Waste deposits

Description

 

Waste is, and always has been, generated around the world, around the clock. But in modern times it has been generated at unprecedented rates: municipal waste alone sums up to more than 2 billion tonnes annually. All this waste, in deposits, in landfills, creates several problems for society. For instance, the presence and extent of buried waste, especially older deposits, may be unknown and this creates difficulties during the establishment of new housing and infrastructure. In addition, landfill areas are often a source of contamination affecting the ground, rivers, lakes and groundwater far beyond their original physical limits. Despite this, waste deposits can also present an opportunity to society. With novel reprocessing techniques, landfills can be mined for recyclable metallic or plastic materials, whilst gas generated within the waste can be captured for power generation, if the structure and content of the landfill can be clarified.

The traditional way to investigate these problems and opportunities are by pointwise investigations, for example by drilling or digging. This is most often expensive, potentially hazardous and the data collected can be rather sparse. To create a more comprehensive picture of the subsurface conditions, different geophysical methods can be used as an efficient complement.

Waste deposit with leachate flow visualized

Old landfills often have high concentrations of heavy metals, nutrients and organic substances in the ground. Decomposition of carbonaceous material can produce methane, carbon dioxide and organic acids that contaminate the environment.

Solutions 

Guideline Geo´s resistivity techniques, utilizing either surface or borehole measurements, can solve most of the common questions regarding waste deposits and landfill areas. They will give a non-destructive and cost-efficient way of gaining a better understanding of the ground conditions, providing better data coverage than is normally achieved with traditional, discrete, point-by-point geotechnical investigations and sampling.

Different materials in the ground will have contrasting resistivities associated with them, and that resistivity can also vary within the material due to changes in composition, mineralogy, water content, and structural integrity. For landfill sites, the make-up of the content itself as well as the volume of water, leachate composition and temperature will affect the recorded resistivity. Areas with contamination will most likely decrease the resistivity, whereas areas with more stone/wood/building material will have a higher resistivity. The mix of materials in a typical waste dump can also create a sizeable IP (induced polarization) effect, indicating higher chargeability than the surrounding natural geology. This effect can delimit the extents of a waste pit more precisely than resistivity values alone, where the seepage of low resistivity leachate can ‘blur’ where the edge of the pit lies.

 

ABEM Terrameter LS 2 is a perfect solution for examining waste deposits

The ABEM Terrameter LS 2 is a perfect solution for examining waste deposits, but also useful for applications such as landfill and environmental surveys

Explore the ABEM Terrameter ls 2

Different waste deposit applications 

Resistivity, IP and SP measurements can be used to inform upon a number of different questions within the area of waste deposits:

  • Extent of waste material, both near-surface and at depth
  • Coverage of landfill, both thickness and fractures
  • Integrity of underlying geology and potential for pollutant pathways
  • Gas and fluid content within the landfill
  • Leachate from the landfill
  • Type of waste within the landfill; metal waste and redox reactions gives high chargeability when measuring IP, as do household waste compared to waste from non-organic origin.

It should be emphasized that a huge benefit of using resistivity is the opportunity to monitor changes over time, for instance, fluid content and leachate movement. More can also be read here.

Using the ABEM LS system, a 3D resistivity and time-domain induced polarisation (IP) survey was carried out over part of a Municipal Solid Waste (MSW) landfill in Helsingborg, Sweden.

Picture 1: Resistivity data from across the landfill site showing low values associated with the waste and leachate.

Picture 2: Induced Polarization data from across the site showing increased chargeability associated with the landfill material

Site of a former municipal landfill facility

Site of a former municipal landfill facility

Other geophysical methods

Guideline Geo also provide GPR and Seismic solutions, which can be beneficial for ground investigations in conjunction with waste deposits and landfill areas.

GPR can be used to map non-conductive material in landfill, the extent of protective clay layers, the thickness of friction soils, the position of utilities and other subsurface constructions around waste deposits etc. It should be noted that GPR is not suitable for investigating the waste itself, as conductive conditions efficiently prevent the radar signals from penetrating the ground.

Seismic methods are commonly used for measuring depth to bedrock, bedrock quality, soil stability or general mapping of geological structures. For landfill areas seismic can give information on the overburden thickness and stability, pit size, underlying geological integrity and the level of compaction within the waste itself; areas with lower compaction will result in a lower elastic modulus.

Note! Both of these methods, plus resistivity, can of course be used to also map and characterize ground conditions prior to the establishment of new waste storage facilities.

Waste deposit survey with the WideRange system

Click the link below to learn more about our solutions for ground penetrating radar

gpr solutions

Seismic survey performed on landfill site with the Terraloc Pro 2 system

Click the link below to learn more about our systems for the seismic methods

SEISMIC solutions

Application PDF

How to map waste deposits using resistivity and IP

References:

Dahlin, T. Rosqvist H., Johansson S., Svensson M., (2012) Resistivity-IP characterisation and short term monitoring at
Filborna waste deposit, Procs. 74th EAGE Conference, Copenhagen, 4-7 June 2012, EAGE, 4 p.

Maurya, P. K., Rønde, V., Fiandaca, G., Balbarini, N., Auken, E., Bjerg, P. L., & Christiansen, A. V. (2017).
Detailed landfill leachate plume mapping using 2D and 3D Electrical Resistivity Tomography – with correlation to
ionic strength measured in screens. Journal of Applied Geophysics, 138, 1-8. DOI:
10.1016/j.jappgeo.2017.01.019

 

 

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