London's £4 billion “supersewer” should be scrapped in favour of a “greener” alternative, a leading environmental consultant has claimed.
Campaigners have proposed a series of hidden drains throughout the capital as an alternative to the planned 24-mile tunnel under the Thames.
Thames Water will submit a planning application for the tunnel next month and building work is due to begin in 2015, uprooting several hundred people from their homes.
The supersewer will add a permanent £80 per year to water bills for all Thames Water customers.
American engineer Dr Mark Maimone urged the Mayor to consider the “cheaper and greener” solution he devised for the US city of Philadelphia.
The Philadelphia model is based on collecting and storing storm water in lots of smaller sites disguised under playing fields, tennis courts, car parks
and plant beds instead of a tunnel. These basins absorb excess water, allowing it to slowly drain back into the ground rather than into the sewage overflow.
Green roofs and tree-lined spaces have also been planted all over Philadelphia, which Dr Maimone said had created jobs, helped reduce crime and improved air quality.
He told a meeting of supersewer opponents: “Philadelphia started with a tunnel too but went on and did a thorough study. I have not seen a similar one being done here.
“It’s not a design problem, it’s a policy problem.”
Campaign group Clean Thames Now and Always, which is submitting a petition against the planning application, believes the sewer will be flooded. Campaigners insist a greener solution could be achieved in a shorter timescale for less money.
Dr Maimone added: “Green infrastructure is applicable to all cities in the world including London.
“I fully support CTNA and having visited London see no reason why it could not be done here.”
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But Phil Stride, Head of Thames Tideway Tunnel at Thames Water, said the Philadelphia model would not work in London because it has a larger population, less space, and different soil type.
He said: “We support the type of measures Philadelphia is seeking to put in place. They could help extend the life of the Thames Tideway Tunnel, but in no way replace the need for it.”
