Supply Chain - River & Coastal Flood Protection - Weirs

Norton and Raveningham Pumping Stations are located near the village of Reedham within the Broads. The Broads comprises of a number of nationally and internationally designated nature conservation sites. They form Britain’s largest protected wetland supporting more than a quarter of our rarest flora and fauna. The Broads are a man-made landscape with the river system perched above the surrounding floodplain, contained within earth flood defence embankments. The only way to manage water levels is to pump excess water from the surrounding floodplain up into the river. History

Faden’s 1797 map of Norfolk shows numerous wind pumps scattered around the Broads. The wind pumps helped drain the marshland and worked in combination with gravity drainage during low tides. However, marshland ground levels reduced due to shrinkage of the peat and with rising sea levels the gravity drainage became increasingly ineffective. The traditional wind pumps were replaced by more reliable steam, diesel and more recently electric pumps.

Norton Pumping Station, constructed in 1945, had suffered major structural failure and required urgent replacement. Funding was secured in January 2022 to consolidate the Norton and Raveningham pumped catchments and build a single replacement pumping station at Norton.

The design and Early Supplier Engagement (ESE) contracts were awarded in April 2022 with the detailed design completed in May 2023. The main construction works commenced in August 2023 with the new pumping station commissioned in August 2024.

The Waveney, Lower Yare & Lothingland Internal Drainage Board (IDB) are part of the Water Management Alliance, a group of seven IDB’s which includes the Broads IDB. Together they operate 55 pumping stations, managing water levels within 22,000 hectares of low-lying land within the Broads, preventing permanent inundation.

[caption id="attachment_25574" align="alignnone" width="1200"] Excavation of flood embankment following installation of temporary piling - Courtesy of Water Management Alliance[/caption] Statutory requirement

The replacement station manages water levels within 788 hectares of sensitive conservation grazing and agricultural land. This land provides important habitat for populations of qualifying species associated with designated nature conservation sites within the Broads. These are termed ‘functional habitats’ and are critical to maintaining Favourable Conservation Status by maximising the ecological potential and enabling the habitats and species, associated with the designated sites, to thrive.

Without pumping, the catchment would fill with water causing flooding and permanent damage to the habitats and key qualifying species such as rare aquatic plants found within the dykes, diverse flora, rare molluscs and breeding and over-wintering birds.

Failure of the pumped system would be a breach of statutory environmental obligations to manage water levels within functionally linked habitat. The result would be uncontrolled flooding of property, agricultural land, National Rail infrastructure, public highways, and utility infrastructure. This would also have serious repercussions for recreation and tourism which generate hundreds of millions of pounds annually for the local economy.

Climate resilience

Rising sea levels and a changing climate make the Broads increasingly vulnerable. The project aligns with the objectives of the Broadlands Futures Initiative, a partnership investigating and establishing future flood risk management.

Climate resilience is improved with a 50% increase in duty capacity accounting for climate change predictions for intense rainfall events. This also ensures the system can better cope with overtopping events, which are likely to become more frequent. Taking into consideration future adaptive pathways to mitigate climate change, the station has the capability to adjust water levels allowing for changes in land management such as paludiculture and wetland habitat creation.

The power, control and motors are elevated above the flood level to ensure continued operation during a flood event.

[caption id="attachment_25566" align="alignnone" width="1200"] Archimedes screw pump being lifted into position - Courtesy of Water Management Alliance[/caption] Fish-friendly screw pump

The screw pump is one of the oldest positive displacement pumps dating back over 2,000 years. The design by Fish Flow Innovations removes the leakage path by fixing the rotating screw augers to the outside casing, resulting in enhanced efficiency and the most fish friendly pump available. The screw is made from GRP composite material which does not corrode and is UV stable providing an expected design life of 80 years.

The replacement station features two Archimedes screw pumps operating in a duty/assist configuration. The 2m diameter screws lift water 4.5m over the flood embankment, and using variable frequency drives, are capable of delivering variable flow rates between 0.3 to 0.75m3/second.

Working closely with National Fisheries specialists, to minimise external stresses on fish and eels passing through the station, a number of initiatives have been incorporated including:

Using fish friendly lightweight HDPE tidal flaps; a cambered outfall chamber ensuring water is conveyed towards the flap valve even during minimum flows. Setting the invert level of the outlet chamber below low water. Remedial measures were required to fit an impact protector to the legs supporting the pump motor and gearbox.

The lessons learnt report has been shared to prevent this issue on future projects using this arrangement.

As part of a national research project, a trial will be undertaken using sensor loaded drone fish and live specimens which will be passed through the station and recovered to confirm fish/eel friendliness.

[caption id="attachment_25569" align="alignnone" width="1200"] The 2m diameter Archimedes screw pumps with combined capacity of 1.5m3/second - Courtesy of Water Management Alliance[/caption] Funding challenges & cost savings efficiencies

Prior to awarding the main construction contract, high inflation significantly increased costs. To help mitigate this, several value engineering opportunities were implemented resulting in £1.1m in cost savings.

These included:

Challenging maintenance access arrangements. Carrying out further investigations to remove the requirement to replace anchored sheet piled retaining wall. Taking a proportionate risk-based decision not to provide erosion protection on a new watercourse and removing covers from the screw pumps. Keeping the existing stations remained operational up until commissioning, removing the requirement for expensive over-pumping.

Significant cost, capital and operational carbon savings have been achieved by combining the Norton and Raveningham catchments and building a single replacement pumping station. This also optimises available water resource during drought periods, improving wetland sequestering capabilities.

Early Supplier Engagement during detailed design ensured the design represented the least cost and carbon option. This included an early decision to maximise the use of steelwork and minimise concrete. Steel coping provides support for the trash rake minimising works on site, speeding up construction and reducing construction carbon.

Additional funding was secured to account for inflationary increases which could not be mitigated through project efficiencies. This enabled the £5.2m NEC4 Engineering and Construction Contract to be awarded to BAM Nuttall Ltd in June 2023.

IDB’s are risk management authorities and can apply for Grant In Aid (GiA) funding for Flood & Coastal Erosions Risk Management projects. The partnership funding calculator attracted 43% Flood Defence GiA with the remaining supplemented by Environmental Statutory Allowance (ESA) funding. ESA funding was introduced in 2021 for projects required to meet statutory environmental obligations.

[caption id="attachment_25572" align="alignnone" width="1200"] Aerial view of works nearing completion - Courtesy of Water Management Alliance[/caption] Norton & Raveningham Pumping Station: Supply chain - key participants Client: The Waveney, Lower Yare & Lothingland Internal Drainage Board IDB) Principal designer & supervisor: Jacobs UK Ltd Main contractor: BAM Nuttall Ltd ECC project & cost manager: Turner & Townsend Condition surveys: Rossi Long Consulting Ltd Temporary works/shoring: Groundforce Shorco Dewatering system: Dewatering Services Ltd Kiosk/transformer piling: Van Elle Piling equipment: Watson & Hillhouse Ltd Directional drilling: SW Drilling Ltd Steelwork package: Fussey Engineering Ltd MEICA: Max Wright Ltd Telemetry: Lee Dickens Ltd Archimedes screw pump, trash system, & flap valves/stop logs: Aquatic Control Engineering (ACE) Archimedes screw pump: Fish Flow Innovations Trash system: Landustrie Traffic Management: TMO Traffic Highways Ltd Scaffolding: Ideal Scaffolding (East Anglia) Ltd Shear studs: SWUK Steel Decking Ltd Resin injection: Restek-Uk Ltd Landscaping: Dobson Enviro LLP Fencing: Dew Fencing Ltd Demolition: Clark Demolition Company Ltd Wildlife mitigation

A carefully planned and implemented water vole mitigation strategy ensured overall net gain of water vole habitat by improving 130m of watercourse.

