a465 Brynmawr to Tredegar; a465 Brynmawr to Tredegar;

A465 Brynmawr to Tredegar, Wales

7.8km upgrade to one of Wales' most important highways

The A465 – known as the ‘Heads of the Valleys’ road – is a strategic transport corridor in South Wales, linking the M4 motorway with important population and employment centres. It is being upgraded to improve journey time reliability, safety and network resilience, with the 7.8km section between Brynmawr and Tredegar the third of six sections being upgraded to dual carriageway standard.

The project was procured using early contractor involvement (ECI), an approach that brings the contractor into a project at an early stage. This allowed Arup and contractor Carillion to jointly develop more efficient and cost-effective design solutions and to implement lower carbon, sustainable construction methods.

Arup’s team worked with Carillion throughout the design and construction phases of this multi-award winning project. We provided a full suite of engineering services as well as specialist expertise in areas such as business case development, carbon modelling, air quality, noise and vibration assessments and the creation of stakeholder communication tools. Arup also provided a full-time site presence during construction.

One of the key successes of the project was a proposal by the Arup-Carillion ECI team to construct an embankment rather than a viaduct across the Carno valley. This design solution shortened the construction programme, provided whole life cost savings, improved safety by reducing working at height requirements, and avoided service diversions. It also cut the project’s overall carbon emissions by 10% and allowed 250,000m³ of material to be reused rather than disposed of offsite.

Completed on time and under budget in September 2015, this project was also the first UK highways scheme to involve creation of a new National Skills Academy.

Delivering with BIM

One of the key factors that enabled the team to develop an economical, high quality and sustainable design was the use of building information modelling (BIM) techniques. By adopting a BIM-focused approach, the project team developed design and delivery plans using 3D and 4D tools. This meant options could be assessed rapidly and accurately – and altered as required. Similarly, programme efficiencies could be easily identified and implemented.

The benefits brought to the project by BIM were extensive. These ranged from improved understanding by all parties of project fundamentals through to risk reduction and increased confidence in design, construction and operational phase costs. BIM allowed for more informed design making and for genuine collaboration across a large project team.

BIM also played an important role in supporting the Welsh Government to communicate the proposed plan for the upgrade to this section of the A465 to stakeholders. This was achieved by use the 3D model of the new design to create a drive-through video for local residents and other stakeholders to view during public consultation events. This video communicated the proposed design to the public powerfully and clearly and in a way that could not be achieved via traditional two-dimensional drawings.

Mine Workings

The A465 traverses an area that was once a centre for the mining industry and extensive mine workings are a legacy of this past. During the scheme’s construction phase, Arup maintained a full-time site presence, allowing risks posed by individual mine workings to be assessed rapidly. By adopting an ‘observational approach’, and by undertaking additional investigation during construction, the project team was able to reduce significantly the extent of required treatment as well as associated costs and construction programme impacts.

High strength geo-grids were incorporated beneath the carriageway to mitigate subsidence risks in mining risk zones - where potential voids were beyond practical depths for excavation and replacement and where grouting might have introduced other consequential risks at high cost.

Throughout construction, Arup’s onsite design team was also able to assist Carillion in developing value engineering initiatives, using real-time information obtained from site. This approach delivered both cost and programme benefits. One example was a decision during construction to replace 100m of bored pile retaining wall with a gravity wall solution, following assessment of data obtained from site.