Geotechnical engineering specialist CAN Geotechnical has been awarded the contract to undertake the necessary stabilisation work at Fort Bovisand in Wembury, bringing both its specialist access capability and drilling expertise.
The 170-year-old Victorian fort – a heritage structure in need of serious renovation – is being turned into 81 apartments by Fort Bovisand Developments Ltd, which is owned by former BBC director general Greg Dyke.
The development will include an events space and a café, maintaining public access.
The critical first element to the overall project is stabilising two gullies immediately beneath the access road leading into the fort complex running along the top of coastal cliff faces. Each location requires specialist equipment and work at height experience.
The project’s geotechnical designer, Red Rock Geoscience, has specified a soil nail and facing solution, to stabilise the gullies and prevent further erosion undermining the access road. The eastern gulley will have 195 R32 stainless steel soil nails installed in a grid pattern over the cliff face, while the western gulley needs 127 of the same type of soil nails. Both gullies will be faced with steel netting and erosion matting.
CAN’s approach is to use an excavator-mounted hydraulic drill rig to install the upper bolts of the netting system, and to drill the rows of soil nails in the face of the crest.
Temporary anchors will then be installed and used to suspend CAN’s in-house designed ‘A Frame’ cliff-mounted drill rigs. These A-frames enable the drill crews to move the rigs to each soil nail location on the cliff face using winches – which they access by abseiling down on to the cliff face and working suspended from ropes to undertake the drilling.
On completion of CAN’s works, a marine contractor will install a rock protection system at the base of the cliffs to protect from future wave action, and repair to a shoreline defensive wall. The combined stabilisation measures will allow the current temporary weight limit to be removed from the access road, enabling the main redevelopment works to begin with safe, unrestricted access to site.