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From: Alex Hamilton [mailto: Sent: Sunday, September 22, 2013 11:34 PM To: Thames Tunnel Subject: Thames Tideway Tunnel examination - Supplementary representation

To: The Planning Inspectorate 3/18 Eagle Wing Temple Quay House 2 The Square Bristol, BS1 6PN I am enclosing a supplementary representation giving further details relating to my original representation , your number 979. Please note that I am enclosing only my main text with this email. (1 document) I refer to 2 reports, ( references (Binnie: 11/3/13) and (Binnie: 17/3/13) in my representation) which provide further evidence. As these are big, I will try to send them separately directly afterwards, in one or two emails. Please let me know if you do not receive them. Regards Alex Hamilton IP unique reference number 10018472 W Alexander H Hamilton MA, CEng, FICE, MCIWEM

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Thames Tideway Tunnel Planning Examination WAHH/ IP1001 8472

(22/09/2013) page1 of 11

Thames Tideway Tunnel Planning Examination

From W Alexander H Hamilton (registered as Interested Party nr 1001 8472)

Supplementary Representation to add to:

Representation No. 979, (received by you on 28 May 2013) Date:22 September 2013

I am a resident of London and payer of the water charges, including those likely to arise from the

project under consideration. I am also a Chartered Engineer with specialist expertise in water,

drainage and energy.

This representation is providing further information relating to the representation no 979 previously

submitted. I have made note of the guidance regarding submissions provided at the preliminary

procedural meeting on 13 September (at which I was present), and have tried to follow these.

1. Introduction: This representation is that planning permission should be refused for the TTT

(the shortcut I intend to use here for the Proposed Development) or made conditional,

because: it is very poor value for money; has serious adverse effects on the UK’s carbon

reduction and climate change mitigation strategy; and provides limited real environmental,

health, aesthetic and social benefits that could not be provided in lower-cost and less

damaging ways – in other words it fails the well established concept of ‘best technical

knowledge not entailing excessive costs’ (‘BTKNEEC’)

2. I am aware that the TTT is included in the WW National Policy Statement, and that means a

presumption that planning permission has to be given. But I note that the Planning Act 2008

allows some exceptions to that , in particular ( I quote from section 104) :

a. Subsection (7): “…. if the Panel or Council is satisfied that the adverse impact of the

proposed development would outweigh its benefits”

b. Subsection (9): “….For the avoidance of doubt, the fact that any relevant national

policy statement identifies a location as suitable (or potentially suitable) for a

particular description of development does not prevent one or more of subsections

(4) to (8) from applying”

3. I am not a lawyer, but that seems to me to mean that Panel should consider

a. the adverse impacts of TTT, related to both to the identified principal issues and to

other arising,

b. and the benefits to be obtained.

and weigh the adverse impacts resulting from the TTT against the added benefits resulting

from the TTT.

4. In my view, the TTT fails the Subsection (7) test and so should be refused development

consent.


(22/09/2013) page2 of 11

5. The benefits that the TTT will provide need to be the actual difference and improvements

that the construction and operation of the TTT will make .

6. TTT and the EU Urban Waste Water Treatment directive: Now the main reason that the TTT

is being pursued is because of pressure from the EU for UK compliance with the UWWTD,

including infraction procedures. However I don’t think compliance is itself a “benefit”, as

the directive is explicitly for the purpose “to protect the environment from the adverse

effects of ….urban waste water discharges [Article1]. So as far as the UWWTD is concerned,

the “benefit” is reduction of adverse effects on the environment.

7. Furthermore, the UWWTD explicitly allows for use of the BTKNEEC concept in relation to

storm overflows in collection systems. In the judgement on the infraction proceedings in the

European Court, that concept is also allowed to relate to waste water treatment . This

could be important because, among other things, a variation on the proposed development

could include an element of BTKNEEC local treatment on the storm overflows obviating the

need for the actual tunnel, so improving the present poor benefit/adverse impacts ratio

8. It is also true that judgement stated that the TTT would comply with BTKNEEC; BUT that was

simply based on the fact that the UK govt already had made plans for TTT; so that statement

does not in any way appear to be a judgement based on the merits of the case.

9. I think therefore that the BTKNEEC concept can still now be relevant to the Subsection (7)

test, and would need to be considered on its merits, rather than simply because the TTT has

been put in the NPS

10. With regard to the NPS, that document argues the TTT will give benefits from improvement

in the following matters:

“London's CSOs overflow into the River Thames tideway approximately 50 times

per year and affect:

• biodiversity by reducing dissolved oxygen (DO) levels in the river

potentially resulting in the death of adult fish and fish fry;

• health by increasing in pathogenic bacteria which potentially pose risks to

users of the river; and

• the attractiveness of the environment due to large quantities of offensive

solid material being discharged into the Thames and deposited on the foreshore.

[from NPS para 2.6.16]

………These costs include direct financial costs such as the costs of measures to

mitigate against low oxygen, fish re-stocking, costs on the health service and the

wider economy due to people falling ill and costs of cleaning up debris.1 The

pollution also imposes wider 'external' social and environmental costs on society.

[from NPS para 2.6.19]”

1 The Thames Recreational Users Study Final Report (2007) - a collaborative partnership project between the City of London Port Health Authority

and the Health Protection Agency


(22/09/2013) page3 of 11

11. So the improvement in these otherwise adverse effects just mentioned that can be expected

to result from the TTT, need to be balanced against the adverse impacts that also can be

expected to result from the TTT. In other words, it is the marginal improvements and

adverse effects consequent on the TTT that need to be examined.

12. If the Panel is not satisfied that the balance is clearly in favour of the Development then the

Panel is entitled to - and should - recommend refusal of development consent.

13. Concurrent developments: I am aware that the Panel has to examine the application as is

and not the possible alternatives. However, the Panel should be aware that other works are

actually proceeding that will have an effect on the impact/benefit balance.

14. In general terms, there are official moves by the Mayor of London, I believe incorporated

into London development plans, for more SUDS and other blue-green developments, which

in the long term should reduce the amount and intensity of storm flows and hence of

operation of CSOs. I believe you have other submissions which will give you many details

about these, and I do not wish to particularly pursue them here. But they will all tend to

diminish the benefits attributable to the TTT. A more substantial actual matter is covered in

my next paragraph.

15. Actual developments going ahead: The following is a quote from a recent report by

Professor Chris Binnie, former chairman of the Thames Tideway Strategic Study (TTSS)

(Report: Thames Tideway Tunnel: Interim measures to improve the river Working draft 11th

March 2013 Report By Professor Chris Binnie MA, DIC, HonDEng, FREng, FICE, FCIWEM

[email protected]) (ref: Binnie: 11/3/13) [ Note: I am including in my submission

email a file containing a pdf of this report, – if not satisfactorily received, please let me

know, and I will send you a copy separately - WAHH.]

“The works already under construction include upgrading of the Mogden, Beckton,

and Crossness STWs. As a response to the 2011 fish kill in the Chiswick area,[ Note:

one of the events stated in the NPA to be involved in the selection of TTT for the

NPA- WAHH] the Thames Water have said “ I do need to assure you that once the

extension is completed in March 2013 the works will be able to handle a similar

situation without even using its storm tanks, let alone discharging to the river.”

Once all the upgrades and the Lee Tunnel ,[ Note: This is another project going ahead

at this time that will affect the TTT- WAHH] are completed, about April 2015, the

volumes of stormwater discharged to the river will fall from about 39 Mm3/year on

average to about 18 Mm3, less than half, [as per]…Table provided by Thames

Water.”

16. Please note that the last comment in the above report extract is supported by a

parliamentary answer by the relevant minister, an extract from which is given below – ref

(http://www.publications.parliament.uk/pa/cm201213/cmhansrd/cm120618/text/120618w

0004.htm accessed 21 September 2013)

Hansard “18 Jun 2012 : Column 747W


(22/09/2013) page4 of 11

Richard Benyon: Thames Water is currently delivering permanent measures

which will improve the Thames tideway. These include upgrades to five major

sewage treatment works in London, and constructing the Lee Tunnel. By the end

of 2014 these improvements will reduce the current level of waste water

discharges into the tidal reaches of the River Thames in a typical year, from 39

million tonnes to around 18 million tonnes. In the longer term, when scheduled for

completion in 2023, the Thames tunnel would reduce this discharge by a further

15.5 million tonnes.”

17. It follows that the benefits associated with the TTT will cover the effect of an annual

reduction of only 15.5million tonnes – a very considerable reduction from the much

greater total that prevailed when the TTT was first under consideration, or even maybe

when it was being considered for inclusion in the NPS.

18. Benefits associated with TTT: The consequence of these developments is that much of the

possible benefit of the TTT that was foreseen when it was incorporated into the NPA, will

already have been taken up by other projects. These will have been completed many years

before the TTT is commissioned, assuming it goes ahead.

19. The benefits associated with TTT have also been very substantially overstated. The following

is a quote from a second recent report by Professor Chris Binnie (Report: Thames Tideway

Tunnel: Costs and benefits analysis and consideration of interim measures with

addenda1,2&3. By Professor Chris Binnie MA, DIC, HonDEng, FREng, FICE, FCIWEM

[email protected] March 2013 (ref: Binnie: 17/3/13)) [ Note: I am including in

my submission email a file containing a pdf of this report, – if not satisfactorily received,

please let me know, and I will send you a copy separately - WAHH.]

“In contrast to the defra CBA report, my analysis shows that, following the

methodology used by defra, and on the basis of the reasons provided, the total

NPV benefit [note: for the TTT- WAHH] would be about £275m. This is about 7%

of the cost of the Thames Tunnel. ………

Benefits at, or near, this level would mean the cost of the tunnel would be

“excessive cost” under UWWTD and “disproportionate cost” under the WFD.

Were the litter benefit, classified as “minor” by eftec, be not £1,000m but, say,

£200m then the total benefits would be negative, being less than the dis-benefits

of the construction process.”

20. I support this analysis, for which further details are given in the report. It should be

considered carefully by the Panel, in particular with respect to the Subsection (7) test. It

has been prepared by an eminent expert, Professor Chris Binnie, who was closely

involved in the studies for the TTT and its selection, but is now fully independent of both

the project and the interested parties.

21. My further representations: General, covering the proposed development (TTT) as a

whole:

a. Points of agreement: I agree that the present state of storm overflows(CSOs)

to the Thames is unsatisfactory, leads to occasional unsatisfactory environmental

and aesthetic conditions in parts of the Thames, and as it stands has been found


(22/09/2013) page5 of 11

to be in contravention of the UWWTD. I also agree that the TTT has been

included in the WWNPS. I agree that as things stand, works are needed at the

existing CSOs to alleviate these occasional conditions. I agree that the present

in-river alleviation measures involving skimming and surface aeration cannot be

considered as a satisfactory long-term measure, being over-dependent on day-

to-day human intervention. (They would, however, be sufficient as a

temporary/interim measure as part of an overall permanent solution).

b. Points of disagreement/opposition: I disagree with the concept of TTT

requiring connection of the CSOs to Beckton. While I agree with the works

intercepting the flow in the present CSOs, I disagree with what is proposed after

that – namely connection to the main TTT tunnel and the tunnel itself.

c. Reasons for opposition: For the reasons already stated and to be expanded

under my principal issues below. These are

i. Excessive energy Intensity

ii. Negative cost benefit

iii. Single purpose without secondary benefits

iv. The environmental benefits do not match the dis-benefits of the carbon

footprint

v. A main benefit is aesthetic, but this in no way matches the cost of the

project and could be achieved more cheaply in other ways.

vi. TTT is being undertaken on account of the UWWTD but is not truly in

accordance with the allowed principle of BTKNEEC

22. Excessive Energy This relates generally to principal issue 6 - Climate change, but also

to the related but unidentified issue of the call on national energy resources..

23. I am looking here at the energy required for operation of the TTT. There is also the

energy involved in its construction, but I propose to cover this in relation to the carbon

footprint.

a. The problem is that the TTT will call for a considerable increase in energy

consumption. . The present situation has little energy requirement except for

operation of the skimmers and aerators. BUT The TTT will require energy input

every time it operates. This is directly for pumping out the tunnel at Beckton, but

there will be a further energy input for subsequent treatment at Beckton.

b. The energy needed for treatment may be slightly offset by increased energy

recovery by biogas, but as the TTT is being built primarily to catch storm

rainwater this may not be very much, as the rainwater is likely to be near-zero

energy content.

c. The annual energy input stated in the Applicants documents associated with the

works at Beckton is 7,282 MWhrs. Of this, the energy associated with the

pumping is said to be just under 5000 MWhrs, spread over 300 hours per year.


(22/09/2013) page6 of 11

The remaining energy appears to be associated with ancillary devices, and is

spread over a longer period per year.

d. I have not found any statement of the additional energy required to treat the

additional flows through Beckton deriving from the TTT. However, it is well

known that modern sewage treatment is energy-intensive. The Parliamentary

Office of Science and Technology made an assessment in Post note April 2007

Number 282 ENERGY AND SEWAGE

(http://www.parliament.uk/documents/post/postpn282.pdf accessed 21

September 2013) that

“Over 10 billion litres of sewage are produced every day in England and

Wales . It takes approximately 6.34 gigawatt hours of energy to treat this

volume of sewage , almost 1% of the average daily electricity

consumption of England and Wales”

I estimate this to give an average energy consumption of about 0.6 KWhrs per

m3 treated. On the assumption of 15Million m3 of flows delivered to Beckton on

account of TTT, this would suggest a further annual energy input of 9,000MWhrs,

ie rather more than the pumping energy. No doubt this is a large over-estimate

for a modern efficient plant such as at Beckton, and for marginal flows, but it still

suggests that the energy required for treatment is considerable. Some of this

energy may be recovered, but I don’t think it would be more than a small fraction.

e. Why does all this matter? The problem is that UK National Policy expects energy

consumption to be reduced in UK. I quote now from Overarching National

Policy Statement for Energy (EN-1)

Para 3.3.26 Reducing demand for electricity is a key element of the

Government’s strategy for meeting its energy and climate change

objectives. The 2050 Pathways Analysis shows that total UK energy

demand from all sectors (heating, transport, agriculture, industry and

electricity demand) will need to fall significantly per head of population by

2050 and in the most extreme scenarios, total energy demand could be

almost 50% lower than 2007 levels by 2050. The analysis highlights the

importance of energy efficiency and the potential that this can have to

help achieve our carbon emission reduction targets.

f. But the TTT is flying directly in the face of this national policy statement, requiring

a substantial increase in long-term energy consumption. This is a serious

adverse impact directly arising from the TTT.

24. As this adverse impact arises from the proposed development it should therefore be

considered as a Subsection (7) issue.

25. Negative cost benefit This relates to Principal Issue 6 - socio-economic effects, but

should perhaps be related to a straight economic issue.

26. I have already quoted reference (ref: Binnie: 17/3/13) which suggests that the economic

benefit of TTT is only in the low hundreds £million, or, depending how the “litter”

reduction benefit is assessed, could actually be negative.

http://www.parliament.uk/documents/post/postpn282.pdf


(22/09/2013) page7 of 11

27. The problem can be summed up that while the economic dis-benefits are generally

readily quantifiable and real, mainly relating to the construction and operation costs, and

the disruption during construction, the benefits are generally subjective – such as

aesthetic, non-commercial fish kill, unquantified biodiversity improvements, and are

largely valued on further subjective bases such as people’s willingness to pay for stated

improvements far in the future.

28. An area which I do not think is properly covered is the opportunity cost of TTT. If it

goes ahead, it will tie up ~ £4Billion of capital, financed by the customers of Thames

Water.

29. But in reality there are other water problems facing these customers, most notably

possible water resources shortages. I could quote to you references that Thames Water,

along with other E and SE England water utilities, faced a serious water resource

shortage in spring 2012, manifested by a hosepipe ban, less than ten years after the

previous such. TWO’s Water Resources Management Plan I understand has recognized

that there is looming issue in this area. The solutions suggested include extensive

replacement of leaking water mains, construction of a large Upper Thames Reservoir

(subject to an planning enquiry a few years ago), water transfers from the Severn

catchment into the Thames catchment, possibly supported by new reservoir construction

there.

30. All these would involve substantial capital investment of similar magnitude to TTT. It

could be said that such endeavours and expenditure would be of greater benefit to the

TW customers, and therefore that spending this capital on TTT instead, represents a

serious opportunity cost to the Thames Water customers, hence disbenefit. I am not

aware of any study of customers’ preference here, despite much of the Applicant’s cost-

benefit analysis being based on surveys of customers preferences and willingness to pay

31. A further economic disbenefit is the loss to the TW customers of the amount of the extra

charges on customers resulting from the TTT (estimated at about £70 per year per

household),. At the present day, recovery from the recent recession is largely being

attributed to the revival of consumer demand. These charges can be expected to have a

small depressive effect on consumer demand.

32. These dis-benefits are all further adverse impacts from the proposed development, and

so should be considered as subsection (7) issues.

33. Absence of secondary benefits This is a disadvantgage of TTT compared to some of

the alternatives, notably SUDS and “green” development to reduce the amount and rate

of runoff; The latter proposals are seen by many, including many of the other IPs, as

providing substantial other social benefits ( with which I would agree).

34. It is possible that this could be thought to be ruled out of consideration as not being part

of the application. However, it is a genuine issue of value. It would come under several

of your principal issues, notably nr 11- socio economic issues, nr 5 – design landscape

etc, nr 2 – Biodiversity etc.

35. The effect of the proposed expenditure on the TTT will be to reduce particularly the

availability of funds, but also political initiative, to pursue these alternatives and potential

secondary benefits. That is a further adverse impact of the proposed development and


(22/09/2013) page8 of 11

therefore comes under the Subsection (7) rule, and adds a further reason why the

application should be refused.

36. The environmental benefits do not match the dis-benefits of the carbon footprint

The main issue here is the carbon footprint of this project. It most nearly relates to

Principal issue 6 – flood risk and climate change, and has factors in common with

another of my my principal issues: Excessive Energy.

37. However, in addition to the issue of CO2 in the operational energy,what needs to be

considered here is there is also the issue of the very considerable carbon footprint of the

construction phase of the TTT. The total carbon footprint including operation is stated in

the submitted document Energy and Carbon Footprint Report Doc Ref: 7.08 Appendix B

to be approx 838, 000 tCO2e (of which about 19,000 tCO2e is for operation) . These

assume decarbonisation interventions both during construction and for the operational

phase ( 2023-2140). For the latter, decarbonisation of the energy supply to zero CO2 by

2035 is assumed.

38. These assumptions may be difficult to implement, particularly that of decarbonisation of

the energy supply, which will be entering on unknown territory. If the latter cannot be

achieved, (I quote from the same source): “The GHG emissions for non- decarbonised

operation (2023-2143) are 532,970 tCO2e.” – A much larger number, albeit spread over

a long period.

39. The reason that these numbers matter and should be considered is, not only the general

impact of the carbon footprint on climate change, but also because there is UK legislation

and policy in place requiring a serious reduction of emissions ,- I quote from the Climate

Change Act 2008:

It is the duty of the Secretary of State to ensure that the net UK carbon account

for the year 2050 is at least 80% lower than the 1990 baseline.……….

(1) The carbon budget—

(a) for the budgetary period including the year 2020, must be such that the

annual equivalent of the carbon budget for the period is at least 26% lower than

the 1990 baseline;

40. The carbon budgets that have been set are apparently as follows , as per a recent

DECC policy announcement:

“Specifically, the carbon budgets limit our greenhouse gas emissions to:

3,018 million tonnes of carbon dioxide equivalent (MtCO2e) over the first

carbon budget period (2008 to 2012)

2,782 MtCO2e over the second carbon budget period (2013 to 2017)

2,544 MtCO2e over the third carbon budget period (2018 to 2022)

1,950 MtCO2e over the fourth carbon budget period (2023 to 2027)”


(22/09/2013) page9 of 11

( ref https://www.gov.uk/government/policies/reducing-the-uk-s-greenhouse-gas-

emissions-by-80-by-2050/supporting-pages/carbon-budgets accessed 22 September

2013)

41. Now the slightly less than 1MtCO2e involved in TTT is certainly quite small in relation to

these targets. However, it is in the wrong direction. These budgets imply a reduction of

832 MtCO2e per 5-year period in the course of ten years during which TTT is

scheduled to be constructed. But TTT will cause a visible increase which will have to be

offset by greater reductions elsewhere.

42. Although I understand that recent climate change budgets have and are being met, that

has been attributed largely to the recent recession; there are severe challenges ahead. I

quote from a recent communication from the statutory Committee on Climate Change

(press release 26 June 2013):

“Although the first carbon budget has been comfortably achieved and the second

budget is likely to be achieved, this is largely due to the impact of the economic

downturn. There remains a very significant challenge delivering the 3% annual

emissions reduction required to meet the third and fourth carbon budgets,

particularly as the economy returns to growth. Government action is required

over the next two years to develop and implement new policies. A failure to do

this would raise the costs and risks associated with moving to a low-carbon

economy.”

( press release 26 June 2013, ref http://www.theccc.org.uk/pressreleases/good-

progress-in-some-areas-but-much-more-needed-to-meet-third-and-fourth-carbon-

budgets-26-june-2013/ (accessed 22 September 2013))

43. The TTT construction would largely come within the apparently challenged third carbon

budget period and would therefore play a part in hindering achievement. This is plainly a

further serious adverse impact of the proposed development and therefore should be

considered as a Subsection (7) issue

44. A main benefit is aesthetic, but this in no way matches the cost of the project and

could be achieved more cheaply in other ways This is a variant on my discussion on

negative cost benefit, and I do not propose to add more here. It relates to Principal Issue

5 – Visual impact, also maybe to Principal issue 11 – social-economic effects.

45. TTT is being undertaken on account of the UWWTD but is not truly in accordance

with the allowed principle of BTKNEEC This is an issue of value for money, which has

some relationship to Principal Issue 6 - socio-economic effects, but is more an issue of

efficiency in public expenditure. This can be expressed as best value for the paying

public, and not spending more than is necessary to achieve a sufficient outcome. If this

is not part of national policy, it should be. Gold-plating of European standards should

not be undertaken unless clearly in the public interest. .

46. The TTT as proposed is aimed at almost full compliance with UWWTD. The only

apparent use made of the allowed BTKNEEC principle is that there are expected still to

be a few overflow incidents every year. This applies only to the collection system.


(22/09/2013) page10 of 11

47. However, the principle can also be applied to treatment in relation to storm events, as

was made clear by the European Court infraction proceedings judgement, as well as in

Annex1 of the directive.. That plainly envisages that it is not possible – so not necessary -

to construct collection systems - and treatment plants - in such a way that all waste water

can be treated to full standard in situations such as unusually heavy rainfall.

48. The Directive therefore calls for measures to limit pollution in receiving waters due to

storm water overflows, invoking the principle of BTKNEEC in this circumstance. Now the

present skimmers and bubblers used for this purpose have certainly been tested in the

infraction proceedings as to whether they are sufficient, and found wanting.

49. But other measures at the storm outflows have not been either proposed or tested for

sufficiency. The only alternatives to the TTT that have been publically identified in the

NPS and in the supporting documents submitted by the Applicant have been more

expensive than TTT, and so have no relevance to BTKNEEC optimization.

50. To illustrate the issue I would like to refer to one of Professor Chris Binnie’s reports

already mentioned : (Binnie: 11/3/13) This includes “interim measures” involving vortex

separators to remove floating matter from the outfalls and return it to the interceptor and

a variety of other measures to mitigate pollution of the river. The preliminary budget

estimate was for about £30million.

51. Now this very low-cost work has not been proposed as a sufficient BTKNEEC measure.

But if more mitigation was needed, it would also be possible to add further measures at

the outfalls for this purpose . One such measure would be to extend the concept of the

vortex separators by modifying the proposed dropshafts in the proposed development to

provide a further degree of separation and return, treatment and oxygenation to the

remaining storm overflow before then releasing it into the river through suggested river

bed diffusers, allowing substantial dilution at point of release.

52. The concept of treating waste water in shafts is a recognized technique. This would

clearly cost considerably more than the Binnie interim measures, but would save the

even greater cost of the main tunnel (and also the related pumping and treatment costs

at Beckton, though there would certainly be other treatment costs in such an

arrangement) . And it would provide a large measure of mitigation of pollution of the river

by storm overflows as called for by the UWWTD, making use of the BTKNEEC principle

53. Now I am aware that you have made very clear that you can only consider the proposed

development itself. I am not asking you to consider these mitigation measures as part of

the proposed development but simply to suggest that best value for money has not been

demonstrated by the proposed development. This is a feature of the adverse impact of

the proposed development and therefore can be considered as a Subsection (7) issue.

54. Conclusion: I have expanded here my original submission requesting that this proposed

development of the TTT should be recommended for rejection, even though it appears in

the Waste Water National Policy Statement; this is on the main grounds that the adverse

impact of the proposed development would outweigh its benefits. This is in accordance

with the provisions of Section 104, Subsection (7) of the Planning Act 2008..

55. Matters contributing to the adverse impact include that It has not properly taken into

account the important BTKNEEC principle of public expenditure. More importantly, It fails


(22/09/2013) page11 of 11

not only direct cost-benefit tests, but also hinders other Government policy and

legislation, notably relating to energy and climate change.

References:

1 (Binnie: 11/3/13) : [Ref: Thames Tideway Tunnel: Interim measures to improve the river. Working draft 11th March 2013 Report By Professor Chris Binnie MA, DIC, HonDEng, FREng,

FICE, FCIWEM [email protected]]

2 (Binnie: 17/3/13) [Thames Tideway Tunnel: Costs and benefits analysis and consideration of

interim measures with addenda1,2&3. By Professor Chris Binnie MA, DIC, HonDEng, FREng, FICE,

FCIWEM [email protected] March 2013]

W Alexander H Hamilton MA, CEng, FICE, MCIWEM

22 September 2013

1

Thames Tideway Tunnel

Costs and benefits analysis and

consideration of interim measures

with addenda1,2&3.

by

Prof Chris Binnie

MA, DIC, HonDEng, FREng, FICE, FCIWEM

[email protected]

March 2013

Tideway Tunnel 2 Response defra cba 2011 17 3 13

2

Executive Summary

The Thames Tideway tunnel is proposed so the Tideway can meet the Urban Waste Water

Treatment Directive and contribute to meeting the Water Framework Directive. The former

has a requirement that “Best Available Technology Not Entailing Excessive Cost” should be

used .The latter has a clause that the cost should not be “Disproportionate”. To assess this

defra has recently issued a report Cost and Benefits of the Thames Tunnel. This is based on

2006 reports by eftec Stated Preference Survey and by NERA Cost Benefit Analysis. defra

increased the assessed benefits due to inflation and also increased benefit due to population

and real income growth. The benefit was assessed by defra to be in the upper half of the

range from £2,969m to £5,058m. This compares with the current estimated capital cost of

£4.1bn. Thus defra concluded that the tunnel will be cost beneficial.

I have reviewed the base documents and the defra Cost Benefit report. The DEFRA revised

CBA estimate has been selective in concentrating on those areas where there is an arguable

case for up-rating benefits estimates: population growth, income growth, and asset life, while

ignoring those uncertainties which support an alternative view that the benefits were

significantly overstated in the first place: overvaluation of health benefits well beyond the

level and severity of illness that could be affected by the tunnel project, the known tendency

of single issue willingness to pay surveys to over-value, and the failure to give respondents

significant information about the scale of avoidable illness. Also, by my maths, the defra

figures are over-valued by about 10%.

The 2006 base valuation was £3,935m. There was no split of this but there was a split of the

2002/3 CBA so I have used that, 60% to health benefit, £2,400m, 15% to fish, £600m, and

25% to sewage litter, £1,000m.

Health benefit

There are about 2,000 recreationalist in the London docklands, water skiers and dinghy

sailors. The docks are a confined body of water and the limited amount of top up water could

be treated at a cost of about £10m.

Those at the main risk of health impact are the 2,000 rowers in the Hammersmith area.

These are some ten times less susceptible to gastric problems than the general population.

The normal method of analysis is QALY. Based on the numbers involved, the frequency of

illness, the length of illness, the value of time, and the long term discount factor, NERA

calculate the benefit as £1.5m, considerably less than £2,400m.

Ecological benefit

Fish kills occurred in 2004 and 2011 but both of these appear to have been caused primarily

by Mogden STW overflow. To deal with this Mogden is being currently uprated by 50%.

Because fish are the most sensitive ecological species the TTSS set the environmental

standards as dissolved oxygen (DO) content of the river water with different levels and return

periods. Trials were done of a suite of fish species to ascertain their response to different DO

levels. The most sensitive species is trout/salmon but salmon are no longer in the Thames

and are not deemed naturally sustainable. The DO standards were set on minimising fish

kills, a more onerous standard than a sustainable fish population.

3

With the sewage treatment upgrades and the Lee tunnel currently under construction the

river goes a long way to meeting the dissolved oxygen standards. A Tideway Fish Risk

Model was developed, taking account of where fish were located, the sections of the

Tideway which would be impacted, and the resistance of each fish species. This showed

that even without the Lee tunnel, the Tideway fish species were sustainable.

Cascade in March 2013 reported that other WTP studies of the existence and biological

benefit of improving to meet the WFD dissolved oxygen standards, and thus minimise

salmon mortality and avoidance, would for the Tideway be about £15m, much less than the

£600m assumed by defra.

Litter

Sewage derived litter is only 10% of all litter. The Health Protection Agency state “Shortly

after discharge floating matter disseminates relatively quickly.” Eftec, consultants to TTSS

stated “Little aesthetics change in the water is to be expected due to Tideway Strategy

Options, and this, together with the low correlation between riverside residence and

involvement in river-based water sports, suggests that any impact of the Tideway options on

property prices is likely to be minor”. Were the £1,000bn benefit to reduce to £200m then,

with the construction disbenefits and the other adjustments, the benefit would become

negative.

Other adjustments

Interviewees were given a single choice so i have adjusted this for multiple choice based on

another analysis. The Thames Lee tunnel tonnage split was wrong and has been corrected.

The appraisal period selected by NERA and in the defra 2007 RIA, has been maintained.

The mid range of the anciliary benefits and disbenefits has been incorporated. I have

updated the economic growth factors and corrected the mathematics.

I have doubts about the validity of the benefit base being increased from Thames Water

customers to all England, the lack of allowance for finance for solving other rivers problems,

the use of mean rather than median values, and the distance/decay analysis. These would

reduce the benefit substantially but I have not adjusted the defra assumptions.

In contrast to the defra CBA report, my analysis shows that, following the methodology used

by defra, and on the basis of the reasons provided, the total NPV benefit would be about

£275m. This is about 7% of the cost of the Thames Tunnel. The analysis is summarised in

the table below.

Benefits at, or near, this level would mean the cost of the tunnel would be “excessive cost”

under UWWTD and “disproportionate cost” under the WFD. Were the litter benefit, classified

as “minor” by eftec, be not £1,000m but, say, £200m then the total benefits would be

negative, being less than the dis-benefits of the construction process.

A SuDs/Blue green sytem would much reduce the storm water runoff and hence the CSO

spills. Thames Water support such measures but consider, with some justification, that

there are insufficient powers to implment such an approach widely and that such measures

would take many years to implement.

