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Lyneham Banks landslip information and ongoing updates
The B4069 at Lyneham Banks has been closed since February 2022, when a major landslip broke up the road, moving it 25 metres downhill. Since then, the council has been working hard to establish the cause of the landslip and assess the best way to rebuild the road and prevent the landslip reoccurring.
The process began with months of careful assessment and detailed ground investigations, including drilling 31 boreholes and 21 trial pits, as well as extensive sampling and monitoring of water levels and ground movement to establish the cause and extent of the landslip. Analysis revealed that the landslip was probably triggered by a combination of factors, including historic weaknesses, increased groundwater flows, and additional loading due to nearby development.
Construction work has now started on site. The construction will include the installation of a piled retaining wall with associated ground anchors. A series of drainage systems will also be installed in the area to help manage groundwater flows.
October update
In recent weeks, the team have been hard at work on essential earthworks that are crucial for the ongoing development of our site. This phase of the project primarily focuses on three critical activities: digging, drainage improvement, and vegetation removal.
Proper drainage is vital to prevent future water-related issues on the site, such as flooding or erosion. Our drainage improvement efforts involve installing new systems and enhancing existing ones to ensure that water flows efficiently away from critical areas. By addressing drainage early in the process, we are taking proactive steps to ensure long-term sustainability
While it's always a priority to preserve as much natural greenery as possible, selective vegetation removal has been necessary to clear the way for construction and infrastructure development. This process has been conducted thoughtfully, with consideration for the local ecosystem.
Our attention has now turned to the installation of the piles on the northern side of the road. The installation of the piles will now take place over the next few weeks with 120 piles being installed to a depth of 11 metres.
Lyneham Banks progress October 2024 1
Lyneham Banks progress update October 2024
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Meet the contractor event
In July we hosted a meet the contractor event at Bradenstoke Village Hall. We were really pleased to meet many of the residents and had a good attendance of more than 100 people stopping by to learn more about the project. Hosting the evening there was representation from both Octavius and Wiltshire Council, with questions about the project and other local works being answered.
Planning
In February 2024 a planning application was submitted with the proposals for the road. The planning application PL/2024/02330 can be viewed through Wiltshire Councils Planning Portal
Whilst movements on the main landslip have slowed considerably, we are still noticing movements further along the B4069 to the west.
We have been undertaking further surveys to help understand those wider and more progressive movements further along the B4069 and explore solutions. Observations have included an extended drone survey which has covered the entire B4069 from the current landslip down to the Clack Hill junction.
We are also undertaking weekly monitoring visits to record and track the current movements and more detailed inclinometer readings at monthly intervals.
Anticipated Programme (Subject to land agreements and planning)
Stage
Timescale
Design Work
Complete
Procurement
Complete
Planning
Complete
Construction
Summer 2024 - Spring 2025
In November 2022 a series of traffic management changes were made to the roads around the B4069. This followed reports of a high number of unsuitable vehicles using the local roads around Lyneham, Bradenstoke and the surrounding parishes. The main changes were:
introduction of a new one way (Northbound only) on Clack Hill
introduction of new waiting restrictions at the southern end of Clack Hill
40mph speed limits and 7.5T weight limits introduced on three local roads (Bowds lane, Trow lane and Cheesley Hill)
We continue to undertake traffic surveys on local roads surrounding the B4069 to monitor and help understand the change in traffic movements as a result of the closure. A copy of the latest traffic survey can be found in the download section of this webpage.
Webinar - progress of the scheme
On Monday 24 April 2023, we held a webinar about the progress of the scheme to repair the B4069 Lyneham Banks, you can watch a recording of this via the link below. Also available, for download, are the webinar presentation, and a document capturing the questions and answers from the session (also listed in the frequently asked questions section below).
The B4069 Lyneham Banks is currently closed to both vehicles and pedestrians due to a major land slip on the road. It is completely inaccessible and impassable for all motor vehicles and bicycles, and anyone who breaks through the fences to access the site on foot is putting themselves in danger of serious harm. Anyone who accesses the site is also in breach of the Traffic Order and could be prosecuted.
It is considered likely that the February 2022 landslip resulted from a combination of factors, including the existing weakness at a historic landslip location, increased groundwater flows following recent storms and increased loading because of earth moving operations in connection with the adjacent development.
The current construction programme shows works being completed in Spring 2025.
We are using a technique known as Continuous Flight Auger (CFA) piling to install the piles across the site. CFA piling method involves drilling to the required depth of 11m using a hollow stem auger. After reaching to its drilling depth, the hollow stem is withdrawn, with concrete being pumped through the hollow stem, concurrently. The reinforcing cage is then placed within the freshly placed concrete within bore created. The CFA piling method is generally vibration free and one of the quietest forms of piling. The CFA method is used in environmentally sensitive areas and can be used in close proximity to existing buildings.
This is a complex scheme. Designing the road is fairly straight forward - but that is only one aspect of the design which also needs to include for remediation works to the area, stabilisation works, extensive drainage interventions, retaining structures and groundworks. There are several different parts of the site which require different interventions and solutions. All these need to be knitted together so that they complement each other.
As well as the design itself there will be other aspects that need to be addressed, including securing funding, land access, and legal arrangements.
The repairs to the main landslip using a piled retaining wall are expected to cost in the region of £5m.
