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.

River ‘coming alive’ upstream of old dam

One of the primary reasons given for removing the Hofmann Dam was to improve the ecosystem in the Des Plaines River, upstream from the dam. And just weeks after the dam was notched, according to the Illinois Department of Natural Resources, that’s already beginning to happen.

Steve Pescitelli, a stream specialist for the IDNR’s Division of Fisheries, told the Landmark last week that there are now at least 20 species of fish living above the old dam site – almost double the number seen there prior to the dam’s removal.

On Aug. 24, a team from the IDNR was on the river between the dam and Salt Creek doing some electrofishing, using a low electrical charge to temporarily stun fish so they can be scooped up and analyzed.

In the past such expeditions in the lagoon behind the dam netted 20 to 30 fish, said Pescitelli. Last week, they caught “hundreds.”

“One of the more remarkable things was the productivity,” said Pescitelli. “There were minnows everywhere, where there were very few before. There were clouds of minnows along the banks. We netted a bunch of those.”

Among the species netted that day were a northern pike and, the most exciting find, a channel catfish.

Pescitelli said the catfish was important, because that fish likely swam upstream from below the dam.

“You don’t find those above dams very often,” he said.

No longer are fish avoiding the formerly murky, still waters of the old lagoon. The channel has narrowed dramatically, but the river is moving swiftly through a chokepoint no more than 15 to 20 feet wide created by a natural shelf of river rock on the Riverside side of the Des Plaines that has accumulated through the decades. The channel is 5-6 feet deep in the narrowest part of that channel.

“It’s really come alive with all the riffle and the flow,” said Pescitelli.