AECOM supported West Cumbria Rivers Trust to restore a stretch of the River Keekle to its natural state. The project aimed to create a natural dynamic river system, improving the environment for wildlife and people, by removing 180 tonnes of plastic liner from the river which was degrading and releasing micro plastics into the watercourse.
Improving water quality, ecology and habitat
The immediate catchment of the upper River Keekle was a former opencast coal site. The river was diverted during mining operations, with a three-metre-thick clay cap installed above the mine waste with a plastic liner and stone boulder weirs to create semi natural river features along a 2.5 km stretch.
Throughout 25 years of operation and various flooding events, the plastic liner was exposed and heavily degraded, shedding an estimated 500kg of microplastic particles into the river system per year. The river had also eroded away parts of the liner and the river flowed under and around the liner in places. Originally put in place as an extra measure in addition to the 3m deep clay barrier to prevent mine contamination, the plastic had become a barrier to the river’s natural development.
Supporting across the project lifecycle
AECOM’s hydromorphology team developed a feasibility study in collaboration with West Cumbria Rivers Trust and supported them through the funding application process. Our hydromorphology and water engineering teams then worked collaboratively to prepare detailed design drawings and specification, suitable for pricing and construction, along with tender document to support the commissioning of the works. The design developed the feasibility assessment, incorporating an active river with functioning meanders, bends, pools and rifle sequences through modelling and assessment of the topography and historic data/maps of the original River Keekle.
AECOM supported the tendering process to appoint a contractor, reviewing methodologies to remove the plastic liner and silt management proposals to avoiding polluting the river during the works. This role extended into the construction phase with AECOM providing NEC3 contract management support and post completion, signing-off the works at substantial completion stage and the end of defects correction.
AECOM was appointed as the Principal Designer under the CDM 2015 regulations for the construction phases of the project, which consisted of a trial site delivered in 2019 and the subsequent full removal of the plastic liner in 2020. During construction, AECOM worked closely with AquaUoS/Dynamic Rivers who undertook the role of the Clerk of Works undertaking regular visits of the site to monitor progress. This facilitated the incorporation of rapid changes into AECOM’s design to take account of natural features exposed during the removal of the plastic liner which benefited the morphology of the river. With active supervision, the rapid reassignment of construction materials from the excavations was also permitted which limited double handling and maximised reuse of the materials with the works.
Providing an enhanced, sustainable environment for wildlife and the community
The aim of the restoration was to remove the plastic liner, restore the hydromorphological function of the river so that it was reconnected with its floodplain and the natural upstream and downstream river reaches. Working closely with West Cumbria Rivers Trust and AquaUoS/Dynamic Rivers, the restoration aimed to ensure as much habitat improvement was achieved in addition to removing the plastic. The scheme created a semi-natural river system, dynamically changing over time, naturalising into a completely natural river system.
The plastic liner debris was fully recycled, with some debris used to create a commemorative bench and picnic table, which is in a public carpark along the river.
Benefits to the environment and local species
Naturally occurring features such as gravel bars, pools, rapids and glides were created to mimic a healthy river system for the species found along the course of the river such as Atlantic salmon, trout, lamprey and eels. Since the completion of the works, 56 species of aquatic plants have been recorded on site along with 8 different fish species.
A prize-winning solution
The project received the River Restoration Centre’s Nigel Holmes Trophy in 2021 for the work done to improve the natural functioning and ecological integrity of River Keekle and the benefits to society of a healthy natural environment.