WSP leads National Highways water plan

WSP has been appointed to support National Highways’ Water Quality Plan, a programme designed to reduce pollution from road run-off across the strategic road network.

The consultancy will act as technical partner to National Highways, supported by Mott MacDonald, Ramboll, Arup, and Aecom. The work will identify and develop designs for treating water from the highest-risk outfalls on the network, where rainwater running off roads can carry oils, suspended solids from tyres, and metals from braking systems into the surrounding environment.

National Highways has committed to address its most impactful discharges from the strategic road network by 2030. The new contract will support programme leadership, technical assurance, and delivery planning, with interventions expected to include both nature-based systems and mechanical treatment options delivered within existing highway boundaries.

The programme sits across highways engineering, drainage design, environmental compliance, and asset management. Road drainage has traditionally been designed to move water away from carriageways to protect safety and network availability. Drainage infrastructure is now also being judged by what it carries into rivers, groundwater, and sensitive habitats.

That shift is creating a wider delivery requirement. Highways authorities need stronger evidence on which outfalls create the greatest environmental risk, which treatment systems are technically appropriate, and how interventions can be delivered without excessive disruption to live road operations. The design work will need to balance hydraulic performance, maintenance access, land constraints, biodiversity value, construction logistics, and whole-life carbon.

Nature-based solutions, including swales, wetlands, and vegetated treatment systems, are likely to form part of the toolkit where land and site conditions allow. Mechanical treatment may be required where highway boundaries are tight, flows are more complex, or treatment performance needs to be delivered in a compact footprint. Each approach will depend on catchment conditions, pollutant load, available space, maintenance requirements, and cost.

The work also reflects growing scrutiny of infrastructure operators’ environmental responsibilities. Road run-off contains pollutants generated by normal network use, and those pollutants can accumulate in drainage systems before being discharged into watercourses. As environmental regulation tightens and public attention on river quality increases, drainage upgrades are moving from peripheral works to a more strategic part of highway asset planning.

The plan points to a growing workload around retrofit environmental infrastructure. Much of the work will be delivered around existing assets, constrained verges, embankments, junctions, culverts, and live traffic management environments. That increases the importance of survey accuracy, phased delivery, temporary works planning, environmental permitting, and coordination with local authorities, regulators, and maintenance teams.

The programme will not remove the need for wider reductions in pollution at source, but it should create a clearer pipeline of targeted drainage and water treatment schemes. If delivered effectively, it could provide a practical model for upgrading existing transport infrastructure to meet environmental standards without waiting for major new-build projects to trigger investment.