Hot topic sewer briefing
BRIEFING NOTE TO ALL COUNCILLORS
Proposed Thames Tideway Tunnel
1. Background
Thames Water’s stated main drivers for the proposed Thames Tideway Tunnel Scheme are:
- to comply with the European Union Urban Waste Water Treatment Directive
- to improve water quality for fish, public health and litter
- to create a “world-class river for a world-class city”
The Thames Tunnel scheme is primarily to prevent the current sewer discharges, which occur during times of heavy rainfall, entering the river. The scheme is about improving river water quality and pollution. The scheme is not designed to mitigate, nor will it prevent, sewer flooding.
The European Union Urban Waste Water Treatment Directive can impose fines where raw sewage is discharged into water courses. Thames Water estimate that approximately 32 million cubic metres of raw sewage is discharged into the Thames annually and the severe weather event in Hammersmith in July 2004 would, for example, have resulted in approximately 500,000 cubic metres of raw sewage discharging into the Thames locally.
Thames Water estimates that the cost for the scheme will be £2.2b and rising and that the cost will be paid for by Thames Water customers.
2. Thames Tideway Tunnel
The Thames Tideway Tunnel scheme is an underground storage reservoir that will capture most of the raw overflow sewage which currently discharges directly into the Thames during times of heavy rainfall. The sewage in the tunnel can then be emptied into the treatment plant in Beckton in east London.
The proposed tunnel would run from somewhere in the vicinity of Chiswick or Hammersmith in the west to Beckton in the east, running mainly directly below the Thames at a depth of approximately 75 metres.
The tunnel is designed to capture key combined storm water and raw sewage discharges from 34 existing Combined Sewer Overflows along the length of the Thames. The scheme also includes improvements to existing sewage treatment works.
Details of the CSO sites in west London are given in Appendix 3 which shows:
1. London borough of Hounslow – 1 CSO
2. London borough of Richmond upon Thames – no CSO’s
3. London Borough of Hammersmith and Fulham – 4 CSO’s (includes one pumped CSO and one which is not proposed to be captured at present)
4. London borough of Wandsworth – 6 CSO’s (includes one pumped CSO and one which is not proposed to be captured at present)
5. Royal Borough of Kensington and Chelsea – 5 CSO’s (includes one pumped CSO)
The three CSO sites in Hammersmith are the Stamford Brook Sewer which discharges near to the Dove Pier in Furnivall Gardens; the storm overflow sewer at the end of Queen Caroline Street just downstream of Hammersmith Bridge and the pumping station at the southern side of western end of Chancellors Road. (Refer to Appendix 3 for site locations)
The milestone dates setting out the reports and decision making leading up to the proposed Thames Tideway Tunnel scheme are set out in detail in Appendix 1.
3. Tunnel Overview
To construct the Thames tunnel and capture the CSO's would take around eight years and work could start as early as 2012.
The tunneling work would be carried out in a number of tunnel drives (probably 5 or 6) and a number of tunneling machines would be required in order to cope with the differing ground conditions along the length of the tunnel.
In order to construct the tunnel, a number of significant sized construction shaft sites are required. These shafts will provide access to the tunnel, both during construction and upon completion
Whilst any construction at a CSO site will cause major disruption, a critical issue is over the selection of the large access shaft sites for construction and disposal of spoil. It is likely and logical that one of these large sites be located at or about at the start of the tunnel. Thames Water explained at the meeting 22 July that the main construction access site to the western end of the tunnel would need to be on the river and with good road access. This led officers to conclude on the basis of limited information available that Furnivall Gardens would be a likely preferred location for Thames Water. A Thames Water map on their website showed diagrammatically the tunnel starting in the vicinity of Ravenscourt Park.
To identify such significant plots of land for construction purposes, whether immediately on the riverside for the CSO, or at alternative location for the main entry points, the sites will require road access for plant and equipment as well as for the delivery or materials. Whilst Thames Water have indicated that spoil would be removed via the river via temporary jetties, the likely level of disruption would be enormous.
The land take for these five major construction sites would be equivalent to two to three football pitches each and a jetty to enable the spoil to be taken away. Although, where appropriate, these may be combined with existing CSO sites, the CSO locations are not a governing factor in selection of the main shaft sites.
