Havant Thicket Reservoir

Securing the South East’s Water Future

Havant Thicket Reservoir, located in Hampshire, is a key infrastructure project being delivered through a groundbreaking partnership between Portsmouth Water and Southern Water. Designed to help secure long-term water supplies for the South East, this reservoir is essential for supporting a region already facing serious water stress.

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A Landmark Development

This will be the first new reservoir constructed in the South East since the 1980s, marking a major step forward in modernising the UK’s water infrastructure. Future Water MJJV, a joint venture between Mackley and Jones Bros, has been appointed by Portsmouth Water to lead the main design and construction phases of the project.

Protecting Precious Water Sources

The reservoir will play a crucial role in reducing reliance on sensitive natural sources such as the chalk streams of the River Test and River Itchen, helping to preserve these valuable ecosystems for future generations.

Meeting the Challenges Ahead

With climate change and a growing population putting increasing pressure on the UK’s water network, the Government is urging water companies to invest in sustainable solutions like new reservoirs and regional water transfers. Havant Thicket is part of this forward-thinking strategy- helping to secure resilient, reliable water supplies while also reducing leaks and encouraging more efficient water use.

Key Facts: Havant Thicket Reservoir

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    Project
    Location

    • Situated between Leigh Park, Havant, and Rowlands Castle in East Hampshire.
    • Total site area: 160 hectares.
    • Dimensions: Approximately 1.7 km east–west and 800–1,200 m north–south.
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    Water Capacity
    & Supply

    • Total storage capacity: 8.7 billion litres of water.
    • Expected daily supply (under current approved plans): 21 million litres per day.
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    Engineering
    & Design

    • Main embankment length: 2.8 km
    • Main embankment height: 22 metres.
    • Smaller embankments will create a separate wetland area on the northern side.
    • Impermeable clay core, with sloped clay shoulders for stability.

Our Responsibilities

Future Water MJJV is a collaborative joint venture between Mackley and Jones Bros Civil Engineering UK, formed specifically to deliver the design and construction of the Havant Thicket Reservoir. However, our role extends well beyond construction — we are also responsible for leading on health and safety, environmental management, quality assurance, communications, and social value, ensuring a holistic and integrated approach to delivering this major infrastructure project.

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    Design &
    Engineering

    • Developing the reservoir’s detailed technical and structural design.
    • Integrating sustainable design practices to protect local ecosystems and watercourses.
    • Engineering essential components, including impermeable clay embankments and newly created wetland areas.
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    Construction & Delivery

    • Constructing the reservoir’s main embankments using site-sourced clay materials.
    • Building associated infrastructure such as access roads, pipelines, and control structures.
    • Delivering environmental mitigation works, including the formation of a new wetland to enhance biodiversity.
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    Health, Safety
    & Wellbeing

    • Maintaining the highest standards of health and safety across all phases of the project.
    • Prioritising the wellbeing of all staff, both on-site and off-site, through proactive health, safety, and support measures including Tool Box Talks.
    • Promoting a positive safety culture that empowers individuals and teams to work safely and responsibly.
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    Sustainability &
    Environment

    • Embedding sustainability and climate resilience into every stage of the design, engineering, and construction process.
    • Working with key environmental stakeholders to ensure responsible delivery that protects and enhances the local ecosystem.
    • We have translocated over two thousand reptiles, macroinvertebrates, and aquatic plants (macrophytes) to ensure their protection.
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    Community Engagement
    & Social Value

    • Collaborating closely with regulatory bodies to ensure the project delivers lasting positive benefits for the local area.
    • Supporting career development in the construction and engineering sectors by providing presentations, workshops, and work experience opportunities for college and university students.
    • Creating local employment opportunities that foster economic growth and skills development within the surrounding communities. We also promote alternative pathways into construction careers.
    • Actively engaging with local schools, residents, and community groups to raise awareness of the project’s goals and benefits.
    • Educational visits to the reservoir site to showcase this vital infrastructure project to children and the wider community.
    • On site, accredited, training facilities providing certification for plant operatives
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    Planning

    • Effective and detailed project planning is at the heart of everything we do. From tender stages and design through to long-term construction scheduling, our planning team ensures that all activities are meticulously mapped out and aligned with project milestones, scope, and compliance with JCT/NEC contracts.
    • Our planners work collaboratively with all stakeholders including clients, consultants, and supply chain partners to proactively manage and mitigate risks while identifying opportunities to improve efficiency throughout the project lifecycle.
    • We integrate our work across every stage of the project from early procurement strategies to final delivery ensuring that each activity is logically sequenced, resourced, and aligned with key milestones. This proactive approach helps maintain programme momentum, prevents avoidable delays, and supports smooth, coordinated delivery from start to finish.