A STRUCTURALLY unsound section of the twoyear-old Jubilee River flood relief channel in Berkshire is being replaced.
Contractor J Breheny is strengthening about 300m of embankments near Datchet.
Investigations by consultant Atkins revealed these could collapse under high flood flows. The work will cost £1M and take until November.
Earth embankments will be ripped out while the river is shored up with cofferdams. The embankments will then be rebuilt using geosynthetic reinforcement.
Atkins identified weaknesses in the original embankments built by Balfour Beatty in a report for the Environment Agency.
It said that the slopes were too steep, with the factor of safety falling below 1.0 in places.
'If we had to call upon the channel to its full design capacity we have some concerns as to whether the embankments would stand up, ' said Environment Agency project manager Tim Chin.
Atkins was called in to investigate the performance of the channel following flooding in January 2003. It assessed the channel's condition, true capacity and necessary repair work.
Operation of the £105M scheme prevented flooding to about 1,000 properties in Maidenhead, Windsor and Eton. But there was widespread flooding downstream of the confluence of the channel with the Thames near Datchet.
Residents' groups have since claimed that water was flowing through the embankments, surcharging a nearby stream running alongside the channel, before flowing across fields into Datchet.
The Environment Agency disputes this claim, but has admitted that the channel's embankments suffered damage in several places during the floods.