11th Biennial Report on Great Lakes Water Quality

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Chapter 3


Contaminated Sediment

Funding for Sediment Remediation

Wastewater Infrastructure Maintenance and Upgrades

Fish and Wildlife Habitat

Waste Sites and Nonpoint Source Pollution

Accountability and Responsibility for Remedial Action Plans

United States Approach

Canadian Approach

Community-based Alliances

Confirming the Status of Restoration Efforts

Keeping the Focus on Beneficial Uses

Funding for Remediation and Planning Efforts

Corporate/Private Spending on Remediation


Progress Toward Restoration

Contaminated Sediment

Sediment in Areas of Concern is often contaminated with industrial or agricultural pollutants, such as PCBs, DDT, mercury or polycyclic aromatic hydrocarbons, presenting both financial and ecological challenges to agencies and communities. Most pollutants in sediment within Areas of Concern were released into the environment long ago and constitute a "legacy of pollution." Other contaminants continue to enter the environment, such as through the burning of fossil fuels and from runoff from agricultural and urban areas.

Toxic chemicals in sediment can enter the food chain and threaten the health of fish, wildlife and humans. For example, contaminated sediment is the major source of contaminants found in fish and results in fish consumption advisories. The risk of adverse health effects from eating contaminated fish is particularly high for pregnant women, fetuses and infants. From an economic standpoint, contaminated sediment can prevent or delay dredging, limiting navigation and recreational boating6. Contaminated sediment also can reduce property values and threaten the multi-billion dollar commercial and sport fish industries7.

Upon confirmation by Remedial Action Plan participants that contaminated sediment at a site poses an unacceptable risk to human or ecosystem health, the practitioners evaluate an array of potential remedial measures for possible use to reduce that risk. These potential measures include source control and natural recovery (attenuation), thick-layer capping and sediment removal through hydraulic or mechanical dredging (Box 5). In addition to these remedial options, there are a variety of dredged material treatment technologies such as thermal desorption, solvent extraction and soil washing. Though they provide a permanent solution, the thermal and nonthermal technologies are costly and are not likely to compete on a cost basis with the disposal of dredged material in a confinement facility8.

To date, it is difficult to assess progress in addressing the sediment remediation problem (Figure 2). In Canada, more than 100,000 cubic meters (132,000 cubic yards) of contaminated sediment have been dredged from its Areas of Concern, and in the United States, more than 1.27 million cubic meters (1.6 million cubic yards) have been dredged from the its Areas of Concern for remedial purposes. According to the U.S. government, "Great Lakes agencies have completed or are currently addressing the remediation of more than 3 million cubic yards of contaminated sediment in the Basin9."

    Figure 2 :
    Status of Contaminated Sediment Remediation.
    (Click on the picture for a larger version).

At this time, the governments are not able to clearly define either their cleanup targets for contaminated sediment or the volumes of sediment still requiring active remediation. The lack of a framework for making prioritized decisions regarding remediation was identified by the Commission in 1997 as an obstacle to progress10. Without endpoints, progress cannot be assessed.

Although priority setting represents a political and institutional challenge, at least three U.S. Areas of Concern-the Kalamazoo River, the Grand Calumet River, and the Lower Green Bay/Fox River-remain severely contaminated and are releasing significant amounts of PCBs and other persistent toxic substances to the open waters of Lake Michigan. Clean up of these sites should be a priority and the Commission notes that remedial actions in these Areas of Concern are currently underway. The information gathered in the Green Bay Mass Balance Study, and the current Fox River Natural Resources Damage Assessment demonstrate progress in arriving at management decisions. Nearly 453,600 kg (one million pounds) of PCBs have been removed from Waukegan Harbour, the largest source to Lake Michigan, and a $330 million (USD) settlement will finance the remediation of the Fox River.

Box 5 :
Contaminated Sediment Management Techniques and Costs

Source Control
Much of the contaminated sediment inventory in the Great Lakes basin exists because of inputs from municipal and industrial sources that predate point source regulation. Although these point sources have been strictly regulated, continued inputs to receiving waters can occur through uncontrolled waste sites and the transport of contaminated material from upland areas including industrial and agricultural sites. Achieving suitable reductions in such sources is referred to as "source control." Failure to address significant inputs of contaminants precludes the successful use of other management options. Because of the wide range of activities that may need to be undertaken to achieve acceptable source control, cost estimates are highly site-specific.

Natural Recovery (Attenuation)
Physical, chemical or biological processes that result in a reduction of the mass, toxicity, mobility, volume or concentration of contaminants are referred to as "natural attenuation." These processes include burial through sedimentation, volatilization, dispersion and biodegradation. Burial with clean sediment is one process that most often results in risk reduction. Natural attenuation in and of itself has no cost, but is preceded by assessment and followed by monitoring.

Thick-Layer Capping
Thick-layer capping is an onsite management technique that involves placing a eight inch, (20-centimeter)- to three feet (1-meter) thick layer of clean material over the area of contaminated sediment. To date, there have been limited demonstrations of capping in the Great Lakes basin. Based on one proposal of full-scale capping, the cost is estimated at $50-$60 (U.S.) per cubic yard of contaminated sediment4.

Environmental Dredging
Environmental dredging is the most commonly used sediment remediation technique. Dredging of contaminated sediment in the Great Lakes basin is accomplished through hydraulic or mechanical dredging. Typical costs are in the range of $100-$200 (U.S.) per cubic yard5. These costs are several times those of navigational dredging. Hydraulic dredging minimizes sediment resuspension, but it requires treatment of large quantities of water. Enhanced designs of mechanical dredges have resulted in improved performance with low volumes of excess water being produced.

Box 6 :
Risk Management Is Helping Target Cleanups in Both the United States and Canada

Researchers in both the United States and Canada are developing methods to assist in making decisions regarding the management of contaminated sediment. These methods help set priorities and assist partners in determining cleanup targets. For example, Canadian researchers have developed the BEnthic Assessment of SedimenT (BEAST) model to determine whether sediment requires remediation11.

The U.S. National Research Council (NRC) publication "A Risk-Management Strategy for PCB-Contaminated Sediments12." provides advice pertinent to contaminated sediment decision making. Decisions for specific contaminated sediment sites must be based on a consideration of the advantages and disadvantages of available options and by balancing the various risks, costs and benefits associated with each option. Of particular relevance to the Commission is the NRC's recommendation that the first priority must be the management of overall risks to humans and the environment rather than the selection of a remediation technology (e.g. dredging, capping or natural attenuation).