Supply Chain - Wastewater Pumping Stations - Technical Documentation

Lower Woodburn Wastewater Pumping Station (WwPS) serves the Greenisland Drainage Catchment and is located close to the town of Carrickfergus on the foreshore of Belfast Lough. The storm outfall from the WwPS flows directly into the lough. Although recognised that discharges have minimal impact on the Belfast Lough Shellfish Water Protected Area (SWPA), there is localised impact and a need to protect and preserve amenity on the accessible shoreline. Upgrading of the WwPS was needed to comply with the Environmental Regulator’s (NIEA) consent requirements. Living with Water Programme

As part of Belfast’s strategic ‘Living with Water Programme’ (LwWP), NI Water has invested £1.8m to upgrade Lower Woodburn WwPS by increasing the volume of storm emergency overflow storage and installing a static screen. The solution also facilitates proposed housing (315 units) and hospitality/recreational developments that discharge directly to the WwPS and delivers storm separation of 17.8 hectares of impermeable ground. The project delivers against the LwWP goals:

PROTECT against Flooding. ENHANCE the Environment. GROW the Economy. [caption id="attachment_12584" align="alignnone" width="1200"] Lower Woodburn WwPS site pre-construction - Courtesy of DAWSON-WAM Ltd[/caption] Project delivery

Delivery partners for this project were appointed through existing NI Water frameworks. Tetra Tech was appointed to provide professional services, (including project management, cost management and site supervision) and to act as NEC Project Manager. The Murphy/ DAWSON-WAM Ltd JV (MDW) was appointed as main contractor.

Building on earlier work done to investigate catchment-wide solutions for Carrickfergus as part of the LwWP, MDW was engaged to develop the design and build solution under an Early Contractor Involvement (ECI) NEC contract. The design was reviewed and approved in collaboration with NI Water, and budgetary approval was granted for construction works under an NEC-ECC Main Option A contract in summer 2023.

Delivery was a collaborative effort between client, consultant and contractor teams to improve water quality and environmental conditions in the receiving Belfast Lough. The works comprised addition of surface water storage in a new concrete cofferdam constructed alongside, and connected to, the existing pumping station wet well. The constrained nature of the site lead to the need for access to neighboring lands from which to operate construction plant and machinery.

The scope was further developed during construction to improve the overall solution performance by installing a non-return valve on the storage overflow to enhance separation between storage and the marine environment and to improve the design life of the pre-existing pumping station.

Change was addressed using the provisions of the NEC contract and was managed within the overall budget for construction works. The new storage tank was integrated from an ICA perspective by linking to NI Water’s telemetry system for effective monitoring of storage levels and overflow incidents.

Throughout construction, regular site inspections were undertaken by Tetra Tech’s Site Supervisor and Health & Safety Manager to affect joint inspections with NI Water’s and MDW’s H&S Managers. This made sure of a combined approach to H&S management; issues were addressed face to face in real time and resulted in an excellent H&S performance throughout, with no accidents or incidents.

[caption id="attachment_12583" align="alignnone" width="1200"] 3D models of new storm storage tank - Courtesy of RPS[/caption] Early contractor involvement (ECI)

The ECI process proved its worth as extensive design and build challenges were overcome and a buildable solution was developed that satisfied the construction brief and costs criteria. This led to Murphy/DAWSON-WAM Ltd being appointed as principal contractor for the design and build of Lower Woodburn WwPS upgrade in August 2023. Contract works involved the design, supply, installation, testing and commissioning of an additional 317m3 of additional gravity storm storage on the existing site.

Certain elements of the project proved extremely challenging, none less than the design and construction of the additional storage tank on an existing site footprint that was extremely compact. Construction was further restricted as access to the site was from the busy A2 road, (the main road corridor from Belfast to Carrickfergus), immediately to the east of the site was a live petrol station with underground fuel tanks, on the west was an existing domestic occupied property and the access to the property and to the local strand, straddled the site on the east and south side. This was further complicated by the fact the existing pumping station had to be kept operational during the entire construction process.

The extensive ECI (which included site investigations, topographical surveys, network modeling, liaison with key stakeholders and utility providers, design development and costs approval), was completed post contract award. MDW appointed RPS as their civil design partner and through collaboration with NI Water and Tetra Tech, overcame the buildability challenges of this compact site.

The ground investigation report undertaken on the footprint of the only available space on the site identified glacial till overlying bedrock which varied from 6 to 8m below ground level. Early tank storage design calculations indicated that a tank depth of approximately 6.1m deep below ground level would maximise the footprint available within NI Water’s site, and enabled a gravity return into the existing pumping station.

[caption id="attachment_12588" align="alignnone" width="1200"] (left) CFA cased auger secant piling cofferdam installation and (right) excavation of storm tank exposing secant piles - Courtesy of DAWSON-WAM Ltd[/caption] Temporary works

Several temporary works solutions were considered to facilitate the tank construction including the use of a steel sheet pile cofferdam. This solution was omitted for several reasons but predominately because of the vibration risk to the surrounding properties and being unable to achieve sufficient embedment into the mudstone bedrock.

For the solution, DAWSON-WAM Ltd developed a secant piled cofferdam design which deployed a hard/hard continuous flight auger with reinforcement cages in every male pile (second pile). Utilising a double auger drive motor, it was capable of coring into the mudstone while maintaining pile verticality.

Working with piling design partner, Cassidy Geotechnical Ltd, a 450mm diameter secant piled cofferdam with 9m long piles was developed as the most viable solution. This was further valued engineered by incorporating the piles as part of the permanent works and introducing a single face, in situ, internal reinforced concrete lining to form the internal wall of the tank. Through design analysis, it was identified in the temporary condition the secant piled cofferdam would require propping during excavation, but this was omitted by collaboration between the piling designer and contractor by introducing a reinforced capping beam that was poured prior to excavation which reduced the deflection enough during excavation to eliminate the requirement of the temporary prop. The capping beam would also provide support the permanent in-site reinforced roof structure.

Pre-construction structural surveys were undertaken on all the surrounding properties and vibration monitors were installed at two locations adjacent to the site during piling operations. The secant method proved a success as the piles were installed to the designed length without triggering any vibration limits and when excavated provided a watertight cofferdam.

[caption id="attachment_12586" align="alignnone" width="1200"] Aerial view of site during storm tank reinforced concrete base slab construction - Courtesy of DAWSON-WAM Ltd[/caption] Lower Woodburn WwPS: Supply chain - key participants Main contractor: Murphy/DAWSON-WAM Ltd JV Project management & professional services: Tetra Tech Civils design: RPS Secant piling design: Cassidy Geotechnical Ltd Civils contractor: DAWSON-WAM Ltd MEICA: J Murphy & Sons Shuttering contractor: Form Builders Mixer: Xylem Water Solutions Static screen: Eliquo Hydrok Ltd Washwater booster pumpset: Dutypoint Ltd Combisafe fall protection: Honeywell Construction Due to the storage requirements of the tank, and given the small site footprint, there was not adequate space on the site to undertake the construction works safely. Therefore, a detailed construction phasing plan was developed by the contractor at the ECI stage which incorporated keeping the existing pumping station in service during construction. This plan identified that by temporarily incorporating the existing access lane (leading to the beach and neighbouring property) as part of the site, construction could be undertaken. An agreement was reached with the owners of the house - who had just recently purchased the property – to delay their relocation to the dwelling until works had been completed, and the council agreed to temporarily close access to the strand to aid construction. [caption id="attachment_12587" align="alignnone" width="1200"] Single sided reinforced concrete wall pours against secant piles to form internal tank walls - Courtesy of DAWSON-WAM Ltd[/caption]

Consultations were carried out through NI Water’s internal communications team and members of the project management team, and included public drop-in meetings and approximately 100 letter drops.

Due to site constraints, the establishment of an off-site construction compound also facilitated just in time delivery of the construction materials to the site, which maximized the small amount of on-site space and reduced site congestion.

MEICA installation included a single Xylem Water Solutions mixer to prevent silt build up in the tank, an Eliquo Hydrok 6mm screen was fitted on the existing 315mm emergency overflow pipe from the pumping station and a new 6 bar washwater booster pumpset was commissioned on site for maintenance of the screen.

Site finishes included a new perimeter fence, EMS area and a wildflower mix was used to finish final surfaces to enhance biodiversity.

Works programme

Construction works commenced on site in August 2023 and were completed on programme and within budget by late April 2024.

