Structural Drainage

Deckdrain, Precast Concrete Arch Bridge - A465 Heads of the Valleys, UK

Client Welsh Government


Consultant Atkins

Deckdrain Drainage Geocomposite




– Flexible and easy to install over curved structure
– Protects waterproofing
– High flow capacity


Project Description

The A465 ‘Heads of The Valleys’ is a strategic east west link road in the south of Wales, linking the A40 at Abergavenny to the M4 at Llandarcy. As part of a re-generation of the Heads Of The Valleys area the road was upgraded to dual carriageway standard. One of the many structures chosen on the project was a concrete arch bridge consisting of pre-cast units which are assembled on site. These bridges use the soil-structure interaction to build economic, high overload structures. The bridge constructed on the Gilwern and Brynmawr section of the carriageway is believed to be the widest spanning concrete arch bridge in the world.

The Challenge

As part of the design, the external surfaces of the bridge are waterproofed and a drainage system is required to relieve pore water pressure at the crown of the structure. A cost effective, quick installation, without the need for specialist handling equipment and without overloading the structure or damaging the waterproofing during construction was necessary. Porous blocks were an expensive solution and presented logistical and construction difficulties, whereas no fines concrete required complex form work, leading to installation difficulties.

The Solution

ABG Deckdrain geocomposite was selected as a solution which offered many practical benefits. ABG Deckdrain was robust enough to protect the waterproofing, but flexible enough to easily follow the profile of the concrete bridge’s arch structure. It is light-weight and easy to handle, so no specialist equipment was required. ABG Deckdrain drainage composite provides manufacturer assured drainage capacity for the lifetime of the structure. Furthermore, ABG Deckdrain geocomposite was supplied in rolls to make the logistics of delivery and storage much easier compared to other traditional options, which required far more vehicle movements to and from site.

ABG Deckdrain Geocomposite

The ABG Service

ABG provided a full technical support service from design to manufacture. ABG provided all the required technical detail for ABG Deckdrain geocomposite to be assessed and approved by Atkins and the Welsh Government.

Contact ABG today to discuss your highways or structural drainage project specific requirements and discover how ABG past experience and innovative products can help.

Additional information