Energy and Climate Change CommitteeSupplementary written evidence submitted by Hafren Power

1. Details of plans for pre-Bill consultation

Hafren Power is actively developing a plan to consult with all stakeholders and especially with the local communities around the proposed barrage site. Hafren Power has appointed two agencies to commence work on this, one in South Wales and one in Bristol. The first stage will be to identify all the relevant local stakeholders and then meet with as many as possible. The purpose of these initial meetings will be to hold a “consultation on consulting”, ensuring that when we move into a formal consultation process, we know who should be consulted and what issues should be considered. We are happy to update the Select Committee as this process continues, and to include members of the Committee, as well as other Parliamentarians, in our pre-consultation exercise.

The Severn barrage will be one of the largest infrastructure projects ever in the UK. Consulting widely, openly and in detail is a vital step. For some time we’ve been informally gathering views and updating our proposals. We are now preparing to begin formal public consultation to gather views and understand needs.

In broad terms we will consult with:

Local people who are likely to be directly and significantly affected.

A wider group of local people who may not be directly affected but who may have strong views.

Elected representatives, civil servants and officers of central and local government.

Non-departmental and non-governmental organisations (NGOs) with an interest in the areas or issues raised.

We’ll use an extensive range of communications channels including:

Exhibitions.

Other face-to-face meetings including steering/working groups.

Dedicated website, email.

Scale model and animations.

Social media such as Twitter and Facebook.

Freephone.

News stories in the local media.

Feedback will allow us to modify our proposals, where we can, to better balance what may well be often conflicting needs and views.

Here’s an example of how we’ll operate with stakeholder groups divided into zones.

Zone	Explanation of zone and consultees	Nature of consultation to be undertaken
A	Immediately adjacent. An area within close proximity of the proposed Barrage and manufacturing sites where people may be significantly and directly affected.	Door-todoor distribution of leaflets, newsletters and questionnaires. Comprehensive touring exhibition, copering local venues—local centres, parish halls, libraries etc local level publicity of events—prasha magazines, local newsletters, local notice boards etc. Meetings with Parish/Town Councils Local level stakeholder groups—residents associations, community groups etc One to one meetings with landowners, businesses etc
B	Wider area. Over which peopme may not be affected but will have fears or strong feelings about it.	Leaflets/newsletters/questionnaires made available in public places. General publicity for exhibitions—posters, websites, press, and area-wide publications. Exhibitions in key public locations—shopping centres, high streets etc. County level stakeholder groups—Chambers of Commerce, County Wildlife Groups etc. Meetings with Local Authorities
C	National/statutory stakeholders General public	One-to-one meetings with statutory stakeholders Opportunity for all to comment via the website

2. Companies which make up Hafren Power (to be disclosed in confidence to Cttee, Q199, Q204)

Hafren Power is a special purpose vehicle, a private company established exclusively to develop the barrage. It has the following current shareholders:

Zercin LLP; a development firm.

Hannah & Mould Solicitors; a commercial law firm specialising in international and UK major project work in the construction and energy industries.

Temporis Capital LLP; a London based financial services firm which focuses on the sustainability sector.

Hafren Power is supported in the business case by Ove Arup & Partners, a global firm providing engineering design, planning and management for projects and Marks Barfield, an award winning architectural firm.

Hafren Power will bring together a world class team of companies to deliver the project. It has obtained strong indications of interest from two of the world’s largest leading engineering consultants and project integrators.

Hafren Power has teamed up with a number of companies and has had detailed discussions with others.

A detailed programme for barrage construction will be drawn up at the detailed design stage. The high-level programme of the barrage construction is presented in Figure 1 below. This programme results in a period to closure of the barrage of 79 months from the start of construction, and full power production is expected by Month 110.

Figure 1

The project is currently in the “pre-construction activities” phase described in Figure 1; it is envisaged that following Royal Assent of the Bill a further two year design phase will be required before construction of the barrage will begin.

