The Challenge:

The River Camel is of high ecological importance being designated as a Special Area of Conservation and a Site of Special Scientific Interest for its range of habitats including wet woodland and wet meadows species of importance including salmon, sea trout and otter.

Ensuring works are carried out in a sensitive manner is therefore of critical importance, particularly with respect to avoiding pollution of the river from bankside works where rock reinforcement needs to be removed and the banks regraded to a more natural slope.

The river at this point is approximately 15 metres wide with highly variable depth and flow subject to local rainfall. Any bank works, therefore, have a high risk of causing sediment pollution which would impact the spawning grounds of protected fish species with potential knock on effects to food availability and distribution of otter for example.  All works needed to be completed within a very short window between mid-August and end of September to avoid key Salmon migration periods.

The Solution:

To deliver the requirements of the Environment Agency’s Environmental Action Plan and prevent any pollution incidents, Kier worked in collaboration with a key subcontractor, Murlac to set up a temporary frame dam and silt curtain along the working section of the river bank.

Once works from the right bank were completed, this would be moved to the left bank of the river. The frame dam is held in place by the force of the water and results in reduced water levels within the working area and significant drop in flow rates; any soils from bank works quickly settles out. Installation of a straw bale wall with floating oil boom also prevents any downstream sediment migration or pollution in the event of a spill from excavators in use.

Additionally, the dam provided a segregated area from which all fish were removed by the EA prior to works commencing. The toe of the reprofiled bank is protected by rolls of brash staked in place and banks are being seeded and covered with a biodegradable coir mesh to prevent erosion from either the river or rainfall. Use of FSC certified ‘bogmats’ (large timber trackway) has minimised damage to woodland areas which will facilitate reinstatement of the area once main works are complete

The Impact:

Use of the dams enabled fish rescue prior to the first stage of the works – a total of 130 fish including 11 salmon parr and 31 trout parr were relocated upstream of the works to a natural holding pool. An additional rescue is planned prior to starting works on the left hand bank of the river.

The value of the dams was also clearly illustrated following significant rainfall events in August when water levels rose by 2ft across the works site. The dams remained in place and works could continue without any delay to programme or requirement to change method of works. 

While some trees have had to be removed to enable works, tree protection measures were established around more significant, older trees and works limited to as small an area as practical. Felled trees are being strategically placed in the channel in line with advice from the Geomorphology team from the design partner, Atkins, and remaining cut vegetation has been used to create refugia for local wildlife. 

" I am delighted to see this river restoration work on the River Camel being delivered on time and very sensitively by Kier. It is an excellent project as it is restoring an iconic river and enabling even more fantastic work to be completed. By working in partnership and investing in this work we are creating a better habitat for wildlife and making it easier for salmon and trout to migrate and spawn. The project also acts as match funding for the 2.2 Million pound ‘Water For Growth Project’, which is bringing long term benefits to local anglers and our tourism industry. "
Lesley Newport Environment Programme Manager Environment Agency

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