M69 Southbound
Drainage Redesign to Support Verge VRS Upgrade
- Completed
Project Overview
Courous Ltd was appointed to develop a compliant surface drainage design for the installation of new Vehicle Restraint Systems (VRS) along the M69 southbound verge. The existing filter drainage, which conflicted with the placement of VRS posts, had to be replaced in line with National Highways regulations.
Challenges & Solutions
Challenge
Filter drains ran directly beneath the proposed VRS locations—no longer permitted due to maintenance and structural concerns. Additionally, drainage performance had to be maintained or improved without altering the highway geometry or introducing risks, especially in Section 3 where over 560 metres of drainage was assessed.
Solution
We delivered a pragmatic and standards-compliant drainage design featuring:
Kerb and gully drainage solutions in place of filter drains
E600-rated kerb drainage units approved for high-load areas
Offset gullies to avoid ironworks in the hard shoulder
Tailored solutions per section, including a mix of kerbs, offset gullies, and pipe repairs
Hydraulic modelling for Section 3, confirming minimal flooding even under 1-in-100-year events with climate change allowance
All existing filter stone was proposed for reuse or replacement to the pipe soffit, and no pollution mitigation was required as there was no expansion of impermeable areas.
Outcome
The design supports safe installation of the VRS while preserving drainage capacity and complying with CD526 and CG501 standards. Flood risk is negligible across all modelled scenarios, and the solution fits within the existing infrastructure and maintenance strategy for National Highways.