10 questions for Thames Water – The Answers
Earlier this year we were invited by Thames Water to ask them 10 questions. Here are the amalgamated answers. We would like to sincerely thanks Richard Aylard at Thames Water for all his help.
Question 1:
The amount of water abstracted from the River Thames has increased to alarming levels. For much of the year the River Thames resembles a lake and there is hardly any flow. Where is water abstracted from on the Thames, how much is abstracted each year by whom, and for what purposes?
Answer 1:
Thames Water abstracts from several intakes (including Datchet, Laleham, Walton and Hampton) under its licence from the Environment Agency (EA) which allows 1818 Ml/d on average over the year. (1Ml/d is one million litres per day). This licence has not been increased since at least 1986. Our abstraction is for public water supply. Other water companies abstract about 400 Ml/d on average and we are not aware of significant abstractions for any other purpose. However, the licensing regime is run by the Environment Agency and they are the only people who could confirm that.
The 1818 Ml/d is an annual average, but there are also strict limits on how much water we have to leave in the river. This is expressed as a residual flow requirement over Teddington weir and is set out in the Lower Thames Operating Agreement (LTOA) between Thames Water and the Environment Agency. We have to allow 800 Ml/d flow over Teddington weir at all times, except when the London reservoirs are drawn down in the summer months. At those times the minimum residual flow is decreased according to the storage in the Thames reservoirs and the time of year. The residual flow is reduced in stages from 800 Ml/d to 600 Ml/d to 400 Ml/d and to a minimum residual flow of 300 Ml/d. In plain language, the lower the reservoirs are, and the earlier in the year this happens, the more serious the risk to London's water supply, and therefore the more water we can take from the river.
You might like to know that we are undertaking an investigation into the impact of abstraction on the ecology of the lower Thames and the Tideway. This investigation will be complete in 2013 and will be used to determine whether there is adverse impact from the abstraction on the lower Thames. ————-
We have asked for more information about the investigation into the impact of abstraction on the ecology of the lower Thames and the Tideway; hopefully this will be forthcoming
Reply (2/3/10) from Richard Aylard, Director of Thames Water, stating:
All I can really say about the investigation at the moment is that we know we need better information on the impacts of abstraction on the river ecology, in order to have a sensible discussion with the Environment Agency about the future of the Lower Thames Operating Agreement, which in turn will affect our water resource planning. So we have made a case for this work to our economic regulator, Ofwat, and they have just approved it. Now we have to scope the study with the Environment Agency and make sure we look at the right things. ————
Question 2:
How often does abstraction occur, who regulates these abstractions, and how are Thames Water balancing the need to provide drinking water whilst also lessening the impact of abstraction on the natural environment?
Answer 2:
Abstraction occurs all the year round and is regulated by the Environment Agency. The LTOA is set up (as described above) to balance the need to provide drinking water against the need to lessen impact on the environment through the progressive reduction in residual flow as reservoir storage declines and so risk to security of supply increases.
We have a statutory duty to supply water to our customers, and to maintain a balance between supply and demand. Our approach starts with reducing demand, through reducing leakage (after some years of under-achievement we have brought it down by 24% in the last four years), increased metering and encouraging water efficiency. If that doesn't provide enough water to meet anticipated demand (and bear in mind that London's population is still growing rapidly) we have to develop new resources. We know we won't be able to take any more water from the Thames above Teddington weir (and, depending on the results of the survey mentioned above, we may need to take less), so we are about to commission a desalination plant on the tidal Thames at Beckton, for use in times of drought. This abstraction is so far downstream that it will make no difference to the flow in the river. In the longer term, we also have plans to build a major new reservoir near Abingdon, by about 2026. This will abstract water from the upper river during the winter, when flows are high, and store it until it is needed in the summer. We will then release that water back into the river, where it will flow downstream (adding to the natural flow) for abstraction at Datchet, Laleham etc. In addition, we are also looking to develop new ways of pumping surplus winter water underground, to recharge the natural aquifers and give us more to draw on in dry summers. We already do this successfully in parts of North London, but in most places the geology is not suitable. ————-
3. Sewage pollution is regularly discharged into the River Thames. What is the highest tonnage of raw sewage discharged at any one time and where and when did this occur?
