Post-Dredging Economic Analysis for Remediation of PCB-Contaminated Sediment in the St. Lawrence River near Massena, New York

The St. Lawrence River Remediation Project entailed the removal of approximately 65,500 m³ (85,600 yd³) of PCB-contaminated sediment from near-shore areas along an approximate 1.2 km (0.75-mile) long reach of the river. The initial budget for the project, prepared at the time the 1998 Record of Decision (ROD) was signed, was $63 million. Cost estimates developed during the design phase were based on completing the entire project in a single construction season (April–November). The final construction estimate, completed just prior to mobilization, was $41 million. Through 2001, actual costs were slightly under the pre-mobilization estimate; however, an abbreviated second construction season (2002) will be needed to complete underwater capping in a small area (0.44-hectare). Although the project encountered significant complications and unexpected conditions throughout the remediation work, the final breakdown of costs does not vary significantly from the pre-mobilization budget estimate. Cost overruns during the 2001 construction season were observed in a number of areas, namely the construction of onshore sediment storage and handling areas, environmental monitoring, sediment processing, demobilization, and construction management. Cost overruns were attributed to a number of factors, including problems in obtaining the required cleanup goals for sediment, which prolonged the overall project and led to considerably more dredging activities; unexpected complications regarding sediment handling and processing; and the need to greatly expand the scope of environmental monitoring activities in response to regulatory and stakeholder concerns.