Supply Chain - Water Mains - Pressure Management

The full route of the steel welded pipeline (Phases 1 & 2) includes crossings of the A1 motorway, three river crossings and two railway crossings. Farrans Construction is contracted to deliver Phase 1 of the project, the pipeline from Lartington to Shildon Service Reservoir, via Whorley Hill Service Reservoir. The chosen pipe material is robustly coated thin-walled steel, with individual pipe lengths of varying sizes (14m maximum) and generally 800mm in diameter. The Phase 1 pipeline is approximately 34km in length, including a section of twin 800mm diameter pipe, with one of the sections forming the starting point for Phase 2.

Various options were explored to determine the most suitable method of the crossing of the River Tees, near Cotherstone Village, Barnard Castle, including pipe bridges and open cut trenches in the riverbed. However, there were several constraints that limited the viability of these options, including significant aquatic life disturbance and differing riverbank heights. The chosen option for the crossing was the construction of a tunnel under the river between two access shafts. The eastern shaft is approximately 46m deep and 7.5m diameter, whilst the western shaft is approximately 32m deep and 8m diameter, with the difference in shaft depth due to the rising topography of the eastern bank of the river. Each shaft has a 221 tonne reinforced concrete base.

Farrans Construction appointed Joseph Gallagher Ltd, an experienced specialist shaft and tunnelling contractor, to construct the river crossing under a sub-contract arrangement.

To construct the shafts and tunnel, the first 2m of rock was excavated and 1m shaft segments bolted together to form a ring. The rings were surrounded with an in situ concrete ‘collar’ to provide structural integrity and ‘set’ the shafts. These rings were checked for plumbness, as this is critical to ensure the overall verticality of the shafts.

Excavation began with each subsequent precast concrete segment ring bolted to the underside of the one above, known as underpinning. To provide structural support, the rings were then back grouted through holes in the segments. This process was repeated with each new metre of rock that was broken, installing the next ring of concrete segments until the required depth was reached. The excavators and mechanical breakers used were relatively small for the hardness of the ground and the excavation depth, due to the constricted dimensions of the two shafts. The excavation process began in June 2023 and was completed in March 2024.

Once the shaft construction was complete, the bases were poured, followed by installation of the 2.24m diameter tunnel boring machine (TBM). The TBM system has a hydraulic jack that pushes it forward through the ground as it excavates the rock strata. The TBM was launched on rails from the east drive shaft. Following the excavation of the rock, the hydraulic jacks were retracted and a 2.5m section of precast reinforced concrete pipe was lowered onto the launch railing at the bottom of the shaft using a 70 tonne crane. The hydraulic jack re-engaged to push the new length of pipe behind the previous one and continue pushing the pipe and TBM forward. The tunnel is 220m long, which required 88 (No.) 2.5m long pipes segments.

The ground material, that consisted of abrasive sandstone and other materials such as quartz, caused significant wear on the cutter heads and pumps of the TBM. This slowed the excavation process significantly, but continuous work by Joseph Gallagher Ltd meant that an average of four pipe sections, or 10m of earth, were still excavated each day.

Video captures the moment tunnel boring machine completes journey under the River Tees

The concrete tunnel acts as a sleeve for the water pipes that will transfer the water supply under the river. Two parallel pipes were used to provide water supply security in case one should fail, and ductile iron was selected as the pipe material to provide additional strength and resilience. Due to the constricted diameter of the shafts, the pipes were lowered down in 5.5m sections, with each section of the pipe being joined to the next as they were fed into the tunnel. Spider supports were used to locate the pipes which were winched through the tunnel from the east to the west shaft. The spider supports, which were used as spacers, were clamped to the pipes at regular intervals and hold the pipes steady as they are pulled through the tunnel. Once the pipes were completed and tested, they were sealed, and grout was pumped in to fill the remaining void space.

Once all piping works are complete and the pipes connected to the cross-country pipeline, the shafts will be backfilled with sand to make future excavation easier should it be required. Approximately 3,500 tonnes of sand will be needed for the eastern shaft and 2,500 tonnes for the western shaft.

During construction of the shafts and tunnel, the hydrogeology of the area and consequent water ingress made the excavation technically difficult. During excavation, there was up to 45 litres/second water ingress in the western shaft; the wettest of the two shafts. To manage this, the water is continually pumped out into a lagoon system located 50m away. The water is then processed in lamella clarifying units, which remove fine sediments, to ensure the water meets the required environmental standards to allow it to be pumped into the River Tees. This was an extensive water management operation, conducted under a permit issued by the Environment Agency, ensuring all activities complied with regulatory requirements and environmental protection standards.

The water management issues continued after the shafts had been excavated, and it was decided that the western shaft would require a concrete plug to be inserted beneath the base slab to halt further water ingress. Consequently, the team had to excavate deeper than originally anticipated so that the plug would not interfere with the tunnel alignment. The plug, which is 2.7m thick and made of approximately 167m3 of concrete, was left to cure for seven days before the water was pumped and work began on the shaft’s structural base. A plug was not required for the eastern shaft.

There have been numerous environmental constraints that have had to be considered and mitigated during the project. A prominent issue facing the construction activities is compaction of excavated soil leading to soil degradation. When soil is compacted, the pore spaces within the soil are reduced, leading to poor soil structure and the erosion of the soil surface layer. To mitigate against this, the topsoil is stripped, stored, and only reinstated when in a suitable, friable condition. Low ground pressure tracked vehicles are also used on the site and traffic restricted prior to topsoil stripping. The topsoil and subsoil are then segregated and stored according to DEFRA codes of good practice.

Construction activities within freshwater environments can pose a significant threat to aquatic life through the release of pollutants, including silt and sediments. Fluming was therefore implemented in several local watercourses to minimise pollution and sedimentation by isolating construction areas and diverting the natural flow of water through temporary piping.

Before fluming was implemented on site, several fish species, all of which are sensitive to almost all types of anthropogenic disturbances, had to be captured and safely relocated. Electrofishing was used to temporarily stun the fish so that they could be collected and moved to a safe location, ensuring the protection of several important species including salmon and trout. The combination of flumes and electrofishing minimised the disruption to the ecosystem, whilst regular monitoring ensured the flume remained effective, preventing leaks and blockages, and allowing for the assessment of fish population health and diversity.

Ground nesting birds were also present at some locations along the pipeline site, including populations of lapwing and curlew; both of which are listed on the UK Red List of Birds of Conservation Concern. To minimise disturbance to these species and other protected species such as badgers, great-crested newts, bats and otters, work was suspended during the nesting/breeding season. In addition, any active nesting sites located near the site were protected, and local authorities such as Natural England and the Environment Agency, were consulted.

Community and stakeholder engagement has been a crucial part of the project to date, with Farrans delivering several schemes in line with Northumbrian Water’s values. Farrans began the engagement process through a ‘Meet the Contractor’ event, held in a local parish hall with attending stakeholders including community groups, local schools and colleges, parish councils, local businesses, and residents. A digital Microsoft form was also sent out to capture the thoughts of those who could not attend the event.

Representatives from Northumbrian Water were also present, and the information gathered was used to identify key issues and concerns raised by the local community and how those issues could be tackled during the project.

To involve the local community, mark the beginning of the tunnelling process, and the arrival of the TBM, Farrans and Joseph Gallagher Ltd ran a competition to name the TBM. This was won by a local girl called Penelope who attended the event with her family, naming the TBM after herself as it was ‘strong, like her.’ Farrans and Joseph Gallagher also asked the community to nominate a local charity that would receive a £1000 donation to mark the project milestone. The Great North Air Ambulance received the most votes and attended the event on the day.

