The Angling Trust have described it as “devastating” and “tragic”, while Thames Water admit that it was regrettable. Thames Water issued an apology last week, after it was forced to allow sewage to spill into the River Crane near Twickenham after a sluice gate became jammed and engineers were unable to re-open it. Thames Water, who have acknowledged blame for this major pollution incident, said:
The six-tonne, cast-iron penstock, used for controlling flows, jammed closed on Saturday morning in a trunk sewer at Cranford Bridge on the A4 Bath Road while engineers carried out routine maintenance.
Attempts to re-open the sluice gate were not successful until 8am on Monday, when engineers used a custom-made lifting device to force it open.
With 3,000 fish now dead and an entire seven-mile span of the West London river uninhabitable, it is reckoned that it will be years, not months, before the river returns to its original, thriving state. The Environment Agency (EA) are in the process of carrying out a full investigation, intimating that prosecution may be an outcome. Since then, Thames Water have issued an apology with Chief Executive Martin Baggs pledging that the company is “committed to put things right over the long term.”
The EA have been working continuously with Thames Water in an effort to minimise any further environmental damage by taking water samples, as well as monitoring levels of dissolved oxygen and ammonia in the river. Although the pollution has now spread into the River Thames, it is reported as having had little impact.
During the crisis, Thames Water were faced with a dilemma: allow the sewage to flow into London’s Heathrow Airport, which may force terminals at the airport to close, or release the sewage into the River Crane. An interesting blog post over at the Guardian comments on the comparable ‘scale of consequence’, as well as Heathrow Airport’s contingency plan.
In june this year, 450,000 tonnes of storm sewage was discharged into the River Thames after a weekend of heavy rain, causing fish to die along a one-kilometre stretch of the river. Sewage was discharged from both the Mogden Sewage Treatment Works and combined sewer overflows (CSOs). Thames Water dosed the polluted water with hydrogen peroxide to add oxygen to the water and deployed oxygenation vessels capable of injecting 30 tonnes of oxygen a day into the water.
While water sampling, oxygenation and chemical dosing can provide a solution to major incidents like these, permanent preventative measures are required to tackle London’s sewage problem.
The London Tideway Improvements Programme will reduce storm sewage discharges to the Thames by upgrading the five major sewage treatment works to increase their capacity. The London Tideway Tunnels programme will also see the construction of the £635m Lee Tunnel which will be the first of two tunnels designed to capture approximately 39 million tonnes of sewage each year from the 35 most polluting CSOs. The other Tunnel, the Thames Tunnel, has just entered a 14-week consultation process (find out more about the consultation here) and will link up with the Lee Tunnel, which is already in the construction phase.
Find out more about how Thames Water is making the River Thames a cleaner, safer place:
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