The Challenge: Securing Ageing Structures
|Groundwork’s for the high security UltraSecure mesh building included landscaping, concreting and installation of a specially designed former base system|
Wessex Water needed to improve the protection of two impounding reservoirs, both of which were constructed in the late 1800s, with modern-day thinking.
Retrofitting security systems to Victorian water engineering can pose challenges. Pioneering in their day, these ageing structures now rely on 21st century ingenuity to extend their service life and bring them in line with modern security and operational standards.
This was true of Wessex Water's project to enhance the protection of two impounding reservoirs in Somerset, constructed in the late 1800s.
The contract involved the design and build of physical and electronic protection measures, compliant with current government guidelines and standards. Central to this has been the engineering of high security access systems for valve towers sited within the reservoirs.
The access solutions have met tough challenges, both in their design and water-borne installation in compliance with construction, safety and hygiene standards. In addition, site logistics needed careful planning to minimise the impact of construction and mobilisation of materials within the sensitive environment.
Differences in the construction of the towers were a further complication.
Luxhay reservoir is served by a tunnel that required a high security door with egress for bats, and a modular mesh cage building to further secure surface access. Access to Leigh reservoir is via a single entry point on top, necessitating the installation of a secure access cover enclosed within a high security cage as an additional deterrent.
|The pontoon solution concludes a rigorously managed three-year programme of security upgrade in line with regulatory standards|
A solution: Towering Feat of Security
A floating platform held the key to security upgrades of valve towers at impound reservoirs – built more than 100 years ago.
Technocover undertook design, manufacture and installation of the high security access equipment. The company offers a concept-to-commission ‘Total Service’ approach to water security projects, focused on delivering best value solutions from its LPCB approved range or bespoke service. This includes site survey, security consultation, in-house design and manufacture, system installation, life-time maintenance of products, and, in the case of Wessex’ impounding reservoirs, acting as principal contractor.
“Work needed to meet the agreed deadline, and weather conditions couldn’t have been worse, with snow, wind, rain, short day-light hours and extreme cold,”
Joe Hughes, site manager,
Integral to the site solution was a pontoon, transporting materials and providing an 8m square work platform around the water-locked towers. As well as supporting up to eight operatives at any one time, it needed to carry a mechanical lifter with 350kg lift capacity for moving components into position.
Using proprietary grid modules, Technocover designed a floating platform for a 1-tonne maximum load capacity over 4m square and a half tonne point load within the same footprint.
It was 90% preassembled bank side and used to transport tools, product components and lifting equipment to the towers accompanied by a safety boat. The final platform section was then added as the pontoon was fixed into position ready for work.
Groundwork’s for the modular mesh cage building system also required special attention.
Following a structural survey, Technocover designed and manufactured a special galvanised steel former system for concrete infill on site to protect an existing staircase from any loadings. This offered a faster method of construction and, therefore, the lowest cost solution.
To ensure programme efficiency, Technocover worked closely with Wessex Water at design and approval stage. This allowed detailed fine-tuning of product design, installation and site logistics for a "right first time" outcome.
Joe Hughes, Wessex Water’s site manager, said: “The product solutions needed to offer an element of flexibility while complying with current legislation, being fit-for-purpose and, as far as possible, visually unobtrusive.
“Technocover refined design details to accommodate all these and other issues including planning permissions, land-owner views, and environmental considerations such as the bat aperture in access doorways.”
The comprehensive planning paid off, even when the April build programme was hit by unexpectedly wintry conditions.
“Work needed to meet the agreed deadline, and weather conditions couldn’t have been worse, with snow, wind, rain, short daylight hours and extreme cold,” said Hughes. “It left Technocover with a vast amount of work to complete in little over two weeks of actual site time, but they managed to achieve it.”
He added: “Any water-borne job in such adverse conditions needs careful workforce supervision and health and safety management. Technocover’s safety manager was present throughout to supervise and react on the spot to any issues.”
In working with restricted operations, the installation team were required to observe a particularly complex set of safe working and hygiene practices. These included strict procedures for chlorination of pontoon components, safety boats and equipment, as well as complying with safety guidelines for working on water, at height and from a floating work platform.
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This article was published in the October 2014 issue of Wet News. Reproduced here with the permission of the publisher.