Induced Polarization: Buried Landfill Delineation

Induced polarization (IP) and resistivity can be very useful tools in mapping environmental features such as buried landfills, but the survey speeds and pseudosection interpretations have been drawbacks. New multichannel receivers with computer-controlled multiplexers now allow extremely fast data acquisition, and two dimensional smooth-model inversion (with topography) provides realistic geo-electric cross sections.

The survey area in this project has been used as a landfill since 1953. Pits or holes left from local brick and clay companies have been filled in with municipal garbage. The location and extent of these pits can only be assumed from aerial photographs. In the early 80's some of the garbage was removed in a random manner. An IP and resistivity survey line was run over the property as a test to determine if the small pits of garbage could be delineated with these methods. To keep expenses to a minimum, Zonge utilized the MX-30 which is a computer-controlled switching interface between a resistivity transmitter, a multichannel receiver such as the GDP-32, and an array of up to 30 electrodes. The data set below consists of three overlapping spreads of dipole-dipole data, each consisting of 236 data points. The reciprocal of each data point was also read (with the transmitter and receiver dipoles reversed), resulting in a total of 1,416 data points, providing measurements at n=0.5 to n=6 at 0.5n increments. A field crew of three was able to acquire this data in about 4 hours.