GIS aids the management of contaminated land

Following the implementation of the contaminated land legislation (Part IIA of the Environmental Protection Act 1990) many local authorities are in the process of preparing their written strategies. A first task for local authorities is to identify both historical and present areas of potential contamination, map key receptors (i.e. schools, residential areas and controlled waters) and use scientifically based knowledge to determine if a pollutant, or several pollutants, is impacting on a receptor.

Given the large amounts of essentially spatial data most authorities are beginning to use Geographical Information Systems (GIS) to collate, view and interpret the many data layers. Several layers of data can be viewed and interpreted at any one time. An example is examining land use change over time, or locating water wells coincident with potentially contaminated sites.

Relevant digital data is now available from a number of sources. The British Geological Survey (BGS) has recently published, under contract to the Environment Agency (EA), Some guidance on the use of digital environmental data, which is available on the EA website ( www.environment-agency.gov.uk/gwcl/publications.htm). The EA is also providing digital data to local authorities on CD-ROM including landfill sites, water abstraction and other hydrological and hydrogeological data. By early 2001 the BGS will have full digital coverage of its geological maps at 1:50,000 scale for use in GIS under licence. In areas where more detail is required digital data can be provided at 1:10,000 scale (already available for London, Glasgow and Bristol). More information regarding geoscience data for authority areas can be viewed on the BGS web site (www.bgs.ac.uk).

In order to assist the interpretation and reporting of data held within the GIS the BGS has developed several modules, in Arc View and Map Info to help non-GIS specialists. A reporting facility allows any number of themes to be selected for a specific site and a user-defined buffer zone. The resultant report (i.e. in Microsoft Word) gives a series of maps and tabular information relating to the chosen themes such as geology, land use, proximity of watercourses etc. A further module makes use of the information within the GIS to perform a risk assessment on each site providing a "score" related to a number of set parameters. This allows a first pass prioritisation of potentially contaminated sites for a District.



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