Reptile mitigation required hibernaculum’s and reptile fencing to be constructed prior to successfully translocating reptiles found within the working area. The old pumping station roof had bat roost potential requiring a ‘soft’ strip of the tiles prior to demolition.

Norton Raveningham Pumping Station Replacement Project

Ground conditions

The ground is relatively weak (soft silt/clay/peat) up to 15m below ground level, requiring a boxed piled cofferdam with pile lengths up to 17.5m. The complexity of the ground and groundwater conditions and the need for multiple level propping during construction, resulted in Plaxis 2D numerical modelling being required to confirm the global stability, displacement and internal forces in the structure forming the pumping station.

Prior to the excavation of the pump chamber, to control the pressure head within the Crag Group, temporary dewatering and pressure relief wells were installed into the sand and gravels. Piezometers within the pump chamber monitored groundwater pressure during the dewatering operations.

Vibro-piling was selected to minimise damage of adjacent sensitive receptors. Disturbance to wintering birds was avoided by monitoring cold weather and imposing restrictions on piling in the event of a cold spell.

Solutions & innovations

An innovative cloud-based telemetry system allows remote real-time monitoring and control of the station. The system records trends and numerous statistics, including the volume of water pumped providing a valuable record for future water resource planning.

An automatic greasing system on the lower bearing of the screw avoids the need to de-water and enter the inlet chamber. The motor and gearbox are easily accessible for future replacement avoiding complex lifting operations. The materials selected for the civils structure requires no treatment or future intervention.

The control kiosk has a black timber effect finish to mimic the traditional agricultural buildings helping minimise the impact on the local landscape. The external lighting, only required during urgent unplanned maintenance operations, has been designed to meet Dark Sky requirements and are bat friendly.

[caption id="attachment_25570" align="alignnone" width="1200"] Norton Pumping Station provides protection to 788 ha of conservation grazing marshland - Courtesy of Water Management Alliance[/caption] Community engagement

Proactive engagement has minimised disruption and kept the local community fully informed of how the project benefits and protects the local community.

The contractor looked to maximise a circular economy approach and created a modest site set up to complement and respect the sensitive environment. The site compound included two electric vehicle chargers, made available to close community neighbours for free as a gesture of goodwill.

The project team carefully planned and delivered activities relating to 13 government National Social Value Themes designed to boost Social and Local Economic Value (SLEV). These have included: site visits from the parish council and local schools, apprenticeship talks and attendance at careers fairs, hosting a T-level work-placement student and an apprentice, donating a community bench and undertaking repairs at the local parish church, and maximising local employment and supply chain spend, where possible.

The team worked with all the surrounding schools to educate the children about the important role pumping stations play in the local landscape. A STEM (science, technology, engineering, and mathematics) exercise and competition tasked Thurlton Primary School to design a pumping station of the future.

The design considered how it might look, work, improve the local environment and nature. The winning entry had the privilege of naming the pumps and starting them during the opening ceremony, further embedding the project’s social value into the local community.

[caption id="attachment_25567" align="alignnone" width="1200"] (left) Thurlton Primary School winning entry for pumping station of the future and (right) Thurlton Primary School site visit - Courtesy of Water Management Alliance[/caption] Awards

The project was awarded the Large Project of the Year at the Institution of Civil Engineers awards in September 2024 in recognition of its importance to enhancing the regions resilience to climate change and protecting vital habitats and communities. The judges were particularly impressed by the project team’s outstanding collaboration during very complex operations, often with limited historic data and tight time constraints.

Conclusion

This project is the first to be delivered as part of a programme that will continue to protect the Norfolk and Suffolk Broads from flooding and help address the challenges associated with climate change.

The Broads IDB secured funding to deliver further replacement pumping stations on the River Thurne, with construction works commencing in 2025.

The Don Regulators comprise three strategically important regulator gates on the River Rother that are owned, operated and maintained by the Environment Agency (EA). The purpose of the regulators is to reduce the risk of flooding to settlements within the Don catchment, by attenuating flows in the River Rother. JBA-Bentley, in a joint venture relationship, are working on the replacement of the three regulators, each being at a different stage of design or construction. Figure 1 illustrates the locations of the three sites. Canklow The Canklow Regulator is the furthest downstream of the three Regulators, approximately 3.5km upstream from the confluence of the River Rother and the River Don at Rotherham. It is located approximately 50m downstream of the A630 Rotherway near junction 33 of the M1. The existing structure, consists of a single electrically powered vertical lifting sluice gate operated by an electric wire rope hoist, comprising drive motor gearbox assembly and cross shaft with integral rope drums and support bearings. To improve resilience and the operation and maintenance of the asset, JBA-Bentley were required to provide a new guillotine gate and associated MEICA and civils infrastructure. The Canklow Regulator is usually the first of the three gates to operate and is activated when trigger levels are reached elsewhere within the catchment. Operating the regulators on the Rother during a significant flood event allows the flood peak on the river to be delayed until the peak on the River Don has passed Rotherham and prevents flooding from the Don. Lowering the gate at Canklow can hold back over 1.5 Mm3 of flood water across seven washlands. [caption id="" align="alignnone" width="1200"] The existing Canklow regulator gate - Courtesy of JBA-Bentley[/caption] Canklow is currently in the detailed design phase of works. Alongside the gate design some additional civil engineering works are required. This includes some remedial works to the existing sheet piled channel walls including new anchors, a new crane pad to be utilised during construction and to facilitate future gate maintenance as well as the substructure for the new motor control centre (MCC). One of the key constraints of the site are high voltage overheads; therefore, the crane pad location and the siting of the EA’s compound with MCC had to carefully considered. To assist in undertaking the design and developing the business case for the project, 3D survey was undertaken to create a 3D Matterport tour of the site. It allows the user to quickly navigate around the site and view all the infrastructure remotely. This proved particularly useful during the pandemic when restrictions were in place and site visits were limited. Woodhouse Mill The Woodhouse Mill Regulator is located on the Rother between Canklow and Meadowgate, upstream of the B6200 Retford Road. It retains water using a single electrically powered vertical lifting gate. It is operated by an electric wire rope hoist, comprising a central drive motor and gearbox assembly and half shafts, with spur and pinion driven, counterweight assisted, rope drums and support bearings. The proposal at this site is to decommission the current regulator and replace this with a passive solution, such as a baffle or orifice plate which spans the width of the channel, to further utilise some of the upstream storage in the washlands. JBA-Bentley are currently undertaking modelling of options for Woodhouse Mill regulator to inform the next phase of the project and the viability of the proposed solution. [caption id="" align="alignnone" width="1200"] The existing Woodhouse Mill regulator gate - Courtesy of JBA-Bentley[/caption] Meadowgate The Meadowgate Regulator is located within the Rother Valley Country Park. The existing regulator consisted of a single fish belly bottom hinged tilting gate, operated by a single electrically powered hydraulic ram. As per Canklow, the new gate will be a top-down vertical control gate improving resilience of the structure; as per the model above. When the new gate is lowered, water levels in the Rother rise and begin to spill into the washlands that are located within the Rother Valley Country Park, which can retain approximately 1.5 Mm3. Temporary set up The civils elements of the scheme have included demolishing the existing buildings and installing new control building. To ensure the gate remained operational during this time a temporary control centre was established during the early part of the scheme; once the gate has been commissioned this will be removed from site. River Don Regulators: Supply chain - key participants Project delivery: JBA-Bentley JV JBA Consulting JN Bentley Principal designer: Callsafe Services Ltd Gate design: Aquatic Control Engineering (ACE) Electrical Installations: IMAC Ltd Building design: JP Chick & Partners Building design: Peter Wells Architects Supporting ECC Supervisor with new gate & associated equipment: KGAL Consulting Engineers Ltd Precast fish pass tiles: Craven Concrete Ltd In situ concrete works : Bells Construction Ltd Metalwork fabrications: Fabtek Green roof: ABG Geosynthetics Ltd [caption id="" align="alignnone" width="1200"] Model of the new Meadowgate regulator - Courtesy of JBA-Bentley[/caption] HAZOP Working closely with the Environment Agency’s Operational and Maintenance teams the gate design and associated infrastructure has been developed to ensure it allows safe access and operation; a Hazard & Operational Study (HAZOP) was undertaken during the early design stages to ensure all requirements were included. Full channel fish pass By removing the bottom hinged tilting gate, there was an opportunity to improve fish passage on the River Rother. Currently, there is a stilling basin immediately downstream of the gate approximately 40m in length, 12m wide and up to 3m deep at the upstream end. Through design development a unique full channel fish pass has been developed which removes the stilling basin by infilling to grade out the bed levels before installing reinforced concrete fish tiles with upstands of varying heights. Computational fluid dynamics (CFD) modelling of fish pass Due to the engineered nature of the channel in this location and the operation of the gate, the fish pass is required to withstand high velocity flows up to 8m/s during extreme events. This proved challenging to the more traditional fish pass construction leading to a heavily engineered solution. [caption id="" align="alignnone" width="1200"] (left) Screenshot of fish pass model - Courtesy of JBA-Bentley, (top right) fish tile mould - Courtesy of Craven Concrete Ltd, and (bottom right) the Meadowgate site - Courtesy of JBA-Bentley[/caption] To refine the design and prove passability for a range of species, the proposed arrangement was modelled using CFD. This allowed the upstand heights to be adjusted to provide the optimum depth and velocities through the range of design flows. Fish pass tiles Once the height and arrangement of the upstands was agreed with the Environment Agency’s National Fish Pass Panel, the structural design of the fish pass tiles began. Each tile measures 2.5m x 2.0m and weigh 4 tonnes; therefore, the design not only had to withstand hydrodynamic forces but also the lifting requirements for construction. In total, 80 fish pass tiles will be manufactured and placed into the channel, within a dry working area. [caption id="" align="alignnone" width="1200"] Precast fish pass tiles - Courtesy of Craven Concrete Ltd[/caption] Temporary works consideration To allow the fish pass to be installed within a dry area of channel, the full river channel needs to be dewatered. This will be achieved by installing an upstream dam and fluming the flow through the working area. The decision to install precast units reduces the risks of in-channel pours and to reduce programme duration for the in-channel works. Summary The replacement Don Regulators will protect Rotherham and the surrounding area from flooding, improve resilience, and ensure the gates can be operated as required both now and as we see the effects of climate change.

