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All dredged up and no place to go : the disposal of contaminated dredged material from greater Vancouver, British Columbia, into the neighbouring strait of Georgia

University of British Columbia

The thesis provides an integrated review and analysis of strategic scientific information from which management procedures for the environmentally acceptable disposal of dredged materials from Greater Vancouver into the Strait of Georgia are determined. An analysis of reported and suspected contamination of Vancouver's waterways identifies trace metals and hydrophobic organic chemicals that warrant concern by authorities responsible for the management of dredged material disposal. The processes, transformations and pathways of these contaminants in the marine environment subsequent to dredged material disposal are reviewed. It is argued that a really confined degradation of suitable disposal sites is of negligible concern, but that release of contaminants from the disposal area, were it to occur, could have unpredictable and perhaps substantial environmental consequences. The major potential pathway of contaminant release from dredged material during or subsequent to disposal is via the resuspension and transport of fine particulate material. Biological accumulation of contaminants and their transport through the food chain is a potentially significant release pathway for hydrophobic organic contaminants. Biological transformation to more soluble metabolites is also potentially significant for mercury and some of the less chlorinated and lower molecular weight organic compounds of concern. Desorptive release of contaminants from the disposed sediments into solution is usually negligible, with the possible exceptions of cadmium and mercury. A review of the physical factors that promote contaminated sediment erosion and dispersion during or subsequent to dredged material disposal identifies oceanographic characteristics where such release will be minimal. There are only four areas within the Strait of Georgia that exhibit these characteristics. Two of these areas are adjacent to valuable and sensitive biological resources and are consequently unsuitable as ocean dumping sites. Dredged material disposal at the other two sites, one near Smelt Bay, Cortes Island, and the other off McNaughton Point, Sechelt Peninsula, should result in minimal adverse environmental impact. Available methodologies to identify dredged materials with contaminant levels that preclude their environmentally acceptable disposal at these recommended sites are discussed.

Text

2010-05-13

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http://hdl.handle.net/2429/24673

Resource Management and Environmental Studies

University of British Columbia

UBCV

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