A ground-breaking project to recover nuclear waste from a shaft beneath Dounreay is in the running for a top award.
The project team has already taken a top in-house award for its safety and environmental performance during a three-year operation to divert groundwater from the shaft.
Now, a panel of experts has nominated it for a top UK award in the technical excellence category.
The 27m shaft isolation project is one of the finalists in the 2009 Ground Engineering Awards to be announced in February.
Randall Bargelt, regional director of the Nuclear Decommissioning Authority, said: "This project delivered world-class performance in terms of its technical, budget and schedule delivery. The nomination reflects great credit on all those who made this project such an outstanding success."
Nuclear waste was disposed of in a 65-metre deep, water-filled shaft between 1958 and 1977.
Retrieving the waste will increase the amount of groundwater that flows into the shaft and gets contaminated, so engineers looked at ways to divert the groundwater to avoid the need for a 200m water treatment plant.
Dounreay hired specialist geotechnical contractor BAM Ritchies, part of the BAM Nuttall group, to fill in the fissures in a 10-metre wide band to create a grout curtain all around the shaft.
BAM Ritchies drilled more than 300 boreholes up to 80 metres deep, stretching a combined distance of 24km.
It took four years from the start of trials to complete the isolation project in spring 2008.
A specialist grout from Sweden was ground down until it was finer than toothpaste, injected through the boreholes and squeezed into the fissures around the shaft where it hardened.
The final evaluation report just published indicates that the amount of water that can get into the shaft during waste retrieval has reduced from an estimated 350m3/day to 12.7m3/day.
Warren Jones, the Dounreay geologist in charge of the project, said: "The specification for hydraulic performance was one of the most challenging ever set.
"That lead to a very high level of team working between the client and contractor based on the new engineering contract. The results they achieved are remarkable."
Alex Tiernan, BAM Ritchies project manager for shaft isolation, said: "The degree of co-operation between client DSRL, BAM Ritchies project team, designer Halcrow and other key elements of the supply chain was crucial to the success of this four-year project. Being selected as one of the GE Awards finalists is a credit to all involved."
Work is now underway to prepare for the construction of the retrieval plant in 2012, with the first waste due to be recovered in 2017.
