Why London ‘super sewer’ may not work, by US city chiefs

by Lucy Purdy, senior reporter Monday, August 22, 2011
4:45 PM

Officials from two cities in the USA have warned Thames Water bosses not to bank on their multi-billion pound “super-sewer” to clean up the Thames.

Experts from Milwaukee and Chicago say that similar deep tunnel schemes in their cities ran over time and over budget, and have failed to stop all sewage from overflowing into nearby rivers.

Bosses at the British utility want to build a 20 mile-long concrete storage tank under the river in an effort to prevent sewage seeping into the river.

The controversial scheme could cost Newham taxpayers as much as £10 more each month.

Flooding

Water bosses in Milwaukee, in the eastern state of Wisconsin, have admitted their tunnel has done nothing to solve the problem of basement flooding after heavy storms, according to Alderman Willie Hines, the president of Milwaukee Common Council.

He said: “If I had billions of dollars to spend, a super-sewer would not be top of my shopping list. I would not be looking at a deep tunnel to solve all of London’s sewage problems because it certainly did not work here in Milwaukee.

“I would only look at a deep tunnel as part of a comprehensive strategy, but it would be the third leg. The first priority would be prevention and improvement work to stop basement flooding.

“The second would be stopping rainwater from entering sewers by disconnecting downspouts, and setting up rain gardens and green roof initiatives.

“Only then would I be looking at a deep tunnel once I knew the scale of the remaining problem with sewage overflows.”

Sean Wiedel, from Chicago City Council, added: “Our storms are becoming more frequent and the deep tunnel simply can’t handle them.”

Across the pond, other US cities including Philadelphia and Cleveland, are looking at greener solutions – such as permeable pavements, green roofs and infiltration trenches – as part of the solution as they stop fresh rainwater flooding into sewers in the first place.

Cllr Stephen Greenhalgh, leader of Hammersmith and Fulham Council said: “For too long people have taken Thames Water’s word for it that their massive super-sewer plan is the best option to making our river cleaner, but now two major American cities are warning us not to bank on this working,” he said.

“Evidence from across the world is increasingly showing that a more modest tunnel combined with green infrastructure solutions, that prevent fresh water from overloading the combined sewer network, is likely to be the way forward.”

Five London councils are sponsoring an independent commission, led by Lord Selborne, to take a fresh look at Thames Water’s assumptions and examine whether there are sensible and more cost effective alternatives to cleaning up the river further with less disruption to Londoners.

Responding to the US state leaders in turn, a Thames Water spokesman told the Recorder: “Regarding Chicago, a sustainable urban drainage systems (SUDS) on its own would cost far more than the Thames Tunnel, take longer to deliver and would not solve the problem.

Discharges

“Although SUDS have a part to play in the long term, studies have shown that unlike the Thames Tunnel scheme, SUDS on their own alone cannot tackle the 39million tonnes of sewage that overflows annually into the River Thames from London’s antiquated sewer network.

“A decade of independent study has shown that the Thames Tunnel, unlike the alternatives, will actually solve the problem.

“Milwaukee’s tunnel did what it set out to do – significantly reduce sewage discharges to the river. And a decade of independent study has shown that the Thames Tunnel is the best way to significantly tackle the sewage.

“The Thames Tunnel is not intended to tackle basement flooding. We have many additional projects, underway and in planning, to tackle sewer flooding, which is a completely separate problem.”

* For more information on Thames Water’s plans visit www.lbhf.gov.uk/supersewer.