A six-week programme of works for a £3.87m flood mitigation project, at Wrangle in East Lincolnshire, has seen impacts minimised at a Site of Special Scientific Interest (SSSI), thanks to the considered sheet pile installation approach suggested by Sheet Piling UK.
In August and September 2023, we undertook sheet pile installation on behalf of contractor, Jackson Civil Engineering, and client Witham Fourth District Internal Drainage Board, to ensure the effective replacement of a 1976 pumping station and better flood defences.
The aim was to increase the protection of 2169 hectares of catchment area, within which there are 117 residential homes and 26 commercial properties. Furthermore, the surrounding arable land is nationally important from a food production point of view, making flood resilience even more paramount.
The project was designed by Stantec, following the provision of funding by the DEFRA Flood Risk Grant in Aid. It involves the incorporation of an innovative Archimedean screw pump, enclosed in a tube, which will ensure safe passage for eels and fish entering the pump.
Having worked closely with Jackson Civil Engineering during the pre-construction stage of this project and absorbed all relevant information, Sheet Piling UK suggested an alternative approach to the original sheet piling plan.
To deliver cost and programme benefits and also mitigate the impacts on wildlife and biodiversity, our hugely experienced in-house design team proposed a hybrid approach to the sheet pile installation works.
Those works required us to facilitate the new pumping station’s construction, by building and installing a temporary cofferdam, formed from 88 pairs of Arcelor Mittal AZ48-700 sheet piles, of varying lengths between 18m and 22m. This had to be installed on the existing Delph watercourse, which provides flood protection in the surrounding area.
Our hybrid installation suggestion took into account the strict constraints applying to these works. The existing earth flood bund could not be disturbed or removed during installation works and the cofferdam needed to cross this. The highly sensitive environment - in a SSSI - also dictated a sympathetic approach.
To achieve all objectives the hybrid plan adopted first saw us installing sheet piles using an ABI TM22 telescopic leader rig with c/w vibratory hammer and a 70Te service crane. These pieces of equipment were deployed in an area where we could construct a level platform over a diverted section of The Delph watercourse.
The second part of the installation process involved the use of a 350Te crawler crane with PVE38M vibratory hammer. Here, we used conventional piling methods, at the location at which the sheet piling needed to straddle the existing flood defences.
Works were carried out in ground conditions that featured 13 metres of tidal deposits and, below these, very stiff clay. Sheet piles were vibrated to refusal point and then impact driven into the stiff clay, using a BSP CX85 impact hammer.
This water management project has been carried out by Sheet Piling UK with more cost and programme efficiency than our partners had anticipated, again proving the huge added value that our in house design team can bring to projects.
If you have a flood mitigation project requiring our sheet piling expertise, or any other type of sheet piling project on land or in a marine environment, please get in touch with us, by calling 01772 794141.
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