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B976 Letterbeg Embankment Stabilisation

Aberdeenshire Council
B976 Between Letterbeg and Castlehill of Strachan
March - April 2019

Work Scope

A section of rural road on the B976 between Letterbeg and Castlehill of Strachan was becoming unstable for several reasons.

From creeping wider over the years to flooding cutting away at the bank below to modern heavy trucks using the road more frequently, the embankment was starting to crack and subside.

CRC was contracted to provide a sustainable solution. We began by excavating any soft and/or organic material off the embankment before rebuilding it with a rock armour face and crushed rock infill.

With a river at the foot of the bank, the rock armour on the lower courses was buried almost entirely below the bed level. This ensured the armour also acted as scour protection for the bank as well as a stabilisation measure for the road above.

Letterbeg embankment close up


The site was particularly tight for space. Essentially, we could only use the existing road for material deliveries. We overcame this challenge by capping the existing road surface with quarry dust and Type 1 to protect it, allowing the rock and backfill required to be tipped onto the road.

From here, the rock and backfill were passed to the lower level using an excavator, where they were picked up by the placing excavator using a grab attachment. Working a ‘face’, the placing excavator prepared the ground by excavating down to the hard ground, laying geotextile and placing the aggregate and rocks. A Banksman/spotter stood at a safe distance from the machinery, guiding the excavations and placements with reference to the setting out positions.

Given the large volumes of aggregate and rock armour that needed to be delivered daily to keep the project on schedule (approx. 1,500 tonnes in total), there were also challenges concerning logistics. However, we overcame this by using our trusted network of hauliers to increase and decrease the delivery capacities as required at short notice.

And to ensure no harm came to the surrounding environment, we undertook comprehensive site flooding risk assessments and adopted strict sediment controls to avoid accidental pollution. As work was taking place next to a river, we implemented silt and oil bar measures in the form of straw bales and geotextile products.

Close up of Letterbeg embankment


This embankment stabilisation project provided Aberdeenshire Council and the community with a long-term, natural, entirely maintenance-free solution.

Feedback from the client was extremely positive, with praise given for our quality finish and quick build while maintaining high safety standards and minimising environmental impact at all times.

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