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Sediment Assessment and Remediation Report

Post-Remediation Sediment Sampling on the Raisin River Near Monroe, Michigan

Executive Summary

In 2001 and 2002 the Great Lakes National Program Office (GLNPO), in conjunction with the U.S. Army Corps of Engineers - Detroit District and the Michigan Department of Environmental Quality conducted an extensive survey of sediment quality conditions within the Raisin River Area of Concern (AOC). The focus of the survey was to evaluate the levels of polychlorinated bi-phenyls (PCB) contamination remaining in the area of the Ford-Monroe sediment removal project completed in 1997. The survey also collected data to evaluate the quality of sediments in the AOC outside the removal area. The assessment focused on PCBs, the primary contaminant of concern within the AOC, but also include analysis of other chemical constituents.

The sediment investigation included the collection of sediment cores and ponar samples for sediment chemistry analysis, whole sediment toxicity testing, benthic community analysis, and whole sediment bioaccumulation testing. Additionally, the agencies conducted caged fish testing at three locations within the AOC. This report summarizes the results of the sediment chemistry, whole sediment bioaccumulation testing, and the caged fish studies. Results of the whole sediment toxicity and benthic community analysis will be provided in a separate report. This report details sampling locations and methods and presents the results of the sediment assessment.

The results of the survey indicate that PCBs are still a significant problem within the AOC, from the sediment removal project, downstream to the mouth of the river. Additionally, the whole sediment bioaccumulation tests and caged fish testing indicate the potential for contaminant uptake into the food web, and suggest that PCBs remaining in the sediment removal area and in downstream areas may continue to present a human health and ecological risk.

A summary of the key findings include:

  1. Elevated PCB concentrations remain in the "Sediment Removal Area" (SRA). Maximum surficial PCB concentrations in SRA are >200 mg/kg (total Aroclors). Maximum total PCB concentration at depth in the SRA is 550 mg/kg (average of RFS and field duplicate);
  2. PCB contamination does not appear to be a problem upstream of the SRA. Surficial PCB concentrations in sediments are all <1 mg/kg based on total aroclor analysis. Maximum PCB concentrations in the deep sediments are all <1.3 mg/kg.
  3. PCB contamination in the sediments is a problem downstream of the SRA where surficial sediment concentrations are found up to 85 mg/kg (total of aroclors), and the deep sediments contain PCB concentrations up to 90 mg/kg.
  4. Heavy metal and PAH contamination are only a minor concern within the study area. Most levels are present below the TEC and PEC sediment screening levels guidelines suggested by MacDonald et al. (2002);
  5. Caged fish results indicate that there is the potential for significant uptake of PCBs into the food web in the areas adjacent to and down-steam of the SRA;
  6. PCB concentrations in caged fish are similar to those measured by MDEQ in 1991 and 1998 caged fish studies, and significantly below the results from a 1988 caged fish study (MDEQ 2001, Figure 72);
  7. Whole sediment bioaccumulation testing results indicate that there is the potential for significant uptake of PCBs into the food-chain in the areas adjacent to and downstream of the SRA;
  8. Bioaccumulation in caged-fish and whole sediment bioaccumulation testing is highest in sediment samples collected within the SRA;
  9. PCB uptake in caged-fish and whole sediment bioaccumulation testing does not appear to be a significant problem upstream of the SRA;
  10. There is not sufficient data to determine the source of PCB contamination remaining in the SRA. It is recommended that on-going sources, sloughing of contaminated sediments from the adjacent navigational channel, and residual contamination from the completed dredging project should all be investigated as potential sources of the PCB contamination in the SRA.

Preliminary estimates of the volume and PCB concentration of sediments remaining in the SRA indicate that approximately 2,600 cubic yards of sediments remain in the SRA with an average surfical concentration of 35 mg/kg, and an average total concentration of 58 mg/kg.

The results of this investigation indicate that there is the potential for significant human health and ecological risk from PCBs within the Raisin River AOC from the SRA downstream. Additional ecological and human health risk assessment is necessary to quantify this risk. State, local, and federal stakeholders need to coordinate in order to formulate a plan to address the remaining PCB contamination in the Raisin River AOC.

 


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