Wednesday, October 13, 2021

1871,1899,1941 Sylvan Slough Canal and Power Dams

Canal: (John A. Weeks IIISatellite)

These notes have the labels of energyHydro and powerhouse because the dams were originally mill dams and later they were replaced by hydropower dams. The USACE #15 Lock and Dam was evidently not needed to help create a head for these dams. The limestone bedrock is at the surface here and the USACE dam was needed to cover the rapids and cascades that existed between Iowa and Rock Island. Although the head for the 1942 dams may have been higher because of the USACE dam. 
The first power dam was built between 1869 and 1871. It started on the south bank of Sylvan Slough on the river bank at Moline, ran along the east shore of Sylvan Island, then crossed the channel of Sylvan Slough to connect with Arsenal Island. Water was drawn in from the Sylvan Slough channel, and exited a 2,100 foot long tailrace canal that was built as part of the 1871 project.
In 1898 and 1899, the 1871 project was removed and a new power plant was built at its current location at the east end of the tailrace canal. This new dam and powerhouse did not cross Sylvan Slough. Rather, a second dam and powerhouse for the Rock Island Arsenal was built across Sylvan Slough to support the US Army factories.
The 1899 power plant was again removed and rebuilt in 1941 and 1942. Those buildings exist today, and are still in use generating hydro power for the Quad Cities area. The generators have been upgraded several times, however, so the plant produces vastly more power today than when it opened in 1942.
The canal itself was cut from limestone, and the bottom is bedrock, which happens to be very near the surface in that area. This shallow bedrock is the reason for the rapids and cascades existing in the Quad Cities area.
The tailrace canal would have been built to bring the lower level of the west end of the Sylvan Slough peninsula further east to the base of the powerhouse to increase the head at the powerhouse.
Nathan Holth
[The bridge in the foreground is made with iron. As Nathan explained, it would have been quite common in the mid 1800s, but it is now a very rare historic bridge in the Midwest.]

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