4

Whichever solution is adopted, there will be many years before it is sufficient, 2023 for the

tunnel. Thus I have proposed intim measures be adopted including metering to reduce water

use and discharge to the sewers, realtime control of sewer flows, the implementation of a

fixed bubbler system in the river to minimise oxygen sags, supported by water quality

monitoring and mobile bubblers to tackle any particular areas giving problems. In addition a

number of booms and skimmers should be provided to collect litter. To improve water

quality in the London docks then water treatment could be provided to the top-up water.

These measures are not expensive, estimated cost some £30m, and should provide a good

cost benefit return. They are measures similar to those which have been successful in

Cardiff harbour for the last five years.

The object of the UWWTD is to limit pollution. Whichever method of meeting the UWWTD is

adpted, the interim measures would provide benefit.

Item 2003/5 2006/7 2011 Comment Adjust

CBA CBA CBA ment

Base amount £3,935m £3,935m

Health 60% combined combined QALY not WTP -60%

Fish 15% combined Economic analysis not WTP To £15m

Litter/aesthetics 25% combined Property benefit minor none

Jurisdiction Admin A+B A+B Benefit Jurisdiction doubt none

Single/multiple single single single Multiple in FBP -60%

Other rivers No allowance. ? half none

Mean/median mean Protest votes none

Distance decay No Yes Yes Results look odd none

Monetary values no No No 15% constant nominal none

Thms/Lee split NO No TT 60% Adjust tonnage -57%

Benefit of Lee T No No No Lee tunnel needed for Thms T none

Appraisal period 60 years 60 years 100years 60 years none

+14% £230m

Reduced hh flood no Entec Table 4.3 +£7m

Disbenefit no no no Half upper of £85m -£42

Base amount 195m

GDP deflator 06-11 +10.6% Accepted +10.6%

2011 2,969m £215m

Population rise No No +14% +14%

amount 3,391m £246m

Real income growth

NO No +33% 2006-2011 zero not 10% 2011 to 2014 half assumed long term, 1% not 2%

+12%

Spill volume Not included

Not included

Fish £15m

Amount 4,502m £290m

Quoted range 2,969-5,058

Wrong maths by defra ?

Mid point benefit 4,013m Defra mid point £3,735m ?

5

Contents

1 Introduction 7

2 Cost benefit stated preference Survey by eftec Dec 2006. 7

Description of the alternative schemes 7

Description of the outputs of the alternative schemes 8

Fish population 9

Sewage litter 10

Risk of suffering illness through contact with river water 12

Administrative/benefits jurisdiction 13

Distance decay analysis 14

3 Thames Tideway cost Benefit Analysis by NERA Dec 2006 16

Single/multiple issue WTP studies 17

Mean or median values 18

Protest votes 18

Monetary values 19

Benefit split 19

Benefit attributable to health risk reduction 20

Validity of stated preference Willingness to Pay methodology. 21

Benefit from reducing fish kills 23

Benefit from reducing sewage derived litter 37

Cost benefit analysis 39

4 Cost and benefits of the Thames Tunnel defra Nov 2011 39

Validity of previous WTP study 39

Other benefits 39

Cost estimates 41

GDP deflator 42

Apportionment of benefit 42

Period of appraisal 43

Disbenefits 46

2011 range of benefit 46

6

2011 Range of benefit increases 47

Population increase 48

Real income growth 49

Spill volumes 51

Benefit conclusion 51

Defra CBA conclusion 52

5. A strategic and economic case for the Thames tunnel, defra, November 2011 53

Current discharges 53

Future discharges 53

London’s reputation etc 54

Alternative options considered 55

Phased approach 55

Jacob Babtie report recommending the west tunnel 55

Paying for the tunnel 57

Uncertainties 58

Conclusions by defra 58

6. Conclusions of the CBA analysis 59

Treasury requirement 61

7. Do minimum system 61

Fixed and mobile bubblers to control dissolved oxygen 61

Litter collection 63

Health aspects 64

Consideration of standards to be met 65

Cost benefit 66

Programme of installation 66

Recommended investigations 66

8 Conclusions 66

9.Recommendations 67

Appendix A Description of the Cardiff Harbour scheme 68

7

1. Introduction

I was the Independent Chairman of the Thames Tideway Strategy Steering group from

2000-2005. I continue to be independent, my time input in preparing this report is not funded

by any party or lobby group, and I live outside the Thames catchment so I would not benefit

from any change in Thames Water charges.

In October 2011 I gave evidence to the Thames Tideway Commission in my Project

Justification Review,(PJR) with 5 subsequent addendums as more information became

available

In November 2011 defra issued a Costs and Benefits of the Thames Tunnel report. This is

based on the 2006 eftec Stated Preference Survey and the NERA Cost Benefit Analysis,

with benefits updated to 2011 and further benefits added.

The defra CBA considers that the benefit of the full Thames tunnel is in the upper half of the

range £2,969m to £5,058m, ie at least £4bn. This is similar to the current estimated cost of

the Thames Tunnel at £4.1bn. Thus defra considered that construction of the full Thames

tunnel is warranted.

I am grateful to defra, Thames Water (TW), the Environment Agency (EA), Cardiff harbour

Authority, and others for the provision of recent data and reports, and for meetings.

My analysis looks at some of the factors in the two base documents and then the CBA and

has concluded that the benefit of the full tunnel could be sufficiently low that the cost, relative

to the benefit, is likely to be classified as “excessive” under the Urban Waste Water

Treatment Directive (UWWTD) and “disproportionate” under the Water Framework Directive

(WFD). My analysis then considers an alternative system along the Treasury “do minimum”

option and whether this system would meet the UWWTD and WFD.

2. Cost benefit Stated Preference Survey by eftec, Dec 2006

Introduction

A Willingness to Pay study was done by Eftec, Thames Tideway-Stated Preference Survey

December 2006, with field testing done in October 2006.This was first used to assess the

comparative cost/benefit of three alternative tunnel systems.

This Eftec report was then used by NERA Thames Tideway Cost Benefit Analysis December

2006, to assess the benefit cost ratio of two groups of three alternative tunnels. Finally the

Eftec and NERA reports were updated by defra to provide cost benefit analysis of the

Thames Tunnel.

First I will consider the Eftec report and the validity of the descriptions used of the tunnel

alternatives and then the validity of the benefit methodology and output.

Descriptions of the alternative schemes

8

Three schemes were tested by Eftec, a “large” storage tunnel 7.2m dia, a “small” storage

tunnel 5m dia, and a “two tunnel” option with a tunnel from Hammersmith to Battersea and

the east, Lee, tunnel.

The large tunnel at 7.2m dia is the same size as the currently proposed Thames Tunnel from

Acton to Abbey Mills. The main tunnel capex is set out on page ii of the NERA Cost Benefit

Analysis Report 2006 as about £2.36bn.

However the concept for the two tunnel scheme at that time was that that would be the final

scheme. Thus the west tunnel was sized at 7.6m dia and the east, Lee, tunnel as 13m dia.

The NERA two tunnel cost is £1.8bn. Insufficient information is provided to examine the

reasons for this but it would appear that the east tunnels are sized at 13m and 10m dia. The

Solutions Working Group Report December 2006 states on page 18 “ The tunnel route

directly between Abbey Mills and Beckton will cross under the cable tunnels currently under

construction, near Abbey Mills. The predicted ground movements and deformation curvature

are very significant for the 13m dia tunnel and will therefore be unacceptable. The potential

impact from the 10mdia tunnel would be less, but still quite significant. ...It is likely therefore

that the 7.2m dia tunnel would be the only practical option.”

Thus the east tunnel, at the sizes chosen, was not feasible. Thus its capital cost would also

have been too high.

An alternative would have been for the two tunnel scheme to be considered as part of a

phased development. Thus the west and east tunnels would be sized at 7.2mdia, or, for the

west tunnel, at some similar size dependent on modelling analysis to balance storage

volume, spill overflows, and pump out time. Certain extra works would be required to pump

out the west tunnel

When, if ever, the two tunnel scheme ceased to meet the standards required, then the full

scheme would be completed, subject to disproportionate cost and BTKNEEC considerations.

This programme would postpone major capital expenditure, albeit resulting in some potential

increase in cost due to remobilisation to construct the intermediate tunnel but such a

programme was not considered.

Description of the outputs of the alternative schemes

The earlier, 2003, willingness to pay analysis split the benefits between the features and had

separate benefits for health, fish, and litter. In contrast the 2006 survey used a compound

table. The description of scheme outputs is given in table 3.1 below.

The eftec 2006 WtP study on page 8 states “the improvements in the attributes now defined

are much more subtle. Therefore, using choice modelling in this study could have resulted in

WTP per attribute estimates to not be statistically different from each other.”

Thus, if the difference in each of the attributes is subtle, and could have resulted in estimates

not much different, then how come the substantial difference in the end WTP for the large

tunnel and the two tunnels ?

9

Below I consider whether the Table, as shown to interviewees, reflects the actual situation

appropriately, or is misleading, whether it reflects the baseline situation, and also whether it

reflects my current proposals for the two tunnels plus some minor, but important, additions.

First let us examine each of attributes in turn.

Fish population

The description is based on the number of “occasions when the oxygen levels in the water

drop low enough to either kill some fish or prevent migration (eg salmon).”

Since 2000 almost no salmon have returned to the Tideway, see my Project Justification

Review. The EA now consider salmon unsustainable in the short to medium term and have

ceased stocking salmon fry. Recent studies reported by Dr Friedland show that climate

change, including increasing temperature, would mean that salmon in southern England

would not be sustainable in the longer term. Thus the prevention of salmon migration is no

longer an issue.

10

Thus consideration now needs to focus on sustainability of the remaining fish in the fish

suite. This is discussed more in section 9 and in Section 3 and in my Project Justification

Review.

The two tunnels scheme is described as resulting in approximately one occasion of fish kill

per year. This is the same description as for the large tunnel. However it does not recognise

that a sustainable fishery can occur with a higher proportion of fish kills than assumed in the

TTSS standards.

Thus, now that salmon are no longer a stocked species or a sustainable species, the

descriptions in the WTP survey do not appear to fit with the situation.

Sewage litter.

Background

Sewage litter is unpleasant and reducing it is a worthwhile objective, providing it can be done

at an appropriate cost. However TTSS concluded that sewage litter accounts for only

approximately 10% of all litter in the River Thames.

The Health Protection Agency report page 22 states “The nature of the tideway is such that there is a consistently high level of turbidity at all times.” Thus the river is a dark turbid muddy colour. A party from the Thames Tideway Strategic Study Group reported: “The river has been inspected during and after a number of rainfall events and the effect of

the CSO discharges on aesthetic quality has been assessed. Large greasy,grey/black slicks

with associated floating sewage-derived material was observed in all of the reaches to which

the CSOs discharge. On the ebb tide, sewage solids are deposited on the foreshore and are

clearly visible. The most badly affected parts of the river are in the Putney to Vauxhall area

but depending on tidal conditions and the operation of the CSOs, other locations can be very

badly affected.”

Consultants for Ofwat,Jacobs Babtie, following a visual survey of sewage litter several days

after a rainfall event, observed that “our opinion is that it would not be immediately apparent

that the debris was any more than windblown litter and vegetation.”

Some of what is perceived as sewage litter is not. After storm events at Mogden in July 2009

complaints were received. The Environment Agency investigated and concluded:

“Our findings indicate that the persistent brown solids seen floating in the river and stranded

on the foreshore are not sewage related. They are a natural organism, mosslike in

appearance, which pose no health risk, but can give the appearance of sewage on the

water. . .

During storm events, faecal solids are discharged in the storm sewage. However, these are

usually broken up and breakdown within two to four days. Other sewage litter can also be

seen immediately after an event but this too usually dissipates fairly rapidly. “

There are, so far as I know, no regulatory powers concerning aesthetics. Many would say

that the Thames flowing through London is an aesthetic asset at most times and places. The

strong demand for residential property overlooking the river is clearly not put off by any

11

potential sights. Efforts by Entec to find a measurable economic impact on housing values

failed.

Dispersal, maceration, and the careful placement of some of Bazalgette’s storm overflows

near and under bridges are no doubt among the reasons why the large volumes of sewage

solids reported in the TW Needs Report 2010 are not noticed by the majority of people.

The Eftec 2006 Stated Preference survey asked how far respondents reported seeing

sewage litter. Of respondents from the Thames area 68% said they were familiar with the

Teddington to Gravesend section of the river, Table 4.5 page 23. They tended to believe that

sewage pollution was an important factor (perhaps prompted by being asked to participate in

a survey about the issue) but the majority had not seen sewage pollution for themselves to

any great extent. Two thirds had never seen human waste, over 80% rarely or never, page

25 see table below.

A majority of those questioned had seen bottles and packaging etc which would not

generally have come from the sewers. A large majority had rarely or never seen condoms,

syringes, sanitary towels, human waste or dead fish. Only approximately 5% of TW

respondents reporting seeing such sewage items “always or often” .

Eftec show cards For the large full tunnel scheme the description is “sewage litter. small amount visible 3

times per year following overflows.”

For the two tunnel scheme the description is “Location-specific. Overall risk reduced by

some two thirds. No change for the overflows not connected, which still cause a higher risk

from 60 overflow events per year.”This is misleading. There is no mention of the number of

overflows that would be collected. The 39Mm3 of overflow currently would, according to the

TW Table handed to me on 21st October 2011, be reduced to 9.5 Mm3 for the two tunnel

scheme. This is a ¾ reduction in overflow volume. Because the worst overflows have been

dealt with, the number of spills a year would be down to a maximum of 40. In addition any

two tunnel scheme should include skimmers, as recommended by Jacob Babtie, which

would pick up floating debris. Thus the description in the WTP survey does not fit with the

two tunnel proposal.

12

Risk of suffering illness through contact with river water.

The description of the large tunnel states “ Higher risk only following the remaining 3

overflows per year.” For the two tunnel scheme the table says.” Location specific. Overall

risk reduced by two thirds. No change for the overflows not connected, which still cause a

higher risk from overflow events per year.” Both also include the comment “High risk at all

other times.”

These comments do not reflect that it is the numbers of people who have contact, and where

people have contact with the river, that matters most. The two main places are the Putney

area for rowers and the docks area for dinghy sailors and water skiers.

The histogram below shows the numbers involved in recreation. The right hand bars are

people downstream of Mucking. This is over 15 miles downstream of the most seaward CSO

at Beckton. The people are mostly dinghy sailors off Southend, another 10 miles seawards.

Thus they would effectively be outside of the influence of the Tideway CSOs. The Tower

Bridge to Thames barrier group are almost entirely dinghy sailors and water skiers in the

London Docks.

Thus the table does not bring out that some 90% of the recreationalists are in two limited

areas of the Tideway.

Thus the original text was somewhat misleading and does not reflect the need or the benefit.

Frequency of overspills.

For the two tunnel scheme the text says “ 60 times per year for some overflows but three

times per year where the tunnel is built.” This is incorrect as the Thames Water table of spill

frequency provided in October 2011 shows the worst spill frequency for the two tunnel

scheme is about 30 times a year for those CSOs not connected. Thus the table does not

reflect the latest sewer modelling. I have been informed that some member states accept

spill frequency of less than 10 times a year as satisfactory and that the Commission at the

infraction proceedings talked about a guideline of about 20 spills a year. Of the 29 CSOs in

the TW schedule in the section of Tideway downstream of the west tunnel, 20 spill on

13

average less than 10 times a year. Thus the text about the two tunnel scheme is again

misleading.

Water bills

All the schemes have the statement “Water bills. Will continue to increase to finance

investments in water supply, leakage reduction and sewage treatment.”

There is no mention of the amount by which the water bill would have risen anyway. The TW

Final Business Plan 2009 shows this as £48/hh/year above inflation (although the ofwat

Final Determination might be slightly lower). For the PR14 determination there is also likely

to be further appreciable bill increases for metering, further leakage reductions, and water

supply. Due to possible sustainability reductions, the Abingdon reservoir at about £1bn,

about £20/hh/year for most customers, could yet be required.

There is also the question as to whether, if interviewees had known that, to pay for the

tunnel scheme, the average bill would increase by about a further £80/hh/year, plus an as

yet unknown amount for other requirements arising from the Water Framework Directive,

whether this would have reduced their willingness to pay. Probably but no account has been

taken of this.

As bills rise so water affordability for some becomes more of an issue.

For the twin tunnel scheme, there is no mention of the significantly reduced capital

expenditure, and hence lower water bill increase. There should have been. Thus, in my view,

the Table is misleading about the two tunnel scheme.

Conclusion

Thus the Table, as shown to interviewees during the WTP survey in 2006, does not, in my

opinion, adequately reflect the actual schemes proposed then. Nor does it reflect the

situation from my proposals for the twin tunnel scheme including the potential benefit of

bubblers and skimmers which are low cost, and in my view, should have been included.

Thus, in my opinion, the CBA of the schemes should have been reconsidered, prior to the

final decision on what scheme should be constructed.

Let us now look at the actual survey data and its interpretation.

Administrative /benefits jurisdiction

TW customers would be the people who would pay for the investment and hence are

referred to in the eftec report as the administrative jurisdiction. However the population that

can potentially benefit from the environmental improvements incorporates all who see, pass

by or purposefully visit the Tideway and hence are called the benefits jurisdiction.

For the 2002/3 stated preference (sp) Willingness to Pay (WtP) study only those in the

administrative jurisdiction were included, see TTSS Cost Benefit Working Group Report

February 2005 page 17, as those are the ones that would have to fund the costs of the

scheme.

14

However, for the 2006 eftec sp, wtp surveys were carried out covering the whole of England

and both the Thames Water administrative area and the full jurisdiction in all England results

calculated. The benefit from the Thames Water administrative jurisdiction alone was found to

be less than the cost of the tunnel so the focus of the subsequent CBA was on the whole of

England, classified as the benefit jurisdiction.

No clear evidence is given as to why the area assumed in the WtP study was changed from

the TW customer area, as used in the 2004 study, to all England in the 2006 WtP study.

It is noticeable that the benefit rises from £66m/year in the Thames Water customer area to

£174m/year in the all England area, see NERA Table 2 page ii. Although many people

outside the Thames Valley will know and appreciate the Tideway, there are many more who

will not. Although many more people live outside the Thames catchment than within it they

are very much less likely to see or benefit from the improvements. Instinctively having the

benefit of those living outside the Thames catchment some 1 and a half times the amount of

those living within the Thames catchment seems high. Respondents outside the Thames

administrative area were not asked whether they would expect reciprocal assistance with

costs falling on their own water company or reminded that Thames sewerage bills are

generally lower than those of neighbouring water companies. Thus there may be doubt as to

the extent of the benefits assessed from the all England benefits jurisdiction.

Presumably the interviewees were expected to assume that the average water charges in

their own company’s area would be going up as historically they had. However they were

asked about paying for a single issue, the Tideway tunnel to improve the water quality of the

tidal River Thames. What would have happened if they had also been asked what they

would also be willing to pay to improve the water quality of the Severn, the Trent, and the

freshwater Thames? Would their willingness to pay for all four have meant the amount they

were willing to pay for the Tideway would have gone down. Almost certainly yes.

As a corollary, would the amount the interviewees in the Thames Water area were willing to

pay have gone down if they had also been asked to pay for water quality improvements in

these other rivers as well, and the improvement of bathing beaches water quality around the

coast. The answer is almost certainly yes. However there is no way of knowing the extent of

the over-assessment due to the use of single feature assessments outside the

administration jurisdiction. My memory is that that was one reason why the TTSS included

only the benefits from within the Thames Water customer area. Thus the figures of benefit

from the all England area should, in my opinion, be treated with caution.

Distance decay analysis

The Eftec Stated Preference Survey report includes the analysis of the three schemes and

considers both the mean analysis and the result based on the distance decay function. It

also splits the results into the administrative jurisdiction, ie the area covered by the Thames

Water sewage function, in effect the River Thames catchment, and the benefits jurisdiction,

assumed to be England. The results vary widely.

The mean estimate is shown in table 6.3. The aggregate WTP, central estimate for the

administrative jurisdiction in £ per year is

15

Large tunnel £123M

Two tunnels £100M.

These numbers are reasonably close and are believable, the lower benefits of the two tunnel

scheme being similar, but somewhat lower than the large tunnel scheme.

The report then analyses the response on the distance decay basis. That means that as the

distance increases the respondents assessment reduces. This seems a logical principle.

However the report does not show the data on which it bases the decay function. Thus one

cannot see the data plots that lead to the distance decay function. That is an unfortunate

deficiency.

For the Thames Water customer in Table 7.1 the distance decay function results in WTP

per year of

Large tunnel £66M

Two tunnel £26M.

This big divergence between the two tables seems odd. The base is the population of the

sewage function. For the total administrative function this is 13.6M. Of these the GLA says

that 7.6M live in London. None of these are more than about 10 miles from the River

Thames. It seems hard to think that there would be much of a decay function within London.

However for the total for the two tunnel scheme to drop to about a quarter of the mean, then

the decay function in London, where no one lives much more than 10 miles from the

Tideway, must be more, on average, than 50%. I asked eftec for the reasons but did not

receive a reply.This does need reconsidering. Since no distance/decay data is provided it is

not possible to examine the reasons. However it does show that the output of the report

does need examination and reconsidering.

Thus the output of the report, until it is reconsidered, must be considered of unproven

reliability.

The all England area decay function for the two tunnel scheme is found to become zero at

Sheffield in Yorkshire, 160 miles from London. Yorkshiremen are known for being frugal.

Would the results have been different if Manchester or Taunton had been chosen as the

distant location? Maybe.

The distance decay function for the large tunnel is found to continue to at least 270miles.

This boosts the large tunnel so that the annual WTP for the jurisdiction area becomes

Large tunnel £174M

Two tunnels £ 43M.

Considering the closeness of the outputs set out in table 3.1 this wide variation in WTP

between the full tunnel and the then two tunnel scheme does seem surprising. The eftec

study on page 8 states “the improvements in the attributes now defined are much more

subtle. Therefore, using choice modelling in this study could have resulted in WTP per

attribute estimates to not be statistically different from each other.”

16

Thus, if the difference in each of the attributes is subtle, and could have resulted in estimates

not much different then how come the substantial difference in the end WTP ? This does

seem surprising. This is probably partly because of the misleading aspects of the

questionnaires.

Conclusion

The description of the full tunnel scheme appears sound.

The description of the two tunnel scheme is misleading and adverse and costs inflated by

taking a diameter for the east tunnel that was impracticable.

The description of the two tunnel scheme does not tally with the Lee tunnel currently being

constructed and the west tunnel. It would be appropriate to consider a phased development

of the full scheme.

The differences between the scheme attributes are described as “subtle “ by eftec’ however

the difference in benefit between the large tunnel and the two tunnel scheme is

considerable. This is not logical and the reasons are not explained.

The distance decay WTP of the two tunnel scheme for the administrative region does not

appear to be consistent with the figures for the mean value.

Although the 2004 CBA analysis had used only the Thames Water Administrative area, the

area of assumed benefit in the 2006 CBA analysis was extended to the whole of England on

the basis that the whole population of England would benefit. This seems challengeable.

3 Thames Tideway Cost Benefit Analysis by NERA December 2006

Introduction

The NERA CBA report of 2006 considers the eftec Stated Preference Survey and then

provides the cost benefit analysis. NERA produced a final report dated January 2007 but the

differences are a few phrases only and make no change to the points made below.

References below are to the NERA report unless noted otherwise.

NERA calculates in Table 7.2 page 32 the net benefit for the full tunnel (option 1c phased)

in the administrative jurisdiction as £1.5bn with discounted cost of £2.05 bn. Thus, for the

administrative jurisdiction, ie the Thames Water customers who would actually pay for the

full tunnel scheme, the cost benefit ratio assessed by NERA was significantly less than 1.

Thus the cost would be likely to be deemed excessive under the UWWTD.

For the full tunne,l for the all England area, the net benefits are £3.9bn. Thus the benefit

cost ratio was 1.9, with no substantial difference between the variants considered (see Table

3 on page iii). As discussed above, there must be doubt about the validity of extending the

benefits to the whole of England where the sewerage charges are generally significantly

already higher than in the Thames Water area.

NERA identifies a number of potential adjustments.

17

Single/multiple issue WTP studies

“It is noted that questions about one environmental benefit, such as a cleaner river, may

yield different higher valuations from questions about allocating money across a wider set of

benefits. We believe that such factors are legitimate reason for caution in reliance on stated

preference results, but we do not consider them further in this report ” , page 27.

My understanding of this comment is that people may have in mind a general amount of

money they would be prepared to spend on environmental benefits in general. Thus if they

are given a wide range of potential benefits, they will scale down the amounts they would be

willing to pay on each of the schemes compared to what they would be prepared to pay on a

single scheme..

Richard Cookson in his paper “Willingness to pay methods in health care” in 2003 states

“investigators have found that people tend to state a similar amount- roughly £50- for any

given magnitude of reduction in the risk of death or injury.” Whilst this statement refers to the

health sector there might well be a similar effect generally, ie £50 to be spread around

however many benefits were being considered. He also notes that Willingness-to-Pay

methods are notably poor at reacting appropriately to the scale of an issue or intervention.

The mean value of the amount Thames Water’s customers were prepared to pay in 2006 for

the full tunnel is shown in Table E1 of the eftec Stated Preference report 2006 as £24.66

/hh/year. This is the basis of the further WTP calculations.

However soon afterwards TW carried out a multi issue WTP for its Business Plan, see below

from Annex C-1 page 61

This shows a Willingness to Pay of some £6.9 per household per year for improvements to

ecological river quality and £3.1 per household per year for recreational river quality. This is

a total of some £10 out of a total willingness to pay of some £43. This of course applies not

just to the Tideway but to all the rivers in the Thames Water catchment. Thus, at best, the

£25/household/year should be reduced to £10 per household/year, a reduction of 60%. Thus

the NERA CBA would appear to be overestimated by about this amount and should be

reduced accordingly.

18

Eftec, during their WtP data collection asked respondents what was their priority for public

spending. Table 4.3 shows “water quality in local rivers” got 6.2% first preference and 10.3%

second preference in the TW area and 11.6% and 9.2% in the non TW areas. This of course

would come out of a larger sum as it included such topics as air pollution, but the amount

would need to cover all rivers. Thus, whilst not monetised, it would indicate that the £10/hh

in £43/hh would be significantly too high, and could be as low as about £5/hh/year, a

reduction of about 80%..

In reality to allow for funding of river issues elsewhere, the reduction ought to be even

greater. However, to be conservative, I have kept with the 60% reduction.

Mean or median values.

Another issue on which there is no unambiguously correct answer is the choice of mean or

median values from the survey results. NERA base numbers are derived from mean

willingness to pay.

Mean values are significantly higher values, but “give weight to those who are willing to pay

more money because they are richer” and to “those with exceptional environmental

preferences over those with average. “ NERA note that “given difficulties with the mean it is

not universally used in cost benefit analysis, “ and that median wtp is more usually used

within government for small reductions in death and injury. (Nera p28)

The comparison is given in Tables 4.16 a a and b as large tunnel entire sample mean

£19.30/hh, median £10/hh. Thus changing from a mean value to a median value would

nearly halve the assessed benefit. As the choice is ambiguous I have not changed from the

mean but it is yet another instance where the benefit assessment may well be too high.

Protest votes

The third material point is what are described as protest votes, ie people who deliberately

give no value to the benefit as a protest.”It could be argued that people’s preferences are

what they say, whatever the reason, and they would presumably vote that way, given the

opportunity...In our Base Case we rely on the data presented by Eftec, which excludes

responses judged by Eftec to represent protest responses.” page 28.

As I understand it protest votes are those who would not fund the scheme as a protest

against some issue. However no evidence is provided that shows that the protesting person

would change their view. Thus I question the basis on which the protest votes were

excluded. In my view there is no evidence on which to do so.

As I understand it the result in excluding the protest response is to include in the calculation

only the amount and numbers of those recorded and excluding the protest vote. This

average is then applied to the whole population including those who might have registered a

protest.

NERA continue “The inclusion or exclusion of such response might make a material

difference. For TW customers their exclusion increases the mean valuations by 20 to 30 per

cent and increases the medians by 50 to 100 per cent. For non-TW customers the effects

are smaller but still material.”

19

Clearly this is a serious issue, particularly for investment in a multi billion pound project.

Were one to assume that for the TW customers the reduction in the full tunnel WTP would

be 30% and for the non-TW customer 20%, then the annual willingness to pay would appear

to drop from £174m to about £140m, a drop of some £34m, or some 20%. Thus the NERA

CBA would appear to be overestimated by about this amount. However I understand that, as

implausibly high values were also discarded and that this is standard practice, I have taken

no reductions of the benefit in my numerical analysis.

Monetary values

NERA states on page 26 “The stated preference questions ask households to express

monetary values in terms of a constant and ongoing increase in their annual water bill.

Unfortunately we do not know whether the values households provided were meant by them

as monetary amounts with constant purchasing power or rather as constant nominal

monetary amounts whose purchasing power will erode with inflation....The first interpretation

is simpler conceptually and in modelling terms and is what NERA has employed in the Base

Case.”

However there may be respondents who took the question literally, and therefore the benefit

amounts used would have been an overestimate. It is not possible to assess the amount of

this overestimate. However the NERA sensitivity analysis in Table 8.1 for the deflated WTP

values shows that the benefit/cost ratio would drop from 2.04 to 1.4, a drop of 31%.

Assuming that 15% of respondents had responded as the second option then the drop in

benefit would be about 5%. However I have not adjusted the numbers in my table for this

effect.

Benefit split

The 2006 WtP survey did not collect data on each of the three benefits separately, just the

overall figure which came to £ 3,935m. However the show card did only mention just the

same three benefits so it would be appropriate to assume that the total would be on the

same basis.

The only evidence on which to split the overall 2006 benefit is on the basis of the 2002/3

survey. This was;

Health 60% £ 2,400m

Fish kill 15% £ 600m

Litter/debris 25% £ 1,000m

Both WtP surveys are for a large tunnel from Hammersmith to Beckton STW. Both talk

about the three benefits of reduced risk of suffering illness, reduced fish kill, and reduced

sewage litter. The first survey was done in November 2002 and the second in October 2006,

thus relatively close in time, so this in itself would not change the split. The only significant

difference is that, between the two surveys, a decision had been taken to improve the

sewage treatment works effluent standards. The footnote on page 12 of the Eftec stated

preference survey states “The only difference between this and the situation that prevails

now," ie the same situation as at the time of the original 2002 survey" is the number of fish

kills” which would reduce.

20

Thus there would be a case for reducing the fish kill proportion and increasing the other two.

However the fish proportion is, anyway, the lowest at 15%, so the scope for reallocation of

fish benefit is very small. For instance, reducing the fish proportion of the benefit to 10%,

would only provide another 5% to be allocated to the other two parts. Of importance, this

would not change the total base amount of the benefit. I have, therefore, kept the same split

as in the 2002/3 WtP survey.

Benefit attributable to health risk reduction

The Health Protection Agency (HPA) report The Thames Recreational Users Study 2007

states on page 48 “The 95 percentile of indicator organisms in the upper tideway

permanently remain above the WHO microbiological standards for recreational water and

this represents a potential health risk to recreational users.” Thus there is a background

health risk in the Tideway irrespective of the CSOs.

