Supply Chain - Sewerage - Contractors

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Esh-Stantec was appointed by NWG to progress the proposed solution; a phased approach whereby, during AMP7, final effluent from both STWs will be transferred to a discharge point on the River Wear via transfer pumping stations. The transfer of flows will be facilitated via new rising mains and gravity sewerage which will connect immediately upstream of the existing outfall from Brasside STW. In line with the phased approach, planned upgrades to Brasside STW in AMP8 will increase its treatment capacity and allow for the eventual abandonment of Plawsworth and Pity Me STWs along with chemical dosing to meet planned phosphorus limits discharging to the River Wear.

The designed solution allows for projected growth across the Plawsworth and Pity Me catchments (including the completion of the significant Sniperley development) with an AMP8 solution transferring all raw flows from Plawsworth and Pity Me to the upgraded Brasside STW for treatment, with final effluent from Brasside STW ultimately discharging to the River Wear.

The objective of this appointment is to provide the assets required to enable to the transfer of flows from Pity Me and Plawsworth STWs in the AMP7 and AMP8 scenarios. It is anticipated that the project will be completed in December 2024.

The first stage of the scheme involves the transfer of fully treated, final effluent to the River Wear, meaning that Plawsworth and Pity Me STWs remain fully operational throughout the construction of all assets which will become live prior to the upgrade of Brasside STW.

Plawsworth Transfer Station: The new transfer assets at Plawsworth STW were carefully designed and sequenced around the limited working room in the site and the requirement to maintain treatment operations during construction. The Plawsworth Transfer Pumping Station comprises:

In AMP7, final effluent flows are intercepted and directed into the new wet well before being pumped to the River Wear. Due to the transfer of final effluent, a reduced emergency storage volume has been provided within the new wet well.

In AMP8, following upgrades to Brasside STW, raw flows will be intercepted upstream of the inlet works and diverted to the new SPS for transfer to Brasside via a new 250mm rising main. As part of the conversion from a treatment works to a terminal pumping station, the existing humus tank will be re-purposed to provide additional emergency storage in line with EA guidelines for the transfer of raw sewage flows and minimise emergency overflow spills to the environment.

In addition to emergency storage, a permanent standby generator has been incorporated into the design which will automatically cut in if there is a loss of power to the site.

The pumping station was designed as a three pump station (duty/assist/standby) to transfer ultimate AMP8 flows up to 32 l/s, however, in the AMP7 scenario,  the pumping station will operate as a duty/standby/standby station, with the individual pumps sized to transfer 24 l/s of final effluent to maintain a minimum velocity in the rising main.

Pity Me Transfer Station: The main works at Pity Me STW comprises the following:

Similar to Plawsworth, the pumping station was designed as a three pump station to transfer 34 l/s in AMP7, with a duty/standby/standby arrangement, and up to 61 l/s in AMP8, after conversion to a duty/assist/standby arrangement. In both the final effluent and raw flow scenarios, pumped flows will exit the works via a new 280mm rising main.

Approximately 2.1km of 250mm PE rising main and associated air valve/washout chambers has been installed from Plawsworth STW. The rising main pipework was installed predominantly via a trenchless technique, namely horizontal directional drilling (HDD), primarily due to lack of available access from the adjacent A167 highway to facilitate traditional open cut construction, as well as unfavourable ground conditions.

A new 280mm  rising main was installed over an 850m length from Pity Me STW. Due to a tight working corridor situated between a garden centre and the Blackdene Burn, as well as the requirement to cross beneath the A167, a highly trafficked highway, the rising mains was also installed via HDD. This use of a trenchless installation technique minimised disruption to local business and removed the requirement for traffic management on a busy commuter route.

eDNA samples taken from ponds adjacent to Pity Me in the feasibility stage confirmed the presents of great crested newts. In lieu of protracted traditional population surveys and subsequent licenced activities to mitigation including fencing and capture to clear the working area, a District Level License (DLL) was secured from Natural England and works were completed under an approved method statement with supervision from a consultant ecologist.

The 280mm and 250mm rising mains from Pity Me and Plawsworth connect to a common chamber located at the high point of the new network, where they will discharge flows to a new DN400 gravity sewer.

