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Case Studies

Brawby Storm Spill Reduction (2026)

Brawby Storm Spill Reduction (2026)

Brawby is a village in North Yorkshire that has historically experienced fluvial flooding, and more recently surface water flooding due to increased population and housing growth. The village is located on flat ground adjacent to the River Seven and is protected by a flood bund constructed in the 1940s. Historically, all highway drainage discharged into a combined sewer system leading to a small sewage treatment works, which was frequently overwhelmed and resulted in the discharge of untreated sewage to the environment. As part of Yorkshire Water’s Storm Spill Reduction Programme, Mott MacDonald Bentley (MMB) has designed and constructed a new surface water sewer and pumping station. Delivered predominantly using tunnelling techniques, the scheme diverts surface water flows directly to the river, bypassing the sewage treatment works. Background and planning
Brawby STW was identified by Yorkshire Water as a frequent source of sewage spills. Investigations by MMB determined that the primary cause was an increase in surface water flows overwhelming the treatment capacity of the works, resulting in discharges via the storm system.

The issue was exacerbated by the receiving watercourse, a poorly maintained ditch connected to the River Seven via a flap valve. During periods of high river levels, the ditch was unable to drain, causing the STW outfall to become surcharged. In extreme events, this resulted in sewage backing up into the village streets.

To address this, MMB proposed the construction of a new surface water sewer to separate surface water from foul flows and discharge it directly to the river.
[caption id="attachment_30608" align="alignnone" width="1200"] Overview of the project - Courtesy of MMB[/caption]
Due to the very flat topography of Brawby, typical of the Vale of Pickering, a pumping station was required to convey flows to the discharge point.

The pumping station would be located within the STW boundary and designed as a caisson shaft to minimise the working footprint on the constrained site. Sections of the new sewer would be constructed using auger boring, with the rising main installed via horizontal directional drilling (HDD), reducing disruption to local residents.
Design & construction
Design commenced in October 2024, with beneficial completion required by March 2025 to meet Ofwat AMP7 requirements. To achieve the accelerated programme, the design was developed and delivered in stages in close collaboration with Yorkshire Water. The civil design was submitted eight weeks after project initiation, with the MEICA design submitted a further two months later; both were accepted first time.

MMB worked closely with the Environment Agency (EA) to secure the Flood Risk Activity Permit (FRAP) required to construct the discharge chamber through the flood bund. While FRAP approvals can typically be a lengthy process, the project aligned directly with the EA’s objectives for waste and water quality, providing confidence that consent could be achieved within the programme constraints.

Specialist tunnelling contractor, HB Tunnelling Ltd, was engaged early to support delivery of the caisson shaft, auger bores and the horizontal directional drilling works. This early collaboration delivered immediate benefits, including a proposal to enlarge one shaft so it could also be used as the auger boring launch point, eliminating the need for a temporary launch pit.
[caption id="attachment_30605" align="alignnone" width="1200"] (left) Sinking a manhole as a caisson shaft, (middle) groundwater rising above ground level, and (right) auger boring from one manhole to another - Courtesy of Mott MacDonald Bentley[/caption]
During construction, groundwater levels were encountered significantly higher than indicated by the ground investigation. Following a review of the borehole logs, the design team concluded that an artesian aquifer is present beneath Brawby, exposed during excavation for a manhole. As conventional construction methods became unworkable, MMB and HB Tunnelling Ltd jointly developed an alternative approach: installing all manholes as caisson shafts and auger boring the sewer between them. As a result, the scope increased from two caisson shafts to six, and from 75m of auger bored sewer to 225m.

As constructed, the system operates as follows:
Surface water is collected via highway gullies and conveyed into the new sewer network. Flows combine into a single pipeline and pass through a petrol interceptor located beneath the road, removing hydrocarbons and silt from the flow. The stormwater then discharges into a 5 m deep pumping station within the STW. Twin pumps transfer the flow through a rising main to a discharge chamber constructed within the existing flood bund. From here, the water gravitates through a flap valve into the River Seven.
Typically, in auger boring, thin steel casings are advanced through the ground behind the cutting head to form a temporary tunnel. Clay jacking pipes are then installed within the casing, which is removed at the reception shaft, leaving a spigot-and-socket pipeline in place. However, as auger bored systems do not incorporate conventional pipe bedding, the presence of loose sand introduced a risk of leakage due to ground movement.

To mitigate this, the steel casings were welded together in the launch pit to form a continuous pipe and were left in situ as the permanent sewer. Corrosion specialists from Mott MacDonald were engaged to verify that the steel pipeline would achieve the required 100-year design life for sewer infrastructure.
[caption id="attachment_30602" align="alignnone" width="1200"] Comparison of construction progress against the design model - Courtesy of Mott MacDonald Bentley[/caption] Brawby Storm Spill Reduction: Supply chain - key participants Client: Yorkshire Water Principal designer: Mott MacDonald Bentley Principal contractor: JN Bentley Pipe corrosion advisor: Mott MacDonald Design/installation of caisson shafts, auger boring & horizontal directional drilling: HB Tunnelling Ltd Electrical installation: Circle Control & Design Systems Supply of petrol interceptor: Hydro International Ltd Submersible pumps: Xylem Water Solutions Valves: AVK UK Ltd MCC: CEMA Ltd Road surfacing: Calder C.A.D. Ltd Community engagement
During construction, updates to the design and methodology created a perception among local residents that the project had stalled. To address this, Mott MacDonald Bentley (MMB) held a community drop-in session at the village hall, building on engagement undertaken at the start of construction. This provided an opportunity to answer questions, explain the evolving works, and maintain transparency with the local community.

Residents and local councillors were supportive of the scheme, despite the disruption caused by roadworks, recognising the long-term benefits it would deliver to the village. The positive relationship between the project team and the community was reflected in the rapport developed on site, with operatives receiving regular cake deliveries from residents!

