What Happened to Dredged Sediments
During dredging, sediments removed from the river were transported by barge through Lock 7 of the Champlain Canal to a processing, treatment and transportation facility built specifically for the project by GE just south of Lock 8.
Up to three barges were able to be moored at the 1,500-foot unloading wharf at any time during dredging. This area of the Canal was widened by 65 feet during construction of the facility to ensure non-project vessels would be able to travel past the area despite the moored barges.
Pumps on the wharf removed accumulated water in the barges and sent it to a nearby tank. Debris, such as large tree trunks or boulders, was removed from the barges and staged for transport. A huge excavator staged on land then lifted the sediment from the barges and placed it into a large piece of equipment called a trommel. The trommel separated finer sediments from the debris, gravel and rocks. The separated debris dropped onto a conveyor and was temporarily stacked until it was loaded onto trucks for transport to the interior of the property.
From the trommel, the remaining sediment was pumped into one of two hydrocyclones, where grit and sand were removed. The slurry that's left was piped along a main road to an 80-foot diameter, above-ground tank called the gravity thickener.
Inside the gravity thickener, polymer was added to clump larger particles together, making them heavy enough to settle at the bottom of the tank. The thickened slurry was then pumped from the bottom of the tank to one of 12 specially manufactured filter presses housed inside a 41,000-square-foot sediment dewatering building.
Filter plates inside the presses squeezed water from the slurry. When the presses opened, the resulting cake-like substance fell into large bins stationed under each press.
Once filled, the bins were transported by truck to one of two twin enclosed staging areas. Inside these 365-foot-long, 50-foot-high structures, the filter cake waited to be loaded onto railcars for disposal at a licensed facility.
With the end of dredging, the processing of sediment came to an end.
The crews loading the material work on the opposite end of the staging areas, loading the filter cake and debris onto railcars in a rail yard constructed along the western perimeter of the site. The yard includes nearly seven miles of track and connects to an existing mainline railroad. Once loaded, the railcars are connected into 81-car trains and sent for disposal.
While no more sediment will be processed until dredging begins again, stormwater collected on the site will continue to be pumped to tanks inside a 27,000-square-foot water treatment building located next door to the sediment dewatering building. Larger than some municipal water treatment plants, the facility is capable of treating two million gallons of water a day. Once filtered and processed, the water either is recycled for use on site or discharged into the Champlain Canal.
