Supply Chain - Contractors - Systems Integration

The Scunthorpe Wastewater Flooding Defence (WFD) Programme aims to reduce the number of spills from key combined sewer overflows (CSOs) during periods of heavy rainfall. For the South Grange, Brigg Road and Grange Lane North CSOs, a sustainable stormwater management solution was required to retain excess water and reduce intermittent storm discharges at all three CSOs, improving the biological oxygen demand (BOD) concentration in Bottesford Beck. As part of Severn Trent’s commitment to environmental compliance and improving water quality, an effective and efficient delivery was critical. Challenges

Tasked with reducing storm discharges to local watercourses, Avove developed a robust delivery model that ensured a seamless process to achieve key project objectives, whilst minimising disruption to residents. To overcome the project challenges, required blending collaboration and innovation in a way that unlocked measurable long-term benefits for Severn Trent and these included:

Location adjustments: At Brigg Road, the proposed shaft tank location was adjacent to an old building with limited space and difficult access. Following a thorough site review, an alternative location was agreed, delivering significant Health, Safety, Environment and Quality (HSEQ) benefits. Confined space: The confined nature of the site at Grange Lane North presented challenges for construction and operations. These constraints were resolved through the utilisation of an empty building, which was repurposed to provide temporary accommodation and a laydown area for materials. Risk Management: A comprehensive risk register was created to outline potential risks and mitigation strategies. For example, infrastructure risks when crossing a gas pipeline were identified, and through careful planning, were addressed by the Avove project delivery team.

All risk reduction meetings and planning phases were underpinned by collaboration, as the combined expertise of the project team played an important role in strategising an effective response to ensure that the project did not deviate from the scope.

[caption id="attachment_25960" align="alignnone" width="1200"] Work area - Courtesy of Active Tunnelling Ltd[/caption] The approach

Collaborative planning and consistent communication was key to a successful delivery across all three sites. Avove prioritised early engagement with suppliers, particularly for precast items, to secure timely deliveries and reduce the likelihood of budget overruns caused by unforeseen delays. This detailed approach delivered important long-term benefits and facilitated open communication and mutual trust throughout the project’s lifecycle.

With overarching principles of communication and collaboration in place, the technical prowess of the project teams was enhanced. With confidence that key materials would be delivered on time, operatives could begin work, using their expertise to ensure an innovative and sustainable completion. This approach entailed:

Early contractor involvement (ECI): Collaborative input from all stakeholders during the preliminary stages helped to develop innovative solutions and reduce later risks. This was particularly important in terms of design planning, as the Brigg Road shaft tank was relocated following an inspection. Multidisciplinary collaboration: Spanning civil, mechanical, electrical, geotechnical, structural and environmental engineering, multidisciplinary collaboration was facilitated through close engagement with sub-consultants. As such, all designs met the programme’s requirements, maintaining continuous alignment with Severn Trent’s team. Coordinated design process: This process enhanced buildability and reduced environmental impacts through a balance of cost, quality and carbon considerations. From minimising energy usage to cutting waste, the project achieved a significant reduction in emissions by removing the need for additional pumps. Effective programme management: Although it was a complex, multi-phase project, the structured approach comprised of regular project meetings to review progress against detailed schedules, ensuring activities were synchronised.

To complete this approach, Avove supported the communication process between the client and local stakeholders, with the project team assisting with land and planning matters. This involved the distribution of letters to residents, the negotiation of land access with owners and occupiers and following up on any concerns during the execution of works.

[caption id="attachment_25953" align="alignnone" width="1200"] Construction continued throughout the night - Courtesy of Active Tunnelling Ltd[/caption] Scunthorpe WFD Programme: Supply Chain - key participants Client: Severn Trent Delivery contractor/main contractor: Avove Land & planning services: Dalcour MacLaren Shaft construction: Active Tunnelling Ltd Mechanical & electrical works: PJT Pumping Services Ltd VacFlush™ system: CSO Group Ltd Drainage works: VP Groundforce Shorco Core drilling: Matte Black Surfacing Plant: Trenchless Plant Ltd Concreting finishing: Overhall Contractors Ltd Concreting finishing: Groundtech (UK) Ltd Tarmac: Cemex The solution

The Scunthorpe WFD project aligned with Severn Trent’s organisational goals of sustainability, biodiversity and environmental responsibility. By constructing large, off-line shaft tanks to manage stormwater flows from existing CSOs, the BOD concentration in Bottesford Beck was improved.

Effective Design & Delivery: Through effective design and delivery, the South Grange shaft tank (25m x 12m deep), Brigg Road shaft tank (12.5m x 14m deep) and Grange Lane North shaft tank (20m x 15m deep) were all successfully installed along with supporting infrastructure. Technical Expertise: The tanks were connected to the existing combined sewerage system through 1,050mm diameter inlet pipes. A twin-pumped return system was activated by telemetry from Yaddlethorpe Sewage Treatment Works, ensuring stormwater was returned, once permitted. Additionally, MCC kiosks, flushing systems, vent stacks, rising mains and sewers were all introduced as part of the comprehensive works. Sustainable Technology: Sustainability was embedded into every stage of the project. For the South Grange scheme and the Grange Lane North scheme, the initially requested pumped washing facility was replaced with the patented VacFlush™ system from CSO Group Ltd. Not only did this reduce maintenance and operational costs, but it lowered power requirements and cut carbon emissions at two of the three shafts. [caption id="attachment_25956" align="alignnone" width="1200"] VacFlush™ system installation - Courtesy of Active Tunnelling Ltd[/caption] The VacFlush™ system is an automated vacuum flushing system designed to clean storm tanks, holding tanks, and sewer networks without requiring manual entry into the tank. It utilises a vacuum pump to draw wastewater into a flush chamber, which is then rapidly released by a diaphragm valve, creating a powerful surge that cleans the tank floor and removes sludge. Key benefits include safe operation without man entry, efficient cleaning of large tanks, minimal maintenance, and automatic operation, often using the stormwater itself for flushing Landscape Preservation: Through effective programme management and the utilisation of design and construction expertise, we avoided tunnelling under the A1029 highway and crossing strategic assets, preserving mature trees in the process. Budget management: Integral to the project’s success and the feasibility of the solution was effective cost management. We maintained robust budget and cost control throughout the programme of works by implementing comprehensive Cost Value Reconciliation (CVR) reports, which were updated monthly to reflect expenditure and forecast completion costs.