2.4km of new DN400 gravity sewerage, with associated manhole chambers, was constructed to receive the pumped flows from both Pity Me and Plawsworth STWs. Careful consideration was given to the design of the new sewerage to ensure capacity (including future growth) and self-cleansing requirements are met in all flow scenarios, including when Pity Me and Plawsworth transfer pumps operate either in isolation or in parallel.

The construction of the new gravity sewer poses some complex crossings and challenging ground conditions. The crossing of Chester Low Road, another busy road for both commuters and customers of a popular local retail park, The Arnison Centre, was originally planned for open cut excavation. However, subsequent on-site observations with regard to topography, a number of high-risk services including high voltage electric cables and a uPVC water main, and running sands within nearby open cut trenches led to the conclusion that it would not be possible to safely support the excavation during construction. Therefore, the road crossing was completed via guided auger bore. Not only did this mitigate the disruption and health and safety risks associated with damaging services, but it also minimised disruption to local businesses and residents as the road remained operational throughout the process.

Further downstream, the new gravity line is also set to cross beneath Network Rail’s East Coast Main Line. The proposal is to install a 610mm sacrificial steel sleeve via a guided auger bore beneath the embankment, once complete the 400mm NB gravity pipe will be sleeved and the anulus grouted. Extensive liaison is ongoing with Network Rail in the lead up to the under track crossing (UTX) to gain the necessary approvals and fully understand the constraints which must be met during construction. These constraints include but are not limited to 24/7 working for the duration of the tunnelling works, installation of track monitoring and an approved contractor on standby in case there is a requirement for emergency track repair.

Approximately 800m upstream of the Brasside STW outfall connection, the sewer crosses a watercourse located within a steep ravine and dense woodland at the existing Brasside Sewage Pumping Station (SPS).

At the optioneering stage of the project, it was proposed that this crossing would take place via an inverted siphon arrangement. However, subsequent hydraulic modelling deemed that, due to topography constraints, it would not be feasible to achieve sufficient capacity while maintaining self-cleansing velocities in both the AMP7 and AMP8 flow scenarios without connecting to the existing outfall further downstream. This would have required construction works within ancient woodland, imposing the requirement for Environmental Impact Assessment (EIA) and potentially preventing the obtention of a Lawful Development Certificate.

Therefore, to mitigate the risk of repeat maintenance issues and potential asset failure, a pipe bridge was progressed as the preferred option having discounted a further interstage pumping station at the low point due to a lack of space within the existing Brasside SPS site and the associated operational carbon and expenditure.

The route of the pipe bridge was designed to mitigate environmental impact, by including bends within the bridge structure and above ground pipework to take advantage of existing operational land and avoid clearance of significant trees within a conservation area. The interface between the bridge structure and the above ground ductile iron pipework has been carefully modelled and iteratively designed to assess the impact of bridge movement and deflection on the pipe joints and select joints which provide appropriate tolerances for these movements.

The design of the WINEP Durham Transfers Scheme serves to meet regulatory deadlines by achieving a sustainable multi-stage solution which meets the needs of the current and future catchment population.

At the time of writing (July 2024), construction is progressing well, and all rising main pipework and transfer station substructures have been installed. The gravity sewer is predominantly complete with the two key crossings remaining, pending final Network Rail approval to complete the rail crossing and final structural design of the pipe bridge to install the above-ground pipework adjacent to Brasside SPS.

The current construction programme shows that flows will be turned in December 2024, transferring final effluent to the River Wear in the interim and, in AMP8, transferring raw flows to Brasside STW for treatment. This will achieve the removal of treated effluent from the Blackdene Burn, in turn significantly improving water quality while meeting WINEP obligations. Furthermore, the completion of the scheme in AMP8 will serve to rationalise the NWG sewage network in the area and improve the resilience of the network by serving catchment growth and improving treatment capacity.

The original project comprised an outline design to improve and redevelop Sanatorium STW with flows forwarded from the ‘old’ Village STW (now called Village TPS) to Sanatorium to be treated and returned. However, this solution was not feasible due to Sanitorium STW having access limitations and general site constraints.