The collaborative approach of the project team effectively delivered a solution to improve the water quality of Belfast Lough, supporting NI Water’s agenda to Protect, Enhance and Grow through the delivery of the Living with Water Programme.

Guildford, the county town of Surrey, sits a commutable 30 miles south west of London and 70 miles from the south coast. Boasting a castle, a cathedral, a picturesque town centre and a university, it is surrounded by Green Belt countryside. The River Wey flows through the town centre and then northwards through water meadows where it provides the outfall for the STW. The Wey eventually discharges into the Thames. The current STW serves a population equivalent (PE) of around 107,000, but the town has a growing population which is expected to grow to circa 125,000 PE by 2041. Background

The town and immediate area are currently served by a sewage treatment works established at the turn of the last century and upgraded over the years. It is located beside the River Wey, to the north of the A3 trunk road and north of Guildford town centre. It lies just south of Slyfield Industrial Estate. The current STW has a capacity to cater for a population equivalent of around 120,000.

Guildford Borough Council’s Local Plan adopted in 2019 allocates a site to the west of the River Wey wrapping around the eastern side of Slyfield Industrial Estate for mixed use development. Part of the 40 Ha allocated site is currently occupied by the existing sewage treatment works.

Weyside Urban Village is a mixed-use regeneration project which will provide some 1,500 new homes, new community facilities, Gypsy and traveller pitches and 6,500m2 of additional light industrial and trade space. 11Ha of the site are allocated for waste management purposes. The plans include a new council depot, a public recycling centre and a new, relocated sewage treatment works.

In order to bring the development site forward, within the plan period to 2034, Guildford Borough Council (GBC) have entered into partnership with Thames Water Utilities Ltd (TWUL) to build the new STW as the first phase of the redevelopment. The new location is slightly further north on the eastern edge of the Industrial site and is a brownfield site, formerly a gravel quarry and subsequently a landfill tip.

[caption id="attachment_26867" align="alignnone" width="1200"] Figure 2: Site overview: BIM model of new Guildford STW - Courtesy of BAM Enpure JV[/caption]

The new sewage treatment works allows for an increase in capacity to serve a population of 125,000 allowing for predicted population growth in the town and surrounding area as well as more stringent effluent discharge standards.

The new site also includes areas within the new works for future expansion and increased treatment capacity as need arises.

Previously in Water Projects

The scheme to build a new sewage treatment works (STW) in Guildford is now mid-way through construction. This article provides an update to the project following on from previous articles published in Water Projects. In 2023, Enpure Ltd’s Project Delivery Director Shaun Christopher described in detail the process and assets being provided in the new works and in 2024, Dan Russell, BAM’s Operational Lead, gave an update on the progress of the project one year into the construction.

This article also covers some of the planning considerations and requirements for the scheme.

Contract

In 2021 TWUL awarded a contract to a BAM-Enpure Joint Venture to design, build and commission a new STW for Guildford, and once operational, to de-commission the existing works. BAM-Enpure Joint Venture (JV) is a non-integrated Joint Venture, formed specifically to combine experienced civil engineering contractor BAM with the process engineering MEICA specialism of Enpure, to deliver a turnkey solution for TWUL.

Construction began in the spring/summer of 2023 with BAM undertaking design and construction of the civils works and Enpure providing process and MEICA design and installation. BAM have employed Arcadis as their main civils designer and the JV has let a number of specialist sub-contractor design packages alongside.

[caption id="attachment_26869" align="alignnone" width="1200"] Figure 3: 3D design using a model hosted by Arcadis, image from Autodesk’s Navisworks viewer - BAM Enpure JV & Arcadis[/caption] The project

The project consists of the following:

A transfer tunnel. An inlet pumping station. Inlet works screening. Primary settlement. Activated sludge treatment. Final settlement. Tertiary treatment of final effluent. Chemical dosing facilities. Storm storage tanks. Import cess and sludge facilities. A new control centre. New welfare building. Outfall into the River Wey.

A detailed description of the process and assets being installed is set out in the previous Water Projects article published in 2023.

Timeline Phase 1: Ground improvement: Started summer 2023 and completed February 2025 Phase 2: Civil engineering: Started summer 2023 with completion due in late 2025. Phase 3: Mechanical & electrical engineering: Started autumn 2024 and is due to complete summer 2026. Phase 4: Commissioning: Starts winter 2025 and is due to complete in spring 2027. [caption id="attachment_26883" align="alignnone" width="1200"] Figure 4: 3D model of the sludge processing area - Courtesy of BAM Enpure JV & Arcadis[/caption] Developing the site

The new site comes with additional challenges in that it is brownfield site formerly used for gravel extraction and then landfilled through the 1960s, 70s and 80s, with mainly domestic and some commercial waste. The site is classified as a waste development such that the local planning authority is Surrey County Council (SCC).

The planning permission granted was subject to a number of conditions and commitments, not only relating to the siting and development of the STW itself such as visual impact, odour, noise and traffic generation, but also to the remediation and reuse of the landfill site. Plans and construction methods needed to ensure that there was no temporary or permanent environmental damage to the surrounding area as a result of the impact on or disturbance of the buried waste material and that operatives working on the new STW were protected from any ill effects of the landfill during operation of the site. The landfill also poses particular constraints and hazards during the construction phase.

The strategy for the site was to leave as much of the landfill waste in situ and build above and through the waste. A detailed remediation strategy formed part of the planning requirements. The plan set out how the construction and operation phases of the project would manage issues of ground water and ground gas, potential ground water contamination and leachates, contaminated solid material including asbestos, and short- and longer-term settlement of the landfill.

Dan Russell’s case study in Water Projects 2023 provided a detailed description of the use of a combination of ground improvement and foundation techniques, which consisted of:

Rapid Impact Compaction (RIC) to improve ground strength and reduce long-term settlement of the landfill. Vertical Rigid Inclusions (VRI), a displacement concrete pile technique which provided support for roads, lighter structures pipes and ducts. Driven concrete piles bedded in the London Clay below the land fill to support large structures, tanks and pipelines.

Figures 5 (below) show the historic gravel extraction map and depth of landfill determined by ground investigation - both images were extracted from the project’s Detailed Remediation Strategy.

[caption id="attachment_26880" align="alignnone" width="1200"] Figures 5: (left) Spatial variation in landfill thickness 2023 and (right) historic site layout (1976) with present day boreholes overlaid - Courtesy of Arcadis[/caption]

However, the impact of the waste material goes beyond its bearing capacity. The site was already being subject to long term monitoring for ground gas and groundwater quality by Thames Water to provide a baseline for the project. Additional boreholes were sunk and a Groundwater & Ground Gas Monitoring Plan was approved by the local authority. Daily and continuous automatic remote monitoring was undertaken during the ground improvement and excavation phases with trigger levels set and exceedances reported back to SCC and a requirement for quarterly summary reporting. Monitoring will continue during commissioning of the site at less frequent intervals.

Asbestos: Asbestos had been discovered in a third of samples taken during the ground investigation and so a monitoring regime was established. Air sampling around the perimeter of the site ensured any airborne particles were detected and works could be stopped if necessary. Proximity asbestos monitoring and identification of asbestos material in excavation has also been used extensively during excavation across the site. The project used Socotec to undertake asbestos monitoring and testing.

Ground gas: A ground gas protection design has been necessary to reduce risk of ground gas entering occupied buildings, kiosks, tanks and chambers where operational or maintenance access is undertaken. A ground gas design protection strategy was set out by Arcadis with PAGeo Contracting Ltd providing expert advice and a detailed ground gas design, PAGeo then supplied gas dispersal matting, venting components and gas membranes. Both the strategy and the detailed design for ground gas protection have been submitted to and approved by SCC.

Independent verification of the gas protection installation has been provided by MTS Ltd as verification of the installation and subsequent reporting to SCC is a planning condition.

[caption id="attachment_26872" align="alignnone" width="1200"] Figure 6: Gas protection void former being laid on stone blanket prior to tank base blinding, Connections to vents at tank perimeter - Courtesy of BAM[/caption]

Surface drainage: On-site surface drainage has been carefully designed such that new impermeable areas are positively drained to the site drainage system to remove the risk of a spill causing environmental pollution. This surface water is then fed into the inlet pumping station for processing through the works. As the permeable area of the site has been greatly reduced this also significantly reduces leachate mobilisation.

