2 Feb 2011

Update on Severn Trent plans for Ruscombe sewers

I have had an update from Severn Trent on plans in the Ruscombe valley and indeed down to The Lake at the Lawns. We raised two particular issues:

Photo: Brook in recent snow

Risks to biodiversity by relining works?

The Severn Trent project scope was approved as a sewer rehabilitation (relining) project during the autumn and their supply chain partners are now working on the detail of this, particularly regarding the ecological issues that were raised as part of the initial habitat surveys. These included issues that Ruscombe Brook Action Group raised.

Assessments are now being carried out by Severn Trent to determine how they can access the various areas of the site to complete the relining work but avoid the particular areas of interest affected by protected species and therefore avoid the need to carry out further detailed habitat surveys. If this is feasible, then they would hope to bring forward when we can carry out the work. Overall, they anticipate disturbance will be minimal but they will need to confirm this once they understand where access can be taken.

Why relining not replacement?

We noted concerns that plans were only for relining. It was our understanding that the sewer did not have enough capacity. Relining will surely just lead to pressure on manholes or other week places along the sewers?

Well Severn Trent say that from their assessments of available data used in developing the project scope, they are satisfied that the relining will not generate any greater risk of flooding or pollution. They note that historically, capacity issues and pollution incidents have been a consequence of serviceability issues with the sewer, i.e. ingress of roots and resultant siltation limiting sewer capacity. The thin wall lining that is inserted into the sewer will prevent root ingress and consequential siltation maintaining sewer capacity overall.

I have written again this weekend on behalf of the action group as we still have concerns re relining. We were told by John O'Leary (Severn Trent) at a presentation to the Stroud Valleys Water Forum last March that relining does not appear to be an option as the pipes are not large enough. His proposal was for specialised 'pipe bursting' and replacement of sewer sections. We are therefore concerned that this project will not be sufficient? I am hoping they can assure us that modelling shows sufficient capacity as the message we got earlier was that there was not enough capacity even with relining. I hope this is not a cost-cutting exercise?

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