Farrans are also involved in educational engagement by joining in with established local programs such as the ‘Start Small, Dream Big’ school initiative, run by the North East Local Enterprise Partnership. The scheme is a national DfE funded pilot aimed at raising aspirations, challenging stereotypes, and helping children connect with the world around them.

Farrans took part by running several STEM workshops, with local children taking part in exercises to design and build water filters, in the context of surviving a ‘Zombie Apocalypse’. In doing so, they learnt about the work Farrans is doing for Northumbrian Water in delivering the Tees Pipeline, as well as the importance of transferable skills and the diversity of roles within the construction and civil engineering sector.

Northumbrian Water appointed a land agent to streamline the engagement of landowners and farmers along the pipeline route who would be impacted by the works. The land agent, Bell Ingram, conducted detailed conversations that began during pre-construction, and have continued throughout the project. This liaison has ensured that key stakeholders are kept fully informed of the progress of the works and any potential impacts it may have on them, including pre-construction investigation, access, and post-construction drainage designs.

Despite some of the technical challenges and ongoing poor weather conditions faced during construction, the project is progressing generally to programme. By July 2024 the Tees tunnel had been completed and approximately 20km of cross-country pipeline had been laid. Proactive stakeholder engagement has contributed significantly to the ongoing success of the project, with positive engagement with landowners and farmers being particularly noteworthy.

The project is on schedule to deliver water into service in early 2025, with reinstatement works to be completed by August 2025.

Yorkshire Water instructed Morrison Water Services to look at delivery options to maximise performance benefits as well as delivering best value for money for customers. After carrying out hydraulic modelling, mains sample tests and site surveys, the proposed delivery plan was to target the mains in the worst condition by lining 6,090m of water main utilising a lining rig from SCHUR-BPH Ltd.

Yorkshire Water have been lining water pipes on its network since the 1960s; originally using cement mortal liners and more recently (from 2006) using polymeric spray liners. For Stockton Lane, Resiline 320, a third-generation aliphatic poly-isocyanate material of the same family of in situ lining products, was used. It is one of only a few DWI Regulation 31 approved lining materials in the UK. Some of the benefits it brings are:

To start the lining process, excavations pits are created to ensure that there are locations for the cleaning process and for the lining head to be inserted into the main to carry out the lining. The cleaning process starts by isolating the water main at two valves and using a hydrant to drain the water main. Once the water main is drained, the Whirlwind is used.

The Whirlwind cleans the main by blowing down swabs, vortexes of air, and stones, that will scratch off any excess materials and dry the pipe; ensuring that the pipe is in a suitable condition to begin the lining process. The condition of the cleaning is checked by carrying out CCTV surveys on the main. The material is applied by using a lining rig from SCHUR-BPH Ltd.

The rig comprises two paint drums that hold the base and activator paints, which are pumped and heated to the optimum temperature required (300 Celsius) to apply the material onto the pipe. A hose situated at the front of the rig holds the base and activator tubes, and this is pulled through the pipe allowing the lining material to be sprayed onto the pipe interior.

The rig uses a computer system to ensure that each specific water main is lined to the required thickness - for the Stockton Lane Rehabilitation Project, the paint application setting is 3mm due to the works being semi-structural. As well as monitoring the paint thickness, the rig also monitors the flow rate of the lining application and the temperature. If any of these factors drop below the thresholds of + or – 5% of the thickness, an alarm will raise, and the rig will shut off as the application of the material will not be to the required standards.

The lining material is made up of two paints; the base and activator, which are combined to make the Resiline 320 material. The paint is mixed by using a lining head that spins at 9000 rpm and applies it onto the pipework.

To ensure that the paint is mixed correctly, the operatives take dip cards. This is a visual check to ensure that the paint is of the correct blue colour and is not brittle, meaning that is it suitable for lining. Once these checks have been completed, the lining head will be guided into the pipe, and it will be electronically pulled through by the lining rig.

The distance that can be lined per day depends on the size of the main. On the Stockton Lane project, approximately 90m of the 3” mains were lined per day; and up 110m of the 4” pipe.

Once the lining head has exited the pipe, cap ends are reapplied and a curing period of an hour is undertaken. After 15 minutes, the water mains can be inspected via CCTV. These checks are carried out are to ensure that the lining is uniform, there have been no misses over joints, fittings etc, and that there is no unmixed material as this would result in the lined section having to be replaced. Once approved by the client and the hour cure time has passed, the water main will be put back into commission and water quality samples will be taken.

On Stockton Lane, all of the above processes were undertaken on a daily basis. As part of the DWI allowance for water mains shut off periods, all the work had to be carried out within 2 hours and 59 minutes. On a good day, the work left the site team a window of between 10-20 minutes due to the process being very vigorous. If there was a risk of the time-frames not being met, decisions were made early enough to ensure that customers are not affected.

Compared to replacing the water mains, the relining option realises cost, carbon and programme savings:

The project has received a great deal of attention by a Designer Liner Group that is looking to create their own lining material, and Yorkshire Water and Morrison Water Services have facilitated site visits for the members of the group. There have been minimal customer complaints throughout the duration of the project and instead, there has been a lot positive feedback on social media outlining the great work that has been carried out on a daily basis.

The Stockton Lane Rehabilitation Project promotes the potential for future sustainable rejuvenation of clean water assets, and creates a method which reduces customer disruption whilst improving services that are provided by Yorkshire Water. Upon completion, Yorkshire Water will move onto the next phase in the series of three that are being delivered as part of the Year 4 AMP7 Improvement Project.

Trimpley WTW is a critical asset in the regional water supply network. However, its single-source dependency presents a significant risk in the event of operational failure, which would result in widespread service disruption, posing risks to public health, customer satisfaction, and regulatory compliance.

As part of the company’s AMP7 programme, which includes a 9% commitment to Second Source Resilience, this project has been identified as a key enabler of supply continuity.

The project was divided into three main sections to facilitate phased delivery and allow for Coffey to begin construction of the critical infrastructure in August 2023.

Section 1: The first section of works involved the installation of 2.75km 500mm internal diameter (ID) ductile iron pipework whilst also undertaking the site investigation (SI) and ground investigation (GI) for the subsequent sections which were under design.

Section 2: The second section of works comprised the installation of 5.54km of ductile iron pipework including four horizontal directional drilling (HDD) 630mm (OD) SDR9 drill shots 1960m in total under carriageway works (A442) and river crossings.

Section 3: The final section of the pipeline encompassed the remaining 3.21km of ductile iron pipework, including two 660m and 400m HDD drill shots located in Coal Authority land and drilling under ancient natural woodland. This phase also includes the connection to Trimpley Top Service Reservoir and installation of 250mm (ID) washout pipework, actuated valves, bypasses, and monitoring equipment as well as the final pressure testing and commissioning of the entire pipeline.

The complex project included myriad of activities to enable seamless construction throughout the phased delivery of the works. Through early contractor engagement, Coffey was able to advise and assist the client in elements such as ecological assessments, design constraints, aerial photogrammetry and third-party utility liaison.

With a strong supply chain of valuable and efficient suppliers, all aspects of the project were constructed with minimal disruption to stakeholders resulting in a long-term valued pipeline and a critical investment in water supply resilience.

The key elements of the project delivery are detailed below.

As part of the project, a series of ecological assessments and reports were conducted to ensure compliance with environmental regulations and to support biodiversity. These included:

As part of the Trimpley to Hampton Loade Pipeline Project, an unmanned aerial vehicle (UAV) photogrammetry survey was conducted along the full pipeline route within a 50m corridor. The aerial data was processed into Autodesk Civil 3D-compatible formats to support precise terrain modelling and route planning.

