A unique floating access solution on the River Severn has allowed contractors to install much-needed Eel Screens.
Midlands-based Attridge Scaffolding has just completed an industry first by providing one of it’s long-standing clients, Integrated Water Solutions (IWS), with a unique access package that combined traditional land-based scaffold with the innovative floating ScaffFloat system to lift and install a set of eel screens afloat.
The scope of works was to provide full access to the vertical concrete penstock face of the riverside water works using traditional scaffold, and then to also to provide two large floating scaffold pontoons for storing and lifting the new eel screens, weighing 2.2t each, into position afloat.
For the land-based scaffold, Attridge used shear plates fixed with anchors into the concrete to enable the saddle to be erected. Once the saddle was in place the design scaffold was erected.
James Attridge said: “This project was almost 12 months in the planning. After an initial site visit with the client, it was a case of putting together a scheme utilising past experience from other projects. The exception being the floating lift rig. This is where our professional working relationship with ScaffFloat enabled both parties to work together to develop a solution.”As one of the main UK Approved Installers of the floating scaffold system they worked with the ScaffFloat team to design a custom design that met the very site-specific client requirements. Access to the water was very limited and so both pontoons were built shoreside as a skeleton framework, this kept the weight for the crane lift down to 1t. Once afloat additional tubes, fittings and boards were craned down and both pontoons were completed afloat bringing their weight up to around 3t each.
The scaffold structure in the pontoons was floated using ScaffFloats patented plastic floats with each one supporting 0.5t – in total over 60 floats were used for both pontoons.
The first pontoon was used as a storage pontoon, with a 6t payload it was used to store components afloat before they were fitted by the team from Edwards Diving.
The second pontoon was fitted with a custom lifting A-frame, this was designed specifically to lift the 2.2t, 6m x 3m Eel Screens. Designed and built to Eurocode standard with a suitable dynamic application and safety factor, it was also proof tested on-site to over 3t. In addition, Richter provided an independent Cat 3 check to provide further safety assurances.“It was a great project and we are proud that we achieved the six lifts ahead of time and without any accidents.”
Toby Budd, MD of ScaffFloat said: “One of the challenges for this lift was water depth. The eel screens were installed just below the surface so there was not enough draft or water depth to have the pontoon above. This meant the 2.2t lifts had to be done over the bow of the pontoon at a distance of 3m.
It was a great project and we are proud that we achieved the six lifts ahead of time and without any accidents. This is another example of how quickly the ScaffFloat system is developing, customers love the versatility and we have a number of other trick lifting jobs in the pipeline.”
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He points out that the lighting installations were fully accessible via clear walkways constructed using Layher’s steel decks.
Limitations in terms of build time and road closures were two important considerations that had to be accommodated, both of which gained from the speed with which the 
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The Layher installation features standards linked in clusters of three using wedge-head swivel couplers which, in turn, are clamped to, and suspended from, the bridge’s own steelwork using girder couplers.
These standards then drop down to connect directly to the Layher FlexBeams installed at up to 5.5 metre intervals, and onto which Layher’s Allround Lightweight steel decking is then located. A choice of decking lengths has enabled I-Scaff to accommodate the diagonal steel sections that form part of the bridge structure, while longitudinal bracing is only required every fourth bay.
Guardrails and edge protection have also been installed, where appropriate, while dropped object netting has been located under the full working area by another Millar Callaghan Engineering Services subcontractor to protect the waterway below.
“The fact that the design, which has been undertaken by Kenneth Redman, Technical Manager at our Livingston depot in Scotland, enables the scaffold to be suspended from the bridge’s own steel structure is extremely beneficial,” adds Sean Pike, Layher’s UK Managing Director.
“The lightweight material has also helped with manual handling procedures, while the greatly reduced number of components has not only played a key role in optimising installation efficiency, it has also made a significant contribution to minimising transport and storage needs,” continues Sean Pike.
As a result, Ross Brown and his team have made full use of the system to deliver the saving in installation time that was an important project target, enabling Millar Callaghan Engineering Services to undertake the gantry removal, repair and reinstallation process more quickly than would otherwise have been possible.
