During the first phase of River Grove dredging, the contractor, Kayden, removed vegetation from the area to be dredged adjacent to the boardwalk (see photo below).

They completed vegation removal last week. They also completed cleaning silt out from under the boardwalk without impacting its stability or support. This week, they’re back with a tiny dredge and a giant mobile dewatering plant.

The Little Dredge That Could

The dredge was selected because it could maneuver in the tight spaces adjacent to the River Grove Boardwalk. It’s 12 feet wide and 51 feet long. The first word that came to mind when I saw it was “cute.” The second thing that came to mind was the child’s story “The Little Engine that Could.” As it sat there chugging away at sand and silt, I thought I could hear the John Deer, 6-cylinder, 13.5 liter diesel engine chanting, “I think I can, I think I can.”

Dewatering Plant Processes Sand for Removal, Returns Water To River

The giant dewatering plant operates much like shakers used in oil field drilling work. Water and sediment are pumped up from the lagoon by the dredge. They enter one side of the dewatering plant. There, they are pumped through centrifuges, then across a series of screens that vibrate. Water falls through the screens into a tank below. Sand accumulates on the screens until they dump it down chutes. From there, a front end loader scoops up the dirt and piles it up until trucks haul it away.

Kayden then pumps the water back into the river.

Dredge Designed for Tight Spaces

River Grove dredging will not move nearly as fast as the dredging that Great Lakes and Callan were doing, but it seems to work well for the location. A major concern is overly aggressive dredging that could undermine the supports for the boardwalk and boat ramp. Another word that comes to mind is “precise.” Think about the difference between a van and an 18 wheeler. The major issue here is fitting in small spaces.

How It All Works Together

Here’s a contractor animation that shows how everything works together. And here are the specs of the equipment. It could conceivably be used for dredging other channel inlets around the lake such as the one at Walden.

Despite the size of the equipment at River Grove, the operation itself is far more compact than previous dredging operations. This could form a model for the dredging of inlets around the lake, like the one at Walden. However, County Engineer John Blount emphasizes that no decisions have been made in that regard yet.

The Safety Moment

If you take your kids to River Grove to see this operation, make sure you stay behind the yellow tape for your own safety.

Also, until the operation is complete in another month or so, remember that traffic at River Grove will be two-way. Just be aware.

Posted by Bob Rehak on 3/4/2020 with photos and video from Josh Alberson

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