However the “WHO guidance is only aimed at bathers” total immersion and risk of ingestion “

and as such is not necessarily indictors of risk to other recreational use such as rowers,

sailing etc...” HPA page 8

“There is evidence to suggest that the influence of secondary treated effluent from Mogden

sewage treatment works is as great as that of the less frequent but common CSO

discharges.” HPA 2007 page 54.

The key information from a major study of health risks to recreational users in the upper part

of the Thames (upstream from Putney Bridge) is summarised in the TW 2010 Needs report:

“An assessment of health impacts upon recreational users of the River Thames was

conducted and reported by the Health Protection Agency in 2007. This report, which quoted

an EA estimate of between 3,000 and 5,000 recreational users of the tidal Thames... While

there was evidence of an elevated health risk (gastric infection) to recreational users in the

upper Tideway two to four days after a CSO spill event, the rate of gastric infection among

recreational users was very low (12.8/1000/year) compared to the general population

(190/1000/year). This may be due to the relative good health and fitness of recreational

users, a greater awareness of hygiene and health and safety issues, and a developed

immune response to infection from repeated exposure, which results in asymptomatic

infection.”

The fact that gastric infection rates among recreational users in the upper Tideway are less

than one tenth of the incidence level in the population as a whole, is a fair indication that the

Thames health baseline, and the possible impact of the intervention, are not significant on a

national scale in terms of the potential health impact. This is discussed further in section 7

and in my Project Justification Review.

NERA do an analysis on the basis of the government guide on Managing Risks to the Public

which discuses the Quality Adjusted Life Year as a tool for cost effectiveness analysis of

health impacts. NERA states that around £30,000 QALY appears to be increasingly

accepted by government as a method of valuing health impacts. NERA do an analysis of the

values of the potential health benefits based on the number of recreational users, annual risk

21

of infection, average duration of illness expressed as % of a year, and value of quality of life

adjusted life year.

“for example, assuming that number of recreational users per year (N) is 5,000, the risk of

infection during each year (R) is 18/1,000, the average duration of illness as a fraction of a

year (D) is 3/365, and the value of a QALY (V) is £30,000, and assuming that the loss of

quality of life during the period of illness is total, this would lead to an estimate of the annual

cost of the health impact (=N*R*D*V) of £22,000. The corresponding discounted present

value of such a stream of annual costs in perpetuity, if discounted the pure time preference

rate for utility of 1.5 per cent specified in the Treasury Green book, is £1.5 million.” Page 29

of the NERA cost benefit analysis.

This is a very small proportion of the 60% of base assessed benefits of £3,935m, about

£2,400m. Thus the total benefit assessed by the WTP survey would be reduced by about

60%. Clearly there is a considerable difference between QALY analysis and WTP analysis. I

consider the validity of sp WtP in the section below.

In addition it would be possible to provide water treatment plants to deal with bacteria in the

top up water for the London docks and this should much reduce the risk there at very low

cost.

A further point is that the west tunnel and treatment of the make up water supplied to the

London docks would deal with some 95% of the population with potential impact.

Validity of stated preference Willingness to Pay methodology.

In para 13 of the 2011 CBA, defra state “Furthermore, there is the general uncertainty

surrounding benefit assessments of this type (ie derived from a survey of Willingness to Pay

for essentially unmarketed goods and services.)”

A relevant paper is Willingness to pay methods in health care written by Richard Cookson

from the Health Policy and Practice Department of University of East Anglia and published in

Health Economics. He states

“First , WTP responses tend to be undersensitive – although not necessarily totally

insensitive – to the magnitude of benefit . ..Using high quality contingent valuation survey

designs, and rigorous experimental methods, investigators have found that people tend to

state a similar amount – roughly £50 – for any given magnitude of reduction in the risk of

death or injury . This has the effect of exaggerating implied monetary values for life and

health for relatively small risk reductions. More generally, under-sensitivity to the magnitude

of benefit tends to inflate valuations of interventions that yield relatively small benefits.”

“Second WTP methods tend to inflate valuations of the specific intervention that respondents

are asked about relative to interventions that respondents are not asked about. Asking

respondents to focus on one specific intervention in isolation acts as a kind of magnifying

glass for stated WTP. When asked to consider an intervention in isolation, people are willing

to pay sums of money far in excessof what they are willing to pay when asked to consider

the same intervention in relation to a range of other interventions....So valuing each item in

isolation can lead to sum totals of WTP in excess of the available budget. WTP methods

22

tend to be biased in favour of ...the particular intervention being evaluated,as opposed to

other ones not being evaluated.

It has been suggested that QALYs are out of date. It is more plausible to suggest that the

WTP approach is out of date. Health care payers have been relucant to embrace cost-

benefit analysis based on WTP methods.”

Expert advice from NERA was to the effect that QALY was an increasingly accepted

valuation tool within government and the health service as a method of valuing health

impacts, being widely used by the National Institute of Clinical Effectiveness (NICE) and the

Health and Safety Executive.

The Treasury guidance on Managing risk to the public recognises the possibility that public

valuation of a risk may not accord with expert assessment of a risk. Para 4.38 is relevant.:

“...it is important to recognise that while all have the same rights to raise their concerns, the

extent to which those concerns are valid should primarily be considered by those who have

the knowledge, skills and experience to measure or estimate the strength of relationships

between cause and effect, the probability of harm occurring, and the range of uncertainty, by

their systematic observation, empirical data collection or rigorous modelling.”

The principles set out in the “Treasury” guidance, see section 2.5, underline the need for

policy to be evidence-based, and for expenditure to be proportionate to the seriousness and

probability of the risk to be managed. One useful step would be to complete a hazard

concern assessment using the methodology outlined in Annex A to HMT guidance Managing

Risks to the Public. Overall it seems likely that under most headings, a concern assessment

would rate the Tideway issues at the lower end of the five point scale. If this is so, a very

expensive solution to Tideway CSOs would not normally be justified.

HMT states that, if action is justified, a more detailed expert risk assessment should be

carried out. This should include,

Hazard identification

Risk characterisation

Risk estimation

Risk evaluation

No expert would value a health intervention without some information on exposure, risk of

developing illness after exposure, and the scale or incidence of illness to be prevented.

Participants in stated preference surveys in both 2003 and 2006 were asked to value health

risk after having been given only one (exposure) of the necessary three heads of

information.

Proportionality is a consideration when the tideway water quality interventions are assessed

in comparative terms with other public heath options. The Thames water quality projects

together will cost some £5bn. A major extension or refurbishment of a London Hospital can

cost £50m. A consistent approach to public health management would question expenditure

equivalent to the cost of 100 hospital refurbishments if it addressed an unknown reduction of

low levels of minor illness in a small, maybe 5,000, more healthy group who decide on their

own level of exposure to the avoidable risk. This is one reason why a QALY valuation of the

23

health benefits of the Thames project should be completed and substituted for the health

element in stated preference survey valuations of benefits.

Thus, to ensure consistency with Treasury Guidance on best practice, the health risk

analysis benefit should be based, not on the sp WtP, but on the QALY based analysis.

In the 2006 field work there was no separation of the wtp of the various elements. However

the elements of health etc were described in a similar way to the 2003 survey so there is no

evidence to change the benefit split. Thus the proportion of the benefit applicable to health

would be about £2.4bn of the total amount assessed by WTP. Assessing the health benefit

by QALY in line with HMT Green Book would reduce this amount to about £1.5m. This is a

reduction of about 60%. This change should be made to the CBA summary table.

Benefit from reducing fish kills.

Previous events

Let us look more closely at the fish kills that have occurred in recent times. In December

2011 I asked the EA for reports on all the relatively recent fish kill events but I have received

evidence of just two. There was a serious fish kill in August 2004 and another fish kill in June

2011.

3rd August 2004 event

The Steering Group report 2005 states “A joint Thames Water/Environment Agency report

identified that the fish kill was due to the combination of storm discharges from Mogden STW

and the CSOs at the head of the Beckton catchment (principally Hammersmith pumping

station) .”

Four significant rainfall events occurred over the London catchment and Mogden catchment

between mid June and later August but without apparent fish kill problems. However on 3rd

August 28.7mm fell over the Mogden STW catchment. The rainfall over the London

catchment was reported as 12.3mm. At the time rainfall events, and resulting suspended

solids loads were being measured at the Acton Storm Tanks. There were events there on

22nd June 2004 and 24th August but on 3rd August no event was measured at Acton and no

high flow was recorded there. Thus there must be doubt as to the overflows from the

Tideway CSOs in this reach on 3rd August 2004.

The Thames Water bubblers were deployed and hydrogen peroxide was injected to raise the

river oxygen levels . The Daily Telegraph of 5th August reported that “Thames Water’s

oxygenation vessels were unable to reach the most polluted part of the river at the

uppermost limit of the tidal reaches because of low flows...The pavement uncovered by the

tide at Kew was strewn with dead 1 ½ inch flounder and bass fry...Among the adult fish

found dead were carp, chub, bream, sea lamprey, dace, and tench... The Environment

Agency said it was the worst sewage pollution in the river since 1986.” The Guardian

reported that 10,000 fish had been killed, see text below with a couple of adult dead fish

Maxine Clement of the EA had collected.

24

The EA report Tideway Pollution Event August 3, 2004 states “The circumstances that made

the August 3 event more significant in terms of the severity of the fish kill were probably due

to the very high flows received by the Mogden sewage treatment works, causing exceptional

operating conditions at the works and leading to large discharges of partially treated

sewage....this reinforces the view that the discharge from Mogden STW was a principal

contributory factor to the fish mortality. ”

The partially treated sewage is probably activated sludge. Activated sludge is particularly

“hungry” for oxygen and is capable of greatly reducing the oxygen content in the river. This

appears to be supported by the statement in Solutions Working Group Report Vol 2

December 2006, page 12 “Due to the poor performance of the final tanks and thereby to

minimise the amount of solids discharged to the River Thames, the works currently has a

reduced consent flow of 690,000m3/d.” The design flow to full treatment was 810,000m3/d.

It is interesting that on 4th May 2004 a storm with three times the discharge volume occurred

but with a much greater proportion over the Hammersmith catchment than the Mogden

catchment. I have been unable to find any report of fish kills for this event. Thus it would

appear that fish kills are much more dependent on Mogden STW overflow than from

downstream CSO overflows.

Although the Hammersmith pumping station may have contributed to the lowering of the

dissolved oxygen level, with the main storm being over the Mogden STW catchment, dead

fish being found at Kew, a short distance downstream of the Mogden outfall but several kms

upstream of the Hammersmith pumping station, and the oxygenation bubblers not being able

to reach the most polluted part of the river at the tidal limit which is well upstream of the

Mogden outfall, all indicate this was an event primarily generated by Mogden STW.

It is important to remember that Mogden STW has its own sewerage catchment and is not

related to the Beckton catchment or the main interceptors. It would not be affected by the

proposed changes to the Beckton sewerage system or the Thames Tunnel. The Mogden

system is being currently dealt with by the Mogden STW upgrade work.

25

Impact of the 2004 event

The sustainability of the 2004 event was reviewed by the person who led the fish trials Dr

Turnpenny in the report Thames Tideway Strategy: Fish and Ecological Objective, August

2005. “The Tideway Strategy Steering group Report refers to the August 2004 event, in

which large numbers of fish were believed to have died, as a vindication of the proposed

scheme....The results of the Tideway Fish Risk model study indicated that for some species,

even though the 1.5mg/l standard was breached, mortalities at the Tideway population level

were below or around the 10% sustainability benchmark, and that for other species where

this was exceeded (e.g. dace salmon), the life-history characteristics of the species may

mean that the predicted mortality levels are sustainable.”

In September 2004 fish counts were done in the vicinity of Beckton, many kms downstream

of the fish kill area. “Instead of finding a significant reduction in fish in the area” compared to

September 2002 “numbers had increased five-fold. It is surmised that some fish may have

been able to run ahead of the hypoxic front and were forced downstream, thereby protecting

them. In this case, the fish might be expected to gradually spread back into the affected

regions when conditions became more favourable.” Thames Tideway strategy: Fish and

Ecology Objective August 2005.

This indicates that more fish may be able to survive such conditions and that even the 2004

fish kill may have been sustainable. Thus, with the improvements to the Mogden STW

currently under construction, the river would be more likely to be sustainable for all fish

without the need for the tunnel.

June 2011 event.

There was another fish kill reported in June 2011. I have been told by Thames Water and

the EA that no report has been complied on this event. TW have also told me that the impact

of this event was primarily due to Mogden STW but with a contribution from Hammersmith

Pumping Station.

The EA have provided me with two press releases they issued. “The incident happened after

the heavy rain over the weekend caused the release of more than 250,000 tonnes of storm

sewage into the river from combined sewer overflows and at least 200,000 tonnes of storm

sewage from the Mogden Sewage Treatment Works in Isleworth...fish deaths along a

kilometre of river.” The press release some three weeks later stated. “More than 26,000 fish

were killed along a 2 kilometre stretch of the river between Barnes and Chiswick.” Thus the

fish kill occurred over a 1-2km stretch, roughly between Chiswick Bridge and Barnes Bridge,

which are 1 to 2kms apart. This is downstream of the Mogden STW outfall but significantly,

about 3km, upstream of the Hammersmith Pumping Station outfall. Thus it is difficult to

conclude that the Hammersmith pumping station outflow had a significant effect on the fish

kill.

“Thames Water has dosed the polluted water with hydrogen peroxide from three different

locations to add oxygen to the water. Its oxygenation vessels “ the mobile bubblers” have

also been deployed to the area and can inject 30 tonnes of oxygen a day into the water.”

Thus, under the tidal conditions at the time, the TW bubblers were able to reach the

Chiswick/Barnes area. CEH monthly report for June shows the flow at Kingston as about 30

m3/sec and the TW reservoirs increasing from 93% to 95% full by the end. This would

26

indicate that TW were likely to have been abstracting from the Thames and thus the flow

over Teddington weir would have been likely to be the normal minimum of about 800Ml/d.

Thus the bubblers would have been able to reach the Chiswick/Barnes area under these

conditions.

Conclusions

Thus one could conclude that the prime cause of both these events would be final tank

effluent overflow from Mogden STW.

Mogden STW upgrade

The text above is from the Thames water website. It states “We are carrying out a £140m

upgrade at Mogden Sewage treatment Works in west London to extend treatment capacity

by 50%. This will significantly reduce the amount of storm sewage overflows into the tidal

stretches of the River Thames after the site becomes overloaded during heavy rainfall. The

improvements will also help us to meet tighter quality standards for the effluent we

discharge.”

Thus it would seem reasonable to assume that the Mogden STW upgrade would mean that

such fish kill events would not occur once the upgrade has been completed, about 2013.

With the improvements to the Mogden STW the upper Tideway is likely to be sustainable

for fish.

Further the general water quality of the river should improve, thus raising the dissolved

oxygen content in the river and reducing the health impact.

27

Frequency and severity of events.

It seems surprising that, since fish deaths due to too low dissolved oxygen content in the

river is stated to be a major driver for expenditure of some £4bn of capital works, that a

major event such as the 2011 event does not have a formal report to support the case for

the scheme.

Location of the fish kills

Of importance these fish kills were some 3km upstream of, Hammersmith. This in turn is

about 16km upstream of London Bridge.

This contrasts strangely with the modelling outputs. From the more recent modelling the

current main area of low dissolved oxygen leading potentially to fish kills, the red line, is

mostly some distance downstream of London Bridge in the vicinity of the River Lee junction

with the Thames. In the image below the vertical line is London Bridge and the downstream

distances are to the right.

This situation is shown as at half tide, the area moving upstream and downstream. “The tidal

effect is up to 15 km/day” TW Needs report p 37. In which case the area of most impact

would move upstream and downstream about 7 ½ km from that shown. Thus, whilst the

upstream overflows would have contributed to lowering of the dissolved oxygen in the water,

the area most at risk is many kms downstream of Hammersmith. This is further confirmation

that the primary reason for the two large fish kills was Mogden STW overflows with little, if

any, contribution from the Tideway CSOs.

The plot above is from the TW Needs report page 53 and shows the most lethal dissolved

oxygen condition, Threshold 4 DO 1.5mg/l for on average 1 tide. This shows that under

current conditions, the red line, there should be many occasions, up to 110, when fish kills

should occur in the period of analysis which I think is 34 years. This would amount to about 3

fish kills a year.

Fish kills occurring downstream of London Bridge cannot be large ones as the Environment

Agency have not been able to provide any reports on them. That does not mean that fish

kills do not occur, as the predatory fish and birds may clear up the evidence of small fish

28

kills, but it does seem a reasonable assumption that, even now, before the Lee tunnel is

completed and the sewage works improved, they are not large fish kills.

Baseline for studies

The baseline conditions have now changed and should now be after the STW improvements

and the Lee tunnel have been constructed. This will remove the very large Abbey Mills

overflow from entering the Thames about 11 km downstream of London Bridge. Interestingly

this is the location where the half tide modelling shows the main dissolved oxygen sag

occurs under current conditions(pre Lee tunnel completion), see diagram above.

Fish Suite

It was necessary for the TTSs to set environmental standards for the Tideway. “it is expected

that, since fish are relatively sensitive to hypoxia compared to other aquatic organisms,

compliance with standards “” aimed at maintaining water quality whereby fish kills are

reduced or eliminated”” will also protect other fauna.” Thames Tideway Strategy : Fish &

Ecology Objective August 2005.

A suite of fish were chosen to be representative of the fish found in the Tideway. This

included dace, flounder, common goby, smelt, sand smelt, bass, and salmon. “The seven

species investigated here were chosen to represent a spectrum of fish sensitivities and to

stand as indicators for the 118 or so fish species that have been recorded in the Tideway.”

Report on the trials page 83. However salmon specimens for testing could not be obtained,

so trout were taken as a surrogate for salmon.

It could be argued that the fish species should have included those fish species that, with

improved oxygen conditions, should be able to colonise the Tideway. I cannot remember this

being discussed by the TTSS specifically. However the Report on the Trials Appendix 7

quotes some species including Twaite Shad as “not strongly established” and sea trout were

not included in the “discussion on fish of conservation interest.”

The trials report states on page 4 about sthe Test Fish species “A number of other Habitats

Directive designated species are of conservation interest although they are presently not

strongly established within the Tideway and were consequently not used in the experimental

work. These include sea lamprey...river lamprey... and the Allis and twaite shads. Such

species are difficult to procure and are protected in law but will need to be considered further

in the future, probably in a national rather than a Thames Tideway context.”

Additional fish species

In response to my challenge on fish based dissolved oxygen standards in my Project

Justification Review, the defra Summary of Responses February 2012 states “ The

standards are appropriate to protect sensitive and vulnerable fish species...such as sea

trout, eels, river and sea lamprey, and twaite shad.” All these species are migrants who

would only spend part of their life cycle in the area affected by the Tideway CSOs.

Eels are one of the most tolerant fish species to low dissolved oxygen conditions. The text

books state about sea lamprey “the adults often pass unscathed through heavily polluted

water during their spawning migration” River lampreys “They are able to survive water with

only 9.5% air saturation for at least 4 days.” This would appear to be less than the level 4

29

Threshold standard of 1.5 mg/l for one tide only once in 10 years. Thus lampreys should be

able to tolerate dissolved oxygen conditions appreciably worse than in the standards.

Whereas, at the time of the trials, sea trout were “not sufficiently established” to be

considered, they are now thought to be spawning in the lower freshwater tributaries of the

Thames. It is unclear how much of their life they spend in the part of the Tideway affected by

the CSOs but probably only a small part. Unlike salmon who seldom spawn again, a

significant number of sea trout will spawn again.

In the fish trials report Twaite shad were described as “not strongly established” and no

notes of their biology were provided on them in Appendix 7 My understanding is that they do

appear on occasion. I have asked the Environment Agency under the Freedom of

Information Act for information about the presence of these species but none has yet been

produced. . The fish trials report page 6 shows American shad as having a 24 hour Lc10 of

1.58 mg/l. This would indicate that shad, as a species, may be relatively tolerant of low

dissolved oxygen, “this genus is more tolerant than Salmo spp.” Trials report page 7.

Before these species could be considered as drivers of major capital investment it would

need to be found out how established they were in the Tideway, how much of their life cycle

they spent in the section of the Tideway affected by CSO spills, and how affected they would

be by low dissolved oxygen conditions.

Fish trials

Trials were carried out and reported in Experimental Studies on the Dissolved Oxygen

Requirements of Fish, 2004. Shown below is the impact of a three tide dissolved oxygen

condition. From this a dissolved oxygen standard of 3 mg/l for 3 tides return period 1 in 3

years was chosen.

30

Dissolved oxygen standards.

There are four dissolved oxygen standards.

There are several reasons why these may not be robust and should be reconsidered. The

full consideration is set out in my Project Justification Review section 9 and summarised

below.

Salmon

The trials report page 96 states “fully grown adult salmon...is clearly the most sensitive of

those tested and the main driver for standards implementation.” This can be seen in the

histogram above where Lc10 for adult trout (surrogate for salmon) is about 3.3 mg/l whereas

the next most sensitive is adult dace at about 2.2 mg/l. Thus, if salmon were not included

in the fish suite, then an appreciable reduction in the dissolved oxygen standards could be

accommodated.

The Regional Fisheries, Ecology and Recreation Advisory Committee paper of 20th

September 2010 states “ Numbers of adult salmon recorded in the Thames since 2004 have

been less than ten fish a year and there has been no evidence of successful breeding.

Without significant progress on these key elements, it is very unlikely that a self-sustaining

salmon population is viable in the Thames over the short to medium term (ie next ten

years).” Previously the EA had stocked the Thames with some 20,000 smolts a year. They

have now ceased that.

The image shows good returns up to 1996, then poor until 2004, and since then almost

none. One question is why are salmon no longer returning, whereas there are reports of sea

trout in the Thames? My understanding is that the water quality of the Thames has

generally improved since the 1980s. There have been no major changes to the sewerage

31

system to result in significant changes to the CSO spills. There have been changes in the

Atlantic and not much is known about them. There have also been rises in temperature and

it is known that salmon are at the limit of their physiological temperature tolerance in

summer. It is likely that sea trout are less tolerant of high temperatures than salmon are.

In October 2011 a Salmon Summit was held to discuss the latest scientific findings of the

SALSEA project. Dr Kevin Friedland gave a paper on behalf of the ICES North Atlantic

Salmon Working group, entitled “How climate and post-smolt growth control marine mortality

in Atlantic salmon: the potential effects of a changing climate on the marine survival of

Atlantic salmon.”

In this he concludes “Temperatures in the rearing habitats are likely to increase and may

produce episodic and sustained periods of thermal stress for juvenile salmon.” This would

appear to mean that, in the longer term, there will be periods when the temperature in the

rearing habitats is such that there will be sustained periods of thermal stress. This could lead

to few, if any, juvenile salmon (smolts) reaching the sea.

Dr Friedland continues “Ocean thermal conditions in key post-smolt nursery areas are

expected to continue to change, making marine survival unsustainable for segments of the

stock complexes from both north America and Europe.” He has confirmed by email that

southern England is one of the vulnerable complexes.

Thus salmon can no longer be deemed naturally sustainable in the Thames and, as such,

should no longer be included in the suite of fish. As they are the most sensitive fish to low

dissolved oxygen, see the histogram above, then not including them in the suite of fish

would change the standards, ie a less stringent dissolved oxygen level could be met.

Standards for limiting fish kill or achieving a sustainable fish population.

The dissolved oxygen standards were set by TTSS on the basis of avoiding fish kill rather

than providing sustainable fish. “... the TTSS standards are designed to avoid visible fish

kills; This requires higher standards than if the criterion was just to create sustainable fish

populations.” Jacobs Babtie report February 2006.Thus breach of the current DO standards

may not necessarily lead to loss of sustainable fish population.

Dr Turnpenny, in his response to the TTSS comments on the Babtie report, see TFR page

48 states “Fish in the Tideway are generally scattered through a number of Tideway zones...

This can mean that there will be heavy fish kills but that mortalities over the Tideway as a

whole would still be sustainable. Sustainability in this context I have previously proposed as

meaning 10% or less mortality per annum for short lived species such as gobies or smelt

and 20% or more for multi-spawning class species such as salmon, flounder or bass.”

Thus most fish species can tolerate a higher level of fish kill and still be sustainable, thus

they could tolerate a lower level of DO. For instance flounder, dace, 10 year life, and bass

can probably tolerate 20% fish kill and remain sustainable. Population dynamics, life span,

and how widespread are all these features, were not included in the previous analysis.

These should have been taken account of when setting the DO standards.

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A further factor is that the standards “were made on the basis of avoiding fish kills and not on

maintaining sustainable fish communities” Thames Tideway strategy: Fish & Ecology August

2005.

The Jacob Babite review dated February 2006 had on its team Dr Andy Turnpenny who had

carried out the TTSS fish trials. This says on page 15 “we consider there is scope to apply

these standards less rigorously or to apply them spatially to reflect the sensitivity of local fish

populations or their ability to swim away from areas deficient in oxygen.”

“If maintaining a sustainable fish community is an acceptable objective, then this would

require much less investment, according to the Tideway Fish Risk Model results. Based on

the August 2004 modelling investigation, the existing conditions are at least close to

allowing for sustainable fish populations. With proposed capital improvements at

Beckton and Crossness” STW” under AMP4,” now under construction” the DO-profile

predictions given in the Steering Group report indicate that the baseline condition should

improve considerably, and the impact of CSO spills on DO status in the Tideway’s middle

reaches will be greatly ameliorated by these measures alone.” In addition the Lee tunnel is

under construction, thus more than halving the future CSO spill volumes. “ Additional

protection appears to be provided by the ability (larger fish at least) to avoid low DOs.”

Thames Tideway Strategy : Fish & Ecology Objective, August 2005.

The TW report Tackling London’s Sewer Overflows, Summary Report December 2006

states on page 17 when referring to TTSS “The re-endorsement of these targets was not

unanimous and discussion centred on the uncertainty of the meaning of achieving a

“sustainable fishery”-could not significant fish mortalities be accommodated and acceptable

within a sustainable context?,,,After discussion with the fishery expert, Dr Turnpenny, the

majority view of the group was that the TTSS standards should remain as a defensible

compromise.”

Thus the dissolved oxygen standards were not set unanimously and were set on the basis of

restricting fish kill rather than achieving a sustainable fishery. Thus the DO standards should

be revisited, reset on the basis of a sustainable fish population, and remodelled. This is

dealt with in more detail in my Project Justification Review .

Likely fish kills under the future baseline conditions.

Let us look first at the most onerous condition, threshold 4, 1.5 mg/l, 1 tide, once in ten

years.

33

It is interesting that for threshold 4 there is barely any discernible difference in the plot

between the situation with the Lee Tunnel and STW improvements, the mauve line, and the

line with the Thames tunnel included. This would indicate there is unlikely to be more than

minimal benefit from reduction in fish kills under these conditions.

Threshold 2, 3mg/l, 3 tides, once in 3 years.

The mauve line, the future baseline condition, does show significant number of failures of

this threshold. However one has to go to the individual species to see how extensive the

effect would be. Looking at the trial plot below, one can see that all the species except trout

and salmon smolts can tolerate much lower dissolved oxygen conditions. Thus it is unlikely

that there would be many, if any, other fish species killed under these conditions. Since

salmon are no longer present and are not deemed naturally sustainable that only leaves the

few sea trout when they are in the relevant part of the river that would be affected.

34

Threshold 3, 2mg/l, 1 tide, once in 5 years.

Threshold 3 model plot above shows that the Lee tunnel and STW improvements come

close to meeting the dissolved oxygen standards at this level. The return frequency is about

double that in the standard. However, this is a one tide standard and this means that there is

a somewhat greater tolerance during this shorter time.

35

Thus all the species except fot trout/salmon can meet this standard. The most sensitive

species is dace. Dace are a long lived species, 10 years in the Trials report Table 6.2 page

76. Thus losing about 10% once every 5 years, ie an average of 2%, would not render the

species unsustainable.

Were the general tideway dissolved oxygen content to be raised 1 mg/l, even this minor

impact would be avoided.

Threshold 1, 4mg/l, 29 tides (1 week) once in 1 year, would not result in any fish kills. It

“was selected to ensure protection against chronic effects; these would include eg effects

such as depression of growth and avoidance of hypoxic areas”. Trials report page 75.

Thus one can conclude that, with the benefit of the Lee tunnel, the number of events

dropping from the future baseline (with the Lee tunnel completed etc), the mauve line, to the

tunnel would be very low, apart from the period when salmon would be in the relevant part

of the Tideway. However salmon are no longer a naturally sustainable fish species in the

river.

Fish risk model

As part of the fish studies and trials a fish risk model (TFRM) was set up “to better assess

the risk of hypoxic (low DO) events. It takes account of the fact that CSO events do not

affect the whole of the Tideway equally and that a breach of a standard is likely to affect

some zones more than others. For instance, if a species were uniformly distributed

throughout the Tideway but the LC10 (lethal concentration for 10% of the population was

exceeded in only 20% of the Tideway habitat, then only 2% of the population(not 10%)

would be likely to die. The TFRM applies this concept using the EA Tideway water quality

Zones to estimate for any given month of the year, for each species/lifestage, what

proportion of the Tideway population are likely to be present in a particular zone. Water

quality (DO) data are then compared against lethality data to estimate the mortality by

species/lifestage and Zone.”

“The TFRM therefore provides the means to assess the effect of a particular water quality

scenario on Tideway fish populations as a whole. This is potentially much more realistic than

using a standards-only approach, which requires compliance across the whole Tideway,

since we can now apply the 10% mortality figure as a sustainability threshold for the whole

population. Put another way, we can allow the standards to be breached in parts of the

Tideway, provided that mortality in the population as a whole does not exceed 10% per

annum.” Thames Tideway Strategy :Fish & Ecology Objective, 2005.

The calculations are set out in detail in the Fish trial report and are summarised in the Table

below.

36

The trials team concluded that, with the AMP4 works, ie with the sewage treatment works

improvements but without the Lee tunnel “the number of “not sustainable “ incidences

reduces to zero.” Fish trials report page 91.

Thus, even without the Lee tunnel, the Tideway fish would be in a sustainable state.

Economic analysis of benefits of fewer fish kills

The HM Treasury Green Book para 5.11 states “Costs and benefits should normally be

based on market prices as they usually reflect the best alternative uses that the goods or

services could be put to.” Rather than the WTP approach is it possible to put a market

based figure to the value of any fish killed?

It is appropriate to try to follow HMT Guidelines and use expert risk assessment of the

economic benefits of fewer fish kills due to construction of the tunnel. Salmon have great

popular appeal, but effectively no longer exist and smelt, and goby are less sort after.

Entec report Environmental costs and market benefits of reducing combined sewer

overflows, December 2006, looked at the effects on commercial fisheries. It then examines

the then current fishery but is not able to identify any financial benefit to commercial fishing

from the CSO spill reduction.

