MMG CIVIL Engineering Systems has supplied three different systems for an environmentally sensitive river realignment project in West Sussex.
Part of client RJB Mining's clean-up of the Orgreave Colliery involved diverting the River Rother towards the site perimeter, increasing its distance from likely pollutants and reducing the risk of contamination. The realignment will also allow the coal seam beneath the original water course to be mined effectively.
The Environment Agency required the river diversion to be carried out in as environmentally sympathetic way as possible but without threatening mining operations, and the new watercourse had to have sufficient erosion protection to ensure it would maintain its new course indefinitely.
MMG advised consultant and designer Binnie Black and Veatch on the appropriate 'soft green' erosion protection measures which could be used most effectively on various sections of the diversion.
Three different systems were supplied for the main zones of the river channel. MMG supplied its stone filled geomatting for the zone between the invert and the low water level (controlled by a rock shute weir downstream).
This contains a bitumen bound crushed stone filling for erosion protection in water velocities of up to 3m/s. The material is porous, allowing grass plants from undersown seeds to establish quickly, forming a natural green surface.
Between high and low water level, MMG's pre-grown reinforced turf was laid. This incorporates a three-dimensional geomat with a mixture of grass species.
The geomat provides a permanent reinforcement to the root zone while the established turf gives immediate erosion protection.
A soil-filled geomatting that encourages rapid establishment of vegetation was used above the high water level on the steep sided batters. This limits erosion from surface run-off and provides permanent reinforcement to the root zone of the seed mixture sown in the topsoil after installation.