Physical oceanographic monitoring of dredging activities at Kilo Wharf

Sea Engineering, Inc. conducted a detailed study to monitor suspended sediment plumes generated in a tropical reef environment by dredging activities during the Kilo Wharf Extension Project, which was performed between October 2008 and December 2009. The monitoring study had two primary components: boat surveys utilizing acoustic backscatter techniques to image and characterize the dredge plume spatially; and, environmental data collection at two in situ control stations to monitor ambient conditions temporally. Results showed that the backscatter surveys successfully imaged dredge plumes and indicated that the plume was typically located near the bottom and adjacent to the silt curtain. In situ measurements at the control stations located to either side of the dredge site indicated no notable change in ambient turbidity or total suspended solids (TSS) concentrations over the study period. Wave data from the acoustic Doppler current profiler (ADCP) wave gages at the control stations indicated that increased wave heights at these sites resulted in increased turbidity and TSS concentrations. Project results indicate that acoustic backscatter surveying techniques in combination with in situ control stations are an effective means for characterizing dredge plumes.