Over recent years, Derby’s city centre has suffered historic river and surface water flooding. In partnership with the Environment Agency, Derby City Council sponsored the £8m Mill Fleam Pumping Station project; a key piece of flood defence infrastructure that barriers off and then over-pumps Markeaton Brook when the River Derwent is in flood. In November 2021, JBA-Bentley, a joint venture between JBA Consulting and JN Bentley Ltd, was awarded a contract to design and construct the pumping station, with a completion date set for April 2023; after just 15 months. Background to the project The site is within a wooded public park adjacent to the city centre. Bats, birds, aquatic life, third-party infrastructure and high-value trees have all been carefully considered and impacts mitigated during the works. Resilience has been considered in all aspects of operation to ensure the station will remain always ready to operate. Funding streams required the station to be designed, procured, constructed and commissioned within 15-months, including planning and stakeholder approvals. To meet these challenges several innovations have been implemented: 3D and augmented reality improved resource use and safety. Off-site and factory manufactured products reduced site-time and enhanced quality. Collaborative design, commissioning, construction and client teams ensured the right solution at the right time. [caption id="" align="alignnone" width="1200"] (top left) Modelling of the scheme included the main temporary works required, (top right) a fish refuge was part of habitat improvements implemented, (bottom left) in-channel works continued through the winter, and (bottom right) buildings were prefabricated and delivered to site pre-commissioned - Courtesy of JBA-Bentley[/caption] Programme management As with all construction projects at this time, Brexit, COVID-19 and the war in Ukraine significantly disrupted the global supply chains and created huge uncertainly. Timely supply of equipment and inflationary uncertainty were significant risks to the project. The team’s procurement strategy centred around early, continued and proactive engagement with the supply chain to minimise impacts. Weekly coordination and update meetings were held with key suppliers. Miro visual planning software was used with each supplier to understand key risk areas, available float and interfaces between activities/disciplines. Potential blockers to progress were identified and owners assigned to manage and mitigate the impact; for example when PLC component lead-time was unacceptably fluctuating an alternative product was specified and then procured. At each key stage of procurement and manufacturing, face-to-face updates and factory visits confirmed status and progress. This resulted in amendments to initial plans and supply chains - however, overall, all critical components were assembled on programme. Due to funding requirements the programme for design and delivery was restrictive. Programme management was crucial to ensure timely delivery and commissioning. Our three levels of programming approach ensured a realistic plan was always in place, with appropriate resources allocated. Innovation 3D-printed concrete: Modern methods of construction and off-site manufacture were implemented where feasible throughout. 3D-printed concrete was used for semi-structural applications including ground bearing access stairs and sheet pile cladding/capping panels. The scheme has been a 3D-printed concrete pathfinder project, where learning and development for future construction applications of the technology has been captured. [caption id="" align="alignnone" width="1200"] (left) 3D concrete printing and (right) installation of steps - Courtesy of JBA-Bentley[/caption] The profile, mix design and finishing of each element was chosen to suit each product location and optimise production. Should additional or duplicate components be required, all printing files and software programming is available. Working with specialist suppliers, the elements were printed and cured in a factory-controlled environment (humidity, temperature etc), and delivered to site ready for immediate installation - saving time, reducing waste, ensuring quality and reducing embodied carbon over baseline solutions. Augmented reality (AR): AR software is cutting-edge in construction, taking gaming-based software to provide enhanced visualisation of site and otherwise unseen features (i.e. below-ground assets). The site is crossed by numerous below-ground services and the works interact with several existing below-ground structures. Generally, the works were designed and methodologies developed to not affect the existing equipment. However, the location of apparatus and intrusive nature of the works presented potential risk to delivery teams. AR was trialled and then used to assist with planning site operations and communicating buried service risks to site teams. The software geolocates and then provides an enhanced view of the existing site in photographic quality with below-ground services and new structures overlaid to essentially make the ground transparent on screen. AR minimised risk to delivery personnel and third-party assets, contributing to the excellent safety record. 4D-modelling and programming: The constrained nature of site made detailed and thorough planning of activities and phasing critical. Parts of the works required numerous engineering disciplines to operate in overlapping/interfacing areas. Early in the project the use of 4D-modelling was identified as essential to ensure safe and efficient delivery. [caption id="" align="alignnone" width="1200"] Extract from Synchro 4D planning software - Courtesy of JBA-Bentley[/caption] The design and construction team opted for Synchro 4D-planning software, which sees the 3D digital model and works programme integrated into the platform. The software then produces a sequence animation of structures and assets being installed. Including the most significant items of temporary works into the model and software allowed teams to understand potential clashes of working space and access and improve resource planning to maximise efficiency. Key challenges Flow presentation: The pumping station will only operate during periods of high flows on the River Derwent (approximately three events per year expected). As the majority of flows under normal rainfall events will pass along the channel, the pumping station is built off the main channel line. To minimise the overall site footprint, flows will turn into the pumping station and then rising mains turn again to the outlet. Bespoke-formed suction intakes are used to ensure what could be uneven flow presentation to the pumps during high flows will not negatively affect pump capacity or efficiency. Existing siphon pipes: The site crossed by a deep sewer. Twin-siphon pipes pass under channel coinciding with the new flood walls. The ground conditions, topography and proximity of the highway determined steel sheet-piles as the most effective structure for the new flood walls. Design details and installation methodology for the sheet-piled walls were agreed with the outside-party engineer from Severn Trent. Details were set in terms of proximity to assets, vibration limits, monitoring and contingency. The pile line steps-up over the siphon pipes at both crossing locations. A waler beam then distributes loads into the adjacent higher capacity piles to support the wall. [caption