Background

The Port of Green Bay relies upon maintenance dredging of the outer harbor and Fox River to provide adequate draft for commercial shipping. The 54-acre Renard Island Confined Disposal Facility (CDF) currently contains approximately 2,700,000 cubic yards of dredge material. Foth was retained to develop a closure plan, which was integrated with the Port’s Dredged Material Management Plan, to close the CDF in a safe, environmentally sound and cost-effective manner. Sediments placed in the CDF contain low levels of polychlorinated biphenyls (PCBs). In addition, the surface of the CDF had become irregular due to settlement and the vegetation had reverted to undesirable invasive species.

Approach

Foth developed a closure plan that addressed control of PCB flux out of the CDF. Foth also engineered a design to minimize the flux to satisfy regulatory requirements.

Results

Our closure plan was approved by the agencies, and included use of an additional 466,000 cubic yards of dredge material to cover the CDF. The design allows consideration of a future end-use as green space for public recreation. More than $5 million in cost savings were realized by using dredge material for the closure.