Contamination of soil and groundwater by pollutants buried without proper treatment has become a social problem around the world. The objective of this project was to develop a Smart Subsurface Barrier System (SSB) that has functions of enclosing pollutants and remediating contaminated soils. This report describes a method for evaluating the hydraulic conductivity of the SSB using a seepage test, and an assumption method for joint defects using a radioisotope method (RI method). Both methods have been put to practical use. A thorough study has shown that the hydraulic conductivity of SSB is less than k=1.0×10^-7cm/sec, which is one of the strictest criteria of the EPA standard, so it is confirmed that the SSB is effective.