Wrangle Pumping Station
The Board have successfully completed the replacement of Wrangle pumping station. The original pumping station was built in 1959 and was at increasing risk of failure due to outdated components and structural defects. The £5.8m construction project was funded by FCERM Grant in Aid and provides flood protection to approximately 143 properties and over 2,000ha of Grade 1 agricultural land.
The new pumping station has a capacity of 2,600 l/s and is located on the East Lincolnshire coast near Boston, draining a low lying catchment protected by a sea bank. It discharges to the The Wash, an intertidal saltmarsh with protected environmental designations providing valuable wetland habitat for migrating and breeding birds.
The Board led the project as Client and Stantec UK were engaged as consultant from the outset for investigations, design, consents and project management. Jackson Civil Engineering (JCE) were the Principal Contractor for the 16-month construction programme and Aquatic Control Engineering (ACE) provided the pumps and controls equipment with support from Paktronic and Smiths Electrical.
Twin 2m diameter screw pumps were installed and manufactured in a durable composite material by Fish Flow Innovations in the Netherlands and were selected for their innovative fish friendly design which encapsulates and fixes the screw within a tube, minimising the risk of harm. The inlet and discharge arrangements were designed with input from the Environment Agency Fisheries team to optimise the safe passage of eels through the system, and a separate elver pass was provided to allow juvenile eel migrating from the sea to bypass the pumping station to the inland drainage network. These features will open up approximately 10km of inland watercourses as new eel habitat.
The new pumps are fitted with variable speed drives and a telemetry system will allow greater control of water levels and a more energy efficient pumping regime. This level of control is beneficial in meeting the ever-growing challenges of balancing flood risk management.
A solar panel installation on the control building roof provides a source of renewable energy with battery storage and export capability. Electric vehicle chargers have been installed in the new compound to further support the Board’s sustainability goals.
Project delivery faced two key constraints: the potential environmental impacts during construction and the foundations required for the very soft ground conditions. Stantec designed the structure to utilise steel sheet piles for the dual purpose of foundations and to form a watertight cofferdam which allowed excavation to progress through the sea bank while maintaining flood defence integrity. Steel sheet piles up to 22m long had to be driven through deep soft silt and into the underlying stiff clay to provide sufficient load bearing capacity. The cofferdam was designed with a 30° turn which allowed the inlet to better align with the main incoming drain whilst ensuring that the outfall is perpendicular to the sea bank. This introduced an added level of complexity to the pile installation which was time constrained by the desire to minimise disturbance to bird habitat. Pile installation was successfully achieved to the design depths and alignments with a combination of initial vibratory driving and then impact hammer. This noisy activity was carefully programmed between birds nesting during spring and migrating birds visiting the saltmarsh to feed during winter.
The project commenced following the 2023 bird nesting season with the sheet piling works completed ahead of the 2023 overwintering bird season. Less intrusive works progressed through the Winter and into the following Spring with various environmental mitigations implemented in accordance with the Habitat Regulations Assessment (HRA) and accompanying Construction Environmental Management Plan (CEMP).
The pump selection, hydraulics and overall design was developed with a focus on sustainability, mindful that the proportion of whole life carbon generated by the project would mostly be associated with operation rather than the construction. The pumps have a long expected service life and are designed to operate at a high level of efficiency with smart controls to optimise running times.
A bespoke control building was positioned on top of the structure to minimise the overall footprint, avoiding the need for separate deep foundations, and to keep electrical equipment resilient to extreme flooding. A Landustrie weed screen with automatic rake was installed by ACE across the inlet and the pumping station was fitted with a telemetry system by Lee-Dickens including multiple CCTV cameras. This allows the IDB to monitor and control the pumping station from their offices and on mobile devices.
Building the coffer dam
Installing the Archimedes screw pumps