Completion of part of the Heads of the Valley road upgrade in south Wales next year will mark a major milestone for the overall project.
Upgrade of the A465 Heads of the Valleys road in south Wales is a major undertaking and the fourth of six sections is now nearing the final stages, putting the overall scheme a step closer to completion (see box). Getting to this point has not been straightforward, with challenging topography demanding extensive use of ground engineering solutions, as well as collaborative working.
Costain is currently working on the £220M Section 2 between Gilwern in the east to Brynmawr in the west and is on course to finish the upgrade of the 8km route in 2019. Nonetheless, work is still underway on the reinforced soil slopes that are key to completing this section and Phi Group is on track to finish these in the autumn.
Costain was first appointed to undertake the Section 2 work in 2011 but, before the geotechnical challenges could be overcome, the scheme went through public consultations and inquiries that lasted until 2015.
The design and build project team for Section 2 consists of Costain, Atkins, CH2M and RPS, with the groundworks being undertaken by Walters Group.
The local topography meant that the requirement for cutting into and extending existing embankments was considerable. Reinforced soil slopes and structures, retaining walls and soil nailing are all solutions widely used to facilitate the widening of the existing carriageway on Section 2.
The use of reinforced soil was quickly identified as the most cost effective solution to the widening of the embankments.
Phi was first approached to provide early design advice in late 2011 after the project team recognised that early input from a specialist geotechnical contractor would be invaluable. The aim was to develop solutions to overcome these significant geotechnical challenges that were cost effective, buildable and which also took into account health and safety considerations.
After this initial period of discussion, Phi was contracted to design a number of reinforced soil slopes using its Textomur system.
During this design phase, Phi senior projects engineer Derek Mulenga spent time every week at the Atkins/CH2M office in Cardiff, where the design of various Textomur slopes was developed and refined.
According to Phi, being involved during the design phase meant that problems and potential issues were identified at an early stage and solutions found. The company says this meant that when works began on site, a more complete solution was already in place, with issues already resolved, minimising the risk of costly delays.
Phi started work on installing its Textomur system at angles from 60° to 70° with steel mesh facing cage and geogrid reinforcement in March last year. On Section 2 of the A465 Phi opted to use the Maccaferri Paragrid product as the reinforcement with locally sourced stone compacted in layers around the Paragrid to form the reinforced soil mass.
Phi has said that the collaborative approach between the project team members that enabled the design process to run smoothly, had to be continued during the construction of these Textomur structures.
Working adjacent to a key arterial route that has to remain open always causes logistical problems. Phi is often working in several locations at once, with up to 45 operatives on site at any one time. As with any project today, the priority for everyone on site is ensuring the work is carried out safely.
Integrating Phi works manager Jamie Knill into the onsite project team has helped the coordination of its work with Costain and Walters, as well as with other trades on site. According to Phi, coordination is key with delivery of materials planned as far in advance as possible.
“It is great to be involved on this scheme working for Costain and the design joint venture,” said Phi managing director Julian Fletcher.
“From a very early involvement over five years ago, both of these parties have worked in a true collaborative way to draw on our experience. This has led to betterment of the project with respect to design and the practicalities of installation of structures with extremely challenging access and time constraints.”
When Phi completes its £2.5M contract in November, the company will have constructed 20 reinforced soil structures – the largest measuring 7,300m² and the smallest just 23m². Getting to the end point will have required more than 110,000m³ of fill to be moved, placed and compacted.
Slopes are not the only challenges that Costain has had to deal with on Section 2 – it has called for a huge amount of civils works. In total there are two major overbridges and five footbridges.
Old mine workings have also required treatment and numerous service diversions have been undertaken. The utility diversions are a major project in their own right with a 100m long tunnel, 20m below ground having to be constructed for a water main. Two high-ressure gas mains also had to be diverted.
The A465 – or Heads of the Valleys road – is one of the Welsh government’s key corridors and international gateways for the south Wales economy.
It connects the M4 at Neath to Abergavenny and Hereford, as well as providing links between west Wales and the Midlands and also links up the northern valleys, supporting regeneration in the communities.
The existing A465 was built in the 1960s and is a single three lane carriageway with two lanes in the uphill direction and one in the downhill direction. A regional traffic study in 1990 identified the need to improve this road and the upgrade is seen as critical to the social and economic regeneration of the Heads of the Valleys area.
The complete project will improve access to key services, jobs and markets supporting inward investment to areas such as the Ebbw Vale Enterprise Zone.
The upgrade was split into six sections and work on the first started in 2005. Three sections have been completed and a further two are set to start later this year with a view to completion of the upgrade by 2020.