Case study:Ennerdale Mill Weir Removal

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Location: 54° 28' 31.05" N, 3° 31' 33.80" W
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Project overview

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Status Complete
Project web site http://westcumbriariverstrust.org/projects/ennerdale-mill-weir-removal
Themes Environmental flows and water resources, Fisheries, Habitat and biodiversity, Hydromorphology, Urban
Country England
Main contact forename Luke
Main contact surname Bryant
Main contact user ID User:WCRT
Contact organisation West Cumbria Rivers Trust
Contact organisation web site http://www.westcumbriariverstrust.org
Partner organisations Natural England & Environment Agency
Parent multi-site project
This is a parent project
encompassing the following
projects
No
The weir at Ennerdale Mill, on the River Ehen in Egremont, prior to removal, showing significant damage to the structure and face of the weir

Project summary

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Ennerdale Mill Weir, located on the River Ehen in Egremont (Grid Ref NY 012099) dates back over 250 years and was constructed to power the Ennerdale Paper Mill. The Weir has not been used as it was intended for many years and has been proven to be a barrier to migratory species of fish in the Ehen catchment, as well as a crucial site for Freshwater Mussels.

A consortium of funders- WCRT, the Environment Agency, Natural England, the European Maritime and Fisheries Fund and James Fisher Nuclear- have combined resources to enable this weir removal project to take place over the summer of 2018. The project was delivered as part of the Cumbria River Restoration Strategy, a partnership between the EA, NE and WCRT.

In June, we mobilized to site to begin the delicate task of removing the weir, without causing ecological damage through the uncontrolled release of silt and sediment into the river system. A specialized contractor, Ebsford Environmental, were chosen to deliver the works, ensuring silt control measures were installed downstream of the weir. In addition, prior to the works, WCRT and Natural England conducted a translocation of freshwater mussels from within the work site, re-locating 48 mussels upstream of Egremont.

The working methodology, developed by WCRT and AECOM, involved river bank re-profiling, berm lowering, re-grading of the existing riverbed & installation of toe protection (boulders that reinforce the river bank to provide protection against erosion), all conducted in a specific order to minimise sediment disturbance. Once the preparation was complete (approx. 4 weeks) we were ready to ‘notch’ the weir which lowered the water levels upstream, allowing the sediment & gravels that had built up over decades to be removed in the dry. Removing the weir structure itself took one week, and throughout that process Durham University were conducting heritage recording of the site so that we have a historic record of the structure of the weir.

With the weir structure removed, the final tasks were to re-profile the riverbed and rapids upstream and downstream, and further strengthen the river banks with stone protection.

Works completely finished on 31st July, meaning the whole project was delivered in around 7 weeks.

The Rivers Trust and the Environment Agency, supported by other partners, have been working with the Marine Management Organisation and Defra to develop a coordinated and funded programme of projects for 2018/19 with the aim of freeing migration routes of barriers to fish.This project is part of that programme funded by over £1.6 million of European Maritime and Fisheries Funds, which is matched by more than £1 million of Agency/Defra funding and £300,000 of other funds.

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Catchment and subcatchment



Site

Name River Ehen
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Heavily modified water body No
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Protected species present No
Invasive species present No
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Project background

Reach length directly affected (m)
Project started 2018/06/01
Works started 2018/07/31
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Reasons for river restoration

Mitigation of a pressure Barriers to fish migration
Hydromorphology
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Measures

Structural measures
Bank/bed modifications Weir removal
Floodplain / River corridor
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Monitoring

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Supplementary Information

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