In situ assessment of sediment erosion and consolidation state using a free-fall penetrometer: Sydney Harbour, Nova Scotia

Abstract

Two in situ geotechnical surveys were undertaken in Sydney Harbour, Nova Scotia, Canada, following the dredging and relocation of 4.2 million m3 of sediment from the shipping channel during the fall and winter of late 2011 and early 2012. The surveys were conducted 9 and 18 months after dredging using a portable, free-fall penetrometer. A new method for rapid assessment of the in situ state of sediment consolidation from free-fall penetrometer data was developed and applied to identify areas of sediment erosion and deposition. Results 9 months after dredging showed an initial accumulation of dredge-resuspended sediments. Eighteen months after dredging, stability, and evidence of consolidation or continued accumulation was found at more than 92% of the 39 sampled locations examined. Evidence of erosion was observed at only 3 locations. The general pattern of sediment stability observed is consistent with the historically low energy and sedimentation environment of the inner regions of Sydney Harbour.