It was through a careful combination of sustainability, innovation and collaboration that a highly effective solution was identified and implemented, helping us achieve a high degree of client satisfaction.

[caption id="attachment_25959" align="alignnone" width="1200"] (left) Roof beams in place, and (right) start of the roof panel installation - Courtesy of Active Tunnelling Ltd[/caption] Benefits

The Scunthorpe WFD project delivered a range of long-term benefits, many of which were wide reaching, both in terms of compliance and structural integrity. Beneficial to both the client and their customers, the project achieved:

Long-term compliance: The solution improved the BOD concentration in Bottesford Beck, meeting the Environment Agency’s ‘Good’ standard. Environmental enhancements: The project supported the improvement of nearby rivers, reducing the risk of pollution incidents whilst contributing to Severn Trent’s broader goal of improved watercourse health. Enhanced innovation: Collaborative working between Avove, Severn Trent and other key partners allowed for greater innovation and the successful delivery of robust off-site holding tanks. Future-proof design: The solution’s design ensures long-term compliance and operational effectiveness for years to come. Operational efficiency: Our team demonstrated technical excellence throughout the project’s delivery, ensuring the new solution was fit for purpose and operationally efficient. Time and cost-effectiveness: A proactive and highly collaborative approach streamlined the entire delivery, saving time and reducing costs. Improved safety: Best-in-class construction methods and thorough planning processes ensured the works were completed safely. [caption id="attachment_25957" align="alignnone" width="1200"] Installation of the roof slabs - Courtesy of Active Tunnelling Ltd[/caption] The results

Working diligently to achieve an expedited programme across all three sites, hard work and commitment ensured a seamless delivery, well within time and budget requirements. With regulatory deadlines to meet, it was imperative that a highly collaborative approach was adopted, with open communication and the implementation of a clear structure guiding the project.

The new off-line tanks effectively retain stormwater, reducing pressure from the existing network and improving water quality much to the benefit of the environment, Severn Trent and their customers.

Leamington Spa is a historic spa town with a growing population and significant development pressures. The River Leam, which flows through the town centre, is a focal point for recreation, including wild swimming, boating, and public parks. The sewerage catchment includes Leamington, Warwick, and surrounding villages, all draining to Longbridge Sewage Treatment Works (STW). Six CSOs were identified for improvement. This requirement was designed to safeguard public health and ensure compliance with the Bathing Water Directive and related water quality with the aim to reduce spill volumes and spill frequency with a variety of interventions; to give an insight into the best approach for bathing waters. Endorsed by Ofwat in 2021, the scheme is part of a broader strategy to support post-pandemic economic recovery through environmental infrastructure investment. The Leamington scheme exemplifies innovation in hydraulic modelling, and collaborative delivery within tight regulatory timeframes. Project overview

The Green Recovery Leamington Spa Sewerage Scheme is a flagship initiative under Severn Trent’s Green Recovery programme, aimed at moving a stretch of the River Leam towards bathing quality. This ambitious project addresses the performance of six critical Combined Sewer Overflows (CSOs) in Royal Leamington Spa, Warwickshire, through a suite of technically advanced designs that test a variety of complementary solutions.

Few projects manage to balance technical complexity with community benefit as seamlessly as the Leamington Spa Sewerage Scheme with live public functional spaces is technically complex but also requires attentive and agile stakeholder engagement, delivering large measurable environmental improvements.

[caption id="attachment_26765" align="alignnone" width="1200"] Surface water separation - Courtesy of Forkers Ltd[/caption]

While early guidance targeted storm overflows with direct discharges into these areas, the programme has since expanded to include overflows that pose wider environmental and public amenity impacts. This includes high amenity areas such as recreational waters and areas of interest to businesses and other organisations, even if they are not formally designated as bathing waters.

The shift reflects a more holistic approach to water quality management, prioritising interventions based on environmental sensitivity, public usage, and the potential impact of overflows. This broader targeting ensures that improvements are aligned with community expectations and environmental stewardship goals.

Hydraulic modelling & option development

The project leveraged the Longbridge Strategic Sewerage Growth model, enhanced with updated flow monitoring and surface water network refinements. Hydraulic solutions were identified early through iterative hydraulic modelling and refined through feasibility and Early Contractor Involvement (ECI) with Forkers Ltd.

By integrating advanced hydraulic modelling and real-time control, the scheme exemplifies the kind of forward-thinking infrastructure needed to meet the challenges of climate resilience and urban growth.

Preferred interventions included surface water separation, pumped and gravity storage, and network optimisation.

[caption id="attachment_26764" align="alignnone" width="1200"] Shaft storm tank precast concrete segments - Courtesy of Forkers Ltd[/caption] Leamington Spa Sewerage Scheme: Supply chain - key participants Deliver contractor: Forkers Ltd Designer: WSP Tunnelling/shafts/timber headings: Active Tunnelling Ltd Electrical/mechanical: STAL (UK) Ltd Ground support & shoring: MGF Ltd Vacuum excavation: VAC UK (Kilkern Ltd) Drainage sub-contractor: Arthur Civil Engineering Ltd Emergency temporary pumping: Selwood Precast concrete pipe & rings: Marshalls Civils & Drainage Precast concrete rings: FP McCann Ltd Plastic storage pipes: Aquaspira Ltd GEOlight® storage tank: SDS Limited Concrete & aggregates: Aggregate Industries | Cemex Plant hire: Flannery Plant Hire (Oval) Ltd Traffic management: RouteOne Traffic Management Ltd Carriageway surfacing: JMC surfacing Ltd Surface water separation (SWS)

A major surface water separation scheme was implemented between Campion Road and Milverton School, delivering significant benefits in surface water management. The project successfully disconnected impermeable areas from the combined sewer network, reducing the volume of stormwater entering the system. Additionally, it incorporated below-ground storage to help manage flood risk, enhancing the area’s resilience to heavy rainfall events and contributing to improved environmental outcomes.

