Vertical radar profiling for the assessment of landfill capping effectiveness

Abstract

In this paper we present the results of the characterization of a large landfill cap by means of ground‐penetrating radar (GPR) measurements. The GPR data were collected in boreholes, using a vertical radar profile (VRP) configuration, where one antenna was kept at the ground surface while the other was progressively lowered into the borehole. This yields a vertical profile of GPR velocity from which a moisture content profile can be obtained. VRPs were conducted in 15 boreholes available on‐site, all having been drilled through the protective cap and the waste mass into the underlying native soil. The separation between the boreholes (many tens of metres) makes it infeasible to characterize the site via other forms of hole‐to‐hole GPR measurements, with the exception of a few pairs of holes drilled at the periphery of the waste mass and therefore of limited usefulness. The VRP data allowed for the characterization of the moisture content profile across the waste body down to the water table, very close to the natural land surface, providing evidence that the waste is generally fairly dry (moisture content less than 10% on average). In order to assess the effectiveness of the cap, two surveys where conducted in March and April 2005 using all the boreholes with the aim of identifying moisture content changes due to natural rainfall and especially artificial irrigation over a limited area surrounding one of the boreholes. The time‐lapse VRP results show that in the irrigated area a measurable amount of water seeps through the cap and changes the waste moisture content. Elsewhere, we basically observed no changes in moisture content due to natural infiltration during the same period: this fact does not confirm or exclude that some degree of leakage can occur. Direct in‐situ permeability measurements, albeit more localized than VRP data, confirm that the landfill cap is not totally impermeable, thus corroborating the results derived from geophysical measurements.

Time‐lapse borehole radar for monitoring rainfall infiltration through podosol horizons in a sandy vadose zone

“…Time-lapse BHR (i.e., repeated BHR surveys) has been used successfully in hydrogeophysical studies, especially in unsaturated zone investigations to monitor flow [Hubbard et al, 1997;Deiana et al, 2007;Day-Lewis et al, 2003;Chang et al, 2004]. Alumbaugh et al [2002] investigated the accuracy and repeatability of soil moisture inferred from crosswell radar experiments, while studies 6, 8, 9, 10, 12, 3 4, 7, 8, 9 5, 7, 8, 9 4, 7, 8, 9 5, 6, 8, 9, 10, 3 5, 7 In this study, we used zero (vertical) offset profiling (ZOP) (i.e., crosswell) [e.g., Rucker and Ferre, 2003] and vertical radar profiling (VRP) (i.e., single-well) [e.g., Buursink et al, 2002;Cassiani et al, 2008] acquisition geometry. The ZOP is a vertical scan where both antennae are lowered into the adjacent wells simultaneously while their midpoints are at the same horizontal level (see examples in Figures 5 and 7b).…”

Advanced Monitoring and Control of Anaerobic Digestion in Bioreactor Landfills

“…It is clear that, with all these operational issues, current monitoring techniques are neither robust nor efficient. The solution for these issues can be realized via two approaches: (1) using nonintrusive surface methods for subsurface monitoring; e.g., for moisture measurements: seismic waves [40], ground penetrating radar [41], and fiber optics [42], or (2) using wireless communication techniques to eliminate the huge capital cost and operational problems associated with conventional wired techniques [43]. Both approaches can also solve the heterogeneity problem in a way that: in the first approach, a three-dimensional image of moisture distribution can be produced, and in the second approach, more wireless sensors can be used to give higher resolution data.…”

Electrical Resistivity Monitoring on an Experimental Landfill Clayey Cover

“…On landfills, damages on protection cover, put above waste, may generate preferential water pathways and an unusual increase of leachate. Up to now, only few studies have been undertaken on the characterization of the cover landfill (Carpenter et al, 1991;Ait Saadi, 2003;Guyonnet et al, 2003;Cassiani et al, 2008). In order to characterize cover, the three following geophysical methods, Electrical Resistivity Tomography (ERT), the Self Potential (SP) and the Automatic Resistivity Profiling (ARP©) were carried out on an hazardous waste landfill (Genelle et al, 2010) and on an experimental site.…”