Towards the end of the construction programme, MMB collaborated with the local highways authority to coordinate road reinstatement works. As the village roads were already scheduled for resurfacing, MMB reinstated the areas affected by construction up to an agreed extent, avoiding duplication of works and saving the local authority approximately 280m of road resurfacing work.
[caption id="attachment_30603" align="alignnone" width="1200"] Horizontal directional drilling minimised disruption - Courtesy of Mott MacDonald Bentley[/caption] Conclusion
Construction was completed over a period of approximately one year, concluding in November 2025, and achieved a 100% record of ‘Perfect Days’. This reflects an exemplary safety performance, with no injuries, lost time incidents, environmental harm, dangerous occurrences, near misses, or utility strikes recorded throughout the project.

The site manager was supported by the Safety, Health, Environment and Quality (SHEQ) team, who conducted fortnightly site visits to inspect works and provide guidance. A strong safety culture was embedded across the entire project team, from office-based staff to site operatives, encouraging proactive reporting and continuous improvement by recognising both good practice and opportunities for enhancement.

From the outset of design, hazard and operability (HAZOP) studies, along with access, lifting and maintenance reviews, were undertaken collaboratively with Yorkshire Water. This ensured that risks to operators were eliminated or mitigated at the design stage, demonstrating a cradle-to-grave approach to safety.

Due to seasonal variations in rainfall, it is too early to quantify the full spill reduction performance of the system. However, early feedback from local residents indicates a significant reduction in flooding, suggesting that surface water flows which previously overwhelmed the treatment works and caused sewage spills are now being effectively intercepted and safely discharged to the river.

case-study
Kirklevington Transfer (2026)

Kirklevington Transfer (2026)

Northumbrian Water’s WINEP Kirklevington Transfer scheme demonstrates the value of challenging the obvious asset-level answer. Rather than adding further treatment capacity at a constrained legacy works, the project team developed and delivered a network-scale solution where flows are transferred to a larger downstream treatment works with available capacity, supported by a new pumping station, balancing storage, rising main and targeted reuse of existing assets. The result was a compliant, lower-impact and more resilient solution delivered through a complex school, highways and strategic water-main interface. Background & project drivers
The driver for the Kirklevington Transfer Scheme was a WINEP requirement to achieve a stringent 0.3 mg/l phosphorus compliance in the final effluent. While the challenge could have been viewed narrowly as a local treatment capacity constraint at the existing sewage treatment works, this would likely have led to adding to or upgrading processes within an already constrained site, bringing increased construction risk, operational complexity, and limited long-term flexibility.

Instead, the project team re-framed the challenge at a network level, identifying an alternative strategy to decommission the local treatment process and transfer flows to a larger treatment works with sufficient capacity to meet regulatory requirements.
[caption id="attachment_32214" align="alignnone" width="1200"] Excavation works to prepare for pre-fabricated tank installation - Courtesy of Esh Stantec[/caption] This approach required robust technical evidence, close engagement with Northumbrian Water and the Environment Agency, and clear evidence that hydraulic performance, treatment capacity and storm overflow resilience would be maintained without transferring risk elsewhere in the system. The solution
The Kirklevington Transfer Scheme replaced the treatment function at Kirklevington STW with a new sewage pumping station and 380m3 balancing tank, supported by a valve chamber, MCC kiosk and chemical dosing arrangement. Calcium nitrate dosing from OMEX Environmental Ltd was incorporated to manage septicity risk within the transferred flows.

Existing assets were reused where they remained appropriate: the inlet screen was modified to accommodate increased inflow, existing storm tanks were retained, and the existing power supply and kiosk were reused where practicable.

Flows will be conveyed via approximately 1.7km of 225mm PE100 SDR17 rising main, discharging to a bespoke chamber before continuing through an upsized combined sewer. A key element of the solution was the adoption and upgrade of existing private sewer infrastructure at Conyers School, avoiding a longer route and removing the need for a more disruptive alignment, including a potential trenchless railway crossing.
Engineering judgement & innovation
The technical significance of Kirklevington is not a single isolated detail; it is the sequence of engineering judgements that changed the project outcome. The team followed a TOTEX-led hierarchy to avoid unnecessary new build, re-use assets where technically defensible, optimise existing network capacity, and only construct new infrastructure where it added clear system value.
[caption id="attachment_32219" align="alignnone" width="1200"] Illustrative visualisation of the proposed works. Base imagery from Google Earth; imagery © 2026 Airbus. Proposed infrastructure has been digitally rendered by Esh-Stantec for illustrative purposes only and do not depict existing site conditions or the final constructed design[/caption]
This hierarchy materially changed the pipeline route. By establishing that the downstream network and the existing private sewer could accept the transferred flows, subject to targeted upsizing and adoption, the team reduced the length of new pipework by approximately half. This reduced material use, land disturbance, highway interface, programme exposure and community disruption.

The balancing tank also reflected practical delivery intelligence. The use of a modular precast concrete tank supported off-site fabrication, reducing site activities, improving installation certainty and shortening the period of open excavation. On a constrained live site, these choices reduced both construction risk and operational interface risk.
Kirklevington Transfer: Supply chain - key participants Principal designer & contractor: Esh Stantec Designer: Stantec UK Contractor: Esh Group Archaeological services: Archaeological Services Durham University Temporary works design: JC Consulting Temporary works cofferdam: MGF Ltd Fencing & groundworks: Stuart Marley Ltd Piling works: Interdrive Piling Ltd Directional drilling installation: Pipeline Drillers Ltd Pipelaying: DMJ Civils Ltd Tanks & chambers: Carlow Tanks (PPR Environmental Ltd) MEICA installation & commissioning: Retroflo Ltd Pipework & fittings: Saint Gobain PAM UK Pumps: Xylem Water Solutions MCC: CEMA Ltd Chemical dosing: OMEX Environmental Ltd Chemical dosing: Yara UK [caption id="attachment_32222" align="alignnone" width="1200"] Construction of the 380m3 balancing tank - Courtesy of Esh Stantec[/caption] Collaboration & project delivery
Kirklevington was delivered through intensive collaboration between Esh Stantec, Northumbrian Water, local stakeholders and specialist subcontractors. Collaborative planning sessions were used to hold the programme against a hard regulatory date. Weekly design and site meetings allowed design development and construction planning to progress in parallel, while regular client progress meetings gave visibility of risks and decisions.

