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Case Study: Pond creation for protected species – Filton Airfield

BAE Systems were required to undertake some mitigation works for the great crested newt population on their Filton Airfield site so they contracted JPR Environmental to construct two wildlife ponds.

This was not a simple construction project as the ponds were designed to hold over 340 cubic meters of water with a range of shelves, slopes and depths to cater for a variety of zones favourable to flora and fauna.

Site security was also a high priority as the main access was through the airfield. Part of the site mobilisation consisted of erecting a security fence around the perimeter of works and redirecting the public footpath that cut across the field in which the ponds were to be constructed.

As the soil was found to be a sandy, friable clay (after initial site investigations), it was determined that a granular bentonite liner would be the most suitable lining material in order to retain the water yet produce an ecologically sound base for the ponds to flourish.

Installation of bentonite requires the over-excavation of the pond shape to lay the liner and then backfilling with suitable media to protect the liner and be compact enough to sandwich the bentonite during the hydration process, creating a waterproof membrane.

Special care needed to be taken during the planting process (particularly when depositing planting media on some of the banks and shelves for the aquatic plants) to ensure that nutrient levels in the pond were not inflated excessively – in some cases, this meant using only topsoil as the planting media.

The final challenge was to fill the ponds – the nearest water access point was situated over 2km away at the other end of the site. The solution was to use a 30 cubic metre water tanker which worked very well.

The aim with both ponds was to create a native, aquatic habitat – instantaneously. Over 1,200 aquatic plants were planted, transforming the ponds into established, natural-looking habitats, fit for the designed purpose. BAE Systems, were very happy with the result and the professionalism of the JPR team.