Great Lakes Contaminated Sediment Removal Using Dredging Technology
The Great Lakes have been affected by the discharge of industrial, agricultural and municipal pollutants over the past several years. The accumulation of these pollutants within bottom sediment and the water column, has had a severe impact on the Great Lakes ecosystem.
The International Joint Commission has identified 43 impaired ecosystems within the Great Lakes, and has designated them as "Areas Of Concern" (AOC). A significant problem in many AOC is the presence of contaminated sediment.
Of these areas, 17 are Canadian, with 5 on boundary rivers shared with the United States. In accordance with the Great Lakes Water Quality Agreement, federal, provincial and state governments from Canada and the U.S. have committed themselves to remediation and the restoration of the 43 AOCs. In each AOC, a federal-provincial Remedial Action Plan (RAP) is being developed.
Steps have been taken to control the levels of pollutants entering the Great Lakes Basin from point and non-point sources. However, remediation of the contaminated sediments is an essential and integral part of the overall cleanup of the AOCs.
On the Canadian side, one major thrust for cleaning up the contaminated sediment comes from the Great Lakes Action Plan (GLAP). Administered by Environment Canada, GLAP provides federal participation in the remediation of the Canadian AOCs through Cleanup Fund.
Environmental Protection is the lead agency in Environment Canada in producing the formulation and implementation of federal programs associated with the remediation of contaminated sediments in AOCs.
The Contaminated Sediment Removal Program was created under the Cleanup Fund to provide leadership in the identification of removal technologies and procedures for contaminated sediment in the Great Lakes. The principal objectives of the Contaminated Sediment Removal Program are:
- Assist development on new technologies.
- Carry out field demonstrations at selected sites for the removal of contaminated sediment.
Promising new technologies are encouraged to be developed to a pilot plant stage that can be subjected to on-site field evaluation to verify performance and cost data. Another objective of the program is to encourage the development of technologies, which could have wide application across the entire Great Lakes Basin, in carrying out routine navigational dredging projects involving contaminated sediment.
The changing regulatory scenario and heightening public concern may render the present methods of dredging (particularly in the Great Lakes) increasingly unacceptable. To achieve these objectives, the program invited participation from a broad range of technical expertise from private research organizations, consulting firms, universities and the dredging community.
The program published a notice across Canada, U.S., Japan and Europe, announcing the program and to extend an invitation to those interested in demonstrating state-of-the-art sediment removal and handling technologies that would provide minimal disturbance and adverse impact on the environment.
Of the 125 respondents, 60 detailed proposals were received. A workshop for manufacturers of equipment was held. Each participant was asked to meet certain operational requirements. The equipment demonstrated had to: cause minimal resuspension, maximum solids content, have good maneuverability, positioning accuracy, mobility and suitability to hydrodynamic conditions.
Canadian regulatory and legal conditions needed to be considered as well. The scope of work entailed that each contractor meet the following list of specific tasks:
- Design and implement pre-demonstration studies such as: Physical and chemical characteristics of sediments; Biological inventory; and Water quality.
- Prepare an environmental screening document, which complies with the Canadian Regulatory Guidelines and Policies associated with environmental protection and assessment.
- Define, identify and remove contaminated sediment.
- Monitor the impact of the project on the environment and audit the equipment operation and performance.
- Identify and/or recommend pre-treatment methods.
- Prepare and submit a final report.
From the workshop, a total of 25 proposals were received from 12 organizations. These documents were reviewed and ranked using a decision matrix prepared by Environment Canada. The evaluation was based upon: State of the development; availability; effectiveness; versatility; cost and compliance with the requirements of the Canadian Environmental Assessment and Review Process (EARP).
A Modified Mud Cat™ 915 ENV dredge manufactured by Ellicott International of Baltimore, Maryland, was used in a demonstration of removing contaminated sediment in the Welland River, near Niagara Falls, Ontario.
These past and future demonstrations will determine management practices for dredging and disposal operations. The demonstration component of the program is designed to evaluate the performance of promising new technologies under actual field conditions.
The purpose of the evaluation was to gather sufficient data on the operation, cost and reliability of the technology to allow a comparison with alternative technologies for sediment removal, transportation and pre-treatment. Ultimately, the results of a technology demonstration project should facilitate sound decisions on the application of technologies at specific AOC sites, as well as at other sites with characteristics resembling those of the test sites.
By identifying applicable technology, together with an assessment of equipment available internationally, Environment Canada is creating a data base, which will result in the application of more efficient processes and techniques in the removal of contaminated sediment in aquatic ecosystems.
Reprinted from WORLD DREDGING Mining & Construction
