Torry Quay

The client requirement for this project, was to create four new berths for the offshore industry which would allow offshore vessels to optimise turnaround time, with easy access to berths with bulk commodities. The project involved the demolition of old structures, the infilling of the River Dee Dock and the creation of 400m of new berthing space with a dredged depth of -7.5mCD. The facility incorporated a network of underground service trenches providing fuel, drilling muds and water to each berth for bunkering of offshore supply vessels. As the construction was in a Special Area of Conservation, there were stringent measures in place to protect wildlife, the bottlenose dolphin and Atlantic salmon in particular. The project was successfully undertaken in two phases which allowed Shell’s quayside operations to continue throughout the construction period of three years.

Careful consideration was given at the feasibility and technical planning stages to the existing structures which required demolition or encapsulation within the new works, namely, old quay structures including sheet piling, timber piling, concrete piling, and the end of an old 1600 tonne slipway. The design considered and used differing forms of construction appropriate to the varying site conditions. This allowed for the most cost effective solutions to be adopted for construction of the works. On this project the phasing of the works proved to be very worthwhile, as the lessons learned on the first phase allowed the contractor to evaluate, plan and resource the second stage more efficiently. It also allowed the design to be refined when further site investigation results were obtained. For the second stage, the contractor was given the opportunity to re-price the work, to a limited extent.

The site was within a busy harbour environment which produced a number of challenges regarding limiting disruption to port operations as far as possible. This required the diversion of existing live services, designing and phasing of the works around existing port users and their associated industrial processes, and phasing of the works to limit the loss of quay space.

The works included the considerable challenge of infilling the River Dee Dock. As the dock required approximately 171,000 m3 of material to be deposited within it, the design required extensive integration with construction methods to ensure temporary works stability. The design also required the cognisance of additional geotechnical challenges associated with poorer ground, with a change in construction to a heavier HZM combined sheet pile wall solution being adopted.

The new quay was constructed on the banks of the River Dee within the harbour and replaced a series of existing structures and former quays that were incumbent on the site. It was fundamentally a sheet pile wall design comprising Arcelor AZ48 sheet piles with a concrete relieving platform behind on bearing piles. This relieving platform was anchored to provide stability to the sheet pile wall with the form of anchorage varying between tie-rods and anchor walls, raking piles or ground anchors dependent on the physical constraints of the site. The quay wall varied slightly in the second phase of the work when soft ground was encountered and the wall was changed to a HZM combi-wall system, using a stronger wall section. An open jetty was constructed at the west end of the works (rather than a closed jetty which would constrict the flow of the River Dee). For this, 700mm tubular piles were used together with a precast and in-situ structural concrete deck. The jetty was sufficiently wide to allow pipe spools to be re-reeled and loaded on the aft end of an offshore vessel.