Planning and Construction

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The reservoir will cost around £340 million to complete and will be funded by payments from Southern Water for water resources over the long term.

It will be the first large-scale new water storage reservoir in the UK since the 1980s and the first time two water companies have worked together in this way to make sure there’s enough reliable water for the future.

Further details on the timeline for the scheme and key aspects of it, such as the new reservoir access routes and pipeline, can be found via the links below. There's also lots of information in the Q&A section of this page.

Planning permission

On 9 June 2021, East Hampshire District Council’s Planning Committee resolved to grant planning permission for Havant Thicket Reservoir. The decision came after councillors in neighbouring Havant Borough gave their support to our reservoir proposals on 3 June 2021, along with our plans for a reservoir pipeline.

Formal planning permission has been granted and the reservoir is due to be completed and operational by 2029. Further details can be found on the links below:

In August 2020, we published our ‘You said, we did’ report, summarising what we people told us during the consultation we held in the spring of that year, as well as setting out how we’re responding to the points raised.

We’ve considered many things as we prepared our updated plan, including:

  • The environmental impact and mitigation
  • Archaeological and cultural heritage on and around the site
  • Traffic impact
  • Water quality and treatment
  • Facilities for the site, including car parking
  • Public access and links to footpaths, cycling routes, bridleways and roads
  • Views of the local communities.

Please note that the reservoir planning application was a ‘hybrid’ proposal - this means part of the scheme was submitted in detail (for example, storage capacity, embankment, access points and viewing areas), and part was submitted in outline (such as, the wetland, control house, visitor centre and car park, access routes and recreational facilities).

The designs for the outline elements of the reservoir are currently illustrative, but within certain parameters - for example, maximum height and footprint or area covered - to ensure that the impacts of the scheme can be properly assessed and the benefits guaranteed.

We’re submitting detailed planning applications for the above elements at the appropriate time, as the reservoir scheme progresses.

Further information can be found in our Havant Thicket Reservoir Design & Access Statement.

The reservoir will cost around £340 million to complete and will be funded by payments from Southern Water for water resources over the long term.

It will be the first large-scale new water storage reservoir in the UK since the 1980s and the first time two water companies have worked together in this way to make sure there’s enough reliable water for the future.

Further details on the timeline for the scheme and key aspects of it, such as the new reservoir access routes and pipeline, can be found via the links below. There's also lots of information in the Q&A section of this page.

Planning permission

On 9 June 2021, East Hampshire District Council’s Planning Committee resolved to grant planning permission for Havant Thicket Reservoir. The decision came after councillors in neighbouring Havant Borough gave their support to our reservoir proposals on 3 June 2021, along with our plans for a reservoir pipeline.

Formal planning permission has been granted and the reservoir is due to be completed and operational by 2029. Further details can be found on the links below:

In August 2020, we published our ‘You said, we did’ report, summarising what we people told us during the consultation we held in the spring of that year, as well as setting out how we’re responding to the points raised.

We’ve considered many things as we prepared our updated plan, including:

  • The environmental impact and mitigation
  • Archaeological and cultural heritage on and around the site
  • Traffic impact
  • Water quality and treatment
  • Facilities for the site, including car parking
  • Public access and links to footpaths, cycling routes, bridleways and roads
  • Views of the local communities.

Please note that the reservoir planning application was a ‘hybrid’ proposal - this means part of the scheme was submitted in detail (for example, storage capacity, embankment, access points and viewing areas), and part was submitted in outline (such as, the wetland, control house, visitor centre and car park, access routes and recreational facilities).

The designs for the outline elements of the reservoir are currently illustrative, but within certain parameters - for example, maximum height and footprint or area covered - to ensure that the impacts of the scheme can be properly assessed and the benefits guaranteed.

We’re submitting detailed planning applications for the above elements at the appropriate time, as the reservoir scheme progresses.

Further information can be found in our Havant Thicket Reservoir Design & Access Statement.

