Supply Chain - Water Mains - Pressure Testing

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.

Over time, deposits of iron and manganese have accumulated within the pipelines. While these minerals do not pose any health risks, they can result in discolouration of the water and be detrimental to the internal condition of the pipe. Due to the ages of the lines and the accumulation of minerals deposited, they now require cleaning and/or rehabilitating. To maintain the water supply, the refurbishment programme will be completed over a phased approach with work on the lines being carried out at different times.

Avove was chosen as the contractor for modernising the Vyrnwy Aqueduct pipelines, adopting innovative ways to inspecting, cleaning and relining the large-scale pipes throughout Cheshire. This includes designing, constructing, testing and commissioning the three pipelines in Phase 1 of the works between Malpas and Tarporley; a distance of approximately 18.75km per line. Avove’s approach will see a significant reduction in carbon emissions across the project.

Lines 1 & 2 - Cast iron pipe: A new slightly smaller diameter plastic pipe will be slip-lined into the old main, creating a brand-new pipe within the host main.

Line 3 - bitumen lined steel pipe: The original scope was using a traditional method of high-pressure jet washing, however, Avove’s design team reviewed the project and recommended the use of air pig technology working with specialist smart pigging partner iNPIPE PRODUCTS™. Air pigging has never been used before to clean this size and length of water pipeline, but after careful consideration, Avove and iNPIPE PRODUCTS™ designed and commissioned an effective, compliant and efficient process, that was approved within the United Utilities specification C05-i2-Spec document for large diameter bitumen lined mains.

The air pigging system utilises an air-propelled cleaning tool, known as a ‘pig’, travelling through the 1m diameter pipes to remove any sediment that has built up from the natural minerals in the water.

The innovative process uses air to push a pig-train, containing a slug of water between two pigs down the host main to lift off and suspend waste deposits off the internal wall for removal at the receiver. Flow rates and pressures are carefully monitored at all times during the cleaning process and after each pigging run.  If required, brush pigs are used to remove hardened materials. These brush pigs have been designed to remove materials without damaging the existing bitumen lining. Following cleaning, a camera pig is run through the pipeline to ensure internal cleanliness is assured.

The ‘pigs’ are vertically launched to reduce the excavation size but can be launched horizontally when height is a concern. ‘Pigs’ are inserted into the pipe section at ground level to reduce working at height and the pipes will then be attached to the host main.

’Pigs’ are traditionally propelled by water, but by using air, the benefits for the Vyrnwy Aqueduct include:

For a large diameter main with manganese deposits, air pigging was a safer system to use and improved the quality cleaning method, due to the contact motion and flexible material of the bespoke cleaning air pig.

Avove designed the type of ‘pigs’ required for the project and worked with partner iNPIPE PRODUCTS™ to manufacture the type of cleaning tool; collaboratively agreeing on the frequency of the ‘pig’ run to ensure optimum cleanliness based upon more than 40 years of experience.

Avove and iNPIPE PRODUCTS™ subsequently ran an integrated camera/data logging system which incorporated gyroscopes and a tracking module mounted within the ‘pig’. This system recorded high-definition quality footage of the water main as it passed through and allowed the team to analyse the pipeline.

The adopted method requires the ‘pig’ passing through the pipe six times:

Avove is continuously striving to innovate and drive carbon reduction within the design and build aspects of the Vyrnwy Aqueduct Modernisation Project. By January 2025, all six sections in Siphon 1 Line 3 had been successfully cleaned and the aqueduct was commissioned and returned into service.

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.

In 2016, and more recently in 2022, low levels of rainfall and hot weather compromised the raw water quality in Abberton Reservoir which led to significant challenges to the biological process at Layer WTW. This meant unprecedented demand was placed upon Essex & Suffolk Water’s chemical works at Hanningfield WTW which in turn drew down the water level in Hanningfield Reservoir to levels not seen since the summer of 1996.

Whilst this low level in Hanningfield was observed, the level in Abberton was healthy due to the process constraints of the biological works at Layer. To mitigate the scenario of having two reservoirs, one relatively full, and another extremely low, occurring in the future, Northumbrian Water applied for enhancement funding in AMP7 to construct a 20km pipeline between the Layer and Langford WTWs, where water from Abberton could be reliably treated. This in turn would allow water from the River Chelmer and River Blackwater, that would normally be treated at Langford, to augment the water level in Hanningfield Reservoir by utilising existing transfer pumping facilities between Langford WTW and Hanningfield Reservoir.

Providing this connectivity, albeit by substitution, would allow Essex & Suffolk Water to balance the water levels in both Abberton Reservoir and Hanningfield Reservoir, and mitigate a potential scenario where no water is available to supply Hanningfield WTW.

