Source control sufficiency assessments are becoming an important part of sediment remediation, particularly in the Pacific Northwest where EPA has begun requiring them as part of the design process for both the Portland Harbor Superfund Site and the Lower Duwamish Waterway. These assessments are necessary to ensure that expensive in-water remediation is not re-contaminated in the near or long term from existing upland contributions. Large river systems are complex with many potential in-water and upland sources that may contribute to contamination in the sediment. Thus, a source control sufficiency assessment must account for all these contributions to accurately assess the potential for recontamination and, if needed, identify mechanisms to prevent recontamination. 

This presentation discusses TIGSED, a modeling approach based on the SEDCAM model that can be used as a line of evidence to determine if sources are sufficiently controlled and, if not, help identify specific sources to control.  TIGSED was developed to handle the complexity of assessing contaminant contributions to sediments in large river systems while being flexible enough to adapt to the specific conceptual model of a given system or area. The model relies on site-specific information and can be conducted at various scales depending on the system under consideration and needs of the analysis.