Costain has been awarded the Crossrail North East Spur contract by Network Rail to upgrade stations between Stratford in east London and Shenfield in Essex.
The contract is worth an initial £150m to Costain. The contractor starts this week on design and professional services work, in collaboration with Network Rail, to develop detailed plans.
Work includes the design and build of major station improvements at Romford and Ilford as well as at other stations including Forest Gate, Goodmayes, Harold Wood, Gidea Park, Chadwell Heath and Brentwood.
The main works will take place between late 2014 and 2017. Major infrastructure improvements will also include upgrading the tracks and overhead electrification equipment as well as extra train stabling capacity and turnback facilities.
Costain chief executive Andrew Wyllie said: “This award further demonstrates our ability to deliver multidisciplinary and integrated services in long-term, strategic collaboration with our customers."