[caption id="attachment_26763" align="alignnone" width="1200"] Surface water separation - Courtesy of Forkers Ltd[/caption] Pumped & gravity storage

The Lower Avenue Combined Sewer Overflow (CSO) scheme involved the installation of an 880m3 shaft tank with a return flow capacity of 30 l/s, located in the Station Approach car park. The shaft tank was designed and constructed by Active Tunnelling Ltd. At Princes Drive 19B, the scheme increased the flow into the existing storm tanks by an additional 75 l/s. Both storage systems were equipped with real-time control (RTC) logic to optimise return flows and minimise the risk of spills into the river, ensuring more efficient and environmentally responsible stormwater management.

Climate change & resilience

To ensure long-term resilience and performance under changing climate conditions, the design rainfall was uplifted by 15% to reflect projected 2050 scenarios. Spill frequency assessments were carried out using Severn Trent’s Technical Standard Rainfall Dataset, representing worst-case conditions to ensure robust system performance. All conveyance infrastructure was sized accordingly to accommodate future climate impacts, supporting sustainable and reliable operation over the asset’s lifetime.

Construction & delivery

The project was delivered under tight AMP7 deadlines, requiring early contractor involvement and agile design development. Forkers Ltd and WSP played key roles in feasibility, site investigation, and outline design.

Key construction innovations included the use of GEOlight® blocks from SDS Limited for modular storage. GEOlight® blocks offer a significant advantage in large-scale infrastructure projects due to their lightweight, corrosion-resistant design, which simplifies installation and reduces long-term maintenance costs compared to concrete or steel alternatives.

[caption id="attachment_26767" align="alignnone" width="1200"] GEOlight® modular storage tank - Courtesy of Forkers Ltd[/caption] Environmental & community benefits

Reducing the impact from CSOs has had significant social implications. Access to clean and safe recreational waters promotes public health and well-being, encouraging outdoor activities and fostering a connection with nature. This initiative does not just solve a problem, it redefines what is possible in urban water management, setting a precedent for future projects across the UK and beyond.

Spill reduction. Flood risk: No detriment demonstrated; some areas show betterment particularly through the implementation of surface water separation in the north-east, the construction of stormwater storage tanks in the south, and comprehensive improvements along the River Leam corridor aimed at enhancing water quality and resilience. Education: Engagement with Milverton School on drainage and sustainability. Broader significance & replicability

The Green Recovery Leamington Spa Sewerage Scheme stands as a testament to the power of innovative engineering and sustainable practices in addressing modern environmental challenges. This project not only resolves immediate issues related to CSOs but also sets a benchmark for future initiatives aimed at enhancing urban wastewater management.

The Leamington Spa Surface Water Separation Scheme, delivered as part of Severn Trent’s Green Recovery Programme, exemplifies a forward-thinking approach to sustainable water management.

Central to the project was the installation of a two megalitre GEOlight® attenuation tank from SDS Limited beneath a playing field adjacent to Milverton Primary School. The tank, connected to newly laid surface water sewers across several roads in Leamington Spa, significantly increases stormwater storage capacity within the network. This enhancement plays a critical role in protecting downstream sewage treatment infrastructure from overload and reducing the frequency of combined sewer overflows into the River Leam.

[caption id="attachment_26768" align="alignnone" width="1200"] Construction of the 2 megalitre attenuation tank - Courtesy of Forkers Ltd[/caption]

The project not only supports Severn Trent’s ‘Get River Positive’ commitments but also aligns with local and national planning policies. By integrating innovative technology with sustainable construction practices, the scheme delivers measurable environmental benefits. It demonstrates how targeted infrastructure investment can contribute to long-term river health, climate resilience, and community wellbeing; setting a precedent for future water management initiatives across the region.

Its success lies not only in the numbers (reduced spills, increased storage, improved water quality) but in the way it brings together engineering excellence, ecological sensitivity, and community engagement. The project’s legacy will be felt not just in the River Leam’s improved health, but in the model, it provides for sustainable, scalable, and socially conscious infrastructure.

Conclusion

The Green Recovery Leamington Spa Sewerage Scheme is a model of integrated water management, combining hydraulic engineering and community recreational benefit. It demonstrates how ambitious environmental goals can be achieved through technical excellence, collaboration, and innovation.

In a sector where impact is often measured in compliance, this scheme goes further; delivering outcomes that resonate with local communities, regulators, and the environment alike.

The project not only safeguards the River Leam for recreational use but also sets a precedent for inland bathing water schemes across the UK and beyond.

Comber is a small town in County Down, located on the shores of Strangford Lough, 4.5 miles from Newtownards and 12 miles from Belfast. All flows from the Comber Catchment arrive at Upper Crescent Wastewater Pumping Station (WwPS), which is the terminal pumping station that pumps flows to Ballyrickard Wastewater Treatment Works (WwTW) for treatment. A study on the drainage network of Ballyrickard/Comber was carried out in January 2010, which identified inadequacies in the system and made recommendations for improving and upgrading the network. Specifically, the study identified that Upper Crescent WwPS did not meet Northern Ireland Environmental Agency (NIEA) requirements for emergency storage volumes. It also identified that Upper Crescent WwPS had been experiencing frequent breakdowns that contributed to high operational costs. Existing works

Upper Crescent WwPS was constructed in the 1970s, and the site contains two pumping stations:

Wastewater pumping station: Pumps foul flows from the catchment to Ballyrickard WwTW in Newtownards for treatment. Storm pumping station: Services stormwater from the local catchment area during large storm events that can overwhelm the sewer network. This pumping station plays a key role in preventing out-of-sewer flooding within Comber during storm events and limits further discharges to Strangford Lough. [caption id="attachment_26824" align="alignnone" width="1200"] Existing site showing proximity of site to neighbouring properties and local park to the north - Courtesy of GRAHAM[/caption] Project team

As principal contractor and principal designer, GRAHAM Construction had overall responsibility to deliver the project on time and within budget. Enisca Brown Ltd was contracted for designing and delivering a turnkey MEICA, process design and build solution for the new works.

