Articles & Case Studies

Southern Water considers wildlife in Technocover’s security solution for disused borehole tunnels

Posted: Thursday 21st May 2009

We’re all familiar with the cat-flap. Now for the water industry there’s the bat-flap, following a bit of lateral thinking by Southern Water and leading secure access provider, Technocover.

Southern Water came up with the unusual adaptation in replacing doors to two hillside tunnels leading to a disused water borebole, near Ventnor on the Isle of Wight.

Dating back to the late 1800s, the tunnels cut deep into the Great Woods hill to a well which once formed part of a spring water collection system feeding the public water supply to Shanklin. Although no longer used, the tunnels and borehole remain part of Southern Water assets, making the company responsible for their upkeep and any related health and safety issues.

Previously, Southern Water had used wooden doors to close off the tunnels and at one time they had even been bricked up. But teenagers curious to explore inside had consistently vandalised the entries, leaving security and public health and safety compromised.

David Nye, Southern Water manager for the Isle of Wight, said: “We needed to look at installing something stronger to safeguard the public and keep youngsters out, while preserving access for the purposes of structural surveys.”


Security access specialist and longstanding supplier, Technocover, was called in to design and manufacture a more appropriate security solution.

Technocover has been supplying Southern Water with LPCB approved high security access covers and associated equipment for almost a decade, for reservoir security upgrades and other applications.

But the door also needed to take into account other factors.

David Nye said: “We suspected that bats might be using the tunnels, so we called in the island’s resident bat expert to consult on how we could accommodate their needs in the design of replacement doors.”

Founder of the Isle of Wight bat hospital with his wife, Donna, Graham Street is an expert in the seventeen bat species found on the island, which are protected by stringent UK and European laws. Graham provides consultancy to companies and individuals on the legalities and practicalities of projects that might encroach on bat habitat, for the purposes of feasibility studies and planning applications.

He has previously advised Southern Water on making provision in tunnel works elsewhere on the island to protect very rare Greater Horseshoe bats identified at the site.


Southern Water takes great care that it works in harmony with nature across all of its operations, which provide water supply and wastewater treatment services in Kent, Sussex, Hampshire and the Isle of Wight.

Graham said: “Southern Water is very conscientious about protecting the welfare of wildlife in any work they undertake, as demonstrated by the care taken in the design and construction of Technocover’s doors.

“After visiting site, I assessed that the tunnels would be an ideal hibernation or roost location for most woodland bats and advised the provision of bat access in the replacement doors.”

Bats can choose unusual places to live, favouring the dark and constant temperature of underground spaces such as tunnels.

In line with Graham’s advice, Technocover provided a 20mm high by 300mm wide bat aperture in the doors, complete with wooden perch to the front and rear, ensuring that there were no sharp edges that could cause injury.

Graham said: “The specification for the bat aperture followed guidelines on dimensions and materials used in the design of proprietary bat boxes, tubes and artificial roosts.”

He added: “The tunnels are likely to be used by species such as the Daubenton’s, Natterer’s, Whiskered and Brandt’s bats.”


While the bat-flap sustains the tunnel as habitat for the local bat population, the door itself provides robust defence against any would-be intruders and the risk of them injuring themselves.

The design is based on Technocover’s leading Ultrasecure LPCB approved doors, using a construction specification in line with one of the highest protection levels. This gives Southern Water peace of mind that the tunnel access will remain firm against intruders during the long periods between inspections.

Located about 25m apart and at different heights, the approx. 5ft high (1500mm) by 2ft (600mm) wide tunnels have different openings, necessitating special door sizes. One required an arched door, 1485mm high by 960mm wide overall, and the other an even smaller, flat-headed door, 1200mm high by 900mm wide.

For a robust appearance, the doors are constructed from durbar plate and secured by 3-point, shoot-bolt locking systems made in-house from stainless steel. They are locked using a suitable LPCB approved padlock giving a high level of protection against physical attack. They also have brackets for an intruder alarm, to link the doors to Southern Water’s central surveillance and alert system.

Long life

The integrity of the doors is further assured by Duragalv long life zinc galvanising, Technocover’s leading corrosion protection system for utilities access systems and fabricated steelwork.

Duragalv is a hot dip post-galvanised zinc coating, applied after fabrication to quality control procedures at Technocover’s in-house galvanising facility. A 70gsm, 100gsm or 140gsm thick zinc coating is applied to the product, based on local corrosivity factors and required service life, usually a minimum of 25 years for access covers, doors and ancillary steel fabrications.

Typical of the company’s innovative approach, Technocover is unique in offering post-galvanising options that tailor system longevity to the location and design life criteria. This ensures a more cost-effective solution and lower maintenance, and the basis for greater accuracy in accounting for security access covers, doors and associated steelwork in whole life costings (WLC).

In addition to design and manufacture, Technocover surveyed the site to assess security needs and application specifics that might need to be addressed in the manufactured door. The company’s engineers also fitted the doors to ensure correct, problem-free installation essential to long-term security performance, another feature of Technocover’s Total Service, its complete partnering to clients.

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