In addition, a utility and ground penetrating radar (GPR) survey was carried out within a 30m corridor to identify existing underground infrastructure and third-party assets and support safe excavation.

Desktop utility mapping complemented the GPR data, reducing the risk of service strikes. Up to date desktop utility searches (DURS) reports were undertaken and, with the data being incorporated with the GPR survey and incorporated into the machine control element of the excavation works.

To facilitate the successful delivery of the pipelaying element of the project, a series of coordinated construction and reinstatement activities were utilised to ensure the efficient delivery of the pipeline using specialist earthworks contractor Collins Earthworks to provide the plant, equipment and expertise suitable for constructing a pipeline of this magnitude.

Through carefully coordinated and planned activities and with the added value of machine control systems, the efficiency and accuracy of the installation process was greatly improved.

Coupled with the GPR survey data, this ensured a zero-service strike rate was achieved across the entire length of the pipeline.

By using the latest technology in machine control systems, this not only accelerated construction timelines but also minimized material wastage and environmental impact.

Additionally, real-time data feedback improved quality control, reduced the risk of human error, while enhancing operator productivity and site safety supporting a cost-effective delivery in adherence to the pipeline design.

The final section of the pipeline encompassed certain areas designated under the jurisdiction of the Coal Authority, which oversees land affected by historical and active coal mining operations. Traversing these areas necessitated specific engineering and monitoring strategies.

Undertaking the horizontal directional drilling within this zone dictated meticulous planning, strict regulatory compliance, and robust risk mitigation strategies to safeguard both public safety and environmental integrity.

Prior to any works commencing, a formal permit was acquired from the Coal Authority, supported by comprehensive documentation including site-specific risk assessments, method statements, and ground investigation reports. These assessments were critical for identifying the potential hazards the land may contain such as subsidence, mine gas emissions, and the presence of abandoned mine workings.

Construction methodologies were adapted to account for ground instability and contingency measures for unexpected ground movement through subsidence.

Continuous engagement with the Coal Authority and the client’s geotechnical representative ensured that all activities aligned with statutory requirements and best practice guidance.

The Gun Hill crossing, comprising a technically complex and challenging 660m section of 630mm SDR9 water main, was delivered using horizontal directional drilling to minimise surface disruption within an environmentally sensitive and geologically challenging area within the Coal Authority Land and in proximity to Ancient Natural Woodland.

Located in the South Staffordshire Coalfield, Gun Hill features challenging geology consisting of a mixture of part of the Pennine Coal Measures Group; prone to instability and mine gas emissions and, Early Devonian Clee Sandstone Formation which varies from hard, abrasive layers to softer, friable sections impacting borehole stability.

Coffey collaborated with specialist HDD contractor Johnston Trenchless Solutions (JTS) to execute the HDD crossing using advanced technology and a state-of-the-art 220 tonne capacity drill rig (the only one in the UK) to navigate the geological challenges and install the 70 tonne HDPE pipe within the permitted land. An advanced de-sander was used to recycle and clean the drilling mud thereby reducing water demand and reduction in disposal costs.

The pilot bore was drilled along the predetermined path using advanced navigation systems for accuracy through coal seams and sandstone. Reaming of the bore to 900mm was conducted in multiple stages to ensure stability. The 70 tonne 630mm SDR9 pipe was then winched into the bore during a 12-hour shift.

The Gun Hill crossing, part of a 1800m trenchless installation across six ground conditions, was a critical milestone.

During the horizontal directional drilling operations at the Gun Hill crossing, the team encountered heavily fractured substrata formations. These geological conditions, combined with the high-pressure fluid injection required for pilot bore advancement, led to instances of drilling fluid loss particularly evident at river crossing points along the alignment.

To address this, Coffey implemented a proactive and robust environmental management strategy. A dedicated frac-out containment team was deployed to monitor the drilling corridor in real time, utilising unmanned aerial vehicles for aerial surveillance and rapid detection of surface fluid emergence. Pre-positioned frac-out mitigation materials were strategically placed along the route, enabling the team to respond swiftly to any fluid escape events. These measures ensured that any drilling fluid that reached the surface was immediately contained and managed, significantly reducing the risk of environmental harm. Through continuous monitoring, rapid response protocols, and effective containment practices, Coffey successfully mitigated the environmental impact of fluid loss incidents, maintaining compliance with environmental standards and safeguarding sensitive habitats throughout the drilling operation.

To support accurate and high-quality land reinstatement following pipeline installation and testing, a UAV-based terrain capture survey was conducted prior to construction commencement. This pre-works aerial mapping provided a precise digital record of existing ground conditions, enabling the reinstatement process to closely match original landform profiles and ensuring compliance with environmental and landowner expectations.

Ground penetrating radar scanning was used across the full working easement and the existing service results were integrating into state-of-the-art computer systems installed into all excavators (machine control technology). This system disabled any excavator working within close proximity to existing services and achieved a groundbreaking milestone: a zero-service strike rate throughout the entire pipeline project. This innovative approach not only enhanced safety and efficiency but also set a new benchmark for precision in underground infrastructure delivery.

Advanced excavators equipped with tilt-rotating attachments were introduced, enabling precise and flexible material handling from outside the trench. This innovation significantly reduced the need for pipelayers to enter the excavation zone, thereby minimizing the people–plant interface. This resulted in a substantial improvement in on-site safety and operational efficiency, setting a new standard for safe excavation practices. During the pilot bore drilling phase, remote-guided advanced navigation systems were implemented to maintain absolute precision in both line and level. This cutting-edge technology ensured that the pipe installation adhered exactly to design specifications. By leveraging real-time data and remote-control capabilities, we enhanced accuracy, minimized manual intervention, and delivered a more efficient and reliable installation process.

The integration of the TONGHAND® XS system into horizontal directional drilling operations marked a significant advancement in safety and automation. This innovative tool enables a single operator to remotely make and break pipe joints directly from within the excavator cab, eliminating the need for manual wrench handling. By reducing physical strain and removing personnel from high-risk zones, both safety and productivity were enhanced, setting a new standard for safety in tough conditions.

The continued deployment of unmanned aerial vehicle  technology played a pivotal role in supporting both the design and construction teams throughout the pipeline project. By providing high-resolution aerial imagery, real-time site monitoring, and accurate topographical data, UAVs have enabled faster decision-making, improved planning accuracy, and enhanced progress tracking.

This innovative approach has not only streamlined workflows but also fostered greater collaboration between teams, ensuring a more agile and informed construction process.

The project is recognised as a strategically important investment in strengthening the resilience of the regional water supply network for Severn Trent. It addresses a critical operational vulnerability by establishing a reliable secondary source, thereby enhancing service continuity and reducing the risk of supply interruptions.

Through meticulous planning and a collaborative approach, Coffey successfully delivered the project in alignment with the client’s expectations. By proactively identifying and managing risks, the team ensured that all works were executed safely, efficiently, and to the highest quality standards. This disciplined execution not only met the technical and regulatory requirements but also reinforced Coffey’s commitment to excellence and client satisfaction.

NI Water is committed to improving the resilience of the water supply infrastructure across Northern Ireland, and as part of their IF105 Integrated Partnerships Framework, identified the need to carry out works to replace 4,200m of 9” diameter asbestos cement (AC) main along the Creveery and Barnish Roads (crossing a dual carriageway and a railway line) with 315mm diameter HPPE main.

