GIS based system aids PartIIA management
This case study from AEA Technology reports on the hands-on experience of Leeds City Council using GroundView, which is stated to be the most widely used GIS based tool to help Local Authorities manage their obligations under Part IIA of the Environmental Protection Act 1990. The system has been is use for more than five years and there are now close to 50 users up and down the country from all types of environments including London Boroughs, industrial cities as well as rural boroughs and districts.The system saves vast amounts of officer time in carrying out the Part IIA process and allows far easier scrutiny of the data by others. GroundView exists as a database linked to GIS (either MapInfo or ArcView/SrcGIS) and enables LAs to manage, store and report on Part IIA relevant information far more effectively. In addition, it contains a fully flexible prioritisation system. The prioritisation method is based on using standard GIS information and a user-definable scoring system for sources, pathways and receptors.
The Part IIA inspection strategy for Leeds is available of their web site at http://www.leeds.gov.uk/downloads/2002222_61239261.pdf. The document was originally prepared by Lucy McLellan although the work is currently being run by Neil Webber and Stella Cassidy.
Leeds City is the UK's second largest Metropolitan district by population and is situated approximately 100km from both the east and west coasts of the UK. From Leeds' beginnings in 1322 the city was transformed by the industrial revolution of the eighteenth and nineteenth centuries, a process which was stimulated by a host of local inventors and the pioneering use of steam. New industries then found a home in Leeds including chemicals, glassworks, potteries and brickworks along with the vital engineering to make all the machinery. In 1758 the Middleton Railway brought coal to the city centre and in 1770 the Leeds- Liverpool canal was opened to service the burgeoning industry in particular leather and cloth making. In the latter decades of the eighteenth century cloth making became the dominant industry in Leeds. During the nineteenth century the industrialisation continued and included foundries to produce much-needed iron and railways, which were an essential component of the transport infrastructure. With the advent of the first and second world wars Leeds industrial portfolio increased to the production of explosives and munitions. All of this led, in the 1970s, to a peak in the population of Leeds at 750,000. During the 1980s, however, the manufacturing capacity of Leeds suffered something of a blow with the collapse of manufacturing. Many sites were left derelict until Leeds began to rejuvenate itself in the 1990s. Today Leeds is again a growing city with more than 60% of its people working in the service sector although there is still a strong foothold in manufacturing. Leeds City Council has been using GroundView (Arcview 3.x version) for its management of the Part IIA process since March 2001 ). One of the key issues for Leeds has been developing a prioritisation scoring system, which is meaningful to it.
The data Leeds have used for the prioritisation has been as shown (top right). Pathways have not been used so far. These are however likely to be considered in the future as Leeds wishes to consider sites where receptors are adjacent to sources but not directly overlapping. In these cases there is likely to be some risk.
The initial approach used by Leeds was to adopt a scoring system of 1-5 for sources. These scores were assigned to site types as detailed in the Leeds strategy (Appendix D). For receptors however a scoring system of 1-4 was adopted.
Initially runs were conducted using this scoring system and variations of it. The results are shown as colour coded images on the GIS which are produced in addition to a tabular listing of sites and scores.
In Image A there are two sites called 1 and 2. Site 1 exists as a source, which coincides with two receptors, whereas site 2 has only one receptor and yet in the two results the two sites appear to be similarly scored.
This was the key issue for the team at Leeds - to create much more of a spread of scores between sites to provide more resolution in the prioritisation. In order to achieve this Leeds moved from adding of scores to multiplying them. The ability to multiply scores between sites is now a standard feature.
Also key was the need to create a natural skew to sites where human beings were present as the receptor. To this end Leeds arrived at a scoring system for receptors using the following approach.
This was arrived at to ensure that any site where there were human receptors being impacted would score more highly that other sites. So, for example, an area where a source polygon had been identified on four epochs of maps (ie four source scores) but which would only impact buildings or groundwater, still would score lower than a single source polygon impacting on human beings. The use of multiplication, together with a modification of scores both for receptors (as shown above) and sources, gave a better spread among this same data as shown in image B.
The overall approach enabled Leeds to focus on top 100 scoring areas and to see how these scores coincided with sites. Further information is then gathered on these areas.
For more information on Groundview contact: Graham Holtom, AEA Technology T 01235 464001 or E firstname.lastname@example.org