London & South East

Environment Agency tackles weir safety issues

Molesey WeirThe Environment Agency is spending almost £10 million on a series of upgrades on the rivers Thames and Kennet. The project involves works to four weirs on the Thames and one on the Kennet. The aim of the project is to replace these five ‘paddle and rymer’ weirs with modern structures, in order to remove the inherent long term health and operational risks associated with their manual operation.  

The five weirs that are the subject of this phase of works are:

• Radcot Weir (River Thames, Oxfordshire)

• Northmoor Weir (River Thames, Oxfordshire)

• Mapledurham Weir (River Thames, Oxfordshire)

• Blakes Weir (River Kennet, Reading)

• Molesey Weir (River Thames, Surrey)Molesey Weir

The Environment Agency’s project manager, Paul Fraser, spoke to Premier Construction, explaining the need to replace the weirs. He said, “These weirs, when operated manually, pose a risk to the operator. We calculated that the lifting involved subjected the operator to around three times the recommended forces and could lead to both short and long-term injuries. This can be avoided by replacing the paddle and rymer weirs with electrically operated modern gates meaning we are better able to respond to changes in river conditions and with a finer level of control”.

JT Mackley have completed the replacement of the weir at the Molesey site, and are also contracted to work on the Northmoor Weir, on which works are due to start soon, having been delayed by opposition from the local community.Molesey Weir

Tom Caldecourtwas Site Agent for the Molesey project with JT Mackley, and told us about the work replacing the old weir and the complexities of the process.

“We laid around 150 bulk bags containing gravel using divers, placing thick polythene sheeting between the bags to dam off the river flow while we were working. It’s a slightly more unconventional method but in this case it was nice and quiet, so as not to disturb residents, and cost-effective compared with piling. However we could not completely stop the water coming through but using the knowledge within the team, mainly from Paul Flowers the foreman for the job, we sectioned areas and using small pumps and silt curtains we managed to get round most tricky problems.”Radcot Weir

The team also installed a new eel-pass. While fish passes, allowing fish and kayakers to by-pass the weir through a channel running around the structure, are commonplace, eel-passes are now required by environmental agency regulations. These enable eels, now an endangered species in British rivers, to wriggle through a channel on a bed of bristles, to the other side of the weir.

Meanwhile, Jackson Civils are undertaking works at three sites: the complete weir replacement in two phases at Radcot, and also smaller-scale works at Mapledurham and Blakes.Radcot Weir

Thames Link Marine Ltd

“Thames Link Marine Ltd are privileged to be invited to work for the Environment Agency and Mackleys on the Molesey Lock contract.  At Thames Link Marine we have been working on the Upper Reaches of the River Thames since 1986. We have seen many changes and look forward to an exciting future on the River Thames”

Thames Link Marine Ltd have supplied a safety boat and marine equipment on the project.



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Premier Construction

1 Comment

  • Unfortunately the Environment Agency is wrong on this. When properly trained, lockkeepers are not exposed to any risk. In fact, there are no documented severe incidents that would underpin that statement. A shame they still use this argument to justify a pointless project that costs the taxpayers £3,000,000 and destroys one of the only remaining weirs of it’s kind. Google Save the Weir and find out the truth.

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