According to the Fish Trials report, after the STW improvements have been completed, there

would be no loss of fish sustainability. With the Lee tunnel completed about 2014, the spill

volumes would be more than halved. However, for the sake of setting an upper bound of

benefit, let us assume that there would be some benefit from the improved dissolved oxygen

contents due to the Thames tunnel. The worst conditions for fish kills would be when the

temperatures are higher and the river flow lower, ie summer. Eftec Table 3.1 assumes the

full tunnel would reduce the number of fish kills or migration interference from 1 or 2 times

per year to less than 1 time per year. Since then the Lee tunnel is being implemented,

further improving the base line fish kill situation. Thus the most fish kill saving would be, at

most, about one a year. It seems reasonable to assume that most of those killed would be

juveniles. Gobies and smelt are not commercially significant. Assume that that leaves about

1,000 fish of possible economic value killed/ year. Assume that the economic benefit of them

would have been £10 each. That would be an economic loss of some £10,000. Spread over

37

the assumed 60 year benefit period of the scheme then the Green Book multiplier would be

26.2285. Saving these fish kills would be an economic benefit of some £ 0.26m.

An alternative way of looking at this is to value the future salmon fishery. Were one to

presume that the tunnel would result in some 300 salmon/ year returning (current average

less than 10), assume that 1 in 10 salmon returning would be caught by anglers, ie 30/year,

and use the value of the salmon fishery of £8,000/salmon caught, then the benefit value

would be some £240,000.

Whilst these numbers are illustrative, they do demonstrate the order of magnitude of the

possible benefit.

Cascade Consultants on 20th March 2013 In their presentation of the draft final report on the

Lower Thames Abstraction Investigation Sixth Stakeholder Workshop reported that the value

of willingness to pay for existence and biological benefit for fish to meet the higher WFD

dissolved oxygen standards had been assessed in several other cost benefit studies and for

the Tideway would be £14.7m, This figure will be confirmed in the Final Report.

Conclusion

Fish kills were about 15% of the TTSS 2004 benefits, see table 1 of the TTSS cost benefit

working group report. Based on the Defra numbers this would amount to some £600m. HMT

recommends using expert economic assessment rather than WTP so this benefit, assessed

as about £ 15m, would replace the relevant WtP figure of about £600m. Thus this economic

analysis would effectively reduce the benefits assessed by about a further 15%. Thus the

CBA analysis should be modified to incorporate this.

Benefit from reducing sewage derived litter

The third element of benefit is the reduction of sewage derived litter. It is generally accepted

that sewage derived litter makes up 10% of the total litter. The figure is from the Tidy Britain

Group. There is limited evidence to support this figure but it is a generally used figure. Thus

90% of the litter/debris is not sewage derived.

“Shortly after discharge floating matter disseminates relatively quickly so the plug of sewage

effluent moves unnoticed with the ebb and flood of the tide.”HPA recreational users report

page 52.

Jacobs Babtie Review for ofwat.

As part of their review Jacobs Babtie team did a trip on the Thames on 31st August 2005 and

reported “...several days after the most recent rainstorms, floating debris was seen in

several locations. The slicks that the TTSS describes in its reports were observed, and, on

close inspection, it was clear that some of the debris contained in them was sewage-derived.

However, our opinion is that it would not be immediately apparent to a casual observer that

the debris was any more than windblown litter and vegetation- a fact reflected in public

responses obtained during the TTSS.” Independent review for ofwat Feb 2006 page 8.

Jacobs Babtie continue on page 9 “In addition to the slicks, litter was seen to have

accumulated on the banks of the Tideway. However much of this is coarse debris which is

38

likely to have originated from sources other than the CSO discharges. Much of the bankside

of the Tideway is overlooked from adjoining residential and commercial buildings or is

accessible to the public, albeit access to the actual waterside is made only infrequently.

Numerous leisure vessels provide visitors to London with river tours. Thus bankside litter

deposits may be considered a very visible aesthetically feature from the public standpoint.”

The DETR 1997 guidance on the UWWTD states to identify an unsatisfactory CSO it would

need to have “a history of justified public complaint.” The Environment Agency have stated

“”Unsurprisingly the number of formal complaints regarding sewage debris is relatively

few.”Bain email. Thus there do appear to be only a few complaints from the public.

On page 11 they quote from the eftec report The Market Benefits of Options for the Thames

Tideway appended to the TTSS Cost Benefit Working Group Report which they say states

“...although reducing CSO events would be associated with reduced amounts of

sewage litter, this is currently only a small (10 per cent) proportion of the total litter

and debris in the Tideway at any one time, and what there is appears to be invisible

much of the time, at least as far as individual perceptions are concerned.

This is one of the findings of the SP (TTSS’s stated preference survey) as well as

being the view expressed by consultees from the London property market. We might

expect certain river users to notice a difference, in particular those who come into

close contact with the water, such as rowers, houseboat owners and those who

frequently walk by the river. However, in general the public are unlikely to detect

much visible difference, and this includes owners of riverside property who, as we

have just argued, tend to partake in river-based activities from a greater distance...

The Thames is a tidal river downstream from Teddington, and levels of suspended

silt and mud in the water are naturally high and always will be. Reducing CSO events

will not have any impact in this regard.

Therefore, little aesthetic change in the water is to be expected due to Tideway

Strategy options, and this, together with the low correlation between riverside

residence and involvement in river-based water sports, suggests that any

impact of the Tideway options on property prices is likely to be minor.”

These statements were made about the baseline in 2003. Since then the baseline now

includes the Lee tunnel, in itself removing more than half the spill volume, as well as

improvements to the water quality and storm overflows from the 5 London sewage treatment

works. Thus the effect from sewage litter would be even smaller for the new baseline.

On the Tideway Tunnel, Jacobs Babtie concluded:

“in general the public are unlikely to detect much visible difference . . . the need for

significant sewerage infrastructure investment to deliver a low level of perceived qualitative

benefit, and remove a low percentage of the total litter is therefore open to challenge....

whilst there is without doubt impact from sewage solids discharges, the evidence to support

investment on the scale proposed is limited. ”

If sewage waste either sinks or breaks down fairly rapidly, is largely un-noticed and difficult

to detect among other larger volumes of litter, it follows that the Tideway investment may not

39

make a great deal of difference to perceptions of litter, except for those recreational users

who get very close.

Benefit

The TTSS derived proportion of aesthetic benefit was 25%. With a base WtP of £3,935m,

this would amount to about £1bn. With only 10% of litter sewage derived, little aesthetic

change expected, and minor effect on property prices, this sum would seem excessive.

Given the statements above a smaller sum would seem more reasonable. However I have

no base for a revised number so I have made no change to the original sum. However I have

done a sensitivity analysis assuming that “minor” were as low as £ 200m.

Cost benefit analysis

NERA in their 2006 report considered a 60 year project appraisal period. They did not

include the Treasury Green Book optimism bias but instead they accepted the project risk

assessment. Based on the then estimated capital costs, now greatly increased, and the

benefits assumed, for the full tunnel the benefit cost ratio was found to be 2.04.

4 Cost and Benefits of the Thames Tunnel, defra November 2011.

Introduction

Since the 2006 fieldwork by eftec ,construction has started on the upgrading of the sewage

treatment works and on the Lee tunnel linking Abbey Mills to Beckton STW. Thus these must

be considered as committed schemes whose benefit must be included in the base case.

The defra CBA dated November 2011 considers the Thames Tunnel which would link Acton

in the west to Abbey Mills and the Lee tunnel in the east.

There is also no consideration of the East/West tunnel system, or more relevant now that the

east (Lee) tunnel is under construction, of the west tunnel addition to the committed works of

the sewage treatment upgrades and the Lee tuneel.

Validity of previous WTP study

DEFRA have taken the 2006 WtP survey results and revalued them at 2011 prices, along

with certain other upward adjustments. However some of the baseline descriptions in the

2006 Stated Preference Survey are no longer valid, such as the impacts on fish populations

and the description of the public health baseline. Economic circumstances and the outlook

for incomes growth is much harsher now than at the time of the 2006 WtP survey. There is

less optimism about income growth, greater fear of redundancy, worse perceptions of the

future for benefits and taxes etc and pressure to constrain spending on other services and

public goods is much greater. A single-issue stated preference survey would now take place

in a wholly changed financial environment. In addition HMT prefers economic expert analysis

rather than stated preference survey and willingness to pay.

Other benefits.

The defra 2011 CBA report states in paragraph 3 a number of benefits for which there is no

assigned financial benefit included in the analysis.

40

“Avoidance of damage to London’s reputation as a business and tourism centre.”

The current reputation is based on the current situation. The eftec report page 25

shows over 80% of respondents rarely or never saw human waste. The defra report

A strategic and economic case for the Thames Tunnel November 2011 states on

page 5, “It is unlikely at present that businesses are put off locating to London due to

the presence of raw sewage in the River Thames.” The situation is being improved

by the construction of the Lee tunnel which will remove about half the current

overflow volumes, and the sewage treatment works upgrades, particularly the

upstream Mogden STW, and the downstream Beckton STW. These schemes are

together costing some £1.2bn. Thus the Tideway water quality will in any case

improve, and, in so far as conditions in the river are noticed, so will London’s

reputation.

“Avoidance of any long-term adverse impact on the desirability and value of riverside

property.”

See comments above. Whilst sewage litter is the most offensive if seen close up by

someone on the water or on the river bank, sewage litter is only estimated to make

up some 10% of all litter, thus totally removing all the sewage litter would only reduce

overall litter by some 10%. Would that be noticeable? In any case the velocity of the

tide is such that the river is generally seen as dark brown and not over attractive.

Even with no litter this will not change.

No scheme will be able to remove all overflows and I understand that there would still

be some 3 overflows a year from the full tunnel. The Thames Water table of October

2011 shows the residual overflows will still be some 2.3Mm3 / year on average.

Entec Environmental costs and market benefits of reducing combined sewer

overflows December 2006,looked at this but found that other factors dominated and

they were unable to put any figure against the benefit of different water qualities.

Thus I accept the eftec conclusion that the benefit on riverside property would be

“minor”.

Reduced sewer flooding in some locations.”

In para 5.2 on page 20 NERA state “The eftec report discusses the possibility that

the options may lead to a reduction in, but not removal of, the risk of sewer flooding

to a small number of households, as the options will reduce the risk of these

properties experiencing sewer flooding in times of heavy rainfall. However, the

magnitude of the reduction in the risk is very uncertain and therefore the impact

values derived from willingness to pay and avoided costs of flood defence are also

very uncertain. Overall, the uncertainty and the magnitude of this impact is

exceptionally high, with a lower bound of zero. For these reasons we consider it

prudent to exclude this estimate from the Base Case. We consider its inclusion in the

sensitivity analysis in section.” The analysis is shown in Table 8.1 on page 38 and

this shows a sensitivity net benefit of £86m.

Entec in its draft report Environmental costs and market benefits of reducing

combined sewer overflows, December 2006 identify some 150 properties at risk of

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flooding and state on page 46 “If all of the 150 properties who may experience a

reduced risk of flooding ...experience a reduction to zero risk, this would be valued at

£20.1million.” However this is the upper bound and in Table 3.4 Entec assess the

Medium value as about £7m. This appears more reliable than the NERA figure. Even

if this were appropriate it would have a minimal affect on the overall benefit and

would not change the overall conclusions.

“Energy generation from extra volumes of sewage sludge captured at Beckton

Sewage Treatment Works (otherwise lost through sewer overflows)” That is true but

is misleading as very much more energy would be used to pump out all the tunnel

contents, some 37 Mm3 per year on average from some 60m to 80m below ground

level. Entec, in their draft December 2006 report Environmental costs and market

benefits of reducing combined sewer overflows, in table 3.8 on page 52 assess this

as about 15GWh/year, 15,000,000 kWh/year.

“Short-term employment, economic growth or regenerations impacts related to

construction.”

True, but there are no UK manufacturers of large tunnel boring machines, and if

investment to finance the tunnel is raised overseas, ( the consortium owning Thames

Water is largely overseas owned), there is a long term loss to the UK in remunerating

it from sewerage charges at the expense of alternative household consumption. This

could be of the order of £200m a year for as long as the impact on charges lasts,

which I believe would be the nominal life of the asset assessed by ofwat when fixing

charges, probably about 60 years.

Whereas a new road or new railway will encourage other long term economic growth

it is difficult to see that the tunnel scheme will lead to significant long term economic

growth.

Cost estimates

“Latest project costs have been taken from Thames Water (version Rev05b dated

September 2011)...Total £4.059m(at 2011 prices).”

These are a big increase on the 2005 TTSS cost estimates of £1.7bn, and the 2006 RIA

estimate of about £2.2bn.

In para 6c defra state “In July 2011 Thames Water identified some additional project costs

arising from extension to the programme to 2022, and changes to the project following

phase 1 and 2 consultations, as well as developing the delivery route. It has been assumed

that these costs (totalling £244m in 2011 prices) are not included in the Rev05b base cost

update above.” This would increase the capital cost of the Acton to Abbey Mills tunnel to

some £4.3 bn, and the cost of the Acton to Beckton tunnels to some £4.9bn.

This estimate compares with the Hammersmith to Beckton tunnels of the TTSS which, in the

2005 reports, were estimated to cost £1.7bn.

The defra Regulatory Impact Assessment March 2007 the cost estimate was about £2.2bn.

42

In the 2010 Stage 1 consultation the Thames Tunnel from Hammersmith to Abbey Mills was

estimated to cost £3.6bn. With the Abbey Mills to Beckton STW Lee tunnel costing £ 0.6 bn,

the scheme cost became £ 4.2bn.

The EFRA Committee interviewed Thames Water and the Committee’s report says that

Thames Water are “confident that the project could be delivered within the current estimate.”

The Stage 2 consultation issued by TW in November 2011 gives the Thames Tunnel cost as

£ 4.1 bn, making a total cost of £ 4.7 bn.

The previous water tunnel under London, the London Water Ring main, was held up for

several months due to hitting a fault with high volumes of water, and, on another occasion,

hitting unrecorded beep piles. The Tideway tunnel is generally deeper so should not hit piled

foundations but knowledge of the geology cannot be complete.

The capital cost increase is much faster than inflation. This must raise doubt as to whether

the out turn cost, in real terms, will not increase further.

There is a Bill now in Parliament called the Water Industry(Financial Assistance) Bill. Defra

state in their press release on 3rd February that “This Bill will enable the Government

to:...provide contingent financial support for exceptionally large or complex water or

sewerage infrastructure such as the proposed Thames Tunnel in London.”

I have been unable to identify at what level it has been agreed that contingent financial

support would be provided. However it does appear that general tax payers are now at risk

should the project exceed some financial limit.

GDP deflator

Defra state in para 9, page 4 “The GDP deflator has been used to update the aggregate

present Value benefit figure from 2006 to 2011 prices- an increase of 10.6%. The resulting

estimate of £4,353m..”

The Treasury GDP deflator does show an inflation increase of about 10.6% over this period.

I have therefore accepted this adjustment.

Apportionment of benefit

NERA in their 2006 report stated “The Abbey Mills discharges are very large...and they

discharge into a river which, relative to the Thames , is very small. This may be of little

consequence at present as the area is little used, but with the Thames Gateway

development this will presumably change.”

The Defra November 2011 CBA report states “The resulting estimate of £4,353m has then

been apportioned 60% to the Thames Tunnel and 40% to the Lee Tunnel. These proportions

are high level estimates based on the share of overall Combined Sewer Overflow tonnage

which will be handled by the two tunnels.”

In my view the comparison should be on the basis of benefit to the rivers Lee and Thames

from the two phases of the scheme. However, accepting the defra assumption, the October

2011 analysis by Thames Water shows the current spill of 39Mm3 and that, with the Lee

tunnel and STW improvement, this would reduce to about 18Mm3. The residual amount is

43

about 2Mm3. Thus the split on a tonnage basis would be about 21/37, ie 57% to the Lee

tunnel not the 40% chosen by defra. By corollary, the benefit to the Thames Tunnel would,

on this basis, fall from 60% to 43%. This is significant and, following the methodology

selected by defra, the CBA analysis should be adjusted accordingly.

Crossness STW overflows

The TW table of performance shows Crossness sewage works and storm tanks as

discharging some 0.5Mm3 /year. The HPA Recreational report 2007 page 26 shows the

Crossness discharge as 25Mm3 in 22 months in 2005/6. This would be about 13Mm3/year.

This would impact on the dissolved oxygen content in the reach with the highest risk of low

dissolved oxygen under current conditions, the River Lee to Crossness. The discrepancy is

large and unexplained. It seems reasonable to assume that the lower numbers will be those

after the STW upgrades. If so then the reduction into the Tideway would be appreciably

larger than shown and, as the tunnel scheme would have no affect on Crossness STW, the

benefit would accrue to the sewage works improvement.

Mogden STW overflows

The HPA Recreational report shows on page 30 that, during the 2005/6 period, Mogden

STW had an spill volume of 4.6Mm3, an average of 2.5Mm3/year. The Mogden STW

upgrade including increased storm tank capacity and ability to treat more sewage to full

standard, programmed for completion in about 2013, would very greatly reduce the spill

amount.

Summary

Thus, if these spill reductions are a result of the sewage treatment works upgrade, then the

spill volume benefit attributable to the Thames tunnel would be even less than assessed by

me.

Lee tunnel

Further, the Thames Tunnel cannot function without the Lee tunnel taking the flow from

Abbey Mills to Beckton STW. Thus part of the benefit of the Thames Tunnel ought really to

be transferred to the Lee Tunnel. It is difficult to assess how much the benefit of the Thames

Tunnel is overestimated due to this effect but a figure of about 10% might be of the sort of

order of magnitude. I have not included this adjustment in my analysis.

Period of appraisal

The Treasury Green Book recommends that “costs and benefits should normally be

extended to cover the life of the assets.” NERA consider the life of the tunnel would be 100

years. The main interceptors have been in place for nearly 150 years and are still in good

condition and are functioning well. (My great grandfather, the first Chief Engineer of London,

was responsible for them for a period and was also responsible for some of the early

sewage treatment at Beckton.) Thus, such an asset as a sewage tunnel, might well reach, or

exceed, the 100 years. However NERA considered and rejected the evaluation period

beyond 60 years.

44

NERA consider, page 6 “ However projecting such costs and, more especially, benefits well

beyond half a century into the future entails considerable uncertainty, potentially of massive

economic, social and/or environmental changes that may render any tunnel worthless, and

without any likely alternative use, or scrap value. Financial cost and benefits are subject to

changing economic conditions and technologies. There is perhaps much more uncertainty

about the environmental baseline, given the potential changes to the physical environment of

the Tideway( arising from for example climate change and changes in urban environment).

There is also uncertainty about whether the preferences of the population will remain

constant over time.

The assumption that outcomes will remain constant over time would imply that the average

number of preventable sewage discharges into the Thames that will occur annually and the

environmental impacts that the option generates remain constant. This assumption, along

with the assumption that preferences remain constant would, in our view, appear unrealistic

over the 100-year life of the tunnel. In our analysis we therefore rely on a shorter appraisal

period of 60 years which, although a significant period of time, is perhaps a more realistic

useful lifetime. In our analysis we therefore rely on a shorter appraisal period of 60 years...”

Thus, while the tunnel is likely to continue to be able to be a physically usable asset beyond

60 years, NERA question whether the risk of change would mean it could not be relied on to

continue to be of benefit thereafter.

Let us look at what could lead to the tunnel not being needed or used sometime in the

future.

Population changes

Interestingly the population of London, as shown by Ian Benstead of Thames Water in his

ICE paper on the London Water Ring Main, peaked at about 8 million in about 1940, and

then fell by over 2 million over about the next 40 years, see diagram below. The natural

growth of London’s current population is fairly neutral. Its main increase is in immigration.

Whilst it is unlikely, it is always possible that immigration stops or is curtailed by government

or EU command. At the same time reduced per-capita water usage could reduce dry

weather flows in the sewers, thus increasing their ability to convey storm flows.

45

SUDS

In the past, SUDS in London has not been incorporated much in new development or as a

retrofit. The2011 defra Water White Paper includes proposals that SUDS should be

incorporated more in future development. This approach is likely to be strengthened further

in the future and would reduce flood runoff and hence the storm runoff.

Energy use

All overflows into the tunnel have to be pumped out for treatment at Beckton STW.

According to the NCE of 15 h December 2011, the Beckton pumping shaft is some 86.5m

deep. Thus one could expect an average pumping head of some 70m. The total spill

currently is some 39 Mm3/year. The spill once the full tunnel is constructed is shown on the

TW table as 2.4 Mm3/year. Thus the annual energy use would be some 37Mm3 pumped

through an average of some 70m. This has been calculated in the 2006 Solutions Working

Group report Vol 1 as about 15GwH/year, 15,000,000 kWh/year.

It is possible that with climate change it becomes no longer allowable to use this much

electrical energy, thus rendering the tunnel unused.

Sea level rise

Sea level rise is currently expected to be rather less than 1m by the end of the century. The

scheme could cope with that. However the current efforts to get countries to agree to reduce

their carbon emissions are having limited effect with Canada recently pulling out of any

agreement. The unknown issues are the feedback loops whereby higher temperatures can

result in yet higher temperatures. For instance melting of part of the Siberian permafrost

would put much methane, a very strong greenhouse gas, into the atmosphere, greatly

accelerating global warming and hence sea level rise. Appreciable sea level rise could

affect operation of the London sewerage system and the Tideway tunnel.

Changed social and environmental standards.

As an illustration, it is not possible to predict years ahead what new Directives will emanate

from Europe. When our coal fired power stations were constructed in the 1960s and 1970s,

who would have envisaged that they would be forced to close by EU Directive in 2015.

Conclusions

With the unknowns of the population changes, benefit of SUDS, European Directives, and

the unpredictable impact of climate change beyond 2080, it is difficult to argue with the

NERA assessment that it is not sensible to assume a longer benefit assessment period than

60 years.

Defra 2007 RIA

Indeed that was what was done by defra in its 2007 RIA analysis “In the defra 2007 RIA an

appraisal period of 60 years was used for the then Tideway options.”, para 10 of defra CBA

2011. In the 2007 RIA page 61 it is said that projecting benefits over a 100 year time frame

“is an area of considerable uncertainty.” It is difficult to see that projecting benefits over the

100 year time frame has got any easier since then.

46

Defra 2011 CBA

In the 2011 CBA it states in para 10 “In this update of the analysis we have taken the

Treasury Green Book recommendation that the appraisal period should be taken as the

useful life of the assets.”The footnote states “In this update we prefer to take the Green Book

recommended appraisal period to maintain consistency with other public projects (especially

in the water and flood management context), and consider uncertainty separately.”

The economic assessment of the Tideway tunnel does not appear to be against any other

water scheme. Certainly I have been unable to find any such comparison in any of the cost

benefit analyses. However there is the need to assess the alternative tunnel schemes

against each other, and also against the key criteria of “Excessive Cost” under the UWWTD

and “Disproportionate Cost “ under the Water Framework Directive. Thus there does not

appear to be a sound case for extending the period from 60 years to 100 years.

However, without further reasoning, defra state “ As such the estimated benefits accruing to

the Thames Tunnel have been extended over the 100 year period, by dividing by the

cumulative Green Book discount factor for 60 years (26.2285) and multiplying by that for 100

years (29.8125).”

Conclusion.

This would amount to an apparent increase in benefit of some 14%. Keeping the 60 year

assessment period would negate this increase. I cannot see a sufficiently robust reason to

extend the period of assessment from the 60 years assumed by NERA and defra in the 2007

RIA and have retained the original 60 year period.

Disbenefits

There may also be some health disbenefits for low income families arising from the steeply

increased cost of water, some £70-80 per household per year,. There may also be some

impact and disbenefits in the course of construction. There would also be general

disbenefits. One is the large amount of energy required to pump out the tunnel. I can find no

reference to those in the NERA or defra cost benefit analysis.

However Entec in their draft 2006 report Environmental costs and market benefits of

reducing combined sewer overflows set out in Table 4.1 the range of a number of effects

during construction. For instance this includes delays to traffic.The upper range comes to

about £85m. My understanding is that these are not included in the cost benefit assessment.

In my view they should be. Thus I have included half the upper bound in my analysis, both of

disbenefits and benefits.

2011 Range of benefit

The CBA 2011 para 10 continues “This gives a 100-year “basic” benefit figure for the

Thames Tunnel in 2011 prices of £2,969m. We take this as the lower end of the likely

benefits range for reasons set out below.”

The benefit appears already to have been increased on weak grounds due to the following.

47

The change from benefit in the Thames Water customer area, as in the 2003 CBA, to all

England but not considering that the sewerage charge in the Thames Water area was,

generally, appreciably lower than in the interviewee area, seems likely to overestimate WtP.

Based on the multiple choice WTP in the TW Business Plan then the single issue WTP

should be reduced to 40%, or even lower.

Using normal Treasury supported QALY function for health risk instead of WTP would

reduce the benefit by some 60%.

The financial analysis of the fish kills would reduce the total benefit by about 15%

The basis of the distance/decay function is not provided and its application appears

inconsistent.

Benefit estimate split between the Thames and Lee tunnels was proposed by defra to be on

a tonnage basis. This was assessed as 60% to the Thames Tideway tunnel. Based on the

October 2011 Thames water modelling It should have been 43%.

The benefit provided by the Lee tunnel to the Thames tunnel was ignored but I have made

no change.

Period of appraisal should not have been increased from 60 years to 100 years, a 14%

increase.

These factors alone would reduce the benefit assessed for the full to tunnel to about £230m,

see table in section 6, about 7% of that quoted in the defra CBA. Thus the statement above

that the revised benefit is the minimum is not robust.

2011 Range of benefit increases

However the defra 2011 CBA report continues in pare 11 “Since the 2007 RIA a number of

issues have emerged which suggest a revised view of aggregate benefit of the Thames

Tunnel should be taken...Two of the issues (population and real income growth-see below)

might have been foreseen at the time, “ they were considered at the time, so this text is

misleading “, see below but given the much lower cost estimate for the tunnel at that point,

there was probably a degree to which the benefits were seen as “high enough” to

demonstrate a good economic case, “ I can find no such mention in the NERA or RIA reports

so no evidence to support this hypothesis “and the return on further analysis was seen as

weak.” Both population change and real income growth were indeed considered by NERA,

see below.

“With the costs of the tunnel somewhat higher “ actually about double “it is now

worthwhile “ essential if the analysis is to have a benefit cost ratio greater than 1 “to revisit

these issues.”, my embolding.

How strong is this argument? The revaluation process seems to have ignored the factors

pointing to overvaluation in 2007, and gone against professional advice by selecting some

means of enhancing valuation which were considered to be weak or inadvisable at the time.

The defra CBA para 11 then considers three further factors which could increase the

benefits, population increase, real income growth, and spill volumes.

48

Population increase

CBA para 11 a) “The original RIA analysis did not take account of the impact of population

growth on benefit. There are two issues here. First, population growth is likely to impact on

the baseline CSO spill frequencies and volumes over time, so the benefits of the tunnel may

be expected to increase against this baseline (subject to the tunnel’s capacity, though

separately Thames water estimate this is not likely to be a constraint given future climate

and population forecasts- which have informed design).”

I have considered the effect on population increase on the dry weather flow in the

interceptors in section 6 of the Project Justification Review. Population increase would, in

theory, increase dry weather flows, thus increasing spill frequencies and volumes. This is

considered in detail in my Project Justification Review.

However, based on a number of assumptions, and the figures in the Thames Water revised

25 year Water Resources Management Plan, reductions in per capita water use due to

better appliance water use efficiency, increasing metering, water charging by incentive

tariffs, and reduced leakage, result in computed dry weather flows in the future being below,

or similar to, those in 2006. See the Table below.

In the same paragraph, see below, defra does acknowledge the numbers in the TW WRMP.

It should use the full set of data available in the WRP tables as above.

“Secondly, as the population increases, so does the “benefits jurisdiction”, ie the number of

people expected to enjoy the environmental benefit of the tunnel. Based on the population

forecasts for London reported in Thames Water’s Water Resources Management Plan... and

no further growth beyond 2035...this leads to an overall increase in aggregate 100-year

present Value benefit from £2,969m ...to £3,391m (an increase of 14% overall).”

It should be pointed out that London’s population went down between 1940 and about 1980

by about 25%. In addition UK natural growth rate is negative and population growth is

49

maintained only by high immigration and the high fertility of immigrants. Immigration could be

stopped by government, or EU action, or by economic conditions Thus, over the next 60 to

100 years consideration period, there can be no guarantee that population will have

increased by the amounts projected. However I have accepted the numbers proposed by

defra.

Real income growth

Defra analysis

The defra 2011 CBA para 11 b states “Similarly, the original RIA analysis did not take

account of the effect of the real income growth over the life of the tunnel on benefits. In fact it

is common practice in environmental appraisal to uprate “Willingness to Pay” based

estimates for public or environmental goods for real income increases...Real income growth

would be expected to increase the benefits of the tunnel – because environmental benefits

are observed to have a positive income elasticity (ie people value the environment more as

wealth increases.)” Note this is increased wealth that correlates with increasing WTP.

“The basic benefit estimate of £2,969m has been uplifted to account for real income growth,

“ note this is real income growth “but assuming only modest growth over the next few years,

in line with the current economic situation. ONS GDP estimates have been used for growth

to the period to 2010, “ para 12 states “It might also be argued that any uplift in nominal

value in the benefits from 2006 to 2011 could also be questionable given the recession over

this period (although not applying the uplift in general prices to the 2006 benefits estimate

would reduce it only by around 10%)”

2006-2011

A report for the GMB reported in the Daily Telegraph of 29th December 2011 stated that the

average fall of living standards when wage rises were compared with inflation over the last

four years had been 5.9%. Newspaper articles are weak evidence and I do not have a copy

of the actual report , but it is likely that the trend is downwards. It is also likely that, as family

incomes get squeezed, falls in living standards could result in a larger fall in willingness to

pay.

Since elsewhere population growth has been used as an adjustment, one measure is the

GDP per capita. Box 1.2 from the 2010 Budget red Book shows that between 2006 and 2010

GDP and GDP per capita fell, see the lower line in the chart below.

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Thus it would be difficult to support any benefit growth from income growth between 2006

and 2011.Thus I have deducted the 10% growth assumed in the defra report.

2011-2014

Para 11 b continues ”followed by Treasury estimates of mid-term growth to 2014” The

OBR Budget forecast, C2 page 77,was “GDP to grow by 2.3% in 2011, rising to 2.7% to

2.9% in the later years of the forecast.” No specific figures have been given in the CBA for

which treasury estimates were taken. Treasury estimates have been downgraded several

times in recent times so these high growth forecasts can no longer be considered robust. As

an instance 2012 GDP growth, forecast to be 2.0 in August 2011, has, by December 2011,

declined to 0.6%.

Thus a reasonable assumption would appear to be that growth estimates to 2014 are

unlikely to be more than half those assumed in the CBA.

2014 onwards

“followed by an assumed return to the long-term real growth rate (2% per annum) beyond.”

Analysis of the period 1982 to 2010 does show a rate that is about 2% a year.

With the current world and euro situation, along with the ever weakening UK economic

situation, the threat of EU tax on the City and the possible downgrade of the credit rating of

both Euro countries (as has happened since this was written) and possibly the UK, this

assumption is unsupported and currently looks appreciably optimistic. Real income growth

rate from 2002 to 2008 averaged 1%. As NERA says in its CBA report, it is important to be

cautious when carrying out economic assessments. I have therefore taken 1% as the long

term growth rate.

“Using this profile leads to an increase in the aggregate present Value benefit estimate of

33% to £3,948m.” This is the uplift of the basic benefit estimate of £2,969m by 33% to come

to £3,948m. Thus the 10% allowed for the period 2006 to 2011, see above, is included within

the 33%. Deducting the 2006 to 2011 nominal growth of 10%, as stated above, would

reduce the total growth to about 23%.

