First successful UK application for Geotube® systems supplied by Maccaferri

08/07/2002

In a UK first, Geotube® systems supplied by Maccaferri Ltd, specialists in retaining structures, slope reinforcement and erosion protection, have been used to create sustainable sea defences to protect a golf course adjacent to the exposed East Anglian coastline. A 400 metre reinforced sand bank has been constructed to shelter the practice ground of the Royal North West Norfolk Golf Club from erosion and inundation during high Spring tides.

The golf course at Brancaster is in a designated SSSI. Until recently erosion protection was provided by the Environment Agency in the form of an existing coastal dune system with hard protection, but this had become expensive to maintain. A decision was taken to adopt a policy of managed retreat and with the demolition of banking to the west, the golf club practice ground would be left unprotected from the sea.

Using independent finance and working in close consultation with the Environment Agency, the Golf Club decided to construct its own new flood bank to protect the practice ground. The Golf Club appointed Peter Lawton of North Norfolk-based ‘St La Haye’ Consulting Engineers with a brief to create a sustainable sea defence, using local materials and construction techniques, that would cause minimal disturbance to the environment.

Local borrow pit material was found to be of poor quality and sand from adjacent tidal flats was suggested as an alternative. English Nature confirmed that there is an area designated 'barren sand' of little environmental value which might be used for this purpose.

Maccaferri was asked to look at a possible containment system for the sand, and the final solution using Geotube® systems was developed by St La Haye in consultation with Maccaferri. Three Geotube® systems were supplied to principal contractor J Breheny Contractors Ltd., each measuring 3.25 metres in diameter and 105 metres long. Filled with locally won sand, they form a solid core to the new coastal defences and will be able to withstand even severe winter storms.

Maccaferri is the exclusive UK distributor for Geotube® systems, which are manufactured in the Netherlands by TenCate Geosynthetics Netherlands bv (former TenCate Nicolon). The system is proven technology and has been used in many successful applications in Holland. Maccaferri and TenCate Geosynthetics work in close partnership and are proud to have introduced Geotube® systems to the UK with this first installation.

Manufactured from Geolon® woven geosynthetic material, Geotube® systems are designed to offer a practical way to use readily available sand to construct an embankment, often in the inter-tidal zone, where construction materials would otherwise be washed away. Geolon® is chemically inert to alkalis and acids, with a reliable long-term tensile strength.

The Geotube® solution has resulted in a number of practical benefits for the construction team, despite the inevitable learning curve in adopting a new construction method. Significant time savings have seen two thirds of the 400 metre stretch of banking constructed in under one week, and Dick Naunton from J Breheny is enthusiastic in support of the Geotube® solution:

"It took us just one and a half days to perfect the installation system, then construction went without a hitch. In fact, smoother than anyone dared hope given the innovative use of technology and specialist plant. I would definitely use Geotube® systems again on similar projects."

The construction process involved inter-tidal working during which the sand was excavated and transported to a stockpile. To transfer it to the site of the new banking, local pump manufacturer, Stuart Pumps Ltd. supplied a specially commissioned mixing tank in which the sand and water were hydraulically mixed in a ratio 1:4. This mix was then pumped over a distance of approximately 500 metres to the Geotube® systems through a 6” pump line using a 8” submersible pump.

Once filled, the Geotube® systems are covered with locally won material which is then profiled and covered with Enkamat erosion protection matting to create a smooth, natural outline. The application has been so successful that the banking may be extended. J Breheny will be back on site during the summer, and a further Geotube® systems may be installed during September.

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.

Geolon® and Geotube® are registered trade names from TenCate Geosynthetics Europe.

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