PT15 Contaminated Harbour and River Sediment
Exhibit Hall
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(PT241) Unique tools for determining the geometry of contaminated sediment deposits.

Biberhofer, J.1, Trapp, B.1, 1 Environment Canada, National Water Research Institute, Burlington, Ontario, Canada

ABSTRACT- Sediment deposit geometry is requisite for the management of contaminated sediments sites. Site managers have to know the inventory of contaminated sediment as related to the capacity of the remedial option(s) under consideration. Any improvement in the resolution of sediment volume estimates translates into more effective planning and utilization of resources. NWRI has employed a unique set of tools to acquire the information for these volume calculations. High-resolution multibeam sonar data mapped the elevation of the upper layer of the deposit for the study area. The thickness of the contemporary sediments was measured with two different probes. A tripod equipped with an acoustic transducer was used in shallow sediments and sediment thickness was estimated from the sounder output. A Seabed Terminal Newton Impact Gradiometer (STING) was deployed throughout the balance of the study area. The STING is a self-contained, tethered probe which can be outfitted with a steel shaft up to three metres protruding from the nose cone. The cone of the probe contains electronics to record pressure and acceleration as it contacts and penetrates into the sediment. The point data from these two instruments is combined and interpolated using geospatial techniques to model the lower level of the deposit. The volume of the deposit can then be calculated for the total extent of the study area under consideration as well as unique polygons for each data point. Individual polygons can then be selected based on existing sediment chemistry and toxicology information. The area and volume can be summed as a group to estimate the volume of sediment for priority zones within the study area.

Key words: deposit geometry, contaminated sediment, remediation

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