Abstract A hydraulic scale model was used in a laboratory experiment for the purpose of understanding the characteristics of a pollutant dispersion in subsurface soil. The experimental site was an area near a radioactive waste repository in the Republic of Korea. The hydraulic scale model was designed and manufactured in geometric similarity to the actual site. The tracer 99mTc which has a short half-life was injected instantaneously into the soil. Numerical simulations were performed to compare the measured radioisotope data and to investigate the overall dispersion patterns. The calculated concentrations are in good agreement with a time series of the measured concentrations at the midpoint of the detection lines.