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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:
- 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);
- 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.
- 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.
- 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);
- 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;
- 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);
- 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;
- Bioaccumulation in caged-fish and whole sediment
bioaccumulation testing is highest in sediment samples collected
within the SRA;
- PCB uptake in caged-fish and whole sediment bioaccumulation
testing does not appear to be a significant problem upstream of
the SRA;
- 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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