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Rhymney resurgent

MANY WELSH landscapes are undergoing regeneration after two decades of neglect following the demise of the regional coal and steel industries.

The Welsh Development Agency and Caerphilly County Borough Council are undertaking one such project in the steep-sided River Rhymney valley, among the former South Wales coalfields.

Here the town of New Tredegar is the beneficiary of a community focused regeneration project.

Space had to be created on riverside land for a primary road - the A4049 - as well as business developments. The council's solution was a BBA (British Board of AgrÚment) Roads and Bridges certificated Tensar Wall System, a reinforced soil technique that uses local colliery spoil.

Tensar won the work from main contractor Alfred McAlpine Capital Projects.

The Rhymney is a typical spate river, subject to sudden floods, and has a run of sea trout and resident brown trout. It was recently re-established after many decades of industrial pollution.

Works to reroute the river and create land for a road corridor and 'business development plateau' meant replacing and extending derelict river walls built in about 1900.

To cater for predicted flood levels and provide suitable landform, workers built reinforced soil walls up to 8.5m high with sloping embankments.

Tensar's Wall System requires little plant or temporary works, which might be vulnerable to flooding. The modular precast blocks have splitface masonry and are dry laid by hand, avoiding potential river pollution that might be caused by insitu concreting. Use of local colliery spoil, instead of piled foundations and reinforced concrete walls, meant cranes and large plant were not needed.

Its banks were excavated by up to 11m. The walls were completed in lifts. Each lift has compacted fill, in this case the colliery spoil, topped by a layer of high strength geogrid reinforcement.

The modular blocks forming the face of the wall were connected to the geogrid using a polymer connector. Tensar says this makes it flexible enough to adapt to changes in height and natural river curves.

This element of the project began in July 2004 and was completed last month.

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