Further detail of the high level construction programme is included in our Business Case online at http://www.hafrenpower.com/media-centre/downloads-links.html

3. Details of how HP might replicate the hypertidal quality of the estuary (Barry Gardiner)

The hypertidal nature of the estuary is not commonly referred to in the literature (which normally uses the term macro-tidal to describe a tidal range >4m). However, the term hypertidal has been defined (DECC 2010) as a tidal range >6m.

Therefore with a predicted 2m suppression of both high water and low water, the peak tidal range at Avonmouth would reduce from 14m to approximately 10m and still fall within the DECC definition of hypertidal. It should also be pointed out that the final predicted range would depend upon how the turbines are operated and we are keen to finalise any design in consultation with a wide range of organisations, NGOs and stakeholders.

With regard to compliance with Habitats Directive (Q.212—Barry Gardiner), hypertidal is not cited as a criterion for SAC, SPA or Ramsar. The JNCC designation specifically does not include the term hypertidal. Therefore, loss of a hypertidal condition will not require compensation or mitigation as such.

The ebb-only generation bulb turbine scheme as reported in the DECC studies (2010) resulted in a basin water level that did not generally drop below mean tide level. The ebb-flood generation of the Hafren Power scheme results in the mean tide level being similar in style to the natural tidal cycle and with the mean water level being approximately unchanged.

The Severn barrage will be a structure with 1,026 turbines evenly distributed for the movement of the tidal waters in both directions past the turbines to generate power. The barrage is therefore essentially a dispersed multi-pathway barrier that can be controlled so that its porosity is variable. In the extreme, the turbines can almost block out the flow, reducing the tidal range considerably upstream. In the other extreme the turbine blades can be feathered (or turned and streamlined) so they provide little resistance to the passage of the flow. With the turbine blades fully feathered the tidal flow in both directions will be very similar to what exists at present, with the main resistance to flow then being virtually just the solid concrete in-fill between the turbines and with the tidal range upstream of the embankment being even closer to the downstream range. By electing periodically to feather the turbine blades the current macro-tidal conditions of the estuary can be closely replicated. This improved degree of macro-tidal replication can be quantified by further modelling with refined frictional resistances in the model representing the porosity of the barrage wall and virtually no turbines. This work has not yet been undertaken but will be done as a research study at Cardiff University.

To replicate the upstream tidal characteristics further then it would be necessary to increase the tidal range to the limit and this would require pumping. DECC studies found that pumping could be beneficial under certain conditions. However the viability and economics of this design would need detailed study. This added facility will be included in the modelling, but it has not been considered at this stage. Therefore, Hafren Power will carry out a full hydrodynamic analysis of pumping capacity and efficiency in conjunction with the turbine manufacturers. The objective will be to determine the role that pump-assisted sluicing and pump priming could have in assisting in the restoration of basin tidal range.

4. Professor Falconer pledged to make his research on flood risk available to Committee prior to their publication in the public domain (see Q154)

Requested papers are being made available to the Committee in draft and are not for publication at this stage. However, the findings are included in public presentations which can be shared (PDF documents).

Professor Falconer has been following up on the two draft papers which he agreed to send to the committee during the evidence session. The papers are in preparation and are submitted in confidence and not for distribution at this stage. The first paper, in draft,1 highlights the necessity for the boundary conditions for any model studies of a Severn barrage flood risk assessment to be provided by a model which has been taken out to at least the Continental Shelf, as originally highlighted in the paper by Adcock et al.2 In Professor Falconer’s view this is an important finding and questions the model studies previously undertaken for DECC in that the boundaries were not taken sufficiently far enough away from the barrage location.

At the time of the Energy and Climate Change Committee meeting, which was also Professor Falconer’s first day back from major neurosurgery, he had two papers on his computer drafted by his former Research Associate Dr Juntao Zhou, but he has since established they were the same paper. He is currently trying to get a copy of the second draft paper from Dr Zhou to share with the Committee (he expects to have it within the next week or so). The second paper shows predictions of the water levels for the far field and in the Bristol Channel and Severn estuary for different barrage configurations and turbine combinations, both with and without a barrage. This gives the water elevations that he referred to in his oral evidence to the committee. This work was undertaken with bulb turbines and is publishable. Furthermore, another Research Associate, Dr Reza Ahmadian, undertook similar work with the 1026 bi-directional VLH type turbines, with assumed coefficients of friction, again giving similar results. He also plans to publish these results in due course and Dr Ahmadian is currently writing a draft of the paper. The predicted water levels for this study are generally similar to those obtained for the bi-directional bulb turbines.

