In July 2016 LLWR was granted planning permission to allow the construction of a final cap over existing and new vaults and seven landfill-style trenches where waste was disposed of prior to the opening of the site’s first vault in 1988. Works are also planned to improve the existing engineered cap over the trenches.

Trench Cap Improvements


Although they have been covered and capped in the past, engineering techniques, materials and construction methods have since been enhanced allowing the improvement of the existing capping system.

One of the first tasks to complete is the landscaping of the perimeter of the site to protect our neighbours from the noise and visual impact of plant and machinery. Another initial task is to remove all the plants and animals that live on the cap and where necessary, move them to other suitable environments. The surveys for these works have been completed.

After all the ecology mitigation work and landscaping is completed, it is planned to excavate the topsoil in place on the current cap and store it for reuse at the end of the improvement works. Once all the topsoil is removed and placed in stockpiles the materials that were placed to over the plastic membrane placed in the past to prevent water infiltrating into the historic trenches, will be smoothed out and an additional plastic membrane or clay layer will be added.

The plastic membrane or clay layer will then be protected using a designed layering system and recovered with the topsoil that was stockpiled at the start of the works. Designated areas of the trenches will be specially prepared to use for the stockpiling of construction materials we have already stored on site to build the final landscape as planned.

Vault 8 Closure

Vault 8 is almost at full capacity and the requirement to close it is approaching.

When all of the containers are in their final positions, engineering materials will be placed above the containers to start building the final landform.

The engineering materials will form the base (sometimes referred to as ‘profiling’) layers for the final capping for Vault 8 and the trenches at the northern end of the site.

Final Cap

3_4 cross sections_02 dev

On completion of the base (profiling) layers, the construction of the final cap will start. The final cap will be a highly engineered cap, constructed in 10 or more layers and be an overall thickness of greater than 2.5m.

8_2 west edge

The final cap is expected to be in place over Vault 8 and the northern section of the Trench Cap by around 2026.

Site Closure

The site is currently set for closure around 2130. The nature of the final closure will depend on the institutional and regulatory arrangements at the time.

Currently, it is assumed that the site will be delicensed as a Nuclear Licensed Site soon after the end of LLW disposal operations, once site remediation activities have been completed.

The area will be returned to a condition suitable for the next planned use of the site, which will continue to be regulated by the Environment Agency to ensure it is properly monitored and controlled.