McAdam provided civil, structural, and geotechnical design services, including the initial enabling and investigatory works carried out at the Early Contractor Involvement (ECI) stage, as well as the detailed design for construction.

The contract delivery team worked in a collaborative manner with NI Water and their project manager AECOM, as well as key suppliers and subcontractors to deliver a robust, effective and modern wastewater pumping station and storm water storage facility. This allows for future growth within the catchment area and protects the environment from discharges during storm events.

Early Contractor Involvement (ECI)

In 2022, GRAHAM undertook Early Contractor Involvement to further develop the scope and complete detailed design for the main construction works. Due to the age of the existing pumping stations, rigorous investigations were carried out to determine their operation and control philosophy, condition and potential for imposing health and safety risks to operatives and the contract team.

The completion of the detailed design, ahead of main contract award, ensured cost certainty for NI Water and lessened the risk of delays due to design changes on site.

[caption id="attachment_26822" align="alignnone" width="1200"] Early excavation works on the cofferdam - Courtesy of GRAHAM[/caption] Upper Crescent WwPS: Supply chain - key participants Client: NI Water Project manager: AECOM Civil contractor: GRAHAM MEICA designer & contractor: Enisca Browne Ltd Civil, structural & geotechnical design: McAdam Cofferdam temporary works design: McErlain Consulting Sheet piling contractor: Ward Piling PLC software & commissioning: Enisca Browne Ltd PLC software & commissioning: Profitec Solutions Ltd Metalwork design/fabrication & installation: Evans Plant Pumps & mixers: Xylem Water Solutions Static storm screen: Eliquo Hydrok Ltd Access covers: JP Corry Pipes & fittings: APP Fusion Group Backup generator: AJ Power Ltd Lifting equipment: Walter Watson Lifting equipment: Barbour Engineering & Fabrication Site security fencing & gates: Kane Fencing Ltd [caption id="attachment_26825" align="alignnone" width="1200"] Installation of the sheet piles for the cofferdam - Courtesy of GRAHAM[/caption] Project description & scope

The existing Upper Crescent WwPS in Comber involved a 2-Phase upgrade plan to complete all activities required:

Phase 1: Early procurement of items with long lead-in times and site preparation:

Early procurement of items such as generator, overflow screen, gantry crane and MCC panel. Relocation of several deep incoming sewer lines around the footprint of the cofferdam. Installation of new motor control panels for the existing Storm PS and new Wastewater PS to ensure uninterrupted operations. Relocation of overhead NIE (Northern Ireland Electricity) cables. Installation of a new upsized NIE transformer. Installation of a new 550kVA backup generator. New NIE incomer panel for connection point to the new NIE TX from the new 550KVA diesel generator.

Phase 2: Construction

Further site investigation works. Construction of new wastewater pumping station. Construction of new valve and flowmeter chambers. Installation of M&E equipment including three pumps, two mixers and static overflow screen. Construction of new inlet and overflow sewers. Construction of new rising main. Demolition of existing wastewater pumping station and associated apparatus. Landscaping and reinstatement. [caption id="attachment_26819" align="alignnone" width="1200"] Final excavation to formation level (minus 10m below ground level) within the cofferdam - Courtesy of GRAHAM[/caption] Construction

One of the biggest challenges was that the two adjacent pumping stations had to remain operational throughout the entire construction phase. The new Upper Crescent WwPS and 687m3 of stormwater storage required the construction of a 26m diameter x 10m deep cofferdam and the new WwPS could not be commissioned until the existing had been decommissioned.

Screw pumps: Each of the screw pumps within the Upper Crescent Storm Pumping Station was individually phased over to the new control panel in a lengthy process, which required a test period of each pump before the next pump could be phased over. Staged changeover was required due to the criticality of their operation during storm events. The pumps could not be taken out of service during storm events due to the potential of out-of-sewer flooding in low lying areas within the Comber Catchment.

Cofferdam construction: Once the programmed critical works within Phase 1 were complete, Phase 2 works could commence on the construction of the circular cofferdam. This was undertaken by specialist piling contractor Ward Piling Ltd with responsibility for:

Temporary works design. Sheet pile installation. Dewatering well installation. Construction of three circular concrete ring beams. Excavation of the cofferdam. Dewatering of the excavation.

A secondary 3-sided cofferdam was also constructed adjacent to the main cofferdam to facilitate the construction of a new inlet manhole.

[caption id="attachment_26828" align="alignnone" width="1200"] Completed cofferdam and 280 ton crawler crane - Courtesy of GRAHAM[/caption]

Craneage: The craneage requirements for the entire project were critical in developing the construction methodology and phasing of the works. Multiple heavy and bulky lifting operations were required to construct the new Upper Crescent Wastewater Pumping Station. These included lifting 25-ton excavators into and out of the cofferdam, lifting of the 10-ton steel plate wall shuttering/formwork used to cast the circular pumping station structure, pulling of the sheet piles with vibro hammer and installation of the large precast roof beams and slabs.

A 280-ton crawler crane was selected as the suitable crane for our project needs. The imposed loading of the crawler crane also had to be considered in the design of the cofferdam, due to the loading it would place onto the cofferdam structure. Early planning of the detailed and complex construction methodology streamlined the construction process and avoided any major delays or unforeseen complexities in the construction of the new WwPS.

Concrete pours & precast roof: Due to the proximity to Comber River/Strangford Lough and the findings from the ground investigation during the ECI, it was anticipated that a high-water table would be encountered with steady flow of groundwater infiltration. However, the reality was much better than expected. The sheet pile installation was much more effective at cutting off groundwater infiltration than anticipated, significantly reducing the dewatering resources.

The new WwPS is a 15m internal diameter reinforced concrete structure with internal dividing wall, which splits the structure into the stormwater storage tank and foul pumping station wet well. The concrete structure was cast in situ in 15 steps. Concrete pours starting with the base slab and followed by five 1.35m high kicker pours to contain the internal benching. [caption id="attachment_26821" align="alignnone" width="1200"] (left) Reinforced concrete pumping station structure under construction and (right) roof beam and completed RC structure - Courtesy of GRAHAM[/caption]

The main walls were then cast; the remaining 7.5m height of the structure in five wall pours (four quarter radius pours and the internal dividing wall pour). The walls were cast using custom adjustable radius steel formwork shutters. Every effort was taken to maximise the speed and ease of construction, and the larger pours reduced the number of construction joints within the wastewater retaining structure.