51

At present future growth in the long term seems speculative. Taking the cautious NERA

approach, there seems no strong reasons to assume the growth more than about half that

assumed in the defra CBA, 23%. That would result in a growth of about 12% and that is the

amount I have used in my analysis.

Spill volumes

Defra 2011 CBA para 11 c states “It has become apparent that the spill volumes from the

Combined Sewer Overflows are somewhat worse under the baseline (no project) case than

previously thought. Thames Water now estimate an annual spill volume of 40Mm3 rather

than 32mm3 used in the 2007 assessment.” I have searched the 2007 eftec report Stated

Preference Survey. The only reference is on page 11 that the information is “presented in

Showcard C3 (see Annex 5) and is also shown in Table 3.1 below.” There is no mention in

Table 3.1, or show card C3 on page 14 of Annex 5, of any spill volume. Thus the

respondents cannot have had any spill volume in mind when responding to the questions.

“Given that the Thames Tunnel reduces volumes to a fixed level consistent with meeting the

Urban Waste Water Treatment Directive, the implied benefit of the tunnel is therefore likely

to be larger than previously estimated.” This is not understood as there is no fixed volume or

spill frequency or “level” in the UWWTD.

“Accounting for a small change since 2007 in the estimated residual spill volume of the

tunnel, the net change is a 24% additional reduction in spill volume arising from the project

(based on current conditions.) Assuming this equates simply to a 24% increase in benefit,

the benefit estimate would be £3,694m. It should be noted that this estimate does not apply

any diminishing marginal benefit in reducing spill volumes however, which may be an

overestimate.”

Benefits depend on both the spill, the existing water quality, and the location. Thus there

would be no health benefit if there were no people in contact with the water. Thus it is

erroneous to assume a direct link between spill volumes and benefit. Thus the so called 24%

increase in benefit is illogical and not supported. As shown in the section above there

appears anyway to have been no mention of spill volumes in the original WTP survey, thus it

is the benefit level, 3 overflows per year, that would have been considered. Thus the 24%

increase is not valid.

In para 12 of the 2011 CBA defra state “...not c which may not be robust”. In line with defra,

my assessment excludes spill volumes.

Benefit conclusions

In para 12 of the CBA defra state “A nominal but arguably conservative “upper bound” on

the range of revised benefits from the Thames tunnel has been calculated by combiing “tests

“ a) and b) above (but not c which may not be robust) which gives a figure of £5,058 as a

100-year present value figure. As such, the quoted range of benefit for the Thames Tunnel is

now put between £2,969m and £5,058m.”

The CBA 2011 para 10 states “This gives a 100-year “basic” benefit figure for the Thames

Tunnel in 2011 prices of £2,969m. We take this as the lower end of the likely benefits range

for reasons set out below.” Taking the 2011 uprated figure of £2,969m, adding the defra

52

assumed 14% for population growth, and the defra assumed figure for real income growth of

33%, my maths gets to an upper bound figure of £4,502m. Thus the defra figure of £5,058m

is not understood and appears to have been overstated by about 10%.

I have considered the various factors above and, for the reasons stated, do not support the

upper bound figure of £5,058m.

“Whilst it might be argued, for the above reasons, that the upper bound could defensibly

form a new “central estimate”, we are cautious about claiming this at this stage, especially

given the delicate economic situation and the uncertain impact of this on real income growth

in the near term. It might also be argued that any uplift in nominal value in the benefits from

2006 to 2011 could also be questionable given the recession over this period (although not

applying the uplift in general prices to the 2006 benefits estimate would reduce it only by

around 10%)...On balance we would argue that the benefit is more likely to be in the upper

half of the range than the lower half.”

By my calculation, the upper half of the range, as calculated by defra, would start at

£3,735m. This compares with the current extimated cost of the Thames tunnel of £4.1bn.

My analysis allows, on a conservative basis, an uplift of 14% for population and an uplift of

23% due to real income growth, an uplift of 40%.

Defra CBA conclusion

The 2011 defra CBA para 14 states “In conclusion, we present a range of estimated

monetary benefit for the Thames Tunnel of £3.0-£5.1bn, but without making a strong

statement about the most likely point within it. Rather we suggest it is reasonable to assume

that benefit will be in the upper half of the range, given some systematic underestimates in

the 2007 analysis.” I have examined the so called underestimates and consider any such

underestimate to be minimal.” Given estimated costs of £4.1bn,” this does not include the

extra costs of £244m shown in para 6 “ this suggests that the tunnel will be cost-beneficial

(ie benefits will be at least as high as costs). Furthermore, given an economic entity (whose

current GDP is broadly £250-£300bn per annum) the broad conclusion that the tunnel is a

net beneficial investment for “UKplc” would appear reasonable.”

“15 The Thames Tunnel cost and benefit estimates above should be viewed as high-level, to

support the ongoing government position on what is ultimately a private sector investment,

but will continue to be developed and refined as the project develops.”

However I have assessed in the sections above that the “Base benefit” could be as low as

about £230m, see table in section 6. In that case, applying the revised a and b factors for

population growth and real income growth, the benefit would rise to £275m. These

compares unfavourably with the current estimate of the capital cost of some £4.1bn. The

CBA should be reconsidered.

53

5. A strategic and economic case for the Thames Tunnel, defra

November 2011

Introduction

In association with the Cost and Benefits report 2011 defra issued a report Strategic and

economic case for the Thames Tunnel 2011. This included a significant repeat of the Cost

and Benefit report so, where this has already been considered by me, I will refer back to the

relevant text in my report.

Current discharges

Page 3 states “In a typical year 39 million cubic metres of untreated sewage discharges into

the River Thames.” As a reason for constucting the Thames tunnel this is misleading on two

counts.

First the Lee tunnel is already being construcuted and, once that is finished in about 2014,

the amount of annual discharge into the Thames will reduce to about 18Mm3, less than half

the figure quoted.

Secondly it is not just untreated sewage that is discharged. This is emotive. It is storm

water, ie rainfall, mixed with some foul sewage. For major storms this is a much diluted

discharge.The TW report SCITTER Storm Sampling 2005 of sampling storm flows at the

Acton Storm Tanks showed that on average storm flows had less than 1% suspended solids

and no smaple exceeded 2 1/2% suspended solids.

Page 4 box “ CSO discharges now happen more than once a week on average”. Whilst

strictly speaking this is true, it does imply that many of the CSOs spill at this frequency. This

of course is not true, a number of the CSOs spilling less than 10 times a year on average.

With the completion of the Lee tunnel and the STW upgrades the frequency of discharge of

the most frequent spilling CSO will reduce to about 40 a year on average, the majority very

much less. Thus this point is misleading.

Future discharges

Page 2 and page 4 refer to the sewer system overflowing “in future even on dry days.”

Page 5 “Without a solution, the river is predicted to deteriorate”

This is based on the TW assumptions that dry weather flow in the sewers increases because

leakage and per capita consumption stay the same in future, thus relating dry weather flow

directly to population growth. Thus spill freqency and volume would increase.

However taking TW figures in their 25 year Water Resources Management Plan, for

population, per capita demand, and leakage, by my analysis, dry weather flow up to 2035

might not excede that in 2006, see my Project Justification Report and the table in the

previous section of this report.

The storm events in winter may increase but are not critical for dissolvedd oxygen because

there is a greater river flow and hence greater dilution, and the winter temperature is much

lower, see image below. The Met Office have said that summer storms are not expected to

54

change for many decades. Thus, on my analysis, it would be unlikely that the interceptor

sewers would overflow more during critcal dry weather conditions for several decades.

Increasing temperature in the river in the future may be an issue. I understand this would be

about 2C by 2050 and about 3C by 2080. This would need careful study. Although I have

asked TW back in October for the temperature data they used in the previous modelling, this

has not been provided.

Page 3 “ An increasing population is leading to more houses, and increasing urbanisation is

leading to a loss of green space to help water drain away.” Whilst this sounds sense for most

expanding towns, London is a finite area and the density of population and buildings is

already very high, and the amount of green space available for new building is very limited.

Currently about half the population live in flats and, in recent years, the new construction has

been greater than 80% flats. The projections are, I believe, for the proportion of flats in new

build to rise even further. In contrast there is greater pressure from central government, see

the recent Water White Paper and Planning Authorities for developments to increase green

space and adopt Sustainable Urban Drainage systems (SUDS) measures with reduced

runoff rates.

London’s reputation

Page 5” Improvements to the water quality in the River Thames through the construction of a

tunnel could lead to wider long-term benefits to London’s reputation ( eg as a tourist

destination) and economy.”

Misleading, see bullet 1 in other benefits in section 4.

Maintain attractiveness for inward investment

Page 5 “ the Thames Tunnel project should help to maintain the attractivenss of London for

inward investment.”

Misleading, see bullet 1 in other benefits in section 4

55

Property value

Page 5 “and could have an impact on the value of existing property and limit future

development.”

Misleading, see bullet 2 in other benefits in section 4

Economic activity

Page 5 “We believe that the project itself will lead to considerable economic activity-funded

in the long run by customers while in the short term it should attract inward investment and

could give a boost to economic activity.”

Very misleading, see bullet 5 in other benefits in section 4. As the words are “customers”

this reads as if written by Thames Water, the scheme promoters. Who else could use such

words?

In any case water charges will go up by some £70-£80/year for householders and similarly

for businesses. Thus the economic activity will reduce because of the money taken out of

the economy to fund the tunnel.

Alternative options considered

The defra Strategic and economic case for the Thames Tunnel report 2011 states on page

9 “The Lee tunnel and Beckton sewage treatment works upgrade will help to reduce the

overall volume of discharges but not by enough to meet environmental objectives.” The

report does not say whether the objectives are the TTSS or the UWWTD. The UWWTD is to

limit environmental pollution. Further, these meaures go a long way to meeting the dissolved

oxygen environmental objectives, see section 3.

The defra report does not consider the use of fixed and mobile bubblers and skimmers and

whether they, with the STW improvments and the Lee tunnel, could meet the UWWTD, see

section 7. Thus this comment might be correct but is misleading as there is an addition, the

fixed and mobile bubblers and skimmers, that have not been considered and probably would

meet the environmental objectives. This alternative does need to be considered properly,

see sections 7, 8 and 9.

Phased approach

Page 10 “Government support to date has been for a tunnel-based solution. However, this

does no necessarily rule out more sophisticated approaches to its construction such as a

phased approach. Advantages of a phased approach are that it could make it easier to

attract capital to the project, it could reduce the costs of capital ( by reducing risks) and it

may require smaller sums of funding over a longer timescale, though the total cost would be

higher.”

Whilst this was written before the Advocate General’s Opinion was issued, it does imply that,

at that time, defra considered that a phased tunnel would meet the UWWTD. This would be

contrary to the opinion put forward by defra at my meeting on Monday 5th March where they

said that only the full length Thames Tideway Tunnel would meet the criterion to collect all

spills except under unusual storm events.

56

Jacobs Babtie report recommending the west tunnel.

The Jacobs Babtie report Independent Review to assess whether there are economic partial

solutions to problems caused by intermittent storm discharges to the thames Tideway phase

1 Final Report dated February 2006 proposed, in additon to the upgrade of the Sewage

Treatment Works, a tunnel from Hammersmith to Heathwall (Battersea), (now called the

west tunnel), plus litter skimmers and oxygenation measures.

CBA Box on page 11. “Defra’s 2007 regulatory impact assessment concluded that the

Jacobs Babtie recommendations would not meet the objectives set within the Thames

Tideway Strategic Study, and so they were not accepted. “ The TTSS standards were set as

higher than the Directive. For instance the UWWTD states “to limit environmental pollution”

with the level unspecified. The TTSS standard is “to limit pollution to the point where

discharges cease to have a significant adverse impact.”

“This was on the grounds that the Jacob Babtie recommendations would still leave frequent

discharges from 19 CSOs between Vauxhall Bridge and the tidal barrier (which would

continue to discharge around 10 million cubic metres per year) and ultimately dissolved

oxygen targets for the River Thames would not be met.”

My understanding is that the water quality modelling, based on various assumptions, shows

that, with baseline conditions, the west tunnel would meet the current DO standards for

sometime ahead. On the basis of modelling in 2006, only in the future with climate change

induced temperature rise, would the west tunnel fail to meet the TTSS dissolved oxygen

standards. There is an indication on page 42 of the TW Needs Case report 2010 that the rise

used could have been “worst case”, appreciably above that now considered appropriate. I

have asked TW what temperature rise they used in the model.They acknowleged the

question but have not, several months later, provided the information. Thus I have doubt

about the validity of that modelling.

Secondly the TTSS DO standards were set at Lc10 with an objective to avoid visible fish

kills. JB page 14 states that the objective should be to acheive a sustainable fish popluation

and that that could be acheived with a higher level of fish kill for most species, thus allowing

the minimum dissolved oxygen content to be set lower.

Thirdly the dissolved oxygen standards were set assuming that salmon were in the suite of

fish. The EA now states, see section 9 of my Project Justification Review, that salmon are

not sustainable in the short to medium term. As set out in my Project Justification Review,

reconsidering the standards without salmon would lower the critical DO standards.

“Also, skimmer and bubbler boats could not be considered an effective strategy under the

UWWTD as they would not prevent pollution entering the river.”

I have been unable to find the words “prevent pollution entering entering the river” in the

UWWTD. Cardiff harbour does, I understand, have CSO discharges frequently but uses

fixed and mobile bubbler systems and litter collection systems to meet the dissolved oxygen

content criterion. A description of the Cardiff harbour system is included in Appendix A. An

alternative system to meet the dissoved oxygen targets, and hence UWWTD, is set out in

Section 7 of this report.

57

Jacobs Babtie assumed that a screening plant at Heathwall would be sufficient to treat

collected sewage. It is now assumed that, once collected, the west tunnel contents would

need to have secondary treatment and the west tunnel scheme now has to assume pump

out to the existing interceptors once the storm flow in them had subsided.

” a twin tunnel approach assumes a certain level of headroom within the existing sewerage

network which does not exist.” page 11 . This statement does not say how much headroom

in the sewers was assumed. I have been told by TW in October 2011 that the available

headroom is 3.2 m3/sec. Since then I have identified another 3 m3/sec, see my Project

Justification Review . This should about halve the time to pump out the west tunnel.

In any cas, the pump out time would depend on the volume in the west tunnel. Studying the

TW Table of performance given to me in October 2011, the west Tunnel section would have

a maximum average spill rate of 4 spills a year. Reducing the storage volume of the west

tunnel would reduce the pump out time but would increase the spill frequency. In the second

phase the loss of storage capacity could be made up by increasing the diameter of the

interconnecting tunnel somewhat. This would need study to find an optimum storage volume

and spill freuency for the west tunnel. However this has not yet been done.

“ Any wait for capacity within the main network would also result in sewage sitting within the

western tunnel for long periods, ” No time scale is mentioned. In any case the wait would

depend not only on the period for the storm flows in the existing network to subside but also

the amount of storm runoff in the west tunnel. For instance a smaller storm would have a

smaller volume in the west tunnel and would be pumped out sooner. The west tunnel would

only become full about 3 or 4 times a year. It is likely that a smaller west tunnel would be

appropriate in which case he wait until full pump out would be less, and might mean that

scepticity would not develop. This is discussed in more detail in my Project Justifiacation

Review.

This might well mean that the west tunnel would meet the new standards for sufficiently long

to enable the completion of the full tunnel to be postponed, possibly for several years.

However, at my meeting with defra on 5th March 2012, defra were adamant that the

UWWTD required a new collecting system to reduce spills below the guideline figure. If that

is so, then the west tunnel, despite potentially meeting the dissolved oxygen standards,

would fail the UWWTD as it would not reduce the spills sufficiently. I discusss this more in

section 8.

Paying for the tunnel

The Strategic and economic case for the Thames Tunnel Nov 2011 states on page 13 “On

the basis of current estimated costs, the tunnel will result in an average maximum annual

customer bill impact of £70-80 at 2011 prices...Ofwat estimates that “this” would see about

15% of households spending more than 5% of their disposalble income on water and

sewerage bills. This would be the second highest by a “water and “ sewerage company,

behind South West Water at 16%.” The government has recently announced a subsidy of

£50/household for South West Water customers, acknowledging that their water bills are too

high. For many Thames Valley water users this bill increase of some £70 to £80 per year on

average, at a time of economic difficulty, would be of appreciable concern.

58

Uncertainties

Page 14, “Some uncertainties are inevitable for a project entailing long, costly, and

geologically complex sewers being built in a heavily urbanised area. ... There are also

uncertainties about whether our estimate of risks is accurate” This reads as if it was written

by Thames Water as only they will know the risks and costs. It would be interesting to know

how much more of this defra report was written by Thames Water. ” and whether the project

can be structured in such a way as to attract the required finance.”

Importantly this section does give cause for concern that the project cost could yet go

higher than the current estimate. This is especially so as the cost estimate has increased

from £1.7bn in 2005 to £4.7bn in 2011. Only about 15% of this increase would be due to

inflation. The London Water Ring Main tunnel struck a water bearing fault and delayed

construction for several months. The knowledge of the geology is limited so is still a

significant risk. Since TW have not provided any scheme cost breakdown or risk allowance it

is not possible to comment further. This must raise doubt as to whether real costs could

increase even further.

On 2nd February 2012 the government submitted the Water Industry (Financial Assistance)

Bill to Parliament. This would give the Secretary of State powers (but not duties) to “provide

contingent financial support for complex water and sewerage infrastructure such as the

Thames Tunnel in London.” The level at which this could/would be provided has not been

disclosed so it is difficult to comment on its likely effect.

Conclusions by defra

Page 15 states “There is an environmental case for action in the Thames: the current level of

discharges from CSOs into the Thames is excessive, resulting in large fish kills”

Two large fish kills have been recorded in the last 10 years, 2004 and 20011, both in the

Kew/Barnes stretch significantly upstream of the CSO interceptor system which starts about

Hammersmith . Thus the Tideway CSOs that would be intercepted by the Thames Tideway

Tunnel were not the prime cause of these fish kills. The cause of these fish kills will be dealt

with by the improvements currently being constructed at Mogden STW, so this is not a

reason for further large capital expenditure on the Tideway Tunnel.

The benefit of bubbler and skimmer systems has not been included in the models.

“adverse health impacts”

The Tideway is not a bathing water so is not covered by the Bathing Water Directive so there

are no specific health standards. The Putney rowers are about ten times as healthy as the

general population.

The only other significant group of recreationalists is the dinghy sailors and water skiiers in

the London Docks. These are confined bodies of water and the small amounts of top up

water could be treated cheaply.

59

“sewage litter”

Only 10% of the litter is sewage derived. From the eftec study of TW customers, 2/3 rarely

or never had seen human waste. The EA has informed me on 18th January 2012 that

“Unsurprisingly the number of formal public complaints regarding sewage debris is relatively

few.” The use of a number of collection booms and skimmers had not been included in the

consideration.

“and odour related problems”

In my time associated with the project I have not seen any reports of an odour problem. I

have also lived in London and, when conditions were worse, worked in an office beside the

river without noticing any odour problems.

These seem weak reasons for the £4bn of capital expenditure.

“In addition there is the economic case to support the tunnel. It will secure at least £3bn to

£5bn worth of economic benefits (where estimable) for a whole life cost of around £4.1bn

(present value before considering financing arrengments). “ See the next section, and the

Table in it, where, by my calculations, the benefits, would be £275m or, if the minor benefit of

litter reduction were to be only £200m in 2006 then the disbenfits of the construction impact

would result in negative benefit. These are very much lower than the cost.

“Finally, the tunnel meets our statutory requirments under the UWWTD and will reduce the

risk of infraction fines against UK.” Yes, but is there a cheaper, or phased, way of acheiving

this?

6 Conclusions of the CBA review

The DEFRA revised CBA estimate has been somewhat selective in concentrating on those

areas where there is an arguable case for up-rating benefits estimates: population growth,

income growth, and asset life, while ignoring those uncertainties which support an alternative

view that the benefits were significantly overstated in the first place: overvaluation of health

benefits well beyond the level and severity of illness that could be affected by the tunnel

project, the provable tendency of single issue willingness-to-pay surveys to over-value, the

failure to give respondents significant information about the scale of avoidable illness, and a

proper sustainability assessment of fish and aquatic ecology.

My analysis appraises the defra cost benefit assessement and, using the same methodology

and on the basis of the reasons provided, suggests that the benefit could be as low as

£290m, see summary table below. This is little more than 7% of the cost estimate of the

Thames Tunnel. It is likely that the benefit assessment is much nearer this figure than the

figures suggested by defra. Were the litter benefit, classifed as “minor” by Eftec and with

“relatively few public complaints regarding sewage debris”, be not £1,000m but £200m then,

because of the adjustments and the disbenefits, due primarily to construction impacts, the

total benefit could become negative.

60

Item 2003/5 2006/7 2011 Comment Adjust

CBA CBA CBA ment

Base amount 3,935m 3,935m

WTP table Parts have a misleading description. Special measures not considered.

none

Water bills No mention of size of TT increase

none

Health Separately combined combined QALY not WTP -60%

Fish Separately combined Cascade WTP To £15m

Litter/aesthetics separately combined Property benefit minor none

Jurisdiction Admin A+B A+B Benefit Jurisdiction doubt none

Single/multiple single single single Multiple in FBP -60%

Other rivers No allowance. ? half none

Mean/median mean Median nearly half none

Protest votes included included Excluded Included none

Distance decay No Yes Yes Results look odd none

Monetary values no No No 15% constant nominal none

Thms/Lee split NO No TTT 60% Corrected split -57%

Benefit of Lee T No No No Lee tunnel needed for Thms T

none

Appraisal period 60 years 60 years 100years 60 years none

+14% £230m

Reduced hh flood no Entec Table 4.3 +£7m

Disbenefit no no no Half upper of £85m -£42

Base amount £195m

GDP deflator 06-11 +10.6% +10.6%

2011 2,969m £215m

Population rise No No +14% +14%

amount 3,391m £246

Real income growth

NO No +33% 2006-2011 zero not 10% 2011-14 half assumed long term, 1% not 2%

+12%

Spill volume Not included

Not included

Fish £15m

Amount 4,502m £290m

Quoted range 2,969-5,058

Wrong maths by defra ?

Mid point benefit 4,013m Defra mid point £3,735m ?

In which case it would appear that the full Thames Tunnel would be “Excessive cost” under

the UWWTD and “Disproportionate cost” under the Water Framework Directive.

The west tunnel of the two tunnel arrangement, along with the adaptations, would have

about half the cost of the full tunnel. However the benefits would not be as much as the full

tunnel. Thus, on the basis of my benefit assessment, then the west tunnel arrangement

would also fail the cost benefit analysis as its cost would also be excessive.

61

Treasury requirement

The HM Treasury Green Book states on page 17, para 5.3 “Creating options.This step

involves preparing a list of the range of actions which government could possibly take to

acheive the identified objectives. The list should include an option where government takes

the minimum amount of action necessary (the do minimum option) so that the reasons for

more intervenist actions can be judged.”

I propose that a do minimum cheaper option be considered as required by the Treasury and

this is set out in the next section.

7 Do minimum system

Introduction

Following Treasury guidelines, I propose that a “do minimum” cheaper system be

considered. Already the river environment will be considerably improved by the uprating and

improvement of the Sewage Treatment Works and the construction of the Lee tunnel. Even

without the Lee tunnel the Fish Risk Model shows the fishery of the Tideway to be

sustainable.

The first action would be the encouragement of a Sustainable Urban Drainage

system(SuDS) and the provision of blue green system. SuDs would require the provision of

storm water storage facilities such as water butts, underground soak aways, and

underground detention tanks. The impermeable surfaces such as roads and parking areas

would be replaced with permeable surface and gravel detention laysers underneath. Blue

Gren would mean the planting of more trees to retain and then evaporate rainfall. Similar

systems have been developed in both Eropeana and American cities.

Thames Water state that they are supportive of such an approach, but are concerned, with

some justification, that there are only limited legal powers to implement such measures and

that the measures would take a number of years to acheive sufficient effect.

In which case one would need interim measures.

The interim measures would include the adaptation of the sewerage system to minimise

discharges to sewers such as increaseed water metering to reduce domistic use and then

discharge of water, minimise flows in the interceptors by diverting sewer flows to other

ccatchments, and providing real time controls of sewer flows to minimise CSO spills. The

dissolved oxygen content in the river could be increased by providing a fixed bubbler

system in the river to minimise oxygen sags, supported by water quality monitoring and

mobile bubblers to tackle any particular areas giving problems. To deal with litter and

aesthetics issues booms where possible as well as mobile litter collectors would be used. If

necessary water treatment works would be provided to treat the top up water for the London

docks where there are dinghy sailors and rowers.

This is based, in part, on the scheme in Cardiff Harbour which, I am told, has “frequent” CSO

overflows. The Cardiff scheme uses fixed and mobile bubblers for dissolved oxygen control

and booms and skimmers for litter control. This utilises a near real time monitoring system to

62

identify any issues so prompt action can be taken. The scheme has provided 5 mg/l

dissolved oxygen for more that 99.9% of the time consistently since 2005. Whilst the Cardiff

harbour scheme operates in a different way, it does demonstrate that such a system can be

implemented and can work.

A similar system has been installed in the Seine in Paris and shows appreciable benefit.

Fixed and mobile bubblers to control the dissolved oxygen

Thames Water dismiss mobile bubblers. In their Stage 2 consultation in the note on options

page 3 they state” We currently use “ mobile “ bubbler...boats to reduce the impact of

untreated sewage overflowing to the River Thames...so our two bubbler boats inject oxygen

into the river helping fish survive sewage discharges.” Thames Water do not appear to have

considered the use also of a fixed bubbler system of diffusers laid up and down the river as

the basis of an oxygenation system.

“There are also severe limitations as to where these boats can go, due to tides and bridge

heights.” There could be restrictions if the boats have to go into the upper reaches above

about Mogden STW at certain tidal and flow conditions. The Daily Telegraph report of the

August 3rd 2004 fish kill event said the oxygenation vessels were not able to reach the

uppermost limit of the tidal reach, presumably the Teddington weir, because of low flows,

and hence low water depth in the river. In the 2011 fish kill incident the EA reported that the

TW bubblers were able to reach the area, presumably the Chiswick/Barnes area where the

event occured. Thus the evidence is that the restrictions are only in the upper reaches close

to Teddington at certain flow and tidal conditions and not in the middle lower reaches or

when the tidal and flow conditions are less onerous.

Further the Mogden STW is being appreciably uprated and, once completed, low oxygen

content should not occur due to Mogden final effluent tank carryover. Thus the need for

bubblers in this stretch should be much reduced.

The modelling shows the potential areas of DO risk of failure is generally downstream of

London Bridge, an area where the only bridge is Tower Bridge (which anyway lifts) and

water depths are sufficient for ocean going vessels, the cruiser HMS Belfast being moored

permanently just downstream of London Bridge.

The most upstream failure of the standards in the half tide plot is about 7km upstream of

London bridge. On page 37 of the TW Needs report the tidal excursion is stated to be up to

15kms. Thus the most upstream point would be some 14 ½ km upstream of London bridge.

This would be close to the Hammersmith Pumping Station, downstream of Hammersmith

Bridge. The charted depth here is about 1 1/2m plus the tidal height.

In any case my proposal is similar to the Cardiff Harbour Authority one where the main

scheme is a fixed bubbler system laid up and down the river with sensors linked by radio

providing near real time monitoring and mobile bubblers only needed should particular

problems occur.

“The boats aren’t an effective long term solution.” Cardiff Harbour Authority scheme is a

permanent bubbler scheme with mobile bubbler back up and it has operated for the last ten

years and, for the last 5 years has met the required DO standard of 5mg/l for 99.9% of the

63

time, thus enabling salmon to pass through the harbour and spawn, see descripton in

Appendix A.

The only way to assess the effect of the in-river system would be by modelling. However I

have done some very back of the envelope calculations to see if the system might work. I

have assumed that raising the dissolved oxygen content of the river water by 1 mg/l would

meet the dissolved oxygen standards and that this could be done by installing a system

which could do this in two days, albeit actually running continuously during the critical period,

whilst temperatures were elevated. I assumed that the most upstream position of the fixed

bubblers would be about Kew. This is about the most upstream point of a DO failure -13km

plus half a tidal cycle of 7km, 20km upstream of london Bridge. I estimate an average cross

section of 1,200m2 amounting to some 24 Mm3. Downstream the chainage where the do

starts to improve naturally is about km 14. Assume 2,000m2 cross section average in this

stretch then the volume would be 28 Mm3. The total would be about 52 Mm3. Assume that

the diffuser system needs to raise the oxygen level by 1mg/l in 2 days. That would require

26,000 tons of oxygen. The Dryden web site states that they supply very fine bubble

diffusers and that one diffuser diffusing 10 cubm/hr of air will add at least 25kg/day of oxygen

to the water. Thus one would need about 1,000 diffusers. Over a 35 km stretch with an

average of 3 lines of diffusers that would be one diffuser every 100m. This could only be

assessed by modelling.

To provide similar air pressures, similar water depths would be appropriate so the fixed air

lines would need to be laid up and down the river. A greater number of diffusers could be

provided in the vicinity of the CSOs where the greatest sags might occur. Like Cardiff there

would need to be a number of air compressor stations along the river bank.This is a more

difficult arrangement than in Cardiff Harbour. However I cannot see a reason why such a

system could not be developed and work satisfactorily to maintain the dissolved oxygen level

above that required.

Anchoring would need to be prohibited in the areas of the air pipes and diffusers to avoid

snagging the air pipes on the river bed. However few vessels anchor in the Thames, those

waiting in stream using buoys. In any case, due to tidal flow, diffusers need not cover all the

river bed and gaps could be left for vessels to anchor if need be.

In addition a number of mobile bubblers would be provided to concentrate on any particular

area where the dissolved oxygen sag was of concern.

Like at Cardiff a near real time monitoring system would be provided giving prompt warning

of any issues and enabling the mobile bubblers to be despatched promptly.

I am informed that the cost of the Cardiff scheme in 2001 was about £ 3 ½ m. The average

width of the river Thames is about 200m. Were such a system to be installed from say

Hammersmith to Beckton STW, a distance of some 30km, then the area covered would be

about 6 sq km, three times that of Cardiff. Based on the quoted cost of the Cardiff scheme

along with inflation and extra facilities for the tideway scheme and the monitoring, then the

cost might come to about £30m.

64

Litter collection

Whereas sewage derived litter is the most offensive litter, it is generally assumed to account

for only 10% of all litter. To collect this a system of booms and skimmers is suggested.

The Cardiff Harbour systems includes booms to concentrate the litter which is then collected

and disposed of. It should be possible to install booms round most of the CSOs to collect

the floating, thus concentrating the sewage litter so it can be promptly collected when a spill

occurs. This should be a cheap scheme to implement.

An additional collection system would be skimmers which would collect floating litter,

including that not sewage derived, thus reducing sewage litter and also improving the

general appearance of the river.

My understanding is that there are currently two skimmer boats. In March 2008, after 6

months service Thames Water stated “ The vessels which have collected over 40 cubic

metres of litter from the River Thames since September 2007 have greatly contributed to

improving its environmental and aesthetic quality, ensuring it is fit for river users, and for this

years Oxford and Cambridge boat race crews. To date, the skimmer vessels have been a

real success story, enabling uss to collect large volumes of litter, which overflows from the

sewers during periods of heavy rain.”

