Volume 1 - Main Report

Data sheet PI-7
Environmental component
Marine invertebrates
Ecosystemic value: Large
Important elements in the marine trophic chain (Gray and Elliott, 2009).
Sociocultural and economic value: Average
Several species are harvested by the population (e.g. blue mussel) (GENIVAR, 2007b).
Source of the effect
Phases: Construction/Modification
Activity: Dredging
Description of the potential effects
• The dredging work will destroy the benthic fauna in the dredged area over a surface area of
9,350 m 2 , which corresponds to the surface area of two sheet pile cells and their stone
ballast.
• Burial of the benthic fauna in the sectors most affected by sedimentation, specifically in the
immediate area of the work and along the coast of Deception Bay in the dispersion plume
diffusion area.
• The suspended matter, from the stirring up of significant volumes of sediment, has a lower
food density than that observed in matter stirred up into suspension during natural
phenomena (turbulence, storms). Saila et al. (1972) say that the low food density included
in the matter stirred up into suspension affects the organisms depending on this food (filter
feeders and detritus feeders).
Degree of disturbance: High Intensity of the effect: High Duration of the effect:
Temporary
Duration-intensity index: Scope of the effect: Local
High
Significance of the effect: Average
Attenuation measures/Monitoring
The renewed suspension and dispersion of dredged sediment can be substantially curtailed by
closely managing the work, the type of equipment used and the operational behaviours; the
following measures are recommended:
Work management
• Restrict the dredging area to a minimum.
• Use a grab positioning system in real time to avoid over-dredging.
• Halt the dredging work during periods of bad weather (e.g. storms, strong winds).
Canadian Royalties Inc.
GENIVAR
101-53046-02 November 2012
212