Supply Chain - Contractors - Reinforced Concrete

Under the Water Retaining Structures Framework, OCU Group is delivering multiple service reservoirs, including schemes at Preston and Chaul End in Luton. These projects are designed to increase storage capacity, improve operational flexibility and support future strategic water transfers.

The WRS Framework is being delivered through an integrated design and build model, combining in-house engineering capability with specialist design partners and a coordinated supply chain.

An early contractor and supplier engagement approach was implemented to align structural design with off-site manufacturing capabilities. This enabled key decisions regarding construction methodology, sequencing and material selection to be made at an early stage.

Early engagement with FLI Precast Solutions enabled OCU Group to align structural design with off-site manufacturing principles. This ensured reservoir structures were optimised for precast construction, improving constructability and reducing interface risks between structural and mechanical elements.  OCU provided overall design coordination, construction delivery, and mechanical and electrical integration across the schemes.

This approach has enabled OCU Group to standardise key elements of design and delivery across multiple sites, improving efficiency, reducing risk and enabling a repeatable delivery model for future schemes.

The focus of this case study is Preston Service Reservoir which is a representative example of the design and construction approach adopted across the framework.

The Preston Service Reservoir comprises a single cell potable water storage structure with a total capacity of 20 megalitres (ML), constructed adjacent to the existing reservoir. Once operational, the combined assets provide approximately 38 ML of storage capacity.

The structure was formed using a reinforced concrete raft foundation combined with a semi-precast superstructure. Precast wall panels, columns and roof planks were manufactured off site and installed sequentially.

OCU Group selected precast construction in response to site constraints and programme requirements. Compared with traditional in situ construction, the approach reduced on-site activities including formwork, reinforcement installation and concrete pours, improving safety and reducing construction duration. It also enables concrete quality control to be carried out within a factory quality-controlled environment where the weather is not an issue.

Precast elements were delivered and installed sequentially upon arrival, minimising on-site storage requirements and improving efficiency within the constrained site footprint.

Off-site manufacturing also enhanced quality control, with structural components produced in a controlled environment, improving consistency and long-term performance.

OCU Group applied Building Information Modelling (BIM) across the framework to support design coordination and construction delivery.

At Preston, a detailed 3D model integrated structural, mechanical and process elements, enabling accurate coordination of pipework, valves and interfaces. This reduced delivery clashes during construction and improved installation efficiency.

The model also enabled assessment of operational requirements, including access, maintenance and asset management considerations. Stakeholders were able to visualise the completed facility and make informed decisions during the design stage.

The completed BIM model provides a comprehensive digital record of the asset, including manufacturing and installation data, supporting long-term maintenance and future upgrades.

The reservoir was constructed on a reinforced concrete raft foundation designed to distribute loads across underlying clay and chalk strata. Geotechnical investigations confirmed consistent ground conditions, allowing for a uniform foundation design. Any localised weak material encountered during construction was excavated and replaced with compacted structural fill to ensure stability.

A key feature of the construction approach was the retention and reuse of excavated materials. Topsoil and subsoil were stored and reused on site for backfilling and landscaping, maintaining a zero net cut-and-fill balance.

OCU Group’s approach reduced vehicle movements, minimised environmental impact and improved site safety. It also enhanced programme resilience by reducing reliance on imported materials and maintaining continuity during adverse weather conditions.

Topographic surveys were undertaken throughout construction to verify earthworks volumes and confirm compliance with design requirements.

At Preston, a carbon assessment undertaken in accordance with ISO 14064 standards identified total construction emissions of approximately 1,062 tonnes of CO2 equivalent.

A primary reduction measure was the use of precast concrete incorporating ground granulated blast furnace slag (GGBS) as a partial replacement for Portland cement. Approximately 50% of the cement content was replaced, with higher substitution levels achieved under favourable conditions.

This resulted in an estimated saving of 138 tonnes of CO2 compared with conventional concrete mixes. Additional reductions were achieved through the use of recycled aggregates, reducing reliance on virgin materials and supporting circular economy principles.

The semi-precast approach also reduced the volume of reinforced concrete required and limited on-site activities, contributing to an estimated 50% reduction in embodied carbon compared with in situ construction.

The Chaul End Service Reservoir in Luton has been delivered using the same design and construction principles established at Preston.

The scheme provides additional potable water storage and adopts a semi-precast structural solution, incorporating off-site manufactured components, a reinforced concrete base and integrated valve arrangements.

The same coordinated, off-site-led approach was applied, enabling efficient delivery within site constraints and maintaining programme certainty.