The local authority highways team was engaged to avoid clashes with nearby contractors and to coordinate at pinch points. Regular communication with local schools enabled safe working during term time, reduced disruption, and ensured reinstatement was completed before the start of the academic year. Design engineers maintained regular site attendance, supporting fast resolution of buildability issues and reducing the risk of design intent being lost during construction.
Trenchless crossing & delivery constraints
One of the most sensitive construction interfaces was the 65m horizontal directional drilling crossing below a main road and a large-diameter raw water main.

The crossing avoided a disruptive road closure and reduced the direct interface with the strategic water asset. It required close collaboration between the site team, lead designers, geotechnical specialists, the HDD contractor, Northumbrian Water network operatives and other stakeholders.

The works were planned during the school summer holiday to reduce the exposure of pupils, parents and staff to construction movements. While this was the correct social and safety decision, it compressed the available programme and in doing so, increased the premium on planning, contingency and rapid decision-making. Joint risk meetings were used to agree the accuracy requirements, escalation strategy and contingency approach before the crossing was undertaken.
[caption id="attachment_32216" align="alignnone" width="1200"] Balancing tank nearing completion - Courtesy of Esh Stantec[/caption] Sustainability & carbon
The main carbon benefit came from changing the asset strategy rather than adding a visible low-carbon product late in the process. By transferring flows to an existing downstream works with capacity, the scheme avoided a more substantial treatment upgrade at Kirklevington and reduced the whole-life operational burden associated with a small local treatment site.

The revised route reduced the new pipeline length by around 50%, cutting the volume of pipe, fittings, excavation, reinstatement and temporary works required. The project material records a 126 tCO2 saving from route selection. The use of existing assets, adoption of private sewer infrastructure, off-site precast construction and local subcontractors further reduced waste, site movements and construction exposure.

There was also a direct environmental outcome. The receiving watercourse now receives no final effluent from the former local treatment works, rather than receiving effluent treated to a lower phosphorus concentration. Archaeological Services Durham University undertook pre-construction archaeological surveys, and the pipeline alignment was selected to avoid working within the flood zone where practicable.
[caption id="attachment_32215" align="alignnone" width="1200"] New hardstanding and access covers to the balancing tank and below-ground pumps - Courtesy of Esh Stantec[/caption] Health, safety & welfare
Safety management was integrated into planning and methodology rather than treated as a separate construction control. Toolbox talks were used for the key construction activities, remote-control plant was adopted where practical, and stakeholder interfaces were managed collaboratively across the delivery team and supply chain.

The decision to programme the school-interface works during the summer holiday reduced public interface risk. Operational safety was also improved through the automation of de-ragging logic, reducing the need for direct human intervention during future operation and maintenance.
Social value & community benefit
The project’s social value was most visible in how it handled its immediate community interfaces. Working around the school calendar reduced disruption to pupils, parents and staff. The revised route and use of existing infrastructure reduced working in the carriageway and lowered the impact on local traffic. The scheme also reduced the need for tanker access through narrow residential streets to the existing works.

The team retained community value in smaller decisions as well as in headline engineering decisions. An ornamental tree carving of an owl was created instead of simply removing a tree, and football strips were provided to a local youth football team. These actions were modest individually, but they helped turn an intrusive infrastructure project into one with visible local benefit.
[caption id="attachment_32218" align="alignnone" width="1200"] Ornamental tree carving of an owl - Courtesy of Esh Stantec[/caption] Outcomes
The scheme achieved operational completion ahead of the regulatory deadline and delivered a significant saving of 25% against the agreed target cost. It modernised critical wastewater infrastructure, reduced the need for future operational interventions at a constrained local works, and delivered a more resilient network-level arrangement.

Its strongest lesson is that the best infrastructure solution is often created before detailed design begins; by asking whether the project has been framed at the right asset boundary.

case-study
Norton, Presteigne & Weobley WwTWs (2023)

Norton, Presteigne & Weobley WwTWs (...