Health aspects

Legal criteria

The Thames Tideway is not a designated bathing water so is not subject to the Bathing

Water Directive. Thus the health of recreationalists is not subject to a Directive.

“The WHO guidance provides a simple indication of the likelihood and level of the risk of

infection...to bathers in marine waters..The guidance is only aimed at bathers and as such is

not necessarily indicactive of risk to other recreational water users such as rowing, sailing,

wind-surfing or angling.” HPA recreational users study page 8.

“Recreational users of the Thames Tideway are predominantly rowers, canoeists, and

anglers and include very few bathers.”HPA Recreational users report page 53

Current health of rowers

The key information from a major study of health risks to recreational users in the upper part

of the Thames (upstream from Putney Bridge) is summarised in the TW 2010 Needs report:

“An assessment of health impacts upon recreational users of the River Thames was

conducted and reported by the Health Protection Agency in 2007... While there was

evidence of an elevated health risk (gastric infection) to recreational users in the upper

Tideway two to four days after a CSO spill event, the rate of gastric infection among

recreational users was very low (12.8/1000/year) compared to the general population

(190/1000/year).” Thus the recreational users in the Putney area are more than ten times

less likely to suffer gastric problems from use of the Tideway than the general population.

65

Source of health impact.

“there is evidence to suggest that the influence of secondary treated effluent from Mogden

sewage treatment works is as great as that of the less frequent but common CSO discharge

events” HPA 2007 page 54.

“The overall trend shows improvements in water quality with the transition downstream from

Kew to Putney, potentially reflecting the importance of Kew’s proximity to, and the influence

of, both the secondary treated effluent and storm tank discharges from Mogden sewage

works. It is also important that the cross sectional volume of the Tideway at Kew is

significantly less than that at Putney and this difference may result in a greater level of

dilution at Putney than at Kew.” HPA Recreational users study page 48. Note the cross

sectional volume continues to increase going downstream from Putney.

Future quality

The quality of the Mogden effluent is being improved, due for completion about 2013. In

addition increased storm tank capacity is being provided to greatly reduce storm tank

overflow. Thus the general river water quality health situation will be improved.

Monitoring and health warning

“indicators can be predicted with an acceptable degree of accuracy given timely information

about discharge events.” HPA page 58. At the time of the HPA study I understand that only

about 7 of the CSOs had discharge instrumentation so such a prediction model could not be

relied on. I understand that now all the CSOs are instrumented so the base data of when

discharges occur should now be available . Thus risk of lower bacterial water quality could

be provided.

“The simplest, and possibly the most cost effective manner of making this information

available to the recreational public would be through existing internet facilities.” HPA 59.

“A simple traffic light system could be used.” HPA page 60. This would be an appropriate

mitigation measure.

Conclusion on the upper Tideway

With the rowers already having one tenth less gastric problems than the general population,

with the fleet of skimmers removing floating debris, MogdenSTW effluent currently being a

great impact but soon this quality will improve, the health impact on the rowers ought to

improve even more. If need be, a warning system of lower bacterialogical quality could also

be provided. Would it be needed or cost effective to do more than this?

Docklands

There are also dinghy sailors and water skiers in the London docks. Were it deemed

appropriate to improve water quality for these, then water treatment could be provided to the

small quantities of top-up water coming from the river. Budget cost £10m.

66

Consideration of standards to be met

It has been argued that the provision of bubblers and skimmers would not meet the TTSS

standards. However the standards to be met are those of the UWWTD, not those of the

TTSS which are higher. For instance the requirement in the UWWTD is “limitation of

pollution of receiving waters due to storm water overflows.” I consider the directive

requirements in more detail in section 8.

Since the fixed and mobile bubbler systems , along with real time monitoring, would provide

a way of dealing with dissolved oxygen sags and the skimmers would deal with floating litter,

both storm water and non stormwater, would that not meet the UWWTD requirement of

limiting pollution to the same level of environmental protection? For the Cardiff scheme the

EU has not taken action against UK for breach of the the UWWTD so presumably the EU

accept this form of scheme as meeting the requirements to limit pollution and thus

conforming to the UWWTD. This is considered in detail in Section 8 below, Directive

Considerations.

Cost benefit

My rough estimates of the cost of such a scheme comes to, fixed bubblers, booms and

skimmers , and the treatment in the London Docks, ,a total of £30m.This would be a cheap

minimum intervention scheme as expected by HMTreasury. It would also have a positive

cost benefit output and would not be either excessive cost or disproportionate cost so would

meet both of those criteria.

Programme for installation

It should be possible to study, design, obtain permission for, and install such a system in a

relatively short time, maybe 2-3 years. That would enable this alternative system to be in

operation for much of the time that the tunnel is under construction, providing an improved

environment during this period.

Recommended investigation

It is recommended that defra set up an independent panel to review and ,if appropriate, reset

the disolved oxygen standards, and to investigate whether a scheme similar to that proposed

would be appropriate, effective, and of reasonable cost.

8. Conclusions My analysis appraises the defra cost benefit assessement and, using the same methodology

and on the basis of the reasons provided, suggests that the benefit could be as low as

£275m. This is little more than 7% of the cost estimate of the Thames Tunnel. It is likely

that the benefit assessment is much nearer this figure than the figures suggested by defra.

Were the litter benefit, classifed as “minor” by Eftec and with “relatively few public complaints

regarding sewage debris”, be not £1,000m but £200m then, because of the adjustments and

the disbenefits, due primarily to construction impacts, the total benefit could become

negative.

67

Although the interim measures are deemed by defra as not capable of meeting the UWWTD,

they are likely to provide some improvement to the river. This, in itself, could be a benefit to

the environment and the community.

However, if the SuDs/blue Green approach were adopted to provide the long term solution,

then the interim measures would be of real benefit in providing environmental improvement

to the river and its water quality rapidly.

There is also the potential infraction fines. As I understand it, if the British government is to

be fined, then it would be on a daily basis until the tunnel is operational. The end date is

likely to be about 2023, or whatever, and there is little one can do to change that. In which

case one can only influence the amount per day. Postscript I have been informed that the

fines could amount to about E2bn but that these are unlikely to be enforced provided the

British Government presses on with solving the problem and meeting the UWWTD.

The AG Opinion 62 states "tolerating discharges of untreated water" which would occur until

the tunnel is operational " will be all the more acceptable the lesser the potential damage

which the untreated water could cause."

Further, were the interim measures to be found to be feasible and to improve the

environmental conditions in the river further, then the fines could be lower still. This would be

a further reason to investigate the viability of the in-river scheme.

9 Recommendations

It is recommended that defra set up independent panels to review;

1. The ability to implement SuDs and Blue Green infrastructure be investigated.

2. The interim measures be investigated and , where feasible, implemented as these

would provide benefit whether the tunnel or the alternative system were to be

implemented.

Chris Binnie MA, DIC, HonDEng, FREng, FICE, FCIWEM 16th March 2012

Postscript

Since the above was written the judgement of the European Court of Justice has been

issued to the effect that the UK is in breach of the UWWTD in not ensuring that CSO spills

only occured in times of unusual rainfall conditions, and that, because the UK has decided to

implement the tunnel scheme, the tunnel scheme cannot be considered excessive cost.

It should be noted that the Ministerial letter to Thames Water to procede with the scheme

was written in March 2007 when the cost of the tunnel scheme was about £2bn, and this has

subsequently been confirmed by the Coalition Government when the cost was about £4bn

plus the cost of the Lee tunnel at about £600m.

68

Appendix A Description of the Cardiff Harbour scheme.

Introduction

In the 1970s Cardiff Harbour was a rundown area with a poor environment. “A neglected

wasteland of derelict docks and mudflats...incapable of supporting most aquatic life.” WEM

Nov 2011 page 27. In the 1990s it was decided to impound the harbour and a barrage was

installed across its mouth. The harbour area had a number of sewage and CSO discharges

into it. The scheme is described in the Special issue of Water and Maritime Engineering

June 2002 and illustrations have been kindly provided by the Cardiff harbour Authority.

Scheme description

Page 84 “Sixteen major sewers have been diverted from the bay prior to impoundment.”

Page 131 “Althugh major sewage and other outfalls have been diverted from discharging

into the impounded water, there are still some inputs of sewage, industrial effluent, and

diffuse inputs from the river catchments and discharges from combined sewer overflows

(CSOs) during high rainfall events....Combined sewer overflows contribute high waste

loads...the discarges were located in the rivers Taff and Ely” I am informed that there are still

frequent CSO discharges.

Fixed and mobile bubbler system for dissolved oxygen content

Page 84 “The original concept for dealing with low oxygen levels was the provision of direct

injection by Vitox units at a number of points around the perimeter of the bay...In practice a

system of aerators has been installed in the bay with the agreement of the Environment

Agency. The aerators inject air into the water body rather than oxygen, and are designed to

operate continuously during the period from March until September each year.”

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The 600 diffusers are connected to air delivery pipes from the compressor stations on the

shore. They both mix the surface and bottom water thereby eliminating stratification and add

air, and hence oxygen, to the water body.

A mobile bubbler is used should such action be required.

Monitoring system

The monitoring system consists of sensors hanging from the 9 buoys providing water quality

data every 15 minutes.

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The image below shows the location of the monitoring points.

The data is relayed and displayed both in the Cardiff Harbour Authority (CHA) and EA

offices and live on the web so anyone can view it in near real time. In addition the historical

data can also be interogated on the web. Below is a sample I downloaded from the web

showing the readings every 15 minutes, in near real time mode for one of the sampling

points.

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This network of sensors and near real time display enables any oxygen sag to be rapidly

identified as it starts and rapid action to be taken at the relevant point in the harbour.

The aeration system has been operating since about 2001. During the early years there

were problems with receiving near real time data from the monitoring buoys. However since

2005 the new arrangement now gives reliable near real time (15 minutes interval) readings

for anyone connected to the web. This has enabled the scheme to meet its 5mg/l DO target

reliably.

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Thus such a scheme can be a very effective and reliable long term solution.

Booms and skimmers for litter collection

For litter collection the Cardiff scheme uses booms, and a litter collection and skimmer

arrangement.

Cardiff harbour ,page 91, “CHA has procured a purpose-built vessel and booms in order to

deal with the considerable amount of debris that builds up in the bay following floods.”

Conclusion

Thus the Cardiff harbour arrangment of fixed and mobile bubblers, a near real time

monitoirng system, and fixed and mobile skimmers, has enabled the Cardiff Harbour to meet

is dissolved oxygen and litter targets, and hence the UWWTD.

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Thames Tideway Tunnel

Interim measures to improve the river.

Working draft 11th March 2013

Report

By

Professor Chris Binnie

MA, DIC, HonDEng, FREng, FICE, FCIWEM

[email protected]

Tideway tunnel interim scheme 28 8 12

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Executive summary

Any long term solution to the Thames Tideway CSO problems would take many years to implement, so I propose interim measures to much improve the Tideway within two to three years.

The European Commission has taken out infraction proceedings against the UK for slow implementation of the UWWTD. The European Court of Justice has found against the UK on the Thames Tideway. Thus it is likely that infraction fines will be imposed. My information is that these could be substantial, based on the current tunnel completion date of 2023 as high as Euros 2.0 bn. I am advised that they would be based partly on the “Environmental impact of non-compliance “. A reduction of one point out of five points on the “environmental impact of non-compliance” or “member state conduct”might save as much as Euro 200 million, about £160m.

Standards for ecology, aesthetics, and health impact have been set for the Tideway. The current STW improvements, and the Lee Tunnel would reduce the spill volume from 39Mm3/year to about 18Mm3/years, a long way to achieving the dissolved oxygen standards. However the Thames Tideway Tunnel will not be operational until about 2023. Thus interim measures could be implemented to reduce “the environmental impact of non-compliance” until the tunnel is operational. The object of these interim measures would not be to meet the standards set for the Tideway but to mitigate the environmental impact to the extent that the substantial fines would be reduced. These measures would also provide an environmental improvement during this period.

CSO spills could be reduced by reducing water use further , by implementing SuDs, by connecting some sewers to other STWs, adjusting the CSO weir levels, removing restrictions in the sewer system, and by implementing real time controls. Booms around the CSO outlets could retain sewage debris and skimmers could collect escaped debris.

Fish are considered the most sensitive ecological species and dissolved oxygen standards have been set to minimise fish kill. A diffuser system using compressed air or oxygen would be able to raise the dissolved oxygen levels in the river to mitigate dissolved oxygen sags and provide fish refuges. Near real time monitoring and mobile oxygen bubbler vessels would supplement.

The Tideway is not a designated bathing water and is not subject to the Bathing Water Directive. For navigation reasons, the PLA has recently banned bathing in the Tideway except with a special licence. Health impact of those in the London Docks can be mitigated by putting in water treatment of the relatively small quantities of top up water. The rowers in the Hammersmith area are already ten times less susceptible to gastric infections than the general public. Improvements to Mogden STW, due for completion in March 2013, will much improve water quality in the Mogden/Hammersmith stretch of the Tideway where there are many rowers. A traffic light system could be provided to warn rowers should adverse conditions occur.

These works should be implementable within two to three years. The cost is estimated to be about £30 million, much less than a one point reduction in the environmental impact of non-compliance, of about £160m. Also the tunnel, when operating, would not eliminate spills entirely and such an interim scheme, if continued to operate, would reduce the volume to be pumped out of the tunnel, thus reducing operational costs and CO2 emissions. During tunnel construction, and the ensuing impact, these measures would demonstrate that everything possible is being done to mitigate the CSO spills and to improve the river environment. The measures would also improve the environment when the tunnel spilled several times each year.

I recommend that such interim measures be studied, and if found to be appropriate, included in the Thames Water Business Plan submission to ofwat and implemented.

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Contents 1 Introduction 4 2 Potential infraction fines 4 3 Protection of ecology and other standards 7 4 Benefit provided by works already under construction 9 5 Reduction in spills and debris collection 10 6 Reducing flows into the sewers 12 7 Suggested measures using in the sewer systems 15 8 In river control of debris 18 9 Dissolved oxygen improvement 25 10 Health improvement 37 11 Conclusion 40 Appendices A Modelling of the river conditions 42 B Information about the River Seine system 44 C Description of the Cardiff Harbour scheme 47 D Locations of the on land diffuser systems 52 E Information about the Hydrospin vortex separation system 53

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1.Introduction

This note is prepared on the basis that the Thames Tideway Tunnel is a committed project but the tunnel cannot be operational until 2023. Even were it decided that Integrated water management/Green Infrastructure/ Sustainable Urban Drainage Systems were to be implemented then it would still take many years for the Tideway to be satisfactory.

However the European Commission has taken out infraction proceedings against the UK for slow implementation. The Advocate General has found against the UK on the Thames Tideway. Thus it is likely that infraction fines will be imposed. I am advised that they would be based partly on the “Environmental impact of non-compliance “ and partly on the length of time between the date for completion assumed by the Commission and the environmental impact being deemed satisfactory. Presumably this would be when the Thames Tideway tunnel becomes operational or any other system reaches a satisfactory situation. My information is that these fines could be substantial, based on the tunnel becoming operational in 2023 possibly as high as Euros 1.5bn.

Standards for ecology, aesthetics, and health impact have been set for the Tideway. The Thames Tideway Tunnel would achieve these standards.

The defra River Basin Planning Guidance Vol 2 August 2008 states “The WFD requirement is to make judgements about the most cost-effective combination of measures.” Since completion of the tunnel is about 11 years away, and it could not provide benefit until complete and operational, should not the WFD consideration also include the interim period?

This report looks at ways that the “environmental impact of non-compliance” could be reduced during the interim period until the tunnel is operational. These would have to be relatively cheap and quick to implement. After completion about 2023 the tunnel would still spill several times a year and these measures, such as the booms, could also provide some long term benefit but that is not a priority. However measures which reduce the sewer flows in the interceptors, would reduce the volume of spill into the tunnel and hence reduce the energy and cost in pumping out the tunnel, as well as reduce the operational CO2 emissions.

In any case the proposed interim measures would provide significant benefit in greatly reducing the impact of CSO spills on the Tideway at limited cost and within about two to three years..

I have discussed this report in early draft form with the Environment Agency and in working draft form three times with Thames Water and have adapted it according to their comments.

2. Potential infraction fines

Infraction proceedings

The European Commission has taken out infraction proceedings against the UK. The Judgement of the Court, case C-301/10 dated 18th October 2012, states in para 95 “Consequently, it must be held that, by failing to ensure: appropriate collection of the urban waste water of the agglomerations of London(Beckton and Crossness collecting systems)..the United Kingdom has failed to fulfil its obligations under that directive.

Thus it is likely that infraction fines will be imposed, based partly on the period of non-compliance.

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Period of non-compliance

The period of non compliance is from the deemed start of non compliance to deemed end. I examine both dates below.

Start of infraction period

The date for compliance specified in the Urban Waste Water Treatment Directive is 31st December 2000.

The Court in its judgement appear to consider that the appropriate date is “the situation prevailing in that Member State at the end of the period laid down in the additional reasoned opinion.” Para 91. The additional reasoned opinion was sent on 1st December 2008. “The additional reasoned opinion dated 1 December 2008 prescribed a period of two months from receipt thereof for the United Kingdom to comply with its obligations resulting from directive 91/271.” Para 75. This date would be 1st February 2009 or very shortly thereafter. It is noteworthy that this date is already some 8 years after the date for compliance in the Directive.

Date of completion

The question then is whether compliance will be deemed to be when the tunnel ” begins” dealing with the problem or when the problem is fully addressed.

I understand that DEFRA takes the view that there will be no penalty proceedings brought against the UK because the Commission will treat compliance as the point at which the tunnel construction begins or is approved, rather than completed.

I understand that the Commission’s view is that compliance is when the system is functioning in accordance with the UWWTD, which would be when the tunnel is completed and operating.

The Commission’s view does seem the logical conclusion.

The Thames Water Stage 2 consultation states in the document Timing “Subject to approval, our provisional start date for the construction period is 2016....(duration is expected to be six to seven years.” That would mean completion in about 2023.

This date compares with the completion date in the Thames Water report of December 2006 Vol 1 Tunnels and shafts page 14 of 2019. Thus the project has already slipped about four years.

The tunnel will be some 20km long. It could not become fully operational until the whole length had been completed. Thus any delays would compromise the scheme becoming fully operational.

Tunnelling is always at risk of unknown geological features. For instance the London Water Ring main tunnel constructed under London in the early 1990s, hit a water bearing fault which required ground freezing to be able to tunnel through it. This delayed the tunnel by several months. As the Tideway tunnel is mostly under the river access from the surface to any problems would be difficult and require special equipment.

Thus it is possible that the date for the tunnel becoming operational, about 2023, could slip further. This could increase the period of non-compliance and hence the infraction fines accordingly.

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Thus the period of infraction could well be from the date in the reasoned opinion, 2009 to the date of completion 2023, a period of 14 years. The analysis below is based on the period from 2017 to 2023, a period of some 6 years.

Amount of the fines.

Only the court can hand down a fine on the Commission’s application. The text below assumes that the period of non-compliance would start in 2017. However this could well be 1st February 2009, more than doubling the fines.

I have not been in touch with the Commission and do not have the relevant documents. However I have received an email from a lawyer who has. He states:

“My team and I have come up with the following estimate of the fine the UK can expect to be liable for in the event that it loses its case before the ECJ. It is EURO 891,845,800. This breaks down as- Lump sum: Euro 2500000 (aimed at punishment) Daily penalty: Euro 395820 (or Euro 144m per year) (aimed at pressuring the UK into compliance) The daily penalty is based on the following calculus which the Commission and the Court use:

600 (flat rate) x 10 (seriousness of infraction) x 3 (duration of infraction) x 21.99 (UK ‘n’ factor). Say the ECJ hands down its decision in Summer 2012. By Summer 2015 the Commission will have brought enforcement proceedings asking the court to recognise that the 2012 judgment has not been complied with and to lay down a fine. By Summer 2017 the Court will have ruled on this application, awarding a lump sum and period penalty. The clock begins to tick on the daily penalty from 2017 If it is not until the Summer 2023 that the tunnel is opened, “ six years” the total liability will be Euro 866,845,800.”

“The seriousness coefficient contains a value of between 1 and 20. I have estimated 10. Using the Commission’s own published guidance and the case law...I have calculated this figure on the basis of the following analysis: Member state conduct – 4 out of 5 Environmental impact of non-compliance – 2 out of 5 Impact on competition – 2 out of 5 Miscellaneous (e.g. size of population affected, importance of compliance with this specific law to the functioning of the EU) – 2 out of 5. The estimates in all these headings are on the conservative side. For example, the Commission could easily press for the maximum on member state conduct... Regarding environmental impact, the

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Commission will probably view this as above rather than (as I have estimated) below average seriousness. Likewise the impact on competition, and in terms of population, London is one of Europe’s most populous cities so, once again, there is real scope for uplift.”

Based on the analysis above, it would be quite possible for the seriousness of infraction to be 15 rather than the 10 used in the analysis, increasing the infraction fine by about 50%. If so the fines could amount to about Euro 1.5bn.

However, were the Commission to assume that the date in the reasoned opinion were to be the date for completion, then the period of noncompliance would be 14 years. Thus the fines would amount to about E2bn. I have been informed that “EU Water Commissioner's office spokesperson has said that they are seeking 2Bn Euro infraction fines to be applied to the UK.”

At a visit to the EC in February 2013, the EC representative said that, provide they could see a solution being progressed, the EC might well not take enforcement action. However this view could well change with change of policy or personnel, especially considering the long infraction period.

However the one criterion I will concentrate on in this report is the “environmental impact of non-compliance”. This can vary between 1 and 5. Based on the calculation above, reducing the impact number by one point would reduce the fine by about 10%, ie by some Euro 200m, about £160m. The Commission might well take a more serious view of this and if so there would be greater scope for improving the environment and reducing the fine further. By showing early improvement in the environmental impact, the interim measures might also help on reducing the size of “member state conduct.”

If so, then interim measures could reduce the extent of the environmental impact of non-compliance and also potentially reducing the size of the infraction fines.

An interim solution would not need to meet all the standards laid down but would need to reduce the environmental impact of non-compliance in a cheap way to a level where the fine would be lower and the net cost beneficial. They would also need to be implementable within two to three years. Such interim measures could also be beneficial in providing an environmental improvement when the tunnel is operating.

The rest of this report looks at how this could be done, and to what extent it would reduce the environmental effect of non-compliance.

3. Protection of Ecology and other standards.

Whilst the aim of the interim standards is to alleviate environmental impact rather than to meet the standards that have been set for the Tideway it is helpful to know what those standards are so one can identify measures to alleviate them.

The objective of the Urban Waste Water Treatment Directive is “to protect the environment from the adverse effects of ...waste water discharges.”

It is to be noted that the UWWTD makes no reference to any actual level of protection or any standards.

This was interpreted by the Thames Tideway Strategy Steering group as “To reduce the frequency of those discharges that cause significant aesthetic pollution, or to limit the pollution caused, to the point where they cease to have a significant adverse impact.”

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The Thames Tideway Tunnel and Treatment (TTTT) report, 2006 Vol 1 Objectives states “since it is generally recognised that fish are the most sensitive indicator of ecological quality, the decision was taken to derive standards that are protective of relevant fish species.” These are set out below

These were arrived at following trials of the dissolved oxygen sensitivity of the various fish species in the fish suite, the most sensitive of which were salmon. The trail results are shown below.

There are effectively no salmon in the Tideway and the EA now say they are not sustainable in the short to medium term (quoted as 2020 but probably meant to be when the tunnel is operational, about 2023). Post 2023 adverse temperature conditions would affect any returning salmon. According to Turnpenny and Liney,2006 the lethall temperature for salmonids is 27.8C but the Freshwater Fish Directive says for salmonids the temperature should not exceed 21,5C. Solomon has shown that salmon did not enter the Avon River when the temperature was above 21C. In the Thames “Migration is under-represented at temperatures above about 22.5 C in July, 22 C in August, and 19 C in September.”Solomon 2011. Turnpenny et al 6-14 says ”Summer temperatures in the ...Thames can reach 23-24 C. “ With climate change these are likely to rise 2 to 3C.Modelling has shown that because of climate change salmon from southern England could not survive in the long term, primarily because of changes in the marine conditions in the post-smolt area of the Atlantic. The standards could still be appropriate if other fish species took the place of salmon. However Sea trout are similar to salmon. Lamprey and eel can tolerate low dissolved oxygen conditions. Sturgeon are being introduced to the Gironde in south west France but it is likely to be about a century before conditions for them are suitable. Twaite shad are rare visitors, and are reported to be more tolerant

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of low dissolved oxygen content than salmon. Thus it may be that the standards set are higher than necessary.

However, the object of the interim measures is to alleviate adverse environmental conditions, not to meet the standards themselves.

Thames Water TTTT Solutions 2006 vol 1 page 19 states“It is unlikely that small-scale meausres (use of bubblers and litter collection vessels) can fully mitigate the effects of not intercepting the CSOs in the middle section of the Tidal Thames.” Since then the Lee tunnel has been authorised. It is not intended that the proposed measures are an alternative to the main measures but as an interim measure. Thus there seems good reason to study the interim meassures to see what can be acheived and whether they are worthwhile implementing.

4. Benefit provided by works already under construction

The works already under construction include upgrading of the Mogden, Beckton, and Crossness STWs. As a response to the 2011 fish kill in the Chiswick area, Thames Water have said “ I do need to assure you that once the extension is completed in March 2013 the works will be able to handle a similar situation without even using its storm tanks, let alone discharging to the river.”

Once all the upgrades and the Lee Tunnel are completed, about April 2015, the volumes of stormwater discharged to the river will fall from about 39 Mm3/year on average to about 18 Mm3, less than half, see Table provided by Thames Water.

Modelling of the river system has been done by Thames Water and shown in the Needs report

2010. Plots have been prepared of the number of breaches in the 34 years of modelling on the y axis and the distance upstream and downstream of London Bridge on the x axis. The plot above shows the situation with the 2mg/l standard. The red line shows the number of breaches with the current CSO and STW system. The standard to be obtained is shown by the dark blue horizontal line. The mauve line shows the situation after the Lee tunnel and STW improvements have been completed. This shows that the current works go a long way towards meeting the required dissolved oxygen standards. The situation with the other three standards is set out in Appendix A.

The most upstream breach of the standard is at chainage -7 km and the most downstream point where the dissolved oxygen content starts to improve is +14km. These are half tide plots. I am informed that the tidal excursion is about 14 kms. Thus the most upstream point of any failure is about -14kms, about the Barn Elms wetland centre and somewhat downstream of the Hammersmith pumping station outfall. and the most downstream +21kms, about the Beckton STW.

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Thus the most upstream position is about the Barnes wetland centre. The most downstream is about Beckton STW. However the most downstream condition is the threshold 1, 4mg/l which is not a standard for fish kill but for potential hypoxia effect. Without this threshold the most downstream point would be 4km plus the 7 km tidal excursion, 11km, about the mouth of the river Lee. In reality, if the system proposed is adopted, the water moving downstream from the mid tide point would already have been aerated so it would probably not need to inject air further downstream than the half tide point +14kms as the aerated water, would be carried naturally downstream during the ebb. Thus, for the downstream position, I have taken +14kms, approximately the mouth of the River Lee.

5. Reduction of spills and debris collection

Objectives

The TTSS adopted as an objective “To reduce the frequency of operation and limit pollution from those discharges which cause significant aesthetic pollution, to the point where they cease to have a significant adverse effect.” This was re-endorsed in the TTTT Objectives report of December 2006.

Environment Agency Assessment

It is very difficult to identify which CSOs are providing debris that results in a significant adverse effect. The Environment Agency developed a protocol. This identified areas of the river which are sensitive to aesthetics impact. In broad terms these were the river from Kew down to Westminster, around Greenwich, and around the Thames Barrier.

The EA then assumed that “the volume of discharge is a key factor in determining the extent of the adverse aesthetic impact created by a particular outfall. Thames Water sewer models were used to estimate the mean volume discharged from each for 21 historic rainfall events. CSOs that discharged an average of greater than 50,000 m3 were assumed to make a significant contribution to the aesthetic impact, whilst those that discharged less than 1,000m3 were assumed to cause no significant impact. CSOs that discharged between 1,000 m3 and 50,000 m3 were assessed for the nature of the area into which the discharged, by reference to figure 1... 35 CSOs were deemed to be unsatisfactory because of the contribution they make to the aesthetic impact of storm sewage discharges.”

I have not been able to find any specfic analysis to support the choice of 50,000 m3/year as the level at which a CSO must have an adverse impact. Thus this analysis is a subjective assessment.

Impact of sewage litter

It is generally accepted that sewage derived litter makes up 10% of the total litter. The figure is from the Tidy Britain Group. There is limited evidence to support this figure but it is a generally used figure. Thus 90% of the litter/debris is not sewage derived.

“Shortly after discharge floating matter disseminates relatively quickly so the plug of sewage effluent moves unnoticed with the ebb and flood of the tide.”HPA recreational users report page 52.

Jacobs Babtie Review for ofwat.

As part of their review Jacobs Babtie team did a trip on the Thames on 31st August 2005 and reported “...several days after the most recent rainstorms, floating debris was seen in several locations. The slicks that the TTSS describes in its reports were observed, and, on close inspection, it was clear that some of the debris contained in them was sewage-derived. However, our opinion is

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that it would not be immediately apparent to a casual observer that the debris was any more than windblown litter and vegetation- a fact reflected in public responses obtained during the TTSS.” Independent review for ofwat Feb 2006 page 8.

Jacobs Babtie continue on page 9 “In addition to the slicks, litter was seen to have accumulated on the banks of the Tideway. However much of this is coarse debris which is likely to have originated from sources other than the CSO discharges. Much of the bankside of the Tideway is overlooked from adjoining residential and commercial buildings or is accessible to the public, albeit access to the actual waterside is made only infrequently. Numerous leisure vessels provide visitors to London with river tours. Thus bankside litter deposits may be considered a very visible aesthetically feature from the public standpoint.”

In which case the collection of all litter by skimmers would be a significant aesthetic improvement.

The DETR 1997 guidance on the UWWTD states to identify an unsatisfactory CSO it would need to have “a history of justified public complaint.” The Environment Agency have stated “ the number of formal complaints regarding sewage debris is relatively few.”Bain email. Thus there do appear to be only a few complaints from the public.

On page 11 Jacob Babties quote from the eftec report The Market Benefits of Options for the Thames Tideway appended to the TTSS Cost Benefit Working Group Report which they say states

“...although reducing CSO events would be associated with reduced amounts of sewage litter, this is currently only a small (10 per cent) proportion of the total litter and debris in the Tideway at any one time, and what there is appears to be invisible much of the time, at least as far as individual perceptions are concerned.

This is one of the findings of the SP (TTSS’s stated preference survey) as well as being the view expressed by consultees from the London property market. We might expect certain river users to notice a difference, in particular those who come into close contact with the water, such as rowers, houseboat owners and those who frequently walk by the river. However, in general the public are unlikely to detect much visible difference, and this includes owners of riverside property who, as we have just argued, tend to partake in river-based activities from a greater distance... The Thames is a tidal river downstream from Teddington, and levels of suspended silt and mud in the water are naturally high and always will be. Reducing CSO events will not have any impact in this regard.