This would provide an effective and sustainable alternative supply to Randalstown, providing mitigation for ongoing issues with the existing supply located on Stiles Way.

The project included the following scope:

Farrans/Glanua Group JV was engaged in early 2021 under a NEC4 Option ‘C’ contract to carry out site investigation works to enable detailed designed. This provided the opportunity to liaise with the necessary specialist contractors and gain their experience, knowledge and input into developing the detailed design and construction methodologies.

The construction contract was awarded under NEC4 Option ‘C’ Target Cost Contract to Farrans/Glanua Group JV. Construction began in February 2022 and took place over a 14-month period at a total cost of £2.4m. Due to the proximity of the works to the A26 and the Belfast to Derry railway line, early engagement and liaison between DFI Roads, PSNI Traffic Branch, Translink, Farrans Construction and the traffic management contractor were required. A collaborative approach among all stakeholder ensured effective traffic management measures were implemented to protect the safety of road users directly affected by the works and those passing by.

Due to favourable ground conditions, sections of the 4.2km stretch were installed via horizontal directional drilling (HDD) methodology.

This trenchless technique provided savings on aggregates, bitmac reinstatement and spoil disposal, while reducing the impact/footprint on the road. The site team strategically placed launch and retrieval pits at air valve and washout hydrant locations, removing the need for additional excavations. The excavations were also located away from driveway entrances, minimising impact and ensuring access was maintained for residents. The remainder of the pipeline was installed via open-cut methodology.

Following testing (Type 2 pressure test), commissioning works were undertaken in preparation for service transfers and bringing the new trunk main into service.

Eight new connections were made to the existing network with 66 services transferred from the existing 6” and 9” AC mains to the new 315mm main. Utilising the existing kiosk and telemetry unit, a new electromagnetic flowmeter and pressure transducer was fitted as part of a new PRV, meter and strainer arrangement to allow NI Operations to monitor flows and pressures over the telemetry network.

Translink was engaged during the ECI phase of the works to understand the requirements/restrictions for installing the trunk main under the railway tracks. Following several months of design and documentation review, a Permit to Work was obtained.

As it was a strategic crossing, NI Water asset standards required the 315mm trunk main crossing to be sleeved inside a 450mm pipe.

The Belfast to Derry railway line under-track crossing (UTX) was completed by horizontal directional drilling (HDD) methodology. During ECI, several bore holes were carried out parallel to the proposed drill shot (launch, centre and retrieval). All bore holes encountered rock (fractured basalt). However, as drilling operations commenced, the specialist contractor identified changing ground conditions.

As the drill shot progressed towards the river, the rock formation ended and changed to a softer ‘clay-like’ formation. This was confirmed via the change in colour and viscosity of the drill muds, indicating a soft formation with a high clay content. The ground conditions did return to rock approximately 15m from crossing under the railway line, but again, changed back to a softer formation as the drill shot approached the retrieval pit. The lack of consistency posed a serious problem for the rock drilling motor as it was difficult to steer back to ground level because of the soft clay formation.

To proceed with the drill shot and deal with the varying ground conditions, the contractor alternated between the rock drilling head and conventional drilling head. However, this meant pulling the drilling rods in and out to change the head and as its size increased, the risk of the bore hole collapsing also increased.

Following an on-site review with the contractor, NI Water and designers, it was decided to abandon attempts to install a 450mm sleeve and instead install the 315mm main directly. Following several weeks of drilling works, the 315mm main was successfully installed under the rail and river.

The railway line was surveyed for a period of two weeks prior to commencement of the works in order to establish baseline level readings via small targets attached to the side of the rails at 2m intervals. For the duration of the works, surveys were undertaken three times per day to monitor settlement and heave. The track was monitored for a further two-month period following completion of the UTX.

The A26 is a major arterial route in Northern Ireland connecting Coleraine in the north to Banbridge in the south of the province. It carries in excess of 30,000 vehicles per day, making it one of Northern Ireland’s busiest carriageways.

Due to the staggered junction between Creevery Road and Barnish Road, lack of available land and ground conditions (rock), a trenchless crossing of the A26 was not feasible. As such, the works were staged and completed in sections to maintain traffic and minimise disruption:

Lengths of 450mm twin wall pipe were installed crossing the carriageway via open-cut methodology. Upon completion, a 315mm string of pipe was welded and successfully slip-lined across the carriageway.

A 1.2m wide tar planer was utilised to remove the asphalt layer on the parallel stretch of carriageway and two main-laying crews worked round the clock to ensure the works were completed on time.

Farrans and NI Water Communications, issued press releases and engaged with a range of stakeholders including Councillors (for roads affected and programme), council staff (bin collections etc), Roads Service (roads impact), Translink (school bus routes), Rivers Agency (River Millburn), landowners, businesses, and schools.

Letter drops took place in advance of each section of road works and closures to advise the residents and businesses of the planned works. Variable message boards were erected on the A26 (north and south bound) and business-specific signage was installed around the works area/diversion routes to reduce the impact to business owners and customers. NI Water’s 24-hour dedicated customer care ‘Waterline’ number, was issued on all correspondence to the public and displayed on all signage which ensured that any queries about the work were dealt with quickly and effectively.

To minimise the impact to the public while working on the A26, 24-hour working was employed to complete the pipelaying in the shortest possible timescale. Additionally, roads were temporarily reopened around holiday periods to minimise disruption.

Testing and commissioning of the new 315mm trunk main began in December 2022 with the final connection to the network completed in February 2023. The new main provides a strategic backup system, bolstering NI Water’s existing infrastructure to reinforce supply to approximately 4,000 properties.

The Ayrshire Resilience Scheme delivers a two-way connection between the drinking water networks  in Greater Glasgow, Ayrshire and East Renfrewshire; significantly enhancing the security and resilience of the water supply. It is Scottish Water’s largest ever water infrastructure investment benefiting almost one million customers across the west of Scotland. The 12km Glasgow Resilience Programme (C1a) is the third phase of the Ayrshire Resilience Project, and involves the transfer of water from Milngavie WTW located north of Glasgow to the Ayrshire and East Renfrewshire regions to the south-west of the city. C1a is a duplication of the southern section of the existing C1 trunk main that currently runs through the centre of Glasgow, however, design optioneering identified routes to minimise impacts to the local community during the construction phase rather than following the existing C1 route.

At the outset, the £95m Glasgow Resilience Programme was Scottish Water’s largest ongoing capital investment, which comprised the installation of 12km of ductile iron pipe through a predominantly urban environment with significant surface features impacting the route. The pipeline was installed through a mix of carriageway, public parks, urban and rural environments.

To achieve the resilience driver for the project, a new 78 MLD pumping station with MCC was required, powered by two new HV transformers and solar PV panels.

Planning for the project started in 2016, with construction starting on site in May 2020 and completing in August 2025. It required highly complex interactions with the existing water network and multiple modes of control at the new pumping station.

Bedrock was encountered throughout the pipe laying route, predominately for the final 500mm before achieving formation level. Whilst this had an impact pipelaying productivity, the depth of the pipe installation did mean that the vast majority of existing utilities did not clash with the new pipeline and no diversions were required. However, due to the close proximity of residential properties, offices, shops, etc, precondition surveys were completed and vibration monitoring in-stalled to record and monitor any issues whilst the rock breaking was being completed.

The new pipeline route called for installation through several public spaces being Bellahouston Park, Lochar Park, Househill Park and Dams to Darnley Country Park. These parks have high amenity value whether it be major music events, local organisation events, sporting events or general walkers, dog walkers and runners.

