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The Camp Bay cliff face

The Camp Bay cliff face is in sharp shadow in the morning, but by the afternoon it is bathed in brilliant sunshine. While locals down tools for an afternoon siesta, CAN works through. It is not work for the faint hearted.

The process of drilling, handling, installing and commissioning 32m long anchors, while suspended part way down an overhanging cliff face, is a unique geotechnical operation, requiring exceptional discipline and teamwork.

Getting the right kind of balance within teams is critical, explains CAN operations director Andy Wingfield. While it is possible to train an experienced driller in rope work and safety procedures, it is equally important to have skilled climbers because they have an innate sense of safety.

Safety consciousness is ingrained into site working practice. Not only the drillers, but every piece of equipment - rigs, tools and materials - is suspended off two capacity tested and firmly anchored ropes at all times.

'Because we specialise in getting to remote places, people assume that we can get anywhere,' Wingfield comments. Progress is understandably slow compared with conventional drilling and anchoring work, and installation of the 135 anchors at Camp Bay will take three crews nearly four months.

Anchors have a design capacity of 500t, achieved from a bond length of 4m. Given the variable condition of the rock, a flexible approach is needed, says Wingfield, with actual anchor length being determined by Golder on a hole-by-hole basis, depending on the ground conditions.

Design responsibility lies with Golder but CAN and Costain have to determine the anchor bond length to meet design load criteria.

Given the warm marine environment, and the fact that the outflow from a desalination plant is discharged right beside the work area, corrosion protection is a key issue. CAN is installing fully corrosion protected Dwyidag strand anchors, complete with epoxy painted, grease-filled head assemblies, which should ensure cliff stability at one of Gibraltar's most important playgrounds for many years to come.

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