Therefore, little aesthetic change in the water is to be expected due to Tideway Strategy options, and this, together with the low correlation between riverside residence and involvement in river-based water sports, suggests that any impact of the Tideway options on property prices is likely to be minor.”

These statements were made about the baseline in 2006. Since then the baseline now includes the Lee tunnel, in itself removing more than half the spill volume, as well as improvements to the water quality and storm overflows from the 5 London sewage treatment works. Thus the effect from sewage litter would be even smaller for the new baseline.

On the Tideway Tunnel, Jacobs Babtie concluded: “in general the public are unlikely to detect much visible difference.”

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Thus, although the Environment Agency have identified 35 CSOs as contributing to the aesthetics impact, that impact does appear to be relatively low. This should be taken into account when assessing the environmental impact of non-compliance.

6. Reducing flows into the sewers

One method to reduce CSO spills is to reduce the flow going into the combined sewers. This can be done by reducing water use, the use of Sustainable Urban Drainage Systems(SuDS) , and by diverting the sewer flows to other catchments. The benefit from reducing flow into the sewers would also be less vulume to pump out of the tunnel, thus reducing pumping costs and CO2 emissions.

Reduce flow into the sewers by reducing water use.

Thames Water have said that population will increase, true, and therefore, assuming constant per capita water use, CSO flows will go up, thus leading to increased CSO spills. I examine this below to see if it is possible to reduce sewer flows during the interim period and hence reduce CSO spills.

The area sewered to the Tideway interceptors is similar to, but somewhat smaller to that supplied by Thames Water with water, so, judging by eye, a factor of about 85% of the water deliverd ending up in the sewers would seem to be a reasonable assumption.

The analysis of water projected to be supplied by Thames Water is given in the Thames Water WRMP 09 , table WRP4-FP. This shows water delivered in 2007/8 as 1633 Ml/d and in 2022/3 1533 Ml/d, a 100Ml/d reduction. Therefore the water delivered, and hence reaching the sewers,is projected to go down during this interim period.

The figure projected for leakage in London 2007/8 was 590 Ml/d and this dropped to 539 Ml/d in JR2011, and is projected to drop to 397 Ml/d in 2022/3, a reduction of about 200 Ml/d. Some of this leakage will end up in the sewers, and a reasonable assumption might be that about half of the leakage reaches the sewers. On this assumption the sewer flows by 2022/3 would reduce by about 100 Ml/d.

Thus already there would appear to be a reduction of about 200 Ml/d in sewer interceptor flow by 2022/3.

A further way to reduce sewer flows would be greater demand management. In its Strategy discussion document TW says it will meter all homes by 2030, an increase in the number set in the previous WRMP of 80%.

There are several lines of interceptor sewers. I have no way of knowing how the flow reductions would split. However, since the lower flows in the higher interceptors should mean even less of a spill into the lower interceptors, a reasonable assumption might be that the sewer flow in the lowest interceptors, ie te ones that spill into the Tideway, would be reduced by about half. If so then the flow in the lower interceptors would reduce by about 100Ml/d by 2022/3.

My proposal is that such action to reduce sewer overflow during the interim period should be studied, and, if viable, implemented.

Sustainable Urban Drainage Sytems

One way to reduce storm runoff into the sewers is Sustainable Urban Drainage Systems. These use swales, soakaways, porous pavements and other detention systems to reduce/delay storm runoff.

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Thames Water in its Strategy Discussion Document spage 17 tates “We will take steps to reduce the amount of rainwater that enters our sewers.” As a strategy in the short term (2015-2020) page 19 “A major part of this long-term goal will involve working with the Environment Agency and local authorities to promote and install sustainable drainage systems.”

This was studied in Appendix E to the 2010 Needs report, for three pilot areas and appreciable reductions in storm runoff were found. The report is difficult to understand but on page 42 quotes a reduction in overflow of greater than 50%.

However it must be recognised that this effect would take time to build up to full amount so only a proportion reduction of storm runoff could be expected in the earlier years.

However, the use of SuDs and blue green infrastructure is the way that many European and American cities are now going to overcome similar problems.

Reduce flow into the interceptor sewer system.

Another way to reduce the spill volume is to reduce the catchment flowing to the interceptors and the Tideway CSOs. I have identified three options.

Divert to the Mogden STW catchment

The plan of the sewerage network below shows a Mogden main sewer coming almost as far as Hammersmith. Connecting this sewer to the Hammersmith sewers and passing the flow to Mogden could reduce the flows in the Beckton interceptors. However I have been told by Thames water that the sewer connecting Chiswick to Mogden is fully loaded during storm conditions. However there may be other similar connections that can be made and such an arrangement ought to be investigated.

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Divert to the Hogsmill STW catchment.

One way for augmenting water resources considered in the rdWRMP09 is to divert some of the flow going to Crossness STW to the Hogsmill STW works upstream of central London. Such a scheme was identified in the dWRMP 09. It was called Hogsmill B with a 20Ml/d (1/4 cumec) diversion.

This would both increase the flow over Teddington Weir, and thus could be used to augment the water resources for London, as well as reducing the dry weather flow in the southern interceptors by about ¼ m3/sec and reducing the CSO spill volumes from them. This dual benefit should be looked at.

Connect to the Thames / Lee tunnel.

There is a tunnel under the Beckton and Crossness sewer catchment that connects the Hampton intake upstream of Teddington Weir to the Lee Valley reservoirs. It is normally for conveying raw water abstracted from the river Thames. The Institution of Civil Engineer paper on the scheme states its capacity as 120mgd, about 500Ml/d or 6m3/sec. However the Cascade LTOA report quotes the abstraction licence as direct from the river to the tunnel with a capacity of 682 Ml/d, a substantial amount. The ICE paper states that there are access shafts at about one mile spacing. The route crosses under the Beckton sewer catchment.

Were it possible to divert storm water into this tunnel, then it would reduce the flow to the sewer interceptors. A separate storm water system would need to be identified, and possibly developed, and connected. Places that could be considered might be based on Holland Park, Kensington gardens, and Hampstead heath. It is possible that a inlet screening would be necessary. Delivery would be to the Lee Valley reservoirs where considerable dilution and some natural treatment would occur. Coppermills water treatment works provides advanced water treatment.

Such a scheme could also provide collect runoff during a dry spell and provide some increase in water resources. I believe such a system has not yet been fully considered but should be.

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7. Suggested meaures in the sewer system

Remove restrictions in the sewer network.

Restrictions in the sewer network can result in more flow being discharged to the local river than necessary.

Appendix B to the Needs report 2010 describes the situation in a number of other cities , mostly European. On page 37 it describes that “80 flow restrictions were eliminated” in Hamburg.

The London sewer network is almost entirely concrete and brick with fixed sizes. This was developed over a a long period so what was considered optimum many years ago may well not be optimum now. The TW sewer model is now much better and more accurate than at the time of the TTSS study in 2004.

As an example I understand that there are a few known restrictions in the London sewer system. For instance I understand that the connection between the Fleet sewer and the lowest interceptor sewer is only about 3 foot across and that this restricts flow in the Fleet sewer from flowing into the low level interceptor, irrespective of whether there is spare capacity in the intrceptor. This results in larger spill from the Fleet CSO. Whilst enlarging the connection may not be easy, because it lies directly below the Blackfriars Bridge road interchange, this illustrates one action that could be taken in the intermediate time to reduce spill volumes.

Whilst the restrictions along the lowest interceptor sewer may have been studied as part of the Tideway Tunnel project, there may well be restricitons in higher parts of the sewer network that could be changed beneficially, thus reducing CSO spils or moving them further downstrem so they have less impact. Thus, as part of the Interim measures, it is proposed that the sewer network be studied to identify the restrictions and whether they could be altered to provide benefit to the system and reduce CSO overflows.

Real time control and detention tanks.

There are many interconnections between the sewers and the interceptors. At present these operate with a fixed weir. However the levels of the weirs were constructed many years ago and may no longer be optimum. Of importance, many of the most polluting storms are in summer when the river flow are lowest. These storms tend to be summer thunderstorms and to be localised. Thus conditions will vary appreciably from one storm to another. Thus ther may be spare capacity in an interceptor because the rain has not fallen in part of the catchment draining to it.

It is reported in Needs case Appendix B that in Barcelona storm events are managed using real time control (RTC) and detention tanks. A RTC system is being developed in Paris. Page 6 also lists RTC as also being implemeted in Lisbon, Marseilles, Vienna. Many cities have also built detention tanks to assist RTC and minimise CSO spill.

The Thames Water Strategy discussion document states on page 19 “Our strategy also includes the increased use of innovative, real-time control and monitoring systems. We have alreday begun installing this technology, whch will help us to manage our network more actively and take swifter action to avoid operational problems.”

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In particular in London there is a system of trunk sewers going down the historic “valleys” and interceptors going largely horizontally to carry away flow to the east. The levels of the interconnector structures are fixed. Thus they are not able to adaprt to the different conditions of summer thunderstorms. Thus there is likely to be appreciable scope for passing more flow down the interceptors and less CSO spill into the river. For instance if more sewer storm flow in the Notting Hill or Hampstead area could be retained in the upper interceptors, then there would be less flow in the Low level sewer and hence less CSO storm spill. These measures would require moveable weirs with actuating motors.

Detention tanks were looked at by TTSS but rejected as a single solution as there was not sufficient spare and such a system could not be sufficient. However, in conjunction with RTC, detention tanks in the less developed areas, particularly south of the Thames, could be looked at as part of RTC. However, detention tanks are long lived assets and it is possible that the short term benefits would not be sufficient to warrant their construction. This would need to be assessed.

Whilst TW has looked at RTC in regards to the lowest interceptor that spills into the Tideway Tunnel , my understanding is that little study has been done of the higher level interceptors.

The sewer model should be run to see what benefit could be obtained from RTC, with or without detention tanks. Were any such measures found to be sufficiently beneficial in reducing CSO spill they should be implementable within about two years, the time scale being considered for interim measures.

Vortex separation of sewage debris

It is the floatables that give rise to most of the aesthetic impact. A vortex can help to separate out the floatables from the remainder of the storm water flow.

Such a system was looked at by Thames Tideway Strategy Steering group in 2003. However, at the time, experience of such a system was limited, most systems needed a significant driving head which was not always available, and such a system would not reduce the frequency of spill events. Thus it could not provide a total system.

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However a vortex separation system could provide part of a suite of interim measures. Since then I have identified a vortex system Hydrospin, provided by Steindardt of Germany. Further information on such a system is given in the technical paper in Appendix E.

This system has been tested and found to result in concentrations of floatables of 85% to 99%, see page 9 of Appendix D. The Steindart web site states on page 4 the “1,000 installations already operate successfully.” Thus the system does appear to have good potential and operating experience such that it warrants considering.

For instance such a system could be considered for Greenwich Pumping Stations where there is both pumping head and a good pass forward flow, see plan below. This pumping station would discharge about 4 Mm3 a year, see Table of Performance in Appendix A. This is one quarter of the post Lee tunnel annual baseline overflow of about 18Mm3/year. Thus such a system, if feasible, could have a significant benefit to the visual impact in the Greenwich and Thames Barrier locations where there are many tourists and the discharge is into a particularly visually sensitive area.

A possible location of the vortex chamber is shown in the plan above.Thames Water have provided me with the designflows from a 15-year 120-minute event of Heathwall 12 m3/sec and Greenwich 36m3/sec. These are very large flows and would need very large vortex structures. Anyway the return period is outside the period for an interim measure to operate primarily for an 8 year period, thereafter flows to the tunnel considerably reducing the flows to the interim measure.

Both options may well be outside the cost range for interim measures on their own. The TW Table of performance shows the post tunnel situation as an annual spill four times a year of 571,000m3 lasting 35 hours. Thus there would still be an appreciable quantity spilling into a prime tourist area. Thus, in this case, there would continue to be a significant impact on the tourism area. This would need to be taken account of in the assessment as to whether the expenditure would be worthwhile or whether it would form part of the permanenet works.

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Were a vortex system not be feasible or economical, then an alternative would be to install screens here as set out in my Project Justification Report. It might be possible to reuse one of the screens that are currently at Abbey Mills and will be redundant on commissioning of the Lee tunnel.

Consideration should also be given to installing such vortex systems at other CSOs where there is both sufficient pumping head to drive the vortex and space to build the vortex. It is possible that some pumps might need to be replaced with ones providing a higher head. Some of the space taken for the tunnel construction might be useable for such a vortex. The other sites with potential might include Lots Road pumping station, Western pumping station ( although under some conditions there is no pass foward flow here), and Heathwall Pumping Station. The problem with the Lots’ Road and Western pumping stations is that they are close together and Ihave been informed that, under some high storm conditions, all there is no pass forward flow at Western PS, all athe flow being pumped into the river. If that is so then, under those conditions, the benefit of a vortex at Lots Road would be small as all the concentrated debris would be pumped out at Western only a limited distance, about 2km, downstream. Looking at the plan of Heathwall there is pass forward flow but the indication is that there would not be sufficient space on the site between the pumping station and the outfall.

Thus it looks quite likely that vortex chambers for the sort of flow in the London sewers would be expensive or there not to be sufficient space. There would then be the question as to whether there would be long run benefit sufficient that it would be worthwhile iplementing anyway and , if done sufficiently early, could form part of the interim measures.

Optimise CSO spill levels.

One measure which Thames Water have examined as part of their planning for the tunnel is the level of the overflow weirs of the CSOs. These are, anyway, to be altered to minimise spill at some CSOs so that the fewest drop shafts are needed.

As an interim measure the sewer model could be run and the CSO weir levels adjusted to provide optimum interim conditions.

Cost of in-sewer systems.

Until further information is available it is not possible to provide any estimate of the cost of such in-sewer measures to reduce discharge to the Tideway of polluting matter. As a budget for removal of restrictions, reductions in contributing flow, Real Time Control, and raising some CSO weir levels, I have allowed a budget of £7m. Some of these works would also benefit the long term.

If the estimated remaining cost of some of the works such as the vortices, exceeded a certain sum, assumed by me to be about £3m but subject to review, then those proposed works are unlikely to meet the cost benefit for interim measures. However they could still be implemented as an early part of the long term measures.

8. In river control of sewage debris

General system

In various places a floatingboom has been used to concentrate the floating litter/debris which is then collected and disposed of. One such installation is at Cardiff Harbour, see the last page of Apendix C. It may be possible to provide similar booms at the Thames CSOs, thus concentrating the floating sewage litter so it can be retained when a spill occurs and not escape into the river.

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I have been in touch with Bolina Booms who supply such booms. The booms would need to both float at high tide and to retain the collected debris when part of them are sitting on the foreshore during low tide. The proposed arrangement consists of vertical piles in the form of a trapezium with the long side the shore and the short side in the river and parallel with the river flow. The booms would be flush faced Bolina environmental booms fitted with alternate kite floats to keep the boom stable and upright when dried out at low water. The boom would be kept in position by four piles at each point of the trapezium/rectangle with floating collara around them to move with the tide. Coner has been expressed as to whether the booms could cope with the 5m tidal range in the Tideway. However, Bolina Booms believe that with the collar system shown on the next page, this should not be a problem

Picture of a typical boom installation

The debris within the booms would need to be collected. It is proposed that this be done by a floating craft. This could be by having a trash trap at the outlet of the boom which is then lifter up, a mechanical grab with fine mesh. For the finer debris a fish pump could be used to suck up the surface water in a similar way to that used for moving fish from one tank to another.

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Picture of a variable water level boom.

Below is a sketch of the iitial boom arrangment when the CSO is in the river wall and also when the CSO is out in the river.

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Location of boomed CSOs

As can be seen above in 2004 the Environment Agency considered 36 CSOs as unsatisfactory.However there have been a number of changessince then. Because of changes since then a number of CSOs now have zero discharge in the Table of performanace. These are Abbey Mills, Wick Lane, Church St, Queen St, and Norfolk St.

Constructing a boom system costs money and anyway a CSO with a low spill volume would not be worthwhile booming. Arbitarily I have taken a limit of 3,000m3/year as a cut off point. This removes Stamford Brook, Smith St, KSP, Grosvenor ditch, Essex St,and Charlton from the list of those to be boomed. The only two schemes left in category 2 are NW Relief 4,100m3/year and Savoy St, 8,500m3/year. From the Admiralaty chart the outlet from the NW Relief looks to be in the river. This would probably preclude it being boomed. Savoy St is small and in a area which is sensitive to view by the public. Thus I would propose to exclude that CSO.

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Holloway is a small CSO spilling about 8,000m3/year into the Tideway well downsream of Tower Bridge so the river is large. The two Jews Road CSOs have a combined discharge of 10,000m3/year with a spill duration of 7 hours. Thus, for an interim measure scheme, it is unlikely to warrant booming them.

An outlet on the bed of the river makes booming more problematical with the high tidal currrents in the Thames. From the Admiralty Chart it would appear that Hammersmith, Heathwall, SW Relief, Lots Rd, Clapham, and Brixton have outlets on the bed of the river at or near low water and any boom might obstruct navigation to/from adjacent wharves or bridges. For the time being I have assumed that these could not be boomed.

From the Admiralty chart it would also appear that Acton, Falcon bridge, and Greenwich also have outlet near low water. However it would appear that a boom here is unlikely to obstruct navigation. The question then is how quickly will the floatables rise to the surface. I have no information on this. I have had, therfore, to make a broad assumption. I have allowed for a rectangle 5m by 25m with the long side parrellel with the tidal flow.

Frogmore CSO discharge is into the River Wandle. I have allowed for an angled boom across the Wandle with a length of 50m. Tideway indicative boom layout

Site name CSO Vol/year Spill time

Against wall Distance to Min width m In river

no k m3 hrs/year

chart datum m bridges/river dimensions

Acton 1 300 163

5m x 25m

W.Putney 5 35 119 Y 30m

Putney bridge 6 70 111 Y 30m 40

Frogmore 7 100 130 River Wandle 50

Falcon Br P/S 9 780 291

5m x 25m

Lots rd 10 1,200 410 Pier

Not posible

Ranalegh 14 300 153 Y 60m

Western P/S 15 2,300 228 Y 30m

Regent St 22 25 19 Y zero

Northmbrlnd 23 80 47 Y zero Fleet (B bridge 27 570 83 Y 10m

50m NE Relief 29 800 300 Y 40m

Deptford 32 1,900 343 Y 40m

Greenwich 33 4,000 240

5m x 25m

Shad P/S 28 100 69

50m

Earl P/S 31 600 207

40m

Hammersmith 4 2,300 690

Heathwall 16 700 240

Brixton 20 270 137

Clapham 19 14 15

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That would result in 15 CSO discharges into the Thames and Frogmore into the Wandle being boomed. The result is that, based on the TW Table of Performance, about 80% of the overflow that is classified by the EA as having an adverse environmental impact would be boomed, thus much restricting the amount of sewage debris that would enter the free flowing Thames.

Approval

Approval from the PLA and the Environment Agency would be needed for the planning and technical aspects of these measures.

Cost

Bolina booms have quoted a budget price of £1,246,000 for the supply, assemble and instlling the above instalation including piles and piling and including Lot’s Road which has subsequently appeared to be a restriction on navigation.

They have made this subject to good acccess to set up pontoons into the Thames near the site and that each site is accessible by river from one to another. They have also excluded the cost of licences to work in the river or the provision of Health & Safety files. They have also made the quote subject to site survey for possible extras including wall seals, engineering design, ground investigation, UXO surveys, permits and permissions, planning aplications and licences plus possible delays due to inopportune weather or tidal conditions. Making a broad brush allowance of £3/4m for these elements and some contingencies would bring the boom cost to £2m.

Retained sewage litter collection.

There are various methods of taking the sewage debris from within the boom. One method is a Trash Trap. This collects the trash in a metal mesh container which can be lifted out by a barge and boom arm and emptied into the hole of the collector vessel.

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Another method if the retained sewage debris is small is to use a fish handling vacuum pump as supplied by Afak techniek BV of Holland. This is normally used to move fish from one tank to another but should be suitable for collecting floating debris and water into a nearby barge.

Such systems would be operated from a powered work boat with a lifting arm and a cargo bay and a screened water discharge system, probably during the upper part of the tidal cycle to provide floating access to the boom structures.

I have no knowledge about the cost of such a powered work boat but assume that about £1m would be a reasonable budget.

In river litter collection

The main in river collection system would be skimmers which would collect floating litter, including that not sewage derived, thus reducing sewage litter and also improving the general appearance of the river.

Thames Water have two such vessels Clearwater 1 and Clearwater 2 which cost £4m and were commissioned in Septemeber 2007. They were designed to operate as far upstream as Kew and to navigate London’s bridges. In operation, the screens sit 450mm deep below the river surface. Debris is direced on to the screens by the inner hulls of the vessel, where the debris is picked up by mechanical screening equipment and conveyed to the rear of the vessel where it is drained ready for disposal into a refuse barge. In March 2008, after 6 months service Thames Water stated “ The vessels which have collected over 40 cubic metres of litter from the River Thames since September 2007 have greatly contributed to improving its environmental and aesthetic quality, ensuring it is fit for river users, and for this years Oxford and Cambridge boat race crews. To date, the skimmer vessels have been a real success story, enabling uss to collect large volumes of litter, which overflows from the sewers during periods of heavy rain.”

Thus the overall aesthetic effect has been beneficial. Thus, with the Lee tunnel and the STW upgrades removing more than half the spill volume, and the potential addition of vortices, screens, and booms controlling some 80% of the remaining overflow, it is likely that no extra litter skimmers would be needed. Thus the craft would continue to operate but now concentrating in the areas where booms were not installed, primarily Hammersmith, Lots Rd, and Heathwall.

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There may be remaining problem of oils and debris that is too fine for the current skimmers to collect. I understand that there are skimmers developed to collect oil and similar, so they could be considered.

Approvals

Such a scheme would need the approval of the Environment Agency and the PLA.

Implementation period

It should be implementable within about two to three years, ie within the period likely to be required by the European Commission.

Cost

The current litter collectors cost £2m each so assume that the oil and fine matrial collector cost a similar amount, say £2m.

9. Dissolved oxygen improvement.

Background

One of the main issues is the impact that the CSO spills have on the dissolved oxygen content of the Tideway. The objective set in the Thames Water report Objectives and Compliance Working Group Report 2006 is “To limit ecological damage by complying with the DO standards specified in the table above.” The Table above is,

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Post the Sewage treatment works upgrades and the Lee tunnel the dissolved oxygen failures are much reduced but still exist, as shown in the plot below.

The objective of the interim measures is, within a limited budget and in a short time, to improve the dissolved oxygen conditions in the river and reduce the impact on fish. One way. that this can be done is by injecting air into the river through fine grained diffusers.

Evidence from elsewhere

The Cardiff Harbour coarse diffuser system, see Appendix C is designed to turn the water over rather than to inject air into the water body. This is done by having on land air compressors pumping air through pipes laid on the bed of the harbour connected to coarse diffusers. Thus this demonstrates that an air injection system using on land air compressors linked to pipes and diffusers can be put in place and can operate satisfactorily.

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In the upper Tideway, a land based oxygen injection system has been used to raise the dissolved oxygen content in the Chiswick/Barnes stretch of the upper Tideway to reduce dissolved oxygen sags emanating from Mogden STW. I believe this is actually based on the Mogden effluent outfall. It has been utilised in the past to reduce the impact of Mogden storm tank discharges into the Upper Tideway.

In Paris the French have used a system of pipes and diffusers to inject oxygen to raise the dissolved oxygen content of the River Seine, see Appendix B for details. This has been used to raise the dissolved oxygen content of the Seine by about 2 mg/l, see image below showing the modelled dissolved oxygen content of the river following a storm in red and the actual conditions achieved in blue.

This shows the substantial benefit that occurred. Thames Water have stated that the Paris system only provides an island of raised dissolved oxygen. However, since its introduction, salmon are reported to be now returning to the Seine. Thus such a system does appear to meet the objective of significantly improving environmental conditions.

Dryden air/oxygen injection system.

Dryden Aqua make fine bubble diffusers. Their web site page headed lake & pond aeration, states “Dryden Aqua manufacture a very fine bubble diffuser that has its own internal ballast. The diffusers are semi flexible tube type diffusers that have the best of ceramic diffusers and membrane diffusers but without the disadvantages...Air is passed through the diffusers and the fine diffusion cloud of air passes through the water... The aeration system will dissolve oxygen into the water, one diffuser code 6.2.10 diffusing 10cum/hr of air will add at least 25 kg oxygen to the water per day...”

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System

The diffusers proposed would not be the coarse discs used in Cardiff harbour and elsewhere to turn bodies of water over, but fine bubble air diffusers designed to increase the oxygen content of the water body. The large surface area of the fine bubbles aids oxygen transfer through the bubble water interface, but also because more water is moved there is also an increased transfer between the surface of the water and the air. Each diffuser is designed to input 1kg of oxygen from the air to the water each hour.

The diffusers are tubes, about 32mm diameter, made in lengths generally about 3m long and just negatively buoyant so they rest on the bottom of the terrain.

They would be attached to an air pipe. This would normally be HDPE and about 200mm diameter laid on the bed of the river.

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Considering the width of the river, it is suggested to have two air pipes, one on each side of the deep water section of the river. This would provide a greater width of aeration, and enable the pipe and diffusers on one side to be maintained or the channel dredged whilst the other system remained in operation.

The EA has provided the longitudinal profile of the modelled dissolved oxygen content of the river during the storm of 6th August 2004. This storm is quoted as having a rainfall return period of 1 in 14 years and 1 in 40 years so its return period is almost certainly beyond that set in the standards. I have marked on this what I understand to be the target dissolved oxygen content to meet the standards. However the object of the interim measures is to improve the DO not to meet standards.

For the Hammersmith section take the lowest dissolved oxygen level and the highest water flow assumed to be 200,000m3/hour then the aeration system of 1km with two pipes and a diffuser every 10m on either side of each pipe equating to 400 diffusers, would input 400 kg of oxygen /hour into the water. In theory this would raise the dissolved oxygen content by 2mg/l. The actual transfer conditions would depend on the storm water CSO overflow volumes and BOD. To assess this the system need to be modelled in the water quality model.

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If a greater transfer rate were appropriate, then oxygen could be pumped through such a system, increasing the transfer rate by a factor of 3.

It is important to note that this is an interim system until the tunnel is operating sufficiently. Thus the object is to alleviate the dissolved oxygen sag. However it would be most helpful to know what the air system can achieve.

Location of installations.

A similar arrangment of diffusers has been installed in Cardiff harbour. This meets a need to turn over the static water in the harbour. This is a different aim than that proposed on the Tideway. However it does demonstrate the ability to install and operate such a system. Further information on the Cardiff arrangment is shown in Appendix C

The Environment Agency report Assessments of Thames Tideway Combined Sewer Overflows, Annex A shows that, downstream of Heathwall, only Deptford and Greenwich have an adverse effect on dissolved oxygen. Thus it would probably be appropriate to space the diffusers upstream and downstream of the identified CSOs, thus minimising cost. There would need to be a number of air compressor stations along the river bank.

The lengths of diffusers would be in stretches, generally both upstream and downstream from an air /oxygen plant. In general the stretches would be up to 2 km in length.

Places where Thames Water own, or have access to, land such as at existing pumping stations, or land obtained for the tunnel construction sites, could be appropriate for on shore air blower or oxygen generation systems. Possible locations were identified as at the pumping stations at Hammersmith PS, Carnwath Road tunnel site, Falconbrook PS, Western PS, Heathwall PS, Shad PS, Chambers wharf, Earl PS , Greenwich PS, Isle of Dogs PS, Woolwich PS , and Becton STW. See plan below for the provisional sitting of the diffuser installations and the lengths covered.

Regarding the space needed I am informed by Dryden Aqua that “The two main air blowers, would measure about 2m x 2m as a foot print in their acoustic enclosures, then one would need at least 1m clearance. The oxygen generator will take up more room. There needs to be spece for the buffer tank and columns. However we can use the air blower to drive the VSA.” On 10th December 2012 Dryden Aqua stated, “The sisze of the system (375 kg/hr) will have a footprint of 12.8 m x 7.3m x6.1m.

I have site plans for almost all of these sites. Shad and Earl look congested so I have assumed that it may well be necessary to replace Shad with Chambers Wharf and have the Greenwich system going more upstream. I have asked for, but have yet to receive plans of the Woolwich site. Lots Road site itself appears too congested, although the adjacent site for the water screens of the defunct power station might be a possible site but it is not on land owned by TW. Falconbridge also looks too congested so this is replaced by Carnwath Road tunnel site. Thus it seems reasonable to assume at this stage that nine diffuser installations could be put in.

It was intended that Appendix D would show the actual proposed site areas for each installation but TW have put a confidentiality restriction on the plans of some of the sites. Whatever, I have now reappraised the information available to me and made the best judgement that I can on the available information.

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Several of these installations are set back from the river wall. However there are CSO conduits of appreciable size connecting these installations to the river and it should be possible to install the air pipes, about 200mm dia, in these conduits without measureable loss of overflow capacity. In general the length from the on-land installation is generally reasonable but the Greenwich installation is nearly 1km from the river.

The longest distance between these installations would appear to be 6.5km, from Heathwall PS to Shad PS. Here there would be a gap of some 4km. However, with a tidal excursion of some 14km, this should still be satisfactory. Thus there would be about 10 stretches of diffusers.

If necessary it would also be technically possible to mount the air compressors on a floating barge, connected to the shore by a flexible electric cable, and to the diffuser system by a flexible air pipe.

Depth of water

From the Admiralty charts, upstream of London Bridge the general charted depth in which the diffusers would be laid would be about 2m. Downstream of London Bridge the general charted depth would be about 5m.

At Tower Pier and Silverton, the predicted tidal heights from the PLA website for July to September, the most critical quarter, are a spring tide high water of about 7.4m. With the charted depth of about 5m then the water depth would be some 12.4m. With the pressure drop along the air pipe, then it is likely that a compressor pressure of at least 1.5 bar would be required.

With a predicted spring water low tide of about 0.2m, then the minimum water depth over the diffusers would be about the 5m chartered depth.

The average water depth over the diffusers here would be the charted depth of say 5m plus the mean tidal height of about 3.7m, a total of about 8.7m. It is proposed to have a screw compressors rated at 2.5bar which would cope with this sort of pressure variation.

In the Chelsea reach area, the predicted maximum tidal height is a spring tide of about 6.7m above chart datum giving a total water depth of about 8.7m.

With a low water of about chart datum the minimum water depth would be about 2m. A minimum depth of 2m is satisfactory when the tide is flowing as the rising bubbles are swept along with the tide. However around low tide when the water flow is slack, the bubbler system might have limited affect.

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The average tidal height appears to be about 3m, giving an average depth of water of about 5m over the tidal cycle. This would be more than sufficient.

The plan below sets out a provisional layout of the most upstream diffuser length, that from Hammersmith pumping station. Being the most upstream this has the shallowest depth and the smallest tidal cubature.

Temperatures

The amount of oxygen in the water varies with the water temperature. There is data in the HPA report of the river water temperature in 2005 and 2006. This shows summer temperature of about 20C, with some readings of 22C and one of about 24C. There is also projected to be a temperature rise in the summer of about 1.4C by 2050 due to climate change.

