M6 Smart Motorway

Environment Protection

Multiple SDS Aqua-Swirls® installed in M6 smart motorway upgrade.

Overview

The M6 J21a to J26 Smart Motorway project represents a £150 million investment in upgrading a 10-mile stretch of the M6 motorway, extending from Warrington’s Junction 21a Croft Interchange to the Orrell Interchange at Junction 26 near Wigan. The primary aim of the project is to increase road user capacity by 30% in both directions, thereby enhancing journey times, safety, and reliability. The scheme involves converting the hard shoulder into an additional lane, creating new emergency areas, and installing advanced roadside technology to optimise traffic management. Importantly, the project reduces environmental impact by eliminating the need for additional land acquisition, which would have been required for road widening, making the upgrade both cost-effective and environmentally responsible.

What we did

SDS was engaged to implement a solution that would protect the surrounding environment from the effects of highway runoff. To address this requirement, we installed multiple Aqua-Swirl® Hydrodynamic Vortex Separators (HVSs) at designated priority outfalls along the motorway.

A combination of Aqua-Swirl® AS-6, AS-7 and AS-9 units was selected to effectively manage peak flow rates of up to 300 litres per second. These separators were strategically positioned between Junctions 22 and 23 and on the slip roads at Junction 21a to ensure that highway runoff was properly treated, preventing contamination of nearby water bodies and groundwater.

Results

The successful deployment of SDS Aqua-Swirl® HVSs has effectively mitigated the environmental impact associated with the increased traffic and surface water runoff generated by the smart motorway upgrade.

Rigorous testing using the Environment Agency’s M-BAT tool confirmed that dissolved zinc and copper levels in the runoff remained within safe, environmentally acceptable limits, with no adverse effects on groundwater recharge. The installation of the HVSs ensured that the treatment of runoff did not disrupt the surrounding environment, fully complying with Highways England’s environmental standards.

Furthermore, the modular design of the Aqua-Swirl® units allowed for seamless retrofitting into the existing drainage infrastructure, overcoming challenges such as depth restrictions and the need for flexible pipe connections.

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