UIG harbour redevelopment
THE BRIEF
Robert West Consulting were commissioned by Mclaughlin and Harvey to prepare tender stage designs forming an alternative tender proposal for parts of the Highland Council’s Uig Harbour Redevelopment project. The Works comprised a 100m long new pier formed by circular sheet pile cofferdams with a capping slab; a new turning dolphin; new linkspan supports; and refurbishment of a variety of other structures. The Employer had completed detail designs for the whole of the Works but sought alternatives designs offering enhanced value.
VALUE-ADDED SOLUTION
An evaluation of the Employer design identified significant risks of maintaining the stability of the circular cofferdams during medium weather events and the possibility of losing whole uncompleted sections during storm events. The programme and weather window was challenging. In addition, the structures were sensitive to the properties of fill material (limiting the availability of suitable sources) and to the upper horizon of the competent ground.
RWC developed an alternative design comprising a twin walled structure with two levels of ties and intermediate cross diaphragms. The pile size was specified to manage expected variations the top level of competent ground and to raise tie levels as high as possible to eliminate diving works and minimise tidal work. The structure was optimised with the Contractor to support high crane loads to allow end of end construction from the shore and eliminate marine plant. Specific attention was given to enabling temporary cross diaphragms to be placed ahead of any weather events to protect the structure.
FINAL OUTCOMES
The alternative designs proposed offered a significantly lower price than the Employer designs by reduction and mitigation of weather and construction risk. The designs were able to accommodate a wider range of fill sources and could be constructed faster and with greater reliability.
