Below is a list of common questions about the tidal lagoon proposals.  If you have any further questions, please do contact us.


Why consider tidal lagoons?

Our island has an abundant and natural tidal energy resource that can be harnessed through tidal lagoons.

Tidal lagoons offer a low cost, renewable source of energy that is capable of providing significant amounts of electricity. The UK is currently highly dependent on fossil fuels but this resource is dwindling. Furthermore, sixteen power stations are coming to the end of their lives between now and 2023, representing a quarter of the UK’s total generating capacity. We urgently need to look at alternative energy sources to meet the UK’s future demands, and to address the legal requirement to reduce carbon emissions.

Since tides are predictable and reliable, with time times varying according to location, tidal lagoons can offer a near continuous power supply, reducing significantly the cost associated with the need for ‘topping up’ with electricity produced from fossil fuels.

What makes Swansea Bay a good site?

The Severn Estuary holds the second highest tidal range in the world. Within the estuary, Swansea Bay benefits from a tidal range of up to 10.5m, which makes it ideal for renewable electricity generation.

In addition to a high tidal range, Swansea Bay has a shallow seabed gradient, which reduces the necessary height of the proposed lagoon seawall (and therefore reduces construction costs) compared to sites with a deeper seabed. The site is also in close proximity to high population centres, which means there will be negligible energy loss through transmission.

The site’s backdrop and connection point of Swansea Docks means that there will be minimal disruption to local traffic and transport during construction. As far as possible, the main bulk of the material for the lagoon wall will be transported by sea. Furthermore, the dockland setting creates opportunities for seafront regeneration, leisure and improved accessibility.

What is a tidal lagoon, and how does it work?

A tidal lagoon is a man-made breakwater wall in the sea that generates power from the motion of the tides. The tallest/deepest part of the wall houses a number of hydro-turbines, which generate electricity when water flows past the turbine blades.

The flow of water past the blades is managed by sluice gates. When the flood tide starts to come in, the sluice gates are closed and the sea outside the wall is held back and rises around the lagoon. This creates a difference in water levels on either side of the seawall, which is known as ‘head’. Once a sufficient head height is reached the sluice gates are opened and water flows through turbines into the lagoon to generate electricity.

The sluice gates are then closed and this process occurs in reverse on the ebb tide: the water is held back inside the lagoon, creating a head height relative to the receding tide in the Bay. The sluices are then opened, releasing the lagoon waters through the turbines back into the Bay.

High and low tides occur inside the lagoon approximately two hours after they occur outside the lagoon, but the height of those tides remains broadly the same as today. Electricity generation will happen on both the flood (in-coming) tide and the ebb (out-going) tide, four times a day in total, for approximately 14 hours per day.

What do we mean by renewable, sustainable and low carbon?

Renewable means that the tide, and therefore the possibility of generating energy using the tide, will not run out. The energy produced by fossil fuels is non-renewable and relies on finite and ever-decreasing amounts of coal, oil and gas.

Sustainable means that the Project has the capacity to endure and support itself in the long term. The tidal lagoon will do this by contributing to the economy, society and to the environment. The tidal lagoon will help to create a vibrant waterfront economy, providing new jobs and increasing tourism, as well as creating recreational and educational opportunities for the local community. It will also benefit the environment by saving 236,000 tonnes of CO2 emissions per year through its generation of renewable energy. For more information see the question on ‘What are the benefits of a tidal lagoon for local communities?’

Low carbon means that tidal lagoons can generate electricity without incurring a high level of CO2 emissions.  The construction of the tidal lagoon requires both materials and energy. However it is estimated that once operational, the CO2 emissions that it saves within the first four years of operation will balance out those produced during construction. For more information see the question ‘What carbon emissions are created in the development of a lagoon?’

Detailed information on the work carried out regarding  carbon footprint and the sustainable aspects of the lagoon is provided in Volume 3 of the Environmental Statement, Appendix 5.1 Sustainability: Carbon Balance, available here

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About the lagoon

Where exactly is the lagoon site?