The application of a standardised delivery approach across both Preston and Chaul End has enabled OCU Group to refine its methodology, improving efficiency, reducing risk and enhancing sustainability performance across the framework.

Through the delivery of the Water Retaining Structures Framework (Bedfordshire and Hertfordshire), OCU Group has enabled significant new potable water storage capacity across multiple sites. The strong collaborative working relationship established between Affinity Water and OCU has been essential to this.

At Preston, 20 ML of additional storage capacity has been delivered, increasing total site capacity to approximately 38 ML and improving supply resilience for the surrounding network.

Across the framework, the adoption of a standardised precast construction methodology has delivered improved programme certainty, reduced embodied carbon and enhanced safety.

The repeatable delivery model established through schemes such as the Preston and Chaul End Reservoirs provides a scalable approach for future reservoir projects, supporting ongoing investment in water infrastructure and strengthening long-term resilience across Affinity Water’s network.

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.

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.

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.

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

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.

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:

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.

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.

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.

The Lower Stondon area contains environmentally sensitive features, including agricultural land and small watercourses, which would require careful management during the design and construction of the project. These factors, combined with the network’s strategic importance, emphasise the need for a technically robust and environmentally responsible solution.

As a result, the Lower Stondon Water Network Reinforcement Scheme was required to support both existing customers and new developments, addressing long-term operational and resilience needs, and providing a scalable platform for future growth. Anglian Water’s @one Alliance was tasked with designing and delivering the £1.7m project.

The overriding issue in the area was the capacity and pressure constraints of the network. Without timely reinforcement, the increasing demand from new residential developments risked reduced network pressure during peak consumption periods, low-pressure incidents in existing properties and an increased likelihood of interruptions or service failures. Hydraulic modelling identified the sections of the existing distribution network that were approaching operational capacity limits, and these findings highlighted the need for targeted reinforcement in four areas of the network to maintain compliance with service standards, regulatory obligations and overall Anglian Water’s customer expectations.

The original AMP7 plan intended for the scheme to be delivered in a single phase. However, detailed investigations revealed constraints that required a 3-phase delivery approach. Stage 1 was to be undertaken and commissioned in 2024, while Stages 2 and 3 were scheduled for delivery during AMP8.

Delivering Stage 1 early allowed the network to see partial benefits, including increased hydraulic capacity and improved pressure, while design and approvals for the later stages were finalised.

During the Stage 3 design, trial holes were excavated along Bedford Road in the summer of 2024 to verify the feasibility of the proposed pipeline route. These investigations revealed that installation along the original alignment would require a full road closure, creating a 37 mile diversion for local traffic.

This proposed diversion was considered unacceptable due to the operational, social and environmental impacts, as this would have caused substantial disruption for residents, commuters and local businesses, while increasing the vehicle emissions along the extended route and potentially provoked negative community perception.

As a result, the @one Alliance project team undertook a redesign of Stage 3, employing collaborative engineering and advanced hydraulic modelling. This alternative solution maintained the necessary hydraulic performance while avoiding the extended road closure, reducing disruption for the local community and supporting operational continuity.

To avoid the closure of Bedford Road, the @one Alliance worked collaboratively with Anglian Water to explore alternative connections within the local distribution network. This resulted in the final solution incorporating a series of cross connections along several local roads, including Brassey Way, Woodpecker Mead, Pollards Way, Bluebell Drive and Applecroft.

These cross connections provide hydraulic capacity and pressure benefits comparable to the original Bedford Road alignment, while enhancing network resilience, redundancy and operational flexibility. By strategically integrating these connections, the system maintains reliable service to existing customers and accommodates future growth without relying on a single linear main.

The reinforcement scheme includes approximately 1.8km of HPPE mains, delivered in multiple diameters to optimise hydraulic flow and maintain network pressure.

Stage 1: The first stage comprised 769m of 225mm HPPE SDR21 main installed by open cut across agricultural land. This stage was commissioned in July 2024, allowing early realisation of network capacity benefits while subsequent stages were designed.

Stage 2: The second stage required the installation of 145m of 225mm HPPE SDR21 pipe and 397m of 180mm HPPE SDR17 pipe by conventional open-cut method across fields and recreational areas. In addition, 82m of 125mm HPPE SDR17 pipe was laid along Loganberry Way and 506m of 225mm HPPE SDR11 pipe installed by directional drilling beneath a disused golf course earmarked for future development.