Since the second paper is not currently available, Professor Falconer has provided two PDF presentations of his team’s work which are in the public domain and show the water levels in the estuary for two-way in comparison to one-way generation; the typical lectures were presented to large audiences in both cases. The first is a lecture given last November to the Institution of Engineering and Technology, held in Cardiff (over 150 delegates)3 and the second was to the Coastal Futures conference (over 250 delegates), presented by Dr Ahmadian while Professor Falconer was on sick leave (ie in January 2013).4 The first model results (IET Lecture) are for two way bulb turbines and the second (CF conference) are for two way VLH type turbines.

5. Written evidence on the expected effects of siltation and how this might be managed (Q247)

Siltation varies as typically the cube of the velocity (depending on the formulae used and whether one is dealing with cohesive or non-cohesive sediments), so even a small reduction in the velocity would result in an appreciable reduction in the concentration of sediment in suspension and, in terms of water quality, this affects the degree of light penetration. The precise equations used to calculate siltation vary, but in the models used by the team at Cardiff University emphasis has been focused on using the classic van Rijn sediment transport formulations, as given for non-cohesive (ie sand and silt) and cohesive sediment (ie mud) transport. Both cohesive and non-cohesive sediments exist in the Severn estuary and Bristol Channel and it is important that both are modelled and treated separately as the processes of transport are quite different.

Based on widely accepted details provided in the literature, Hafren Power understands that the current sediment load in suspension varies from about 30 million m³ at spring tide to about 5 million m³ at neap tide. Under the schemes assessed by DECC in its 2010 study, it was expected that there would be a great reduction in suspended sediment, much of which would settle on a one time only basis over a lunar cycle immediately after the barrage was completed and closed.

We believe that our revised proposal addresses the problem identified by DECC in 2010, as the settling out of siltation will be more uniform with our model for the barrage, due to the more uniform velocity distribution across the estuary, as the turbines are spread across the breadth of the estuary, particularly along the barrage line where there will be turbines sited all the way across the barrage and not just across the middle third. By siting turbines across the whole wall, the velocity through the turbines will be lower, typically of the order of a third, thereby: reducing the level of turbulence, wake length, and degree of local scour (due to the significantly increased velocities in the region of the turbines); removing large scale horizontal circulation (a major factor in causing deposition and shoreline erosion); and, in particular, making the threat to fish less damaging—regardless of type of turbine used.

Hafren Power has not yet undertaken its own detailed computational morphological modelling of the estuary. To date, the company has focused more on the hydrodynamic impact of the barrage. However, bearing in mind that the new barrage design will not reduce the basin currents as much as the previous STPG scheme and that the suspended sediment concentration is roughly proportional to the third power of velocity, then the anticipated erosion and deposition in the estuary is expected to be less than that for the previously studied scheme. Hafren Power will not base its figures on the current estimates, as the effects of our proposal will be different, so we propose to carry out our own studies using experts in this field.

6. You have claimed in your evidence that the barrage would result in 60% less loss of intertidal habitat when compared to the previous proposal for a Cardiff-Weston barrage. Can we see the methods used for calculating the amount of intertidal habitat which will be lost?

Our engineering consultants calculated the amount of lost intertidal habitat by using a hydrodynamic model, coupled with input from the turbine manufacturer. The manufacturer’s IPR is confidential.

The loss of intertidal habitats was also calculated directly within the model used by Professor Falconer’s team by calculating the loss of computational grid cells which are flooded for the peak spring flood tide for the existing estuary and which are not flooded for the equivalent case with the Severn Tidal Power Group (STPG) scheme and then for the Hafren Power (HP) scheme with two-way bi-directional turbines. By evaluating the number of cells which are permanently dry for the STPG and HP schemes and multiplying by the area of each cell, one can evaluate the area of intertidal habitat lost through the design of each scheme.

