Targets defined by Transport Scotland’s newly established A83 taskforce includes the aim to have an alternative road to the landslide-hit Rest and be Thankful route built within 12 weeks.
News that £1.5M in funding has been committed to construction of the 4km long emergency diversion emerged following the first meeting of the taskforce last week.
Scottish transport minister Keith Brown chaired the meeting in Arrochar on 15 August, which set out the remit of the group that will meet monthly and also oversee delivery of a permanent solution to landslides in the area.
Transport Scotland’s term maintenance contractor Trans Serv has already started work on the eastern end of the 4km diversion route - a section shared by the two proposed options.
The geometry means it is not suitable for two-way traffic so we will use convoys travelling at low speed to guide traffic through
“Work on a section of the diversion owned by the Forestry Commission is already in progress,” said Transport Scotland head of network maintenance Graham Edmund. “We are currently in negotiations with a private land owner and the Forestry Commission over the final route but parts of it will follow the forest track and also use the old military road that was part of the A83 up until the 1930s.
“This previous use of the route as the main road means that part of the route is already paved but we will need to strengthen a couple of bridges and carry out work to around 20 culverts to allow the route to be opened to all traffic.”
Edmund stressed that the diversion will not be a permanent solution. He said: “The geometry means it is not suitable for two-way traffic so we will use convoys travelling at low speed to guide traffic through when the route is in use.” According to Edmund, the diversion route is expected to be completed by the end of November.
During the taskforce meeting some local stakeholders levelled criticisms at Transport Scotland that plans were not put in place before now. TRL head of ground engineering and regional director for Scotland Mike Winter told NCE that, given the country’s mountainous terrain, landslides were inevitable. Nonetheless, he added that concern about the debris flows at Rest and be Thankful had been increasing in recent years.
“In the last 23 years I cannot remember a year without a landslide on the Rest and be Thankful stretch of road, but in the last five years there has been a change in the pattern of landslides focused on a section a few kilometres long on the south west flank of Beinn Luidhean where the slopes are at around 36o,” he said.
“There is shallow or discontinuous soil cover in this area and there is high translational movement. Over the last few years the slope mobilisation has increased and there has been an intense change at the site with previously active stream channels becoming dry and new stream channels becoming active.”
Winter headed a team that undertook a study of landslide risks at Transport Scotland between 2004 and 2009, and he said that Rest and be Thankful was rated as being one of the highest hazard and highest risk sites studied in the report. The report recommended two approaches - the first being management of the landslide risk. But at higher risk sites, such as Rest and be Thankful, a range of mitigation options were set out, and Winter said that these are now being acted on at the site.
Longer term solution
Winter said the slope mobilisation at Rest and be Thankful means that the risk to road users has reached unacceptable levels and he supports Transport Scotland’s plans for the area. Winter added that there are other sites across Scotland that are at high risk from landslides but none are at the same level as the risks posed at Rest and be Thankful.
Once the temporary diversion route is in place, the taskforce will focus on finding a longer term solution for the whole route. “Jacobs is currently working on a report looking at the landslide risks and pinch points on the whole A83,” said Edmund. “We expect to have the report available to us at the end of October and hope to publish it by the end of the year.”