The Kier BAM joint venture has contracts with EDF Energy to carry out £100m+ of site preparation works for the Hinkley Point C nuclear power station in Somerset.
The work includes excavation, earthworks, terracing, the installation of construction site infrastructure and formation of roads and networks to allow main construction to start.
The contract is estimated to create 350 jobs - including a significant amount of local employment - while the main construction works will see up to 25,000 people work on site over the course of the project.
The Hinkley Point C power station is set to generate about six per cent of the UK's electricity - all of which will be low carbon - enough to serve around five million homes.
Commenting on the award, Kier Group chief executive Paul Sheffield said: "Both Kier and BAM have an excellent track record in the nuclear industry and enjoy a long-standing relationship built over many years of working together in joint venture. The Kier BAM team is looking forward to supporting EDF in its plans to deliver the first new nuclear power station in the UK for over two decades."