Progress Toward Restoration
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.