Sainsbury's Alsager
Sainsbury’s Alsager River Daylighting and Trash Screen
Client: Sainsbury’s Stores Limited and Basebuild Services
Status: Complete 2025
Services
Flood Risk Services
- Flood Risk Assessment (FRA)
- Sustainable Drainage Strategy
- Flood Defence (Mitigation) Strategy
- Flood Investigation
- Hydrology & Hydraulic Modelling
- Flood Emergency Plan
- Basement Impact Assessment (BIA)
- Groundwater Flooding
- Expert Witness
Environmental Services
- Nutrient Neutrality
- Flow & Water Quality Monitoring & Sampling
- River Geomorphological Survey & Assessment
- Water Framework Directive (WFD) Assessment
- Water Resources Assessment
- Environmental Impact Assessment (EIA)
- Air Quality Assessment (AQA)
- Catchment Management Plans
- Environmental Permits, Licences & Consents
- Expert Witness
Engineering Services
- Sewerage Design
- Sustainable Drainage Systems (SuDS) Design
- Landscape Amenity & Sport Facility Drainage
- Earthworks Design
- River Design
- Roads & Driveways
- Expert Witness
Project details
A significant amount of effort and research was required in order to match the real-world flooding observations with the model results in order to give confidence to the client, the community, the Local Planning Authority, the Highways Authority and the Lead Local Flood Authority and to understand the particular special circumstances which lead to flooding of the road and the residential properties.
The modelling identified that the problem was to do with the inlet to a large culvert becoming blocked, and in order to address this we had to rebuild the inlet to the culvert on a live river. Technically this exercise was extremely difficult. The culvert was at a depth of between 4m and 7m below ground level, and immediately adjacent to the highway, so any excavation would have a potential risk of collapse in the highway.
Ground conditions were challenging and it was not possible to use traditional methods like sheet pilest was essential to ensure that the river did not become polluted during construction, even in the event of flooding.
Our solution was to keep the river flowing inside the culvert throughout construction of the new inlet, river approach and trash screen. The final stage of the exercise was to cut the culvert and lift it out of the excavation so that the river could flow into the new culvert inlet. We worked with the groundworker and structural engineer to design the sequencing of the construction to ensure that the project went smoothly.