Peconic River Sediment Trap Constructed

March 2002

Peconic River Sediment Trap Constructed

Construction of the Peconic River sediment trap in 2002

Background

Wastewater from BNL operations is processed and treated at the Sewage Treatment Plant before being discharged into the Peconic River on BNL property. The discharged water is monitored at the discharge point and at several other up-and downstream locations. Historical practices resulted in the discharge of chemical and radiological contaminants that were then deposited in the river sediment. Numerous investigations of the sediment, fish, and plants were conducted and sampling indicated there were elevated levels of mercury in sediment onsite and just downstream of the BNL boundary. Low levels of metals, PCBs, perticides, and radionuclides were co-located with the mercury in the river sediment.

BNL proposed a cleanup plan for the Peconic River in 2000. After public comments and concerns over potential impacts of sediment removal on river wetlands and wildlife, BNL agreed to evaluate other options for the cleanup.

Installation of the Sediment Trap

While BNL conducted pilot studies on alternative technologies to clean the sediments and formulating a new cleanup plan, a sediment trap was installed in the Peconic River near the BNL boundary in March 2002. The trap was designed to minimize the potential for migration of contaminants beyond the BNL boundary.

The trap consisted of two layers of different-sized stones. The water slowed down as it passed through the stones allowing suspended sediment to deposit on the river bottom or become trapped in the spaces between the stones. The trap was built on a layer of geofabric, which allowed water to move through its tiny pores and minimized the settling of the stones into the river bottom. The trap remained in place for the duration of the Peconic River restoration program.