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Lyneham Banks landslip information and ongoing updates
In February 2022, a major landslip occurred on the B4069 at Lyneham Banks. The landslide continued until significant movement ceased later in 2022, when approximately 70 metres of the B4069 had been dislocated and transported about 25 metres downslope.
Following a period of significantly reduced ground movement during summer 2022 we were able to access the site and begin intrusive ground investigations, which has allowed us to consider options for repairing the road.
Ground Investigations took place at the end of 2022, and the information has helped Wiltshire Council to gain a better understanding of how the land failed and to develop design options for repairing the road. A copy of the factual Ground Investigation Report can be found in the downloads section of this page.
We have explored options for repairing the road. There are a number of key factors that will need to be addressed to ensure the road can be safely rebuilt. These include the removal of excess fill from the site, the installation of new drainage features and measures to ensure the structural stability of the road and adjoining hillside. A number of options were considered, but the initial investigations identified three main options for repairing the road and stabilising the bank. These were:
excavate and replace material
soil Stabilisation
bored pile retaining wall
Having reviewed the options the preferred option is the installation of a bored pile retaining wall with enhanced drainage measures.
Programme
Stage
Timescale
Design Work
Spring 2023 - Winter 2023
Procurement
Winter 2023 - Spring 2024
Construction
Spring 2024 - Winter 2024
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, 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 programme shows design work being undertaken throughout the remainder of 2023 with a view to begin construction works in Spring 2024 and completing by the end of 2024.
Drone surveys were undertaken between March and October to understand the extent of the landslip and to determine whether the land was still moving. At the end of 2022 when it became safe to do so, ground investigations were undertaken to help understand how the slip occurred and how the road can be repaired.
Options for repairing the road have been considered in order to identify a preferred option. Detailed design work is now being undertaken on the measures required to stabilise the hillside and repair the road.
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.
While assessment work is still going on, we don't yet know what the full cost of restoring the road will be. However, it will be significant.
Funding for the repairs will likely have to come from Wiltshire Councils road maintenance funding. There isn't currently a source of funding available from the Department of Transport, but this will be explored further when the costs have been identified.
The options considered, range in construction costs between £12.4 million and £5.9 million. The current preferred solution is the least expensive.
We have installed 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.
Please 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.
The January 2023 event is located to the rear of the Motorholics site and is unconnected to the February 2022 event. It does, however, confirm that the stability of the area is very sensitive.
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.
We are currently exploring options to make some of the temporary signage in the area to more permanent to reduce the maintenance requirements and ensure they are visible at all times.
The original planning application no. 19/00670/FUL was for "Demolition of existing dwelling, garage, workshop and erection of detached two storey dwelling, garage with associated works". The application was not for earthworks in the wider setting of the replacement dwelling. In the event, works which have taken place for the replacement dwelling are not in accordance with 19/00670/FUL and so are unauthorised, and the earthworks in the wider setting are also unauthorised.
The 'Live' planning application PL/2022/02224 seeks to regularise the unauthorised dwelling that has been partially constructed. This application remains under consideration and is awaiting additional information from the applicant - notably a structural survey of the buildings and driveway areas.