Health & Safety was the primary concern through these areas and involved careful planning around upcoming events and robust security arrangements.

In addition, a number of the deep shafts were required for the trenchless works within these areas, again calling for alternative security arrangements which included semi-permanent security fencing to secure these works areas.

Approximately 60% of the pipeline was laid within public highways, through residential streets. The 900mm diameter ductile iron pipes were 7m in length and weighed approximately 2.4 tonnes. The project had to consider the most efficient and safest methodology of working in such areas and it became clear that this would involve significant road closures, traffic management and likely disruption through the centre of Glasgow.

A close relationship was developed with the local roads authorities with plans put in place to allow such major road closures. In conjunction with the project’s Customer Communications Team, information on the closures, diversions and timelines were issued to nearby residents whilst the wider public were informed through VMS and radio adverts. Post completion of the works, it was apparent that the road closures actually minimised disruption in comparison to traffic lights as motorists were likely to find alternative routes.

As expected in laying pipe through urban environments, the project encountered multiple utilities; both charted and uncharted. The pipeline design considered this aspect, with the crown level of the new pipe being such that it would be below the standard installation levels of other assets. This proved to be a success with no utility diversions needed, however, it did slow production as the teams had to carefully identify all utilities in the area and feed the new pipeline both between and under these exposed utilities.

The incredible utility avoidance record achieved throughout the course of the pipelaying activities should be highlighted; with 720 utilities encountered along the pipeline route, 33% of which were uncharted. All utilities were successfully located and crossed. This outstanding record of zero damage was achieved through industry leading utility location and safe excavation practices across the project.

In addition to the management of traffic movements, the project also had to consider the logistics of moving such large pipes and materials around the pipeline route. This involved the procurement of bespoke pipe cradles for transportation as well as procuring additional storage areas throughout the route.

The pipe route included four sections where trenchless methods were required to install the pipe. The drive lengths ranged from 54m up to 264m. Shaft depths ranged from 9m to 24m incorporating shaft diameters of 6m and 8.2m to allow a 1500mm tunnel boring machine (TBM).

Within these drives, assets that were crossed included one of the busiest motorway sections in Scotland (M8 motorway) leading into Glasgow, three separate Network Rail under-track crossings (UTXs) and two watercourses. Engagement with the asset owners (Network Rail & Transport Scotland) were sought at an early stage to understand any constraints that there may be and continued, regular dialogue ensured that all relevant permissions were obtained in a timely manner.

On completion of the tunnels, the project team then had to install the permanent 900mm diameter DI pipe. This involved a complex operation by lowering the pipe into the shafts, connecting and winching the pipes through the concrete jacking pipe. Bespoke spiders were procured and installed ensuring a smooth transition where on completion, the pipe was pressure tested before subsequently being grouted into place.

Through the design process, it became apparent that the flows from Milngavie WTW to the next downstream pumping station could be managed hydraulically via gravity only. This is a route of approximately 30km. However, to achieve the resilience driver, it was identified that a new pumping station would be required.

The pumping station is required to manage 78 MLD which saw the design incorporate three 250kW pumps on a duty/duty/standby basis. To power these pumps, and again to support the resilience element, two independent HV power supplies were installed via two HV transformers which allows a backup supply should there be a power outage on the primary supply.

To support the power requirements of the pumping station, the footprint of the pumping station roof allowed the installation of 50kW SolarEdge solar PV system comprising of 135 Trina Vertex-S panels. In addition to the PV panels to helping work towards Scottish Water’s Net Zero targets, electrical vehicle charging points have been installed with the facility to upgrade to 75Kw chargers in the future.

The pumping station is linked to additional Scottish Water assets  (including Thornliebank and Gorbals PS) via a SoGEA inter-site communications system. This allows the full network to be controlled remotely, ensuring a calm network response to any issue. The software enables monitoring of tank levels and control of the overall network, primarily fed back via a flow control valves, flow meters, needle valves and a comprehensive array of level sensor instrumentation. This allows the main to be predominantly controlled in gravity flow mode, reducing pump use, power usage and ultimately, lowering operating costs and CO2 emissions.

The new asset discharge into two existing distribution service reservoirs (DSR) within the Gorbals PS footprint. Both discharges required access to the reservoirs to complete civils elements of works which required close engagement with the Scottish Water CSD Team, Networks and Public Health.

One of the DSR’s was constructed relatively recently which allowed a clearer understanding of previous construction techniques so the project teams methodology to break into the tank was therefore well understood, however, the second DSR was constructed around 150 years ago. There was a degree of the unknown whilst breaking through into this tank, however, a careful and methodical approach was implemented to minimise risk to the structure.

The new pipeline was subjected to several pressure tests, to an average of 11 bar as well as completing a thorough cleaning and chlorination regime. This involved early dialogue with Scottish Water Networks as well as the reservoir engineers for the raw water reservoir where the flows would be discharged.

On completion of the chlorination activities and subsequent approval from Scottish Water Public Health, the water was able to be put into supply to allow the future commissioning activities to commence which required large volumes of water. This was an important project milestone.

Wooden bog mats in conjunction with reusable plastic track mats have been used extensively instead of the traditional temporary stone access roads throughout the parks. This has saved the requirement of 12,000 tonnes of stone being brought in and out and saved approximately 1,200 HGV movements in the local community. This has proved an exceptional sustainable approach as the wooden bog mats and reusable plastic track mats can be reused and helps reduce the carbon impact in many ways while making the community streets greener and safer.

Restrained joints have been used on the project pipeline to allow CWA and Scottish Water to remove concrete thrust blocks, therefore further reducing embodied carbon associated with the capital aspects of the project. This totals an estimated 5,500m3 of concrete which has reduced carbon by approximately 16,000 tonnes; 15,000 from concrete and 1000 from transporting the concrete.

Solar panels will also offset the power demands at the new pumping station, with the new trunk mains also utilising increased gravity capacity to further reduce operational power consumption by 60%. The project site welfare and accommodation also utilised solar power and hybrid options. They also have a number of energy saving features which improve U-values such as high levels of insulation and passive infrared sensors to operate LED lighting.

The team also hosted a virtual consultation platform to share project information with customers and stakeholders to avoid the need to travel to community events.

Scottish Water and Caledonia Water Alliance have supported impacted customers and communities. The project team recognised that working closely with local schools would be important. The team arranged to supply pupils with school branded high-vis vests to make sure they are safe when they leave the school for outdoor learning.

They also spent time facilitating talks to teach children how to stay safe around construction sites; pupils were able to visit the site to learn more about the project and took part in a site safety poster competition. The school’s Head Teacher said that there was no doubt that the team had put the needs of the school community at the heart of their work.

The extent of the pipe route gave the opportunity to engage with a number of local schools. For the tunnelling operations, CWA set up competitions to name the tunnel boring machine. Fantastic winning names were chosen and got the community talking about the project. One name was ‘Cruella di Drill’ and another winner was named by the local primary school Crookston Castle as the ‘Crookie Monster’.

Other activities which CWA undertook with stakeholders included:

Linking supply systems ensured that the high quality drinking water continues to be supplied to current customers and for generations to come. The investment in new pipelines and associated infrastructure below ground will also support the continued development above ground in communities across these areas and will enable them to continue to grow and thrive. CWA tapped into the skills from their diverse, integrated team to ensure they delivered an innovative, sustainable and cost effective project whilst supporting a flourishing Scotland.

CWA employed self delivery teams locally, trained a number of apprentices, and engaged local suppliers throughout the project.

