Current situation
The convoy system is working and we have installed new vehicle safety barriers where the bypass joins the A816. This was needed to repair barriers damaged by the landslide.
When signed off as safe, we intend to put in hard-wired traffic lights as wireless lights would be unreliable. Cost options for this are being worked on.
We will create catch-pits and bunds at the base of the unstable slope once the land agreement for the last of the temporary works has been made. We expect this to be soon and there will be four to six weeks work once the agreement has been signed. This will allow traffic back on to the original road, as long as the hillside remains stable.
We’ll monitor the hillside with CCTV, saturation level and rainfall forecast. The temporary diversion will be used if there is a risk of material flowing from the hillside.
In the long-term, the current diversion route will be widened to become the permanent diversion route through Kintraw. This could take two to five years to progress.
Last updated - 22nd April 2024
How it happened
On Saturday 7 October there was a significant weather event where around a month’s worth of rain fell in a 36 hour period in a number of areas across Argyll and Bute. This rain fell onto already very wet, and in places saturated ground.
At the A816, south of Kintraw there was a significant debris flow (often referred to as a landslide) where approximately 6000tonnes of material came down the hillside blocking the road over approximately 200 metres. Two vehicles were trapped in the landslip; fortunately nobody was hurt.
The hillside was not stable and some material, including boulders continued to slip down the hillside, particularly in the wet weather. The hillside continued to change shape as more material moved and exposed further rocks. These rocks were precariously perched on the hillside, with the largest being over 200 tonnes, and some being as high as 120 metres above the road.
Following the landslip on the A816, making the hillside safe enough for the road to be used was the priority.
We cleared debris from the road, however; wet weather conditions continued to have an impact - parts of the hillside were ‘scaled’ of loose rocks however, many rocks had yet to be moved and more rocks emerged following rain which washed away the slurry/soil covering them. This process exposed more rocks with soils and silt washing down the hillside, changing its shape which presented new challenges. We cleared more than 15,000 tonnes of material.
Due to ongoing movement on the hillside, particularly in wet weather, and the number and size of boulders, we had to progress an emergency diversion road to provide resilience and to open up a route in as short a timescale as possible.
The emergency diversion route was the most certain, and therefore fastest, way of getting a route along the A816 reopened. Following intensive and complex operations, we were pleased to open the emergency route, for use under convoy, on Saturday 16 December.
The emergency road will also provide an alternative route for the A816 during very wet conditions when the hillside will be less stable.
Long-term, depending on how stable the hillside becomes, it is very likely that we will divert the road on a permanent basis. This would be subject to the necessary permissions and consents required with a permanent road which take time. Therefore, in the short term we will continue with the clean-up and works to make the hillside safe enough for the main road to be used, as well as progressing the emergency route.
Emergency diversion route
Delivering this route involved multiple steps from securing agreement with the landowner about accessing land, and agreeing use with Historic Environment Scotland archaeologists, to laying foundations and surfacing the new road.
Part of the thinking behind choosing the location of the relief road is that it is more naturally protected from weather effects.
We were able to deliver this route for its opening date by constructing it as an emergency route so not to the same construction as a permanent road. It should be able to take most types of traffic, including some heavier vehicles like buses, supermarket delivery trucks etc. .
Main A816 road
We had hoped to re-open the A816 mid to end of November, and we will were working to stabilise the hillside along the A816 sufficiently to get that road re-opened as soon as it is safe to do so. Unfortunately the emerging challenges mentioned above meant it took longer than we had initially hoped.
Our ongoing work includes building in additional protection along the route, by creating a bund to provide a barrier between the road and the hillside, and catch pits to collect any material from the hillside. To create the bund, we are going to use some of the material we have recovered from our work on the hillside.
Questions we have been asked
Is the situation at Ardfern the same as at the Rest and Be Thankful (A83)?
The situation at Ardfern is quite similar to the position at the Rest and Be Thankful (RABT) with landslips occurring prior to there being netting and catch pits in place. There were periods a number of years ago when the RABT was closed for several weeks to facilitate both land agreements and physical works to take place. The RABT was only opened when it was safe for road users
One of the fundamental differences with Ardfern and the most recent debris flow on the RABT is that the material which flowed on the RABT was controlled by the catch nets which slowed the flow, the material then landed in the catch pits with little reaching the road (this is the catch pit section, not the A83 by the A815 which has no netting or pit protection).
The A83 and A815 debris flows brought down approx. 6000 tonnes of material in total (compared to approx. 13000 tonnes at Ardfern). This material was cleared in a matter of days and the various locations were relatively easy to deal with due to the more gentle slopes from where material had flowed from. This means that the risk of falling rocks and debris flow onto the road is significantly less than at Ardfern.
We are using the same assessment techniques and taking advice from the same engineering geologist that has previously assessed the RABT and is currently advising on the stability of the A815. The overall view is that the A815 is safe with the monitoring that is in place whilst the Ardfern site carries a significant level of risk and therefore not suitable for public access until protective measures are in place.
At Ardfern, the clearing of the carriageway was the first stage in the complex process towards reopening the road. The next stage is the construction of a bund which has been designed to stop further material reaching the road in the majority of any future flow events. This needs to be completed before the road can be opened up safely to the public.
The precarious nature of the hillside means it continues not to be safe for members of the public to travel through. The team that are working there are experienced working in these situations and have a number of safety measures in place not least each individual having a radio which operates as an emergency warning process allowing staff to evacuate should stability become more of an issue.
Furthermore the staff working clearing the face are working in or near large machines which can withstand material collisions, within reason.
Discussions have taken place with BEAR and Transport Scotland so we can draw on effective practice from there. Furthermore, we have engaged the services the expert geo engineers (Geo Rope) who provide advice and guidance on slope stability for the RABT and a number of other sites which BEAR and TS are involved in).
Can I buy some of the boulders from the hill?
Sorry no - we are using boulders from the hillside to form a bund at the side of the road (as part of the measures we are taking to make the road safe for use).
Bus services –what are you doing about bus services to Oban via Inveraray?
We have been asked specifically about re-routing the Ardrishaig to Oban bus service via Inveraray.
We made additions to Service 428 to provide public transport connections from Ardrishaig/Lochgilphead to Oban via connection with Citylink service at Inveraray and return.
Visit our Timetables Directory to check the latest timetables/routes before setting off on your journey.
Schools – how will pupils get to school in Lochgilphead?
We made arrangements for pupils to get to and from school. These include arranging boats for return Ardfern/Crinan journeys, for pupils and teachers. Feedback is that this is working well. For consistency, this arrangement will continue w/b 18 December, although the emergency route is now open.
Remaining seats on the boats can be booked free of charge by members of the public directly with Venture West.
Additional background information
In addition to steps outlined above we engaged specialist geotechnical engineering experts who carried out a detailed drone survey of the hillside. The drone survey information has been used to build a digital model of the hillside.
The purpose of the model is to provide valuable detailed information including:
-
Calculating the angles of the hillside
-
Calculating the volume of material slipped already and by using the model as a comparator, monitor any further or potential movement
-
Model trajectory paths for any further flows
We made an agreement with Forest and Land Scotland to dispose of the material at a former quarry site nearby. This material will then be used to restore the quarry. The process was quite complex with SEPA requirements, quarrying regulation requirements and a formal agreement to occupy the site, all having to be completed before works can start.