Page images
PDF
EPUB
[blocks in formation]

Building a Butterfly Dam

A

By William Hard

S the sewage of Chicago, pouring into the Chicago River from all the houses in an area of some two hundred square miles, goes down the South Branch into the Drainage Channel and down the Drainage Channel to the Illinois River and to the Mississippi, it will encounter, near Lockport, a new and a wonderful kind of dam, a "butterfly" dam, a dam that will be capable of being swung around bodily, in the current of the stream, on two enormous metal pins.

It is perhaps a mistake to say that the sewage of Chicago will itself encounter this dam. By the time the water of the Drainage Channel reaches Lockport it is

astonishingly clean and clear. Running water, like a successful man, purifies itself as it advances and if it goes far enough no one can reproach it with its past sins. Lockport is only about thirtyfive miles from Chicago, but by the time the polluted waters of Lake Michigan and of the Chicago River have arrived at that point they look as innocent as if they had never had any past at all.

It is water, then, and not sewage which will float toward the "butterfly" dam. But it will not float over it. That is the curious thing about "butterfly" construction. The water will float by the dam. The dam will swing aside to let it pass, just as a bridge swings aside to let an ore-steamer go down the Calumet River.

[graphic][merged small][merged small][ocr errors]

CHANNEL WHERE WATER, WHICH NOW GOES DOWN BED OF OLD DES PLAINES RIVER, WILL RUN.
The butterfly dam may be seen in the distance.

This remarkable dam will be one of the greatest curiosities in that museum of curiosities, the Chicago Drainage Channel. The spectacle of a river flowing the wrong way against its natural inclination, the mountainous cañons of clay and rock through which the sewage of a great

of a big steel girder, will be some ten feet wide. With body and wings, the butterfly dam will stretch almost two hundred feet across the channel from bank to bank and, when it chooses, will absolutely stop the whole flow from Lake Michigan to the Mississippi.

EXCAVATION WORK AND CONSTRUCTION OF DAM.

city is conducted across the quiet plains of an inland state, the gigantic concrete caverns through which, near Joliet, the waters of the channel will plunge downward, making electricity as they plungethese things will not attract a larger number of amazed spectators than the dam which flutters its wings in imitation of the beautiful insect after which it is named.

It will be a rather large butterfly. Each of its two wings will be some ninety feet long. Its body in the middle, consisting

The butterfly's body, the central girder, has just been completed. It is the largest girder ever put together in a workshop in Chicago. A few days ago, when it was lying on its side in the long, grimy room which was its birthplace, it looked more like a New York flat than like a girder.

Many a New York flat is less spacious. This girder is a big oblong box of steel, thirty-two and a half feet in length. It has seven rooms inside of it. Each of these rooms is nine feet high and eleven feet long. Their average width is about five feet. Seven rooms placed end to end, seven chambers of hard steel-that is the girder which will form the body of the butterfly dam; and many a family paying a high rent can be seen living in less extensive quarters.

When this overgrown monster had been put together (it grew originally in more than three hundred separate steel-pieces and now enjoys the possession of more than seven thousand steel rivets which hold its three hundred steel limbs together and serve it as joints), when this body of the butterfly was finally ready for shipment, with all of its seven thousand rivets hammered red-hot into place with air-driven hammers, the railroad hunted all over its lines for a long time to find a car that would be capable of moving it. That car was never found. The railroad officials at last. contented

[graphic]
[merged small][graphic][merged small][merged small][merged small][graphic]

BEAR TRAP DAM, OVER WHICH WATER NOW POURS INTO OLD DES PLAINES BED. This is the present terminus of the drainage canal. The new channel will run parallel to the Des Plaines.

THE TECHNICAL WORLD MAGAZINE

[graphic]

CUTTING AWAY ROCK FOR COMPLETION OF THE DRAINAGE CANAL.

[graphic][merged small]
[merged small][merged small][graphic][ocr errors][subsumed][subsumed][subsumed]

beneath the bed of the stream and assist ing the metal of the dam to withstand the push of the waters of the Drainage Channel, the waters of the Chicago River and the waters of Lake Michigan.

At the bottom, then, the mass of concrete. Above it, the little-brother girder, reposing on its side. Above that the, big girder, standing upright and rising to the surface of the water. All these in the center of the stream.

On each side of the big girder, spanning the distance between its huge bulk and the banks of the channel, will stretch the wings.

Each of these wings will have seven ribs, seven ribs of steel. Each rib will be ninety feet long. If the construction should stop at this point the dam would

whole dam will be practically one big piece of metal.

Between Chicago, therefore, and Joliet, which is the end of the Drainage Channel, there will rise at Lockport this strong steel barrier, reaching from bank to bank of the Drainage Channel and restraining all possible excessive ambitions on the part of the waters of Lake Michigan.

The top of the butterfly dam will rise. to exactly the same height above sea level as the surface of the waters of Lake Michigan. Not one drop from the lake will be able to flow to Joliet or to St. Louis when the dam is closed. It is clear, therefore, that in a way the butterfly dam will be the southwestern shore of Lake Michigan. It will represent the farthest southwestern reach of that lake

[ocr errors]
« PreviousContinue »