Short Term – A sustainable, affordable and quick-to-deploy scheme

Chris Binnie is the ex independent chair of the Thames Tideway Strategic Study (2000-05), which recommended the Thames Tunnel in 2005 as a solution to the Thames’ CSO issues. Though since retired, the water expert recently reviewed Thames Water’s proposed scheme to clean the Tideway and concluded it’s no longer an optimal solution.

Instead, he now advocates a solution, which very successfully transformed Cardiff Bay from a neglected wasteland of derelict docks, incapable of supporting most aquatic life in the 1980’s to one of Europe’s only capital river bodies with salmon spawning within[1].

The scheme consists of a bubbler system fixed on the riverbed which mitigates oxygen sags[2], supported by real time water quality monitoring so mobile bubbler boats can be deployed to tackle any punctual issue. Booms are installed to contain litter and a fleet of skimmers deals with residues (of which only about 10% is estimated to be sewage-related in the Thames). Since 2005, this solution has been providing in excess of 5mg/l dissolved oxygen, 99.9% of the time in Cardiff[3].

Where relevant, additional innovative, low cost and low disruption technologies such as the Japanese «Hydrospin» screen[4] or the German control system «Luritec» could be deployed locally.

If still found wanting, partial tunnel solutions and/or local treatment facilities as envisaged by the independent Jacobs Babtie study commissioned by Ofwat in 2005 could be considered.

Benefits of the short term solution


This solution would improve the quality of the Tideway within a few years, vs. over a decade for the Thames Tideway Tunnel and provide objective and real time measures of water quality. Likely infraction proceedings from the EU under the UWWTD, resulting in substantial fines (order of £1bn) against the UK, mean time is running very short[5].


The carbon footprint of such a solution would be reasonable and a clear positive balance compared to the benefits afforded[6], neither would it necessitate the near annihilation of some riverside communities for nearly a decade (including primary schools and sheltered homes), or cause gridlock on roads due to the hundred of thousand of lorry movements required.

Transparent metrics

As in Cardiff, this solution would deliver clear, real time and transparent metrics of water quality in the short run[7]. This would facilitate the incremental implementation of solutions after objective measurement, so as not to overshoot the need with an excessive solution, which would necessarily induce its own array of issues.


This solution is affordable at an estimated £60m. This compares favourably with the £4.1bn estimate for the Thames Tideway Tunnel, which still presents a significant upward risk[8]. In fact, the Thames Tideway Tunnel’s anticipated cost is such that taxpayers’ help has already been secured to bail it out – though unlike some financial institutions, the taxpayer wouldn’t even own the bailed out asset.

Prof Binnie also conducted a comprehensive Cost-Benefit Analysis for the Thames Tunnel and found its benefits to be of the order of £310m, meaning its cost is in gross disproportion[9]

  1. [1] The Environment Agency has concluded that salmon isn’t sustainable in the Thames on ground of rising temperatures.
  2. [2] Although the Tideway’s implementation would be about three times larger than Cardiff’s, its tidal nature would actually help better disperse oxygen.
  3. [3] This is better than the 3-4mg/l minimum target set by the Environment Agency in its Environment Quality Standards.
  4. [4] Data analysis from Japan shows that up to 78% of the floatables and suspended solids can be removed from overflows using HydroSpin. (Nakamura et al., 2010)
  5. [5] In Jan 2012, an EC Advocate General found against the UK for non-observance of the 1991 Urban Waste-Water Treatment Directive, which required compliance by 31/12/2000. By some estimates, fines could start accruing from around 2017 and reach €1.1-1.5bn by the time the Thames Tideway Tunnel might be commissioned in summer 2023 (assuming no delays).
  6. [6] More analysis is required to quantify this but it doesn’t take much imagination to gauge that it would be a fraction of the impact of the Thames Tideway Tunnel, despite mitigating the same issue, albeit more cheaply and quickly…
  7. [7] Real-time data on Cardiff Bay’s water quality is available around the clock here, whereas much current data for the Thames is based on disputed models
  8. [8] This has already worryingly escalated from the original £1.7bn estimate in 2005. The cost for comparison today is £4.7bn (a 2.75x increase) as the 2005 estimate included the £600m Lee Tunnel.
  9. [9] This is relevant to the UWWTD infraction as the Thames Tunnel would manifestly fail a “best technical knowledge not entailing excessive cost” (BTKNEEC) test