Non-Invasive Characterisation of NAPL-Contaminated Land by Spectral Induced Polarisation (SIP) Tomography

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Objectives

The main aims of this project are to:

  • research the complex geoelectric properties, in the frequency bandwidth mHz to kHz, of Triassic sandstone aquifer rocks contaminated by common industrial Non-Aqueous Phase Liquids (NAPLs), eg chlorinated solvents, hydrocarbons, coal-tars
  • study SIP images obtained from controlled release NAPL experiments in a medium-scale laboratory sand tank to provide a physical insight on NAPL behaviour in porous and fractured media
  • develop and test new 2.5D mathematical algorithms for the robust inversion and reconstruction of SIP images for the full SIP frequency range
  • undertake field trials at well characterised industrial sites to check SIP spectra, laboratory results and imaging code against known contaminant models and ground-truth.

Location

West Midlands

Approach

The project comprises five main work packages, each of which is subdivided into specific tasks as follows:

Work package 1: Laboratory characterisation of NAPL-contaminated and clean samples to relate SIP phase spectra to known chemical, mineralogical and pore-fluid properties

Task 1: Petrophysical and mineralogical characterisation.

Task 2: Chemical analysis of contaminated samples.

Task 3: Measurement of the SIP spectra of the samples.

Work package 2: Model tank/column experiments using controlled releases of NAPLs to correlate SIP spectra and images against known geometries, media properties, flow-paths and hydraulic parameters

Task 4: Controlled release of NAPLs.

Work package 3: Development and testing of 2.5D numerical inversion software

Task 5: Development of 2.5D forward modelling scheme for full SIP frequency bandwidth.

Task 6: Development of 2.5D inversion software.

Work package 4: Field trials at industrial sites to validate laboratory and interpretive criteria

Task 7: Trial surveys undertaken in the West Midlands conurbations, much of which are underlain by Triassic sandstone.

Work package 5: Project management

Task 8: Overall co-ordination of the principal research tasks, reports, maintaining schedules, budget control, QA and liaison with EPSRC by the British Geological Survey.

Start date/duration

April 1999 Three years

Lead Organisations

British Geological Survey

University of Birmingham

Deliverables

This project will develop SIP as a cost-effective, non-invasive geophysical scanning technique to map and monitor organic contaminant distributions. In addition, 2.5D code will be developed to cover the full SIP frequency range (mHz to kHz).

Users

Environment Agency

Chemical and construction industries

Water companies

Planning and regulatory authorities

Land re-developers

Insurance or financial houses for risk assessment

Health and Safety authorities

Further Details

Further information is available from the following contacts:

Lead Researcher: Dr R D Ogilvy

Tel: 0115 936 3359, Fax: 0115 936 3261, e-mail: r.ogilvy@bgs.ac.uk

URGENT Programme Manager: Graham Leeks

Tel: 01491 692203, Fax: 01491 692313, e-mail: gjll@ceh.ac.uk