Halcrow is supporting Nuttall as designer on this design & construct target cost contract with UKAEA. The project is one of several enabling projects being undertaken as part of the Dounreay shaft and silo ILW reclamation programme. This work follows earlier Halcrow shaft related projects for UKAEA stretching back to 1995 and two earlier phases of concept development with Nuttall.

This project is technically demanding and involves the use of advanced grouting technology and hydro-geological mathematical modelling.  It is widely regarded as one of the UK’s most challenging remediation projects. 

The major components of the contract comprise supplementary site investigation, extensive detailed trials and scheme design, followed by construction and validation of a 10 m wide, 100m perimeter multi stage grout ring in rock to surround the shaft and extend below its base to a depth of 80m. The grout ring is required to minimize potential inflows during shaft dewatering, which is to be undertaken as part of the future reclamation of nuclear waste deposited in the shaft in the 1960s and 70s. This is a technically demanding requirement which entails the use of advanced grouting technology and hydro-geological mathematical modelling techniques.

The scheme also includes shoreline reclamation using roller compacted concrete with an in-situ face to create a suitable working platform, strengthening of the stub tunnel plug that separates the shaft from an adjacent sub-sea low level liquid effluent discharge tunnel and infilling of part of the tunnel.

The Halcrow team is working closely with Nuttall and its subsidiary Ritchies to provide fully supported and verified designs, specifications, trials programmes and method statements. Halcrow is also providing technical support to the site investigations, field trials and the scheme construction.