Engineers find solution to the Pennan crack: 30ft nails

Published on Tuesday 24 November 2009 21:50

PLANS to remove hundreds of tonnes of soil, rock and rubble from an unstable cliff face threatening to block the only access road to Local Hero village Pennan have been abandoned.

It was, engineers said, a "risk too far". Instead, infrastructure experts are planning to make the cliff face safe by using massive steel rods to "nail" the slope to the bedrock.

The 125,000 scheme, which could take three weeks, is expected to begin at the weekend. The new plan means there will be no need for the 22 residents of the coastal hamlet to leave their homes while the work goes on.

Fears for the vital access road were raised last week after a huge crack, 25 yards long and a foot wide, appeared close to the top of the cliff face, towering over the community, following days of torrential rain.

Iain Gabriel, Aberdeenshire Council's infrastructure director, revealed yesterday that a second five-yard crack had appeared in the cliff face at Pennan and that there had been further movement on the fragile cliff face. But the situation appeared to have stabilised.

He said geotechnical consultants hired by the council had concluded that the original plan to remove the unstable soil and rock would not be safe.

"The concern was that to get access, we would have to build up above the road and that would be dead weight above the road and you would then have movement by vehicles taking the material out," Mr Gabriel said.

"The concern was that would disturb the integrity of the existing road and potentially lead to a failure of that road. Clearly, that would be catastrophic and a risk we are not prepared to take.

"When we began to do the risk assessment, the feeling was that that was just a risk too far and that we should go back and look at an alternative. The preferred option now is to leave the material in situ, simply because it is too risky to take it down, and to use soil nails – ten-metre-long rods – and nail the slope back into the bedrock and cover the entire area with a mesh.

"Clearly, that's less risky in terms of how the work is done. One of the advantages is that the road can be left open to residents, which is important, and there is less risk in terms of any potential further failures."

Mr Gabriel went on: "I will be recommending to the council that we accept a tender from a specialist contractor for the work. This remains a complex piece of work, however, and the safety of workers and the community will remain our top priority throughout the process.

"A lot has been achieved in a very short space of time and we would like to thank the Pennan community for their patience while the best course of action was determined."

A council spokesman said: "This course of action means access in and out of the village will be maintained during the course of work, removing the need for any householders to find alternative accommodation.

"Subject to council approval, work would start next week and be complete before Christmas. Further sections either side of this area will be considered for similar treatment in the new year."