- 17th May 2022
- Posted by: Laura O'Connell
- Category: Projects
Location: South Ferriby, North Lincolnshire Client: Environment Agency
In response to a tidal surge in December 2013, which resulted in £50m worth of flood damage, including 129 residential properties, the Environment Agency commissioned our strategic partner JBA Bentley at South Ferriby to protect a total of 150 residential properties – plus a large CEMEX cement factory – from future potential tidal flooding from the River Humber. Close collaboration with our Environmental team at JBA Consulting was vital to ensure construction was successfully executed in such a way as to prevent any disturbance to the local natural environment, including protected species.
The Humber Estuary is recognised as one of the most important estuaries in Europe for wildlife and is designated as a site of nature conservation importance under national and international legislation. The area around South Ferriby is particularly important for bird species including (but not limited to) avocet, knot and shelduck. The Scheme area and its wider surrounding landscape were found to support a number of protected species including water vole, Daubenton’s bat, great crested newt and barn owl.
Sustainability was at the heart of this scheme, combining flood protection with innovative carbon reduction in a highly environmentally sensitive area. We designed and constructed approximately 2.7km of flood embankments, 200m of sheet piled walls, 150m of reinforced concrete flood walls plus the installation of a large 13m wide flood gate and, demountable flood defences across the sluice and the strengthening of existing defences.
Close collaboration with CEMEX saw 240,000 tonnes of clay supplied for the embankments from their on-site quarry as their contribution to the works. The clay was quarried less than two miles from the embankment and eliminated the need for import (which would have required a 100-mile round trip). Instead, 240,000 tonnes made a maximum round trip of 5.4km, with some journeys via conveyor. 3D modelling enabled exact required volumes to be calculated, to reduce material waste. This approach significantly reduced the scheme’s carbon footprint by 10,000t CO2e.
The Humber Estuary is a designated Special Protection Area (SPA), Ramsar and a Site of Special Scientific Interest (SSSI): much of the works had the potential to disturb internationally designated important birds and other species such as the protected Daubenton’s Bat, whose roost was within the sluice. Close collaboration with our environmental specialists and Natural England ensured construction was successfully executed in such a way as to prevent any disturbance.
Mitigation measures in relation to habitats and species included:
- Design and timing of works to avoid impacts on Humber Estuary SPA and Ramsar designated bird species
- Reinstatement and creation of habitats to mitigate habitat loss
- Installation of a new replacement barn owl nest box to mitigate the temporary closure of the existing one
- Precautionary working under a Natural England low impact licence for great crested newt (GCN)
- Water vole displacement and habitat enhancement
- Creation of a ditch specifically for water vole use
- Timing of works at South Ferriby Sluice to avoid Daubenton’s bat maternity roost
- Precautionary working method statements to prevent damage to reptiles, and removal of vegetation to take place outside of the breeding bird season
To compensate for trees that were felled to facilitate construction, we committed to replanting three new trees for each removed, creating a community woodland.
Rebuilding the community’s trust in the Environment Agency was the key to delivering a successful project with greater than 50% partnership contributions via Grant in Aid as opposed to public funding.
The project not only delivered in providing vital flood protection for residential and commercial properties, but it did so with cost and carbon savings, on programme, with minimal environmental impact and whilst helping to rebuild community trust in the client.
Since completion, the scheme has enjoyed industry recognition at the Green Apple, ICE Yorkshire & Humber and national CECA Awards and was recently ‘officially opened’ at a ceremony attended by Sir James Bevan, Chief Executive of the Environment Agency.
From a Client’s perspective, trust and pragmatism were key to achieving what we did at South Ferriby. Thank you JBA Bentley, for your collaboration and assessment of risk, cost and programme as we reviewed project viability and latterly made changes to the scope to deliver better outcomes. Without that trust, it would have been very difficult to make some of the key decisions that made this project a success.
Nick Lupton, Environment Agency Project Executive.