Valve and washout spurs have been incorporated at both ends of the HDD section, enabling future diversions to accommodate planned developments without interrupting network supply.

Stage 3: The final stage involved installing 549m of 180mm HPPE SDR17 pipe across agricultural fields using a combination of open‑cut excavation and directional drilling. This section included crossings of an Internal Drainage Board (IDB) brook and Bedford Road. A further 48m of 180mm HPPE SDR11 was laid along Brassey Way to complete the final connection.

Cross connections included 130m of 180mm HPPE SDR17 across recreational grounds and Pollards Way, 179m of 125mm HPPE SDR17 along Woodpecker Mead, and  6m of 125mm HPPE SDR17 connecting existing mains between Bluebell Drive and Applecroft.

The project used a hybrid construction methodology, combining open-cut excavation and horizontal directional drilling. Open-cut methods were applied where feasible, providing efficient installation and straightforward connection to existing infrastructure. HDD was undertaken by Harper Services in constrained areas, reducing surface disruption and avoiding environmentally sensitive zones.

Construction was carefully phased to maintain operational continuity, ensuring uninterrupted water supply throughout the works. With temporary isolation points and controlled tie-ins having been implemented for Stage 2 and Stage 3 mains to minimise operational risk and maintain system performance during installation.

The successful delivery of the Lower Stondon project has relied on close collaboration across a wide range of technical and supply-chain partners.

Environmental protection has been fully integrated into the planning and delivery of the Lower Stondon scheme. The use of directional drilling has minimised surface disturbance and protected local habitats, while careful phasing and alignment adjustments have reduced road closures, lowering traffic-related emissions and limiting disruption to the local community. Soil management, reinstatement and drainage measures comply with recognised environmental best practices and avoiding major diversion routes has further prevented unnecessary fuel consumption and greenhouse gas emissions.

These measures contribute to a sustainable and environmentally responsible delivery of essential infrastructure. At the same time, the project has delivered measurable carbon and environmental benefits, including an 84% reduction in capital carbon compared with the baseline design. Together, these measures demonstrate how modern engineering solutions can successfully balance operational performance, environmental responsibility, and community impact.

The Lower Stondon Scheme also provides a wide range of operational benefits. By increasing hydraulic capacity, the reinforced network now supports both existing customers and the 764 new homes being delivered in the area. The improvements resolve previously identified low-pressure issues across the catchment, ensuring stable and reliable water supply during peak demand periods. The combination of reinforced mains and cross connections strengthens operational continuity, allowing the network to maintain performance under both routine and exceptional conditions.

At the time of writing (March 2026), the Lower Stondon Growth Scheme is nearing completion, delivering a reinforced potable water network that meets the needs of both existing residents and the growing number of new homes in the area. The project has strengthened the network’s hydraulic capacity, improved pressure performance and enhanced operational resilience, ensuring that customers can continue to receive a reliable water supply even as demand increases.

The scheme has also delivered a number of tangible community and environmental benefits. Careful planning and a phased delivery approach allowed Stage 1 benefits to be realised in 2024, while the final stages of construction are now being completed. Throughout the works, operational continuity has been maintained through thoughtful network management, temporary isolation points, and controlled tie-ins, ensuring that customers experience minimal interruption to their water supply.

The Lower Stondon Scheme highlights the value of careful design, advanced hydraulic modelling and close collaboration across multidisciplinary teams. By integrating innovative engineering solutions with environmental and community considerations, the project demonstrates how modern water network reinforcement can meet the demands of growth, improve resilience and deliver sustainable outcomes.

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:

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.

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:

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.

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.

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.

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:

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.

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

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.

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.

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:

Phase 2: 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:

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

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 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.

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.

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.

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.

During the optioneering stage, a range of interventions were assessed to address the storm overflow impact, including catchment‑scale rainfall disconnection, increased pass‑forward flow, nature‑based treatment and conventional storage. Catchment disconnection was discounted due to the high levels of customer disruption required, while increasing pass‑forward flow was not feasible due to downstream hydraulic constraints. Given the overflow’s location adjacent to open land by the river, a nature‑based solution was identified as the most effective and deliverable option.

A two-stage approach was chosen to maximise success, with an aerated reed bed providing initial intensive solids capture followed by two Integrated Constructed Wetland (ICWs) in series, providing effluent polishing and an opportunity for the industry to research wetland treatment in this application.

The favourable topography enabled a gravity system, eliminating the need for lifting flows and in turn, reducing operational energy demands. The field’s proximity to New Inn’s residents also allowed for place-making features for the local community, such as footpaths, an outdoor classroom and natural play areas, enhancing community engagement and educational opportunities.