The proposed tidal lagoon is located in the central part of Swansea Bay, directly south of Swansea Docks. It will form a 9.5 km-long, U-shaped, seawall starting from the entrance to the River Tawe adjacent to Swansea Dock (Swansea Port) running 3.5 to 4 km out to sea before curving back to re-join land adjacent to Swansea University’s new Bay Campus (SUBC). Access to the Project (and supporting onshore facilities) will be from Fabian Way via these two (Swansea Port and Campus) landfalls. The lagoon sits between the two main rivers in the Bay, the Tawe and the Neath, which are free to flow either side of the lagoon. A location map can be seen on the bottom ribbon of our homepage.

What will it look like?

The hydro turbines are permanently submerged, out of sight, so the resulting view is of a U-shaped harbour wall with one section of concrete casing.  We are proposing to build a 9.5 km-long wall enclosing 11.5 km2 of foreshore and seabed. At low water there will be a maximum of around 12 m of visible wall and at high water it will be about 3.5 m. As a guide, the lagoon seawall is not dissimilar in height to that of Swansea Docks' existing eastern breakwater wall on the River Tawe.

Our interactive 3D model provides an easy-to-interpret overview of the Project and its surroundings. You can manipulate the angle of the image to see what the lagoon will look like from a perspective important to you, and view it at high and low tide, day or night.

We have also produced a full set of computer generated images of the proposed lagoon, which are set against actual photographs of Swansea Bay. The goal of these photomontages is to show ‘visually verified’ (i.e. accurate and to scale) ‘before’ and ‘after’ images at low, mid and high tides. This is done from a range of viewpoints around the Bay agreed with local planning authorities and other regulators. The photomontage work is provided as part of the Environmental Impact Assessment (EIA) and is viewable on our website. Please note that these photomontages have been provided on our website as a quick reference only, and are designed to be viewed in a specific manner on a specified paper size. You can view the images at the correct size at any of the locations listed here.

How much energy will the tidal lagoon produce?

We are planning to install 16 turbines, each with a maximum output of 20 megawatts (MW), giving a maximum generating capacity of 320 MW from which we will be able extract a net annual output of approximately 495 gigawatt hours (GWh) or 495,000MWh.

This is enough to power 155,000 homes and is therefore more than the annual domestic electricity use of Swansea (109,000 households). It is equivalent to about 90% of the annual domestic use of Swansea Bay (173,000 households) and 11% of the annual Welsh domestic use (1,369,000 households).

What carbon emissions are created in the development of a lagoon?

The exact carbon footprint of creating the lagoon can only be identified once final designs and quantities of materials are confirmed.  We estimate that the construction and installation of the lagoon will produce at least 642,000 tonnes of CO2 emissions during construction.  Once operating, we estimate that the lagoon will save at least 236,000 tonnes of CO2 every year, which is roughly the same as the emissions produced by 81,000 cars. This means the lagoon will balance out the CO2 emissions produced during its construction to become carbon neutral within four years of its 120 year lifespan. After this the lagoon will be saving CO2 emissions.

Detailed information on the work carried out regarding carbon footprint and the sustainable aspects of the lagoon is provided in Volume 3 of the Environmental Statement, Appendix 5.1 Sustainability: carbon Balance, available here.

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What effect will there be on the environment in Swansea Bay?

We recognise that any development of this size will have an effect on its environment. A process of Environmental Impact Assessment (EIA) has been carried out over 2 years, and the outcomes of the wide array of assessments undertaken to inform this process have been submitted to the Planning Inspectorate and Natural Resources Wales as part of our respective applications. These outcomes are contained in a 4,000 page document called the Environment Statement (ES), which can be viewed here. A Non-Technical Summary of this document is available here in English and Welsh.

The EIA is a standard process for major projects such as this. We commissioned independent experts to conduct detailed studies in order to understand the potential impacts of the lagoon locally and further afield; during construction, operation and decommissioning; and in combination with other proposed developments in the area. From this understanding, the lagoon design has incorporated measures to minimise its effects, and to create positive benefits, wherever possible.

The EIA has been central to the development of the Project and we have aimed to be as comprehensive, collaborative and transparent as possible. In late 2012, we established the baseline situation across a range of environmental topics. This represents the current state of the environment, against which we can measure and model any impacts of building a tidal lagoon. The Preliminary Environmental Impact Report (PEIR) and its Non-Technical Summary (NTS) can be viewed here and were available at statutory consultation carried out from 4 July to 5 August 2013.

