The A602 in Stevenage had a persistent water problem. Poor drainage meant standing water on the road during wet weather — a safety risk that National Highways needed fixed. Civcon were brought in alongside Carnell to upgrade the drainage infrastructure from the ground up, completing the works over four months.
The Challenge
The drainage system needed a significant overhaul, with new pipes going in at depths of up to five metres depending on where they sat along the route. Digging that deep on a live road requires careful planning at every stage — trench stability, pipe placement, and making sure the road stayed open to traffic wherever possible throughout.
What We Did
The work centred on two main elements: deep drainage pipes and vortex chambers. The pipes were installed at varying depths between 1.5 and 5 metres, following the profile of the road and the volumes of water each section needed to handle. The vortex chambers were integrated into the system to regulate flow during heavy rainfall — they take the stress off the pipes by controlling how water moves through rather than letting it overwhelm the system at once.
Trenches were excavated, pipes laid, chambers installed, and the road surface reinstated in sections. Traffic management was handled throughout to keep disruption to a minimum, with the road remaining open where the works allowed.
The Result
The A602 now has a drainage system that can handle what gets thrown at it. Standing water on the carriageway is no longer the issue it was, and the infrastructure underneath is in far better shape to last. Four months, done properly, with the road kept moving throughout.