The roof beams were precast on site due to their size and weight; 1m deep cross sections weighing approximately 20 tonnes each. A steel platform was constructed on site, on which each of the roof beams was cast while the tank structure was under construction.

The roof slabs were set into pockets cast into the top of the tank walls, with a H-shape beam over the wet well to accommodate large access covers for the three submersible pumps and two mixer pumps. The roof deck consisted of 22 precast slabs, which were cast off site due to insufficient space on site. The largest slab weight was 14 tonnes.

Inlet manhole: Upper Crescent WwPS receives incoming flows from the Comber Catchment via three gravity sewers entering from three corners of the site. The sewers all combine in the new inlet manhole, which was constructed adjacent to the new WwPS. Within the new inlet chamber, there are two manually operated penstocks. These can be used to direct flows into the wet well or storm tank as required, via the two independent pipelines shown. This provides NI Water operatives the opportunity to isolate the wet well during period of maintenance and utilise the storm tank to receive the incoming flows. [caption id="attachment_26820" align="alignnone" width="1200"] (left) Roof beam and completed RC structure and (right) incoming sewers - Courtesy of GRAHAM[/caption] Turn of flows

The commissioning of the new pumping main required a temporary shutdown of the WwPS to disconnect the existing pumping station and connect the new pumping station to the pumping main. This critical activity required meticulous planning and detailed coordination between the contract team and NI Water.

The work was programmed for forecasted dry days to ensure flows were reduced during the operation. Regular commissioning meetings were held with NI Water and the contract team in advance of the proposed works. Detailed discussions concerned the proposed works, programme and specific requirements in a systematic approach to confirm with relevant stakeholders that all eventualities had been considered before the works were progressed.

The final connection to the rising main was programmed to take place at night, during an 8-hour period when incoming flows would be at a minimum. The works would also be very weather dependant, as wet weather would dramatically reduce the amount of time available to complete the connection. The additional stormwater in the combined network could potentially overwhelm the on-site storage more rapidly than the team could complete the connection.

[caption id="attachment_26829" align="alignnone" width="1200"] Wet well pumps - Courtesy of GRAHAM[/caption] The existing Upper Crescent WwPS was taken out of service on 26 February at 23.00. The inlet pipe to the new WwPS was opened and the existing pipeline to the old WwPS isolated. The existing pumping station wet well was pumped down to its lowest possible point possible to provide maximum storage. Then approximately 500m of 450mm HDPE diameter rising main was drained back to the existing pumping station wet well. The new pumping station was used to provide additional on-site storage of 687m3. The team worked through the night and the rising main connection was completed by 05:00 the next morning. Commissioning

Once the pumping main connection was completed, the new Upper Crescent Wastewater Pumping Station became operational and a 28-day trial period to verify the station’s functionality/reliability to the client commenced. During the 28-day trial, the existing wastewater pumping station was methodically demolished, down to the basement levels ensuring that the new WwPS was not affected.

The excavation was backfilled with engineered fill to ground level in preparation for final hardstanding construction and landscaping, which was completed during the final weeks of construction.

[caption id="attachment_26823" align="alignnone" width="1200"] Demolition of the existing WwPS - Courtesy of GRAHAM[/caption] Community engagement

Upper Crescent WwPS is located at the end of a cul-de-sac and corner of a public park. Ahead of construction commencing on site and throughout the work, a number of public relations activities were employed to inform the many stakeholders about the project and in particular the piling activities, removal of spoil from site and turn of flows when commissioning the new pumping station. These included: regular briefings to local elected representatives; one-to-one meetings with stakeholders; letter drops; house calls; school visits to the site; press releases and social media announcements.

During the project’s construction phase, GRAHAM needed some additional lands to enable the construction of the new Upper Crescent WwPS, as the pumping station would occupy most available lands within the existing site. The construction team where therefore required to obtain a section of the neighbouring Muckers Park owned by Ards and North Down Borough Council to form a temporary site compound and provide additional land for a crane platform. The crane platform required a diversion of footpath used by the local Park Run.

Upper Crescent WwPS: Timelapse video

Early engagement with Comber Park Run enabled successful diversion of footpaths for the weekly race and patrons of the park. The diversion had to be artificially lengthened, to ensure that the length of the park run circuit was not shortened. During the construction of the new WwPS, GRAHAM provided refreshments for a number of park runs, distributing NI Water reusable water bottles and provided a cake for the Park Run’s 10th Anniversary.

On completion of the WwPS, the park was reinstated to its original configuration and handed back to the Ards and North Down Borough Council. Upper Crescent WwPS was operational from 27th February 2025 with site-wide testing and commissioning of the plant successfully undertaken for handover to NI Water in June 2025.

Dearne Reach is a 4.3-hectare Integrated Constructed Wetland (ICW) in Clayton West, Huddersfield, designed to enhance water quality along 4km of the River Dearne. Delivered by Mott MacDonald Bentley on behalf of Yorkshire Water, this ICW will reduce levels of un-ionised ammonia and improve storm flow treatment in line with the salmonid fundamental intermittent standards. To deliver this nature-based solution, Mott MacDonald Bentley excavated 13 wetland cells covering over 44,000m2 (equivalent of 7 football pitches!), creating space to house more than 350,000 wetland plants. Project background

As an alternative to the traditional grey infrastructure solution, which initially would have entailed 7,000m3 of additional storm storage and a 4.5km diversion of final effluent to a lower river reach, the Dearne Reach ICW offers a sustainable approach to pollution mitigation. Funded by Yorkshire Water as part of their capital delivery programme, it is currently the largest ICW developed in the UK to improve water quality while increasing storm storage resilience.

Aligning with Yorkshire Water’s WFD drivers and net zero ambitions, this project pioneers an ICW tailored for intermittent storm overflows, distinguishing itself from conventional ICWs that require constant inflow. Its innovative design ensures effective management of stormwater variability and will contribute to driving continuous innovation in nature-based solutions across the water industry.

