Groundwater, Engineering, Environmental & Mining
Landfill Characterization (Induced Polarization/Resistivity)
Induced polarization (IP) and galvanic resistivity surveys were conducted as a part of the Integrated Geophysics Program at the Mixed-Waste Landfill Integrated Demonstration (MWLID) test site, Sandia National Laboratories (Albuquerque, New Mexico, USA), to demonstrate the effectiveness of integrating several surface geophysical techniques to non-intrusively characterize mixed-waste landfill sites (Hasbrouck 1993). The test site was at the Chemical Waste Landfill where the locations of two waste pits (Chromic Acid and Organics Pits) were known from historical records. Although data from numerous profiles were acquired and analyzed, this example is from Line 20E that crosses both known pits.
Certain chemicals react with clays to produce substances that have a characteristic response to the complex galvanic resistivity method, as described by King and Olhoeft (1991) and Olhoeft (1986). In addition to possibly identifying broad classes of wastes in the pits, the complex resistivity response will delineate the chemical interaction boundary and, thus, the waste-pit boundaries.
Complex galvanic resistivity data were acquired using an Androtex TDR-6 multichannel resistivity-IP-SP receiver and a Phoenix IPT1 transmitter. Ten IP windows were measured on as many as six dipoles simultaneously. All data were stored in the instrument's internal memory in a format compatible with the Geosoft IP Plotting System computer software. Different types of electrode arrays were used to minimize the effects of nearby cultural features (e.g., metal fences) and electromagnetic coupling and to maximize the amount of useful data. Only data from the parallel-dipole (equatorial-dipole) configuration with 10-foot a spacings and n = 1 to 6, dipoles perpendicular to the fence and a distance na away, are shown in this example.
Figure 1 is the interpreted complex galvanic resistivity data from the parallel-dipole array. A near-surface disturbed area (possibly related to contaminants) is interpreted in the parallel-dipole data as the relatively low-resistivity zone to approximately n=3, which corresponds to a depth of investigation of less than 8 feet (Roy and Apparao, 1971). Within that disturbed area, locations of both the Chromic Acid and Organics Pits are interpreted within the IP data; agreement between the historical and interpreted pit boundaries are good (Chromic Acid Pit historical versus interpreted boundaries equals Stations 103 to 118 versus Stations 103 to 123; Organics Pit historical versus interpreted boundaries equals Stations 137 to 154 versus Stations 132 to 148). A slightly increased IP response is present within the Chromic Acid Pit compared with the Organics Pit. This increased response is interpreted as indicating different anomalous sources; however, these different responses cannot be directly attributed to specific chemical compounds.
Figure 1: Line 20E, interpreted, parallel-dipole array, complex galvanic resistivity data
Hasbrouck, J.C., 1993. Final Report, TTP AL921102, An Integrated Geophysics Program for Non-Intrusive Characterization of Mixed-Waste Landfill Sites, GJPO-GP-7, U.S. Department of Energy, Grand Junction Projects Office, Grand Junction, Colorado.
King, T.V.V., and G.R. Olhoeft, 1991. Adsorption of Toxic Substances onto Clays as Detected by Mid-Infrared and Complex Resistivity Measurements, U.S. Geological Survey Open-File Report 90-288, P. 11.
Olhoeft, G.R., 1986. "Field Data" in Proceedings NWWA/API Conference on Petroleum Hydrocarbons and Organic Chemicals in Ground Water, pp. 284-305.
Roy, A., and A. Apparao, 1971. "Depth of Investigation in Direct Current Methods", Geophysics, Vol. 36, No. 5, pp. 943-959.
Hasbrouck Geophysics, Inc.
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Last Modified: 10 November 2004 @ 15:45