It is recognised that further works will be required on the B4069 west of the main landslip before the road can be re-opened. The detailed costs of these repairs is yet to be quantified.
In February 2024 a planning application was submitted with the proposals for the road. The planning application PL/2024/02330 can be viewed through the Wiltshire Council Planning Portal.
We have installed semi permanent signage to inform road users of the official diversion route, which takes the A3102 and the A4. The following measures will also be implemented to further help the traffic issues in the surrounding area:
Clack Hill now has a one-way traffic restriction in place with no entry from the B4069
double yellow lines will be implemented at the junction of Clack Hill and Hollow Way to protect the junction
temporary speed limits on Hollow Way - 40mph, 30mph and 20mph on different sections - and a 40mph limit on Sodom Lane
speed and weight limits on Bowd's Lane, Trow Lane, and Cheesley Hill
speed reduction on the A3102 at the junction of Bowd's Lane
additional temporary signage around the local road network over the coming weeks
We are also looking at the impacts on the wider road network as a result of the closure.
No, it is extremely dangerous and people should not attempt to access the site on foot, by bicycle or on a skateboard. Anyone who accesses the site is also in breach of the Traffic Order and could be prosecuted.
No other roads are directly affected or closed by the landslip. However, we have introduced some restrictions on the local road network to stop these single-track roads being used by large volumes of traffic.
Yes, access to local businesses has been maintained, and we would encourage people to continue to support businesses that may be affected by this emergency closure.
The B4069 is a classified road which provides important connectivity for the local community and within the wider area. Prior to the landslide the road was carrying over 5,500 vehicles per weekday and over 35,000 vehicle movements per week.
The B4069 is part of the existing Highway network. Wiltshire Council has a duty as Highway Authority to repair the existing road and can implement repairs through its statutory powers.
Alternative solutions such as a new route would be significantly more expensive, require a planning application and potentially a Public Inquiry as it would require the land for the new route to be secured. A scheme to deliver a totally new route would likely take many years to come forward even if funding and consents could be secured.
Yes. The intention is to stabilise the failed section of hill side and to replace the road along its original alignment. However, to do this we will require land, access routes and easements across adjacent land holdings.
A bridge spanning the area of the landslip is not considered to be a feasible solution to remediate the landslip for the following reasons:
The required span would be in the order of 80-90 metres, which would result in an extremely large deck structure (and associated abutment foundations). If a multi-span structure was adopted, intermediate pier foundations would be located within the landslip itself, and potential subject to high lateral forces. This would necessitate large piled foundations - which would not be feasible to construct on an active landslip.
Bridge structures require a large amount of inspection and maintenance (compared to retaining walls) and therefore the whole life cost of the structure is likely to be significantly greater than the preferred retaining wall solution.
A bridge structure would not address the underlying landslip failure which is currently impacting the land to the north of the B4069, as well as providing a health and safety risk to the public and adjacent landowners. It is considered necessary to address this risk.
Whilst it is well established that vegetation can play an important role in slope stability, the relationship is complex and vegetation can both improve, as well as hinder the stability of the slope. Given the magnitude of the landslip that has occurred at Lyneham Banks, reintroducing vegetation alone would not be sufficient to improve the stability of the slope to allow the reconstruction, and reopening of the B4069.
The landslide has resulted in the road being dislodged, broken up and displaced by approximately 25 metres.
The remote monitoring equipment installed as part of the ground investigation work indicates the hill side is still creeping albeit at a significantly reduced and relatively imperceptible rate.
Wiltshire Council recognises that the landslide situation at Lyneham Banks will be having an impact on the local community including local businesses and is working diligently to bring forward a solution as soon as possible.
Efforts have been made to mitigate the impact including the erection of "Business as Usual" signage where appropriate, but there is no right for businesses to have passing trade, and passing trade can be affected by a range of matters.
Wiltshire Council is keen to support local businesses and is keen to share the process that Business Rate payers can follow to appeal the rateable value whilst the issue is remedied.
Refer to the Economic Development section of the Wiltshire Council website to find out more as to what support may be available.
Having two separate carriageways may have advantages in some cases but is unlikely to offer benefits in this case. The retaining wall must be deep enough to stabilise the hillside, and constructing two would add significantly to the cost. The weight of vehicles on the road is less significant than the weight of the earth being retained. Because of the unstable ground it is important to make an effective repair to reduce the need for future maintenance.
A key consideration of the design is the stabilisation work needed prior to the road construction itself. If we were to simply build a new section of carriageway without undertaking the stabilisation measures, then it is likely that there would be significant future failures again.
The preferred solution includes for the removal of deposited material on the upper slopes to reduce the load; installation of cut off drainage at the top of the slope; the installation of a positive drainage system along the road; and drainage interventions within the lower slopes, which all contribute to the long term stabilisation solution.
At this stage there are no plans to make amendments to the operation of the B4069 in terms of speed or weight limits, but these could be considered in due course. At the moment the priority is to reopen the road to reduce the current disruption.
Wiltshire Council continue to inspect roads and will make repairs to roads as and when necessary to the nearby road network.
There are no plans to return Clack Hill to two-way traffic whilst the B4069 remains closed. It should be possible to return it to two-way operation when the B4069 is reopened.