[caption id="attachment_25943" align="alignnone" width="1200"] Construction of the first cells - Courtesy of MMB[/caption] Integrated constructed wetlands

Constructed wetlands are engineered ecosystems that harness natural processes to treat wastewater, stormwater, and industrial effluents. Sometimes described as ‘nature’s kidneys’ because of their ability to filter and clean wastewater by mimicking natural wetlands, these systems use porous media beds and emergent plants to remove contaminants through physical, chemical, and biological mechanisms.

Various treatment wetland types exist, including free water surface wetlands - also known as integrated constructed wetlands (ICWs).

ICWs allow water to flow above the soil through aquatic plants, enabling the removal of suspended solids, nutrients, and pathogens. These passive systems, closely resembling natural wetlands, rely on processes such as adsorption, precipitation, sedimentation, and filtration to improve water quality.

[caption id="attachment_25944" align="alignnone" width="1200"] Cell construction - Courtesy of MMB[/caption] Advantages for Dearne Reach

The ICW at Dearne Reach offers numerous advantages:

Water quality improvement: Effective removal of nutrients, heavy metals, pathogens, and organic pollutants. Carbon sequestration: Capturing carbon within plant biomass and soil, contributing to achieving net zero goals. Biodiversity enhancement: Providing habitats for birds and other wildlife, supporting ecological balance. Community benefits: Creating green spaces for public enjoyment and research opportunities. Versatility: Adapting to varying wastewater loads and flows, making it highly efficient at stormwater management. Low operational costs: Passive systems with minimal maintenance and no chemical requirements over decades, unlike conventional treatment plants. Plantings

At Dearne Reach, 52 different species of plants have been designed to sit in 13 adjacent cells in which over 350,000 plants adsorb nutrients from storm overflow discharges and wastewater flowing out of the Clayton West Wastewater Treatment Works.  These have been specifically selected for the treatment capacity, and alongside the enhancement of existing hedgerows across the site, has enabled a staggering 38% biodiversity net gain in terrestrial habitats.

[caption id="attachment_25945" align="alignnone" width="1200"] Liner installation - Courtesy of MMB[/caption] Variable stormwater discharges

The project introduced an ICW specifically designed to treat intermittent storm overflows. Unlike traditional ICWs, which are effective only with constant inflow, this innovative design can handle the variability and unpredictability of stormwater discharges. The wetland is divided into multiple cells, each optimised for maximum retention time and pollutant removal.

Advanced hydraulic controls and computational fluid dynamics (CFD) simulations were employed to model and optimise the flow through the wetland, ensuring effective treatment of fluctuating volumes and pollutant loads.

Pumping station & rising main

A new wetland pumping station has been designed to raise up to 350 l/s of flows from Clayton West WwTW to the ICW through a new rising main constructed using HDD trenchless methods. Once the water reaches the head of the wetlands, the entire system is passively flowing through two precast concrete distribution chamber structures and fourteen 1.4m wide cascades to transfer the water through each of the 13 cells.

Harnessing solar power

The innovative design harnesses solar power to operate a level sensor and flow meter chamber to successfully manage stormwater variability whilst achieving a passive system ICW with no additional power requirements. The introduction of the solar panels mean that the flow monitoring chamber could be installed to provide future quantity and quality monitoring data, which can be shared to support the evidence base of these emerging infrastructures.

As the largest ICW developed in the UK, its unique design and successful results will contribute to driving continuous innovation in nature-based solutions for storm management across the water industry. It stands as an excellent example of the power of collaboration between civil engineering and nature-based solutions to mitigate the impacts of climate change and promoting sustainable development.

[caption id="attachment_25941" align="alignnone" width="1200"] All cells constructed - Courtesy of MMB[/caption] Collaborative approach

To successfully design and build a wetland on the scale of Dearne Reach it was clear from the project outset that a collaborative design approach would be key to both a successful programme and commercial output. Therefore, collaboration between the design team, digital delivery team and geotechnical experts was fundamental. The challenges facing the site included, high shallow perched groundwater, sandy, gravelly clay requiring high degrees of compaction, and a requirement for over 13,000m3 of material for topsoil reuse. Alongside construction on a complex site within a coal mining legacy area, with archaeological potential and intersecting with a public right of way.

Dearne Reach ICW: Supply chain: key participants Principal designer & contractor: Mott MacDonald Bentley Outline design: Stantec UK Pressure testing: Ant Hire Groundworks: Lowthers Groundwater treatment: Siltbuster Group HDD rising main: Joseph Gallagher Ltd Liner suppliers: SIG Construction Accessories Precast structures: Craven Concrete Ltd Headwalls: Althon Ltd Treatment works package: HB Tunnelling Electrical package: Circle Control & Design Systems Ltd MCC installation: Technical Control Systems Ltd Communications instruments: Churchill Controls Ltd Wetland plant suppliers: Salix River and Wetland Services Grass & flower seed: Hurrells & Mclean Seeds Ltd Erosion protection: Geogrow Gate valves: Affco Flow Control (UK) Ltd Actuators: Glenfield Invicta Ltd Instrumentation: Marlec Instrumentation: IFM Electronic Ltd Flow meter: SIRIS Environmental Pipework: Aquaspira Ltd [caption id="attachment_25946" align="alignnone" width="1200"] Planting completed in all the cells - Courtesy of MMB[/caption] HDPE pipework & couplers: Westwood Pipelines Ltd HDPE pipework & couplers: Radius Systems DI pipework: George Green (Keighley) Ltd DI pipework: Electrosteel Castings (UK) Ltd DI pipework: UTS Engineering Ltd Metalwork: Fabtek Duct pits: Advanced Infrastructure Systems Pipe supports: Midland Fixings Ltd Drainage pipework: Wolseley UK ltd Drainage pipework: Myers Building Supplies Drainage pipework: Keyline Civils Specialist Ltd Pumps: Xylem Water Solutions Lifting gantry: Peter Cassidy (Leeds) Ltd Welfare cabins: Nixon Hire | Wernick Group Bolt-sets: BAPP Industrial Supplies Bolt-sets: VULCAN Industrial Fasteners RoadCem access roads: DNS Aggregates: Hague Plant ltd Concrete: Heidelberg Materials Plant hire: Lynch Plant Hire Plant hire: Grantham Industries Ltd Plant hire: Flannery Plant Hire (Oval) Ltd [caption id="attachment_25937" align="alignnone" width="1200"] Filling the first cells with water - Courtesy of MMB[/caption] Construction achievements

