FULTON, NY — Except for a quick break Tuesday (Sept. 2) to meet the state senator, the Groh Dredging & Marine team has been hard at work pulling sediment from the bottom of Lake Neatahwanta since dredging began July 25 and grid one is expected to be finished any day.
The dredging company owner Tim Groh said he has kept everything going according to plan. “Everything is on track right now,” the dredge boss told Oswego County Today in an interview on Tuesday.
Working from a six-section grid of 300 feet x 300 feet squares, the goal is to remove the sediment from the lake bed in order to create greater depth and reveal natural springs in the lake bed.
Several scientific surveys conducted in the past two decades indicate that dredging is the next step to helping the little lake by the big lake recover from its current unhealthy state.
Groh said predicted depth levels according to the surveys have been right on target.
“I think there’s going to be about 10,000 cubic yards in grid one,” Groh said. “There’s a lot of sediment out there. I think the calculations are pretty snug.”
The dredge barge that can be seen with its paddles churning water just off Stevenson Beach was trucked to Fulton from Groh’s home base in Illinois and has an unseen 10 foot cutter head and a cutter box beneath the surface.
The two star wheels that can be seen pushing water at the rear of the dredger allow the operator to navigate the vessel.
Meanwhile, on the lake bed “the cutter box chews up the sediment and forms a slurry so the pump can suction it into the pipeline,” Groh said. “We’ve probably got about 1,800 feet of pipeline out.”
The pipeline runs from the dredger to the lake shore, then along the road behind the War Memorial.
Groh said the slurry is then pumped through the pipeline onto land with one more major step integral to the process.
“Once onshore there is an environmentally safe polymer injected into the slurry and that brings the smaller sediment particles together to form a larger particle that will fall out of solution,” Groh said. “It flocculates.”
Without binding the particles Groh said the fine sediment would block the openings in the geotextile, completely inhibiting dewatering – the release of water from containment.
“If we didn’t have the polymer to bind the particles the slurry would just look like chocolate milk,” he added.
The slurry is then pumped alternately into two awaiting containment tubes that look like long black bladders lining the shoreline at the base of the street behind the War Memorial.
The water seeps out of the 200 foot tubes and drains back into the lake, leaving the sediment contained inside.
Every few minutes Groh employee John Ceglarek opened a valve on the manifold connected to the tubes to collect a sample of the slurry in a five-gallon bucket.
Groh swirled the liquid sample in the bucket, looking to see how the sediment was binding and how fast it settled to judge the degree of flocculation. “This is very organic material so you’re going to get good consolidation,” Groh said.
Ceglarek then radioed Groh’s assessment back to the crew at the other end of the pipeline so they could adjust the amount of polymer as needed.
Groh noted that the generic name for the sludge containment tubes is geotextile and for the Lake Neatahwanta project Groh is using geotextiles manufactured by Geo-synthetics Inc., of Waukesha, Wisc. http://www.geo-synthetics.com/
Groh said there is probably another week’s worth of dredging left in grid one, then another survey will be taken to determine sediment levels and next actions.
He added, “The only thing that stops the dredger is lightning … and ice.”
Meanwhile, efforts are under way through the Fulton Community Revitalization Corp. to raise more money to keep the dredge working in Fulton and Lake Neatahwanta as long as Groh can stay.