Suds lessons from the US
Dr Ian Pallett, technical director of British Water, reports on a mission to the US to find out how sustainable urban drainage systems (Suds) can help to manage and maintain water resources, and provide environmental and amenity benefits
In 2004, the Foresight Future Flooding Report, sponsored by the Office of Science and Technology, estimated that annual average flood damages could increase by between two and 20 times by the end of the century. The same report says that "80,000 properties are at risk in towns and cities from flooding caused by heavy downpours that overwhelm urban drains - so-called 'intra-urban' flooding. In England and Wales alone, over 4 million people and properties valued at over £200B are at risk."
The majority of stormwater in the UK is currently combined with foul sewage, though there are some networks of separate stormwater drains and sewers that convey runoff to a convenient watercourse or other receiving water body. Other than oil interception, only in Scotland is it compulsory that stormwater discharges should be treated, despite the quantity of pollution it collects on its way to the drains, although this is likely to have to change to meet the demands of the European Water Framework Directive. We have to find better ways of controlling stormwater, and so with the support of the Global Watch Service of the Department of Trade and Industry (www.globalwatchonline.com), British Water, the trade association for the industry, organised a Global Watch Mission to assess US methodologies, management systems and engineering techniques.
We aimed to find out how sustainable urban drainage systems (Suds) solutions and their relative cost benefits can help to manage and maintain adequate water resources, as well as providing environmental and amenity benefits within developments. We saw high-density housing developments,the Centre for Watershed Protection, the US Environmental Protection Agency's Low Impact Development Centre and its Wet Weather Centre. We attended the Hydro International conference on The Changing Face of the Stormwater Industry, participated in a seminar on US water and Suds regulation and research, and examined maintenance issues by watching small and large storm drain systems being cleaned. The report and seminar proceedings are available via the website.
Perhaps the most obvious difference between what happens in the US and Britain is the openness of information and the effect that has on public involvement.The regulation of the water industry in the US centres on the 1972 Clean Water Act (CWA).
This set ambitious targets for improving the country's watercourses and getting rid of pollution, and demanded that municipal and industrial wastewater should be treated before being discharged. It also allowed federal finance to be made available for the construction of municipal treatment plants, while insisting that individual states should be responsible for the everyday implementation of the law.
The aim was to make discharge of pollutants disappear by 1985 and try to make water suitable for fishing and swimming by mid-1983. More than 20 years on, they have not achieved those targets - but they have made considerable progress.
There are a number of websites dealing with different aspects of pollution and wastewater control - there's even an online learning module called Understanding the Clean Water Act.
Portland, Oregon is a city with rainfall similar to that of London. Here stormwater taxes are totally separate from sewage and water supply charges are based on connected impervious surfaces, so it could pay to plant a lawn rather than pave a yard. Residents are encouraged to disconnect their downspouts from the system and use the water in rain gardens, and many people proudly display "we have disconnected" signs in their front yards. Schools have stormwater gardens and Portland State University has a large scale system to use rain water directly for flushing toilets.
Portland is a city we felt we could learn from in this country. Any change in the tax system here to separate stormwater charges in this way would be controversial and highly political, as well as running counter to the modern trend to pave your front garden to provide extra parking space, but it could be a simple and practical way forward.
In Massachusetts we found metering has led to water usage reduction of 454Ml/d. Water usage is now the same as in 1911. Many in the industry would like to see metering made compulsory in the UK. Metered sewage and wastewater is a new idea here, but follows logically from metered water. However, the public perception is that the water companies are to blame for all the problems with our system through their inefficiency and excessive profits; metering remains generally unpopular and an issue few politicians are prepared to tackle.
Nonetheless, the summer's dry spells have made people more aware of the issues surrounding water, and we need to maintain that interest and get their support, by providing more, easily available, accurate information.In many parts of the US, including Portland, they use the landscape to help dispose of stormwater.
Green roofs are becoming increasingly common and they can absorb up to 90% of water. Mature trees are very effective at managing both the quality and the quantity of the storm water, and a scheme in Baltimore County in Maryland gives people £5.30 towards the cost of buying a new tree. Authorities in Boston have backtracked from a single large-scale storage CSO solution for stormwater control to many smaller local options that have nearly halved the cost. Traffic calming measures often include plant islands, mostly cared for by the local community and we realised that co-operation between highway and traffic authorities and the water industry can be very effective.
A little further up the west coast in Seattle, the transportation department was unhappy about a project to provide a natural drainage system using the landscape rather than pipes and grids, because it involved a narrowing of roads.
The original Street Edge Alternatives Project (SEA Streets) reduced the total volume of stormwater entering the sewage system by at least 98% in its first three years - but it was costly. Impervious surfaces were reduced by 11%, planted swales were created to hold excess water and let it gradually seep into the soil and over 100 evergreen trees and 1,100 shrubs were planted. Residents took over the care of the gardens, which helped to foster an increased sense of community in the area.
More such streets are gradually being introduced - experience has reduced the costs, and the safe access concerns of the transportation department have been accommodated along with a beneficial slowing of traffic. And while we're on the subject of vehicles, if stormwater taxes applied here, and a charge applied to impermeable areas, there would be a financial incentive to build more car parks with sustainable surfacing.
Back in the UK, there is growing evidence of attempts at integrated management of wastewater systems such as the holistic approach being undertaken in Glasgow. Here "communities need to systematically understand and characterise their stream, conveyance and storm sewer infrastructure systems". In Cardiff there has been a 12-month monitoring programme on key sewers in the network to help understand how these Victorian systems actually work. Suds have been incorporated into the Manor and Castle redevelopment in Sheffield, emphasising amenity value with public involvement and educational projects.
Programmes such as these should be extended and continuous, as our research proved to us that the results can be valuable for a comparatively limited investment. The mission was so useful that we're considering another expedition next year, this time to see how our European colleagues handle the situation.
It will take time to work out the best solutions for the UK. Changes to drainage systems are expensive, and we need to make sure that all the work we undertake in the next few years is part of a carefully considered plan based on best practice.