The Rivers Lugg and Wye have been identified as having high levels of phosphorus, which is causing eutrophication of these watercourses. Norton Wastewater Treatment Works (WwTW) discharges treated final effluent to the Norton Brook, a tributary of the River Lugg. Presteigne WwTW discharges treated final effluent directly into the River Lugg downstream of the Norton Brook confluence and Weobley WwTW discharges to Newbridge Brook, a tributary of the River Arrow and then River Lugg before joining the River Wye in Hereford. Norton WwTW Norton WwTW is a biofilter works located in Powys serving a population of 320. All wastewater flows arrive to the works by gravity and are treated on site before being discharged. The site previously had a descriptive consent and an unconsented storm discharge. The project driver was to reduce phosphorus to achieve a Total P of 0.65mg/l, with a regulatory completion date of 31 December 2021. Due to the proximity of Norton WwTW to Presteigne WwTW (approximately 3km), an identified option was to pump the Norton flows to the Presteigne catchment. An assessment of the hydraulic and biological capacity of Presteigne WwTW and the Presteigne sewerage network determined there was sufficient capacity to accept the pump-away solution whilst maintaining compliance with all permits. Therefore, the agreed solution was to replace Norton WwTW with a terminal pumping station, pump sewage into the existing sewer network draining to Presteigne WwTW. Consequently, the Norton WwTW would be decommissioned. [caption id="" align="alignnone" width="1200"] Norton SPS progressive cavity pumps - Courtesy of Morgan Sindall Infrastructure[/caption] Norton WwTW: Supply chain - key participants Designer: Arup Main contractor (WwTW & rising main): Morgan Sindall Electrical supply & installation: Protocol Control Systems (PCS) Ltd Inlet screens: Haigh Engineering Mechanical design/installation & steelwork: Industrial Pipework Services (IPS) Ltd Main pumps: Netzsch Pumps Washwater booster: Dutypoint Ltd MCC supply/install: Bridges Electrical Engineers Ltd Transfer to Presteigne Progressive cavity (PC) pumps were selected as the pumping method due to the complex nature of the 2km long rising main. The rising main has a number of peaks and troughs with washouts, air valves and sections operating under gravity. Furthermore, the inverted siphon section of the main may be susceptible to soft blockages which PC pumps were determined to be better suited to than submersible centrifugal pumps. Submersible pumps would be more susceptible to pressure fluctuations caused by potential air gulping in the downhill section of the main. The PC pumps are positioned on an above-ground slab along with valves and pipework to enable good operator and maintenance access. Split stator casing pumps were specified to provide ease of rotor replacement. To protect the PC pumps against ragging and wear, an inlet screen and grit chamber were set up upstream of them. The inlet screen is an Ace Screener® from Haigh Engineering Ltd, equipped with an integrated compactor and liquid separator unit. It is located beside the screen to facilitate the discharge of waste material into a skip. [caption id="" align="alignnone" width="1200"] Norton SPS: MCC kiosk and Haigh Engineering inlet screen - Courtesy of Morgan Sindall Infrastructure[/caption] Rising main Due to the length of the rising main, and the low flows coming into the pumping station on a regular basis, the output from the SPS would have been likely to suffer from septicity. This would cause particular odour problems as the discharge makes its way through the Presteigne network towards Presteigne WwTW. It was decided that potable water dosing be included within the design to reduce the risk of septicity. This has the added benefit of assisting in moving solids along the long rising main, which reduced the risk of soft blockages in the inverted siphon section of the main. During the construction of the rising main, a spider plough was utilised for sections within fields. This allowed for simultaneous excavation, pipe-laying, and covering to take place, resulting in minimal visual impact on the landscape. Additionally, this approach resulted in reduced staff involvement during this stage of construction, which was another advantage. A final air valve was required on the rising main before discharge, which is in close proximity to local housing and a children’s park. To prevent any odour-related complaints that might arise from the air valve, a carbon filter has been installed to scrub odours from the air released from the air valve. The chosen filter is a passive filter that can be easily installed within the air valve chamber. [caption id="" align="alignnone" width="1200"] Spider plough operation to construct the Norton WwTW pump away rising main - Courtesy of Morgan Sindall Infrastructure[/caption] Presteigne WwTW Presteigne WwTW is a biofilter works serving a population of 1,906 with a driver to reduce Total P to 1mg/l. The proposed solution is to provide chemical dosing at Presteigne to treat all the Presteigne network flows along with the additional pumped flows from Norton WwTW. The chosen system was ferric dosing with primary dosing upstream of the existing primary settlement tank (PST). A ferric delivery area design included a bunded tanker area in case of ferric spillages. This area had drainage with an interlock system, which meant the drainage penstock would close during ferric filling to prevent uncontrolled spillage to the environment. Innovative new dosing pipelines were utilised of flexible reinforced PVC type ‘hose-within-hose’ to provide double containment and an integral leakage detection system and alarm. This meant long continuous hose lengths can be run without breaks. An anti-ragging static mixer and pipework were located above ground to reduce health and safety risks, costs and environmental impacts associated with excavation works. To cope with the increased sludge production due to primary ferric dosing, a new sludge pumping station using PC pumps was designed. This is located alongside the existing PST de-sludge chamber. This was an above-ground element of mechanical plant, with access provided for operation and maintenance. Split casing pumps were specified to provide ease of rotor replacement. The progressive cavity pumps (duty/standby) couple directly into the sludge hopper chamber of the PST. [caption id="" align="alignnone" width="1200"] Presteigne WwTW: Ferric point of application (PoA) unit - Courtesy of Morgan Sindall Infrastructure[/caption] Alkalinity dosing was required as a result of the new ferric dosing. The identified solution for this was a small bag dosing plant with on-site mixing to create a liquid dose. A new point of application facility located on the side of the existing PST which discharges to the biological filter. It was determined that this point had enough hydraulic mixing for an effective alkalinity dose. The new works is achieving its ammonia consent with the current loading, but it had been identified that ammonia compliance could be a risk during AMP9. Nitrifying sand filters have been proposed as a technology to treat the ammoniacal nitrogen as a tertiary treatment solution. This has an added benefit of tertiary solids removal to give confidence in the total phosphorus consent. However, given the excellent performance of the works against consent and nitrifying capacity of the existing biofilters, the nitrifying sand filters will be phased into the works when required. Works included a new sampling arrangement with sampling kiosk, complete with an upstream diversion and reception chamber for when the nitrifying sand filter is constructed. Presteigne WwTW: Supply chain - key participants Designer: Arup Main contractor: Morgan Sindall Electrical supply & installation: Protocol Control Systems (PCS) Ltd Ferric dosing: Colloide Mechanical design/installation & steelwork: Industrial Pipework Services (IPS) Ltd Alkalinity dosing - BiCarb: Rospen Industries Primary settlement tank auto-desludge: SEEPEX UK Ltd Motor control centre supply & installation: GPS Group [caption id="" align="alignnone" width="1200"] Presteigne WwTW: Ferric dosing system and safety shower - Courtesy of Morgan Sindall Infrastructure[/caption] Innovations A number of innovations have been developed throughout the detailed design stage of Presteigne, including removing a number of pumping operations, thereby simplifying the process, and reducing costs and environmental impacts. The design also allowed for the removal of motorised mixing points for chemical dosing in favour of using the works hydraulics for mixing. Furthermore, a conventional solution would have called for an additional PST and humus settlement tank (HST) to provide redundancy to the works. By investigating the process performance, it was determined that the existing single PST and HST were sufficient across the operating range of the works. Therefore, the design proposed temporary bypass connection points upstream of both the PST and HST, with identified lay-down areas for temporary settlement units to be brought on site if required. This meant that the construction works could be completed within the existing site land boundary and saving capital and operational cost and carbon emissions. Weobley WwTW Weobley WwTW is a biofilter works located in Herefordshire serving a population of 1,153. All flows arrive to the works by gravity and are treated on site before being discharged. The works has P removal driver to achieve a Total P of 1.5mg/l. As at Presteigne WwTW, the proposed solution was to provide chemical dosing to reduce phosphorus. A ferric dosing system with primary dosing upstream of the existing PST complete with a ferric delivery area was provided. Given the added ferric dosing, it was expected there would be more sludge production. The existing sludge holding tanks had low abilities for controlling decant. The solution included for a new discharge tree with access arrangement to the existing sludge holding tanks for better operation. The existing works had no inlet screening, with only a macerator on site upstream of primary settlement. A Huber Technology RO9 screen with integrated screenings handling was installed in the existing inlet channel and provided new mechanical flooring with removable sections to provide flexibility for operating and maintenance of the screen. [caption id="" align="alignnone" width="1200"] Weobley WwTW: (left) Huber Technology inlet screen and (right) flow to full treatment pump station - Courtesy of Morgan Sindall Infrastructure[/caption] This provided significant cost and embodied carbon savings compared to a completely new screening installation. Downstream of the screen, an inlet flume was provided for flow measurement and control of the downstream lift pumping station. The flume was constructed off-site, allowing for greater dimensional accuracy than an on-site constructed flume, as well as reduced downtime for the site. A new lift pumping station for all incoming flows for treatment was required to provide a separate lift to the balancing tanks then the unscreened storm flows. The existing inlet pumping station was re-purposed as the storm pumping station, meaning the more efficient pumping station was operating for more of the time compared to the older storm pumping station, which only operated intermittently - hence saving on energy usage and operational carbon. An existing multi-use returns pumping station was used to pump humus returns and storm returns to the head of the works. This asset consisted of outdated and poorly operating pumps and valve work. A solution was developed to replace mechanical equipment within the existing dry-well, saving the need for a new complete pumping station. Weobley WwTW: Supply chain - key participants Designer: Arup Main contractor: Morgan Sindall Electrical supply & installation: Protocol Control Systems (PCS) Ltd Mechanical design & installation: Whitland Engineering MCC supply & installation: Lloyd Morris Electrical Ltd Pumps & package pump station: Xylem Water Solutions Potable water booster supply: Dutypoint Ltd Ferric dosing supply: Colloide Inlet screen supply: Huber Technology Safety shower supply: Hughes Safety Showers [caption id="" align="alignnone" width="1200"] Weobley WwTW: Ferric point of application units - Courtesy of Morgan Sindall Infrastructure[/caption] BIM BIM capabilities were utilised at all three sites to design the schemes, and the wider engineering team used site-wide 3D models to great effect to review the works and propose any improvements. Furthermore, this provided an engaging and relatable interface to present the schemes solution to stakeholders, as well as using engineering drawings. Project completion Welsh Water’s have invested £5.9m at the Norton and Presteigne WwTWs and £2.7m at Weobley WwTW. These phosphorous removal schemes are the first tranche to be completed of a programme of upgrades to existing wastewater treatment works that will improve water quality in the Wye and Lugg river basin catchments. Learnings from these schemes have been used by Arup and Morgan Sindall and shared with the Welsh Water Capital Delivery Alliance partners to improve scheme delivery of other rural wastewater treatment works. Through early engagement with chemical dosing suppliers, potable water designs and DfMA MCC suppliers, design enabling efficiencies in design and construction costs to be realised have been standardised. Norton & Presteigne WwTWs were commissioned in March 2022 and Weobley WwTW was commissioned in March 2023.