Intuitively, is clear that much more intertidal habitat will be preserved than under previous schemes. Unlike ebb-only schemes, there is no damming of the estuary. Ebb-flow generation allows the tides to more closely follow their natural flows, except for taking 2m off the top of the tide and adding 2m to the bottom.

7. A fixed shore-to-shore barrage on this scale has never been attempted and there are significant uncertainties about the possible impacts; many commentators are advocating that we should “start small” to minimise financial and environmental risk. What is your response to those organisations advocating a more incremental, step-by-step approach to tidal power development?

We do not believe there is uncertainty about the fundamental question: the capability of the barrage to deliver 5% of the UK’s energy supplies over a minimum 120 year period.

According to Professor Tim Broyd, representing the UK engineering industry at the January 10 oral evidence session, the barrage is the only cost-effective way to harness the power of the estuary. He said:

“I was a member of the expert panel used by DECC a couple of years or so ago to assess five different schemes, and there were three barrage schemes and two tidal lagoon schemes. We also looked briefly at reefs and tidal fences. Of those, the only one—and it was pretty much head and shoulders above the rest for any return on investment at all—was the barrage along the line, the type of line that Hafren Power are suggesting. Other schemes were less viable. They certainly produced less power. But of course a barrage itself, and again harking back to what has been said earlier today, does not prevent other types of renewable energy being tapped within the regions.”

As we mentioned in our oral evidence, tidal range, tidal stream, wave and offshore wind can all co-exist in the Severn estuary. The issue is to place them all in their most efficient and effective locations. None conflicts with the barrage.

To make tidal power commercially viable and competitive with other, more established, technologies, the nation requires economies of scale to keep costs down. Only a tidal range scheme on the scale of the Hafren Power barrage would provide sufficient financial incentive for major turbine manufacturers and engineering firms to progress their concept designs through to production. Barrage technology is tried and tested. Our delivery team have built caissons and embankments of similar size elsewhere in the world. An incremental approach through a pilot project will not provide any data that does not already exist.

One example of an “incremental, step-by-step approach” others have advocated might be the Stepping Stone tidal power scheme. Lagoons and the Stepping Stones scheme are untried and unproven and would have similar impacts on ecology and wildlife to a barrage, which would need to be addressed. They would also take approximately eight years to become operational from now. This would mean that the first test data would only become available in approximately nine years’ time. The smaller Stepping Stones scheme would only produce about 1.2 terawatt-hours per year, while the barrage offers 16.5 terawatt-hours per year. Thus, the UK would lose about six years of a much larger energy source while it faces a looming electricity gap of 60 TWh by 2025.

One of the key points to appreciate in generating hydro-electric power in an estuary is that:

Power (symbol to be inserted) A H²

This equation demonstrates that the amount of power generated is determined by two factors: the head of water across the area impounded by the barrage (H) and the area of water that it impounds (A).

Whilst the Severn barrage project seems huge, it is attractive to private investors because it is highly efficient to be able to impound such a large body of water with a relatively short impoundment wall. It is well known that the estuary has the second largest tidal range in the world, but it is rarely appreciated that the barrage will impound a huge water body with a plan surface area of 500 km², equivalent in area to approximately 150% of the area of Lake Garda. The impounded perimeter is approximately 210 km, while the constructed wall length is only 18 km. By comparison, a lagoon the size of 1,000 football fields, like the proposed Swansea Bay lagoon, requires a perimeter wall of 9 km just to impound an area of 5 km². While the perimeter wall would therefore be half the length of the barrage, the lagoon would produce only around one fortieth of the electricity available from the barrage. These vast disparities in output and efficiency speak for themselves. In the unique Severn estuary, an enormous amount of power can be derived from a very short barrage wall.

It is worth reiterating that the construction of a barrage would not inhibit the development of other marine and wind power projects either elsewhere in the Severn estuary or in other parts of the UK. Indeed, we would encourage the Committee to consider supporting these developments. However, only the barrage has the potential to provide such a large proportion of the UK’s energy needs and to do so on an economically feasible basis.

If the Committee agrees that the potential of the Severn estuary’s tidal energy should be harnessed in full, then we believe that work on the barrage should begin as soon as possible.

For further analysis of this topic, please see the submission by Blue Marble Sustainable Solutions Ltd.

Figure 2 has been designed to provide a rule of thumb of comparative statistics in respect of the potential output of different types of power generation. While this table does not purport to provide a precise comparison, it provides a reasonable rough guide.

Figure 2

Comparison of electricity generating sources	Offshore wind	Nuclear	Tidal stream	Tidal fence	Lagoons	Severn barrage
Number of equal output of Severn barrage(1)	2,500 wind turbines over 2,750 km2	3–4 reactors	9,200 turbines over 226 km2 of sea-bed, in depths of >30m	Between 5 and 19	7, each the size of 1,000 football pitches	1
Capital cost to equal output of Severn barrage (16.5TWh)(2)	£50bn	£21bn	£80bn	£35.5bn	£55.5bn	£19bn
Capital cost per MWh over life of asset to generate 16.5TWh	£206	£47	£309	£137	£98	£33
Flood defence	x	x	x	x	x	√
Legacy	None	Decommissioning	Export	Export	Export	Flood protection, storm surge, protection, exports
Investment stays in UK?	x	x	√	√	√	√
Potential to be world market leader?	x	x	√	√	√	√
Shipping impact	Minimal, if placed outside shipping channels	None	Minimal, if placed outside shipping channels	Accelerates currents through channel	Acceleration of current and navigational hazard	Locking time through barrage and reduced peak water basin levels
Predictable electricity?	x	√	√	√	√	√
Daily period of transmission	Intermittent and unpredictable	24h	15.25h	15.25h	15.25h	15.25h
Lifespan (years)	15–25	60	20–25	20–25	120–250	120–250
Need for consumer support?	√	√	√	√	√	√
Price support as % of lifespan	100%	50%	100%	100%	25%	25%
Levelised cost per MWh(3)	£192 (2015), with a target of £100 by 2010	£88	£325	£226	£148	£48

8. Experience from the Bay of Fundy barrage in Canada has led to the Canadians abandoning further barrage developments due to “rapid, unpredictable consequences and no foreseeable return to a state of dynamic equilibrium” within river ecosystems. Are you familiar with this research and what in-field studies have you undertaken so far to assess the possible impacts on the estuary’s morphology?

On the specific question of the Bay of Fundy, we are aware of a wide range of research, but do not believe this example is directly comparable to the Severn estuary. Furthermore, Professor Falconer has personally looked at the Bay of Fundy and concluded unequivocally that this site was not suitable for a barrage.

First and foremost Canada is a sparsely populated country compared to the UK and, in contrast, ideally suited to small scale hydro-electric schemes. It also has considerable potential for small scale hydro-electric dams, which have been, and continue to be exploited. Because of the scale of the country there are difficulties in having a high concentration of power generated in a relatively sparsely populated part of the country.

Secondly, and more importantly, there have been several key hydrodynamic modelling papers on the Bay of Fundy and by some of the world’s leading ocean modellers in the field. Aretxabaleta et al. (2008)5 highlight the complexity of the flows in the Bay of Fundy. These results, together with the low population density of Canada, led Professor Falconer to his conclusion.

It may also be of interest to the Committee to note that more recent highly regarded modelling research, Cousineau et al (2012),6 shows that even small coastally attached lagoons in the upper part of the Bay of Fundy have a marked effect on the water levels further seawards and will significantly affect currents. This highlights the point that whilst much concern is raised about the hydro-environmental impact of barrages even relatively small lagoons can have a significant adverse impact on the hydro-environmental impact in semi-enclosed environmental water bodies.