Biodiversity: Another planning condition is the provision of Biodiversity Net Gain (BNG). In conjunction with GBC, the project provides 10% net biodiversity gain by use of on-site planting and off-site enhancement of the land directly to the north of the new STW. A Site of Natural Green Space, biodiversity enhancements to an area of farmland, and a marshy meadow along the River Wey are being provided.

The Environment Agency have also constructed a new fish pass in this area allowing fish to migrate around Old Bucks Weir.

Guildford STW: Civils works supply chain - key participants

Main contractor: Bam Nuttall Ltd Planning consultant: Adams Hendry Consulting Ltd Civil engineering design: Arcadis Group Ltd Boreholes & testing: Geo-Environmental Services Ltd Asbestos monitoring: Socotec Ltd Rapid impact compaction: Cofra Ltd (Boskalis Group) Vertical rigid inclusions: Foundation Piling Ltd Concrete piling: Aarsleff Ground Engineering Ltd Temporary works specialist: Mabey Hire Ltd Temporary works specialist: MGF Ltd Tunnels & shafts: Joseph Gallagher Ltd In situ concrete works: Kelly Formwork Ltd In situ concrete works: DJ Civils Ltd Precast concrete manufacturer: FLI Precast Solutions Precast concrete manufacturer: A-Consult Ltd Pipe supplier: Electrosteel Castings (UK) Ltd Pipe supplier: Saint Gobain PAM UK Soil processing: Remediation Waste Management Services Concrete supplier: Heidelberg Materials Gas protection: PAGeo Contracting Ltd Gas protection system installation verification: MTS Ltd [caption id="attachment_26876" align="alignnone" width="1200"] Figure 7: Sludge processing area: MCC kiosk (grey in foreground), sludge blending tanks (top left), poly dosing kiosks (top right) - Courtesy of BAM[/caption] Overview of project progress

As of summer 2025, civils works are nearing completion and MEICA fit out has started.

The installation of piled supports has been undertaken, and all major structures are complete. Installation of the below-ground pipework and buried ducting is in progress and the welfare building is watertight and available for equipment installation. Moving towards installation of MEICA equipment, the water testing of structures started in the February of 2025.

Steel staircases and high-level walkways are mostly complete. The inlet screens and grit removal system are in place. GRP tanks for sludge processing are being installed and many control kiosks are in place. Electrical supply buildings are near completion.

MEICA work commenced in February 2025, overlapping with completion of civils to maximise programme efficiencies. Designed alongside the civils elements of the site, the MEICA installation has taken place apace with the first bridges on the final settlement tanks attached, the larger glass coated steel tanks for the sludge area in place, and generators and some kiosks have been installed.

BAM has started the installation of the above-ground pipework and cable pulling in buried ducts, and the fit out of control rooms will commence shortly. Construction of MCC basements has been completed and two of the three MCC kiosk, and power supply and distribution works are nearing completion.

[caption id="attachment_26878" align="alignnone" width="1200"] Figure 8: Sludge processing area: (left) the bases for elevated cake silos, (middle), sludge belt presses, and (right) the poly prep & dosing kiosks - Courtesy of BAM[/caption] Guildford STW: MEICA works supply chain - key participants Main designer/contractor: Enpure Ltd CFD analysis: The Fluid Group Cake silo: Saxlund International PST scrapers & ferric dosing plant: Colloide Inlet works & PST odour covers: Power Plastics Ltd Grit remover plant: Jacopa Escalator screens: Longwood Engineering Imported sludge Strainpress: Huber Technology Sludge thickening & dewatering: Kent Stainless Ltd Odour control plant: Odour Services International Ltd FBDA grids & blowers: Xylem Water Solutions Cloth pile filters: Eliquo Hydrok Ltd Storm tank cleaning system: Sulzer Pumps Wastewater Ltd Tank logging system (WASP): JR Pridham Services Ltd Glass lined steel tanks: Balmoral Tanks Ltd Sludge tank mixing: Landia UK Ltd Tunnel

A 1.5m diameter gravity tunnel, 1.5km long, transfers flows from the existing works and intercepts minor sewers en route. There are six shafts along the tunnel route, some of which act as junctions between the new tunnel and the existing sewers. Shafts were sunk by Joseph Gallagher using the caisson method and the tunnel was driven between them using a full-face tunnel boring machine, (named Daphne by a local school). The tunnel and shafts were completed in 2024 and the final work remaining are the completion of the large inlet pumping station (IPS), shaft (E2) at the new works and connection of Guildford’s main sewer to the head of the tunnel, which will allow all flows to be diverted to the new tunnel.

[caption id="attachment_26873" align="alignnone" width="1200"] Figure 9: (top left) 3D model of the Inlet Pumping Station (IPS) - Courtesy of Arcadis, (bottom left): steel fixing to IPS internal walls - Courtesy of BAM Enpure JV, and (right): IPS shaft construction - Courtesy of BAM[/caption] Inlet pumping station

The new inlet pumping station (IPS) is a 12.5m diameter shaft with a depth of 17m, which houses six pumps with the capacity to lift flows of around 2,500 l/s from the tunnel entry, at the base of the shaft, to the inlet works where all flows are screened. The shaft is complete except for the internal walls and installation of penstocks which allow isolation of half the well at any time for maintenance of the pumps. This will be completed in the autumn of this year.

Storm tanks & inlet works

Two storm tanks provide a combined capacity of approximately 8 million litres to which flow can be diverted to temporarily hold sewage arriving at the new works should flows exceed the capacity of the works. Constructed onto in situ bases, the walls of the storm tanks were prefabricated, placed and post-tensioned by A Consult Ltd.

The inlet works and larger chambers were entirely cast in situ due to lack of repeatable sections and logistics. In situ concrete work for these was undertaken by Kelly Formwork. The inlet screens have been installed and walkways are in place.

[caption id="attachment_26874" align="alignnone" width="1200"] Figure 10: Circular precast storm tanks and Inlet works (August 2025) - Courtesy of BAM[/caption] Primary settlement, activated sludge plant & final settlement tanks

Screened flows from the inlet works will then pass through primary and secondary treatment tanks comprising rectangular primary settlement tanks (PSTs) and activated sludge plant (ASP) tanks. The walls for these tanks were designed and supplied by FLI Precast Solutions Ltd and installed by BAM and DJ Civils Ltd on in situ bases prepared by Kelly Formwork Ltd. These tanks are complete with pipework being fitted and the ASP has commenced water testing.

To ensure watertightness of the larger rectangular tanks, Heidelberg Materials and Sika’s concrete technology were used.

Concrete containing Sika WT-200 P was utilised for the PSTs and the ASP. Sika WT-200 P is a combined water-resisting and crystalline waterproofing admixture used to reduce the permeability of concrete, making it suitable for water retaining structures.

Gas protection has been laid under all large tanks. Materials were supplied by PAGeotechnial Ltd and verified by MSL Ltd. Void former mating laid on a bed of single grade 40mm stone provides a preferential escape path for ground gases and is connected to vents at the tanks periphery allowing ground gases to vent to atmosphere.

These tanks are not habitable spaces and only require a dispersal system to discourage any build-up of gas below the large tank bases.

[caption id="attachment_26875" align="alignnone" width="1200"] Figure 11: From top: Activated sludge plant, primary settlement tank, and two of the four final settlement tanks - Courtesy of BAM[/caption] Final settlement tanks

The four final settlement tanks were also precast, supplied, installed and post-tensioned by A-Consult Ltd onto in situ bases prepared by Kelly Formwork Ltd. The FSTs are complete with bridges and scrapers installed and are currently being water tested.

Tertiary treatment plant & outfall

Following final settlement, flows will pass through final filtration in the tertiary treatment plant before being discharged to the River Wey via new, twin outfall pipes. Civil construction is complete and MEICA installation of cloth pile filters and drums from Eliquo Hydrok Ltd is underway.

The outfall pipework has been fully installed across the water meadow and the headwall has been constructed at the discharge point into the River Wey.

[caption id="attachment_26877" align="alignnone" width="1200"] Figure 12: Tertiary treatment plant construction (August 2025) - Courtesy of BAM[/caption] Sludge processing

The project also provides a dewatering facility for imported sludge from other small treatment works. This area is nearing completion with the larger coated glass sludge blending tanks in place and the smaller buffer tanks being installed. Gas vent pipes have been installed below the extensive concrete slabs to allow venting of ground gases to the atmosphere.