The project was redesigned to incorporate a third location at the site of the ‘old’ village reed beds (now called Village STW). Upgrades here were built off-line and comprise a PST distribution splitter chamber, two PSTs, an MBR system, de-sludge and sludge tanks, chemical dosing and sludge thickening. Flows from Village TPS will still be forwarded for treatment at the Sanatorium site, enabling full flow treatment from both catchments to be screened and the sent to Village STW for full treatment, from where flows will be split back to each respective site’s FE sample chamber for quality monitoring.

The goal of the project is to meet tightened discharge permits and improve operational efficiency and resilience, by upgrading and replacing outdated infrastructure and implementing a new, innovative technology for enhanced treatment.

The scope of the project is extensive and included the following:

Coffey appointed SPIRAC Ltd to deliver the new inlet works package. This comprised a new stainless-steel reception tank where the forwarded flows from Village TPS would be blended with the current Sanatorium flows before passing through inlet screens. The inlet works package included:

Stortec Engineering Ltd installed two 12m diameter primary settlement tanks constructed from ULTRASTORE® high-grade stainless-steel panels. Each tank will be installed with a reverse U-type GRP launder channel fitted with V-Notch weir plates, scum boards and associated drop box. Each PST will be fitted with rotating half bridge scrapers.

The 4.6m x 3.1m x 2.8m cast in situ PST splitter chamber was constructed by DS Construction (UK) Ltd. This was installed with a PST bypass and penstock control. Steel access platforms and stairs were provided by Steelway.

The MBR system is designed to meet stringent discharge permits and deliver high-quality effluent. Each MBR process stream includes fine screens, denitrification tanks, containerised Oxi/aeration tanks equipped with FBDA membrane diffusers and blowers, six membrane modules per stream, and a technical room fitted with pumps for membrane cleaning, chemical dosing and blowers.

The MBR system is a complex, innovative challenge to develop a containerised solution that conforms to Severn Trent’s requirements and standards. The system had to be developed to incorporate redundancy during design, which meant a shift-away from technical room mounted local control panels to an intelligent MCC for each stream. The FFT of 22.5 l/s is ditributed evenly across three streams vis a new equalisation tank. Constructed by DS Construction, the equalisation tank is 17.3m long x 12m wide with a depth ranging from 4m to 5.2m at the sump. A steel access system was constructed by Steelway along the width of the tank with each MBR stream fed via pumps with power and control from the MBR MCCs.

To accommodate the MBR system, an extensive civils programme had to be undertaken to provide all feed and permeate pipework, drainage, washwater, manholes, ducting and draw pits to each stream. Once all services were in place, a base slab was constructed for each stream.

The MBR system was manufactured by Coftec with membranes from Blue Foot Membranes. The system is a modular containerised arrangement comprising three parallel treatment streams, each engineered for optimal biological and membrane filtration performance. All the tanks have been coated with protective coatings from Belzona Ltd, expertly prepared and painted by Barnett Engineering.

Upon delivery to site, the MBRs were craned into position onto the pre-constructed bases prior to the end of 2024. Extensive mechanical works were undertaken by Jones Site Services & Installation (JSS&I) and electrical installation works by Elsym Installations Ltd.

In total, over 1.7 km of pipelines were laid using various techniques including pipe ploughing, open cut works and horizontal directional drilling (HDD) under roads and watercourses.

Rising mains (pipe ploughing): Pipe ploughing was undertaken by ATP Cable Plough for nearly 1km of three rising mains, two fibre ducts and one National Grid HV supply between Sanatorium and Village STW.

This innovative method was selected by Coffey because of environmental and ground reinstatement issues; the cable plough’s efficient and low-impact method means that any complications when restoring and subsequently handing back land are dramatically reduced.

Pipe ploughing is effective on almost any terrain and because it causes minimal disruption to the ground’s geological structure, it offers a significant reduction in time, money and risk for the client and contractor. This is particularly significant when working in areas which are particularly sensitive to ecological and environmental issues. It also works very effectively on soft ground and marshland and consequently, it provides designers with an opportunity to soften the impact of schemes when route planning.

