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In the future, when people talk about the great Hofmann Dam demolition project of 2012, they won't just be talking about the removal of the concrete dam built in 1950 on the Des Plaines River between Riverside and Lyons. They'll be talking about three different dams.
Last week, Illinois Constructors Corp., the company hired to do the demolition work, began pounding away at two older dams that survived after the 1950 dam was built further to the east. The horseshoe-shaped dam of 1908 turned out to be a pretty substantial structure made of reinforced concrete.
A backhoe fitted with a jackhammer pounded the 1908 dam into large chunks of concrete, which were hauled over to the Lyons side of the river. But an earlier dam located immediately behind the 1908 dam also remained.
Jeff Zuercher, the project manager from the U.S. Army Corps of Engineers, said the oldest structure appeared to be "rock cribs" or wood boxes filled with rocks. Piles of lumber and rocks could also be seen on the south bank of the Des Plaines last week.
With the dam structures removed, work will shift to restoring the banks on each side of the river, Zuercher said.
One part of that restoration will be to reshape the large boulders, or tow stones, that had been placed along the banks at the beginning of the project. The stones will be moved, so they won't be located as high up on the banks.
Crews will also work to reshape the banks immediately adjacent to the remnants of the 1950 dam. The banks will be realigned to match the outer "wings" of the dam and then planted, "so it'll make a nice meandering corridor and look more like a river path," said Zuercher.
Access roads built of wood and stone on either side of the river will also be removed, said Zuercher, and the ground will be regraded to blend into the natural landscape there. All debris will also be removed and hauled away, he said.
Zuercher said all of the work along the river upstream of the dam should be completed by the end of September.
"I'd be very surprised if they are out there in October," Zuercher said.
And the second phase of the dam removal project - the regrading of Swan Pond Park will begin in earnest this week. ComEd finished its power line replacement project in the park on Aug. 31.
"By Wednesday or Thursday, work should really be starting to move," Zuercher said.