In 2018, Maccaferri delivered a full design and supply solution for a ParaGrid reinforced soil slope for Russell Homes, supporting a residential development along Macclesfield Road in Holmes Chapel, Cheshire. The reinforced slope was successfully constructed in summer 2018 and formed a critical boundary retention system for the site.

As part of the engineered design, robust erosion control measures were installed on the slope face. These included a 150 mm deep MacWeb cellular soil confinement system filled with topsoil and seeded with a wildflower mix to promote vegetation. To further enhance surface stability and prevent soil erosion, Enkamat 7010 erosion control matting was installed over the topsoil layer.

In February 2021, following a period of intense and prolonged rainfall, Russell Homes reported a localised failure where part of the topsoil layer had slipped down the slope towards the adjacent road. Maccaferri conducted a detailed site inspection to assess the issue.

The investigation confirmed that the ParaGrid reinforced soil structure remained stable and structurally sound. However, the failure was attributed to construction deviation from the original design specification. The topsoil layer had been installed at approximately 400 mm depth, exceeding the specified 150 mm by an additional 250 mm.

This excessive topsoil thickness created significant overburden on the slope face. During heavy rainfall, the surplus soil became saturated, dramatically increasing its weight. The original erosion control system, designed for the specified depth, was not intended to resist this additional load. Consequently, the saturated overburden led to instability, resulting in the topsoil slipping down the slope.