The Strategic Pipeline Alliance (SPA) is one of biggest environmental projects being undertaken in Europe and is the most important in Anglian Water’s history. As the pressures of climate change and population growth demand more from existing water networks the SPA will ensure that water flows to the areas that need it most, future-proofing the region’s water infrastructure for generations to come.

The SPA comprises Farrans, MMB, Costain and Jacobs, and once complete, over 580 km of pipeline will have been laid in sections ranging from 9 km to 90 km, that will eventually join together. The Alliance has adopted number of cost saving and environmentally responsible methods to construct the pipeline, including pipe ploughing, new welding techniques, and water-less commissioning.

The entire pipeline has been designed to have the lowest carbon footprint possible, in line with Anglian Water’s pledge to reach net zero carbon by 2030.

Anglian Water’s @one Alliance was tasked by Anglian Water and SPA to deliver the £70m, 36km pipeline between Little Whelnetham near Bury St Edmunds to Wherstead Reservoir in Raydon, south of Ipswich. From solving engineering challenges to preserving local heritage, and complying with regulatory environmental requirements, the LRT pipeline exemplifies what can be achieved when innovation, collaboration and resilience come together.

This case study highlights the engineering progress, environmental responsibility, and lessons learned from the LRT pipeline, showcasing the importance of collaboration and forward-thinking in delivering both infrastructure and environmental stewardship.

The LRT pipeline is a critical infrastructure project connecting Bury St Edmunds to East Suffolk, forming an essential part of the wider Strategic Pipeline Alliance network. Spanning 36 kilometres, the pipeline includes 26 km of 630mm pipe and 10 km of 450mm pipe.

This pipeline includes major crossings, including under the A12 and the Ipswich to London railway line, further demonstrate the complexity of this project.

At the time of writing (May 2025) construction is well advanced and several significant milestones have been achieved:

Prior to the team starting construction, it was necessary to complete archaeological digs which uncovered a Roman settlement from the 1st and 2nd centuries. Also, ancient structures, artifacts, and remnants of a thriving community were found alongside this too. The team worked in partnership with archaeologists to carefully document and preserve these findings, ensuring that this important history was respected throughout the construction process.

Collaboration with local farmers and landowners have also been at the heart of this project, ensuring minimal disruption to their land while promoting sustainable use. Through a Soil Management Plan (SMP), developed alongside the National Farmers Union (NFU), the team has conducted daily soil sampling to monitor moisture levels and determine optimal conditions for handling. This has allowed the team to ensure transparent communication with local communities by keeping everyone informed and engaged; ensuring a successfully delivery of the project.

As with any engineering project, adverse weather can play its part. However, the team’s commitment to resilience has currently ensured that any lost time has been recovered through weekend working and proactive solutions. These challenges only demonstrate the team’s adaptability and its unwavering focus on delivering the project on time and with the highest quality standards.

One particularly intriguing aspect of this project has been its focus on protecting dormice habitats. Dormice are a legally protected species in the UK, which means any infrastructure project that impacts their habitat must adhere to strict regulations. These requirements include minimising disruption, creating new habitat corridors, and long-term monitoring to ensure that conservation measures are effective.

In line with these regulations, the LRT project team implemented a range of innovative conservation strategies.

In addition, advanced monitoring techniques, such as footprint tunnels, nesting boxes, and camera traps were deployed to track dormice activity, while regular environmental assessments ensured ongoing compliance with biodiversity regulations.

At the time of writing the team are yet to detect any dormice on the site and as the project progresses, CCTV monitoring will continue throughout the remainder of the construction phase. As a result of findings for this project, the outcome presents an opportunity for Anglian Water to contribute to a wider discussion on evidence-based conservation policies. By sharing the results from this project, Anglian Water can help inform future environmental assessments, ensuring that investments in biodiversity are targeted, effective, and justified.

The LRT Pipeline is a prime example of how engineering excellence, environmental stewardship, and community collaboration can coexist and thrive. The project is not only pushing the boundaries of modern pipeline engineering but also showing how forward-thinking infrastructure can respect historical and environmental legacies.

Engagement with landowners, communities and specialists has been central to the project’s success, fostering strong partnerships and ensuring that diverse interests were respected. Furthermore, the commitment to biodiversity compliance, even when the real-world necessity of certain interventions is questioned, demonstrates the project’s commitment to both environmental responsibility and regulatory adherence.

The experiences from the Little Whelnetham to Raydon Pipeline  Project offer valuable lessons for future infrastructure projects:

This project is a powerful testament to the fact that bold, innovative engineering can deliver essential infrastructure while prioritizing environmental and regulatory responsibilities.

Ultimately, once complete the LRT Pipeline will not only enhance the resilience of the water network but also contribute to a healthier, more sustainable environment for communities, wildlife, and future generations. It is a shining example of how infrastructure can be developed with both the present and the future in mind; achieving the balance between modern engineering and environmental responsibility.

The Water Resources Management Plan 2019 (WRMP19), and subsequently updated for WRMP24, sets out Southern Water’s response to the water supply challenge in Hampshire. The response consists of a strategic new source of supply, new and increased bulk supplies from neighbouring water companies, demand management, and new strategic transfer pipelines across the region. SWS were required to identify the optimal infrastructure and associated operational controls required to transfer the new supply from Otterbourne Water Supply Works (WSW) to the’ existing distribution networks supplied from Testwood WSW (Southampton) and River Way WSW (Andover).

The Southampton and Andover Link Main Schemes are potable water transfer schemes which are required to link up key SWS operational sites across Hampshire to ensure continued sustainable, reliable water supplies.

Principally, the proposed schemes consist collectively of approximately 41km of new trunk mains ranging in size from DN500-DN900, operating in conjunction with a number of existing strategic trunk mains, connecting key WSW’s and Water Service Reservoirs (WSR) across a number of Water Resource Zones (WRZ). Additionally, the schemes include new pumping and storage assets to support the water transfers.

Through the scheme optioneering phase, which started in early 2022, a Network Control and Optimisation (NCO) study was undertaken to align with and build on previous work undertaken in WRMP and other strategic network modelling studies.

The aim of the NCO study was to assess the resilience of the proposed new strategic transfer pipelines, often referred to as the Western or Hampshire Grid, and how different options might exhibit varying levels of resilience across business as usual (BAU) and drought operation. The study was completed with the understanding that the infrastructure architecture could not be determined unless the associated operation was also defined. The study was conducted in parallel to engineering design development to determine the preferred options for design, construction and commissioning as part of the wider Water for Life Hampshire programme, ensuring a holistic approach across the region.

The study utilised a proprietary AI software product, Optimizer, to develop optimal asset configurations and was chosen to reduce program costs and expenditures. A traditional approach would typically involve hydraulic models using an iterative “trial and error” method, but the large number of options would make it impossible to evaluate all possible outcomes.

Using Optimizer, with which the Southern Water InfoWorks network model was linked as an embedded hydraulic engine, enabled the automatic evaluation of thousands of trial solutions computing cost and performance, and incorporating operating constraints and design criteria. Optimizer produces a range of least-cost network solutions, including asset sizes and maximising the efficiency of network operational performance, considering both BAU and drought supply/demand scenarios.

The tool produces a set of plans along a Pareto front that represents the optimal-performing configuration for a budget cost, and therefore quickly identifies options to be analysed in further detail. This process enabled efficient development of the engineering design as the scheme architecture was refined quickly with focus on key assets required.

Through 2022 as the scheme transitioned into concept design, various route corridor options were considered between the fixed strategic sites identified within Otterbourne, Southampton and Andover.

