Soft engineered ‘Green Swale Grass Channel’ attenuates road run-off water, filters suspended solids, and traps hydro carbons and heavy metals, significantly improving water quality.

Pinning C125BN erosion control blanket over the HydraCX
Spraying HydraCX onto Type 1 fill
Light scattering of topsoil over Bionet C125BN
A11 drainage channels vegetating
Pinning C125BN erosion control blanket over the HydraCX
Spraying HydraCX onto Type 1 fill
Light scattering of topsoil over Bionet C125BN
A11 drainage channels vegetating

Green swales reduce pollution. Salix worked with Balfour Beatty and the Highways Agency to create a highly effective large scale SuDS project for 18 km along the side of the A11.

The new soft engineered ‘Green Swale Grass Channel’ attenuates road runoff water, filters suspended solids, and traps hydro carbons and heavy metals, significantly improving water quality.

Due to the presence of special protection aquifers in this area of the A11, the Highways Agency’s environmental statement required a green drainage solution to slow the flow of water and help cleanse hydrocarbons, salt and other road pollutants carried by the water before it reached the soakaways.

Robust scour proof erosion control

HydraCX and TerrAffix products, a hydraulic erosion control solution, was sprayed onto a Type 1 fill. This was used as it has been tested in extreme environments and ensured rapid vegetation of the drainage channels.

A tough grass selection was added to the straw, cotton, polymer and tackifier mix, these plants could withstand the level of pollution being washed off the road.

A surface erosion control blanket of biodegradable coir – Bionet C125BN – was installed over the top of the HydraCX to prevent scour erosion during storm events.

These erosion control blankets are designed to provide immediate erosion protection and vegetation establishment assistance, they then degrade after the root and stem systems of the vegetation are mature enough to be stable and withstand heavy flows of water.

Products Used

TerrAffix Soil Solutions

TerrAffix biochar stabilises & restores degraded soils, providing plants with nutrients whilst actively reducing pollutants in the soil & locking in carbon

Details

Client: Balfour Beatty and Highways Agency
Location: Norfolk
Green Infrastructure, SUDS & Drainage Channels, Soil Remediation