Added to this, as it cuts, installs and back-fills all in one operation, pipe ploughing eliminates any risk of trench-collapse and associated health and safety concerns, resulting in a huge increase in productivity over traditional ways of working.

Rising mains - A53 crossing: The A53 crossing required 6 (No.) 80m HDD shots at a depth of 4.0m as stipulated by the local authorities. This incurred the challenge of a significant element of open cut works to link the pipe ploughed runs to the HDD pipework, as ploughing is limited to a 2m maximum depth. Fincher Utilities Ltd was brought in to fulfil this requirement, along with all associated SRD pipework welding and setting out.

Rising mains - Hemphill Brook crossing: Because of limited point-to-point visibility caused by forestry, newt lakes, and the brook itself, the crossing required 6 (No.) 120m gyroscopic drill shots. Additionally, this required a considerable amount of open cut work to connect the ploughed runs to the HDD pipework.

Due to the client-driven changes with the design and land access, the pipelaying work fell during the winter months, with challenging weather conditions; in particular significant rainfall and high winds bringing trees down along the main Sanatorium access route. Throughout this stage of the project, the project team operated in 24-hour shifts to achieve the completion date of December 2024 for this phase of the works.

Due to challenges found during the HDD drilling processes, accumulated air within the rising mains was found during commissioning; resulting in additional open-air vents and air release valves. During design, the intent was to mitigate this requirement due to the field being used for farming activities where significant complications of in-field structures would have been present. An innovative adaptation in the design was for a designated kiosk to be positioned in a safe location on the field boundary.

The transfer pumping station shaft tank was required to transfer crude FFT flows to the Village STW. The pumping station incorporates stormwater storage capacity of 320m3, duty/assist/standby transfer pumps, access steelwork, a UMON4 MCERTS flow meter on the pumping main to Village STW, a bypass arrangement for tank maintenance and an EDM level sensor for UMON3 compliance.

The transfer pumping station shaft tank at Sanatorium was designed and constructed by Active Tunnelling Ltd and the scope included:

Colloide provided chemical dosing plant and ferric sulphate storage with a walk-in dosing kiosk for four-point simultaneous dosing in accordance with Severn Trent’s template design. The primary dosing point is into PST distribution chamber. The secondary dosing location is into each of the three denitrification tanks and is configured to forward feed control based on the pre-MBR ortho-P monitor and the MBR stream feed pumping station flow.

Each dosing point and MBR stream has duty/standby pumps with automatic switchover to the standby; requiring eight pumps in total. Standby dosing lines are required to each duty dosing line; requiring 16 dosing lines in total.

Colloide provided 10m3 of ferric sulphate storage capacity along with chemical reception, chemical storage, and dosing kiosk bunds, and dual-contained dosing lines with capped off dual-contained standby lines. Emergency shower and eyewash stations are installed at the chemical dosing area, the poly dosing kiosk and the MBRs.

The sludge thickening solution is a containerised S-DISC thickener from Huber Technology. In addition, a glass coated sludge buffer tank and thickened-sludge holding tank were supplied by Goodwin Tanks along with duty/standby primary settlement tank desludge pumps from EMS Industries Ltd.

The S-DISC sludge thickener is a robust, efficient and reliable system using a long-life stainless steel filter cloth with minimal water, energy, and chemical usage. It offers a number of benefits including a compact design with a high sludge volume reduction of up to 90% and reduced disposal costs.

The electrical infrastructure is designed to support a complex array of mechanical, process, and instrumentation systems across both the Village and Sanatorium sites. The design ensures operational resilience, safety, and seamless integration with control and telemetry systems. Intelligent MCCs are housed in dedicated kiosks at both the Sanitorium and Village sites to provide power and control for the FINEGUARD™ screens, the SPIROWASH® screenings washing units, the pumping stations and to the MBR stream.

Enhanced supply capacity was required to meet increased load demands and this included new transformers to supply both Village STW and Sanatorium STW.

