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HAER;
Satellite, gone)
A butterfly dam is a movable dam. Gates the full depth of the canal hang from a swing truss. This one would normally be open as shown because it was intended to help with flood protection. Evidently MWRD wanted to make sure that they could divert excess water through the
control structure that is just beyond the dam on the left in this photo, which is looking upstream. Since this dam design is so rare, I have added the "wwDamTech" label on this post. The only other movable dam I remember reading about was an
emergency swing dam on the Canadian side of the St. Marys River.
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Photo from HAER ILL,99-LOCK,3A--7 (CT) from il0434
VIEW OF THE CHICAGO SANITARY AND SHIP CANAL BUTTERFLY DAM FROM THE NORTH - Lockport Historic District, Chicago Sanitary & Ship Canal, Butterfly Dam, Lockport, Will County, IL
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The Butterfly Dam was constructed in the middle of the
Chicago Sanitary and Ship Canal for the purpose of
providing flood protection for Joliet and other points on
the canal west of Lockport. The dam is unique in that it
is suspended from a Pratt truss bridge which is supported
by two concrete piers. The dam is on a pivoting mechanism,
so it can be turned to cross the canal and block the flow
of water. It is 30 feet high, and has six electrically
operated valves on each leaf. The need to use the dam for
flood prevention seems never to have arisen. [HAER-data]
You can clearly see the dam in the middle of the navigation channel in this old photo. I include part of the control structure to provide context for the location.
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MWRD posted
Construction of the Butterfly Dam on March 18, 1907, looking south from the north end the Chicago Sanitary and Shipping Canal (CSSC) channel extension at Lockport. Between 1903 and 1907, the Sanitary District of Chicago (now MWRD) extended the CSSC and built the Lockport Powerhouse and Lock in order to generate hydroelectric power and to allow passage of watercraft between the Des Plaines River and the CSSC. The Butterfly Dam was built in 1907 and was intended to prevent downstream flooding in the case of a failure of any part of the channel extension structures including the channel walls, powerhouse or lock. The steal leaf of the dam could be rotated to close off the flow of water in case of an emergency. Such an emergency never occurred and the Butterfly Dam was removed in 1985.
 Top FanIn the background is the first image I have seen of the 9th Street Bridge. |
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MWRD posted on Dec 10, 2022
Construction of the Butterfly Dam on March 18, 1907, looking south from the north end the Chicago Sanitary and Shipping Canal channel extension at Lockport, Illinois.
[Same photo as above but cropped differently?] |
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Photo from HAER ILL,99-LOCK,3A--6 from il0434
6. View of the south end of the dam looking northwest with Lockport visible in the background - Lockport Historic District, Chicago Sanitary & Ship Canal, Butterfly Dam, Lockport, Will County, IL
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As the above photo shows, we can't trust the directions in the photo captions. But it doesn't matter because the dam was symmetrical. We can see six electric motors for the six "valves." It is not at all clear to me what the open position of the "valves" looks like.
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Photo from HAER ILL,99-LOCK,3A--3 from il0434
3. North end of the butterfly dam showing stone abutment - Lockport Historic District, Chicago Sanitary & Ship Canal, Butterfly Dam, Lockport, Will County, IL
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Photo from HAER ILL,99-LOCK,3A--4 from il0434
4. Center section of the dam showing the pivoting mechanism - Lockport Historic District, Chicago Sanitary & Ship Canal, Butterfly Dam, Lockport, Will County, IL
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MWRD posted on Oct 8, 2022
Construction of the butterfly dam on May 16, 1907, in the Chicago Sanitary and Shipping Canal (CSSC) channel extension at Lockport, Illinois. |
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MWRD posted
Construction of the Butterfly Dam, at left, and the west wall of the Chicago Sanitary and Shipping Canal (CSSC) channel extension at Lockport, Illinois, on June 18, 1907. Between 1903 and 1907, the Sanitary District of Chicago (now MWRD) extended the CSSC and built the Lockport Powerhouse and Lock in order to generate hydroelectric power and to allow passage of watercraft between the Des Plaines River and the CSSC. The Butterfly Dam was built in 1907 and was intended to prevent downstream flooding in the case of a failure of any part of the channel extension structures including the channel walls, powerhouse or lock. The steal leaf of the dam could be rotated to close off the flow of water in case of an emergency. Such an emergency never occurred and the Butterfly Dam was removed in 1985.
Gary Ward: The Ninth St swing bridge is visible in the background.
MWRD posted |
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MWRD posted on Jan 29, 2022
Construction of the Butterfly Dam on June 18, 1907, looking southwest in the Chicago Sanitary and Shipping Canal (CSSC) channel extension at Lockport, Illinois. Between 1903 and 1907, the Sanitary District of Chicago (now MWRD) extended the CSSC and built the Lockport Powerhouse and Lock in order to generate hydroelectric power and to allow passage of watercraft between the Des Plaines River and the CSSC. The Butterfly Dam was built in 1907 and was intended to prevent downstream flooding in the case of a failure of any part of the channel extension structures including the channel walls, powerhouse or lock. The steal leaf of the dam could be rotated to close off the flow of water in case of an emergency. Such an emergency never occurred and the Butterfly Dam was removed in 1985. |
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MWRD posted on Oct 19, 2022
A view to the south showing the Butterfly Dam in the closed position on August 14, 1907. The dam was built in 1907 and was intended to prevent downstream flooding in the case of a failure of any part of the channel extension structures including the channel walls, Lockport Powerhouse or lock. The steal leaf of the dam could be rotated to close off the flow of water in case of an emergency. Such an emergency never occurred, and the Butterfly Dam was removed in 1985. |
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MWRD posted on Apr 3, 2023
A view to the south showing the butterfly dam in the closed position on August 20, 1907. |
A couple of colorized postcards.
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