In February, Yapi Merkezi and Mota-Engil Africa were hired for the project.
The signing of the deal will enable the contractor to kick off works by January next year.
The re-introduction of toll stations is, however, likely to face huge legal encounters.
Kenya has recently embarked on projects aimed at opening up the northern corridor.
Bechtel has been picked to build the Mombasa-Nairobi Expressway.
Engineered Material Arresting System is cheaper than the traditional technique.
The project has faced numerous challenges including hiccups in relocating utility lines.
The investors have urged Nakuru County to revive the project.
The facility is expected to open up the Northern Kenya tourism belt.
Dredging works that began in October last year are well underway.