or more bridge
dams in use in France and the NOV
able dam formerly used to close the
canal of the Sault ST. Marie, are of
altogether different details from the
one that will attract the attention of
the engineering world to Sterling as
long as il continues to be a novelty.
The war department at Washing
ton has approved the plans for the
dam, with the exception of only few
minor details, and has returned the
plans to Capt. l.. l.. Wheeler. the de-
signer of the work, who expects TO
the middle of next summer. 1t will
be several years, however, before the
steel work, which will be let to some
bridge company, will be put up. Capt.
Wheeler states that it will probably
be four or five years before the canal
is entirely finished, and as the dam
will not be needed until then, il will
not be put up until the end of canal
work is much nearer than it is at
present. The big lake formed by the
dam is therefore not to be spread
out over the lowlands east of town
for some time, and when il is made,
the dam will be removed each year
at the close of the season of naviga-
tion and the water will recede to the
natural channel of the river for
two months or longer during each
winter.
Gates to Hold Back Water.
The water will be held back by a |
series of gates let down upon solid |
sill on the river bed. The gates will |
raise the water seven feet six inches |
above the sill, the total depth being |
ten feet ON the upstream side of the |
dam. At the ordinary stage the wat
err ON the site of the dam is not over |
two feet deep, so there will he raise |
of eight feet above the present sur
face of the river, allowing for six in
ches of water TO run over the gates.
The dam is to cross the river |
squarely. which will give ii IA direc
ton slightly toward the northeast,
touching the Sterling shore between
Broadway and Eleventh avenue and
a l. II. Ill. 4 l.. ]
entrance of the canal feeder. The
estimated cost of the structure is
sSs. OI5.2S. There will be two abut-
ments and seven piers of concrete,
the iers 156 feet apart from center
10 center. making the total structure
1850 feet between the banks. The
piers will be eight feet thick and
twenty-seven feet wide. They will
have n cutwater incline on the up
stream side.
Upon the piers a Pratt truss steel
bridge will be erected. The trusses
will have vertical end posts, instead
# sloping end posts such as are on
he free bridge. These vertical posts
will be used to help lift and lower
he gates. Ii should be stated that
he bridge will not be II thoroughfare
IF any kind and will not be open to
he public or used by any railroad.
[ will be merely a necessary adjunct
o the dam to allow the operation of
he mechanical parts and to brace
he structure for the strain caused
~ holding back the immense body of :
water in the lake.
To Escape Damage.
\ x.-il lNa fin a
he bridge and to the sill of the dam,
nd these metal beams will hold the
-ates in place. An ingenious safety
Iool< invented by Capt. Wheeler Will
asten the beams to the bridge by
means of which any beam may be re-
eased and swung down stream or