id="" align="alignnone" width="1200"] Pile installation methods suit ecology and service locations - Courtesy of JBA-Bentley[/caption] Ecology and pile installation: A large colony of Daubenton’s bats is known to live in the upstream culvert, using the downstream watercourse within site for feeding. While the works did not directly affect the colony, all works near the culvert were approved by a licensed bat-worker. The approved methodology included assessment of anticipated noise/vibration limits for pile installation. Assessment considered proximity to sensitive receptors, ground conditions, equipment used and historic data for similar installations. Generally traditional displacement hammer piling was used; areas closer to the culvert were installed with an excavator-mounted MOVAX attachment. Watching briefs and monitoring confirmed no bat disturbance. Combining temporary and permanent works: The baseline solution included a full structural concrete wet-well. Typically this would be constructed using a temporary sheet-pile cofferdam and framing arrangement. Use of carbon modelling tools and programme scrutiny identified significant carbon and critical path savings by value engineering this structure. Working across disciplines (hydraulic, geotechnical, structural) and with the client, the temporary works were incorporated into the permanent structure, with the otherwise temporary steel sheet piles made permanent and vertical structural concrete omitted. Corrosion control, flow presentation to the pumps and long-term geotechnical stability were all analysed and engineered to realise the benefit. Over 17-tonnes of carbon were saved, and four-weeks from the critical path. [caption id="" align="alignnone" width="1200"] Sheet piling incorporated into the permanent solution - Courtesy of JBA-Bentley[/caption] Mill Fleam Pumping Station: Supply chain - key participants Designer & delivery contractor: JBA-Bentley JV JBA Consulting JN Bentley Environmental clerk of works: Tetra Tech Sheet piling & anchors: Sheet Piling UK Concrete installation: Rebar Formworks Solutions 3D concrete printing: Weber Beamix Mitre gates & actuation system: Hunton Engineering Design Weedscreens & non-return valves: Aquatic Control Engineering (ACE) Pumps & canisters: Bedford Pumps Control panel & electrical installation: IMAC Ltd Containerised generator: A&M Generators GRP enclosure: NPS Engineering Group Pipework & fittings: Electrosteel Castings (UK) Ltd Metalwork: APT Marine Engineering Concrete supply: Tarmac H&S fall protection: J-Safe Ltd Landscaping & fencing: Leveret Contracting Carbon reduction and environmental management In operation the pumping station will be the most efficient of its type. High-efficiency pump motors coupled with variable frequency drives and intelligent control will ensure pump operation is optimised for all flow conditions. Carbon has been monitored and removed at each stage in the asset lifecycle; the table below summarises the most important embodied carbon savings: [caption id="" align="alignnone" width="1200"] Embodied carbon savings[/caption] As described above, the wet-well structure was reviewed and carbon modelling tools used to remove concrete from structures, and utilised structural steelwork where design life and flow management wouldn’t be adversely affected. Scrutiny of programme and early procurement of critical MEICA equipment allowed the phasing of works to be revised, and pumping station commissioned early. Bypassing flows using the pumping station then enabled reduction of the cofferdam arrangement and associated invert slabs. Winter working was inevitable; JBA-Bentley worked with specialist suppliers to review and challenge mix designs. A higher proportion of cement replacers were used than standard specified winter mixes in conjunction with site controls to ensure quality nor programme was affected. Concrete installation continued through winter with minimal cost increase while significantly reducing embodied carbon over baseline. There were a number of environmental enhancements including re-landscaping the surrounding parkland and a fish refuge to provide shelter for aquatic life in low and high-flows; enhancing habitats of the reach. Existing trees, vegetation and access pathways were replaced or improved. Over 75 new trees will be established, with bird and bat habitats improved. During the in-channel construction works, a ‘bubble curtain’ mitigated silt disturbance and managed fish passage. All site plant and equipment utilised hydrogenated vegetable oil (HVO) in place of traditional gas oil. Whilst more expensive, HVO significantly reduces CO2 emissions. Planning and communication The design, construction and commissioning Mill Fleam Pumping Station required a wide range of engineering expertise including geotechnical, civil, structural, hydraulic, mechanical, and electrical. Addition specialist consultant advice was required around planning permissions, ecology, fire risk, and landscaping. Effective coordination across these teams and disciplines was crucial to successful project delivery. The restrictive 15-month design and delivery programme required activities to be delivered simultaneously. Weekly collaborative workshops were held throughout the planning, design and continued into the delivery phases to ensure engineering disciplines effectively communicated design intent and interfaces were fully managed. Extensive and detailed live 3D digital modelling of the scheme enabled the coordination and clash detection between internal and external teams, always ensured a single point of reference and the latest information available to all. Early in the project common platforms/ software or compatible products were tested to ensure effective integration of modelling from all disciplines. Mill Fleam Pumping Station - Design, construction & innovation [video width="1920" height="1080" mp4="/wp-content/uploads/article_photos/2023/munio_mill_fleam_10.mp4"][/video] Introductory video to Mill Fleam Pumping Station - Courtesy of JBA-Bentley Safety management The project has an excellent safety record, borne out of great engagement from the team. All interventions (preventative, corrective or otherwise) are recorded to monitor for trends. At Mill Fleam Pumping Station, the positive intervention reporting rate was 3,447 per 100,000 hours worked, far in-excess of the minimum expected and organisational average across directly-employed and sub-contractor personnel. This demonstrates an excellent safety culture (company expectation is 1,550 per 100,000 hours). As well as great engagement, key to safety is planning. The use of off-site manufacture and digital tools reduced site hazards and enabled delivery teams to manage and then communicate risks. The 3D-model provided not only a digital twin of the permanent works but included main items of temporary works and plant. This allowed teams to plan positions of equipment, temporary phasing of installations and access routes/systems. Visualisation of methods and equipment in this way ensured the correct deployment of resource and equipment to deliver the works safely. Summary The contract was awarded to JBA-Bentley in November 2021; with design, planning submissions and procurement undertaken in early 2022. Site enabling works were undertaken in February 2022, and the main site works commenced in May. The main station works were completed and the pumps initially commissioned in December 2022. Site works were finalised in April 2023.