During construction, several notable achievements were made:

Groundwater management: As a result of high groundwater levels on the site, the system hydraulics were analysed, and cell height adjusted. This optimised the cut-fill balance and ensured no material import would be required to construct the embankments, ultimately preserving resources and reducing material waste whilst ensuring there would be no flotation risk

Bypass pipework reductions: Through the development of robust future access and maintenance plans, an opportunity was realised to eliminate unnecessary bypass pipework infrastructure. Initially, this had been proposed to allow each cell to be isolated for future maintenance. The removal of this pipework scope significantly reduced the carbon footprint and project costs.   

Sustainable lining solution: As the existing ground did not have a suitable impermeability to protect the underlying groundwater, the ICW had to be lined. To avoid the use of extensive plastic on site, a geosynthetic clay liner was used to create a self-sealing, resilient hydraulic barrier while minimising environmental impact.

Archaeological and geological integrity: The team ensured the coal mining legacy areas remained undisturbed, with archaeological trenching conducted site-wide to ensure any potential pre medieval features were not disturbed during construction.

RoadCem technology for sustainable access: Traditional concrete access roads were replaced with Roadcem soil stabilisation technology to reduce the required material import and associated carbon footprint with use of extensive artificial concrete.

Biodiversity commitment: 350,000 locally sourced plants were installed, arranged in seven planting zones, achieving a 38% biodiversity net gain in terrestrial habitats.

Public right of way enhancements: Social value was equally important to the project and the team collaborated with the local council to enhance the public right of way, improving accessibility with a wheelchair-friendly, 2m-wide footpath along the perimeter of the ICW, featuring timber fencing for optimal wetland viewing points to support community health and well-being.   

Carbon savings: The project has achieved a 60% reduction in embodied carbon and 40% reduction in operational carbon across its lifecycle – delivering a more environmentally friendly solution in comparison to the original grey infrastructure solution.

[caption id="attachment_25940" align="alignnone" width="1200"] Fully planted wetland - Courtesy of MMB[/caption] Innovative digital construction

From the outset, early collaboration with Mott MacDonald Bentley’s digital delivery team identified an opportunity to pilot the use of intelligent plant machinery, alongside a ‘Smart Construction Dashboard’ during the build.

Prior to mobilisation on site, the model and delivery programme was shared for upload into the Smart Construction/Earthbrain software. These platforms initially use Artificial Intelligence to generate an efficient delivery output, detailing size, type and number of machines required. They also generate a powerful earth shifting model, highlighting the most efficient distribution workflow for the cut/fill material to travel and be placed.

This was most useful to compare the tendered assumptions and check for any oversights in the planning phases. This approach improved accuracy, efficiency, and most importantly, improved health and safety standards on site. This marked a first-of-its-kind trial for deploying intelligent plant in the construction of a nature-based solution.

The site team reported significant benefits, particularly given the scale of the excavation, such as:

Model-driven excavation optimised material use, eliminating unnecessary cutting/filling and promoting a right-first-time methodology. Automated systems reduced manual surveying and minimised plant-people interaction, ensuring safer site operations. Precision excavation reduced material waste while moving 65,000m3 (117,000 tonnes) of soil, limiting reliance on imported fill. [caption id="attachment_25939" align="alignnone" width="1200"] Wetland plants developing - Courtesy of MMB[/caption] Successes & summary

The Dearne Reach ICW Project exemplifies sustainable development by delivering a low-carbon stormwater management solution. Leveraging natural processes such as sedimentation, filtration, and biological uptake, the wetland effectively removes pollutants and reduces the ammonia levels in stormwater in line with the salmonid fundamental intermittent standards. This enhances water quality and strengthens local biodiversity, aligning with global climate adaptation efforts.

The project’s innovative approach to managing stormwater discharges aligns with Yorkshire Water’s efforts to mitigate and adapt to the effects of climate change. It stands as an excellent example of the power of collaboration between civil engineering and nature-based solutions to mitigate the impacts of climate change and promoting sustainable development.

This first-of-its-kind trial has set a new benchmark for future wetland and nature-based solution projects across the water industry, with lessons learned shared to inspire continuous innovation in sustainable construction.

Old Leake and Wrangle are rural Lincolnshire communities set within the low‑lying coastal plain east of Boston. The area features dispersed settlements, agricultural land, and an extensive network of drainage channels and waterways that shape both the landscape and the supporting infrastructure. Supplying reliable drinking water in this environment presents unique engineering challenges - demand can vary widely, pipe routes stretch across long rural corridors, and with limited alternative supply routes, maintaining network resilience is essential. Old Leake Distribution Zone

The Old Leake Distribution Zone (DZ) played a vital role in supplying homes, farms, and local businesses across the area. Water is supplied via the North Boston Trunk Main, boosted at Haltoft End, and stored at Old Leake Water Tower, which regulates pressure across the network.

For many years the system operated reliably, however, changes to supply routes, ageing infrastructure, and increasing demand pressures had reduced network resilience, making the system more vulnerable during peak consumption periods.

Recognising the importance of securing long-term supply reliability for the community, Anglian Water commissioned Anglian Water’s @one Alliance to deliver a strategic reinforcement scheme to protect water services for over 1,300 properties.

The issue

In recent years, peak demand periods had exposed a supply-and-demand imbalance within the Old Leake Network. During times of high-water use, such as warm weather, irrigation demand, or simultaneous domestic consumption, the network struggled to maintain adequate pressure. This resulted in low pressure affecting up to 1,366 properties across Old Leake and Wrangle and increased the risk of temporary supply interruptions. While pressure typically recovered once demand reduced, the recurring nature of these events created a growing risk to service reliability and customer satisfaction.

