Slit Trench & Trial Hole Investigation Works, Sellafield


Morgan Sindall




Oct 2020 – April 2021

The Project

The scheme involved the planning and excavation of 18 investigative trial holes and slit trenches at the Sellafield nuclear site in Cumbria as part of early construction work for the new £600m Sellafield Repack Project. Historically, the Sellafield site has a large amount of uncharted buried services which must not be disturbed or damaged during new construction projects for nuclear safety, security, and operational reasons.

The new Sellafield Repack facility is to be constructed on a brownfield site which previously housed munitions and nuclear manufacturing facilities dating back to the 1940’s.

Ground investigation work was required to find and chart numerous services including electricity up to 11KV, essential data and telecommunications, water, drainage, and foul water services which are related to essential operations, production, and nuclear safety at the site.

Each investigation required meticulous:

  • Planning and preparation of the Safe Systems of Work
  • Stakeholder Engagement with operational and maintenance departments as well as other contractors
  • Non-intrusive surveys using Cat & Genny and Ground Penetrating Radar
  • Hand digging and vacuum excavation of trial holes and slit trenches
  • Preparation and submission of reports and CAD drawings
  • Reinstatement of the excavations

During the works, over 1,000 Tonnes of spoil was removed, and numerous live and previously uncharted services were safely found, exposed, and charted ready for the main construction project to commence.

Our site team worked closely with operational stakeholders to organise service isolations and surveys to safely identify all services.

Challenges And Successes

Our stakeholder engagement expertise and best in class surveying and excavating techniques meant that the works were completed to schedule with ZERO damage to any underground services and ZERO unplanned loss of services. Furthermore, all ground investigation reports were submitted on time to allow the client designers to complete the permanent works detailed design ahead of the project milestone.

Client Benefits

Our work allowed the Sellafield Project & Programme Partners to complete the detailed design phase of the Sellafield Repack Project ahead of schedule with no delays or costs caused by isolations or disruption to the adjacent operational facilities. Our client now also has a full record of all buried services in this area for future reference.

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