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Heigham Holmes Floating Pontoon Swing Bridge

Eadon Consulting carried out the design of the operating equipment for the replacement floating swing bridge at Heigham Holmes in Norfolk. The river crossing at Martham Ferry provides access to the environmentally sensitive island of Heigham Homes. This area of land requires ongoing land management to maintain it, access for farm vehicles is therefore important.

Key facts

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Location

Heigham Holmes, Norfolk

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Client

The National Trust

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In Partnership with

Ramboll

The previous bridge in this location was a floating pontoon swing bridge that was raised and lowered onto the concrete abutments by pumping water into and out of the buoyancy tank. The bridge was swung by the operator pulling on a chain linked to the nose of the bridge, which required a reasonable amount of physical effort.

This area of the fens is particularly popular with sailing boats and as such the bridge has to be left in the river open position, this means that when the bridge is swung into the position, once the vehicle has been driven over it, the operator has to row back onto one side of the river, open the bridge and then row back to the other side to carry on their journey. This makes the operation of the bridge very slow and inconvenient.

Original Heigham Holmes floating Swing Bridge

The physical effort required to operate the bridge and the inefficient procedures requiring the operator to row across the river meant that the land owner, the National Trust, decided it would be prudent to replace it. Ramboll UK were commissioned to initially carry out a condition survey of the existing bridge, and then to look at the different options for replacing it. Ramboll employed Eadon Consulting to act as specialist subcontractors to review and develop different concepts for the operating mechanism for the bridge.

A number of different bridge concepts were considered including traditional design bascule lift bridges and swing bridges. However due to the surrounding area and architecture, it was felt that a floating swing bridge similar in concept to the existing pontoon design was the most suitable.

A number of operating mechanisms were considered drawing on Eadon’s experience of moveable bridge as well as lock gate design. As well as this, Eadon helped assess the feasibility of the pumping system to be used within the buoyancy tanks of the bridge and its effects on the overall operating sequence of the bridge. This information was then used to produce budget costs for the whole project.

Eadon produced the detailed design of the mechanical equipment and closely supervised the design and construction of the hydraulic and electrical systems. Further support was given with the carrying out of the CE marking of the structure to demonstrate compliance with the Machineries Directive.