Options considered additional alternative Southern Water operational sites to interconnect with and how to transfer water between these sites to provide further system resilience. These options were refined initially through careful review of desktop environmental, ecological and heritage constraints information, later supplemented by data obtained through site visits, and field surveys (non-intrusive and intrusive).

Options considered the location of the pipeline easement, access routes, pipeline materials and construction methodology. A key intermediate site selected to integrate into the system was Yew Hill WSR, located to the south-west of Winchester. This provided opportunity to utilise common sections of pipeline transfer from Otterbourne to serve SLM and ALM whilst maximising existing transfer capability. This also provided opportunity to expand potable water storage capacity in a network location capable of providing numerous resilience options.

From the initial assessments, high level route corridors were established and broken down into a series of segments. The segments were then appraised in detail following a Red, Amber, Green (RAG) classification by environmental, ecological, heritage, engineering and construction specialists.

Different route options were demonstrated with different segments, with some segments having sub options within. Through a desk-based process, each discipline provided their feedback on the key constraints within each segment, and where mitigation could be required and the form it could take.

Where there were options between or within segments, a preference was stated by each discipline with clear factual reasoning. From these preferences, the route was selected depending on which constraints for each segment were most critical to avoid, whilst balancing constructability and land access constraints.

Following internal SWS project delivery process, agreement on a single option to progress to outline design was made based on a combination of technical, operational and environmental considerations.

The general design and construction principles used to develop the initial pipeline route of the schemes were to minimise:

The proposed pipeline routes and design were subsequently further refined taking into account environmental constraints identified through field surveys, archaeological investigation, community considerations and engineering capabilities clarified through intrusive ground investigation.

All desktop and survey data was made available to all project disciplines via the utilisation of Mott Macdonald’s Moata digital platform, specifically Moata Geospatial and Moata Land Management. This provided all teams withs access to information at every stage of the project, allowing cross-disciplinary teams to collaborate in real time.

The integration of the Moata platform was so successful that it won Best Project – Innovation at the Institution of Civil Engineers South East England Engineering Excellence Awards in 2025.

The key components selected to form the scope for the SLM are as follows:

The scheme will provide a transfer between Hampshire Southampton East WRZ and Hampshire Winchester WRZ and a transfer between Hampshire Winchester WRZ and Hampshire Southampton West WRZ. Specifically, the scheme will transfer water from Otterbourne WSW to Yew Hill WSR and onward to Rownhams WSR and Testwood WSW.

Key design constraints for the scheme included:

The key components selected to form the scope for the ALM are as follows (NB: At the time of writing (July 2025) scheme refinements are ongoing and some of the following may be subject to change):

The scheme will provide a transfer between Hampshire Winchester Water Resource Zones and Hampshire Andover Water Resource Zones, specifically the scheme will transfer water from Yew Hill WSR to Crab Wood WSR and onward to Micheldever Road WSR and the Andover distribution network.

Key design constraints for the scheme included:

In 2022, MGjv was appointed as Principal Contractor and Principal Designer to undertake Early Contractor Engagement (ECE) support across both schemes; assisting with development of the concept design. As scheme development moved into 2023, MGjv coordinated and undertook extensive site investigation works to verify ground conditions. The scope of the investigation comprised trial pitting, cable percussion boreholes, rotary core boreholes, downhole geophysical testing, surface geophysical surveying, laboratory testing and the preparation of factual reporting.

In parallel, numerous excavations at different locations along the two proposed pipeline routes were undertaken to explore the potential for buried archaeological remains. Initially, an extensive programme of archaeological trial trenching was completed which informed the requirement for subsequent selected strip, map and sample works.

In late 2023, Southern Water submitted requests for EIA Screening Opinions on each scheme to the Local Planning Authorities to confirm requirements for planning consent. Final responses were received in Spring 2024. The outcome of the requests was that SLM was not deemed EIA Development and therefore retained Permitted Development (PD) Rights where applicable. In comparison, ALM was deemed EIA Development and requires a full Planning Application and Environmental Statement (ES) to be submitted for approval.

A summary of site investigation works is as follows (as of early 2024):

Following confirmation of the planning requirements for both schemes in Spring 2024, MGjv was contracted to deliver the full design and delivery of the SLM as the scheme was able to progress under PD Rights for the pipeline. Separate discrete assessments were undertaken that clarified the new Yew Hill WSR, which was also confirmed as PD. The expansion of the Otterbourne WSW HLPS would be subject to a planning application.

The requirement on the ALM scheme for full planning and ES required additional design and survey/investigation works to be undertaken and so MGjv has continued in an ECE role until mid-2025 to support the application, due late 2025. The procurement strategy for the full design and delivery is currently being developed.

The Southampton and Andover Link Main Schemes will provide a new strategic supply backbone across Hampshire to maintain security of supply to customers and help protect the county’s rare and sensitive chalk streams.

The schemes will provide additional BAU resilience whilst also providing capability to mitigate important drought restrictions being placed on the River Test and River Itchen, impacting key operational sites within the region.

Further articles will follow in due course covering the detail design, construction and commissioning phases of the schemes.

Given the critical nature of these water mains, the construction of the new A428 demanded a carefully orchestrated diversion strategy to ensure minimal disruption to the water supply network. This case study explores the challenges faced by the Anglian Water @one Alliance, the innovative solution that was implemented, and the benefits that the project delivered to the community and the region’s future growth.

The A428 corridor is a vital route connecting key regions in Bedfordshire and Cambridgeshire. Stretching between the Black Cat Roundabout at the junction of the A1 and the A421 in Roxton, Bedfordshire, and Caxton Gibbet at the junction of the A428 and the A1198 in Cambridgeshire, this stretch serves as a critical link for commuters, local communities, and businesses in the area. The area is made up of a mix of residents, agricultural land, and growing commercial hubs, highlighting its importance as a dynamic economic region.

The construction of the new A428 dual carriageway presented a significant infrastructure challenge, with several existing water mains needing to be diverted to facilitate the road’s development. These water mains are integral to the region’s water distribution network, supplying water to residential, commercial, and agricultural users along the A428 corridor.

Specifically, the project involved diverting eight water mains of varying sizes, as well as replacing an outfall pipeline from the Potton Road Reservoir. The impacted areas included:

These diversions were critical to allow for the construction of the new A428 without compromising water supply reliability or impacting the hydraulic performance of the network. The challenge lay not only in the physical relocation of these pipelines but also in ensuring that water flow rates and pressure levels remained consistent throughout the transition.

Also, the design criteria for this project required a 50-year design horizon, necessitating robust engineering solutions to accommodate future demand growth and operational resilience. The project also navigated complex geographical and environmental constraints, including road crossings and land ownership boundaries.

To address these challenges, Anglian Water’s @one Alliance was tasked with implementing a strategic and meticulously planned solution. Funded by National Highways, the project required the diversion of eight water mains; each carefully designed to meet the required flow rates and maintain system integrity. The construction approach included directional drilling to minimise environmental impact, reduce excavation requirements, and limit disruption to local communities and traffic. The works included:

All new pipelines were designed as ‘like for like’ replacements, ensuring that water flow rates and pressures were maintained across the network. To future-proof the solution, the design horizon was set at 50 years; ensuring the new infrastructure met long-term demands.

The successful diversion of water mains ensured an uninterrupted water supply for local communities and businesses throughout the construction period. By maintaining consistent flow rates and pressures, the project safeguarded the reliability of water services, allowing daily activities to continue without disruption. This seamless transition was crucial in maintaining public confidence and supporting local economies during the infrastructure upgrade.

