Boskalis Westminster were the main contractor for Aberdeen Harbour Board undertaking capital dredging works to deepen and widen the approaches to Aberdeen Harbour involving the removal of approximately 400,000m³ of clays, silts, sands and rock to tolerances of -0.3m vertical and +10m horizontally with a final bar sweep.
The project was carried out using the trailing suction hopper dredger Crestway, to remove the soft material from the outer approaches, with the backhoe dredger Nordic Giant and split barges removing the remaining clays and rock. Trial trenches were dug with the Nordic Giant to assess the strength of the rock and, from these trials, it was deemed possible to excavate the rock without pre-treatment. Strengthening modifications were made to a 9.5m³ rock bucket and, by careful positioning of the dredger over high waters in relation to the rock bedding planes, the Nordic was able to pull the hard material. This innovative approach led to the works being complete two months ahead of schedule, hence allowing the client to accommodate larger vessels earlier than anticipated.