[caption id="attachment_29049" align="alignnone" width="1200"] Preparing for a section of open cut pipe installation - Courtesy of @one Alliance[/caption]

Several factors contributed to the problem, including limited network capacity as the existing pipe diameters and flow capacity were insufficient to maintain pressure during peak demand.

Other contributing issues included restricted treated water storage, as storage at Old Leake Water Tower was not sufficient to buffer high demand events; ageing pipe materials, with sections of asbestos cement (AC) and cast iron (CI) mains experiencing a high burst frequency, particularly during demand surges; and reduced system resilience, as historically the network had benefited from additional supply routes, but damage to former supply mains had reduced redundancy, leaving the zone more vulnerable.

Because the low pressure only occurred during peak demand and not continuously, affected properties were not eligible for inclusion on the DG2 Register. Nevertheless, the situation posed operational risks, including potential ODI penalties for interruptions to supply and pressure failures. And without intervention, the frequency and severity of pressure issues were likely to increase over time.

Supply chain

The successful delivery of the Old Leake reinforcement scheme relies on the collaborative expertise of @one Alliance and its specialist supply chain partners, including:

Client: Anglian Water Project delivery: @one Alliance Principal contractor: Balfour Beatty Horizontal directional drilling: Barhale HPPE water main: SIMONA Peak Pipe Systems Ltd Pressure control: i2O Water Ltd Pressure reducing valves: AVK UK Ltd Pressure reducing valves: Wolseley UK Bi-directional pressure relief valve: CLA-VAL UK Ltd Traffic management: Clancy Traffic Management (CTM) Road reinstatement: WN Surfacing Ltd The solution

To address these challenges, Anglian Water’s @one Alliance are nearing completion a £3.2m reinforcement scheme designed to improve hydraulic capacity, stabilise pressure, and strengthen overall network resilience. At the core of the project was the installation of approximately 4.7km of new 225mm high-performance polyethylene (HPPE) water main, creating a stronger and more reliable supply route across the distribution zone.

To minimise disruption to residents and road users, most of the pipeline was installed using horizontal directional drilling to minimise excavation. This approach significantly reduced traffic disruption, reinstatement work, and the overall environmental impact.

[caption id="attachment_29051" align="alignnone" width="1200"] (left) Start of a section of open cut works and (right) pipe installation underway - Courtesy of @one Alliance[/caption]

Shorter sections were installed using open-cut methods where appropriate, including field crossings and limited road sections. A strengthened SDR11 pipe was used beneath the Hobhole Drain to ensure durability at this critical crossing point.

The new reinforcement main replaced ageing galvanised iron pipework and enabled the removal of sections of climate-vulnerable mains, improving long-term reliability and reducing the likelihood of future failures.

To maintain consistent pressure during high demand, the scheme incorporated modern pressure control and monitoring technology, including:

Installation of pressure reducing valves (PRVs) to stabilise pressure. District metering and flow monitoring systems. Intelligent pressure control using i2O technology. Real-time telemetry for performance monitoring. Additional isolation valves to improve operational flexibility.

These smart systems enabled dynamic pressure management, allowing the network to respond in real time to changes in demand while reducing stress on infrastructure.

Targeted pipe replacements and new cross-connections were installed to improve how water could be routed around the local network. This allowed operators to redirect flows during peak demand, maintenance activities, or unexpected incidents, ensuring customers remained supplied at all times of the day.

Hydraulic modelling confirmed that the upgraded system would meet required flow demands without negatively affecting the wider distribution network.

The delivery approach prioritised sustainability alongside engineering performance, including extensive use of horizontal directional drilling to reduce excavation and reinstatement impacts, and efficient materials selection to improve durability and lifespan.

Construction methods contributed to a 64% reduction in embodied carbon compared with historic benchmarks. This project also aligned with Anglian Water’s commitment to delivering low-carbon infrastructure around the region, while improving resilience at the same time.

[caption id="attachment_29048" align="alignnone" width="1200"] Traffic management in place - Courtesy of @one Alliance[/caption] Community impact

Clear communication and minimising disruption were key priorities throughout the project. Around 190 nearby customers received advance notification letters, supported by press releases, social media updates, and SMS reminders. Messages were tailored for residents close to construction areas, explaining what to expect; such as potential noise, site activity, and accurate timelines. Also, information boards were installed at the site compound so passers-by could easily understand the purpose of the works. Local parish councils were engaged early and kept informed throughout, ensuring community questions and concerns were listened to and addressed.

In addition to infrastructure improvements, the team sought to leave a positive local legacy. Some team members supported a volunteering initiative in Old Leake, working with the parish council and community groups to complete a litter pick in early 2026, filling 18 bags of litter on a road that was closed during our traffic management periods.

Works were carefully planned to minimise disruption to everyday life. No public rights of way or local bus routes were affected, businesses were contacted directly to coordinate access, and the main site compound was positioned on The Gride to further limit community impact.

This proactive approach ensured construction could progress safely while maintaining access and supporting normal local activity.

[caption id="attachment_29047" align="alignnone" width="1200"] Teams members working with community groups to pick up litter - Courtesy of @one Alliance[/caption] Conclusion

The project is a vital investment in strengthening water supply resilience for the Lincolnshire communities of Old Leake and Wrangle. By installing a new reinforcement main, upgrading pressure management systems, and improving network flexibility, it has resolved long‑standing peak‑demand issues and significantly reduced the risk of low pressure and supply interruptions.

Beyond the improvements themselves, the project demonstrated the value of community engagement, educational outreach, and local volunteering in delivering infrastructure that benefited both customers and the wider community.

Set to complete in mid-2026, the upgraded network will provide more consistent water pressure during peak demand, reduced burst risk, improved reliability, smarter monitoring, and proactive network management. It will also enhance resilience during operational incidents and peak flows, with a lower carbon impact through the team’s project delivery and engineering methods.

Through innovative engineering, collaborative delivery, and meaningful community engagement, Anglian Water’s @one Alliance is strengthening essential infrastructure and helping secure a resilient water supply for future generations across this rural Lincolnshire community.