Supply Chain - Contractors - Reinforced Concrete

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.

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.

Portadown is a large town in County Armagh, Northern Ireland located approximately 24 miles south-west of Belfast and nestled along the banks of the Upper River Bann. Over recent years, Portadown has transformed from a historically industrial town into a modern hub with a rapidly growing logistics sector and retail environment attracting high footfall and continued economic growth. Meadow Lane Wastewater Pumping Station (WwPS), located within the central retail area of the town, was constructed in 1966. The site forwards flow to a downstream gravity sewer system before subsequently flowing into the southern inlet of Seagoe WwPS, approximately 1.5 miles away. Need for upgrade

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:

Existing pumps showed signs of extensive wear (supported by observed power loadings). Control motors were identified as being installed pre-1975. The existing motor control centre (MCC) did not satisfy current asset standards.

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.

[caption id="attachment_26864" align="alignnone" width="1200"] Secant piles with reinforced concrete capping beam - Courtesy of BSG Civil Engineering Ltd[/caption]

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:

Meadow Lane One CSO. Meadow Lane Two CSO. Portmore Street CSO. Clonavon Avenue CSO. Meadow Lane Health Centre CSO.

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.

Early Contractor Involvement (ECI)

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.

[caption id="attachment_26863" align="alignnone" width="1200"] Liner wall formwork using Peri Rundflex - Courtesy of BSG Civil Engineering[/caption] Meadow Lane WwPS: Supply chain - key participants Project delivery: BSG Civil Engineering Ltd Civil, hydraulic & process designer: McAdam Temporary works design: MEA Ltd Earthworks: BSG Civil Engineering Ltd Specialist piling contractor: Quinn Piling Limited Formwork: Peri UK Reinforced concrete works: ONCCE Ltd Tunnelling contractor & TBM: B&W Tunnelling Ltd Open cut pipe installation: Phace Contracts Ltd Open cut pipe installation: O’Neill Contracts & Plant Hire Open cut pipe installation: AG Wilson Civil Engineering Groundworks: RMG Metalwork & FST designer/installer: RJ Smyth Engineering Precast roof beams: Macrete (Ireland) Ltd Precast roof slabs: Creagh Concrete Precast concrete pipes: Tracey concrete Screens: Eliquo Hydrok Ltd Submersible pumps & float switches: Xylem Water Solutions Flow meters: Siemens Control panels: Motrol Ltd Kiosks: Quinshield Ltd Primary drivers

The purpose and drivers of this project were as follows:

Ensure a reduction in spill frequency and volume through the provision of adequate storage facilities within the Meadow Lane catchment area. Closure of the five unscreened UIDs (identified by the NIEA) and subsequent provision of sewer upgrades in the upstream catchment to transfer flows from the closed UIDs and provide online storage. Resolution of three DG5 properties within the Meadow Lane area. Essential replacement of Meadow Lane WwPS with provision of a screened emergency overflow. [caption id="attachment_26865" align="alignnone" width="1200"] Pouring of 400m3 base slab - Courtesy of BSG Civil Engineering[/caption] What the upgrade involved

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:

The installation of 380m of 1,500mm diameter tank sewer approximately 7m below ground level. The installation of 350m of sewers ranging in diameter from 300mm to 1500mm via open cut techniques in depths ranging from 2m to 7m below ground level. The demolition of the existing Meadow Lane WwPS. The construction of a new inlet chamber, wet well pumping station and 1,500m3 storage tank at the existing Meadow Lane WwPS site. The installation of a new MCC panel and associated glass reinforced plastic (GRP) kiosk. The installation of three 37kW foul pumps and two 9kW hydro ejectors. The installation of three screens from Eliqua Hydrok Ltd. The closure of five unscreened UIDs. 1,500mm tank sewer installation

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.

[caption id="attachment_26861" align="alignnone" width="1200"] Pipejacking operation within launch pit - Courtesy of BSG Civil Engineering[/caption]

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.

Storm retention tank, inlet chamber & wet well pumping station

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.

[caption id="attachment_26853" align="alignnone" width="1200"] Installation of concrete beams - Courtesy of BSG Civil Engineering Ltd[/caption]

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.

Open cut sewer installation

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.

[caption id="attachment_26858" align="alignnone" width="1200"] Open cut sewer installation at Manhole No. 4 - Courtesy of BSG Civil Engineering Ltd[/caption] MEICA installation

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:

Inlet screen chamber: 600l/sec Mecmex™ screen. Foul pumping station overflow screen chamber: 70l/sec static Peak Screen™. Storage tank overflow screen: 264 l/sec static Peak Screen™. [caption id="attachment_26855" align="alignnone" width="1200"] Pump remote enclosures and actuators - Courtesy of BSG Civil Engineering[/caption] Additional construction challenges

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.

[caption id="attachment_26857" align="alignnone" width="1200"] (left) Fluvial flooding event in 2024 within the site compound, and (right) utilising the new storm tank for temporary storage following an outlet pumping main failure - Courtesy of BSG Civil Engineering Ltd[/caption] Stakeholder communication

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.

