PCB Cleanup: How Dredging Is Performed

GE is dredging the Hudson River in Upstate New York to remove PCBs in one of the largest and most complex environmental cleanups in U.S. history.

Dredging is conducted around the clock for six months a year. The U.S. Environmental Protection Agency estimates the work will continue for five to seven years.

Dredging activities are completed for 2011 and are planned to begin again in spring 2012. You can see where PCB dredging has been performed here.

The goal is to remove 350,000 cubic yards of sediment from the river each year. Water is squeezed out of the sediment and PCBs are removed from the water at a specialized processing and dewatering facility GE built for the project. The sediments are shipped by train to federally permitted disposal facilities outside of New York State.

GE used PCBs in the manufacture of electrical equipment at two plants on the Upper Hudson River. When available, the company held valid permits to use and discharge the compound but discontinued its use in the mid-1970s when PCB use was phased out in the United States. In 2002, after a 25-year public and scientific debate over whether the river bottom should be dredged or left alone, EPA selected dredging of PCB-containing sediments for the river. GE committed to conduct and pay for the project. All of GE’s work on the Upper Hudson is approved and overseen by EPA. The first phase of dredging took place in 2009. The second, final phase is being conducted now.

GE selected Cashman Dredging & Marine Contracting Co., LLC, a leading national dredging contractor, to perform the dredging work. Shaw Environmental and Infrastructure operates the processing facility and Finger Lakes Railway operates the rail yard.

Dredging is being performed in the river approximately 200 miles north of New York City, along the shorelines of Washington and Saratoga counties. Dredging is proceeding from north to south in the main stem of the Hudson. Approximately two to three dredges operate simultaneously.

Dredged material is loaded onto 195-foot-long hopper barges that, when filled, are pushed by tugboats to a processing, treatment and transportation facility located on the Champlain Canal one mile upstream from the Hudson River. The 110-acre property where the facility is located was vacant farmland and is situated between the Champlain Canal and an existing rail line.

Loaded barges are moored at the facility’s 1,500-foot unloading wharf. Prior to the start of dredging in 2009, this area of the Canal was widened by 65 feet to ensure non-project vessels would be able to travel past the area despite the moored barges.

Accumulated water and large debris, such as tree trunks or boulders, is removed from the barges. A land-based excavator then lifts the sediment from the barges and place it into a hopper that feeds a large piece of equipment called a trommel. The trommel separates finer sediments from debris, gravel and rocks.

From the trommel, the remaining finer sediment passes through additional processing steps to remove pea gravel, sand and grit. The remaining fine sediment is pumped into a gravity thickener for further processing, then is sent to one of 12 specially manufactured filter presses housed inside a 41,000-square-foot sediment dewatering building. Filter plates inside the presses push together to squeeze water from the slurry. When the presses open, the resulting cake-like substance falls into large bins stationed under each press.

Once filled, the bins are transported by truck to one of two enclosed staging areas. Inside these 365-foot-long, 50-foot-high structures, the filter cake waits to be loaded onto railcars for disposal at a permitted hazardous waste disposal facility. The debris, rock, gravel and sand removed from the sediments during processing are transported by truck to on-site staging bins where it too awaits being loaded onto railcars. A geomembrane liner installed under all areas where PCB-containing sediments are processed, managed or staged ensures PCBs do not migrate from the site.

Water removed during the dewatering process is pumped to tanks situated 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 to meet New York State’s strict water quality standards, the water is discharged into the Champlain Canal.

If you have additional questions about the Hudson River PCB cleanup or dredging in the Hudson River, email info@hudsondredging.com or contact us at 518-792-4087, or toll-free at 1-888-596-3655.