Two new telemetry outstations were installed and commissioned and a fibre network provides high-speed communication between MCCs, outstations, and control rooms. A new telemetry PLC was manufactured by RSE Control Systems (Blackburn Starling) and in addition, network node boxes were installed for network reliability between Sanatorium STW & Village STW.

Village Transfer Pumping Station was modified to forward all flows of up to 21 l/s to Sanatorium. This required new duty/standby pumps, new iMCC & kiosk, integration of the existing works to accept all flows to Sanatorium and return flows back to the sample chamber for final effluent monitoring.

A key element of the Loggerheads scheme is to match the flow forwarded from the Village TPS to the Sanatorium STW to enable matching flow to be returned to the Village TPS outfall. The initial scope was for the Village TPS iMCC to be integral to the fibre ring for comms interface, however due to challenges and complications over resilience a new approach was adopted. The method used incorporated a new flow matching flow meter and bypass arrangement on the pumped main as it passes through Village STW to the inlet works at Sanatorium STW, where average flows over a 15-minute periods are measured and recorded.

Within the new Village STW, post-MBR treatment there is am outfall pumping station. From here, flows are separated to each respective site with an on-site redesigned solution of constant gravity flow back to Sanatorium STW outfall and a pumped arrangement back to Village TPS outfall. The pumped flow is continually matched to the measured 15-minute average of the flow matching flow meter.

It was necessary to ensure that the pumps were not starved meaning flow matching would be compromised. The original design was adjusted to a complete gravity weir arrangement, ensuring a constantly flooded wet well. This was one of several innovations that ensured the system performed without compromise and the programme pace was kept.

Design change from a 2-site to 3-site solution: The project is complex, with the number of inter-site interfaces and many innovative assets and methods used. There was no programme extension to allow for the third location (the reed bed site) and there were land access complications. This complication led Coffey to adopt 7-day working for a number of months and during key phases, 24-hour working to ensure the expanded scope could still be delivered.

Complex logistics: The integration of multiple pumping stations, rising mains, and treatment units required precise coordination and phased commissioning.

Temporary works: The temporary works at Loggerheads were extensive. The vast range has been from trench boxes for laying pipework and rising mains, through to the installation of various large manhole ring pumping stations and, at the works return, where two 3m wide by 6m deep structures were constructed.

Environmental compliance: Meeting stringent discharge permits (0.3 mg/l Total Phosphorus at Village STW) required advanced process control and real-time monitoring. A vast array of commissioning and temporary measures were required to facilitate this operation.

Mechanical, electrical & commissioning works: This element of the project has been significant as shown by the sheer volume of electrical control assets required. The subsequent electrical installation has been met with competency and support by Elsym Installations Ltd to meet the significantly condensed programme. This same intensity has been met by Jones Site Services & Installation for the mechanical requirements on a challenging scheme.

The Loggerheads Sanatorium STW AMP7 Q WFD project serves as a prime example of contemporary wastewater infrastructure implementation. By utilising innovative design, fostering collaboration, and prioritising environmental results, the project aims to provide enduring advantages for both the community and the environment. With completion anticipated in early 2026, it is positioned as a benchmark for upcoming AMP8 initiatives.

In April 2025, the project received the ‘Triumph in face of Adversity’ Award from Severn Trent.

The existing system bifurcated into two pathways; one leading to a trunk sewer along the Foyle Embankment, which flows north along the embankment to a pumping station and another discharging directly into the River Foyle via a surface water outfall. The sewer was therefore at risk of discharging wastewater directly to the River Foyle at various locations, potentially resulting in pollution incidents. The River Foyle is tidal, which resulted in the existing sewers being heavily silted, which had led to known grease and odour issues in the area.

The Foyle Street Network Upgrades Project was a critical investment by NI Water to extensively upgrade the existing sewer and storm network, reducing pollution and malodours while ensuring compliance with environment standards. The scheme also increases capacity to support future urban development.

To safely and efficiently execute the works, a full road closure was implemented on Foyle Street between Shipquay Street and Water Street. Prior enabling works included the relocation of city centre bus services that operated on Foyle Street to a temporary bus facility which was constructed within the existing Foyle Street car park. Pipelaying on Foyle Street commenced only once this temporary bus facility was fully operational and the road closure granted.

