Project Consulting Engineers, Pick Everard designed a robust revetment that could withstand the exposure conditions. The 500m long revetment structure would stabilise and protect the sand dune system. 0.5m thick Reno Mattresses were selected to protect the sloped revetment and a low height crest wall constructed from gabions would retain the runway and control wave overtopping. A similar solution had been adopted successfully at a MOD Firing Range elsewhere on Benbecula

Due to the dynamic loading conditions and the potential for the foundation conditions to change over the life of the structure, there was the possibility of differential settlement. Therefore, double-twist woven steel wire mesh gabions were selected as their inherent flexibility would enable the structure to accommodate differential settlement without sustaining damage.

Preserving the natural shoreline, the box gabions and heavy Reno Mattresses were filled with more than 8,000 tonnes of locally quarried stone. These heavy revetment mattresses provided a natural-looking solution, which would soon accrete sands and silts in which vegetation could establish.

Construction of the revetment was carried out by contractor Aggregate Industries UK Ltd of Stornoway. Maccaferri assisted Pick Everard with technical advice on the project. Maccaferri’s 130 years of experience in hydraulic and coastal works led to specific details being incorporated into the project to enhance the performance of the solution.