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  • Share We have all noticed the significant problems with the soil from the reservoir’s construction being washed into the Hermitage Stream depositing on its way and then dumping huge amounts of it out into Langstone Harbour I would like to ask: What chemicals are the contractors using on site to reduce the silt problem in the surface water leaving the site? Do the chemicals pose any downstream risks to the ecology of the stream, and do you have a written consent from the Environment Agency to use these chemicals? What controls are there in place to make sure there is not excessive use of these chemicals which would then wash downstream? Are the staff who are administering these chemicals highly trained to do so? Is there careful monitoring at all times? Are the bi products of the treatment which will inevitably end up in Langstone harbour biodegradable? Thank you on Facebook Share We have all noticed the significant problems with the soil from the reservoir’s construction being washed into the Hermitage Stream depositing on its way and then dumping huge amounts of it out into Langstone Harbour I would like to ask: What chemicals are the contractors using on site to reduce the silt problem in the surface water leaving the site? Do the chemicals pose any downstream risks to the ecology of the stream, and do you have a written consent from the Environment Agency to use these chemicals? What controls are there in place to make sure there is not excessive use of these chemicals which would then wash downstream? Are the staff who are administering these chemicals highly trained to do so? Is there careful monitoring at all times? Are the bi products of the treatment which will inevitably end up in Langstone harbour biodegradable? Thank you on Twitter Share We have all noticed the significant problems with the soil from the reservoir’s construction being washed into the Hermitage Stream depositing on its way and then dumping huge amounts of it out into Langstone Harbour I would like to ask: What chemicals are the contractors using on site to reduce the silt problem in the surface water leaving the site? Do the chemicals pose any downstream risks to the ecology of the stream, and do you have a written consent from the Environment Agency to use these chemicals? What controls are there in place to make sure there is not excessive use of these chemicals which would then wash downstream? Are the staff who are administering these chemicals highly trained to do so? Is there careful monitoring at all times? Are the bi products of the treatment which will inevitably end up in Langstone harbour biodegradable? Thank you on Linkedin Email We have all noticed the significant problems with the soil from the reservoir’s construction being washed into the Hermitage Stream depositing on its way and then dumping huge amounts of it out into Langstone Harbour I would like to ask: What chemicals are the contractors using on site to reduce the silt problem in the surface water leaving the site? Do the chemicals pose any downstream risks to the ecology of the stream, and do you have a written consent from the Environment Agency to use these chemicals? What controls are there in place to make sure there is not excessive use of these chemicals which would then wash downstream? Are the staff who are administering these chemicals highly trained to do so? Is there careful monitoring at all times? Are the bi products of the treatment which will inevitably end up in Langstone harbour biodegradable? Thank you link

    We have all noticed the significant problems with the soil from the reservoir’s construction being washed into the Hermitage Stream depositing on its way and then dumping huge amounts of it out into Langstone Harbour I would like to ask: What chemicals are the contractors using on site to reduce the silt problem in the surface water leaving the site? Do the chemicals pose any downstream risks to the ecology of the stream, and do you have a written consent from the Environment Agency to use these chemicals? What controls are there in place to make sure there is not excessive use of these chemicals which would then wash downstream? Are the staff who are administering these chemicals highly trained to do so? Is there careful monitoring at all times? Are the bi products of the treatment which will inevitably end up in Langstone harbour biodegradable? Thank you

    Sally asked 5 months ago

    Thank you for contacting us and apologies for not providing you with our answers sooner.

    We have taken the issue of silt run-off extremely seriously and appreciate the opportunity to address your questions.   

    To share some context, we have been working on the reservoir site since 2021 and have a good track record of managing surface water run-off by building channels called ‘grips’, and using natural materials such as hay bales to slow down the flow of water and silt screens to filter out sediment.

    With the increased construction activity on site in 2023, we took advice from national expert advisers in surface water management. Following these discussions, we significantly improved the site drainage system, with a considerable increase in the number of silt screens, larger drainage channels with rock-filled dams to slow down the flow and settlement ponds for water to be held in so that clay and silt could settle before clean surface water ran off downstream.

    Unfortunately, we had exceptionally wet weather over the winter and spring and while the measures we installed were partially effective, this high level of rainfall exceeded the capacity of our surface water management system.

    The main problem that we came across, other than the sheer volume of rainfall, is the fact that the silt from the clay is so fine that it cannot settle using conventional means.

    We therefore took further steps to improve the quality of surface water leaving the site. We sought the help of external experts to help us understand what can be done and have been working very closely with the Environment Agency.

    Additional, lined channels were created to direct surface water to four further settlement ponds, more than doubling our water storage capacity to over 23,000m3 (equivalent to over nine Olympic-sized swimming pools). We brought pipes and pumps to the site, so that during heavy rain we can pump water from the streams that enter the site to the north, through pipes that cross the whole site and discharge it directly into streams to the south of the site. In this way, much of the water will not pick up silt or clay from the construction areas.