TLSB presented the draft results of the EIA (following consultation carried out in the summer of 2013) to the public and key stakeholders at an event at the Liberty Stadium on 17 October 2013. A draft of the ES was then sent to select key stakeholders for consultation in November/December 2013. The final ES was submitted in February 2014 as a core part of the application documents, and will be a central pillar in the determination of the applications.

We are committed to minimising any adverse impacts through the EIA process and by amending our design appropriately where possible. One of our priorities is to look for opportunities to provide positive impacts for the ecology and environment of Swansea Bay.

Have you considered the impact on sands and sediment movement in the Bay?

Swansea Bay is a highly dynamic system of sand and sediment flows. The lagoon’s effects on this system during construction, operation and decommissioning are a key part of the EIA. It is important to us that our development has minimal impact on sand/sediment movement in the Bay, as well as surrounding areas. Over the last two years, we have studied 14 different lagoon designs and multiple turbine configurations in our efforts to find the best solution with regard to energy generation, environmental impact and cost viability. The resulting preferred design is shown on our homepage.

As part of this work, a hydrodynamic model has been developed that uses recent and historic data to depict the flow of water in the Bay. This model has been used to assess the impact of a tidal lagoon structure on the water flows and sediment processes around the Bay, and extending out into the Severn Estuary. We have used independent expert modellers who communicated the results to our engineering team, who then adjusted the design to minimise the impact where possible.

The Non-Technical Summary of the Environmental Statement provides basic information on all elements of the Environmental Impact Assessment including the issues above.  Detailed information on this assessment is provided in Volume 1 Chapter 6 of the Environmental Statement, Coastal processes, sediment transport and contamination, available here.

What is the lagoon’s impact on bathing, beaches & water quality?

There are two designated bathing beaches within Swansea Bay (Aberafan Sands and Swansea Bay), which the Project avoids so as to preserve these amenities. Studies suggest there will be no impact on bathing beaches outside Swansea Bay. The site selected for the lagoon is on an intertidal area, which is not a designated bathing area, and which is predominantly backed by the Swansea docklands. We hope visitors to the lagoon will swim and enjoy watersports within its walls where access was previously difficult or unsafe.

Swansea Bay faces complex water quality issues related to its major rivers, waste water facilities and industrial heritage for example. Water quality within the Bay is key to the enjoyment of the area and the local economy, and to our ambitions for leisure use of the lagoon. It is important to us that our development has minimal adverse impact on water quality in the Bay, as well as surrounding areas. The lagoon’s effect on water quality during construction, operation and decommissioning is a key part of the Environmental Impact Assessment (EIA), and the following areas have been assessed:

  • Water quality at the designated bathing beaches in the Bay and surrounding area
  • Water quality at the designated shellfish monitoring points and shellfish waters, and
  • Water quality with respect to the objectives of the EU Water Framework Directive.

The EIA used a water quality model already approved for use in Swansea Bay by Dwr Cymru Welsh Water. An independent team of experts has applied the model to the 14 lagoon designs, and to various options for water quality treatment. As for other parts of the EIA, the results were communicated to our engineering team who adjusted the design to minimise the impact where possible. Results presented in our ES show that, with installation of additional storm water storage and/or treatment at Swansea Waste Water Treatment Works, we may have a net positive impact on water quality in the Bay.

The Non-Technical Summary of the Environmental Statement provides basic information on all elements of the Environmental Impact Assessment including the issues above.  Detailed information on this assessment is provided in Volume 1 Chapter 7 of the Environmental Statement, Marine Water Quality Assessment, available here.

What are the likely effects on fish and marine mammals?

Although not a major fishing port, commercial and recreational fishing is important to local residents as well as to the local economy – and many people are concerned about ecology for its own sake. Direct and indirect impacts on fish and marine mammals have been assessed for the construction, operation and decommissioning phases of the lagoon. We have consulted experts and local-interest groups to gain further input into our assessment approach and ensure we have considered all possible impacts.

Assessments including noise/vibration disturbance, changes in habitat and changes in water quality were carried out to understand the impact. The significance of these potential impacts has been presented in our ES, and where possible we have identified measures to minimise any potential impacts.