The land take for each of the CSO sites would require land of approximately a half to one football pitch during the construction stage. Upon completion the access and entry shafts into the tunnel would be capped.
The larger construction access shafts which are likely to be around 30 metres in diameter would probably require some small and permanent building above the shaft at ground level for future maintenance and access purposes. It is not envisaged that any significant above ground structures would be required at the remaining CSO sites (shafts about 10 metres in diameter).
In Kensington and Chelsea for example they have CSO sites at locations where the Chelsea Flower Show is held as well as historic sites such as the Chelsea Hospital.
4. Background to proposal and Thames Water communications
Thames Water’s consultation information concerning their 25 year plan gave details of their intension to construct the Thames Tideway Tunnel. Their literature then indicated that the tunnel would run from Chiswick in the west to Beckton in the east.
Thames Water’s initial letter to the council on 26 June 2008, and similar letters to all the adjoining riparian London boroughs in west London, put a contrary view that the tunnel would run from Hammersmith in the west rather than Chiswick.
Thames Water were challenged over this change at a meeting with the Leader and Deputy Leader and council officers on 22 July. Acknowledging the contradiction between their assertion that there was no pre-determination of the start of the tunnel and the major western construction access and their letter stating that it would be in Hammersmith & Fulham, Thames Water offered to clarify the position. They then replied on 31st July copied to Hounslow, Richmond and Wandsworth. Whilst there was no retraction of their earlier letter they did indicate that the starting point of the tunnel had not been determined and would be subject to consultation. Copies of these letters and the minutes of the meeting are attached below.
» Letter one (pdf)
» Letter two (pdf)
5. The Council View
The Council does not want to see raw sewage being discharged into the Thames but the benefits from the Thames Tunnel scheme have to be considered against the much greater environmental impact of eight years of major construction, severe traffic congestion in neighbouring roads and the substantial loss of green space.
Thames Water themselves stated in their twenty five year plan that there have been enormous efforts to clean up the Thames and that is now generally acknowledged as one of the cleanest metropolitan rivers in the world.
The council’s primary objection to the proposed Thames tunnel is that this is the wrong solution to the wrong problem. The scheme does nothing to deal with the increasingly frequent serious flooding of houses, businesses and community facilities in the borough.
Half of Hammersmith & Fulham suffered last year when heavy rainfall overloaded the inadequate drainage infrastructure. Hundreds of residents saw serious flooding of their properties causing enormous disruption and hardship. Worse still, the flooding brought raw sewage into hundreds of houses - a far more serious threat to health than sewage entering the river.
Thames Water have no plans to increase the capacity of the public sewers to resolve sewage flooding and yet the very same residents are now being threatened with loss of parkland and massive disruption with no prospect of relief from flooding. The critical issue for borough residents is not pollution of the Thames from combined sewer overflows but flooding and the direct discharge of raw untreated sewage surcharging into their properties.
The potential impact of these works, not only for Hammersmith and Fulham but for all London boroughs fronting onto the river will, be enormous and the justification for the schemes needs to be challenged. The benefits to borough residents will be small and the impact both in terms of cost through the water rate and from the construction disruption will be enormous.
It would appear that the analysis of options which led to the decision to pursue this scheme did not take adequate account of the impact of the construction land take in each of the densely populated boroughs to be able to locate sufficient land at the river frontage or within its immediate vicinity and to determine the likely disruption that this would cause.
The failure to address the likely implications of this level of land take and disruption need to be challenged and taken up with London Councils and the Government.
Earlier reports to London Council’s – copies attached at Appendix 2, have outlined the work which has gone into the development of this scheme. The Thames Tideway Strategic Study took the Environment Agency, the Department for Environment Food and Rural Affairs and the Greater London Authority more than three years to arrive at the current proposal. This was also reviewed by independent consultants before the government, some six years later, finally gave the go ahead.
Whilst other options have been investigated and discounted (see Appendix 2 report to London Council’s on alternative options) the issues are whether, over the long intervening period since the initial concept started, the impact of the current proposal have been thoroughly considered and how the construction and cost of this scheme will impact upon London and its residents.
