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 and installation of toe protection (boulders that reinforce the river bank to provide protection against erosion) all conducted in a specific order to minimize 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.
|Before: a failing weir, degraded concrete and a significant barrier to fish including Salmon and Trout||After: no barrier, a re-naturalised river and strengthened river banks|
|Durham University Heritage Recording||12.61 MB|