case-study
Sindlesham & Bearwood WBS Phase 1 (2026)

Sindlesham & Bearwood WBS Phase 1 (2...

Major developments within the Arborfield Garrison near Wokingham, Berkshire, are currently being planned and constructed, which are anticipated to be completed by 2030. These developments comprise 3,500 new residential properties, two primary schools, a secondary school and community facilities. The developments are increasing demand on the clean water network, requiring the implementation of network upgrades and reinforcement to the Sindlesham Water Booster Station (WBS) to prevent anticipated low pressures. Project overview, drivers & challenges
Sindlesham Water Booster Station (WBS) is fed from Early Service Reservoir (SR), boosting flows to the service reservoir at Bearwood, where a separate WBS feeds the network demand. Sindlesham WBS previously delivered approximately 84 l/s during peak demand, however, a capacity assessment completed in 2021 showed that peak demand for 2024 and beyond will rise to 100 l/s, thereby creating the project driver for the upgrades described in this case study.
[caption id="attachment_32130" align="alignnone" width="1200"] Sindlesham WBS proposed solution overview - Courtesy of Ward & Burke[/caption]
The maximum permissible outage at any time for Sindlesham WBS is 2 hours, at which point the level in Bearwood SR will be such that the Bearwood WBS will be inhibited from operation to protect its assets. Furthermore, if Bearwood WBS is inhibited or not operational for any reason, there would be direct customer impact within 20 minutes. These limitations were the main considerations for the resultant upgrade solutions and construction methodology and sequencing.
Solution overview
The existing installation at Sindlesham comprised of two 18.5kW pumps, which delivered approximately 84 l/s to Bearwood SR via a 4.2km, DN300 pipeline. The solution requires two 55kW end suction centrifugal pumps in a duty/standby configuration.