Detailed fish computer modelling was undertaken for key species, including behaviour modelling (the likelihood of the various fish species coming into the lagoon area) and entrainment modelling (the effect on any fish that pass through the turbines). The size of the turbines (7-8m in diameter) mean that there will be large gaps through which fish can pass, and the modelling has been carried out to understand the extent of this. Furthermore, the use of sluice gates will allow free passage of fish in and out of the lagoon in the latter part of the tidal cycle.

There will be some disruption to local fishermen, especially to any who ‘pot’ within the Project area. During operation, the lagoon would not be accessible to any fishing vessels which currently use this area of the Bay and therefore this would result in a loss of some fishing grounds within the lagoon footprint.

We are also investigating the potential for developing mariculture. The formation of a new rocky reef as part of the Project would provide habitat and encourage colonisation by local marine species.  Research indicates there could be opportunities for the reintroduction of the native oyster as well as for fostering habitats for lobsters and kelp. We are continuing to investigate these benefits in association with local experts.

Detailed information on the above can be found in the following sections of the Environmental Statement:

Volume 1 Chapter 9 Fish, including recreational and commercial fisheries

Volume 1 Chapter 10 Marine mammals

Volume 1 Chapter 8 Intertidal and subtidal benthic ecology and Volume 1 Chapter 22 Economy, tourism and recreation – details mariculture proposals

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Engineering & technology

Has this technology or construction method been used before?

The design concepts, construction techniques and turbine technology have all been used independently in other applications around the world, but they have never been brought together in one development. As such the tidal lagoon has the advantage of using tried-and-tested technologies in a low risk proposal while still being a pioneering project. The proposal will be the world’s first purpose-built, tidal lagoon power plant.

The lagoon wall will comprise a UK standard sand-core breakwater or rock bund. There are two design options covered by the application for a Development Consent Order.  The first uses geotextile material (woven plastics) to encase locally-dredged sandy material, which has been used in many marine construction schemes worldwide, from highway bridge foundations to coastal defences. The second is a quarry run, rubble mound, traditional breakwater, similar to many seen in coastal defence schemes and harbour walls. 

The hydro turbines themselves will be the same ‘low head’ operating mechanisms that have been used for decades in river hydro-electricity schemes and the few existing tidal barrages.

The Non-Technical Summary of the Environmental Statement provides basic information on the technological and construction elements of the project.  Detailed information on these areas is provided in Volume 1 Chapter 4 of the Environmental Statement, Project description, available here.

How do geotextiles work?

Geotextiles are filled with dredged material from within the lagoon footprint, largely sands and gravels, which are pumped in hydraulically. The water from this hydraulic pumping process is then forced out through the permeable geotextile membrane leaving very strong, compact, sand-filled tubes which form the core structure of the wall. The tubes are positioned in a pyramid shape and the gaps between the tubes are levelled out with more dredged material and sand to create an even surface.  The structure is covered with another layer of geotextile and large rock armour to protect against degradation.

Will the lagoon really generate electricity 365 days a year?

Yes it will. There will be obligatory downtime for maintenance of the turbines to ensure they are operating optimally, but our design allows each turbine to be isolated and maintained individually while the other turbines continue to generate.

Will the lagoon connect into the local grid or be independent?

Due to the scale of the power generated by the plant the connection point will be direct into the national grid at a 275kV connection. The cable route is expected to run entirely underground.

The Non-Technical Summary of the Environmental Statement provides basic information on the grid connection elements of the project.  Detailed information on the grid connection is provided in:

Volume 1 Chapter 4 of the Environmental Statement, Project description, and

Volume 7.1 of the DCO application documents: Cable and Grid connection Statement

Will construction take place from sea or land?

Construction will take place from both sea and land. The greater proportion of the work on lagoon walls and turbine housing will be done at sea, minimising the work and disruption on land. We plan to use Swansea Port’s infrastructure for onsite construction areas and access.

There is a good supporting road transport network into Swansea Port, as well as good seaward access. As such there are both land and marine options for bringing materials to the site. The Environmental Impact Assessment (EIA) has assessed the potential effects of the additional traffic on the roads in terms of access routes, potential disturbance to existing road users, and effects of additional traffic on air quality.

