The Enquirer understands that Bam Nuttall will be working in a joint venture with M&E specialist VVB Engineering.
Sources close to the project said the win was a surprise with Balfour Beatty the early favourite for the job which is expected to last more than three years.
The project involves refurbishment of the main airport road tunnel and cargo tunnel at Heathrow.
Work will include the installation or replacement of the ventilation equipment, fixed fire suppression, lighting and electrical systems, telephones and CCTV systems.
The main 630m twin bore tunnel was built in 1950s and is the primary entrance to the central terminal area.
The cargo tunnel, built in 1960s, is longer at 830m and comprises 630m of bored tunnel and 100m of ‘cut and cover’ sections at each end.
One failed bidder said: “This has been very competitive and most people expected it to go to Balfour so seeing Bam and VVB take it is a bit of a surprise.”
The job will be the latest in a series of wins for Essex based VVB who are heavily involved in the construction of Crossrail.