Dam removal presents a unique set of challenges, and the proper tools can make all the difference. So when the Army Corps of Engineers awarded Illinois Constructors Corp. the contract to remove the Hofmann Dam across the Des Plaines River near Riverside, IL, the company relied on specialized tools to complete the project.
Elburn, IL-based Illinois Constructors Corp. has established a reputation for the successful building of roadway, railway and marine projects. “We are a small- to mid-size general contractor,” reports Jim Carson, project manager.
The company traces its roots in the Chicago area back to the mid-1920s. The general contractor has the ability to self-perform work with its own skilled union workforce, and generally performs structural and site demolition, excavation and concrete forming and placement.
“Our company is predominately heavy civil construction — mainly bridges and structural work,” says Carson. The company also removes dams and rehabilitates shorelines.
The scope of the $3.1 million Hofmann Dam project went well beyond the dam removal. “The removal of the dam really wasn’t a large amount of work,” says Carson. “There were quite a lot of other things that had to happen.”
First, stone needed to be strategically placed along the river banks to prevent erosion. “We had to place about 9,000 tons of toe stone, which is basically a rounded cobblestone, upstream of the dam along the river banks to prevent the bank from eroding into the river,” says Carson.
This would be no easy feat. “We had to install 75% of the toe stone prior to removal of the dam,” Carson notes. Much of this material needed to go underwater, which meant equipment operators would be unable to see where it was being placed.
But before any stone could be laid, the equipment had to be able to access the site. “To start off, the main challenge was to establish a location where we could put a road into the river,” says Carson. The thickness of the required road also had to be calculated to support the weight of the equipment used to place the stone.
In addition, there was a downstream portion of the project in Riverside. “It was a low point that was protected by walls on both sides,” recalls Carson. One or two times each year, this area would flood the adjacent park. “It would not drain properly. The only way for the water to drain out would be for the water to evaporate. We re-graded that whole pond and installed a culvert, so when it does flood, it will drain out properly.”
Putting the Stones Into Place
Illinois Constructors owns an extensive fleet of equipment that includes excavators ranging from 15,000 to 125,000 lbs., as well as friction and hydraulic cranes. However, specialized equipment was required to most efficiently complete all phases of the dam removal project.
“This is a very unique project that requires a very specific scope of work,” says Carson. “If we think it is the best way to do it, we will obviously put the equipment in the bid to get the job done.”
Illinois Constructors rented an LBX Link-Belt 240 LX Long Front. This is a 58,900-lb. excavator with a 26-ft. 3-in. arm length and a 48-ft. digging depth. It can handle buckets ranging from .82 to .95 cu. yds. The long-front machine made it possible to effectively reach into the river and place the toe stone.
To get the stone from the staging area to the excavator, Illinois Constructors rented a Morooka MST-2200 rubber track dump carrier, which has a hydrostatic transmission and is able to navigate river terrain. “Basically, it was capable of handling 9,000 or 10,000 lbs. of stone,” says Carson. “We used that machine to track back and forth in the water between where the long-boom machine was placed and the rock.”
The company’s Link-Belt 300 loaded rock into the dump carrier from the stockpile. “The Morooka was moving the rock to the job location where the long-boom machine would place it,” Carson explains. “That was basically the operation for about a month and a half — placing the toe stone in the river along the river embankments.”