In addition to maintaining continuity of service, the project significantly enhanced infrastructure resilience. The newly installed pipelines, made from PE100 materials, offer superior durability and resistance to corrosion compared to the previous cast iron and PVC systems. This upgrade reduces the risk of leaks or failures, enhancing the long-term reliability of the water network. The robust design ensures a stable water supply, minimizing the need for emergency repairs and contributing to overall operational efficiency.

Environmental and safety considerations were central to the project’s planning and execution. By employing trenchless construction techniques, the project minimised ground disturbance, preserving environmentally sensitive areas and reducing the ecological impact.

Additionally, the implementation of dualled pipelines beneath the new A428 increased safety and reliability, ensuring the security of water supply even in the event of unexpected issues with one of the pipelines. This strategic design choice highlights the project’s commitment to both environmental stewardship and public safety.

Beyond technical achievements, the water main diversions were essential for the construction of the new A428 dual carriageway. The new route will significantly reduce congestion, cut travel times and boost economic growth across Bedfordshire and Cambridgeshire. By facilitating better transport links, the project supporting is local businesses, encouraging investment, and contributing to the prosperity of the surrounding communities.

Looking to the future, the new water mains have been designed with a 50-year horizon, ensuring they can accommodate projected population growth and increased water demand. This future-proofed approach guarantees a sustainable and reliable water supply for generations to come. By anticipating future needs, the project demonstrates a forward-looking vision, laying a strong foundation for continued community and economic development.

This comprehensive infrastructure upgrade showcases a successful blend of innovation, environmental responsibility, and strategic planning, delivering long-term benefits to both local communities and the broader region.

This project exemplified how strategic infrastructure planning and innovative engineering can harmoniously integrate essential utility services with large-scale development projects. By delivering these water main diversions efficiently and effectively, the Anglian Water @one Alliance not only supported the construction of a vital new road but also safeguarded the water supply network for the future.

This collaborative effort showcased the commitment to sustainable infrastructure solutions that balanced community needs, environmental stewardship, and economic growth. The successful completion of the new A428 symbolizes progress, connectivity, and a brighter future for the region.

The success of this project is a testament to the power of strategic planning, technical excellence, and a commitment to delivering long-term value to the communities served by Anglian Water. The @one Alliance is proud to have played a key role in shaping a resilient, connected, and stronger future for the region.

Severn Trent is keen to explore the potential of low-carbon, natural, biological water treatment processes in conjunction with conventional, chemical treatment to remove pollutants from the water abstracted from the River Trent. Historic data revealed that nitrate levels in the River Trent have occasionally exceeded the 50 Mg/l concentration value prescribed by the DWI, and regularly breached Seven Trent’s own, more stringent standard.

As a result, a natural, biological solution in the form of floating wetlands to provide preliminary water treatment is being combined with refurbishing the existing abstraction infrastructure at the lakes (called the Raw Project) to supply water to the new water treatment works being constructed in Church Wilne.

This is the first time in the UK that wetlands have been used for operational water pre-treatment on this scale and in the ‘real world’, but theoretical studies show that, on average, these floating wetlands could remove in the region of 40-60% of both total nitrogen (ammonia, organic and oxidised nitrogen) and total suspended solids (particles >2 microns), helping to considerably reduce the amount of energy and chemicals used in the traditional water treatment process.

Floating wetlands were selected over conventional or static wetlands because Witches Oak floods regularly during the winter.

The pontoons can rise and fall with the water level, so are resilient to changes in load and seasonal fluctuations, whereas a static wetland would be submerged during a flood event, diminishing process benefits provided by the vegetation. This has been thoroughly tested in winter 2023/24 when the site experienced extensive 1 in 100-year flood events. The floating solution also typically requires less maintenance, including no watering or fertilisation.

The Biomatrix floating ecosystems selected for Witches Oak mimic elements of self-sustaining, naturally occurring riparian wetlands. Water quality is improved by the root mass, which provides a large surface area for the microbial communities needed to remove pollutants. Planted with several types of sedge, hard rush and flowering species, including purple loosestrife and meadow sweet, these islands provide biological treatment to reduce the turbidity and nitrates in the raw water.

In December 2022, Mott MacDonald Bentley initially focused on the construction and launch of three trial wetlands in Lake 2, as well as the removal of a redundant man-made wetland from the lake. Since then, a further 28 floating wetlands have been installed on the three northern most lakes during summer 2023.

The 31 floating treatment wetlands were positioned in the natural water flow path in Lakes 1, 2 and 3.

Work is also being undertaken to upgrade of the existing pumping station and river intake, along with the installation of a new fish recovery system and three new transfer pumps.

This is a true ‘One Mott MacDonald’ project with members of the consultancy teams having worked on the feasibility of the wetlands’ abilities to pre-treat water and then their outline design, before handing over to colleagues at Mott MacDonald Bentley through early contractor involvement and then design and build delivering the detailed design, pre-construction and construction activities.

To minimise the environmental impact, temporary track mats were used for the base of the works’ compound and launch area at Lake 2, allowing the site to return to managed grassland when the mats were lifted.

A silt curtain was erected in the lake to prevent debris from the old wetland polluting the water. This was important because the wetland was colonised by invasive species, mostly Himalayan balsam on land and zebra mussels below water. The curtain also ensured that sediment disturbed by the removal work did not spread.

The design has also had to accommodate regular site flooding; in particular for the temporary works around the river intake where, as an example, the cofferdam was designed specifically to account for controlled and safe flooding of the excavation to manage the high river levels experienced on-site.

Launching and anchoring the 31 floating wetlands was the first phase of the Raw Project. Phase two is refurbishing the abstraction pumping station built in the 1990s to enable raw water to be supplied to Witches Oak WTW.

Located on the western shore of Lake 3, the pumping station is undergoing a complete refurbishment, including the installation of three new transfer pumps to deliver up to 96 Ml/d of pre-treated water; enough for a city the size of Derby.

The design layout for the station also includes a new water quality kiosk and a wash-water booster set to clean the fish screens.

The river intake in the north-east corner of Lake 1 is also more than 25 years old and is being modified. The design will help to protect both fish and the gravel lakes. Two new 2.5m x 4m concrete channels will be constructed to create a flow low enough to allow fish and eels to swim back to the river, while two large, actuated intake penstocks will be installed to protect the lakes if there is a river pollution incident.

The introduction of new recirculation pipework will enable water to be pumped back to the river from the pumping station when necessary. Under the proposals, river water quality will in future be monitored upstream of the intake as well as at the intake itself.

Barbel, bream, chub and roach are common fish species found in the River Trent and two new screens will be fitted to filter fish and debris out of the water drawn in by the pumps at Witches Oak Water. The fish recovery system will consist of an above-ground pipe connecting the pumping station intake culverts to Aston Brook, which runs alongside the river, and from where fish can eventually return to the Trent.

Witches Oak is one of seven projects that form Severn Trent’s Green Recovery Programme, worth more than £700m, which aims to develop low-carbon water resources, improve river water quality, replace redundant lead pipes, install smart metering and make urban areas more resilient.

The additional water supply from Witches Oak will help meet demand for water from a growing population and improve the resilience of supplies during hotter, drier summers.

By restoring natural functions to these gravel lake ecosystems, the project is promoting biodiversity recovery and contributing to enhanced ecosystem services. The wetlands provide amazing biodiversity benefits including:

In addition, positive social outcomes and community engagement are key elements of Severn Trent Water’s 25-year water resources management plan. The delivery team presented to the local girl guide group to tell them about the work we’re doing, and a visitor engagement centre has been installed to showcase this exciting project to local school and community groups.