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Southampton Link Main: Otterbourne to Testwood

We're investing over £100 million to build a new 19km pipeline and pumping stations to connect our Otterbourne, Yew Hill and Rownhams sites. This will allow us to move water between them to where it’s needed the most, protecting water supplies and the environment during a drought.

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What are we doing and why?

 

 

In a drought, we need to make sure there is enough water for everyone and for the environment. To do this, we're transforming the way we source, treat and supply water across Hampshire. As part of our ‘Water for Life – Hampshire’ programme we are building a network of new pipelines to link up our key sites and also allow additional transfers of water from neighbouring water companies. The Southampton Link Main is one of these pipelines.

By doing this, we can reduce how much water we take from the River Test and the River Itchen. This will protect and enhance the county’s rare and sensitive chalk streams, while maintaining supplies for our communities and the local economy.  As well as meaning greater resilience for the area’s water supplies, the new pipeline will reduce the impact of any burst pipes, mechanical failures or sudden leaps in future demand.

The Southampton Link Main is a large project and, so we plan the work in stages as it is complex. We started construction work in 2025 and anticipate that we’ll complete the project in 2028. The works will be delivered in partnership with MGjv, a joint venture between M Group Water and Galliford Try, working closely with landowners and local authorities to keep disruption to a minimum.

As part of this work, we’ve also started tunnelling on key sections of the route. This began in September 2025 and will continue through to May 2026, with the main tunnelling taking place between November and December 2025. We’re using a 6,500kg manually operated Tunnel Boring Machine, named Ancasta by local school children. The machine is one of two being used to create deeper underground sections of the pipeline where trenches aren’t suitable, helping us avoid major roads, railways and sensitive ecological areas.

You may be also interested in:

Andover Link Main: Otterbourne to Andover The Hampshire Grid

Project timeline

Here's a timeline of what we've done so far and how we plan to complete the project. 

1

Autumn/winter 2025

We hope to reinstate the land from the pipelaying work carried out earlier in the year. We'll then start work on the next section of the pipeline. We currently expect the project to be completed in 2028.

2

Spring/summer 2025

We’ll be on site in and around Otterbourne and we'll be working to improve their access. Where required, we'll be creating compounds at various locations to support pipelaying and tunnelling work. We’ll then connect pipework to Otterbourne Water Supply Works and Yew Hill Reservoir near Compton. 

3

Winter 2024

We completed the final design for the necessary pipeline, structures and facilities and submitted the planning applications. We made preparations to start the main construction, making sure we did not disturb local wildlife during bird nesting season at our pipelaying locations.

4

Spring/autumn 2024

We spoke to residents directly affected by the pipeline in Otterbourne and heard their feedback. We plan to hold a general customer event for all residents later this year.

5

Spring 2024

We submitted our request for an EIA Screening Opinion to the Local Planning Authorities, Winchester City Council and Test Valley Borough Council, to confirm requirements for planning consent. They confirmed that the pipeline is Permitted Development.

6

Autumn 2023

We looked at all the data from the surveys to decide which is the best route for the new pipeline. We engaged with the relevant planning authorities and stakeholders to understand which consents we need.

7

Spring/summer 2023

We undertook site investigation works to check the ground conditions, and further environmental and archaeological surveys.

8

Autumn/winter 2022-23

We completed environmental, ecology and archaeological surveys.

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Previous updates

Construction on the project has started. Most of the pipeline will be laid by digging trenches, installing the pipeline and then backfilling them with earth. However, in some areas, it will be installed by digging tunnels deeper underground to avoid disruption to major roads, railway lines or precious ecological sites. 

The route was determined following engagement with local landowners and people who live and work nearby, as well as being informed by environmental and ecological information, surveys and assessment.

Since summer 2024, we have finalised the design for the pipeline and secured the necessary planning permissions and consents. We’ve worked with residents in Otterbourne who are directly impacted by the project.

In late 2024, we invited over 1,600 households to a community drop-in event. At the event our engineers, ecology team, and archaeologists were available to answer questions and share their fascinating discoveries along the pipeline route. Preparation for main construction has already begun, and we’ve taken steps to limit the impact on wildlife and local habitats. We are now preparing to set up working areas along the pipeline route to support construction. 

Since summer 2022, we have undertaken desk based and walk over surveys and investigations of potential pipeline routes.

In summer 2023, we  conducted several excavations at different locations along the two proposed pipeline routes. Some of these were to explore the potential for buried archaeological remains.

Others enabled us to investigate ground conditions and groundwater levels that will affect how we design and construct the proposed pipeline. As part of this work, you may have seen small teams of people excavating in these areas. The land will be reinstated when the excavations are completed.

The information we gain from this work will help us to refine the proposed pipeline route, and our construction techniques. It will also enable us to assess the potential environmental effects associated with the construction and operation of the pipelines. This information was used as part of a formal submission we will made to Winchester City Council and Test Valley Borough Council in Autumn 2023 to determine whether we need to complete an Environmental Impact Assessment of our proposals.

During 2023 we undertook desk based and walkover surveys and investigations of the potential pipeline route.

We conducted exploratory excavations at various locations along the proposed pipeline route. Some of these excavations explored the potential for buried archaeological remains, recording and preserving those uncovered.

Others enabled us to confirm ground conditions and groundwater levels that will affect how we finalise the design and construction of the proposed pipeline. As part of this work, you may have seen small teams of people excavating in these areas. The land will be reinstated when the excavations are completed. 

Contact the team

We’re committed to working with you throughout the construction works in an open and collaborative way.

If our works causes you any concerns, we want to hear from you so we can put it right or improve the way we do things. If you have further queries then please contact Laura Gale, MGjv Customer Liaison Officer on 07706 322744 or email SLMcomms@MGJV.co.uk

Alternatively, please call Southern Water, out of hours, on 0330 3030 368. Just tell us you’re calling about Capital Projects, with Project Reference Number (PRN) 710026, so we can help you more quickly. Or you can email us at capitalcomms@southernwater.co.uk

We would like to thank you for your support and patience whilst we undertake this essential work.

Frequently asked questions

Here are some of your questions which are often asked about this pipeline work. 

We’ll be using a mixture of open-cut (trenching) and no-dig (tunnelling) construction methodology to build this pipeline. 

We make sure that we build most of the pipeline through farmland to keep disruption to a minimum. Some sections of the pipeline will be in more built-up locations, and we will make sure that we work with the community to minimise any impact.

We won’t affect your water supply but you’re likely to notice general construction activity around your community. Some sections of the pipeline will run through more built-up areas, and we will make every effort to minimise disruption to you.

During 2025, we’ll close the far-left corner of Oakwood Park Recreation Ground at the boundary with Otterbourne Water Supply Works. The football pitch and children’s play park will be open as usual for use.

Most of the work will take place on farmland. Where work is in built up areas or near to a road you will see us. At night, we’ll use lighting to make sure we work safely. We’ll place barriers around noisy equipment, and we’ll monitor noise from the works to ensure compliance with local regulations.

You may notice an increase in construction traffic during the works. We have traffic management plans in place to ensure we minimise the impact to the local communities. 

We will have temporary compounds at each of our main sites. There will be car parking for the workers on site, away from residential areas.

Construction hours will fall between 7am and 6pm Monday to Friday, with the following exceptions.

  • During shaft and pit construction we’ll be working 7am-7pm
  • During pipeline excavation we’ll also be working Saturdays 8am-4.40pm
  • During Otterbourne tunnelling activities we plan to work every other weekend.
  • While we are tunnelling under the M3, where we’ll need to work 24 hours a day, 7 days a week.

We will reinstate the land to its original condition after our works.