    We introduced a coagulation system, similar to potable water treatment, to separate the silty material from the water. This required special permits and licensing. Proprietary silt treatment machines are now installed to remove silt from the water before it leaves the site. As a result of all of this work, we have seen improvements.

    To answer your specific questions:

    What chemicals are the contractors using on site to reduce the silt problem in the surface water leaving the site?  

    Flocculants and coagulants are industry accepted chemicals that are added to the water. They are designed to separate liquids from solids and are used throughout the construction and water treatment industries to prevent site pollution.

    Do the chemicals pose any downstream risks to the ecology of the stream, and do you have a written consent from the Environment Agency to use these chemicals? 

    When flocculants and coagulants are used correctly by specialists, there is no impact to the environment. Regulators are generally supportive of the use of flocculants, provided that other means for controlling silt from site have been trialled and deemed not sufficient. Relevant applications have been made to the Environment Agency which outlines the treatment processes used at the Havant Thicket Reservoir site.   

    What controls are there in place to make sure there is not excessive use of these chemicals which would then wash downstream?

    Monitoring of the chemical levels is continuous, and dosing levels automatically changed as required. Dosing is controlled within the specialist proprietary treatment system. Dosing is automatically stopped to prevent exceedances of dosing parameters. Water flow through to the treatment plant is also stopped.

    Are the staff who are administering these chemicals highly trained to do so? 

    Yes. Future Water Ltd has contracted specialist water filtration companies and implemented trials, testing suitable water filtration systems to achieve the best possible mitigation measures to reduce silt entering the water course, while ensuring no additional risk to the environment.

    Is there careful monitoring at all times?

    Yes. The monitoring of water silt treatment using flocculant chemicals are monitored regularly to ensure the acrylamides do not exceed the drinkable Water Environment Quality Standard Directive (EQS) limit of 10ug/l.

    Are the by-products of the treatment, which will inevitably end up in Langstone Harbour. biodegradable? 

    Independent water tests have shown between EQS, 0.1 to 0.5 Ug/L, post-treatment on site, so no by-products are expected at Langstone Harbour.

    The Future Water monitoring regime includes continual sampling and analysis to monitor any potential deviations from acceptable levels, ensuring any issues are promptly addressed. Future Water remain transparent at all times and maintain records of all turbidity and chemical test readings.

    We hope our responses reassure you that the project is implementing appropriate measures to minimise the impact on local watercourses and the environment.

    Havant Thicket Reservoir is an environmentally led project that will help to protect internationally rare chalk streams in Hampshire, as well as providing a new green leisure facility for the local community.

    The scope of the project is not just limited to the reservoir site, and we are committed to delivering a net gain to wildlife habitats for the local area. Over the coming years we are improving over 5.6km of local water courses, including Hermitage Stream, to improve the overall quality of wildlife habitats in the area.   This will include creating new ephemeral streams, ponds, and restoring some existing streams by removing concrete. This is just one example of our work which will increase biodiversity for the area as a whole.

    If you have any further questions, comments, or concerns, please do not hesitate to contact us.

    Kind regards,

    Ruari Maybank,

    Havant Thicket Reservoir Project Director,

    Portsmouth Water.

  • Share Who is the designer rather than the contractor?50 years ago l worked on the Brenig where Binnies were the designers. I worked for Sir Lindsay Parkinson subsequently Faircloughs, the contractors on Facebook Share Who is the designer rather than the contractor?50 years ago l worked on the Brenig where Binnies were the designers. I worked for Sir Lindsay Parkinson subsequently Faircloughs, the contractors on Twitter Share Who is the designer rather than the contractor?50 years ago l worked on the Brenig where Binnies were the designers. I worked for Sir Lindsay Parkinson subsequently Faircloughs, the contractors on Linkedin Email Who is the designer rather than the contractor?50 years ago l worked on the Brenig where Binnies were the designers. I worked for Sir Lindsay Parkinson subsequently Faircloughs, the contractors link

    Who is the designer rather than the contractor?50 years ago l worked on the Brenig where Binnies were the designers. I worked for Sir Lindsay Parkinson subsequently Faircloughs, the contractors

    Bert Simmons asked almost 2 years ago

    Hi there, the design for the reservoir has been developed by Atkins to date, with Future Water MJJV now taking this on as the appointed contractor for the reservoir construction. Future Water is a joint venture between Mackley and Jones Brothers, which have over 150 years of civil engineering experience between them. Atkins will still be involved, to provide input and oversight into the final design work.

    For the reservoir pipeline, Ward & Burke have been appointed to design and build this.