The Don Regulators comprise three regulator gates on the River Rother that are owned, operated, and maintained by the Environment Agency (EA). The purpose of the regulators is to reduce the risk of flooding to settlements within the River Don catchment by attenuating flows in the River Rother. JBA-Bentley has completed the design and installation of the first regulator gate. The detailed design of the second gate is currently being undertaken, while the third regulator is being modelled as part of the optioneering phase. In addition to the installation of the first regulator gate, a bespoke full-channel fish pass has been installed directly downstream to improve migratory fish passage. Meadowgate Regulator

The Meadowgate Regulator is located within the Rother Valley Country Park. The historic regulator consisted of a single fish belly bottom-hinged tilting gate, operated by a single electrically powered hydraulic ram.

[caption id="attachment_14798" align="alignnone" width="1200"] (left) location of the regulator gates and (right) the new Meadowgate top-down vertical control gate[/caption]

In 2023, JBA-Bentley replaced the gate with a top-down vertical control gate, improving the resilience of the structure. Alongside the regulator gate, a new control building and EA Office have been constructed. Both buildings have green roofs and EV charging. The gate was commissioned in February 2024 and is ready to operate during a flood event.

The gate is operated to ensure a maximum of 60m3/s forward flow is always maintained. When flows exceed 60m3/s the new gate is lowered and water levels in the Rother rise and begin to spill into the washlands located within the Rother Valley Country Park, which can retain approximately 1.5 million m3.

Meadowgate full channel fish pass

The removal of the bottom tilting gate provided an opportunity to improve fish passage on the River Rother through the installation of a unique full-channel width fish pass. This fish pass is designed with 4-tonne reinforced concrete ‘fish tiles’ featuring varied-height upstands supplied by Craven Concrete Ltd.

The tiles were designed with the aid of computational fluid dynamics modelling to ensure they influenced the nature of the flow to allow for varied fish species to migrate upstream while also withstanding hydrodynamic forces during extreme events. The fish species focused on are coarse fish, European eels, brown trout, large migratory salmonids, and lamprey.

The 40m long stilling basin has been removed by building up the existing concrete channel bed and grading out the levels to create a uniform slope. The ‘fish tiles’ have been laid onto the regraded channel. This is the first fish pass of its kind in the world.

[caption id="attachment_14802" align="alignnone" width="1200"] Precast concrete ‘fish tiles’ from Craven Concrete Ltd positioned in the channel - Courtesy of JBA-Bentley[/caption] Meadowgate temporary works solution: Syphon pumps & contingency planning

The fish pass installation required the full channel as a dry working area. To achieve this, an innovative syphon system, designed by Dutch water specialist Vanderkamp UK, was installed. The solution involved complex temporary works and contingency planning.

To form the upstream dam, the new regulator gate was dropped to bed level, allowing upstream water levels to build up. The gate was designed to operate this way; hence no further calculations were required. Four syphon intake pipes were installed upstream of the gate to divert up to 12m3/s of flow out of the channel for 115m, around the working area.

The syphons were primed using electric vacuum pumps which expelled all the air from the system to draw water through the pipes. By utilizing the existing gate and power supply, the syphons had a far lesser environmental impact than a typical cofferdam and over-pumping solution. The total embodied carbon associated with the syphon solution was 464 tons.

Due to the scale of the flows being diverted, the loads imposed on the riverbanks by the pipes when full were considerable. JBA-Bentley and Vanderkamp UK worked together to design a temporary support system involving ground-bearing improvements, steel and timber supports, and retaining structures. Checks were also carried out on the existing channel wall where the forces from the syphons acted upon it.

[caption id="attachment_14797" align="alignnone" width="1200"] (left) The dewatered channel and (right) ‘fish tile’ installation - Courtesy of JBA-Bentley[/caption]

In addition to work to ensure the stability of the syphons, an energy dissipation system was designed and installed at the syphon outlets to combat scour, and a bubble curtain was installed upstream to deter fish from entering the syphons. The installation of the system was done via a temporary crane pad. Due to the nature of the site and its space constraints, this was a challenging design. JBAB worked closely with the landowner, Rother Valley Country Park, to balance the desire to allow continual access into the park with ensuring the crane was safe to carry out the required lifts. To achieve this, the crane had to be placed in close proximity to the riverbank. Slope stability modelling and bearing capacity calculations were undertaken to ensure the crane could be operated safely.

Recent storm events have recorded flows higher than the syphon capacity. To manage the risk of this occurring during the programmed works, a contingency plan was developed.

The basis of the plan was developed from a bespoke JBA flow forecasting system, which forecasted the flow over a 2-day period. Using the data from the forecasting system, flow monitoring data provided by Vanderkamp UK, upstream gauge data, and the storage capacity of the washlands upstream of the gate, JBAB could make informed decisions on whether the gate needed to be raised to allow flow to pass forward.

This decision was made with the aid of hydraulic calculations and decision flow charts within the contingency plan, allowing for quick and effective decision-making, ensuring flood risk was not impacted upstream and the safety and well-being of the site team working in the channel was never put at risk.

[caption id="attachment_14801" align="alignnone" width="1200"] Syphon outlet - Courtesy of JBA-Bentley[/caption] Don Regulators: Supply chain - key participants Client: Environment Agency Project delivery: JBA-Bentley JV JBA Consulting JN Bentley Ltd Principal designer: Callsafe Services Ltd Gate design: Aquatic Control Engineering (ACE) Syphon design: Vanderkamp UK Electrical installations: IMAC Ltd Building design: JP Chick & Partners Building design: Peter Wells Architects Supporting ECC Supervisor with new gate & associated equipment: KGAL Consulting Engineers Ltd Precast fish pass tiles: Craven Concrete Ltd In situ concrete works: Bells Construction Ltd Metalwork fabrications: Fabtek Green roof: ABG Geosynthetics Ltd Canklow Regulator

The Canklow Regulator is the furthest downstream of the three Regulators, approximately 3.5km upstream from the confluence of the River Rother and the River Don at Rotherham.

The existing structure consists of a single electrically powered vertical lifting sluice gate operated by an electric wire rope hoist, comprising a drive motor gearbox assembly, cross shaft with integral rope drums, and support bearings.

To improve resilience and the operation and maintenance of the asset, JBA-Bentley is completing the detailed design and build of a new vertical regulator gate and associated MEICA and civils infrastructure.

The MEICA structure consists of a 20.3-ton vertical gate, mounted on a new steel bridge and working platform, which shall also house 13.5 tons of drive equipment for operating the gate.

Two 4kW motors, working in a duty/standby configuration, will provide drive to the gate via bevel and gearboxes, which turn a single driveshaft spanning the width of the gate. On this driveshaft, one at either end of the gate, are rack and pinion gear assemblies, which convert the rotation of the driveshaft to the vertical motion of the gate. The total gear ratio from motor to driveshaft is an approximate reduction of 4410:1, allowing relatively small motors to be specified.

[caption id="attachment_14807" align="alignnone" width="1200"] (top left) the existing Canklow regulator gate (bottom left) 3D model of the new Canklow Regulator and (right) bathymetry of Woodhouse Mill Washland - Courtesy of JBA-Bentley[/caption] The power supply to the gate will be a three-phase supply routed via a new MCC, which will contain the control modules, centralised drive units, and the telemetry system for remote monitoring and operation of the gate. The operation of the gate will be from on-site or via telemetry, with some semi-automated functions. The facility for future full automation of the site has been incorporated into the design. The MCC and electrical components will all be located within a kiosk mounted on a raised steelwork platform to lift the electrical components above the 0.1% AEP flood level. Also on this raised platform will be the DNO kiosk bringing power onto the site from the national grid, and a standby generator to provide resilience in case of power failure.

To support the new gate structure over the next 50 years, a new anchor restraint system has been designed. A buried sheet-piled ‘dead-man’ wall will be installed with ten 36mm anchor rods, evenly spaced, connecting to a waling beam on the wet side of the existing channel wall. This will be mirrored on both riverbanks.

The new infrastructure replicates the existing system, which has been determined to be past its design life and insufficient in supporting the new gate.