I have taken a look at data back as far as 2000 – the largest daily CSO discharge recorded was from Abbey Mills on 30th October 2000, and this showed 2,245,568 m3. There was only one other discharge of more than 2 million m3, being 2,113,677 m3 on the 8th February 2001. What I can't easily assess from these daily figures is timing, for instance whether a discharge continued for more than 24 hours continuously, which I would expect if there was continuing heavy rain. For example, there were discharges of more than 400,000 m3 on both of the two days preceding the 30th October 2000, but I can't say if these were three separate discharges or one discharge over three days. Prolonged wet periods will result in large volumes, even if not a continuous discharge; 'New Year' 2002/3 was very wet – the total for 29/12- 3/1 was almost 7 million m3.
Question 4:
Please can you tell us exactly where combined sewage overflows are situated and how much rain is required to cause a discharge event.
Answer 4:
A map is attached CLICK HERE, showing the locations of the 57 combined sewer overflows (CSOs) that overflow into the River Thames. As little as 2mm of rainfall can trigger a discharge event, although individual CSOs have different levels of sensitivity to rainfall.
Question 5:
Sewage treatment works in the Thames region are due to be increased by on average thirty percent, with Mogden being the first works to be completed in 2013. The Lee and Thames Tideway Tunnels, which are expected to receive planning permission in 2011 and be completed by 2010, will capture the most polluting sewer overflows. Together these enhancements are expected to solve the problem for 40 years, up until at least 2060.
Please can you tell us about the criteria you used in your computer models and explain why a longer lasting solution was not decided upon.
Answer 5:
First of all, I need to correct some of the dates in the question.
The Lee Tunnel has received planning permission (subject to conditions) and construction is planned to start any day now. The provisional date for its completion is 2014.
We anticipate submitting our formal planning application(s) for the Thames Tunnel for approval in late 2011. Planning permission is expected in 2012, with completion due in 2020.
With regards to the Lee and Thames Tunnels and Sewage Treatment Works (STW) upgrades being expected to solve the most polluting combined sewer overflows (CSOs) up until at least 2060, we’re not sure where the date of 2060 has arisen from. If it was something I said at the rowers' meeting then please take this note (which has been cleared by our technical expert) as a better answer.
The design life of both the Lee and Thames Tunnels is 120 years, with the fabric of the tunnels likely to last even longer than this.
In 2000, the Thames Tideway Strategic Study (TTSS) was set up to consider the environmental impact of storm discharges to the tidal River Thames and to propose solutions that would comply with the EU Urban Wastewater Treatment Directive. This work provided the basis for the decision on the Lee Tunnel and Thames Tunnel solutions. The reports from this study are all available to download on our website: www.thameswater.co.uk/tidewaytunnels
Criteria used in the TTSS for compliance testing of the feasible solutions included; reducing sewage-derived litter, compliance with microbiological quality standards, and compliance with dissolved oxygen standards.
As there were no recognised criteria for the tidal Thames, the TTSS group developed a series of dissolved oxygen standards that would deliver sustainable fish populations in the Tideway. The standards are approved by the Environment Agency. Each tunnel solution was tested to ensure that the dissolved oxygen thresholds were met.
A comprehensive computer model of London’s sewer system was used to calculate the CSO discharge flows for a wide range of rainfall events. Generally, historic rainfall data was used rather than design rainfall data, as this includes all the spatial and temporal variation for such a large catchment, i.e. it does not rain the same amount over all of the catchment all of the time. Typical large rainfall events were selected upon which to design the system.
The rainfall data was also modified to incorporate climate change predictions and the latest UK climate projections (UKCP09) have been taken into account. This incorporates predictions for impact on rainfall for 2080. These effects have been modelled, showing that the Thames and Lee Tunnels in conjunction with the increased capacity of the sewage treatment works will still limit the number of residual CSO discharges to a similar number. Obviously it is difficult to predict further into the future than this.
The principle longer term challenge of climate change is likely to be the general increase in temperature, leading to an increase in river water temperature. This will impact on the dissolved oxygen levels in the river water making it more susceptible to pollution. It has been calculated that even if all residual CSO discharges were eliminated entirely it is likely that the target threshold levels for dissolved oxygen would not be quite met in the future should the climate change predictions be realised. However this potential future breach of the targets is likely to be marginal and obviously if the tunnels and STW upgrades were not to be carried out, the failure to meet targets would be very significant, extensive and immediate.
