The construction of the North Hykeham Relief Road is progressing in Lincolnshire, with the new route set to provide an important connection between the A46 Lincoln roundabout and the A15 Sleaford Road roundabout at the southern end of the Lincoln Eastern Bypass.
The scheme includes new junctions at South Hykeham Road, Brant Road and Grantham Road and is being delivered by Lincolnshire County Council (LCC). As the route has progressed, its footprint has impacted a number of existing Anglian Water assets, creating the need for significant diversion works before the new road infrastructure can be completed.
Working on behalf of Anglian Water, the @one Alliance was tasked to deliver a £5.6 million programme of water and wastewater asset diversions to facilitate the wider highways scheme, all while maintaining the resilience and performance of the existing network.
The programme involves the diversion of eight clean water assets and one foul asset, with around 4km of water and wastewater infrastructure being diverted across the route. The works span several locations, including South Hykeham Road, Station Road, Grantham Road, Sleaford Road and Wath Lane.
The affected infrastructure ranges from smaller distribution mains through to major trunk assets, including a 500mm water main. Several of the existing assets cross the footprint of proposed junctions, roads and other infrastructure, meaning they need to be relocated before construction of the relief road can progress.
At the A46 roundabout, three potable water mains are affected by the proposed highway works. These include two existing 180mm assets and a 125mm main, requiring approximately 614m of replacement infrastructure.
Further along the route, an existing 90mm main alongside South Hykeham Road is being diverted to accommodate the future roundabout, while an existing 180mm main at Station Road is being relocated to allow for a new roundabout and bridge.
The works at Grantham Road are particularly complex, with two significant potable water assets requiring diversion. These include an existing 500mm main and a 355mm main. At Sleaford Road, an existing 300mm raw water main is also being diverted to accommodate the new roundabout.
With the highways programme progressing, the challenge for the @one Alliance has been to deliver these diversions safely and efficiently, while maintaining water supplies and coordinating closely with LCC and other stakeholders.
The Solution
The @one Alliance has adopted a phased approach to the programme, sequencing the diversions around the wider North Hykeham Relief Road construction programme.
This has required close coordination between the design, construction and project delivery teams, Anglian Water, Lincolnshire County Council and other affected stakeholders. The approach has ensured that assets are diverted ahead of the relevant highway construction activities, reducing the risk of clashes and helping the wider scheme maintain its programme.
A combination of open-cut construction and slip-lining techniques is being used across the project, selected according to the location, existing infrastructure and requirements of the new road layout.
At South Hykeham Road, the existing 90mm main is being replaced with new PE100 infrastructure. Parts of the new main are being installed by open cut, while sleeving and slip-lining techniques are being used where the route crosses proposed highway infrastructure and existing services.
The Grantham Road works involve some of the largest assets within the programme. The existing 500mm main is being replaced with a new 560mm PE100 main, while the existing 355mm main is being replaced with a new 355mm PE100 main.
The two new mains are being installed together along the same route, with appropriate separation maintained between the assets. Where the new route crosses Grantham Road and the proposed highway, sleeves are being installed to allow the new mains to be installed beneath the road.
This approach limits disruption and provides additional protection to the new assets as the wider highway infrastructure is constructed above them.
At Sleaford Road, the existing 300mm raw water main is being replaced with a larger 355mm PE100 main. The new main is being installed through a combination of open-cut construction and sleeving beneath the proposed highway and access infrastructure.
The design of each diversion has also been supported by hydraulic modelling to ensure that replacing and relocating the assets does not adversely affect the performance of Anglian Water’s network.
For example, modelling of the Grantham Road 500mm main confirmed that replacing the existing asset with a 560mm PE100 main would not impose an undue restriction on potential maximum flows. Similarly, the proposed 355mm replacement at Grantham Road provides a like-for-like hydraulic solution for the existing 355mm main.
At Sleaford Road, modelling demonstrated that the proposed 355mm PE100 replacement provides broadly equivalent hydraulic performance to the existing 300mm ductile iron main, while providing sufficient capacity for the expected flows from Dunston Water Treatment Works.
This design-led approach has allowed the project team to develop solutions that are practical to construct while maintaining the operational requirements of the water network.
Benefits of the solution
The primary benefit of the programme is that it is enabling the North Hykeham Relief Road to progress while maintaining the operation of Anglian Water’s network.
By completing the required diversions ahead of the relevant highway construction activities, the @one Alliance is removing potential clashes between the new road infrastructure and existing water assets.
This is particularly important given the scale of the highways scheme and the number of interfaces along its route. Without the diversion programme, existing water and wastewater infrastructure would continue to sit within the footprint of the proposed road, junctions and associated infrastructure.
The project is also providing an opportunity to replace a number of existing assets with new polyethylene infrastructure, supporting the long-term resilience of the network.
The use of larger replacement mains in selected locations has been informed by hydraulic modelling and site requirements, ensuring the new infrastructure has the necessary capacity to support existing operational requirements.
Construction techniques such as sleeving and slip-lining are also helping the team manage the constraints associated with working around existing roads, services and infrastructure. Rather than relying solely on traditional open-cut construction, the project is using the most appropriate installation method for each location.
The phased approach is another key benefit. With the diversion works forming part of a much larger infrastructure programme, careful sequencing has been essential to ensure the works can be completed in line with LCC’s requirements.
The programme has therefore required more than simply moving existing pipes. It has involved detailed planning around multiple construction interfaces, existing services, private connections, highway works and the operational requirements of Anglian Water’s network.
As the project moves towards completion, the majority of the diversion programme is now well advanced, bringing the wider highways scheme closer to being able to progress without the constraints posed by the affected water assets.
Supply chain
Delivering a programme of this scale and complexity has required close collaboration across the @one Alliance supply chain.
The project team has worked alongside Anglian Water and Lincolnshire County Council, as well as:
| Supply chain partner | Role / contribution |
| Paul Richardson Recycling | Supplied recycled aggregates, delivering significant savings on backfill materials |
| Aliaxis | Supplied PE pipework |
| Wolseley | Supplied a wide range of fittings and ancillary materials |
| PAM Saint-Gobain | Supplied ductile iron pipework and fittings |
| AVK | Supplied valves and hydrants critical to the network installation |
| CPC Civils | Delivered high-quality reinstatement works across the scheme |
| WN Surfacing | Delivered high-quality surfacing and reinstatement works across the scheme |
Conclusion
With the North Hykeham Relief Road continuing to take shape, the £5.6 million Anglian Water diversion programme is now approaching its final stages.
Across the route, the @one Alliance is delivering the diversion of eight clean water assets and one foul asset, with approximately 4km of water and wastewater infrastructure being relocated to make way for the new road.
From smaller distribution mains to a 500mm trunk main, the programme has involved a wide range of technical challenges and construction environments. The team has responded through a combination of detailed hydraulic modelling, phased delivery, open-cut construction, sleeving and slip-lining.
The work has also demonstrated the importance of early coordination when water infrastructure forms part of a wider infrastructure project. By working closely with Lincolnshire County Council, Anglian Water and the wider supply chain, the @one Alliance has been able to coordinate the diversions around the highway programme and ensure that the water network continues to operate effectively.
As the final works are completed, the project is helping remove a major infrastructure constraint from the North Hykeham Relief Road, supporting LCC’s plans to deliver a new strategic route while ensuring Anglian Water’s network remains resilient and capable of serving the communities across the area.
The successful delivery of the diversions highlights how effective collaboration between water companies, infrastructure alliances, local authorities and the wider supply chain can help complex infrastructure programmes progress safely and efficiently – even where multiple major projects need to be delivered within the same footprint.
