Automated time-Lapse Electrical Resistivity Tomography (ALERT) is a novel geophysical monitoring concept highly applicable to waste management problems.
The Veolia Environmental Trust, with support from English Partnerships, has commissioned BGS to develop an ALERT system specifically for the automated time-lapse monitoring of landfills (Project RES/C/6034).
ALERT sensors would remotely detect temporal changes in leachate distribution, fluid and gas flow, hydrochemistry and saturation levels.
A permanent installation would reduce the risk of boreholes penetrating natural barriers, opening up new pathways, or changing the hydraulic model.
Perched leachate levels could be distinguished from the leachate levels within the waste mass, and this could lead to improved operational control of gas/leachate generation.
The principal aim of the project was to develop a new non-invasive 4D electrical imaging system for the automated time-lapse monitoring of landfills.
In-situ sensors, data loggers and inversion software were developed to remotely detect temporal changes in leachate distribution, fluid and gas flow, hydrochemistry and saturation levels.
Permanently installed instrumentation facilitates 'on demand' imaging via a telemetric link to the office. It is intended to offer this technology to the waste industry as a commercial service or under licence.
As part of this research, BGS has established a hydrogeophysical testing facility within the grounds of the Keyworth site.
Field-scale hydraulic test cells filled with high-grade silica sand and equipped with simulated boreholes and a pumping system provide a means for undertaking hydraulic experiments such as tracer tests, flow simulations and periodic variations of the water table/phreatic surface.
Saline tracer transport along a uniform flow field was monitored with the newly developed ALERT system.
Cross-borehole ERT using a fence of nine boreholes was employed to generate a time-lapse 2D image of the conductive plume migrating along the test cell ( Animation 1).
Direct water sampling from multilevel sampling ports showed good agreement with the electrical images.
A similar experiment was carried out to prove 4D ALERT imaging. A grid of 3×3 boreholes was used to carry out time-lapse 3D ERT measurements during tracer transport through the test cell.
Volumetric reconstruction allowed us to assess the behaviour of the plume spatially and over time. Resistivity isosurfaces were used to visualise the evolution of the experiment in 4D (Animation 2).
All experiments were monitored remotely using the newly developed ALERT instrumentation.
The Veolia Environmental Trust is a charity and an environmental body registered under the Landfill Tax Regulations established to protect, preserve and improve the environment for the benefit of the public.
The Veolia Environmental Group plc has supported Veolia Environmental Trust through its landfill operating companies by contributions of £28 m. To date, the Trust has awarded this money to over 480 projects nationally since its launch in 1997.
For further information please contact:
Dr Oliver Kuras
Tel: +44 (0)115 936 3416
Email: Dr Oliver Kuras
Dr Jonathan Chambers
Team Leader - Geophysical Tomography
Tel: +44 (0)115 936 3428
Email: Dr Jonathan Chambers