Failing Weir Removal Restores River Ehens Natural Flow Ennerdale Weir Removal

In partnership with the Environment Agency and Natural England, West Cumbria Rivers Trust led this project to remove a redundant weir and re-naturalise a section of the river Ehen immediately upstream and downstream of the Barrier.

Ennerdale Mill Weir on the River Ehen was a key part of the West Cumbrian Rivers Trust initiative to allow for improved ecology and river safety.

In recent years West Cumbria Rivers Trust and the Environment Agency had been surveying the weir and monitoring the damage to it caused by erosion. A significant risk of the weir failing completely was identified, with signs that it is at risk of collapsing.

Showing signs of failure, the centuries old weir function of powering the long gone paper mill was obsolete and served as not just an obstacle to the free flow and movement of Salmon, Trout and England’s only breeding population of freshwater mussels, but was a potential flood risk for the surrounding land and properties.

Ebsford Environmental Ltd have were appointed to carry out the work due to their experience of working in sensitive watercourses and their knowledge and success in weir removal and river reprofiling.

The methodology for removal was designed around protection of the downstream riverine environment with works phased to allow dry work areas. Using large excavators, Ebsford carefully dismantled the barrier and re-profile the river up and downstream of this section (approximately 350m), so there is a steady gradient over the area of the former weir.  Materials from the weir itself, including stone and sediment build up were reused to install natural features including, berms and in channel rapids and meanders to adapt the river and restore a naturally functioning healthy river system. Concrete and metal waste currently in the weir was disposed of off-site.

To ensure there were no adverse effects on the Freshwater Mussel colony and fish population, oxygen levels were being monitored across the site at regular intervals, before during and after the work. Sedimats (sediment capture mats) were installed to prevent any material from the weir being carried downstream and polluting the river. The Freshwater Mussel colony was also be monitored, translocating where necessary, to ensure they suffered no adverse effects from the work site. Ahead of works starting 48 mussels were safely translocated upstream by licensed trust staff members working alongside Natural England.

Ebsford successfully removed the weir undertaking river restoration allowing the river to follow its natural topography. Re-profiling of the riverbank also took place with materials such as stone from the Weir dismantling process. Further seeding of the riverbank ensured high levels of silt won’t be washed into the river in future.