Environmental Dredging in the St. Lawrence River: A Case Study

The St. Lawrence River (SLR) Sediment Removal Project was part of an ongoing site-wide CERCLA remediation program addressing polychlorinated biphenyl (PCB)-impacted sediments and soil at General Motor's (GM's) 270-acre manufacturing facility property and adjacent off-site areas located in Massena, New York. The Record of Decision (ROD) issued for this site specified a sediment PCB target cleanup goal of 1.0 part per million (ppm), to the extent technically practicable. The sediment removal was conducted in accordance with the ROD and a Unilateral Administrative Order (UAO) issued by the United States Environmental Protection Agency (USEPA). In order to meet the project's cleanup goal, approximately 18,000 cubic yards (cy) of sediment rock and debris were removed via hydraulic and mechanical dredging during the summer and fall of 1995, and a sediment cap was designed and installed to address an area where final PCB levels in the sediment remained above 10 ppm, even after excessive attempts. Annual monitoring and maintenance activities are currently being performed at the site to ensure the integrity of the sediment cap. The sediment removal portion of this program was completed with the effective cooperation and teamwork of GM, USEPA Region 2, the New York Department of Environmental Conservation (NYSDEC), the St. Regis Mohawk Tribe (SRMT), Environment Canada, Blasland, Bouck & Lee, Inc. (BBL), and Sevenson Environmental Services. This paper provides a comprehensive overview of many aspects of this extensive river-dredging project, including studies, project scoping, contracting, sediment removal, and environmental monitoring.