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Sediment Contamination in the St. Louis River
The St. Louis River Area of Concern (AOC) has several impaired uses due to contaminated sediments, including fish consumption advisories and restrictions on dredging. The sediments were contaminated by a number of historical sources in the watershed, and continue to be contaminated by several nonpoint sources today. The Sediment Contamination Work Group is charged with providing scientific and technical advice to the CAC concerning the development of recommendations to alleviate contaminated sediment problems in the AOC. In addition, the group is an important sounding board to government, tribal and university researchers who are conducting a number of contaminated sediment investigations in this AOC.
Membership
The Sediment Contamination Work Group is currently composed of about 30 people. These include private citizens, as well as representatives from industries (e.g., Georgia-Pacific Corp., Minnesota Power, Potlatch Corporation), nonprofit organizations (e.g., Muskies, Inc.), the Western Lake Superior Sanitary District (WLSSD), universities, the Fond du Lac Band of Lake Superior Chippewa, consultants and government agencies (local, state, tribal and federal). Staff from the Douglas County Board of Supervisors, Minnesota Pollution Control Agency (MPCA) and Wisconsin Department of Natural Resources (WDNR) are the most active government representatives. New members are always welcome.
Meetings
Meetings are held bimonthly, excluding the summer months. The meetings are typically held from 6:30 to 8:30 p.m. at selected locations in Duluth, such as the WLSSD conference room. The meetings are sometimes educational in nature (e.g., presentations about contaminated sediment research in the AOC) and sometimes involve discussion of specific topics, such as remediation options for two Superfund sites on the river in Duluth. Meeting minutes can be found on the CAC Meeting Minutes page.
RAP Sediment Strategy
During 1993, the MPCA and WDNR committed to a three-phase sediment strategy to reduce impairments associated with sediment contamination in the St. Louis River AOC. This strategy consists of: (1) assessment studies to locate sediment hot spots (i.e., areas of elevated contamination), (2) development of hot spot management plans, and (3) implementation of remediation (i.e., clean up) actions. This strategy provides an incentive to remediate upstream sites first, so that downstream sites will not be cleaned up and then re-contaminated.
MPCA has conducted several sediment investigations to implement this sediment strategy. These projects have been conducted with the cooperation and financial assistance of either the U.S. Environmental Protection Agency (EPA) or EPA's Great Lakes National Program Office. The MPCA has also worked with interested stakeholders (e.g., WDNR, CAC work groups and industry) to carry out these projects. For additional information about the studies listed below, contact Judy Crane (MPCA) at 1-800-657-3864 or visit the MPCA's Contaminated Sediment Web Page.
Phase 1--Assessment:
Preliminary Assessment of Contaminated Sediments and Fish in the Thomson, Forbay, and Fond du Lac Reservoirs. These reservoirs are located in the upstream portion of the AOC and received several wastewater discharges prior to 1978. Fish and sediment core sections (from depositional areas) were analyzed for mercury, polychlorinated biphenyls (PCBs), and 2,3,7,8-TCDD (dioxin) during 1992 and 1993. Sediment toxicity tests were also performed. This study indicated that the greatest contaminant concentrations occurred in the deeper sediments, and that these sediments were toxic. Although dioxin was not detected in collected fish tissue, mercury and PCB contamination was of concern in selected fish species (Schubauer-Berigan and Crane, 1996).Survey of Sediment Quality in the Duluth/Superior Harbor: 1993 Sampling Results. This survey included the collection of sediment cores from 40 depositional sites, most of which had suspected sediment contamination. A Vibrocorer system on the research vessel (R/V) Mudpuppy was used to collect the sediment cores throughout the Duluth/Superior harbor. Thirty centimeter core segments were analyzed for a suite of contaminants, some of which included PCBs, polycyclic aromatic hydrocarbons (PAHs), pesticides, heavy metals, mercury, dioxins/furans, ammonia and total organic carbon. In addition, sediment toxicity was assessed on selected surficial samples. As a result of this survey, sites were ranked for further hot spot investigations (Schubauer-Berigan and Crane, 1997).
