Formatted Title:

Remedial Dredging Occurred in 2016, Monitoring of Remedy Shows Elevated Levels of PCBs in River Raisin Area of Concern

Background/Objectives:

The River Raisin Area of Concern (AOC), located in the southeast corner of Michigan’s lower peninsula, is one of the state’s 13 AOCs. Connected to Lake Erie through its mouth at Monroe Harbor, the River Raisin serves as a major hub for the transportation of commodities throughout the Great Lakes. Designated as an AOC in 1987 by the Great Lakes Water Quality Agreement, the lower 2.6 miles of the River Raisin was determined to have nine out of 14 possible beneficial use impairments (BUIs). Over the last 40 years, investigations have found historical evidence of large discharges of oils, polychlorinated biphenyls (PCBs), and heavy metals into the River Raisin from the surrounding industrial sites.

Since 2002, efforts to remove PCBs from River Raisin sediments have been ongoing. PCBs are the primary contaminant of concern within the AOC and contribute to four of the AOC’s nine BUIs. In 2012, the U.S. Environmental Protection Agency’s Great Lakes National Program Office (EPA GLNPO) began a two-phased $44.2 million Great Lakes Legacy Act (GLLA) sediment remediation project with the goal of removing PCBs and non-aqueous phase liquids from the river’s sediments. The remedial approach utilized mechanical dredging and placed an engineered cap over 1.5 acres of TSCA level PCBs (>50 ppm). Upon completing the project in 2016, a total of 132,400 cubic yards of contaminated sediment were remediated.

Approach/Activities:

Since the completion of the GLLA project, EPA GLNPO has collaborated with EPA’s Office of Research and Development (ORD), the U.S. Fish and Wildlife Service, the U.S. Geological Survey, and the Michigan Department of Environment, Great Lakes, and Energy, to monitor the effectiveness of the remedy using a multiple lines of evidence approach. While some sampling was focused on the remedial footprint, samples were also taken AOC-wide to monitor ecosystem recovery. Data collected from herring gulls, eagles, fish, invertebrates, spiders, and sediments within the AOC from 2022-2024 have consistently shown elevated levels of PCBs. Sediment samples collected in 2023 indicated the presence of TSCA level PCBs outside of the GLLA project footprint, raising concerns about potential ongoing sources of PCBs to the River Raisin.

Results/Lessons Learned:

The TSCA material located during 2023 sediment sampling was found in a dynamic system outside of the 2012 GLLA project remedial footprint. Although the River Raisin is a ‘management actions complete’ AOC, additional characterizations and delineations are necessary to understand the extent of this newly discovered contamination. Further sediment core sampling is under way in coordination with U.S. Army Corps of Engineers Operations Division, and avian data are currently being analyzed. Continued communication with state and federal partners is essential to monitor ecosystem recovery, and the multiple lines of evidence approach will help define the methods used to address the issues facing the River Raisin AOC.

Brian Crone

Affiliation

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(Group 2, Poster Board #75) Remedial Dredging Occurred in 2016, Monitoring of Remedy Shows Elevated Levels of PCBs in River Raisin Area of Concern