A transient analysis carried out on the existing network by Hydraulic Analysis Ltd on behalf of Ward & Burke, outlined the requirement for a 1.5m3 suction side surge vessel to be installed, as well as a 10.5m3 discharge vessel to protect the network. These were to be served by two compressors in a duty/standby configuration, housed within a GRP kiosk.

A new MCC from Bilfinger UK will supply power and control for the site, while a new standby generator and dedicated double skin fuel tank provided backup power for the site.
[caption id="attachment_32138" align="alignnone" width="1200"] Inside the Sindlesham WBS before the upgrade - Courtesy of Ward & Burke[/caption]
Replacing the existing assets raises major risks around the operation of the pumping station and the direct impact any downtime or failures would have on the network.

The solution therefore needed to allow for the required redundancy for the critical assets and overall system. The result of which ensured that power supply and pump operation had sufficient redundancy, and automatic control in the case of any failures.

Maintaining visibility and feedback of the site on regional site SCADA for both existing and new assets added another layer of protection for site operations should any failures occur, meaning they could be addressed promptly.
Sindlesham WBS: Supply chain - key participants Main designer & contractor: Ward & Burke GPR & topo survey: Brunel Surveys Ltd Hydraulic analysis: Hydraulic Analysis Limited HAZOP & ALM studies: Streamflow Engineering Electrical installation: LDC Electrics MCC & system integration: Bilfinger UK Kiosk: Morgan Marine Ltd Excavation supports: MGF Ltd Surge vessels: Quantum Engineering Developments Ltd Underpressure tapping & in-line valves: R2M Limited Pipework: Saint Gobain PAM UK Pipework: Electrosteel Castings (UK) Ltd Stainless steel pipework: ABC Stainless Ltd Pipework fittings: Frazer Utilities Pipework disinfection: WSM Associates Ltd Testing equipment: VP Stopper Specialist (Groundforce) Lowara pumps: Xylem Water Solutions Valves: AVK UK Ltd Pressure & flow instruments: ABB Pressure switches: IFM Electronics Ventilation systems: Air Technology Systems Standby generator & fuel tank: DTGen Temporary works
Works commenced late April 2025, with the installation of the temporary site backup generator. This allowed for the existing defunct diesel generator to be removed from the WBS building and the accompanying external fuel tank to be removed from the rear of the building.

These works freed up much-needed space in an already confined site for new equipment, without reducing the site’s redundancy with respect to power supply.

The construction sequence then centred around completing as much of the off-line works as possible, so that once pump changeover started, the site overall always had backup power and pumping capabilities. Civil works could now be undertaken which included ducting, drainage and slab works for the new kiosk, fuel tank and standby generator.
[caption id="attachment_32131" align="alignnone" width="1200"] New generator & fuel tank slab - Courtesy of Ward & Burke[/caption] First shutdown
Full site shutdowns meant that all pumping was stopped for a short period of time. The first of these required a 90 minute shutdown to complete the necessary enabling works on the existing pipework and replace two 90° bends with tees on the suction side of the WBS.

This was required for:
An external connection for the new suction surge vessel from Quantum Engineering Developments Ltd, and; An internal connection to install a new double acting air valve upstream of the pumps.
Completing these pieces of work together ensured that the surge vessel could later be connected and commissioned without disturbing supply to customers. Following these connections, the civils works to the southern and eastern sides of the WBS could be completed.
Underpressure tappings & in-line valves
Due to the limitations on site, shutdowns, and the availability of existing valves, underpressure tappings and in-line valves were used wherever possible, to ensure minimal disruption to the pumping operations and customers. One of these opportunities was for the discharge surge vessel connection.
[caption id="attachment_32140" align="alignnone" width="1200"] (left) Discharge surge vessel underpressure tapping and (right) WBS discharge in-line valve - Courtesy of Ward & Burke[/caption] This connection was completed via underpressure tapping by R2M Limited to provide a DN250 connection off the existing DN300 DI rising main. Further downstream on the same line, an in-line valve was installed as there was no existing isolation valve on the 4.2km rising between Sindlesham WBS and Bearwood SR. This valve would be used to isolate the discharge side of Sindlesham WBS for the second shutdown. Second shutdown
The second full site shutdown was required to provide the discharge connection for Pump No. 2 within the WBS. Again, opportunities to reduce shutdowns as far as practicable was priority and so works were also planned to coordinate the removal of a non-return valve on the same line, but 4km away at the Bearwood SR site.

Hydraulic analysis indicated that an existing non-return valve on the rising main entering Bearwood was a major contributor to potential surge events associated with the operation at Sindlesham. The valve posed such a risk that the analysis recommended its removal.

As these works would also require shutdown of Sindlesham WBS, they were scheduled to be undertaken together during the 105 minute shutdown.

A temporary air valve was fitted to the new connection to ensure adequate air removal during refilling of the line and reverting the pumping station back to normal operation.
[caption id="attachment_32136" align="alignnone" width="1200"] (left) Pump No. 2 discharge connection and (right) removal of the NRV at Bearwood - Courtesy of Ward & Burke[/caption] In-building & external works
Works within the building continued in parallel to external works with installation of steelwork to support the existing precast slab ceiling that previously enclosed the generator room. Removal of this precast ceiling was identified in the project’s Design Risk Assessment as a high-risk activity and as such, solutions were sought to remove the risks associated with its removal, while still allowing the block wall dividing the building to be removed.

Once the block wall was removed, the new MCC could be installed, behind the existing MCC, in preparation of the pump installation.