As principal contractor, BSG Civil Engineering Ltd held overall responsibility for delivering the project on time and within budget, a goal successfully achieved through close collaboration with the wider project team.

Arup’s role encompassed both NEC Project Management & Supervision duties, as well as responsibility for the detailed design. This involved design input from several disciplines, including drainage, geotechnical, highways and pavement engineering teams.

The success of this project was largely attributed to the outstanding collaboration among all the project team. From the beginning, everyone was dedicated to maintaining clear and open lines of communication. Regular check-ins and collaborative tools kept everyone on the same page, enabling the team to address issues promptly and adapt to changes when required. As a result, the project was completed on time, within budget, and to a high standard of quality, demonstrating the power of effective teamwork.

There were a number of key risks including:

An early contractor involvement (ECI) phase was undertaken as a key part of the project’s planning and risk mitigation strategy. This collaborative approach between NI Water, Arup, and BSG enabled informed decision making during the pre-construction stage and brought significant value to the delivery of the Foyle Street Network Upgrades.

During the Early Contractor Involvement (ECI) phase, Arup’s design development identified an opportunity to replace the initially proposed pumped solution with a gravity sewer. This optimisation, informed by detailed analysis and site investigations, removed the need for a pumping station, reducing programme duration, capital and operational costs, while still meeting all project objectives.

Another critical outcome of the ECI phase was the decision to adopt an online construction strategy, installing the new sewers along the alignment of the existing combined sewer rather than pursuing an offline route. This approach was selected based on several technical, logistical, and practical considerations:

The ECI stage also enabled a series of early investigations, including slit trenches and trial holes, to confirm ground conditions and identify buried services. In addition, the existing system was CCTV surveyed, jet-cleaned, and dye tested to check for blockages and confirm any misconnections, allowing for design adjustments before construction began.

Importantly, the ECI phase also created an opportunity to coordinate the replacement and upgrade of the existing watermain that ran along Foyle Street. Rather than delaying this work and potentially requiring future excavations and disruptive road closures, the project team opted to complete the watermain upgrade in parallel with the sewer works.

This forward-thinking decision reduced the likelihood of future inconvenience to the public and eliminated the need for another road closure in this busy city centre location.

Additionally, early stakeholder engagement formed a central part of the ECI process. Due to the project’s location and associated road closures, early and ongoing communication with local businesses, public bodies and other key city centre stakeholders helped inform phasing, traffic management, and access arrangements. This engagement proved vital in building local support, managing expectations, and ensuring that construction impacts were minimised throughout the duration of the works.

Works commenced within the Foyle Street car park as part of the enabling phase, allowing for a phased approach to construction on the street while ensuring uninterrupted services for Translink. The existing car park was converted into a six-bay bus loading zone, along with three waiting bays.

To facilitate bus movements, a new ingress point was created from the Foyle Embankment into the car park area, with vehicle egress via the existing exit location. Automated entrance and exit barriers were installed to manage height restrictions and bus shelters were provided for passenger convenience.

As part of this reconfiguration, Arup’s designers liaised closely with the Department for Infrastructure (DfI) and undertook a road safety audit to ensure the temporary arrangement met all safety requirements. With these modifications in place, a phased plan for bus operations and passenger access was implemented, enabling the main network upgrades to commence at the Water Street junction.

Phase 1 of the upgrade involved works at the first access chamber, an existing manhole containing a 300mm pipe connected to an existing outfall pipe leading to the River Foyle. Within this chamber, a Tideflex valve was installed prior to commencing pipelaying activities. Approximately 15m of pipe were then laid to reach the first newly constructed storm manhole and a new foul manhole which provided the connection into the existing foul line. These two manholes, positioned side by side, formed the starting point of the new foul and storm lines along Foyle Street, linking into various other manholes installed in accordance with the detailed design specifications.