The indirect monetary value of these wider benefits was captured in the decision-making stage via the use of CIRIA’s B£ST estimation tool, which estimated £12m in realised benefits over the next 40 years across social, natural and other capitals; something none of the grey solutions offered.

The existing storm overflow (SO) was located amongst trees on the edge of the field. The incoming pipe laid in the eastern corner of the field meant the SO could be relocated into a new compound, which will contain the following chambers and plant:

Design for Manufacture and Assembly principles were adopted to several elements of the compound. The screening and bypass chamber were fabricated off site by FP McCann Ltd, reducing the need to cast these chambers in situ.

Both the kiosks were prefabricated off-site by Morgan Marine Ltd to save time and reduce on-site activities in the construction phase.

The design team carried out a catchment Flow & Load Survey to ensure a better understanding of the design parameters required to achieve the ‘No Impact’ outcome. The survey gave insight into the challenges around pollutant loads in intermittent discharges, with varying concentrations of biochemical oxygen demand (BOD) and ammonia found in the excess diluted sewage; especially the difference between accommodating the ‘first flush concentration’ and weaker dilutions as a storm event continued.

Working collaboratively with the reed bed and ICW suppliers early in this stage, increased confidence in achieving the necessary pollutant removal in the final effluent.

A Flood Consequence Assessment (FCA) was completed as part of the planning application and the findings required the reed bed and wetlands to be moved further away from the river, reducing the size of the originally allocated footprint. The revised layout however, still provided sufficient treatment area (3,000m2 for the reed bed and a combined ICW treatment area of 2,400m2) and created additional space for the public to enjoy.

The planning application was critical to the success of this project, which was well received by local councillors and relevant bodies, in part, due to the extensive up-front work done by Arup’s planning team. Arup specialist teams carried out predictive odour and noise modelling of the solution to address concerns raised by the planning authority. The project team also engaged extensively with the local community through both in-person and online events, ensuring the design met local needs and preferences.

To align with the Sustainable Approval Body (SAB) requirements as part of planning approval, the design team implemented sustainable drainage features across the site. The maintenance track and vehicle areas in the compound were constructed from permeable TruckCell™ paving, made from recycled plastic, whilst vegetated swales and depressions were incorporated alongside the impermeable access track and footpaths. This reinforced the project’s low‑carbon and sustainable design ethos.

Construction started in January 2024, with Morgan Sindall Infrastructure mobilising to bring the nature-based solution system online before the regulatory deadline of 31 March 2025. The team navigated challenges including invasive species within the compound area and persistent groundwater during the large excavations, requiring an extensive dewatering activity (under approved Abstraction Licences).

Working with the sub-contractors, Natural Wastewater Solutions (NWS) for the reed bed, and Salix River and Wetland Services and Vesi Environmental Ltd for the integrated constructed wetland, 33,904 tonnes of soil were removed and the ground re-profiled. 30,000 tonnes was re-used off site, whilst 3,000 tonnes was recycled and re-used on site, with the final 904 tonnes taken to landfill, due to the presence of Japanese knotweed.

Due to the impermeable nature of the soil, the reed bed and constructed wetland both required under-draining to minimise the impact on the groundwater table. Once the under-drains were installed, the basins were constructed, which included the following:

The site team pushed to see the first flows through the system just 12-months later, ahead of the 31 March deadline and handled the heavy rainfall from Storm Eowyn on 24 January without any issue.

A robust sampling regime is currently underway to understand the performance of the individual stages and final effluent from the nature-based solution. This will inform future permitting of these types of solutions in cooperation with the environmental regulator, Natural Resources Wales (NRW).

The initial sampling results are promising, with significant reductions in BOD, ammonia, total suspended solids (TSS) and phosphorus in the final effluent. River water quality sampling upstream and downstream of the outfall is also being carried out to understand the impact of the scheme on the Afon Lwyd.

Welsh Water is participating in the Chemical Investigation Programme (2025–2030) with UKWIR, where samples from the wetlands are currently being used to help understand bio-accumulation of emerging substances such as pharmaceuticals in intermittent discharges.

With the site due to open to the public soon, Pont-y-felin Lane exemplifies a paradigm shift in storm overflow management, demonstrating how nature-based solutions can deliver technical excellence, environmental restoration, and community enrichment, all while setting a precedent for low-carbon infrastructure in the water sector. The forward‑thinking optioneering, combined with the client’s commitment to selecting a nature-based solution, over traditional ‘grey’ options, has resulted in a scheme that proves natural solutions can deliver more sustainable outcomes, for less.

