Dredging involves removing sediment from the riverbed and pumping the dredged sediment as slurry to a processing facility in Green Bay where the sediment goes through a dewatering process prior to disposal. (Click here to view a video demonstration of the dredging operation.)
The Fox River Cleanup Project is using three different dredges in 2015 - two 10-inch hydraulic dredges and an eight-inch hydraulic dredges.
Hydraulic dredging was selected based on the sediment characteristics, simplicity of transporting the slurry and the ability to meet the project goals and project schedule. The dredging equipment sizes for the Fox River Cleanup Project were selected based on the thickness of the sediment "face" to be dredged and the water depth. The dredging equipment is located in areas of the river to accommodate production goals given the changing dredge slurry densities and flow rates. These particular dredges were highly successful in Little Lake Butte des Morts.
The 10-inch dredges are being used where larger thicknesses of contaminated sediment are present. The eight-inch dredge is used where there are thinner accumulations of contaminated sediment and to complete dredging to the required elevation where the 10-inch dredges have removed the overlying sediments.
In addition, the eight-inch dredge is constructed to operate in waters as shallow as two feet deep. This allows for dredging in areas traditionally requiring mechanical dredging (e.g., clamshell bucket on a crane loading into barges), increasing production and shortening the overall cleanup schedule while reducing the amount of clean sediment that is dredged.
Crews are conducting dredging activities 24 hours a day, five days a week, avoiding peak times for recreational boaters on Saturdays and Sundays.
After contaminated sediment is dredged from the river it is pumped through a pipeline anchored along the bottom of the river to the Green Bay Processing Facility. There it goes through several processing steps before being shipped to a landfill.
The dredging operations on the lower Fox River are guided by GPS systems.
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