Murphy has won a £60m electrification enabling works contract for the London Overground route between Gospel Oak and Barking.
Network Rail has awarded the deal to Murphy on behalf of the Department for Transport and Transport for London.
Murphy said the deal was worth more than £60m. Work will include track lowering of plain line and switches, and the installation of slab track.
The contractor will also reinforce embankments and cuttings, modify signals and refurbish existing bridge parapets.
It will replace an existing bridge and reconstruct platforms at Walthamstow station, as well as installing foundations for electrification masts along the line.
Murphy CEO Steve Hollingshead said the contract demonstrated Murphy’s growth, building on its “established reputation in the rail sector”.
Amey is the project designer and specialist contractor Stobart Rail is reponsible for the specialised slab track works.