The sludge belt presses from Kent Stainless Ltd for sludge dewatering and thickening have been installed adjacent to the bases for the elevated sludge cake silos. The silos from Saxlund International have been sized to provide storage of seven days’ worth of processed sludge, which can be discharged to trucks for export from site.

Power & control

Power supply and distribution infrastructure is now in place. The three MCCs have been constructed in sequence and the first two are being fitted out.

Welfare building

A new welfare building houses the automated systems for running the new plant and controlling effluent quality as well as office and mess space for Thames Water staff and operatives. The building is watertight with cladding being installed and the fit out of building fixtures and plant control equipment is in progress.

[caption id="attachment_26871" align="alignnone" width="1200"] Figure 13: Welfare building housing plant control systems - Courtesy of BAM[/caption] 3D modelling

Design has utilised a 3D model hosted by Arcadis with each designer adding in modelling information as their design capabilities have allowed. This has enabled precise integration of designers individual input and interrogation of the integrated design

The model is used extensively by engineers on site. 3D modelling has, for example, allowed duct chambers to be precast with precision positioning of cable openings, saving on in situ working and substantially reducing programme on these installations.

Piling & ground improvement

To enable the STW to be constructed on the site without the waste being removed a combination of ground improvement techniques have been employed including driven concrete piles, Rapid Impact Compaction, and Vertical Rigid Inclusions.

The Rapid Impact Compaction work undertaken by Cofra was completed in late summer of 2023. From July 2023 to the spring of 2024, to support the larger structures, tanks and main process critical pipelines, 3500 concrete piles were driven through the landfill into the clay. The design and installation of this piling operation was undertaken by Aarsleff Ground Engineering.

[caption id="attachment_16135" align="alignnone" width="1200"] (left) Driving precast concrete piles and (right)Vertical Rigid Inclusion installation - Courtesy of Bam Nuttall Ltd[/caption]

In areas where settlement criteria were less critical, but needed controlling (for example roadways and minor pipework), a Vertical Ridged Inclusion (VRI) piling technique was used. The system involves displacement drilling a column in the landfill and filling the void with concrete. This works by consolidating the soil around the pile, transferring load to lower layers, thus increasing bearing capacity and reducing settlement over time.

Since 2024 the installation of VRIs by Foundation Piling has been completed with 7500 inclusions installed across the site. During detailed design, the project was able to remove the need for a load transfer platform above the VRIs across much of the site. This was done by detailed analysis of the 3D model to target differing requirements for support and by reducing inclusion spacings, thereby reducing the expected landfill removal by 37,500m3.

The load transfer platform remains below roads, but pipework sits within the grid of VRIs.

The year ahead

Completion of the mechanical works is expected in the first part of 2026 with installation of electrical and control systems expected to complete in the second part of 2026. Dry and wet commissioning will be undertaken sequentially across the site throughout the coming year, ensuring the new works is ready to commence process commissioning.

The final, and arguably most challenging activity, will be to connect the existing sewer network to the new tunnel, diverting flows from the existing STW to the new STW. A series of interventions will be required to intercept the various sewers, along the route of the tunnel, all the whilst ensuring the new STW is performing within strict limits and the existing STW is able to maintain its performance during the ramp down of flows.

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.

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.