The Non-Technical Summary of the Environmental Statement provides basic information on the construction process proposed for the project. Detailed information is provided in:

Volume 1 Chapter 4 of the Environmental Statement, Project description, and

Volume 6 Appendix 4.1 Construction Environmental Management Plan (CEMP)

Are local companies being used to develop or build the lagoon?

Several local and South Wales organisations are already involved in the development of the Project. Our company ethos is to use local businesses as much as possible for the manufacture and assembly of the component parts.  From consultation with local industry representatives we believe much of the following could be sourced within a small radius of the site: turbine housings, sluice gates, flood doors, electrical controls, hydraulics, precast concrete components, visitor centre and ancillary building components.  The proposed investment for these components will be significant.

TLSB has devised a supply chain and procurement strategy which is under ongoing review. This strategy has involved extensive engagement with relevant stakeholders.

Many of the jobs created by TLSB will be for the duration of the Project (approximately three years) with a mix of medium and long term employment opportunities for workers. A procurement strategy is currently being developed which will focus on maximising local procurement through working with the Tidal Lagoon Industry Advisory Group as well as the following organisations:

i. Welsh Government;

ii. Confederation of British Industry;

iii. Institute of Directors;

iv. CCSC and NPTCBC;

v. Chambers of Commerce in Swansea, and South and West Wales;

vi. Local further education facilities, such as Neath Port Talbot College; and

vii. Local organisations working with long term unemployed, such as Jobs Growth Wales.

The strategy will be given high importance and, so far as European law permits, focuses on the following:

a) Local employment;

b) Local / UK supply and manufacture;

c) Training and up-skilling of the local workforce; and

d) Opportunities for long-term unemployed.

Where specialist suppliers are based outside the UK (e.g. turbine manufacturers), TLSB is working with those suppliers in order to maximise the potential in developing a supply chain within Wales and the UK to meet their needs and achieve TLSB’s target spend of 50 per cent in Wales, and 65 per cent in the UK.

Detailed information on the above can be found in the Volume 8 of the planning application: 8.2 Planning Statement: Appendix 3 Outline supply chain strategy.

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Community benefits

What are the benefits of a tidal lagoon for local communities?

Our aim is to create a power plant that provides something positive for everyone who lives in the vicinity of Swansea Bay. We hope that the lagoon will be viewed and used as a core local amenity and tourist attraction. We have a strategy for it to become an art and cultural icon and major Welsh recreation and sports centre. Besides renewable energy generation our plans for the lagoon include:

Recreation and tourism

  • Cycle paths and promenade walkways.
  • Recreational fishing opportunities, including platforms and wall access.
  • Visitor Centre to cater for the estimated 70 to 100,000 visitors per year.


  • Sports training facilities for local and national use.
  • National and international sporting events in sailing, open water swimming, triathlon and rowing.

Education and art

  • Education programmes and resources to help young people develop their skills and knowledge around environmental themes.
  • An arts programme to create a forum for artists, scientists and communicators to stimulate the production of local community art.

Job creation

  • Up to 1,900 jobs will be created and sustained during the construction of the lagoon
  • About 35 jobs will be created in quarrying stone for the seawall
  • Approximately 31 permanent jobs will be created in operations and maintenance
  • Approximately 50 permanent jobs will be created in the visitor facilities.

Will this help the coastal regeneration plans for South Wales?

The Project holds the potential to form a cornerstone development of the Swansea Bay City Region and to stimulate a vibrant waterfront economy. Our ambition is that the substantial lagoon investment will bring positive regeneration benefits to Swansea Bay and South Wales.

The Non-Technical Summary of the Environmental Statement provides basic information on all elements of the Environmental Impact Assessment including the issues above. Detailed information on this assessment is provided in Chapter 22 of the Environmental Statement, Economy, tourism and recreation, available here.

Further details of the art and education programmes are provided in Volume 8 Planning Statement Document 8.2, Appendices 1 and 2

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How much will the Project cost?

The Project will cost up to £15 million to achieve a development consent order, with an overall project cost of about £1 billion to achieve construction and connection to the national grid.

Who is funding the Project?

Private investment will be used to develop the tidal lagoon. Equity shareholders in the development phase include the local community, Tidal Lagoon Power management, high net worth individuals and corporations.  Further information on the investment opportunity is available here.

How will it affect my electricity bill?

