Phase 1b of the Rochdale and Littleborough FRMS make progress with creation of wetland reservoir
The team, working on behalf of the Environment Agency, on Phase 1b of the Rochdale and Littleborough Flood Risk Management Scheme (FRMS) are creating a natural wetland reservoir at the Gale site. The reservoir will have the capacity to hold 74,000 cubic metres of water.
The team have completed the construction of the concrete structures in both the Gale West and Gale East areas of site. These structures, together with a realigned River Roch, will form the inlet and outlet points of the reservoir. The reservoir will be formed from the construction of earth embankments and a sheet pile wall, installed by VolkerGround Engineering, which runs alongside the main Manchester to Leeds Railway. When completed, the reservoir will function as a buffer to slow down the River Roch and the Greenvale Brook waters flowing into Littleborough and Rochdale.
A spillway has also been constructed to control the water level in the reservoir. When the reservoir is full, it will prevent floodwater from overtopping onto the railway or nearby gardens.
The team brought a Liebherr 500T crane to site to lift the culvert units into place, each culvert weighing 26T. The culvert units were placed adjacent to the existing units and winched into position using the reaction force of the existing units. This completed the Network Rail culvert crossing, linking Gale East and Gale West.
The main challenges for the team involved in this element of work were:
- Using a crane adjacent to Network Rail
- Dewatering was required as the culvert is below the water table
- There was confined space operation within the culvert
- Extremely poor ground conditions requiring a substantial crane platform
- Wind.
When the project is complete, in flood conditions, the culvert will carry diverted water from Greenvale Brook via the Gale East diversion structure under the railway to Gale West, where it will then run down a new channel to join with the new alignment of the River Roch. The channel will then continue into the concrete orifice structure, which is the outlet from the new reservoir.
The diversion structure also contains an orifice (this is a reduced opening channel), the orifice limits the flow of Greenvale Brook. In times of high flow, when the water backs up at the orifice, it passes over a weir and into the culvert and then into the Gale West Reservoir.
“Upon its completion the wetland reservoir, together with the new linear defences and enhanced existing flood defences, will significantly reduce the risk of flood damage to the homes and businesses in Littleborough and Rochdale. These measures will provide long-term resilience, helping to protect the community from future flood events. Beyond flood protection, the wetland reservoir will also create valuable wildlife habitats, enhancing biodiversity and supporting the local ecosystem."
Richard Walsh Senior Project Manager
Now that the main structure concrete works have been completed, earthworks have commenced on site. This will see the team bring over 60,000m3 of imported materials to site, which will be used to construct a new embankment to form part of the impoundment reservoir.
Learn more about the scheme by accessing The Flood Hub: https://thefloodhub.co.uk/rochdale-and-littleborough/