In 2019, Essex & Suffolk Water teams began to plan a route between Layer WTW and Langford WTW for a pipeline that could support flow rates up to 50 Ml/d. This figure was determined as the optimum flow rate to allow balancing of the reservoirs to take place and ensure security of supply when faced with long term drought conditions. The pipeline would take advantage of the capacity and capability of the existing pumping station at Abberton which can deliver up to 255 MLD of water to Layer WTW.

The route would begin with a strategic connection into the existing raw water mains that deliver water from Abberton Reservoir into Layer WTW. From this point a route was sought that would allow water to run under gravity to Langford WTW, where it would be discharged into two existing bankside storage reservoirs each with a capacity of 35 ML.

One of the main components of construction work was the horizontal directional drilling (HDD) that was necessary to cross the two main rivers, the River Blackwater and the Langford Cut.

Northumbrian Water competitively tendered this package with a number of HDD contractors operating in the sector. After an assessment of both cost and quality, the project team awarded this package of work to Complete Moling Services (CMS) based in Rochester, Kent.

Essex & Suffolk Water obtained an exemption from flood risk activities by following the Environment Agency guidelines. This included designing the HDD such that it was within 10° of perpendicular to the river flow, the drill depth was greater than 1.5m beneath the riverbed and the location of the launch and reception pits were greater than 8m from the riverbank.

The HDD began in early September 2023 with NWG excavating the launch and reception pits either side of the two rivers. Each of the pits was approximately 7m x 6.5m x 1.5m; large enough to site the directional drill rig. Drilling work began with a 165mm pilot bore entering the ground at -15° to horizontal and proceeding on this trajectory for 45.5m. The drill angle was then ‘steered’ to a flat trajectory for a further 100m before being ‘steered’ upwards at +15° to horizontal to exit within the reception pit. The pilot drill, now in the reception pit, had its head changed to a 250mm reamer which is then rotated and pulled back through the alignment created by the pilot bore and into the launch pit.

The process was repeated, increasing the diameter of the reamer each time to 350mm, 500mm, 600mm and finally 800mm.

Throughout the course of the drilling work, drilling muds were used to keep open the annulus of the drill and remove all cuttings from the reamed bore annulus. Once the bore was completed and stabilised a 630mm OD, MDPE pipe was drawn through the bore between the reception pit and the launch pit creating a pipeline beneath the two rivers. The whole process was completed twice meaning two 630mm OD MDPE pipe crossings were achieved providing resilience to the overall pipeline should one line become damaged. During the course of the work, the drilling team encountered ground conditions that were not expected and this increased the duration and cost of the work; albeit marginally. Even so, the cost of directional drilling the river crossings was significantly less than the alternative open cut method. This activity on the project was completed in late 2023.

During 2024, with the strategic crossings outlined above completed, the project team could focus on the delivery of the 20km pipeline between Layer WTW in Colchester, and Langford WTW in Maldon. Topsoil stripping began in January 2024 and took place along a reduced width corridor of 25m with further reductions at ecologically sensitive areas (such as hedge row crossings) and small watercourse crossings (such as ditches). Adopting this approach limited the environmental impact of the scheme and the post construction compensation provided to landowners.

Deliveries of ductile iron pipework from Electrosteel Castings (UK) Ltd began to arrive at various compounds along the route from February 2024. Pipes were received on site and then strung out along the route of pipeline. The careful coordination of pipeline deliveries and installation meant a rolling installation programme that maintained a reasonably constant installation rate of 60m per pipelaying gang per day. Using two gangs through the construction programme, with a late summer peak of three gangs, enabled the installation of the 20km of pipe to be completed between April and November 2024. The installation technique was a traditional open cut method using trench boxes in excavations where gasket installation and jointing could be undertaken safely.

During the construction phase, the site team implemented both pre and post-land drainage schemes to mitigate the impact of water ingress into excavations and ensure that the downstream impacts of the construction activity did not impact on existing drainage schemes within impacted land parcels which primarily comprised arable fields.

Perhaps the most innovative approach adopted by the project team was not regards to technology, but the approach the team took to planning the scheme.

The route was deliberately designed to avoid designated areas such as SSSIs and SPAs and this, combined with a robust approach to mitigating any significant lasting impact allowed the team to work with the local planning authorities to agree the project could be delivered through Permitted Development. This created an opportunity to reduce the programme duration to omit EIA scoping and planning application submission and approvals with the associated cost reduction.

Essex & Suffolk Water believe that this is perhaps the first time a 900mm diameter, 20km trunk main extends across multiple planning authorities, which has been delivered using Permitted Development Rights.

The pipeline delivered a flow rate of 20 MLD into the bankside storage reservoirs at Langford in March 2025. The flow rate was deliberately restricted to 20 MLD rather than full flow design of 50 MLD due to operational constraints at the time.

Remaining work to complete the integration of the flow control system into the existing site-wide SCADA system and the chemical dosing system to control Invasive Non-Native Species (INNS). This work will be completed in late spring/summer 2025. The project was delivered for less than the business plan allowance and within the Regulatory Deadline.