6. Officer Meeting with Thames 25 September
A new factor which emerged from a meeting between Thames Water and council officers at this meeting is that any sites upstream of Hammersmith Bridge will have difficulty taking waste out by river because of the low head room under Hammersmith Bridge. This would suggest that Furnivall Gardens and Ravenscourt Park may be less likely to be preferred locations for the main western construction access point, but this cannot be assumed.
Thames Water provided confirmation of the proposed combined storm overflow sites in west London – see Appendix 3.
Thames Water explained that Halcrow had been appointed to manage the design development and delivery of the tunnel projects. Additionally Scott Wilson had been appointed as their Planning Environmental Consultants to look at the environmental impact of these proposals. They are currently preparing a draft methodology for the site selection process for prioritising the site locations for both the main and intermediate construction sites.
Local planning authorities will be consulted on this draft methodology and during the selection process.
Thames Water propose to issue a report that outlines the technical elements of each of the shaft site types; a site selection methodology and a consultation strategy. These documents will be issued to the Boroughs and statutory stakeholders for a 12-week consultation period. During this period, officers will be invited to a workshop to discuss the proposals.
Their intention is to develop a long list then short list and ultimately preferred list of sites based on the methodology developed through the initial consultation exercise. Ongoing consultation intentions will be outlined in the papers. Venues for the public consultation and the format of any workshops and presentations have still to be determined.
The formal consultation process is expected to start in the autumn.
7. Site Investigations
Thames Ecology and Heritage Team requested authority on 4 September to sink two small boreholes in Furnivall Gardens.
» Ground excavation plan (pdf)
Officers have been told that all CSO sites will require such investigations and that there was no special predetermination in selecting the Furnivall Gardens site. Thames are able to use their powers under the Water Industries Act to undertake exploratory works (which would not be particularly disruptive and would last only a few days) but would prefer to work with the local authority to determine a location which would be least disruptive and intrusive to local residents.
Members have instructed officers to decline this request.
Therefore for this work to proceed Thames Water will have to seek a warrant from the Magistrates Court to use their powers under the Water Industries Act.
Site investigations within Chancellors Road and Queen Caroline Street could be accommodated within the public highway where Thames Water already have powers to undertake street works.
There will have to be further separate reports on the individual sites once the draft site selection process has been published and the Council will have to develop a strategy and stance over future engagement with Thames Water.
8. Planning Process
The Planning Bill is still not finalised but at the moment it proposes to set up an Infrastructure Planning Commission which will determine 'nationally significant infrastructure projects'. Pipelines seem to be included in the definition of such projects.
It should be therefore be noted that planning permission for these works may come under the remit of the proposed Planning and Infrastructure Commission and as such would not be determined by the council as the local planning authority.
9. Public Meeting
The Council is planning to hold a public meeting in November 2008.
Briefing prepared by
Environment Services Dept
13 October 2008
Appendices
February 2000
Thames Water Tideway Strategic Study TTSS set up (OFWAT & Environment Agency)
www.thameswater.co.uk/cps/rde/xchg/SID-6988D537-F9F14696/corp/hs.xsl/6118.htm (opens new window)
» Executive summary (pdf)
February 2005
TTSS concluded that there was a need to improve the existing Sewer Treatment Works (STW) and to capture 36 of the most polluting combined sewage outfalls on the Thames Tideway
(Note that the Thames Tideway Tunnel will only pick put 34 of the CSOs – two others at Abbey Mills and Wick Lane will be picked up but under separate schemes)
August 2005
OFWAT commissioned Jacobs Babtie to carry out an independent review of these proposals
July 2006
The government instructed Thames Water (TW) to evaluate two options for a tunnel under the tidal Thames
December 2006
Thames Water submitted a report to government on the assessment of the two options detailing costs and benefits
» Map - proposed route (pdf)
» Overflows summary report (pdf)
March 2007
Minister Ian Pearson announced the government’s decision to support the development of the tunnels
March 2008
TW appointed consultants to assist with the delivery of the Thames Tideway Tunnel
Appendix 2 - Reports to London Councils
» Thames Tideway Tunnel – Alternative Options - Item 5 July 2007 (pdf)
» Thames Tideway Tunnel – Update Report – Item 3 13 September 2007 (pdf)
Appendix 3 - Existing Combined Sewer Outfall discharge locations West London boroughs
» Map (pdf)
» Consultation document (pdf)
Page last updated: 22/10/2008