The Canadians abandoned the Bay of Fundy scheme when research indicated it would result in sea level rises on the US eastern seaboard, which would give rise to possible legal action. A similar far-field rise in water level was found by early studies for the Severn barrage. However, this is thought to have been caused by the limited model boundary, which only stretched as far as Ireland and Anglesey. When Professor Falconer extended his model to the continental shelf these far field effects became insignificant.

Professor Falconer would be pleased to host any members of the committee wishing to visit Cardiff University to see his modelling in person.

9. We understand from your evidence that the turbine design may be based on a concept design by Rolls Royce/Atkins. Do you have a commitment from these companies to work in partnership with Hafren Power to develop the design?

We do not now have any business relationship with Rolls-Royce, who have withdrawn from the tidal-stream turbine market following the sale of its subsidiary, Tidal Generation Limited, to Alstom. However, Rolls-Royce did not sell the IPR on the bidirectional VLH turbines. We are in discussion with four potential turbine manufacturers, all of which are confident that they will be able to manufacture the turbines we require to the specification we require. This may involve acquiring the IPR from Rolls-Royce.

10. Do you currently have a commitment from manufacturers to build turbine plants in South Wales and the South West?

We have agreement in principle, but negotiations have not reached the point of detailed commitment.

11. Do the contra-rotating blades spin at the same time?

Yes, the contra-rotating blades do spin at the same time. The two sets of blades are separated by a gap of more than 1.5m, which is enough to allow the largest salmon through with full-body clearance. This will be studied further by our fish experts, and optimised during turbine development.

12. What studies have you undertaken to determine the effectiveness of measures such as fish passes?

We are aware of a number of studies looking at this area. This is being explored by researchers in the US and in Europe. We will take account of any practical tests being conducted, such as those by the DoE in Idaho and MJ2 Technologies in France.

We are currently in discussion with Dr Andrew Turnpenny (Director of Turnpenny Horsfield Associates), an expert in this field. His evidence to the Parliament Science and Technology Select Committee states: “there are much better prospects of quantifying possible damage to fisheries and, more importantly, designing and operating turbines to be more ‘fish-friendly’. The development of acoustic fish guidance has advanced in the last ten years from concept to reality. The possibilities of safely diverting fish around a turbine should now be realisable.” We intend for full studies to be made of this area during the next phase of the project.

13. Have you carried out any tests of fish (salmon—adults and juveniles; shad—adults and juveniles; eels—adults and elvers; lamprey—adults and juveniles) strike mortality in the bi-directional turbine?

Hafren Power has not conducted tests itself at this point, but quite a lot of testing has been done. See, for example the research conducted by Idaho National Laboratory showing that a tip speed of 12.2m/s, significantly above the tip speed of the VLH turbines, is at the “limit of negligible mortality” for fish passage through a turbine. However, further study is needed to confirm that these conclusions apply to all types of fish, at all stages of their development.

As previously indicated, testing the migratory patterns of fish and the effects of the turbines on them will be part of the next phase of the project. Swansea University will lead the study. We will also investigate various mitigation and compensation measures. Hafren Power’s aim is to accomplish zero mortality for fish passage through its turbines.

Attention should be drawn to the fact that MJ2 Technologies have developed a fully operational VLH turbine which is accepted by the French authorities for deployment in environmentally sensitive locations. This turbine is now being exported to a number of European countries. Full scale field tests using live European eels have led to iterative development of the original production model. Some eels were being pinched at the outer edge. With a minor adjustment to blade design, this was resolved. These turbines now provide for 100% survival of eels of up to 1.0m in length. This is a highly vulnerable and endangered species particularly prone to turbine damage, and the 100% survival rate clearly marks a significant step forward in fish friendly turbine design. MJ2 technologies are carrying out tests on salmon smolts during 2013 and will be updating Hafren Power with their results. This indicates to us that computer aided turbine design to optimise output and minimise fish damage factors is a highly effective and reliable tool.

Hafren Power will seek ways to improve the spawning conditions of migratory fish by, if appropriate, removing weirs that block shad and providing salmon rearing facilities.

