ConSEPT has been developed by the BGS to provide initial screening of potentially contaminated sites within a GIS environment. This is primarily to help Local Authorities meet the requirements of Part IIA (Contaminated Land) of the Environmental Protection Act 1990 in terms of prioritising potentially contaminated sites. ConSEPT provides a GIS site-screening tool that:

• identifies potentially contaminated land
• provides a semi-quantitative ranking of potentially contaminated sites
• assesses and prioritises sites according to the potential for pollutant linkage
• achieves a first tier assessment using generally available data
• provides an assessment in a manner that is rational, ordered and efficient

The benefit of using an integrated GIS system lies in the automation of the process, particularly the spatial linkage, which paper or spreadsheet products require to be manually entered.

The GIS tool generates a report document for each site as required, listing the sources, receptors and pathways identified for each site, along with the scoring. The scores thus obtained can also be mapped for an area of interest, to establish where high priority sites occur within an area of responsibility.

Features

• Easy and rapid operation in a GIS environment
• Interrogation of database to score sources, pathways and receptors
• Semi quantitative evaluation of potential pollution linkages
• Sites prioritised on pollution linkage criteria
• Flexibility for user to incorporate local knowledge

The model is based around the pollutant linkage concept:

Source

Pathway

Receptor

Example

Clarke Avenue, Loscoe, Derbyshire, April 1986

Three of the occupants were seriously injured. It was the UK’s worst landfill gas explosion.

The source, pathway, receptor linkage here was: Putrescible matter in the landfill site (source) escaped as gas and migrated up through the porous soil and rock matrix (pathway). It accumulated inside the house on Clarke Ave, causing it to explode (receptor).

This explosion could have been avoided had an assessment been carried out at the site, the potential linkage identified and either the source, pathway or receptor removed.

Characterisation of sources, pathways and receptors requires

• various geographical data
• data on hydrogeology
• hydrological information
• geological data

All of these are incorporated in the GIS to bring together a wide range data for a large number of potential sources, pathways and receptors for a required area.

How the scoring works

The method adopted by ConSEPT to evaluate datasets is based loosely on the Canadian National Classification System for Contaminated Sites, 1992.

Scores are assigned to evaluation factors using a set of scoring criteria which interrogates the data by

1. Spatial queries e.g. occurrence of a feature within a specified buffer zone
2. Numerical queries e.g. number of epochs during which the site is active, from which we derive duration of activity

Scoring criteria

Each evaluation factor can be weighted to suit the unique conditions prevalent in an area, or to satisfy specific concerns (e.g. emphasis on human receptors) or to allow for gaps in the data.

These can then be combined to give source scores, pathway scores and receptor scores.

ConSEPT combines these to give pollutant linkage scores, which estimate the likely risk of pollutant linkage as realistically as possible.

ConSEPT outputs

Site Prioritisation reports – Facility which writes site specific reports to a word document. Each report provides a description of the site together with the database queries used by ConSEPT to assess pollutant linkage for the site.

Dialogue with users has helped with identification of operational requirements and useful features to assist in achieving the above objectives and in individual reporting of the results of assessment. These include:

• simplicity
  • ease of use
  • results are easy to understand
• detailed reporting
  • scoring process is traceable through its various stages
  • individual site assessments can be examined
  • expert interpretation of results is facilitated
  • information sources
  • procedural guide, to assist expert interpretation
• user control
  • adjust weightings
  • evaluation scores
  • add new data

The ConSEPT module is available for ArcGIS 9 and MapInfo.

For more information please contact:

BGS Central Enquiries
British Geological Survey
Keyworth
Nottingham
NG12 5GG

tel: 0115 936 3143
email: enquiries@bgs.ac.uk
www.bgs.ac.uk

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