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Overflow dredging in Great Lakes
Marine Pollution Bulletin
development of a regional plan. The plan will address problems, including contamination by toxics and pesticides originating from shoreline industrial and agricultural activities; nutrient over-enrichment leading to 'red tide' blooms; destruction and degradation of wetlands and seagrass beds resulting in loss of habitats and nursery grounds; loss of freshwater inputs to the Gulf caused by diversions; and increased human exposures to contaminants and the resulting public health effects caused by reduced flushing rates in estuaries.
Overflow Dredging in Great lakes The US General Accounting Office (GAO) has recently released a report that examines the practice of overflow dredging in the Great Lakes. This dredging method is used to increase the amount of sediment that can be loaded on a dredge during a given trip to a site. The dredge is simply kept on site and sediment is brought on board the dredge even after the sediment bin is filled. The excess water and lighter sediments are allowed to overflow back into the lake until the sediment bin is filled with heavier sediments. Environmentalists have called for tighter restrictions or, preferably, a ban on the method, which has been used for more than half of all dredging conducted in the Great Lakes in recent years. The environmentalists claim that overflow dredging of contaminated sediments causes resuspension and dispersal of contaminated sediments where they can enter the food chain and, thus, impact lake resources and humans. The GAO study found that neither EPA nor the US Army Corps of Engineers were studying the impacts of this dredging practice which is regulated differently by the several states surrounding the Great Lakes. Ohio does not restrict the practice in any way; five states do not allow overflow dredging in certain contaminated
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areas; and Minnesota and Wisconsin have totally banned the procedure in their state waters. The study found only one instance when the Corps of Engineers used overflow dredging on highly contaminated sediments. Sediments in the Saginaw River that were contaminated with heavy metals were dredged by the method, but the Corps did not use the practice nearby where elevated PCB levels were known to exist. The Corps of Engineers has resisted efforts to restrict overflow dredging in non-polluted areas since the practice allows fewer trips to a dredge site to be made and, thus, saves money. The Corps has estimated a ban of the dredging method would increase dredging costs by 3055%. The regional EPA headquarters is empowered under the Clean Water Act to specify sediment sampling and testing criteria, but it has, to date, only required the Corps to sample each dredge site within the five years prior to dredging.
Round-the-World News Denmark Denmark has received a loan of 7.5 million Ecus (DKr60 million) from the European Investment Bank to modernize and extend the Esbjerg sewage system. At present, sewage from the town of Esbjerg is discharged into the German Bight where abnormal increases in aquatic vegetation and algae, and disturbances in oxygen levels have resulted. It is hoped that the Esbjerg investment scheme will contribute to the improvement in quality of this sensitive area of the North Sea. The improvement scheme includes the addition of biological and chemical treatment phases together with an increase in capacity aimed at reducing the discharge of organic matter by 97% and that of phosphorus and nitrogen by 90%.
development of a regional plan. The plan will address problems, including contamination by toxics and pesticides originating from shoreline industrial and agricultural activities; nutrient over-enrichment leading to 'red tide' blooms; destruction and degradation of wetlands and seagrass beds resulting in loss of habitats and nursery grounds; loss of freshwater inputs to the Gulf caused by diversions; and increased human exposures to contaminants and the resulting public health effects caused by reduced flushing rates in estuaries.
Overflow Dredging in Great lakes The US General Accounting Office (GAO) has recently released a report that examines the practice of overflow dredging in the Great Lakes. This dredging method is used to increase the amount of sediment that can be loaded on a dredge during a given trip to a site. The dredge is simply kept on site and sediment is brought on board the dredge even after the sediment bin is filled. The excess water and lighter sediments are allowed to overflow back into the lake until the sediment bin is filled with heavier sediments. Environmentalists have called for tighter restrictions or, preferably, a ban on the method, which has been used for more than half of all dredging conducted in the Great Lakes in recent years. The environmentalists claim that overflow dredging of contaminated sediments causes resuspension and dispersal of contaminated sediments where they can enter the food chain and, thus, impact lake resources and humans. The GAO study found that neither EPA nor the US Army Corps of Engineers were studying the impacts of this dredging practice which is regulated differently by the several states surrounding the Great Lakes. Ohio does not restrict the practice in any way; five states do not allow overflow dredging in certain contaminated
58
areas; and Minnesota and Wisconsin have totally banned the procedure in their state waters. The study found only one instance when the Corps of Engineers used overflow dredging on highly contaminated sediments. Sediments in the Saginaw River that were contaminated with heavy metals were dredged by the method, but the Corps did not use the practice nearby where elevated PCB levels were known to exist. The Corps of Engineers has resisted efforts to restrict overflow dredging in non-polluted areas since the practice allows fewer trips to a dredge site to be made and, thus, saves money. The Corps has estimated a ban of the dredging method would increase dredging costs by 3055%. The regional EPA headquarters is empowered under the Clean Water Act to specify sediment sampling and testing criteria, but it has, to date, only required the Corps to sample each dredge site within the five years prior to dredging.
Round-the-World News Denmark Denmark has received a loan of 7.5 million Ecus (DKr60 million) from the European Investment Bank to modernize and extend the Esbjerg sewage system. At present, sewage from the town of Esbjerg is discharged into the German Bight where abnormal increases in aquatic vegetation and algae, and disturbances in oxygen levels have resulted. It is hoped that the Esbjerg investment scheme will contribute to the improvement in quality of this sensitive area of the North Sea. The improvement scheme includes the addition of biological and chemical treatment phases together with an increase in capacity aimed at reducing the discharge of organic matter by 97% and that of phosphorus and nitrogen by 90%.