“Envolve’s Collaborative approach to delivery achieved a one team approach. We collectively worked to overcome challenges, delivering a successful project ahead of programme. This approach resulted in project risks either being mitigate or managed by drawing on knowledge from across the team, resulting in the overall project being delivered under budget.”

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 project included the following scope:

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

The proposed route for the new trunk main was along the Strabane Old Road; a dense urban area often used as an alternative route to the existing A5, for commuters coming in and out of the city. Traffic surveys recently completed identified that 7000 vehicles per day (VPD) were using the road.

As a result, early engagement and liaison between DFI Roads, Translink, Farrans Construction and the Traffic Management Contractor were required. A collaborative approach among all stakeholders ensured effective traffic management measures were implemented to protect the safety of road users directly affected by the works and those passing by, minimising disruption as best as possible while the works progressed.

The works were carried out under local road closures and lane closures. Due to the size of the pipe, existing services and rock, all the pipe was installed via open-cut methodology.

A 1m wide asphalt planer was utilised to remove the asphalt layer in the pipe track. This greatly saved time in comparison to the traditional method of an excavator and breaker.

Due to a limited working area, 12m lengths of 450mm diameter PE pipe were delivered from compound to the works area as required via a Hiab. The pipe was then butt-welded and pulled into the trench using rollers and pipe trolleys.

Crescent Link Trunk Main was chosen to trial Control Point’s Bluebox Quality Assurance System (Joint Assist). Joint Assist is a mobile application that records and uploads data for electrofusion joint assemblies, enabling real-time inspection, compliance and comprehensive asset management. In addition to Farrans’ own quality procedures, Control Point’s Bluebox provided NI Water with third party quality assurance.

The construction contract was awarded under NEC4 Option ‘C’ Target Cost Contract to Farrans/Glanua Group JV. Construction began in May 2022 and took place over a 12-month period at a total cost of £2.5m.

The Dungiven Road is categorised as type 1 road with recent traffic surveys recording approximately 1500 VPD using the road. As a result, the works were carried out at night (7pm to 6am) to minimise disruption.

Lengths of 600mm twin wall pipe were installed in the road via open-cut methodology and completed in sections. This allowed time for the road to be backfilled, temporarily reinstated at the end of each shift and opened in time for the morning traffic.

Once all the twin wall pipe was installed, a 450mm string of pipe was welded and successfully sliplined through the twin wall pipe with only one joint/bend required. Once all works were completed in the road, a planer was used to remove the temporary asphalt and allow the permanent reinstatement to be completed.

Following testing (Type 2 pressure test), commissioning works were undertaken in preparation for connections to the existing network.

Seven new connections were made to the existing network which allowed for the existing 10” spun iron main to be abandoned.

Utilising existing kiosk and telemetry units, new electromagnetic flow meters and pressure transducers were fitted as part of a new PRV, meter and strainer arrangements at Tamnymore SR and Dennett Gardens to allow NI Operations to monitor flows and pressures over the telemetry network.

Farrans’ PR manager, Sarah Heffernan, worked closely with NI Water Comms to implement a proactive engagement strategy to ensure all key stakeholders were informed of the work in a timely manner. Letter drops took place in advance of each section of pipelaying to advise the residents and businesses of the planned works and variable message boards were erected along the route. Business-specific signage was installed around each works area and press releases issued to inform the wider public. Communication with other stakeholders, including elected representatives, landowners, roads and transport authorities was maintained throughout the scheme.

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 Dungiven Road, works were carried out at night with increased working hours in order to complete the pipelaying in the shortest possible timescale. Additionally, roads were temporarily reopened around holiday periods to minimise disruption.

Whilst working through the most congested and built-up area of the project (Strabane Old Road), Farrans’ in-house Stakeholder and Social Value Team along with NI Water engaged with the local primary school. The site team visited the school delivering a site safety talk, ensuring the pupils understood the dangers that construction sites can bring and how to stay safe around the works.

Following this, the site team facilitated two site visits where the pupils were brought onto the live construction site to see works and the watermain being laid. They were given a presentation by the site engineer covering a variety of topics on all things engineering, the water cycle, how water gets from source to tap and why works were being carried out in their area. There was great engagement from the pupils during the visits and pupils went back to their classroom with an engineering superhero colouring competition to help remember everything they had learnt on their site visit.

Seeing first-hand the construction works and learning why the work needed to be undertaken hopefully helped the pupils to think further about STEM subjects and the different career options available to them in the future.

Testing and commissioning of the new 450mm trunk main began in March 2023, with the final connection to the network completed in April 2024. The new Crescent Link Trunk Main will provide a sustainable supply in of wholesome drinking water to the Waterside area in Derry/Londonderry, bolstering Northern Ireland Water’s existing infrastructure and reinforcing supply to approximately 17,500 customers.