The existing superstructure of the control houses will be demolished, the foundations will be retained and extended where required to support the new gate structure using cast-in bolt sets.

A new permanent crane pad will be constructed on the south bank for the construction, maintenance, and decommissioning of the gate. This will double as parking spaces for EA operatives when not being used by a crane.

The JBA-Bentley team worked collaborative to optimise the delivery. This meant that site constraints were identified, and the design was completed with buildability and safety as the focus. A key constraint on the scheme is the proximity of the Northern Power sub-station and overhead power lines. The design of the dead-man walls, crane pad, and steelwork platform was completed to ensure that the plant and temporary works required for construction and installation were outside of the powerline exclusion zones.

[caption id="attachment_14796" align="alignnone" width="1200"] Overhead power exclusion zones within model - Courtesy of JBA-Bentley[/caption] Woodhouse Mill

The Woodhouse Mill Regulator is situated between Canklow and Meadowgate. It uses a single electrically powered vertical lifting gate to retain water. This gate is operated by an electric wire rope hoist, which includes a central drive motor and gearbox assembly, half shafts, spur and pinion driven rope drums, and support bearings, all counterweight assisted.

JBA-Bentley is currently carrying out hydraulic modelling on behalf of the EA as part of the optioneering phase. The options include passive solutions, such as a baffle or orifice plate spanning the width of the channel to continue to utilize the upstream storage. Due to the size of the Don catchment, the modelling required three individual models to be run together:

The Rother. Don/Dearne. Lower Don.

Multiple return periods are being considered, resulting in hundreds of models runs. The modelling also uses a continuous simulation approach, which adds to the complexity of the model runs.

Summary

The upgrading of infrastructure of the Don Regulators will ensure continued flood risk benefits into the future for the Don Catchment and surrounding area with improved resilience and reliability of the new assets. Alongside the reduction in flood risk, the environment and biodiversity will improve in the River Rother as a result of the Meadowgate Fish Pass.

Keadby Terminal Assisted Outfall (TAO) is a strategically important asset, protecting homes, businesses and agricultural land from flooding in the Isle of Axholme. The TAO was originally constructed in 1939 and required upgrading and modernisation to ensure the continued operation of the pumping station as resilience and reliability had been lost due to age, obsolescence and general wear and tear, resulting in the need for a major investment. Keadby TAO is the outfall for the River Torne within the Isle of Axholme to the tidal River Trent. It originally comprised a gravity sluice which maintained water levels within the Isle of Axholme and discharged fluvial flow to the tidal Trent when tide levels permitted. High flows were pumped via six pumps, providing approximately 32m3/s discharge capacity when required. Finding a viable solution

Previous business cases had failed to find a viable solution and detailed design work had developed plans for the project to completely renew the existing facility. However, multi-disciplinary teams from the Environment Agency, Arcadis, WSP and Galliford Try Binnies JV (GBJV) worked collaboratively to deliver value engineering achieving savings greater than £12m by re-using existing assets.

The new solution made a switch to fish-friendly electric pumps, avoiding the long-term management of fish and eel screening, and recommended refurbishing rather than replacing the station which would deliver environmental benefits, operational savings and a 90% carbon saving.

[caption id="attachment_14188" align="alignnone" width="1200"] Outfall construction (November 2021) - Courtesy of GBJV Ltd[/caption] Project scope

The upgrade included:

A comprehensive heavy electrical system replacement. Replacement of all pipework Replacement of the entire control system. The installation of six bespoke vertical lift pumps providing 19.2m3/s discharge capacity against a hydrostatic head of 3.7m when required. A complete redesign of the outfall structure to provide three individual discharge cells which will allow safe access to the twelve (1.8m wide) gravity/pumped culverts and twelve 1.8m tidal flaps for inspection and maintenance purposes.

The project team assisted in the development of the strategic case for investment alongside an update to the Isle of Axholme Flood Risk Management Strategy, and worked closely with the strategy asset management and delivery group ensuring that stakeholder engagement was central to the delivery of the project.

Undertakings

GB JV Ltd, a joint venture between Binnies UK Ltd and Galliford Try, has been the sole engineering design and build provider for the Outline Business Case (OBC), Final Business Case (FBC), and design/construction stages. This ‘cradle to grave’ approach has provided many benefits including the complex construction sequence document (for the whole scheme) created during the FBC which considered severe site constraints and proved an invaluable guide during the design and build phase.

[caption id="attachment_14184" align="alignnone" width="1200"] Outfall construction constraints - Courtesy of GBJV Ltd[/caption] Keadby Terminal Assisted Outfall Pumping Station: Supply chain - key participants Designer & delivery contractor: GB JV Ltd Binnies UK Ltd Galliford Try Client NEC project management: Turner & Townsend Client technical advisors: KGAL Consulting Engineers Ltd Client cost consultant: Arcadis Electrical enabling works: Fairfield Control Systems Sheet piling: Keltbray Ltd Mechanical installation: Alpha Plus Ltd Outfall construction: CPC Civils Ltd Electrical installation: Centrica MCC/PLC/HMI/SCADA & systems integration: Blackburn Starling Ltd - now RSE Control Systems (Blackburn Starling) Penstocks & flap valves: Glenfield Invicta Large knife gate valves: Ebro Valves Ltd Large knife gate valves: Stafsjö Valves Pumps: Pentair Fairbanks Nijhuis Stop logs: Aquatic Control Engineering (ACE) HV switchgear: Midland Power Networks Transformers: Wilson Power Solutions Ltd Standby generator: YorPower Ltd GRP kiosks: Industrial GRP Ltd Constructability challenges

The design involved constructability challenges as the Environment Agency operational team could only allow the release of two pumps at any one time to ensure that the operational plant was never compromised in terms of readiness for flood resilience. It also involved innovative fish pass solutions as site constraints prevented the use of traditional fish ladders and passes.

Binnies’ design team provided a solution which allowed the retention of the existing structure while completely refurbishing the installation. This was achieved by replacing the existing ‘carbon-hungry’ diesel-driven centrifugal flow pumps with electrically driven permanent magnet motors and vertically mounted axial flow pumps within the existing building envelope.

[caption id="attachment_14186" align="alignnone" width="1200"] Aerial view of final pour - Courtesy of GBJV Ltd[/caption]

Given the age of the buildings on site, the initial concept design was for the complete demolition of the existing reinforced concrete structure to make space for a new installation. A solutions-focused team looked at plans differently and included extensive early supplier engagement with pump suppliers that crucially unlocked the re-use of the existing structure; a cornerstone of the significant cost and carbon savings. A complete refurbishment rather than the replacement of the existing delivered effective resilience to future climate change.

Fish and eel friendly pumps

The existing facility presented a barrier for fish and eel migration and The England and Wales Eels Regulations (2009) required the installation to be upgraded to allow migration of elvers past the facility.

Accordingly, the fish-friendly pumps allow fish to pass downstream safely when pumping and an innovative ‘Elver Mode’ was added into the software controlling the sluicing operation allowing elver access during their migration period and subsequently safe passage into the Three Rivers Catchment and the wider Isle of Axholme, with 224km of main river available to fish and eel passage.

Pentair Fairbanks Nijhuis, the pump supplier, developed a fish-friendly impeller design that ensures fish are not struck on entering the pump, by incorporating vanes to guide them unharmed through the system. The impeller design in conjunction with the variable speed drives ensures optimal efficiency at all times. Low running speeds also improve passage for fish and reduce noise and vibration.

[caption id="attachment_14183" align="alignnone" width="1200"] Pump hall - Courtesy of GBJV Ltd[/caption] Operational access

Binnies’ design has also improved operational access to the culverts and flap valves which previously posed significant health and safety risks. Previously, some areas were accessible only by divers and other areas have never been accessed since the TAO was commissioned in 1939 as it was considered too dangerous.

