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(PM150A) Nearshore Contaminated Sediment Investigations at Britannia Beach, British Columbia.

Hagen, M, McCandless, R, More, B, Yao, A, Colodey, A,

ABSTRACT- The Britannia copper mine, 45 km north of Vancouver, B.C., discharged about 40 million tonnes of mine tailings into Howe Sound between about 1905 and 1974. The mine will continue to discharge metals-contaminated drainage and runoff until a wastewater treatment plant is completed in 2006. Environment Canada (EC) investigated the shallow, nearshore marine environment at Britannia Beach, Howe Sound during 2001-2002. Bottom habitat at depths of less than about twenty meters is the most biologically productive zone and also the maximum practicable depth for any cost-effective sediment remediation, should any be necessary. Multiple lines of evidence were used to obtain a more complete understanding of the nearshore benthic environment than provided through traditional sediment sampling methodologies. EC conducted or contracted six surveys between April 2001 and March 2002. Video was used to map seabed substrate type, morphology, and the types and distribution of organisms. More traditional studies included analyses for sediment particle size and sediment chemistry (including measures of bioavailability), water and sediment bioassays, bioaccumulation (both in situ and in amphipods exposed in the lab), and benthic invertebrate community analysis. Integrating the lines of evidence suggested that the Britannia Beach study area can be divided into four sub-areas which range from background conditions to areas of severe impact. The priority for management action is an area north of Britannia Creek and the deep outfall area stretching about 1,100 m alongshore where conclusive sediment-related effects were demonstrated. Sediment metals were high, bioavailable, induced toxicity in bioassays, and the abundance and diversity of benthic invertebrate communities was reduced. We recommend re-assessment of the benthic community and the impact of sediment contamination after the proposed mine water treatment plant has operated for at least three years because mine water deposits may be a major contributor to the impacts found.

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