One of the Project’s objectives is to enable a low cost, locally generated, electricity tariff for residents around the Bay area. Given existing legislation this is not straightforward to achieve, but it is one of our main goals, and a precedent has been set for cheaper energy for homes within a set radius of a wind farm in Cornwall. We are exploring how we can follow this lead within current and proposed legislation.

Are you supported by a government incentive scheme?

Tidal range technologies (including tidal lagoons) are able to apply for a Contract for Difference (CfD), which is this Government’s mechanism for supporting low carbon power generation. For more information about the economics of tidal lagoons, watch a video based upon a study by consultants, Poyry, here.

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Timelines & consultation

The project timeline can be found here.

How long have you been working on the Project?

Our development team has been working on the Project since early 2011 to assess its feasibility and to optimise the construction methods, energy output, and environmental benefits of the scheme. Consultation has taken place with many statutory consultees, and the proposals have been presented to more than 440 local stakeholders, as well as over 1,800 members of the public. All have been invited to feed back their thoughts, ideas and concerns to the team.

The Non-Technical Summary of the Environmental Statement provides basic information on all elements of the Environmental Impact Assessment including the consultation carried out. Detailed information on the consultation carried out in relation to the project is provided in Volume 5 of the Planning Application, available here

When will the lagoon be connected to the grid?

The earliest possible date to connect to the grid is early 2019 and that is our goal. We strongly believe that renewable energy is an urgent matter of national importance and should be considered in the shortest possible timeframes without risking due diligence on a major proposal.

How long will construction take?

Our engineering partners have set out a programme for the wall construction that will last for approximately thirty six months.

How did TLSB respond to the pre-application consultation?

Responses to pre-application consultation were a key factor in the shaping of the scheme. During our non-statutory consultation we spoke to many statutory consultees, more than 230 local stakeholders, and over 400 members of the public (at events we held around the Bay in April 2013). Statutory consultation with statutory consultees and the general public was carried out from 4 July to 5 August 2013.

Every comment received during the statutory consultation was considered before we submitted our application for development consent, and this is set out in our detailed Consultation Report. The Planning Inspectorate would not have accepted our application for consideration had we not carried out an adequate consultation and shown how we have taken into account responses in order to shape the scheme.

The Non-Technical Summary of the Environmental Statement provides basic information on all elements of the Environmental Impact Assessment including the consultation carried out. Detailed information on the consultation carried out in relation to the project is provided in Volume 5 of the Planning Application, available here

What is the planning process? Who decides if consent is granted?

The scale of the Project and its energy output qualifies it as a ‘Nationally Significant Infrastructure Project’ (NSIP) for which a different planning system applies to the one most people are familiar with. The decision to grant consent is not made by the local authority (City & County of Swansea or Neath Port Talbot County Borough) but by the Secretary of State for Energy & Climate Change, at the end of a process managed by the Planning Inspectorate. A marine license is also required from Natural Resources Wales on behalf of the Welsh Government. Advice notes about the planning process can be read on the planning inspectorate's website http://infrastructure.planningportal.gov.uk/legislation-and-advice/advice-notes/. Advice notes 8.1 to 8.5 provide an overview of the process and how to have your say.    

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Further information

Where can I find out more information?

If you have specific questions or ideas that you feel would be useful to the development team at this stage, you can write to us at: info@tidallagoonpower.com.

If you would like information about the process then you can email us on the above address. You can also seek procedural advice from the Planning Inspectorate on 0303 444 5000 or by emailing: SwanseaTidal@infrastructure.gsi.gov.uk.

How can I receive regular updates on progress?

You can register for project updates and newsletters here. There will be regular communications issued throughout the progress of the project and we will use all signed-up email addresses to update stakeholders as news becomes available.  To view all previous newsletters please click here.

Can you come and talk to my organisation about the Project?

We would be happy to arrange a meeting or presentation for your organisation if the resource is available. Please email us at info@tidallagoonpower.com with full details of your organisation (whatever its size and purpose) and we will do our best to assist you.

3D Model

Download and explore an interactive 3D model of the lagoon.

Interactive 3D Model

The Project

Click on the image below to view the project film.

Second Map


See how the lagoon will bring a range of positive benefits.



View our Planning Application.