Sediment Assessment of Hot Spot Areas in the Duluth/Superior Harbor. Site-specific assessments of sediment contamination, toxicity and benthic community structure (i.e., Sediment Quality Triad approach) were performed at eight hot spot areas that were identified during the 1993 survey, as well as at a reference location. The R/V Mudpuppy was used to conduct the sediment sampling during 1994. PAHs and mercury were found to be widespread contaminants of concern throughout the harbor. Acute sediment toxicity was observed at a few of the hot spot sites. The benthological community structure was dominated by tubificid oligochaetes (aquatic earthworms), chironomids (blood worms) and the polychaete Manayunkia speciosa (Crane et al., 1997).
Regional Environmental Monitoring and Assessment Program (R-EMAP) Surveying, Sampling, and Testing: 1995 and 1996 Sampling Results. A R-EMAP project is being conducted in the St. Louis River AOC as a collaborative effort between the EPA, MPCA and Natural Resources Research Institute (NRRI). A statistically based sampling plan has been used to identify areas having acceptable and sub-minimal quality with respect to surficial sediment contamination, sediment toxicity and benthic community structure. Statistical analyses are being used to associate sediment contaminants with observed ecological effects. This project will establish a baseline for status and trends monitoring. A report will be finalized during the winter of 1999-2000.
Bioaccumulation of Contaminants in the Duluth/Superior Harbor. For this project, six bioaccumulation tests will be run using the aquatic earthworm, Lumbriculus variegatus. Sediment sites will be limited to moderately contaminated areas in the Duluth harbor at Slip C and Minnesota Slip. The bioaccumulation of PAHs, PCBs and mercury will be measured in L. variegatus exposed to surficial sediments (0-5 cm) for 28 days. Site-specific, biota-sediment accumulation factors (BSAFs) will be determined. Sediment samples will be collected during April 1999 for screening toxicity tests and bioaccumulation tests; these tests, and associated analytical analyses, will be conducted by AScI Corporation (Duluth).
Development of Sediment Quality Guidelines for the St. Louis River Area of Concern. A biologically based approach for deriving sediment quality guidelines for the St. Louis River AOC is being developed. These guideline values will be used to address a variety of sediment management issues in the St. Louis River AOC. MacDonald Environmental Sciences Ltd. (Nanaimo, British Columbia) has been retained by the MPCA to conduct most of this work. As one phase of this project, a draft manuscript on the development of an ecosystem-based approach to the assessment and management of contaminated sediments in the St. Louis River AOC has been developed (MacDonald and Crane, in prep.).
Phase II--Hot Spot Management Plans:
Sediment Remediation Scoping Project at Slip C in the Duluth Harbor. Sediment cores were collected from Slip C during June 1997 to further delineate the extent and depth of selected sediment contaminants (PAHs, PCBs, mercury and lead). The volume of contaminated sediments in this slip will be estimated, and a short list of sediment remediation options will be developed for further consideration. The draft report is due early in 1999.
Sediment Remediation Scoping Project for Minnesota Slip, Duluth Harbor (starting Oct. 1, 1998). Field sampling will be conducted during the spring of 1999 to delineate sediment contamination profiles for PAHs, PCBs, mercury, lead and toxaphene. A second phase of this project will need funding at a later date to determine contaminant loads entering the slip from stormwater outfalls and other sources in the harbor.
Phase III--Remediation:
MPCA has not yet conducted any remediation projects in the St. Louis River AOC. However, MPCA staff are working with the Potentially Responsible Parties for two Superfund sites in the harbor to develop sediment remediation plans.
WDNR is working with the City of Superior and Murphy Oil to remediate sections of the Hog Island Inlet/Newton Creek area in Superior.
References:
Crane, J.L., M. Schubauer-Berigan, and K. Schmude. 1997. Sediment assessment of hotspot areas in the Duluth/Superior harbor. U.S. Environmental Protection Agency, Great Lakes National Program Office, Chicago. EPA-905-R97-020.
MacDonald, D.D., and J.L. Crane. In prep. Development of an ecosystem-based approach to the assessment and management of contaminated sediments in the St. Louis River Area of Concern. (To be submitted to the Journal of Great Lakes Research and included in the EPA report for this project).
Schubauer-Berigan, M., and J.L. Crane. 1996. Preliminary contaminant assessment of the Thomson, Forbay and Fond du Lac Reservoirs. Minnesota Pollution Control Agency, Water Quality Division, St. Paul. 80 pp. + appendices.
Schubauer-Berigan, M., and J.L. Crane. 1997. Survey of sediment quality in the Duluth/Superior Harbor: 1993 sample results. U.S. Environmental Protection Agency, Great Lakes National Program Office, Chicago. EPA 905-R97-005.