The scheme will see the eight-car platforms at the stations extended to 12-car platforms, resulting in the contruction of two kilometres of new platforms.
Amey will be responsible for stations in the Outer Area from Elstree and Borehamwood north to Bedford.
The work will be managed by one of Amey's design offices in Birmingham and will be supported by two other consultancy offices in Swindon and York.
Amey will remain on site providing construction support until the end of 2011 when the project will be completed.
