A major soil erosion problem has been tackled at a water treatment works in Inanda Valley on the outskirts of Durban, KwaZulu-Natal.

The platform that the treatment works is built on was situated above a steep, unstabilised fill embankment. Excessive surface water from the platform was scouring the platform and the embankment. Eventually, if left untreated, this scouring would have resulted in the failure of the platform and large-scale damages to the treatment works.

To stabilise the embankment, Kaytech’s Paul Lombard recommended Neoweb and SoilSaver as the most effective products for the project.

Neoweb is a strong, cellular confinement system manufactured from a textured HDPE alloy. When its honeycomb structured geocells are filled with soil, a composite system is formed that stabilises soft soils.

It is also a high quality, sustainable and durable reinforcement solution in load support applications. SoilSaver is a woven 100% jute yarn that forms a coarse 65% open, mesh structure that protects bare soil from natural elements while also conserving vital ground moisture.

A mass gravity structure was constructed at the base of the embankment using gabions. To stabilise the steep gradient, 1825 m2 of Neoweb 100 mm was installed and secured in a concreted anchor trench at the top of the slope.

This trench would double as a formalised V-drain for the road surface runoff as well as for the treatment works. The runoff from this V-drain was then piped and discharged below the embankment to avoid future damage to the embankment.

Whereas the Neoweb geocells in the V-drain were filled with concrete, those on the slope were filled with topsoil. By confining the soil on a gradient, Neoweb not only prevents excessive erosion, but also allows vegetation to proliferate.

Lightweight SoilSaver (1004 m2) was then rolled out and pegged down over the Neoweb and hydro-seeded to promote rapid grass growth that would further bind the soil.

Its quick and easy installation reduces labour costs. Since SoilSaver retains up to five times its own weight in moisture, vegetation is swiftly established thereby preventing any erosion.

This combination of formalised drainage will prevent any future erosion or damage to the water treatment works.