14. Over the course of a tidal cycle and the barrages lifetime, by how much does the generator efficiency vary and how does this affect the amount of intertidal habitat which is lost?

Hafren Power is confident that there will be little variance in turbine efficiency. In 46 years of continual operation, the turbines at La Rance have not needed to be replaced, which indicates how efficient turbine technology has proven to be. Precise estimates of the effect of turbine design on the intertidal habitat will be determined as part of the wider studies we intend to conduct during the next phases of the project.

15. In your evidence you state that you are “studying the option” of building a Bridgwater Bay bund to protect the Somerset levels. When will you make a decision on this and have you made an assessment of the planning and mitigation requirements of this extra project?

The decision on whether to proceed with a Bridgwater Bay bund will be made as part of the Environmental Impact Assessment, based on whether it is a necessary part of mitigating the impact of a Severn barrage. An assessment has been made of the planning and mitigation requirements of this extra project. As we understand it, the impact of such a bund would be positive, protecting the Somerset levels from flooding and the habitat of the shelduck.

The DECC studies of an ebb-flood tidal power lagoon in this area showed that the basin water level closely followed the natural level. Regarding flooding, the sluices or turbines could be shut during exceptionally high sea level conditions thus protecting the Somerset levels from marine flooding. When fluvial flooding occurred, the basin water level could be maintained close to low-tide level, thus allowing the Somerset levels to be drained much more effectively.

16. Who will pay for the maintenance of the bund?

Should the Environmental Impact Assessment process indicate that a Bridgwater Bay bund is needed as part of the environmental mitigation for the barrage, Hafren Power will take responsibility for the costs of ongoing maintenance.

17. The barrage will offer protection against upstream tidal flooding and storm surges, however downstream river flooding, tide-locking issues and erosion of existing flood defences are likely to cause “very significant additional costs” according to the Environment Agency. How do you propose to address these flood risk issues within your proposal? (if not covered by Professor Falconers response on this issue)

Modelling the peak sea level on the stretch of coast up to about 40km downstream of the barrage shows flooding would marginally reduce. Therefore, the barrage will reduce flood risk along the coast not increase it. Furthermore there will be even less risk of tide locking.

The DECC scheme with basin water level barely going below mean tide level was found to result in significant tide locking of the outfalls. This was analysed in the Severn Tidal Power Feasibility Study (STPFS). Mitigation works such as pumping stations were identified and costed at £80 million. With the Hafren Power proposal—an ebb-flood generation scheme—the basin water level is very much lower and the capital works required would be substantially reduced or eliminated.

The DECC scheme would have used bulb turbines which required a 3 to 4m head to start generation, whereas Hafren Power will use VLH contra-rotating turbines which have a much lower starting head requirement. They will therefore be able to start generation sooner. As a result, the period of high water stand is appreciably reduced. This would significantly reduce the risk of erosion due to high water stand, compared to the ebb-only DECC scheme.

It would appear that the Environment Agency arrived at “very significant extra costs,” because its submission to the Committee was based on modelling results relating to the previous ebb-only DECC scheme and not that of Hafren Power, which, as explained above has very different characteristics, Nonetheless, all of this would be studied in detail and any necessary mitigation measures such as pumping facilities or shore protection would be provided.

18. Since the evidence session, have you had any further discussions with DEFRA regarding flood risk and savings? In particular, have they been able to verify your estimates for flood defence savings (see Q180)?

Hafren Power has submitted a 50-page analysis of flood costs to Defra. Defra is currently in the process of reviewing the document. At this stage it has not yet verified our estimates for flood defence and damage savings. We have agreed to further meetings to clarify any outstanding questions Defra may have.

19. You mentioned that the price support for the barrage “only lasts for 25 [years]” (Q206). Can you clarify this with regard to the previous suggestion that a 30-year CfD period would be necessary?

The transcript (uncorrected evidence) was incorrect. The corrected evidence now reads: “We would be around for 120 years. The price support only lasts for 25% of the barrage’s life” (30 years of a total of at least 120 years).

March 2013