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Bundle of joy

A giant bund is shielding residents from the noise and traffic at Gatwick’s new taxi stand

A giant screening bund that was constructed at Gatwick Airport has rapidly settled into the surrounding countryside.

Screening villages

The 350m long, 16m high embankment is part of a £43m investment in the airport, and is designed to screen nearby villages from the new aircraft stands and taxi-ways being built to handle the planes that will be housed there (NCE 30 June).

The six new aircraft stands cover over 100,000m² and are sited at the north-western side of the airport. They provide remote parking for aircraft, and include two areas capable of housing the Airbus A380 - the world’s largest commercial passenger airliner.

Although the nearest village was over 2km away, hiding the tail fins of the huge planes was a serious concern

Although the nearest village to the airport’s perimeter was over 2 km away, the possible visual impact of the development was still a serious concern to the airport’s operators, Gatwick Airport Ltd, who felt an existing 8m high bund was not tall enough to hide the tail fins of the huge planes.

Following consultation with local parish and town councils and a visual impact assessment of the site, the height, length and overall shape of the bund was agreed. Consultants Scott Wilson conceived a structure which would, from the village perspective, be as natural in appearance as possible, with a varied profile and heavily vegetated to blend in with the local woodland setting.

Steeper face

At the airport side, a much steeper, 63° face was proposed to minimise the land take required for the bund. At 3:1, the slope face required geogrid reinforcement and Scott Wilson brought in Oxford-based geotechnical specialists Maccaferri.

Their solution was a reinforced soil structure, using the company’s Paragrid Geogrid, in combination with large quantities of structural fill materials available on the airport site.

Paragrid is a biaxial soil reinforcement grid comprising composite geosynthetic straps with a polyester core within a protective polyethylene sheath. It is designed to be placed horizontally between layers of compacted structural back-fill, nominally 600mm in thickness.

Recycled backfill

Overall, the Gatwick bund used over 97,000m² of Paragrid, together with 180,000t of backfill, the majority of which was recycled granular materials and site-won clay, reclaimed from other areas of the site.

Biomac, a bio-degradable erosion protection blanket also from Maccaferri, was used to face the sloped surface of the geogrid wrap. This allowed the inclusion and retention of a face layer of compacted top-soil, which was later hydro-seeded to promote rapid establishment of vegetative cover.

Made from either coir fibres or a combination of straw and coir fibres, Biomac protects vulnerable plant shoots from damage by rain impact, moisture evaporation and erosion of the topsoil by surface water run-off.

Each 600mm thick reinforced soil step was set back 200mm to achieve the desired 63° face angle. It also allows more rainfall to penetrate the top-soil facing-layer and helps the vegetation to grow - an important factor in the long term stability of the bund, especially at such a steep angle.

The new screening bund was built in front of and over the existing smaller structure and despite challenging weather conditions, was completed in early spring 2010. Since then, the bund has rapidly matured and now blends well with the surrounding Surrey countryside.

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