The Wildfowl and Wetlands Trust approached Base Structures with a specific problem for their proposed new exhibit housing Redshanks and Avocets. They needed a world class enclosure that did not feel enclosed, had an exceptionally low environmental impact and was as affordable as possible to construct, install and maintain. A fundamental requirement was also for the fabric of the structure to be wader bird friendly; these species are very fragile and if spooked can easily damage themselves on solid obstructions.
Paul Pattison, Development Projects Officer, Slimbridge WWT
Andy Traynor, Project Manager, Base Structures
To provide as natural an environment as possible, the enclosure uses tough 25x25mm knotted polyethelene, a surprisingly unobtrusive material that is not visually dominating. From inside the enclosure the netted walls appear to be almost nonexistent against the surrounding landscape, providing an incredibly natural environment for the birds. This is enhanced by the supporting timber posts and netting surfaces being installed at various angles, creating a natural effect with no perpendicular lines, helping to minimise the man-made appearance of the enclosure. To offer protection to the delicate wading birds the supporting timber posts around the edge of the enclosure are all placed outside the netting, preventing possible injuries if the birds are scared into flight.
The biggest environmental savings were achieved by using construction techniques that did not require the use of any concrete. As such, the supporting structure was installed using alternative foundation techniques that did not literally cost the earth. Fully engineered timber posts hold up the entire net structure, providing the necessary support with a natural, renewable material that is no more intrusive within the enclosure than a few slender trees.
A key requirement from the Trust was to ensure that the structure would be as economical as possible to maintain in the future. As a critical design requirement from the very beginning of the project, we managed to engineer a solution into the structure that alleviated the need for carrying out inspection or repair at any great height. We achieved this with a very simple system; the netting is attached to metal rings that are slightly larger in diameter than the structural timber posts, these rings are hoisted up and down the posts by a system of ropes and pulleys from ground level – being simply tied off to hold the netting in final position. Thus the whole netting structure can be easily and quickly lowered down the supporting timbers for any work to be carried out at ground level, ensuring significant costs for the lifetime of the structure.
We worked closely with the Trust to supply this enclosure in kit form, allowing them to use their own equipment and expertise to install the structure with minimal supervision from ourselves. Our comprehensive survey provided the exact locations and angles for the timber posts, after these were installed by the Trust we fitted the cabling, in turn enabling the Trust to install the netting themselves and complete the installation. Once installation was successfully completed the team at the Trust had also gained the necessary experience to undertake any future maintenance themselves.
The Trust are thrilled with their new visitor attraction, the cost savings achieved in construction and the knowledge that the enclosure will continue to perform in the future for minimal outlay. The birds have settled in superbly and exhibit their natural behaviour, presenting visitors with a privileged experience; to see the birds acting naturally at close quarters without feeling you are confined in a restricted space. The Trust have commented that they hope the birds may eventually breed, a sure sign of success! This would then become an even bigger attraction for visitors, helping to develop visitor empathy and fondness for the birds which is beneficial to the broader WWT conservation efforts.
in Bristol
