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Water experts shun grey infrastructure

So-called “grey” infrastructure solutions for water engineering, such as large concrete storage tanks, are outdated and inappropriate for modern times, experts said last week at a seminar hosted by consultant Aecom.

Speaking on creating water sensitive cities in the UK water experts said that large-scale hard engineering solutions for drainage and flooding issues are old fashioned and inefficient. Water sentitive urban design — a term referring to urban design that incorporates multi-functional sustainable drainage systems (Suds) and makes water infrastructure environmentally, socially and financially beneficial — is more appropriate for the 21st century, they said.

Aecom sustainability associate director Celeste Morgan said developers and town planners tend to favour infrastructure that keeps water out of sight. “We have to stop hiding water, and bring it into the public realm,” she said. Morgan compared the planned Thames Tunnel mega-sewer project in London to solutions in Philadelphia, where surface water runoff will be tackled by retrofitting a third of the city’s roads with permeable paving. “Is London really being a leader?” she asked.

Aecom landscape architect Deborah Kuh cited an example of an unnamed development where a planned concrete storage tank underneath a road was swapped for a large-scale Suds pond which also functions as a natural swimming pool, contributing to ecology and local amenity and providing a revenue opportunity for the local council.

Construction industry research and information association (Ciria) associate Paul Shaffer said infrastructure such as Bazalgette’s large sewer tunnels were a good solution for the 19th century but may not be “fit for purpose” in the modern world.

Readers' comments (3)

  • "Paul Shaffer said infrastructure such as Bazalgette’s large sewer tunnels were a good solution for the 19th century but may not be “fit for purpose” in the modern world."

    This seems strange, particularly on the day that the NCE Magazine is reporting that Thames Water are advising Mr. Walliams not to continue his charity swim in the Thames because of high sewage levels in the water! I always understood that Bazalgatte's very effective and efficient interceptor sewage tunnel scheme was primarily to cut off sewage overflows from cess pits etc and stop them entering the Thames.

    The comments regarding surface water retention and drainage systems are sensible engineering suggestions, but what does Mr Shaffer believe is a viable alternative to Bazalgatte' sewage tunnels - open channels for seage transport?

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  • We all subscribe to the vision of water sensitive cities and to the principals of Water Sensitive Urban Design. But moving from aspiration to delivery will be challenging and complex. WSUD provides an opportunity to look at Urban Water Management from a Macro perspective, looking at the water cycle holistically, as Paul Shaffer argues on his recently posted blog at It’s a good place to look to find out more about his views on WSUD.

    No doubt, we need to bring our stormwater to the surface. But in our moves towards Green Infrastructure we must be careful not to completely demonise grey infrastructure. While Green is the goal, often the best solutions require a toolbox of techniques to be effective, to account for example for space or water quality treatment constraints. Prof Bob Andoh’s blog on Blue, Green and grey infrastructure also at is helpful.

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  • I wonder if Celeste is advocating the use of open channels through London conveying combined sewage “We have to stop hiding water, and bring it into the public realm,” .

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