The U.S. Army Corps of Engineers last week revealed its latest plans for notching the Hofmann Dam, stabilizing and planting the exposed banks of the Des Plaines River, and regrading Swan Pond Park, work which is still planned to take place in 2012.
On Aug. 24, the Army Corps put those plans on display as it began officially seeking bids from contractors for the $5 million project. It’s the second phase of a two-phase effort, which also includes the removal of the Fairbank Dam that spans the Des Plaines a few hundred yards east of the Hofmann Dam. The first phase of the project, which was supposed to have been completed last winter, still has not broken ground.
But Phase II plans make clear several details that until August were not known, including exactly where heavy construction staging would take place, the extent of improvements to the concrete river wall in Swan Pond, just how the park would be graded to facilitate drainage and the location of a permanent pathway along the river in Swan Pond.
Even those final plans will be amended, said officials from both the Army Corps of Engineers and the village of Riverside. Representatives from the two agencies met Aug. 25 to discuss the plans posted a day earlier by the Army Corps for the purpose of seeking bids.
“There are a few small changes, and we’re looking at that,” said Jeff Zuercher, project manager for the Army Corps of Engineers. “We’re still working with the village in terms of their requests.”
Bids will be opened at 2 p.m. on Sept. 26 in the lobby of 111 N. Canal St. in Chicago.
Prior to that date, however, the village of Riverside will host a town hall meeting to answer questions and hear additional concerns on Monday, Sept. 12 at 10 a.m. in Room 4 of the Riverside Township Hall, 27 Riverside Road. The public is encouraged to attend that meeting.
“Our hope is to allow residents to come in, meet with the IDNR and the corps to go over the plans,” said Riverside Village Manager Peter Scalera.
The 24-page set of plans issued last week indicate that heavy equipment staging for the notching of Hofmann Dam will be located on the Lyons side of the river in the forest preserve area just east of the Barrypoint bridge.
Creating that staging area will require the removal of several trees on the south bank, and an access road along the riverbank from the staging area to the dam will provide a way to remove debris from the construction site.
Plans indicate that work to remove the dam will be in the river way itself, and no coffer dam, which would divert the river around the work area, will be allowed.
In addition, whoever wins the job will need to search for remnants of the so-called horseshoe dam located up river from the previous dam. Any remnants of that dam are to be removed as part of the project, and any damage done to the concrete retaining walls or the historic Hofmann Tower during construction is to be repaired.
A second dam removal access road on the Lyons side, according to the plans, will be located in line with Leland Avenue through property owned by the Des Plaines Valley Mosquito Abatement District at 8130 Ogden Ave. That road will also provide access to the river bank for restoration/stabilization efforts after the dam is notched.
Two access roads to the river are indicated on the Riverside side of the river. The longer of the two is marked as access for bank seeding. The other, closer to the dam, is marked as a site not only for seeding but also for dam removal. It’s unclear how heavily that access point will be used for that purpose.
Swan Pond Park will be extensively regraded, with drainage focused on a depression that flows into an 18-inch culvert that empties into the Des Plaines River. The plans for the Swan Pond re-grading, released by the Army Corps on Aug. 24, still face amendments.
For example, the current plan shows the culvert emptying into an area covered by riprap stone. According to Zuercher, while not shown on the plan, the riprap stone will be replaced with a more natural-looking cobble and boulder.
“It’s been changed to a cobble-and-boulder mix that has a more natural feel to it,” said Zuercher. “It looks more like a riverine habitat. It’s more expensive, but we felt it was worth it.”
The regrading itself will necessitate the removal of about 20 trees, according to the plan.
“It’s based on the need for the grading,” Zuercher said. “We want to get the grading done correctly and plant new trees if that’s what’s desired.”
The re-grading is critical, Zuercher said.
“It will give Swan Pond new life in terms of drainage and ensure much more usage and earlier accessibility after water comes in and goes back down. We’re confident that over time it will get back to the way people expect to see that park.”
In addition, an 8-foot-wide concrete walkway, extending from the base of the sledding hill to the Fairbank Dam, has also been altered. The path will extend all the way to Barrypoint Bridge, and it will be made of “grasscrete,” a permeable paver that allows grass to grow through it. Examples of such pavers already exist atop the sledding hill.
Plans also call for repairing sections of the crumbling retaining wall along the river and clearing invasive species between the wall and the river. More sections of wall could be targeted for repair as work moves forward, according to Zuercher.
“The contractor will walk the wall to find areas not listed and repair those damaged areas,” Zuercher said.
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