[caption id="attachment_26859" align="alignnone" width="1200"] Completed Meadow Lane WwPS (July 2025) - Courtesy of BSG Civil Engineering Ltd[/caption] Outcomes

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.

The Carmoney to Strabane Strategic Trunk Main represents the completion of nine years of planning and construction, backed by a £17 million investment from NI Water. This major infrastructure project delivers a new strategic water main connecting Carmoney Water Treatment Works (WTW) in Eglinton to Castletown Service Reservoir (SR) in the Strabane area. Identified as a priority in both NI Water’s 2012 Water Resource Plan (WRP) and the 2017 Water Resource & Strategic Resilience Plan (WR&SRP), the project enhances connectivity between the Northern and Western water resource zones. By establishing this vital link, the scheme addresses key infrastructure gaps, strengthens supply resilience, and supports the continued delivery of high-quality drinking water to the region. Project scope

To achieve the goal of enhanced interzonal connectivity and meet regulatory requirements, the Carmoney to Strabane Strategic Trunk Mains Project was divided into three distinct phases:

Phase 1: Completed in June 2024: This phase involved the construction of the new Avish Water Pumping Station at Carmoney WTW. The facility, with a capacity of 17 million litres per day (MLD), was designed to pump water to Corrody Service Reservoir (SR). Phase 1a: Finalised in April 2025: This phase comprised the installation of approximately 10 km of 500 mm diameter trunk main from Edenreagh Road junction to Corrody SR. A key feature of this phase was a 400m horizontal directional drill beneath the River Faughan; a watercourse of international significance due to its Atlantic salmon population and designation as a Special Area of Conservation (SAC). Phase 2: The final phase: Not yet commenced, but will involve the construction of a new water pumping station at Corrody SR and approximately 22km of trunk main extending to Castletown SR. This phase will traverse both private and public lands and include multiple trenchless crossings.

This paper focuses in detail on Phases 1 and 1a of the project.

[caption id="attachment_26644" align="alignnone" width="1200"] HPPE trunk main being strung out during installation - Courtesy of DAWSON-WAM & NI Water[/caption] Project aims & drivers

The primary objectives of the Carmoney to Strabane Strategic Trunk Main are to eliminate supply-demand balance deficit and to enhance resilience for 17ML/d within the Western Resource Zone in the event of incidents or outages at water treatment works.

Phase 1: This phase replaced the existing water pumping station (WPS), which is over 25 years old and equipped with MEICAT systems that have exceeded their operational life. The new infrastructure delivers increased operational robustness and improved security of supply within the Northern Resource Zone. Phase 1a: This phase reinforced the Caugh Hill–Corrody Trunk Main and supports the completed Northern Resilience Phase 3 project. It enables larger flow transfers to Corrody SR during outages at Carmoney WTW, without negatively impacting high-level customers in DMAs directly supplied from the trunk main. This enhancement further strengthens system resilience and security of supply in the Northern Resource Zone. Phase 2: This phase will enable bi-directional water transfer between the Northern and Western Resource Zones, up to 17 ML/d westwards and 8 ML/d northwards. Once complete, it will significantly increase operational flexibility and resilience across both zones. [caption id="attachment_26646" align="alignnone" width="1200"] Mains laying operations - Courtesy of DAWSON-WAM & NI Water[/caption] Carmoney to Strabane: Supply Chain - key participants Client: NI Water NEC project management: McAdam Principal contractor: Murphy/DAWSON-WAM JV Civils contractor: DAWSON-WAM Ltd MEICA contractor: Murphy Process Engineering Ltd Civil design: RPS Ireland Ltd MEICA sub-contractor: Pronto Automation Systems Ltd HDD contractor: Peter McCormack & Sons Ltd Archaeological services: Gahan & Long Ltd Pipe & fittings: APP Fusion Group Quarry products & reinstatement: P Woods & Son Ltd W & J Chambers Ltd Northstone NI Ltd Phase 1 - Avish Water Pumping Station

This phase involved the complete demolition of the existing facility and the construction of a new, purpose-built water pumping station (WPS) to supply both Avish Service Reservoirs (SRs), with onward pumping to Corrody SR via the Edenreagh Road infrastructure. The station operates using three pump sets (duty/assist/standby) and was prioritised as Phase 1 due to planning application and approval constraints. The works were successfully completed in June 2024.

[caption id="attachment_26643" align="alignnone" width="1200"] The new Avish Pumping Station - Courtesy of DAWSON-WAM & NI Water[/caption]

In addition to the three pump sets, the new installation includes a surge vessel, a new motor control centre (MCC), and associated pipework at both the water pumping station and Avish Service Reservoirs.