To ensure the safety of the workforce, public, pedestrians, and local stakeholders, secure hoarding was installed around active work areas, marking the start of Phase 2A/B. As part of the stakeholder-focused approach, a local artist decorated the hoarding with designs promoting the local community and creating a more visually appealing area during construction. The works were carefully phased to minimise disruption and maintain access for essential services like deliveries and taxis, helping local businesses and residents maintain a sense of normality. A manned barrier was also positioned to manage access effectively and promptly address stakeholder needs throughout the project.

Various temporary works were used to manage existing services and laterals. Over-pumping was initially required to control tidal ingress, a challenge that eased as construction moved further along the street. A vacuum excavator was employed to safely expose critical services, reducing the risk of strikes in the complex and densely serviced city centre environment.

Phase 2A/B progressed ahead of schedule, allowing the decision to be made to remove all hoarding and fully reopen the road for one month over the 2024 festive period. This provided improved access during a time of heightened activity for local businesses. Following the festive break, works resumed in January 2025 with the commencement of Phase 3A/B. Adjustments were made to the layout of the open side of the street to maintain delivery and taxi access, while also enhancing accessibility for blue badge motorists. Hoarding was reinstated and pedestrian ramps were introduced to ensure safe passage through the area.

Upon completion of the twin sewer installation, the existing 10” cast iron watermain, was replaced with a new 225mm PE pipe along with updated valve arrangements. Given the poor condition of the existing infrastructure, it was deemed prudent to undertake this work concurrently with the sewer works. This proactive approach minimised future disruption to the public and city centre stakeholders.

During the construction of the water main, one of the key challenges was locating the unknown positions of tees and valves on the existing asset. To overcome this, a non-intrusive under-pressure CCTV technique was procured by BSG Civil Engineering Ltd, successfully identifying these features. Without this approach, extensive excavation works would have been required, leading to additional disruption, cost and time.

Phase 4 involved constructing a new manhole at the junction of Foyle Street and Water Street. Works in this area required intercepting an existing storm lateral that previously discharged into the culvert. This lateral was redirected into the existing storm chamber at Orchard House, which contains a Tideflex valve as mentioned in Phase 1.

A Manhole was installed at the head of the existing culvert line within the junction, providing a dedicated jetting point to facilitate future maintenance and de-sludging.

Following completion of works in the Foyle Street area, a full kerb-to-kerb road overlay was carried out, including a section of the Water Street junction, in agreement with DfI. This allowed normal traffic and Translink buses to return to Foyle Street, enabling the temporary bus facility to be decommissioned and reinstated as a car park on a like-for-like basis.

NI Water and the project team were acutely aware of the potential negative impacts arising from such a large-scale pipeline project 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 strategy the project team held early briefings with a range of stakeholders including elected representatives; Derry City & Strabane District Council; Department for Communities; Department for Infrastructure (DfI); Translink; City Centre Initiative; Londonderry Chamber of Commerce; Visit Derry; Millennium Forum; Foyleside Shopping Centre; taxi companies, coach operators and local businesses.

Dedicated briefings were held for businesses on Foyle Street and questionnaires circulated to capture the operational needs of all the shops in the area. The information gathered was fundamental in shaping the different phases of the project and helped keep disruption to a minimum.

Letter drops and project updates were circulated to stakeholders in advance of each new phase of work commencing and press releases issued to the local media to keep the wider public informed. Signage and variable message boards were erected on the main routes to Foyle Street and large-scale project boards helped to convey the huge investment being made by NI Water and the resulting benefits for the city.

Street art and children’s paintings adorned the construction hoarding to improve the visual appearance of the works area and boards, highlighting the historical importance of the area, which created further interest and information for passers-by.

NI Water and the project team are indebted to the myriad stakeholders for their help during the year-long project. Completing the work on Foyle Street ahead of schedule is a testament to the scale of support received and the close working relationships developed.

The Foyle Street Network Upgrades Project was completed ahead of schedule and under budget, successfully achieving its primary objectives of enhancing sewer capacity, reducing pollution and odour issues, and ensuring compliance with environmental regulations. Stakeholder engagement was central to the project’s delivery, contributing to its smooth execution and overall success.

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

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

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

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

The NIEA had identified the following five CSOs as UIDs:

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

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

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

The purpose and drivers of this project were as follows:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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