Salinity conditions

The Environment Agency has shown a low flow profile of salinity with about 2,000mg/l at London Bridge, effectively fresh water, and up to about 6,000 mg/l at Becton STW, the most downstream installation.

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Design conditions.

There is very little information on which to base the design of the system. However a few general considerations can be made. As can be seen from the FARL report, the cold conditions in winter do not give rise to a significant number of potential failures. As temperature rises then the saturation level of water reduces, meaning it can carry less oxygen. However the reduction in oxygen solubility with increasing temperature is not the main issue. When water temperature increases the biochemical activity of bacteria increase exponentially. The bacteria can then exert their BOD and reduce the oxygen content of the water.

Air diffusers have a greater effect the lower the oxygen content of the water. For instance at 2mg/l, the transfer is about 2kg of O2/diffuser/hour whereas at 4mg/l of O2, a diffuser will do some 0.5 to 1.0 kg of O2/hour/diffuser. Thus above 5mg/l of O2, the diffuser system would have reduced benefit.

Thus the air/oxygen diffuser system would be appropriate at below about 5 mg/l.

Assuming that the diffusers would be sized to raise the oxygen level by 1mg/l in one 12 hour tide, then this would require about 100,000 kgs of oxygen /day. The Dryden Aqua web site states that each diffuser diffusing 10 cu.m/hr of air will add “ at least 25kg/of oxygen”. Thus some 4,000 diffusers would be required.

Dryden have reviewed the limited amount of information available and believe that a diffuser system with two lengths of pipe averaging 1km each and a diffuser each side at 10m spacing would provide 400 diffusers and 10 such lengths would provide about 4,000 diffusers. With occasional use of oxygen, should be able to maintain a dissolved oxygen content in the river above 4mg/l., thus meeting the environmental target of 4mg/l.

What is needed to firm up the design is information about the BOD and COD of the river water and the CSO spills.

Potential negative issues

Frequency of operation

It had been suggested on the basis of the post Lee tunnel number of failures at standard 3, 20 failures of the dissolved oxygen (DO) standard in 40 years, that the diffuser system would not be worthwhile. Use once every two years might well be too small a benefit. However the reality is that the most frequent failure of the DO standards is standard 1. The plot in the TW Needs report, Appendix A of this report, shows for standard 1, about 75 failures in what appears to be 34 years. That is already 2 ½ times a year. In addition there would be a number of “near misses” and the operators would need to operate the diffuser system to try an ensure that a failure did not occur. Because failure would be difficult to predict, there could well be another 3 to 6 times a year. Thus the diffuser scheme would be required to operate a sufficient number of times a year to warrant its installation.

Grounding.

In a note by Thames Water they state that “any structure on the bed of the river would be very vulnerable, especially at low water when it is not uncommon for craft to ground.” First there is no evidence provided of how frequently craft ground. Below London Bridge the depth would be about 5m at spring low tide and significantly more at other times. There are very few ships of this size still

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using the river. Above London Bridge the minimum water depth for the diffusers is about 2m. Few private river craft draw this much. The tourist craft and the waste craft are under professional masters who seldom, if ever, run aground. In any case should a vessel run aground on top of the plastic pipes or diffusers, then they would be pushed into the underlying soft river sediments.

Silt.

“The Thames is a very silty river and the system would require considerable maintenance.”The river is indeed a very silty river. However the air would be going out through the diffusers so would effectively clear off any silt lodged in the outer part of the diffusers. As shown below it would be quick and easy to raise the sections of the system for inspection and maintenance.

Dredging.

It is possible that the PLA would wish to dredge part of the channel. For this to happen, then the pipe and diffuser system would be made to float and recovered in sections, see the section on maintenance.

Buoyancy of small craft

Adding air to water reduces its buoyancy, which can theoretically be a problem with swimmers and small craft. However, given the depth of the water and the volume of air passed through the diffusers, the change in water density is so small as not to result in a problem. Such systems have been used previously in natural swimming areas.

Anchoring of other craft

There would need to be a prohibition on anchoring in the vicinity of the system. This should not be a problem as few craft anchor in the Tideway, they either pick up a large buoy or go alongside. In any case the system would not cover the full length , there being gaps between the stretches where anchoring could take place. In any case the system would be requird to obtain the approval of the PLA.

Onshore installation

The onshore installation would consist of one or two air compressors within a sound proof structure. There would also need to be a power supply. Presumably, since most of the sites are current pumping stations, there would be sufficient spare capacity in the incoming power supply. However the appropriate switchgear would also need to be provided.

During peak times, it might be necessary to pump oxygen and air through the diffusers. What would be required to do that is a couple of Vacuum Pressure Swing Absorbers, effectively a couple of vertical tanks. These can be mounted above the air compressors.

From the plans of the installations found on the Thames Water Tunnel web site, it would appear that there may well be space for such an installation at the proposed sites.

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Operation

The air system becomes much less effective when the dissolved oxygen content of the river exceeds about 5mg/l. This is because the oxygen transfer coefficient drops appreciably. Thus close monitoring would need to be provided using monitoring buoys and near real time readings. Thus, were there to be a plume of low dissolved oxygen water then, as it was carried back and forth by the tide, then the relevant diffuser stretches could be switched on and off automatically as necessary to oxygenate the water. This limited operational period would save in operational costs.

Maintenance

Dryden Aqua have developed a way of bringing the pipe and diffusers to the surface by attaching the air pipe to another pipe. Normally this second pipe sits on the bed of the river with water in it. When it is required to bring the diffusers to the surface for inspection or repair, the second pipe is filled with air and both pipes float to the surface, bringing the diffusers with it. To sink the system again, the second pipe is filled with water and the system sinks.

Benefits for fish

Dryden Aqua comment by email” We went through a similar exercise for the Manchester ship canal, which is on the same scale... The diffusers will create a path for the migratory fish will follow. Also if the aeration system does not maintain a complete path, each air diffuser can act as a life support island of oxygen to support the fish. One diffuser can support around 1 tonne of fish, and will provide a safe zone during period of heavy pollution or during the DO drop that will occur at night.” Appropriate modelling In my view the only way of analysing the future conditions, and trying to see what the benefit of a normal rise of DO due to the proposed air diffuser system, say, to a 1mg/l rise, would be to put the various potential alleviation schemes into the TW water quality model, try various alternatives, and see what the benefit and outcome would be. That is the approach that I have proposed.

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Monitoring

A near real time monitoring system would be provided, similar to that at Cardiff Harbour, to measure the dissolved oxygen content in the river every 15 minutes and to give prompt warning of any issues and unusual dissolved oxygen conditions. There are already several monitoring points in the river but it may be necessary to provide a few more.

Floating bubblers

Should a dissolved oxygen sag become an issue then the monitoring system would enable the two existing mobile bubblers to be despatched promptly. (See the front cover for a picture of one of the bubblers.) However this would only be a standby measure and not part of the routine measures to raise dissolved oxygen levels in the river.

Thames Water , in their Stage 2 consultation in the note on options page 3 state “We currently use “mobile” boats to reduce the impact of untreated sewage overflowing to the River Thames...so our bubbler boats inject oxygen into the river helping fish survive sewage discharges...There are severe limitataions as to where these boats can go due to tides and bridge heights.” That may be true at present when the most damaging condition is an overflow of final tank effluent from Mogden STW which can then be taken upstream by the tide.

However the Needs case modelling figure 5.2 , see Appendix A of this document, shows that, with the Mogden STW improvements and the Lee tunnel, the base case, there would be no half tide failure further upstream than 8kms above London Bridge. With a half tide flow of another 7km, there would be no failure of the standard further upstream than 15kms. This is downstream of Hammersmith Bridge. Thus Hammersmith Bridge would generally be the upstream limit of operation during the interim period.

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Admiralty chart 3319 gives the tidal depths upstram of Hammersmith Bridge can drop as low as 0.7m on a spring tide and there is seldom 2m charted depth. Downstream of Hammersmith Bridge the water depth is appreciably greater, charted depth generally being about 2m. The chart also gives bridge clearances at Highest Astronomical Tide (HAT), the highest spring tide expected in any one year and lasting only an hour or so. The chart gives a minimum clearance at HAT of 4.5m (Albert Bridge). However Hammersmith Bridge (south) is only 3.1m clearance at HAT. Studying the pictures of the bubblers, see front cover of this report, it would appear that the bubblers are unlikely to be significantly constained when operating downstream of Hammersmith Bridge, as they would during the interim period.

Cost

The cost of the diffuser system is estimated by Dryden Aqua at some £10m. In addition I consider it appropriate to allow for a contingency element, and the enhanced monitoring system. Thus I consider an appropriate budget cost for this system to be about £12m.

Conclusion

I cannot see a reason why such a system based on injecting air through diffusers to raise the background dissolved oxygen content could not be developed and work satisfactorily to raise the dissolved oxygen sag and alleviate the environmental impact. I don’t know how such a scheme would turn out, but, considering the potential benefit in reducing the environmental impact of non-compliance, and the amount of the potential infraction fine, then it does seem to me worth modelling to identify how much benefit such an scheme might bring. At the moment the EA is refusing to do this, despite a requirement in the River Basin Management Plans guidelines to assess the benefit of any combination of measures.

10. Health improvement.

Bathing.

On 1st July 2012 the Port of London Authority enacted “a new byelaw to control swimming in the busiest part of the Thames between Putney Bridge and Crossness by making it necessary to get the prior consent from the harbour master.” “Here you encounter a fast running tide, bridges and eddies which can drag a person underwater in a trice. And there are also passenger vessels which carry over six million people a year and 1,000 tonne barges carrying freight.”

Putney to Crossness is almost all the length of the Tideway affected by CSOs.

There is a quote about a swimmer having to have “the event carefully planned and managed with safety boats in attendance at all times.” Presumably the event would be managed to be several days after a significant CSO spill so water quality conditions would be improved.

In any case none of the Tideway is designated as a bathing water under the Bathing Water Directive and so there is no statutory designation to be met.

Identification of other recreation

The number of recreationalists was surveyed and the numbers reported in the document “Recreational Use of the Thames estuary.”

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The numbers found in each reach is shown on the histogram below.

This shows that the two most important recreational areas are the Hammersmith area, mostly rowers, and those in the general area of the London Docks.

Rowers in the Hammersmith area.

The Health Protection Agency (HPA) report The Thames Recreational Users Study 2007, states on page 1 “there is little evidence to link the presence of high levels of bacterial indicators of faecal pollution to the level of risk to human health.”

page 48 “The 95 percentile of indicator organisms in the upper tideway permanently remain above the WHO microbiological standards for recreational water and this represents a potential health risk to recreational users.” Thus there is a background health risk in the Tideway irrespective of the CSOs.

However the “WHO guidance is only aimed at bathers” total immersion and risk of ingestion “ and as such is not necessarily indictors of risk to other recreational use such as rowers, sailing etc...” HPA page 8.

“There is evidence to suggest that the influence of secondary treated effluent from Mogden sewage treatment works is as great as that of the less frequent but common CSO discharges.” HPA 2007 page 54.

Since then improvements are being made to Mogden STW including much increasing the flow to full treatment, improving the normal discharge quality, and greatly reducing the storm overflows. Following the storm of 2011 which killed many fish in the Chiswick area, Thames said “ I do need to assure you that once the extension is completed in March 2013 the works will be able to handle a similar situation without even using its storm tanks, let alone discharging to the river.”

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The key information from a major study of health risks to recreational users in the upper part of the Thames (upstream from Putney Bridge) is summarised in the TW 2010 Needs report:

“An assessment of health impacts upon recreational users of the River Thames was conducted and reported by the Health Protection Agency in 2007. This report, which quoted an EA estimate of between 3,000 and 5,000 recreational users of the tidal Thames... While there was evidence of an elevated health risk (gastric infection) to recreational users in the upper Tideway two to four days after a CSO spill event, the rate of gastric infection among recreational users was very low (12.8/1000/year) compared to the general population (190/1000/year). This may be due to the relative good health and fitness of recreational users, a greater awareness of hygiene and health and safety issues, and a developed immune response to infection from repeated exposure, which results in asymptomatic infection.”

The fact that gastric infection rates among recreational users in the upper Tideway are less than one tenth of the incidence level in the population as a whole, is a fair indication that the Thames health baseline, and the possible impact of the intervention, are not significant on a national scale in terms of the potential health impact.

In any case the improvements at the Mogden STW will significantly improve the water quality in the Chiswick/ Hammersmith/Putney area, one of the main areas for rowers.

The HPA study and the PLA announcement was done after the EA assessment. Thus the Environment Agency assessment should be reconsidered, taking on board the evidence from the HPA study and the PLA restriction. It is likely that this would then much reduce the assessed health impact from the upper Tideway CSOs.

The HPA study does state on page 58 that “Predictive models of microbiological parameters... indicate that levels of these indicators can be predicted with reasonable accuracy given timely information about discharge events.” I understand that since then Thames water has implemented a monitoring system at each overflow so it is likely that such information could be provided. “The simplest and possibly most cost effective manner of making this information available to the recreational public would be through existing internet facilities.” “ A simple “traffic light” system could be used.” Thus the interim measures could include the provision of such information.

Thus a further interim measure, in addition to the upgrading of Mogden STW, could be the development of the microbiological model and the running of it to provide the traffic light system. A budget cost estimate for this could be about £100,000, within the accuracy of the overall cost estimates.

Recreation in the London Docks

From the histogram above one can see that the other major area of recreational use is in the Tower Bridge to Thames Barrier reach. Looking at the details in the Recreational Use of the Thames Estuary report these are very largely dinghy sailors and water skiers in the London Docks. These are discrete non-tidal bodies of water where the only contact with the River Thames water is the abstraction of a small amount of waterto top up the docks following loss from evaporation or leakage.

Assuming that the evaporation per year is about 600mm and that this occurs over a period of 200 days then the evaporation rate would be about 3mm/day. Allow a similar amount for seepage making a total of 6mm/day. Taking the areas of the Royal Docks as about 84ha, then the top up rate would be about 5Ml/d. A similar calculation for the West India Docks gives about 2Ml/d.

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Whilst Thames Water are not responsible for the quality of the water in the docks, by their STW discharges and CSO spills, they do influence its water quality. Should the water quality in the docks used for recreation not be sufficient, and the quality of the Tideway water be an issue, then, as part of the interim scheme it is suggested that water treatment be provided to the top up water. These would have to cope with significant turbidity at times. One method that could be considered would be some form of moving bed sand filter to remove solids and disinfection using hypochlorite. Such a scheme might well also provide some long term benefit and could continue as an element of the permanent scheme.

Cost estimate.

A broad brush estimate of cost for the traffic light scheme and the two small water treatment plants is, I am advised, about £2million for the Royal Docks and about £1m for the West India Docks, a total of about £3 million. Such a system should be implementable within two years.

11. Conclusions.

The British government has been taken to court by the European Commission for failing to meet the UWWTD on the Thames Tideway and the Advocate General has found against it on the Thames Tideway sewer system. Thus the imposition of fines seems quite possible.

On the basis of the information given to me, the fines depend on the length of time of infraction and the environmental impact of non-compliance. These could be as high as Euro 2.0bn. A reduction of one point out of five points on the environmental impact of non-compliance might save as much as Euro 200 million, about £160m. Two points better out of five would double the benefit.

The current works of upgrades to the Tideway sewage treatment works and the Lee tunnel, will reduce the volume of spill from the current 39 mm3/year to about 18 Mm3/year and much reduce the number of dissolved oxygen failures.

CSO spill volumes could be reduced by reducing the amount of water entering the sewers by reducing the amount of water delivered to customers by demand management methods, reducing the leakage from the water mains some of which would finish up in the interceptor sewers, connecting part of the system to another STW, Mogden or Hogsmill , adjusting the CSO weir levels, removing restrictions in the sewer system, and by implementing real time controls. Studies would need to be carried out to assess the scope and cost of such measures.

Discharge of sewage debris to the river can be reduced by constructing a vortex system or screens where appropriate, and by installing booms around the CSO outlets. The retained debris can be collected and skimmers used in the river to collect that which escapes.

Fish are considered the most sensitive ecological species and dissolved oxygen standards have been set. The current works of the improvements to the sewage treatment works, particularly Mogden STW and the Lee tunnel, go a long way towards reaching the DO standards. A diffuser system using compressed air or, on occasion, oxygen would be able to raise the dissolved oxygen levels to reduce fish kills further and greatly mitigate the dissolved oxygen sags and provide fish refuges.

The Tideway is not a designated bathing water and is not subject to the Bathing Water Directive. For navigation reasons, the PLA has recently banned bathing in the Tideway except with a special licence. Health impact of those in the London Docks can be mitigated by putting in water treatment of the relatively small quantities of top up water. The rowers in the Hammersmith area are already ten times less susceptible to gastric infections than the general public. Improvements to Mogden

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STW will much improve water quality in the Chiswick/Mogden stretch of the Tideway where there are many rowers. A traffic light system could be provided to warn rowers when adverse conditions due to CSO spills occur.

These interim works should be implementable within two to three years.

These interim measures would demonstrate to the those living, working, or being near the Tideway, that, during the construction of the tunnel and the impact that that will have, everything possible is being done to improve the environmental quality of the river.

The measures would also reduce the volume of the spills into the tunnel, thus reducing the appreciable tunnel pump-out energy use and operational cost and CO2 emissions.

Interim measures, such as those proposed, would do much to reduce the “environmental impact of non-compliance.”

The cost is estimated/budgeted to be

Flow diversion, in-sewer measures, RTC, etc £ 7m

Vortices (or as early part of long term measure) £ 3m

Booms around CSOs £ 2m

Workboat to collect boom debris £ 1m

Oil and fine litter skimmer £2m

Fixed diffuser system and monitoring £ 12m

Docks water treatment and warning system £ 3m

Total about £ 30 million,

This is about 20% of the cost of a one point reduction in the scale of five on the “environmental impact of non-compliance” of £160m. Thus the cost benefit should be good.

However these costs are at concept stage. Proper feasibility study and costing is required to identify what is feasible, with what benefit. Only Thames Water with its consultants would be able to do that.

I recommend that such interim measures be studied, and, if found to be appropriate, incorporated into the Thames Water Business Plan and, subject to ofwat approval, implemented.

Normally Ofwat would only approve costs that are statutorily required. However, in this case, since compliance with the Directive was required in 2000, and it will be about another ten years before compliance is achieved, then there seems a good argument that these interim measures to get close to providing the environmental standards, are also statutorily required, and thus approvable.

Professor Chris Binnie, MA, DIC, Hon D Eng, FREng, FICE, FCIWEM.

11th March 2013.

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Appendix A modelling of the river conditions and Table of performance.

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Table of performance

Total Volume (m 3 ) a. No of Spills a. Spill Duration

(hrs) a. Total Volume

(m 3 ) a. No of Spills a. Spill Duration (hrs) a.

Total Volume (m 3 ) a. No of Spills a. Spill Duration

(hrs) a.

CS01X Cat 1 Acton Storm Relief 312,000 29 152 325,800 30 163 0 0 0 CS02X Cat 2 Stamford Brook Storm Relief 500 2 2 500 2 2 400 2 2 CS05X Cat 1 West Putney Storm Relief 34,300 26 113 36,400 28 119 1,500 1 4 CS37X Cat 3 LL1 Brook Green 0 0 0 0 0 0 0 0 0 CS03X Cat 2 North West Storm Relief 2,800 1 1 ,100 1 1 00 1 1 CS04X C t 1 H th P p g St 2,208,000 50 648 2,362,100 51 690 103,600 1 3 16 CS06X Cat 1 Putney Bridge 68,100 33 107 70,800 33 111 1,600 1 3

Upstream Putney Bridge Total / Maximum b 2,626,000 50 1,023 2,800,000 51 1,086 108,000 3 26

CS07A Cat 1 Frogmore SR - Bell Lane 17,300 26 124 18,100 27 130 500 1 4 CS07B Cat 1 Frogmore SR - Buckhold Road 85,600 19 68 88,600 21 72 1,500 1 3 CS08A Cat 1 Jews Row - Wandle Valley SR 300 1 2 2,900 1 5 0 0 0 CS08B Cat 3 Jews Row - Falcon Brook SR 7,400 2 7 7,500 2 7 7,500 2 7 CS09X Cat 1 Falcon Brook Pumping Stn 708,900 40 263 779,300 42 291 56,200 4 26 CS10X Cat 1 Lots Rd Pumping Stn 1,135,000 38 346 1,263,000 42 410 91,600 4 31 CS11X Cat 2 Church Street 0 0 0 0 0 0 0 0 0 CS12X Cat 2 Queen Street 0 0 0 0 0 0 0 0 0 CS13A Cat 2 Smith Street Main Line 1,400 4 8 1,500 4 8 1,500 4 8 CS13B Cat 2 Smith Street Relief 0 0 0 0 0 0 0 0 0 CS14X Cat 1 Ranelagh 283,000 26 142 305,700 27 153 18,500 2 10 CS15X Cat 1 Western Pumping Stn 2,046,200 37 200 2,323,900 41 228 244,500 4 24 CS17X Cat 1 South West Storm Relief 227,900 12 38 238,400 13 40 3,900 1 3 CS16X Cat 1 Heathwall Pumping Stn 654,900 34 200 748,300 38 246 62,500 4 26 CS18X Cat 2 Kings Scholars Pond Storm Relief 1,400 2 4 1,800 3 5 500 1 2 CS19X Cat 1 Clapham Storm Relief 12,700 5 12 14,400 6 15 7,900 1 5 CS20X Cat 1 Brixton Storm Relief 264,600 28 131 278,600 29 137 5,700 1 4 CS21X Cat 2 Grosvenor Ditch 2,600 3 7 3,000 4 9 500 1 3 CS39X Cat 3 Horseferry 3,400 3 7 3,800 3 7 300 1 2 CS40X Cat 3 Wood Street 0 0 0 0 0 0 0 0 0 CS22X Cat 1 Regent Street 22,200 4 12 25,700 8 19 0 0 0 CS23X Cat 1 Northumberland Street 71,500 13 34 88,400 14 43 300 1 2 CS24X Cat 2 Savoy Street 8,400 18 47 8,500 18 47 1,400 4 7 CS25X Cat 2 Norfolk Street 0 0 0 0 0 0 0 0 0 CS26X Cat 2 Essex Street 2,100 3 6 2,300 3 6 0 0 0 CS2 X Cat 1 Fleet Main 521,100 20 3 5 1,200 23 83 36,800 1 CS42X Cat 3 Pauls Pier 0 0 0 0 0 0 0 0 0 CS55X C t 4 L B g 8,300 7 14 8,900 7 14 4,300 5 10

Downstream Putney Bridge to London Bridge Total / Maximum b 6,086,000 40 1,745 6,784,000 42 1,975 546,000 5 191

CS28X Cat 1 Shad Thames Pumping Stn 91,900 15 70 100,400 15 69 71,300 4 14 CS43X Cat 3 Battle Bridge 0 0 0 0 0 0 0 0 0 CS44X Cat 3 Beer Lane 0 0 0 0 0 0 0 0 0 CS45X Cat 3 Iron Gate 200 1 2 200 1 2 300 1 2 CS46X Cat 3 Nightingale Lane 0 0 0 0 0 0 0 0 0 CS49X Cat 3 Cole Stairs 0 0 0 0 0 0 0 0 0 CS50X Cat 3 Bell Wharf 0 0 0 0 0 0 0 0 0 CS29X Cat 1 North East Storm Relief 782,400 31 286 847,400 31 303 84,300 4 32 CS51X Cat 3 Ratcliffe 0 0 0 0 0 0 0 0 0 CS31X Cat 1 Earl Pumping Stn 539,000 26 184 593,900 30 207 50,500 4 26 CS30X Cat 1 Holloway Storm Relief 7,800 8 18 8,400 9 23 7,000 2 9 CS52X Cat 3 Blackwall Sewer 0 0 0 0 0 0 0 0 0 CS36X Cat 2 Wick Lane 0 0 0 0 0 0 0 0 0 CS32X Cat 1 Deptford Storm Relief 1,471,500 36 252 1,976,000 39 343 161,300 4 29 CS33X C t 1 G h P p g St 8,322,500 51 672 3,940,100 28 240 571,500 4 35

Downstream London Bridge to Greenwich Total / Maximum b 11,215,000 51 1,484 7,466,000 39 1,187 946,000 4 147

CS56X Cat 4 Isle of dogs Pumping Stn (Foul only) 12,900 6 9 13,100 6 10 13,100 6 10 CS35X Cat 1 Abbey Mills Pumping Station from STATION F 15,319,000 56 873 0 0 0 0 0 0 CS35X Cat 1 Abbey Mills Pumping Station from STATION A 4,099,800 45 403 0 0 0 0 0 0 CS57X Cat 4 Canning Town Pumping Stn 0 0 0 0 0 0 0 0 0 CS34X Cat 1 Charlton Storm Relief 600 2 3 900 2 3 900 2 3 CS53X C t 3 H l R 0 0 0 0 0 0 0 0 0

D t G h t H l R T t l / Maximum b 19,432,000 56 1,288 14,00 6 13 14,000 6 13

Crossness STW Storm Tanks 308,300 5 27 50,200 3 8 50,600 3 9

Tideway CSO 609,100 3 19 698,30 3 22

Total / Maximum b to the River (CSO + Tunnel Overflow) 39,667,000 56 5,567 17,723,000 51 4,288 2,363,00 6 408

Beckton Catchment 444,610,000 8784 508,290,000 8784 508,240,000 8784 Tunnel Pump Out n/a n/a 6,201,000 791 22,128,000 1551 Beckton STW (Catchment + Tunnel Pump Out) 444,610,000 8784 514,490,000 8784 530,370,000 8784 Crossness STW 200,560,000 8784 230,940,000 8784 230,280,000 8784

Notes a. All CSO spills less than 100m3 have been removed. Volume, number and duration of spills have been adjusted accordingly. b. For Volume and Duration, the sum of all CSO spills in the reach is reported. For Number of Spills, the maximum number of spills in the reach is reported. c. Typical Year Model simulation is only for 270 days. The table includes infilling the remaining days with average daily DWF for Beckton and Crossness STW.

LTT ID EA Cat CSO Name

Existing System & Existing STW 2006 (June 2011)

STW Improvements and Lee Tunnel 2021 (June 2011)

Recommended Phase 2 Consultation Scheme 2021 (June 2011)

Sewarage Treatment Works c.

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Appendix B Information about the Seine system

The Seine at Paris is a large river and Paris is a smaller city than London. The Seine at Paris also well upstream of the tdal limit, thus te river continues to flow seawards. As I understand it, there are five oxygen injection stations in the Sene immediatly downsteam of Paris. These are able to inject liquid oxygen into the Seine.

A picture of the diffusers is shown below.

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There are six such installations just downstream of Paris.

The picture below shows the size of the Seine and the diffusers in operation.

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There is one plot of the benefit they have brought, as shown in the plot below for Bougival. This shows the dissolved oxygen content of the river following a storm on 7th june. The blue shaded area is when the diffusers were operating. The red line is what the water quality model of the river prdicted would have happened. As can be seen for a day the dissolved oxygen content would have been between zero dissolved oxygen and 1mg/l. This would have resuslted in severe fish mortality.The blue line is what the diffusers wer actually able to acheive. At no time did the dissolved oxygen drop below 2mg/l and the drop below 3mg/l was only about 4 hours. Based on the Tideway fish trials suite of fish only salmon would have been significantly affected. This shows the substantial benefit that such dosing can bring.

Elsewher in the presentation it implies that the river flow at the time was some 200m3/sec.

This demonstrates the gret benefit that can be obtained by installing diffusers and injecting air/oxygen into the river water.

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.Appendix C Description of the Cardiff Harbour scheme.

Introduction

In the 1970s Cardiff Harbour was a rundown area with a poor environment. “A neglected

wasteland of derelict docks and mudflats...incapable of supporting most aquatic life.” WEM

Nov 2011 page 27. In the 1990s it was decided to impound the harbour and a barrage was

installed across its mouth. The harbour area had a number of sewage and CSO discharges

into it. The scheme is described in the Special issue of Water and Maritime Engineering

June 2002 and illustrations have been kindly provided by the Cardiff harbour Authority.

Scheme description

Page 84 “Sixteen major sewers have been diverted from the bay prior to impoundment.”

“Althugh major sewage and other outfalls have been diverted from discharging

into the impounded water, there are still some inputs of sewage, industrial effluent, and

diffuse inputs from the river catchments and discharges from combined sewer overflows

(CSOs) during high rainfall events....Combined sewer overflows contribute high waste

loads...the discarges were located in the rivers Taff and Ely” I am informed that there are still

frequent CSO discharges.

Fixed and mobile bubbler system for dissolved oxygen content

Page 84 “The original concept for dealing with low oxygen levels was the provision of direct

injection by Vitox units at a number of points around the perimeter of the bay...In practice a

system of aerators has been installed in the bay with the agreement of the Environment

Agency. The aerators inject air into the water body rather than oxygen, and are designed to

operate continuously during the period from March until September each year.”

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The 600 coarse bubble diffusers are connected to air delivery pipes from the compressor

stations on the shore. Thus this installation show that it is feasible to lay pipes on the bed of

a water body and bubble air through them. The object is not to increase the dissolved

oxygen content of the water but to turn over the water such that the surface water and the

low oxygen bottom water are turned over, thereby eliminating stratification and raising the

dissolved oxygen content of the water body.

A mobile bubbler is used should such action be required.

Monitoring system

The monitoring system consists of sensors hanging from the 9 buoys providing water quality

data every 15 minutes.

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The data is relayed and displayed both in the Cardiff Harbour Authority (CHA) and EA

offices and live on the web so anyone can view it in near real time. In addition the historical

data can also be interogated on the web. Below is a sample I downloaded from the web

showing the readings every 15 minutes, in near real time mode for one of the sampling

points.

.

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This network of sensors and near real time display enables any oxygen sag to be rapidly

identified as it starts and rapid action to be taken at the relevant point in the harbour.

The aeration system has been operating since about 2001. During the early years there

were problems with receiving near real time data from the monitoring buoys. However since

2005 the new arrangement now gives reliable near real time (15 minutes interval) readings

for anyone connected to the web. This has enabled the scheme to meet its 5mg/l DO target

reliably.

Thus such a scheme can be a very effective and reliable long term solution.

Booms and skimmers for litter collection

For litter collection the Cardiff scheme uses booms, and a litter collection and skimmer

arrangement.

Cardiff harbour ,page 91, “CHA has procured a purpose-built vessel and booms in order to

deal with the considerable amount of debris that builds up in the bay following floods.”

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Conclusion

Thus the Cardiff harbour arrangment of fixed coarse grained diffusers and mobile bubblers,

a near real time monitoirng system, and booms and mobile skimmers, has enabled the

Cardiff Harbour to meet its dissolved oxygen and litter targets, and hence the UWWTD.

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Appendix D Location of onland diffuser systems. It had been intended to include plans showing the loaction of the air diffusers/oxygen generators on each site. However, for security reasons, TW have required that the plans be considered confidential. Locations proposed. Hammersmith PS Carnwarth Road tunnel site Western PS Heathwall PS Chambers Wharf tunnel site Greenwich PS Isle of Dogs PS Woolwich PS plan awaited Beckton PS big site, presumed space somewhere

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Appendix E Information about the Hydrospin vortex separation system

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