The contract is to refurbish one of the two runways at RAF Valley as well as link taxiways and provide a new section airside perimeter road, new visual aids, aeronautical lighting and signage.
North Stone and Whitemountain are subsidiaries of Farrans and Lagan Group respectively.
RAF Valley is primarily a fast jet training base, with pilots mostly flying Hawk aircraft. The strength of the existing taxiways is sufficient for Hawk aircraft but not for other aircraft such as Hercules, Tornados and Typhoons.
The runway to be refurbished was last fully resurfaced in 1995. The new works should extend the life of the runway by a further 25 years.
The work is expected to take a year, with construction starting in March 2016 and completing in February 2017.
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