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Hard SuDS

Sustainable Urban Drainage Solutions have been given a new lease of life in the government’s latest water strategy. But is the strategy ignoring below ground solutions?
That climate change is driving the need for innovative solutions for surface water management is incontrovertible. Average UK annual temperatures may rise by 2degC to 3.5degC by the 2080s.

Seasonal rainfall distribution is also set to change with winters becoming wetter and summers drier. Sea levels are expected to rise by between 90mm and 690mm and there is likely to be an increase in the prevalence of extreme weather events.

The result: longer, dryer summers with less water available for consumption and more flooding as a result of extreme storms similar to those of last summer when 57,000 homes were affected by surface water flooding, with the damage estimated at £3bn.

Now, 80,000 UK homes have a 10% chance of being flooded by surface water each year, at a cost of around £270M per annum.

Government is not asleep to this threat and has, in the last six years, taken several steps towards addressing it, starting in 2002 with Approved Document H. This changed the hierarchy of drainage and drainage design considerably and introduced the concept of Sustainable urban Drainage Solutions (SuDS).

In theory, SuDs employ a whole suite of techniques to effectively manage drainage at source. But in reality, SuDS are seen as swales and drainage ditches acting as storm water attenuation ponds. Development of them has been slow with water companies reluctant to adopt them and developers unwilling to waste valuable land installing them. The alternative is below ground storage based on modular tanks or large diameter pipes. Both have advantages and disadvantages.

The government’s most recent PPS25 planning policy document placed more pressure on drainage capacity. It calls for the Environment Agency to upsize drainage capacity by over 20% to cope with future building and climate change. Last November, the Scottish government’s Sewers for Scotland strategy paralleled the PPS25 position.

This February, the Department for Environment Food and Rural Affairs took its most positive step yet, launching its Future Water strategy. It sets out how the government wants the water sector to look by 2030 with the following main aims:

- Reducing water demand by cutting average per capita water consumption from 150l/p/d to 130l/p/d, largely through more efficient and better labelled domestic appliances
- Improving water supply with more reservoirs and fewer abstraction licenses
- Improving water quality in the natural environment, largely through the implementation next year of the Water Framework Directive
- Improving surface water drainage by implementing SuDS
- Reducing flooding risk from rivers and coasts through more integrated strategic planning
- Reducing the water sector’s greenhouse gas emissions
- Near universal water metering in water stressed areas

Surface water drainage was the first to be hit with a consultation which ran until the end of last month.

Its aim was to establish surface water management plans, promote increased use of SuDS, remove the barriers to developing SuDS by clarifying the adoption and management issues, and review the automatic right to connect to public sewers.

It drew some rather fiery responses from developers of underground SuDS due to its perceived bias in favour of the traditional attenuation ponds.

“We support the Government’s Future Water strategy. Climate change is dictating that we must use and manage our water resources more effectively. However, we also feel that the government consultations are limited in their appraisal of SuDS,” says Polypipe Civils development director Jason Shingleton.

“The consultation documents appear to concentrate on above ground SuDS and do not give enough recognition of the role that below ground solutions already play and will continue to play in the future,” he says. “The market for modular cells is worth £60M since 2002, so we’re already doing lots.

“Furthermore, there is a disconnect between the government’s drive for higher density housing and brownfield development and the apparent preference for above ground SuDS.

“The consultation needs to deal with SuDS in a more holistic manner as both above and below ground solutions are required to effectively manage surface water sustainably. Designers need choice,” he adds.

Shingleton and Polypipe created Polypipe Water Management Solutions in January 2007. It is a team of dedicated water & drainage engineers who can help clients, specifiers and contractors find the best drainage solution with a focus on the latest developments in sustainable water management.

The firm is also launching a new large diameter pipe called Ridgistorm XL, claimed to be ideal for creating underground storage. It joins Asset International, which already offers large diameter pipes for stormwater attenuation.

“Modular cells have a place, but the issue is that water companies are reluctant to adopt them,” says Polypipe Water Management Solutions marketing manager Rachel Smith.

Pipes could well be the future.

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