National Highways Identifies 182 Priority Road Runoff Sites for Remediation by 2030

National Highways has released a detailed list of 182 outfalls and soakaways across England’s Strategic Road Network (SRN) that will be upgraded to tackle road runoff pollution by 2030—an announcement environmental groups have described as a “major step forward.”

The publication follows the agency’s recent Design Playbook, which sets out its approach to preventing toxic contaminants from reaching waterways.

Earlier criticism argued that the playbook lacked sufficient urgency, especially after investigations revealed that many runoff ponds—intended to filter polluted surface water—had been neglected for decades. Satellite reviews showed several of these basins heavily overgrown despite recommended maintenance intervals of 10–15 years.

Campaigners Welcome ‘Long-Awaited’ Progress

Jo Bradley, UK operations director at Stormwater Shepherds, said the new list represents a breakthrough after years of pressure.

“Seeing a defined list and a firm commitment to upgrade 182 outfalls and soakaways is encouraging,” Bradley said. “The Department for Transport’s decision to ring-fence funding for this work is particularly significant—we’ve been waiting a decade for this level of commitment.”

The SRN contains around 15,000 outfalls and 6,600 soakaways. As part of its playbook development, National Highways assessed 1,236 of these assets by early 2025, identifying 107 that required mitigation. Subsequent checks increased the number of sites expected to need intervention by 2030 to around 250, although only 182 have been formally listed so far.

Remediation Programme Structure

National Highways has categorised the planned works into phases:

• Tranche 0 – Five schemes already in design for delivery across 2025/26 and 2026/27

• Tranche 1 – 30 schemes scheduled for 2027/28

• Tranche 2 – 53 schemes earmarked for delivery between 2027/28 and 2028/29

• Future Tranche – 94 schemes due before 2030

Of the 182 sites, 139 are outfalls and 43 are soakaways, with most coming from National Highways’ original prioritisation work and the remainder identified more recently.

Practical Challenges Ahead

Bradley cautioned that delivering the programme will likely prove complicated.

“There will be difficulties—landowner objections, lack of space for treatment systems, or design challenges,” she said. “But the more National Highways works through these sites, the more efficient and capable its teams will become.”

She encouraged local river groups to continue gathering evidence on runoff impacts, noting that many are already questioning why their local assets are not on the list.

“They now have a window of around three years to build a case for inclusion in the next phase,” she added. “Ultimately, every one of these outfalls needs attention.”

Concerns About Long-Term Maintenance

While Bradley welcomed the new commitments, she emphasised the importance of ensuring the schemes remain functional once built.

“There’s a very real risk that 182 schemes are installed and then left without maintenance,” she warned. “It’s essential for MPs and local representatives to press the DfT to secure long-term funding for upkeep.”

A Growing Environmental Priority

Road runoff contains pollutants including hydrocarbons, microplastics and heavy metals. Despite its environmental impact, it has historically received far less scrutiny than agricultural or sewage pollution.

The Office of Rail and Road (ORR), National Highways’ regulator, will monitor delivery of the 182 projects.

A National Highways spokesperson reiterated the organisation’s commitment:“We are determined to reduce pollution risks from road runoff. Our Water Quality Plan 2030 outlines the programme needed to deliver this, and we will complete upgrades at all high-priority sites by 2030.”