| Efficient assessment of contaminated sites
As cities grow, they become peppered with abandoned sites where industry once flourished. Gas works, factories, fuel depots, landfill sites and chemical works are closed down, hidden behind fences and abandoned. The waste of land, often well placed for local transport and services, is both a challenge and an opportunity for sustainable cities. Redeveloping these ‘brownfield’ sites is a crucial element of the European Commission’s strategy for urban sustainability.
|A NORSIC engineer uses an on-site analytical laboratory.|
But each site is unique, and finding out what pollutants are present can be costly and may take months. A risk assessment is then needed to ensure the place is suitable for the proposed use. New software developed by the NORISC project will enable planning authorities, land owners and investors through the process to cut the cost and the duration of brownfield site assessment.
NORISC (Network Oriented Risk assessment by In-situ Screening of Contaminated sites) was a three-year project completed in 2003. It involved the city authorities of Cologne and Stockholm, the regional planning authority of Thessaloniki, Greece, seven academic groups from many disciplines including chemistry, biology, hydrology and geophysics, and two environmental engineering companies.
With current techniques, assessment of pollution on a contaminated site is often not thorough enough to assess risk accurately. Soil is sampled from boreholes at intervals across the site. There may be no information about what happens between the boreholes. Patches of pollution can be missed or turn up later when the site is under development, and scientists may have to return several times. The cost and the unpredictability of the process discourages developers. "There are lots of contaminated sites in our city centres," says project leader Barbara Möhlendick. "But investors prefer to develop new areas on the outskirts where there is no risk."
The NORISC partners have devised an integrated approach to assessment that gathers as much information as possible from the outset, improving the efficiency of surveying. The appropriate depths for soil samples and the right location for groundwater samples depend on the site’s geology and topography. Underground surveys can detect buried features like tanks that could be pollution sources, or areas of rock that change the way water flows. Such information improves the accuracy of samples, reducing the risk of unexpected costs.
Results in a week
NORISC compiled information on pollutants associated with different land uses, on methods available for measuring them, and on geophysical, biological and hydrological methods of characterising sites. They charted the cost and reliability of each method, along with any drawbacks - pipes, pylons or wells interfere with some methods, for example. All the information is held in a piece of software known as a Decision Support System (DSS). "We have over 100 assessment methods," says Möhlendick. "The software selects an optimum combination for your particular site, with quality and cost information that will assure insurers and investors."
Engineering companies tested the software on four sites that had already been surveyed conventionally. NORISC recommends that a team of environmental engineers carry out a full survey in one visit to the site. Samples are analysed in a mobile laboratory so further samples can be taken immediately if necessary. Visualisation software built into the DSS presents results in a three-dimensional site map. It may all sound rather expensive for a local authority, but in fact, the method reduced the cost of site investigation by up to 50%, and the time it took by 80%. "This is a one-stage investigation that can be completed within a week," says Möhlendick.
NORISC’s software also completes a risk assessment for human health, based on legislative guidelines for different pollutants. Risk assessment considers the pathways pollutants must travel to affect people. Toxic metals in the soil pose no risk if locked deep underground, for example - but if they can be reached by groundwater, or if the site is to be used by young children, the risk is substantial.
The consortium is forming a multinational company to develop and market the NORISC DSS. "Our holistic approach required people from different disciplines to learn a common language," Möhlendick recalls. "But the benefits are huge. Scientists developing new technologies around Europe now have a much broader view of the context for their work."
Making investment in contaminated land more attractive will benefit European cities, for brownfield redevelopment can help to bring city centres back to life by reducing urban sprawl and traffic congestion. It also offers commercial opportunities, providing a stimulus for development of environmental clean-up technologies that are applicable worldwide.