Meadow Lane WwPS was identified as requiring significant base maintenance interventions due to the antiquated nature and condition of existing pumps, pipework and control assets which require a high level of maintenance; thus, imposing a risk of potential significant failure. The following observations were made on site:

NI Water Technical Support had also advised of occurrences of flooding within the dry well as a direct result of leaking pumps which required reactive maintenance and tankering operations.

Additionally, following completion of the 2007 Portadown Drainage Area Study, Meadow Lane WwPS was identified as a required output. It was outlined to NI Water the need for the existing Meadow Lane WwPS to deliver flow to full treatment (FFT) if the upstream network spill performances are to meet the Northern Ireland Environment Agency (NIEA) requirements for the Meadow Lane catchment area.

Model updates were completed in 2016 following flow monitoring surveys, and further inspections confirmed that the existing pumps could not deliver the required FFT. Therefore, the five CSOs identified by the NIEA as Unsatisfactory Intermittent Discharges (UIDs) could not be closed without significant intervention/upgrade at Meadow Lane WwPS. Model updates were also completed in 2020 to reflect predicted future 2040 flows.

The NIEA had identified the following five CSOs as UIDs:

Failure to address spills would lead to potential prosecution by NIEA and associated reputational damage due to potential serious sewage flooding and pollution to the Annagh River, Upper River Bann and the surrounding area.

NI Water appointed BSG Civil Engineering Ltd as the main contractor under an NEC3 Early Contractor Involvement (ECI) Contract. As the main contractor, BSG provided multi-disciplinary design, project and supply chain management and civil engineering and MEICA works for the contract from inception to completion.

The ECI phase allowed BSG to align resources and integrate objectives with the client, NI Water, and project managers, McAdam, at an early stage to benefit overall project delivery. This allowed for enhanced collaboration, innovation, value, efficiency and reduced whole life cycle costs for the project.

The purpose and drivers of this project were as follows:

The upgrade of Meadow Lane WwPS and the associated network was a large-scale infrastructure project located within a complex urban environment. The project saw:

Meadow Lane is an arterial route through Portadown town centre, providing access to several shopping facilities, restaurants and medical facilities. It was identified that significant traffic management, potentially involving lengthy diversions, would be required for an extended period to undertake the installation of the 1,500mm diameter tank sewer along Meadow Lane using open-cut methods.

Therefore, it was determined that a trenchless pipejacking method of installation would be adopted to install the full 380m of 1,500m tank sewer. Additionally, the use of a tunnel boring machine (TBM) would allow for a reduced potential environmental impact due to the reduction in surface disruption, dust, noise and vibrations; and provide enhanced safety for construction staff due to the automated installation process.

Due to the unstable ground conditions, a closed face slurry system was used as this technique allowed the area around the TBM to be supported with a pressurised bentonite mix, preventing collapse and ensuring stability. During this process the excavated material was pumped from the face of the TBM, through the installed tunnel, to an above-ground separation system where the excavated material was removed from the bentonite mix, allowing it to be recycled and returned to the tunnel face for reuse.

The tunnelling operation was undertaken in three stages with launch and reception pits installed to facilitate each drive stage alongside ancillary tunnelling operations; drive stages varied in length between 70m to 230m. Due to the varying and difficult ground conditions present along the proposed tunnelling route, launch pits and reception chambers were installed using a combination of both segmental shafts and traditional cofferdams.

The storm retention tank, inlet chamber, and wet well pumping station was designed as one structure. Due to the difficult ground conditions, high water table and proximity to existing NI Water assets, it was determined that secant piling would be implemented as a means of providing temporary support to facilitate safe excavation.

A specialist piling contractor was utilised to install 140 (No.) 750mm diameter secant piles to a depth of 18m below ground level before the installation of a reinforced concrete capping beam to complete the excavation support system. Once installed, the secant piled wall provided a watertight structure. Localised dewatering within the secant piled structure was used to ensure excavated material remained dry and suitable for reuse on site. Approximately 3500m3 of material was removed from the 21m diameter, and 10m deep excavation.

Construction of the storm tank consisted of a 1200mm deep reinforced concrete base, a 400mm thick external liner wall, and a 500mm internal dividing wall. The liner wall formwork was designed as a single sided system using Peri Rundflex and constructed in two lifts to meet temporary works restrictions.