The upgraded WPS provides the NI Water Operations team with the ability to remotely manage and optimise system performance via telemetry, offering four distinct daily process control modes:

Mode 1 - Level control: Pump operation is based on reservoir level setpoints. Pumps start and stop according to low and high level thresholds, with flow rate automatically reduced as the reservoir approaches its maximum level. The assist pump is enabled or disabled based on flow demand. Mode 2 - Volume control: This mode delivers a specified volume of water either as a one-time operation or on a recurring schedule. Mode 3 - Flow control: In this mode, the system maintains a constant flow rate. The duty pump adjusts speed to meet a defined setpoint, with the assist pump activated if the flow target cannot be achieved by the duty pump alone. Mode 4 - Pressure control: Designed for use in abnormal operating conditions (e.g. bypassing a reservoir during maintenance or washing), this mode maintains a constant delivery pressure. The duty pump modulates speed to meet the pressure set point, and the assist pump engages as required.

To optimise operational expenditure (OPEX), the system also incorporates controls for managing high-tariff and pre-high-tariff top-ups, ensuring more efficient energy use during periods of peak demand.

[caption id="attachment_26645" align="alignnone" width="1200"] HDD drilling rig in operation - Courtesy of DAWSON-WAM & NI Water[/caption] Phase 1a: Edenreagh to Corrody Trunk Main

This phase involved the construction of 10 km of trunk main from the Edenreagh Road infrastructure to Corrody Service Reservoir (SR), consisting of approximately 9.6 km of 500 mm diameter ductile iron pipework and 0.4 km of 560 mm diameter high-performance polyethylene (HPPE) main installed via horizontal directional drilling beneath the River Faughan.

While the majority of the pipeline was laid through private agricultural land, the route also included several road crossings, most notably the A6; and a section along Trench Road within the public domain.

To support integration with the existing network, new flow meters, inlet control valves, scour and air valves, and cross-connections were installed, ensuring full inter-connectivity between the new and existing mains.

The entire works were delivered with no disruption to customers and successfully removed 17 District Metered Areas (DMAs) from the DG2 register. In addition to improving supply reliability, this phase significantly enhanced the resilience and security of supply within the Northern Resource Zone.

[caption id="attachment_26648" align="alignnone" width="1200"] Pipe bridge installation - Courtesy of DAWSON-WAM & NI Water[/caption] River crossings

The scheme included two significant watercourse crossings: the previously mentioned horizontal directional drill (HDD) beneath the River Faughan and the construction of a pipe bridge across the Burngibbagh River. For both crossings, maintaining ongoing communication with the Northern Ireland Environment Agency (NIEA) was essential. In line with NIEA requirements, sheet piles were installed at the drill entry and exit points to prevent any potential contamination of the River Faughan; recognised for its ecological importance as a designated watercourse.

The project team also carefully considered the findings of the ecology survey and the Habitats Regulations Assessment to ensure full environmental compliance. Environmental challenges, including the presence of Japanese knotweed and active badger setts within the working area, were effectively managed and mitigated without impacting the programme.

Archaeological discoveries & historic preservation

Throughout the course of the project there were numerous archaeological and historical discoveries. Ancient structures and artifacts were discovered, with the team collaborating closely with archaeologists and HED to carefully document and preserve these findings, ensuring the site’s historical significance was respected throughout the construction process.

[caption id="attachment_26649" align="alignnone" width="1200"] Archaeological operations - Courtesy of DAWSON-WAM & NI Water[/caption] Environmental awareness

As the pressures of climate change and population growth in the North-East region increase, the Edenreagh Road to Corrody SR trunk main was constructed to ensure security of supply and cleaner water for the wider Northern Zone.

This 10km pipeline was constructed whilst adopting a number of cost saving and environmentally responsible methods, namely maximising the amount of reused excavated materials through a screening process. This minimised the amount of imported material and reduced the number of deliveries to site by a significant amount.

Additionally, where practicable, materials and aggregates were sourced from local suppliers near the site to reduce transportation distances and minimise the project’s carbon footprint.

Community & landowner engagement

It was recognised early in the Early Contractor Involvement (ECI) period that building strong relationships with landowners would be critical to the project’s success, with early engagement meetings held with the Ulster Farmer’s Union. As such, collaboration with local farmers and landowners remained a core focus throughout, ensuring minimal disruption to their land and promoting sustainable land use practices.

To support this approach, a dedicated Lands Liaison Officer was appointed for the duration of the works. Their role was to build and maintain strong relationships with landowners and to ensure transparent, ongoing communication with the local community—keeping all stakeholders informed and engaged throughout and contributing to the successful delivery of the project.

[caption id="attachment_26647" align="alignnone" width="1200"] Mains laying operations - Courtesy of DAWSON-WAM & NI Water[/caption] Health & Safety initiatives

The project was recognised by the Considerate Contractors Scheme for its health and safety initiatives, with the Contractor (Murphy DAWSON-WAM JV) receiving a Gold award for the project as a whole, but in particular for the installation of single use defibrillators within all excavators across the project.

The outcome

The Carmoney to Strabane Strategic Trunk Main is a great example of how the NI Water project team including consultants and contractors can successfully collaborate and engage with the local community to deliver a vitally important piece of infrastructure, whilst respecting the local environment.

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.