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Evaluation of environmental impacts of riverbed dredging : a proposed project on the lower Caroni River, Venezuela

University of British Columbia

The purpose of this research thesis is to identify social, economic and environmental impacts associated with dredging in riverbed settings and potential preventive actions. This project uses a mining dredging project (Caroni Project), currently at an early stage, as a case study. Increases in river water turbidity, changes in drinking water quality for the nearby cities, and increased mercury mobilization are the main environmental impacts this thesis project evaluates. A diversity of non-environmental factors also influence the feasibility of the Caroni Project, and for that reason an integrated environmental, social and economic approach is required. It was found that increases in river water turbidity during dredging operations can be prevented by using a combination of pneumatic high density suction dredging methods and an underwater crusher or a cutterhead dredger where hard pan layers are located. Regardless of the low fines content expected in the river, these procedures must be accompanied by preventive measures against turbidity like turbidity curtains and low impact cutterheads, due to the extreme sensitivity of the dredging area. It was also found that the main potential environmental impacts are linked to mercury recovery, waste water and sludge treatment. The removal of metallic mercury contained in the sediments can be achieved during the processing stage by gravity concentration and retorting. The residual mercury is expected to be associated with fine concentrates that could be treated by electrochemical methods if required. Encapsulation of metallic mercury and organic mercury bearing sludge is possible by commercially available methods. The development of a Sustainable Business Case and the implementation of the Mining, Minerals and Sustainable Development - Seven Questions Methodology as a tool for monitoring sustainability would both contribute to better foreseen opportunities to negotiate mutually beneficial agreements among stakeholders of the Caroni Project, and reduce the risk of land use conflict with hydro-electric company (EDELCA), former artisanal miners and other potential actors not yet identified. This research project provides an opportunity to propose specific sustainable practices not only applicable to the mineral dredging industry but also to junior mining company project.

Thesis/Dissertation

application/pdf

2009-10-28

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http://hdl.handle.net/2429/14263

Mining Engineering

University of British Columbia

UBCV

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