New residential homes built on historic Berry Hill site overlooking Mansfield

02/01/2002

Overlooking the town of Mansfield, Nottinghamshire, the historic site of Berry Hill Park has been a local landmark for centuries. The vantage point of kings when hunting in Sherwood Forest, more recently it has been quarried for building materials. The site is now being reclaimed to create a unique residential area incorporating a design from Maccaferri Ltd, specialists in retaining structures, slope reinforcement and erosion protection. Products supplied by Maccaferri have been specified to provide a retaining structure to the spine road.

A number of major house builders are involved in the development, which will include provision for open spaces, footpaths, a cycleway and community facilities in addition to housing. The prime site of 'Kings Stand' on the southern perimeter is being developed by McLean Homes Northern, and the first show homes opened in Summer 2001.

'Kings Stand' is on the upper rim of the disused quarry, and a retaining structure was required to stabilise the site adjacent to the spine road. Design consultants, Eastwood and Partners contacted Maccaferri requesting proposals for an environmentally friendly solution offering overall stability within a structure in harmony with the surrounding countryside.

To achieve these criteria, Maccaferri recommended a reinforced soil solution incorporating a Green Terramesh® retaining wall with a Terram ParaDrain geogrid manufactured by Yorkshire based Linear Composites at the base.

The first use of a composite Green Terramesh® and Geogrid solution within the UK, the very long (7 metre) tail lengths required the inclusion of ParaDrain to ensure overall stability. In addition it also enabled a lower 'Ru' value to be adopted for the base layers of silty sand backfill found on the site.

The proposal was accepted by both McLean Homes and Eastwood and Partners. The main construction contract was awarded to Newark Development, with sister company Loates Construction undertaking the earthworks and construction of the retaining structures. Maccaferri was confirmed as designer and supplier for the Green Terramesh® and supplier of the Paradrain material.

Work commenced on site in March 2001, with the show homes overlooking the retaining structure opening in late June. The site works benefited from a period of dry weather through May and June. With more frequent rainfall in July, the structure began to ‘green up’ as the seed mix germinated. This created a visually appealing and stable structure in harmony with the surrounding environment.

To ensure a seed mix appropriate to the area, Maccaferri's Bio-Engineering team worked closely with McLean Homes’ landscape architect and the local wildlife conservation group. By using site won topsoil behind the face of the Terramesh units, existing plant species were retained within the structure in addition to the species re-introduced through the specialist seed mix.

Over 300 metres in length, the Green Terramesh® retaining wall is up to 8.5 metres in height. Tailored to meet environmental concerns, the design includes planting terraces of varying width along the length of the structure. When planted up with local tree species, these will create a natural effect and help the final slope from looking too 'engineered'.

Green Terramesh® units are formed from a single sheet of hexagonal, double-twist woven steel mesh. When installed, it is formed into three sections, a horizontal soil reinforcement tail, a facing section and a horizontal return top section.

Triangular support brackets behind the front face provide added rigidity and allow easy installation of the grid by eliminating the need for temporary formwork. Behind the front face, an in-built layer of biodegradable coir geotextile is used to retain the topsoil and allow the establishment of the vegetation.

Installing Green Terramesh® is quick and easy, bracing triangles ensuring accurate installation. Units are either laced or can be fixed together with special rings dispensed using a ‘Spenax’ pneumatic tool, available from Maccaferri Ltd.

By combining Green Terramesh with Paradrain, which provides the strength of a grid and also dissipates excess pore water, it has been possible to use site-won silty sand as backfill, obviating the need to use expensive granular material.

Terram Paradrain, manufactured by Linear Composites and supplied by Maccaferri, is a geosynthetic material which combines reinforcement with drainage. Each strip consists of two elements, a polyethylene coated polyester cored reinforcement strip and a built in drainage channel with a bonded non-woven fabric layer acting as a filter which allows water to drain away from deep within the reinforced soil block whilst retaining the backfill material.

Maccaferri Ltd specialises in the supply of gabions, geotextiles, geogrids and geomats. In addition to a full range of products for retaining structures, slope reinforcement and erosion protection, the company offers an in-house design and consultancy service.

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