The 'Red Option' is Transport Scotland's method of mitigating landslides at the Rest and Be Thankful. We considered a range of options which could help minimise the frequency and duration of road closures. The Red Option, as outlined below, provided a similar level of benefits to other options for a significantly lower costs over the same time period.
The Red Option consists of a range of hazard risk reduction measures proposed along the line of the existing road. The works will include:
- additional fencing
- debris netting
- drainage improvements
- enhancement to slope vegetation
- culvert improvements
During these works, the Old Military Road below the A83 was available as a local diversion route as required. The works continued until the measures implemented demonstrated a sufficient level of protection to the A83.
All phases of the Red Option debris netting are now in place. During the landslide event on 5 December 2015 during Storm Barbara, our debris nets were successful in preventing approximately 1,000 tonnes of debris from reaching the trunk road.
A 2015 study, undertaken by AECOM consultants, to assess the performance of existing risk reduction measures considered historical and recent landslide activity. The outcome of this study made recommendations on further improving the existing risk reduction measures over a range from High to Low frequency of each phase.
The current package of works encompasses the highest frequency events identified in the study and invited options from tenderers for special structure solutions to provide the additional protection at Phases 5, 7 and 9. The returned tenders included options for more debris flow netting and catch-pits. The tender offering the catch-pit solution was assessed as providing the best solution to reduce the risk at the high frequency channels and the best whole-life cost. The tender was awarded on 24 February 2017 on the basis of a catch-pit solution at each of the high frequency channels.
The planting of vegetation and forestry on the hillside, upslope of the A83 Trunk Road, is in the design and planning stage within the Forestry Commission, which will further reduce the risk of landslides. The benefits here will only be realised around 15 to 35 years after planting.