The firm has been working on Phase 4 under an early contractor involvement contract.
The project will see the existing A4440 between Ketch and Powick roundabouts dualled, including Carrington Bridge over the Severn, a notorious bottleneck.
A new bridge will be constructed with a 1.5 metre gap from the existing bridge which would continue to be used for traffic in both directions until its counterpart was complete.
The proposed 200m long bridge will have just three spans rather than six built before to minimise construction works within the floodplain and adjacent to the River Severn.
The three-span arrangement requires a more substantial superstructure to achieve the longer spans but also reduces construction time by seven weeks.
A new steel single span cycle and pedestrian bridge is planned over Hams Way (A4440) to the west of Powick roundabout. To achieve the required 5.7m clearance above the A4440, 125m long approach ramps are being proposed at both ends.
Main construction works on the design and build contract are expected to start in March 2019 and take two years to complete.
Alun Griffiths picked up phase three works to reconfigure the Norton roundabout three years ago and is due to complete now. The firm also picked up the smaller £8m phase two contract which is now complete.