External to the building, the generator and fuel tank were being installed, followed by the kiosk and the surge vessels.
Final shutdown
The final site shutdown could be scheduled, and this was to install a new valve on the existing discharge manifold. The installation of this valve ensured that the first booster pump could be replaced off-line, removing the risk of unplanned pumping outages and ensuring undisturbed supply for customers. The shutdown lasted approximately 60 minutes.
[caption id="attachment_32132" align="alignnone" width="1200"] (left) First new pump installed with the standby provisions in the background and (right) MCC installation - Courtesy of Ward & Burke[/caption] Pump No. 1 replacement
Works then continued to remove Pump No. 1 and replace with the new 55kW Lowara end suction unit from Xylem Water Solutions.

During this period, the site was operating without a standby pump. Provisions were made for the removed pump to be kept on site, adjacent the existing operating unit and beneath temporary lifting equipment. This would allow site operations and/or Ward & Burke to act promptly should an issue arise with the duty pump, when the first new pump was being commissioned and put into service.
Proving period
At this juncture, the site was ready to begin operating on the new pump and begin a 14-day proving period. This new pump was powered and controlled by the new MCC, with backup power provided by the new standby generator. Pump signals were temporarily hard-wired to the telemetry outstation to ensure site operations and regional SCADA had remote visibility of the new pump operation status.
[caption id="attachment_32135" align="alignnone" width="1200"] Surge vessel - Courtesy of Ward & Burke[/caption]
A hard-wired duty signal was also installed between the new MCC PLC, and the existing MCC control logic, which replaced the old pump input signals. This meant that if the new pump tripped, or failed in any capacity, the existing MCC would be provided an input and automatically start the existing pump. In other words, the site was running on two separate pumps, power and control systems during this period, working in a duty/standby arrangement, ensuring complete redundancy of the new system.

Following successful completion of this proving period, the existing pump and MCC could be removed and close out works could begin.

A partition wall was erected between the new MCC and the pumps to create an MCC room, separate to the pump room. The new ventilation system was installed and commissioned, alongside completion of all electrical installation works. Finally, a new non-slip floor finish was applied, walls and ceilings painted and new floor trench covers were installed to complete the project.
Conclusion
Handover was completed in December 2025, marking the end of the first phase in the wider contract, ensuring sufficient flows for future demand are fed to Bearwood Service Reservoir. The second phase of works requires a full upgrade of Bearwood WBS, to ensure that the future flow demands can be delivered directly to customers in the growing Arborfield area.

case-study
Carmoney to Strabane Strategic Trunk Main (2025)

Carmoney to Strabane Strategic Trunk...

The Carmoney to Strabane Strategic Trunk Main represents the completion of nine years of planning and construction, backed by a £17 million investment from NI Water. This major infrastructure project delivers a new strategic water main connecting Carmoney Water Treatment Works (WTW) in Eglinton to Castletown Service Reservoir (SR) in the Strabane area. Identified as a priority in both NI Water’s 2012 Water Resource Plan (WRP) and the 2017 Water Resource & Strategic Resilience Plan (WR&SRP), the project enhances connectivity between the Northern and Western water resource zones. By establishing this vital link, the scheme addresses key infrastructure gaps, strengthens supply resilience, and supports the continued delivery of high-quality drinking water to the region. Project scope
To achieve the goal of enhanced interzonal connectivity and meet regulatory requirements, the Carmoney to Strabane Strategic Trunk Mains Project was divided into three distinct phases:
Phase 1: Completed in June 2024: This phase involved the construction of the new Avish Water Pumping Station at Carmoney WTW. The facility, with a capacity of 17 million litres per day (MLD), was designed to pump water to Corrody Service Reservoir (SR). Phase 1a: Finalised in April 2025: This phase comprised the installation of approximately 10 km of 500 mm diameter trunk main from Edenreagh Road junction to Corrody SR. A key feature of this phase was a 400m horizontal directional drill beneath the River Faughan; a watercourse of international significance due to its Atlantic salmon population and designation as a Special Area of Conservation (SAC). Phase 2: The final phase: Not yet commenced, but will involve the construction of a new water pumping station at Corrody SR and approximately 22km of trunk main extending to Castletown SR. This phase will traverse both private and public lands and include multiple trenchless crossings.
This paper focuses in detail on Phases 1 and 1a of the project.
[caption id="attachment_26644" align="alignnone" width="1200"] HPPE trunk main being strung out during installation - Courtesy of DAWSON-WAM & NI Water[/caption] Project aims & drivers
The primary objectives of the Carmoney to Strabane Strategic Trunk Main are to eliminate supply-demand balance deficit and to enhance resilience for 17ML/d within the Western Resource Zone in the event of incidents or outages at water treatment works.
Phase 1: This phase replaced the existing water pumping station (WPS), which is over 25 years old and equipped with MEICAT systems that have exceeded their operational life. The new infrastructure delivers increased operational robustness and improved security of supply within the Northern Resource Zone. Phase 1a: This phase reinforced the Caugh Hill–Corrody Trunk Main and supports the completed Northern Resilience Phase 3 project. It enables larger flow transfers to Corrody SR during outages at Carmoney WTW, without negatively impacting high-level customers in DMAs directly supplied from the trunk main. This enhancement further strengthens system resilience and security of supply in the Northern Resource Zone. Phase 2: This phase will enable bi-directional water transfer between the Northern and Western Resource Zones, up to 17 ML/d westwards and 8 ML/d northwards. Once complete, it will significantly increase operational flexibility and resilience across both zones. [caption id="attachment_26646" align="alignnone" width="1200"] Mains laying operations - Courtesy of DAWSON-WAM & NI Water[/caption] Carmoney to Strabane: Supply Chain - key participants Client: NI Water NEC project management: McAdam Principal contractor: Murphy/DAWSON-WAM JV Civils contractor: DAWSON-WAM Ltd MEICA contractor: Murphy Process Engineering Ltd Civil design: RPS Ireland Ltd MEICA sub-contractor: Pronto Automation Systems Ltd HDD contractor: Peter McCormack & Sons Ltd Archaeological services: Gahan & Long Ltd Pipe & fittings: APP Fusion Group Quarry products & reinstatement: P Woods & Son Ltd W & J Chambers Ltd Northstone NI Ltd Phase 1 - Avish Water Pumping Station
This phase involved the complete demolition of the existing facility and the construction of a new, purpose-built water pumping station (WPS) to supply both Avish Service Reservoirs (SRs), with onward pumping to Corrody SR via the Edenreagh Road infrastructure. The station operates using three pump sets (duty/assist/standby) and was prioritised as Phase 1 due to planning application and approval constraints. The works were successfully completed in June 2024.
[caption id="attachment_26643" align="alignnone" width="1200"] The new Avish Pumping Station - Courtesy of DAWSON-WAM & NI Water[/caption]
In addition to the three pump sets, the new installation includes a surge vessel, a new motor control centre (MCC), and associated pipework at both the water pumping station and Avish Service Reservoirs.

