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Road to Rhondda a relief for Porth residents

SITE REPORT - With 7.3 km of carriageway, 11 bridges and 25 retaining walls, the Porth and Lower Rhondda Fach relief road is the largest highway scheme procured by a local authority in the UK. Joanna Booth reports

'THE IDEA for this project first came up 200 years ago, ' says Costain project director Darren James. 'A mine owner from the Rhondda valley felt the transport was inadequate and should be improved. The present scheme has been seriously on the cards for 25 years.' After a long wait the locals are finally seeing changes being made that should reduce the terrible congestion that clogs Porth town centre.

The Rhondda was originally a coal valley served by a railway. The new road follows the path of the railway ? a common pattern for transport development in south Wales. There are 18 opencast coal mines, the last of which closed in the late 1980s, along the route of the relief road.

Now the valley, which splits into two at Porth ('gateway' in Welsh) is full of dormitory towns.

A stream of commuters descends into Cardiff in the morning and back out at night. The relief road will extend from the southern end of Porth at Trehafod to a new roundabout north of the town on the A4233 at Pontygwaith.

The project is funded by a transport grant from the Welsh Assembly and forms part of its strategy to regenerate the valleys, which took an enormous blow economically and socially when the coal industry foundered. It fell to Rhondda Cynon Taf county council, the client on this job, to procure what is currently the largest highway scheme for a local authority in the UK. Undaunted, it hired Glamorgan Engineering Consultancy as designer and put the scheme out to competitive tender. It chose an Early Contractor Involvement contract and brought Costain into the picture sooner rather than later, which proved invaluable.

The contract was signed at the end of March 2005, and af ter a six-week evaluation period it became evident that the design had shot over-budget.

What was meant to be a fine-tuning stage turned into an intense, 12-week value engineering exercise.

Working with Glamorgan Engineering Consultancy, Costain was able to slash the construction cost by £18 million, taking it down to £54 million.

'We changed most of the vertical alignment of the scheme, ' says Mr James. 'By making the road follow the hills and troughs of the valley we could delete about 80 per cent of the retaining walls and reduce the surplus of earthwork materials in the process.' Significant savings were made here. The retaining walls were a costly option.

'The temporary works being done to allow the build of the design were more expensive than the permanent works themselves, ' notes Mr James.

Cutting out retaining walls also made good sense from a health and safety point of view, with a dramat ic reduct ion in the need to work at height.

In one area Costain purchased surplus land so that a roundabout could be constructed without diverting a river. It reconfigured the layout so that two footbridges could be deleted with no material detriment to the finished scheme.

The team ? Costain, its supply chain, and Rhondda Cynon Taf council ? is keen to prove that ECI is the way forward for road developments and has submitted an entry for the Institution of Highways and Transportation Award for Effective Partnerships.

The new design still satisfied planning constraints and work on site started in June 2005. Eight buildings needed demolition plus five bridges over the former railway line.

Operations kicked off in earnest at the Wattstown roundabout site. Rather than perform extensive works to redirect the river, Costain decided to buy a tract of neighbouring land and move the road instead. Omitting the river retaining wall is saving time and greatly reducing the environmental impact of the scheme. But it does require the road to cut across the toe of the Wattstown slip.

'Around the last ice age the side of the valley slipped, ' says Mr James. 'We've pinned the side up with 75 piles.' Bachy Soletanche sank the 600 mm-diameter, 11 m-long bored piles.

As the new road runs rarely more than 10 m away from the river, the Environment Agency has taken an active interest in the project.

'There are permissible seasons to work in the river, ' Mr James explains. 'It's a salmon river and they lay eggs. Our technicians are sensitive to that.

'All the bridges will have otter holts and bird and bat boxes, fulfilling Environment Agency guidelines.

'Considering it was a coal mining valley there is significant ecological interest here. We have a full time environmental liaison officer working with the construction team.' The ecologist also agreed a strategy to deal n See page 31 with the Japanese knotweed that is prevalent on the site. Excavated material containing the pernicious weed will be buried in a designated valley lined with a water permeable geotextile membrane.

Porth town centre will host the project's architectural statement, the Rheola Bridge.

The bow string arch bridge has a span of 150 m and passes over the railway line, two rivers, and the busy A4233.

Ground works are complete, and one approach span has been erected. The team is currently awaiting the delivery of the main span, which is expected later this month.

Despite an October that was wet even for Wales, the project is on time. The road is due to open to traffic in December this year, with contractual completion in April 2007.

Costain hopes to win further road projects in Wales off the back of its success here, so Porth may live up to its name and turn out to be a gateway in more ways than one.