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 Ards Peninsula is a scenic area in County Down, situated on the north-east coast of Northern Ireland. It separates Strangford Lough from the north channel of the Irish Sea and its coastal towns and villages are popular with day trippers and caravanners alike. By 2020, the wastewater treatment works serving the villages of Carrowdore and Ballywalter were operating at full capacity. NI Water investment was required to ensure that these areas could meet future EU and Northern Ireland Environment Agency (NIEA) standards. The area of Ballywhiskin only had primary settlement, which was not deemed sufficient, and the caravan parks and small settlements in the Ballywalter area were served by septic tanks, which again only offered primary settlement of wastewater before discharge to nearby watercourses. The beaches in the area represent significant tourist amenity and an extensive treatment scheme was essential to meet future bathing water quality standards in line with NIEA standards. What the scheme involved The two-year Ards North Wastewater Improvement Scheme involved the rationalisation of the Carrowdore, Ballywhiskin and Ballywalter catchments so that all wastewater flows from these areas could be transferred to a new state-of-the-art wastewater treatment works (WwTW) constructed on a greenfield site off the Ganaway Road in Ballywalter. In addition to these catchments, the new treatment works has been designed to treat wastewater flows from nearby caravan parks and small settlements, which previously had no treatment facilities. The scheme was split into two contracts; one for the design and construction of new pumping stations, pipelines and a modern wastewater treatment works, which was awarded to BSG Civil Engineering, and another for the design and installation of a new long sea outfall, which was awarded to Farrans. Project management/technical support for both contracts was provided by Tetra Tech. This article focuses on the work carried out to construct the new WwTW, pumping stations and pipelines by BSG Civil Engineering to serve the combined catchments and cope with seasonal fluctuations in population to protect the tourism potential of the area for many years to come. [caption id="" align="alignnone" width="1200"] Bulk excavation - Courtesy of BSG Civil Engineering Ltd[/caption] Early contractor involvement/design and build contract BSG Civil Engineering was appointed by NI Water as the main contractor in November 2018 under an NEC 3 Early Contractor Involvement (ECI) contract. BSG provided multi-disciplinary design, project and supply chain management and all civil engineering, process and MIECA works for the contract from start to completion. The ECI phase allowed BSG to align resources and integrate objectives with NI Water and their project management team from Tetra Tech at an early stage to benefit delivery. This proactive approach led to enhanced collaboration, innovation, value, efficiency and reduced whole life costs for the project. Primary drivers The purpose and drivers for this project were as follows: Achieve compliance with current and future EU directives on effluent discharge standards. Meet Registered Discharge Standards set by the Northern Ireland Environment Agency (NIEA). Provide a flexible design to cater for future flows and the significant summer/winter fluctuations. Minimise impacts to community and environment. Support local development, tourism and economic growth. Deliver best value for money construction making use of existing assets. [caption id="" align="alignnone" width="1200"] Ards North WwTW - Inlet works overview - Courtesy of BSG Civil Engineering Ltd[/caption] Scope of works The main elements of work included: Installation of 14km of pumping main between WwTW & new/upgraded pumping stations via directional drilling and open cut methods. 2km of gravity sewer installed between pumping stations. 6mm inlet screening and storm storage for 2 hours/3x DWF) Grit treatment and removal. 3 (No.) 131m3 primary settlement tanks with automatic desludge and scum removal. Return activated sludge (RAS)/surplus activated sludge (SAS) pumping station. Anti-septicity treatment at source at the pumping stations. 3 (No.) 12m diameter final settlement tanks with automatic desludge and scum removal. Sludge holding tank. Sludge thickening and processing. Two-stage odour control plant. 330KVA standby power generation. 52.28 kwP roof mounted solar PV array, complete with dual 22kWh EV charging points. Process flows, levels, and quality monitoring; ancillary processes to support the main process units and intelligent motor control centre (MCC) with telemetry. Programmable logic controller (PLC) and human machine interface (HMI) control system. Installation of new long sea outfall pipe (detailed in a separate article). Design criteria for the Ards North WwTW Due to the large number of caravans in the area expected to be served by the new Ards North WwTW, the plant needed to be designed to deal with significant variations in flow and load to ensure satisfactory treatment could be achieved throughout the year. This meant that the works had to cope with a summer population equivalent (PE) of 8508 and a PE of 4809 in winter months. Inlet works & flow control/balancing Flows up to Formula A from the outlying stations can arrive at WwTW simultaneously. The inlet balancing chamber balances out flows going forward to the inlet screening plant. The inlet screening plant consists of two duty/standby incline screens and a cross conveyor. Each screen has a manual inlet penstock installed to enable isolation for maintenance purposes, or for bypass through the static 6mm bar screen. [caption id="" align="alignnone" width="1200"] Inlet works side view - Courtesy of BSG Civil Engineering Ltd[/caption] Screened raw sewage continues to the grit removal plant. The grit settles in a sump underneath the grit paddle. Any grit that settles in this sump is periodically aerated using the grit blower and then removed. From here the grit is transported out of the grit plant by the grit classifier and is deposited into the grit skip. From here it is removed off site for disposal. After the wastewater has passed through the grit removal plant, flow continues to the FFT pumping station. Here influent is collected, and FFT of 48.2 l/s (summer) & 29.6 l/s (winter) is pumped to the PST flow splitting chamber. Ards North Wastewater Improvement Scheme: Supply chain - key participants Client: NI Water Project management: Tetra Tech Principal designer/contractor: BSG Civil Engineering Ltd Structural, hydraulic & process design: Doran Consulting MEICA design: BSG Civil Engineering Ltd Temporary works design: MEA Ltd Electrical installations: AW Control Systems Dewatering: Causeway Geotech Aeration equipment: Xylem Water Solutions Aeration blowers: Aerzen Machines Sludge thickeners: Huber Technology MCC: LMP Controls Inlet screening: M and N Electrical and Mechanical Services | Hydro International Grit treatment: Jacopa Storm screening: Eliquo Hydrok Ltd Actuators: Rotork Septicity dosing & booster pumps: FM Environmental Half bridge scrapers & access flooring/metalwork: Graham Steelworks & Engineering Ltd Odour control plant: John Cockerill Environment Pipes & fittings: APP Fusion Group Standby generators: PM Power Poly dosing plant: ProMinent Fluid Controls (UK) Ltd Micro-strainers: Whitewater Care Photovoltaic solar farm: Solmatix Renewables Ltd DO/MLSS & turbidity instrumentations: Hach Lange Flow meters & ultrasonics: Siemens Tipping buckets: CSO Group Ltd Precast concrete supplies: FP McCann Stormwater storage When incoming flows exceed FFT, the FFT pumping station will start to fill and eventually overflow to the blind storm tank. Once the blind storm tank has reached maximum capacity, flow will backup, allowing the level within the FFT pumping station to increase further. A higher-level overflow pipe allows flows to pass to the online storm tank. Once maximum capacity is reached here, flows will pass to the Ganaway Burn via the 6mm overflow screen and flow meter. Storm return will occur when the FFT pumping station is at a suitable low level. The storm tanks will return flow to the FFT pumping station in sequence i.e. blind tank first. Both tanks are fitted with automated penstocks which will open to return the contents of each storm tank to the FFT pumping station. Both storm tanks are fitted with tipping bucket cleaning systems from CSO Group Ltd, which help prevent build-up on the tank floor to achieve that ‘brushed floor effect’ when empty. The tipping bucket will operate when each of the storm tanks has reached the empty level. [caption id="" align="alignnone" width="1200"] (left) Ards North WwTW - Courtesy of NI Water, and (right) storm tanks tipping bucket installation - Courtesy of BSG Civil Engineering Ltd[/caption] Primary treatment The PST flow splitting chamber receives flows from the FFT pumping station and return liquors pumping station. Flow from the PST flow splitting chamber passes to three primary settlement tanks. These tanks are hopper bottomed and are desludged using automated valves to the primary sludge pumping station. Wastewater continues through to the PST collection manhole which mixes with RAS upstream of the ASP distribution chamber to feed the three ASP lanes. Sludge and scum drawn from the three PSTs arrives in the primary sludge pumping station. This station consists of two submersible pumps in duty/standby arrangement and is used to transfer sludge and scum removed from the PSTs to the thin sludge tank. Activated sludge plant The ASP lanes are identical in design and equipment. Each lane comprises an anoxic zone and an aeration zone. Each anoxic zone is equipped with a mixer. Each aeration zone is equipped with an aeration grid, air control actuator, air flow meter transmitter, two dissolved oxygen probes and an MLSS probe. Each aeration zone is fitted with mixers and aeration grids with fine bubble disc diffusers, which are attached to a central manifold which then connects to the ASP blowers. The influent entering these zones is controlled to maintain a set dissolved oxygen and MLSS level. The dissolved oxygen demand is supplied via the ASP blowers, configured in a duty/assist/standby arrangement. The blowers’ manifold is monitored by a pressure transmitter, a temperature transmitter and an air flow meter transmitter. [caption id="" align="alignnone" width="1200"] Aeration plant air manifold control valves and instrumentation - Courtesy of BSG Civil Engineering Ltd[/caption] Final treatment Flow from the ASP Lanes gravitates to the FST flow split chamber, fitted with adjustable weirs where the flow is split evenly to the three final settlement tanks. Each tank is identical and is equipped with a half bridge scraper, sludge blanket detector, ladder position switch and a proximity switch. Scum travels to the scum collection chamber and furthermore to the FST scum pumping station. The station is equipped with a duty/standby pump set which pumps its contents to the thin sludge tank. The tanks desludge is controlled via flow meters through actuated hydrostatic valves located in separate chambers that adjoin the RAS/SAS pumping station. Each tank’s settled effluent hydraulically discharges into the tank’s outlet launder channel to the final effluent/washwater pumping station. Final effluent Final effluent flows into the final effluent/washwater pumping station and on to the final effluent sample chamber. Here, the final effluent is monitored for turbidity and temperature levels and is also the dedicated location for the auto sampler. The final effluent/washwater pumping station contains two submersible fixed speed final effluent/washwater pumps in a duty/standby arrangement. These are used for supplying the washwater tank with the necessary effluent for washing the screens, sludge thickeners, etc. Final effluent is returned through a packaged plant automatic backwash strainer system located inside the control building. The automatic backwash strainer system, situated inside the sludge thickening building, is a filter that is used to remove particles from the final effluent returned from the final effluent/washwater pumping station. Final effluent flows from the sample chamber which is connected to the long sea outfall pipe. Sludge pumping, treatment & storage The RAS/SAS pumping station is equipped with two sets of pumps. RAS pumps and SAS pumps, a level ultrasonic and high-level floats are used to control both sets of pumps. The duty pump returns the desludge from all FSTs back to the PST collection manhole, continuing to the aeration distribution channel. The SAS pumps, also arranged in a duty/standby configuration, periodically pump forward sludge to the thin sludge tank. The frequency is operative set to maintain a desirable MLSS level within the ASP lanes. [caption id="" align="alignnone" width="1200"] RAS/SAS pumping station - Courtesy of BSG Civil Engineering Ltd[/caption] The thin sludge tank is equipped with an external mixer for the blending of the tank’s contents to feed the sludge thickening plant. A level ultrasonic with low and high-level floats are used in the control of the mixer. Mixed sludge from the thin sludge tank is pumped to the sludge thickening plant via the two thickeners feed pumps. These pumps are progressive cavity pumps and are arranged in duty/standby configuration. The pumps are VSD controlled to allow the flow to the thickening plant to be controlled. There are two sludge thickeners, with an individual throughput of 8.3 m3/hr @ 1.3% DS with a discharge of no more than 6%, based on a 5-hour day, 7-days per week operation at 100% of the maximum design load. The thickeners are arranged in a duty/standby configuration with two actuated isolation valves installed on the feed pipework allow this to be fully automated. If one thickener was to develop a fault, the standby thickener can resume operations without manual intervention. Polyelectrolyte is made up on site to be added to the sludge fed to the sludge thickening plant. The addition of this chemical aids flocculation and makes thickening easier. This plant is a liquid polymer set. The liquid poly is delivered within IBCs for the makeup process. The set mixes the poly from the IBC with water to a preset concentration rate and is then transferred to the poly storage tank. The duty poly dosing pump doses to the thickener’s sludge feed pipework from here. Thickened sludge from the sludge thickening plant is transferred to the thick sludge tank. Here thickened sludge is stored for removal off site. A collection tanker removes the tank’s contents off site by coupling to the tank’s Bauer Coupler connector. [caption id="" align="alignnone" width="1200"] PST No 1 & control building - Courtesy of BSG Civil Engineering Ltd[/caption] The tank is equipped with a decant valve arrangement to facilitate settlement of the tank’s contents. The tank is also equipped with a level ultrasonic, low and high-level floats for level status and control of an externally fitted mixer for tank agitation. The return liquors pumping station receives liquors from the following areas: inlet works drains, thin sludge tank decants and overflow, thick sludge tank decants and overflow, sludge thickening plant bund, FE and washwater drains and odour control plant drains. The station comprises of two fixed speed pumps, which are arranged in duty/standby arrangement. These return liquors to the activated PST splitting chamber. Washwater pumping The final effluent washwater & potable water booster sets are positioned within the sludge building. A ’dual washwater tank’ system is in place to feed both sets of pumps. The GRP dual washwater tank is designed with a lower compartment which holds 6m3 and an upper compartment which holds 1m3. The lower compartment is designed to contain the final effluent delivered via the final effluent/washwater pumping station, which in turn feeds the final effluent booster set which boosts the pressure as required for the washwater of the inlet screens, sludge thickeners, odour control, and the storm tank tipping buckets. The upper compartment is designed to contain potable water which in turn feeds the potable water booster set, which boosts the pressure as required for the nine retractable hose reels around the site for wash down, poly makeup plant water and poly carrier water. [caption id="" align="alignnone" width="1200"] Low level structures RC concrete installation - Courtesy of BSG Civil Engineering Ltd[/caption] Odour control plant The 2-stage odour control unit (bio & carbon filter) is connected to the various strategic areas. The odour control unit comprises of two odour fans, which are arranged in duty/standby arrangement. Actuated valve, flow meters, pressure transmitters and temperature transmitters are used to control the odour control system. Only odour omitted from the sludge thickening building (due to their extreme odorous compounds) will bypass the biofilter and go directly to carbon filter for treatment. Outlying pumping stations Existing treatment facilities at Ballywhiskin and Carrowdore were decommissioned and replaced with new pumping stations, while a completely new pumping facility was constructed at Sandycove Caravan Park where no NI Water asset previously existed. The last of the outlying WwPS to be upgraded was Ballywalter Fowler Terminal Pumping Station (TPS). This facility was completely refurbished with larger capacity pumps, a new MCC and additional storm storage capacity. Fowler Way TPS pumps to Sandycove WwPS which in turn pumps to the new Ards North WwTW, while the pumping stations at Ballywhiskin and Carrowdore pump directly to Ards North. [caption id="" align="alignnone" width="1200"] (left) Ballywhiskin TPS - Courtesy of NI Water, and (right) Carrowdore WwPS - Courtesy of BSG Civil Engineering Ltd[/caption] Civil construction challenges There were various challenges throughout the construction phase of the works that had to be overcome to ensure that the contract programme was achieved. As the project spanned over a 20km distance, there were varying ground conditions to deal with from very loose running sand in the gravity pipeline sections at Sandycove; soft, deep peat at Carrowdore WwPS; extremely hard rock at Ballywhisken to stiff clays with loose gravels at the WwTW site. This led to a variety of temporary works systems having to be designed and employed to deliver the works safely. Groundwater levels also varied across the scheme with various dewatering techniques used to maintain dry working spaces. Artesian water pressure and groundwater under tidal influence presented difficulties during the construction of these works. Overhead services also presented a construction issue at the WwTW site. As a result, carefully planned construction sequencing and specialised plant were employed. 13.5km of pumping main was installed along roads within this rural area. In order to keep to programme, pipe installation had to be carried out using a minimum of two separate teams at all times. Due to the limited options for suitable diversionary routes in the area, the pipe installation programme had to be carefully managed and continually communicated to the roads authority to ensure both pipe installation squads had consecutive sequencing of works throughout the pipeline installation phase of the scheme. [caption id="" align="alignnone" width="1200"] (left) Sandycove WwPS and (right) Ballywalter Fowler Way TPS - Courtesy of NI Water[/caption] Sustainability To boost the sustainability of the treatment facility, 138 solar PV panels from Solmatix Renewables Ltd were fitted to the roof of the new control building which will produce over 45,000 kWh per annum. This renewable energy could save NI Water up to £300k over 25 years. Charging points for NI Water’s growing fleet of electric vehicles have also been installed at the new treatment works. Communications & PR NI Water and its project management team developed a proactive comms and PR strategy for the Ards North Wastewater Improvement Scheme which included circulation of project brochure, issuing of regular press releases, letters to residents, briefings for elected representatives, circulation of progress updates, safety events with children, and face-to-face meetings with landowners. Myriad stakeholders were kept up to date with progress and informed in advance of pipelaying works and associated traffic management arrangements. Following completion of the project, a site tour of the new WwTW was organised to give local elected representatives the opportunity to view the modern facility first hand. Feedback from the visit was extremely positive. [caption id="" align="alignnone" width="1200"] NI Water, TetraTech, BSG Civil Engineering Ltd and Farrans along with local elected representatives to mark completion of the £18m Ards North Wastewater Improvement Scheme - Courtesy of NI Water[/caption] Conclusion A collaborative, forward-thinking approach between NI Water, BSG Civil Engineering and Tetra Tech has produced whole-life cost, programme and carbon savings in the delivery of this project. Phased flows were brought into the new Ards North WwTW between the months of November 2022 and January 2023. During this time, a process optimisation phase took place before the plant was rigorously tested and commissioned under varying flow and load scenarios. The plant was then put through a period of intensive detailed process sampling achieving highly performing results during separate 14 and 28-day sampling periods during Spring 2023. The project was successfully completed and handed over to NI Water ahead of the 2023 summer tourist season. The new Ards North WwTW is ensuring that high-quality effluent is being discharged out to sea, helping to improve the bathing water quality along this part of the Ards Peninsula in line with the project objectives.

