Two weeks into the Hofmann Dam notching operation, crews have pretty much removed the portion of the concrete dam in the direction of Riverside.
Last week, workers with jackhammers chipped away at the concrete to create the edge of the northern “wing” of the dam. The large excavator that’s been pounding away on the Riverside half of the dam will now turn its attention to the Lyons side.
Meanwhile, on June 27 the Army Corps of Engineers determined that the remnants of the older U-shaped dam that become visible behind the newer, straight concrete structure, will be removed to bedrock.
According to Jeff Zuercher, the Army Corps’ project manager, about two feet of stone will be removed and redistributed in the area between the two dams on a “20-to-1 slope” to allow for passage of fish and help make that part of the river safely navigable.
“We’re putting things in place for the river to shape itself naturally,” Zuercher said.
The Army Corps is also assessing how to finish the placement of “toe stone,” the large boulders along the banks of the river, upstream of the access road on the Riverside side of the Des Plaines River. The toe stone was placed on the banks upstream of the dam to stabilize sediment that has built up behind the dam over the decades and keep it from washing downstream.
The village has asked that no more trees be removed upstream of the dam, so the Army Corps will have to determine whether it can get a machine down the north bank from the Riverside access road. If not, said Zuercher, it may be possible to “ford” the river from the Des Plaines Valley Mosquito Abatement District property to install the toe stone on the opposite bank.
Also within the next two weeks, the contractor will begin to remove the gravel access roads on either bank of the river immediately upstream of the former dam. Those roads will be removed and the area smoothed out in preparation for planting, said Zuercher.
Planting already has begun farther upstream on both the Lyons and Riverside sides of the Des Plaines.
As for when the work to regrade Swan Pond Park will begin, it’s anyone’s guess at this point.
While the Army Corps, the Illinois Department of Natural Resources and ComEd have signed a contract for the replacement of three power poles in the park, ComEd gave a tentative start date of July 23 for that work.
The regrading work is on hold until that project is complete, which could take between two and three weeks.
Scalera and Zuercher both said that the Army Corps and IDNR are working to see if they can get ComEd to move up the date for the power pole replacement to start.