The improved operational safe design has minimised ongoing maintenance difficulties.

Outcomes

Through collaboration with partners and the supply chain the team delivered the OBC and FBC stages to time and budget winning the Best Business Case of the Year at the Environment Agency’s ‘Flood and Coast Excellence Awards’ (2019). GB JV Ltd attained partial sectional completion of the flood defence asset at the end of April 2021 (four pumps operational and available for beneficial use), resulting in the Environment Agency attaining 80% of its stated outcome measures; the reduction in flood risk to 2484 of the total 3105 properties to be delivered by this project.

The remaining 621 properties were realised in November 2021 upon successful integration of the two remaining pumps. This was achieved despite COVID-19 disrupting construction work and storms in 2019 and in 2020 when the Environment Agency needed to operate the diesel pumps to reduce flood risk to the catchment, preventing construction work for approximately three months.

The former pumping station had six large and dangerously loud diesel engines (over 98 dBA when measured outside with the doors closed) and emitted large amounts of exhaust fumes. It was not safe to be inside the building with the pumps operating (even with ear defenders). The building is within 100m of residential properties so pumping activities disturbed the local community.

The new pumps are much quieter with the standby generator designed to be less than 60dBA at 1m. As the pumps can run 24 hours a day for several weeks at a time, the local community have greatly benefited from the removal of noise and air pollution.

[caption id="attachment_14187" align="alignnone" width="1200"] Outfall structure including fenders - Courtesy of GBJV Ltd[/caption]

The site is immediately adjacent to the Port of Keadby on the tidal River Trent. Close management was required with both PD Ports Ltd and ABP who had equipment within the working area, so the team worked with the port to respond to and work around vessel movements and port operations. A new river fender structure was designed and installed to reduce the risk of damage to the outfall structure from berthing vessels.

In conclusion, the carbon footprint was reduced by 90% throughout the project’s lifecycle using modern efficient fish-friendly electric pumps negating the need for a 3mm eel screen and reduced ongoing lifetime operational expenditure by the use of the existing structure.

When COVID-19 restrictions prevented foreign travel to the pump supplier in Holland, the team implemented remote attendance to witness the programme-critical Factory Acceptance Testing, allowing us to maintain programme. This also enabled a wider team to witness the testing and provided a learning opportunity for team members that would not otherwise have been able to attend. The approach continued with Design Workshops that avoided the need for the Design Team to physically attend site, without compromising the quality of work. The reduced travel also contributed to carbon reduction.

Awards

The project has won a number of awards including:

Environment Agency ‘Project Excellence Awards 2019 Winner Best Business Case of the Year at the Environment Agency’s ‘Flood and Coast Excellence Awards’. Highly Commended Asset Management Project of the Year at the Environment Agency’s ‘Flood & Coast Excellence Awards’. Institution of Civil Engineers, East Midlands Branch Large Project Award 2023. Sustainability Award 2023.

The town of Ammanford, Carmarthenshire has a history of flooding. Several significant flood events have been recorded since 1979 and most recently in 2009, with homes, businesses, roads, the Heart of Wales railway line and a local college inundated. Natural Resources Wales (NRW) commissioned Arup and Walters to design and construct a solution to reduce the community’s flood risk and improve fish passage. This project innovatively aligns solutions to reduce risk to the community from flooding with two other previously separate schemes; safeguarding a critical sewer crossing found to be in poor condition and addressing a significant barrier to migratory fish. Project scope

With limited public funding and the increasing need for multifunctional infrastructure enhancements, the scheme offers lessons in the delivery of multiple benefits. The scheme comprises:

Seven concrete flood walls. Two earth flood bunds. Four blockstone pre-barrages step water levels to allow fish passage, with adjacent ground lowering to increase flood capacity. Landscape planting and public realm enhancements, including nearby Bonllwyn Green and the Llandybie Community Woodland Project. Ecological enhancements for otters, bats, birds and invertebrates, focussed on improving connectivity, diversity and ecosystem resilience. Reducing flood risk to homes and businesses

Ammanford is located at the confluence of the rivers Loughor, Lash and Marlas. The rivers respond rapidly to rainfall and their channel capacity is limited. Much of the town is built on low-lying land adjacent to the river and overtopping is predicted at multiple locations. If nothing was done to reduce flood risk, 198 homes and 25 business would remain at risk of flooding from the 1 in 100 (1%) annual chance event.

NRW studies demonstrated a strong case for change. The study area was one of the top communities at risk of flooding from main rivers within Western Wales, and facing one of the largest increases in flood risk as a result of climate change. Flooding in the area was predicted to cost the UK some £7.9m in today’s prices over the next century.

With options to slow flows upstream infeasible, optioneering focused on better containment of flood waters in the river corridor. No single flood defence would be able to meet the project objectives, so a combination of raised defences throughout was adopted as the preferred solution.

The scheme was designed to reduce flood risk up to the 1% AEP event, allowing for the impact of climate change over the scheme’s 100-year lifetime; benefiting 349 homes and 37 businesses.

[caption id="attachment_14722" align="alignnone" width="1200"] (left) Project overview - Courtesy of Arup and (right) fish passage with adjacent ground lowering works - Courtesy of Walters[/caption] Improving fish passage

Separately, NRW had identified the case for improvements to Tir-y-Dail weir at the downstream extent of the scheme. The weir was a partial barrier for upstream migration of adult Atlantic salmon and trout, and a complete barrier to adult lamprey and juvenile European eel. Fish passage improvements would unlock 20km of river to migratory fish. The weir was in poor condition but encased a critical main sewer and enabled upstream river level gauging.

Scheme design and innovation

The design phase of the scheme involved comprehensive investigations and modelling to understand flood dynamics and identify effective solutions. Key design considerations and innovations are presented below.

Positive solutions to mitigate detriment

At the outset, the team identified a risk of conflict between the initially separate fish passage and flood scheme objectives. A further challenge was mitigating potential flood detriment to other areas. Flood modelling indicated that raising flood defences and making fish passage improvements to the Tir-y-Dail weir would cause unacceptable detriment elsewhere. Typical measures to mitigate the detriment were investigated but were found to be either ineffective or excessively costly (such as additional raised defences upstream) jeopardising the business case justification for the scheme.

The team identified and developed from first principles an innovative solution to locally address issues in proximity to the weir, including an area of ground lowering within the field adjacent to the existing weir and fish passage pre-barrages. This provided additional conveyance around the existing weir and proposed pre-barrages in more extreme flood events, mitigating potential detrimental increases in flood risk associated with both the flood defence and fish passage improvements.

To maximise the benefits of the ground lowering, soils generated from this area were used within the construction of the Tir-y-Dail flood bund, improving the scheme’s earthworks balance and reducing import volumes. The area was also landscaped to provide additional area of riparian habitat.

Balancing earthworks

Two factors made creating an earthworks balance on the project challenging. Firstly, the nature of the scheme and site constraints resulted in limited areas of fill. Secondly, the engineering and chemical parameters of some of the soils excavated were unfavourable.

[caption id="attachment_14724" align="alignnone" width="1200"] Tir-y-Dail flood bund following construction - Courtesy of Walters[/caption]

To minimise the volume of excavated soils that would need to be disposed of off site, the team first addressed the chemical properties of the made ground. Site-specific risk assessments were undertaken to derive appropriate re-use criteria for human health and controlled waters. These were developed into a material re-use strategy, which considered appropriate legislative frameworks and was able to demonstrate that the majority of made ground was chemically suitable for re-use in appropriate scenarios.

