Evaluation of the Proper Electrode Spacing for ERI Surveys in Open Dumpsites Using Forward Modeling

Electrical resistivity imaging surveys are widely conducted in waste disposal sites due to their ease
of operation and accurate results; however, some essential measurement parameters, such as optimal
electrode spacing, have not been thoroughly evaluated. Accordingly, this study aims to identify the
optimal electrode spacing for electrical resistivity surveys in open dumpsites. An electrical resistivity
survey was conducted at the Nonthaburi disposal site, Thailand, and the results were compared to
synthetic cases simulated using the forward modeling technique. Electrode spacing values of 2, 2.5, 4,
and 5 m were used. The models were evaluated using the Nash–Sutcliffe model efficiency coefficient,
model sensitivity, and root mean square error. The real case survey results illustrate that small electrode
spacings of 2 and 2.5 m provide a realistic model, however, the root mean square error is higher due
to the use of more outlier electrodes during measurement. Consistent with the synthetic case studies,
electrode spacing values of 2 and 2.5 m yielded accurate inverted models. Overall, this study illustrates
the benefits of using a forward modeling technique for selecting the optimal electrode spacing for open
dumpsite surveys.