With these potential climate change effects in mind it may therefore be necessary to further improve the quality of the treated effluent from the STWs to further improve background conditions in the river. This would enable it to better maintain dissolved oxygen levels under conditions of increased temperature in the future.
Question 6:
In 2004 a heavy summer storm resulted in the output of thousands of tons of untreated sewage being discharged into the river from the Mogden Sewage Treatment Works. This resulted in a huge mortality of fish and included all species and all size ranges. In your Biodiversity Policy you state that “[we are committed to the following Objectives to] Manage our land and water holdings to conserve and, where possible, enhance biodiversity”. What has Thames Water done to see that the river is restocked with fish that have died because of pollution entering the river from Thames Water outfalls?
Answer 6:
The August 2004 storm was unusual, even by the standards of Tideway storm discharges. A full month's rain fell on west London in a few hours. All the combined sewer overflows ended up discharging. At the same time, Mogden sewage treatment works received far more sewage than it could treat. Once the storm tanks were full there was no option but to discharge screened sewage to the river, in order to prevent sewage flows backing up into streets and homes (and in accordance with our storm discharge consent from the Environment Agency). All this sewage entered a warm, low and deoxygenated river, with inevitable and distressing consequences. But the hard fact is that there was literally nowhere else for the sewage to go. That is why we have a consent for storm discharges and why we sometimes need to use it. I know it will be small comfort to all those whose sport was damaged in this and other similar incidents, but increasing the treatment capacity at Mogden by more than 50%, in the project which has just started, will make this sort of incident much less likely from completion in March 2013.
There was of course a significant fish kill in August 2004 and there have been smaller ones since. I have discussed restocking with the Environment Agency. Their view is as follows "the species lost during this event were adapted to living in the tidal Thames. Whilst it is freshwater, there is a significant and constantly changing tidal flow. With the exception of our Calverton Fish Farm (source of the Wandle restockees) supplies of river adapted coarse fish are very limited. In the case of the tidal Thames we believe a natural recovery of the fish population was the best option with migration from up and downstream of the affected reach. Movement of fish from a stillwater environment to a fast flowing tidal river carries a risk of post-stocking mortality and the evidence points to poor long term establishment of the introduced fish to such habitats. We will keep the situation under review by monitoring results of our fisheries surveys and angler catches."
Following fish kills on other rivers we have paid for both restocking and enhancement projects. These payments include £500,000 over five years for the River Wandle, a £250,000 project on the River Thame near Aylesbury and £50,000 for the Grand Union Canal (Blenheim AS). In each of these cases we have been able to monitor results in comparatively confined areas. Also, whenever we have the opportunity for restocking from our own resources we take it. We recently had to remove a large number of specimen roach which had become trapped in our Walton water treatment works. We had high hopes that these could be restocked into the Wandle. But when the EA did health checks they were found to have a parasitic infection and were therefore released into the Thames near Walton, rather than being moved to a different environment. As far as restocking the tidal Thames is concerned, we share the EA view (above) that this would not make sense at the moment. The area concerned is so large that what we need to do is clean up the river so that it can take care of itself. The major improvements at all five of the tidal sewage works between now and 2014, plus the Lee tunnel by 2015 and the Thames tunnel by 2020 will bring big improvements.
Question 7:
Thames Water is a natural resource company which depends immensely on the aquatic environment. While you implement many terrestrial conservation projects in proximity to your sewage treatment works, in contrast it appears that you do little for the aquatic environment. Please can you tell us about any aquatic conservation projects that Thames Water has been involved in and also detail funding that Thames Water has made available for scientific studies of the river environment. In particular, please can you tell us about any research conducted or funded by Thames Water on the impacts of your outfalls on aquatic communities.