The Exmouth Outfall Project is a multi-phased upgrade designed to bolster water quality, ensure regulatory compliance, and enhance the resilience of wastewater assets in Exmouth and the surrounding catchment. Following the successful offshore construction of a new long sea outfall near Sandy Bay in early 2024, the next phase focuses on modernising two key sewage pumping stations (SPS) and implementing additional environmental safeguards. These upgrades support compliance with the Environment Agency’s Emergency Overflow Policy, provide improved resilience to extreme weather events, and significantly reduce the environmental impact of storm discharges into coastal waters. The project’s location near sensitive natural and recreational areas, including a Blue Flag beach and a major holiday park, required detailed coordination to maintain public access, reduce ecological disturbance, and respect the operational needs of local stakeholders. Project overview

The Exmouth Outfall Project is part of the broader Exmouth Shellfish Water Nutrient Delivery (SW_ND) initiative. This integrated investment programme is designed to ensure that wastewater infrastructure in the region operates to the highest standards of reliability, sustainability, and environmental protection. The current phase focuses on the following objectives:

Increased flow capacity: Improvements at two pumping stations ensure that the system can effectively manage larger stormwater volumes, reducing the risk of emergency discharges during peak rainfall events. Enhanced screening & compliance: New systems will ensure that all discharges are appropriately screened, improving water quality in receiving waters. Improved reliability & resilience: Upgrades include improved power systems and control mechanisms to ensure consistent operations, even under adverse conditions.

These enhancements play a key role in improving the overall performance of the wastewater network while supporting the water quality designations of nearby shellfish harvesting zones and bathing waters.

Engineering & infrastructure upgrades - pumping stations

The project includes substantial mechanical and electrical improvements at both Maer Road and Phear Park Pumping Stations, along with associated upgrades at Maer Lane Sewage Treatment Works (STW).

The improvements involve replacing older pumping equipment with high-efficiency variable speed drives, optimised to handle varying flows while minimising energy consumption. The control panels and instrumentation are being replaced with new, robust systems that allow for greater automation and remote monitoring. Where possible, old infrastructure is being re-purposed or carefully integrated into new systems to reduce waste and maintain operational continuity.

Sites have also been equipped with enhanced power resilience features. These include alternative power supplies or standby systems designed to ensure uninterrupted service during grid outages. Structural improvements have also been made to allow for safer maintenance practices, such as the installation of load-handling equipment to support future repairs or replacements.

[caption id="attachment_23557" align="alignnone" width="1200"] (top left) Transformer cofferdam, (top right) transformer reinforcement base slab, (bottom left) transformer cofferdam formwork, and (bottom right) electrical infrastructure upgrades completed - Courtesy of Galliford Try[/caption] Screening enhancements

Improved mechanical screening is a core element of the upgrades, ensuring that all flows are treated to meet current discharge consent requirements. New systems are capable of capturing fine debris from storm overflows, minimising the impact on the environment. This supports South West Water’s commitment to safeguarding designated bathing waters and ecologically sensitive marine areas.

Resilient control systems

New digital systems have been introduced to allow more intelligent control of pump speeds and flow management. This ensures that during storm events, flows can be managed efficiently without overloading downstream treatment facilities. These systems are designed to integrate with the broader telemetry network used by South West Water, allowing operators to respond in real-time to system performance.

Phear Park & Maer Road SPSs: Supply chain - Key participants Project management for SWW: ChandlerKBS Main designer & contractor: Galliford Try Civils design: Eastwood Consulting Engineers HV designers: ITP Electrical HVAC design & installation: Air Technology Systems FRC installation: D&P Reinforcements High voltage connections & earthing: High Voltage Power Services (SW) Transformer: Wilson Power Solutions Ltd Screens: Eliquo Hydrok Ltd Composite steel-reinforced pipes: Aquaspira Ltd Diamond drilling: 24/7 Diamond Drilling & Sawing Services Lifting, transport & storage: Spence Crane Hire Ltd Sustainability & environmental stewardship

Environmental protection has been a key focus of every phase of the Exmouth Outfall Project. The works are being delivered with sustainability in mind, both in terms of construction practices and long-term operational efficiency.

Some of the key initiatives include:

Recycling of construction materials: The project has employed advanced separation techniques to reclaim and reuse drilling fluids and other construction by-products, helping to reduce the demand for fresh resources and minimise waste. Low-carbon construction: By using efficient scheduling, modular build techniques, and energy-conscious planning, the project has reduced its overall carbon footprint by an estimated 40 tonnes of CO2. Screening performance: The enhanced screening systems help prevent plastics and other materials from entering natural watercourses, contributing to the long-term health of local marine ecosystems.

These initiatives are aligned with SWW’s wider environmental objectives and support national efforts to improve the health of UK rivers and coastal waters.

[caption id="attachment_23555" align="alignnone" width="1200"] Maer Road SPS: Enhanced electrical supply and routing works - Courtesy of Galliford Try[/caption] Construction logistics & stakeholder coordination

Delivering this project within such a high-profile and environmentally sensitive location presented unique challenges. The proximity of a busy tourist destination – one of the UK’s largest holiday parks – required careful planning to minimise disruption.

Key actions included:

Seasonal delivery: All construction activities were carefully scheduled during the winter maintenance window to avoid peak visitor periods. This minimised disruption to both the public and local businesses. Environmental controls: Rigorous sediment, noise, and dust control procedures were implemented throughout the construction phase. Ecological assessments and ongoing monitoring ensured the protection of flora and fauna in the surrounding area. Community & stakeholder engagement: SWW and Galliford Try worked closely with local residents, businesses, and regulators to communicate construction milestones, respond to concerns, and provide updates on progress. Dedicated community liaison officers helped maintain positive relations and ensure transparency throughout the delivery period. Knowledge sharing & industry learning

Galliford Try and South West Water are committed to using the Exmouth Outfall Project as a benchmark for future schemes. Lessons learned are being captured and shared internally across both organisations to inform best practices on future water infrastructure projects.

Internal knowledge sharing has included presentations to more than 250 employees across multiple business units. Topics covered include the use of sustainable construction methods, approaches to stakeholder engagement, and the integration of new digital controls.

[caption id="attachment_23554" align="alignnone" width="1200"] Old pipework - Courtesy of Galliford Try[/caption] Conclusion

The Exmouth Outfall Project exemplifies a forward-thinking approach to infrastructure delivery, combining technical excellence with environmental responsibility and community engagement. These upgrades are not only vital for regulatory compliance and operational resilience, but they also play a crucial role in enhancing the quality of life for residents and visitors alike.

As the project continues to progress on time and on budget, South West Water is well-positioned to meet its long-term targets for stormwater management, coastal protection, and sustainable wastewater treatment. Galliford Try is proud to support this vision through the safe and efficient delivery of complex infrastructure in sensitive locations.

This case study highlights what is possible when innovation, collaboration, and environmental stewardship are placed at the centre of infrastructure delivery.

The Bangor Beach Road Sewage Pumping Station (SPS) Project is part of Dŵr Cymru Welsh Water’s (DCWW) work to reduce the water quality impact of sewer overflows on the Menai Shellfish Waters. The Menai Strait is a unique marine environment between Anglesey and North Wales, with the water quality directly impacting the shellfish quality and hence the local fishing economy and importantly, the ability to sell shellfish to European markets. Bangor Beach Road SPS is located in the northeast of Bangor in the Hirael area, close to the sea front promenade, next to King George’s Field playing field. Project background & solutions options

The Bangor Beach Road SPS Project was developed after feasibility and assessments studies had been completed for the wider wastewater catchment, including extensive hydraulic and coastal water quality modelling.

These showed that the Bangor Beach Road SPS was an impacting asset and that a solution, to reduce storm overflows here, was an effective approach to improving water quality. The asset was on the National Environment Programme list to reduce its impact on the shellfish waters, placing obligation on Welsh Water to deliver the solution by April 2025.

Solution options were investigated at the SPS including increasing pass forward flow, local treatment, and flow removal, however, to deliver the outcome within the timeframe, storage was the best solution.

[caption id="attachment_24319" align="alignnone" width="1200"] Bangor Beach Road PS Project - Courtesy of Griffiths Ltd[/caption] Project drivers & goals

The aim of the project was to divert storm flow (from overflowing to the Menai) to the new storm storage tank, where it will be stored offline until flows have reduced, at which point it is returned to the network for treatment.

The solution included:

Retrofitting the existing sewage pumping station. Provision of new storm pumps to deliver up to 1,000 l/s to a new 4,300m3 below-ground stormwater storage tank (under the adjacent playing field). Associated mechanical and electrical equipment. Reinstatement of the playing field facilities. Project scope & undertakings

The project forms part of wider catchment interventions including sewer improvements, tidal ingress removal, infiltration removal and future increases in treatment capacity at the receiving wastewater treatment works. The project comprises of two key elements:

Retrofitting of the existing SPS with new storm pumps. A new below-ground (off-line) storm storage tank.

Welsh Water contracted the project as separate civil (stormwater storage tank) and mechanical and electrical (sewage pumping station) elements, with Arup acting as Welsh Water civil design consultant, Griffiths Ltd as civil contractor and Eric Wright Water as MECIA design consultant and contractor.

Bangor Beach Road SPS: Supply chain - key participants Civil design inc. geotechnical, coastal & pipelines: ARUP Civil contractor: Griffiths Ltd M&E design & contractor: Eric Wright Water Storm tank design & construction: FP McCann Ltd Storm pumps: Xylem Water Solutions Pipework supply: Saint Gobain PAM UK Pipework & mechanical installation: Mectec Engineering NW Ltd Sewage pumping station retrofit

The existing SPS takes wastewater from the Bangor catchment and pumps it up to Treborth WwTW for treatment. During storm conditions, when the flows to treatment are exceeded, storm flows had historically been screened and then pumped via a long sea outfall to the Menai.

[caption id="attachment_24318" align="alignnone" width="1200"] (left & bottom right) New storm pump 4 & 5 and (top right) the existing SPS retrofit - Courtesy of Eric Wright Water[/caption]

The SPS was constructed on an area of largely made ground, set out from the sea front. During the optioneering stages, the location was considered costly and complicated to add new wet wells or pumping stations. This drove the design team to investigate options for retrofitting the existing SPS, which would have the additional benefit of less carbon and cost than constructing a new asset.

The existing SPS has three wet wells, which served the flow to treatment and overflows to the long sea and short sea outfalls. One of the overflow wells was re-purposed to locate the new pumps which serve the new storm tank. Design reviews including suppliers ensured that the existing wet wells were of sufficient dimension and could achieve the designed flow conditions with the new pumps.

Eric Wright’s mechanical and electrical works within the SPS also included mechanical pipework, valves, controls and power for the storm pumps and ensuring the integration of existing controls. This was complicated because of the multiple weirs and screens within the existing asset and the multiple overflow routes. This was a collaborative approach supported by hydraulic modelling (by Arup) and surge analysis and system checks by specialist consultants.

Stormwater storage tank

The new stormwater storage tank is a 4,300m3 below-ground prefabricated concrete tank, located below the King Georges playing field adjacent to the SPS. The required volume of storage was determined from earlier modelling, which showed that this size would retain storm flows for all but the largest storm events; reducing overflow to 10 times per year on average, which would achieve the required water quality improvement.

[caption id="attachment_24321" align="alignnone" width="1200"] The new below-ground stormwater storage tank under construction - Courtesy of Griffiths Ltd[/caption] The storm tank was designed and delivered by FP McCann, and is a rectangular arrangement made from precast concrete walls and roof, with a cast in situ base. The tank is approximately 28m by 48 m and ranges from 3 to 4m deep. The tank has a slight longitudinal fall and is divided into lanes by internal walls to aide flow distribution and reduce siltation risks. Access points were provided at each end of the tank lanes. The design had to accommodate constraints on access points due to the playing field above the tank - no manhole covers could be situated within the football pitch area. Rising main

The 900mm diameter rising main pipe between the sewage pumping station and the stormwater storage tank posed various design challenges. The pipeline needed to exit the pumping station, aligning to existing connection points, traverse the SPS revetment in the marine zone, cross a flood bund (by others) and promenade (by others) to the storm tank. With the added complication of two designers undertaking the above and below-ground sections respectively and third parties working on other construction projects within the vicinity.

[caption id="attachment_24317" align="alignnone" width="1200"] New external pipework to storm tank - Courtesy of Eric Wright Water[/caption] King George’s Field playing field reinstatement

Coordination of the tank works, and construction of the associated pipework and civil elements were undertaken by Alun Griffiths. Arup, as Welsh Water’s designers, and Alun Griffiths worked extensively with landowners of the playing field to provide a reinstatement design for the football pitch; providing a valuable community asset to a high quality standard. The final design included a pitch drainage system, tree planting and tied into surrounding improvements to the promenade (by others).

Innovations, cost savings & carbon reduction

Carbon savings for this project were realised from the decision to retrofit the existing facility and not building a new storm pumping station, and by choosing to re-purpose the wet well within the existing SPS. This also reduced time on site and hence is assumed to reduce the health and safety risks.

Eric Wright worked with the pump suppliers and engaged specialist hydraulic advice to ensure the system would operate as designed. Although retrofitting was difficult and attention needed to be paid to the condition of existing equipment, especially at interfaces, this approach reduced carbon, the need for land purchase, and provided a resilient asset for the long term.

[caption id="attachment_24316" align="alignnone" width="1200"] Pipework in the sewage pumping station connecting with the stormwater storage tank - Courtesy of Eric Wright Water[/caption]

For the new stormwater storage tank, precast concrete proved suitable for the given ground conditions and the sewage application and offered savings in time, in design and on site.

The location of the tank also posed a risk to Welsh Water Operations, with no easy access for inspections. CCTV was therefore included to monitor conditions within the tank without the need to enter the tank and help plan maintenance. The internal arrangement of the tank was designed with the aim to reduce the need for maintenance and entry to the tank for cleaning. It was laid out in profiled lanes with an inlet manifold to flush flows down each lane.

The football pitch above the tank was a general use playing field before the project. Welsh Water has reinstated this community asset, with the design including pitch drainage and additional trees in the surrounding area. Welsh Water worked extensively with the local council (landowner of the field) to ensure the solution was in keeping with their recent improvements to facilities in the area and provided a long-term community benefit. [caption id="attachment_24314" align="alignnone" width="1200"] CCTV image inside new storm tank during commissioning - Courtesy of Eric Wright Water[/caption] Conclusion/summary

The retrofit of the Bangor Beach Road Sewage Pumping Station and the stormwater storage tanks retrofit were commissioned in March 2025; achieving the NEP regulatory date. This provides Welsh Water with a new asset and will contribute to water quality improvements in the Menai.

Limited storms have occurred since completion, but the improved SPS and tank have been shown to operate as designed. At the time of writing (July 2025), the team are on site finalising the reinstatement and completing a small element of coastal protection.

Welsh Water will continue to make improvements within the catchment, with planned schemes to increase storm treatment capacity at the receiving WwTW and further targeted sewer improvements to reduce infiltration and reduce risks of saline intrusion. Locations across the catchment feasible for RainScape (including SuDs) have been identified for future catchment resilience.

South West Water looks after the water and wastewater services for 1.8 million customers across Cornwall, Devon, the Isles of Scilly and parts of Dorset and Somerset. As part of its commitment to drive improvements in its performance, the company has collaborated with AUMA Actuators Limited on valve speed actuation and calm networks at its specialist Network Training Centre. South West Water’s Network Training Centre comprises a purpose-built laboratory where network components are installed and tested to record the effect of different operating conditions, and educate network engineers on the importance of calm networks. The work carried out between AUMA Actuators and South West Water focused on the effects on pipeline pressure transients by applying a simple variable speed actuation profile to the closing of a quarter turn valve. Clive Dumbleton is  a member of the Resource & Production team at South West Water. He explains:

“South West Water is invested in ‘Calm Networks’ training, in tandem with our focus on pressure management and the basics of pressure control. The research that we conducted with the team at AUMA aimed to determine the effects of variable speed actuation on pipeline pressure transients, and mitigate the risk of water hammer.”

Tests were carried out by firstly closing the valve at a constant speed and measuring the pressure transients upstream of the valve. This is what is referred to as the benchmark. A simple speed profile was then set in the variable speed actuator. First, drive full speed to 20% open, then at the slowest variable speed to closed. Next, drive full speed to 20% open, then at half speed to closed. Finally, drive full speed was set to 20% open, then at quarter speed to closed. The results of the four tests were recorded and the upstream pressure transient and the system flow rate for each of the profiles were compared for a conclusion to be reached. [caption id="attachment_22847" align="alignnone" width="1200"] Profox actuators - Courtesy of AUMA Actuators Limited[/caption] Colin Borrows is Operations Manager at AUMA Actuators Limited. He worked alongside Clive Dumbleton during the tests:

“It was evident that with a constant speed actuator, an unwanted pressure spike was created that was over twice the system pressure. It was also clear that with a slow variable speed profile the pressure transient was removed entirely, but the time taken to close the valve was more than double the fixed speed. The quarter speed variable setting provided the best compromise of speed of response against minimising transient pressure surges, reducing the ‘spike’ from over 100% of the system pressure to a much smaller 17% transient.”

This is a relatively simple test to demonstrate the effectiveness of a variable speed actuator in the mitigation of risk of ‘water hammer’. The actuator can be configured to a more sophisticated speed profile with multiple speed changes through the stroke if needed. Colin Borrows concludes:

“What is clear in this test is that having the flexibility of variable speed in the actuator, the system designer can introduce tolerance in the system both before and after installation making it perfect for new and retrofit applications.

“Variable speed actuators help control aged assets in the field, minimising leaks, damaged valves, and expensive call-outs. This experiment clearly demonstrates the effectiveness of variable speed actuators in calm networks.”

What is water hammer? Water hammer happens when there is a surge in pressure and flow rate of fluid in a pipeline, causing rapid changes in pressure or force. Very high pressures can result in pipeline failure, such as leaking joints or burst pipes. Support components can also be subjected to strong forces from surges or sudden flow reversal. Water hammer can be a significant issue in many applications. Valve seats may suffer if they are driven hard to their end positions whenever the valve is closed. A variable speed actuator, gives the control engineer the opportunity to specify the speed of actuation at different points in the cycle. Variable speed actuators can be set so that the valve moves quickly through the majority of its cycle, slowing down as it nears the close position, minimising water hammer problems and extending the life of the valve seat. For emergency situations a ‘fast close’ speed can still be specified. For further information about AUMA’s comprehensive range of actuators, controls, drives and gearboxes visit www.auma.co.uk   For more information contact AUMA Actuators Ltd | +44 (0) 1275 871141 | www.auma.co.uk About AUMA Actuators Limited Based in Clevedon, near Bristol, AUMA Actuators Limited is the UK subsidiary of the global AUMA Reister GmbH and Co., the world’s largest manufacturer of electric valve actuators, operating on every continent, with 2,300 employees in 30 locations. AUMA is the world leader in modular electric valve actuators and gearboxes, supplying a full range of actuators right across the process, water, petrochemical and energy sectors. AUMA manufactures robust, reliable equipment with sophisticated control and connectivity options, backed up with exceptional service support. AUMA benefits include: Rugged and reliable products. Double-sealed actuator housing to protect the electronics. Tough and resilient finish. Powerful, with multi-turn actuators from 7 to 59,000 ft lb (10 to 80,000 Nm) and thrust acceptance up to 900,000 lbs (4,000 kN) and part-turn actuators from 18 to 498,000 ft lb (25 to 675,000 Nm). Worldwide availability and support. Modular, user-friendly design which provides key benefits such as: Supply subcontractors with the appropriate components to allow-pre-assembly Reduce time on site – plug and play Mount gearboxes up to 100m from the actuator controls to aid access and minimise health and safety risks ACE Technician Scheme ACE Technicians can be in-house or part of your service organisation. The ACE (AUMA Certified Engineering) programme has three levels, allowing operatives to be certified for installation or for advanced configuration, troubleshooting and repair. The ACE scheme means that you can have trained, card-carrying AUMA ACE Technicians as part of your own organisation or as part of your service partner’s staff, working in partnership with the service offered by AUMA UK’s head office in Bristol.