Project Description
The A19 is a major trunk road which runs from Doncaster through to Newcastle upon Tyne. It is a mix of dual and single carriageway road with numerous at grade junctions. The Testos interchange roundabout is close to Newcastle upon Tyne and suffered from heavy congestion due to the annual average daily traffic flow of approximately 50,000 vehicles. The £159 million redesign of the interchange involved removal of the existing at grade roundabout to replace it with a free flowing dual carriageway over-bridge. Costain started work on the scheme in 2019, with the completed road opening in 2021.
The Challenge
The overbridge required abutment drainage to alleviate hydrostatic pressure at the back of the buried structures. CL513 of the Specification for Highways Works details that only block works or no fines concrete are permitted solutions. A departure from the traditional methods to find a carbon and time saving alternative would be the preferred option for the project however.
The Solution
ABG suggested the use of their Deckdrain 1200S/ST170 and worked with Costain and their consultant Jacobs to gain approval, helped by the fact that the use of ABG’s geocomposite solutions for structural drainage have been previously approved on similar National Highways projects. ABG’s Deckdrain 1200S/ST170 is a BBA approved product that replaces the traditional porous block method, with many advantages over concrete based drainage options. By comparison Deckdrain is very light-weight and simple to install, with no manual handling equipment or form work required. The Deckdrain is placed up against the completed structural waterproofing layer and fixed in place using self-adhesive stick pins. The Deckdrain is applied to the structure with the filter geotextile facing outwards, ready to be backfilled with structural fill. The geotextile then acts as a filter to prevent any fines from blocking the drainage core.
Function diagram to show key Deckdrain features
The ABG Service
ABG also supplied their UK manufactured Fildrain Type 6 and Type 10 products for highways edge drainage on the approach and exit sections of the new A19 dual carriageway. ABG’s Fildrain Type 6 is a carbon and cost saving alternative to a granular narrow filter drain that was used alongside the trapezoidal concrete channel to HCD F18.