To address the imbalance in volumes, the design of the Tir-y-Dail flood bund was reviewed as the primary fill area within the scheme. Flood bunds are most commonly constructed from a homogenous clayey material. This would need to be imported due to a lack of suitable on-site sources. The flood bund was therefore designed to have a ‘cap’ of imported clay to ensure performance against flooding, while the main core was formed from variable site-won material. Slope stability assessment undertaken under various scenarios demonstrated that, as long as the clay cap material was appropriately controlled, the geotechnical parameters for the core material could be significantly reduced.

To allow the contractor flexibility of the site-won materials placed in the core of the bund depending on the sequencing of their works, a project-specific soil material class was created. This was based on a combination of observational and basic material classification controls. This approach resulted in a reduction of 270 wagon loads of soil movements, reducing carbon and impact on local residents.

Sensitive detailing of flood defences

Measures were adopted to ensure the flood defences were sensitively integrated into the local landscape.

Flood walls in publicly viewable areas were finished with brick cladding, form liner finish and imitation stone copings to match local architecture. Coping stones were designed to be structurally integral to the flood wall to minimise their overall height, as well as reduce maintenance and public safety risk. Pillar features were incorporated into the facing of brick cladding at regular spacings to provide visual interest along the expanse of the wall.

[caption id="attachment_14725" align="alignnone" width="1200"] (left) Lightweight shuttering utilised in constrained working corridors and (right) brick cladding works to flood walls - Courtesy of Walters[/caption]

Design of the Tir-y-Dail flood bund was tailored to mitigate its impact on the open views from a nearby public right of way. In plan, a curved alignment was specified to conserve an irregular field pattern. In section, slopes were slackened and rounded at the top and bottom to create a naturalistic landform.

A fundamental element of the scheme design was determination of the alignment and form of the flood defences to minimise tree loss along the riparian corridor. An arboriculturist, who was integral to all major design decisions, was embedded within the design team. Every tree was considered individually so that as many trees as possible could be maintained. The resulting designs/design adaptations included micro-siting of flood walls and localised modifications to flood wall foundations in the vicinity of root protection zones.

Ammanford Flood Risk Management: Supply chain - key participants Designer & ECC project management: ARUP Design sub-consultant: Fishtek Ltd Main contractor: Walters UK Ltd Environmental consultants: Yellow Sub Geo Ecology: Sylvan Ecology Arboriculture: Mackley Davies Associates Coping stone design: Quad Consult Floodgates: MM Engineering FRC works: Trueform Civil Engineering Ltd Waterproofing: Tywi Damp Proofing Treatments Metalwork: Cambrian Foundry Reinforcement: Express Reinforcement Asbestos disposal: Gavin Griffiths Brick & stonework: JW Masonry Surfacing: Laymak Ltd Rail contractors: Protech Infrastructure Rock armour: Tarmac Ltd Landscapes: Afan Group [caption id="attachment_14728" align="alignnone" width="1200"] Visualisation of Bonllwyn Green pocket park - Courtesy of Arup[/caption] Nature and people thriving together

The project is in the heart of Ammanford, with interventions required in a combination of residential, commercial and public spaces. Multiple rounds of public engagement supported the scheme development, including:

Public drop in events with questionnaires on specific issues and feedback forms. Online consultation during Coronavirus period, as well as letterbox information drops to ensure all parts of the community were engaged. Regular newsletters, press releases, social media updates and a project website were provided throughout the design and construction phase of the scheme. For public realm enhancements to Bonllwyn Green, visualisations and schematics were prepared to effectively communicate the scheme proposals and help local residents have their say on the design.

In line with NRWs strategic objectives, enhancements to public space and ecological habitats were fundamental to the scheme design, in addition to reducing flood risk. To provide biodiversity net benefit through increasing connectivity, diversity and ecosystem resilience of the high value riparian corridor, enhancements delivered as part of the scheme included:

Improved fish passage for multiple species through the existing weir on site. Otter ledges beneath two existing road bridges. Log piles for invertebrates, hedgehog nesting boxes and bat and bird boxes. Where tree loss was unavoidable, they were replaced at a ratio of 3:1. Appropriate native species of local provenance and were designed to maintain and enhance habitat connectivity, while maintaining an appropriate amenity setting for the local community. [caption id="attachment_14721" align="alignnone" width="1200"] Heol Hayden public realm improvements - Courtesy of Walters[/caption]

Improvements to public spaces in the vicinity of the flood defence works, but also within the wider community, were also delivered as part of the scheme as summarised below:

Where flood defences were constructed in public spaces and within the local college, the surrounding areas were enhanced with additional trees, swathes of bulb planting and new seating areas. Timber from trees felled as part of the scheme was reused to construct new benches. At the Heol Hayden Flood Wall, the need for improved delineation of space between an existing riverside footpath and the adjacent gardens which fronted directly on to it was identified through community engagement and the Landscape and Visual Appraisal. A new hedgerow with small clusters of trees better defined the space and provided additional privacy to the local residents. The existing Bonllwyn Green Park in the heart of the town was enhanced offering an amenity for local residents. The parks existing features were kept, but the space enhanced through avenue planting of specimen trees; drifts of bulb planting; interpretation boards; seating areas and informal play features formed from trees felled as part of the scheme. As part of the scheme, NRW worked in partnership with Carmarthenshire County Council to deliver the nearby Llandybie Community Woodland Project, which comprised1.58ha of community broadleaved woodland with public access. Protecting the environment

Environmental impacts were assessed through the Environmental Constraints and Opportunities Record (ECOR), with mitigation and enhancements integrated at an early stage into scheme development, heavily influencing the design process. Potential impacts upon trees, protected species, local community, archaeology, and local landscape, are some of the many that were assessed and mitigated.

The ECOR informed the Environmental Action Plan which formed part of the works information for the scheme and enabled key environmental mitigation measures to be communicated and tracked during the construction phase. The mitigation and protective measures implemented were comprehensive, covering the local community, protected species and environmental quality.

[caption id="attachment_14723" align="alignnone" width="1200"] Llandybie community woodland project - Courtesy of NRW[/caption] Considerate construction

The works were spread across nine locations in Ammanford comprising residential, commercial and public areas. Each location presented unique challenges and constraints. To ensure that the project was executed safely and efficiently, significant effort was made to tailor methods of construction in each location.

The team’s focus on careful planning and attention to detail ultimately resulted in the successful completion of the project.

Early contractor investigation works captured potential clashes with existing utilities and structures. A collaborative working approach from all parties ensured potential issues were rectified before the main construction works commenced.

Working methodology, plant and equipment choices were tailored to the environment at each location to minimise disturbance. Due to the nature of restricted access in some locations, alternative construction methods were implemented. This included the use of a lightweight shuttering system that could be safely manually handled into position.

Collaborative working between the client, contractor and designers allowed early access for in-river works. Note only did this result in the fish passage works being completed with minimal impact on the ecosystem, but also reduced the overall construction programme by many months.

Summary

The Ammanford Flood Risk Management and Fish Passage Scheme is a testament to the importance of comprehensive planning, innovative design, and community involvement in flood risk management. By addressing the unique challenges of Ammanford, the scheme significantly reduces the flood risk for hundreds of properties and unlocks 20km of river to passage, as well as providing numerous other environmental enhancements. This case study highlights the critical role of such projects in building resilient communities and enhancing the environment.

The scheme was successfully tested whilst still under construction in September 2023.

[caption id="attachment_14726" align="alignnone" width="1200"] Flood event in September 2023 - Courtesy of Walters[/caption]