The roof structure was constructed using 1250mm by 900mm precast beams and 450mm thick precast hollow core slabs. Structural screed was then poured to complete the structure.

The complex roof slab arrangement consisted of a variety of construction techniques including in situ reinforced concrete elements, precast concrete primary and secondary beams, structural steel beams and hollow core precast slabs. The complete design of the roof structure was provided by five different design companies working in collaboration ensuring each element adhered to the tight tolerances required for accurate placement.

Six sections of open-cut sewer installation were completed in this scheme. Boxed systems were used to provide temporary works excavation support for the pipe installations. Sewers were installed to depths of up to 7m below ground level in sites with limited working room. Traffic flows were controlled by complex traffic management systems.

The MEICA installation was completed in two stages. A new MCC was installed within the new GRP kiosk, and once all building services were installed, the NI Electricity supply was diverted to the new MCC panel which then backfed a supply to the existing MCC panel until turn of flows in April 2025.

Once civils construction had sufficiently advanced, the second phase of the mechanical fit out commenced, where the three 37Kw foul pumps and associated pipework were installed from the foul pumping station to the flow meter chamber. A 250mm Siemens MAG 5100w was then installed to measure the outgoing flow-rate. Two pump stools, 9Kw hydro ejectors and pipework were installed within the storage tank to jetwash the tank during storm events.

Three Eliquo Hydrok Ltd screens were installed into the following areas:

The main challenges faced during the delivery of Meadow Lane WwPS were a combination of site-specific constraints, environmental constraints and equipment/asset failures during the construction period. Some of the additional challenges experienced during the construction stage have been outlined below.

Portadown has been identified within the Northern Ireland Flood Risk Management Plan as an area of significant flood risk, due to regular fluvial flooding from the Upper River Bann and its tributaries. The most recent significant flood event was recorded in 2024, which saw substantial flooding across the entire work site. This fluvial flood event led to a halt in works on site for approximately one week and caused damage to plant.

The 500mm diameter outlet pumping main from the existing Meadow Lane Pumping Station ruptured on two occasions during the construction programme. To carry out the repair on the outlet pumping main, both Meadow Lane and Annagh WwPS had to be shut down and seven tankers were mobilised to transfer effluent to other NI Water treatment facilities. BSG Civil Engineering Ltd was able to utilise the newly constructed storm tank to create temporary storage and prevent any out-of-sewer flooding during the emergency repair works. BSG received positive feedback from NI Water on how these critical network emergency repair works were managed and rectified in a safe, collaborative and timely manner.

NI Water and the project team recognised the potential negative impacts which could arise from undertaking such a large-scale project within a busy town centre location and from an early stage embarked on a strategic communications strategy to ensure key stakeholders were informed of the works and kept updated throughout.

As part of the public relations programme the project team and NI Water Communications held early briefings with a range of stakeholders including elected representatives, town centre management, chamber of commerce, health care centre, council, roads authority, landowners and local businesses.

In addition to the numerous one-to-one meetings, letter drops were carried out in advance of each section of road works commencing and press releases issued to the local media to advise the wider public of traffic management. Variable message boards were erected on main routes and large-scale project boards helped to convey the huge investment being made by NI Water and the resulting benefits for the public.

Key project milestones were publicised along with facts and figures relating to the construction work and tunnelling exercise.

Regular project updates and lookahead bulletins were issued to stakeholders to keep them up to date on progress and advise them of future traffic management requirements. Town centre management were invited to site at key stages of the project to view progress and hear firsthand about the benefits the NI Water investment will bring to Portadown.

BSG provided a point of contact for operational queries and this, along with NI Water’s wider stakeholder communications, helped to ensure a smooth-running construction programme.

NI Water directed significant financial investment into upgrading the existing sewer network and Meadow Lane WwPS within the Meadow Lane area of Portadown. The proposed works oversaw the closure of five CSOs within the Meadow Lane WwPS catchment area through connection into the new 1,500mm tank sewer alongside the resolution of three DG5 properties.

The collaborative effort between NI Water, BSG Civil Engineering Ltd and McAdam resulted in the smooth completion of the programme and successful testing, commissioning and handover to NI Water in July 2025. The benefits of the new infrastructure will be realised almost immediately through a reduction in spill frequency and volume within the Upper River Bann and Annagh River.

This project showcased the capabilities of NI Water, BSG Civil Engineering Ltd and McAdam to coordinate and undertake sensitive high-risk activities such as a large-scale turn of flow without issue and within a complex urban environment.