Contaminated sediments are a significant problem in the Great Lakes basin. Although significant progress over the past 20 years has substantially reduced the discharge of toxic and persistent chemicals to the Great Lakes, persistent high concentrations of contaminants in the bottom sediments of rivers and harbors have raised considerable concern about potential risks to aquatic organisms, wildlife, and humans. As a result, advisories against fish consumption are in place in most locations around the Great Lakes.
To help determine the nature and extent of sediment contamination in the Great Lakes Areas of Concern, the Great Lakes National Program's Research Vessel Mudpuppy II conducts sampling across the Great Lakes tributaries and rivers.
Typically, projects use a two-phased sediment assessment approach:
- The first phase includes a comprehensive sampling of the entire AOC to help pinpoint the location of "hot spots."
- In the second phase, the "hot spots" are then defined to provide information necessary for making decisions to correct the contamination.
The overall goal is to generate the information needed to make scientifically defensible remediation decisions.
EPA typically works closely with state agencies and local communities involved in the Remedial Action Plan process to develop sampling plans, testing protocols, and Quality Assurance Project Plans for individual projects.
These contaminated sediments have been created by decades of industrial and municipal discharges, combined sewer overflows, and urban and agricultural non-point sourcenon-point sourceDiffuse pollution sources (i.e., without a single point of origin or not introduced into a receiving stream from a specific outlet). The pollutants are generally carried off the land by storm water. Common nonpoint sources are agriculture, forestry, urban, mining, construction, dams, channels, land disposal, saltwater intrusion, and city streets. runoffrunoffWater that flows off land into lakes and streams.. Buried contaminants posing serious human and ecological health concerns can be dredged up by storms, ship propellers, and bottom-dwelling organisms. Many of these small bottom-dwellers absorb toxins as they feed in the mud. As larger animals eat these smaller animals, the toxins move up the food chain, with their concentrations getting higher, often thousands of times higher. Fish at the top of the food chain, such as lake trout and salmon, can be unsafe to eat in some areas because of the heavy concentrations of toxic substances in their tissues. Fish-eating birds, including the bald eagle, may suffer low reproductive rates or produce offspring with birth defects.
While the problem of contaminated sediments persists in the Great Lakes, efforts are being made in the pursuit of remediating these contaminated sediments. In the years 1997 through 2007, 5.5 million cubic yards of contaminated sediments have been remediated in the U.S. Great Lakes Basin. The following graphs show the progress of sediment remediation, with yearly totals from 1997 through 2007. It is anticipated that the rate of sediment remediation activities will accelerate with the availability of Great Lakes Legacy Act funding opportunities.
EPA has been responding to the need for gathering high-quality sediment information to assist AOCs in making remedial action decisions. EPA provides technical, financial, and field support for federal, state, and tribal partners to assist in addressing contaminated sediments and work aimed towards reaching remedial decisions and environmental restoration.
Problem harbor and tributary areas in the Great Lakes basin have been identified and labeled as Areas of Concern. They are locations where any of 14 beneficial uses are impaired. To address these impairments, each AOC developed a Remedial Action Plan. All RAPs have identified contaminated bottom sediments as a significant problem that must be addressed to attain beneficial uses. Before developing specific plans that detail how to remediate these contaminated sediment problems, it is critical to characterize the nature and extent of sediment contamination. Most AOCs, however, had access to only limited sediment information to assist them in addressing characterization and remediation questions.
While the problem of contaminated sediments persists in the Great Lakes, efforts are being made to remediate these contaminated sediments. The rate of sediment remediation activities, removal of beneficial use impairments and delisting of AOCs has accelerated since the Great Lakes Legacy Act and Great Lakes Restoration Initiative funding programs were implemented.