Balfour Beatty has won a five-year £50m building and civils contract with Network Rail.
The reactive contract will see the contractor carry out rail infrastructure repairs and projects at short notice on the Great Western route from London to Penzance.
Balfour said it planned to open an office in the Swindon area to service the contract, which will began this month.
The firm will set up an eight-strong team to oversee the contract, including two graduates.
Last month Network Rail awarded Balfour Beatty a £115m deal to supply a fleet of vehicles to carry out track maintenance across two of its busiest routes.
Balfour Beatty managing director for rail and utilities Mark Bullock said: “This contract award is testament to the strength of Balfour Beatty’s relationship with Network Rail and our ability to deliver at short notice a range of reactive work from track through to buildings and general infrastructure repair.”
This week a Balfour Beatty joint venture landed a HKD$4bn (£370m) contract to build three hi-rise residential towers in Hong Kong.