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Lake District stream un-straightened in concrete project

Pre-cast concrete panels were used in an unusual project to carry out the ‘re- meandering' of a historically straightened section of Swindale Beck in the Lake District.

The project included installing a Coanda screen, fish pass wall and Crump WeirThe project included installing a Coanda screen, fish pass wall and Crump Weir

Whites Concrete supplied its pre-cast Rockwall and Groundwall panels so that Coffey Construction could quickly and efficiently form a new Coanda screen, fish pass walls and a Crump Weir to Swindale Beck, which is an upstream sub-catchment of Cumbria’s River Eden.

The channel, which had been straightened over 160 years ago, included a beck that had become heavily armoured with rock on both sides from generations of farmers clearing it out and depositing material on the banks. This had resulted in the straightened channel being effectively cut-off from the surrounding floodplain, which greatly accelerated flow through the valley. This also meant that when the banks were over-topped, water wasn't able to flow back into the channel. Instead it pooled on the meadows either side, significantly reducing their value both botanically and agriculturally. In width and depth and bed substrate size, the straightened channel was also very uniform with no shallow landforms, gravel bars or pools. The net result was large volumes of gravel and silts being deposited downstream at the drinking water intake.

The new Coanda screen constructed by Coffey Construction (utilising Whites Concrete’s pre-cast panels) allows maximum transfer of water into the intake while filtering particulate matter such as sand, gravel, stones and leaves. Meanwhile, the Crump Weir measures the flow and volume of water.

John Paul Ruane, Project Manager at Coffey Construction, commented: “Our choice of Whites Concrete’s pre-cast wall sections made installation much easier and quicker for us, which given the contract’s time constraints, was very important.  In dealing with the river flow we were able to drop in the wall sections, which effectively acted as a training wall to guide the flow”.

He added: “We responded to this challenging contract with an innovative fast-track construction solution, which meant that the project was completed in one season, rather than the three that was originally proposed”.

Offering lower overheads, less build time and reduced cure time, Whites Concrete’s pre-cast Rockwall is cast as ‘L’ shaped wall sections with heights up to 3.8m, whilst the Groundwall panels are thicker and able to withstand higher loads.

Part of the new route of the straight channel ran through a hay meadow designated as a Site of Special Scientific Interest (SSSI), so measures had to be taken to protect this area. These included not storing any excavated spoil on the SSSI and only allowing machines to track within the footprint of the channel on a specifically created haul route of bog mats and terram membrane.

The project resulted in 890m of new/restored sinuous channel, replacing the straightened 750m length. A further 110m of smaller sinuous channel was also created to connect two tributaries into the restored route.  The new channel is already considerably more biologically diverse.  The old channel was in-filled and re-seeded with brush harvested seed from the SSSI meadow.

Author: James Brockett,
Topic: Water Resource Management
Tags: construction , fish , concrete

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