Answer 7:
As part of our commitment to environmental protection and our approach to sustainability, we run a number of conservation projects and programmes, often involving a range of partners including the Wildlife Trusts and local environmental groups. These benefit a range of habitats across our sites and the wider Thames Water region, including terrestrial, marginal and aquatic environments (in many cases, terrestrial and aquatic conservation projects won't be mutually exclusive – new bankside or marginal vegetation can provide feeding opportunities and habitat for macro-invertebrates and fish, as well as riverside mammals and nesting birds; they can also help filter forms of diffuse pollution, such as agricultural run-off). Some highlights from recent years that you may be interested in include:
Upper River Kennet Rehabilitation project – This was a major five-year river restoration project that has delivered long-lasting environmental benefits along the upper Kennet in Wiltshire. The river is a Site of Special Scientific Interest and supports nationally important chalk stream habitat (a key Biodiversity Action Plan habitat). Our work with the Environment Agency, English Nature (Natural England), Action for the River Kennet (ARK) and local landowners saw improvements to 10km of the river. The project was featured in a variety of publications, including River Restoration News (see http://www.therrc.co.uk/newsletters/issue8.pdf) and on the ARK website (http://www.riverkennet.org/projects_rehabilitation_project.php). As part of the project, we produced a technical CD and DVD which is still available. Copies can be supplied by Nick Lutt, Environmental Consultant at Thames Water (nick.lutt@thameswater.co.uk).
Farmoor reservoir nature reserves – At our Farmoor reservoir in Oxfordshire, we've worked with a wide range of partners (including the Environment Agency, Pond Conservation, Oxfordshire Ornithological Society and others) to create a suite of three award-winning nature reserves. These include a range of terrestrial, wetland and aquatic habitats, as well as an accessible wetland trail for visitors. The site has become one of the top birdwatching venues in Oxfordshire as a result and includes some of the most-studied ponds in the country according to Pond Conservation. Further details are on our website at http://www.thameswater.co.uk/cps/rde/xchg/corp/hs.xsl/3602.htm or http://www.farmoor.iofm.net/reserve.htm.
River Ray restoration at Swindon Sewage Treatment Works – working with Wiltshire Wildlife Trust to create riffles and eddies, and plant reeds to improve aquatic habitats.
Seven Springs Pumping Station (Brassey Site of Special Scientific Interest) – scrub clearance to benefit the mire community on the river there which has now been classified as 'recovering' by Natural England.
Crossness Sewage Treatment Works Nature Reserve and Southern Marshes Project (east London) – Major wetland restoration (including open water, grazing marsh and ditch networks) in partnership with London Wildlife Trust and others (see http://www.thameswater.co.uk/cps/rde/xchg/corp/hs.xsl/6249.htm and http://www.thameswater.co.uk/cps/rde/xchg/corp/hs.xsl/6247.htm). The site is now a stronghold for water voles in London.
Kempton Nature Reserve (west London) – Over the past 10 years, we've created an internationally important wetland nature reserve at our Water Treatment Works (for more detail, see http://www.thameswater.co.uk/cps/rde/xchg/corp/hs.xsl/6254.htm).
We have undertaken a wide variety of other projects and partnerships as well – wetland habitat creation at Bicester sewage works, working with the RSPB at Otmoor Nature Reserve (Oxfordshire), supporting the River Crane Valley partnership in London, funding the South West London Water Bodies Special Protection Area study, and involving our own staff as volunteers on environmental activities (like litter-clearing from the tidal Thames foreshore in London with Thames21).
We publish details of many of these projects in our annual Corporate Responsibility report – our latest report can be accessed here: http://www.thameswater.co.uk/cr/ (some of our earlier reports provide detail on these projects too and can be found at http://www.thameswater.co.uk/cps/rde/xchg/corp/hs.xsl/3116.htm).
Funding that Thames Water has made available for scientific studies of the river environment / research conducted or funded by Thames Water on the impacts of outfalls on aquatic communities:
Our Pollution Control / Environmental Protection teams work with the Environment Agency to identify misconnected drains and prevent pollution to watercourses across our region. Last year, we significantly improved the quality of 37 polluting outfalls. Our team also made 1,022 visits to known pollution hotspots from commercial and industrial premises, often in partnership with the EA. This has a substantial impact on improving the aquatic environment. You can find out more here: http://www.thameswater.co.uk/cr/wastewater/pollution-prevention/ and here http://www.thameswater.co.uk/cps/rde/xchg/corp/hs.xsl/8202.htm.