The upgraded WPS provides the NI Water Operations team with the ability to remotely manage and optimise system performance via telemetry, offering four distinct daily process control modes:
Mode 1 - Level control: Pump operation is based on reservoir level setpoints. Pumps start and stop according to low and high level thresholds, with flow rate automatically reduced as the reservoir approaches its maximum level. The assist pump is enabled or disabled based on flow demand. Mode 2 - Volume control: This mode delivers a specified volume of water either as a one-time operation or on a recurring schedule. Mode 3 - Flow control: In this mode, the system maintains a constant flow rate. The duty pump adjusts speed to meet a defined setpoint, with the assist pump activated if the flow target cannot be achieved by the duty pump alone. Mode 4 - Pressure control: Designed for use in abnormal operating conditions (e.g. bypassing a reservoir during maintenance or washing), this mode maintains a constant delivery pressure. The duty pump modulates speed to meet the pressure set point, and the assist pump engages as required.
To optimise operational expenditure (OPEX), the system also incorporates controls for managing high-tariff and pre-high-tariff top-ups, ensuring more efficient energy use during periods of peak demand.
[caption id="attachment_26645" align="alignnone" width="1200"] HDD drilling rig in operation - Courtesy of DAWSON-WAM & NI Water[/caption] Phase 1a: Edenreagh to Corrody Trunk Main
This phase involved the construction of 10 km of trunk main from the Edenreagh Road infrastructure to Corrody Service Reservoir (SR), consisting of approximately 9.6 km of 500 mm diameter ductile iron pipework and 0.4 km of 560 mm diameter high-performance polyethylene (HPPE) main installed via horizontal directional drilling beneath the River Faughan.

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

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

The entire works were delivered with no disruption to customers and successfully removed 17 District Metered Areas (DMAs) from the DG2 register. In addition to improving supply reliability, this phase significantly enhanced the resilience and security of supply within the Northern Resource Zone.
[caption id="attachment_26648" align="alignnone" width="1200"] Pipe bridge installation - Courtesy of DAWSON-WAM & NI Water[/caption] River crossings
The scheme included two significant watercourse crossings: the previously mentioned horizontal directional drill (HDD) beneath the River Faughan and the construction of a pipe bridge across the Burngibbagh River. For both crossings, maintaining ongoing communication with the Northern Ireland Environment Agency (NIEA) was essential. In line with NIEA requirements, sheet piles were installed at the drill entry and exit points to prevent any potential contamination of the River Faughan; recognised for its ecological importance as a designated watercourse.

The project team also carefully considered the findings of the ecology survey and the Habitats Regulations Assessment to ensure full environmental compliance. Environmental challenges, including the presence of Japanese knotweed and active badger setts within the working area, were effectively managed and mitigated without impacting the programme.
Archaeological discoveries & historic preservation
Throughout the course of the project there were numerous archaeological and historical discoveries. Ancient structures and artifacts were discovered, with the team collaborating closely with archaeologists and HED to carefully document and preserve these findings, ensuring the site’s historical significance was respected throughout the construction process.
[caption id="attachment_26649" align="alignnone" width="1200"] Archaeological operations - Courtesy of DAWSON-WAM & NI Water[/caption] Environmental awareness
As the pressures of climate change and population growth in the North-East region increase, the Edenreagh Road to Corrody SR trunk main was constructed to ensure security of supply and cleaner water for the wider Northern Zone.

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

Additionally, where practicable, materials and aggregates were sourced from local suppliers near the site to reduce transportation distances and minimise the project’s carbon footprint.
Community & landowner engagement
It was recognised early in the Early Contractor Involvement (ECI) period that building strong relationships with landowners would be critical to the project’s success, with early engagement meetings held with the Ulster Farmer’s Union. As such, collaboration with local farmers and landowners remained a core focus throughout, ensuring minimal disruption to their land and promoting sustainable land use practices.

To support this approach, a dedicated Lands Liaison Officer was appointed for the duration of the works. Their role was to build and maintain strong relationships with landowners and to ensure transparent, ongoing communication with the local community—keeping all stakeholders informed and engaged throughout and contributing to the successful delivery of the project.
[caption id="attachment_26647" align="alignnone" width="1200"] Mains laying operations - Courtesy of DAWSON-WAM & NI Water[/caption] Health & Safety initiatives
The project was recognised by the Considerate Contractors Scheme for its health and safety initiatives, with the Contractor (Murphy DAWSON-WAM JV) receiving a Gold award for the project as a whole, but in particular for the installation of single use defibrillators within all excavators across the project.
The outcome
The Carmoney to Strabane Strategic Trunk Main is a great example of how the NI Water project team including consultants and contractors can successfully collaborate and engage with the local community to deliver a vitally important piece of infrastructure, whilst respecting the local environment.

case-study

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