We also work in partnership with other bodies including the National Misconnection Strategy Group, UK Water Industry Research (UKWIR) and Water UK on research and studies to improve the aquatic environment. Over the next year, for example, we will be working with UKWIR on a sewer misconnection project to further understand the impacts of misconnections on river water quality and how they will affect achievement of local and national Water Framework Directive targets. This is a huge issue in London where many properties have had their foul drainage connected to surface water discharges (either deliberately or through ignorance). The project will be starting soon so limited information is available at present but brief details are at: http://www.ukwir.org/content/default.asp?PageId=65202.
In January 2009, we worked with Water UK and the EA to produce a good practice guide on investigation and resolution of drainage misconnections. The report can be accessed online at :
We also carry out investigations into the impacts of abstraction on the aquatic environment. There are some areas where abstracting water can contribute to low flows in rivers, which can cause environmental or ecological concerns. We are continuing to work on a programme, agreed with our regulators, to limit the amount of water we take and work to improve the situation on stretches of river suffering from low flows. In 2008/09, we completed a scheme to enable high quality treated effluent to be pumped into the River Cherwell upstream of where it would normally enter the watercourse, so that the river continues to flow all year round. In June 2008, we finalised an operating agreement with the EA to enable this scheme to be used in future low-flow periods. We are also investigating at key sites where it is thought that the water we take may be causing low flows.
In 2008/09, we completed three studies at Seven Springs and Blockley Brook, both in the Cotswolds, and at Cress Brook, near Slough. In each case, the investigation confirmed no requirement to reduce our abstractions. And of course there is the major study pending on the impacts of abstraction on the lower Thames.
Question 8:
Thames Water state that “being sustainable means doing the right thing for people, the planet and our own performance, both now and in the future. It means ensuring our decisions and actions as a business do not disadvantage future generations.” In contrast to this statement, Thames Water’s sewage treatment works do not routinely remove endocrine disrupting chemicals from effluent. These chemicals cause serious damage to the hormonal and reproductive development of fish and other aquatic organisms. For a company which made £435m in profits in 2009 and which states "We are committed to cleaning up the tidal River Thames”, surely it would be a show of your commitment to environmental sustainability if you were to implement activated carbon water filtering to remove these very damaging chemicals from water before it is discharged into the Thames? Consequently we would like to know exactly what your policy is on stripping endocrine disrupting chemicals from effluent before it is returned to the river.
Answer 8: Our approach to endocrine disrupting chemicals ("EDCs") is entirely consistent with doing the right thing for people, the planet and future generations. Based on studies from a range of treatment works, we do already achieve a substantial removal of steroid oestrogens – the principal EDCs identified in terms of fish impacts – across the treatment process at our works. It is not disputed that high concentrations of EDCs have been linked with the appearance of the intersex condition in fish in some rivers, although this is most frequently reported where there is little or no dilution for sewage effluent. We are not aware that there is any suggestion of the intersex condition being 'an issue' in the Tideway – and quite clearly there is the more pressing concern of periodic low dissolved oxygen concentrations in any case, which of course will be addressed by our projects to improve the five main Tideway sewage works.
Question 9:
At the Rowers Meeting in Putney on 28 January 2010, we were informed that activated carbon filters were too expensive to fit to the water treatment process to remove damaging endocrine disrupting chemicals from effluent but that research into their use was ongoing. Please can you tell us what research you are conducting and what the results have been so far? —
Answer 9:
It would be technically possible – if largely impracticable and at huge carbon footprint cost – to provide activated carbon tertiary treatment for the tideway treatment works. Indeed, the technology exists to turn sewage effluent into water of potable quality, if required and albeit at high cost. That we could do it does not mean that we should, or that to do so routinely is the right thing for our customers or the planet, bearing in mind the energy costs and waste streams that would generated. I think the issue here will become clearer when you see the sheer scale of the operation at Mogden As I mentioned at the rowers' meeting, we have been participating in a national project to evaluate the costs and effectiveness of different types of treatment, including novel tertiary treatment, to enable additional reductions of EDCs to be achieved. We expect this research to be reported in the next few months, but in the meantime I can say that our contribution – testing an activated carbon filter at full scale – was confirmed as very expensive, and at our works appeared to offer little additional reduction beyond secondary treatment.
Question 10:
Also at the Rowers Meeting email notification of sewage discharges was discussed. Please can you tell us when this will be operational and how anglers can sign up to receive this alerts.
Answer 10:
